Contemporary human genetic strategies in aging research

High-throughput sequencing analysis of nuclear-encoded mitochondrial genes reveals a genetic signature of human longevity

Mitochondrial dysfunction is a well-known contributor to aging and age-related diseases. The precise mechanisms through which mitochondria impact human lifespan, however, remain unclear. We hypothesize that humans with exceptional longevity harbor rare variants in nuclear-encoded mitochondrial genes (mitonuclear genes) that confer resistance against age-related mitochondrial dysfunction. Here we report an integrated functional genomics study to identify rare functional variants in ~ 660 mitonuclear candidate genes discovered by target capture sequencing analysis of 496 centenarians and 572 controls of Ashkenazi Jewish descent. We identify and prioritize longevity-associated variants, genes, and mitochondrial pathways that are enriched with rare variants. We provide functional gene variants such as those in MTOR (Y2396Lfs*29), CPS1 (T1406N), and MFN2 (G548*) as well as LRPPRC (S1378G) that is predicted to affect mitochondrial translation. Taken together, our results suggest a functional role for specific mitonuclear genes and pathways in human longevity.

Chinese liquor extract attenuates oxidative damage in HepG2 cells and extends lifespan of Caenorhabditis elegans

Chinese liquor is obtained from various grains by fermentation and complex processes. Chinese liquor contains complex ingredients. However, the low contents and presence of ethanol restricted the flavor substances function study. In current study, a flavor substance, homofuraneol (HOMO) was isolated from the Chinese liquor and the potency against H2O2-induced oxidative damage in HepG2 cells and lifespan-extending ability in Caenorhabditis elegans were explored. Results indicated that HOMO increased the HepG2 cells cytoactive by eliminating excessive intracellular free radicals, upregulating antioxidant enzyme activity and inhibiting the phosphorylation of mitogen-activated protein kinases (MAPKs) pathway. Further study revealed that HOMO extended the lifespan of N2 nematodes under normal and oxidative stress conditions. Moreover, RT-PCR results showed that paraquat activated the expression of PMK-1 and SKN-1 was significantly regulated by HOMO. Of note, our results indicated that HOMO recovered the redox states of HepG2 cells by targeting MAPKs and upregulating the stress resistance of nematodes by modulating the expression of stress-responsive genes, such as DAF-16.

Comparação do controle postural em cinco tarefas de equílibrio e a relação dos riscos de quedas entre idosas e adultas jovens

RESUMO O envelhecimento é um processo natural que acarreta mudanças intrínsecas e extrínsecas ao organismo. O objetivo é analisar cinco tarefas de equilíbrio postural em idosas através da Plataforma de força, correlacionando com o risco de quedas avaliado pelo teste Timed Up and Go (TUG). Participaram do estudo 43 idosos e 40 adultos jovens, todos do sexo feminino, que foram avaliadas em uma plataforma de força com um protocolo padrão: descalças, com os braços ao longo do corpo nas tarefas bipodal e semitandem, ambos olhos abertos e fechados, apoio unipodal utilizando o centro de oscilação postural (COP) e as velocidades nos eixos anteroposterior (Vel AP) e médio-lateral (Vel ML). Após 5 minutos de descanso, realizou-se o TUG. Os resultados mostraram que as idosas tiveram maior instabilidade postural (p<0.05) em relação às adultas jovens, e a tarefa que mais desafiou o equilíbrio foi o apoio unipodal COP 10,02 (cm2) Vel AP 3,00 (cm/s) e Vel ML 3,32 (cm/s), e as idosas tiveram um tempo médio no TUG de 9,01 segundos considerando um baixo risco de quedas. Conclusão: Idosas apresentam um maior déficit no equilíbrio em relação às jovens, sendo a tarefa de apoio UNP a que mais apresentou desafios no controle postural das duas populações. Idosas saudáveis apresentaram um baixo risco para as quedas, nenhuma correlação foi encontrada entre o equilíbrio postural através da plataforma de força e risco de quedas do TUG.

Uncoupling associations of risk alleles with endophenotypes and phenotypes: insights from the ApoB locus and heart-related traits

Traditionally, genomewide association studies (GWAS) have emphasized the benefits of large samples in the analyses of age‐related traits rather than their specific properties. We adopted a realistic concept of genetic susceptibility to inherently heterogeneous, age‐related traits driven by the elusive role of evolution in their properties. We analyzed in detail the associations of rs693 and rs562338 polymorphisms representing the Apolipoprotein B locus with endophenotypes (total cholesterol [TC] and high‐density lipoprotein cholesterol) and phenotypes (myocardial infarction [MI] and survival) in four large‐scale studies, which include 20 748 individuals with 2357 MI events. We showed that a strong, robust predisposition of rs693 and rs562338 to TC (β = 0.72, P = 7.7 × 10⁻³⁰ for rs693 and β = −1.08, P = 9.8 × 10⁻⁴² for rs562338) is not translated into a predisposition to MI and survival. The rs693_A allele influences risks of MI and mortality after MI additively with lipids. This allele shows antagonistic effects—protecting against MI risks (β = −0.18, P = 1.1 × 10⁻⁵) or increasing MI risks (β = 0.15, P = 2.8 × 10⁻³) and mortality after MI, in different populations. Paradoxically, increased TC concentrations can be protective against MI for the rs693_A allele carriers. Our results uncouple the influences of the same alleles on endophenotypes and phenotypes despite potential causal relationships among the latter. Our strategy reveals virtually genomewide significance for the associations of rs693 with MI (P = 5.5 × 10⁻⁸) that is contrasted with a weak estimate following the traditional, sample‐size‐centered GWAS strategy (P = 0.16) in the same sample. These results caution against the use of the traditional GWAS strategy for gaining profound insights into genetic predisposition to healthspan and lifespan.

Relação da pressão plantar e amplitude de movimento de membros inferiores com o risco de quedas em idosas

RESUMO Objetivou-se verificar a influência das variáveis de pressão plantar e amplitude de movimento (ADM) de quadril, joelho e tornozelo sobre o risco de quedas em idosas. Participaram 39 idosas, avaliando-se a Pressão Máxima e Média sobre a plataforma de baropodometria. Em seguida, realizou-se o teste Timed Up and Go (TUG) e posteriormente a avaliação da ADM de flexão de quadril e joelho e flexão plantar e dorsal de tornozelo por meio de um goniômetro. As variáveis baropodométricas (Pressão Máxima e Pressão Média) tenderam a influenciar os valores do TUG conforme valor do teste de hipótese (p=0,051), demonstrando correlação moderada (r=0,487), com destaque para a Pressão Máxima, que apresentou correlação significativa com o TUG (p<0,005). Entretanto, a ADM articular de quadril, joelho e tornozelo não apresentaram correlações significativas entre as variáveis baropodométricas e risco de quedas. Sobre a análise da associação entre o TUG, categorizado em baixo e médio risco de quedas, e as quedas, não foram observadas diferenças (p=0,475). O aumento da pressão máxima apresentou relação com o risco de quedas, mas a ADM de quadril, joelho e tornozelo não apresentaram relação sobre o risco de quedas e as variáveis baropodométricas na população investigada.

Increasing Sibling Relative Risk of Survival to Older and Older Ages and the Importance of Precise Definitions of "Aging," "Life Span," and "Longevity"

The lack of a formal definition of human longevity continues to generate confusion about its genetic and nongenetic determinants. In order to characterize how differences in birth year cohorts and percentiles of survival are associated with familial contribution to variation in survival, we estimated sibling relative risk of living to increasingly rare percentiles of survival based on a dataset of 1,917 validated sibships each containing at least one individual living to age 90 years. About 1,042 of the sibships included at least one individual who survived to age 100 and 511 included at least one individual who survived to age 105 and older. We show that sibling relative risk increases with older ages, sex, and earlier birth year cohorts of the proband and siblings of male 90-year-olds (5th percentile of survival) have 1.73 (95% CI: 1.5; 2.0) times the chance of living to age 90, while siblings of both male and female probands who survived to age 105 years (~0.01 percentile of survival) have 35.6 (95%CI: 15.1; 67.7) times the chance of living to age 105 compared with population controls. These results emphasize the importance of consistently defining the longevity phenotype in terms of rarity of survival for appropriate comparisons across studies.

Meta‐analysis of genetic variants associated with human exceptional longevity

Despite evidence from family studies that there is a strong genetic influence upon exceptional longevity, relatively few genetic variants have been associated with this trait. One reason could be that many genes individually have such weak effects that they cannot meet standard thresholds of genome wide significance, but as a group in specific combinations of genetic variations, they can have a strong influence. Previously we reported that such genetic signatures of 281 genetic markers associated with about 130 genes can do a relatively good job of differentiating centenarians from non-centenarians particularly if the centenarians are 106 years and older. This would support our hypothesis that the genetic influence upon exceptional longevity increases with older and older (and rarer) ages. We investigated this list of markers using similar genetic data from 5 studies of centenarians from the USA, Europe and Japan. The results from the meta-analysis show that many of these variants are associated with survival to these extreme ages in other studies. Since many centenarians compress morbidity and disability towards the end of their lives, these results could point to biological pathways and therefore new therapeutics to increase years of healthy lives in the general population.

Unraveling genetic origin of aging-related traits: evolving concepts

Discovering the genetic origin of aging-related traits could greatly advance strategies aiming to extend health span. The results of genome-wide association studies (GWAS) addressing this problem are controversial, and new genetic concepts have been fostered to advance the progress in the field. A limitation of GWAS and new genetic concepts is that they do not thoroughly address specifics of aging-related traits. Integration of theoretical concepts in genetics and aging research with empirical evidence from different disciplines highlights the conceptual problems in studies of genetic origin of aging-related traits. To address these problems, novel approaches of systemic nature are required. These approaches should adopt the non-deterministic nature of linkage of genes with aging-related traits and, consequently, reinforce research strategies for improving our understanding of mechanisms shaping genetic effects on these traits. Investigation of mechanisms will help determine conditions that activate specific genetic variants or profiles and explore to what extent these conditions that shape genetic effects are conserved across human lives and generations.

Genomics of human health and aging

Despite notable progress of the candidate-gene and genome-wide association studies (GWAS), understanding the role of genes contributing to human health and lifespan is still very limited. We use the Framingham Heart Study to elucidate if recognizing the role of evolution and systemic processes in an aging organism could advance such studies. We combine throughput methods of GWAS with more detail methods typical for candidate-gene analyses and show that both lifespan and ages at onset of CVD and cancer can be controlled by the same allelic variants. The risk allele carriers are at highly significant risk of premature death (e.g., RR=2.9, p=5.0 × 10(-66)), onset of CVD (e.g., RR=1.6, p=4.6 × 10(-17)), and onset of cancer (e.g., RR=1.6, p=1.5 × 10(-6)). The mechanism mediating the revealed genetic associations is likely associated with biological aging. These aging-related phenotypes are associated with a complex network which includes, in this study, 62 correlated SNPs even so these SNPs can be on non-homologous chromosomes. A striking result is three-fold, highly significant (p=3.6 × 10(-10)) enrichment of non-synonymous SNPs (N=27) in this network compared to the entire qualified set of the studied SNPs. Functional significance of this network is strengthened by involvement of genes for these SNPs in fundamental biological processes related to aging (e.g., response to stimuli, protein degradation, apoptosis) and by connections of these genes with neurological (20 genes) and cardio-vascular (nine genes) processes and tumorigenesis (10 genes). These results document challenging role of gene networks in regulating human health and aging and call for broadening focus on genomics of such phenotypes.

Biogenetic mechanisms predisposing to complex phenotypes in parents may function differently in their children

This study focuses on the participants of the Long Life Family Study to elucidate whether biogenetic mechanisms underlying relationships among heritable complex phenotypes in parents function in the same way for the same phenotypes in their children. Our results reveal 3 characteristic groups of relationships among phenotypes in parents and children. One group composed of 3 pairs of phenotypes confirms that associations among some phenotypes can be explained by the same biogenetic mechanisms working in parents and children. Two other groups including 9 phenotype pairs show that this is not a common rule. Our findings suggest that biogenetic mechanisms underlying relationships among different phenotypes, even if they are causally related, can function differently in successive generations or in different age groups of biologically related individuals. The results suggest that the role of aging-related processes in changing environment may be conceptually underestimated in current genetic association studies using genome wide resources.

Genes against aging

Individual mutations in mice can slow aging: They extend life span by retarding a wide range of harmful, age-dependent changes in multiple cells and tissues. Evolutionary changes-by definition, changes in DNA sequence-can lead to even more dramatic postponement of age-dependent deterioration. Genetic variation within a species, for example among breeds of dogs, can also lead to major changes in aging rate, although there is not yet any strong evidence for similar genetic variation that modulates aging in rodents or humans. This essay compares different strategies for using genetic information to clarify questions in biogerontology, suggesting an emphasis on genes that can retard multiple forms of age-dependent dysfunction in parallel.

Genetic signatures of exceptional longevity in humans

Like most complex phenotypes, exceptional longevity is thought to reflect a combined influence of environmental (e.g., lifestyle choices, where we live) and genetic factors. To explore the genetic contribution, we undertook a genome-wide association study of exceptional longevity in 801 centenarians (median age at death 104 years) and 914 genetically matched healthy controls. Using these data, we built a genetic model that includes 281 single nucleotide polymorphisms (SNPs) and discriminated between cases and controls of the discovery set with 89% sensitivity and specificity, and with 58% specificity and 60% sensitivity in an independent cohort of 341 controls and 253 genetically matched nonagenarians and centenarians (median age 100 years). Consistent with the hypothesis that the genetic contribution is largest with the oldest ages, the sensitivity of the model increased in the independent cohort with older and older ages (71% to classify subjects with an age at death>102 and 85% to classify subjects with an age at death>105). For further validation, we applied the model to an additional, unmatched 60 centenarians (median age 107 years) resulting in 78% sensitivity, and 2863 unmatched controls with 61% specificity. The 281 SNPs include the SNP rs2075650 in TOMM40/APOE that reached irrefutable genome wide significance (posterior probability of association = 1) and replicated in the independent cohort. Removal of this SNP from the model reduced the accuracy by only 1%. Further in-silico analysis suggests that 90% of centenarians can be grouped into clusters characterized by different “genetic signatures” of varying predictive values for exceptional longevity. The correlation between 3 signatures and 3 different life spans was replicated in the combined replication sets. The different signatures may help dissect this complex phenotype into sub-phenotypes of exceptional longevity.

Whole genome sequences of a male and female supercentenarian, ages greater than 114 years

Supercentenarians (age 110+ years old) generally delay or escape age-related diseases and disability well beyond the age of 100 and this exceptional survival is likely to be influenced by a genetic predisposition that includes both common and rare genetic variants. In this report, we describe the complete genomic sequences of male and female supercentenarians, both age >114 years old. We show that: (1) the sequence variant spectrum of these two individuals' DNA sequences is largely comparable to existing non-supercentenarian genomes; (2) the two individuals do not appear to carry most of the well-established human longevity enabling variants already reported in the literature; (3) they have a comparable number of known disease-associated variants relative to most human genomes sequenced to-date; (4) approximately 1% of the variants these individuals possess are novel and may point to new genes involved in exceptional longevity; and (5) both individuals are enriched for coding variants near longevity-associated variants that we discovered through a large genome-wide association study. These analyses suggest that there are both common and rare longevity-associated variants that may counter the effects of disease-predisposing variants and extend lifespan. The continued analysis of the genomes of these and other rare individuals who have survived to extremely old ages should provide insight into the processes that contribute to the maintenance of health during extreme aging.