Dietary restriction and glucose regulation in aging rhesus monkeys: a follow-up report at 8.5 yr

Targeting Cell Senescence and Senolytics: Novel Interventions for Age-Related Endocrine Dysfunction

Multiple changes occur in hormonal regulation with aging and across various endocrine organs. These changes are associated with multiple age-related disorders and diseases. A better understanding of responsible underling biological mechanisms could help in the management of multiple endocrine disorders over and above hormone replacement therapy (HRT). Cellular senescence is involved in multiple biological aging processes and pathologies common in elderly individuals. Cellular senescence, which occurs in many older individuals but also across the lifespan in association with tissue damage, acute and chronic diseases, certain drugs, and genetic syndromes, may contribute to such endocrine disorders as osteoporosis, metabolic syndrome, and type 2 diabetes mellitus. Drugs that selectively induce senescent cell removal, "senolytics,", and drugs that attenuate the tissue-destructive secretory state of certain senescent cells, "senomorphics," appear to delay the onset of or alleviate multiple diseases, including but not limited to endocrine disorders such as diabetes, complications of obesity, age-related osteoporosis, and cancers as well as atherosclerosis, chronic kidney disease, neurodegenerative disorders, and many others. More than 30 clinical trials of senolytic and senomorphic agents have already been completed, are underway, or are planned for a variety of indications. Targeting senescent cells is a novel strategy that is distinct from conventional therapies such as HRT, and thus might address unmet medical needs and can potentially amplify effects of established endocrine drug regimens, perhaps allowing for dose decreases and reducing side effects.

Long-term Hyperandrogenemia and/or Western-style Diet in Rhesus Macaque Females Impairs Preimplantation Embryogenesis

Hyperandrogenemia and obesity are common in women with polycystic ovary syndrome, but it is currently unclear how each alone or in combination contribute to reproductive dysfunction and female infertility. To distinguish the individual and combined effects of hyperandrogenemia and an obesogenic diet on ovarian function, prepubertal female rhesus macaques received a standard control (C) diet, testosterone (T) implants, an obesogenic Western-style diet (WSD), or both (T + WSD). After 5 to 6 years of treatment, the females underwent metabolic assessments and controlled ovarian stimulations. Follicular fluid (FF) was collected for steroid and cytokine analysis and the oocytes fertilized in vitro. Although the T + WSD females exhibited higher insulin resistance compared to the controls, there were no significant differences in metabolic parameters between treatments. Significantly higher concentrations of CXCL-10 were detected in the FF from the T group, but no significant differences in intrafollicular steroid levels were observed. Immunostaining of cleavage-stage embryos revealed multiple nuclear abnormalities in the T, WSD, and T + WSD groups. Single-cell DNA sequencing showed that while C embryos contained primarily euploid blastomeres, most cells in the other treatment groups were aneuploid. Despite yielding a higher number of mature oocytes, T + WSD treatment resulted in significantly reduced blastocyst formation rates compared to the T group. RNA sequencing analysis of individual blastocysts showed differential expression of genes involved in critical implantation processes between the C group and other treatments. Collectively, we show that long-term WSD consumption reduces the capacity of fertilized oocytes to develop into blastocysts and that the addition of T further impacts gene expression and embryogenesis.

Modestly Increased Incidence of Ketosis in Caloric Restriction Does not Significantly Alter the Effects of Caloric Restriction

OBJECTIVES

Caloric restriction (CR) has been shown to slow the aging processes in a number of preclinical studies and reduces expression of aging-associated biomarkers in human trials. We hypothesized that CR would lead to increased incidence of ketosis and that ketosis in CR individuals would alter the aging-protective effects of CR or biomarkers thereof.

DESIGN/SETTING/PARTICIPANTS

We analyzed data from the "Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE, Phase 2)" Public Use Database available at calerie.duke.edu. In this study, non-obese adults between the ages of 21 and 50 were randomized to 25% CR or control (ad lib) diet groups and extensively monitored for two years. Given our focus on the effect of caloric restriction on ketosis, individuals with detectible ketones during the baseline visit (pre-randomization) and those with missing data for ketone testing were excluded from the analysis, leaving 71 control and 117 CR participants.

MEASUREMENTS

We analyzed the incidence of ketosis as well as ketosis free survival in control and CR participants and assessed the effect of ketosis on a number of clinical lab values, functional assessments, and participant survey data related to aging biology.

RESULTS

We report that CR was associated with modestly increased incidence of ketosis (4.4% in CR vs 1.9% in control), though CR-associated changes in T3, VO2, SUMPT-WT (weight normalized composite strength score - peak torque), physical functioning, and general health did not appear to be altered by the presence or absence of ketosis. Additional observations of interest include: 1) striking patterns of biomarker expression changes (MCP-1, TNFα, TGF-β1, GH) in both the control and CR participants between the baseline visit and the 24-month post-randomization visit and 2) pro-growth/anti-inflammatory baseline (pre-randomization) biomarker expression profile in CR individuals that later test ketone positive relative to other CR individuals.

CONCLUSIONS

CR modestly increases the incidence of ketosis in healthy adults, yet the increase in ketosis in CR patients did not significantly affect the aging-protective effects of CR. However, given the relatively small number of participants who were ketone positive, further investigation in larger study cohorts is still required for definitive conclusions.

Age-related Effects of Heroin on Gene Expression in the Hippocampus and Striatum of Cynomolgus Monkeys

Objective

The aim of this study was to investigate differentially expressed genes and their functions in the hippocampus and striatum after heroin administration in cynomolgus macaques of different ages.

Methods

Cynomolgus monkeys were divided by age as follows: 1 year (A1, n = 2); 3 to 4 years (A2, n = 2); 6 to 8 years (A3, n = 2); and older than 11 years (A4, n = 2). After heroin was injected intramuscularly into the monkeys (0.6 mg/kg), we performed large-scale transcriptome profiling in the hippocampus (H) and striatum (S) using RNA sequencing technology. Some genes were validated with real-time quantitative PCR.

Results

In the hippocampus, the gene expression of A1H was similar to that of A4H, while the gene expression of A2H was similar to that of A3H. Genes associated with the mitogen-activated protein kinase signaling pathway (STMN1, FGF14, and MAPT) and γ-aminobutyric acid-ergic synapses (GABBR2 and GAD1) were differentially expressed among control and heroin-treated animals. Differential gene expression between A1S and A4S was the least significant, while differential gene expression between A3S and A2S was the most significant. Genes associated with the neurotrophin signaling pathway (NTRK1 and NGFR), autophagy (ATG5), and dopaminergic synapses (AKT1) in the striatum were differentially expressed among control and heroin-treated animals.

Conclusion

These results suggest that even a single heroin exposure can cause differential gene expression in the hippocampus and striatum of nonhuman primates at different ages.

Is Rapamycin a Dietary Restriction Mimetic?

Since the initial suggestion that rapamycin, an inhibitor of target of rapamycin (TOR) nutrient signaling, increased lifespan comparable to dietary restriction, investigators have viewed rapamycin as a potential dietary restriction mimetic. Both dietary restriction and rapamycin increase lifespan across a wide range of evolutionarily diverse species (including yeast, Caenorhabditis elegans, Drosophila, and mice) as well as reducing pathology and improving physiological functions that decline with age in mice. The purpose of this article is to review the research comparing the effect of dietary restriction and rapamycin in mice. The current data show that dietary restriction and rapamycin have different effects on many pathways and molecular processes. In addition, these interventions affect the lifespan of many genetically manipulated mouse models differently. In other words, while dietary restriction and rapamycin may have similar effects on some pathways and processes; overall, they affect many pathways/processes quite differently. Therefore, rapamycin is likely not a true dietary restriction mimetic. Rather dietary restriction and rapamycin appear to be increasing lifespan and retarding aging largely through different mechanisms/pathways, suggesting that a combination of dietary restriction and rapamycin will have a greater effect on lifespan than either manipulation alone.

Caloric Restriction and Healthy Life Span: Frail Phenotype of Nonhuman Primates in the Wisconsin National Primate Research Center Caloric Restriction Study

Calorie restriction without malnutrition increases longevity and delays the onset of age-associated disorders in multiple species. Recently, greater emphasis has been placed on healthy life span and preventing frailty than on longevity. Here, we show the beneficial effect of long-term calorie restriction on frailty in later life in a nonhuman primate. Frail phenotypes were evaluated using metabolic and physical activity data and defined using the Fried index. Shrinking was defined as unintentional weight loss of greater than 5% of body weight. Weakness was indicated by decline in high intensity spontaneous physical activity. Poor endurance or exhaustion was indicated by a reduction in energy efficiency of movements. Slowness was indicated by physical activity counts in the morning. Low physical activity level was measured by total energy expenditure using doubly labeled water divided by sleeping metabolic rate. Weakness, poor endurance, slowness, and low physical activity level were significantly higher in control compared with calorie restriction (p < .05) as was total incidence of frailty (p < .001). In conclusion, we established a novel set of measurable criteria of frailty in nonhuman primates, and using these criteria, showed that calorie restriction reduces the incidence of frailty and increases healthy life span in nonhuman primates.

The effect of different levels of dietary restriction on glucose homeostasis and metabolic memory

Over the past 50 years, dietary restriction (DR) has been shown to extend the life span of a wide variety of organisms. A hallmark feature of DR is improved glucose homeostasis resulting in increased glucose tolerance and insulin sensitivity of animals ranging from rodents to humans. In this study, we demonstrate the early effects of varying levels of DR on glucose tolerance. Within 10 days of 40% DR, glucose tolerance was significantly improved and by 120 days; 10 and 20% DR also showed enhanced glucose tolerance. All three levels of DR showed reduced adiposity, increased expression of genes involved in fat turnover, and a reduction in the expression for markers of inflammation. Studies have shown that mice fed a DR diet retained metabolic memory in terms of improved glucose tolerance even after DR is discontinued. We show that 40% DR not only has an early effect on glucose tolerance but also maintained it after DR was discontinued for 2 months. Therefore, improvement in glucose tolerance is brought about by all three levels of DR but the metabolic memory is not dose responsive.

Nutrition modulation of human aging: The calorie restriction paradigm

Globally, the aging population is growing rapidly, creating an urgent need to attenuate age-related health conditions, including metabolic disease and disability. A promising strategy for healthy aging based on consistently positive results from studies with a variety of species, including non-human primates (NHP), is calorie restriction (CR), or the restriction of energy intake while maintaining intake of essential nutrients. The burgeoning evidence for this approach in humans is reviewed and the major study to date to address this question, CALERIE (Comprehensive Assessment of the Long-term Effects of Reducing Intake of Energy), is described. CALERIE findings indicate the feasibility of CR in non-obese humans, confirm observations in NHP, and are consistent with improvements in disease risk reduction and potential anti-aging effects. Finally, the mechanisms of CR in humans are reviewed which sums up the fact that evolutionarily conserved mechanisms mediate the anti-aging effects of CR. Overall, the prospect for further research in both NHP and humans is highly encouraging.

Nutrition, metabolism, and targeting aging in nonhuman primates

This short review focuses on the importance of nonhuman primate nutrition and aging studies and makes the case that a targeted expansion of the use of this highly translatable model would be advantageous to the biology of aging field. First, we describe the high degree of similarity of the model in terms of aging phenotypes including incidence and prevalence of common human age-related diseases. Second, we discuss the importance of the nonhuman primate nutrition and aging studies and the extent to which the outcomes of two ongoing long-term studies of caloric restriction are congruent with short-term equivalent studies in humans. Third, we showcase a number of pharmacological agents previously employed in nonhuman primate studies that display some potential as caloric restriction mimetics. Finally, we present nonhuman primates as an important model for translation of mechanisms of delayed aging identified in studies of shorter-lived animals. Proof of efficacy and safety of candidate longevity agents in nonhuman primates would be a cost-effective means to bring these exciting new avenues a step closer to clinical application.

Caloric restriction improves health and survival of rhesus monkeys

Caloric restriction (CR) without malnutrition extends lifespan and delays the onset of age-related disorders in most species but its impact in nonhuman primates has been controversial. In the late 1980s two parallel studies were initiated to determine the effect of CR in rhesus monkeys. The University of Wisconsin study reported a significant positive impact of CR on survival, but the National Institute on Aging study detected no significant survival effect. Here we present a direct comparison of longitudinal data from both studies including survival, bodyweight, food intake, fasting glucose levels and age-related morbidity. We describe differences in study design that could contribute to differences in outcomes, and we report species specificity in the impact of CR in terms of optimal onset and diet. Taken together these data confirm that health benefits of CR are conserved in monkeys and suggest that CR mechanisms are likely translatable to human health.

Caloric restriction (CR) delays ageing of model organisms, but whether it works in nonhuman primates has been controversial. Here, the authors pool and reanalyse data from two long-running CR primate studies, concluding that moderate CR indeed improves health and survival of rhesus monkeys.

Central injection of fibroblast growth factor 1 induces sustained remission of diabetic hyperglycemia in rodents

Type 2 diabetes (T2D) is among the most common and costly disorders worldwide. The goal of current medical management for T2D is to transiently ameliorate hyperglycemia through daily dosing of one or more antidiabetic drugs. Hypoglycemia and weight gain are common side effects of therapy, and sustained disease remission is not obtainable with nonsurgical approaches. On the basis of the potent glucose-lowering response elicited by activation of brain fibroblast growth factor (FGF) receptors, we explored the antidiabetic efficacy of centrally administered FGF1, which, unlike other FGF peptides, activates all FGF receptor subtypes. We report that a single intracerebroventricular injection of FGF1 at a dose one-tenth of that needed for antidiabetic efficacy following peripheral injection induces sustained diabetes remission in both mouse and rat models of T2D. This antidiabetic effect is not secondary to weight loss, does not increase the risk of hypoglycemia, and involves a novel and incompletely understood mechanism for increasing glucose clearance from the bloodstream. We conclude that the brain has an inherent potential to induce diabetes remission and that brain FGF receptors are potential pharmacological targets for achieving this goal.

Hyperinsulinemia/diabetes, hearing, and aging in the University of Wisconsin calorie restriction monkeys

The purpose of this study was to determine the effects of hyperinsulinemia/Type 2 diabetes mellitus (HI-T2DM) on hearing impairment using rhesus monkeys to obtain control over diet and lifestyle factors that confound human studies. The study is a retrospective evaluation of rhesus monkeys from the Wisconsin National Primate Research Center (WNPRC) study on caloric restriction and aging. The research questions were the following: 1. Is HI-T2DM related to hearing impairment? 2. If so, what is the site of lesion in the auditory system? and 3. What physiological factors affect the risk of hearing loss in HI-T2DM? Three groups of eight monkeys each were matched by sex and age; the caloric restricted (CR) monkeys had a reduced risk of diabetes, the normal control (NL) group had a normal risk, and the hyperinsulinemia/diabetes (HI-D) group had already developed HI-T2DM. Auditory testing included distortion product otoacoustic emissions (DPOAEs) with f2 frequencies from 2211 to 8837 Hz and auditory brainstem responses (ABRs) obtained with clicks and tone bursts (8, 16, and 32 kHz). DPOAEs had signal-to-noise ratios 8-17 dB larger in the NL group than in the HI-D and CR groups, signifying that cochlear function was best in the NL group. ABR thresholds were 5-8 dB better in the NL group than in the HI-D group, although no significant differences across the groups were evident for the thresholds, latencies, interwave intervals, or amplitudes. Correlations were significant for quadratic relations between body mass index (BMI) and DPOAE, with largest DPOAEs for animals in the middle of the BMI range. ABR thresholds elicited with 16 and 32 kHz signals were significantly correlated, positively with BMI and HbA1c, and negatively with KG (glucose tolerance), SI (insulin sensitivity index) and DI (disposition index). These findings suggest that the hearing loss associated with HI-T2DM is predominantly cochlear, and auditory structures underlying the higher frequencies are at risk with HI-T2DM. Loss of auditory function begins in the hyperinsulinemia, pre-diabetic state.

Plasma diacylglycerol composition is a biomarker of metabolic syndrome onset in rhesus monkeys

Metabolic syndrome is linked with obesity and is often first identified clinically by elevated BMI and elevated levels of fasting blood glucose that are generally secondary to insulin resistance. Using the highly translatable rhesus monkey (Macaca mulatta) model, we asked if metabolic syndrome risk could be identified earlier. The study involved 16 overweight but healthy, euglycemic monkeys, one-half of which spontaneously developed metabolic syndrome over the course of 2 years while the other half remained healthy. We conducted a series of biometric and plasma measures focusing on adiposity, lipid metabolism, and adipose tissue-derived hormones, which led to a diagnosis of metabolic syndrome in the insulin-resistant animals. Plasma fatty acid composition was determined by gas chromatography for cholesteryl ester, FFA, diacylglycerol (DAG), phospholipid, and triacylglycerol lipid classes; plasma lipoprotein profiles were generated by NMR; and circulating levels of adipose-derived signaling peptides were determined by ELISA. We identified biomarker models including a DAG model, two lipoprotein models, and a multiterm model that includes the adipose-derived peptide adiponectin. Correlations among circulating lipids and lipoproteins revealed shifts in lipid metabolism during disease development. We propose that lipid profiling may be valuable for early metabolic syndrome detection in a clinical setting.

Glucose intolerance induced by blockade of central FGF receptors is linked to an acute stress response

Objective

Central administration of ligands for fibroblast growth factor receptors (FGFRs) such as fibroblast growth factor-19 (FGF19) and FGF21 exert glucose-lowering effects in rodent models of obesity and type 2 diabetes (T2D). Conversely, intracerebroventricular (icv) administration of the non-selective FGFR inhibitor (FGFRi) PD173074 causes glucose intolerance, implying a physiological role for neuronal FGFR signaling in glucose homeostasis. The current studies were undertaken to identify neuroendocrine mechanisms underlying the glucose intolerance induced by pharmacological blockade of central FGFRs.

Methods

Overnight fasted, lean, male, Long-Evans rats received icv injections of either PD173074 or vehicle (Veh) followed 30 min later by performance of a frequently sampled intravenous glucose tolerance test (FSIGT). Minimal model analysis of glucose and insulin data from the FSIGT was performed to estimate insulin-dependent and insulin-independent components of glucose disposal. Plasma levels of lactate, glucagon, corticosterone, non-esterified free fatty acids (NEFA) and catecholamines were measured before and after intravenous (iv) glucose injection.

Results

Within 20 min of icv PD173074 injection (prior to the FSIGT), plasma levels of lactate, norepinephrine and epinephrine increased markedly, and each returned to baseline rapidly (within 8 min) following the iv glucose bolus. In contrast, plasma glucagon levels were not altered by icv FGFRi at either time point. Consistent with a previous report, glucose tolerance was impaired following icv PD173074 compared to Veh injection and, based on minimal model analysis of FSIGT data, this effect was attributable to reductions of both insulin secretion and the basal insulin effect (BIE), consistent with the inhibitory effect of catecholamines on pancreatic β-cell secretion. By comparison, there were no changes in glucose effectiveness at zero insulin (GEZI) or the insulin sensitivity index (S_I). To determine if iv glucose (given during the FSIGT) contributed to the rapid resolution of the sympathoadrenal response induced by icv FGFRi, we performed an additional study comparing groups that received iv saline or iv glucose 30 min after icv FGFRi. Our finding that elevated plasma catecholamine levels returned rapidly to baseline irrespective of whether rats subsequently received an iv bolus of saline or glucose indicates that the rapid reversal of sympathoadrenal activation following icv FGFRi was unrelated to the subsequent glucose bolus.

Conclusions

The effect of acute inhibition of central FGFR signaling to impair glucose tolerance likely involves a stress response associated with pronounced, but transient, sympathoadrenal activation and an associated reduction of insulin secretion. Whether this effect is a true consequence of FGFR blockade or involves an off-target effect of the FGFR inhibitor requires additional study.

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icv FGFR antagonist causes glucose intolerance in rats.

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This effect is associated with robust sympathoadrenal activation.

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The sympathoadrenal response is rapid in onset, but clears rapidly.

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Reduced insulin secretion contributes to FGFR inhibitor-induced glucose intolerance.

Impaired preadipocyte differentiation into adipocytes in subcutaneous abdominal adipose of PCOS-like female rhesus monkeys

Metabolic characteristics of polycystic ovary syndrome women and polycystic ovary syndrome-like, prenatally androgenized (PA) female monkeys worsen with age, with altered adipogenesis of sc abdominal adipose potentially contributing to age-related adverse effects on metabolism. This study examines whether adipocyte morphology and gene expression in sc abdominal adipose differ between late reproductive-aged PA female rhesus monkeys compared with age-matched controls (C). Subcutaneous abdominal adipose of both groups was obtained for histological imaging and mRNA determination of zinc finger protein 423 (Zfp423) as a marker of adipose stem cell commitment to preadipocytes, and CCAAT/enhancer binding protein (C/EBP)α/peroxisome proliferator-activated receptor (PPAR)δ as well as C/EBPα/PPARγ as respective markers of early- and late-stage differentiation of preadipocytes to adipocytes. In all females combined, serum testosterone (T) levels positively correlated with fasting serum levels of total free fatty acid (r(2) = 0.73, P < .002). PA females had a greater population of small adipocytes vs C (P < .001) in the presence of increased Zfp423 (P < .025 vs C females) and decreased C/EBPα (P < .003, vs C females) mRNA expression. Moreover, Zfp423 mRNA expression positively correlated with circulating total free fatty acid levels during iv glucose tolerance testing (P < .004, r(2) = 0.66), whereas C/EBPα mRNA expression negatively correlated with serum T levels (P < .02, r(2) = 0.43). Gene expression of PPARδ and PPARγ were comparable between groups (P = .723 and P = .18, respectively). Early-to-mid gestational T excess in female rhesus monkeys impairs adult preadipocyte differentiation to adipocytes in sc abdominal adipose and may constrain the ability of this adipose depot to safely store fat with age.

Long-term calorie restriction decreases metabolic cost of movement and prevents decrease of physical activity during aging in rhesus monkeys

BACKGROUND

Short-term (<1 year) calorie restriction (CR) has been reported to decrease physical activity and metabolic rate in humans and non-human primate models; however, studies examining the very long-term (>10 year) effect of CR on these parameters are lacking.

OBJECTIVE

The objective of this study was to examine metabolic and behavioral adaptations to long-term CR longitudinally in rhesus macaques.

DESIGN

Eighteen (10 male, 8 female) control (C) and 24 (14 male, 10 female) age matched CR rhesus monkeys between 19.6 and 31.9 years old were examined after 13 and 18 years of moderate adult-onset CR. Energy expenditure (EE) was examined by doubly labeled water (DLW; TEE) and respiratory chamber (24 h EE). Physical activity was assessed both by metabolic equivalent (MET) in a respiratory chamber and by an accelerometer. Metabolic cost of movements during 24 h was also calculated. Age and fat-free mass were included as covariates.

RESULTS

Adjusted total and 24 h EE were not different between C and CR. Sleeping metabolic rate was significantly lower, and physical activity level was higher in CR than in C independent from the CR-induced changes in body composition. The duration of physical activity above 1.6 METs was significantly higher in CR than in C, and CR had significantly higher accelerometer activity counts than C. Metabolic cost of movements during 24 h was significantly lower in CR than in C. The accelerometer activity counts were significantly decreased after seven years in C animals, but not in CR animals.

CONCLUSIONS

The results suggest that long-term CR decreases basal metabolic rate, but maintains higher physical activity with lower metabolic cost of movements compared with C.

Age-related cardiovascular disease and the beneficial effects of calorie restriction

Aging is a well-recognized risk factor in the development of cardiovascular disease, which is the primary cause of death and disability in the elderly population. The normal process of aging is associated with progressive deterioration in structure and function of the heart and vasculature. These age-related changes likely act as both a catalyst and accelerator in the development of cardiovascular disease. Since the aging population is one of the fastest growing segments of the population, it is of vital importance that we have a thorough understanding of the physiological changes that occur with aging that contribute to the high incidence of cardiovascular disease in this population. This insight will allow for the development of more targeted therapies that can prevent and treat these conditions. One such anti-aging strategy that has received considerable attention as of late is calorie restriction. Calorie restriction has emerged as one of the most effective and reproducible interventions for extending lifespan, as well as protecting against obesity, metabolic disorders, and cardiovascular disease. Herein, we review the multiple beneficial effects that calorie restriction and resveratrol exert on the cardiovascular system with a particular focus on aging. Although calorie restriction and resveratrol have proven to be very effective in preventing and treating the development of cardiovascular disease in animal models, studies continue as to whether these profound beneficial effects can translate to humans to improve cardiovascular health.

Adenylyl cyclase type 5 in cardiac disease, metabolism, and aging

G protein-coupled receptor/adenylyl cyclase (AC)/cAMP signaling is crucial for all cellular responses to physiological and pathophysiological stimuli. There are nine isoforms of membrane-bound AC, with type 5 being one of the two major isoforms in the heart. Since the role of AC in the heart in regulating cAMP and acute changes in inotropic and chronotropic state are well known, this review will address our current understanding of the distinct regulatory role of the AC5 isoform in response to chronic stress. Transgenic overexpression of AC5 in cardiomyocytes of the heart (AC5-Tg) improves baseline cardiac function but impairs the ability of the heart to withstand stress. For example, chronic catecholamine stimulation induces cardiomyopathy, which is more severe in AC5-Tg mice, mediated through the AC5/sirtuin 1/forkhead box O3a pathway. Conversely, disrupting AC5, i.e., AC5 knockout, protects the heart from chronic catecholamine cardiomyopathy as well as the cardiomyopathies resulting from chronic pressure overload or aging. Moreover, AC5 knockout results in a 30% increase in a healthy life span, resembling the most widely studied model of longevity, i.e., calorie restriction. These two models of longevity share similar gene regulation in the heart, muscle, liver, and brain in that they are both protected against diabetes, obesity, and diabetic and aging cardiomyopathy. A pharmacological inhibitor of AC5 also provides protection against cardiac stress, diabetes, and obesity. Thus AC5 inhibition has novel, potential therapeutic applicability to several diseases not only in the heart but also in aging, diabetes, and obesity.

A calorie-restricted diet decreases brain iron accumulation and preserves motor performance in old rhesus monkeys

Caloric restriction (CR) reduces the pathological effects of aging and extends the lifespan in many species, including nonhuman primates, although the effect on the brain is less well characterized. We used two common indicators of aging, motor performance speed and brain iron deposition measured in vivo using magnetic resonance imaging, to determine the potential effect of CR on elderly rhesus macaques eating restricted (n=24, 13 males, 11 females) and standard (n=17, 8 males, 9 females) diets. Both the CR and control monkeys showed age-related increases in iron concentrations in globus pallidus (GP) and substantia nigra (SN), although the CR group had significantly less iron deposition in the GP, SN, red nucleus, and temporal cortex. A Diet X Age interaction revealed that CR modified age-related brain changes, evidenced as attenuation in the rate of iron accumulation in basal ganglia and parietal, temporal, and perirhinal cortex. Additionally, control monkeys had significantly slower fine motor performance on the Movement Assessment Panel, which was negatively correlated with iron accumulation in left SN and parietal lobe, although CR animals did not show this relationship. Our observations suggest that the CR-induced benefit of reduced iron deposition and preserved motor function may indicate neural protection similar to effects described previously in aging rodent and primate species.

Circulating factors induced by caloric restriction in the nonhuman primate Macaca mulatta activate angiogenic processes in endothelial cells

Moderate caloric restriction (CR) without malnutrition increases healthspan in virtually every species studied, including nonhuman primates. In mice, CR exerts significant microvascular protective effects resulting in increased microvascular density in the heart and the brain, which likely contribute to enhanced tolerance to ischemia and improved cardiac performance and cognitive function. Yet, the underlying mechanisms by which CR confer microvascular protection remain elusive. To test the hypothesis that circulating factors triggered by CR regulate endothelial angiogenic capacity, we treated cultured human endothelial cells with sera derived from Macaca mulatta on long-term (over 10 years) CR. Cells treated with sera derived from ad-libitum-fed control monkeys served as controls. We found that factors present in CR sera upregulate vascular endothelial growth factor (VEGF) signaling and stimulate angiogenic processes, including endothelial cell proliferation and formation of capillary-like structures. Treatment with CR sera also tended to increase cellular migration (measured by a wound-healing assay using electric cell-substrate impedance sensing [ECIS] technology) and adhesion to collagen. Collectively, we find that circulating factors induced by CR promote endothelial angiogenic processes, suggesting that increased angiogenesis may be a potential mechanism by which CR improves cardiac function and prevents vascular cognitive impairment.

Calorie restriction reduces the influence of glucoregulatory dysfunction on regional brain volume in aged rhesus monkeys

Insulin signaling dysregulation is related to neural atrophy in hippocampus and other areas affected by neurovascular and neurodegenerative disorders. It is not known if long-term calorie restriction (CR) can ameliorate this relationship through improved insulin signaling or if such an effect might influence task learning and performance. To model this hypothesis, magnetic resonance imaging was conducted on 27 CR and 17 control rhesus monkeys aged 19-31 years from a longitudinal study. Voxel-based regression analyses were used to associate insulin sensitivity with brain volume and microstructure cross-sectionally. Monkey motor assessment panel (mMAP) performance was used as a measure of task performance. CR improved glucoregulation parameters and related indices. Higher insulin sensitivity predicted more gray matter in parietal and frontal cortices across groups. An insulin sensitivity × dietary condition interaction indicated that CR animals had more gray matter in hippocampus and other areas per unit increase relative to controls, suggesting a beneficial effect. Finally, bilateral hippocampal volume adjusted by insulin sensitivity, but not volume itself, was significantly associated with mMAP learning and performance. These results suggest that CR improves glucose regulation and may positively influence specific brain regions and at least motor task performance. Additional studies are warranted to validate these relationships.

Nonhuman primates and other animal models in diabetes research

Animal models are important for determining the pathogenesis of and potential treatments for obesity and diabetes. Nonhuman primates (NHPs) are particularly useful for studying these disorders. As in humans, type 2 diabetes mellitus is the most common form of diabetes in NHPs and occurs more often in older obese animals, with a metabolic progression from insulin resistance (IR) and impaired glucose tolerance to overt diabetes. Histopathologic changes in pancreatic islets are also similar to those seen in humans with diabetes. Initially, there is islet hyperplasia with abundant insulin production to compensate for IR, followed by insufficient insulin production with replacement of islets with islet-associated amyloid. Diabetic NHPs also have adverse changes in plasma lipid and lipoprotein concentrations, biomarkers of obesity, inflammation, and oxidative stress, and protein glycation that contribute to the numerous complications of the disease. Furthermore, sex hormones, pregnancy, and environmental factors (e.g., diet and stress) affect IR and can also contribute to diabetes progression in NHPs. Additionally, due to their similar clinical and pathologic characteristics, NHPs have been used in many pharmacological studies to assess new therapeutic agents. For these reasons, NHPs are particularly valuable animal models of obesity and diabetes for studying disease pathogenesis, risk factors, comorbidities, and therapeutic interventions.

The caloric restriction paradigm: implications for healthy human aging

Underlying the importance of research on the biology of aging is the fact that many nations face the demographic reality of a rapidly aging populace and the looming healthcare challenges that it brings. This reality is a result of aging itself being the most significant risk factor for a range of the most prevalent diseases, including many cancers, cardiovascular disease, and diabetes. Accordingly, interventions are sorely needed that would be able to delay or prevent diseases and disorders associated with the aging process and thereby increase the period of time that aging individuals are in good health (the health-span). Caloric restriction (CR) has emerged as a model of major interest as it is widely agreed that CR is the most potent environmental intervention that delays the onset of aging and extends life span in diverse experimental organisms. A better understanding of the mechanisms by which CR delays aging will reveal new insights into the aging process and the underlying causes of disease vulnerability with age. These novel insights will allow the development of novel treatments and preventive measures for age-associated diseases and disorders.

Analysis of glucose metabolism in cynomolgus monkeys during aging

This study was designed to investigate the effect of aging on the glucose metabolism on cynomolgus (Macaca fascicularis) monkeys. A total of 33 cynomolgus monkeys in three aged groups were monitored for glucose levels, serum parameters in fasting state and somatometric measurements. Intravenous glucose tolerance test (IVGTT) and insulin tolerance test (ITT) were also performed. Aging associated changes lies in the less secretion of insulin and C-peptide during IVGTT in cynomolgus monkeys. It was also found that impaired insulin sensitivity occurred in female monkeys during aging based on HOMA-IR and K(ITT) value. In addition, triglyceride level also rose with the increase of age. Less insulin secretion and impaired insulin sensitivity in female were the characteristic during the aging of cynomolgus monkeys in this study. Body mass index, weight and waist hip rate may be the relevant factors in insulin resistance of cynomolgus monkeys.

Caloric restriction: powerful protection for the aging heart and vasculature

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the United States. Research has shown that the majority of the cardiometabolic alterations associated with an increased risk of CVD (e.g., insulin resistance/type 2 diabetes, abdominal obesity, dyslipidemia, hypertension, and inflammation) can be prevented, and even reversed, with the implementation of healthier diets and regular exercise. Data from animal and human studies indicate that more drastic interventions, i.e., calorie restriction with adequate nutrition (CR), may have additional beneficial effects on several metabolic and molecular factors that are modulating cardiovascular aging itself (e.g., cardiac and arterial stiffness and heart rate variability). The purpose of this article is to review the current knowledge on the effects of CR on the aging of the cardiovascular system and CVD risk in rodents, monkeys, and humans. Taken together, research shows that CR has numerous beneficial effects on the aging cardiovascular system, some of which are likely related to reductions in inflammation and oxidative stress. In the vasculature, CR appears to protect against endothelial dysfunction and arterial stiffness and attenuates atherogenesis by improving several cardiometabolic risk factors. In the heart, CR attenuates age-related changes in the myocardium (i.e., CR protects against fibrosis, reduces cardiomyocyte apoptosis, prevents myosin isoform shifts, etc.) and preserves or improves left ventricular diastolic function. These effects, in combination with other benefits of CR, such as protection against obesity, diabetes, hypertension, and cancer, suggest that CR may have a major beneficial effect on health span, life span, and quality of life in humans.

A pathophysiological framework of hippocampal dysfunction in ageing and disease

The hippocampal formation has been implicated in a growing number of disorders, from Alzheimer's disease and cognitive ageing to schizophrenia and depression. How can the hippocampal formation, a complex circuit that spans the temporal lobes, be involved in a range of such phenotypically diverse and mechanistically distinct disorders? Recent neuroimaging findings indicate that these disorders differentially target distinct subregions of the hippocampal circuit. In addition, some disorders are associated with hippocampal hypometabolism, whereas others show evidence of hypermetabolism. Interpreted in the context of the functional and molecular organization of the hippocampal circuit, these observations give rise to a unified pathophysiological framework of hippocampal dysfunction.

Relationship of aqueous outflow resistance to age and total volume perfused in rhesus and cynomolgus monkeys

PURPOSE

The effect of total volume perfused on outflow resistance (the reciprocal of outflow facility) and the effect of age on the rate of change in resistance as a function of total volume were determined in rhesus and cynomolgus monkeys.

METHODS

Outflow facility was measured under general anesthesia by two-level constant pressure perfusion in one eye of 22 rhesus and 17 cynomolgus monkeys (ranging in age, respectively, from 4 to 25 and from 3 to 12 years). Total volume perfused was calculated from data obtained during the perfusion.

RESULTS

Resistance decreased in both cynomolgus and rhesus monkeys as total volume perfused increased (-0.085 ± 0.021 and -0.022 ± 0.011 mm Hg/μL/min/μL(tot); P = 0.001 and P = 0.047, respectively). Rate of change in resistance significantly increased in cynomolgus monkeys as total volume perfused increased (0.0018 ± 0.0.0007 mm Hg/μL/min/μL(tot), P = 0.033); however, this was not the case in rhesus monkeys. After accounting for total volume perfused, the rate of change in resistance significantly decreased with increasing age in rhesus monkeys (-0.0068 ± 0.0026 [mm Hg/μL/min]/μL(tot)/y, P = 0.017). There was no significant difference in rate of change in resistance with age, after accounting for total volume, in the cynomolgus monkeys.

CONCLUSIONS

The present study supports previous findings indicating that total washout is largely dependent on perfusion volume. However, in populations with old/elderly animals, such as our rhesus group, we found that age does play a significant role in rate of change in resistance, and may be an even more important factor to consider in the rate of resistance change than volume perfused in aged animals.

Rhesus macaques develop metabolic syndrome with reversible vascular dysfunction responsive to pioglitazone

BACKGROUND

The metabolic syndrome (MetS) is a constellation of clinical features that include central obesity, hypertension, atherogenic dyslipidemia, and insulin resistance. However, the concept remains controversial; it has been debated whether MetS represents nothing more than simultaneous co-occurrence of individual risk factors or whether there are common shared pathophysiological mechanisms that link the individual components.

METHODS AND RESULTS

To investigate the emergence of metabolic and cardiovascular components during the development of MetS, we identified MetS-predisposed animals (n=35) in a large population of rhesus macaques (Macaca mulatta, 12.7±2.9 years old, n=408), acclimated them to standardized conditions, and monitored the progression of individual component features over 18 months. In 18 MetS animals with recently developed fasting hyperinsulinemia, central obesity, hypertension, and atherogenic dyslipidemia, we found that individual metabolic and cardiovascular components track together during the transition from pre-MetS to onset of MetS; MetS was associated with a 60% impairment of flow-mediated dilation, establishing the mechanistic link with vascular dysfunction. Pioglitazone treatment (3 mg/kg body weight/d for 6 weeks), a peroxisome proliferator-activated receptor γ agonist, reversibly improved atherogenic dyslipidemia and insulin resistance and fully restored flow-mediated dilation with persistent benefits.

CONCLUSIONS

Coemergence of metabolic and cardiovascular components during MetS progression and complete normalization of vascular dysfunction with peroxisome proliferator-activated receptor γ agonists suggest shared underlying mechanisms rather than separate processes, arguing for the benefit of early intervention of MetS components. Predictive nonhuman primate (NHP) models of MetS should be highly valuable in mechanistic and translational studies on the pathogenesis of MetS in relation to cardiovascular disease and diabetes mellitus.

Comparison between surrogate indexes of insulin sensitivity/resistance and hyperinsulinemic euglycemic glucose clamps in rhesus monkeys

The euglycemic glucose clamp is the reference method for assessing insulin sensitivity in humans and animals. However, clamps are ill-suited for large studies because of extensive requirements for cost, time, labor, and technical expertise. Simple surrogate indexes of insulin sensitivity/resistance including quantitative insulin-sensitivity check index (QUICKI) and homeostasis model assessment (HOMA) have been developed and validated in humans. However, validation studies of QUICKI and HOMA in both rats and mice suggest that differences in metabolic physiology between rodents and humans limit their value in rodents. Rhesus monkeys are a species more similar to humans than rodents. Therefore, in the present study, we evaluated data from 199 glucose clamp studies obtained from a large cohort of 86 monkeys with a broad range of insulin sensitivity. Data were used to evaluate simple surrogate indexes of insulin sensitivity/resistance (QUICKI, HOMA, Log HOMA, 1/HOMA, and 1/Fasting insulin) with respect to linear regression, predictive accuracy using a calibration model, and diagnostic performance using receiver operating characteristic. Most surrogates had modest linear correlations with SI(Clamp) (r ≈ 0.4-0.64) with comparable correlation coefficients. Predictive accuracy determined by calibration model analysis demonstrated better predictive accuracy of QUICKI than HOMA and Log HOMA. Receiver operating characteristic analysis showed equivalent sensitivity and specificity of most surrogate indexes to detect insulin resistance. Thus, unlike in rodents but similar to humans, surrogate indexes of insulin sensitivity/resistance including QUICKI and log HOMA may be reasonable to use in large studies of rhesus monkeys where it may be impractical to conduct glucose clamp studies.

Nonhuman primate calorie restriction

Calorie restriction (CR) is the only dietary intervention that repeatedly extends both median and maximal lifespan in a broad range of species. Although there has been considerable interest in CR and its ability to retard aging, the mechanism has remained elusive. In contrast to studies in rodent and nonmammalian systems that are now beginning to provide mechanistic insights into how CR promotes longevity, the efficacy of CR in delaying primate aging has yet to be fully demonstrated. Here we review some of the insights from CR studies in short-lived species. We describe the advantages of using the rhesus monkey as a model for human aging and detail how CR can be successfully implemented in this species. We discuss the findings from our ongoing longitudinal study and outline the effects to date of CR on rhesus monkey health. Finally, we highlight the importance of primate studies in the context of aging research and its potential to advance our understanding of human aging and health.

Calorie restriction and aging in nonhuman primates

In the 75 years since the seminal observation of Clive McCay that restriction of calorie intake extends the lifespan of rats, a great deal has been learned about the effects of calorie restriction (CR; reduced intake of a nutritious diet) on aging in various short-lived animal models. Studies have demonstrated many beneficial effects of CR on health, the rate of aging, and longevity. Two prospective investigations of the effects of CR on long-lived nonhuman primate (NHP) species began nearly 25 years ago and are still under way. This review presents the design, methods, and main findings of these and other important contributing studies, which have generally revealed beneficial effects of CR on physiological function and the retardation of disease consistent with studies in other species. Specifically, prolonged CR appears to extend the lifespan of rhesus monkeys, which exhibited lower body fat; slower rate of muscle loss with age; lower incidence of neoplasia, cardiovascular disease, type 2 diabetes mellitus, and endometriosis; improved insulin sensitivity and glucose tolerance; and no apparent adverse effect on bone health, as well as a reduction in total energy expenditure. In addition, there are no reports of deleterious effects of CR on reproductive endpoints, and brain morphology is preserved by CR. Adrenal and thyroid hormone profiles are inconsistently affected. More research is needed to delineate the mechanisms of the desirable outcomes of CR and to develop interventions that can produce similar beneficial outcomes for humans. This research offers tremendous potential for producing novel insights into aging and risk of disease.

Caloric restriction delays aging-induced cellular phenotypes in rhesus monkey skeletal muscle

Sarcopenia is the age-related loss of skeletal muscle mass and function and is characterized by a reduction in muscle mass and fiber cross-sectional area, alterations in muscle fiber type and mitochondrial functional changes. In rhesus monkeys, calorie restriction (CR) without malnutrition improves survival and delays the onset of age-associated diseases and disorders including sarcopenia. We present a longitudinal study on the impact of CR on early stage sarcopenia in the upper leg of monkeys from ~16 years to ~22 years of age. Using dual-energy X-ray absorptiometry we show that CR delayed the development of maximum muscle mass and, unlike Control animals, muscle mass of the upper leg was preserved in CR animals during early phase sarcopenia. Histochemical analyses of vastus lateralis muscle biopsies revealed that CR opposed age-related changes in the proportion of Type II muscle fibers and fiber cross-sectional area. In contrast the number of muscle fibers with mitochondrial electron transport system enzyme abnormalities (ETS(ab)) was not significantly affected by CR. Laser capture microdissection of ETS(ab) fibers and subsequent PCR analysis of the mitochondrial DNA revealed large deletion mutations in fibers with abnormal mitochondrial enzyme activities. CR did not prevent stochastic mitochondrial deletion mutations in muscle fibers but CR may have contributed to the maintenance of affected fibers.

Glycolytic inhibition as a strategy for developing calorie restriction mimetics

Calorie restriction (CR) remains the most robust environmental intervention for altering aging processes and increasing healthspan and lifespan. Emerging from progress made in many nonhuman models, current research has expanded to formal, controlled human studies of CR. Since long-term CR requires a major commitment of will power and long-term negative consequences remain to be determined, the concept of a calorie restriction mimetic (CRM) has become a new area of investigation within gerontology. We have proposed that a CRM is a compound that mimics metabolic, hormonal, and physiological effects of CR, activates stress response pathways observed in CR and enhances stress protection, produces CR-like effects on longevity, reduces age-related disease, and maintains more youthful function, all without significantly reducing food intake. Over 12 years ago, we introduced the concept of glycolytic inhibition as a strategy for developing mimetics of CR. We have argued that inhibiting energy utilization as far upstream as possible might offer a broader range of CR-like effects as opposed to targeting a singular molecular target downstream. As the first candidate CRM, 2-deoxyglucose, a known anti-glycolytic, provided a remarkable phenotype of CR, but turned out to produce cardiotoxicity in rats. Since the introduction of 2DG as a candidate CRM, many different targets for development have now been proposed at more downstream sites, including insulin receptor sensitizers, sirtuin activators, and inhibitors of mTOR. This review discusses these various strategies to assess their current status and future potential for this emerging research field.

Effects of moderate calorie restriction on testosterone production and semen characteristics in young rhesus macaques (Macaca mulatta)

We have previously reported a modest influence of moderate calorie restriction (CR) on testicular gene expression in young adult rhesus macaques (Macaca mulatta); however, it is unclear if these modifications correspond to subsequent changes in testicular function or sperm physiology. This study extends our earlier findings to examine potential physiological differences due to this differential gene expression. Animals were subjected to 30% CR (CR, n = 5) or were fed a standard control diet (CON, n = 5) starting during their peripubertal period. Circulating testosterone (T) levels were measured across a 24-h period after 7 yr of dietary treatment and were found to be similar in CR and CON males; however, maintenance of daily minimum T levels was significantly higher in the CR animals. Semen collection was performed on the same cohort of animals three times per male (CR, n = 4; CON, n = 4) after 8 yr of treatment, and samples were assessed by a variety of measures. Parameters, including semen quality and sperm cell viability and function, showed less variability in semen samples taken from CR males, but overall testicular function and sperm quality were comparable regardless of diet. There is mounting evidence that CR may promote health and longevity in a wide range of organisms, including nonhuman primates. Importantly, our data suggest that moderate CR has no obvious lasting detrimental effect on testicular function and sperm parameters in young adult primates and may in fact help maintain higher levels of circulating T.

A calorie-restricted diet decreases brain iron accumulation and preserves motor performance in old rhesus monkeys

Caloric restriction (CR) reduces the pathological effects of aging and extends the lifespan in many species, including nonhuman primates, although the effect on the brain is less well characterized. We used two common indicators of aging, motor performance speed and brain iron deposition measured in vivo using MRI, to determine the potential effect of CR on elderly rhesus macaques eating restricted (n = 24; 13 males, 11 females) and standard diets (n = 17; 8 males, 9 females). Both the CR and control monkeys showed age-related increases in iron concentrations in globus pallidus (GP) and substantia nigra (SN), although the CR group had significantly less iron deposition in the GP, SN, red nucleus, and temporal cortex. A diet x age interaction revealed that CR modified age-related brain changes, evidenced as attenuation in the rate of iron accumulation in basal ganglia and parietal, temporal, and perirhinal cortex. Additionally, control monkeys had significantly slower fine motor performance on the Movement Assessment Panel, which was negatively correlated with iron accumulation in left SN and parietal lobe, although CR animals did not show this relationship. Our observations suggest that the CR-induced benefit of reduced iron deposition and preserved motor function may indicate neural protection similar to effects described previously in aging rodent and primate species.

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.

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.

Effects of long-term calorie restriction and endurance exercise on glucose tolerance, insulin action, and adipokine production

Calorie restriction (CR) slows aging and is thought to improve insulin sensitivity in laboratory animals. In contrast, decreased insulin signaling and/or mild insulin resistance paradoxically extends maximal lifespan in various genetic animal models of longevity. Nothing is known regarding the long-term effects of CR on glucose tolerance and insulin action in lean healthy humans. In this study we evaluated body composition, glucose, and insulin responses to an oral glucose tolerance test and serum adipokines levels in 28 volunteers, who had been eating a CR diet for an average of 6.9 +/- 5.5 years, (mean age 53.0 +/- 11 years), in 28 age-, sex-, and body fat-matched endurance runners (EX), and 28 age- and sex-matched sedentary controls eating Western diets (WD). We found that the CR and EX volunteers were significantly leaner than the WD volunteers. Insulin sensitivity, determined according to the HOMA-IR and the Matsuda and DeFronzo insulin sensitivity indexes, was significantly higher in the CR and EX groups than in the WD group (P = 0.001). Nonetheless, despite high serum adiponectin and low inflammation, approximately 40% of CR individuals exhibited an exaggerated hyperglycemic response to a glucose load. This impaired glucose tolerance is associated with lower circulating levels of IGF-1, total testosterone, and triiodothyronine, which are typical adaptations to life-extending CR in rodents.

Impact of Moderate Calorie Restriction on the Reproductive Neuroendocrine Axis of Male Rhesus Macaques

The impact of moderate calorie restriction on reproductive neuroendocrine function was investigated in young adult male rhesus macaques (Macaca mulatta). The animals were subjected to either 30% calorie restriction (CR; n=5), or were fed a standard control diet (CON; n=5), starting during their peripubertal period. Plasma LH and testosterone concentrations were examined after 7 years of differential dietary treatment, and were found to be similar in both groups, both during the day and during the night. Microarray profiling of pituitary gland and testicular gene expression was performed after 8 years of treatment, using GeneChip® Rhesus Macaque Genome Arrays (Affymetrix), and showed very little effect of caloric restriction. Using a 1.5-fold difference threshold, our microarray analysis revealed differential expression of only 145 probesets in the pituitary gland and 260 in the testes, out of a total of >54,000. Semi-quantitative RT-PCR performed on pituitary gland mRNA corroborated the microarray findings for selected modulated genes, including TSH receptor (TSHR) and sperm-specific antigen 2 (SSFA2). Most notably, significantly lower expression of TSH receptor mRNA was observed in the pituitary of CR compared to CON animals. Also, significantly lower expression of the glycoprotein hormone alpha subunit (CGA) was observed in CR animals, and this finding was further corroborated using quantitative real-time RT-PCR. No significant diet-induced changes were detected in the testis for genes associated with reproduction, circadian clocks, or oxidative stress. There is mounting evidence that CR may promote health and longevity in a wide range of organisms, including nonhuman primates. Importantly, our data suggest that moderate CR has no obvious lasting detrimental effect on the reproductive neuroendocrine axis of long-lived primates, and has only a modest influence on pituitary and testicular gene expression.

Could Sirt1-mediated epigenetic effects contribute to the longevity response to dietary restriction and be mimicked by other dietary interventions?

Dietary restriction (DR) increases lifespan in a range of evolutionarily distinct species. The polyphenol resveratrol may be a dietary mimetic of some effects of DR. The pivotal role of the mammalian histone deacetylase (HDAC) Sirt1, and its homologue in other organisms, in mediating the effects of both DR and resveratrol on lifespan/ageing suggests it may be the common conduit through which these dietary interventions influence ageing. We propose the novel hypothesis that effects of DR relevant to lifespan extension include maintenance of DNA methylation patterns through Sirt1-mediated epigenetic effects, and proffer the view that dietary components, including resveratrol, may mimic these actions.

High-risk pregnancy in rhesus monkeys (Macaca mulatta): a case of ectopic, abdominal pregnancy with birth of a live, term infant, and a case of gestational diabetes complicated by pre-eclampsia

BACKGROUND

Cases of abdominal pregnancy, in the form of intra-abdominal mummified fetuses, have been described in nonhuman primates. Gestational diabetes and pre-eclampsia are common pregnancy complications in women.

METHODS

Two timed-bred rhesus monkeys had high-risk pregnancies, an abdominal pregnancy with delivery of a live term infant, and a case of gestational diabetes that later developed pre-eclampsia.

RESULTS

The monkey that had abdominal pregnancy later died from septic peritonitis. The monkey had a colonic adenocarcinoma that may have allowed leakage of intestinal contents into the abdomen. Her infant was fostered to another female and survived. The monkey with gestational diabetes and pre-eclampsia was treated with a regimen similar to that used in women, and a live infant was delivered at day 157 of gestation by Caesarian section.

CONCLUSION

These cases underscore the value of timed-breeding and the similarities between pregnancy complications in women and in nonhuman primates.

Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys

Caloric restriction—reducing the calories ingested by around 30% of that of a normal, fit individual—leads to substantial increases in life span in experimental animals. In an extensive study of caloric restriction in primates, Colman et al. (p. 201 ) report that rhesus monkeys, which were subjected to caloric restriction as adults and followed for the last 20 years, show decreased mortality and delayed onset of age-related diseases when compared to normally fed control animals. If compliance with such a diet were not so difficult, many humans would be strongly tempted to enjoy the decreased incidence of brain degeneration, cardiovascular disease, diabetes, and cancer apparent in this population of monkeys.

Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys

Caloric restriction—reducing the calories ingested by around 30% of that of a normal, fit individual—leads to substantial increases in life span in experimental animals. In an extensive study of caloric restriction in primates, Colman et al. (p. 201 ) report that rhesus monkeys, which were subjected to caloric restriction as adults and followed for the last 20 years, show decreased mortality and delayed onset of age-related diseases when compared to normally fed control animals. If compliance with such a diet were not so difficult, many humans would be strongly tempted to enjoy the decreased incidence of brain degeneration, cardiovascular disease, diabetes, and cancer apparent in this population of monkeys.

Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys

Caloric restriction—reducing the calories ingested by around 30% of that of a normal, fit individual—leads to substantial increases in life span in experimental animals. In an extensive study of caloric restriction in primates, Colman et al. (p. 201 ) report that rhesus monkeys, which were subjected to caloric restriction as adults and followed for the last 20 years, show decreased mortality and delayed onset of age-related diseases when compared to normally fed control animals. If compliance with such a diet were not so difficult, many humans would be strongly tempted to enjoy the decreased incidence of brain degeneration, cardiovascular disease, diabetes, and cancer apparent in this population of monkeys.

Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys

Caloric restriction—reducing the calories ingested by around 30% of that of a normal, fit individual—leads to substantial increases in life span in experimental animals. In an extensive study of caloric restriction in primates, Colman et al. (p. 201 ) report that rhesus monkeys, which were subjected to caloric restriction as adults and followed for the last 20 years, show decreased mortality and delayed onset of age-related diseases when compared to normally fed control animals. If compliance with such a diet were not so difficult, many humans would be strongly tempted to enjoy the decreased incidence of brain degeneration, cardiovascular disease, diabetes, and cancer apparent in this population of monkeys.

Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys

Caloric restriction—reducing the calories ingested by around 30% of that of a normal, fit individual—leads to substantial increases in life span in experimental animals. In an extensive study of caloric restriction in primates, Colman et al. (p. 201 ) report that rhesus monkeys, which were subjected to caloric restriction as adults and followed for the last 20 years, show decreased mortality and delayed onset of age-related diseases when compared to normally fed control animals. If compliance with such a diet were not so difficult, many humans would be strongly tempted to enjoy the decreased incidence of brain degeneration, cardiovascular disease, diabetes, and cancer apparent in this population of monkeys.

Caloric restriction delays disease onset and mortality in rhesus monkeys

Caloric restriction (CR), without malnutrition, delays aging and extends life span in diverse species; however, its effect on resistance to illness and mortality in primates has not been clearly established. We report findings of a 20-year longitudinal adult-onset CR study in rhesus monkeys aimed at filling this critical gap in aging research. In a population of rhesus macaques maintained at the Wisconsin National Primate Research Center, moderate CR lowered the incidence of aging-related deaths. At the time point reported, 50% of control fed animals survived as compared with 80% of the CR animals. Furthermore, CR delayed the onset of age-associated pathologies. Specifically, CR reduced the incidence of diabetes, cancer, cardiovascular disease, and brain atrophy. These data demonstrate that CR slows aging in a primate species.

Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys

Caloric restriction—reducing the calories ingested by around 30% of that of a normal, fit individual—leads to substantial increases in life span in experimental animals. In an extensive study of caloric restriction in primates, Colman et al. (p. 201 ) report that rhesus monkeys, which were subjected to caloric restriction as adults and followed for the last 20 years, show decreased mortality and delayed onset of age-related diseases when compared to normally fed control animals. If compliance with such a diet were not so difficult, many humans would be strongly tempted to enjoy the decreased incidence of brain degeneration, cardiovascular disease, diabetes, and cancer apparent in this population of monkeys.