$771,393 Donated to the SENS Research Foundation at the End of 2018

The philanthropists of our community, of greater and lesser means, stepped up to provide more than three quarters of a million dollars to the SENS Research Foundation in the last months of 2018. The work of the SENS Research Foundation depends on our support: building the foundations for rejuvenation therapies that would not otherwise be constructed, unblocking important research that is stuck, cultivating vital but neglected fields of science. Look at the yearly reports for much more detail. This non-profit is entirely dependent on philanthropic donations to power the vital work undertaken by its staff and allies in the research community.

Thank you very much to everyone who contributed to 2018's Reimagine Aging end-of-year fundraising campaign. The original General Fund goal of $500,000 was our most ambitious yet, and you enabled us to exceed this goal for an incredible $771,393 total! We are grateful beyond measure for your generosity and support to continue our mission of curing age-related disease. Every dollar you give helps bring the future we all want to bring into existence.

A very special thanks to Vitalik Buterin for his incredible gift of $350,000 in Ethereum, as well to IAS, Josh Triplett, Reason, Christophe and Dominique Cornuejols, Didier Coeurnelle, and Olivier Roland for providing matching grants during this campaign.

Here at Fight Aging!, Josh Triplett, Christophe and Dominique Cornuejols, and I put up a challenge fund for SENS Patrons, the monthly donors that supply a steady stream of funding to the foundation. For several years now we've aimed to grow that community of grassroots donors. They are steady folk; 80% of all of those who sign up stick around for at least a year, and the more donations that arrive on a schedule, the easier it becomes for the SENS Research Foundation staff to plan ahead and organize longer-term projects. We didn't do as well in 2018 as in 2017, only hitting 50% of our goal: $29,987 out of the $54,000 target - but it wasn't very many years ago that this would have been a sizable set of funding for the small organization that the SENS Research Foundation was back then.

In general, 2018 was a more muted environment for charitable fundraising. It would have been hard to top the end of 2017, at the height of the cryptocurrency bubble, when a great deal of philanthropic funding was disbursed to many research organizations. Now we are back to the point of having to work hard once again to grow our community, to persuade people that, in the midst of enthusiasm over clearance of senescent cells as a rejuvenation therapy, there is a great deal more necessary work to accomplish. One success does not complete the job at hand - there are still forms of age-related damage for which the science continues to languish, and each of them is enough on its own to produce age-related disease and death.

The efforts of the SENS Research Foundation and allied groups such as the Methuselah Foundation are just as vital now that the first rejuvenation therapies have been achieved as they were when only the vision existed. The road is only partly traveled, the journey only just begun, and our help is still required.

One of the Ways Researchers Narrow the Search for Drugs to Slow Aging

Small molecule and drug candidate libraries are huge. Much of modern medical research is a process of screening subsets of those libraries in search of molecules that can produce benefits with minimal side-effects. Usually the output of a successful screen is taken as a starting point for further exploration and molecular tinkering, to improve the effect or minimize undesirable side-effects. The great hope for gene therapy is that it will render all of this largely obsolete by offering ways to directly influence a molecular mechanism to a configurable degree without meaningful side-effects. That remains a way off in the future, however, and meanwhile a very sizable slice of medical research is still all about finding which cataloged molecules might be interesting to work with.

Thus when it comes to aging, a majority of efforts are focused on adjusting the operation of metabolism via small molecules from the catalogs, interacting with one of the known aging-related mechanisms discovered via examination of the biology of calorie restriction, or autophagy, or other stress response mechanisms. This is somewhat depressing: none of this work offers either hope or possibility of doing more than slightly increasing human life span, yet it is where most the funding and effort is focused. An increasing fraction of those initiatives are concerned with ways to speed up this process, to make it more rational, to cut down the number of molecules to be assessed. These advances are interesting to the degree that they can be applied more generally, to any area of development. There are parts of the SENS rejuvenation research portfolio in which small molecule drug discovery might lead to useful therapies, for example.

Several bioinformatic methods have been developed to identify potential geroprotective drugs. For instance, caloric restriction (CR) mimetics have been identified, by comparing genes differentially expressed in rat cells exposed to serum from CR rats and rhesus monkeys with gene expression changes caused by drugs in cancer cell lines. Structural and sequence information on ageing-related proteins have been combined with experimental binding affinity and bioavailability data to rank chemicals by their likelihood of modulating ageing in the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Drug-protein interaction information has also been used to predict novel pro-longevity drugs for C. elegans, using a set of effective and ineffective lifespan-extending compounds and a list of ageing-related genes. A similar approach used chemical descriptors of ageing-related compounds from the DrugAge database together with gene ontology terms related to the drug targets. Enrichment of drug targets has been assessed for a set of human orthologs of genes modulating longevity in animal models to identify new anti-ageing candidates.

Despite the increasing interest in drug-repurposing for human ageing, research has tended to focus on predicting life-extending drugs for animal models. However, the translation from non-mammalian species to humans is still a challenge, and certain aspects of ageing may be human-specific. Only a few studies have focused on data from humans. For instance, researchers applied the GeroScope algorithm to identify drugs mimicking the signalome of young human subjects based on differential expression of genes in signalling pathways involved in the ageing process. Another study correlated a set of genes up- and down-regulated with age in the human brain with drug-mediated gene expression changes in cell lines from the Connectivity Map.

In the present study, we rank-ordered drugs according to their probability of affecting ageing, by measuring whether they targeted more genes related to human ageing than expected by chance, by calculating the statistical significance of the overlap between the targets of each drug and a list of human ageing-related genes. Additionally, to enhance the power of the approach, we mapped the drugs' gene targets and ageing-related genes to pathways, gene ontology terms, and protein-protein interactions, and repeated the analysis. We found that, independently of the data source used, the analysis resulted in a list of drugs significantly enriched for compounds previously shown to extend lifespan in laboratory animals. We integrated the results of seven ranked lists of drugs, calculated using the different data sources, into a single list, and we experimentally validated the top compound, tanespimycin, an HSP-90 inhibitor, as a novel pro-longevity drug.

Link: https://doi.org/10.1371/journal.pcbi.1006639

What is Known of the Behavior of Regulatory T Cells in Aging Fat Tissue

Visceral fat tissue produces chronic inflammation through its interactions with the immune system. Numerous mechanisms are involved: generation of additional senescent cells and their inflammatory signaling; normal fat cells secreting signals similar to those of infected cells; DNA debris from dead fat cells; and others. In younger individuals, problematic inflammation arises through having too much fat tissue, being overweight or obese. In older individuals, however, many of the same problems of chronic inflammation arise even given lesser amounts of visceral fat tissue. This paper reviews some of the relevant mechanisms, comparing aging with obesity, looking for the differences under the hood in T cell behavior.

Basic aging mechanisms such as cellular senescence and diminished number or dysfunction of immune progenitor cells are causative factors of development of low-grade inflammation. Immunosenescence is a term to describe the decline of immune function associated with aging, which can lead to increased susceptibility to infections, cancer, and metabolic and autoimmune disorders. During the state of infection or tissue damage in healthy young individuals, the immune system moves quickly. After the effective removal of the invading pathogen, the host immune response must be deactivated and return to a quiescent state to prevent further tissue damage. A subset of T lymphocytes called regulatory T cells are responsible for suppressing the deleterious effects of immune response.

In general, both innate and adaptive immune systems are affected by aging, but adaptive immunity, especially T lymphocytes, are most susceptible to the detrimental effects of aging. Gradual deterioration of the immune system over the course of time leads to a mismatch between proinflammatory and anti-inflammatory signals that may disrupt inflammatory homeostasis causing inflammaging.

Inflammation in adipose tissue, mainly evidenced by increased accumulation and proinflammatory polarization of T cells and macrophages, has been well-documented in obesity and may contribute to the associated metabolic dysfunctions including insulin resistance. Studies show that increased inflammation, including inflammation in adipose tissue, also occurs in aging. Aging-associated inflammation in adipose tissue has some similarities but also differences compared to obesity-related inflammation. In particular, conventional T cells are elevated in adipose tissue in both obesity and aging and have been implicated in metabolic functions in obesity.

However, the changes and also possibly functions of regulatory T cells in adipose tissue are different in aging and obesity. In this review, we summarize recent advances in research on the changes of these immune cells in adipose tissue with aging and obesity and discuss their possible contributions to metabolism and the potential of these immune cells as novel therapeutic targets for prevention and treatment of metabolic diseases associated with aging or obesity.

Link: https://doi.org/10.3389/fimmu.2018.02945

Ceramides in Extracellular Vesicles Increase with Age and Induce Cellular Senescence

Much of the signaling that passes between cells travels via varieties of extracellular vesicle, tiny membrane-bound packages that contain a wide variety of presently poorly cataloged molecules. The varieties of vesicle are also poorly catalogued, and are at present given a loose taxonomy based on size. No doubt there are many subtypes within any given size category, depending on circumstance and mechanism, with the contents varying characteristically by subtype. Nothing is simple in cellular biology.

Vesicles are currently a subject of growing interest in many fields of medical research. In regenerative medicine, for example, it is hoped that harvesting vesicles from stem cells in culture and delivering them to patients can replicate much of the beneficial effects of stem cell therapies, but at a lower cost and with fewer complicating factors. Vesicles should not provoke immune reactions, for example, and thus do not require patient-matched or otherwise carefully chosen and engineered cells. In most cell therapies used to date, the transplanted cells die out quite rapidly. Beneficial outcomes result from the signals that they secrete, inducing changes in the native cell behavior. Thus why not just stop using the cells for this class of treatment?

Another area of interest is the way in which senescent cells manage to wreak havoc in tissues even when they are present in small numbers. They generate a potent mix of signals that creates chronic inflammation, destructively remodels the surrounding extracellular matrix, and alters the behavior of other cells for the worse, directly or indirectly. Moreover, senescent cells encourage other cells to become senescent. Therefore we should expect to see intracellular signals in the aged environment that can induce senescence. Those are starting to be discovered: versican is one example, to go along with the very long chain ceramides noted in today's paper.

The vesicles containing these molecules may be secreted by senescent cells. Or they may be generated in other ways, implying that the state of senescence is more readily achieved in older, damaged tissues independently of existing senescent cells. Or both. Knowing more about these mechanisms will inform the appropriate use of senolytic drugs to remove senescent cells in the years to come: if senescence occurs more often in old tissues, then senolytic drugs should be used more often rather than less often by older people. If, on the other hand, new senescence is largely driven by existing senescence, then much more infrequent use is all that is needed.

Very Long-Chain C24:1 Ceramide Is Increased in Serum Extracellular Vesicles with Aging and Can Induce Senescence in Bone-Derived Mesenchymal Stem Cells

Emerging patterns of disease progression suggest that degenerative changes in one organ or system are likely to contribute to degenerative changes in other organs and systems. For example, reductions in lean mass and bone loss have both been observed to precede the age-related development of cognitive impairment and Alzheimer's disease. Thus, cross-talk among various cells, tissues and organs may underlie non-autonomous aging in different cell and tissue populations. This concept is supported by studies in which young cells exposed to aged serum exhibited changes characteristic of older cells.

A barrier to progress in correcting the problem of age-related tissue dysfunction is the poor understanding of the molecular and cellular mechanisms underlying these non-autonomous cellular communication pathways. Exosomes are small (40-150 nm) and microvesicles are larger (more than 100 nm) membrane-derived structures that are released into the extracellular space by a variety of cell types. These membrane-bound extracellular vesicles (EVs) can transport proteins, lipids, and mRNAs between cells, delivering these molecules to target cells. EVs are highly enriched in the sphingolipid ceramide, which is known to promote cell senescence and apoptosis. In addition, EVs play a key role in a number of pathologies in vivo such as cancer metastasis and neurodegenerative disease. Thus, EV-derived ceramide is one potential aging factor that may promote degeneration in multiple organs and tissues.

We investigated the ceramide profile of serum exosomes from young (24-40 years) and older (75-90 years) women and young (6-10 years) and older (25-30 years) rhesus macaques to define the role of circulating ceramides in the aging process. EVs were isolated using size-exclusion chromatography and specific ceramide species were identified with lipidomic analysis. Results show a significant increase in the average amount of C24:1 ceramide in EVs from older women (15.4 pmol/sample) compared to those from younger women (3.8 pmol/sample). Results were similar in non-human primate serum samples with increased amounts of C24:1 ceramide (9.3 pmol/sample) in older monkeys compared to the younger monkeys (1.8 pmol/sample).

In vitro studies showed that primary bone-derived mesenchymal stem cells (BMSCs) readily endocytose serum EVs, and serum EVs loaded with C24:1 ceramide can induce BMSC senescence. Elevated ceramide levels have been associated with poor cardiovascular health and memory impairment in older adults. Our data suggest that circulating EVs carrying C24:1 ceramide may contribute directly to cell non-autonomous aging.

Large Genome-Wide Study Finds Only a Few Genetic Influences on Human Longevity

The influence of genetic variants on natural variations in human longevity is a very complex matter. The evidence to date supports a model in which thousands of genes have individually tiny, conditional effects. Near all associations identified in any given study population have failed to appear in any of the other study populations, and effect sizes for the very few longevity-associated genes that do appear in multiple studies are not large in the grand scheme of things. These variants provide a small increase in the odds of living to be very old, but the individuals bearing them are still diminished and damaged by aging. The genetics that determine how cellular metabolism gives rise to variations in aging are of great scientific interest, but there is nothing here that can act as the foundation for therapies that will help people to live significantly longer.

The extent of the role of genetic variation in human lifespan has been widely debated, with estimates of broad sense heritability ranging from around 25% based on twin studies to around 16.1% based on large-scale population data. One very recent study suggests it is much lower still (less than 7%), pointing to assortative mating as the source of resemblance amongst kin. Despite this modest heritability, extensive research has gone into genome-wide association studies (GWAS) finding genetic variants influencing human survival. Only two robustly replicated, genome-wide significant associations (near APOE and FOXO3) have been made to date, however.

An alternative approach is to study lifespan as a quantitative trait in the general population and use survival models to allow long-lived survivors to inform analysis. However, given the incidence of mortality in middle-aged subjects is low, studies have shifted to the use of parental lifespans with subject genotypes, circumventing the long wait associated with studying age at death in a prospective study. In addition, the recent increase in genotyped population cohorts around the world, and in particular the creation of UK Biobank, has raised GWAS sample sizes to hundreds of thousands of individuals, providing the statistical power necessary to detect genetic effects on mortality. A third approach is to gather previously published GWAS on risk factors thought to possibly affect lifespan, such as smoking behaviour and cardiovascular disease (CVD), and estimate their actual independent, causal effects on mortality.

Here, we blend these three approaches to studying lifespan and perform the largest GWAS on human lifespan to date. First, we leverage data from UK Biobank and 26 independent European-heritage population cohorts to carry out a GWAS of parental survival. We then supplement this with data from 58 GWAS on mortality risk factors. Finally, we use publicly available case-control longevity GWAS statistics to compare the genetics of lifespan and longevity and provide collective replication of our lifespan GWAS results.

We identified 11 novel genome-wide significant associations with lifespan and replicated six previously discovered loci. We also replicated long-standing longevity SNPs near APOE, FOXO3, and 5q33.3/EBF1 - albeit with smaller effect sizes in the latter two cases - but found evidence of no association (at effect sizes originally published) with lifespan for more recently published longevity SNPs near IL6, ANKRD20A9P, USP42, and TMTC2. Despite studying over 1 million lives, our standard GWAS only identified 12 variants influencing lifespan at genome-wide significance. This contrasts with height (another highly polygenic trait) where a study of around 250,000 individuals found 423 loci.

This difference can partly be explained by the much lower heritability of lifespan (0.12 versus 0.8 for height), consistent with evolution having a stronger influence on the total heritability of traits more closely related to fitness and limiting effect sizes. In addition, the use of indirect genotypes reduces the effective sample size to 1/4 for the parent-offspring design. When considering these limitations, we calculate our study was equal in power to a height study of only around 23,224 individuals, were lifespan to have a similar genetic architecture to height. Under this assumption, we would require a sample size of around 10 million parents (or equivalently 445,000 nonagenarian cases, with even more controls) to detect a similar number of loci.

Individual genetic variants that increase dementia, cardiovascular disease, and lung cancer - but not other cancers - explain the most variance in lifespan. We hoped to narrow down the search and discover specific genes that directly influence how quickly people age, beyond diseases. If such genes exist, their effects were too small to be detected in this study. The next step will be to expand the study to include more participants, which will hopefully pinpoint further genomic regions and help disentangle the biology of ageing and disease.

Link: https://doi.org/10.7554/eLife.39856

Blood-Brain Barrier Dysfunction as an Early Driver of Dementia

The blood-brain barrier surrounds blood vessels in the brain, enforcing restrictions on the passage of molecules and cells between brain and blood supply. Like all bodily systems, the blood-brain barrier breaks down with aging, yet another consequence of rising levels of cellular damage and disarray. The passage of inappropriate cells and molecules into the brain is thought to cause a range of issues, but, as is the case for all aspects of the biochemistry of the brain, this is a very complex environment and set of processes. Firm answers are ever elusive, and a great deal of the fine detail of the aging of the brain has yet to be robustly cataloged. The relative importance of different forms of damage and dysfunction are not well established in many cases. It is challenging to make that sort of determination given the many interacting forms of degeneration that combine to cause dementia in old age, but results such as those presented here are nonetheless intriguing.

Leaky capillaries in the brain portend early onset of Alzheimer's disease as they signal cognitive impairment before hallmark toxic proteins appear. This finding could help with earlier diagnosis and suggest new targets for drugs that could slow or prevent the onset of the disease. A five-year study, which involved 161 older adults, showed that people with the worst memory problems also had the most leakage in their brain's blood vessels - regardless of whether abnormal proteins amyloid and tau were present. In healthy brains, the cells that make up blood vessels fit together so tightly they form a barrier that keeps stray cells, pathogens, metals, and other unhealthy substances from reaching brain tissue. Scientists call this the blood-brain barrier. In some aging brains, the seams between cells loosen, and the blood vessels become permeable.

Participants in the study had their memory and thinking ability assessed through a series of tasks and tests, resulting in measures of cognitive function and a clinical dementia rating score. Individuals diagnosed with disorders that might account for cognitive impairment were excluded. The researchers used neuroimaging and cerebral spinal fluid analysis to measure the permeability, or leakiness, of capillaries serving the brain's hippocampus, and found a strong correlation between impairment and leakage. "The results were really kind of eye-opening. It didn't matter whether people had amyloid or tau pathology; they still had cognitive impairment."

Link: https://news.usc.edu/153475/usc-alzheimers-research-leaky-capillaries/

Accelerated Bone Regeneration via Transplant of Engineered Perivascular Stem Cells

Reprogramming stem or progenitor cells to adjust their behavior is growing in popularity as an approach to regenerative medicine. The large reductions in the cost of exploring cellular mechanisms achieved over the past twenty years mean that there is now a much greater understanding of relevant mechanisms, as well as a greater capacity to discover novel targets of interest for specific goals in altered cell behavior. The more straightforward outcome in this part of the field is simply to increase stem cell activity, to reduce the amount of time these cells spend quiescent rather than actively supplying tissue with new daughter somatic cells to assist in repair. As today's open access paper illustrates, there are certainly other options on the table, however.

Many stem cell populations are multipotent, meaning that they are capable of generating several different types of somatic cell. If only one type is desired for regeneration, then steering the stem cells into creating only that type for a while is effectively the same thing as speeding up their activity in general. Researchers here do this for cells that create both fat and bone tissue, identifying a regulatory protein, WISP1, that determines which is produced. These cells can then be harvested, engineered to express a higher level of WISP1, and used as a cell therapy to accelerate bone regrowth. That, at least, is the hope, given the initial evidence here from an animal study.

Stem Cell Signal Drives New Bone Building

Stem cells have the potential to develop into a variety of cell types including those that make up living tissues, such as bones. Scientists have long sought ways to manipulate the growth and developmental path of these cells, to repair or replace tissue lost to disease or injury. Previous studies showed that a particular type of stem cell - perivascular stem cells - had the ability to become either bone or fat, and that the protein WISP-1 plays a key role in directing these stem cells.

In a new study, researchers engineered stem cells collected from patients to block the production of the WISP-1 protein. Looking at gene activity in the cells without WISP-1, they found that four genes that cause fat formation were turned on 50-200 percent higher than control cells that contained normal levels of the WISP-1 protein. The team then engineered human fat tissue stem cells to make more WISP-1 protein than normal, and found that three genes controlling bone formation became twice as active as in the control cells, and fat driving genes such as peroxisome proliferator-activated receptor gamma (PPARγ) decreased in activity in favor of "bone genes" by 42 percent.

The researchers next designed an experiment to test whether the WISP-1 protein could be used to improve bone healing in rats that underwent a type of spinal fusion. The researchers mimicked the human surgical procedure in rats, but in addition, they injected - between the fused spinal bones - human stem cells with WISP-1 turned on. After four weeks, the researchers studied the rats' spinal tissue and observed continued high levels of the WISP-1 protein. They also observed new bone forming, successfully fusing the vertebrae together, whereas the rats not treated with stem cells making WISP-1 did not show any successful bone fusion during the time the researchers were observing.

WISP-1 drives bone formation at the expense of fat formation in human perivascular stem cells

The vascular wall within adipose tissue is a source of mesenchymal progenitors, referred to as perivascular stem/stromal cells (PSC). Those factors that promote the differentiation of PSC into bone or fat cell types are not well understood. Here, we observed high expression of WISP-1 among human PSC in vivo, after purification, and upon transplantation in a bone defect. Next, modulation of WISP-1 expression was performed, using WISP-1 overexpression, WISP-1 protein, or WISP-1 siRNA. Results demonstrated that WISP-1 is expressed in the perivascular niche, and high expression is maintained after purification of PSC, and upon transplantation in a bone microenvironment.

In vitro studies demonstrate that WISP-1 has pro-osteogenic/anti-adipocytic effects in human PSC, and that regulation of BMP signaling activity may underlie these effects. In summary, our results demonstrate the importance of the matricellular protein WISP-1 in regulation of the differentiation of human stem cell types within the perivascular niche. WISP-1 signaling upregulation may be of future benefit in cell therapy mediated bone tissue engineering, for the healing of bone defects or other orthopedic applications.

Suppression of Neural Plasticity in the Visual Cortex Reversed in Adult Mice

Researchers here identify a mechanism that suppresses neural plasticity in the visual cortex of adult mice, a part of the developmental process that permits greater plasticity in childhood, but then restricts it in adults. This plasticity is the generation and integration of new neurons into neural circuits. Increased plasticity in adults may be beneficial, allowing for better maintenance and regeneration in the aging brain. That benefit must be balanced against whatever functional reason has led evolution to establish diminished plasticity with advancing age. If resistance to cancer is the answer, similar to the explanation for reduced stem cell function throughout the body in later life, then this can be addressed along the way. If there are other functional reasons for lower levels of plasticity in adults, and thus increased plasticity might damage the adult brain in some way, such as by causing disarray in established neural networks, then this will be more challenging to resolve.

The human brain is very plastic during childhood, and all young mammals have a critical period when different areas of their brains can remodel neural connections in response to external stimuli. Disruption of this precise developmental sequence results in serious damage; conditions such as autism potentially involve disrupted critical periods. "It's been known for a while that maturation of inhibitory nerve cells in the brain controls the onset of critical period plasticity, but how this plasticity wanes as the brain matures is not understood. We've had some evidence that a set of molecules called SynCAMs may be involved in this process, so we decided to dig deeper into those specific molecules."

The study focused on the visual cortex, the part of the brain responsible for processing visual scenes, in which plasticity has been examined in many species. The researchers were able to measure activity of neurons in awake mice freely responding to visual stimuli. They found that removal of the SynCAM 1 molecule from the brain increased plasticity in the visual cortex of both young and adult mice. Further research found that SynCAM 1 controls a very specific type of neuronal connection termed synapses: the long-distance synapses between the visual thalamus, located beneath the cerebral cortex, and inhibitory neurons in the cortex. SynCAM 1 was found to be necessary for the formation of synapses between thalamus and inhibitory neurons, which in turn helps inhibitory neurons to mature and actively restrict critical period plasticity.

The researchers liken inhibitory neurons to a dial controlling when brain plasticity can occur. Plasticity is needed during early development, as the function of different brain areas matures. Mature function is then cemented into place by molecules like SynCAM 1. "Therefore, the limited ability of the mature brain to change is not simply a consequence of age but is directly enforced by the SynCAM 1 mechanism. This allows us to target the mechanism to re-open plasticity in the mature brain, which could be relevant for treating disorders like autism. Combined with the latest approaches in genetic manipulation, this may prove to be a new path to tackle both childhood disorders and brain injury in adults."

Link: https://now.tufts.edu/news-releases/brain-plasticity-restored-adult-mice-through-targeting-specific-nerve-cell-connections

MANF Declines with Age and is Required for Parabiosis Benefits to the Liver

Researchers have identified MANF as a factor responsible for at least some of the benefits provided to the older of two animals with linked circulatory systems. Joining two animals, usually mice, in this way is known as parabiosis. It has been used a tool to explore the role of the signaling environment of blood and tissues in aging. Stem cell function, for example, declines with age, and a sizable part of that decline appears to be a reaction to the changing, damaged environment rather than inherent damage in the stem cells themselves. Thus signals must exist to mediate the altered behavior of cells in response to what is going on around them.

If signals exist, then they can be overridden. Some research groups are searching for factors in young blood that might be used to boost stem cell function and tissue function in old mice. Other groups are convinced that the effect is due to dilution of harmful factors in old blood rather than the addition of helpful factors in young blood. The evidence on both sides is compelling, and the conflicts are yet to be resolved. While that debate is ongoing, it seems reasonable to expect further discoveries of signals and regulators that can increase stem cell activity in old tissues to some degree. That tends to help spur greater tissue maintenance and repair, but with some presently unknown additional cancer risk as damaged cells are forced back to work.

Older mice who are surgically joined with young mice in order to share a common bloodstream get stronger and healthier, making parabiosis one of the hottest topics in age research. Researchers report that MANF (mesencephalic astrocyte-derived neurotrophic factor) is one of the factors responsible for rejuvenating the transfused older mice. Researchers also show the naturally-occurring, evolutionarily-conserved repair mechanism protects against liver damage in aging mice and extends lifespan in flies.

While researchers have yet to understand why MANF levels decrease with age, MANF deficiency has obvious hallmarks. Flies genetically engineered to express less MANF suffered from increased inflammation and shorter lifespans. MANF-deficient mice had increased inflammation in many tissues as well as progressive liver damage and fatty liver disease. Older mice who shared blood with MANF-deficient younger mice did not benefit from the transfusion of young blood.

"MANF appears to regulate inflammatory pathways that are common to many age-related diseases. We are hoping its effects extend beyond the liver, we plan to explore this in other tissues. The search for systemic treatments that would broadly delay or prevent age-related diseases remains the holy grail of research in aging. Given that MANF appears to modulate the immune system, we are excited to explore the larger implications of its therapeutic use. We are also cautious. There are many tissues and organ systems to evaluate in terms of MANF and we have yet to determine its effects on lifespan in the mouse."

Link: https://www.buckinstitute.org/news/manf-identifed-as-a-rejuvenating-factor-in-parabiosis/

Nattokinase and Reversal of Atherosclerotic Lesions

Atherosclerosis is one of the great killers. Fatty deposits form in blood vessels walls, narrowing and weakening the vessels. Eventually something ruptures, and the result is a stroke or heart attack, but even absent that the condition can narrow vessels sufficiently to cause fatal coronary artery disease. Even with modern medicine, the condition is inexorable: the toolkit doesn't yet include a way to more than slightly reverse the buildup of these plaques, and medical professionals must focus on ways to incrementally slow the progression of atherosclerosis rather than delivering any true cure.

One of the side-effects of starting a company, Repair Biotechnologies, that is working on a way to reverse atherosclerotic plaque is that I've been doing a great deal more reading on the topic of atherosclerosis than I would otherwise have done in the course of writing Fight Aging! Thus I turn up interesting items from the past few years that I missed at the time because I lacked the context to understand why they were worthy of notice, or just didn't have the sort of focus on atherosclerosis that I have at the moment. The papers I'll share today fall into this category, providing evidence for nattokinase, a very simple and readily available supplement, to have a surprisingly large effect on atherosclerotic lesions in humans. After six months of treatment, a third of the lesions were removed.

A clinical study on the effect of nattokinase on carotid artery atherosclerosis and hyperlipidaemia

All enrolled patients were from the Out-Patient Clinic of the Department of TCM at the 3rd Affiliated Hospital of Sun Yat-sen University. Using randomised picking method, all patients were randomly assigned to one of two groups, nattokinase (NK) and statin (ST) group. NK Group-patients were given NK at a daily dose of 6000 FU and ST Group-patients were treated with statin (simvastatin 20 mg) daily. The treatment course was 26 weeks. Common carotid artery intima media thickness (CCA-IMT), carotid plaque size and blood lipid profile of the patients were measured before and after treatment.

A total of 82 patients were enrolled in the study and 76 patients completed the study. Following the treatments for 26 weeks, there was a significant reduction in CCA-IMT and carotid plaque size in both groups compared with the baseline before treatment. The carotid plaque size and CCA-IMT reduced from 0.25±0.12cm2 to 0.16±0.10cm2 and from 1.13±0.12mm to 1.01±0.11mm, repectively. The reduction in the NK group was significantly profound, a 36.6% reduction in plaque size in NK group versus 11.5% change in ST group. Both treatments reduced total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG).

Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases

Nattokinase (NK), the most active ingredient of natto, possesses a variety of favourable cardiovascular effects and the consumption of Natto has been linked to a reduction in cardiovascular disease mortality. Recent research has demonstrated that NK has potent fibrinolytic activity, antihypertensive, anti-atherosclerotic, and lipid-lowering, antiplatelet, and neuroprotective effects. This review covers the major pharmacologic effects of NK with a focus on its clinical relevance to cardiovascular disease.

This effect size on atherosclerotic lesions is big enough to be suspicious, given that nattokinase is a supplement in common use, and the dose used is not outrageously large. We seem to be seeing a lot of that sort of thing these days, however; sometimes significance goes unnoticed, but equally sometimes it is an issue with the study that will be corrected later. It is hard to tell which without meaningful further effort. Does bisphosphonate treatment actually extend life expectancy by five years, and did this really did go unnoticed despite its widespread use in older people? Is fisetin actually a significantly effective senolytic compound in humans despite being widely used; did the very high senolytic dose in comparison to the usual supplement dose successful hide this property? How did nearly twenty years of earnest development and use of they chemotherapeutic dasatinib go past without anyone noticing that it killed enough senescent cells to improve health and measures of aging in mice and people? And so forth.

Over the past few decades, hundreds of millions of dollars (at the very least) have been spent on clinical trials to try to reverse atherosclerosis - to give existing repair systems in the body sufficient breathing space or increased capacity, allowing them to break down the fatty deposits that form in blood vessels. The sponsors of any of those trials would have been ecstatic to find a reliable reversal of atherosclerotic plaque that was half the size of that noted in the nattokinase trial here. One might take a look at a 2012 review paper that surveys the degree to which treatments at the time could achieve the goal of reversing atherosclerosis. A reversal of 15-20% in an unreliable fraction of patients was about the best that could be done. Most approaches were considerably less effective than that. Not a lot has changed in this high level picture since then.

At present the dominant approach to treatment of atherosclerosis is reduction of blood cholesterol, the cholesterol attached to LDL particles, or LDL-C. Statins are the long-standing approach, and are now being joined by even more effective treatments such as PCSK9 inhibitors. This slows down atherosclerosis by (a) lowering overall cholesterol, and thus freeing up some fraction of the macrophage cells that would otherwise have had to shovel it out of blood vessel walls, but more importantly (b) lowering oxidized cholesterol, which is very damaging to macrophages. When considering atherosclerosis and its treatments it is important to consider macrophages: they are drawn to the fatty lesions, and their task once there is to mine cholesterol from the lesion, ingest it, and hand it off to HDL particles that carry it back to the liver for excretion. This is called reverse cholesterol transport.

Atherosclerosis exists because macrophages become overwhelmed, mostly by oxidized cholesterol, but also by sheer volume of cholesterol, or by an overly inflammatory environment. They become agitated, call for help, become foam cells (some of which become senescent, causing further issues) or die. Most of a plaque is made up of the debris of dead macrophages, and the plaque itself is a self-expanding disaster area that calls ever more macrophages to their doom. Reducing the LDL-C slows down this feedback loop, but it cannot do much for existing plaques. There is some regression (the aforementioned 15-20% at best) because macrophages are given some breathing room, but plaques continue to grow at the new slower pace, and people continue to die.

There has been a considerable amount of work undertaken over the years on alternatives to lowering LDL-C. Researchers have tried all sorts of ways to improve the ability of macrophages to mine cholesterol and send it back to the liver. They have tried increased numbers of HDL particles (which are formed from APOA1 protein). They have tried altered forms of APOA1 found in some human populations that are associated with lower levels of atherosclerosis. They have tried the introduction of artificial HDL particles to swell the numbers. They have tried upregulation of the ABCA1 and ABCG1 proteins that perform the actual handoff of cholesterol molecules to APOA1. There is more in the same vein.

All of these things work pretty well in mice; the current best approaches produce 50% reversion of atherosclerotic lesions in animal studies. Yet all of those tried in humans, meaning the HDL and APOA1 approaches, have failed miserably in clinical trials. What this means is that there is something that the research community doesn't yet understand in the low-level detailed differences between human and mouse reverse cholesterol transport. That is a big roadblock for anyone turning up to propose some form of enhanced cholesterol transport as a therapy, even if intending to try one of the varied effective-in-mice approaches that hasn't yet been trialed in humans.

In this context, one can see that evidence for a common supplement to manage 36% reversion of lesions in humans is both welcome and jarring. It will certainly have to be replicated before many researchers in the LDL-C-focused side of the scientific community are likely to take it all that seriously. Any simple, easily obtained improvement should be welcome. Nonetheless, it is still only reversion by a third. The disease will still progress, and will still kill people. The research community has to do better than this.

The Second Ending Age-Related Diseases Conference will be Held in July 2019

The second Ending Age-Related Diseases conference, hosted by the Life Extension Advocacy Foundation (LEAF) staff and volunteers, will be held in New York this coming July. It will bring together entrepreneurs, investors, and researchers to discuss progress towards bringing aging under medical control, and thus creating true cures for age-related conditions. I attended last year's inaugural conference in the series, and recommend it. LEAF puts on a good conference, so consider registering.

After the incredible success of the conference Ending Age-Related Diseases 2018, the Life Extension Advocacy Foundation is happy to announce its second annual conference, Ending Age-Related Diseases 2019, which is to be held at Cooper Union in New York City on July 11-12th, 2019. The conference is aimed at focusing the NYC business community's attention on the current state of aging and rejuvenation research that has the potential to prevent and cure age-related diseases. With multiple research projects targeting the underlying processes of aging in order to develop preventive medicines, promoting collaboration between academia, the rejuvenation industry, and investors becomes an increasingly important task.

The list of confirmed speakers already includes renowned researchers and visionaries, such as Dr. Aubrey de Grey (SENS Research Foundation), Michael Greve (KIZOO Technology Ventures, Forever Healthy Foundation), Dr. Vadim Gladyshev (Harvard Medical School), Dr. Vera Gorbunova (University of Rochester), Dr. Alex Zhavoronkov (Insilico Medicine), and Reason and Bill Cherman (Repair Biotechnologies), with more speakers from rejuvenation biotechnology companies and the investment sector to be confirmed soon.

"This year's conference will focus on two main topics. The first topic will be progress in aging research, from fundamental studies to the interventions that are being tested in human clinical trials and the development of reliable biomarkers of aging. The second topic will be devoted to the hurdles of implementing these emerging rejuvenation biotechnologies into clinical practice, with a special focus on investment, the regulatory landscape, and the preparedness of the medical community. This way, we hope not only to attract the attention of investors to these very promising medical innovations but also to promote public dialogue on how to ensure their availability and accessibility to our aging society."

Link: https://www.leafscience.org/nyc2019-pr/

Versican May Increase Cellular Senescence and Calcification in the Blood Vessels of Hyperglycemic Patients

I found this paper quite intriguing, as it links together a number of themes in vascular aging and the similar forms of vascular dysfunction seen in metabolic syndrome and diabetes. The molecular damage of aging in blood vessel walls causes stiffness of blood vessels, which in turn causes hypertension. This is one of the more important means by which low level biochemical damage is translated to high level structural damage to tissues, as raised blood pressure causes all sorts of harm. The damage that leads to vascular stiffness includes (a) cross-linking, in which sugary metabolic byproducts form links between molecules of the extracellular matrix, impeding its elasticity, (b) calcification, in which cells begin to inappropriately deposit calcium into the extracellular matrix, also degrading elasticity, and (c) failure of the vascular smooth muscle cells to perform appropriately when constricting or dilating blood vessels.

This last item has a number of poorly mapped underlying causes, but chronic inflammation appears to be a contributing issue. Chronic inflammation is also implicated in calcification. Chronic inflammation is one of the downstream consequences of cellular senescence, and there is evidence for the presence of senescent cells to be involved in calcification in blood vessel walls. So these items are already quite well connected together. The paper here closes the loop further by finding a form of intracellular signaling that is likely present in hyperglycemic individuals, who also exhibit raised levels of cross-linking, that spurs the formation of more senescent cells in blood vessel walls. Hyperglycemia is just the excessive case: everyone who consumes the usual modern amount of dietary sugar is probably in an incrementally worse position over the long term than people who consume less sugar, due to this and related mechanisms.

A major determinant of vascular aging is vascular calcification, characterized by vascular smooth muscle cells (VSMCs) calcification. Transdifferentiation of VSMCs into osteoblasts is considered to be the most critical pathophysiological of VSMCs calcification. There is accumulating evidence suggesting that VSMCs calcification/senescence have central roles in the development and progression of diabetes-related cardiovascular disorders.

The vascular response to hyperglycemia is a multifactorial process involving endothelial cells (ECs) and VSMCs, although the mechanism by which the information in circulating blood are transferred from ECs to VSMCs is yet to be understood. Signaling between ECs and VSMCs is crucial for the pathogenesis of diabetic vascular calcification/aging. However, how does circulating high glucose affect the calcification/senescence of VSMCs that are not directly contact with the blood? Exosomes, small vesicles with a diameter of 40-100 nm released from various cell types, have gained much attention for their role in intercellular communication. Exosomes can transfer active proteins, lipids, small molecules, and RNAs from their cell of origin to the target cell. ECs have been demonstrated to secrete exosomes, and the transfer of signaling molecules by exosomes may thus provide a way for communicating between ECs and VSMCs. Similarly, prior study has demonstrated that exosomes from senescent ECs promotes VSMCs calcification.

Exosomes from human umbilical vein endothelial cells (HUVEC-Exos) were isolated from normal glucose (NG) and high glucose (HG) stimulated HUVECs (NG/HG-HUVEC-Exos). Exosomes isolated from HG-HUVEC-Exos induced calcification/senescence in VSMCs. HG-HUVEC-Exos significantly increased lactate dehydrogenase (LDH) activity, as well as the product of lipid peroxidation, and decreased oxidative stress marker activity, as compared with NG-HUVEC-Exos. Moreover, mechanism studies showed that mitochondrial membrane potential and the expression levels of mitochondrial function related protein HADHA and Cox-4 were significantly decreased in HG-HUVEC-Exos compared to controls. Proteomic analysis showed that HG-HUVEC-Exos consisted of higher level of versican (VCAN), as compared with NG-HUVEC-Exos.

VCAN is mainly localized to the mitochondria of VSMCs. Knockdown of VCAN with siRNA in HUVECs, inhibited HG-HUVEC-Exos-induced mitochondrial dysfunction and calcification/senescence of VSMCs. Our data suggest a functional role for VCAN inside VSMCs. VCAN carried by HG-HUVEC-Exos promotes VSMCs calcification/senescence, probably by inducing mitochondrial dysfunction. Since VSMCs calcification/senescence could induce vascular dysfunction, blockage of the exosome-mediated transfer of VCAN between these two cells may serve as a potential therapeutic target against diabetic vascular complications. More work will be needed to explore this possibility and to better understand the intracellular roles of VCAN.

Link: https://doi.org/10.1186/s13578-018-0263-x

Impressions from the January 2019 Juvenescence Gathering

The JP Morgan Healthcare conference took place in San Francisco this past week. The conference is less interesting in and of itself, but it is the spur for any number of other short gatherings of various biotech investment and business interest groups. So in the middle of last week, Jim Mellon and the other Juvenescence principals were in town to host their second annual showcase for startups working on aging, and the BioAge and Felicis Ventures folk hosted the overlapping Extending Human Lifespan event on the same day. I had to miss that second one, as I was presenting Repair Biotechnologies at the Juvenescence event to a small crowd of other entrepreneurs, angel investors, and venture capitalists of varied allegiances, and stayed for the whole event to see the other presentations.

Many of our fellow travelers associated with SENS rejuvenation research and Methuselah Foundation spheres were present to meet and greet: the SENS Research Foundation folk; much of the Oisin Biotechnologies team; Doug Ethell of Leucadia Therapeutics; Frank Schüler of Forever Healthy Foundation; a number of angel investors I've interacted with in the past while we were interested in the same companies; and many others arriving and leaving as they moved between events.

One thing that caught my eye is that the theme of diversity and new hypotheses in Alzheimer's research (or outright rebellion against the past two decades of relentless focus on clearing amyloid via immunotherapies, present it as you will) has robustly made its way to the commercial development stage. Leucadia Therapeutics were presenting their latest work on ferrets as an animal model to illustrate that the development of Alzheimer's occurs due to blocked drainage of cerebrospinal fluid though the cribriform plate. Related company Enclear Therapies was not present, but was a topic of discussion given that their founders have very similar thoughts on filtration of cerebrospinal fluid. Maxwell Biosciences principals presented their work on the LL-37 antimicrobial peptide as a test of the microbial theories of Alzheimer's disease, in which infection is provoking greater aggregation of amyloid and inflammation to accelerate other aspects of the condition. An attempt at intervention is perhaps the best way to clear up questions of causality here: do we see microbial infections in the Alzheimer's brain because they are an important cause, or because immune dysfunction in general tends to be more advanced in these patients?

A further contingent of startups at the Juvenescence event were similarly of interest for having a good shot at answering scientific questions very much faster than the academic community can, due to the influx of resources from the venture community. Elevian falls into this category, with their work on GDF11. Early work on parabiosis, joining the circulatory systems of an old and young mouse, pointed to GDF11 as a possible factor in conveying benefits to the old mouse. There is now some debate over why parabiosis works, however, casting doubt on the argument of beneficial factors in young blood. Similarly, there has been some back and forth in the research community regarding whether or not past work on GDF11 is as it appears to be, but the Elevian staff claim to have resolved the conflicts. In many cases, the best way to resolve a debate of this nature is to just forge ahead and try to build a therapy; that effort can pull in much greater funding more rapidly than the academic community can manage via the usual channels available to researchers.

Another item that caught my attention, and seems worthy of consideration, is that the infrastructure and drug discovery companies in our space of treating aging as a medical condition are the furthest ahead in terms of building out relationships with venture concerns, obtaining larger funding, and breaking ground on their larger and later projects. This may reflect the focus of groups like Juvenescence from the past couple of years, their approach to establish an initial presence in a field. Examples of this trend include In Silico Medicine and Ichor Therapeutics' portfolio company Antoxerene, both of which offer faster, cheaper discovery of small molecule drugs for any sort of use, but both of which happen to have founders very interested in aging and longevity over and above any of the myriad other uses for their technologies. In Silico Medicine in particular is clearly advancing by leaps and bounds in Asia as they gather support from the high-end venture groups there.

(I'll confess that I've never found the development of lower level biotechnological infrastructure all that interesting as a topic. Obviously it is vital, and acceleration of technological progress is achieved by making common tasks easier, faster, and cheaper. Someone has to do it, invest in it, and focus on it, but that someone will never be me. I am far more interested in specific implementations of rejuvenation therapies, the development groups who might end up using the infrastructure to build a given treatment).

San Francisco is ever a hub of connections for the venture and technology spaces. It is the base of operations and home for a sizable number of high net worth individuals, agents for other high net worth individuals, fund partners deploying sizable amounts of capital, successful founders turned angel investors, successful angel investors turned founders - all rubbing shoulders, bumping into one another at the supermarket, and two degrees of separation removed at most. It is through this very connected network that interest in the biotechnologies of rejuvenation has been spreading these past fifteen years, pushed along by the presence of the SENS Research Foundation in the Bay Area. This occurred slowly at first, given that the focus was initially philanthropic funding of research rather than startups, but much more rapidly these past few years now that the first rejuvenation biotechnology startups are arriving on the scene.

At a small gathering after the Juvenescence event, those attending included an older AI-focused entrepreneur-turned-investor who has a growing interest in biotechnology, and a recently successful young founder from the technology space who is now taking life science classes to get up to speed on what he considers to be his next area of interest. The next day I met with an angel investor who attended the Juvenescence event, and who is cheerfully incorporating biotech companies into his previously tech-company-heavy portfolio. This dynamic is similarly reflected in venture firms such as Y Combinator, Felicis Ventures, and (closer to our community) Kizoo Technology Ventures led by Michael Greve, among others. They are transitioning into biotechnology, and the interest in doing something about aging is a driving motivation for many involved. For others, it is the realization that successful rejuvenation therapies will lead to a market so enormous as to make a pittance of near everything that has come before. Self-interest is a machine to be harnessed in these matters: while fundamental research is very cheap, later commercialization and distribution of medical therapies to millions of patients is enormously expensive. We need the deep pockets to enter this space, and to pull in all of their allies and other interested parties, if we are to see a reasonable rate of progress in moving rejuvenation therapies from lab to clinic.

The only other alternative is some form of major, lasting revolution in the regulatory environment, as that is the dominant cause of cost and delay. Therapies could be brought to market just as safely as they are today at a fraction of the present cost; the majority of cost and time imposed by the FDA, EMA, and the like is entirely unnecessary, some of it the debris of regulatory capture used by larger pharmaceutical entities to suppress competition, some of it the consequences of bureaucrats going to any lengths to avoid negative press, even by the means of preventing most new technologies from ever being approved. I'm certainly in favor of great upheaval in the development of medical therapies, but tearing down the present edifice is a vast project, and arguably one that will be much less costly and difficult to undertake given the existence of the first rejuvenation therapies and the public demand for more.

A final thought on investors and the science of rejuvenation: most of the newcomers are still finding their way to an understanding of the science in this space. They cannot yet tell the difference between projects likely to produce significant gains in human life span, those based on repair of the damage that causes aging, and those that cannot in principle produce large gains, those based on, say, upregulation of stress responses, such as mTOR inhibitors. Investors are guided by potential for financial gains, but that metric is not in fact a great way to tell the difference between better and worse approaches to aging. The typical competently run medical biotechnology company is acquired or goes public before the final determination of effectiveness of their programs; perhaps somewhere just after the first human trial, or even prior to that when the market is hot. Companies can do this after showing marginal benefits, or even just potential for marginal benefits, with a therapy that will never produce large or reliable benefits in larger patient populations, and yet still realize large gains for the early investors. So this is a challenge, and an opportunity for patient advocates to make a difference - to help guide those people chasing gains into obtaining those gains by backing better rather than worse technologies.

Tau Impairs Both Mitochondrial Function and Quality Control

Researchers here show that tau protein, a feature of late stage Alzheimer's disease, causes issues with mitochondrial quality control mechanisms responsible for removing damaged or dysfunctional mitochondria. Since tau also harms the function of mitochondria, this is particularly pernicious, and may be a significant component of the cell death that follows tau aggregation. Mitochondrial dysfunction is a feature of most neurodegenerative diseases, causing cellular processes in the brain to falter for lack of energy, but the question of where it sits in the web of cause and consequence in relation to other disease mechanisms remains to be resolved. Is the case that Alzheimer's tends to occur more readily in people with worse age-related mitochondrial dysfunction, or does one or more of the other aspects of Alzheimer's, such as tau aggregation, produce the observed greater level of mitochondrial dysfunction as a downstream effect? Or both? This sort of question is surprisingly hard to answer in conditions that have many contributing causes.

Accumulation of clumps of tau is a well-established hallmark of Alzheimer's disease and other neurodegenerative disorders, as is the aggregation of damaged mitochondria, the powerhouse of a cell. However, the interaction between tau and mitochondria is still being explored, and new research has found an additional disruptive function of tau in terms of mitochondrial health. "It has long been known that there is an accumulation of abnormal mitochondria in neurodegenerative diseases, including Alzheimer's disease. More specifically, tau has previously been shown to impair different aspects of mitochondrial function, and here, we find that tau also impairs the degradation of mitochondria. This causes a toxic cycle whereby tau both damages mitochondria and then also prevents their removal."

One of the ways by which tau causes cell damage is by preventing the removal of damaged mitochondria, a process referred to as mitophagy. Normally, damaged mitochondria are trafficked to the lysosome (the waste remover of the cell) for destruction, by a molecule called Parkin, which moves from the intracellular fluid to the impacted mitochondria to start the trafficking process. However, researchers found tau impaired this process by interacting "aberrantly" with the Parkin protein in the intracellular fluid before it could reach the mitochondria, thereby preventing the removal process, and with damaging consequences for the cell.

Link: https://qbi.uq.edu.au/article/2018/12/how-alzheimer%E2%80%99s-protein-impairs-brain-cells

PUM2 and MFF in the Dysregulation of Mitochondrial Fission in Aging

Mitochondria, the power plants of the cell, become dysfunctional over the course of aging. This is a general process in all mitochondria, and not the same thing as the severe mitochondrial DNA damage that occurs in only a few cells, but that has a widespread detrimental effect. In this more general mitochondrial malaise, there are changes in shape and important functions decline; energy-hungry tissues such as brain and muscle suffer as a consequence.

Mitochondria are the descendants of ancient symbiotic bacteria, and thus act much like bacteria in carrying out fission and fusion, and passing component parts around between one another. In recent years, researchers have found that imbalances between fission and fusion appear in aging, this impairs the ability of autophagic processes to remove damaged mitochondria, and that provoking more fission or less fusion slows aging in short-lived species. Researchers continue to investigate the mechanisms underlying this imbalance; the results noted here are an illustrative example of the progress taking place in this part of the field.

Mechanisms based on mRNA transcription, a very important step in gene expression, are a part of the complex regulatory mechanisms in our cells. RNA-binding proteins (RBPs) bind mRNA molecules and regulate their fate after gene transcription. In this study, scientists screened cells from old animals to identify any RBPs that change upon aging. The screening showed that one particular protein, Pumilio2 (PUM2), was highly induced in old animals. PUM2 binds mRNA molecules containing specific recognition sites. Upon its binding, PUM2 represses the translation of the target mRNAs into proteins.

Using a systems genetics approach, the researchers then identified a new mRNA target that PUM2 binds. The mRNA encodes for a protein called Mitochondrial Fission Factor (MFF), and is a pivotal regulator of mitochondrial fission - a process by which mitochondria break up into smaller mitochondria. Having high levels of MFF also allows the clearance of broken up, dysfunctional mitochondria, a process called mitophagy.

The study found that this newly identified PUM2/MFF axis is dysregulated upon aging. Evidence for this came from examining muscle and brain tissues of old animals, which were found to have more PUM2, and, consequently, fewer MFF proteins. This leads to a reduction of mitochondrial fission and mitophagy, and without the ability to chop up and remove smaller mitochondria, the aged tissues start accumulating bigger and unhealthy organelles.

But removing PUM2 from the muscles of old mice can reverse this. "We used the CRISPR-Cas9 technology to specifically target and inactivate the gene encoding for Pum2 in the gastrocnemius muscles of old rodents. Reducing Pum2 levels, we obtained more MFF protein and increased mitochondrial fragmentation and mitophagy. Notably, the consequence was a significant improvement of the mitochondrial function of the old animals."

Link: https://actu.epfl.ch/news/targeting-an-rna-binding-protein-to-fight-aging/

Old Tissues Have Many Mutations, Even Absent Cancer

Cancer is the result of random mutational damage to nuclear DNA, but most such damage has no real effect, not even to the behavior of the affected cell. Cells in old tissues are riddled with mutations, but it is an open question as to how much this accumulated damage contributes to aging beyond cancer risk. Does it produce sufficient disarray in tissue function to be measured? A mutation capable of meaningfully altering cell behavior (a small subset of all possible mutations) can only have a noticeable affect when it occurs in many cells, a significant fraction of those present in a tissue. One slightly defective cell is a drop in the ocean, provided it isn't actively cancerous.

Many researchers consider that the outcome of clonal expansion of mutations in adult tissue can be achieved when the original mutation occurs in a stem cell of some kind. The mutation can spread with the long-term delivery of a supply of daughter somatic cells and their descendants. Along these lines, the studies noted in the article below raise the possibility that cancer-associated mutations can also grant this ability to spread through excessive replication, yet without immediately resulting in the production of a tumor.

The field lacks definitive studies and models that would enable researchers to put numbers to the contribution of mutational damage to degenerative aging and age-related diseases other than cancer. Clearly the boundary between production of cancer and production of functional damage isn't sharply drawn if expansion of mutations is a feature of the pre-cancerous state. Fixing the damage is usually the best way to proceed when answering this sort of question, but that is very hard to achieve for random DNA damage in isolation of all the other aspects of aging. Every cell needs custom work. More practically, delivering newly created, undamaged stem cell populations to replace old stem cell populations is a feasible form of future therapy, but it certainly doesn't isolate DNA damage as the only altered variable.

Mutations differ in normal and cancer cells of the oesophagus

Errors in DNA replication can alter a cell's DNA sequence. If such alterations occur early enough in embryonic development, the changes are inherited by all of an organism's cells. But if the alterations arise later in adult life, it is more difficult to track such changes in a small number of cells in a specific tissue, so the extent of these alterations in normal tissues is poorly understood. It is thought that cancer is initiated when cells acquire a minimum compendium of genetic alterations needed to trigger tumour formation. Understanding when such initiating mutations occur in normal cells is crucial for enabling reconstruction of the early events that lead to cancer.

Researchers have analysed the extent of mutations in human epithelial tissue from the healthy oesophagus, and how this relates to the processes that drive cancer development. They sequenced 74 cancer-associated genes in 844 tissue samples taken from the upper oesophagus of 9 healthy donors who differed in gender, age and lifestyle. For 21 of these samples, the authors also determined whole-genome sequences. A previous study assessing mutations in healthy skin cells reported between two and six mutations per million nucleotides of DNA. By contrast, here the mutations in oesophageal cells arose at a roughly tenfold lower rate. This difference is unsurprising, because skin cells are exposed to more DNA-damaging agents, such as ultraviolet light, than are oesophageal cells.

Instead, the surprise is that, compared with healthy skin, the healthy oesophagus has more mutations in cancer-associated genes. Moreover, at least a subset of these altered genes was under strong positive selection, meaning that the genetic alterations promoted cell proliferation, leading to the formation of cell clones. Compared with the samples from younger people, the overall number of mutations, the number of mutations in cancer-associated genes and the size of the clones were all greater in the samples from older people. The authors found that the donors' samples had an average of about 120 different mutations in NOTCH1, a known cancer-associated gene, per square centimetre of normal oesophageal tissue.

The clonal expansion of normal oesophageal cells after cancer-promoting genes have mutated seems to be necessary, but not sufficient, to drive cancer, so something else must happen to the cells for tumours to form. For example, gaining a large-enough number of alterations in cancer-promoting genes might be needed. Few of the mutations were present in all the cells of the normal clones, and many of the cancer-promoting mutations were often found in spatially distinct subclones. This suggests that none of the normal cells had acquired enough cancer-promoting alterations to start cancer formation.

More on TREM2 and Immune Function in Alzheimer's Disease

You might recall research published early last year on TREM2 as a possible regulator of immune cell clearance of amyloid in Alzheimer's disease. Researchers here provide a further update on their investigations of the role of TREM2 in this process. To the degree that the immune system falters in this task of clearing metabolic waste with age, and to the degree that this issue can be reversed or overridden, this may prove to be a useful approach to age-related protein aggregates in the brain, and their contribution to neurodegenerative disease. As is so often the case, however, a treatment cannot be immediately and straightforwardly constructed based on manipulation of TREM2. Its relationship with immune cell activity and the Alzheimer's disease state is complex.

A hallmark of Alzheimer's disease is the formation of toxic deposits in the brain, so-called plaques. Specialized immune cells termed microglia protect the brain by clearing it from these toxic debris. TREM2 is a key factor in activating microglia and thus serves as an important target for novel therapeutic approaches. To further explore these therapeutic options, scientists undertook a detailed analysis of disease development in mice with and without a functional TREM2 gene.

In mice with healthy TREM2, microglia cluster around small emerging plaques early in the disease process and prevent them from enlarging or spreading. Researchers were able to show that microglia are specifically attracted to amyloid plaques. They surround individual plaques and engulf them piece by piece. In contrast, in mice lacking TREM2, microglia were unable to carry out this important task. Therapeutic activation of TREM2 in an early stage of the disease could thus help counteract the formation of toxic amyloid-beta protein aggregates.

However, the study results also call for caution when implementing such a therapy. While TREM2 prevents plaque formation early in disease progression, it may have the opposite effect later on. In more advanced stages of the disease, the plaques grew faster in mice with functional TREM2 than in mice lacking the corresponding gene. The researchers discovered that this could be explained by the fact that TREM2 induces microglia to produce a substance called ApoE, which enhances aggregate formation. "Our study shows that we have to be extremely careful and investigate a new therapeutic approach thoroughly in animal models before testing it on humans. According to our findings, it could have dramatic consequences if we over-activate microglia. In the future, it will be important to treat Alzheimer's disease in a stage-specific manner."

Link: https://www.dzne.de/en/news/public-relations/press-releases/press/detail/defective-immune-cells-in-the-brain-cause-alzheimers-disease/

Declining Autophagy Implicated in Tau Aggregation in the Aging Brain

Tau aggregation, the formation of solid deposits of altered tau protein called neurofibrillary tangles, is thought to be the most damaging of the processes underlying Alzheimer's disease. The earlier accumulation of amyloid-β only sets the stage for the later accumulation of altered tau. When looking at why protein aggregates such as amyloid-β and tau accumulate only in later life, one of many candidate mechanisms is the decline of autophagy that takes place with aging. Autophagy is the name given to a collection of cellular maintenance processes responsible for clearing out damaged structures and other unwanted waste, such as protein aggregates. A range of interventions shown to slow aging in laboratory species involve raised levels of autophagy: if cells are more aggressively maintained, there is less of a chance for damage and dysfunction in cellular processes to spread and cause further harm. The other side of the coin is that lower levels of autophagy mean more metabolic waste, more damaged components, and more downstream consequences.

Early in the course of Alzheimer's disease, neurons in the brain become clogged with toxic tau proteins that impair and eventually kill the neurons. A new study found that tau accumulates in certain types of neurons, probably because the cellular housekeeping system of autophagy is less effective in these neurons. Researchers have long known that neurodegenerative diseases like Alzheimer's affect some neurons but not others, even leaving neighboring neurons unharmed. But the reasons for this selectivity have been difficult to identify.

The new study was only possible because of new techniques that allow researchers to probe individual cells in the brain. Researchers detected signs that the components of a cellular cleaning system were less abundant in the neurons that accumulate tau proteins. To confirm the connection between the cleaning system and tau buildup, the researchers manipulated BAG3, a regulatory protein in autophagy, in mouse neurons. When the researchers decreased BAG3 levels in mouse neurons, tau piled up. But when BAG3 expression was enhanced, the neurons were able to rid themselves of excess tau.

The researchers have tantalizing, still unpublished data that the same housekeeping deficiencies found in vulnerable neurons occur with aging, which might explain the link between advanced age and Alzheimer's disease. "If we can develop therapies to support these natural defense mechanisms and stop tau from accumulating, then we might be able to prevent, or at least slow, the development of Alzheimer's and other tau-related neurodegenerative diseases."

Link: https://www.cuimc.columbia.edu/news/neurons-good-housekeeping-are-protected-alzheimers

Wary of the Beautiful Fairy Tale of Near Term Rejuvenation

One might compare this interview with researcher Leonid Peshkin to last year's discussion with Vadim Gladyshev. There is a spectrum of caution and pessimism regarding near term progress towards rejuvenation; the pessimists in the research and development communities are not all alike in their viewpoints, and nor do they all have the same take on the complexity of cellular metabolism as a hurdle to progress.

If a researcher thinks that small molecule drugs or gene therapies to alter the operation of metabolism into a state in which aging is slowed are the only way forward, then yes, it is reasonable to consider that progress will be slow and incremental. Metabolism is far from fully mapped, and thus the detailed progression of aging is also full of unknowns. Yet why take the hard path when there is an easier way forward? The whole point of the SENS approach to aging, based upon repair of root cause damage, is to bypass this complexity and lack of knowledge. Remove the known and well-catalogued damage at the root of aging, and a sizable fraction of the consequences will be repaired by the normal processes of tissue maintenance; we know this because we have the example of youthful individuals and their metabolism to draw on.

Of course, it is then possible to debate whether or not the short-term repair projects that can be achieved in the next ten to twenty years will produce large enough gains in life expectancy to enable people to live to see success in the long-term, harder repair projects. Senolytics, breaking of glucosepane cross-links, clearance of protein aggregates, cell replacement therapies, and more, will all be going concerns in the 2020s. But projects such as repair of stochastic mutations in nuclear DNA or damaged nuclear pore molecules in long-lived and critical populations of neurons are well beyond present capabilities.

An Interview with Dr. Leonid Peshkin

As a way of introduction, I'd like to offer a caricature of the currently popular sensationalist view in the field of aging: "We are the chosen generation. Singularity is near. Rejuvenation therapy is almost here. Not one, several a-la-carte: stem cells, factors from young blood, senolytics, Skulachev's ions, NAD, etc. Companies backed up by luminaries from business and science are already sorting out the remaining details, helped by the formidable force of AI technology called 'deep learning'." This fairy tale is beautiful, and deep in my heart, I hope I am mistaken, but I think that at the moment, this positive mysticism is not justified and is rather counterproductive. The excessive optimism is, unfortunately, standing in the way of progress, as I will try to explain.

There are many proposed models of aging, such as the Hallmarks of Aging, SENS, and the deleteriome. Which, if any, of these models do you believe reflects the reality of aging?

I would not want to take part in religious wars. People get very passionate and clash about often vaguely defined terms. Which of the observed hallmarks of aging, from the molecular to the organism levels, are correlates and which are causes of aging is hard to say. Biology has not yet matured to become an exact science. Perhaps owing to my training in quantitative science I take a "model" to mean a level of quantitative understanding that allows for "modeling"; that is, forecasting and answering "what if" questions. Such a model might not be ultimately expressed by a set of crisp human-readable mathematical formulae but rather a large set of tuned parameters in an artificial neural net or some other representation that has not yet been invented. It must, however, provide a way to assess the current state of an organism and predict its lifespan and healthspan in a stable environment, outside of a major perturbation, and then go further to allow for perturbations and adjust the predictions.

Today, I can't even say that there is an agreement in the field of what is a useful definition of "aging". I like "increase of hazard rate (i.e. the probability of dying) with time", which is admittedly a very mathematical notion - precise and not terribly useful. Inverting this formula, we get a curious metaphor - a life without aging can be imagined as a life where, say, once a year, you undergo a treatment that rejuvenates you a year in biological age, or, with some small but non-negligible probability, kills you. Life is a game of chance.

Do you believe that aging is a one-way process or something that is flexible and amenable to intervention?

It is both. Imagine one dramatic intervention: one day, we invent a way to cryo-protect a warm-blooded organism like ours so that it can undergo a freeze-thaw cycle without damage. Now, you are faced with a challenge to design a schedule that determines when, and in what size fractions, you'd like to use up your lifespan. While you are frozen, time stops. While you are alive, you age: the "deleteriome" kicks in, ionizing radiation wrecks your DNA, your defrosted friends and family du jour stress you out, etc. That's what things would look like ad absurdum, illustrating the tradeoffs.

Now, back to the interventions: I imagine a process not unlike a beauty salon, in which you do your nails and hair and get an occasional facelift; all of these are tradeoffs, even if people do not recognize it. Beauty treatments make you look younger at the moment, but cosmetics products may poison your skin and accelerate actual aging. There is evidence of such tradeoffs across organisms in nature; extending lifespan in many species can be accomplished at the expense of reproduction, and in cold-blooded organisms, you can multiply the lifespan several-fold by just cooling the environment down or slowing down metabolic processes in other ways. I believe that the first results will be not so much in giving people free tickets to longer lives but in making the tradeoffs more explicit, educating people and putting them in control of decision making.

Do you consider epigenetic alterations as a cause of aging or a downstream consequence?

Neither cause nor downstream. There is no linear causal chain with the two links of "aging" and "epigenetic alterations"; instead, there are loops and amplifiers in the circuits of aging. Epigenetic alterations have to be caused by something else; these, in turn, control many things. On the other hand, DNA damage is clearly pretty early in the causal network but is hard to undo. There is more hope to proofread and fix "epigenetic alterations". I am very much interested in this direction of research, so much so that we are planning an experiment looking at changes in the distributions of cell types in cell populations that make up young and old individuals. The expectation is that epigenetic alterations lead to de-differentiation and mis-differentiation of cells in old organisms, which could be characterized and further used as end-points for aging interventions.

Age-Related Oxidative Stress Contributes to Excess Cholesterol in the Liver

The presence of oxidative molecules in our biochemistry rises with aging, and cells react to this in many different ways. Internally to cells, this sort of damage can be rapidly repaired and brief bursts of oxidative molecule creation even serve as a signal for many necessary processes, such as the beneficial reactions to the stresses of exercise. Chronic oxidative stress produces dysfunction, however, whether that is via the production of toxic oxidized lipids or through through more direct means of causing cells to act in a harmful manner.

Chronic inflammation and mitochondrial dysfunction are two of the upstream causes of increased numbers of oxidative molecules. Among the downstream consequences can be found all sorts of detrimental cellular reactions, many of which are only poorly explored at best. The open access paper here is an example of the type. The best solution to this class of age-related problem is to go after the upstream causes, though mitochondrially targeted antioxidants appear to provide a beneficial suppression of oxidative stress in at least some situations.

The production of reactive oxygen species (ROS) is progressively increased in aging and is one of the key factors in cellular damage. It is known that ROS, including free radicals and peroxides, adversely affects cells and tissues and causes an imbalance in the biological system, contributing to the development of many aging-related diseases. In addition, oxidative stress plays an important role in hepatic disease. Aging increases fibrotic responses and is also associated with the development of a variety of liver diseases including nonalcoholic fatty liver disease and alcoholic liver disease. In particular, the prevalence of nonalcoholic fatty liver disease tends to increase with age, and thus, aging and lipid metabolism in the liver may be closely related. In addition, evidence suggests that increased oxidative stress due to various factors leads to increased lipid accumulation in the liver, while decreased oxidative stress has a lipid-lowering effect in hepatocytes.

Lipid supply to liver tissue consists of three main pathways: dietary intake, peripheral lipolysis, and de novo lipogenesis. Fatty liver occurs when the lipid supply exceeds the hepatic lipid removal. In many previous studies, triglyceride and cholesterol metabolism disorders and accumulation have been reported to be closely related to aging. For example, in the senescent-associated mouse, the cholesterol content in the liver was increased compared with control mice. In this study, we investigated the mechanisms for the increase in cholesterol accumulation during aging. We found that the increased ROS in aging plays an important role for the accumulation of cholesterol in the liver by increasing cholesterol uptake and cholesterol synthesis via increasing glucose uptake.

The mRNA expression of GLUT2, GK, SREBP2, HMGCR, and HMGCS, genes for cholesterol synthesis, was gradually increased in liver tissues during aging. When we treated HepG2 cells and primary hepatocytes with the ROS inducer, H2O2, lipid accumulation increased significantly compared to the case for untreated HepG2 cells. H2O2 treatment significantly increased glucose uptake and acetyl-CoA production, which results in glycolysis and lipid synthesis. Treatment with H2O2 significantly increased the expression of mRNA for genes related to cholesterol synthesis and uptake. These results suggest that ROS play an important role in altering cholesterol metabolism and consequently contribute to the accumulation of cholesterol in the liver during the aging process.

Link: https://doi.org/10.1111/acel.12895

Delivery of Extracellular Vesicles for Skin Repair and Rejuvenation

To what degree can skin be restored to a more youthful state just by changing cell behavior? That question will be explored comprehensively in the years ahead, and not just for skin. Many research groups are taking the approach of harvesting extracellular vesicles from stem cells and delivering them into tissues, a potential form of therapy that appears to produce many of the same benefits as first generation stem cell transplants, and with less expense and complexity.

What fraction of these benefits are a matter of overriding unfortunate cellular reactions to damage, or putting damaged cells back to work, hopefully without reaching the threshold at which this would produce an increased cancer risk? How much is a genuine clean-up of metabolic waste or damaged components in cells? That remains to be determined, but it is worth bearing in mind that there are forms of metabolic waste and cell damage that our biochemistry cannot deal with, no matter how fired up it might be. Ultimately, the research community must do better than simply instructing our cells to work harder. Tools must be provided to break down that waste, irreparably damaged stem cells replaced, and more.

Stem cells have attracted great interest from the scientific community since their discovery. Their capacity to differentiate into various cell types and hence provide tissue repair made them promising tools in the treatment of such pathologies as neurodegenerative disorders, organ failure, and tissue damage. However, stem cells such as mesenchymal stem/stromal cells (MSCs) exert their functions via paracrine effects and not by the replacement of dead cells.

The term secretome refers to the complex mixture of factors released by virtually all cell types, including stem cells, to the extracellular space. Once released by stem cells, this combination of different classes of molecules can modify microenvironments by controlling inflammation as well as inducing selective protein activation and transcription. This secreted milieu of molecules may culminate in tissue regeneration. Recent evidence about this paracrine mechanism has opened up a new paradigm in stem cell therapy and stimulated the search for strategies that explore the concept of "cell therapy without cells."

The most well-studied and dynamic part of the growing field of secretomics is extracellular vesicles (EVs). EVs represent an important fraction of virtually any cell type's secretome. Extensive research is currently being conducted to elucidate the healing potential of stem cell EVs in numerous disease processes. EVs released by stem cells to the extracellular space have been shown to improve vascularization, immunomodulation, and cardiac and central nervous system regeneration.

Stem cell-conditioned media from endothelial precursor cells differentiated from human embryonic stem cells have been used in skin rejuvenating research with interesting results. The injection of conditioned media from those cells improved the aspect of skin wrinkles and skin aspect in women. UV light damage and aging affect extracellular matrix collagen and elastin depots, both of which are key in the prevention of skin dehydration as well as in firmness and elasticity preservation. The beneficial effects of stem cell EVs for cellular matrix maintenance and collagen production as described previously could contribute to this effect, considering that vesicles are important components of stem cell-conditioned media.

Furthermore, reports have suggested that purified stem cell EVs could play a role in rejuvenating skin cells. A report indicated that EVs from induced pluripotent stem cells (iPSCs) could restore the function of aged human dermal fibroblasts. The authors reported that dermal fibroblasts pretreated with iPSC EVs resisted photoaging with UVB and did not overexpress matrix-degrading enzymes MMP-1/3 but, on the contrary, displayed a high expression of collagen I, as young fibroblasts do. Other researchers studied the capacity of human umbilical cord stem cell EVs to rejuvenate skin by modulating collagen production and permeation. They also investigated whether EVs acceptance could accelerate fibroblast proliferation. Not only did skin cells proliferate more after EVs endocytosis, but a better production of collagen and elastin in human skin models was also observed in their study. Altogether, these studies indicate that stem cell EVs could be good candidates for therapeutic strategies against aging.

Link: https://dx.doi.org/10.3390/bioengineering6010004

Is it Safe to Greatly Reduce LDL Cholesterol, Far Below Normal Levels?

The dominant approach to slowing atherosclerosis remains a mix of pharmaceuticals that can, separately, reduce blood pressure and LDL cholesterol (LDL-C) in the bloodstream. In the latter case, new therapies such as PCSK9 inhibitors and improved combinations of statins are capable of doing far more than just return raised LDL-C to normal levels. It is in fact possible to reduce blood cholesterol to something like a half or quarter of normal levels, and this produces incrementally greater benefits in reduction of atherosclerosis risk. But is it safe over the long term? And if it is, why did we evolve to have the observed normal levels of cholesterol in blood?

Atherosclerosis is the build up of fatty plaques that narrow and weaken blood vessels, ultimately leading to a fatal rupture of some form. Raised blood pressure accelerates this process through mechanisms that are incompletely explored - but it is obviously the case that, at later stages, more pressure and weaker blood vessels combines to increase the risk of fatal structural failure. Cholesterol is another input, arriving from the bloodstream. The final input is the activity of the immune system, and local inflammatory signaling, as the immune cells called macrophages attempts to clean up cholesterol from blood vessel tissues and return it to the liver to be disposed of.

Atherosclerotic plaques start and grow due to the presence of damaged, oxidized cholesterol more than overall cholesterol, but the more cholesterol in total, the more oxidized cholesterol is mixed in. That proportion increases with age, as rising levels of oxidative molecules throughout the body lead to ever more oxidative damage to molecules. Macrophages respond to the presence of cholesterol, arrive, become overwhelmed by oxidized cholesterol, and become inflammatory foam cells or die. In either case they produce signaling that leads to a further influx of macrophages, a feedback loop that only worsens with time. The bulk of atherosclerotic deposits is made up of the debris of dead cells and the cholesterol they failed to clear away, a significant fraction of it oxidized cholesterol.

Thus lower blood cholesterol is good in the sense that it will slow down this process by reducing one of the inputs. Unfortunately it doesn't appear to significantly reverse atherosclerosis. Established atherosclerotic plaques remain, and the fatal end result is only put off to some degree, even for the very dramatic reductions in blood cholesterol discussed here. Better approaches are needed, such as ways to destroy oxidized cholesterol, or make macrophages resistant to oxidized cholesterol, or otherwise improve the process by which macrophages mine cholesterol from plaques and export it back to the liver. The past twenty years has seen a fair amount of innovation on the latter option, but sad to say that it has failed in human trials, even while producing as much as a 50% reversion of plaque in mice.

Is very low LDL-C harmful?

LDL-C is deposited in the arterial wall and promotes the inflammation process through the attraction of monocytes and macrophages at the site of cholesterol deposition, thus resulting in the development of atherosclerotic plaques and overt cardiovascular (CV) disease. An abundance of evidence has shown a linear relationship of LDL-C levels with the risk for CV events. Several lipid-lowering treatments such as statins, ezetimibe and the novel proprotein convertase subtilisin kexin 9 (PCSK9) inhibitors were found to offer significant benefits in the reduction in LDL-C and importantly in the amelioration of the overall CV risk of patients with hyperlipidemia with or without CV disease.

Towards this direction, the European Society of Cardiology and the European Society of Atherosclerosis recommend the reduction in LDL-C to lower than 70 mg/dl or a reduction of at least 50% if the baseline values are between 70 and 135 mg/dl in very high-risk patients, to lower than 100 mg/dl or a reduction of at least 50% from baseline values between 100 and 200 mg/dl in high-risk patients, and to less than 115 mg/dl in low to moderate risk patients. The 2017 American Association of Clinical Endocrinologists and American College of Endocrinology Guidelines for Management of Dyslipidemia and Prevention of Cardiovascular Disease suggest even lower LDL-C targets of <100 mg/dl, <70 mg/dl, and <55 mg/dl, in high, very high, or extreme risk diabetic patients.

The necessity for the reduction in LDL-C levels to provide significant CV beneficial effects has been shown and is recommended by all international guidelines. However, there are concerns for the optimal lower limit in which LDL-C can be reduced to achieve optimal CV benefit without causing potential adverse events. The purpose of this review is to present available data for the safety of reducing LDL-C to low or very low levels as it comes from studies of lipid-lowering drugs that achieved such levels.

In general, intensive lipid-lowering studies with statins showed that there is no increased risk of adverse events with reducing LDL-C to levels of approximately 40-50 mg/dl. The most important data for reducing LDL-C to such levels are provided from PCSK9 inhibitors studies where remarkable reductions in LDL-C levels were achieved and no increased rates of adverse events were noted with evolocumab. The slightly concerning findings with alirocumab in the ODYSSEY LONG TERM trial were not verified in the ODYSSEY OUTCOMES study. More importantly, the potential neurocognitive decline with low LDL-C was not observed in several post-hoc analyses and in the EBBINHAUS trial that was specifically designed to evaluate such events. However, it has to be noted that in most trials, the follow-up period and the exposure of the patients in low LDL-C was rather short and trials with longer study periods are needed to unveil potential harms.

Last, higher incidences of hemorrhagic stroke and cancer were not observed in these studies, even at very low LDL-C levels. In conclusion, reduction of LDL-C to less than 50 mg/dl seems safe and provides greater CV benefits compared with higher levels. Data for achieved LDL-C lower than 20-25 mg/dl is limited, although findings from the above mentioned studies are encouraging. However, further evaluation is needed for future studies and post-hoc analyses.

More Evidence for Excess Fat Tissue to Contribute to Hypertension

Hypertension, or increased blood pressure, is one of the more important ways in which the low-level molecular damage of aging is converted into high-level structural damage to tissues. Hypertension produces increased rupture of capillaries and other forms of pressure damage to delicate structures of the brain and other organs, resulting in loss of function and, ultimately, death. It also accelerates the progression of atherosclerosis, the creation of fatty plaques that weaken and narrow blood vessels, with the end result of stroke or heart attack as an important blood vessel suffers structural failure.

Being overweight or obese is strongly associated with risk and degree of hypertension. The underlying mechanisms are easy to speculate on: the chronic inflammation produced by visceral fat tissue causes dysfunction in the smooth muscle cells that control blood vessel dilation and constriction, for example. That breaks the feedback mechanisms controlling blood pressure, leading to hypertension. The diet needed to become overweight likely contributes to greater cross-link formation, stiffening blood vessel tissues to produce much the same outcome. And so forth through a laundry list of other low-level damage that manifests in blood vessel walls.

Among the cardiovascular disease (CVD) risk factors, age is considered as the most important predictor of CVD events and hypertension is a major cause of CVD mortality. Age-related increase in blood pressure (BP) is recognized as a universal feature of human aging. Previous epidemiological surveys have shown a progressive increase in systolic blood pressure (SBP) with age, whereas diastolic blood pressure (DBP) also initially increases with age but falls at latter ages. Thus, effective control of BP is essential for improving population health.

Studies of BP associated with adiposity-related genetic variants and controlled trials of weight loss interventions have established the causal relationship between adiposity and BP. Regardless of age and other unmodifiable CVD risk factors such as sex and race, there are many risk factors that are manageable and can be controlled through lifestyle modification, including reduction of obesity. However, there are inconsistencies as to whether a general or central adiposity is more strongly associated with BP and different opinions about which variable is the strongest predictor of BP.

The present study aimed to investigate how BP and body composition change within different age groups and their correlation across the adult age span. We also investigated the contribution of body composition measures (including body mass index (BMI), lean mass percent (LM%), and visceral fat rating (VFR) to the age-related alteration of BP across ten 5-year age groups ranging from 18-79 years in a sample of healthy Chinese adults. We demonstrated that mean SBP showed an age-related increase and mean DBP showed an inverted U-shape across the age span, and this trend was closely associated with the age-related body composition changes. Furthermore, we found that the association between BP and body composition indices was weaker in the elderly compared to the younger subjects.

As demonstrated in our study, all measures of general obesity, central obesity, and LM% were correlated to BP at the whole population level, and among them the relationships with BP were similar across most of the body composition indices. Some studies have suggested that general adiposity was more strongly correlated with BP, while other studies suggested central or visceral adiposity was more strongly correlated with BP than general adiposity. In this study, we didn't find significant differences between these two kinds of obesity indices.

To examine whether body composition was a factor influencing BP throughout the whole adult age span, we further analyzed the association of BP with BMI, LM% and VFR in each specific age-group (at 5-year ranges). After adjustment for education level, smoking status, alcohol consumption, and residential location, BMI and VFR were positively associated with BP in each age group, suggesting that adiposity was an important risk factor for the increased BP, whereas LM% was negatively associated with BP, the latter indicating its protective effect on BP. The correlation between BP and all these three measures (BMI, LM%, and VFR) was weaker in the elderly than younger adults. Thus, as demonstrated by our study, we may infer that factors associated with increased BP may be more complicated in the elderly compared to the younger age groups.

Link: https://doi.org/10.3389/fphys.2018.01574

Protein Aggregation versus Infection Hypotheses of Alzheimer's Disease

The amyloid hypothesis has dominated the past twenty years of failed attempts to build therapies to treat Alzheimer's disease. However, it is only very recently that immunotherapies and other methods of reducing amyloid-β levels in the aging brain have started to show signs of working. As a consequence, the field is in a state of some upheaval when it comes to choice of strategy going forward. Alternative views of Alzheimer's and its development have emerged and gained enough support to raise sufficient funds to compete. In the long run, this is all to the good, I think. A diversity of approaches always beats out a top-down monoculture when it comes to finding viable paths forward. The open access paper noted here examines a few different hypotheses that have risen to prominence.

In this review, we focus on four Alzheimer's disease (AD) hypotheses currently relevant to AD onset: the prevailing amyloid cascade hypothesis, the well-recognized tau hypothesis, the increasingly popular pathogen (viral infection) hypothesis, and the infection-related antimicrobial protection hypothesis. In briefly reviewing the main evidence supporting each hypothesis and discussing the questions that need to be addressed, we hope to gain a better understanding of the complicated multi-layered interactions in potential causal and/or risk factors in AD pathogenesis.

As a defining feature of AD, the existence of amyloid deposits is likely fundamental to AD onset but is insufficient to wholly reproduce many complexities of the disorder. A similar belief is currently also applied to hyperphosphorylated tau aggregates within neurons, where tau has been postulated to drive neurodegeneration in the presence of pre-existing Aβ plaques in the brain.

Although infection of the central nervous system by pathogens such as viruses may increase AD risk, it is yet to be determined whether this phenomenon is applicable to all cases of sporadic AD and whether it is a primary trigger for AD onset. Lastly, the antimicrobial protection hypothesis provides insight into a potential physiological role for Aβ peptides, but how Aβ/microbial interactions affect AD pathogenesis during aging awaits further validation. Nevertheless, this hypothesis cautions potential adverse effects in Aβ-targeting therapies by hindering potential roles for Aβ in anti-viral protection.

Unlike familial AD, sporadic AD may evolve from a combination of various genetic and environmental factors. Neuroinflammation, tau pathogenesis, and viral infection have all been implicated to play important roles in AD; however, these factors do not appear to be pathogenic triggers that are specifically relevant to AD. Thus, specific causal mechanisms that drive AD onset have yet to be clearly defined, which may lead to the identification of new therapeutic targets. It is now widely accepted that sporadic AD is a complicated syndrome.

Link: https://doi.org/10.1186/s40035-018-0139-3

The Harm Done by Senescent T Cells

Senescent cells accumulate with age in all tissues, and their presence is one of the root causes of aging. Cells become senescent in large numbers at all ages, and under a variety of circumstances: toxins, wound healing, ordinary somatic cells reaching the Hayflick limit, random mutational damage to important genes, and so forth. Senescence irreversibly shuts down cellular replication, making it a useful defense against cancer. Near all newly senescent cells are destroyed quickly. They either self-destruct or they are destroyed by the immune system, but both paths to a reliable natural clearance of senescent cells falter with the damage and dysfunction of aging.

Lingering senescent cells that have evaded destruction never rise to more than a few percent of all cells by number, even in very late life, but that is more than enough to produce major disruption to tissue function. Senescent cells secrete a potent mix of signals that remodel the extracellular matrix, encourage nearby cells to become senescent, produce chronic inflammation and immune system overactivation, and generally make a mess of things in many other ways. This is particularly disruptive for regenerative capacity, even though senescent cells are necessary for wound healing: their activity is generally useful in the short term for specific circumstances like this, it is when the signaling continues for the long term that the problems arise.

Immune cells, such as the T cells of the adaptive immune system, can also become senescent. Since these cells roam the body, the detrimental consequences can be broad and varied, unlike the case for senescent cells that reside in a given organ. Some of those consequences are examined in the open access review paper noted below. Roaming or not, it is the case that selective destruction of these cells via some form of senolytic therapy will provide benefits. We might think of the signals produced by senescent cells as a mechanism that actively maintains a more aged, damaged state of the body and brain. Destroying these cells is a narrow form of rejuvenation, turning back one of the causes of aging wherever it can be achieved.

The impact of senescence-associated T cells on immunosenescence and age-related disorders

Immunosenescence is age-associated changes in the immunological functions, including diminished acquired immunity against infection, pro-inflammatory traits, and increased risk of autoimmunity. The proportions of memory-phenotype T cells in the peripheral T cell population steadily increase with age, but the relationship between this change and immunosenescent phenotypes remains elusive. Recently, we identified a minor memory-phenotype CD4+ T cell subpopulation that constitutively expressed PD-1 and CD153 as a bona fide age-dependent T cell population; we termed these cells senescence-associated T (SA-T) cells. SA-T cells exhibit characteristic features of cellular senescence, with defective T cell receptor-mediated proliferation and T cell cytokine production.

The T cell receptor (TCR) responsiveness of the overall CD4+ T-cell population, in terms of proliferation and regular cytokine production, diminished gradually with age. Our careful studies, however, revealed that these effects were attributed primarily to the increase in the proportions of SA-T cells with age, given that the residual naïve and PD-1- (CD153-) MP CD4+ T cells in aged mice exhibited TCR responsiveness comparable to those from young mice. Senescent cells tend to resist apoptosis; consistent with this, SA-T cells were quite stable over long-term culture, probably accounting for the progressive accumulation of SA-T cells with age despite their defective proliferation capacity.

The age-dependent increase in SA-T cells could be due to CD4+ T cell-intrinsic effects or to the tissue environment of aged individuals. We found that the naïve CD4+ T cells transferred from young mice robustly proliferated in an aged host environment and underwent significant conversion to SA-T cells, whereas in young hosts, the same T cells barely proliferated and generated few SA-T cells. Thus, the aged, but not young, host environment plays a crucial role in the development of SA-T cells from naïve CD4+ T cells.

Accumulating evidence indicates that the SA-T cells are markedly increased in the tissues under persisted inflammation, often in association with the tertiary lymphoid tissues, of chronic inflammatory disorders. Recent evidence indicates that the selective elimination of tissue senescent cells leads to a significant improvement of age-associated tissue dysfunctions with prolonged lifespan. Consequently, tissue senescent cells are emerging as a crucial target for preventive and therapeutic intervention of age-related chronic disorders. Targeted elimination of SA-T cells represents a promising strategy for controlling chronic inflammatory disorders and possibly cancer.

Persistent Chronic Inflammation Raises the Risk of Neurodegenerative Disease

In this open access paper, the authors present evidence for chronic inflammation to contribute to the development of neurodegenerative disease. A great deal of research into the late stage disease state robustly connects inflammation to pathology, and given the risk factors for neurodegeneration, such as excess visceral fat tissue, it is entirely reasonable to think that inflammation is important. It accelerates the development of many other age-related conditions, after all. Less work has been carried out on the early stages of development of neurodegenerative diseases in humans, however, due to the lack of good data sets that span the necessary decades of time. There are already many good reasons to minimize chronic inflammation throughout life, to as great a degree as is possible. This one can be added to the stack.

Although it has become clear over the last several decades that inflammation plays a role in the pathogenesis of Alzheimer's disease and other forms of dementia, the precise nature and temporal characteristics of the neurodegeneration-inflammation relationship have remained largely unknown. Several lines of research have identified inflammation, both within the brain and within the periphery, as a potential driver of neurodegenerative brain changes and cognitive decline. Chronic low-grade inflammation, in particular, has received considerable attention, as translational studies suggest that it may play a causal role in dementia, late-life cognitive decline, and a number of other age-related phenotypes.

Although evidence from animal models indicates that chronic inflammation can perpetuate, or even initiate, neurodegenerative changes, this hypothesis has been challenging to examine in human studies. This is largely due to a lack of longitudinal data on inflammatory biomarkers in cohort studies which examine neurocognitive outcomes in older adults. In a recently published study of participants from the Atherosclerosis Risk in Communities (ARIC) Cohort, we were able to clarify the relationship between long-term (21-year) patterns of systemic inflammation and late-life neurodegenerative changes.

In this study, we found that individuals who both demonstrated elevated inflammation before or during middle adulthood and maintained high levels of inflammation over the subsequent two decades had greater white matter hyperintensity volume and reduced white matter microstructural integrity as older adults, compared to those who maintained low levels of inflammation. These findings support the idea that systemic inflammation can initiate or perpetuate neurodegenerative brain changes which underlie cognitive impairment and dementia.

Link: https://doi.org/10.18632/aging.101704

Claiming Cellular Senescence for the Hyperfunction Theory of Aging

This mildly infuriating commentary well illustrates just why it is that theories of aging are so very diverse. Even a mechanism as well understood as cellular senescence can be fairly convincingly argued into one camp or another. For those who see aging as damage accumulation, lingering senescent cells are clearly a form of damage, a byproduct of normal metabolism that grows slowly over time and produces tissue dysfunction in proportion to the number of such cells. For those who consider the hyperfunction theory of aging, in which aging is the result of developmental programs failing to shut down in adult life, it is fairly easy to argue that the prevalence of cellular senescence in old people is an embryonic development mechanism or wound healing mechanism run wild. Cellular senescence does indeed play important roles in those circumstances.

Senolytics are drugs that extend lifespan and delay some age-related diseases by killing senescent cells. I want to draw your attention to the paradoxes associated with senolytics, which argue against the dogma that says aging is a functional decline caused by molecular damage. This dogma predicts that senolytics should accelerate aging. If aging is caused by loss of function, then killing senescent cells would be expected to accelerate aging, given that dead cells have no functionality at all. Instead, however, senolytics slow aging, which highlights a contradiction in the prevailing dogma.

The theory of hyperfunctional aging addresses this paradox. Killing senescent cells is beneficial because senescent cells are hyperfunctional. The hypersecretory phenotype or Senescence-Associated Secretory Phenotype (SASP) is the best-known example of universal hyperfunction. Most such hyperfunctions are tissue-specific. For example, senescent beta cells overproduce insulin and thus activate mTOR in hepatocytes, adipocytes, and other cells, causing their hyperfunction, which in turn leads to metabolic syndrome and is also a risk factor for cancer. SASP, hyperinsulinemia and obesity, hypertension, hyperlipidemia and hyperglycemia are all examples of absolute hyperfunction (an increase in functionality).

In comparison, relative hyperfunction is an insufficient decrease of unneeded function. For example, protein synthesis decreases with aging, but that decrease is not sufficient. In analogy, a car moving on the highway at 65 mph is not "hyperfunctional." But if the car were to exit the highway and enter a residential driveway at only 60 mph it would be "hyperfunctional," and stopping that car would likely prevent damage to other objects. Similarly, killing hyperfunctional cells can prevent organismal damage. Senolytics eliminate hyperfunctional cells, which otherwise damage organs.

Link: https://doi.org/10.18632/aging.101750

A Selection of Recent News in Parkinson's Disease Research

Today I'll note a selection of recent news from the Parkinson's disease research community. Alzheimer's disease may be where the lion's share of funding goes when it comes to research and development related to neurodegenerative conditions, but work on Parkinson's disease is nonetheless well funded and diverse. This condition is characterized by aggregation of α-synuclein and the death of a small but vital population of dopamine generating neurons. The loss of those neurons results in the loss of motor control observed in patients, but there is a great deal of other damage done to the operation of the brain as a result of abnormal biochemistry downstream of α-synuclein aggregation.

Setting aside the older pharmaceuticals that do little but slow the condition or mask the symptoms, the dominant approaches to development of new therapies involve replacement of the lost dopamine neurons and clearance of α-synuclein. However, there are plenty of other places in which researchers have sought to intervene, in mechanisms that may or may not be downstream of α-synuclein. For example, it was recently demonstrated that cellular senescence in glial cells in the brain contributes meaningfully to the progression of Parkinson's - and thus near future senolytic therapies may produce patient benefits here as in many other age-related conditions. It is also the case that age-related decline in mitochondrial function accelerates the loss of neurons in Parkinson's disease. Where Parkinson's is connected with mutations, such as in the parkin gene, these are mechanisms affecting the maintenance of mitochondria.

Parkinson's disease is similar at the high level to other major neurodegenerative conditions: aggregation of damaging proteins; abnormal inflammatory behavior of the immune system in the brain; faltering mitochondrial function. The lower level details are wildly different, but the theme is the same. To talk about curing any neurodegenerative condition is to talk about curing aging. These conditions are the result of forms of molecular damage and waste buildup that cause aging itself; they can only be effectively dealt with by repairing this damage, and preferably early enough to prevent it from ever reaching pathological levels.

A Proposed Roadmap for Parkinson's Disease Proof of Concept Clinical Trials Investigating Compounds Targeting Alpha-Synuclein

The convergence of human molecular genetics and Lewy pathology of Parkinson's disease (PD) have led to a robust, clinical-stage pipeline of alpha-synuclein (α-syn)-targeted therapies that have the potential to slow or stop the progression of PD and other synucleinopathies. To facilitate the development of these and earlier stage investigational molecules, the Michael J. Fox Foundation for Parkinson's Research convened a group of leaders in the field of PD research from academia and industry, the Alpha-Synuclein Clinical Path Working Group. This group set out to develop recommendations on preclinical and clinical research that can de-risk the development of α-syn targeting therapies.

This consensus white paper provides a translational framework, from the selection of animal models and associated endpoints to decision-driving biomarkers as well as considerations for the design of clinical proof-of-concept studies. It also identifies current gaps in our biomarker toolkit and the status of the discovery and validation of α-syn-associated biomarkers that could help fill these gaps. Further, it highlights the importance of the emerging digital technology to supplement the capture and monitoring of clinical outcomes. Although the development of disease-modifying therapies targeting α-syn face profound challenges, we remain optimistic that meaningful strides will be made soon toward the identification and approval of disease-modifying therapeutics targeting α-syn.

Improved stem cell approach could aid fight against Parkinson's

Scientists have taken a key step towards improving an emerging class of treatments for Parkinson's disease. It addresses limitations in the treatment in which, over time, transplanted tissue can acquire signs of disease from nearby cells. It could aid development of the promising treatment - known as cell replacement therapy - which was first used in a clinical trial this year. Experts hope the approach, which involves transplanting healthy cells into parts of the brain damaged by Parkinson's, could alleviate symptoms such as tremor and balance problems.

Researchers have created stem cells - which have the ability to transform into any cell type - that are resistant to developing Parkinson's. They snipped out sections of DNA from human cells in the lab using advanced technology known as CRISPR. In doing so, they removed a gene linked to the formation of toxic clumps, known as Lewy bodies, which are typical of Parkinson's brain cells. In lab tests, the stem cells were transformed into brain cells that produce dopamine - a key brain chemical that is lost in Parkinson's - in a dish. The cells were then treated with a chemical agent to induce Lewy bodies. Cells that had been gene-edited did not form the toxic clumps, compared with unedited cells, which developed signs of Parkinson's.

"We know that Parkinson's disease spreads from neuron-neuron, invading healthy cells. This could essentially put a shelf life on the potential of cell replacement therapy. Our exciting discovery has the potential to considerably improve these emerging treatments."

Parkinson's disease protein buys time for cell repair

Parkin is absent or faulty in half the cases of early onset Parkinson's disease, as well as in some other, sporadic cases. In a healthy brain, Parkin helps keep cells alive, and decreases the risk of harmful inflammation by repairing damage to mitochondria, which are responsible for supplying energy to cells. Damaged mitochondria could trigger the cell's internal death machinery, which removed unwanted cells by a cell death process termed apoptosis.

"We discovered that Parkin blocks cell death by inhibiting a protein called BAK. BAK and a related protein called BAX are activated in response to cell damage, and begin the process of destroying the cell - by dismantling mitochondria. This ultimately drives the cell to die, but low-level mitochondrial damage has the potential to trigger inflammation - warning nearby cells that there is potential danger."

The team showed that Parkin restrains BAK's activity when mitochondria are damaged. Parkin tags BAK with a tiny protein called ubiquitin. With normal Parkin, BAK is tagged and cell death is delayed. Parkin 'buys time' for the cell, allowing the cell's innate repair mechanisms to respond to the damage. Without Parkin - or with faulty variants of Parkin that are found in patients with early-onset Parkinson's disease - BAK is not tagged and excessive cell death can occur. This unrestrained cell death may contribute to the neuronal loss in Parkinson's disease.

Results from a Pilot Human Trial of Senolytics versus Idiopathic Pulmonary Fibrosis

Researchers here report on results from an initial pilot trial of the use of a senolytic therapy to treat idiopathic pulmonary fibrosis. The data is perhaps much as expected for a first pass at removing senescent cells associated with a specific condition, using the tools available today: a starting point, benefits observed, but definitely room for improvement. The particular senolytic combination used here is cheap and readily available and can remove as much as half of senescent cells in some tissues in mice, but the degree of clearance varies widely by tissue type, and the optimal human dose is yet to be determined. Typically the next trial following an initial feasibility study will test a range of doses.

The past few years of animal data have indicated that the inflammatory signaling of senescent cells, the senescence-associated secretory phenotype (SASP), plays an important role in producing and maintaining age-related fibrosis in multiple tissues, but may not be the only process involved. Fibrosis is an outcome of disarray in regenerative and tissue maintenance, in which scar-like connective tissue is laid down in place of correctly formed tissue. Organ function is degraded as a result. In the case of idiopathic pulmonary fibrosis death follows within a few years of diagnosis, as the lungs fail.

Cellular senescence is a key mechanism that drives age-related diseases, but has yet to be targeted therapeutically in humans. Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal cellular senescence-associated disease. Selectively ablating senescent cells using dasatinib plus quercetin (DQ) alleviates IPF-related dysfunction in bleomycin-administered mice.

A two-center, open-label study of intermittent DQ (D:100 mg/day, Q:1250 mg/day, three-days/week over three-weeks) was conducted in 14 participants with IPF to evaluate feasibility of implementing a senolytic intervention. The primary endpoints were retention rates and completion rates for planned clinical assessments. Secondary endpoints were safety and change in functional and reported health measures. Associations with the senescence-associated secretory phenotype (SASP) were explored.

The retention rate was 100% with no DQ discontinuation; planned clinical assessments were complete in 13 of the 14 participants. One serious adverse event was reported. Non-serious events were primarily mild-moderate, with respiratory symptoms (16 events), skin irritation/bruising (14 events), and gastrointestinal discomfort (12 events) being most frequent. Physical function evaluated as 6-minute walk distance, 4-minute gait speed, and chair-stands time was significantly and clinically-meaningfully improved. Pulmonary function, clinical chemistries, frailty index (FI-LAB), and reported health were unchanged. DQ effects on circulating SASP factors were inconclusive, but correlations were observed between change in function and change in SASP-related matrix-remodeling proteins, microRNAs, and pro-inflammatory cytokines.

IPF appears to be relentlessly progressive: in large IPF drug trials, no improvements in 6-minute walk distance have been observed in the placebo-control arms. Pulmonary function in this IPF patient population did not change during the course of this preliminary study. It is likely that in this pilot exploration, the follow-up period is too short and the sample size too modest to assess effects on long-term trajectories, especially in a complex chronic disease such as IPF. If resolution of pulmonary scarring and fibrosis does indeed occur, it may take considerable time after clearance of senescent cells from the lung.

Link: https://doi.org/10.1016/j.ebiom.2018.12.052

The Prospects for Cell Therapy to Restore Lost Neurons in Parkinson's Disease

Generating and transplanting dopamine-generating neurons into the brains of Parkinson's disease patients, to replace the cells destroyed by processes such as aggregation of α-synuclein, is one of the longer-running lines of development in modern cell therapy research. While the regenerative medicine community has advanced a long way past the first, mixed attempts at treating Parkinson's disease in this way, a great deal of work yet lies ahead in order to produce a reliable approach to the replacement of damaged cells. Most of the challenges are relevant to all attempts to introduce new, functional cell populations into the aging body: ensuring the cells survive; preventing the age-damaged environment from overwhelming any benefits that are produced; establishing cost-effective sources of cells, preferably derived from the patient's own tissues.

Current approaches to cell replacement therapy in Parkinson's disease (PD) are strongly focused on the dopamine system, with the view that restoring dopaminergic inputs in a localized and physiologic manner will provide superior benefits in terms of effect and longevity compared with oral medication. Experience using transplants of fetal tissue containing dopaminergic cell precursors has provided valuable proof that the approach is feasible, and that engrafted cells can survive and function over many years. However, multiple drawbacks and procedural complications are recognized in using fetal cells.

Recent strides in stem cell technology now make it possible to overcome some of the barriers associated with fetal tissue. The first generation of stem cell-derived dopaminergic neurons now in the pipeline is predicted to perform at least at an equivalent level to human fetal cells, but in a more robust and reproducible manner, providing a stable, expandable, and readily accessible cell source for transplantation. As such the therapy is expected to provide a better way of treating the dopamine responsive features of PD using a targeted, physiological delivery of dopamine to the striatum, but it is not a disease modifying treatment, nor a cure.

Many questions remain to be addressed. For example, PD pathology is not cell-autonomous, and the spread of pathology potentially affecting graft function is an oft-repeated although unsubstantiated objection to cell therapy. While current evidence supports absence of any major effect, it does raise the question of whether a combinatorial therapy comprising grafting and, for example, a biologic or small molecule to abrogate spread of alpha-synuclein pathology would be desirable.

In this article we have only discussed use of dopaminergic cells, whereas a stem cell source allows growth of any cell type. Other neural networks would be much more difficult to rebuild, but it is tempting to speculate that, for example, cholinergic neurons could be helpful in addressing cognitive function, or balance. There is a long road ahead in demonstrating how well stem cell-based reparative therapies will work, and much to understand about what, where, and how to deliver the cells, and to whom. But the massive strides in technology over recent years make it tempting to speculate that cell replacement may play an increasing role in alleviating at least the motor symptoms, if not others, in the decades to come.

Link: https://doi.org/10.3233/JPD-181488

Recent Papers on the Cellular Senescence Produced by Visceral Fat Tissue

Today, I thought I'd point out a couple of papers that touch on different aspects of the overlap between visceral fat tissue and senescent cells in aging. In the first paper, researchers show that the ability of visceral fat tissue to generate the markers of senescence is suppressed when the circulatory system of an old mouse is linked to a younger mouse. All of the ongoing, unresolved arguments over why this sort of modest rejuvenation occurs apply here; my money is still on it being dilution of harmful factors in an aged bloodstream. In the second paper, researchers link yet another aspect of dysfunction in the brain to the presence of senescent cells, in this case disorders such as anxiety and depression that are linked to fat tissue. The senescent cells can be used to explain that association with excess fat tissue.

Excess visceral fat tissue is harmful in many different ways, damaging the body and the brain. It is metabolically active, distorting the normal operation of cellular metabolism and tissue functions throughout the body. Further, it generates chronic inflammation via what appears to be quite a wide variety of mechanisms, from inappropriate cell signaling to DNA debris from dead fat cells. Short bursts of inflammation are a normal part of the response to injury and infection. When those mechanisms become stuck, however, activated without cease for the long term, then they become very damaging. Chronic inflammation accelerates the progression of all of the most common disabling and ultimately fatal age-related conditions. Being overweight speeds up that process.

As ever more of the research community becomes convinced (finally) that senescent cells are an important root cause of degenerative aging, more attention is being directed to all of the inflammatory conditions and states, searching for the senescent cells that no doubt cause a sizable fraction of that inflammation. Even in very old people, it is thought that there are only a small number of senescent cells present in tissues - perhaps a few percent of all cells at most. Yet these errant cells have a sizable detrimental effect, as the damage they do is mediated by the signal molecules that they generate, influencing the behavior of countless other cells near and far. Pro-inflammatory signals are one of the better understood consequences of cellular senescence, and the reason why these cells are a significant cause of inflammatory disease in old age.

Thus fat tissue doesn't have create many more senescent cells, in absolute numbers, in order to place a significant burden of damage and dysfunction on the rest of the body. Sadly, it does indeed create those cells. We can quite accurately say that being overweight results in an acceleration of aging, a consequence reflected in mortality rates, disease risk, and medical expenditure. The overweight and the obese have shorter, less healthy, more expensive lives, with all of those disadvantages scaling with the amount of excess visceral fat tissue, and the length of time it is carried. That isn't all down to senescent cells - there are plenty of other issues to consider in the harmful biochemistry of large amounts of fat tissue. I am sure that the development of senolytic therapies to destroy senescent cells will lead to a quantification of just how much of the damage done by being overweight is down to cellular senescence. Building therapies is the fastest way to obtain answers to this sort of question.

Adipose tissue senescence and inflammation in aging is reversed by the young milieu

Visceral adipose tissue (VAT) inflammation plays a central role in longevity and multiple age-related disorders. Cellular Senescence (SEN) is a fundamental aging mechanism that contributes to age-related chronic inflammation and organ dysfunction, including VAT. Recent studies using heterochronic parabiosis models strongly suggested that circulating factors in young plasma alter the aging phenotypes of old animals. Our study investigated if young plasma rescued SEN phenotypes in the VAT of aging mice.

With heterochronic parabiosis model using young (3 months) and old (18 months) mice, we found significant reduction in the levels pro-inflammatory cytokines and altered adipokine profile that are protective of SEN in the VAT of old mice. These data are indicative of protection from SEN of aging VAT by young blood circulation. Old parabionts also exhibited diminished expression of cyclin dependent kinase inhibitors (CDKi) genes p16 (Cdkn2a) and p21 (Cdkn1a/Cip1) in the VAT.

In addition, when exposed to young serum condition in an ex-vivo culture system, aging adipose tissue-derived stromovascular fraction cells (SVFs) produced significantly lower amounts of pro-inflammatory cytokines (Mcp-1 and IL-6) compared to old condition. Expressions of p16 and p21 genes were also diminished in the old SVFs under young serum condition. Finally, in 3T3 pre-adipocytes culture system; we found reduced pro-inflammatory cytokines (Mcp-1 and IL-6) and diminished expression of CDKi genes in the presence of young serum compared to old serum. In summary, current study demonstrates that young milieu is capable of protecting aging adipose tissue from SEN and thereby inflammation.

Obesity-Induced Cellular Senescence Drives Anxiety and Impairs Neurogenesis

Cellular senescence entails a stable cell-cycle arrest and a pro-inflammatory secretory phenotype, which contributes to aging and age-related diseases. Obesity is associated with increased senescent cell burden and neuropsychiatric disorders, including anxiety and depression. To investigate the role of senescence in obesity-related neuropsychiatric dysfunction, we used the INK-ATTAC mouse model, from which p16Ink4a-expressing senescent cells can be eliminated, and senolytic drugs dasatinib and quercetin.

We found that obesity results in the accumulation of senescent glial cells in proximity to the lateral ventricle, a region in which adult neurogenesis occurs. Furthermore, senescent glial cells exhibit excessive fat deposits, a phenotype we termed "accumulation of lipids in senescence." Clearing senescent cells from high fat-fed or leptin receptor-deficient obese mice restored neurogenesis and alleviated anxiety-related behavior. Our study provides proof-of-concept evidence that senescent cells are major contributors to obesity-induced anxiety and that senolytics are a potential new therapeutic avenue for treating neuropsychiatric disorders.

Interfering in the Interaction between Amyloid-β and Prion Protein as a Treatment for Alzheimer's Disease

The damage of Alzheimer's disease mediated by aggregation of amyloid-β and tau protein deposits isn't so much due to the aggregates, but rather the surrounding halo of complex interactions and related proteins. One of those thought to be important is between oligomeric amyloid-β and cellular prion protein, the latter of which is also of note in transmissible spongiform encephalopathy. Researchers here sought to interfere in this interaction, and achieved interesting results, at least in a mouse model of Alzheimer's disease. The usual caveats apply, in that Alzheimer's mouse models are highly artificial constructs, since nothing resembling Alzheimer's naturally occurs in that species. The relevance of these varied models to the real condition is very dependent on the details of the model and the details of the treatment - there is plenty of room for later failure even given good results in mice.

Researchers have identified a drinkable cocktail of designer molecules that interferes with a crucial first step of Alzheimer's and even restores memories in mice. The binding of amyloid beta peptides to prion proteins triggers a cascade of devasting events in the progression of Alzheimer's - accumulation of plaques, a destructive immune system response, and damage to synapses.

Researchers screened tens of thousands of compounds looking for molecules that might interfere with the damaging prion protein interaction with amyloid beta. They found that an old antibiotic looked like a promising candidate but was only active after decomposing to form a polymer. Related small polymers retained the benefit and also managed to pass through the blood-brain barrier. They then dissolved the optimized polymeric compound and fed it to mice engineered to have a condition that mimics Alzheimer's. They found that synapses in the brains were repaired and mice recovered lost memory.

A collaborating team reported a positive response when they delivered the same cocktail to cells modeled to have Creutzfeldt-Jakob Disease, a devasting neurological condition caused by infection with misfolded prion protein. The next step is to verify the compounds aren't toxic in preparation for translation to clinical trials for Alzheimer's disease.

Link: https://news.yale.edu/2019/01/02/new-compound-shows-promise-treatment-alzheimers

Life Extension Advocacy Foundation 2018 Retrospective

The Life Extension Advocacy Foundation (LEAF) staff members have grown their efforts considerably over the past year, including the launch of a yearly conference series and a network of angel investors focused on startup companies engaged with the aging process. The LEAF blog should probably be on your reading list. Insofar as a position on aging goes, the Life Extension Advocacy Foundation folk appear more guided by the Hallmarks of Aging view than the SENS view, but there is a significant overlap, and many of their past fundraising efforts have directly supported the SENS Research Foundation. The more fellow travelers the better; there is certainly the need for a great deal more patient advocacy for the treatment of aging than presently takes place.

In May, we officially announced our first conference held in New York City, Ending Age-Related Diseases: Investment Prospects and Advances in Research, which would then be held in July. The Longevity Investor Network, LEAF's own initiative to foster a flourishing rejuvenation biotech ecosystem, was also launched in May under the lead of Javier Noris; speaking of investments, at around the same time, a generous anonymous donor decided to invest both money and trust in us by becoming a Lycium-level Lifespan Hero and pledging $2,000 a month. We'd like to express our most sincere gratitude to this donor as well as to all our Heroes for all they do for us.

Although organizing the upcoming New York City conference took a great deal of effort and time, we still got quite a few interviews out in July. This was not all, as one of our most important projects was also launched in July - the Rejuvenation Roadmap, a curated database of hallmark-categorized, work-in-progress rejuvenation therapies, the companies developing them, and their current state of development. The Roadmap is our way of answering the question, "How far are we from defeating aging?", and it has grown quite a bit since it was first announced; hopefully, it'll grow much more in 2019!

In August, Michael Kope from SENS Research Foundation joined our newly formed Industry Advisory Board (IAB) and will provide business guidance and advice to LEAF as our organization continues to grow and develop. Michael and the other members of the IAB will be a great asset in helping us to achieve our goals. The AgeMeter biomarker scan, which was successfully crowdfunded in late 2017 on Lifespan.io, became available for purchase on its own website near the end of August. We also should have an update regarding data access for project backers early in the new year.

In mid-September, we launched our most recent crowdfunding campaign on Lifespan.io, the NAD+ Mouse Project which was aimed at studying whether the administration of the NAD+ precursor nicotinamide (NMN), in both normal and accelerated-aging mice, confers the rejuvenative benefits that were first observed in previous studies.

As we look back on the year, we have published over 400 articles, with a corresponding 10-fold increase in traffic from our readers over the previous year. We have also hosted 10 pitch meetings to help young rejuvenation startups connect with investors as part of the Longevity Investor Network, a project aimed at bringing together researchers and investment funding. We hope that 2019 will be at least as intense as its predecessor, and given the all-around progress in the field and the growing interest in it, we're sure that we can look forward to it.

Link: https://www.leafscience.org/looking-back-at-2018-a-year-in-rejuvenation-biotechnology/

Tau and Amyloid-β Synergize to Impair Neural Activity in Alzheimer's Disease

The mainstream of the Alzheimer's research community remains primarily interested in clearing deposits of amyloid-β from the aging brain. That said, there is a growing interest in tackling tau aggregation as well, particularly given the long years of failure to achieve meaningful results through clinical trials of immunotherapies that target amyloid-β. The current consensus on the development of the disease is that increased amyloid-β, leading to solid deposits of amyloid in and between cells, is an early phenomenon, and may in and of itself do little more than create mild cognitive impairment. However, amyloid-β aggregation sets the stage for the later production of neurofibrillary tangles, consisting of an altered form of tau protein, and these are far more harmful to brain function.

Both tau and amyloid-β protein aggregates are biochemically complex, with a surrounding halo of many varieties of harmful molecule. It is the halo rather than the deposits that do the damage to brain cells and their function, or so present thinking goes. Further, more recent research suggests that while tau is the more harmful of the two, tau synergizes with amyloid-β to causes greater damage than it would on its own.

This view of the condition may explain why attempting to intervene late in the process with anti-amyloid therapies fails to produce sizable benefits, but nonetheless does appear to help to some degree, particularly in animal models. So perhaps amyloid-β clearance as an approach is best harnessed for prevention or slowing of early development of the condition. Still, that leaves the challenge of treating later stages of the condition for present patients, and thus a growing number of researchers are working on ways to remove tau aggregates. Many of those scientists advocate for the development of therapies that clear both tau and amyloid-β at the same time, a strategy that seems very reasonable given the evidence to date.

Tau protein suppresses neural activity in mouse models of Alzheimer's disease

A new study sheds light on how the hallmarks of Alzheimer's disease - amyloid-beta (A-beta) plaques and neurofibrillary tangles containing the protein tau - produce their damaging effects in the brain. The findings suggest that strategies directed against both pathologic proteins, rather than one or the other, might be promising therapeutic options. "Our current study reinforces growing evidence suggesting that A-beta and tau work together to impair brain function and that, for certain aspects of that impairment, tau predominates. We are intrigued to learn how they are interacting at a molecular level, in order to find ways of blocking that synergy."

Studies with two mouse models that overexpress different forms of tau found, for the first time, that elevated levels of the protein were associated with a significant reduction in neural activity whether or not tau had aggregated into tangles. Experiments with a novel mouse model that overexpresses both A-beta and tau found that, in the presence of both pathological proteins, A-beta-associated hyperactivity was abolished and tau's neuronal silencing effect predominated. The findings were duplicated in mice regardless of their age, including animals too young to exhibit the loss of neurons typically seen in animals that only overexpress tau.

The authors note that their findings could help explain why clinical trials of A-beta-blocking therapies have had difficulty improving symptoms of patients with Alzheimer's disease. "One implication of our work is that approaches combining anti-A-beta and anti-tau therapies might be more effective than either alone, at least from the perspective of neural activation. Finding that tau and A-beta work in a synergistic fashion opens the doors to new research into understanding exactly how that interaction works."

Tau impairs neural circuits, dominating amyloid-β effects, in Alzheimer models in vivo

The coexistence of amyloid-β (Aβ) plaques and tau neurofibrillary tangles in the neocortex is linked to neural system failure and cognitive decline in Alzheimer's disease. However, the underlying neuronal mechanisms are unknown. By employing in vivo two-photon Ca2+ imaging of layer 2/layer 3 cortical neurons in mice expressing human Aβ and tau, we reveal a dramatic tau-dependent suppression of activity and silencing of many neurons, which dominates over Aβ-dependent neuronal hyperactivity.

We show that neurofibrillary tangles are neither sufficient nor required for the silencing, which instead is dependent on soluble tau. Surprisingly, although rapidly effective in tau mice, suppression of tau gene expression was much less effective in rescuing neuronal impairments in mice containing both Aβ and tau. Together, our results reveal how Aβ and tau synergize to impair the functional integrity of neural circuits in vivo and suggest a possible cellular explanation contributing to disappointing results from anti-Aβ therapeutic trials.

Considering Mesenchymal Stem Cell Therapy for Atherosclerosis

Mesenchymal stem cell (MSC) therapies as presently practiced, even given considerable differences in what exactly is meant by "mesenchymal stem cell", fairly reliably reduce the chronic inflammation of aging for an extended period of time. They are much less reliable at inducing regeneration of tissues, and where that does occur it probably results from dampened inflammation. One of the many detrimental consequences of the always-on inflammatory signaling that arises with age is a disruption of regenerative capacity. Given the ability of MSC transplantation to suppress inflammation, it is possible that this could be at least marginally useful as a therapy for any age-related condition in which inflammation is an important component.

Here, researchers consider MSC therapies as a way to slow down atherosclerosis, as inflammation strongly influences the pace at which this condition progresses. They also suggest that atherosclerosis is linked to the age-related failure of native MSCs to regulate inflammation. There are several possible reasons for this. Firstly, inflammation goes hand in hand with oxidative stress, the presence of greater levels of oxidizing molecules. This means it also leads to more of the oxidized lipids that cause macrophages attempting to clean up atherosclerotic lesions to become harmful foam cells that instead accelerate growth of the lesions. Secondly, macrophage behavior is influenced by the state of inflammatory signaling. Macrophages that are normally helpful can be coerced into amplifying inflammation, switching to an aggressive inflammatory mode rather than assisting in repair of lesions.

Atherosclerosis, a chronic inflammatory disease of the wall of large- and medium-sized arteries, is the most common pathological process leading to cardiovascular disease (CVD). The hallmark lesion in atherosclerosis is the atherosclerotic plaque. An alternative strategy to target inflammatory pathways for CVD therapy could be enhancing physiological mechanisms that antagonize inflammation. Key cellular targets for this approach are multipotent mesenchymal stromal cells (MSC). MSC are non-hematopoietic clonogenic perivascular multipotent stromal cells that can be induced to differentiate in vitro into osteoblasts, chrondrocytes, or adipocytes. MSC function as pivotal regulators of inflammation by modulating innate and adaptive immune cells. This does not require long-term engraftment of MSC in target tissues. The crosstalk between MSC and immune cells is mainly mediated by secreted bioactive molecules.

Limited data are available for MSC from patients with atherosclerosis. Specifically, the contribution of MSC dysfunction to the persistence of chronic inflammation and plaque progression are ill-defined. This relates in part to the lack of specific markers that can identify MSC in vivo in human arteries. We have overcome this obstacle by using an alternative approach. Thus, we have characterized adipose derived MSC from atherosclerotic patients (i.e. subjects undergoing coronary artery bypass graft surgery) and compared their function with MSC from non-atherosclerotic patients. Immunopotency (i.e. the MSC capacity to suppress the proliferation of allogenic activated T-cells) was used as the main readout of MSC function. Initial findings confirmed that atherosclerotic-MSC have impaired immunomodulatory capacity and a pro-inflammatory secretome, both contribute to the state of chronic low-grade inflammation that promotes atherosclerosis progression. Moreover, we demonstrated that MSC immunopotency can indeed be enhanced by modulating inflammatory components of the MSC secretome.

There are multiple potential implications of these data. First, the therapeutic effectiveness of atherosclerotic-MSC is likely compromised when compared to their non-atherosclerotic counterparts. Accordingly, only non-atherosclerotic MSC should be used in clinical trials. Second, the ability to modulate the redox state of MSC is a possible strategy to enhance the therapeutic efficacy of autologous atherosclerotic-MSCs. Third, increasing age is an established independent risk factor for the development of atherosclerosis. Notably, mitochondrial dysfunction is not only associated with aging, but also with premature or accelerated atherosclerosis. Our study was not designed to address the contribution of MSC dysfunction to atherosclerosis onset or progression. However, our results strongly suggest this link, and we have set the stage to test this hypothesis in the future.

Link: https://doi.org/10.18632/aging.101735

The Uncertain Details of Retinal Aging

This open access paper examines what is known of the aging of the retina, and notes the difficulties inherent in relating any of those changes to specific declines in vision. The research community has an increasingly detailed view of exactly what differentiates an old retina from a young retina, structurally, chemically, and in the changing behavior of the various types of cell that make up retinal tissue. It is a challenge to relate data obtained in laboratory animals to loss of specific aspects of visual function, however, particularly the more subtle ones. One can't ask mice and rats to sit through the same test procedures as humans undergo, and obtain useful feedback via that approach.

Visual aging is linked to a decline in functional activity causing lower visual acuity, lower contrast sensitivity and impaired dark adaptation. However, although it has been reported that the age-related visual impairment is mainly due to a neuronal malfunction together with cell loss, the specific reasons of aging are still uncertain. How, and at what level, are the diverse neuronal populations affected? And how much are other retinal players involved?

By characterizing retinal aging in experimental animals (pigmented and albino rats) under controlled and healthy conditions, we found that the retinal function, as measured with full field electroretinograms, decreased ~50% at 22-months compared with 2-month-old rats. Whether neuronal malfunction or cell loss is mainly responsible for this reduced functionality is still an open question, even though structural changes in the optical components may contribute to this reduction. Interestingly, several studies suggest cell loss based on the retinal thinning that occurs with aging. However, although when we measured the retinal layers in vivo we observed a decrease in thickness ~14%, we also saw that the constant retinal growth was responsible for the retinal thinning, since volumetric and quantification analyses indicated that the thinning did not involve neuronal loss.

The retina is a highly organized and specialized tissue. The light-sensitive photoreceptors are essential for an effective signal transduction and to initiate the efficient transmission of impulses through the retina. They are vulnerable to light-induced damage and many publications have shown the degeneration of outer segments during aging. The central retina probably receives greater light exposure triggering different metabolic requirements that increases metabolic stress. In fact, a deficiency in DNA repair enzymes, damage induced by excitatory amino acids, specific age-related metabolic changes, a general decline in autophagy activity, and reduced energy production by mitochondrial metabolism collectively result in oxidative stress that may affect photoreceptor functionality. All that in addition to lipofuscin accumulation, morphological alterations and damage in the retinal pigmented epithelium accompanied by a para-inflammatory response are the signature signs of aging in the retina.

To preserve visual function, the eyes and brain require precisely tuned machinery. Any of the above-mentioned changes related to aging, including synapse remodelling or neuronal loss in response to age may contribute or play a crucial role in the continuous and irreversible decline in vision. Importantly, age may end causing a partial or complete distorted image formation, more so in a timeframe where our lifespan is increasing. So, could this retinal dysfunction be prevented or restored?

Link: https://doi.org/10.18632/aging.101734

An Initial Assessment of the Phenotypic Age Metric

Today's open access paper adds to the growing number of attempts to construct a useful biomarker of aging from a combination of simple, available metrics. The Phenotypic Age measure described here uses a few fairly standard measures from blood samples as a basis, which might lead us to suspect it is heavily biased towards measuring immune system aging. Insofar as immune system function is important to overall health, and immune system function declines with age, then so far so good. The challenge with all of these potential biomarkers is less how well they do in the world of natural aging, to predict who will have a higher mortality in the years ahead, and more how they respond to specific classes of rejuvenation therapy.

The primary rationale for spending any time on the development of a biomarker of aging is to produce a fast, low-cost way of assessing the results of an alleged rejuvenation treatment. At present only life span studies can reliably determine how well such a treatment performs. Such studies are expensive and slow in mice, and out of the question in humans. This is a major impediment to progress. What is needed is an approach that enables researchers to treat older animals and people, and then a month later run a quick test to assess the results. That would speed up development in this field immensely. The work carried out in recent years on epigenetic clocks suggests that a robust biomarker of aging is a feasible goal.

The most important question remains to be answered, however: how will all of the various potential biomarkers of aging react to specific classes of rejuvenation therapy, such as senolytic drugs to clear senescent cells? A biomarker heavily based on immune cell characteristics may provide results that are of little relevance to changes taking place in the tissues of important inner organs, and vice versa. Until these interactions are well quantified by researchers, the biomarkers are not terribly useful - the output will provide a number, but what does that number really mean? Building biomarkers and building rejuvenation therapies will, at least at the outset, have to proceed in parallel, with the two sides incrementally validating one another.

A new aging measure captures morbidity and mortality risk across diverse subpopulations from NHANES IV: A cohort study

One method for determining whether a person appears younger or older than expected on a biological or physiological level is to compare observable characteristics, reflecting functioning or state, to the characteristics observed in the general population for a given chronological age. A number of aging measures have been proposed using molecular variables, the most prominent being epigenetic clocks (expressed as DNA methylation age, in units of years) and leukocyte telomere length. We and others have previously shown that while these measures are phenomenal age predictors - especially DNA methylation age - their associations with aging outcomes above and beyond what is explained by chronological age is weak to moderate. Conversely, aging measures based on clinically observable data, or phenotypes, tend to be more robust predictors of aging outcomes.

The differences in prediction between these two types of measures could reflect that molecular measures may only capture one or a small number of changes involved in the multifactorial aging process, while on the other hand, clinical measures may represent the manifestations of multiple hallmarks of aging occurring at the cellular and intracellular levels. While composite scores based on traditional clinical chemistry measures are not mechanistic, their better performance and relative affordability and practicality compared to current molecular measures may make them more suitable for evaluating the effects of aging interventions on an organismal scale, and/or identifying groups at higher risk of death and disease.

Among the existing clinical measures, the majority were generated based on associations between composite variables and chronological age - with no integration of information on how the variables influence morbidity and mortality. Given that individuals vary in their rate of aging, chronological time is an imperfect proxy for building an aging measure. Recently, we developed a new metric, Phenotypic Age (in units of years), that incorporates composite clinical chemistry biomarkers based on parametrization from a Gompertz mortality model. Rather than predicting chronological age - as previous measures have done - this measure is optimized to differentiate mortality risk among persons of the same chronological age, using data from a variety of multi-system clinical chemistry biomarkers.

In general, a person's Phenotypic Age signifies the age within the general population that corresponds with that person's mortality risk. For example, two individuals may be 50 years old chronologically, but one may have a Phenotypic Age of 55 years, indicating that he/she has the average mortality risk of someone who is 55 years old chronologically, whereas the other may have a Phenotypic Age of 45 years, indicating that he/she has the average mortality risk of someone who is 45 years old chronologically.

All analyses were conducted using NHANES IV (1999-2010, an independent sample from that originally used to develop the measure). Our analytic sample consisted of 11,432 adults aged 20-84 years and 185 oldest-old adults top-coded at age 85 years. We observed a total of 1,012 deaths, ascertained over 12.6 years of follow-up. Proportional hazard models and receiver operating characteristic curves were used to evaluate all-cause and cause-specific mortality predictions. Overall, participants with more diseases had older Phenotypic Age. For instance, among young adults, those with 1 disease were 0.2 years older phenotypically than disease-free persons, and those with 2 or 3 diseases were about 0.6 years older phenotypically.

After adjusting for chronological age and sex, Phenotypic Age was significantly associated with all-cause mortality and cause-specific mortality (with the exception of cerebrovascular disease mortality). Results for all-cause mortality were robust to stratifications by age, race/ethnicity, education, disease count, and health behaviors. Further, Phenotypic Age was associated with mortality among seemingly healthy participants - defined as those who reported being disease-free and who had normal BMI - as well as among oldest-old adults, even after adjustment for disease prevalence.

Towards a Biomarker of Aging Based on the Gut Microbiome

A low-cost, low-effort way to accurately assess biological age, meaning the burden of molecular damage and the countless harmful cellular reactions to that damage, would greatly speed development of rejuvenation therapies. Ideally researchers would be able to apply a therapy and then within a month obtain a measure of how greatly it affects aging. At present the only reliable way to fully assess means of slowing or reversing aging is to run life span studies, which are slow and expensive in mice, and simply not feasible in humans.

Thus a fair amount of effort is presently devoted to the development of biomarkers and combinations of biomarkers that might one day serve this purpose. In this preprint paper, researchers outline their work on the use of the gut microbiome as a basis for a biomarker of aging. It is known that characteristic changes occur in the microbiome with age, many of them detrimental and associated with the development of age-related disease, but there is a high degree of variability between individuals and study populations. Thus these results will certainly need a much broader replication as a part of any further development.

Although infant microbiome succession is well studied and can be used to assess the risks of various health conditions, its transition to adult microbiome is less understood. More so, composition variability attributed to geographic location, medical history, diet, and other factors make it hard to analyze adult microbiomes as effectively as those of infants. Age-related studies of human microbiome have failed to produce a straightforward theory of gut flora aging.

Some studies indicate decreasing biodiversity in the elderly gut. However, that is not the case for all data sets, and elderly healthy people may have microbiomes as diverse as the younger population. Other findings include changes in specific taxa abundance in aging microbiota. Such bacterial genera as Bacteroides, Bifidobacterium, Blautia, Lactobacilli, Ruminococcus have been shown to decrease in the elderly, while Clostridium, Escherichia, Streptococci, Enterobacteria increase. However, these patterns are not strictly established as results vary greatly across different studies. This may be attributed to different methodologies as well as unbalanced data sets that may contain people of different lifestyles.

Despite these complications, the consensus is that the elderly gut has lower counts of short chain fatty acid (SCFA) producers such as Roseburia and Faecalibacterium and an increased number of aerotolerant and pathogenic bacteria. Such shifts can lead to dysbiosis, which in turn contributes to the onset of multiple age-related diseases.

The standard way of separating the gut microbiome into three chronological states - child, adult, and elderly microbiomes - lack a clear set of rules. Among them, adult microbiome remains the greatest mystery. It has no established succession stages, as in newborns, and does not normally reflect gradient detrimental processes typical for an old organism. This poses a question whether normal adult microbiome progresses at all or it is in a state of stasis. Considering the aging process is gradual and involves accumulation of damage and other deleterious changes (as also indicated by a number of biomarkers such as DNA methylation clocks), it is logical to suppose that gut microbiome succession is also gradual. However, attempts to use microbiome-derived features to predict chronological age have been inconclusive.

Here, we developed a method of predicting the biological age of the host based on the microbiological profiles of gut microbiota using a curated dataset of 1,165 healthy individuals. Our predictive model, a human microbiome clock, has an architecture of a deep neural network and achieves the accuracy of 3.94 years mean absolute error in cross-validation. The performance of the deep microbiome clock was also evaluated on several additional populations. This approach has allowed us to define two lists of 95 intestinal biomarkers of human aging. We further show that this list can be reduced to 39 taxa that convey the most information on their host's aging. Overall, we show that (a) microbiological profiles can be used to predict human age; and (b) microbial features selected by models are age-related.

Link: https://doi.org/10.1101/507780

NAD+ and Cellular Senescence in Intestinal Tissue Organoids

Organoids are a useful intermediary step between cell cultures and animal studies, allowing for investigations to be carried out in a structured tissue that is much closer to the real thing than cells in a petri dish. Researchers here use intestinal tissue organoids derived from old mice to show that raised levels of NAD+ suppress markers of cellular senescence - which most likely indicates suppression of activity rather than outright destruction of senescent cells to any great degree, given what we know of how calorie restriction affects NAD+ and senescent cells.

NAD+ levels are connected to mitochondrial function, and fall with age. A growing industry is now selling various means to raise NAD+ in order to improve mitochondrial function and thus tissue function. Some of these appear to be beneficial in early trials, while others seem ineffective. Past research has connected NAD+ with cellular senescence, or mitochondrial function with cellular senescence, but rigorous data on the size of the effect has yet to be produced. This narrow slice of the benefits of increased mitochondrial function is unlikely to compare favorably with the effects of senolytics, the outright destruction of senescent cells in large numbers.

Here we have demonstrated that the important stem cell marker Lgr5 was epigenetically silenced by trimethylation of histone H3K27, inducing suppression of Wnt signaling and a decrease of cell proliferation in intestinal epithelial organoids derived from aged mice. In these organoids, we also observed accumulation of SA-β-gal, a decrease in the expression of DNA methyltransferases and an increase in the expression of p21, indications of cellular senescence.

Epigenetic silencing of Lgr5 and induction of senescence occurs in aged intestinal organoids. The stem cell marker Lgr5 was substantially expressed in young intestinal epithelial organoids, whereas it was faintly expressed in aged intestinal organoids. Examination of DNA methylation levels around the Lgr5 promoter region revealed no significant difference in DNA methylation between young and aged intestinal organoids. Since Lgr5 is an activator of the Wnt signaling pathway, epigenetic silencing of Lgr5 results in suppression of Wnt signaling, which may lead to decreased cell proliferation and activation of senescence-associated genes such as p21 due to suppression of DNA methylation.

Recently, calorie restriction experiments have highlighted Sirt1 as a possible longevity gene. Sirt1 has histone acetyl transferase activity and its expression is regulated by the concentration of NAD+. Aging leads to a reduction of NAD+ in the body, and it has been reported that supplementation of NAD+ induces longevity and stem cell activation. Here, intestinal epithelial organoids derived from aged mice grew larger, forming crypt-like structures after treatment with NMN, a key NAD+ intermediate. The aged intestinal epithelial organoids treated with NMN showed an increase of proliferative activity, activation of Lgr5 and Sirt1, and suppression of p21 and p16, suggesting that treatment with NMN was able to ameliorate senescence-related changes in intestinal epithelia and could have potential application as an anti-aging intervention.

Link: https://doi.org/10.1038/s41514-018-0031-5

Ambrosia Health and the Downsides of Developing Marginal Therapies

One of the many good reasons to be guided by the SENS approach to aging, meaning a focus on repairing molecular damage as close to the causes of aging as possible, is that it has a greater likelihood of resulting in a viable therapy. Benefits should turn out to be sizable, broadly applicable to many age-related conditions, and reliable. The present best example of the type is provided by senolytic therapies that clear senescent cells. The more prevalent and popular strategy of tinkering with metabolism or adjusting the late-stage, dysfunctional disease state, throwing signals into the mix to override cellular reactions to damage, or upregulate stress responses, and while hoping for the best, has a high failure rate in larger human trials. With few exceptions, benefits tend to be unreliable, narrowly applicable to just a handful of conditions, and small.

Unfortunately, once development has reached the stage of a funded company focused on developing a particular therapy, it is hard for anyone involved to back down and admit failure to achieve good results. A few companies, Ambrosia and Alkhahest, are currently in this position when it comes to the use of blood and plasma transfusions to try to recreate the benefits observed in parabiosis studies. In these animal studies, the circulatory systems of old and young mice are linked; the young mice suffer accelerated measures of aging and they old mice gain some reversal of measures of aging. Unfortunately, research completed after these companies were established, and then the data generated by the companies themselves, shows that there is nothing here of interest. If there is an effect resulting from transfusion, it is small and unreliable. For one, transfusion is a terrible way to try to recreate the effects of a complete joining of circulatory systems, and secondly the evidence now strongly indicates that benefits in the old mice in parabiosis studies are more a matter of dilution of harmful factors in old blood rather than the delivery of beneficial factors in young blood.

The media are sharks and will cheerfully build a narrow pedestal for a company and its founders one day, uncritically accepting all company statements as fact without challenge, and then turn on a dime to knock all it down the moment that the data fails to live up to unrealistic expectations. They will be unkind about failure, regardless of how deserving the people involved actually are; they will mix together all possible reasonable and unreasonable accusations while constructing their narrative, as illustrated in today's article below. This is another thing to bear in mind when considering what sort of medical biotechnology to pursue, and how to pitch it at the outset.

The article here assembles a grab-bag of complaints about Ambrosia, some of which are valid and useful, and some of which are quite pernicious, such as the leading presentation of the death of an aged trial participant, or the way the authors played the public opinion game with blood banks. Most of the technical complaints about lack of effect for the therapy could just as well be leveled at Alkahest, but Ambrosia is an easier target given their non-traditional approach to trials and present diminished position. For my part, I see nothing wrong with patient paid trials that are responsibly conducted. It allows for tests of potential therapies that might otherwise never happen. There is an unseemly hostility to this approach to trials, sad to say, both in the research community and in the media. Objections on that front when a company fails to produce good results are irrelevant and unhelpful. On the other hand, calling out the founders of companies that continue with a failed program because no-one has the moral courage to admit failure and call a halt is a good thing, and it is a pity that it isn't done in most such cases.

Jesse Karmazin, the founder of the startup Ambrosia, had a pitch journalists couldn't resist: For a fee, he could help his clients combat aging and its related ills with infusions of blood plasma from the young. Teen donors, vampiric undertones, a serious-sounding study, an $8,000-per-person price tag and rumors that venture capitalist Peter Thiel might be interested earned Ambrosia more than 100 press mentions in just two years.

But despite declaring the study a success and announcing plans this week to accept new clients, Karmazin never showed any proof that the transfusions actually helped people. In the media, he touted impressive results, but almost a year after his study officially concluded in January 2018, he hasn't released them. Scientists have criticized the study as flawed and the procedure as medically unnecessary and not without risk; in rare cases, transfusion complications can be fatal. One of the doctors Karmazin hired had previously been disciplined by a state medical board for unprofessional conduct.

Karmazin himself cannot legally practice medicine in any state; he is explicitly prohibited from practicing in Massachusetts by authorities. Ambrosia's president and chief operating officer quietly left the company in late December, leaving Karmazin as the sole employee. And the only patient who spoke publicly about Ambrosia's transfusions - treatments he hoped would help him live healthier into old age - died at 65 after going into cardiac arrest.

We found that at least some of Karmazin's young plasma came from a nonprofit blood bank in Texas that recruited teenage donors for "saving lives," but noted on a consent form that their blood components could also be used for "any other medical purpose." The bank abruptly decided to stop selling young plasma after we reached out, according to an employee email.

Ambrosia, which declined to comment on whether the company has any investors, is only one of many firms investigating how to help people feel younger for longer. But Ambrosia's ability to attract paying clients and years of positive press coverage - without providing scientific data to back up its claims - shows just how easy it can be for promises to outpace the research when Silicon Valley gold-chasing mixes with Americans' fear of death.

Link: https://www.huffingtonpost.com/entry/ambrosia-young-blood-plasma-jesse-karmazin_us_5c1bbafce4b0407e9078373c

An Incomplete Survey of Novel Approaches to Alzheimer's Disease

This open access paper is illustrative of a dogmatic mainstream of Alzheimer's disease research in which treatments must be immunotherapy approaches to clearance of amyloid-β or tau, or lifestyle changes and other means of management of risk factors such as blood pressure. Little else is acceptable. Yet many other lines of investigation do exist, such as drainage or filtration of cerebrospinal fluid, or tageting viral causes of amyloid-β accumulation, and some have progressed as far as development in biotech startups. They are nowhere to be found in this review paper.

Alzheimer's disease (AD), the most prevalent neurodegenerative disease of aging, affects one in eight older Americans. Nearly all drug treatments tested for AD today have failed to show any efficacy. There is a great need for therapies to prevent and/or slow the progression of AD. The major challenge in AD drug development is lack of clarity about the mechanisms underlying AD pathogenesis and pathophysiology. Several studies support the notion that AD is a multifactorial disease.

While there is abundant evidence that amyloid plays a role in AD pathogenesis, other mechanisms have been implicated in AD such as neurofibrillary tangle formation and spread, dysregulated protein degradation pathways, neuroinflammation, and loss of support by neurotrophic factors. Therefore, current paradigms of AD drug design have been shifted from single target approach (primarily amyloid-centric) to developing drugs targeted at multiple disease aspects, and from treating AD at later stages of disease progression to focusing on preventive strategies at early stages of disease development.

Here we focus on current AD therapeutic strategies which comprise of mechanism-based approaches including amyloid-beta (Aβ) clearance, tau protein deposits, apolipoprotein-E (ApoE) function, neuroprotection and neuroinflammation, as well as non-mechanism based approaches including symptomatic cognitive stimulation, AD prevention, lifestyle modifications, and risk factor management including non-pharmacological interventions.

Link: https://doi.org/10.1186/s13024-018-0299-8

Giant Mole-Rats Exhibit Greater Gene Expression Stability with Aging than Rats

A number of African mole-rat species live significantly longer than similar-sized rodents, and show very little age-related decline until very late life. Where examined in detail, their biochemistry is an odd mix. In some respects they exhibit the usual signs of damage and dysfunction associated with mammalian aging, such as raised oxidative stress and the presence of senescent cells, but don't appear all that affected by it. Elsewhere they exhibit clearly superior mechanisms, such as improved protein quality control, a layered set of anti-cancer mechanisms that provide near immunity to cancer, and - the topic of this paper - a well preserved pattern of gene expression. This latter case may be something of a tautology: dysregulation of gene expression, or changes in gene expression that are reactions to underlying damage, are a downstream consequence of the causes of aging. When an organism ages more slowly, or exhibits only a lesser degree of aging until very late life, then one would naturally expect gene expression patterns to remain more stable over time.

Compared to short-lived mammals, long-lived mammals have repeatedly been shown to exhibit fewer age-associated changes in numerous physiological parameters related to the functional decline during aging. Recent RNA-seq studies have suggested that much of the remarkable lifespan diversity among mammals is based on interspecies differences in gene expression. However, those studies focused on identifying particular genes and pathways that are differentially expressed between species with divergent longevities. Whether short-lived and long-lived species differ at the transcript level with respect to their amount of differentially expressed genes (DEGs) during aging (hereinafter referred to as "gene expression stability") has, to the best of our knowledge, not been explored yet.

Here, we examined age associated transcriptome changes in two similarly sized rodent species with different longevities: the laboratory rat (Rattus norvegicus), which has a maximum lifespan of 3.8 years, and the giant mole-rat (Fukomys mechowii), which has a maximum lifespan of more than 20 years. In giant mole-rats, longevity is significantly correlated with the reproductive status. Breeding animals outlive non-breeders by far. In the current study, we examined only non-breeding males. Male non-breeding giant mole-rats have a maximum lifespan of approximately 10 years and an average lifespan of approximately 6 years, still clearly exceeding the life expectancy of the laboratory rat.

For both species, we performed RNA-seq on tissue samples from five organs (blood, heart, kidney, liver, and skin; hereinafter called simply tissues) of young and elderly adults. The tissues were collected from young and elderly cohorts of laboratory rats (0.5 and 2.0 years) and giant mole-rats (young: approximately 1.5 years at average; elderly: approximately 6.8 years at average). For each species, we determined DEGs between the two respective time points and searched for enriched functional categories.

Our findings show that giant mole-rats exhibit higher gene expression stability during aging than rats. Although well-known aging signatures were detected in all tissue types of rats, they were found in only one tissue type of giant mole-rats. Furthermore, many differentially expressed genes that were found in both species were regulated in opposite directions during aging. This suggests that expression changes which cause aging in short-lived species are counteracted in long-lived species. Taken together, we conclude that expression stability in giant mole rats (and potentially in African mole-rats in general) may be one key factor for their long and healthy life.

Link: https://doi.org/10.18632/aging.101683