Increase In Maximum Life Span Research Articles

Chronobiotics KL001 and KS15 Extend Lifespan and Modify Circadian Rhythms of Drosophila melanogaster

Chronobiotics are a group of drugs, which are utilized to modify circadian rhythms targeting clock-associated molecular mechanisms. The circadian clock is known as a controller of numerous processes in connection with aging. Hypothesis: KL001 and KS15 targeting CRY, affect lifespan, locomotor activity and circadian rhythm of Drosophila melanogaster. We observed a slight (2%, p < 0.001) geroprotective effect on median lifespan (5 µM solution of KL001 in 0.1% DMSO) and a 14% increase in maximum lifespan in the same group. KS15 10 µM solution extended males’ median lifespan by 8% (p < 0.05). The statistically significant positive effects of KL001 and KS15 on lifespan were not observed in female flies. KL001 5 µM solution improved locomotor activity in young male imagoes (p < 0.05), elevated morning activity peak in aged imagoes and modified robustness of their circadian rhythms, leaving the period intact. KS15 10 µM solution decreased the locomotor activity in constant darkness and minimized the number of rhythmic flies. KL001 5 µM solution improved by 9% the mean starvation resistance in male flies (p < 0.01), while median resistance was elevated by 50% (p < 0.0001). This phenomenon may suggest the presence of the mechanism associated with improvement of fat body glucose depos’ utilization in starvation conditions which is activated by dCRY binding KL001.

Glycine supplementation extends lifespan of male and female mice.

Diets low in methionine extend lifespan of rodents, though through unknown mechanisms. Glycine can mitigate methionine toxicity, and a small prior study has suggested that supplemental glycine could extend lifespan of Fischer 344 rats. We therefore evaluated the effects of an 8% glycine diet on lifespan and pathology of genetically heterogeneous mice in the context of the Interventions Testing Program. Elevated glycine led to a small (4%–6%) but statistically significant lifespan increase, as well as an increase in maximum lifespan, in both males (p = 0.002) and females (p < 0.001). Pooling across sex, glycine increased lifespan at each of the three independent sites, with significance at p = 0.01, 0.053, and 0.03, respectively. Glycine‐supplemented females were lighter than controls, but there was no effect on weight in males. End‐of‐life necropsies suggested that glycine‐treated mice were less likely than controls to die of pulmonary adenocarcinoma (p = 0.03). Of the 40 varieties of incidental pathology evaluated in these mice, none were increased to a significant degree by the glycine‐supplemented diet. In parallel analyses of the same cohort, we found no benefits from TM5441 (an inhibitor of PAI‐1, the primary inhibitor of tissue and urokinase plasminogen activators), inulin (a source of soluble fiber), or aspirin at either of two doses. Our glycine results strengthen the idea that modulation of dietary amino acid levels can increase healthy lifespan in mice, and provide a foundation for further investigation of dietary effects on aging and late‐life diseases.

Growth hormone in adipose dysfunction and senescence

Growth hormone (GH) is an important modulator of maturation, adiposity, and metabolism in mammals. It also has profound effects on age-related disease onset and healthspan [1]. GH-deficient and -resistant mice have up to a 78% increase in maximum lifespan and are protected from age-related metabolic dysfunction and cancer [2]. Although lifespan does not appear to be extended in humans with GH resistance, these individuals are protected from a variety of age-related pathologies, particularly diabetes and cancer [3]. Several mechanisms have been proposed and likely contribute to the pro-survival effects of curtailed GH action, including enhanced stress resistance, xenobiotic metabolism, and insulin sensitivity in combination with reduced inflammation [1]. In contrast, both mice and humans with excess GH develop phenotypes indicative of premature aging and have greater disease burden and mortality risk [1, 2]. Furthermore, mice and humans with altered GH action also display profound changes in adipose tissue homeostasis and lipid distribution. GH-deficient and -resistant mice preferentially deposit lipid in subcutaneous adipose depots, whereas humans with Laron Syndrome exhibit markedly increased subcutaneous and visceral adiposity [1, 2]. Despite the development of obesity, the overwhelming majority of these mice and human subjects are safeguarded from metabolic dysfunction. Conversely, transgenic GH-overexpressing mice and human acromegaly patients remain lean throughout life, yet often develop insulin resistance and an elevated pro-inflammatory status [1]. These observations suggest GH may accelerate declines in adipose tissue homeostasis, which has previously been linked with age-related perturbations in systemic inflammation and metabolism [4]. Adipose tissue functional capacity declines with advancing age [4]. This deterioration is particularly evident in subcutaneous depots, which promotes increased visceral adiposity, ectopic lipid deposition, and concomitant metabolic disturbances. Preadipocyte proliferation and differentiation potential are curtailed with aging and result in reduced lipid deposition in subcutaneous adipose tissue [4]. Pro-inflammatory cytokines, chemokines, and extracellular matrix proteases are believed to play a central role in preadipocyte dysfunction and adipose tissue remodeling with aging. Senescent cells, which possess a highly pro-inflammatory secretome, accumulate in adipose tissue with advancing age, and thus, have emerged as a potential contributor to adipose tissue dysfunction [4]. Interestingly, the elimination of senescent cells preserves adipose tissue mass and enhances healthspan in mice with an accelerated aging phenotype [5]. Given that GHdeficient and -resistant mice appear to be protected from age-related lipid redistribution and metabolic dysfunction, we hypothesized that GH action would be predictive of subcutaneous adipose tissue lipid storage capacity and senescent cell burden. To test our hypothesis, we evaluated adipose tissue functional capacity and senescent cell accumulation in several models with altered GH action. Our study, now published in Aging, establishes a relationship between GH action, lipid deposition, and adipose tissue senescent cell accumulation [6]. To start, we confirmed that both GH-deficient and -resistant models are protected from age-related lipid redistribution as evidenced by greater subcutaneous to visceral adipose tissue ratios than their respective control littermates at 18 months of age. These findings were supported by the observation that GH-resistant mice also accumulated less hepatic triglycerides during this time. We subsequently determined that primary subcutaneous preadipocytes from 20-month old GH-resistant mice possess greater differentiation capacity than those from age-matched controls; providing a potential explanation for enhanced lipid storage capacity of subcutaneous adipose tissue in mice with curtailed GH action. Considering the close connection between inflammatory status, adipose tissue homeostasis, and GH action, we sought to determine if our previous findings were associated with adipose tissue senescent cell accumulation. We found that GH-deficient and -resistant mice exhibited far less senescent cell burden in several adipose tissue depots compared to control littermates at 18 months of age. Conversely, GHoverexpressing (10 months of age) and GH-injected (19 months of age) mice accumulated more senescent cells within adipose tissue than their controls, which we later determined was similar to 24-month old chronologically aged mice. We conclude that senescent cell accumulation in adipose tissue is linked with GH activity and may play a key role in age-related adipose tissue dysfunction. It is currently unclear if GH directly promotes cellular senescence in adipose tissue through geroconversion [7], or if GH-mediated effects on insulin-like growth factor-1 (IGF-1) and insulin signaling pathways play a more dominant role [1, 2]. Future investigation of the role these distinct, yet related, signaling pathways play in the emergence of cellular senescence will provide insights into links among aging, cellular senescence, and adipose tissue dysfunction. Studies using a new class of drugs that selectively clear senescent cells, senolytic agents [8], in experimental animals and eventually humans with obesity and excess or diminished GH and IGF-1 action will be a path towards testing if these links are causal.

Independent chemical regulation of health and senescent spans in Drosophila

Curcumin feeding of Drosophila larvae or young adults inhibits TOR and other known longevity genes and induces an extended health span in a normal-lived Ra strain adult. Combining larval curcumin feeding with an adult dietary restriction (DR) diet does not yield an additive effect. The age-specific mortality rate is decreased and is comparable with that of genetically selected long-lived La animals. Feeding Ra adults with the drug their whole life, or only during the senescent span, results in a weak negative effect on median longevity with no increase in maximum lifespan. The La strain shows no response to this DR mimetic. Thus, curcumin acts in a life stage-specific manner to extend the health span. Histone deacetylase inhibitors decrease the longevity of Ra animals if administered over the health span only or over the entire adult lifespan, but these inhibitors increase longevity when administered in the transition or senescent spans. Their major effect is a reduction in the mortality rate of older flies, raising the possibility of reducing frailty in older organisms. Their life stage-specific effects are complementary to that of curcumin. Use of stage-specific drugs may enable targeted increases in health or senescent spans, and thus selectively increase the quality of life.

Dietary and caloric restriction and age‐related spinal osteoarthritis: a longitudinal study of primates (1025.7)

Dietary and/or caloric restriction have been shown to decrease the rate of senescence and increase maximum life span in several species, but how it impacts age‐related degenerative processes, such as osteoarthritis, is unclear. Like humans, Rhesus macaques develop spontaneous osteoarthritis with age and have been studied under dietary/caloric restriction protocols for almost two decades. We hypothesized that restricted macaques would develop less spinal osteoarthritis with age than monkeys fed a normal diet.We assessed osteoarthritis in the thoracolumbar spine of macaques from dietary/caloric restriction studies at the Wisconsin National Primate Research Center and the National Institute on Aging. We assessed osteophytosis (OST) and disc space narrowing (DSN) from annual radiographs of 68 macaques from the WNPRC (males, n=41 (20 restricted); females, n=27 (13 restricted)) and 104 macaques from NIA (males, n=52 (26 restricted); females, n=52 (22 restricted)) studies. A positive association between age and both OST (p&lt;0.001) and DSN (p&lt;0.001) was found in macaques from both sites, but no difference was found between normally fed and restricted animals (WNPRC: OST p=0.222, DSN p=0.574; NIA: OST p=0.238, DSN p=0.386) when adjusted for sex and body mass.Dietary/caloric restriction does not affect spinal osteoarthritis, which perhaps implicates loading as a contributor to the etiology of osteoarthritis.

Diet fatty acid profile, membrane composition and lifespan: An experimental study using the blowfly (Calliphora stygia)

The membrane pacemaker theory of ageing proposes that the polyunsaturated fatty acid (PUFA) composition of membrane lipids of a species is an important determinant of its maximum lifespan. We report three experiments using the blowfly Calliphora stygia, where this theory was tested by manipulation of dietary fat profile. Although the fat profile of the larval diet resulted in small alterations of individual membrane fatty acids, it had no effect on the peroxidation index (PI) of membrane lipids and furthermore had no effect on maximum lifespan. Similarly, manipulation of the fat profile of the adult diet resulted in small changes in individual fatty acids, but had no effect on the PI of membrane lipids. There was a small increase in maximum lifespan when adult diet was supplemented with PUFA in form of vegetable oils but no effect when diet was supplemented with pure PUFA. This difference is possibly due to antioxidant content of vegetable oils. The relative refractoriness of membrane PI to dramatic changes in response to diet is similar to the situation in the rat. These results also indicate the blowfly is unable to convert 18-carbon PUFA to more highly polyunsaturated 20- and 22-carbon PUFA.

Regulation of longevity and oxidative stress by nutritional interventions: Role of methionine restriction

Comparative studies indicate that long-lived mammals have low rates of mitochondrial reactive oxygen species production (mtROSp) and oxidative damage in their mitochondrial DNA (mtDNA). Dietary restriction (DR), around 40%, extends the mean and maximum life span of a wide range of species and lowers mtROSp and oxidative damage to mtDNA, which supports the mitochondrial free radical theory of aging (MFRTA). Regarding the dietary factor responsible for the life extension effect of DR, neither carbohydrate nor lipid restriction seems to modify maximum longevity. However protein restriction (PR) and methionine restriction (at least 80% MetR) increase maximum lifespan in rats and mice. Interestingly, only 7weeks of 40% PR (at least in liver) or 40% MetR (in all the studied organs, heart, brain, liver or kidney) is enough to decrease mtROSp and oxidative damage to mtDNA in rats, whereas neither carbohydrate nor lipid restriction changes these parameters. In addition, old rats also conserve the capacity to respond to 7weeks of 40% MetR with these beneficial changes. Most importantly, 40% MetR, differing from what happens during both 40% DR and 80% MetR, does not decrease growth rate and body size of rats. All the available studies suggest that the decrease in methionine ingestion that occurs during DR is responsible for part of the aging-delaying effect of this intervention likely through the decrease of mtROSp and ensuing DNA damage that it exerts. We conclude that lowering mtROS generation is a conserved mechanism, shared by long-lived species and dietary, protein, and methionine restricted animals, that decreases damage to macromolecules situated near the complex I mtROS generator, especially mtDNA. This would decrease the accumulation rate of somatic mutations in mtDNA and maybe finally also in nuclear DNA.

Curcumin is an early-acting stage-specific inducer of extended functional longevity in Drosophila

Larval feeding with curcumin induces an extended health span with significantly increased median and maximum longevities in the adult fly. This phenotype is diet insensitive and shows no additive effect on longevity when combined with an adult dietary restriction (DR) diet, suggesting that curcumin and DR operate via the same or overlapping pathways for this trait. This treatment significantly slows the aging rate so that it is comparable with that of genetically selected long lived animals. The larval treatment also enhances the adult animal's geotactic activity in an additive manner with DR, suggesting that curcumin and DR may use different pathways for different traits. Feeding the drug to adults during only the health span also results in a significantly extended health span with increased median and maximum life span. This extended longevity phenotype is induced only during these stage-specific periods. Feeding adults with the drug over their whole life results in a weakly negative effect on median longevity with no increase in maximum life span. There are no negative effects on reproduction, although larval curcumin feeding increases development time, and also apparently accelerates the normal late-life neuromuscular degeneration seen in the legs. Gene expression data from curcumin-fed larvae shows that the TOR pathway is inhibited in the larvae and the young to midlife adults, although several other genes involved in longevity extension are also affected. These data support the hypothesis that curcumin acts as if it is a DR mimetic nutraceutical. These data also suggest that the search for DR mimetics may be enhanced by the use of stage-specific screening of candidate molecules.

Modulation of Longevity and Tissue Homeostasis by the Drosophila PGC-1 Homolog

In mammals, the PGC-1 transcriptional coactivators are key regulators of energy metabolism, including mitochondrial biogenesis and respiration, which have been implicated in numerous pathogenic conditions, including neurodegeneration and cardiomyopathy. Here, we show that overexpression of the Drosophila PGC-1 homolog (dPGC-1/spargel) is sufficient to increase mitochondrial activity. Moreover, tissue-specific overexpression of dPGC-1 in stem and progenitor cells within the digestive tract extends life span. Long-lived flies overexpressing dPGC-1 display a delay in the onset of aging-related changes in the intestine, leading to improved tissue homeostasis in old flies. Together, these results demonstrate that dPGC-1 can slow aging both at the level of cellular changes in an individual tissue and also at the organismal level by extending life span. Our findings point to the possibility that alterations in PGC-1 activity in high-turnover tissues, such as the intestine, may be an important determinant of longevity in mammals.

A role for Ras signaling in modulating mammalian aging by the GH/IGF1 axis

The discovery that mutations in single genes can modulate aging was not only fascinating but it provided researchers with animal models with which to study aging in cohorts of different aging rates [1-2]. According to the GenAge database [3], at the time of writing, genetic manipulations in 68 genes have been shown to affect lifespan in mice. Among mouse genes in which mutations extend lifespan, a number are part of the growth hormone/insulin-like growth factor 1 (GH/IGF1) axis. As such, it is widely acknowledged that decreased GH/IGF1signaling in mice can extend lifespan, while increased GH levels may accelerate aging [4-5]. Although the GH/IGF1axis is one of the major pathways regulating aging in mammals, its precise downstream mechanisms remain a subject of debate and scrutiny. In this year's March issue of AGING, Borras et al. show that mice deficient in Rasgrf1, a guanine nucleotide–releasing factor for Ras, exhibit a significant increase (~20%) in average and maximum lifespan. This increase in lifespan was independent of cancer mortality and was accompanied by a retardation in age–related functional and physiological decline [6]. Ras homologues have been associated with lifespan modulation in yeast [7], so it seems that Ras signaling is another example of an evolutionary conserved pathway modulating aging. Rasgrf1 is unique among Ras family members, however, as it is only expressed in a few specific tissues, in particular in pancreatic β–cells and in some regions of the brain. Thus far, Rasgrf1 has been primarily associated with learning and memory [6,8-9]. Because of its expression in the brain, Rasgrf1 has been shown to regulate the synthesis and release of GH, and previous studies showed that Rasgrf1 deficient mice have lower levels of GH [9-10]. In line with these previous studies, and given that GH impacts on IGF1 levels, Rasgrf1 deficient mice showed lower IGF1 levels [6]. Decreased GH/IGF1 signaling results in stunted growth and reduced adult body size, which has been associated with life-extension in numerous models [11]. Borras et al. and other authors also observed that Rasgrf1deficient mice are smaller than controls [6,9-10]. Therefore, it is likely that decreased GH/IGF1 signaling is the mechanism by which Rasgrf1 impacts on aging. Changes in GH/IGH1 have also been hypothesized to be related to the mechanisms of caloric restriction [4-5], which is in line with the observation by Borras et al., that Rasgrf1 deficient mice have metabolic profiles similar to mice under caloric restriction. Because Rasgrf1 mutants have altered GH/IGF1 signaling, I had predicted that they would be long-lived [12]. Moreover, it was reported that bi-maternal mice are long-lived and, because Rasgrf1is an imprinted gene expressed from the paternal allele in neonates, it is possible that bi-maternal mice are long-lived due to Rasgrf1 effects [12-13]. Although conducted in different labs and strains, bi–maternal mice had a similar increase in average lifespan (28%), though a more modest increase in maximum lifespan (~5%). Rasgrf1 deficient mice are therefore another model to study the modulation of aging by the GH/IGF1 axis. Interestingly, mice expressing Rasgrf1from both alleles have increased body size and higher IGF1 levels [9]. Although the lifespan of these animals is unknown, they could be seen as a complementary model to the Rasgrf1 knock-outs. Consequently, since they are available with both increased GH (biallelic Rasgrf1 mice) and decreased GH levels (Rasgrf1 knock outs), the different Rasgrf1 mutant mice may be an excellent new model to study aging and its modulation by the GH/IGF1 axis.

Impact of 6‐month Caloric Restriction on Autonomic Nervous System Activity in Healthy, Overweight, Individuals

Caloric restriction (CR) increases maximum lifespan but the mechanisms are unclear. Dominance of the sympathetic nervous system (SNS) over the parasympathetic nervous system (PNS) has been shown to be a strong risk factor for cardiovascular disease. Obesity and aging are associated with increased SNS activity, and weight loss and/or exercise seem to have positive effects on this balance. We therefore evaluated the effect of different approaches of CR on autonomic function in 28 overweight individuals participating in the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) trial. Participants were randomized to either control, CR: 25% decrease in energy intake, CREX: 12.5% CR + 12.5% increase in energy expenditure, or LCD: low-calorie diet until 15% weight reduction followed by weight maintenance. Autonomic function was assessed by spectral analysis of heart-rate variability (HRV) while fasting and after a meal. Measurements were performed at baseline and 6 months. HR and SNS index decreased and PNS index increased in all intervention groups but reached significance only in CREX. HR and SNS index increased and PNS index decreased in response to the meal in all intervention groups. The results therefore suggest that weight loss improved SNS/PNS balance especially when CR is combined with exercise.

Heart rate, lifespan, and mortality risk

An increasing body of scientific research and observational evidence indicates that resting heart rate (HR) is inversely related to the lifespan among homeothermic mammals and within individual species. In numerous human studies with patients stratified by resting HR, increased HR is universally associated with greater risk of death. The correlation between HR and maximum lifespan seems to be due to both basal metabolic rate and cardiovascular-related mortality risk. Both intrinsic and extrinsic factors are already postulated to determine how the biological clock works, through regulating and modulating the processes such as protein oxidation, free radical production, inflammation and telomere shortening. Given the remarkable correlation between HR and lifespan, resting HR should be seriously considered as another possible cap on maximum lifespan. Future research is needed to determine whether deliberate cardiac slowing, through methods like lifestyle modification, pharmacological intervention, or medical devices, can decelerate biological clock of aging, reduce cardiovascular mortality and increase maximum lifespan in humans in general.

Dietary Restriction and Cold Temperature Both Acutely Reduce Senescence in C. elegans

Cold/hypothermic induced longevity (CHIL) increases maximum lifespan, but the acute effects of CHIL on se- nescence, herein defined as the acceleration in mortality rate with age, have not been examined. Furthermore, dietary re- striction (DR) also increases maximum lifespan, but the effect of DR on senescence remains controversial. Here, we dem- onstrate that in C. elegans, both DR and CHIL significantly reduce senescence. Furthermore, even at midlife, transfer to or from a life-extending condition acutely changes the rate of senescence. These results are consistent with the hypothesis that previous temperature or dietary conditions cause irreversible damage to the organism, but future acceleration of this damage is solely dependent on the current temperature or dietary regimen.

Do We Age on Sirt1 Expression?

Aging leads to a progressive decline in multiple organ systems, including the heart. Heart failure in response to cellular aging and chronic or acute cellular stresses represents one of the major burdens of the western civilization. Over the last 15 years, the interest in the therapeutic use of caloric restriction to prevent aging has emerged. However, it is difficult to determine whether caloric restriction influences longevity in humans because no validated biomarker exists, which can serve as a surrogate marker of aging and it is impossible to conduct a randomized, diet-controlled longterm survival study in humans. Nevertheless, caloric restriction has been shown in several studies to lower fasting plasma glucose concentration and serum low-density lipoprotein cholesterol, to decrease insulin resistance, visceral fat mass and the levels of inflammatory markers. Most of these markers are known to be risk factors for coronary heart disease. Thus, even it is not known whether caloric restriction does prolong maximum life-span, it could increase life expectancy and the quality of late life by reducing the burden of chronic diseases. However, the precise biological and cellular mechanisms responsible for aging and the antiaging effects of caloric restriction are not known. Moreover, even if caloric restriction would result in an increase in maximum life span in humans, it will be difficult to maintain long-term caloric restriction in modern society. Therefore, one major interest is to develop caloric restriction mimetics to provide all of the “healthy” physiological, metabolic and hormonal effects of caloric restriction without the need to reduce food intake. Based on these ideas, it has been proposed, that resveratrol increases lifespan in several different organisms, mimicking the effects of caloric restriction.1 Recent reports indicate, that resveratrol can even restore the health and lifespan of mice on a high calorie diet to levels seen in mice on a normal diet, rising the hope of “guilt-free gluttony” when adding resveratrol as a dietary supplement.1,2 But how does resveratrol induce these caloric restriction-like effects on the molecular level? An in vitro screen for activators of the sirtuin/Sir2 family of NAD-dependent deacetylases identified resveratrol as the most potent of 18 inducers of Sir2 deacetylase activity. 3 Subsequent work has shown that resveratrol extends the lifespans of S. cerevisiae, Caenorhabditis elegans and Drosophila melanogaster, but only if the gene that encodes Sir2 is present in these organisms, providing further evidence that the observed effects of resveratrol are because of an activation of Sir2. 3,4 Sirtuins are a conserved family of NAD-dependent deacetylases (class III histone deacetylases) that were named after the founding member, the Saccharomyces cerevisiae silent information regulator 2 (Sir2) protein. 5 In yeast, worms and flies, overexpression of the genes that encode sirtuins are reported to extend lifespan,6–8 suggesting that sirtuins are evolutionarily conserved mediators of longevity. Moreover, sirtuins are suggested to play a role in lifespan extension

Is the Mitochondrial Free Radical Theory of Aging Intact?

The present state of the mitochondrial free radical theory of aging is reviewed. Available studies do not support the hypothesis that antioxidants control the rate of aging because: (a) they correlate inversely with maximum longevity in vertebrates, and (b) increasing their concentration by different methods does not increase maximum lifespan. On the other hand, comparative studies consistently show that long-lived mammals and birds have low rates of mitochondrial reactive oxygen species (ROS) production and low levels of oxidative damage in their mitochondrial DNA. Furthermore, caloric restriction, which extends longevity, also decreases mitochondrial ROS production at complex I and lowers mtDNA oxidative damage. Recent data show that these changes can also be obtained with protein restriction without strong caloric restriction. Another trait of long-lived mammals and birds is the possession of low degrees of unsaturation in their cellular membranes. This is mainly due to minimizing the presence of highly unsaturated fatty acids such as 22:6n-3 and emphasizing the presence of less unsaturated fatty acids such as 18:2n-6 in long-lived animals, without changing the total amount of polyunsaturated fatty acids. This leads to lower levels of lipid peroxidation and lipoxidation-derived protein modification in long-lived species. Taken together, available information is consistent with the predictions of the mitochondrial free radical theory of aging, although definitive proof and many mechanistic details are still lacking.

Statistical methods for testing effects on “maximum lifespan”

It has been noted that certain interventions such as caloric restriction may increase maximum lifespan, whereas other interventions may increase mean or median lifespan but not maximum lifespan. Here the term “maximum lifespan” is used to refer to the upper percentiles of the distribution of lifespan. This is of great interest because increasing maximum lifespan may be an indicator that an intervention is slowing the general process of aging and not merely retarding the development of specific diseases. However, formal methods for testing maximum lifespan have not been elucidated. Herein, we show via simulation that conditional t-test (CTT), a method that is sometimes used, is invalid. We then offer a new method based on quantile regression and we show that this method is, at worst, conservative and remains powerful and valid.

Caloric restriction, gene expression and aging

Caloric restriction (CR) increases maximum life span in many species. In laboratory rodents, CR started either early in life or in middle-age opposes the development of age-associated biological and pathological changes. Three main questions are being asked by CR investigators. How does CR retard aging and disease processes? There is evidence that CR lowers oxidative stress generated by mitochondrial oxidative energy (i.e., calorie) metabolism. This lowering is most profound in post-mitotic tissues. Using microarrays, we have described the gene expression profile of aging skeletal muscle, heart and brain in mice and its alteration by CR. We observed that CR opposes the development of many age-associated changes while shifting the level of expression for many genes which are stable in expression with aging in normally fed mice. Does CR retard aging in primates? Two ongoing studies in rhesus monkeys on CR plus epidemiological data support the idea of human translatability. Whether CR extends life span in monkeys should become known in ∼15 years. Studies in humans on CR were launched by the NIA in 2002. Can substances be found which mimic the beneficial actions of CR? The search for “CR mimetics” should benefit from genomic and proteomic approaches.

Small molecule activators of sirtuins extend Saccharomyces cerevisiae lifespan.

In diverse organisms, calorie restriction slows the pace of ageing and increases maximum lifespan. In the budding yeast Saccharomyces cerevisiae, calorie restriction extends lifespan by increasing the activity of Sir2 (ref. 1), a member of the conserved sirtuin family of NAD(+)-dependent protein deacetylases. Included in this family are SIR-2.1, a Caenorhabditis elegans enzyme that regulates lifespan, and SIRT1, a human deacetylase that promotes cell survival by negatively regulating the p53 tumour suppressor. Here we report the discovery of three classes of small molecules that activate sirtuins. We show that the potent activator resveratrol, a polyphenol found in red wine, lowers the Michaelis constant of SIRT1 for both the acetylated substrate and NAD(+), and increases cell survival by stimulating SIRT1-dependent deacetylation of p53. In yeast, resveratrol mimics calorie restriction by stimulating Sir2, increasing DNA stability and extending lifespan by 70%. We discuss possible evolutionary origins of this phenomenon and suggest new lines of research into the therapeutic use of sirtuin activators.

Caloric restriction, gene expression, and aging.

Abstract Caloric restriction (CR) increases maximum life span in many species. In laboratory rodents, CR started either early in life or in middle-age opposes the development of age-associated biological and pathological changes. Three main questions are being asked by CR investigators. How does CR retard aging and disease processes? There is evidence that CR lowers oxidative stress generated by mitochondrial oxidative energy (i.e., calorie) metabolism. This lowering is most profound in post-mitotic tissues. Using microarrays, we have described the gene expression profile of aging skeletal muscle, heart and brain in mice and its alteration by CR. We observed that CR opposes the development of many age-associated changes while shifting the level of expression for many genes which are stable in expression with aging in normally fed mice. Does CR retard aging in primates? Two ongoing studies in rhesus monkeys on CR plus epidemiological data support the idea of human translatability. Whether CR extends life span in monkeys should become known in ∼15 years. Studies in humans on CR were launched by the NIA in 2002. Can substances be found which mimic the beneficial actions of CR? The search for “CR mimetics” should benefit from genomic and proteomic approaches.

Caloric restriction: life span extension and retardation of brain aging

Caloric restriction (CR) increases maximum life span in many species. In laboratory rodents, it opposes the development of age-associated biological and pathological changes. Although most rodent studies start CR early in life (∼1–3 months of age), CR from middle age also retards the aging process. Reviewed herein is the approach we are taking to address three questions concerning CR. How does CR retard aging and disease processes? There is evidence that CR lowers oxidative stress generated by mitochondrial oxidative energy (i.e. calorie) metabolism. This lowering is most profound in post-mitotic tissues. We have used microarrays to describe the gene expression profile of aging skeletal muscle, heart and brain (neocortex and cerebellum) in mice and its alteration by CR. In both brain regions, aging resulted in an expression profile indicative of a marked inflammatory response, oxidative stress, and reduced neurotrophic support. CR attenuated the age-associated inductions of genes involved in inflammatory and stress responses while shifting expression levels for several genes not changing with age. Does CR retard aging in primates? Two ongoing studies in rhesus monkeys on CR plus epidemiological data support the idea of human translatability. Whether life extension occurs in monkeys on CR should become known in ~15 years. Studies in humans on CR were launched by the NIA in 2002. Can substances be found which mimic the beneficial actions of CR? The search for ‘CR mimetics’ should benefit from the use of genomic and proteomic approaches.