G. De Benedictis

Mitochondrial DNA inherited variants are associated with successful aging and longevity in humans

Mitochondrial DNA (mtDNA) is characterized by high variability, maternal inheritance, and absence of recombination. Studies of human populations have revealed ancestral associated polymorphisms whose combination defines groups of mtDNA types (haplogroups) that are currently used to reconstruct human evolution lineages. We used such inherited mtDNA markers to compare mtDNA population pools between a sample of individuals selected for successful aging and longevity (212 subjects older than 100 years and in good clinical condition) and a sample of 275 younger individuals (median age 38 years) carefully matched as to sex and geographic origin (northern and southern Italy). All nine haplogroups that are typical of Europeans were found in both samples, but male centenarians emerged in northern Italy as a particular sample: 1) mtDNA haplogroup frequency distribution was different between centenarians and younger individuals (P=0.017 by permutation tests); and 2) the frequency of the J haplogroup was notably higher in centenarians than in younger individuals (P=0.0052 by Fisher exact test). Since haplogroups are defined on the basis of inherited variants, these data show that mtDNA inherited variability could play a role in successful aging and longevity.—De Benedictis, G., Rose, G., Carrieri, G., De Luca, M., Falcone, E., Passarino, G., Bonafé, M., Monti, D., Baggio, G., Bertolini, S., Mari, D., Mattace, R., Franceschi, C. Mitochondrial DNA inherited variants are associated with successful aging and longevity in humans. FASEB J. 13, 1532–1536 (1999)

Variability of the SIRT3 gene, human silent information regulator Sir2 homologue, and survivorship in the elderly

The human sirtuin 3 (SIRT3) gene encodes a putative mitochondrial NAD-dependent deacetylase (SIRT3) which belongs to the evolutionary conserved family of sirtuin 2 proteins. Studies in model organisms have demonstrated that SIR2 genes control lifespan, while no data are available regarding a possible role of SIRT3 in human longevity. By analysing the genotype-specific survival function relevant to the G477T marker of SIRT3, we found that in males the TT genotype increases (p=0.0272), while the GT genotype decreases (p=0.0391) survival in the elderly. Since SIRT3 lies in a chromosomal region (11p15.5) where four genes potentially associated with longevity are located (HRAS1, Insulin-like Growth Factor 2, Proinsulin, and Tyrosine Hydroxylase) we tested for linkage-disequilibrium between G477T alleles and alleles of the above genes. The disequilibrium was not significant in any case, thus suggesting that SIRT3 itself, or a gene strictly linked to SIRT3, may have a role in human longevity.

Gene/longevity association studies at four autosomal loci ( REN, THO, PARP, SOD2 )

The possibility that four loci (REN, THO, PARP, SOD2) are associated with longevity was explored by comparing the genotypic pools of subjects older than 100 years with those of younger subjects matched for sex and geographic area (northern and southern Italy). The markers (all located within the respective gene) were HUMREN4; HUMTHO1; HUMPARP (gt)845nt; SOD2(C/T)401nt. In order to reduce the number of genotypes, multiallelic polymorphisms were recoded as diallelic according to allele size and frequency patterns (small: S, and large: L, alleles). A significant loss of LL homozygous genotypes was found at the THO locus in male but not in female centenarians with respect to matched controls. On the other hand no significant difference was found between case/control genotypic frequencies at REN, PARP, SOD2 loci. The latter loci therefore do not affect inter-individual variability in life expectancy (at least in terms of qualitative variants associated with the tested markers). However, the data is consistent with an association between the THO locus and longevity.

Recent advances in human gene-longevity association studies

This paper reviews the recent literature on genes and longevity. The influence of genes on human life span has been confirmed in studies of life span correlation between related individuals based on family and twin data. Results from major twin studies indicate that approximately 25% of the variation in life span is genetically determined. Taking advantage of recent developments in molecular biology, researchers are now searching for candidate genes that might have an influence on life span. The data on unrelated individuals emerging from an ever-increasing number of centenarian studies makes this possible. This paper summarizes the rich literature dealing with the various aspects of the influence of genes on individual survival. Common phenomena affecting the development of disease and longevity are discussed. The major methodological difficulty one is confronted with when studying the epidemiology of longevity involves the complexity of the phenomenon, which arises from the polygenic nature of life span and historical mortality change. We discuss this issue and suggest new methodological approaches.

Do men and women follow different trajectories to reach extreme longevity

Gender accounts for important differences in the incidence and prevalence of a variety of age-related diseases. Considering people of far advanced age, demographic data document a clear-cut prevalence of females compared to males, suggesting that sex-specific mortality rates follow different trajectories during aging. In the present investigation, we report data from a nationwide study on Italian centenarians (a total of 1162 subjects), and from two studies on centenarians living in two distinct zones of Italy, i.e., the island of Sardinia (a total of 222 subjects) and the Mantova province (Northern Italy) (a total of 43 subjects). The female/male ratio was about 2:1 in Sardinia, 4:1 in the whole of Italy, and about 7:1 in the Mantova province. Thus, a complex interaction of environmental, historical and genetic factors, differently characterizing the various parts of Italy, likely plays an important role in determining the gender-specific probability of achieving longevity. Gender differences in the health status of centenarians are also reported, and an innovative score method to classify long-lived people in different health categories, according to clinical and functional parameters, is proposed. Our data indicate that not only is this selected group of people, as a whole, highly heterogeneous, but also that a marked gender difference exists, since male centenarians are less heterogeneous and more healthy than female centenarians. Immunological factors regarding the age-related increase in pro-inflammatory status, and the frequency of HLA ancestral haplotypes also show gender differences that likely contribute to the different strategies that men and women seem to follow to achieve longevity. Concerning the different impact of genetic factors on the probability of reaching the extreme limits of the human life-span, emerging evidence (regarding mtDNA haplogroups, Thyrosine Hydroxilase, and IL-6 genes) suggests that female longevity is less dependent on genetics than male longevity, and that female centenarians likely exploited a healthier life-style and more favorable environmental conditions, owing to gender-specific cultural and anthropological characteristics of the Italian society in the last 100 years.

Age‐related changes of the 3′APOB‐VNTR genotype pool in ageing cohorts

The analysis of seven different age cohorts (697 individuals from 10 to 109 years old) revealed age‐related changes in the 3′APOB‐VNTR genotype pool. By recoding the 3′APOB‐VNTR alleles into three size‐classes (small, S, 26–34 repeats; medium, M, 35–39 repeats; large, L, 41–55 repeats), an age‐related convex trajectory of the frequency of SS homozygotes was found. The frequency of SS in the genotype pool increased from the group aged 10–19 years (3.06±1.74%) to that aged 40–49 years (8.51±4.07%). Then it declined reaching the minimum value in centenarians (1.58±0.90%). The observed trajectory is in agreement with that expected by assuming crossing of mortality curves relevant to subgroups of individuals having different genotypes.

Genes, ageing and longevity in humans: problems, advantages and perspectives.

Many epidemiological data indicate the presence of a strong familial component of longevity that is largely determined by genetics, and a number of possible associations between longevity and allelic variants of genes have been described. A breakthrough strategy to get insight into the genetics of longevity is the study of centenarians, the best example of successful ageing. We review the main results regarding nuclear genes as well as the mitochondrial genome, focusing on the investigations performed on Italian centenarians, compared to those from other countries. These studies produced interesting results on many putative “longevity genes”. Nevertheless, many discrepancies are reported, likely due to the population-specific interactions between gene pools and environment. New approaches, including large-scale studies using high-throughput techniques, are urgently needed to overcome the limits of traditional association studies performed on a limited number of polymorphisms in order to make substantial progress to disentangle the genetics of a trait as complex as human longevity.

DNA multiallelic systems reveal gene/longevity associations not detected by diallelic systems. The APOB locus

Abstract To identify possible genetic factors affecting human longevity we compared allele pools at two candidate loci for longevity between a sample of 143 centenarians (S) and a control sample of 158 individuals (C). The candidate loci were APOB and TPO, which code for apolipoprotein B and thyroid peroxidase, respectively. Both restriction fragment length (RFL) (XbaI2488 and EcoRI4154) and variable number of tandem repeat (VNTR) (3′APOB-VNTR) polymorphisms were analysed at the APOB locus; the TPO-VNTR polymorphism (intron 10) was analysed at the TPO locus. The main result of the investigation was that there is an association between the APOB locus and longevity that is revealed only when multiallelic polymorphisms are considered. In particular: (i) the frequency of 3′APOB-VNTR alleles with fewer than 35 repeats is significantly lower in cases than in controls; (ii) the linkage disequilibrium between the XbaI-RFLP and the EcoRI-RFLP is significantly different from 0 in cases but not in controls; (iii) the EcoRI-RFLP and XbaI-RFLP allele frequencies do not discriminate between cases and controls. The differences observed between case and control allele pools are specific to the APOB locus, since no significant difference was observed at the TPO locus.

The effects of APOE and tau gene variability on risk of frontotemporal dementia

Frontotemporal dementia (FTD) is a complex dementing syndrome whose genetic/non genetic risk factors are mostly unknown. Aim of the present work was to investigate whether APOE and/or tau gene variability does affect the risk of FTD. A sample of FTD cases (sporadic: n = 54; familial: n = 46, one subject per family) was collected in a genetically homogeneous population (Calabria, southern Italy) and analyzed in comparison with an age- and sex-matched control group (n = 180) extracted from the same population. Logistic regression analysis showed that APOE gene variability affects the probability of disease, with allele epsilon4 increasing (exp(beta1) = 2.68 with [1.51-4.76] 95% confidence interval; p = 0.001) and allele epsilon2 decreasing (exp(beta1) = 0.28 with [0.12-0.66] 95% confidence interval; p = 0.003) the risk of FTD. On the contrary, tau gene variability was ineffectual (exp(beta1) non significantly different from 1 for either H1 or H2 haplotypes), although a small effect was observed by the H1 haplotype in increasing the protective effect of the epsilon2 allele (p = 0.007).

Inherited Variability of the Mitochondrial Genome and Successful Aging in Humans

Abstract: Increasing data indicate that polymorphic variants of nuclear loci can affect rate and quality of aging in humans. However, the mitochondrial genome is another good candidate, because of the central role played by mitochondrial genes in oxidative phosphorylation (OXPHOS) and cell metabolism. A characteristic of the mitochondrial genome (mtDNA) is the high level of interindividual variability that ensues from high mutation rate and unilinear inheritance. Related groups of germline/inherited mtDNA polymorphisms (haplogroups) have been identified as continent‐specific sets of stable/ancient/associated restriction fragment length polymorphisms in the mtDNA coding region, representing markers capable of exactly depicting the mtDNA pool of a specific population. The hypothesis can be put forward that mtDNA variants included in a haplogroup may have similar OXPHOS efficiency and therefore act as genetic factors predisposing to individual successful or unsuccessful aging. This idea can be explored by sampling groups of individuals of different ages from a well‐defined population and comparing the pools of mtDNA haplogroups between samples. The results obtained by screening mtDNA haplogroups in about 800 Italians of different ages, including more that 200 centenarians, agree with the hypothesis that the inherited variability of the mitochondrial genome is associated with the chance of successful aging and longevity in humans.