Elsevier

Experimental Gerontology

Volume 119, May 2019, Pages 53-60
Experimental Gerontology

Novel biomolecules of ageing, sex differences and potential underlying mechanisms of telomere shortening in coronary artery disease

https://doi.org/10.1016/j.exger.2019.01.020Get rights and content

Highlights

  • Long LTLs associate with 64 % lower frequency of previous MI in patients with CAD

  • LTLs correlate to age, exclusively in women with CAD

  • GDF11 and SIRT1 strongly correlate, indicating common intracellular pathways

  • Long LTLs associate with high GDF11/SIRT1 expression in women and less inflammation in both gender

  • Possible sex-dimorphism in LTL dynamics and regulation

Abstract

Telomere length (TL), growth differentiate factor (GDF)11, insulin growth factor (IGF)1, sirtuin (SIRT)1 and inflammatory processes have been related to ageing and age-related diseases, like coronary artery disease (CAD). We aimed to investigate the associations between leukocyte TLs (LTLs), chronological age, sex and comorbidities in CAD patients. Any covariations between LTL, GDF11, IGF1, SIRT-1 and pro-inflammatory cytokines were further assessed.

Methods

In 300 patients with stable CAD (age 36–81 years, 20% females), DNA and RNA were isolated from whole blood for PCR analysis and relative quantification of LTLs and gene-expression of GDF11, IGF1,SIRT1, IL-12, IL-18 and IFNƴ, respectively. Serum was prepared for the analyses of circulating IL-18, IL-12, IL-6 and TNFα.

Results

Patients with previous myocardial infarction (MI) presented with 20% shorter LTLs vs. patients without (p = 0.019) indicating LTLs to be of importance for CAD severity. The observation however, was only observed in men (p = 0.009, n = 115), in which the upper LTL quartile associated with 64% lower frequency of previous MI compared to quartile 1–3 (p = 0.005, adjusted). LTLs were not differently distributed according to sex or comorbidities such as hypertension, diabetes type 2 and metabolic syndrome. LTLs and GDF11 were inversely correlated to age (r = −0.17; p = 0.007 and r = −0.16; p = 0.010, respectively), however, separated in gender, LTL only in women (r = −0.37) and GDF11 only in men (r = −0.19) (p = 0.006, both). GDF11 and SIRT1 were strongly inter-correlated (r = 0.56, p ≤ 0.001), suggesting common upstream regulators. LTLs were moderately correlated to GDF11 and SIRT1 in overweight women (BMI ≥ 25 kg/m2) (r = 0.41; p = 0.027 and 0.43; p = 0.020, respectively), which may reflect common life-style influences on LTLs and these markers.

In all women, we observed further that the highest LTL quartile associated with higher GDF11 and SIRT expression and lower circulating levels of IL-12, IL-18 and TNFα, as compared to quartile 1, which may indicate lifestyle influences on female LTLs. In men, the highest LTL quartile associated with lower IFNƴ expression and lower circulating TNFα. Overall, the results indicate an association between chronic low-grade inflammation and LTLs.

Conclusions

Shorter LTLs in CAD patients with previously suffered MI may indicate telomere attrition as part of its pathophysiology in men. The inverse association between LTLs and age exclusively in women underpins the previously reported decline in attrition rate in men with increasing age. As elevated GDF11 and SIRT1 along with attenuated pro-inflammatory cytokines seem to positively affect LTL in women, we hypothesize a potential sex-dimorphism in LTL regulation, which may implicate sex- adjusted health-preventive therapies.

Introduction

Ageing is now widely hypothesized as a consequence of telomere shortening (Mikhelson and Gamaley, 2012). Telomeres consist of repetitive nucleotide structures (TTAGG) at the end of chromosomes that protect DNA from deterioration (Blackburn, 1991). Telomere lengths decline with increasing chronologic age due to loss of the repetitive DNA sequences during cell-division. Consequently, and when the shorten telomeres are reduced below a critical length, cells are triggered into replicative senescence (Takubo et al., 2010). Little knowledge also exists on sex differences in telomere length regulation, other than reported dissimilar telomere shortening curves throughout life (Barrett and Richardson, 2011; Needham et al., 2014). Inflammation, oxidative stress, life-style and environmental factors are all thought to influence the rate of the senescence process and shortened telomeres have been associated with the onset of age-related diseases like cardiovascular disease (CVD) states (Zhang et al., 2016; Samani and van der Harst, 2008; von Zglinicki, 2002). However, the molecular mechanisms behind these effects are uncertain.

In recent research, several potential regulators of life-span and telomere lengths have been suggested. Growth differentiation factor 11 (GDF11), a member of the TGFβ superfamily with homology to myostatin, retards the ageing process via yet unknown mechanisms. In parabiosis experiments, it was demonstrated that older mice sharing blood supply with younger developed a younger phenotype with improved olfaction, regression of myocardial injury and better memory, and it was suggested that GDF11 was the rejuvenating factor causal for these alterations (Loffredo et al., 2013; Katsimpardi et al., 2014). However, due to questions concerning methodology (Rodgers, 2016) and reported increased circulating levels of GDF11 with increasing age both in mice and humans (Egerman et al., 2015), its influence on lifespan is unclear.

Ageing research has lately also payed attention to the intracellular mechanistic target of rapamycin (mTor) signaling pathway, mediated by the growth hormone and insulin growth factor1 (IGF1) (Junnila et al., 2013), sensitive to insulin and caloric restriction. IGF1 is commonly shown to be higher in subjects affected by age-related diseases or obesity than in healthy and lean subjects, however, low circulating IGF1 levels have also been associated with increased all-cause mortality in several population studies (Laughlin et al., 2004).

Sirtuins (SIRT 1–7), localized in different cell compartments, are another group of mediators that are associated with promoted longevity. By deacetylating histones or non-histone substrates in a nicotinamide adenine dinucleotide (NAD+) dependent manner, sirtuins and especially SIRT1, located in the nucleus, can regulate gene-expression. Because NAD+ levels are sensitive to diet and exercise, sirtuins are involved in metabolism and sense life-style changes, thus impacting health status (Grabowska et al., 2017). Being capable to translocate into cytoplasm, SIRT1 also seems to affect the production of reactive oxygen species (ROS) and to influence apoptosis. However, the role of SIRT1 in human ageing is still unclear (Razi et al., 2017).

Chronic low-grade inflammation with elevation of pro-inflammatory cytokines increases with age and has also been associated with reduced length of telomeres (Zhang et al., 2016), although the link between inflammation and telomere lengths is not well understood.

Due to accessibility, leukocyte telomere length (LTL) is now widely used as a measure of telomere lengths, which seems highly correlated to telomere lengths in other cells and tissue, although debated (Friedrich et al., 2000; Wilson et al., 2008; Okuda et al., 2002; Booth and Charchar, 2017).

Ageing is one of the strongest non-modifiable disease-risk factors, especially for CVD (Niccoli and Partridge, 2012), thus more research is needed to explore molecular mechanism associated with ageing in these patients. We therefore aimed to investigate associations between LTLs and 1) chronological age, sex and comorbidities in patients with coronary artery disease (CAD) 2) leukocyte gene expression of the potential telomere length regulators GDF11, IGF1 and SIRT1 and 3) levels of selected pro-inflammatory cytokines, partly as genetically expressed and circulating proteins.

Section snippets

Study population

The present investigation is a sub-study of the Norwegian ASCET trial (ASpirin non-responsiveness and Clopidogrel Endpoint Trial), which included angiographically verified stable CAD patients (Pettersen et al., 2012). This cross-sectional analysis was performed on baseline data from the 300 first included patients in the main trial (age range 39–81 years, 20% women, 97% of Western European descent). Relatedness in the population was <1%. The ASCET study was approved by The Regional Committee of

Results

Demographic data for the cohort in total and as related to sex are presented in Table 1, showing normal distribution on most of the variables and statistically significantly higher age, total-, low density lipoprotein (LDL)- and high density lipoprotein (HDL)-cholesterol in women compared to men, and numerically higher number of previous MI in men versus women.

Discussion

In this exploratory study of patients with stable CAD, we observed a sex-specific influence in the association between 1) LTLs and age, with stronger correlation in women, 2) LTLs and CAD severity, with significantly lower frequency of previous MI in the upper quartile of LTLs in men, 3) LTL and its covariation with the investigated lifestyle and lifespan-regulating factors, GDF11 and SIRT1, which was only present in women and 4) LTLs,GDF11, SIRT1 and pro-inflammatory cytokines, which was

Acknowledgement

MSc Sissel Åkra and MSc Vibeke Bratseth are acknowledged for laboratory assistance including cytokine measurements in the ASCET trial.

Funding

The work was funded by the Norwegian Council for Cardiovascular Diseases and Stein Erik Hagen Foundation for Clinical Heart Research, Oslo Norway. Theses funding sources were not involved in the research and preparation of the article.

Conflict of interest

None.

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