Genetics of aging: lessons from centenarians

Centenarians: An excellent example of resilience for successful ageing

Centenarians are remarkable not only because of their prolonged life, but also because they compress morbidity until the very last moments of their lives, thus being proposed as a model of successful, extraordinary ageing. From the medical viewpoint, centenarians do not escape the physiological decline or the age-related diseases or syndromes (i.e. frailty), but the rate of such processes is slow enough to be counterbalanced by their increased intrinsic capacity to respond to minor stresses of daily life (i.e. resilience). These new concepts are reviewed in this paper. Allostatic stresses lead to a chronic low-grade inflammation that has led to the proposal of the "inflammaging" theory of ageing and frailty. The biology of centenarians, described in this review, provides us with clues for intervention to promote healthy ageing in the general population. One of the major reasons for this healthy ageing has to do with the genetic signature that is specific for centenarians and certainly different from octogenarians who do not enjoy the extraordinary qualities of centenarians.

Characteristics of centenarians' lifestyles and their contribution to life satisfaction: A case study conducted on Hainan Island

BACKGROUND

Centenarians represent an intriguing model for healthy aging. They appear to have adapted well to their lives and are likely to be influenced by previous lifestyle habits, and their life satisfaction is influenced by mental and psychological health.

OBJECTIVE

The aim of this study is to explore centenarians' lifestyles by sex and their potential contribution to life satisfaction.

METHOD

In order to examine the common characteristics of centenarians in Hainan and the potential differences between men and women, a cross-sectional survey was conducted with 223 cognitively-intact Chinese centenarians. We also explored the association between life satisfaction and other physical factors using binary logistic regression and principal component analysis.

RESULTS

The results provided supplementary evidence indicating that women tended to live longer than men. However, the difference in life satisfaction observed between the sexes was not obvious (p = 0.659). The proportion of physical factors between each sex showed a similar trend in distribution. Most centenarians' lifestyles were similar, in that they followed a light diet and did not smoke or drink alcohol. Centenarians in better physical condition and with higher self-assessment, as well as those with "alcohol and tobacco habits," were more satisfied with their life. Of the factors examined in the binary logistic regression, sleep satisfaction was the only factor significantly positively correlated with life satisfaction (p < .01).

CONCLUSION

The research findings elucidated physiological and psychological health in centenarians and provided a model of healthy aging strategies for reference purposes.

Relationship between lifespan indicators and elemental background values: A case study in Guangdong Province, China

There was a significant difference in the distribution of centenarians at county-level in Guangdong Province, China. To carry out an integrated analysis on elemental background values and their relation to lifespan level, samples of environmental media such as drinking water, staple rice and soil were collected in ten counties (non-longevity and longevity areas) in Guangdong Province. Meanwhile, lifespan indicators were calculated based on census data in 2010: the percentage of population aged 80 to 90years (octogenarian index, 80-90%, OI%), the percentage of population aged 90 to 100years (longevity index, 90-100%, LI%), centenarians per one hundred thousand inhabitants (CH). Grey relational analysis (GRA) and stepwise multiple linear regression analysis (SMLR) were conducted. The major results show that the contents of Se, Mo, Ni, K and Zn in drinking water and rice and the content of Se in soil in longevity areas are significantly higher than those in non-longevity areas. Significantly positive correlation between elemental background values (Se, K, Mo, Ni and Zn) and three lifespan indicators shows an increasing trend in the order of OI, LI and CH. However, element Al in rice and soil shows a negative correlation with CH. In addition, the influence degree of elemental background values on LI and CH can be ranked as Se>Mo>K>Zn>Ni. The explanatory power of elemental background values (Se, K, Mo, Ni and Zn) to difference in LI/CH in longevity and non-longevity areas can be ranked: drinking water>rice>soil. The elemental background values (Se, K, Mo, Ni and Zn) have a positive impact on human lifespan, especially for those who live longer than 90years old.

Association between Longevity and Element Levels in Food and Drinking Water of Typical Chinese Longevity Area

OBJECTIVES

To carrying out an integrated analysis on regional environment and human health in China and to detect the association between longevity and daily element intake from food and drinking water.

DESIGN

Cross-sectional study.

SETTING

All the 18 cities and counties in Hainan Province.

MEASUREMENTS

The distribution of elderly population and longevity indexes at a county level in Hainan Province were investigated. Quality of food and drinking water in Hainan was evaluated by comparing the chemical elements with National Standards. In addition, the association between element concentrations in food and water and longevity was examined using spearman's rank correlation.

RESULTS

The proportion of elderly people is higher in the northern part of the province compared with southern counties. Food contributes a greater proportion of daily element intake than drinking water. Compared with the National Standards, reaching rates for elements were over 85% for both food and drinking water. There was a positive correlation between daily intake of Cu, Se, and Zn from food and water and aging and longevity indexes, and a negative correlation between Pb intake and these indexes.

CONCLUSION

The quality of food and water in Hainan Province are good and that, compared with water, food is a more important source of trace elements. An appropriate supply of Cu, Se, and Zn is important, whereas excessive intake of Pb should be avoided. The findings also provide basic data to support further studies on regional variations in longevity and their relationship to diet and drinking water.

Effect of age and activity level on lower extremity gait dynamics: an introductory study

Elderly adults should perform exercises that maintain or improve balance to reduce risk of injury from falls. Bone fractures secondary to falls in the elderly, particularly sedentary females, continue to pose a major health and economic problem. A greater understanding of the processes that contribute to the propensity for falling may be obtained by considering changes in gait biodynamics with age and activity level. Therefore, the purpose of this study was to quantify the relationships between age/activity level and selected biodynamic parameters of the lower extremity during normal gait. Seventeen healthy women, 9 young and 8 elderly, were divided into groups of 9 active and 8 sedentary subjects. Three-dimensional (3D) video motion and force platform kinematic and kinetic data were collected from the hip, knee, and ankle of the right lower extremity as the subjects walked at self-selected speeds. Data were analyzed as functions of age and activity level by using a 2-way analysis of variance. As expected, our results show that the elderly group had significantly greater (p < 0.05) functional and mobility limitations in their lower extremity joints than did the younger group. Significant, age-related lower-limb gait alterations were manifested primarily at the ankle, whereas activity-related alterations were manifested most prominently at the hip. The knee showed the fewest changes accompanying age or activity level. Thus, age and activity level affect gait, which may have a role in the subsequent development of a predisposition to gait-related imbalances and resultant falling and increased hip fracture risk. Strength and conditioning professionals may consider these factors related to age and activity level when individualizing exercise regimens for their older, or sedentary, clients. Prophylactic physical activities involving specific, controlled 3D body movements may help prevent abnormal lower-limb joint kinematics (and their hypothetically coupled, intrinsic postural control strategies), thereby reducing fall and fracture propensity.

Effects of soil trace elements on longevity population in China

Based on background concentrations of elements in soils and the sixth population census data of China, this study discussed the distribution characteristics of soil elements and longevity population at province level in China. Percentages of the aging population are high in Southwest China and the eastern coastal region but low in western and northwestern regions. Provinces in South and Southwest China gain a high level of longevity, while the northern part of China has a low level of longevity. The background concentration of Se in soil has a significant positive correlation with longevity index, while Ba and Ni have a significant negative correlation with longevity indexes. By regression analysis, longevity index C/100,000 can be expressed as C/100,000 = 1.679-0.205 Ni + 0.413 Co + 0.006 Se (with R (2) = 0.402 and p < 0.01), C/65+ can be expressed as C/65+=3.425-0.262 Ni + 0.435 Co + 0.006 Se (with R (2) = 0.369 and p < 0.01).

Inflammation and genetics: an insight in the centenarian model

The number of centenarians is growing worldwide. This specific cohort has aroused the attention of scientists worldwide and is considered one of the most valuable models to study the mechanisms involved in the aging process. In fact, they have reached the extreme limits of human life span and, most important of all, they show relatively good health being able to perform their routine daily life. Because they have escaped the common lethal diseases, the role of their genetic background has been brought into focus. In fact, sequence variations, in a variety of pro- or anti-inflammatory cytokine genes, have been found to influence successful ageing and longevity. The key role played by cytokines has been also confirmed in centenarians as we know that inflammation has been related to several pathological burdens (e.g., obesity, atherosclerosis, and diabetes). Successful ageing seems to be related to an optimal functioning of the immune system, pointing out that polymorphisms for the immune system genes, which are involved in the regulation of immune-inflammatory responses, may play a key role in the genetics of ageing. This review provides an update in the field of ageing related to inflammation and genetics.

Effects of several environmental factors on longevity and health of the human population of Zhongxiang, Hubei, China

Increasing human health and longevity is of global interest. Environmental, genetic, and stochastic factors all affect longevity. Among these factors, the environment is extremely important. To investigate the relationship between the environment and longevity, we studied the environment in Zhongxiang (China), where the inhabitants commonly have long life spans. Air was analyzed for negative oxygen ions, SO2, and inhalable particles, while drinking water and rice were analyzed for macro- and micro-elements. The air quality in this area was determined to be grade I with high negative oxygen ion content and low SO2 and inhalable particle contents. Apart from Fe, Mn, and F, all tested elements and the pH were within national standards and World Health Organization guidelines. The percentage of long-lived people in the area was closely related to the macro- and micro-element contents of their staple food, rice. The elements in rice could be classified into three categories according to their effect on longevity: Sr, Ca, Al, Mo, and Se, which were positively correlated with longevity; Fe, Mn, Zn, Cr, P, Mg, and K, which had a weak effect on local longevity, and Cu and Ba, which had a negative effect on longevity.

Association of mitochondrial DNA haplogroups with exceptional longevity in a Chinese population

Background

Longevity is a multifactorial trait with a genetic contribution, and mitochondrial DNA (mtDNA) polymorphisms were found to be involved in the phenomenon of longevity.

Methodology/Principal Findings

To explore the effects of mtDNA haplogroups on the prevalence of extreme longevity (EL), a population based case-control study was conducted in Rugao – a prefecture city in Jiangsu, China. Case subjects include 463 individuals aged ≥95 yr (EL group). Control subjects include 926 individuals aged 60–69 years (elderly group) and 463 individuals aged 40–49 years (middle-aged group) randomly recruited from Rugao. We observed significant reduction of M9 haplogroups in longevity subjects (0.2%) when compared with both elderly subjects (2.2%) and middle-aged subjects (1.7%). Linear-by-linear association test revealed a significant decreasing trend of N9 frequency from middle-aged subjects (8.6%), elderly subjects (7.2%) and longevity subjects (4.8%) (p = 0.018). In subsequent analysis stratified by gender, linear-by-linear association test revealed a significant increasing trend of D4 frequency from middle-aged subjects (15.8%), elderly subjects (16.4%) and longevity subjects (21.7%) in females (p = 0.025). Conversely, a significant decreasing trend of B4a frequency was observed from middle-aged subjects (4.2%), elderly subjects (3.8%) and longevity subjects (1.7%) in females (p = 0.045).

Conclusions

Our observations support the association of mitochondrial DNA haplogroups with exceptional longevity in a Chinese population.

Relationships between distributions of longevous population and trace elements in the agricultural ecosystem of Rugao County, Jiangsu, China

Soil, plant, and water, as well as trace elements they contain, can influence human health through the food chain. A survey was conducted on distributions of trace elements in soils, plants, and drinking water in Rugao County, Jiangsu Province, China, an agricultural area with a high level of centenarians and nonagenarians. The ratio of people over 90 years old per 100,000 inhabitants (90-rate) based on village (about 4,000 residents in 4 km(2)) was correlated with trace elements in soil, drinking water, and rice by means of correlation analysis and/or principal component analysis. Although the average 90-rate in the whole area was as high as 277, the rates were not uniform across the entire region. The 90-rate in the area of loamy and strongly-developed Anthrosols and Cambosols was about 330, significantly higher than the 255 in the areas of sandy and strongly-developed Cambosols and of clayey and weakly-developed Cambosols. The concentrations of available Se, B, Ni, and Mo in soils of the area with the high 90-rate were markedly greater than those in the area with the low 90-rate. This was demonstrated by highly positive correlations between the 90-rate and available Se (r = 0.33), B (r = 0.21), Ni (r = 0.17) and Mo (r = 0.17) at the p < 0.01 level and high loadings of available Se (0.851), B (0.535), Ni (0.594) and Mo (0.394) in the longevous factor. Similar relationships between the available elements in soils and elements in water and rice were found. These results suggest that: (1) the available forms of elements in soil were more crucial to elemental bio-availability in the ecosystem and human health than total elements in soil; and (2) the element association above might have affected the 90-rate positively and could be an important environmental geochemical factor influencing the longevity of humans.

Reduced expression levels of the senescence biomarker clusterin/apolipoprotein j in lymphocytes from healthy centenarians

Clusterin/apolipoprotein J (CLU) is a conserved, ubiquitously expressed secreted glycoprotein that has been implicated in several physiological processes and was found to accumulate in many severe physiological disturbances. We have previously shown that the CLU gene and protein are upregulated during replicative senescence, stress-induced premature senescence, in vivo aging, and in several age-related diseases. In this study we have examined the CLU gene relationship to human longevity. We recruited and further analyzed 96 blood samples from Italian and Greek healthy donors of different ages, including 49 centenarians. We found that although the CLU gene expression levels increase during aging, in the centenarians' samples CLU levels were lower than those found in old donors. We then investigated the possible existence of a genetic polymorphism related to longevity at the CLU structural locus. A neutral noncoding sequence variant was detected 35 nucleotides upstream from exon 6, which does not correlate, however, with the age of the donor. We conclude that CLU gene accumulation during in vivo aging does not directly relate to chronological age, but rather indicates increased levels of organismal stress due to a progressive failure of homeostasis and/or to prolonged exposure to a stressful environment.

Proteasome dysfunction in mammalian aging: Steps and factors involved

Mammalian aging is a natural biological process, determined by both genetic and environmental/stochastic factors, that results in the gradual decline of physiological function and the eventual failure of organism homeostasis. The proteasome is one of the major proteolytic systems of mammalian cells. It is responsible for the degradation of normal proteins as well as of abnormal proteins (like misfolded and oxidized proteins) that tend to accumulate during aging. Impaired proteasome function has been tightly correlated with aging both in vivo and in vitro. Given the fundamental function of proteasome for retaining cellular homeostasis, this review article examines the steps and the factors involved in proteasome dysfunction during mammalian aging. We discuss the proteasome structural organization, its activities and biosynthesis during aging and senescence as well as the genetic and environmental causes of its age-dependent alterations. Finally, we provide insights on the possibilities of proteasome activation that may retard the appearance of the senescent phenotype.

Gene expression changes reveal patterns of aging in the rat digestive tract

Similarly to other organs, the human digestive system is adversely affected by aging presenting physiologic manifestations that include compromised absorption and secretion, decreased motility, weakened mucosal barrier and as well as a high incidence of colon cancer. As biomedical advances enable the population to live longer, our understanding of molecular events that govern aging and disease states is enhanced through methodical analyses of temporal tissue-specific gene expression profiles. Recently, DNA microarray analyses have been employed to examine age-associated transcriptional profiles in the mammalian digestive tract. Gene expression patterns revealed that the magnitude and trend of age-associated changes differ in the rat colon and duodenum. Interestingly, the expression of genes involved in energy-generating metabolic pathways was decreased in the duodenum and increased in the colon. Microarray analyses detected modulations in expression of genes associated with compromised intestinal function and propensity for colon cancer in the aged population. Furthermore, altered expression was observed for certain genes implicated in governance of aging and lifespan in other organisms suggesting intriguing commonalities across species. Thus, these studies demonstrated feasibility and usefulness of DNA microarrays for identifying pathways involved in the molecular pathophysiology of the aging process and lifespan control in complex organisms.

Characterization of the hsp70 response in lymphoblasts from aged and centenarian subjects and differential effects of in vitro zinc supplementation

Human centenarians attract increasing interest as they hold some still undefined molecular mechanisms resulting in the achievement of exceptional old age. Recent data suggest the ability of centenarians to efficiently counter the increased cellular stress normally associated with ageing. The ubiquitous heat shock (HS) protein HSP70, expressed under the control of the heat shock transcription factor 1 (HSF-1), is recognized as one of the main chaperones associated with cell protection against stresses. In fact, HSP70 protein induction by heat, a classic well characterized cellular stress, was recently reported to be reduced in cells of most aged humans but not in centenarians. In order to investigate the molecular basis of this feature, we analyzed in vitro the time course expression of the hsp70 gene and the activation of HSF-1 in heat treated Epstein Barr virus transformed B-lymphocytes of centenarians. Our study demonstrates that lymphoblasts from centenarians maintain the transcriptional response of hsp70 gene to heat stress similar to young subjects. Such normal induction of hsp70 is associated to higher binding activity of HSF-1 that compensates an age-dependent delay in HSF-1 phosphorylation. Moreover, in vitro zinc supplementation had an age-dependent effect on hsp70 expression, indicating a role for this nutritionally important molecule and suggesting its involvement in cellular stress responses.

Overexpression of proteasome beta5 assembled subunit increases the amount of proteasome and confers ameliorated response to oxidative stress and higher survival rates

The proteasome is the major cellular proteolytic machinery responsible for the degradation of both normal and damaged proteins. Proteasomes play a fundamental role in retaining cellular homeostasis. Alterations of proteasome function have been recorded in various biological phenomena including aging. We have recently shown that the decrease in proteasome activity in senescent human fibroblasts relates to the down-regulation of beta-type subunits. In this study we have followed our preliminary observation by developing and further characterizing a number of different human cell lines overexpressing the beta5 subunit. Stable overexpression of the beta5 subunit in WI38/T and HL60 cells resulted in elevated levels of other beta-type subunits and increased levels of all three proteasome activities. Immunoprecipitation experiments have shown increased levels of assembled proteasomes in stable clones. Analysis by gel filtration has revealed that the recorded higher level of proteasome assembly is directly linked to the efficient integration of "free" (not integrated) alpha-type subunits identified to accumulate in vector-transfected cells. In support we have also found low proteasome maturation protein levels in beta5 transfectants, thus revealing an increased rate/level of proteasome assembly in these cells as opposed to vector-transfected cells. Functional studies have shown that beta5-overexpressing cell lines confer enhanced survival following treatment with various oxidants. Moreover, we demonstrate that this increased rate of survival is due to higher degradation rates following oxidative stress. Finally, because oxidation is considered to be a major factor that contributes to aging and senescence, we have overexpressed the beta5 subunit in primary IMR90 human fibroblasts and observed a delay of senescence by 4-5 population doublings. In summary, these data demonstrate the phenotypic effects following genetic up-regulation of the proteasome and provide insights toward a better understanding of proteasome regulation.

The compression of morbidity debate in aging: an empirical test using the gerontological and geriatric population studies in Göteborg, Sweden (H70)

The H70 longitudinal study of aging, Göteborg, Sweden is used to empirically test the compression of morbidity theory advanced by. We reconceptualize compression as postponement of morbidity in the sense of decreasing amounts of illness for increasingly long life spans. Operationally, morbidity is defined as the average number of hospital days in the last year of life. The date of death and the date of 1-year prior to death define the risk period. The linear regression model with age at death, age at death squared, year of birth, and sex are statistically significant with the oldest having the fewest hospital days. The findings offer partial support for the compression of morbidity theory.

Cloning of differentially expressed genes in skin fibroblasts from centenarians

Normal human fibroblasts undergoing serial passaging have been extensively used to identify genes linked with aging. Most of the isolated genes relate to growth retardation signals and the failure of homeostasis that accompanies aging and senescence. In contrast, there is still limited knowledge regarding the nature of the genes that influence positively the rate of aging and longevity. Healthy centenarians represent the best example of successful aging and longevity. Studies using samples from these individuals have proved very valuable for identifying a variety of factors that contribute to successful aging. The aim of the current work was to take advantage of skin fibroblast cultures established from healthy donors including centenarians in order to clone differentially expressed genes in centenarians. First, we demonstrate that centenarian derived cultures follow the typical Hayflick curve and they enter senescence after serial passaging. Application of differential screening techniques in minimally passaged cultures of four control donors of different ages (18-80 years old) and four centenarians has resulted in the cloning of six differentially expressed genes in centenarians. Four of the cloned genes, namely adlican, KBL, EST 38 and EST 39, were over-expressed in centenarians, while VDUP1 and OCIF were down-regulated in the same samples. We have also compared the expression levels of two representative cloned genes in cultures of human embryonic and adult fibroblasts to establish potential links with replicative senescence. Interestingly, VDUP1 was found over-expressed in late passage cells, while EST 39 was down-regulated in the same cultures. Thus our work demonstrates that a combination of the use of both biopsies derived cells and classical in vitro cells passaging will facilitate the better understanding of the biology of aging and longevity.

Central role of the proteasome in senescence and survival of human fibroblasts: induction of a senescence-like phenotype upon its inhibition and resistance to stress upon its activation

Normal human fibroblasts undergo a limited number of divisions in culture and progressively they reach a state of irreversible growth arrest, a process termed as replicative senescence. The proteasome is the major cellular proteolytic machinery, the function of which is impaired during replicative senescence. However, the exact causes of its malfunction in these conditions are unknown. Using WI38 fibroblasts as a model for cellular senescence we have observed reduced levels of proteasomal peptidase activities coupled with increased levels of both oxidized and ubiquitinated proteins in senescent cells. We have found the catalytic subunits of the 20 S complex and subunits of the 19 S regulatory complex to be down-regulated in senescent cells. This is accompanied by a decrease in the level of both 20 S and 26 S complexes. Partial inhibition of proteasomes in young cells caused by treatment with specific inhibitors induced a senescence-like phenotype, thus demonstrating the fundamental importance of the proteasome for retaining cellular maintenance and homeostasis. Stable overexpression of beta1 and beta5 subunits in WI38 established cell lines was shown to induce elevated expression levels of beta1 subunit in beta5 transfectants and vice versa. Transfectants possess increased proteasome activities and most importantly, increased capacity to cope better with various stresses. In summary these data demonstrate the central role of the proteasome during cellular senescence and survival as well as provide insights toward a better understanding of proteasome regulation.

Medical history, cognitive status and mobility at the age of 90. A population-based study in Tampere, Finland

BACKGROUND AND AIMS

The oldest-old population is expanding rapidly. There is a new need for clinical information about this group, which is actively using social and health care. We studied the population of people born in 1907-1910 and living in the city of Tampere (Finland) at the age 90 (N=916, 79.4% women, 20.6% men); 71.7% of the population lived in the community and 28.3% in institutions.

METHODS

Medical records of 832 (90.8%) nonagenarians were obtained. We registered diagnoses of chronic diseases or diseases that required hospitalization at any time of their lives, as well as physicians' notes on their memory and mobility. Diseases were coded and grouped according to ICD-10.

RESULTS

The most common diagnosis groups were cardiovascular diseases (78.3%), gastrointestinal diseases (58.6%), infections (53.6%) and trauma (49.6%). There was an average of 8 chronic or severe diseases mentioned in patient records. The diagnosis of dementia was mentioned in 26.7% of cases, most of them living in institutions; a problem with memory--from forgetfulness to dementia--was mentioned in 35.9% of cases; 37.5% were able to move using no or a light support, 8.3% were bedridden.

CONCLUSIONS

We conclude that this age group suffers from numerous chronic diseases influencing mobility and cognition. Dementia seems to be the most important symptom leading to institutionalization.

Aging: the fitness-stress continuum and genetic variability

Assuming the stress theory of aging, longevity depends upon primary selection for stress resistance and metabolic efficiency. Predominantly based upon experimental studies in the insect Drosophila melanogaster, high genetic variability for fitness, especially mortality, occurs under extreme stress. Isofemale strains derived from the progeny of recently collected single inseminated Drosophila females from the wild should provide useful biological material for extrapolating to quantitative genetic studies in man. Furthermore, environments from the benign (hormetic) to the extreme can be incorporated. Survival to old age may depend upon genes for metabolic efficiency that respond to the environmental challenges of living as limits to adaptation are approached. Under this scenario the survival of longevity mutants in man to ages analogous to the extreme life spans found in some experimental organisms under benign or protected laboratory conditions is unlikely. More future emphasis is needed on genetic variation of longevity in natural populations of experimental organisms under an array of realistically stressful environments to act as an evolutionary model for longevity in our own species.

Lifespan in captive baboons is heritable

The effects of aging are evident in multiple organ systems, tissues, cell types, and molecules; all complex phenotypes affected by multiple shared and unique environmental factors and genes, which makes identifying the role of genetics in human aging difficult. Researchers have used yeast, nematodes, fruit flies, and mice to search for genes that influence the aging process. Given the phylogenetic distance and anatomic and physiologic dissimilarities of these organisms from humans, directly extrapolating these results to our species is problematic. However, nonhuman primates have a high degree of genetic, anatomic and physiologic similarity with humans and, thus, they may assist in the detection, characterization, and identification of genetic and environmental influences on human aging. Our goal is to demonstrate that effects of genes on variation in lifespan, a surrogate measure of aging, can be detected in a nonhuman primate species. Using variance component analysis, heritability of age at death was estimated to be 0.23+/-0.08 (P=0.0003) in 674 baboons from the Southwest Foundation for Biomedical Research (SFBR). This research demonstrates that lifespan is under partial genetic control. Given these findings, we believe that the baboon has potential as a model of human aging.

Genetic determination of biological age in the Mennonites of the Midwestern United States

Numerous studies have shown that longevity is moderately heritable in human populations. Longevity, however, contains limited information on functional status, since individuals may exhibit differential survival patterns. In this study, we employed a stepwise multiple regression approach to estimate biological aging in a Mennonite population, using chronological age as a dependent variable and various predictors of chronological age including subphenotypes related to diabetes, coronary heart disease, hypertension, renal function, and markers of functional ability. The residual (the difference between chronological and predicted ages) is considered a marker of biological age. In fact, two different data sets were used to obtain residuals due to the availability of data. In each analysis, chronological age was regressed on predictor variables in a stepwise manner, retaining the variables significant at the 5% level. The first analysis (N=729) included 6 significant predictors (R(2)=44.3%): glucose, blood urea nitrogen (BUN), cholesterol, albumin, systolic blood pressure (SBP), and ln potassium, and the second analysis (N=232) included 9 significant predictors (R(2)=71.5%): BUN, albumin, SBP, low-density lipoprotein cholesterol, forced expiratory volume in 1 sec (FEV1), grip strength, trunk flexibility, reaction time, and FEV1xsex. Using a variance components approach, we found that the data set-specific residuals were significantly heritable (h(2)+/-SE): first analysis=0.265+/-0.106, and second analysis=0.469+/-0.180. The residuals from the second data set appear to be more informative for biological aging, perhaps due to the inclusion of functional ability-related phenotypes in addition to the blood chemistry variables. In summary, we have shown that markers of biological aging in Mennonites are under substantial additive genetic influences.

Ageing research in Greece

Ageing research in Greece is well established. Research groups located in universities, research institutes or public hospitals are studying various and complementary aspects of ageing. These research activities include (a) functional analysis of Clusterin/Apolipoprotein J, studies in healthy centenarians and work on protein degradation and the role of proteasome during senescence at the National Hellenic Research Foundation; (b) regulation of cell proliferation and tissue formation, a nationwide study of determinants and markers of successful ageing in Greek centenarians and studies of histone gene expression and acetylation at the National Center for Scientific Research, Demokritos; (c) work on amyloid precursor protein and Presenilin 1 at the University of Athens; (d) oxidative stress-induced DNA damage and the role of oncogenes in senescence at the University of Ioannina; (e) studies in the connective tissue at the University of Patras; (f) proteomic studies at the Biomedical Sciences Research Center Alexander Fleming; (g) work on Caenorhabditis elegans at the Foundation for Research and Technology; (h) the role of ultraviolet radiation in skin ageing at Andreas Sygros Hospital; (i) follow-up studies in healthy elderly at the Athens Home for the Aged; and (j) socio-cultural aspects of ageing at the National School of Public Health. These research activities are well recognized by the international scientific community as it is evident by the group's very good publication records as well as by their direct funding from both European Union and USA. This article summarizes these research activities and discuss future directions and efforts towards the further development of the ageing field in Greece.

Living longer--but better?

The highest attained age has increased by about 20 years since the beginning of the 19th century. In the course of the 1990s, more than ten individuals reached 115 years or more, including Jeanne Calment who attained the age of 122 years. In low-mortality countries, the number of centenarians has doubled every decade since 1950. This dramatic increase was mainly due to periodical effects related to the drastic fall in mortality among the elderly. The fact that centenarians are survivors does not mean that they are healthy. A high prevalence of comorbidity is found, and many centenarians have survived major diseases thanks to medical treatment and surgery. It is, however, possible that the comorbidity is less serious than in younger elderly. Certain personality traits may also be important in surviving health-threatening conditions. Furthermore, a number of biological and cognitive functions seem to be well-preserved in several centenarians. The influence of the apoE-gene and other genes involved in fundamental mechanisms illustrates that with advancing age and increasing mortality even small risks may have a substantial effect on survival to 100 years. A small proportion of long-livers may be considered as relatively autonomous, and this proportion will probably increase in the future. We are living longer and seem to postpone the terminal dependent phase to higher ages. Longevity may thus be perceived as part of our postmodern condition with its mix of pleasure and suffering.

Clusterin/apolipoprotein J is a novel biomarker of cellular senescence that does not affect the proliferative capacity of human diploid fibroblasts

Normal human fibroblasts have a limited replicative potential in culture and eventually reach a state of irreversible growth arrest, termed senescence. In a previous study aiming to identify genes that are differentially regulated during cellular senescence we have cloned clusterin/apolipoprotein J (Apo J), a 80 kDa secreted glycoprotein. In the current report we pursue our studies and show that senescence of human diploid fibroblasts is accompanied by up-regulation of both Apo J mRNA and protein levels, but with no altered biogenesis, binding partner profile or intracellular distribution of the two Apo J forms detected. To analyze the causal relationship between senescence and Apo J protein accumulation, we stably overexpressed the Apo J gene in primary as well as in SV40 T antigen-immortalized human fibroblasts and we showed no alteration of the proliferative capacity of the transduced cells. Despite previous reports on tumor-derived cell lines, overexpression of Apo J in human fibroblasts did not provide protection against apoptosis or growth arrest induced by hydrogen peroxide. Overall, our results suggest that Apo J overexpression does not induce senescence but it is rather a secondary consequence of the senescence phenotype. To our knowledge this is the first report that provides a functional analysis of human Apo J during replicative senescence.

Mathematical modeling of the aging processes and the mechanisms of mortality: paramount role of heterogeneity

Main problems of modeling the link between aging processes and mechanisms of mortality are addressed. Various applications of Gompertz's law, which allowed to formulate some fruitful hypotheses on the field, are reviewed. Some pitfalls occurring in its applications are also discussed using a model built on purpose to overcome these difficulties. The role played by heterogeneity emerges as the common cause of some relevant failure in using Gompertz's law and the necessary key ingredient of any model aimed to interpret the link between aging and mortality correctly. Though a number of problems are related to inter-individual variability, the search for their solution can lead to an intriguing approach to the study of aging and mortality. Living beings can be considered as complex systems and their age-related changes can be described at the light of complex system theory.

Age-associated changes in gene expression patterns in the duodenum and colon of rats

In humans, decreased intestinal motility, compromised nutritional status and increased risk of colon cancer are commonly associated with aging. Here, we used the cDNA microarray analysis to detect age-associated changes in duodenal and colonic gene expression in male Fischer 344 rats. The primary finding of this study is that the magnitude and direction of age-associated changes in gene expression differs in the colon and duodenum. In the colon, 56 genes showed altered expression, whereas expression of only 25 genes was altered in the duodenum. The magnitude of change was greater in the colon than in the duodenum. The direction of change also differed; in the aged colon, expression of 51 genes increased and only five genes decreased. In contrast, in the aged duodenum, only seven genes increased, whereas 18 genes decreased in expression. In the duodenum of aged rats, expression of genes involved in ATP-generating pathways is decreased. In contrast, in the colon of aged rats, expression of genes involved in energy generating pathways and in lipid oxidation is increased. In addition, in the aging colon, an increased expression of genes that show an aberrant regulation in colon cancer, including CD44, ras, and maspin is observed. Collectively, these findings provide clues to molecular events that may be related to compromised intestinal function and the high incidence of colon cancer in the aged population.

Translating basic aging research into geriatric health care

Aging processes are amenable to molecular genetic analyses. Two aspects of such research have been selected for discussion in this paper because of current great interest and their relevance to human aging. Studies on telomeres have revealed new insights on the control of cellular replicative senescence and provided a means to extend the cell's life span during in vitro cultivation. Emerging studies on genetic biomarkers have identified genes that appear to be associated with longevity or with risk factors for aging-related diseases, and raised considerations of ways to reduce disease expression. An interchange between basic scientists and clinicians would encourage new thoughts on the feasibility of translating these fundamental studies into interventions that promote healthier longevity.

Fibroblast cultures from healthy centenarians have an active proteasome

Healthy centenarians represent the best example of successful ageing. Various studies have shown that centenarians have escaped the major age-associated diseases, they have several well-conserved immune parameters and at least one gene allele has been identified and linked with their increased longevity. During ageing there is an accumulation of oxidised proteins, a phenomenon that has been related to an impaired function of the 20S proteasome in aged cells. We have, therefore, analysed the expression and the proteolytic activity of the proteasome in centenarian cells. Four fibroblast cultures derived from healthy centenarians were studied and compared with cultures derived from adult donors of different ages. Analysis of several proteasome subunits RNA expression levels, determination of one peptidase activity and identification of oxidised proteins in these samples revealed that centenarian cultures have a functional proteasome. In addition, it was found that the centenarian cultures exhibit characteristics similar to the younger rather than the older control donors derived cultures in all three assays. These data indicate that centenarian cells may be different from elderly donors cells, thus opening up new dimensions for the identification and characterisation of factors that are linked with longevity.