Common gene variants, mortality and extreme longevity in humans

Genetic scores for predicting longevity in the Croatian oldest-old population

Longevity is a hallmark of successful ageing and a complex trait with a significant genetic component. In this study, 43 single nucleotide polymorphisms (SNPs) were chosen from the literature and genotyped in a Croatian oldest-old sample (85+ years, sample size (N) = 314), in order to determine whether any of these SNPs have a significant effect on reaching the age thresholds for longevity (90+ years, N = 212) and extreme longevity (95+ years, N = 84). The best models were selected for both survival ages using multivariate logistic regression. In the model for reaching age 90, nine SNPs explained 20% of variance for survival to that age, while the 95-year model included five SNPs accounting for 9.3% of variance. The two SNPs that showed the most significant association (p ≤ 0.01) with longevity were TERC rs16847897 and GHRHR rs2267723. Unweighted and weighted Genetic Longevity Scores (uGLS and wGLS) were calculated and their predictive power was tested. All four scores showed significant correlation with age at death (p ≤ 0.01). They also passed the ROC curve test with at least 50% predictive ability, but wGLS90 stood out as the most accurate score, with a 69% chance of accurately predicting survival to the age of 90.

N-Acetyl-Cysteine: Modulating the Cysteine Redox Proteome in Neurodegenerative Diseases

In the last twenty years, significant progress in understanding the pathophysiology of age-associated neurodegenerative diseases has been made. However, the prevention and treatment of these diseases remain without clinically significant therapeutic advancement. While we still hope for some potential genetic therapeutic approaches, the current reality is far from substantial progress. With this state of the issue, emphasis should be placed on early diagnosis and prompt intervention in patients with increased risk of neurodegenerative diseases to slow down their progression, poor prognosis, and decreasing quality of life. Accordingly, it is urgent to implement interventions addressing the psychosocial and biochemical disturbances we know are central in managing the evolution of these disorders. Genomic and proteomic studies have shown the high molecular intricacy in neurodegenerative diseases, involving a broad spectrum of cellular pathways underlying disease progression. Recent investigations indicate that the dysregulation of the sensitive-cysteine proteome may be a concurrent pathogenic mechanism contributing to the pathophysiology of major neurodegenerative diseases, opening new therapeutic opportunities. Considering the incidence and prevalence of these disorders and their already significant burden in Western societies, they will become a real pandemic in the following decades. Therefore, we propose large-scale investigations, in selected groups of people over 40 years of age with decreased blood glutathione levels, comorbidities, and/or mild cognitive impairment, to evaluate supplementation of the diet with low doses of N-acetyl-cysteine, a promising and well-tolerated therapeutic agent suitable for long-term use.

Investigating the association of testosterone with survival in men and women using a Mendelian randomization study in the UK Biobank

Life expectancy in the developed West is currently stagnated and remains shorter in men than women. Well-established evolutionary biology theory suggests lifespan trades-off against reproductive success, possibly sex-specifically. We examined whether a key driver of reproductive success, testosterone, affected survival using a Mendelian randomization longevity study in the UK Biobank to obtain unbiased estimates, along with control exposures. We applied published genetic instruments for testosterone to obtain inverse variance weighted estimates of associations with survival to (i.e., age at) recruitment, in 167,020 men and 194,174 women. We similarly obtained estimates for a positive control (smoking initiation), and a negative control (absorbate), a marker of vitamin C metabolism. Testosterone was associated with poorer survival (0.10 years younger at recruitment per effect size of testosterone, 95% confidence interval (CI) 0.004 to 0.20). As expected, smoking initiation was also associated with poorer survival (0.37 years younger, 95% CI 0.25 to 0.50), but not absorbate (0.01 years younger, 95% CI - 0.09 to 0.11). Several aspects of a healthy lifestyle (low animal fat diet) and several widely used medications (statins, metformin, dexamethasone and possibly aspirin) may modulate testosterone. Explicitly designing interventions sex-specifically based on these insights might help address stagnating life expectancy and sexual disparities.

Age and sex specific effects of APOE genotypes on ischemic heart disease and its risk factors in the UK Biobank

APOE genotypes are associated with ischemic heart disease (IHD), several other cardiovascular diseases and dementia. Previous studies have not comprehensively considered all genotypes, especially ε2ε2, nor associations by age and sex, although IHD incidence differs by sex. In the UK Biobank, including 391,992 white British participants, we compared effects of APOE genotypes on IHD and its risk factors. Compared to the ε3ε3 genotype, ε2ε2 was not clearly associated with IHD but was associated with lower plasma apolipoprotein B (apoB). The ε2ε3 genotype conferred lower IHD risk, systolic blood pressure (SBP), pulse pressure and plasma apoB than ε3ε3. ε3ε4 and ε4ε4 conferred higher IHD risk, higher pulse pressure and plasma apoB, but lower glycated haemoglobin (HbA1c) than ε3ε3. The associations by age and sex were fairly similar, except ε2ε2 compared to ε3ε3 was marginally positively associated with IHD in the younger age group and nominally inversely associated with SBP in men. ε3ε4 compared to ε3ε3 was nominally positively associated with SBP in women. APOE genotypes affect IHD risk increasingly from ε2ε3, ε3ε3, ε3ε4 to ε4ε4, with similar patterns for pulse pressure and plasma apoB, but not for diabetes. Associations with blood pressure differed by sex. Greater understanding of products of APOE and their effects might generate targets of intervention.

Lifestyle factors of people with exceptional longevity

OBJECTIVES

To assess lifestyle factors including physical activity, smoking, alcohol consumption, and dietary habits in men and women with exceptional longevity.

DESIGN

Retrospective cohort study.

SETTING

A cohort of community-dwelling Ashkenazi Jewish individuals with exceptional longevity defined as survival and living independently at age 95 and older.

PARTICIPANTS

Four hundred seventy-seven individuals (mean 97.3 ± 2.8, range 95-109; 74.6% women) and a subset of participants of the National Health and Nutrition Examination Survey (NHANES) I (n = 3,164) representing the same birth cohort as a comparison group.

MEASUREMENTS

A trained interviewer administrated study questionnaires to collect information on lifestyle factors and collected data on anthropometry.

RESULTS

People with exceptional longevity had similar mean body mass index (men, 25.4 ± 2.8 kg/m² vs 25.6 ± 4.0 kg/m² , P=.63; women, 25.0 ± 3.5 kg/m² vs 24.9 ± 5.4 kg/m² ; P = .90) and a similar proportion of daily alcohol consumption (men, 23.9 vs 22.4, P = .77; women, 12.1 vs 11.3, P = .80), of regular physical activity (men: 43.1 vs 57.2; P = .07; women: 47.0 vs 44.1, P = .76), and of a low-calorie diet (men: 20.8 vs 21.1, P=.32; women: 27.3 vs 27.1, P=.14) as the NHANES I population.

CONCLUSION

People with exceptional longevity are not distinct in terms of lifestyle factors from the general population, suggesting that people with exceptional longevity may interact with environmental factors differently than others. This requires further investigation.

Genome-wide association study (GWAS)-identified disease risk alleles do not compromise human longevity

A set of currently known alleles increasing the risk for coronary artery disease, cancer, and type 2 diabetes as identified by genome-wide association studies was tested for compatibility with human longevity. Here, we show that nonagenarian siblings from long-lived families and singletons older than 85 y of age from the general population carry the same number of disease risk alleles as young controls. Longevity in this study population is not compromised by the cumulative effect of this set of risk alleles for common disease.

Single nucleotide polymorphisms in obesity-related genes and all-cause and cause-specific mortality: a prospective cohort study

Background

The aim of this study was to examine the associations between 16 specific single nucleotide polymorphisms (SNPs) in 8 obesity-related genes and overall and cause-specific mortality. We also examined the associations between the SNPs and body mass index (BMI) and change in BMI over time.

Methods

Data were analyzed from 9,919 individuals who participated in two large community-based cohort studies conducted in Washington County, Maryland in 1974 (CLUE I) and 1989 (CLUE II). DNA from blood collected in 1989 was genotyped for 16 SNPs in 8 obesity-related genes: monoamine oxidase A (MAOA), lipoprotein lipase (LPL), paraoxonase 1 and 2 (PON1 and PON2), leptin receptor (LEPR), tumor necrosis factor-α (TNFα), and peroxisome proliferative activated receptor-γ and -δ (PPARG and PPARD). Data on height and weight in 1989 (CLUE II baseline) and at age 21 were collected from participants at the time of blood collection. All participants were followed from 1989 to the date of death or the end of follow-up in 2005. Cox proportional hazards regression was used to obtain the relative risk (RR) estimates and 95% confidence intervals (CI) for each SNP and mortality outcomes.

Results

The results showed no patterns of association for the selected SNPs and the all-cause and cause-specific mortality outcomes, although statistically significant associations (p < 0.05) were observed between PPARG rs4684847 and all-cause mortality (CC: reference; CT: RR 0.99, 95% CI 0.89, 1.11; TT: RR 0.60, 95% CI 0.39, 0.93) and cancer-related mortality (CC: reference; CT: RR 1.01, 95% CI 0.82, 1.25; TT: RR 0.22, 95% CI 0.06, 0.90) and TNFα rs1799964 and cancer-related mortality (TT: reference; CT: RR 1.23, 95% CI 1.03, 1.47; CC: RR 0.83, 95% CI 0.54, 1.28). Additional analyses showed significant associations between SNPs in LEPR with BMI (rs1137101) and change in BMI over time (rs1045895 and rs1137101).

Conclusion

Findings from this cohort study suggest that the selected SNPs are not associated with overall or cause-specific death, although several LEPR SNPs may be related to BMI and BMI change over time.

Genomic studies in ageing research: the need to integrate genetic and gene expression approaches

Genome-wide and hypothesis-based approaches to the study of ageing and longevity have been dominated by genetic investigations. To identify essential mechanisms of a complex trait such as ageing in higher species, a holistic understanding of interacting pathways is required. More information on such interactions is expected to be obtained from global gene expression analysis if combined with genetic studies. Genetic sequence variation often provides a functional gene marker for the trait, whereas a gene expression profile may provide a quantitative biomarker representing complex cellular pathway interactions contributing to the trait. Thus far, gene expression studies have associated multiple pathways to ageing including mitochondrial electron transport and the oxidative stress response. However, most of the studies are underpowered to detect small age-changes. A systematic survey of gene expression changes as a function of age in human individuals and animal models is lacking. Well designed gene expression studies, especially at the level of biological processes, will provide hypotheses on gene-environmental interactions determining biological ageing rate. Cross-sectional studies monitoring the profile as a chronological marker of ageing must be integrated with prospective studies indicating which profiles represent biomarkers preceding and predicting physiological decline and mortality. New study designs such as the Leiden Longevity Study, including two generations of subjects from longevity families, aim to achieve these combined approaches.

Genome survey for loci that influence successful aging: results at 10-cM resolution

OBJECTIVE

A systematic genome survey was initiated to identify loci that affect the likelihood of reaching age 90 with preserved cognition (successful aging).

METHODS

The genome survey was conducted at 10-cM resolution for simple sequence tandem repeat polymorphisms (SSTRPs) that identify genes for Successful AGing (SAG loci) by virtue of linkage disequilibrium. Efficiency was enhanced by genotyping pools of DNA from 100 cognitively intact elders and 100 young (18-25 years) adults. The comparison groups included equal numbers of white men and women of similar ethnicity that were recruited from the southwestern Pennsylvania region.

RESULTS

Our genome survey identified nine SAG candidate loci that may influence the likelihood of reaching age 90 or more with preserved cognition. Two of the autosomal SAG loci revealed stronger allelic associations with successful aging in men than women (D1S1728, D8S264) and two were located on sex chromosomes (DXS9902, DYS390). DXS9902 resides within a predicted gene, whereas six of the SAG loci are located within regions previously reported to show linkage to other phenotypes.

CONCLUSIONS

The results of our study suggest that loci with differential effects on the successful aging of men and women may be common. The majority of the SAG candidate loci detected in this study overlap with regions previously reported to show linkage to susceptibility genes for cardiovascular disorders, psychiatric disorders, and the accumulation of tissue damage resulting from oxidative stress.

Genetic determinants of exceptional human longevity: insights from the Okinawa Centenarian Study

Centenarians represent a rare phenotype appearing in roughly 10-20 per 100,000 persons in most industrialized countries but as high as 40-50 per 100,000 persons in Okinawa, Japan. Siblings of centenarians in Okinawa have been found to have cumulative survival advantages such that female centenarian siblings have a 2.58-fold likelihood and male siblings a 5.43-fold likelihood (versus their birth cohorts) of reaching the age of 90 years. This is indicative of a strong familial component to longevity. Centenarians may live such extraordinarily long lives in large part due to genetic variations that either affect the rate of aging and/or have genes that result in decreased susceptibility to age-associated diseases. Some of the most promising candidate genes appear to be those involved in regulatory pathways such as insulin signaling, immunoinflammatory response, stress resistance or cardiovascular function. Although gene variants with large beneficial effects have been suggested to exist, only APOE, an important regulator of lipoproteins has been consistently associated with a longer human lifespan across numerous populations. As longevity is a very complex trait, several issues challenge our ability to identify its genetic influences, such as control for environmental confounders across time, the lack of precise phenotypes of aging and longevity, statistical power, study design and availability of appropriate study populations. Genetic studies on the Okinawan population suggest that Okinawans are a genetically distinct group that has several characteristics of a founder population, including less genetic diversity, and clustering of specific gene variants, some of which may be related to longevity. Further work on this population and other genetic isolates would be of significant interest to the genetics of human longevity.

Lipoprotein particle profiles mark familial and sporadic human longevity

BACKGROUND

Genetic and biochemical studies have indicated an important role for lipid metabolism in human longevity. Ashkenazi Jewish centenarians and their offspring have large low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particles as compared with control individuals. This profile also coincided with a lower prevalence of disease. Here, we investigate whether this observation can be confirmed for familial longevity in an outbred European population and whether it can be extended to sporadic longevity in the general population.

METHODS AND FINDINGS

NMR-measured lipoprotein profiles were analyzed in 165 families from the Leiden Longevity Study, consisting of 340 long-lived siblings (females >91 y, males >89 y), 511 of their offspring, and 243 partners of the offspring. Offspring had larger (21.3 versus 21.1 nm; p = 0.020) and fewer (1,470 versus 1,561 nmol/l; p = 0.011) LDL particles than their same-aged partners. This effect was even more prominent in the long-lived siblings (p < 10(-3)) and could be pinpointed to a reduction specifically in the concentration of small LDL particles. No differences were observed for HDL particle phenotypes. The mean LDL particle sizes in 259 90-y-old singletons from a population-based study were similar to those in the long-lived siblings and thus significantly larger than in partners of the offspring, suggesting that the relevance of this phenotype extends beyond familial longevity. A low concentration of small LDL particles was associated with better overall health among both long-lived siblings (p = 0.003) and 90-y-old singletons (p = 0.007).

CONCLUSIONS

Our study indicates that LDL particle profiles mark both familial and sporadic human longevity already in middle age.

Cardiovascular risk-associated allele frequencies for 15 genes in healthy elderly French and Chinese

In order to investigate possible ethnic differences in genetic and environmental determinants, we investigated several cardiovascular disease-associated genetic variations in successful ageing populations of France (Nancy) and China (Hong Kong). Allelic frequencies of these genetic variations were compared between healthy elderly Chinese (n=103) and French populations (n=100). A multi-locus assay was used to genotype 15 genes for 29 biallelic sites, genes implicated in lipid and homocysteine metabolism, thrombosis, leukocyte adhesion, and blood pressure regulation. For most of the candidate markers within lipid metabolism genes, the less frequent alleles were more common in the Chinese population compared with the French population, while the less frequent alleles of the majority of the other markers were detected only or more commonly in the French population. In conclusion, polymorphisms in 13 genes exhibited statistically significant differences in allelic frequencies between the two populations. Since the two populations were selected as examples of successful ageing, we could hypothesise that genetic factors that could play a role in a successful ageing process may be different between the two populations.

Disentangling the genetic determinants of human aging: biological age as an alternative to the use of survival measures

The choice of a phenotype is critical for the study of a complex genetically regulated process, such as aging. To date, most of the twin and family studies have focused on broad survival measures, primarily age at death or exceptional longevity. However, on the basis of recent studies of twins and families, biological age has also been shown to have a strong genetic component, with heritability estimates ranging from 27% to 57%. The aim of this review is twofold: first, to summarize growing consensus on reliable methods of biological age assessment, and second, to demonstrate validity of this phenotype for research in the genetics of aging in humans.

Shuttling between species for pathways of lifespan regulation: A central role for the vitellogenin gene family?

Studies to find genes that affect maximum lifespan aim at identifying important determinants of ageing that may be universal across species. Model organisms show insulin signalling can play an important role in ageing. In view of insulin resistance, such loci can also be important in human ageing and health. The study of long-lived humans and their children points to the relevance of lipoprotein profiles and particle size for longevity. If ageing pathways are conserved, then the genes mediating such pathways may also be conserved. Cross-species sequence comparisons of potential longevity loci may reveal whether the pathways that they represent are central themes in lifespan regulation. Using bioinformatic tools, we performed a sequence comparison of the genes involved in lipid metabolism identified in humans as potential longevity loci. This analysis revealed that lipid storage and transport may be a common theme related to longevity in humans, honeybees and nematodes. Here, the vitellogenin family emerges as a potential key connection between lipid metabolism and the insulin/IGF-1 signalling pathway.

The Future of Aging Interventions: Current Status of Efforts to Measure and Modulate the Biological Rate of Aging

Biomarkers of aging would be highly desirable, but so far, a definitive panel of biomarkers to predict mortality risk has not been obtained, even though many traits that vary with age have been identified. This lack hinders the search for interventions that may retard the rate of aging in mammals. The recent discovery and characterization of many longevity genes in animal model systems, such as nematodes, fruit flies, and mice, are providing new targets for research by providing insight into mechanisms of longevity regulation in these model systems. It is hoped that this will ultimately lead to interventions to delay the development of age-related pathology in humans.

Polymorphic metabolic susceptibility genes and longevity: a study in octogonarians

In order to investigate possible associations of genetic variants in genes of xenobiotic metabolism with longevity, we compared allele frequencies and genotype distributions of polymorphic genes between 205 octogenarians and a non-cancer reference group of 294 persons aged less than 80 years. We analyzed common sequence variations in the cytochrome P-450 genes CYP1A1 T461N, 3801 T > C and CYP1B1 V432L, and in the glutathione S-transferase genes GSTM1 (deletion), GSTT1 (deletion), and GSTP1 (I105V). In octogenarians, the CYP1B1 432L allele was less prevalent than in the reference group (allele frequency 0.49 versus 0.60; odds ratio, OR, 0.63, 95% confidence limits (CI) 0.40-1.00). Octogenarians turned out to have marginally significant more GSTM1 negatives (frequency 0.56 versus 0.48; OR 1.41, 95% CI 0.97-2.05), but less GSTT1 deficient genotypes (frequency 0.14 versus 0.21; OR 0.64; 95% CI 0.38-1.06). In octogenarians without cancer, GSTT1 negative carriers were less prevalent than in the aged with cancer (frequency 0.12 versus 0.27; OR 2.81; 95% CI 1.00-7.38). Polymorphic metabolic susceptibility genes could become relevant for processes of aging when toxic defense mechanisms decline.

The APOE Gene and Differences in Life Expectancy in Europe

Common alleles of the apolipoprotein-E gene (APOE) are associated with different risks of ischemic heart disease, Alzheimer's disease, and other chronic conditions in European populations. Also, the APOE allele frequencies vary widely among European countries. We estimated the proportion of differences in mortality and differences in life span that are attributable to differences in APOE allele frequencies in Europe. Mortality rates by age, sex, and APOE genotype for six countries (Denmark, Finland, France, Italy, the Netherlands, and Sweden) were used to standardize mortality rates to the allele frequencies in Italy. Differences in APOE allele frequencies explain 12%-17% of the variation among these countries in mortality in people older than 65 years and 1%-2% of the variation in life span in those older than 65 years. Differences by genotype in mortality in people older than 15 years account for about 3.5% of the genetic contribution to the variation in life span in Denmark.

The effect of aging on the immunohistochemistry of apolipoprotein E in the liver

Apolipoprotein E (apoE) is involved in hepatic disposition of chylomicron remnants, which is impaired in old age. Isoforms of apoE have been implicated in age-related diseases and possibly the aging process itself. Because the effects of old age on expression and distribution of apoE in the liver have not been reported, we studied the effect of old age on the immunohistochemistry of apoE in the livers of humans and the non-human primate, Papio hamadryas. Overall, old age was not associated with marked changes in the expression of apoE between adult (48+/-19 years) and old (82+/-5 years) humans. However, there was a change in the distribution of apoE staining. The livers of older humans displayed increased hepatocyte cytoplasmic staining and reduced peri-sinusoidal staining. Similar trends were noted in the livers from the baboons. Such findings are suggestive of altered apoE recycling in old age and have implications for age-related dyslipidaemia.

Effect of six candidate genes on early aging in a French population

BACKGROUND AND AIMS

The objective of this study was to examine the association between an aging indicator previously defined from a nationwide population study, and lipids and apolipoproteins, angiotensin converting enzyme, paraoxonase activities, and six candidate genes related to the aging process.

METHODS

Two hundred and fifty-six healthy Caucasian men (69.8 +/- 4.0 years) were included in the study. Total cholesterol, triglycerides, HDL-cholesterol, lipoprotein(a), apolipoprotein A1, B and E concentrations, and the activities of paraoxonase, arylesterase, and angiotensin-converting enzymes were determined by standardized laboratory methods. A multiplex assay was used to genotype the studied polymorphisms: apolipoprotein E, lipoprotein lipase, paraoxonase, methylenetetrahydrofolate reductase, cystathionine beta-synthase and angiotensin-converting enzymes.

RESULTS

Paraoxonase polymorphism at codon 192 (Gln/Arg) was the only one significantly associated with the aging indicator, Gln homozygotes being more advanced in aging compared with Arg allele carriers. It was also observed that the aging indicator was positively correlated with serum concentrations of total cholesterol, triglycerides and apolipoprotein B, and negatively with the activities of basal and stimulated paraoxonase and arylesterase. Multiple regression analysis showed that triglycerides and basal paraoxonase activity explain 13.6% of the variance of the aging indicator.

CONCLUSIONS

Triglyceride concentration and paraoxonase gene and activities may contribute to the aging process. Taking into account the smallness of the sample size, and the poor level of significance due to the im-plication of paraoxonase polymorphism at codon 192, these results need to be verified in further studies on a greater number of subjects.

Healthy ageing: a question of stress, damage and repair. Meeting on mechanisms of biological ageing

Meeting on mechanisms of biological ageing

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.

Modification of brain aging and neurodegenerative disorders by genes, diet, and behavior

Multiple molecular, cellular, structural, and functional changes occur in the brain during aging. Neural cells may respond to these changes adaptively, or they may succumb to neurodegenerative cascades that result in disorders such as Alzheimer's and Parkinson's diseases. Multiple mechanisms are employed to maintain the integrity of nerve cell circuits and to facilitate responses to environmental demands and promote recovery of function after injury. The mechanisms include production of neurotrophic factors and cytokines, expression of various cell survival-promoting proteins (e.g., protein chaperones, antioxidant enzymes, Bcl-2 and inhibitor of apoptosis proteins), preservation of genomic integrity by telomerase and DNA repair proteins, and mobilization of neural stem cells to replace damaged neurons and glia. The aging process challenges such neuroprotective and neurorestorative mechanisms. Genetic and environmental factors superimposed upon the aging process can determine whether brain aging is successful or unsuccessful. Mutations in genes that cause inherited forms of Alzheimer's disease (amyloid precursor protein and presenilins), Parkinson's disease (alpha-synuclein and Parkin), and trinucleotide repeat disorders (huntingtin, androgen receptor, ataxin, and others) overwhelm endogenous neuroprotective mechanisms; other genes, such as those encoding apolipoprotein E(4), have more subtle effects on brain aging. On the other hand, neuroprotective mechanisms can be bolstered by dietary (caloric restriction and folate and antioxidant supplementation) and behavioral (intellectual and physical activities) modifications. At the cellular and molecular levels, successful brain aging can be facilitated by activating a hormesis response in which neurons increase production of neurotrophic factors and stress proteins. Neural stem cells that reside in the adult brain are also responsive to environmental demands and appear capable of replacing lost or dysfunctional neurons and glial cells, perhaps even in the aging brain. The recent application of modern methods of molecular and cellular biology to the problem of brain aging is revealing a remarkable capacity within brain cells for adaptation to aging and resistance to disease.

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.

The genetics of aging

The genetic analysis of life span has only begun in mammals, invertebrates, such as Caenorhabditis elegans and Drosophila, and yeast. Even at this primitive stage of the genetic analysis of aging, the physiological observations that rate of metabolism is intimately tied to life span is supported. In many examples from mice to worms to flies to yeast, genetic variants that affect life span also modify metabolism. Insulin signaling regulates life span coordinately with reproduction, metabolism, and free radical protective gene regulation in C. elegans. This may be related to the findings that caloric restriction also regulates mammalian aging, perhaps via the modulation of insulin-like signaling pathways. The nervous system has been implicated as a key tissue where insulin-like signaling and free radical protective pathways regulate life span in C. elegans and Drosophila. Genes that determine the life span could act in neuroendocrine cells in diverse animals. The involvement of insulin-like hormones suggests that the plasticity in life spans evident in animal phylogeny may be due to variation in the timing of release of hormones that control vitality and mortality as well as variation in the response to those hormones. Pedigree analysis of human aging may reveal variations in the orthologs of the insulin pathway genes and coupled pathways that regulate invertebrate aging. Thus, genetic approaches may identify a set of circuits that was established in ancestral metazoans to regulate their longevity.

Variations of cardiovascular disease associated genes exhibit sex-dependent influence on human longevity

This article investigates the relationship between the polymorphic variations in genes associated with cardiovascular disease and longevity in the Danish population. A new procedure that combines both demographic and the individual genetic information in determining the relative risks of the observed genetic variations is applied. The sex-dependent influences can be found by introducing sex-specific population survival and incorporating the risk of gene-sex interaction. Three genetic polymorphisms, angiotensinogen M/T235, blood coagulation factor VII (FVII) R/Q353 and FVII-323ins10, manifest significant influences on survival in males, with reduced hazards of death for carriers of the angiotensinogen M235 allele, the F VII Q353 allele, and the FVII-323P10 allele. The results show that some of these genotypes associated with lower risk of CVD could also reduce the carrier's death rate and contribute to longevity. However, the presence of sex-dependent effects and the fact that major CVD-associated genes failed to impose detrimental influence on longevity lead us to concur that the aging process is highly complicated.

Biological ageing research in the Netherlands

After an introduction on the development of biological ageing research in the Netherlands during the past decades, 606 papers on aging published by Dutch institutes in the period 1991-2000, collected from PubMed, were analysed for their relevance to research into biological ageing. For the period 1996-2000, the total number of research papers on biological ageing amounted to 142, which accounts for 23% of all publications on ageing in that period. The number of publications per year did not change. On the basis of these papers and additional information provided by research groups a comprehensive overview of biological ageing research in the Netherlands is presented, together with an extensive literature list. Ageing of the central nervous system (CNS), of the endocrinological system and of the cardiovascular system are the topics most studied. It is concluded that general biological ageing research has not increased in the Netherlands over the last ten years, and that the infrastructure for basic biological ageing research in the Netherlands is weak.

Polymorphisms of drug-metabolizing enzymes in healthy nonagenarians and centenarians: difference at GSTT1 locus

Drug metabolizing enzymes are involved in the detoxification of several drugs, environmental substances, and carcinogenic compounds, and their polymorphisms have been associated with risk for a variety of cancer. In this paper, we compared the frequency of polymorphisms in cytochrome P450-1A1 gene (CYP1A1), a phase 1 gene (oxidation, activation), and of two polymorphisms of glutathione S-transferase enzymes (GSTM1, GSTT1), two phase 2 genes (conjugation, detoxification). Two groups were studied and compared, i.e., 94 nonagenarians and centenarians and 418 control subjects of younger age. A significant difference in the proportion of nonagenarians and centenarians homozygotes for a GSTT1 deletion (28%) was observed in comparison to control subjects (19%, P = 0.03). The distribution of the other gene polymorphisms did not differ in the two groups. These findings on phase 2 drug-metabolizing enzyme gene polymorphisms may help in disentangling gene-environmental interactions which can have a role in successful aging and longevity, as well as in cancer incidence in the oldest old.