[The relationship between the relative length of leukocyte telomeres and mtDNA copy number and acute coronary syndrome in a 15-year follow-up.]

We studied the relationship between the leucocyte telomere length (LTL) and the copy number of mitochondrial DNA (CNmtDNA) and the development of acute coronary syndrome during 15 years of follow-up. A random population sample was examined at baseline in 2003-2005 (n=9 360, men and women 45-69 years old, Novosibirsk, the HAPIEE project) and followed-up for 15 years. In the frame of nested case-control design, we selected cases - incident myocardial infarction/acute coronary syndrome (MI/ACS) among those free from baseline CVD (n=256) and sex- and age-stratified control among those free from baseline CVD and cancer and alive by the end of follow-up (n=799). The relative LTL and CNmtDNA were assessed using quantitative real-time PCR. Results. The carriers of shorter telomeres had increased 15-year risk of MI/ACS with adjusted OR=1,87 (95% CI 1,70-2,06) per 1 LTL decile independent of other factors. Fewer CNmtDNA was associated with increased risk of MI/ACS with adjusted OR=1,19 (95% CI 1,12-1,26) per 1 CNmtDNA decile. The identified associations were confirmed in tertile analysis and in stepwise analysis with continuous variables of both biomarkers. All associations persisted after adjusting for gender, age, and traditional CVD risk factors. Conclusion. The LTL and CNmtDNA were independent predictors of the 15-year risk of MI/ACS in the middle- and elderly Siberian (Caucasoid) population cohort. These findings highlight the need for further research to elucidate the mechanisms by which LTL and mtDNA copy number may affect human health.

[Mitochondrial DNA copy number of leucocytes as ageing marker and risk factors for age-related diseases in human.]

We used quantitative real-time PCR method to analyse mtDNA copy number in a random subsample (n=996; 358 men aged 66,31±7,24 years; 468 women aged 67,62±7,1 years) selected from a population cohort (n=9 630) examined at baseline in international project HAPIEE in Novosibirsk, Russia, in 2003-2005. The participants were re-examined after 12 years in 2015-2017. The average relative number of mtDNA copies in peripheral blood leukocytes was greater in women than in men, independently of age and smoking (p=0,001). mtDNA copy number was inversely correlated with age both in men (p=0,005) and women (p<0,001). In age adjusted analysis, mtDNA copy number was inversely associated with waist, hip and heart rate in both sexes. In addition, mtDNA copy number in women was inversely associated with triglycerides and glucose, aterogenity index and positively with HDL cholesterol. In men, mtDNA copy number was positively associated with physical activity. The age-adjusted mean of mtDNA copy number among male never-smokers was greater than in smokers (p=0,003), and the mean mtDNA copy number was lower in women with diabetes than in women without diabetes (p=0,005). In both sexes, subjects with baseline history of hypertension had lower mtDNA copy number after 12-year follow-up than those without hypertension (p=0,05). This broadly supports the hypothesis that mtDNA copy number may act as biomarker of ageing.

How Genes Modulate Patterns of Aging-Related Changes on the Way to 100: Biodemographic Models and Methods in Genetic Analyses of Longitudinal Data

BACKGROUND AND OBJECTIVE

To clarify mechanisms of genetic regulation of human aging and longevity traits, a number of genome-wide association studies (GWAS) of these traits have been performed. However, the results of these analyses did not meet expectations of the researchers. Most detected genetic associations have not reached a genome-wide level of statistical significance, and suffered from the lack of replication in the studies of independent populations. The reasons for slow progress in this research area include low efficiency of statistical methods used in data analyses, genetic heterogeneity of aging and longevity related traits, possibility of pleiotropic (e.g., age dependent) effects of genetic variants on such traits, underestimation of the effects of (i) mortality selection in genetically heterogeneous cohorts, (ii) external factors and differences in genetic backgrounds of individuals in the populations under study, the weakness of conceptual biological framework that does not fully account for above mentioned factors. One more limitation of conducted studies is that they did not fully realize the potential of longitudinal data that allow for evaluating how genetic influences on life span are mediated by physiological variables and other biomarkers during the life course. The objective of this paper is to address these issues.

DATA AND METHODS

We performed GWAS of human life span using different subsets of data from the original Framingham Heart Study cohort corresponding to different quality control (QC) procedures and used one subset of selected genetic variants for further analyses. We used simulation study to show that approach to combining data improves the quality of GWAS. We used FHS longitudinal data to compare average age trajectories of physiological variables in carriers and non-carriers of selected genetic variants. We used stochastic process model of human mortality and aging to investigate genetic influence on hidden biomarkers of aging and on dynamic interaction between aging and longevity. We investigated properties of genes related to selected variants and their roles in signaling and metabolic pathways.

RESULTS

We showed that the use of different QC procedures results in different sets of genetic variants associated with life span. We selected 24 genetic variants negatively associated with life span. We showed that the joint analyses of genetic data at the time of bio-specimen collection and follow up data substantially improved significance of associations of selected 24 SNPs with life span. We also showed that aging related changes in physiological variables and in hidden biomarkers of aging differ for the groups of carriers and non-carriers of selected variants.

CONCLUSIONS

. The results of these analyses demonstrated benefits of using biodemographic models and methods in genetic association studies of these traits. Our findings showed that the absence of a large number of genetic variants with deleterious effects may make substantial contribution to exceptional longevity. These effects are dynamically mediated by a number of physiological variables and hidden biomarkers of aging. The results of these research demonstrated benefits of using integrative statistical models of mortality risks in genetic studies of human aging and longevity.

[Length telomere leukocytes as ageing markers and risk factors for age-related diseases in humans]

The purpose of the research was studying of leukocyte telomere length association with age, sex, risk factors for age-related diseases in Russian people of pre-retirement and retirement age. By quantitative real-time PCR method we studied the leukocyte telomere length in 398 men (56,3±7,2 years) and 365 women (56,6±7,1 years) selected from a population sample of 45-69 year-old residents of the Oktyabrsky and Kirovsky districts of Novosibirsk (9 400 people). The selection was formed in the course of work on the international project HAPIEE. As a result, an inverse correlation of telomere length with age (r=-0,159, р<0,001), with the ratio waist / hips (r=-0,107, p=0,003) was found out. The average length of telomeres in women significantly more than in men, p=0,031.The correlation of telomere length in males with weight (r=0,140, p=0,005), waist size (r=0,111, p=0,027) was found out. In women, there is an inverse correlation of telomere length with a waist size (r=-0,127, p=0,015), the ratio of waist / hips (r=-0,141, p=0,007). The length of telomeres is an inverse correlation with correlation with quantity of the cigarettes smoked (r=-0,121, р=0,024). The length of telomeres leukocytes correlates with age, smoking, and a number of phenotypical signs. In men with the family anamnesis burdened by malignancies leucocytes telomere length was found to be greater than in men without such anamnesis.

Genetics of aging, health, and survival: dynamic regulation of human longevity related traits

Background: The roles of genetic factors in human longevity would be better understood if one can use more efficient methods in genetic analyses and investigate pleiotropic effects of genetic variants on aging and health related traits.

Data and methods: We used EMMAX software with modified correction for population stratification to perform genome wide association studies (GWAS) of female lifespan from the original FHS cohort. The male data from the original FHS cohort and male and female data combined from the offspring FHS cohort were used to confirm findings. We evaluated pleiotropic effects of selected genetic variants as well as gene-smoking interactions on health and aging related traits. Then we reviewed current knowledge on functional properties of genes related to detected variants.

Results: The eight SNPs with genome-wide significant variants were negatively associated with lifespan in both males and females. After additional QC, two of these variants were selected for further analyses of their associations with major diseases (cancer and CHD) and physiological aging changes. Gene-smoking interactions contributed to these effects. Genes closest to detected variants appear to be involved in similar biological processes and health disorders, as those found in other studies of aging and longevity e.g., in cancer and neurodegeneration.

Conclusions: The impact of genes on longevity may involve trade-off-like effects on different health traits. Genes that influence lifespan represent various molecular functions but may be involved in similar biological processes and health disorders, which could contribute to genetic heterogeneity of longevity and the lack of replication in genetic association studies.

The co-occurrence of mtDNA mutations on different oxidative phosphorylation subunits, not detected by haplogroup analysis, affects human longevity and is population specific

To re-examine the correlation between mtDNA variability and longevity, we examined mtDNAs from samples obtained from over 2200 ultranonagenarians (and an equal number of controls) collected within the framework of the GEHA EU project. The samples were categorized by high-resolution classification, while about 1300 mtDNA molecules (650 ultranonagenarians and an equal number of controls) were completely sequenced. Sequences, unlike standard haplogroup analysis, made possible to evaluate for the first time the cumulative effects of specific, concomitant mtDNA mutations, including those that per se have a low, or very low, impact. In particular, the analysis of the mutations occurring in different OXPHOS complex showed a complex scenario with a different mutation burden in 90+ subjects with respect to controls. These findings suggested that mutations in subunits of the OXPHOS complex I had a beneficial effect on longevity, while the simultaneous presence of mutations in complex I and III (which also occurs in J subhaplogroups involved in LHON) and in complex I and V seemed to be detrimental, likely explaining previous contradictory results. On the whole, our study, which goes beyond haplogroup analysis, suggests that mitochondrial DNA variation does affect human longevity, but its effect is heavily influenced by the interaction between mutations concomitantly occurring on different mtDNA genes.