Gene variants as determinants of longevity: focus on the inflammatory factors

Effects of Chronic Viral Infection on Lymphocyte Populations in Middle-aged Baboons (Papio anubis)

Aging of the immune system is characterized by the loss of naïve T-cells, increased inflammation, and immune function impairment. Chronic infection with cytomegalovirus is thought to play a role in age-related changes in immunity. Therefore, to assess the effect of pathogens such as cytomegalovirus on the immune system, we determined lymphocyte populations and inflammatory markers over a 3-y period in captive, middle-age baboons, with various exposure to pathogens and shedding pressure. Groups included SPF (i.e., pathogen-negative; n = 14); large-group, conventionally housed (CONV LG; pathogen- positive; n = 14), and small-group, conventionally housed (CONV SM; pathogen-positive; n = 7). All baboon groups showed a decrease in CD45RA+ CD28+ (i.e., naive) cells over time during middle age, but the rate of decline appeared faster in CONV LG baboons than in the other groups. In addition, the reduction in CD45RA+ CD28+ cells in the CONV LG baboons coincided with higher IgG levels against baboon cytomegalovirus, increased serum cortisol concentration, and a greater inflammatory phenotype. The results of this project support a role for cytomegalovirus infection in immune system alterations in middle-aged baboons.

Interaction Between the FOXO1A-209 Genotype and Tea Drinking Is Significantly Associated with Reduced Mortality at Advanced Ages

On the basis of the genotypic/phenotypic data from Chinese Longitudinal Healthy Longevity Survey (CLHLS) and Cox proportional hazard model, the present study demonstrates that interactions between carrying FOXO1A-209 genotypes and tea drinking are significantly associated with lower risk of mortality at advanced ages. Such a significant association is replicated in two independent Han Chinese CLHLS cohorts (p = 0.028-0.048 in the discovery and replication cohorts, and p = 0.003-0.016 in the combined dataset). We found the associations between tea drinking and reduced mortality are much stronger among carriers of the FOXO1A-209 genotype compared to non-carriers, and drinking tea is associated with a reversal of the negative effects of carrying FOXO1A-209 minor alleles, that is, from a substantially increased mortality risk to substantially reduced mortality risk at advanced ages. The impacts are considerably stronger among those who carry two copies of the FOXO1A minor allele than those who carry one copy. On the basis of previously reported experiments on human cell models concerning FOXO1A-by-tea-compounds interactions, we speculate that results in the present study indicate that tea drinking may inhibit FOXO1A-209 gene expression and its biological functions, which reduces the negative impacts of FOXO1A-209 gene on longevity (as reported in the literature) and offers protection against mortality risk at oldest-old ages. Our empirical findings imply that the health outcomes of particular nutritional interventions, including tea drinking, may, in part, depend upon individual genetic profiles, and the research on the effects of nutrigenomics interactions could potentially be useful for rejuvenation therapies in the clinic or associated healthy aging intervention programs.

A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity

BACKGROUND

Caloric restriction (CR), energy intake reduced below ad libitum (AL) intake, increases life span in many species. The implications for humans can be clarified by randomized controlled trials of CR.

METHODS

To determine CR's feasibility, safety, and effects on predictors of longevity, disease risk factors, and quality of life in nonobese humans aged 21-51 years, 218 persons were randomized to a 2-year intervention designed to achieve 25% CR or to AL diet. Outcomes were change from baseline resting metabolic rate adjusted for weight change ("RMR residual") and core temperature (primary); plasma triiodothyronine (T3) and tumor necrosis factor-α (secondary); and exploratory physiological and psychological measures.

RESULTS

Body mass index averaged 25.1 (range: 21.9-28.0 kg/m(2)). Eighty-two percent of CR and 95% of AL participants completed the protocol. The CR group achieved 11.7±0.7 %CR (mean ± standard error) and maintained 10.4±0.4% weight loss. Weight change in AL was negligible. RMR residual decreased significantly more in CR than AL at 12 months (p = .04) but not 24 months (M24). Core temperature change differed little between groups. T3 decreased more in CR at M12 and M24 (p < .001), while tumor necrosis factor-α decreased significantly more only at M24 (p = .02). CR had larger decreases in cardiometabolic risk factors and in daily energy expenditure adjusted for weight change, without adverse effects on quality of life.

CONCLUSIONS

Sustained CR is feasible in nonobese humans. The effects of the achieved CR on correlates of human survival and disease risk factors suggest potential benefits for aging-related outcomes that could be elucidated by further human studies.

Conservation of pro-longevity genes among mammals

Genes which confer a relative longevity advantage may be regulated at the level of transcription or translation. Alternatively, pro-longevity genes may mediate their effects at the level of protein structure-functional relationships that are beneficially optimized in long-lived species. Longevity associated genes (LAGs) may be operationally defined as genes that confer beneficial effects and are relatively more conserved among long-lived species. Global and local protein sequence alignments of over 10,000 genes across at least 30 mammalian species were examined to identify LAGs. Known LAGs, including growth hormone receptor (GHR), and breast cancer 1, early onset (BRCA1), have strong associations with maximum lifespan by our analysis. Several common categories of protein function were observed among genes ranked with the strongest associations with MLS identified by all regression models. These genes included those that function in the immune system, cell cycle regulation, and DNA damage response. We provide a ranking of genes with the strongest associations with species maximum lifespan (MLS) by several phylogenetic generalized least squares regression models, including adjustment for confounding variables such as body weight and gestation length.

Evidence from case-control and longitudinal studies supports associations of genetic variation in APOE, CETP, and IL6 with human longevity

In this study, we investigated 102 single-nucleotide polymorphisms (SNPs) covering the common genetic variation in 16 genes recurrently regarded as candidates for human longevity: APOE; ACE; CETP; HFE; IL6; IL6R; MTHFR; TGFB1; APOA4; APOC3; SIRTs 1, 3, 6; and HSPAs 1A, 1L, 14. In a case-control study of 1,089 oldest-old (ages 92-93) and 736 middle-aged Danes, the minor allele frequency (MAF) of rs769449 (APOE) was significantly decreased in the oldest-old, while the MAF of rs9923854 (CETP) was significantly enriched. These effects were supported when investigating 1,613 oldest-old (ages 95-110) and 1,104 middle-aged Germans. rs769449 was in modest linkage equilibrium (R (2)=0.55) with rs429358 of the APOE-ε4 haplotype and adjusting for rs429358 eliminated the association of rs769449, indicating that the association likely reflects the well-known effect of rs429358. Gene-based analysis confirmed the effects of variation in APOE and CETP and furthermore pointed to HSPA14 as a longevity gene. In a longitudinal study with 11 years of follow-up on survival in the oldest-old Danes, only one SNP, rs2069827 (IL6), was borderline significantly associated with survival from age 92 (P-corrected=0.064). This advantageous effect of the minor allele was supported when investigating a Dutch longitudinal cohort (N=563) of oldest-old (age 85+). Since rs2069827 was located in a putative transcription factor binding site, quantitative RNA expression studies were conducted. However, no difference in IL6 expression was observed between rs2069827 genotype groups. In conclusion, we here support and expand the evidence suggesting that genetic variation in APOE, CETP, and IL6, and possible HSPA14, is associated with human longevity.

Are aging biomarkers clinically relevant in oncogeriatrics?

Immunosenescence and inflammaging have been depicted for long as age-related heterogeneous blood phenotypic changes ("immunoaging"). Some of them can be reproduced in animal models either by accelerating telomere shortening or by forcing DNA damage response. According to these models, "immunoaging" is the consequence of replicative senescence of hematopoietic stem cells. This increasing knowledge may impact oncogeriatrics in the future since (1) an increasing evidence links hematopoietic and cancer stem cells regulations; (2) immunosenescence may be linked to cancer immunotolerance and the increasing rate of cancer incidence with age; (3) immunoaging has a major consequence during cancer treatment, since it explains increased hematological toxicities observed in the elderly and (4) it favors secondary cancers and mainly hemopathies. For all these reasons, aging biomarkers, among which are telomere length peripheral blood sampling but also analyses of telomere-linked proteins like shelterin complex or DNA-damage markers will probably be clinically relevant in the future.

Structural, functional and molecular analysis of the effects of aging in the small intestine and colon of C57BL/6J mice

BACKGROUND

By regulating digestion and absorption of nutrients and providing a barrier against the external environment the intestine provides a crucial contribution to the maintenance of health. To what extent aging-related changes in the intestinal system contribute to the functional decline associated with aging is still under debate.

METHODS

Young (4 M) and old (21 M) male C57BL/6J mice were fed a control low-fat (10E%) or a high-fat diet (45E%) for 2 weeks. During the intervention gross energy intake and energy excretion in the feces were measured. After sacrifice the small and large intestine were isolated and the small intestine was divided in three equal parts. Swiss rolls were prepared of each of the isolated segments for histological analysis and the luminal content was isolated to examine alterations in the microflora with 16S rRNA Q-PCR. Furthermore, mucosal scrapings were isolated from each segment to determine differential gene expression by microarray analysis and global DNA methylation by pyrosequencing.

RESULTS

Digestible energy intake was similar between the two age groups on both the control and the high-fat diet. Microarray analysis on RNA from intestinal scrapings showed no marked changes in expression of genes involved in metabolic processes. Decreased expression of Cubilin was observed in the intestine of 21-month-old mice, which might contribute to aging-induced vitamin B12 deficiency. Furthermore, microarray data analysis revealed enhanced expression of a large number of genes involved in immune response and inflammation in the colon, but not in the small intestine of the 21-month-old mice. Aging-induced global hypomethylation was observed in the colon and the distal part of the small intestine, but not in the first two sections of the small intestine.

CONCLUSION

In 21-month old mice the most pronounced effects of aging were observed in the colon, whereas very few changes were observed in the small intestine.

Genetic variants influencing human aging from late-onset Alzheimer's disease (LOAD) genome-wide association studies (GWAS)

Genetics plays a crucial role in human aging with up to 30% of those living to the mid-80s being determined by genetic variation. Survival to older ages likely entails an even greater genetic contribution. There is increasing evidence that genes implicated in age-related diseases, such as cancer and neuronal disease, play a role in affecting human life span. We have selected the 10 most promising late-onset Alzheimer's disease (LOAD) susceptibility genes identified through several recent large genome-wide association studies (GWAS). These 10 LOAD genes (APOE, CLU, PICALM, CR1, BIN1, ABCA7, MS4A6A, CD33, CD2AP, and EPHA1) have been tested for association with human aging in our dataset (1385 samples with documented age at death [AAD], age range: 58-108 years; mean age at death: 80.2) using the most significant single nucleotide polymorphisms (SNPs) found in the previous studies. Apart from the APOE locus (rs2075650) which showed compelling evidence of association with risk on human life span (p = 5.27 × 10(-4)), none of the other LOAD gene loci demonstrated significant evidence of association. In addition to examining the known LOAD genes, we carried out analyses using age at death as a quantitative trait. No genome-wide significant SNPs were discovered. Increasing sample size and statistical power will be imperative to detect genuine aging-associated variants in the future. In this report, we also discuss issues relating to the analysis of genome-wide association studies data from different centers and the bioinformatic approach required to distinguish spurious genome-wide significant signals from real SNP associations.

Inflammation and oxidative stress as biomarkers of premature aging in persons with intellectual disability

The decline in cognitive ability and physical performance in older adults with intellectual disabilities (ID) is accompanied by less participation in social activities and a sedentary lifestyle; however the pathogenesis is not clear yet. It was recently suggested that chronic disease, adverse drug reactions, and aging create a cascade of events that can be best characterized as an asymptomatic inflammatory process. This cascade of events is mediated by cytokine interleukins 1 and 6 (IL-1α, and IL-6), nitric oxide (NO) and total oxidative stress (OS). Our hypothesis was that chronic inflammation in the bloodstream of persons with ID contributes to their "premature aging". To test this hypothesis, we measured and compared the levels of inflammatory molecules in persons with and without ID. Fifteen adults with, and 15 adults without ID (control group) participated in this study. The levels of NO metabolites (NOx), IL-1α, and IL-6 were obtained from participants' serum. OS markers were drawn from participants' capillary. Western blot, RT-PCR and specific chemical analysis were used as measurement tools. The levels of inflammatory molecules and OS were significantly higher in persons with ID compared to the control group. Asymptomatic inflammation in the bloodstream of the older adults with ID might explain the "premature aging" of these individuals. Monitoring the levels of inflammatory molecules could serve as biomarkers of "premature aging" which may allow early diagnosis and intervention, and improve the quality of care for persons with ID.

Can biogerontologists and geriatricians unite to apply aging science to health care in the decade ahead?

Biogerontologists and academic geriatricians are both dedicated to promoting a healthier longevity for our society from their perspectives of scientific research on aging and education as part of clinical care for older persons. Yet at the present time, the prospects for translating research advances made by the biogerontologists to improve the outlook for health care provided by the geriatricians are limited by a "gulf" that exists between them, with little shared dialogue or scientific interchange. This article sets forth a basis for a union between both disciplines to prepare for the potential application of basic aging research to the provision of health care, with the aim ultimately to extend "health span" during our life span.