Instruct: Given a question, retrieve documents that answer the question.
Query: telomeres
Relatively short telomere length may serve as a marker of accelerated aging, and shorter telomeres have been linked to chronic stress. Specific lifestyle behaviors that can mitigate the effects of stress might be associated with longer telomere lengths. Previous research suggests a link between behaviors that focus on the well-being of others, such as volunteering and caregiving, and overall health and longevity. We examined relative telomere length in a group of individuals experienced in Loving-Kindness Meditation (LKM), a practice derived from the Buddhist tradition which utilizes a focus on unselfish kindness and warmth towards all people, and control participants who had done no meditation. Blood was collected by venipuncture, and Genomic DNA was extracted from peripheral blood leukocytes. Quantitative real time PCR was used to measure relative telomere length (RTL) (Cawthon, 2002) in fifteen LKM practitioners and 22 control participants. There were no significant differences in age, gender, race, education, or exposure to trauma, but the control group had a higher mean body mass index (BMI) and lower rates of past depression. The LKM practitioners had longer RTL than controls at the trend level (p=.083); among women, the LKM practitioners had significantly longer RTL than controls, (p=.007), which remained significant even after controlling for BMI and past depression. Although limited by small sample size, these results offer the intriguing possibility that LKM practice, especially in women, might alter RTL, a biomarker associated with longevity. Copyright © 2013 Elsevier Inc. All rights reserved.
Caregivers of Alzheimer’s disease patients endure chronic stress associated with a decline of immune function. To assess the psychological and immunological changes of caregivers, we compared depressive symptoms, PBMC composition, in vitro activation-induced proliferation and cytokine production, and telomere length and telomerase activity of 82 individuals (41 caregivers and 41 age- and gender-matched controls). We found depressive symptoms were significantly higher in caregivers than in controls (p < 0.001). Correspondingly, caregivers had significantly lower T cell proliferation but higher production of immune-regulatory cytokines (TNF-α and IL-10) than controls in response to stimulation in vitro. We examined the impact of these changes on cellular replicative lifespan and found that caregivers had significantly shorter telomere lengths in PBMC than controls (6.2 and 6.4 kb, respectively, p < 0.05) with similar shortening in isolated T cells and monocytes and that this telomere attrition in caregivers was not due to an increase of shorter telomere possessing T cell subsets in PBMC. Finally, we showed that basal telomerase activity in PBMC and T cells was significantly higher in caregivers than in controls (p < 0.0001), pointing to an unsuccessful attempt of cells to compensate the excessive loss of telomeres in caregivers. These findings demonstrate that chronic stress is associated with altered T cell function and accelerated immune cell aging as suggested by excessive telomere loss.
Healthy life span is rapidly increasing and human aging seems to be postponed. As recently exclaimed in Nature, these findings are so perplexing that they can be dubbed the 'longevity riddle'. To explain current increase in longevity, I discuss that certain genetic variants such as hyper-active mTOR (mTarget of Rapamycin) may increase survival early in life at the expense of accelerated aging. In other words, robustness and fast aging may be associated and slow-aging individuals died prematurely in the past. Therefore, until recently, mostly fast-aging individuals managed to survive into old age. The progress of civilization (especially 60 years ago) allowed slow-aging individuals to survive until old age, emerging as healthy centenarians now. I discuss why slow aging is manifested as postponed (healthy) aging, why the rate of deterioration is independent from aging and also entertain hypothetical use of rapamycin in different eras as well as the future of human longevity.
Aging affects all organisms and its basic mechanisms are expected to be conserved across species. Oxidation of proteins has been proposed to be one of the basic mechanisms linking oxygen radicals with the basic aging process. If oxidative damage to proteins is involved in aging, long-lived animals (which age slowly) should show lower levels of markers of this kind of damage than short-lived ones. However, this possibility has not been investigated yet. In this study, steady-state levels of markers of different kinds of protein damage--oxidation (glutamic and aminoadipic semialdehydes), mixed glyco- and lipoxidation (carboxymethyl- and carboxyethyllysine), lipoxidation (malondialdehydelysine) and amino acid composition--were measured in the heart of eight mammalian species ranging in maximum life span (MLSP) from 3.5 to 46 years. Oxidation markers were directly correlated with MLSP across species. Mixed glyco- and lipoxidation markers did not correlate with MLSP. However, the lipoxidation marker malondialdehydelysine was inversely correlated with MLSP (r2=0.85; P<0.001). The amino acid compositional analysis revealed that methionine is the only amino acid strongly correlated MLSP and that such correlation is negative (r2=0.93; P<0.001). This trait may contribute to lower steady-state levels of oxidized methionine residues in cellular proteins. These results reinforce the notion that high longevity in homeothermic vertebrates is achieved in part by constitutively decreasing the sensitivity of both tissue proteins and lipids to oxidative damage. This is obtained by modifying the constituent structural components of proteins and lipids, selecting those less sensitive to oxidative modifications.
Dietary factors, including dietary fat, may affect the biological aging process, as reflected by the shortening of telomere length (TL), by affecting levels of oxidative stress and inflammatory responses. We examined the direct relations of total and types of dietary fats and fat-rich foods to peripheral leukocyte TL. In 4029 apparently healthy postmenopausal women who participated in the Women’s Health Initiative, intakes of total fat, individual fatty acids, and fat-rich foods were assessed by a questionnaire. TL was measured by quantitative polymerase chain reaction. Intake of short-to-medium-chain saturated fatty acids (SMSFAs; aliphatic tails of ≤12 carbons) was inversely associated with TL. Compared with participants in other quartiles of SMSFA intake, women who were in the highest quartile (median: 1.29% of energy) had shorter TLs [mean: 4.00 kb (95% CI: 3.89, 4.11 kb)], whereas women in the lowest quartile of intake (median: 0.29% of energy) had longer TLs [mean: 4.13 kb (95% CI: 4.03, 4.24 kb); P-trend = 0.046]. Except for lauric acid, all other individual SMSFAs were inversely associated with TL (P < 0.05). In isoenergetic substitution models, the substitution of 1% of energy from SMSFAs with any other energy source was associated with 119 bp longer TLs (95% CI: 21, 216 bp). Intakes of nonskim milk, butter, and whole-milk cheese (major sources of SMSFAs) were all inversely associated with TL. No significant associations were found with long-chain saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. In conclusion, we found that higher intakes of SMSFAs and SMSFA-rich foods were associated with shorter peripheral leukocyte TL among postmenopausal women. These findings suggest the potential roles of SMSFAs in the rate of biological aging.
Longevity, lifespan, cancer, cellular transformation, energy, calorie restriction, diabetes--what can tie together such a diversity of hot topics in biomedical research? Emerging findings suggest that the answer lies in understanding the functions of the recently discovered family of proteins known as Sirtuins. Barcelona hosted the first scientific meeting completely focused on these evolutionary conserved protein deacetylases, bringing together experts in the biochemistry to cellular biology, mice models, drug targeting and pathophysiology of these molecules. Their work, summarized here, establishes the Sirtuins as major players in cellular homeostasis and human diseases that act through a whole range of biochemical substrates and physiological processes. Undoubtedly, this is an increasingly expanding field that it is here to stay and growth.
BACKGROUND: Centenarians are exceptionally long living individuals who escaped the most common age-related diseases. In particular they appear to be effectively protected from cancers. The mechanisms that underlie this protection are quite complex and still largely unclear. AIM: To critically analyse the literature in order to propose a unifying hypothesis that can account for this cancer protection in centenarians. METHODS: Review of the scientific literature regarding three main players in tumourigenesis such as IGF-1, inflammation and p53, and centenarians. RESULTS: Centenarians appear to be characterised by low IGF-1-mediated responses and high levels of anti-inflammatory cytokines such as IL-10 and TGF-beta, a condition that results in protection from cancer. Both inflammation and IGF-1 pathway converge on the tumour suppressor p53. Accordingly, some studies indicate that genetic variants of p53 are associated with human longevity by providing protection from cancer mortality. CONCLUSIONS: The available data let us to hypothesise that among other possible mechanisms, well-preserved p53-mediated responses are likely a key factor contributing to protection from cancer in centenarians.
Sirtuins (SIRTs), a family of nicotinamide adenine dinucleotide (NAD)-dependent deacetylases, are emerging as key molecules that regulate aging and age-related diseases including cancers, metabolic disorders, and neurodegenerative diseases. Seven isoforms of SIRT (SIRT1–7) have been identified in mammals. SIRT1 and 6, mainly localized in the nucleus, regulate transcription of genes and DNA repair. SIRT3 in the mitochondria regulates mitochondrial bioenergetics. Initial studies in yeasts, nematodes, and flies indicated a strong connection of SIRT with the life-prolonging effects of calorie restriction (CR), a robust experimental intervention for longevity in a range of organisms. However, subsequent studies reported controversial findings regarding SIRT roles in the effect of CR. This review describes the functional roles of mammalian SIRTs and discusses their relevance to mechanisms underlying the longevity effect of CR.
Cellular senescence is an in vivo and in vitro phenomenon, accompanied by physiological changes including cessation of division and disturbances of organelle structure and function. Review of the literature was undertaken to determine whether there is evidence that whole organism aging and cell senescence share a common initiation pathway. In vivo aged cells of different lineages, including aged T lymphocytes, show high expression of the INK4A-p16 gene. In cell culture when telomeres are shortened past a key length or state, the Arf/Ink gene system (p16/p14 humans, p16/p19 mice) switches on and activates p53, which suppresses further cell division. The p53 gene is a key tumor suppressor and its deletion or mutation allows cancerous growth. The switching on of p53 also causes changes in fatty acid metabolism, especially down-regulation of both fatty acid synthase and stearoyl-CoA (delta-9) desaturase. The co-suppression of these genes together with enhanced uptake of extracellular fatty acids, leads to raised levels of cellular palmitate and induction of either apoptosis or senescence. In senescent cells, the fatty acid composition of the cellular membranes alters and leads to changes in both structure and function of organelles, especially mitochondria. Animal models of accelerated aging exhibit repression of stearoyl-CoA desaturase activity while anti-aging calorie restriction stimulates the same enzyme system. It is concluded that aging in cells and whole organisms share a common initiation pathway and that cellular senescence is protective against cancer. Healthy longevity is likely to be most enhanced by factors that actively suppress excessive cell division.
BACKGROUND This study examined the effects of brief daily yogic meditation on mental health, cognitive functioning, and immune cell telomerase activity in family dementia caregivers with mild depressive symptoms. METHODS Thirty-nine family dementia caregivers (mean age 60.3 years old (SD=10.2)) were randomized to practicing Kirtan Kriya or listening to relaxation music for 12 minutes per day for eight weeks. The severity of depressive symptoms, mental and cognitive functioning were assessed at baseline and follow-up. Telomerase activity in peripheral blood mononuclear cells (PMBC) was examined in peripheral PBMC pre- and post-intervention. RESULTS The meditation group showed significantly lower levels of depressive symptoms and greater improvement in mental health and cognitive functioning compared to the relaxation group. In the meditation group, 65.2% showed 50% improvement on the Hamilton Depression Rating scale and 52% of the participants showed 50% improvement on the Mental Health Composite Summary score (MCS) of the SF-36 scale; compared to 31.2% and 19% respectively in the relaxation group (pp<0.05). The meditation group showed 43% improvement in telomerase activity compared to 3.7% in the relaxation group (p=0.05). CONCLUSION This pilot study found that brief daily meditation practices by family dementia caregivers can lead to improved mental and cognitive functioning, and lower levels of depressive symptoms. This improvement is accompanied by an increase in telomerase activity suggesting improvement in stress-induced cellular aging. These results need to be confirmed in a larger sample.
This article discusses that the traditional analogy of an aging organism with a rusting (albeit self-repairing) car is misleading. The true analogy is a speeding car that enters a low-speed zone and damages itself because it does not and cannot slow down. For such a car without brakes (and actually without a driver), aging from rusting never occurs. Using simple analogies (although turning gerontology upside down), this article discusses the origin of aging, how overactivation of the mTOR (Target of Rapamycin) pathway causes aging, why aging causes damage (organ damage) not damage causes aging, the link between aging and age-related diseases, slow aging versus aging tolerance and suppression of aging with rapamycin.
Dietary restriction (DR) extends the lifespan of a wide range of species, although the universality of this effect has never been quantitatively examined. Here, we report the first comprehensive comparative meta-analysis of DR across studies and species. Overall, DR significantly increased lifespan, but this effect is modulated by several factors. In general, DR has less effect in extending lifespan in males and also in non-model organisms. Surprisingly, the proportion of protein intake was more important for life extension via DR than the degree of caloric restriction. Furthermore, we show that reduction in both age-dependent and age-independent mortality rates drives life extension by DR among the well-studied laboratory model species (yeast, nematode worms, fruit flies and rodents). Our results suggest that convergent adaptation to laboratory conditions better explains the observed DR-longevity relationship than evolutionary conservation although alternative explanations are possible. © 2012 The Authors. Aging Cell © 2012 Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland.
The mammalian target of rapamycin (mTOR) plays a key role in the regulation of cellular metabolism, growth and proliferation. It forms two multi-protein complexes known as complex 1 (mTORC1) and 2 (mTORC2). Raptor and Rictor are the core proteins for mTORC1 and mTORC2, respectively. This study examines the relationship between mTORC1, Rictor and Raptor mRNA expression and human breast cancer. Furthermore, the correlation between mTORC1 and hTERT was investigated. Breast cancer tissues (n=150) and normal tissues (n=31) were analysed using reverse transcription and quantitative PCR. Transcript levels were correlated with clinicopathological data. Higher mTOR expression was noted in breast cancer tissue (P=0.0018), higher grade tumours (grade 2 vs. 3, P=0.047), in ductal tumours (P=0.0014), and was associated with worse overall survival (P=0.01). Rictor expression was significantly higher in background breast tissues compared with tumours and was inversely related to the Nottingham Prognostic Index (NPI1 vs. 2, P=0.03) and tumour grade (grade 1 vs. 3, P=0.01) and was associated with better overall (P=0.037) and disease-free survival (P=0.048). The mRNA expression of Raptor was higher in tumours compared with normal tissues. Furthermore, the expression of Raptor was associated with a higher tumour grade (grade 1 vs. 3, P=0.027). A highly significant positive correlation between mTOR and hTERT (P<0.00001) was observed. These observations are consistent with the role of mTORC1 in the anti-apoptosis pathway and suggest that selective inhibitors of mTORC1 may be more efficacious in human breast cancer. Our findings support the hypothesis that mTORC1 is an important upregulator of telomerase in breast cancer.
Over the last decade, the notion that tumors are maintained by their own stem cells, the so-called cancer stem cells, has created great excitement in the research community. This review attempts to summarize the underlying concepts of this notion, to distinguish hard facts from beliefs and to define the future challenges of the field.
Dietary restriction (DR) and reduced growth factor signaling both elevate resistance to oxidative stress, reduce macromolecular damage, and increase lifespan in model organisms. In rodents, both DR and decreased growth factor signaling reduce the incidence of tumors and slow down cognitive decline and aging. DR reduces cancer and cardiovascular disease and mortality in monkeys, and reduces metabolic traits associated with diabetes, cardiovascular disease and cancer in humans. Neoplasias and diabetes are also rare in humans with loss of function mutations in the growth hormone receptor. DR and reduced growth factor signaling may thus slow aging by similar, evolutionarily conserved, mechanisms. We review these conserved anti-aging pathways in model organisms, discuss their link to disease prevention in mammals, and consider the negative side effects that might hinder interventions intended to extend healthy lifespan in humans.
Restriction of food intake by 10-50% of ad libitum on a per unit of weight or energy content basis can extend the lifespan of a wide variety of species and prevent or delay age-related disease. This review first briefly summarizes the data delineating mortality trajectories of various species' populations maintained on restricted diets to provide insight into the effects of nutrient deprivation on distinct components of the aging process. Next, I discuss a number of important studies that have addressed the question whether it is the lack of calories and/or specific nutrients that determines the longevity response to dietary restriction. Finally, I review the evidence for hormesis as a proximate mechanism underpinning the impact of dietary restriction on lifespan. In aggregate, the currently available demographic data suggest that dietary restriction can both slow the age-related progressive accumulation of cellular damage and also enhance the ability of organisms to cope with irreversible injury. Restriction of essential nutrients as well as calories may affect life expectancy, perhaps in a species specific fashion. Hormesis, i.e. an evolutionary conserved stress response routine providing protection against a wide variety of (other) hazards in response to low levels of stress, is very likely to contribute to the beneficial health effects of dietary restriction. Copyright Â© 2011 Elsevier Inc. All rights reserved.
Dietary restriction (DR) without malnutrition is widely regarded to be a universal mechanism for prolonging lifespan. It is generally believed that the benefits of DR arise from eating fewer calories (termed caloric restriction, CR). Here we argue that, rather than calories, the key determinant of the relationship between diet and longevity is the balance of protein to non-protein energy ingested. This ratio affects not only lifespan, but also total energy intake, metabolism, immunity and the likelihood of developing obesity and associated metabolic disorders. Among various possible mechanisms linking macronutrient balance to lifespan, the nexus between the TOR and AMPK signaling pathways is emerging as a central coordinator.
Many experts in the biology of ageing believe that pharmacological interventions to slow ageing are a matter of ‘when’ rather than ‘if’. A leading target for such interventions is the nutrient response pathway defined by the mechanistic target of rapamycin (mTOR). Inhibition of this pathway extends lifespan in model organisms and confers protection against a growing list of age-related pathologies. Characterized inhibitors of this pathway are already clinically approved, and others are under development. Although adverse side effects currently preclude use in otherwise healthy individuals, drugs that target the mTOR pathway could one day become widely used to slow ageing and reduce age-related pathologies in humans.
During the last decade, biogerontologists have labored to understand the biological basis of the aging process by studying the genes and signaling pathways that regulate it. But the last year has seen a breakthrough in a different direction: toward treatments that might slow aging by mimicking the effects of dietary restriction.
Hormesis is a term used by toxicologists to refer to a biphasic dose response to an environmental agent characterized by a low dose stimulation or beneficial effect and a high dose inhibitory or toxic effect. In the fields of biology and medicine hormesis is defined as an adaptive response of cells and organisms to a moderate (usually intermittent) stress. Examples include ischemic preconditioning, exercise, dietary energy restriction and exposures to low doses of certain phytochemicals. Recent findings have elucidated the cellular signaling pathways and molecular mechanisms that mediate hormetic responses which typically involve enzymes such as kinases and deacetylases, and transcription factors such as Nrf-2 and NF-κB. As a result, cells increase their production of cytoprotective and restorative proteins including growth factors, phase 2 and antioxidant enzymes, and protein chaperones. A better understanding of hormesis mechanisms at the cellular and molecular levels is leading to and to novel approaches for the prevention and treatment of many different diseases.
Significance: The free radical theory of aging has provided a theoretical framework for an enormous amount of work leading to significant advances in our understanding of aging. Up to the turn of the century, the theory received abundant support from observations coming from fields as far apart as comparative physiology or molecular biology. Recent Advances: Work from many laboratories supports the theory, for instance showing that overexpression of antioxidant enzymes results in increases in life-span. But other labs have shown that in some cases, there is an increased oxidative stress and increased longevity. The discovery that free radicals can not only cause molecular damage to cells, but also serve as signals; led to the proposal that they act as modulators of physiological processes. For instance, reactive oxygen species (ROS) stimulate physiological adaptations to physical exercise. Critical Issues: A critical blow to the free radical theory of aging came from epidemiological studies showing that antioxidant supplementation did not lower the incidence of many age-associated diseases but, in some cases, increased the risk of death. Moreover, recent molecular evidence has shown that increasing generation of ROS, in some cases, increases longevity. Future Directions: Gerontologists interested in free radical biology are at a crossroads and clearly new insights are required to clarify the role of ROS in the process of aging. The hurdles are, no doubt, very high, but the intellectual and practical promise of these studies is of such magnitude that we feel that all efforts will be generously rewarding. Antioxid. Redox Signal. 19, 779–787.
Senescent T-cells accumulate with age, lowering the naïve T-cell repertoire and increasing host infection risk. As this response is likely to be influenced by certain lifestyle factors, we examined the association between aerobic fitness (VO(2max)) and the age-related accumulation of senescent T-cells. Blood lymphocytes from 102 healthy males (18-61 yr) were analyzed for KLRG1, CD57, CD28, CD45RA, CD45RO surface expression on CD4+ and CD8+ T-cells by 4-color flow cytometry. Advancing age (yr) was positively associated with the proportion (%) of senescent (KLRG1+/CD57+; KLRG1+/CD28-) CD4+ (B=1.00; 1.02) and CD8+ (B=0.429; 1.02) T-cells and inversely associated with naïve (KLRG1-/CD28+) CD4+ (B=-1.000) and CD8+ (B=-0.993) T-cells. VO(2max) was inversely associated with senescent CD4+ (B=-0.97) and CD8+ (B=-0.240). Strikingly, age was no longer associated with the proportions of senescent or naïve T-cells after adjusting for VO(2max), while the association between VO(2max) and these T-cell subsets withstood adjustment for age, BMI and percentage body fat. Ranking participants by age-adjusted VO(2max) revealed that the highest tertile had 17% more naïve CD8+ T-cells and 57% and 37% less senescent CD4+ and CD8+ T-cells, respectively, compared to the lowest tertile. VO(2max) was not associated with latent cytomegalovirus (CMV), Epstein-Barr virus (EBV) or herpes simplex virus-1 (HSV-1) infection, indicating that the moderating associations of VO(2max) were not confounded by persistent viral infections. This is the first study to show that aerobic fitness is associated with a lower age-related accumulation of senescent T-cells, highlighting the beneficial effects of maintaining a physically active lifestyle on the aging immune system. Copyright © 2011 Elsevier Inc. All rights reserved.
Ageing is a challenge for any living organism and human longevity is a complex phenotype. With increasing life expectancy, maintaining long-term health, functionality and well-being during ageing has become an essential goal. To increase our understanding of how ageing works, it may be advantageous to analyze the phenotype of centenarians, perhaps one of the best examples of successful ageing. Healthy ageing involves the interaction between genes, the environment, and lifestyle factors, particularly diet. Besides evaluating specific gene-environment interactions in relation to exceptional longevity, it is important to focus attention on modifiable lifestyle factors such as diet and nutrition to achieve extension of health span. Furthermore, a better understanding of human longevity may assist in the design of strategies to extend the duration of optimal human health. In this article we briefly discuss relevant topics on ageing and longevity with particular focus on dietary patterns of centenarians and nutrient-sensing pathways that have a pivotal role in the regulation of life span. Finally, we also discuss the potential role of Nrf2 system in the pro-ageing signaling emphasizing its phytohormetic activation.
In metazoans, TOR is an essential protein that functions as a master regulator of cellular growth and proliferation. Over the past decade, there has been an explosion of information about this critical master kinase, ranging from the composition of the TOR protein complex to its ability to act as an integrator of numerous extracellular signals. Unfortunately, this plethora of information has also raised numerous questions regarding TOR function. Currently, the prevailing view is that mammalian TOR (mTOR) exists in at least two molecular complexes, mTORC1 and mTORC2, which are largely defined by the presence of either RAPTOR or RICTOR. However, additional co-factors have been identified for each complex, and their importance in mediating mTOR signals has been incompletely elucidated. Similarly, there are differences in mTOR function that reflect the tissue of origin. In this review, we present an alternative view to mTOR complex formation and function, which envisions mTOR regulation and signal propagation as a reflection of cell type- and basal state-dependent conditions. The re-interpretation of mTOR biology in this framework may facilitate the design of therapies most likely to effectively inhibit this central regulator of cell behavior.
Summary With the aging of the population, we are seeing a global increase in age-related disorders, especially in developed countries. Chronic diseases disproportionately affect the older segment of the population, contributing to disability, a diminished quality of life, and an increase in healthcare costs. Increased life expectancy reflects the success of contemporary medicine, which must now respond to the challenges created by this achievement, including the growing burden of chronic illnesses, injuries, and disabilities. A well-developed theoretical framework is required to understand the molecular basis of aging. This, in turn, is a prerequisite for developing the clinical interventions that will constitute an efficient response to the challenge of age-related health issues. This review critically analyzes the experimental evidence that supports and refutes the Free Radical/Mitochondrial Theory of Aging, which has dominated the field of aging research for almost half a century.