Greater Waist Circumference, Greater Risk of Dementia

In recent years, epidemiologists have found that waist circumference is a better measure of the burden of excess visceral fat tissue than body mass index (BMI). Progress towards making better use of this information has been slow, as is usually the case in the world of epidemiology. Visceral fat tissue generates chronic inflammation through a variety of mechanisms, from DNA debris activating the immune system to inappropriate signaling by fat cells to an accelerated pace of generation of senescent cells. Chronic inflammation disrupts function and accelerates the progression of all of the common age-related conditions. People who are overweight have a shorter life expectancy and higher lifetime medical costs as a result.

A 2015 large-scale retrospective cohort study of nearly 2 million people from the United Kingdom Clinical Practice Research Datalink showed that the incidence of dementia continued to fall for every increasing BMI category. Two Mendelian randomization studies showed no association between obesity and dementia. BMI is not a perfect measure of adiposity because it cannot discriminate between fat and lean body mass. Waist circumference is a more accurate indicator of abdominal visceral fat level than body mass index (BMI) in the elderly. Studies have been limited, however, and focused on the relationship between waist circumference and dementia in older persons. One study showed that central adiposity, represented by waist circumference, predicted an increased risk for cognitive decline during a 2-year follow-up period in older patients with diabetes. Another study reported that waist circumference was correlated with lower overall cognition and executive performance in older women with type 2 diabetes.

To help determine a healthy waist circumference, researchers compared relative risk of dementia associated with waist circumference and BMI categories using the Korea National Health Insurance Service program. The program is a mandatory social health insurance program that enrolls about 98 percent of Koreans who participate in biannual standardized health examinations. The study population comprised 872,082 participants aged 65 years and older who participated in the Korean national health screening examination between January 1, 2009 and December 31, 2009. The study population was observed from baseline until the date of development of dementia, death, or until December 31, 2015, whichever came first.

The results of the study showed participants with a waist circumference of greater than or equal to 90cm for men and 85cm for women had a significantly increased risk of dementia after adjusting for other factors such as age, BMI, blood pressure, cholesterol, liver function tests and various lifestyle factors. As for the association between BMI categories with dementia in older men and women who were underweight, they experienced a significant increased risk of dementia compared with normal weight individuals after factoring in comorbidities and various lifestyle factors. The relationship with BMI and dementia may be a result of the adverse effects of sarcopenia in the elderly.

Link: https://www.eurekalert.org/pub_releases/2019-11/tos-hwc103119.php

Selectively Removing Mutant Proteins by Binding them to Autophagy Components

Researchers here demonstrate a proof of principle for an interesting approach to tackling the aggregation of damaged, altered, or misfolded proteins that is a feature of most neurodegenerative conditions. They target the mutant huntingtin protein, which is probably an easier task than targeting, say, a misfolded protein with a normal sequence. The basic idea is to deploy a linking molecule that binds to the problem protein with high specificity, and also binds to an essential component of autophagy - in this case LC3B, involved in the generation of autophagosomes responsible for carrying materials to lysosomes. This ensures that the whole linked set of molecules is dragged into an autophagosome and transported to a lysosome where it is broken down and recycled.

Several neurodegenerative diseases involve the slow accumulation of a misfolded protein in neurons over many years. The proteins involved in these diseases might differ, but the result is similar - eventually, the neurons die from the build-up of toxic misfolded proteins. Scientists have long been searching for ways to reduce the levels of the disease-driving proteins without also clearing their wild-type counterparts, which typically have myriad crucial functions. Researcher snow show that this can be accomplished using compounds that interact specifically with both the misfolded part of the protein and the neuron's protein-clearance machinery.

The researchers chose to focus on Huntington's disease, which is caused by an abnormally long stretch of glutamine amino-acid residues in the huntingtin (HTT) protein. This expanded polyglutamine tract causes HTT to misfold. Cells are able to degrade the mutant huntingtin (mHTT) through autophagy - a clearance mechanism that involves engulfment of proteins by a vesicle called the autophagosome. Researchers hypothesized that compounds that bind to both the mutant polyglutamine tract and the protein LC3B, which resides in the autophagosome, would lead to engulfment and enhanced clearance of mHTT. But no such compounds had been reported. The authors therefore conducted small-molecule screens to identify candidate compounds.

Researchers initially identified two candidates, dubbed 10O5 and 8F20. These compounds had been shown to inhibit, respectively, the activity of the cancer-associated protein c-Raf and kinesin spindle protein (KSP), which has a key role in the cell cycle. The team found that 10O5 and 8F20 were able to clear mHTT independently of their effects on these other proteins. The researchers showed that the regions of 10O5 and 8F20 that interacted with mHTT and LC3B in the screen shared structural similarities. Next, they screened for compounds that shared these structural properties but were structurally distinct. This led them to discover two more compounds, AN1 and AN2, that link mHTT to LC3B and thereby selectively reduce levels of mHTT.

Researchers validated their discovery by showing that the four compounds reduced levels of the full-length mHTT protein (not just the protein fragment used in the screen). The compounds lowered levels of mHTT both in vitro - in mouse neurons and neurons derived from the biopsied skin cells of people with Huntington's disease - and in vivo, in mouse and fly models of the disease.

Link: https://doi.org/10.1038/d41586-019-03243-7

Poor Results from an Initial Human Trial of Nicotinamide Mononucleotide

Mitochondria are the power plants of the cell, responsible for packaging energy store molecules that power cellular processes. NAD+ is an essential metabolite for mitochondrial function, but levels decline with age. The proximate causes of this decline are fairly well mapped, and involve insufficient resources in a variety of pathways for synthesis or recycling of NAD+. The deeper reasons are poorly understood, however, meaning how these pathway issues emerge from the underlying molecular damage to cells and tissues that causes aging. Ways to force an increase in NAD+ levels have been shown to improve mitochondrial function in old animals, reversing some of the losses that occur with age. Loss of mitochondrial function is implicated in age-related diseases, particularly those in energy-hungry tissues such as the brain and muscles.

There are a number of ways to raise NAD+ levels: delivery of sizable amounts of NAD+ directly via infusion, of which a tiny fraction makes it into cells where it is needed; delivery of various precursor molecules that are used to manufacture NAD+; or delivery of factors known to improve recycling of NAD+. Most present effort is focused on the second of those options, via supplements such as nicotinamide riboside or nicotinamide mononucleotide, though groups like Nuchido are trying to produce better means of raising NAD+ levels that target multiple mechanisms at once.

Nicotinamide riboside has been trialed in humans, in a small number of people, with data showing reductions in age-related increases in blood pressure through improvement in the function of vascular smooth muscle. A similarly small trial of nicotinamide mononucleotide took place in Japan, and in today's open access paper, the researchers involved report on the results. As you can see from their summary, this approach achieved none of the benefits noted in the trial of nicotinamide riboside. At least some of the patients were old enough to expect some positive outcome on blood pressure, but none was observed.

Recent studies have revealed that decline in cellular nicotinamide adenine dinucleotide (NAD+) levels causes aging-related disorders and therapeutic approaches increasing cellular NAD+ prevent these disorders in animal models. The administration of nicotinamide mononucleotide (NMN) has been shown to mitigate aging-related dysfunctions. However, the safety of NMN in humans have remained unclear. We, therefore, conducted a clinical trial to investigate the safety of single NMN administration in 10 healthy men of 40 to 60 years of age.

A single-arm non-randomized intervention was conducted by single oral administration of 100, 250, and 500 mg NMN. Clinical findings and parameters, and the pharmacokinetics of NMN metabolites were investigated for 5 hours after each intervention. Ophthalmic examination and sleep quality assessment were also conducted before and after the intervention.

The single oral administrations of NMN did not cause any significant clinical symptoms or changes in heart rate, blood pressure, oxygen saturation, and body temperature. Laboratory analysis results did not show significant changes, except for increases in serum bilirubin levels and decreases in serum creatinine, chloride, and blood glucose levels within the normal ranges, independent of the dose of NMN. Results of ophthalmic examination and sleep quality score showed no differences before and after the intervention. Plasma concentrations of N-methyl-2-pyridone-5-carboxamide and N-methyl-4-pyridone-5-carboxamide were significantly increased dose-dependently by NMN administration. The single oral administration of NMN was safe and effectively metabolized in healthy men without causing any significant deleterious effects. Thus, the oral administration of NMN was found to be feasible, implicating a potential therapeutic strategy to mitigate aging-related disorders in humans.

Link: https://doi.org/10.1507/endocrj.EJ19-0313

Cardiovascular Aging Contributes to Brain Aging

The brain is an energy-hungry organ, and is sensitive to reductions in the blood supply of oxygen and nutrients. Cardiovascular aging can reduce that supply, whether through conditions such as heart failure, or the progressive loss of density in capillary networks that occurs throughout the body with advancing age, or an accelerated pace of rupture of tiny vessels in the brain, or disruption of the blood-brain barrier, allowing unwanted molecules and cells to enter the brain. Thus, as researchers here note, we would expect to see correlations between cardiovascular disease, or risk factors for cardiovascular disease, and damage and dysfunction in the brain.

Age-related changes in the cerebrovascular system include structural reorganization of the vascular beds, reduced vessel elasticity, and disintegration of the blood-brain barrier. Further observations include reduced cerebral perfusion, and increased lesion burden in the cerebral white matter. Lesions can be observed as white-matter hyperintensities (WMHs) upon magnetic resonance imaging (MRI). They arise from ischemia, hypoperfusion, blood-brain-barrier breakage, and inflammation and are considered manifestations of cerebral small-vessel disease. WMHs are highly prevalent in aging and predictive of broad-ranged cognitive decline, dementia, and mortality.

Dopamine (DA) has been identified as an important modulator of cognitive functions. Maladaptive DA signaling typically gives rise to cognitive impairment, whereas increased DA transmission, if not excessive, may improve performance. Numerous positron emission tomography (PET) studies have demonstrated reduced availability of DA constituents in older individuals, with links to reduced cognitive performance. The age sensitivity of the DA system has therefore been suggested to modulate cognitive trajectories in aging. Research suggests relationships among vascular function, DA status, and atrophy in pathological and normal aging. Cognitive impairments in Parkinson's disease (PD) have been related to deficits in perfusion and DA decline, which are exacerbated in presence of WMHs. Increased WMH burden in normal aging is paralleled by decreased grey-matter and white-matter volume, and has been associated with reduced DA transporter and D1 receptor availability.

Thus we evaluated the interrelation among WMH burden, cerebral perfusion, DA D2-receptor (D2DR) availability, grey- and white-matter structure, and cognition in 181 healthy, older adults aged 64-68 years. Higher cardiovascular risk as assessed by treatment for hypertension, systolic blood pressure, overweight, and smoking was associated with lower frontal cortical perfusion, lower putaminal D2DR availability, smaller grey-matter volumes, a larger number of white-matter lesions, and lower episodic memory performance. Taken together, these findings suggest that reduced cardiovascular health is associated with poorer status for brain variables that are central to age-sensitive cognitive functions, with emphasis on DA integrity.

Link: https://doi.org/10.1002/acn3.50927

The MicroRNA mir-83 Disrupts Autophagy in Aging Nematode Worms

Researchers here find a proximate cause of age-related impairments in autophagy in nematode worms. The cellular maintenance processes of autophagy, responsible for recycling unwanted and damaged molecules and structures, are well known to decline with age. This dysfunction contributes to numerous age-related conditions, particularly in tissues containing significant populations of very long-lived cells, in which the build up of damaged components becomes disruptive to function. Upregulation of autophagy, on the other hand, is a feature of many interventions shown to slow aging in laboratory species. In some cases, as for calorie restriction, autophagy is required for the beneficial effects on life span.

Macroautophagy, a key player in protein quality control, is proposed to be systematically impaired in distinct tissues and causes coordinated disruption of protein homeostasis and ageing throughout the body. Although tissue-specific changes in autophagy and ageing have been extensively explored, the mechanism underlying the inter-tissue regulation of autophagy with ageing is poorly understood. Here, we show that a secreted microRNA, mir-83, homologous to mammalian miR-29, controls the age-related decrease in macroautophagy across tissues in Caenorhabditis elegans.

Upregulated in the intestine by hsf-1 with age, mir-83 is transported across tissues potentially via extracellular vesicles and disrupts macroautophagy by suppressing CUP-5, a vital autophagy regulator, autonomously in the intestine as well as non-autonomously in body wall muscle. Mutating mir-83 thereby enhances macroautophagy in different tissues, promoting protein homeostasis and longevity.

Our results not only show that a secreted microRNA is an inter-tissue messenger controlling autophagy for protein homeostasis but also indicate that tissues other than the nervous system (e.g., the intestine) broadcast signals for protein homeostasis throughout the body. Similarly, transcellular chaperone signaling from muscle to intestine and neurons is important in the response against proteotoxic stress.

Link: https://doi.org/10.1038/s41467-019-12821-2

TRIB1 Regulates Uptake of Oxidized Lipids into Macrophages, and thus Drives Atherosclerosis

Atherosclerosis is a condition of dysfunctional macrophages. Macrophages are responsible for clearing out lipids that end up in blood vessel walls, ingesting these misplaced lipid molecules and handing them off to HDL particles to be carried to the liver for excretion. This works just fine in youth, in an environment of low oxidative stress and few oxidized lipids. Aging brings chronic inflammation, oxidative stress, and oxidized lipids, however. Macrophages cannot process oxidized lipids all that well, and so become pathological, turning into inflammatory foam cells packed with lipids, and unable to do more than send signals for help. The plaques that form to narrow and weaken blood vessels in atherosclerosis might start out as lipid deposits, but become macrophage graveyards as they grow, as ever more macrophages arrive to try and fail to clear the damage.

A number of new approaches to atherosclerosis based on interfering in this process are under development. My company, Repair Biotechnologies, works on a way to allow macrophages to break down oxidized cholesterol in situ. Underdog Pharmaceuticals works on sequestration of the worst oxidized lipid, 7-ketocholesterol. And so forth. The work here, in which researchers identify the gene TRIB1 as a regulator of macrophage uptake of oxidized lipids, offers a new avenue of attack. The evidence presented is fairly compelling for some form of inhibition of TRIB1 to be the basis for a therapy. If this could be done for an extended period of time, then in principle atherosclerosis could be reversed, as macrophages become able to go about their duties and meaningfully clean up atherosclerotic lesions.

Sheffield scientists identify new potential treatment pathway for cardiovascular disease

Research has shown for the first time that a protein expressed in a subset of immune cells contributes towards the build-up of fatty deposits in arteries, which leads to cardiovascular disease. These fatty deposits are caused by macrophages, a subset of immune cells known to take up surplus cholesterol. When this is present in excess, they mature into larger cholesterol-laden cells known as foam cells which accumulate and cause blockages inside arteries. The study shows for the first time that levels of a protein called Tribbles-1 (TRIB1) inside macrophages controls the amount of oxidized cholesterol taken up by foam cells. The research shows that higher levels of TRIB1 increased specific cholesterol uptake receptors, promoting arterial disease, whereas decreasing TRIB1 reduced disease. The findings of this study suggest that inhibiting TRIB1 in macrophages could be a viable therapeutic target in treating cardiovascular disease.

Myeloid Tribbles 1 induces early atherosclerosis via enhanced foam cell expansion

Atherosclerosis, a progressive disease of arterial blood vessels and the main underlying cause of stroke, myocardial infarction, and cardiac death, is initiated by the conversion of plaque macrophages to cholesterol-laden foam cells in the arterial intima. In the early-stage atherosclerotic plaque, this transformation is induced by the uptake of both low density lipoprotein-cholesterol (LDL-C) and oxidized LDL (oxLDL), which may serve a beneficial purpose; but unrestrained, the crucial function of plaque macrophages in resolving local inflammation is compromised, and the development of unstable, advanced lesions ensues.

Tribbles 1 (Trib1) has been detected in murine plaque-resident macrophages, and variants at the TRIB1 locus have been associated with increased risk of hyperlipidemia and atherosclerotic disease in multiple populations. However, no study had examined the macrophage-specific cellular processes dependent on myeloid-specific Trib1 expression and how these tally with the assumed atheroprotective properties of this pseudokinase. At the whole-body level, one study has shown that Trib1-deficient mice have markedly reduced numbers of M2-like macrophages in multiple organs, including adipose tissue. Hence, these studies strongly implicated that loss of macrophage-Trib1 expression within the arterial wall would lead to excessive atherosclerotic plaque inflammation and/or impair inflammation resolution and promote atheroma formation.

In the current study, we found that contrary to expectations, myeloid-specific knockout of Trib1 is atheroprotective, while myeloid-specific Trib1 expression is detrimental. In brief, Trib1 increased OLR1 RNA and protein expression, oxLDL uptake, foamy macrophage formation, and atherosclerotic burden in two distinct mouse models of human disease. The expression of these two genes, as well as those of LPL and SCARB1 (which mediates selective HDL-cholesterol uptake), is also tightly linked in human macrophages. Collectively, our studies reveal an unexpected beneficial effect for selectively silencing Trib1 in arterial plaque macrophages.

Reviewing Leucine Supplementation as a Treatment for Sarcopenia

Sarcopenia is the name given to the characteristic loss of muscle mass and strength that takes place with advancing age. A surprisingly large fraction of this loss is self inflicted: few people undertake the necessary exercise and strength training to maintain muscle in later life. But the rest of the losses are to some degree inevitable, a consequence of damage and disarray in muscle stem cells, neuromuscular junctions, and various processes necessary to muscle tissue maintenance. There is evidence for one those issues to be a growing inability to process leucine, an essential amino acid. Leucine supplementation may thus slow the onset of sarcopenia, even while being a compensatory approach that in no way addresses the underlying causes of this form of age-related degeneration.

One of the main ways in which sarcopenia contributes to disease is that it alters muscular turnover and metabolism. Moreover, older adults exhibit a decreased anabolic response to protein feeding, which is a mechanism underpinning the loss of muscle mass in sarcopenic individuals. Compared to younger adults, those aged over 65 years require ∼70% more protein per meal to maximally stimulate muscle protein synthesis. Furthermore, at a global level, only 40% of older adults meet the recommended daily allowance for protein (0.8 g/kg/day) and 10% of older women do not even meet the estimated average requirement of 0.66 g/kg/day.

One strategy to increase the muscle protein synthesis that has been investigated is the supplementation of diets with leucine, an essential branched-chain amino acid with important regulatory actions in muscles, which are at least partially mediated by the mammalian target of the rapamycin pathway. Leucine modifies protein turnover in skeletal muscles, by decreasing proteolysis and by increasing protein synthesis. Physiological research reports have shown that leucine can enhance muscle protein-synthesis. Furthermore, leucine can stimulate insulin release by pancreatic cells, showing that besides its beneficial effect in enhancing skeletal muscle glucose uptake, it is also an important anabolic signal in skeletal muscle.

Based on the above, administration of leucine-containing supplements is therefore a promising approach for treating sarcopenia. We took a systematic approach to analysing the current scientific evidence in this area, and to ascertaining whether the administration of leucine-containing supplements is effective in the treatment of sarcopenia. We also included interventions that used whey protein as a supplement, because these contain large amounts of leucine (approximately 13 g leucine/100 g protein) and the consumption of whey protein appears to be the most effective at increasing muscle protein synthesis.

In overall terms, published study results show that administration of leucine or leucine-enriched proteins (in a range of 1.2 g to 6 g leucine/day) is well-tolerated and significantly improves sarcopenia in elderly individuals, mainly by improving lean muscle-mass content and in this case most protocols also include vitamin D co-administration. The effect of muscular strength showed mixed results, however, and the effect on physical performance has seldom been studied.

Link: https://doi.org/10.3390/nu11102504

3-D Printing of Skin with Embedded Vasculature

Researchers continue to take incremental steps towards the creation of engineered living tissues containing the vascular networks needed to support it. Absent blood vessels, numerous varieties of functional tissue can be generated from cell samples: lung, liver, kidney, and so forth. These organoids are limited in size to a few millimeters, however, the distance the nutrients and oxygen can perfuse. Generating blood vessel networks is a serious technical challenge, and the major obstacle to the production of entire organs for transplantation. Consider that natural capillary networks exhibit a density of hundreds of vessels passing through every square millimeter of tissue cross-section. Even the best of present efforts are distant from that scale, though in laboratory demonstrations they suffice to produce essentially functional larger tissue sections.

Researchers have developed a way to 3D print living skin, complete with blood vessels. The advancement is a significant step toward creating grafts that are more like the skin our bodies produce naturally. "Right now, whatever is available as a clinical product is more like a fancy Band-Aid. It provides some accelerated wound healing, but eventually it just falls off; it never really integrates with the host cells."

A significant barrier to that integration has been the absence of a functioning vascular system in the skin grafts. Researchers have been working on this challenge for several years, previously showing that they could take two types of living human cells, make them into "bio-inks," and print them into a skin-like structure. Researchers now show that if they add key elements - including human endothelial cells, which line the inside of blood vessels, and human pericyte cells, which wrap around the endothelial cells - with animal collagen and other structural cells typically found in a skin graft, the cells start communicating and forming a biologically relevant vascular structure within the span of a few weeks.

"As engineers working to recreate biology, we've always appreciated and been aware of the fact that biology is far more complex than the simple systems we make in the lab. We were pleasantly surprised to find that, once we start approaching that complexity, biology takes over and starts getting closer and closer to what exists in nature." Once the team grafted the engineered tissue onto a mouse, the vessels from the printed skin began to communicate and connect with the mouse's own vessels. In order to make this usable at a clinical level, researchers need to be able to edit the donor cells using something like the CRISPR technology, so that the vessels can integrate and be accepted by the patient's body. "We are still not at that step, but we are one step closer,."

Link: https://news.rpi.edu/content/2019/11/01/living-skin-can-now-be-3d-printed-blood-vessels-included

Cardiomyocytes Expressing SOX10 are Vital to Zebrafish Heart Regeneration

A few higher animal species, such as salamanders and zebrafish, are capable of regeneration of limbs and internal organs, regrowing lost and injured tissue without scarring or loss of function. Numerous research groups are engaged in investigating the biochemistry of proficient regeneration, attempting to find the specific differences between species that might explain how it happens and why adult mammals are largely incapable of such feats of regrowth. Today's open access research is an example of the type, in which the authors narrow down on a specific cell population that appear in zebrafish hearts during regeneration, but not in human tissues.

It may be the case that the mechanisms and capacity for adult regeneration do still exist in mammals, but are suppressed in some way, as suggested by the fact that the human ARF gene can shut down zebrafish regeneration. After all, we all managed to undertake the process of growing organ tissue during embryonic development. Alternatively perhaps a single crucial part of the adult regeneration mechanisms was lost over evolutionary time, and thus there is an opportunity to reinsert it into mammalian tissues via gene therapy or some other form of modern biotechnology. It still remains to be seen as to whether there are simple paths towards enabling greater adult mammalian regeneration, or, as seems equally likely, the situation is a complex mess that will take decades to decipher, and offers no easy path to therapy.

Special cells contribute to regenerate the heart in Zebrafish

In mammals, including humans, the heart muscle has a very limited capacity to recover after injury. After an acute myocardial infarction, millions of cardiac muscle cells, named cardiomyocytes, die, and are replaced by a scar. Unlike mammals, other vertebrates can recover much better from a cardiac damage. This is the case of some fish, including the zebrafish, a well-established animal model in biomedical research which shares with humans most of its genes.

Zebrafish are extremely well suited to study organ regeneration. After heart injury, zebrafish cardiomyocytes can divide and the scar is replaced by new cardiac muscle. Now the researchers show that not all cardiomyocytes in the zebrafish heart contribute equally to regenerate the lost muscle, but that there is a specific subset of cardiomyocytes with enhanced regenerative capacity.

A small subset of cardiomyocytes in the zebrafish heart, marked by sox10 gene expression, expanded more than the rest of myocardial cells in response to injury. These cells differed from the rest of the myocardium also in their gene expression profile, suggesting that they represented a particular cell subset. Furthermore, experimental erasure of this small cell population, impaired heart regeneration. The researchers want to find out whether the absence of such a sox10 cell population in mammals could explain why their heart does not regenerate well. If this is the case, the researchers believe that this finding could be of great importance in stimulating the repair process in the human heart.

Adult sox10+ Cardiomyocytes Contribute to Myocardial Regeneration in the Zebrafish

Like mammals, zebrafish cardiomyocytes (CMs) derive from first and second heart field progenitors. However, in the zebrafish, the neural crest represents a third progenitor population that contributes to the developing heart. Cell transplantation and fluorescent dye tracing experiments suggested that cardiac neural crest cells incorporate not only into the areas of the outflow tract, as in mammals and birds, but also into the atrium and ventricle. Moreover, genetic lineage tracing using sox10 as a neural crest cell marker revealed a cellular contribution of sox10+ cells to the zebrafish heart and suggested that sox10-derived CMs are necessary for correct heart development. Noteworthy, it is still unclear if a sox10+ neural crest population differentiates into CMs or if alternatively, a sox10+ CM subset is relevant for heart development.

Here, we assessed the contribution of sox10-derived cells to the adult zebrafish heart. We found that embryonic sox10-derived cells contributed to significant portions of the adult heart. We also identified adult sox10+ CMs that expanded to a higher degree upon injury than other CMs and significantly contributed to cardiac regeneration. Their transcriptome differed from other CMs in the heart, and their genetic ablation impaired recovery from ventricular injury.

Extracellular Vesicles from Embryonic Stem Cells Make Mesenchymal Stem Cells More Effective in Therapy

Mesenchymal stem cell (MSC) is a category so broad as to be near meaningless, but many varieties are widely used for therapeutic purposes. MSCs are taken from any one of a variety of sources, expanded in culture, and introduced to the patient. Researchers here show that applying extracellular vesicles from embryonic stem cells to the cultured MSCs reduces the usual issues that arise when expanding cells in culture, such as senescence, and improves the effectiveness of MSCs as a therapy when tested in mice. On a practical basis, one would imagine that induced pluripotent stem cells would serve just as well as a source of extracellular vesicles with this capability.

Mesenchymal stem cells (MSCs), derived from several kinds of tissues such as placenta, umbilical cord, bone marrow, and adipose tissue, are multipotent stem cells that can differentiate into many cell types. MSCs have been recognized as important candidates for the treatment of many degenerative diseases or injuries. Furthermore, MSCs can be expanded by continuously passage in vitro, to obtain a sufficient number of cells that can be used for clinical applications. Along with the continuous passage in vitro, MSCs exhibit the senescence-associated features, including enlarged morphology, irreversible growth arrest, enhanced SA-β-gal activity, decreased stemness of stem cells, increased cell apoptosis and DNA damage foci, and telomere attrition.

For senescent MSCs, the characteristics of stem cell are lost, and their therapeutic effects are limited. Therefore, researchers attempt to find a better way to block the cellular senescence. Mouse embryonic stem (ES) cells, derived from the blastocyst stage embryos, are distinguished by their ability to self-renew and differentiate into all cell types. The major barriers to the possible transplantation of ES cells into patients are immune rejection and the risk of forming tumors. It has been reported that conditioned medium from ES cells (ES-CM) has beneficial effects on cell proliferation and tissue regeneration via the factors secreted from ES cells.

Recently studies suggested that extracellular vesicles (EVs), which are biological particles released by many cell types, could be considered for therapeutic utility. The EVs transfer proteins and nucleic acids between cells and play an important role in the target cells. Moreover, EVs isolated from various types of stem cells have different properties such as anti-apoptosis, pro-angiogenesis, and anti-fibrosis. In this study, we explored the effects of EVs derived from ES cells (ES-EVs) on the senescent MSCs. Our results indicated that ES-EVs rejuvenated the senescent MSCs and enhanced their therapeutic effects in a mouse cutaneous wound model.

Link: https://doi.org/10.7150/thno.35305

Success for the MitoMouse Crowdfunding Project

The latest mitochondrial rejuvenation research project to be crowdfunded by the Lifespan.io and SENS Research Foundation teams focused on proving out allotopic expression of mitochondrial gene ATP8 in mice with a loss of function mutation in that gene. I'm pleased to note that the community rallied around and the project was fully funded, including its stretch goals.

Mitochondria have their own small genome; allotopic expression is the process of placing a copy of a mitochondrial gene into the nuclear genome, suitably altered to enable the proteins produced to find their way back to the mitochondria where they are needed. This backup source of proteins allows mitochondria to function normally even when their own DNA is damaged. The technique, when applied to single genes, allows for the treatment of inherited mitochondrial conditions, as demonstrated by Gensight Biologics. More importantly, however, when applied to all thirteen mitochondrial genes it will prevent mitochondrial DNA damage from contributing to the aging process.

The MitoMouse campaign has ended, and what a final few days it has been! Thanks to the efforts of the community, an amazing total of $77,525 has been raised in support of this mitochondrial repair project of the SENS Research Foundation. There were 319 people who backed the project and helped to make this the most successful fundraiser on Lifespan.io to date, even higher than the previous record breaker, the NAD+ mouse project. This is very impressive and shows that support for the field is growing and that the tide has really turned.

We would like to give special thanks to LongeCity.org, which generously stepped in once we reached the first stretch goal and agreed to fully fund the project all the way to the second stretch goal! Thanks to LongeCity, the project not only hit the final stretch goal, which greatly expanded the scope of the project, the total funds raised went well over that goal. We are confident that the extra money will be put to good use by the MitoMouse team, and a few more boxes of mouse food and laboratory supplies are sure to come in handy.

Big thanks to everyone who supported the project, including the team at SENS Research Foundation, John Saunders, the Foster Foundation, Patrick Deane, and the volunteers and staff at LEAF for pulling together to make this happen. Hopefully, MitoMouse will enjoy the same success as the previous MitoSENS project, and we will be one step closer to having a solution to mitochondrial damage and potential cures for inherited mitochondrial conditions as well as age-related diseases.

Link: https://www.leafscience.org/mitomouse-smashes-all-fundraising-goals/

GDF11 as a Calorie Restriction Mimetic

GDF11 was one of the first factors in blood identified as a possible explanation for the outcome of heterochronic parabiosis. When a young and old mouse have their circulatory systems joined, some aspects of aging reverse in the old mouse, and some aspects of aging are accelerated in the young mouse. GDF11 levels decline with age, and it was thought that increased levels of GDF11 provided by the young animal could act to improve function of cells and tissues in the older animal - though it was not well understood as to how GDF11 worked to produce these results.

Since then there has been some debate over whether or not the original GDF11 research was technically correct, as well as some debate over whether or not factors in young blood are in fact responsible for parabiosis effects. Researchers have demonstrated benefits in old mice by delivery of GDF11 as a treatment, however. A company, Elevian, was founded to carry forward the development of GDF11 as basis for clinical therapy.

Meanwhile, research into GDF11 and aging continues elsewhere in the scientific community. Today's very interesting open access research provides evidence for GDF11 to produce benefits in large part through triggering many of the same mechanisms as calorie restriction. If this is the primary mechanism of action, it would make GDF11 much less interesting as a basis for human therapy. Firstly because calorie restriction already exists, and is essentially free, and secondly because the practice of calorie restriction produces much larger effects on life span in short-lived species than it does in long-lived species.

A blood factor involved in weight loss and aging

In a previous study using mouse models, scientists observed that injecting aged mice with blood from young mice rejuvenated blood vessels in the brain, and consequently improved cerebral blood flow, while increasing neurogenesis and cognition. Scientists put forward the theory that, since calorie restriction and supplementation with young blood were effective in rejuvenating organs, they most likely have certain mechanisms in common.

They therefore examined the molecule GDF11, which belongs to the GDF (Growth Differentiation Factor) protein family and is involved in embryonic development. GDF11 was already known to scientists for its ability to rejuvenate the aged brain. By injecting this molecule into aged mouse models, researchers noticed an increase in neurogenesis and blood vessel remodeling. The scientists also observed that the mice administered with GDF11 had lost weight without changing their appetite. This observation led them to believe that GDF11 could be a link between calorie restriction and the regenerating effects of young blood.

The next step was to confirm this theory by studying adiponectin, a hormone secreted by adipose tissue which induces weight loss without affecting appetite. In animals that have undergone calorie restriction, the blood levels of this hormone are high. In animals that were administered GDF11, researchers also observed high levels of adiponectin, and this shows that GDF11 causes metabolic changes similar to those induced by calorie restriction. Until recently, there has been controversy over the role of GDF11 in aging, and its mechanisms were largely unknown. The findings of this study show that by inducing phenomena similar to those reported for calorie restriction leading to the stimulation of adiponectin and neurogenesis, GDF11 contributes to the birth of new neurons in the brain.

Systemic GDF11 stimulates the secretion of adiponectin and induces a calorie restriction-like phenotype in aged mice

Here, we present evidence that GDF11 induces a healthy calorie restriction-like phenotype together with brain rejuvenation in aged mice, and it acts by stimulating the secretion of adiponectin directly on adipocytes. We demonstrate a potent role for GDF11 as a metabolic actor in the aged organism based on the following findings: (a) systemic administration of GDF11 induced healthy weight loss as early as 1 week after treatment, (b) this weight loss reached a plateau throughout the rest of the treatment and was maintained for 3 weeks beyond the end of the treatment, (c) GDF11 levels were increased in aged mice that were subjected to calorie restriction, (d) metabolic changes were independent of GDF15 activation or anorexia, but correlated with changes in adiponectin levels and the insulin/IGF-1 metabolic pathway, (e) GDF11 activated adiponectin secretion directly from adipocytes, and (f) all the above changes correlated with a brain rejuvenation phenotype in aged mice.

Modulating Gut Microbe Populations to Generate More Butyrate, thus Raising BDNF Levels and Improving Cognitive Function

The microbial populations of the gut have an influence on health and the progression of aging via the molecules that they generate, and which our cells react to. It isn't entirely clear as to the ordering of cause and effect in the detrimental changes that take place with aging in intestinal tissue, immune system, diet, and microbial populations. Studies have shown, however, that restoring more youthful populations can influence the function of tissues throughout the body, including the brain. The authors of this open access paper discuss modulating gut microbial populations in rats so as to upregulate butyrate production and BDNF levels, thereby improving some aspects of cognitive function. Similar examples exist in the literature for a range of other organs and tissues; it is an interesting area of research, though ultimately the size of the effects are probably not all that different from those relating to exercise or diet.

Neuroinflammation is correlated with a decline in cognitive function and memory, primarily because inflammation of the hippocampus tends to cause deleterious changes in synaptic transmission and plasticity. Because BDNF helps to sustain and enhance long-term potentiation (LTP) induction, it serves an essential role in cognitive function. Aging is associated with decreased levels of BDNF, suggesting that the maintenance of adequate BDNF concentrations could potentially help to preclude or delay the onset of cognitive impairment.

One convenient way to raise BDNF levels is supplementation of butyrate, a short-chain fatty acid (SCFA) that functions as a histone deacetylase inhibitor. Butyrate maintains the relaxation of chromatin and thereby enhances BDNF expression in the hippocampus. Secretion of pro-inflammatory cytokines may also be inhibited by BDNF, as the latter molecule interferes with activation of nuclear factor-kappa beta (NF-κβ). In addition, the expression of enzymes involved in the production of glutathione (GSH) may also be triggered by butyrate secretion. GSH is an antioxidant enzyme that relieves oxidative stress - another neurodegenerative risk factor.

The intestinal microbiota is responsible for a significant proportion of SCFA production. However, levels of SCFA decline with age due to dysbiosis, a microbial imbalance that often results in a considerable increase in pathological bacteria (Proteobacterium) at the expense of mutualistic ones (Bifidobacterium). Progression of gut dysbiosis has been linked to chronic systemic inflammation, including inflammation of the brain. Supplementation with probiotics and prebiotics may counteract the damaging effects that aging has on the brain by not only lessening inflammation and oxidative stress but also by increasing neurotrophic factors and neuronal plasticity.

A study was conducted to test how probiotic and prebiotic supplementation impacted spatial and associative memory in middle-aged rats. The results showed that rats supplemented with the symbiotic (both probiotic and prebiotic) treatment performed significantly better than other groups in the spatial memory test, though not in that of associative memory. The data also showed that this improvement correlated with increased levels of BDNF, decreased levels of pro-inflammatory cytokines, and better electrophysiological outcomes in the hippocampi of the symbiotic group. Thus, the results indicated that the progression of cognitive impairment is indeed affected by changes in microbiota induced by probiotics and prebiotics.

Link: https://doi.org/10.4103/bc.bc_34_19a

HDAC9 in Vascular Calcification

Researchers here show that HDAC9 plays a role in the calcification of blood vessel walls, a process that contributes to the stiffening of blood vessels that leads to hypertension and all of the damage that chronic raised blood pressure causes to delicate tissues throughout the body. That mice lacking HDAC9 are more resistant to calcification suggests that there may be a mechanism here that can serve as the basis for a therapy to slow down the progression of calcification in human tissues. That said, it is worth comparing effort such as this with the potential for senolytic drugs to achieve similar results, based on the evidence for senescent cells to contribute to vascular calcification.

Arterial wall calcification is the buildup of calcium in the blood vessel walls, which can often be a predictor of serious cardiovascular events like heart attacks and strokes. A new study looked at more than 11,000 people and found patients with significant blood vessel calcification were more likely to have a specific variant of HDAC9. This high-risk variant of HDAC9 is present in about 25 percent of the population. In follow-up mouse studies, the researchers also found HDAC9 caused abnormal changes in the cells of the vessel walls, resembling that of human bone cells.

"Our research proved HDAC9 is not just associated with cardiovascular disease but can actually cause it by changing the makeup of those vascular cells. We then investigated it at the molecular level and looked at what would happen if we knocked out HDAC9." The researchers found that inhibiting HDAC9 in mice preserved normal function in vascular cells and prevented vascular calcification, therefore identifying HDAC9 as a target for the potential treatment of cardiovascular disease. "Currently, there are no heart drugs available to patients that would prevent this type of hardening of the arteries. These findings are exciting in that they harness genetics to open the door for future pathways to heart disease prevention."

Link: https://www.eurekalert.org/pub_releases/2019-10/mgh-sir102919.php

Assessing Gene Therapy to Upregulate Three Longevity-Associated Genes in Mice

Today's open access research materials report on results obtained in mice using gene therapy to upregulates protein production of several longevity-associated genes. As expected from prior research into these genes and their influence on the operation of metabolism, health is improved in mouse models of age-related disease. As might also be expected based on past results, some combinations are not effective for reasons that remain to be explored: metabolism is complicated, and pulling on levers and turning dials rarely does exactly what was expected.

Evolution does not produce optimal organisms, as seen from the perspective of the individual. This is well illustrated in mice, where any number of single gene alterations, even just dialing up or down the amount of protein produced over time, leads to better health, less disease, longer lives. Why haven't any of these small alterations taken place via random mutation and thereafter prospered and spread through the species over the course of evolutionary time? Because evolutionary competition in the wild is a race to the bottom, in which lineages engineered for early life success at the cost of later life collapse tend to outcompete those with a biochemistry more friendly to the individual.

This applies as much to humans as it does to mice. There are variant human genes that offer much reduced risk of cardiovascular disease, found in a small fraction of the population. Why don't we all have those variants? Because evolution doesn't place much emphasis on late life health and survival. Further, many of the alterations known to improve health and longevity in mice should be expected to at least improve health in humans. So at some point in the years ahead, the use of gene therapies to improve human metabolism so as to reduce age-related disease and improve longevity will be a going concern. It will start with therapies for adults that don't integrate with the genome and are not passed on to children, and at some point, once the will is there, the medical community will start to engineer better human lineages.

This class of approach most likely won't be the most important road to increased longevity in the near future, however. The gains that can be achieved through periodic repair of the human biochemistry that we have today should be far greater than those produced by engineering an improved biochemistry that is more resilient to damage. We know that a youthful mammalian biochemistry works pretty well, and the differences between youth and age emerge from forms of cell and tissue damage, such as accumulation of senescent cells and persistent metabolic waste products. To the degree that the research community can repair that damage, rejuvenation will be the outcome. Yes, that repair may take the form of gene therapies, such as to deliver novel enzymes capable of breaking down metabolic waste, but this is a very different approach in comparison to the type of gene therapy tested in the research noted here, which is an attempt to shift the operation of cellular metabolism into a more resilient state, not to repair damage.

Combination gene therapy treats multiple age-related diseases in mice

Researchers honed in on three genes that had previously been shown to confer increased health and lifespan benefits when their expression was modified in genetically engineered mice: FGF21, sTGFβR2, and αKlotho. They hypothesized that providing extra copies of those genes to non-engineered mice via gene therapy would similarly combat age-related diseases and confer health benefits. The team created separate gene therapy constructs for each gene using the AAV8 serotype as a delivery vehicle, and injected them into mouse models of obesity, type II diabetes, heart failure, and renal failure both individually and in combination with the other genes to see if there was a synergistic beneficial effect.

FGF21 alone caused complete reversal of weight gain and type II diabetes in obese, diabetic mice following a single gene therapy administration, and its combination with sTGFβR2 reduced kidney atrophy by 75% in mice with renal fibrosis. Heart function in mice with heart failure improved by 58% when they were given sTGFβR2 alone or in combination with either of the other two genes, showing that a combined therapeutic treatment of FGF21 and sTGFβR2 could successfully treat all four age-related conditions, therefore improving health and survival. Administering all three genes together resulted in slightly worse outcomes, likely from an adverse interaction between FGF21 and αKlotho, which remains to be studied.

A single combination gene therapy treats multiple age-related diseases

Comorbidity is common as age increases, and currently prescribed treatments often ignore the interconnectedness of the involved age-related diseases. The presence of any one such disease usually increases the risk of having others, and new approaches will be more effective at increasing an individual's health span by taking this systems-level view into account. In this study, we developed gene therapies based on 3 longevity associated genes: fibroblast growth factor 21 (FGF21), αKlotho, soluble form of mouse transforming growth factor-β receptor 2 (sTGFβR2). The gene therapies were delivered using adeno-associated viruses, and we explored their ability to mitigate 4 age-related diseases: obesity, type II diabetes, heart failure, and renal failure.

Individually and combinatorially, we applied these therapies to disease-specific mouse models and found that this set of diverse pathologies could be effectively treated and in some cases, even reversed with a single dose. We observed a 58% increase in heart function in ascending aortic constriction ensuing heart failure, a 38% reduction in α-smooth muscle actin (αSMA) expression, and a 75% reduction in renal medullary atrophy in mice subjected to unilateral ureteral obstruction and a complete reversal of obesity and diabetes phenotypes in mice fed a constant high-fat diet. Crucially, we discovered that a single formulation combining 2 separate therapies into 1 was able to treat all 4 diseases. These results emphasize the promise of gene therapy for treating diverse age-related ailments and demonstrate the potential of combination gene therapy that may improve health span and longevity by addressing multiple diseases at once.