Fight Aging! Newsletter, July 10th 2017

One of the major physiological changes that arises with aging is the loss of subcutaneous white adipose tissue (sWAT). White adipose tissue is known to be involved in energy storage, in the form of lipids, but also in immunity, adipokine and inflammatory cytokine production. Different fat depots can be found in both humans and mice, which appear to have distinct functions. Subcutaneous fat works as an endocrine organ, secreting, in particular, the hormones leptin and resistin. Its role is to store triglycerides and free-fatty acids in order to prevent their ectopic deposition. In the case of lipoatrophy, sWAT's ability to store energy is impaired, which results in ectopic fat deposition either in visceral depots or in non-adipose sites.

The investigation of premature aging syndromes has had a considerable impact on the understanding of some of the bases of physiological aging. One of these syndromes is the Hutchinson-Gilford Progeria Syndrome (HGPS), commonly known as Progeria, a rare genetic disease characterized by clinical features resembling certain aspects of premature aging. Although several mutations have been reported to cause HGPS, this disease most often results from a de novo point mutation in the LMNA gene. Progerin accumulates at the inner nuclear membrane causing distortion of the membrane and disrupting nuclear functions. Accumulation of progerin is thought to be responsible for abnormal functional changes associated with HGPS including suppressed Nrf2 antioxidant pathway signalling and impaired adult stem cell function.

HGPS shares several features with normal aging, one of them being the loss of sWAT. Several studies have revealed the presence of low levels of progerin or rare progerin-expressing cells in normal fibroblasts (between 0.5% and 3%) and arteries (between 0.001% and 1.97%), with amounts sometimes increasing during aging. Low tissue levels of progerin can either be attributed to low expression in many cells, or to high expression in a small fraction of cells. However, it is still arguable that low levels of progerin significantly contribute to the reduced tissue function associated with aging.

In this study, we used a mouse model with sustained long-term expression of human progerin in a low frequency of cells of the adipose tissue to determine the contribution of progerin to progressive sWAT depletion. Our results provide evidence that adipose tissue is highly sensitive to progerin expression and further emphasize progerin's possible causal role in certain tissue alterations during aging. However, the frequency of progerin positive cells in the sWAT of our mouse model was higher than what was observed in healthy human sWAT, in which progerin could not be detected on protein level. Other researchers have suggested a hypothetical model whereby aging of adipose tissue results in cellular senescence and consequent tissue pathology. Our results provide evidence that a similar mechanism is to be found in subcutaneous fat, with progerin accumulation during aging triggering a cascade of events contributing to progressive tissue depletion.

We propose that with chronic exposure to low numbers of progerin expressing cells, sWAT pathology begins, initially with hyperproliferation. Hyperproliferation in turn contributes to abnormal cellular development and subsequent senescence. As paracrine activity is high in adipose tissue, senescence spreads to surrounding cells through activation of the senescence-associated secretory phenotype (SASP). Simultaneously, aging sWAT accumulates DNA double-strand breaks, which upon reaching a certain threshold lead to an increase in cell death, encouraging macrophage infiltration, as well as exacerbating the senescence phenotype. This pro-inflammatory environment of the adipose tissue ultimately activates the immune system machinery resulting in systemic inflammation.

Our sense of smell is key to the enjoyment of food, so it may be no surprise that in experiments, obese mice who lost their sense of smell also lost weight. What's weird, however, is that these slimmed-down but smell-deficient mice ate the same amount of fatty food as mice that retained their sense of smell and ballooned to twice their normal weight. In addition, mice with a boosted sense of smell - super-smellers - got even fatter on a high-fat diet than did mice with normal smell. The findings suggest that the odor of what we eat may play an important role in how the body deals with calories. If you can't smell your food, you may burn it rather than store it.

These results point to a key connection between the olfactory or smell system and regions of the brain that regulate metabolism, in particular the hypothalamus, though the neural circuits are still unknown. Mice as well as humans are more sensitive to smells when they are hungry than after they've eaten, so perhaps the lack of smell tricks the body into thinking it has already eaten. While searching for food, the body stores calories in case it's unsuccessful. Once food is secured, the body feels free to burn it.

The smell-deficient mice rapidly burned calories by up-regulating their sympathetic nervous system, which is known to increase fat burning. The mice turned their beige fat cells - the subcutaneous fat storage cells that accumulate around our thighs and midriffs - into brown fat cells, which burn fatty acids to produce heat. Some turned almost all of their beige fat into brown fat, becoming lean, mean burning machines. In these mice, white fat cells - the storage cells that cluster around our internal organs and are associated with poor health outcomes - also shrank in size. The obese mice, which had also developed glucose intolerance - a condition that leads to diabetes - not only lost weight on a high-fat diet, but regained normal glucose tolerance.

The regulation of whole-body energy homeostasis relies on an intricate balance between food intake and energy expenditure. This balance requires the coordinated response of peripheral and central neuronal inputs including hormones, multiple peptides, and neurotransmitters. In the hypothalamus, the melanocortin system in the arcuate nucleus (ARC) controls feeding in response to circulating insulin and leptin levels. Among the many sensory stimuli that influence behavioral decisions about food choice, olfactory inputs are likely to contribute to the regulation of energy homeostasis. Remarkably, the sensory perception of a hidden food cue, without its ingestion, at least transiently switches the activation state of AgRP and POMC neurons. In mice and other rodents, the hypothalamus receives indirect inputs from olfactory sensory neurons (OSNs) through signals entering from the main olfactory bulb (MOB) and transmitted to the centers of the olfactory cortex. Therefore, olfactory signals may prime the activity of key homeostatic neurons in the hypothalamus to adapt systemic metabolism under conditions of anticipated food intake.

We investigated the role of OSNs in the control of energy balance. To this end, we examined the consequence of genetically ablating the ability of animals to smell, by disrupting OSNs, on whole-body energy homeostasis in lean and obese animals. We find that mice with reduced olfaction, i.e., hyposmia, are leaner upon diet-induced obesity (DIO) either before or after the onset of obesity. These animals exhibit increased energy expenditure and enhanced fat burning capacity as a consequence of enhanced sympathetic nerve activity in brown adipose tissue (BAT) and inguinal white adipose tissue (iWAT). Conversely, we describe that conditional ablation of the IGF1 receptor in OSNs results in enhanced olfactory perception. Complementing the results observed in the hyposmic animals, these hyperosmic mice have increased adiposity and insulin resistance. Collectively, the results reveal a critical role for olfactory sensory perception in coordinately regulating peripheral metabolism via control of autonomic innervation.

The finding that OSNs can control peripheral metabolism is intriguing, and multiple mechanisms could be engaged in this circuitry. It is mainly thought that the hypothalamus receives indirect inputs from OSNs through the MOB and transmitted to the centers of the olfactory cortex. Interestingly, direct connections between discrete subpopulations of OSNs and several nuclei from the hypothalamus have been observed, reinforcing the idea that an active circuitry initiated in OSNs might influence metabolic homeostasis. Our data strongly indicate a circuit that relays information to autonomic neurons and may require central neurons. In line with this hypothesis, fiber photometry recording of AgRP and POMC neurons activity in the hypothalamus of awake, behaving animals shows that the perception of food rapidly switches the activation state of these neurons upon hunger and can be immediately reversed by removing the food cues. Additionally, olfactory inputs may be integrated by a complex interplay of different hypothalamic and brainstem nuclei expressing appetite-modulatory neuropeptides. Regardless, the potential of modulating olfactory signals in the context of metabolic syndrome or diabetes is attractive. The data presented here show that even relatively short-term loss of smell improves metabolic health and weight loss, despite the negative consequences of being on a high-fat diet.

"Autophagy," which means "self-eating" based on its Greek roots, is the normal physiological process the body's cells use to remove viruses, bacteria, and damaged material from the cell. Autophagy also helps cells "clean house" by recycling building blocks - similar to the way we recycle glass, plastic and metal. In recent years, defective autophagy has been linked to age-related diseases such as cancer, neurodegeneration and heart disease. "Increasingly, researchers are asking whether there is an age-related decline in autophagy and if it's connected to diseases that occur more frequently in older individuals. Exposing how autophagy becomes faulty with age may reveal opportunities for us to therapeutically intervene and correct the process to promote health aging."

Autophagy is a dynamic, multi-step process that starts with the formation of a double-membrane sac in the cell cytoplasm called the isolation membrane (IM). These structures engulf cellular material and debris, expanding in size to form vesicles called autophagosomes (APs). Finally, APs fuse with lysosomes to form autolysosomes (ALs) that digest and release the breakdown products for re-use, much like a recycling plant would repurpose incoming trash. "A major challenge with understanding how aging impacts autophagy is that researchers have been capturing a dynamic process with static measurements. Autophagy is most commonly monitored by counting the number of APs, which really only provides a snapshot of the process - similar to how counting the number of garbage trucks on the street doesn't tell you how much garbage is actually being recycled at the plant. And typically older organisms have an increased number of APs, but we don't know exactly why."

"We wanted to ask how age impacts autophagy - is it at the beginning of the process by increasing the rate at which APs are formed, or, by analogy, how many garbage trucks are rolling out on the street - or is it at the end of the process by blocking the conversion of APs to ALs, i.e., how much recycling is taking place at the recycling plant. Either one of these scenarios would cause an increased number of APs, but knowing which one would help pinpoint where interventions may be helpful. We found that there is indeed an age-dependent decline in autophagy over time in all tissues examined. We further provide evidence that the increase in APs results from an impairment at a step after APs are made. So basically the autophagy recycling process becomes incomplete with age by stopping somewhere after APs are formed. This research is important because it helps provide time- and site-of-action information for potential future interventions directed at sustaining autophagy to extend lifespan. Our next step will be to perform biochemical research to further pinpoint exactly how autophagy fails to complete its cycle, possibly providing targets to develop specific interventions."

Macroautophagy (hereafter referred to as autophagy) is a multistep cellular recycling process in which cytosolic components are encapsulated in membrane vesicles and ultimately degraded in the lysosome. As interest in this pathway and its pathophysiological roles has increased, it has become clear that measurement of autophagic vesicle levels at steady state, without monitoring the overall pathway flux, can lead to controversial results. Autophagy is commonly monitored by enumerating APs under steady-state conditions, also referred to as the AP pool size, using a GFP-tagged Atg8 marker. During AP formation, Atg8 is cleaved, conjugated to phosphatidylethanolamine, and inserted into the vesicle membrane, thus serving as a marker for IMs and APs. However, GFP-Atg8 only reports on the size of the IM and AP pools, not the rate by which IMs and APs are formed, or converted to ALs. For example, an increase in GFP-Atg8 could result from increased formation of APs or blockade of the downstream steps.

A tandem-tagged mCherry-GFP-Atg8 reporter, which separately monitors both IMs/APs and ALs can help distinguish between these possibilities.Specifically, when used in combination with chemical inhibitors of autophagy tandem-tagged reporters can assess autophagic activity in so called autophagic flux assays. Although tandem-tagged Atg8 markers have been used extensively to monitor autophagy in mammalian cells, as well as in adult Drosophila melanogaster and in Caenorhabditis elegans embryos, this reporter has not previously been used in adult C. elegans, and no comprehensive spatial or temporal analyses of autophagic activity have been reported in any animal thus far.

Autophagy plays important roles in numerous cellular processes and has been linked to normal physiological aging as well as the development of age-related diseases. Furthermore, accumulating evidence in long-lived species demonstrates that autophagy genes are required for extended longevity. In particular, autophagy is essential for lifespan extension by inhibition of the nutrient sensor mTOR. In C. elegans, autophagy genes are also required for the long lifespan induced by other conserved longevity paradigms, such as reduced insulin/IGF-1 signaling, germline ablation, and reduced mitochondrial respiration, and all these longevity mutants have increased transcript levels of several autophagy genes.

To better understand how aging affects autophagy in C. elegans, we employed a GFP-tagged and a novel tandem-tagged (mCherry/GFP) form of LGG-1 (a C. elegans ortholog of Atg8) to investigate the spatial and temporal autophagy landscape in wild-type (WT) and long-lived daf-2 mutants and germline-less glp-1 animals. Our data indicate that WT animals displayed an age-dependent increase in AP and AL numbers in all tissues, which flux assays suggest reflects a decrease in autophagic activity over time. In contrast, daf-2 and glp-1 mutants showed unique age- and tissue-specific differences consistent with select tissues displaying elevated, and in one case possibly reduced autophagic activity compared with WT animals. Moreover, tissue-specific inhibition of autophagy in the intestine significantly reduced the long lifespan of glp-1 mutants but not of daf-2 mutants, suggesting that autophagy in the intestine of daf-2 mutants may be dispensable for lifespan extension. Our study represents the first efforts to comprehensively analyze autophagic activity in a spatiotemporal manner of a live organism and provides evidence for an age-dependent decline in autophagic activity, and for a complex spatiotemporal regulation of autophagy in long-lived daf-2 and glp-1 mutants.

Biologist Eric Verdin considers aging a disease. His research group famously discovered several enzymes, including sirtuins, that play an important role in how our mitochondria - the powerhouses of our cells - age. His studies in mice have shown that the stress caused by calorie restriction activates sirtuins, increasing mitochondrial activity and slowing aging. In other words, in the lab, calorie restriction in mice allows them to live longer. His work has inspired many mitochondrial hacks - diets, supplements, and episodic fasting plans - but there is not yet evidence that these findings translate to humans.

Why is there so much energy and excitement surrounding aging research right now?

Something happened in the 1990s. There were three groups that did an experiment that was really unexplained. Those groups all identified unique mutations in laboratory species that could actually increase lifespan. At that time, it was a quite astute observation in the way they completely turned upside down our conception of what aging was. The whole idea of aging was sort of an entropy problem where everything falls apart like your car rusting, but what these papers showed is that you can make a single change in one whole organism like C. elegans with a 100 million base pair genome, and you can double its lifespan. That by itself was mindboggling for a lot of people and suggested there might be pathways to regulate aging, and if there are pathways that means there are proteins, and that means you can eventually develop drugs. Today we're at a point where people are considering starting clinical trials. This is why there is so much excitement and interest.

The Buck Institute focuses on research aimed at increasing healthspan. What do you mean by healthspan?

The whole mission of the Buck is not only to increase healthspan but also lifespan, but we don't want to increase lifespan at the expense of healthspan. Every decade over the last hundred years, lifespan has increased by two years. That's amazing because we've gone from an average life expectancy in the 1900s, which was around 47, to 77 today. That's an incredible achievement, but this extended lifespan is not all rosy. We also have an epidemic of what we call the chronic disease of aging.

Can those incredible increases in lifespan continue? Is there an upper limit?

There currently is an upper limit, and the upper limit is probably around 115, 120. You have a very large number - 100 billion people to choose the number of people that have ever lived - and you have only one who has made it through to 122, Jeanne Calment. The second oldest was 119. That's already a pretty good limit. If we could all live to 110 healthy and a disease in the last five years of life, I think most people would sign for this. But this does not anticipate future developments in biology. I've been in experimental biology for about 30 years. What we're doing today is just amazing in comparison to what we were doing when I started. You can't imagine what we will be able to do in biology in 30, 50, 100 years. That's why I don't like the idea that there's an absolute upper limit that man will never live above 120.

Why isn't there more interest in aging research in the larger biomedical community?

Aging research is a real paradigm shift in a way that really changes much of what we think about these chronic diseases. I think the biggest resistance is from medicine because medicine is organized in a way that is not so compatible with what we're doing. Medicine is organized based on organs. You have a heart attack, you go see a cardiologist, and he's going to take care of your heart by deferring the risk for heart attacks and controlling high blood pressure or high cholesterol. What our field is proposing is that aging is the major risk factor for all of these diseases. We should start targeting not cholesterol and blood pressure. I mean, you still have to do this, but if you start targeting the mechanism of aging, you will have a much more profound effect against all of these diseases. That really is the promise of what we're doing.

It is not uncommon for people to accept, rather uncritically, the stale cliché according to which life gets its meaning from death, and without the latter, it would not have meaning. If rejuvenation can stave off death and extend lives indefinitely, will these extended lives be utterly meaningless? No. Time and time again have I said this before, but I still fear that this misconception may be one of the worst enemies of rejuvenation; consequently, I spend much time thinking about its roots and how to debunk it. Whether life gets its meaning from death or not, people who think it does implicitly admit that life has no meaning per se. In a general sense, this is correct. Meaning is not an intrinsic property of anything. To paraphrase a common adage, meaning lies in the head of the beholder, and that's where you should expect to find the meaning - if any - of anything, life included. In other words, it is up to you to find meaning in your life, and you should neither expect it to have meaning by default, nor let others decide for you what the meaning of your life is.

It is obvious why a strong wish to live exists: if I fear death and try to avoid it by all possible means, I stand a better chance to live long enough to reproduce than somebody who isn't so afraid. Therefore, evolution has penalised creatures who did not have a strong survival instinct, and rewarded those who did. This is why we hold our lives so dear. Human intelligence made us extremely fit for survival; our curiosity and drive to answer questions that we ourselves ask are among the things that make us unique on this planet. Eventually, they made us wonder why we die. Evolution has made us fear death and wish to live indefinitely, but at the same time, it has not given us the means to fulfill that wish.

The first and most evident sign of our attempts to address this problem are religions. Yes, we fear death and don't want it, but we don't really die, only the body does, or so is the claim. Some of us have resorted to accepting it, which seems to boil down to convincing yourself there's nothing to fear in death and you're okay with it. The final way to circumvent the death paradox is the fabled 'meaning of life'. What better way can there be to rationalise death and escape our mortal fear of it than making it what gives life itself its meaning? Far from being something we should fear or avoid, death becomes thus essential, for without it, life would have no point.

What does it even mean, to give meaning to life? Most would probably agree that filling your life with activities, people, and things you love and enjoy is a valid candidate for the meaning of life; so is helping others, or doing something for the common good; something that we feel is appreciated by others, and are thus gratified by. Giving meaning to life might mean doing some of these things, and clearly, none of these potential meanings is given to life by death. However, these are viable options but aren't the answer, because there is no single answer. You decide what is the meaning of your life; not old legends, not old myths, not clichés, not other people; you do. Thus, the only way death could be the meaning of your life would be if you decided so, which I hope you won't do. Ultimately, there's nothing especially wise in accepting death. The natural length of our lifespans is the result of a meaningless, purposeless process that happened for no other reason than the fact it could.

Researchers have grown 3D cellular structures which, once transplanted into mice, developed into normal, functioning bile ducts. Bile ducts are long, tube-like structures that carry bile, which is secreted by the liver and is essential for helping us digest food. If the ducts do not work correctly, for example in the childhood disease biliary atresia, this can lead to damaging build of bile in the liver. The study suggests that it will be feasible to generate and transplant artificial human bile ducts using a combination of cell transplantation and tissue engineering technology. This approach provides hope for the future treatment of diseases of the bile duct; at present, the only option is a liver transplant.

The researchers extracted healthy cells (cholangiocytes) from bile ducts and grew these into functioning 3D duct structures known as biliary organoids. When transplanted into mice, the biliary organoids assembled into intricate tubular structures, resembling bile ducts. The researchers then investigated whether the biliary organoids could be grown on a 'biodegradable collagen scaffold', which could be shaped into a tube and used to repair damaged bile ducts in the body. After four weeks, the cells had fully covered the miniature scaffolding resulting in artificial tubes which exhibited key features of a normal, functioning bile duct. These artificial ducts were then used to replace damaged bile ducts in mice. The artificial duct transplants were successful, with the animals surviving without further complications.

"Our work has the potential to transform the treatment of bile duct disorders. At the moment, our only option is liver transplantation, so we are limited by the availability of healthy organs for transplantation. In future, we believe it will be possible to generate large quantities of bioengineered tissue that could replace diseased bile ducts and provide a powerful new therapeutic option without this reliance on organ transplants. This demonstrates the power of tissue engineering and regenerative medicine. These artificial bile ducts will not only be useful for transplanting, but could also be used to model other diseases of the bile duct and potentially develop and test new drug treatments."

According to the disposability hypothesis of aging, functional decline results from the accumulation of stochastic damage, for example, due to somatic mutations, and is counteracted by investment into somatic maintenance and repair. Accumulation of DNA damage due to decreased repair can accelerate aging, as is observed in progeroid syndromes in humans and mouse models. Similarly, increased exposure to DNA damaging agents, for instance during chemotherapy, can lead to a phenotype of acquired premature progeroid syndrome. Accelerated accumulation of DNA damage and premature aging phenotypes are typically well correlated, but whether improved DNA damage repair (DDR) can extend organismal life span remains largely unclear.

In the fruit fly (Drosophila melanogaster), a well-studied model for dissecting the mechanisms of aging, spontaneous somatic mutations accumulate with age, and defective DNA repair is associated with reduced life span. However, overexpression of DNA repair factors in the fly seems to have highly variable, sometimes contradictory effects that depend on sex, developmental stage, and the tissue of intervention. For instance, PARP-1 modifies histones, transcription factors and repair enzymes in response to DNA breaks, and its endogenous activity is well correlated with life span in several mammalian species. In Drosophila, overexpression of PARP-1 prolongs life span in both sexes, yet only when restricted to the adult nervous system. Similarly, overexpression of Gadd45, a regulator of DNA repair and cellular stress responses, in the nervous system increases fly life span but ubiquitous expression is lethal. Thus DNA repair factors can affect Drosophila life span and stress resistance either positively or negatively, depending on the sex and on whether overexpression is ubiquitous or limited to the nervous system. Interestingly, all repair factors that were expressed throughout the adult fly body were found to shorten life span.

Here, we examine the role of adult-specific overexpression of the DNA repair factor Prp19 in affecting life span, stress resistance, and DNA damage in Drosophila. Biochemically, PRP19 interacts with multiple players in the DNA repair pathways. Apart from its role in the DNA damage response, an intriguing aspect of PRP19 function is its concomitant and essential involvement in co-transcriptional splicing, where the PRP19 complex regulates the rearrangement of the spliceosome.

In support of a role for PRP19 in the aging process, it has previously been shown that decreased levels of PRP19 accelerate the induction of cellular senescence in mouse embryonic fibroblasts, reduce self renewal of mouse hematopoietic stem cells, increase UV-A-induced skin aging in mice and decrease differentiation of human adipose-derived stromal cells. Conversely, increased levels of PRP19 extend the replicative potential and total life span of cultured human endothelial cells. However, the role of PRP19 in organismal life span is unknown. Here, we show that ubiquitous overexpression of the Drosophila ortholog of PRP19, dPrp19, reduces DNA damage and extends organismal life span of adult female flies. Our results suggest that PRP19 plays an evolutionarily conserved role in the DNA damage response, aging, and stress resistance.

The second phase of the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE 2) trial demonstrated that it's feasible for humans to limit calories for an extended period. In addition, participants who cut back on calories lost weight and kept it off for the duration of the study. There were no adverse effects on quality of life and the participants netted improvements in blood pressure, cholesterol, and insulin resistance - all risk factors of age-related diseases. Significant changes in the study's primary end points -resting metabolic rate and core body temperature - didn't materialize, however. These two factors are believed to slow aging in animal models of caloric restriction.

Scientists have known since the 1930s that restricting calories by roughly 20% to 50% without malnutrition dramatically extends the healthspan and lifespan of some strains of rodents, and in the decades that followed, caloric restriction has been shown to increase the healthy lifespan of creatures ranging from yeast to guppies to monkeys. It's still an open-ended question whether dietary intervention - or any intervention at all - can dramatically extend humans' maximum lifespan. But epidemiological evidence and cross-sectional observations of centenarians and groups that voluntarily cut their calories strongly suggest that the practice could help people extend their average lifespan and live healthier, as well. While participants in the CALERIE 2 trial did benefit from the intervention, they likely would have had better results had they achieved a full 25% reduction in calories.

"You can prescribe whatever you want, but it's another story to have the people following that religiously." Having come to terms with this reality, scientists have been seeking more practical approaches. They've increasingly become interested in fasting-based analogues to daily caloric restriction, such as intermittent or alternate-day fasting. The results of a recent phase 2 trial published earlier this year suggest that less severe energy restriction could provide bigger improvements with fewer fasting days per month. In the trial, dieters only had to restrict their calories 60% for 5 consecutive days a month over 3 months to get the benefits of the so-called "fasting-mimicking diet."

Researchers initially tested this diet in middle-aged mice, subjecting them to 4 consecutive days of the fast twice a month until their deaths. Mice on the diet lived an average of 11% longer than control mice and had fewer cancers, less inflammation, less visceral fat, slower loss of bone density, and improved cognitive performance. Autopsies revealed that fasting shrunk the rodents' kidneys, hearts, and livers, but the refeeding period appeared to kick start regeneration, increasing bone marrow-derived stem cells and progenitor cells and returning organs to normal weights. Researchers also tested the diet in a small pilot clinical trial. After 3 monthly cycles of a 5-day fasting-mimicking diet, the 19 generally healthy participants in the intervention group reported no major adverse effects and had decreased risk factors and biomarkers for aging, diabetes, cardiovascular disease, and cancer compared with the control group, which maintained its normal caloric intake. Those results were confirmed in a larger phase 2 trial reported this year, which enrolled 100 generally healthy participants.

Research suggests that mitochondrial changes are a driving force, rather than a consequence, of the aging process and Alzheimer's disease pathogenesis. Although point mutations of mitochondrial DNA have been hypothesized as being a critical cause of aging, there is evidence that they may not be fully explanatory. Mitochondria are dynamic organelles with very short half-lives. Continuous replication of mitochondrial DNA (mtDNA) is required for assignment to new mitochondria, resulting in a significant error rate and accumulation of mutated in mtDNA genome over time and space. We hypothesized that, beyond point mutations, different types of mtDNA rearrangements should be extensively distributed in aging cells. As these rearrangements are often not detected by routine methods such as polymerase chain reaction, we applied the approach of directly sequencing mtDNA from isolated mitochondria derived from fresh frozen brain samples.

Our data show that different types of mitochondrial rearrangements are very common in both the aging brain and Alzheimer's disease (AD) brain. Three types of mitochondrial DNA (mtDNA) rearrangements have been seen in post mortem human brain tissue from patients with AD and age matched controls. These observed rearrangements include deletion, F-type rearrangement, and R-type rearrangement. F-type rearrangement is defined as fragments with two different sections of mtDNA joined together in the same direction. R-type rearrangement is defined as rearrangement of mtDNA originating from two different orientations of mtDNA fragments. We detected a high level of mtDNA rearrangement in brain tissue from cognitively normal subjects, as well as the patients with Alzheimer's disease (AD). The rate of rearrangements was calculated by dividing the number of positive rearrangements by the coverage depth. The rearrangement rate was significantly higher in AD brain tissue than in control brain tissue (17.9% versus 6.7%). Of specific types of rearrangement, deletions were markedly increased in AD (9.2% versus 2.3%).

Evidence indicates that mitochondrial dysfunction has an early and preponderant role in Alzheimer's disease. Our data supports this, as the AD brain samples had more than 2.7 times the recombinant rate of similarly-aged controls. Significantly, the rate for deletion in AD was 4 times that of the control samples. The position of deletion joining points was not evenly distributed across the entire genome and instead was concentrated between regions 6kb and 15kb of the mitochondrial genome, which happens to be the area containing the DNA sequences for synthesizing all three cytochrome oxidases necessary for correct electron transport chain function. This makes it is reasonable to advance the concept that increased deletions in this area may affect the ability of mtDNA to synthesize cytochrome oxidase. Our results are consistent with reports of decreased cytochrome oxidase activity in AD brain samples.

Researchers have reached important milestones in their quest to engineer replacement tissue in the lab to treat digestive system conditions. They have verified the effectiveness of lab-grown anal sphincters to treat a large animal model for fecal incontinence, an important step before advancing to studies in humans, and also achieved success in implanting human-engineered intestines in rodents. The lab-engineered sphincters are designed to treat passive incontinence, the involuntary discharge of stool due to a weakened ring-like muscle known as the internal anal sphincter. The muscle can lose function due to age or can be damaged during child birth and certain types of surgery, such as cancer. Current options to repair the internal anal sphincter include grafts of skeletal muscle, injectable silicone material or implantation of mechanical devices, all of which have high complication rates and limited success.

The team has been working to engineer replacement sphincters for more than 10 years. In 2011, the team was the first to report functional, lab-grown anal sphincters bioengineered from human cells that were implanted in immune-suppressed rodents. The current study involved 20 rabbits with fecal incontinence. The sphincters were engineered using small biopsies from the animals' sphincter and intestinal tissue. From this tissue, smooth muscle and nerve cells were isolated and then multiplied in the lab. In a ring-shaped mold, the two types of cells were layered to build the sphincter. The entire process took about four to six weeks. In the animals receiving the sphincters, fecal continence was restored throughout a three month follow-up period, compared to the other groups, which did not improve. Measurements of sphincter pressure and tone showed that the sphincters were viable and functional and maintained both the muscle and nerve components. Currently, longer follow up of the implanted sphincters is close to completion with good results.

The intestine project is aimed at helping patients with intestinal failure, which is when the small intestine malfunctions or is too short to digest food and absorb nutrients essential to health. Intestinal transplant is an option, but donor tissue is in short supply and the procedure has high mortality rates. "A major challenge in building replacement intestine tissue in the lab is that it is the combination of smooth muscle and nerve cells in gut tissue that moves digested food material through the gastrointestinal tract." Through much trial and effort, the team has learned to use the two cell types to create "sheets" of muscle pre-wired with nerves. The sheets are then wrapped around tubular molds made of chitosan.

In the current study, the tubular structures were implanted in rats in two phases. In phase one, the tubes were implanted in the omentum, which is fatty tissue in the lower abdomen, for four weeks. Rich in oxygen, this tissue promoted the formation of blood vessels to the tubes. During this phase, the muscle cells began releasing materials that would eventually replace the scaffold as it degraded. For phase two, the bioengineered tubular intestines were connected to the animals' intestines, similar to an intestine transplant. During this six-week phase, the tubes developed a cellular lining as the body's epithelial cells migrated to the area. The rats gained weight and studies showed that the replacement intestine was healthy in color and contained digested food.

Inside the cell, proteins need to be folded to be functional and active. Molecular chaperones are key enzymes that assist in folding proteins by stabilizing nascent polypeptide chains and by facilitating interactions that help stabilize a final structure. These chaperones also prevent the aggregation of newly formed proteins and can shunt misfolded proteins toward degradation pathways. In addition to interacting with newly synthesized proteins, chaperones also help to maintain cellular homeostasis by triaging toxic protein aggregates, which are responsible for causing neurodegenerative diseases.

Two proteins that can form these toxic aggregates are tau and α-synuclein, which form tangles in Alzheimer's disease and Lewy bodies in Parkinson's disease, respectively. These proteins aggregate to form small, soluble aggregates termed oligomers and long fibrils often termed amyloids, both of which are thought to be toxic. Here we show that a chaperone, cyclophilin 40 (CyP40), interacts with and dissolves tau and α-synuclein aggregates. CyP40 may accomplish this by interacting with proline residues in these proteins, which are known to play a key role in fibril stability. We show that CyP40 both lowers tau fibrils and oligomers in mice that overexpress tau protein and preserves cognition in these transgenic animals.

While being the first human PPIase to display disaggregation activity, CyP40 is not the first disaggregase to be identified. Certain chaperone complexes have been shown to facilitate the disaggregation of oligomers and fibrils. The existence of amyloid disaggregases presents a new avenue for therapeutic strategies. The procognitive effects of CyP40 overexpression in the tauopathic brain suggest that strategies to either induce or deliver disaggregases to the central nervous system could halt or even rescue cognitive deficits associated with neurotoxic amyloids.

Though CyP40 can directly interact with the chaperone heat shock protein Hsp90, the effects described here do not appear to be Hsp90 dependent. Further studies are required to determine if there are endogenous mechanisms to increase CyP40 activity either through the up-regulation of CyP40 expression, by increasing CyP40 stability, or by increasing the enzymatic activity of CyP40. Recent work suggests that upon cellular stress Hsp90 may dissociate from CyP40, leading to an increased pool of more catalytically active CyP40. This may hint at a possible mechanistic pathway by which CyP40 may be "turned on" in response to stress, including toxic amyloid build-up. In addition to CyP40, there are currently 41 known human PPIases within the cyclophilin, FKBP, and parvulin families. Therefore, future screening may reveal additional PPIases with activities similar to CyP40, including disaggregation. Additionally, CyP40 and other PPIases should be further characterized for disaggregation activity against proline-containing amyloids, especially those associated with disease.

A personal cancer treatment vaccine that targets distinctive "neoantigens" on tumor cells has been shown to stimulate a potent, safe, and highly specific immune anti-tumor response in melanoma patients. Antigens are molecules that are displayed on the surface of cells and stimulate the immune system. Neoantigens are molecules on cell's surfaces that are produced by DNA mutations that are present in cancer cells but not in normal cells, making neoantigens ideal targets for immune therapy against cancer. The vaccines used in the phase I trial contained up to 20 neoantigens, derived from an individual patient's tumor. The vaccines were administered to patients to train their immune system to recognize these neoantigens, with the goal of stimulating the immune system to destroy the cancer cells that display them.

While other immunotherapies, such as checkpoint inhibitor drugs, also trigger immune responses against cancer neoantigens, they are not designed to be specific. They can also induce responses against normal tissue antigens, leading the immune system to attack normal tissues and cause toxicity in a subset of patients. The researchers found that the personal vaccine induced a focused T cell response against several tumor neoantigens, beyond what is normally seen in response to existing immunotherapies.

The vaccine was administered to six patients with melanoma whose tumors had been removed by surgery and who were considered at high risk for recurrence. The vaccinations were started at a median of 18 weeks after surgery. At a median of 25 months after vaccination, four of the six patients showed no evidence of cancer recurrence. In the other two patients, whose cancer had spread to their lungs, the disease recurred after vaccination. At that point, they began treatment with the drug pembrolizumab, which inhibits the PD-1 immune checkpoint. Both patients had complete resolution of their tumors and remain free of disease according to imaging scans.

The study results suggest, that a personalized neoantigen vaccine can potentially overcome two major hurdles in cancer therapy. One is the heterogeneity of tumors - the fact that they are made up of cells with a variety of different traits, which often allows cancers to evade drugs targeted to malignant cells having a single genetic abnormality. The vaccine, because it contains many different neoantigens from the tumor, targets multiple genetic types of tumor cells. A second hurdle in cancer is to generate an immune response sharply focused on cancer cells while avoiding normal cells and tissues. This aim was achieved by the vaccine, which appeared to have few "off-target" effects, causing only flu-like symptoms, fatigue, rashes, and irritation at the site of the vaccine injection, according to the report.

Mildly stressing muscle metabolism boosts levels of a beneficial hormone that prevents obesity and diabetes in mice, according to a new study. The new findings show that triggering a certain type of metabolic stress in mouse muscle cells causes them to produce and secrete significant amounts of fibroblast growth factor-21 (FGF21), which then has widespread beneficial effects on whole-body metabolism. The mice in the experiments were completely protected from obesity and diabetes that normally develop due to aging or eating a high-fat diet. Moreover, triggering the FGF21 production after the mice had become obese and diabetic reversed these conditions and returned the mice to normal weight and blood sugar levels.

"There is a biological phenomenon known as hormesis where a little bit of stress a can be a good thing." Researchers used genetic engineering to reduce levels of a mitochondrial protein called OPA1 in the muscles of mice. Mitochondria are tiny organelles that produce a cell's energy. This OPA1 deficiency disrupted muscle metabolism and caused a small amount of muscle loss in the mice. Despite the mild muscle atrophy, which did decrease grip strength, the older mice with OPA1 deficiency had greater endurance on the treadmill than older control mice. In addition, activity levels and energy expenditure that normally decline in mice as they age were preserved in OPA1 deficient mice.

Interestingly, the altered mice also were completely protected from the weight gain and glucose intolerance that normally develop in mice as they age or when they eat a high-fat diet. Moreover, the research team showed that reducing OPA1 levels in muscle, after mice had become obese and diabetic, reversed these problems - normalizing body weight and reversing glucose intolerance even though the high fat diet continued. These metabolic improvements correlated with increased levels of circulating FGF21. The researchers were able to prove that muscle was the source of the FGF21 by creating a mouse that had the OPA1 deficiency and also was missing the FGF21 gene in muscle. These mice were no longer able to produce FGF21 in muscle in response to OPA1 deficiency, and, just like control mice, they became obese and developed diabetes. "These experiments prove that muscle is the source of circulating FGF21 in the OPA1 deficient mice, and that muscle-derived FGF21 prevents diet-induced obesity and insulin resistance in these mice."

Further investigation demonstrated that the small degree of mitochondrial stress induced in muscle by the reduction of OPA1 is sufficient to activate another cellular stress response pathway called endoplasmic reticulum (ER) stress, which then dramatically increases FGF21 levels. "The follow up work on this will be understanding how a little bit of mitochondrial stress can actually increase the ER stress response and if we can mimic that safely. There are agents that have been used to activate ER stress pathways. So, I think the opportunity here would be to find ways to turn on this pathway in a very controlled way to get enough of this subsequent FGF21 response in muscle to be of benefit."