Temuri Budagov

Evolution in health and medicine Sackler colloquium: Genetic variation in human telomerase is associated with telomere length in Ashkenazi centenarians.

Telomere length in humans is emerging as a biomarker of aging because its shortening is associated with aging-related diseases and early mortality. However, genetic mechanisms responsible for these associations are not known. Here, in a cohort of Ashkenazi Jewish centenarians, their offspring, and offspring-matched controls, we studied the inheritance and maintenance of telomere length and variations in two major genes associated with telomerase enzyme activity, hTERT and hTERC. We demonstrated that centenarians and their offspring maintain longer telomeres compared with controls with advancing age and that longer telomeres are associated with protection from age-related diseases, better cognitive function, and lipid profiles of healthy aging. Sequence analysis of hTERT and hTERC showed overrepresentation of synonymous and intronic mutations among centenarians relative to controls. Moreover, we identified a common hTERT haplotype that is associated with both exceptional longevity and longer telomere length. Thus, variations in human telomerase gene that are associated with better maintenance of telomere length may confer healthy aging and exceptional longevity in humans.

Genetic variation in human telomerase is associated with telomere length in Ashkenazi centenarians

Telomere length in humans is emerging as a biomarker of aging because its shortening is associated with aging-related diseases and early mortality. However, genetic mechanisms responsible for these associations are not known. Here, in a cohort of Ashkenazi Jewish centenarians, their offspring, and offspring-matched controls, we studied the inheritance and maintenance of telomere length and variations in two major genes associated with telomerase enzyme activity, hTERT and hTERC. We demonstrated that centenarians and their offspring maintain longer telomeres compared with controls with advancing age and that longer telomeres are associated with protection from age-related diseases, better cognitive function, and lipid profiles of healthy aging. Sequence analysis of hTERT and hTERC showed overrepresentation of synonymous and intronic mutations among centenarians relative to controls. Moreover, we identified a common hTERT haplotype that is associated with both exceptional longevity and longer telomere length. Thus, variations in human telomerase gene that are associated with better maintenance of telomere length may confer healthy aging and exceptional longevity in humans.

Humanin: A Novel Central Regulator of Peripheral Insulin Action

Background Decline in insulin action is a metabolic feature of aging and is involved in the development of age-related diseases including Type 2 Diabetes Mellitus (T2DM) and Alzheimers disease (AD). A novel mitochondria-associated peptide, Humanin (HN), has a neuroprotective role against AD-related neurotoxicity. Considering the association between insulin resistance and AD, we investigated if HN influences insulin sensitivity. Methods and Findings Using state of the art clamp technology, we examined the role of central and peripheral HN on insulin action. Continuous infusion of HN intra-cerebro-ventricularly significantly improved overall insulin sensitivity. The central effects of HN on insulin action were associated with activation of hypothalamic STAT-3 signaling; effects that were negated by co-inhibition of hypothalamic STAT-3. Peripheral intravenous infusions of novel and potent HN derivatives reproduced the insulin-sensitizing effects of central HN. Inhibition of hypothalamic STAT-3 completely negated the effects of IV HN analog on liver, suggesting that the hepatic actions of HN are centrally mediated. This is consistent with the lack of a direct effect of HN on primary hepatocytes. Furthermore, single treatment with a highly-potent HN analog significantly lowered blood glucose in Zucker diabetic fatty rats. Based upon the link of HN with two age-related diseases, we examined if there were age associated changes in HN levels. Indeed, the amount of detectable HN in hypothalamus, skeletal muscle, and cortex was decreased with age in rodents, and circulating levels of HN were decreased with age in humans and mice. Conclusions We conclude that the decline in HN with age could play a role in the pathogenesis of age-related diseases including AD and T2DM. HN represents a novel link between T2DM and neurodegeneration and along with its analogues offers a potential therapeutic tool to improve insulin action and treat T2DM.

Human longevity and common variations in the LMNA gene: a meta-analysis

A mutation in the LMNA gene is responsible for the most dramatic form of premature aging, Hutchinson–Gilford progeria syndrome (HGPS). Several recent studies have suggested that protein products of this gene might have a role in normal physiological cellular senescence. To explore further LMNA’s possible role in normal aging, we genotyped 16 SNPs over a span of 75.4 kb of the LMNA gene on a sample of long‐lived individuals (LLI) (US Caucasians with age ≥ 95 years, N = 873) and genetically matched younger controls (N = 443). We tested all common nonredundant haplotypes (frequency ≥ 0.05) based on subgroups of these 16 SNPs for association with longevity. The most significant haplotype, based on four SNPs, remained significant after adjustment for multiple testing (OR = 1.56, P = 2.5 × 10−5, multiple‐testing‐adjusted P = 0.0045). To attempt to replicate these results, we genotyped 3619 subjects from four independent samples of LLI and control subjects from (i) the New England Centenarian Study (NECS) (N = 738), (ii) the Southern Italian Centenarian Study (SICS) (N = 905), (iii) France (N = 1103), and (iv) the Einstein Ashkenazi Longevity Study (N = 702). We replicated the association with the most significant haplotype from our initial analysis in the NECS sample (OR = 1.60, P = 0.0023), but not in the other three samples (P > 0.15). In a meta‐analysis combining all five samples, the best haplotype remained significantly associated with longevity after adjustment for multiple testing in the initial and follow‐up samples (OR = 1.18, P = 7.5 × 10−4, multiple‐testing‐adjusted P = 0.037). These results suggest that LMNA variants may play a role in human lifespan.

Telomere length is a novel predictive biomarker of sensitivity to anti-EGFR therapy in metastatic colorectal cancer

Background:Telomeres are TTAGGG tandem repeats capping chromosomal ends and partially controlled by the telomerase enzyme. The EGFR pathway putatively regulates telomerase function, prompting an investigation of telomere length (TL) and its association with anti-epidermal growth factor receptor (EGFR) therapy in metastatic colorectal cancer (mCRC).Methods:Colorectal cancer cell lines were treated with multiple drugs and sensitivity determined. Clinical information was gathered from 75 patients who had received anti-EGFR drugs. Telomere length was measured using a validated qRT–PCR technique.Results:In CRC cell lines, TL independently predicted cetuximab sensitivity. Cells with shorter TL had growth inhibition of 18.6±3.41% as compared with 41.39±8.58% in longer TL (P=0.02). These in vitro findings were validated clinically, in a robust multivariate model. Among patients with KRas WT tumours, those with longer TL had a superior median progression-free survival (PFS) of 24.9 weeks than those with shorter TL; median 11.1 weeks, HR 0.31; P=0.048.Conclusion:Telomere length could be a potential unique biomarker predictive of clinical benefit (PFS) of mCRC patients treated with anti-EGFR therapy. This is the novel demonstration of a complex hitherto undescribed interaction, placing anti-EGFR therapy, EGFR pathway, and the telomerase complex within a clinical context.

The GH receptor exon 3 deletion is a marker of male-specific exceptional longevity associated with increased GH sensitivity and taller stature

The d3-GHR genetic variant polymorphism modulates GH responsiveness throughout life span and positively affects male longevity. Although both growth hormone (GH) and insulin-like growth factor 1 (IGF-1) signaling were shown to regulate life span in lower organisms, the role of GH signaling in human longevity remains unclear. Because a GH receptor exon 3 deletion (d3-GHR) appears to modulate GH sensitivity in humans, we hypothesized that this polymorphism could play a role in human longevity. We report a linear increased prevalence of d3-GHR homozygosity with age in four independent cohorts of long-lived individuals: 841 participants [567 of the Longevity Genes Project (LGP) (8% increase; P = 0.01), 152 of the Old Order Amish (16% increase; P = 0.02), 61 of the Cardiovascular Health Study (14.2% increase; P = 0.14), and 61 of the French Long-Lived Study (23.5% increase; P = 0.02)]. In addition, mega analysis of males in all cohorts resulted in a significant positive trend with age (26% increase; P = 0.007), suggesting sexual dimorphism for GH action in longevity. Further, on average, LGP d3/d3 homozygotes were 1 inch taller than the wild-type (WT) allele carriers (P = 0.05) and also showed lower serum IGF-1 levels (P = 0.003). Multivariate regression analysis indicated that the presence of d3/d3 genotype adds approximately 10 years to life span. The LGP d3/d3-GHR transformed lymphocytes exhibited superior growth and extracellular signal–regulated kinase activation, to GH treatment relative to WT GHR lymphocytes (P < 0.01), indicating a GH dose response. The d3-GHR variant is a common genetic polymorphism that modulates GH responsiveness throughout the life span and positively affects male longevity.

Telomere Length and Telomerase Activity; A Yin and Yang of Cell Senescence

Telomeres are repeating DNA sequences at the tip ends of the chromosomes that are diverse in length and in humans can reach a length of 15,000 base pairs. The telomere serves as a bioprotective mechanism of chromosome attrition at each cell division. At a certain length, telomeres become too short to allow replication, a process that may lead to chromosome instability or cell death. Telomere length is regulated by two opposing mechanisms: attrition and elongation. Attrition occurs as each cell divides. In contrast, elongation is partially modulated by the enzyme telomerase, which adds repeating sequences to the ends of the chromosomes. In this way, telomerase could possibly reverse an aging mechanism and rejuvenates cell viability. These are crucial elements in maintaining cell life and are used to assess cellular aging. In this manuscript we will describe an accurate, short, sophisticated and cheap method to assess telomere length in multiple tissues and species. This method takes advantage of two key elements, the tandem repeat of the telomere sequence and the sensitivity of the qRT-PCR to detect differential copy numbers of tested samples. In addition, we will describe a simple assay to assess telomerase activity as a complementary backbone test for telomere length.

The Rhesus Monkey: A Nonhuman Primate Model For T2DM- Associated Gene Screening

To examine the genetic basis of the spontaneous development of Type 2 diabetes mellitus (T2DM), we have conducted an initial genome wide association study (GWAS) using Affymetrix 6.0 gene chip arrays on 8 normal (Controls), and 14 insulin resistant(IR)/prediabetic(preDM)/T2DM rhesus monkeys ( Macaca mulatta ). Both IR/preDM and T2DM were classified as cases as they could be clearly defined in this model as either in the early progression toward overt DM or already overtly diabetic. The successful call rate on all chip assays averaged 91.9% with high heterozygosity (42%), demonstrating the project applicability for genotyping the rhesus monkey using the human platform. Principal component analysis classified the groups accurately according to their source – i.e. case or control. Five SNPs (Chr 18, and 1 of the human and rhesus genomes) passed the tests for multiple comparison correction and were of complete homology between the rhesus monkey and human SNPs. We identified on our Affymetrix 6.0 array 9 out of the reported 18 SNPs associated with T2DM by prior GWAS in humans (candidate human genome sequence polymorphisms with T2DM), that were present on the 6.0 array. Eight were of the same genotype, and in one SNP representing the WFS1 gene all monkeys except for one control, carried the non-ancestral allele at this position. Resequencing of the 4 most significant SNPs in 51 additional NPH subjects revealed a SNP in the same location as in human that was of significantly higher prevalence in T2DM animals and two others that were at a different location then the homolog human SNPs and were not differently distributed among the NHPs T2D patients and controls. Expression levels (measured in heart, liver and muscle) of these four candidate genes demonstrated reduced expression of CBLN2 compared to normal animals following adjustments. In addition, CBLN2 SNPs were significantly associated with HOMA-IR in patients from a Finland and Sweden Type 2 diabetes GWAS. These data demonstrate the successful use of human SNP platforms to identify genetic variants associated with T2DM in rhesus monkeys.