Caloric restriction delays disease onset and mortality in rhesus monkeys

Lifelong protection from global cerebral ischemia and reperfusion in long-lived Mclk1(+/)(-) mutants

To achieve a long life span, animals must be resistant to various injuries as well as avoid or delay lethality from age-dependent diseases. Reduced expression of the mitochondrial enzyme CLK-1/MCLK1 (a.k.a. Coq7), a mitochondrial hydroxylase that is necessary for the biosynthesis of ubiquinone (UQ), extends lifespan in Caenorhabditiselegans and in mice. Here, we show that long-lived Mclk1(+/)(-) mutants have enhanced resistance to neurological damage following global cerebral ischemia-reperfusion (I/R) injury induced by transient bilateral common carotid artery occlusion (BCCAO). Both young ( approximately 100days old) and relatively aged ( approximately 450days old) mutants display increased resistance as indicated by a significant decrease in the amount of degenerating cells observed in forebrain cortex and in hippocampal areas after ischemia and reperfusion. Furthermore, less oxidative damage resulting from the procedure was measured in the brain of young Mclk1(+/)(-) animals. The finding that both young and old mutants are protected indicates that this is a basic phenotype of these mutants and not a secondary consequence of their slow rate of aging. Thus, the partial resistance to I/R injury suggests that Mclk1(+/)(-) mutants have an enhanced recovery potential following age-dependant vascular accidents, which correlates well with their longer survival. By relating this neuroprotective effect to previously reported characteristics of the Mclk1(+/)(-) phenotype, including altered mitochondrial metabolism and increased HIF-1alpha expression, this study establishes these mutants as useful models to analyze the mechanisms underlying tolerance to ischemia, particularly those associated with ischemic preconditioning, as well as to clarify the relation between aging and age-dependent diseases.

From estrogen-centric to aging and oxidative stress: a revised perspective of the pathogenesis of osteoporosis

Estrogen deficiency has been considered the seminal mechanism of osteoporosis in both women and men, but epidemiological evidence in humans and recent mechanistic studies in rodents indicate that aging and the associated increase in reactive oxygen species (ROS) are the proximal culprits. ROS greatly influence the generation and survival of osteoclasts, osteoblasts, and osteocytes. Moreover, oxidative defense by the FoxO transcription factors is indispensable for skeletal homeostasis at any age. Loss of estrogens or androgens decreases defense against oxidative stress in bone, and this accounts for the increased bone resorption associated with the acute loss of these hormones. ROS-activated FoxOs in early mesenchymal progenitors also divert ss-catenin away from Wnt signaling, leading to decreased osteoblastogenesis. This latter mechanism may be implicated in the pathogenesis of type 1 and 2 diabetes and ROS-mediated adverse effects of diabetes on bone formation. Attenuation of Wnt signaling by the activation of peroxisome proliferator-activated receptor gamma by ligands generated from lipid oxidation also contributes to the age-dependent decrease in bone formation, suggesting a mechanistic explanation for the link between atherosclerosis and osteoporosis. Additionally, increased glucocorticoid production and sensitivity with advancing age decrease skeletal hydration and thereby increase skeletal fragility by attenuating the volume of the bone vasculature and interstitial fluid. This emerging evidence provides a paradigm shift from the "estrogen-centric" account of the pathogenesis of involutional osteoporosis to one in which age-related mechanisms intrinsic to bone and oxidative stress are protagonists and age-related changes in other organs and tissues, such as ovaries, accentuate them.

Recent advances in vertebrate aging research 2009

Among the notable trends seen in this year's highlights in mammalian aging research is an awakening of interest in the assessment of age-related measures of mouse health in addition to the traditional focus on longevity. One finding of note is that overexpression of telomerase extended life and improved several indices of health in mice that had previously been genetically rendered cancer resistant. In another study, resveratrol supplementation led to amelioration of several degenerative conditions without affecting mouse lifespan. A primate dietary restriction (DR) study found that restriction led to major improvements in glucoregulatory status along with provocative but less striking effects on survival. Visceral fat removal in rats improved their survival, although not as dramatically as DR. An unexpected result showing the power of genetic background effects was that DR shortened the lifespan of long-lived mice bearing Prop1(df), whereas a previous report in a different background had found DR to extend the lifespan of Prop1(df) mice. Treatment with the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, enhanced the survival of even elderly mice and improved their vaccine response. Genetic inhibition of a TOR target made female, but not male, mice live longer. This year saw the mTOR network firmly established as a major modulator of mammalian lifespan.

Induction of hypothalamic Sirt1 leads to cessation of feeding via agouti-related peptide

Silent information regulator (SIR)2 is an nicotinamide adenine dinucleotide dependent deacetylase implicated in the regulation of life span in species as diverse as yeast, worms, and flies. Mammalian Sirt1 is the most closely related homolog of the SIR2 gene. Pharmacological activators of Sirt1 have been reported to increase the life span and improve the health of mice fed a high-fat diet and to reverse diabetes in rodents. Sirt1 links the energy availability status with cellular metabolism in peripheral organs including liver, pancreas, muscle, and white adipose tissue. Insulin and leptin signaling regulate food intake by controlling the expression of orexigenic and anorexigenic neuropeptides in the arcuate nucleus of the hypothalamus via Forkhead box O (Foxo)-1 and signal transducer and activator of transcription-3. Sirt1 has been reported to improve insulin sensitivity in vitro, but the role of hypothalamic Sirt1 in regulating feeding has not been addressed. We found that hypothalamic Sirt1 protein levels increase on feeding, and this induction is abrogated in diet-induced obese mice and db/db mice. We also demonstrate for the first time that Sirt1 protein turnover is regulated by the proteasome and ubiquitination in a hypothalamic cell line and in vivo by feeding, and this regulation is not seen in a pituitary cell line AtT20. Forced expression of wild-type Sirt1 in the mediobasal hypothalamus by adenovirus microinjection suppressed Foxo1-induced hyperphagia, a model for central insulin resistance. Moreover, Sirt1 suppressed Foxo1-dependent expression of the orexigenic neuropeptide Agouti-related peptide in vitro. We propose that on feeding, Sirt1 protein is stabilized in the hypothalamus, leading to decreased Foxo1-dependent expression of orexigenic neuropeptide Agouti-related peptide and cessation of feeding.

Favorable glucose tolerance and lower prevalence of metabolic syndrome in offspring without diabetes mellitus of nonagenarian siblings: the Leiden longevity study

OBJECTIVES

To explore measures of metabolic syndrome and glucose metabolism in families with exceptional longevity.

DESIGN

Case-control study.

SETTING

A university hospital in Leiden, the Netherlands.

PARTICIPANTS

One hundred twenty-one offspring of nonagenarian siblings, who were enriched for familial factors promoting longevity, and 113 of their partners. No subject had diabetes mellitus.

MEASUREMENTS

Prevalence of metabolic syndrome was determined according to the criteria of the Third Report of the National Cholesterol Education Program. Glucose tolerance was assessed according to a 2-hour oral glucose tolerance test.

RESULTS

The offspring of nonagenarians siblings had a lower prevalence of metabolic syndrome (P=.03), similar body composition, lower mean fasting blood glucose levels (4.99 vs 5.16 mmol/L; P=.01), lower mean fasting insulin levels (5.81 vs 6.75 mU/L; P=.04), a higher mean homeostasis model assessment of insulin sensitivity (0.78 vs 0.65; P=.02), and a more-favorable glucose tolerance (mean area under the receiver operating characteristic curve for glucose (13.2 vs 14.3; P=.007) than their partners. No significant differences were observed between the offspring and their partners in beta-cell function (insulogenic index 13.6 vs 12.5; P=.38).

CONCLUSION

Despite similar body composition, the offspring of nonagenarian siblings showed a lower prevalence of metabolic syndrome and better glucose tolerance than their partners, centralizing the role of favorable glucose metabolism in familial longevity.

A commonly carried allele of the obesity-related FTO gene is associated with reduced brain volume in the healthy elderly

A recently identified variant within the fat mass and obesity-associated (FTO) gene is carried by 46% of Western Europeans and is associated with an approximately 1.2 kg higher weight, on average, in adults and an approximately 1 cm greater waist circumference. With >1 billion overweight and 300 million obese persons worldwide, it is crucial to understand the implications of carrying this very common allele for the health of our aging population. FTO is highly expressed in the brain and elevated body mass index (BMI) is associated with brain atrophy, but it is unknown how the obesity-associated risk allele affects human brain structure. We therefore generated 3D maps of regional brain volume differences in 206 healthy elderly subjects scanned with MRI and genotyped as part of the Alzheimer's Disease Neuroimaging Initiative. We found a pattern of systematic brain volume deficits in carriers of the obesity-associated risk allele versus noncarriers. Relative to structure volumes in the mean template, FTO risk allele carriers versus noncarriers had an average brain volume difference of approximately 8% in the frontal lobes and 12% in the occipital lobes-these regions also showed significant volume deficits in subjects with higher BMI. These brain differences were not attributable to differences in cholesterol levels, hypertension, or the volume of white matter hyperintensities; which were not detectably higher in FTO risk allele carriers versus noncarriers. These brain maps reveal that a commonly carried susceptibility allele for obesity is associated with structural brain atrophy, with implications for the health of the elderly.

Calorie restriction: what recent results suggest for the future of ageing research

BACKGROUND

Calorie Restriction (CR) research has expanded rapidly over the past few decades and CR remains the most highly reproducible, environmental intervention to improve health and extend lifespan in animal studies. Although many model organisms have consistently demonstrated positive responses to CR, it remains to be shown whether CR will extend lifespan in humans. Additionally, the current environment of excess caloric consumption and high incidence of overweight/obesity illustrate the improbable nature of the long-term adoption of a CR lifestyle by a significant proportion of the human population. Thus, the search for substances that can reproduce the beneficial physiologic responses of CR without a requisite calorie intake reduction, termed CR mimetics (CRMs), has gained momentum.

MATERIAL AND METHODS

Recent articles describing health and lifespan results of CR in nonhuman primates and short-term human studies are discussed. Additional consideration is given to the rapidly expanding search for CRMs.

RESULTS

The first results from a long-term, randomized, controlled CR study in nonhuman primates showing statistically significant benefits on longevity have now been reported. Additionally, positive results from short-term, randomized, controlled CR studies in humans are suggestive of potential health and longevity gains, while test of proposed CRMs (including rapamycin, resveratrol, 2-deoxyglucose and metformin) have shown both positive and mixed results in rodents.

CONCLUSION

Whether current positive results will translate into longevity gains for humans remains an open question. However, the apparent health benefits that have been observed with CR suggest that regardless of longevity gains, the promotion of healthy ageing and disease prevention may be attainable.

Anti-aging medicine: molecular basis for endothelial cell-targeted strategies - a mini-review

Due to improvements in lifestyle and healthcare, the proportion of aged people is rising steadily, especially in developed countries. With aging, some physiological functions are altered and resemble those occurring in disease conditions such as hypertension, chronic coronary disease and diabetes. Thus, there is the urge to better understand molecular and cellular mechanisms underlying aging and aging-related diseases. In rodents and possibly primates, calorie restriction is an effective approach to extend lifespan by reducing free radical-induced damage. Increased production of oxygen-derived free radicals plays an important role in the process of aging. Reactive oxygen species are generated by different intracellular molecular pathways principally located in the cytoplasm and in the mitochondria. The mitochondrial protein p66(Shc) is considered a longevity assurance gene since its genetic deletion extends the lifespan of rodents and displays protective effects in several models of cardiovascular disease. Silent mating type information regulation 2 homolog 1 Saccharomyces cerevisiae (SIRT1) is a nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylase that may also be involved in aging and diseases. SIRT1 also deacetylates a number of nonhistone target proteins, including p53, endothelial nitric oxide synthase and forkhead box protein. This review focuses on the latest scientific advances in understanding aging as well as delineates the possible therapeutic implications of p66(Shc) and SIRT1 in this process.

High-fiber diet promotes weight loss and affects maternal behavior in vervet monkeys

The dramatic increase in obesity in western societies has shifted the emphasis in nutrition research from the problems of undernutrition to the adverse consequences of being overweight. As with humans, Old World monkeys are at increased risk for type II diabetes and other chronic diseases when they gain excessive weight. To prevent overweight and obesity, promote animal health, and provide a more natural level of fiber in the diet, the standard commercial monkey chow diet at a vervet monkey breeding colony was changed to a higher fiber formulation in 2004. The new diet was also higher in protein and lower in carbohydrate and energy density than the standard diet. Because maternal behavior is known to be sensitive to differences in resource availability, data on weight and mother-infant interactions for 147 mothers with 279 infants born from 2000 through 2006 were assessed for effects of the diet change. The results showed that, even though food was provided ad libitum, the mean body weight of breeding females was 10% lower after the transition to the high-fiber diet. Behaviorally, mothers on the high-fiber diet were significantly more rejecting to their infants, and their infants had to play a greater role in maintaining ventral contact in the first few months of their lives. The effects of the diet change on maternal rejection were significantly related to the mother's body weight, with lower-weight mothers scoring higher in maternal rejection. These results demonstrate that maternal behavior is responsive to changes in maternal condition, and that beneficial changes in the diet may have unintended consequences on behavior.

Extending healthy life span--from yeast to humans

When the food intake of organisms such as yeast and rodents is reduced (dietary restriction), they live longer than organisms fed a normal diet. A similar effect is seen when the activity of nutrient-sensing pathways is reduced by mutations or chemical inhibitors. In rodents, both dietary restriction and decreased nutrient-sensing pathway activity can lower the incidence of age-related loss of function and disease, including tumors and neurodegeneration. Dietary restriction also increases life span and protects against diabetes, cancer, and cardiovascular disease in rhesus monkeys, and in humans it causes changes that protect against these age-related pathologies. Tumors and diabetes are also uncommon in humans with mutations in the growth hormone receptor, and natural genetic variants in nutrient-sensing pathways are associated with increased human life span. Dietary restriction and reduced activity of nutrient-sensing pathways may thus slow aging by similar mechanisms, which have been conserved during evolution. We discuss these findings and their potential application to prevention of age-related disease and promotion of healthy aging in humans, and the challenge of possible negative side effects.

Dietary restriction modifies certain aspects of the postoperative acute phase response

BACKGROUND

Lifespan extension is achieved through long-term application of dietary restriction (DR), and benefits of short-term dietary restriction on acute stress and inflammation have been observed. So far, the effects of short-term DR in humans are relatively unknown. We hypothesized that short-term DR in humans reduces the acute phase response following a well defined surgical trauma.

METHODS

Thirty live kidney donors were randomized between 30% preoperative dietary restriction followed by 1 d of fasting (n=17) or a 4 d ad libitum regimen (n=13) prior to surgery. Leukocyte subsets and numbers and serum cytokine levels were determined. Whole blood was stimulated with lipopolysaccharide (LPS) and cytokine production was determined.

RESULTS

A clear trend towards lower numbers of postoperative circulating leukocytes was observed in the DR group. IL-8 serum levels were significantly higher in the DR group over the first 6 postoperative d (P=0.018). After LPS stimulation, significantly less TNF-α (P=0.001) was produced by blood obtained postoperatively compared with preoperative blood from the DR group. This was not observed in the control group.

CONCLUSIONS

A relatively short preoperative dietary restriction regimen was able to modify certain aspects of the postoperative acute phase response. These data warrant further studies into the dietary conditions that improve stress resistance in humans. (Dutch Trial Registry number: NTR1875).

The genetics of ageing

The nematode Caenorhabditis elegans ages and dies in a few weeks, but humans can live for 100 years or more. Assuming that the ancestor we share with nematodes aged rapidly, this means that over evolutionary time mutations have increased lifespan more than 2,000-fold. Which genes can extend lifespan? Can we augment their activities and live even longer? After centuries of wistful poetry and wild imagination, we are now getting answers, often unexpected ones, to these fundamental questions.

More than the sum of its parts? Nutrition in Alzheimer's disease

The aim of this article is to emphasize the importance of malnutrition and micronutrient deficiencies in Alzheimer's disease and discuss recent supplementation trials. Alzheimer's disease (AD) is a devastating neurodegenerative disease with increasing socio-economic impact. It leads to cognitive decline over the years, finally resulting in brain atrophy and gradually destroying a person's ability to learn, reason, make judgments, and communicate. Most of the cases are sporadic and risk factors evolve. There is evidence that malnutrition, oxidative stress, and homocysteine-related vitamins play a role in the pathogenesis of AD. A plethora of epidemiologic studies have explored the associations between nutrients and AD. In addition, more and more data from recent trials are evolving to analyze the impact of micronutrient supplementation in AD and incipient AD concerning B vitamin status and antioxidants. Available data do not support definitive conclusions regarding specific recommendations on micronutrient supplementation for the prevention or treatment of AD; however, more data from prospective trials are needed. Approaches with multiple nutritional components might be promising.

Dietary interventions to extend life span and health span based on calorie restriction

The societal impact of obesity, diabetes, and other metabolic disorders continues to rise despite increasing evidence of their negative long-term consequences on health span, longevity, and aging. Unfortunately, dietary management and exercise frequently fail as remedies, underscoring the need for the development of alternative interventions to successfully treat metabolic disorders and enhance life span and health span. Using calorie restriction (CR)-which is well known to improve both health and longevity in controlled studies-as their benchmark, gerontologists are coming closer to identifying dietary and pharmacological therapies that may be applicable to aging humans. This review covers some of the more promising interventions targeted to affect pathways implicated in the aging process as well as variations on classical CR that may be better suited to human adaptation.

Rapamycin extends maximal lifespan in cancer-prone mice

Aging is associated with obesity and cancer. Calorie restriction both slows down aging and delays cancer. Evidence has emerged that the nutrient-sensing mammalian target of rapamycin (mTOR) pathway is involved in cellular and organismal aging. Here we show that the mTOR inhibitor rapamycin prevents age-related weight gain, decreases rate of aging, increases lifespan, and suppresses carcinogenesis in transgenic HER-2/neu cancer-prone mice. Rapamycin dramatically delayed tumor onset as well as decreased the number of tumors per animal and tumor size. We suggest that, by slowing down organismal aging, rapamycin delays cancer.

Energy balance, the PI3K-AKT-mTOR pathway genes, and the risk of bladder cancer

We evaluated the association between energy balance and risk of bladder cancer and assessed the joint effects of genetic variants in the mammalian target of rapamycin (mTOR) pathway genes with energy balance. The study included 803 Caucasian bladder cancer patients and 803 healthy Caucasian controls matched to cases by age (+/-5 years) and gender. High energy intake [odds ratio, 1.60; 95% confidence interval (95% CI), 1.23-2.09] and low physical activity (odds ratio, 2.82; 95% CI, 2.10-3.79) were each associated with significantly increased risk of bladder cancer with dose-response pattern (P(trend) < 0.001). However, obesity (body mass index, > or =30) was not associated with the risk. Among 222 single nucleotide polymorphisms, 28 single nucleotide polymorphisms located in six genes of mTOR pathway were significantly associated with the risk. Further, the risk associated with high energy intake and low physical activity was only observed among subjects carrying a high number of unfavorable genotypes in the pathway. Moreover, when physical activity, energy intake, and genetic variants were analyzed jointly, the study population was clearly stratified into a range of low- to high-risk subgroups as defined energy balance status. Compared with subjects within the most favorable energy balance category (low energy intake, intensive physical activity, low number of unfavorable genotypes), subjects in the worst energy balance category (high energy intake, low physical activity, and carrying > or =7 unfavorable genotypes) had 21.93-fold increased risk (95% CI, 6.7-71.77). Our results provide the first strong evidence that physical activity, energy intake, and genetic variants in the mTOR pathway jointly influence bladder cancer susceptibility and that these results have implications for bladder cancer prevention.

Aging and disease: connections to sirtuins

The sirtuins are highly conserved NAD-dependent deacetylases that were shown to regulate lifespan in lower organisms and affect diseases of aging in mammals, such as diabetes, cancer, and inflammation. Most relevant to the amelioration of disease, the SIR2 ortholog SIRT1 has been shown to deacetylate many important transcription factors to exert an overarching influence on numerous metabolic pathways. Here we discuss several diseases of aging for which SIRT1 has been recently shown to confer protection. These findings suggest that manipulating sirtuin activity pharmacologically may be a fruitful area to improve human health.

Dietary restriction and aging, 2009

Dietary restriction (DR) is a robust nongenetic, nonpharmacological intervention that is known to increase active and healthy lifespan in a variety of species. Despite a variety of differences in the protocols and the way DR is carried out in different species, conserved relationships are emerging among multiple species. 2009 saw the field of DR mature with important mechanistic insights from multiple species. A report of lifespan extension in rapamycin-treated mice suggested that the TOR pathway, a conserved mediator of DR in invertebrates, may also be critical to DR effects in mammals. 2009 also saw exciting discoveries related to DR in various organisms including yeast, worms, flies, mice, monkeys and humans. These studies complement each other and together aim to deliver the promise of postponing aging and age-related diseases by revealing the underlying mechanisms of the protective effects of DR. Here, we summarize a few of the reports published in 2009 that we believe provide novel directions and an improved understanding of dietary restriction.

Long-term effects of calorie restriction on serum sex-hormone concentrations in men

Calorie restriction (CR) slows aging and consistently reduces circulating sex hormones in laboratory animals. However, nothing is known regarding the long-term effects of CR with adequate nutrition on serum sex-hormone concentration in lean healthy humans. In this study, we measured body composition, and serum total testosterone, total 17-beta-estradiol, sex hormone-binding globulin (SHBG), and dehydroepiandrosterone sulfate (DHEA-S) concentrations in 24 men (mean age 51.5 +/- 13 years), who had been practicing CR with adequate nutrition for an average of 7.4 +/- 4.5 years, in 24 age- and body fat-matched endurance runners (EX), and 24 age-matched sedentary controls eating Western diets (WD). We found that both the CR and EX volunteers had significantly lower body fat than the WD volunteers (total body fat, 8.7 +/- 4.2%; 10.5 +/- 4.4%; 23.2 +/- 6.1%, respectively; P = 0.0001). Serum total testosterone and the free androgen index were significantly lower, and SHBG was higher in the CR group than in the EX and WD groups (P < or = 0.001). Serum 17beta-estradiol and the estradiol:SHBG ratio were both significantly lower in the CR and EX groups than in the WD group (P < or = 0.005). Serum DHEA-S concentrations were not different between the three groups. These findings demonstrate that, as in long-lived CR rodents, long-term severe CR reduces serum total and free testosterone and increases SHBG concentrations in humans, independently of adiposity. More studies are needed to understand the role of this CR-mediated reduction in sex hormones in modulating the pathogenesis of age-associated chronic diseases such as cancer and the aging process itself.

Targeting the autophagy pathway for cancer chemoprevention

Autophagy is crucial for maintaining cellular homeostasis, coping with metabolic stress, and limiting oxidative damage. Several autophagy-deficient or knockout models show increased tumor incidence, implicating autophagy as a tumor suppressor. Autophagy is involved in multiple processes that may curb transformation, including the control of oncogene-induced senescence (OIS), which can limit progression to full malignancy, and efficient antigen presentation, which is crucial for immune cell recognition and elimination of nascent cancer cells. Activation of the autophagy pathway may therefore hold promise as a chemoprevention strategy. Caloric restriction, bioactive dietary compounds, or specific pharmacological activators of the autophagy pathway are all possible avenues to explore in harnessing the autophagy pathway in cancer prevention.

Reduced mortality and moderate alcohol consumption: the phospholipase D-mTOR connection

Many studies have suggested that moderate alcohol consumption reduces mortality. There is also substantial evidence that lifespan is extended with suppression of TOR (target of rapamycin). It was reported recently that rapamycin is able to extend the lifespan of a mammal--implicating the mammalian TOR (mTOR). mTOR has a requirement for the lipid second messenger phosphatidic acid (PA), which is generated by phospholipase D (PLD). Therefore, in principle, suppression of PLD would be similar to treatment with rapamycin. Significantly, PLD utilizes ethanol preferentially over water in the hydrolysis reaction that ordinarily generates PA. In the presence of ethanol, phosphatidyl-ethanol is generated at the expense of PA leading to the suppression of mTOR. This reaction, known as the transphosphatidylation reaction, provides a mechanistic basis for the reduced mortality observed with moderate consumption of alcohol--that being the suppression of mTOR.

Resveratrol, sirtuins, and the promise of a DR mimetic

Dietary restriction (DR) delays or prevents age-related diseases and extends lifespan in species ranging from yeast to primates. Although the applicability of this regimen to humans remains uncertain, a proportional response would add more healthy years to the average life than even a cure for cancer or heart disease. Because it is unlikely that many would be willing or able to maintain a DR lifestyle, there has been intense interest in mimicking its beneficial effects on health, and potentially longevity, with drugs. To date, such efforts have been hindered primarily by our lack of mechanistic understanding of how DR works. Sirtuins, NAD(+)-dependent deacetylases and ADP-ribosyltransferases that influence lifespan in lower organisms, have been proposed to be key mediators of DR, and based on this model, the sirtuin activator resveratrol has been proposed as a candidate DR mimetic. Indeed, resveratrol extends lifespan in yeast, worms, flies, and a short-lived species of fish. In rodents, resveratrol improves health, and prevents the early mortality associated with obesity, but its precise mechanism of action remains a subject of debate, and extension of normal lifespan has not been observed. This review summarizes recent work on resveratrol, sirtuins, and their potential to mimic beneficial effects of DR.

Regulation of selenoproteins and methionine sulfoxide reductases A and B1 by age, calorie restriction, and dietary selenium in mice

Methionine residues are susceptible to oxidation, but this damage may be reversed by methionine sulfoxide reductases MsrA and MsrB. Mammals contain one MsrA and three MsrBs, including a selenoprotein MsrB1. Here, we show that MsrB1 is the major methionine sulfoxide reductase in liver of mice and it is among the proteins that are most easily regulated by dietary selenium. MsrB1, but not MsrA activities, were reduced with age, and the selenium regulation of MsrB1 was preserved in the aging liver, suggesting that MsrB1 could account for the impaired methionine sulfoxide reduction in aging animals. We also examined regulation of Msr and selenoprotein expression by a combination of dietary selenium and calorie restriction and found that, under calorie restriction conditions, selenium regulation was preserved. In addition, mice overexpressing a mutant form of selenocysteine tRNA reduced MsrB1 activity to the level observed in selenium deficiency, whereas MsrA activity was elevated in these animals. Finally, we show that selenium regulation in inbred mouse strains is preserved in an outbred aging model. Taken together, these findings better define dietary regulation of methionine sulfoxide reduction and selenoprotein expression in mice with regard to age, calorie restriction, dietary Se, and a combination of these factors.

How increased oxidative stress promotes longevity and metabolic health: The concept of mitochondrial hormesis (mitohormesis)

Recent evidence suggests that calorie restriction and specifically reduced glucose metabolism induces mitochondrial metabolism to extend life span in various model organisms, including Saccharomyces cerevisiae, Drosophila melanogaster, Caenorhabditis elegans and possibly mice. In conflict with Harman's free radical theory of aging (FRTA), these effects may be due to increased formation of reactive oxygen species (ROS) within the mitochondria causing an adaptive response that culminates in subsequently increased stress resistance assumed to ultimately cause a long-term reduction of oxidative stress. This type of retrograde response has been named mitochondrial hormesis or mitohormesis, and may in addition be applicable to the health-promoting effects of physical exercise in humans and, hypothetically, impaired insulin/IGF-1-signaling in model organisms. Consistently, abrogation of this mitochondrial ROS signal by antioxidants impairs the lifespan-extending and health-promoting capabilities of glucose restriction and physical exercise, respectively. In summary, the findings discussed in this review indicate that ROS are essential signaling molecules which are required to promote health and longevity. Hence, the concept of mitohormesis provides a common mechanistic denominator for the physiological effects of physical exercise, reduced calorie uptake, glucose restriction, and possibly beyond.

The genetics of ageing

The nematode Caenorhabditis elegans ages and dies in a few weeks, but humans can live for 100 years or more. Assuming that the ancestor we share with nematodes aged rapidly, this means that over evolutionary time mutations have increased lifespan more than 2,000-fold. Which genes can extend lifespan? Can we augment their activities and live even longer? After centuries of wistful poetry and wild imagination, we are now getting answers, often unexpected ones, to these fundamental questions.

Neural mechanisms of ageing and cognitive decline

During the past century, treatments for the diseases of youth and middle age have helped raise life expectancy significantly. However, cognitive decline has emerged as one of the greatest health threats of old age, with nearly 50% of adults over the age of 85 afflicted with Alzheimer's disease. Developing therapeutic interventions for such conditions demands a greater understanding of the processes underlying normal and pathological brain ageing. Recent advances in the biology of ageing in model organisms, together with molecular and systems-level studies of the brain, are beginning to shed light on these mechanisms and their potential roles in cognitive decline.

Impact papers on aging in 2009

The editorial board of Aging reviews research papers published in 2009, which they believe have or will have a significant impact on aging research. Among many others, the topics include genes that accelerate aging or in contrast promote longevity in model organisms, DNA damage responses and telomeres, molecular mechanisms of life span extension by calorie restriction and pharmacologic interventions into aging. The emerging message in 2009 is that aging is not random but determined by a genetically-regulated longevity network and can be decelerated both genetically and pharmacologically.

The new biology of ageing

Human life expectancy in developed countries has increased steadily for over 150 years, through improvements in public health and lifestyle. More people are hence living long enough to suffer age-related loss of function and disease, and there is a need to improve the health of older people. Ageing is a complex process of damage accumulation, and has been viewed as experimentally and medically intractable. This view has been reinforced by the realization that ageing is a disadvantageous trait that evolves as a side effect of mutation accumulation or a benefit to the young, because of the decline in the force of natural selection at later ages. However, important recent discoveries are that mutations in single genes can extend lifespan of laboratory model organisms and that the mechanisms involved are conserved across large evolutionary distances, including to mammals. These mutations keep the animals functional and pathology-free to later ages, and they can protect against specific ageing-related diseases, including neurodegenerative disease and cancer. Preliminary indications suggest that these new findings from the laboratory may well also apply to humans. Translating these discoveries into medical treatments poses new challenges, including changing clinical thinking towards broad-spectrum, preventative medicine and finding novel routes to drug development.

SIRT1/eNOS axis as a potential target against vascular senescence, dysfunction and atherosclerosis

Sir2 (silent information regulator-2), an NAD(+)-dependent histone deacetylase, is highly conserved in organisms ranging from archaea to humans. Yeast Sir2 is responsible for silencing at repeated DNA sequences in mating-type loci, telomeres and rDNA, and plays critical roles in DNA repair, stress resistance and longevity.The phenomenon of human aging is known to be a critical cardiovascular risk factor. Senescence of endothelial cells has been proposed to be involved in vascular dysfunction and atherogenesis. Recent studies have demonstrated that mammalian Sirt1 NAD(+)-dependent protein deacetylase, the closest homologue of Sir2, regulates vascular angiogenesis, homeostasis and senescence. This review focuses on SIRT1 as a potential therapeutic target against atherosclerosis.

Sestrin as a feedback inhibitor of TOR that prevents age-related pathologies

Sestrins are conserved proteins that accumulate in cells exposed to stress, potentiate adenosine monophosphate-activated protein kinase (AMPK), and inhibit activation of target of rapamycin (TOR). We show that the abundance of Drosophila sestrin (dSesn) is increased upon chronic TOR activation through accumulation of reactive oxygen species that cause activation of c-Jun amino-terminal kinase and transcription factor Forkhead box O (FoxO). Loss of dSesn resulted in age-associated pathologies including triglyceride accumulation, mitochondrial dysfunction, muscle degeneration, and cardiac malfunction, which were prevented by pharmacological activation of AMPK or inhibition of TOR. Hence, dSesn appears to be a negative feedback regulator of TOR that integrates metabolic and stress inputs and prevents pathologies caused by chronic TOR activation that may result from diminished autophagic clearance of damaged mitochondria, protein aggregates, or lipids.

Absence of uncoupling protein-3 leads to greater activation of an adenine nucleotide translocase-mediated proton conductance in skeletal muscle mitochondria from calorie restricted mice

Calorie restriction (CR), without malnutrition, consistently increases lifespan in all species tested, and reduces age-associated pathologies in mammals. Alterations in mitochondrial content and function are thought to underlie some of the effects of CR. Previously, we reported that rats subjected to variable durations of 40% CR demonstrated a rapid and sustained decrease in maximal leak-dependent respiration in skeletal muscle mitochondria. This was accompanied by decreased mitochondrial reactive oxygen species generation and increased uncoupling protein-3 protein (UCP3) expression. The aim of the present study was to determine the contribution of UCP3, as well as the adenine nucleotide translocase to these functional changes in skeletal muscle mitochondria. Consistent with previous findings in rats, short-term CR (2 weeks) in wild-type (Wt) mice resulted in a lowering of the maximal leak-dependent respiration in skeletal muscle mitochondria, without any change in proton conductance. In contrast, skeletal muscle mitochondria from Ucp3-knockout (KO) mice similarly subjected to short-term CR showed no change in maximal leak-dependent respiration, but displayed an increased proton conductance. Determination of ANT activity (by measurement of inhibitor-sensitive leak) and protein expression revealed that the increased proton conductance in mitochondria from CR Ucp3-KO mice could be entirely attributed to a greater acute activation of ANT. These observations implicate UCP3 in CR-induced mitochondrial remodeling. Specifically, they imply the potential for an interaction, or some degree of functional redundancy, between UCP3 and ANT, and also suggest that UCP3 can minimize the induction of the ANT-mediated 'energy-wasting' process during CR.

Effects of caloric restriction on cardiovascular aging in non-human primates and humans

Approximately one in three Americans has some form of cardiovascular disease (CVD), accounting for one of every 2.8 deaths in the United States in 2004. Two of the major risk factors for CVD are advancing age and obesity. An intervention able to positively impact both aging and obesity, such as caloric restriction (CR), may prove extremely useful in the fight against CVD. CR is the only environmental or lifestyle intervention that repeatedly has been shown to increase maximum life span and to retard aging in laboratory rodents. This article reviews evidence that CR in nonhuman primates and people has a positive effect on risk factors for CVD.

Forty percent methionine restriction decreases mitochondrial oxygen radical production and leak at complex I during forward electron flow and lowers oxidative damage to proteins and mitochondrial DNA in rat kidney and brain mitochondria

Eighty percent dietary methionine restriction (MetR) in rodents (without calorie restriction), like dietary restriction (DR), increases maximum longevity and strongly decreases mitochondrial reactive oxygen species (ROS) production and oxidative stress. Eighty percent MetR also lowers the degree of membrane fatty acid unsaturation in rat liver. Mitochondrial ROS generation and the degree of fatty acid unsaturation are the only two known factors linking oxidative stress with longevity in vertebrates. However, it is unknown whether 40% MetR, the relevant methionine restriction degree to clarify the mechanisms of action of standard (40%) DR can reproduce these effects in mitochondria from vital tissues of strong relevance for aging. Here we study the effect of 40% MetR on ROS production and oxidative stress in rat brain and kidney mitochondria. Male Wistar rats were fed during 7 weeks semipurified diets differing only in their methionine content: control or 40% MetR diets. It was found that 40% MetR decreases mitochondrial ROS production and percent free radical leak (by 62-71%) at complex I during forward (but not during reverse) electron flow in both brain and kidney mitochondria, increases the oxidative phosphorylation capacity of brain mitochondria, lowers oxidative damage to kidney mitochondrial DNA, and decreases specific markers of mitochondrial protein oxidation, lipoxidation, and glycoxidation in both tissues. Forty percent MetR also decreased the amount of respiratory complexes I, III, and IV and apoptosis-inducing factor (AIF) in brain mitochondria and complex IV in kidney mitochondria, without changing the degree of mitochondrial membrane fatty acid unsaturation. Forty percent MetR, differing from 80% MetR, did not inhibit the increase in rat body weight. These changes are very similar to the ones previously found during dietary and protein restriction in rats. We conclude that methionine is the only dietary factor responsible for the decrease in mitochondrial ROS production and oxidative stress, and likely for part of the longevity extension effect, occurring in DR.

Stress-induced obesity and the emotional nervous system

Stress and emotional brain networks foster eating behaviors that can lead to obesity. The neural networks underlying the complex interactions among stressors, body, brain and food intake are now better understood. Stressors, by activating a neural stress-response network, bias cognition toward increased emotional activity and degraded executive function. This causes formed habits to be used rather than a cognitive appraisal of responses. Stress also induces secretion of glucocorticoids, which increases motivation for food, and insulin, which promotes food intake and obesity. Pleasurable feeding then reduces activity in the stress-response network, reinforcing the feeding habit. These effects of stressors emphasize the importance of teaching mental reappraisal techniques to restore responses from habitual to thoughtful, thus battling stress-induced obesity.

Auditory function in rhesus monkeys: effects of aging and caloric restriction in the Wisconsin monkeys five years later

Caloric restriction (CR) slows aging in many species and protects some animals from age-related hearing loss (ARHL), but the effect on humans is not yet known. Because rhesus monkeys are long-lived primates that are phylogenically closer to humans than other research animals are, they provide a better model for studying the effects of CR in aging and ARHL. Subjects were from the pool of 55 rhesus monkeys aged 15-28 years who had been in the Wisconsin study on CR and aging for 8-13.5 years. Distortion product otoacoustic emissions (DPOAE) with f2 frequencies from 2211 to 8837 Hz and auditory brainstem response (ABR) thresholds from clicks and 8, 16, and 32 kHz tone bursts were obtained. DPOAE levels declined linearly at approximately 1 dB/year, but that rate doubled for the highest frequencies in the oldest monkeys. There were no interactions for diet condition or sex. ABR thresholds to clicks and tone bursts showed increases with aging. Borderline significance was shown for diet in the thresholds at 8 kHz stimuli, with monkeys on caloric restriction having lower thresholds. Because the rhesus monkeys have a maximum longevity of 40 years, the full benefits of CR may not yet be realized.

Metabolic reprogramming, caloric restriction and aging

Caloric restriction (CR) without malnutrition slows the aging process and extends lifespan in diverse species by unknown mechanisms. The inverse linear relationship between calorie intake and lifespan suggests that regulators of energy metabolism are important in the actions of CR. Studies in several species reveal tissue-specific changes in energy metabolism with CR and suggest that metabolic reprogramming plays a critical role in its mechanism of aging retardation. We herein describe common signatures of CR and suggest how they can slow aging. We discuss recent advances in understanding the function of key metabolic regulators that probably coordinate the response to altered nutrient availability with CR and how the pathways they regulate can retard the aging process.

Short-term dietary restriction and fasting precondition against ischemia reperfusion injury in mice

Dietary restriction (DR) extends lifespan and increases resistance to multiple forms of stress, including ischemia reperfusion injury to the brain and heart in rodents. While maximal effects on lifespan require long-term restriction, the kinetics of onset of benefits against acute stress is not known. Here, we show that 2-4 weeks of 30% DR improved survival and kidney function following renal ischemia reperfusion injury in mice. Brief periods of water-only fasting were similarly effective at protecting against ischemic damage. Significant protection occurred within 1 day, persisted for several days beyond the fasting period and extended to another organ, the liver. Protection by both short-term DR and fasting correlated with improved insulin sensitivity, increased expression of markers of antioxidant defense and reduced expression of markers of inflammation and insulin/insulin-like growth factor-1 signaling. Unbiased transcriptional profiling of kidneys from mice subject to short-term DR or fasting revealed a significant enrichment of signature genes of long-term DR. These data demonstrate that brief periods of reduced food intake, including short-term daily restriction and fasting, can increase resistance to ischemia reperfusion injury in rodents and suggest a rapid onset of benefits of DR in mammals.

Mosaic aging

Although all multicellular organisms undergo structural and functional deterioration with age, senescence is not a uniform process. Rather, each organism experiences a constellation of changes that reflect the heterogeneous effects of age on molecules, cells, organs and systems, an idiosyncratic pattern that we refer to as mosaic aging. Varying genetic, epigenetic and environmental factors (local and extrinsic) contribute to the aging phenotype in a given individual, and these agents influence the type and rate of functional decline, as well as the likelihood of developing age-associated afflictions such as cardiovascular disease, arthritis, cancer, and neurodegenerative disorders. Identifying key factors that drive aging, clarifying their activities in different systems, and in particular understanding how they interact will enhance our comprehension of the aging process, and could yield insights into the permissive role that senescence plays in the emergence of acute and chronic diseases of the elderly.

Evolution in health and medicine Sackler colloquium: Evolution of the human lifespan and diseases of aging: roles of infection, inflammation, and nutrition

Humans have evolved much longer lifespans than the great apes, which rarely exceed 50 years. Since 1800, lifespans have doubled again, largely due to improvements in environment, food, and medicine that minimized mortality at earlier ages. Infections cause most mortality in wild chimpanzees and in traditional forager-farmers with limited access to modern medicine. Although we know little of the diseases of aging under premodern conditions, in captivity, chimpanzees present a lower incidence of cancer, ischemic heart disease, and neurodegeneration than current human populations. These major differences in pathology of aging are discussed in terms of genes that mediate infection, inflammation, and nutrition. Apolipoprotein E alleles are proposed as a prototype of pleiotropic genes, which influence immune responses, arterial and Alzheimer's disease, and brain development.

Calorie restriction and cancer prevention: metabolic and molecular mechanisms

An important discovery of recent years has been that lifestyle and environmental factors affect cancer initiation, promotion and progression, suggesting that many malignancies are preventable. Epidemiological studies strongly suggest that excessive adiposity, decreased physical activity, and unhealthy diets are key players in the pathogenesis and prognosis of many common cancers. In addition, calorie restriction (CR), without malnutrition, has been shown to be broadly effective in cancer prevention in laboratory strains of rodents. Adult-onset moderate CR also reduces cancer incidence by 50% in monkeys. Whether the antitumorigenic effects of CR will apply to humans is unknown, but CR results in a consistent reduction in circulating levels of growth factors, anabolic hormones, inflammatory cytokines and oxidative stress markers associated with various malignancies. Here, we discuss the link between nutritional interventions and cancer prevention with focus on the mechanisms that might be responsible for these effects in simple systems and mammals with a view to developing chemoprevention agents.

Epigenetic regulation in the pathophysiology of Alzheimer's disease

With the aging of the population, the growing incidence and prevalence of Alzheimer's disease (AD) increases the burden on individuals and society as a whole. To date, the pathophysiology of AD is not yet fully understood. Recent studies have suggested that epigenetic mechanisms may play a pivotal role in its course and development. The most frequently studied epigenetic mechanisms are DNA methylation and histone modifications, and investigations relevant to aging and AD are presented in this review. Various studies on human postmortem brain samples and peripheral leukocytes, as well as transgenic animal models and cell culture studies relevant to AD will be discussed. From those, it is clear that aging and AD are associated with epigenetic dysregulation at various levels. Moreover, data on e.g. twin studies in AD support the notion that epigenetic mechanisms mediate the risk for AD. Conversely, it is still not fully clear whether the observed epigenetic changes actually represent a cause or a consequence of the disease. This is mainly due to the fact that most clinical investigations on epigenetics in AD are conducted in samples of patients already in an advanced stage of the disease. Evidently, more research is needed in order to clarify the exact role of epigenetic regulation in the course and development of AD. Research on earlier stages of the disease could provide more insight into its underlying pathophysiology, possibly contributing to the establishment of early diagnosis and the development of more effective treatment strategies.

Mini-review: impact of recurrent hypoglycemia on cognitive and brain function

Recurrent hypoglycemia (RH), the most common side-effect of intensive insulin therapy for diabetes, is well established to diminish counter-regulatory responses to further hypoglycemia. However, despite significant patient concern, the impact of RH on cognitive and neural function remains controversial. Here we review the data from both human studies and recent animal studies regarding the impact of RH on cognitive, metabolic, and neural processes. Overall, RH appears to cause brain adaptations which may enhance cognitive performance and fuel supply when euglycemic but which pose significant threats during future hypoglycemic episodes.

Autophagy in health and disease. 1. Regulation and significance of autophagy: an overview

Macroautophagy is a vacuolar degradation pathway that terminates in the lysosomal compartment after formation of a cytoplasmic vacuole or autophagosome that engulfs macromolecules and organelles. The identification of ATG (autophagy-related) genes that are involved in the formation of autophagosomes has greatly increased our knowledge of the molecular basis of macroautophagy, and its roles in cell function, which extend far beyond degradation and quality control of the cytoplasm. Macroautophagy, which plays a major role in tissue homeostasis, is now recognized as contributing to innate and adaptive immune responses. Recently, several mediators of apoptosis have been shown to control macroautophagy. Deciphering the cross talk between macroautophagy and apoptosis probably should help increase understanding of the role of macroautophagy in human disease and is likely to be of therapeutic importance.

The impact of acute caloric restriction on the metabolic phenotype in male C57BL/6 and DBA/2 mice

Caloric restriction (CR) extends healthy lifespan in many organisms. DBA/2 mice, unlike C57BL/6 mice, are reported to be unresponsive to CR. To investigate potential differences underlying the CR response in male DBA/2 and C57BL/6 mice, we examined several metabolic parameters following acute (1-5 weeks) 30% CR. Acute CR decreased body mass (BM) in both strains, with lean and fat mass decreasing in proportion to BM. Resting metabolic rate (RMR) was unaltered by CR, following appropriate corrections for BM differences, although RMR was higher in DBA/2 compared to C57BL/6 mice. Acute CR decreased fed blood glucose levels in both strains, decreased fasting blood glucose in C57BL/6 mice but increased fasting levels in DBA/2 mice. Glucose tolerance improved after 1 week of CR in C57BL/6 mice but improved only after 4 weeks in DBA/2 mice. Acute CR had no effect on insulin levels, but lowered insulin sensitivity and decreased insulin-like growth factor-1 (IGF-1) levels in both strains. DBA/2 mice were hyperinsulinaemic and insulin resistant compared to C57BL/6 mice. These strain-specific differences in glucose homeostatic parameters may underlie the reported unresponsiveness of DBA/2 mice to CR. We also demonstrate delineation in the response of insulin and IGF-1 to acute CR in mice.

Short photoperiod initiated during adulthood sustains reproductive function in older female siberian hamsters more effectively than short photoperiod initiated before puberty

Reproductive aging in female mammals is characterized by a progressive decline in fertility and fecundity. Many women delay their first full-term pregnancy until an age at which their reproductive potential has already declined. No treatment is presently available to delay the aging process. In a limited number of rodent species, caloric restriction sustained reproductive function in older females, and in most investigations, sexual maturation was delayed because caloric restriction was initiated at weaning. We have previously reported similar outcomes in female Siberian hamsters that were reared in short photoperiod (SP), which profoundly inhibits reproductive physiology. When compared to hamsters held in long photoperiod (LP), females reared in SP matured much later and had greater reproductive success at 9 mo of age. Herein, we determined if delayed onset of sexual maturation was necessary for SP to decelerate reproductive aging. We initiated a 6-mo period of SP before or after sexual maturation and measured the reproductive success of females at 12 mo of age. Maintenance of hamsters in SP beginning after puberty was associated with significantly greater litter success (77%) compared to imposition of SP before puberty (35%); the difference in weaning success was even greater (73% and 12%, respectively). Regardless of which SP regime was used, litter success of females exposed to SP was substantially greater than that of 12-mo-old females held continuously in LP (6%). The efficacy of SP in decelerating female reproductive aging is manifest at several life stages and is greater when treatment is initiated after rather than before puberty.

The molecular basis of longevity, and clinical implications

The determinants of length of life are multifactorial and involve complex processes, most of which are not as yet understood completely. Tremendous advances have, however, been made in recent times in understanding some of the key molecular mechanisms that influence ageing and lifespan. Herein we highlight many of the more important findings and their potential clinical implications. Most of the intracellular factors involved in the ageing process, such as members of the sirtuin family, as well as insulin and insulin-like growth factor-I and their genes, are part of interconnected pathways. The manipulation of these and other genes in animal models can increase or decrease lifespan. Transcriptional and post-transcriptional regulatory mechanisms, some of which involve microRNAs, as well as modifications to chromatin and histones, can influence longevity. A decline in the function of stem cells might also be responsible for some aspects of mammalian ageing. Calorie restriction, polyphenols such as resveratrol, rapamycin, spermidine and angiotensin I converting enzyme inhibitor, are able to increase lifespan by modulation of branches of the longevity pathways. Molecular genetic studies of long-lived subjects have identified several potential candidate genes, but genetic research on ageing is in its infancy. Large genome-wide association studies should provide insights. Although new biomarkers for ageing and health, such as ones that might reveal telomere dysfunction, have been described, advances in the genetics and molecular biology of longevity will require interdisciplinary approaches if the much-hoped for success in alleviating the diseases of ageing, and an extension of both lifespan and healthspan is to be achieved.