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- The Opening Decades of an Era of Greater Health and Longevity
- The Option of Organ Farming
- Senolytic Drugs Can Become a Future Regenerative Medicine
- A Significant Association Between Periodontal Bacteria and Mortality Rates
- Nauk1 Inhibition as a Treatment for Tauopathies
- Latest Headlines from Fight Aging!
- Interfering in the Spread of Alpha-Synuclein to Treat Synucleopathies
- PGC-1α Gene Therapy Slows Alzheimer's Progression in Mouse Model
- PRG3 Promotes Neural Regeneration
- Mouse Ovary Tissue and Eggs Engineered from Cells
- The Potential Benefits of Better Dental Plaque Control
- Mitochondrially Targeted Antioxidant Slows Alzheimer's Progression in Rat Model
- Calorie Restriction Protects Neurons From Excess Calcium
- Enhanced Mitochondrial Catalase has Different Effects in Young and Old Mice
- Exploring the Mechanisms of Neural Regeneration in Zebrafish
- Why the Lingering Pockets of Hostility Towards SENS Rejuvenation Research?
The Opening Decades of an Era of Greater Health and Longevity
Life span has been steadily increasing these past three decades, a trend made clear in the paper I'll point out today. Yet when it comes to the scope of history, the state of the present, and the future ahead, most people are quite pessimistic. Millennialism never really goes away. The past is seen in rose-tinted hues, the present is experienced against a backdrop of media emphasis on the fearful and the terrible, and the future is commonly painted as a descent into the pit. Yet in truth we live in an age of tremendous positive progress, in which wealth, access to medicine, security, comfort, and healthy longevity are on average increasing year by year. This has been true for more than two centuries in some parts of the world, those first into the industrial revolution, and certainly for at least a lifetime elsewhere. When it comes to biotechnology and medicine, there is a massive shift underway, a gathering of forces for even greater progress. Computing, materials science, and the life sciences are all accelerating, and nowadays researchers are turning their attention towards the treatment of the causes of aging rather than merely patching over and slightly slowing its consequences. The future of human health will be far more than a simple continuation of the gentle upward trend of the past. Great leaps lie ahead.
We're all aware that the past few decades have seen improved health and longevity across most of the world. This is as much a matter of growing wealth as it is a combination of new medicine made better and old medicine made cheap. Many regions are far wealthier today than even a generation ago, and that makes a sizable difference in the statistics of health and mortality: better control over infectious disease, better nutrition, greater awareness of common health practices, less exposure to pollution, and so on and so forth, a longer list than simply greater access to modern medical technology throughout life. Where do the statistics of life and death come from, however? As it happens, there is a fair-sized industry of researchers who mine and manage human mortality data from around the world. It is a massive undertaking, made challenging by the poor nature of much of that data on mortality, and especially mortality due to age-related disease, in many parts of the world. Even in wealthier countries, until fairly recently data on the oldest people was notably inaccurate, characterized by a tendency for medical staff to enter "old age" or similar general category as a cause of death rather than something more specific. Cleaning up large-scale databases and obtaining good statistical results with a high confidence of correctness and utility is a specialized business.
The open access paper linked below gives some idea of the sort of toil that goes into pulling together mortality data from countless reporting bodies into a useful set of working data. You should certainly click through and take a look at the full text, particularly the explanations (complete with diagrams and flow charts) of how researchers go about building the analysis from raw data. Given the doom-laden zeitgeist of this age of ours, as much of the blurb is concerned with inequality, healthcare costs, and regional declines as it is with simply presenting the data. It is unarguably the case, however, that the state of medicine and health has greatly improved over the past three decades, and that process of improvement continues. Progress is the true spirit of the age, for all that many do not want to see it. That progress is both good and necessary, as there is much left to be accomplished in the quest to end suffering; the tools to achieve an end to disease, step by step, are both foreseeable and in some cases already under development. The more of that, the better.
Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980-2015: a systematic analysis for the Global Burden of Disease Study 2015
Comparable information about deaths and mortality rates broken down by age, sex, cause, year, and geography provides a starting point for informed health policy debate. However, generating meaningful comparisons of mortality involves addressing many data and estimation challenges, which include reconciling marked discrepancies in cause of death classifications over time and across populations; adjusting for vital registration system data with coverage and quality issues; appropriately synthesising mortality data from cause-specific sources, such as cancer registries, and alternative cause of death identification tools, such as verbal autopsies; and developing robust analytical strategies to estimate cause-specific mortality amid sparse data. The annual Global Burden of Disease (GBD) analysis provides a standardised approach to addressing these problems, thereby enhancing the capacity to make meaningful comparisons across age, sex, cause, time, and place.
Global life expectancy at birth increased by 10.2 years, rising from 61.7 years in 1980 to 71.8 years in 2015, equating to an average gain of 0.29 years per year. By 2015, male life expectancy had risen by 9.4 years, increasing from 59.6 years in 1980 to 69.0 years, whereas female life expectancy improved by 11.1 years, climbing from 63.7 years to 74.8 years. On average, an additional 0.27 and 0.32 years of life were gained per year for males and females, respectively, since 1980. Global gains in life expectancy were generally gradual but steady, although catastrophic events, including the Rwandan genocide and North Korean famines, and escalating mortality due to HIV/AIDS, had worldwide effects on longevity. Slower gains were achieved for life expectancy at 50 years, or the average number of additional years of life 50 year olds can anticipate at a given point in time. On average, 50-year-old females saw an increase of 4.5 additional years of life since 1980, and 50-year-old males experienced an increase of 3.5 years. Total deaths increased by 4.1% from 2005 to 2015, rising to 55.8 million in 2015, but age-standardised death rates fell by 17.0% during this time, underscoring changes in population growth and shifts in global age structures. The result was similar for non-communicable diseases (NCDs), with total deaths from these causes increasing by 14.1% to 39.8 million in 2015, whereas age-standardised rates decreased by 13.1%. Globally, this mortality pattern emerged for several NCDs, including several types of cancer, ischaemic heart disease, cirrhosis, and Alzheimer's disease and other dementias.
At the global scale, age-specific mortality has steadily improved over the past 35 years; this pattern of general progress continued in the past decade. Progress has been faster in most countries than expected. Against this background of progress, some countries have seen falls in life expectancy, and age-standardised death rates for some causes are increasing. Despite progress in reducing age-standardised death rates, population growth and ageing mean that the number of deaths from most non-communicable causes are increasing in most countries, putting increased demands on health systems.
The Option of Organ Farming
At some point in the foreseeable future, it will become possible to grow functional replacement organs and large tissue patches from a patient skin sample in bioreactors. This capability will replace the present insufficient and unreliable donor sources of organs for transplantation. The cost and logistics will be much less onerous, especially if tissue engineering is paired with reversible vitrification, allowing replacement organs to be generated and then kept in storage until needed. Given the present state of tissue engineering, in which an increasing number of functional tissues can be generated in small sizes, and the trajectory of regenerative medicine as a whole, it seems inevitable that these capacities will come to pass. Whether or not they are widely used is an economic question, a race yet to be run between organ engineering for transplantation on the one hand and in situ repair and rejuvenation of existing organs on the other. Some combination of cell therapies and first generation SENS rejuvenation treatments to clear out metabolic waste, senescent cells, and the like could well prove a better choice for patients than undergoing the major surgery of transplantation, even if the transplanted organ is of a higher quality than the repaired aged organ.
There is a way to go yet before organs can be reliably grown from cells in bioreactors, however. Yet on the way to that goal, there are a number of potential shortcuts and transitional technologies that might be (a) be realized more rapidly, (b) allow the creation of useful organs for transplantation, and (c) provide a more reliable and less expensive option than the present system of organ donation. For example, the use of decellularization may provide incremental gains in the number of organs available, and reduce some of the hazards of transplantation. Decellularization involves taking a donor organ, which might include one that wouldn't make the cut for present day transplantation due to cell damage, stripping all of its cells, and then repopulating the organ using a mix of the patient's own cells. This has been accomplished in the laboratory, and perhaps the most interesting implication of this line of research is that the organ need not be human. Pigs have organs of about the right size, for example, and genetic engineering to remove the known problem proteins that might remain in a decellularized porcine organ is a project of feasible scope. Hard, but not impossible. There are research groups working towards this goal today, some already in the commercial stage of development.
Humanized organs in gene-edited animals
Treatment of chronic diseases has resulted in the successful use of cell therapy for the treatment of hematopoietic diseases and cancers as well as device therapies for the treatment of heart disease, diabetes and osteoarthritis. These therapies, while effective, have not been broadly applied to end-stage disease. Currently, curative therapies for advanced end-stage organ failure require transplantation, which is limited by donor organ availability. While millions of patients could benefit from such therapy, the scarcity of organs severely limits the number of transplantations that are performed. This disparity has fueled intense interest focused on alternative organ sourcing and regenerative medicine.
The use of human cells or lineages in a nonhuman animal has been extensively pursued in biomedical research. For example, the incorporation of human hematopoietic stem cells into early, preimmune fetal lamb embryos was demonstrated in the 1990s. These investigators observed significant, long-term, multilineage engraftment of these cells in sheep bone marrow and blood. Additionally, in 2005, functional human neurons in the mouse were developed by injecting human embryonic stem cells into the ventricles of mice. Humanized liver models in mouse have been well established and are currently used for the study of pharmacokinetics and toxicity. In 2001, the repopulation of a mouse liver with human hepatocytes was described. In 2004, human hepatocytes were transplanted into an immunodeficient mouse model to generate chimeric mice with an 80-90% humanized liver. The utility of these chimeric mice in studying human toxicity and dosing and disease is well recognized. More recently, 3D vascularized and functional human livers have been generated by transplanting human liver buds, developed in vitro, into mice. Various studies have demonstrated the capacity for targeted organ chimeras using blastocyst-complementation strategies. For example, a rat pancreas was produced in a mouse by the process of blastocyst complementation. In these studies, blastocysts mutant for Pdx1, the master regulatory gene for pancreatic development, were injected with pluripotent stem cells from wildtype rats. Transfer of the pluripotent stem cells from wildtype rats injected blastocysts and, subsequently, into surrogate mouse dams gave rise to mouse chimeras with functional pancreata composed of rat cells. These studies emphasized the importance of generating blastocysts, deficient for a key developmental regulatory factor, in which the embryo completely lacks the target organ. The blastocyst-complementation strategy has also produced organs such as the kidney and liver in rodents, and recently, the pancreas in pigs. The results of this latter study are significant, because it supports the notion of generating human patient-specific organs in pigs that can be subsequently used for transplantation or advanced therapies.
Groundbreaking scientific advances are bringing the scientific field closer to the reality of developing human organs in nonhuman animals. First, the advances in developmental biology have identified master regulators that are both necessary and sufficient to specify stem cells and direct them to differentiate to distinct lineages. Second, the ability to reprogram human somatic cells to a pluripotent stem cell state, human induced pluripotent stem cells (hiPSCs), has revolutionized the field of regenerative science and medicine. Third, genome-editing technologies, such as clustered regularly interspaced short palindromic repeat, allow for site-specific genome editing. Fourth, the ability to successfully perform somatic cell nuclear-transfer technology (i.e., cloning) in large animals has allowed for the genetic engineering of large animal models. The intersection and combination of these four emerging technologies makes feasible the ability to delete the genes that govern tissue or organ development in a host, thereby establishing a niche for humanized cells. In addition, the use of complementation experiments, where hiPSCs are transferred to a mutant blastocyst, followed by the transfer into a pseudopregnant host, could result in the potential rescue of the host phenotype rescue with a humanized organ. Therefore, it may be possible to engineer personalized organs in large animals and/or engineer unique human disease models in a large animal for preclinical testing of potential therapeutic agents.
Thus farming may well turn out to be one noteworthy component of the organ engineering industry that will arise over the next few decades: harvesting organs from animals, probably genetically engineered lineages specifically created for this purpose. With sufficiently advanced genetic engineering and use of implanted organ seeds or other strategies, the organs being grown in these animals could be completely human. Growing the organ of one species in an individual of another is also something that has been achieved in the laboratory. If you, like most people, happen to be comfortable with the ethics of eating meat, you should probably also be comfortable with farming organs for medical use.
For my part I think that there is a lot to be said for not undertaking the mass generation and killing of entities capable of suffering purely for one's own convenience, but given that I support the necessity of laboratory animals in medical research, my objection is clearly more utilitarian than absolutist. At the present time relinquishing the use of laboratory animals in the medical sciences would be worse than continuing use. In any case, in comparison to farming for food, organ farming and other research community use of animals is a drop in the ocean. Still, to my eyes both farming and laboratory studies of living beings are things that we should use technology to do away with - to cease these activities as soon as possible. This is as much a part of the goals of the Hedonistic Imperative as is eliminating suffering in humans. To end the farming of animals is in fact already possible, and could be accomplished given the will to do so. On the other side of the house, progress in computation and simulation will eventually enable the retirement of mice, flies, worms, and other species that researchers use in their studies. So all in all, it would be pleasant should the future include less farming of animals for organs and more generation of organs in bioreactors, but it is hard to predict how these things will pan out in advance. It all depends on the twists and turns of the economics of clinical application.
Senolytic Drugs Can Become a Future Regenerative Medicine
Today I thought I'd share a recent commentary on cellular senescence research to treat aging. A growing amount of work is taking place on the fundamentals of clearing senescent cells as a method of partial rejuvenation. The presence of newly founded companies pushing forward towards clinical translation, and results showing life extension and improved tissue function in normal mice are drawing more funding into the field. Folk in our grassroots community are also helping where they can, such as by crowdfunding the first studies to be carried out by the Major Mouse Testing Program earlier this year, or providing seed funding for promising companies. All of this effort is not before time: it is nearing fifteen years since SENS rejuvenation biotechnology advocates first gathered the evidence supporting senescent cell accumulation as a fundamental cause of aging, and began calling for more research on this topic. Various research groups are now focusing on different methods of clearance and their effects on specific tissues and organs, seeking to prove or disprove effects on degenerative aging. We should expect to see a mix of benefits and absence of benefits once the dust settles: senescent cells are only one of the seven broad classes of age-related damage enumerated in the SENS research proposals. Their presence may contribute to many or even all of the common age-related conditions, but they are not significant causes of all of the specific forms of secondary and later cell and tissue dysfunction in the aging body.
To pick one example, earlier this year researchers published a study of the effects of reduced senescent cell counts on aspects of vascular aging. It was indeed a mix of benefits and absence of effects: fewer senescent cells led to reduced calcification of blood vessel walls, associated with blood vessel stiffening with age, but it didn't have much of an impact on the development of atherosclerotic plaques. Both of these items are about as serious in their consequences over the long run. Stiffening of blood vessels drives hypertension, which in turn produces damage to delicate tissues such as the brain and kidneys as tiny blood vessels suffer structural failure at a greater rate. It also provokes remodeling of heart tissue, leading to heart failure, and along the way helps to turn atherosclerosis into a fatal condition. The fatty, inflamed plaques that distort blood vessels eventually grow to the point of rupture, which either blocks or breaks important large vessels. That is a frequently fatal occurrence. This mixed outcome was an interesting result, as one of the characteristics of senescent cells is that they produce greater levels of chronic inflammation via the mix of signals they generate, the senescence-associated secretory phenotype. This signaling is how small numbers of senescent cells, perhaps 1% of the cells present in an organ, can distort the function of the other 99%. Inflammation is pretty important to the pace of progression of atherosclerosis, so one might expect a reduction in the number of senescent cells to slow the pace of that condition - but apparently not in this particular scenario.
The recently published commentary linked below is a celebration of the fact that the scientific community has finally achieved some traction in the matter of a treatment for the root causes of aging, one likely to produce reliable, if partial, degrees of rejuvenation. It is not unreasonable at this point to expect senescent cell clearance to achieve larger and more robust results on aging and age-related disease than much of the rest of present day medicine, and to do so in a way that is additive to other methodologies. That capability will emerge fairly soon in clinics, a few years to a decade from now, varying with the regulatory environment and where the products are offered. This is the true benefit of focusing on reverting the fundamental damage that is the cause of aging, rather than tinkering with later stages of disease and malfunction.
Senescent cell death brings hopes to life
Life expectancy in the developed countries is continuously increasing. However, age-related diseases lead to late life complications and remain the most prevalent cause of mortality. One of the cellular components that is present in sites of age-related pathologies and accumulates during aging is senescent cells. These cells are formed when a stress signal triggers terminal cell cycle arrest in proliferating cells. Entrance to a state of senescence deprives damaged cells of their proliferative potential and thus limits tumorigenesis and tissue damage. Despite the protective role of cellular senescence, the long term presence of senescent cells is harmful to their environment. These cells secrete a plethora of pro-inflammatory factors that might aid their removal by the immune system. However, at advanced age senescent cells gradually accumulate in tissues and the secretory phenotype promotes a chronic "sterile" inflammation which is a hallmark of unhealthy aging. Elimination of senescent cells in mice by a genetic approach led to a decreased burden of age-related disorders, and an increased median survival of the mice. Therefore, pharmacological elimination of senescent cells in-vivo is a promising strategy for treatment of age-related diseases associated with accumulation of senescent cells. An attractive method to implement this strategy would be to induce apoptosis preferentially in senescent cells. The scientific basis of this approach relies on an understanding of the molecular mechanisms that distinguish the regulation of apoptosis in senescent cells from other cells.
Resistance of senescent cells to both extrinsic and intrinsic pro-apoptotic stimuli testifies for complex regulation of apoptosis in these cells. We recently demonstrated that senescent cells, induced to senesce by different kind of insults, upregulate proteins of the anti-apoptotic BCL-2 family. Combined knockdown of these proteins or their inhibition by a small molecule inhibitor, ABT-737, selectively skew cell-fate decision in senescent epithelial cells in-vivo toward apoptosis. Therefore, the expression of BCL-2 family members endowed senescent cells with resistance to apoptosis. The senolytic activity of the ABT-737 molecule was demonstrated in in-vivo models of senescence. DNA damage-induced senescent cells were formed in the lungs upon ionizing irradiation of mice. Administration of ABT-737 rapidly reduced the number of senescent cells, concomitantly with an increase in apoptosis.
Alongside with the BCL-2 family inhibitors, other approaches for selective elimination of senescent cells, also termed senolytic approaches, have been identified. For example, the combination of 2 drugs, dasatinib and quercetin, was shown to exert killing potential of senescent preadipocyte and endothelial cells. Elimination of senescent cells could also be achieved by adapting tools from the field of cancer therapy. One such possibility is utilization of common immunotherapy practices following identification of senescence-specific markers. The immune system is a natural resource that is able to recognize and eliminate senescent cells. Using its properties in combination with immunotherapy approaches or with emerging senolytic drugs might lead to more specific and efficient elimination of senescent cells. However, no matter what would be the approach of choice, it is necessary to keep in mind that senescent cells participate in variety of essential physiological functions such as in wound healing, tumor suppression, regulation of glucose levels and embryonic development. In order to develop efficient senolytic approaches it is necessary to dissect beneficial and detrimental functions of senescent cells in different physiological and pathophysiological conditions using in-vivo models.
Successful development of senolytic drugs will bring senescent cells to the forefront of anti-aging therapies. However, it is necessary to understand the effect of elimination of senescent cells on diverse cell communications in the complex tissues. Elimination of senescent cells by ABT-737 or ABT-263 was followed by increased proliferation of stem cells in both skin and haematopoietic system. These results suggest that senolytics can have an impact on tissue regeneration and can potentially be used in regenerative medicine. This approach will combine elimination of damaged cells with stimulation of proliferation of healthy progenitors, in a way that could restore tissue fitness in diseases associated with reduced tissue function. In summary, senolytic drugs can become a future regenerative medicine. Treatment with senolytic drugs results in the elimination of senescent cells, thus blocking tissue degeneration and late life complications. In turn, elimination of senescent cells leads to the proliferation of stem cells, allowing tissue regeneration. This joined effect of senolytic drugs will restore tissue fitness and will help restraining age-related pathologies.
A Significant Association Between Periodontal Bacteria and Mortality Rates
It is fairly settled that periodontal disease, inflammation of the gums, increases the risk of developing cardiovascular disease, among other conditions. Chronic inflammation drives faster progression of all of the common age-related diseases, and gum disease is a potent source of inflammation. To pick one example from the many supporting research results, you might look to a recent study that demonstrated reduced markers of chronic inflammation achieved through nothing more than better dental hygiene. People better equipped to remove dental plaque on a daily basis exhibited reduced inflammation as a result, and that reduced inflammation will translate to a modestly lower risk and severity of a range of age-related conditions. If you dig further in the Fight Aging! archives, you'll find all sorts of unpleasant correlations involving gum disease, such as with the amyloid deposits associated with Alzheimer's disease, and with cognitive decline in general. Thus taking greater care of your teeth and gums is just a really good idea on many fronts.
An open access paper I noticed today adds more evidence to the existing body of work on this topic. Without looking at inflammation in any depth, the researchers found that specific forms of bacteria found in the mouth are associated with an elevated risk of death. Dental plaque and gum disease of course originates in the unwanted activities of bacteria resident in the mouth, but there are many different species involved. As pointed out by the researchers, it is the interactions between these species that seem as important as the presence of one or another: specific combinations appear to produce the worst outcomes, not just one type of bacteria. This is interesting research when considered in the broader context, as there is considerable enthusiasm in the dental research community in finding ways to get rid of specific bacterial species from the mouth, such as those that cause cavities, or those that build plaque and inflame the gums. This is a challenging task, unfortunately: removing bacteria from the mouth is one thing, but doing so selectively and then keeping the unwanted species from quickly returning is quite another. This is a technological capability yet to be developed into a useful and reliable form, but the benefits of achieving this goal will clearly extend far beyond the health of teeth.
Associations between Periodontal Microbiota and Death Rates
Mucosal surfaces, including the oral mucosa, are colonized by a complex and dynamic microbial ecosystem called "microbiota" that has important implications for human health and disease. While more epidemiological evidence is warranted, periodontal microbiota has been identified as a causative agent of periodontitis, which is one of the most prevalent diseases in human population. Interestingly, some animal and human observational evidence supports that periodontitis is not just an oral, in situ disease. The disease also contributes to several systemic diseases including diabetes and cardiovascular diseases (CVD). The chronic inflammatory processes of periodontitis are considered to be responsible for the etiologies. In the oral cavity, the inflammatory and immunologic reactions following periodontitis induce the production of pro-inflammatory cytokines resulting in the breakdown of periodontal epithelium and connective tissues. Systematically, the chronic trickling of periodontal microbiota into the bloodstream elicits a systemic inflammation response resulting in elevated levels of various inflammatory mediators and cross-reactive systemic antibodies, which promote risk for many systemic diseases. Importantly, it has been shown that the increased periodontitis-related all-cause and CVD mortalities are comparable with, but independent of, diabetes-related mortality.
It is believed that complex interactions between specific periodontal pathogens and different bacterial combinations are more relevant to periodontitis than are individual species. We therefore hypothesize that a similar phenomenon exists in the association between periodontal microbiota and mortality rates. To test our hypothesis, we related 21 serum immunoglobulins G (IgGs) against periodontal bacteria to the rates of all-cause, diabetes-related, and hypertension-related mortalities in a death cohort from a representative sample of the US population, the Third National Health and Nutrition Examination Survey (NHANES III). In this study, we found that two baseline serum IgG patterns, Factor 1 and Factor 2, were significantly associated with higher all-cause and/or diabetes-related mortality rates among people without history of diabetes, CVD, and cancers. While only Factor 2 was related to all-cause mortality, both Factor 1 and Factor 2 were related to diabetes-related mortality. To our best knowledge, this is the first data showing that specific oral microbiota may have an impact on the rate of death in humans.
Serum IgGs reflected human systemic response to the corresponding periodontal bacteria and studies have shown that individual periodontal bacterial quantities were significantly correlated with corresponding serum antibody levels. Therefore, the serum IgG levels can be considered as host-related phenotypes of periodontal microbiota. Our analysis showed that, although the two mortality-related IgG patterns that we characterized featured several bacteria, which were also featured in periodontitis-related complexes, they were in different combinations. It seemed that different bacterial combinations have different impacts on human health. Interestingly, our findings coincide with the hypothesis of Porphyromonas gingivali (PG) as a keystone pathogen. It is conceived that the mere presence of a keystone pathogen, even at very low colonization levels, can modulate host response in ways that alter the amount and composition of subgingival microbiota, thereby triggering adverse effects on human health. It has been demonstrated in a periodontal model that the introduction of PG, even at low numbers, in cooperation with other dysbiotic bacteria led to a marked acceleration in pathological alveolar bone loss, but PG alone failed to induce periodontitis. Importantly, our findings from Factor 1 and Factor 2 also, respectively, suggested that active periodontitis may increase diabetes-related death rate, and that, even without clinically significant periodontitis, the presence of PG at very low colonization levels increase total and diabetes-related death rate. It seemed that the elimination of PG is crucial in reducing risk for both periodontitis and mortality.
Our findings collaborated with previous observations that periodontitis, a result of polymicrobial infection, increased the risk for several major diseases, such as diabetes, CVD, cancers, and mortalities as well. The etiologies may involve several pathological consequences leading to uncontrolled inflammation, such as elevated levels of systemic proinflammatory cytokines, oxidative stress, formation of advanced glycation end products, disturbed microbe-host nutrition and metabolism interaction, etc. These mechanisms may be responsible not only for the initiation but also for the promotion and progression of the diseases as well, and thus lead to higher death rates. However, it has been shown that periodontal microbial interactions are complex and that numerous genes related to motility, metabolism, and virulence in one bacterium are differentially regulated in the presence of others. The detailed mechanisms relating specific combinations of periodontal bacteria to specific diseases or death rates warrant further study. The information would be valuable in developing personalized therapeutic and prevention strategies.
Nauk1 Inhibition as a Treatment for Tauopathies
Tauopathies are conditions in which altered forms of tau protein accumulate into solid deposits in the brain. How this causes cell death and dysfunction is comparatively poorly understood, or at least well debated, but researchers are making inroads into mapping the relevant mechanisms. As is the case for other types of misfolded or altered protein that show up in aged tissues, it isn't so much the protein itself, but rather aspects of the surrounding processes that are the cause of harm. Still, getting rid of the altered tau would be a good way to reduce all of these problems, even in absence of understanding: young tissues don't have tau and work just fine, old tissues do have it and don't work so well, and the logic moves forward from there. If in doubt, identify the fundamental differences and remove them. Alzheimer's disease is the the most familiar of tauopathies, for all that much of the research community is focused on the form of amyloid that accumulates in Alzheimer's patients. Amyloid-β in Alzheimer's is another example of a protein that forms solid deposits and is accompanied by a surrounding set of mechanisms that harm cells when the amyloid is present in large amounts. For all that amyloid-β and tau are completely different, there are many high level similarities in their separate relationships with neurodegenerative conditions. It is becoming clear that the neurofibrillary tangles of tau in Alzheimer's disease are just as important as the amyloid, though the full story of how the disease starts and progresses, and how its components interact with one another, has yet to be written.
Everyone ends up with tau and amyloid in the brain to some degree as they age; even those that live to a very late age accumulate a fair amount of the stuff. The interesting question is why some people end up with so very much more than others and slip into full blown dementia as a result. Based on the clearly established risk factors, which are much the same as those for most age-related conditions, being obesity, lack of exercise, and so forth, the triad of chronic inflammation, cardiovascular health, and metabolic syndrome are important. As for other age-related conditions, it seems to me that one of the best courses to produce near term results is to aim at the production of safe methods to clear out amyloid and tau. The research community is working hard on the former, with most of the effort going towards immunotherapies that are just now starting to produce meaningful results, but tau clearance is a fair way behind in funding and progress.
Behind doesn't mean lacking in paths forward, however, as illustrated here. The research presented below isn't clearance, however, but rather a reduction in the pace of creation of unwanted tau, achieved through mechanisms yet to be explored in great depth. For preference we'd want to see a therapy that removed tau without altering the operation of cellular metabolism - this is why immunotherapies are attractive, putting immune cells to work on the problem of clearing out the junk in a selective way, while other cells keep on doing exactly what they were doing beforehand. The problem with therapies that only slow the accumulation of damage or metabolic waste rather than removing it outright is that they are inefficient and limited in the scope of the good they can do. You have to keep taking the treatment on an ongoing basis, and you still end up in the same place in the end, just later. A therapy that removed tau could be undergone once every few years, or even less frequently, repeated only as needed to prevent pathological levels of tau from ever arising. One of the fundamental and very important problems in medicine today is that far too much research and development is focused on slowing damage rather than repairing damage.
Study reveals potential new strategy to prevent Alzheimer's disease
"Scientists in the field have been focusing mostly on the final stages of Alzheimer's disease. Here we tried to find clues about what is happening at the very early stages of the illness, before clinical irreversible symptoms appear, with the intention of preventing or reducing those early events that lead to devastating changes in the brain decades later." The scientists reasoned that if they could find ways to prevent or reduce tau accumulation in the brain, they would uncover new possibilities for developing drug treatments for these diseases. Cells control the amount of their proteins with other proteins called enzymes. To find which enzymes affect tau accumulation, the scientists systematically inhibited enzymes called kinases.
The scientists screened the enzymes in two different systems, cultured human cells and the laboratory fruit fly. Screening in the fruit fly allowed the scientists to assess the effects of inhibiting the enzymes in a functional nervous system in a living organism. "We inhibited about 600 kinases one by one and found one, called Nuak1, whose inhibition consistently resulted in lower levels of tau in both human cells and fruit flies. Then we took this result to a mouse model of Alzheimer's disease and hoped that the results would hold, and they did. Inhibiting Nuak1 improved the behavior of the mice and prevented brain degeneration. Confirming in three independent systems - human cells, the fruit fly and the mouse - that Nuak1 inhibition results in reduced levels of tau and prevents brain abnormalities induced by tau accumulation, has convinced us that Nuak1 is a reliable potential target for drugs to prevent diseases such as Alzheimer's. The next step is to develop drugs that will inhibit Nuak1 in hope that one day would be able to lower tau levels with low toxicity in individuals at risk for dementia due to tau accumulation."
In the future it might be possible to treat people at risk for Alzheimer's disease by keeping tau low. Think of how taking drugs that lower cholesterol has helped control the accumulation of cholesterol in blood vessels that leads to atherosclerosis and heart disease. "When people started taking drugs that lower cholesterol, they lived longer and healthier lives rather than dying earlier of heart disease. Nobody has thought about Alzheimer's disease in that light. Tau in Alzheimer's can be compared to cholesterol in heart disease. Tau is a protein that when it accumulates as the person ages, increases the vulnerability of the brain to developing Alzheimer's. So maybe if we can find drugs that can keep tau at levels that are not toxic for the brain, then we would be able to prevent or delay the development of Alzheimer's and other diseases caused in part by toxic tau accumulation."
Reduction of Nuak1 Decreases Tau and Reverses Phenotypes in a Tauopathy Mouse Model
Many neurodegenerative proteinopathies share a common pathogenic mechanism: the abnormal accumulation of disease-related proteins. As growing evidence indicates that reducing the steady-state levels of disease-causing proteins mitigates neurodegeneration in animal models, we developed a strategy to screen for genes that decrease the levels of tau, whose accumulation contributes to the pathology of both Alzheimer disease (AD) and progressive supranuclear palsy (PSP). Integrating parallel cell-based and Drosophila genetic screens, we discovered that tau levels are regulated by Nuak1, an AMPK-related kinase. Nuak1 stabilizes tau by phosphorylation specifically at Ser356. Inhibition of Nuak1 in fruit flies suppressed neurodegeneration in tau-expressing Drosophila, and Nuak1 haploinsufficiency rescued the phenotypes of a tauopathy mouse model. These results demonstrate that decreasing total tau levels is a valid strategy for mitigating tau-related neurodegeneration and reveal Nuak1 to be a novel therapeutic entry point for tauopathies.
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Interfering in the Spread of Alpha-Synuclein to Treat Synucleopathies
Researchers here demonstrate a method of interfering in the spread of alpha-synuclein aggregates, an approach that may slow the progression of synucleopathies such as Parkinson's disease. Like a number of other age-related neurodegenerative conditions, these are associated with and probably driven by the growing presence of specific misfolded or damaged proteins. The ideal approach is to find ways to safely remove these proteins, or understand and resolve the underlying reasons for their accumulation, both of which are paths that are so far proving to be more challenging than expected. Much of the research community remains focused on attempts to alter the late stage biochemistry of disease progression, however, as is the case here, rather than taking aim at root causes. This can be effective, but it is usually going to be much harder to prevent pathology without fixing the root causes than it is by going after those root causes.
Researchers report they have identified a protein that enables a toxic natural aggregate to spread from cell to cell in a mammal's brain - and a way to block that protein's action. The new findings hinge on how aggregates of alpha-synuclein protein enter brain cells. Abnormal clumps of alpha-synuclein protein are often found in autopsies of people with Parkinson's disease and are thought to cause the death of dopamine-producing brain cells. A few years ago, researchers published evidence for a novel theory that Parkinson's disease progresses as alpha-synuclein aggregates spread from brain cell to brain cell, inducing previously normal alpha-synuclein protein to aggregate, and gradually move from the "lower" brain structures responsible for movement and basic functions to "higher" areas associated with processes like memory and reasoning. "There was a lot of skepticism, but then other labs showed alpha-synuclein might spread from cell to cell."
The researchers knew they were looking for a certain kind of protein called a transmembrane receptor, which is found on the outside of a cell and works like a lock in a door, admitting only proteins with the right "key." They first found a type of cells alpha-synuclein aggregates could not enter - a line of human brain cancer cells grown in the laboratory. The next step was to add genes for transmembrane receptors one by one to the cells and see whether any of them allowed the aggregates in. Three of the proteins did, and one, LAG3, had a heavy preference for latching on to alpha-synuclein aggregates over nonclumped alpha-synuclein. The team next bred mice that lacked the gene for LAG3 and injected them with alpha-synuclein aggregates. "Typical mice develop Parkinson's-like symptoms soon after they're injected, and within six months, half of their dopamine-making neurons die. But mice without LAG3 were almost completely protected from these effects."
Antibodies that blocked LAG3 had similar protective effects in cultured neurons, the researchers found. "We were excited to find not only how alpha-synuclein aggregates spread through the brain, but also that their progress could be blocked by existing antibodies." Antibodies targeting LAG3 are already in clinical trials to test whether they can beef up the immune system during chemotherapy. If those trials demonstrate the drugs' safety, the process of testing them as therapeutics for Parkinsons' disease might be sped up, he says. For now, the research team is planning to continue testing LAG3 antibodies in mice and to further explore LAG3's function.
PGC-1α Gene Therapy Slows Alzheimer's Progression in Mouse Model
It is always a good idea to look closely at the biochemistry involved in any potential Alzheimer's disease therapy that shows promise in mouse models. There is perhaps more uncertainty for Alzheimer's than most other age-related conditions when it comes to the degree to which the models are a useful representation of the disease state in humans - which might go some way towards explaining the promising failures that litter the field. In the research here, the authors are aiming to suppress a step in the generation of amyloid-β, one of the proteins that aggregates in growing amounts and is associated with brain cell death in Alzheimer's disease. They achieve this goal using gene therapy to increase the level of PGC-1α, which in turn reduces the level of an enzyme involved in the production of amyloid-β. Interestingly, increased levels of PGC-1α have in the past been shown to produce modest life extension in mice, along with some of the beneficial effects to health associated with calorie restriction.
Current therapies for Alzheimer's disease (AD) are symptomatic and do not target the underlying amyloid-β (Aβ) pathology and other important hallmarks including neuronal loss. PPARγ-coactivator-1α (PGC-1α) is a cofactor for transcription factors including the peroxisome proliferator-activated receptor-γ (PPARγ), and it is involved in the regulation of metabolic genes, oxidative phosphorylation, and mitochondrial biogenesis. We previously reported that PGC-1α also regulates the transcription of β-APP cleaving enzyme (BACE1), the main enzyme involved in Aβ generation, and its expression is decreased in AD patients. We aimed to explore the potential therapeutic effect of PGC-1α by generating a lentiviral vector to express human PGC-1α and target it to hippocampus and cortex of APP23 transgenic mice at the preclinical stage of the disease.Four months after injection, APP23 mice treated with hPGC-1α showed improved spatial and recognition memory concomitant with a significant reduction in Aβ deposition, associated with a decrease in BACE1 expression. hPGC-1α overexpression attenuated the levels of proinflammatory cytokines and microglial activation. This effect was accompanied by a marked preservation of pyramidal neurons in the CA3 area and increased expression of neurotrophic factors. The neuroprotective effects were secondary to a reduction in Aβ pathology and neuroinflammation, because wild-type mice receiving the same treatment were unaffected. These results suggest that the selective induction of PGC-1α gene in specific areas of the brain is effective in targeting AD-related neurodegeneration and holds potential as therapeutic intervention for this disease.
PRG3 Promotes Neural Regeneration
Researchers here identify a protein that increases regeneration in the central nervous system following injury, or to restore lost plasticity and ability to adapt in later life. Spurring greater regrowth of damaged nerves is of great interest to the research community, and a range of approaches are underway at various stages of development. Despite promising results in animal studies so far the practical outcomes for human medicine are all fairly marginal, however. This will change in the years ahead, but at this point it is hard to say just where or when, or which of the avenues will prove to be the first one that works well enough to follow through to widespread clinical availability.
Neuronal plasticity and structural remodelling are fundamental feature of the developing nervous system and plays also an essential role during learning and injury-dependent remodelling and regeneration. In development, axons extend over long distances and form contacts with their target structure and facilitate functional connections. These neuronal connections become stabilized and restricted during maturation and secure proper functioning of the brain. Conversely, sprouting and regeneration is limited after decline of intrinsic axonal remodelling activity in aging brain and in an microenvironment rich in neurite growth inhibitors after neurological injury.
Several extracellular ligands account for the neurite growth inhibitory environment after maturation and injury. These ligands converge on the RhoA-Rho kinase pathway mediating the final signal transduction for neurite retraction and axon growth inhibition. Pharmacological and genetic interfering with the ligands Nogo/NgR or LPA promotes axonal regeneration and functional recovery after central nervous system injury. An essential step during development and regeneration is the initiation of actin-rich membrane protrusions termed filopodia or microspikes. These structures are involved in cell attachment, migration and neurite growth. Filopodia initiation and neural growth depends on cytoskeletal dynamics regulated to a large extent by the small molecular weight GTPases of the Rho family. Here, we describe the individual morphogenic activity of the integral membrane proteins Plasticity Related Genes also termed Lipid Phosphate Phosphatases Related genes (PRG 1-5 or LPPR 1-5). They are differentially expressed in the developing brain and re-expressed in regenerating axons after a lesion. In particular, PRG3 induces the formation of filopodia and promotes axonal growth. The sequence of PRG3 is highly related to PRG5 which also promotes morphological changes in neurons. However, our comparative analysis revealed a hierarchy with PRG3 displaying the strongest outgrowth promoting activity among the entire PRG family.
Transgenic adult mice with constitutive PRG3 expression displayed strong axonal sprouting distal to a spinal cord lesion. Moreover, fostered PRG3 expression promoted complex motor-behavioral recovery compared to wild type controls as revealed in the Schnell swim test (SST). Thus, PRG3 emerges as a developmental RasGRF1-dependent conductor of filopodia formation and axonal growth enhancer. PRG3-induced neurites resist brain injury-associated outgrowth inhibitors and contribute to functional recovery after spinal cord lesions. Here, we provide evidence that PRG3 operates as an essential neuronal growth promoter in the nervous system. Maintaining PRG3 expression in aging brain may turn back the developmental clock for neuronal regeneration and plasticity.
Mouse Ovary Tissue and Eggs Engineered from Cells
In the context of ongoing work on the beneficial effects of young ovaries in old mice, it is interesting to note that researchers have now managed to engineer functional mouse ovary tissue that produces eggs. The starting point was a cell sample, converted into induced pluripotent stem cells. It is a good example of the current state of the art in tissue engineering, in which many types of correctly functioning organ tissue can be produced in small amounts given just a small patient tissue sample to work with. Each tissue and organ requires its own recipe of signals and environment, and the discovery of working approaches is a slow grind, but once a methodology is established then the door is open for that particular tissue type.
Scientists have for this first time reprogrammed murine embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) into fully functional oocytes in the laboratory. In mice, oocytes are derived from primordial germ cells (PGCs), which form around day 6.5 of embryonic development. In female embryos, the PGCs make their way to what will turn into the ovary and enter meiosis to form primary oocytes, which begin to mature following puberty. Previously, researchers reported the ability to differentiate murine ESCs and iPSCs into PGC-like cells - a process that takes about five days in vivo - that could then develop into oocytes when transplanted into adult mice. The researchers also showed that mouse-derived PGCs can be used to produce fertile oocytes in the lab.
In the present study, researchers have now extended their culturing technique to encompass the entire embryonic stem cell to oocyte differentiation, which takes about 30 days in vivo. Starting with either stem cell type, the researchers first created the PGC-like cells by inducing expression of several genes and then mixed these cells with female gonadal somatic cells - which support germ cell development - to create "reconstituted ovaries" in vitro. The cells gradually lost expression of PGC markers and began to express oocyte markers. By three weeks of growth in culture, the team observed primary oocytes in meiosis prophase I within structures that resembled secondary follicles. One of the key components at this stage was the need to add an estrogen inhibitor to get the early stage oocytes to build ovarian follicles in vitro. The researchers then added follicle-stimulating hormone and two other factors to the medium and separated each follicle-like structure - inside which oocytes continued to grow for 11 more days - resembling full-size germinal vesicle oocytes. In the third phase, the germinal vesicle oocytes were cultured for one day in maturation culture medium to become meiosis II-arrested oocytes. "The stumbling block for a long time that this research group finally managed to overcome is coordination of the female germ cell development with its somatic environment at every step along the way"
Altogether, the team conducted three separate culture experiments that produced 58 reconstituted ovaries and 3,198 germinal vesicle oocytes, of which 28.9 percent matured to the meiosis II stage. Testing the quality of the meiosis II-arrested oocytes, the team found that about 78 percent had the correct number of chromosomes. Then, using RNA-sequencing on pooled oocytes, the researchers observed expression in the culture-derived oocytes comparable to that of meiosis II oocytes derived from in vivo adult and newborn pup ovaries. There were 424 genes that were either up- or downregulated compared to in vivo-derived meiosis II oocytes, particularly, mitochondrial function genes. To test whether the lab-cultured meiosis II oocytes were fully functional, the team fertilized the oocytes with wild-type sperm in vitro, and implanted the embryos into surrogate females, which resulted in healthy pups that were slightly heavier compared to wild-type pups but that developed normally and were fertile at 11 months.
The Potential Benefits of Better Dental Plaque Control
Improved control over plaque and unwanted bacteria in the mouth could improve long-term health. There is a demonstrated link between dental plaque, consequent gum disease, and whole-body inflammation. Higher levels of inflammation raise the risk of suffering heart disease and other conditions: chronic inflammation speeds the development and progression of all of the common age-related diseases. Thus any large improvement in everyday dental technology should also slightly slow the pace of degenerative aging via a reduction in inflammation. The results reported here are a very modest example of this type of progress, nothing to get too excited about: it is more in the way of a suggested change in the culture and methodology of brushing teeth. The researchers take an approach used by dentists, staining plaque to make it easier to remove, and package it for everyday use. Nonetheless, even something as simple as that can make some difference to inflammation. Consider this as a reminder to pay attention to the march of technology in this field, as the outcomes are relevant to much more than the health of teeth.
For decades, research has suggested a link between oral health and inflammatory diseases affecting the entire body - in particular, heart attacks and strokes. The results released today from a randomized trial of a novel plaque identifying toothpaste, show statistically significant reductions in dental plaque and inflammation throughout the body. Inflammation throughout the body is accurately measured by high sensitivity C-reactive protein (hs-CRP), a sensitive marker for future heart attacks and strokes. In this trial, all randomized subjects were given the same brushing protocol and received a 60-day supply of toothpaste containing either the plaque-identifying toothpaste or an identical non-plaque identifying placebo toothpaste. To assess dental plaque, all subjects utilized a fluorescein mouth rinse, and intraoral photographs were taken under black light imaging. For hs-CRP, levels were measured by an independent laboratory using an enzyme linked immunosorbent assay.
"While the findings on reducing dental plaque extend a previous observation, the findings on decreasing inflammation are new and novel." This is the first toothpaste that reveals plaque so that it can be removed with directed brushing. In addition, the product contains unique combinations and concentrations of cleaning agents that weaken the core of the plaque structure to help the subject visualize and more effectively remove the plaque. Based on these findings, researchers are drafting an investigator initiated research grant proposal to the National Institutes of Health (NIH). This large scale randomized trial will test whether the toothpaste reduces risks of heart attacks and strokes.
Mitochondrially Targeted Antioxidant Slows Alzheimer's Progression in Rat Model
There has been a fair amount of news regarding the SkQ class of mitochondrially targeted antioxidant this past year, most likely because clinical development in Europe is moving ahead. Having one or more for-profit entities involved, even when they are fairly young companies, tends to bring more funding into ongoing research, both directly and indirectly. This type of antioxidant, unlike the antioxidant supplements you can buy in a store, has been shown to modestly slow aging in short-lived laboratory species. It is theorized that additional antioxidants localized to mitochondria soak up some of the oxidants produced by the mitochondria before those molecules can damage mitochondrial DNA. Alternatively, it is possible that the more important mechanism is that a reduction in the flux of oxidants at that point leads to other beneficial changes in cell metabolism, as mitochondrial oxidants are a signaling mechanism as well as a source of damage. Certainly many of the methods shown to slow aging in the laboratory involve altered mitochondrial function, especially insofar as it relates to the rate at which oxidant molecules are generated. The effects of mitochondrially targeted antioxidants on inflammation have proven to be larger and more easily measured, however, which is why present clinical development is focused on inflammatory eye conditions. Still, a steady flow of studies like the following are emerging to show benefits in a range of animal models for various age-related conditions:
Alzheimer's disease (AD) is a progressive, age-dependent neurodegenerative disorder featuring progressive impairments in memory and cognition and ultimately leads to death. According to the most widely accepted theory, the "amyloid cascade" hypothesis, AD arises when amyloid precursor protein (APP) is processed into amyloid-β, which accumulates in plaques. There is growing evidence that mitochondrial damage and oxidative stress lead to activation of the amyloid-β cascade and, accordingly, the mitochondrial dysfunction is a significant contributing factor of the onset and progression of AD. According to the "mitochondrial cascade hypothesis" amyloid-β is a marker of brain aging, and not a singular cause of AD. Many studies have confirmed that mitochondrial dysfunction is likely to be the leading cause of synaptic loss and neuronal death by apoptosis, representing the most likely mechanism underlying cortical shrinkage, especially in brain regions involved in learning and memory, such as the hippocampus. The mitochondrial changes increase amyloid-β production and cause its accumulation, which in turn can directly exert toxic action on mitochondria, thus aggravating the neurodegenerative processes.
Here, using OXYS rats that simulate key characteristics of sporadic AD, we set out to determine the role of mitochondria in the pathophysiology of this disorder. OXYS rats were treated with a mitochondria-targeted antioxidant SkQ1 from age 12 to 18 months, that is, during active progression of AD-like pathology in these animals. Dietary supplementation with SkQ1 caused this compound to accumulate in various brain regions, and it was localized mostly to neuronal mitochondria. Via improvement of structural and functional state of mitochondria, treatment with SkQ1 alleviated the structural neurodegenerative alterations, prevented the neuronal loss and synaptic damage, increased the levels of synaptic proteins, enhanced neurotrophic supply, and decreased amyloid-β protein levels and tau hyperphosphorylation in the hippocampus of OXYS rats, resulting in improvement of the learning ability and memory. Collectively, these data support that mitochondrial dysfunction may play a key role in the pathophysiology of AD and that therapies with target mitochondria are potent to normalize a wide range of cellular signaling processes and therefore slow the progression of AD.
Calorie Restriction Protects Neurons From Excess Calcium
Calorie restriction is demonstrated to slow the progression of neurodegenerative disease in numerous species, but picking out specific relevant mechanisms from the sweeping changes in cellular behavior that occur as a result of a lower calorie intake has proven to be a challenge. The scientists involved in the research noted here focus on just one, relating to dysfunction of calcium metabolism in neurons. As might be imagined, this is the tiniest slice of the complete picture of calorie restriction and health, considered at the cellular level. A full accounting of exactly how calorie restriction works to improve health and delay aging remains to be created. It is a job of staggering size, one that must proceed in parallel with the equally large task of producing a comprehensive map of metabolism and how it changes with age. It seems plausible that researchers will still be working on this well after the first suite of rejuvenation therapies after the SENS vision are a going concern. It is fortunate that the faster and more effective approach to treating aging described in the SENS proposals exists: if it didn't, our prospects for longer, healthier lives would be far worse.
Studies of different animal species suggest a link between eating less and living longer, but the molecular mechanisms by which caloric restriction affords protection against disease and extends longevity are not well understood. The results of new in vitro and in vivo experiments include the finding that a 40% reduction in dietary caloric intake increases mitochondrial calcium retention in situations where intracellular calcium levels are pathologically high. In the brain, this can help avoid the death of neurons that is associated with Alzheimer's disease, Parkinson's disease, epilepsy and stroke, among other neurodegenerative conditions. Calcium participates in the process of communication between neurons. However, Alzheimer's disease and other neurological disorders can cause an excessive influx of calcium ions into brain cells due to overactivation of neuronal glutamate receptors. This condition, known as excitotoxicity, can damage and even kill neurons.
To verify the effect of caloric restriction on excitotoxicity, scientists compared two groups of mice and rats. The control animals were given food and water ad libitum for 14 weeks and were overweight at the end of the experiment. The other group received a 40% caloric restriction (CR) diet for the same period. In the first test, the animals were injected with kainic acid, a glutamate analogue with a similar effect in terms of inducing neuronal calcium influx, albeit more persistent. In rodents, it can cause brain damage, seizures and neuronal cell death due to overactivation of glutamate receptors in the hippocampus. It is used in the laboratory to mimic epilepsy. "We administered a small dose to avoid killing the animal. Even so, kainic acid caused seizures in the control group. It had no effect on the CR group."
The next step was to see what happened when the mitochondria isolated from each group were treated with cyclosporin, a drug known to increase calcium retention. While calcium uptake did indeed increase in the mitochondria from the control group, it remained unchanged in the CR group, eliminating the difference observed in the previous test. "Cyclosporin's target in mitochondria is well known. The drug inhibits the action of a protein called cyclophilin D, leading to increased mitochondrial calcium retention." In this case, however, cyclophilin D levels were found to be the same in both groups. The researchers therefore decided to measure the levels of other proteins that might be interfering with cyclophilin D's action in the organism. "We discovered that caloric restriction induces an increase in levels of a protein called SIRT3, which is capable of modifying the structure of cyclophilin D. It removes an acetyl group from the molecule in a process known as deacetylation, and this inhibits cyclophilin D, so that the mitochondria retain more calcium and become insensitive to cyclosporin." Just as other research groups had already found, the team also observed an increase in the activity of antioxidant enzymes such as glutathione peroxidase, glutathione reductase and superoxide dismutase in the CR rodents' mitochondria. These results suggest an enhanced capacity to manage cerebral oxidative stress, a condition that contributes to the onset of several degenerative diseases.
Enhanced Mitochondrial Catalase has Different Effects in Young and Old Mice
Mitochondria are important in aging, and this appears to be related to the generation of oxidative molecules that takes place as a side-effect of the creation of chemical energy stores. A fair number of the ways to modestly slow aging in short-lived species change the operation of mitochondria so as to also change the output of oxidants. These reactive molecules can disrupt cellular machinery, but also act as signals, so it is still far from clear as to which are the most important secondary consequences in the various contexts of interest. In the longer term, it is plausible that these oxidants are causing DNA damage in the mitochondria themselves, something that has the potential to spiral out of control to lead to dysfunctional mitochondria, a dysfunctional cell, and damage that can spread out into surrounding tissues. One potential way to suppress the output of oxidative molecules is genetic engineering to increase levels of natural antioxidant compounds localized to the mitochondria, and one of the earliest attempts to do this targeted mitochondrial catalase in laboratory mice. This has produced varied outcomes, however, ranging from little effect to slowed aging. The paper noted here might go some way towards explaining why research groups have seen mixed results from this approach, as the age of the mice used in these studies appears to be a crucial factor:
Reactive oxygen species (ROS) are associated with the progression of a broad spectrum of pathologies including aging. Mechanistically, this has largely been attributed to oxidative modification of cellular macromolecules, including lipids and proteins. While ROS have been widely regarded as a major component of aging since the 'free radical theory of aging' was proposed in the 1950s, there is an increasing appreciation that ROS also serve important physiological signaling roles. It is therefore important to closely examine both negative and positive consequences of therapeutic interventions that target ROS. Given that oxidative modifications can impair the activity of macromolecules, and the well-documented correlation between oxidative damage and aging reported in almost all models studied, it has been tempting to conclude that this is a likely mechanism for aging. However, there are many observations at odds with this theory of aging. Clinical trials of dietary antioxidants have thus far shown little to no efficacy. Some have shown adverse outcomes. In mice, deletion of many antioxidant enzymes has little effect on lifespan and, importantly, overexpression of several antioxidants including superoxide dismutase and peroxisomal catalase has failed to extend lifespan.
Our group has previously shown that mice overexpressing mitochondrial-targeted catalase (mCAT), but not nuclear or peroxisomal catalase, have an approximately 20% increased median and maximal lifespan, suggesting that reducing ROS specifically in the mitochondria is key to achieving a beneficial effect on aging. mCAT has been shown to reduce oxidative modification of DNA and proteins and delays the progression of multiple pathologies. We have also demonstrated that mCAT is protective against cardiac aging. However, it has been increasingly recognized that ROS has beneficial roles in signaling, hormesis, stress response, and immunity. We therefore hypothesized that mCAT might be beneficial only when ROS approaches pathological levels in older age and might not be advantageous at a younger age when basal ROS is low. We analyzed abundance and turnover of the global proteome in hearts and livers of young (4 month) and old (20 month) mCAT and wild-type (WT) mice. In old hearts and livers of WT mice, protein half-lives were reduced compared to young, while in mCAT mice the reverse was observed; the longest half-lives were seen in old mCAT mice and the shortest in young mCAT. Protein abundance of old mCAT hearts recapitulated a more youthful proteomic expression profile. However, young mCAT mice partially phenocopied the older wild-type proteome. Age strongly interacts with mCAT, consistent with antagonistic pleiotropy in the reverse of the typical direction. These findings underscore the contrasting roles of ROS in young vs. old mice and indicate the need for better understanding of the interaction between dose and age in assessing the efficacy of therapeutic interventions in aging, including mitochondrial antioxidants.
Exploring the Mechanisms of Neural Regeneration in Zebrafish
Highly regenerative species such as zebrafish can regrow limbs and organs, and are also capable of far greater regrowth in response to damage in the brain than is the case in mammals. Researchers here explore the mechanisms involved in the zebrafish response to an Alzheimer's-like environment and neural cell death. As is the case for many research projects involving zebrafish, the goal is to pin down enough of the biochemistry of exceptional regeneration to understand how it differs from humans, and thus how this capability might be recreated in our species.
Zebrafish have an extensive ability to replenish the lost neurons after various types of damage, and the researchers have shown that it can also do so after Alzheimer-like neurodegeneration. This is an ability humans do not have. Evolutionarily, the zebrafish and human beings are very similar: the cell types in the zebrafish brain and their physiological roles are very similar to humans, and more than 80 percent of the genes humans have are identical in the zebrafish. Therefore, zebrafish are an ideal model for studying complex diseases of humans in a very simplistic way. "We believe that understanding how zebrafish can cope with neurodegeneration would help us to design clinical therapy options for humans, such as for Alzheimer's disease. Within this study, we observed Alzheimer-like conditions in the fish brain. We found that zebrafish can impressively increase the neural stem cell proliferation and formation of new neurons even after Alzheimer's-like pathology. This is amazing because to treat Alzheimer's we need to generate more neurons. And this all starts with neural stem cell proliferation, which fails in our diseased brains."
This study has shown that Alzheimer's disease symptoms can be recapitulated in the zebrafish brain using a short section of human APP protein that is a hallmark of Alzheimer's disease (Amyloid-β42). This protein part causes the death of neurons, inflammation, loss of neuronal connections and deficits in memory formation in zebrafish. The researchers found that the immune-related molecule Interleukin-4 (which is also present in the human brain) is produced by the immune cells and dying neurons in the fish brain. This molecule alerts the neural stem cells that there is danger around. Stem cells then start to proliferate through a cell-intrinsic mechanism involving another protein of central function called STAT6. The importance of this study lies in the notion that the diseased brain and the inflammatory milieu there can be modulated to kick-start neural stem cell proliferation, and this is exactly what successfully regenerating vertebrates do. The next steps towards an understanding of Alzheimer's disease are clearly defined: "We will go on identifying more factors required for a successful 'regeneration' response in fish brain after an Alzheimer's disease-like situation. By doing so, we can get a more complete picture of the molecular programs beneficial for tackling this atrocious disease. Zebrafish will tell us the candidate genes we should focus on in our brains for possible regenerative therapies."
Why the Lingering Pockets of Hostility Towards SENS Rejuvenation Research?
There are still people who really don't like SENS rejuvenation research, both within and outside the scientific community. This contingent has faded over time as the funding for SENS-related research programs increased and more teams produced meaningful results in SENS-related areas such as allotopic expression of mitochondrial genes and senescent cell clearance. There are numerous research groups working on aspects of that latter project at the moment, as well as funded startup companies moving towards clinical translation of therapies. These days one has to have a very selective memory and view of the world to mock SENS, since the SENS proposals have included senescent cell clearance as a potential treatment for aging since the beginning, based on the broad range of evidence available in the scientific community even then. SENS advocates have for near fifteen years been calling for greater funding and progress in selective senescent cell destruction as one possible and plausible method of rejuvenation - and with mouse life span studies in hand now, that has been shown to be the case. Nonetheless, there are those who still propagate the irrational view that SENS isn't a legitimate part of the medical science community. One has to wonder what the true motivation is here; perhaps these people are one reason or another are uncomfortable with the idea that aging is a medical condition amenable to treatment. That seems to me a rather sad, resigned, and limited conceptual space to find oneself in, if it is the case.
You probably are not aware that, earlier this month, there was a bit of a Facebook flamewar between a few SENS opposers and some life-extensionists, some (or even all, I don't know) of whom were SENS supporters. This incident got me thinking. Why does SENS face such a fierce opposition? Why all these clearly emotional, gut-driven reactions? A lot of people over the years have raged against SENS and labelled it as quack science, a fraud, nonsense, and what you have, while having no evidence that this was the case. Sure, SENS is not fully established science yet, and who knows, maybe it will never be; we don't know for a fact. But isn't this case with tons of other research projects? Isn't the very purpose of research to establish what works and what doesn't? If SENS critics are so sure that SENS will never work, they really don't need to bother throwing challenges to disprove it and attacking it so ferociously. They could just sit back and watch as the SENS Research Foundation prove themselves wrong through their own research. On top of that, even if SENS were wrong, all the data coming from their work will certainly prove itself invaluable for future research endeavours. Win-win.
Personally, I came to the conclusion that what caused SENS to be so unpopular (at least initially) amongst the experts of the field might be its clearly stated goal of curing ageing. Biogerontologists are not immune to the pro-ageing trance by default; also, as far as I know, at the time when Aubrey de Grey first introduced SENS to the world he was practically unknown and quite new on the scene. To top it all, he was from a different field. I can see how other experts would be rather pissed at an outsider who comes out of nowhere and claims he's got the solution to a problem they mostly weren't even trying to solve. Maybe SENS wouldn't have faced any opposition if it had kept a low profile and disguised itself as mere research-for-the-sake-of-research, as it was customary in the field of gerontology back in the day.
On the other hand, people like David Sinclair and Bill Andrews too are set on bringing ageing under medical control, and to the best of my knowledge, they don't face nearly the same opposition as SENS does. Maybe it's because they followed a more traditional career path than Aubrey de Grey. Maybe their approaches are more orthodox, or maybe SENS has more media exposure and thus is more likely to be criticised. Maybe it's because of Aubrey's bold claim that the first person to reach 1000 years of age has already been born. People generally don't get this one right. He does not say that we will soon develop therapies that will make us live 1000 years. That doesn't even make sense in the context of SENS, which is a panel of therapies that would need to be periodically reapplied. What Aubrey says is that we'll probably get around 30 extra years of healthy life with the first round of SENS; during this time, perfected versions of the same therapies are likely to have been developed, granting even more extra years of healthy living, and so on. This concept is known as longevity escape velocity. I don't know for a fact why SENS faces such fierce criticism. All I know is that, quite likely, if Aubrey de Grey hadn't been shouting from the rooftops for the past 16 years that we can and should cure ageing, this tremendous problem wouldn't be receiving nearly as much attention as it does today.