Telomere length in blood and skeletal muscle in relation to measures of glycaemia and insulinaemia

The effects of exercise on epigenetic modifications: focus on DNA methylation, histone modifications and non-coding RNAs

Physical activity on a regular basis has been shown to bolster the overall wellness of an individual; research is now revealing that these changes are accompanied by epigenetic modifications. Regular exercise has been proven to make intervention plans more successful and prolong adherence to them. When it comes to epigenetic changes, there are four primary components. This includes changes to the DNA, histones, expression of particular non-coding RNAs and DNA methylation. External triggers, such as physical activity, can lead to modifications in the epigenetic components, resulting in changes in the transcription process. This report pays attention to the current knowledge that pertains to the epigenetic alterations that occur after exercise, the genes affected and the resulting characteristics.

A sex-specific association of leukocyte telomere length with thigh muscle mass

OBJECTIVES

Telomeres are DNA-protein complexes at the ends of linear chromosomes that protect against DNA degradation. Telomeres shorten during normal cell divisions and therefore, telomere length is an indicator of mitotic-cell age. In humans, telomere shortening is a potential biomarker for disease risk, progression and premature death. Physical activity has been associated with longer leukocyte telomere length (LTL) in some studies. In the current study the relationship between LTL, thigh muscle mass and adipose tissue distribution was explored.

METHODS

We performed anthropometric measurements and magnetic resonance imaging (MRI) measurements of the thigh in 149 healthy subjects (77 male, 72 female). LTL was measured using qPCR. Additionally, the subjects answered a questionnaire concerning their training behaviour.

RESULTS

In male subjects, LTL was significantly associated with thigh muscle mass, independent of age and body mass index (p=0.006). In addition, a slight association of LTL with weekly endurance units in the male group was found. These relations could not be observed in females.

CONCLUSIONS

In conclusion, we observed a sex-specific association of LTL and thigh muscle mass in healthy males. The reason of this sex-specific association is currently unclear, but could be related to different training effects and/or hormonal pathways in men and women.

Potential Antiaging and Hepatoprotective Effects of Acanthopanax senticosus Extracts in Adult Rat Models

Data regarding plant extracts with antiaging properties, particularly through the biological process involving telomeres and telomerase, are limited. Thus, this study aimed to investigate the effects of Acanthopanax senticosus extract (ASE) supplementation on leukocyte telomere length (LTL), telomerase, and inflammatory and metabolic markers in adult animal models. A freeze-dried product of ethanol extracts was prepared using a mixture product of stem and root ASE. In a 24-week experiment that included 24-week-old Sprague Dawley male rats, experimental rats (n = 10) were administrated with 7 mg/day of ASE dissolved in saline and control rats (n = 10) with saline. All rats had access to chow and tap water ad libitum. Their LTL and plasma levels of telomerase and inflammatory and metabolic markers were assayed and compared between the two groups. The experimental rats showed significantly longer LTL (p < 0.05) and lower plasma levels of alanine aminotransferase (p < 0.05) and aspartate aminotransferase (p = 0.08) compared with the control. In addition, LTL was correlated with the aforementioned biochemical parameters of liver function test among experimental rats only. No significant differences in plasma levels of telomerase and inflammatory and metabolic markers were observed. These findings indicate that ASE supplementation may attenuate LTL shortening and reduce liver biochemical parameters, indicating its potential antiaging and hepatoprotective effects without any adverse metabolic response.

Regular, Intense Exercise Training as a Healthy Aging Lifestyle Strategy: Preventing DNA Damage, Telomere Shortening and Adverse DNA Methylation Changes Over a Lifetime

Exercise training is one of the few therapeutic interventions that improves health span by delaying the onset of age-related diseases and preventing early death. The length of telomeres, the 5'-TTAGGG n -3' tandem repeats at the ends of mammalian chromosomes, is one of the main indicators of biological age. Telomeres undergo shortening with each cellular division. This subsequently leads to alterations in the expression of several genes that encode vital proteins with critical functions in many tissues throughout the body, and ultimately impacts cardiovascular, immune and muscle physiology. The sub-telomeric DNA is comprised of heavily methylated, heterochromatin. Methylation and histone acetylation are two of the most well-studied examples of the epigenetic modifications that occur on histone proteins. DNA methylation is the type of epigenetic modification that alters gene expression without modifying gene sequence. Although diet, genetic predisposition and a healthy lifestyle seem to alter DNA methylation and telomere length (TL), recent evidence suggests that training status or physical fitness are some of the major factors that control DNA structural modifications. In fact, TL is positively associated with cardiorespiratory fitness, physical activity level (sedentary, active, moderately trained, or elite) and training intensity, but is shorter in over-trained athletes. Similarly, somatic cells are vulnerable to exercise-induced epigenetic modification, including DNA methylation. Exercise-training load, however, depends on intensity and volume (duration and frequency). Training load-dependent responses in genomic profiles could underpin the discordant physiological and physical responses to exercise. In the current review, we will discuss the role of various forms of exercise training in the regulation of DNA damage, TL and DNA methylation status in humans, to provide an update on the influence exercise training has on biological aging.

Expression of Telomeric Repeat-Containing RNA Decreases in Sarcopenia and Increases after Exercise and Nutrition Intervention

Sarcopenia is defined as aging-related loss of muscle mass and function. Telomere length in chromosomes shortens with age and is modulated by telomeric repeat-containing RNA (TERRA). This study aimed to explore the impact of aging and sarcopenia on telomere length and TERRA expression, and changes following strengthening exercise and nutrition intervention (supplement of branched-chain amino acids, calcium and vitamin D3) for 12 weeks in the sarcopenic population. Older adults (≥65 years old) were divided into non-sarcopenic controls (n = 36) and sarcopenic individuals (n = 36) after measurement of grip strength and body composition. The relative telomere length of leukocytes in all research participants was evaluated using the T/S ratio (telomere/single copy gene), and relative TERRA expression of leukocytes was determined by reverse-transcription qPCR (RT-qPCR). Generalized estimating equation (GEE) was used to analyze the influence of sarcopenia and intervention on the outcomes. There was no significant difference in telomere length between control subjects and participants with sarcopenia. TERRA expression was lower in sarcopenic participants compared to that in non-sarcopenic controls (5.18 ± 2.98 vs. 2.51 ± 1.89; p < 0.001). In the sarcopenic group, intervention significantly increased TERRA expression, but not telomere length. The GEE analysis demonstrated that TERRA expression was negatively associated with sarcopenia (β coefficient = −2.705, p < 0.001) but positively associated with intervention (β coefficient = 1.599, p = 0.023). Sarcopenia is associated with a decrease in TERRA expression in leukocytes. Rebound TERRA expression (returning to the level similar to the non-sarcopenic controls) was observed in the sarcopenic group after exercise and nutrition intervention. Future studies are warranted to examine the potential of TERRA as a biomarker for sarcopenia and its subsequent responses to intervention.

[Telomere biology and metabolic disorders: the role of insulin resistance and type 2 diabetes]

BACKGROUND

Insulin resistance accelerates the aging process, but its speed depends on the individual characteristics of the metabolism. One of the reasons for the different aging rates in individuals with insulin resistance is the initially different "genetic protection" of cells, which many scientists associate with replicative cellular aging.

AIMS

to study the relationship between the state of carbohydrate metabolism and markers of replicative cell aging in individuals with different sensitivity to insulin.

MATERIALS AND METHODS

The observation study included 305 patients. The parameters of glucose metabolism and telomere biology were studied.

RESULTS

The mean age of the patients was 51.5±13.3 years. Patients were divided into three groups depending on presence of insulin resistance: healthy, with insulin resistance and with type 2 diabetes. The mean age of healthy patients was 48.82±13.87 years, in insulin resistance group - 53.04±12.8, in 2 diabetes mellitus - 58.4±7.90. The median telomere length was 9.76. The median telomerase activity was 0.48. Both telomere length and telomerase activity progressively decrease as insulin resistance increases. In patients with diabetes, short telomere lengths and low telomerase activity predominated. The insulin resistance index has the greatest impact on the risk of detecting "short" telomeres. In patients with insulin resistance, an increase in glycated hemoglobin increases the likelihood of detecting short telomeres by 2.4 times, and in diabetes mellitus by 4.26 times, an increase in fasting plasma glucose by 90%, and an increase in HOMA-IR by 35%. An increase in insulin resistance increases the risk of detecting «low» telomerase activity by 53% and the risk of detecting «very low» telomerase activity by 92%. A decrease in synsulin resistance increases the chance of increasing telomerase activity to «very high» by 51%.

CONCLUSION

Shorter telomeres are associated with more pronounced disorders of carbohydrate metabolism and a higher degree of insulin resistance. Further studies of metabolic status are necessary to personalize their lifestyle and treatment goals.

Biochemical profile, eating habits, and telomere length among Brazilian children and adolescents

OBJECTIVES

Lifestyle, obesity, and eating habits are emerging as determinants for the instability of telomeres. The increase in childhood and adolescent obesity and the association of biochemical profiles and dietary components with telomere length (TL) makes it an important issue in nutritional research. The aim of the present study was to investigate TL and its association with ethnic background, adiposity, clinical and biochemical parameters, and dietary patterns among Brazilian children and adolescents.

METHODS

A cross-sectional study encompassing 981 children and adolescents between 7 and 17 y of age was performed. Dietary intake habits, anthropometry, and clinical data were collected. TL analysis was performed by quantitative polymerase chain reaction.

RESULTS

Children presented significantly longer TL than adolescents (P = 0.046). Participants who self-declared as black, mulatto, or brown (P < 0.001) also showed longer TL than those who were white. Regarding biochemical parameters, individuals with altered glucose levels had shorter TL than normoglycemic participants in the total sample (P = 0.014). Such difference remained statistically significant in adolescents (P = 0.019). Participants who reported eating fruits and vegetables regularly had longer TL than those who did not (P < 0.001).

CONCLUSION

The results suggested that both biochemical parameters and the intake of antioxidant-rich food, such as fruits and vegetables, are associated with the stability of telomere biology among young Brazilians.

Leukocyte telomere length is associated with elevated plasma glucose and HbA1c in young healthy men independent of birth weight

Telomeres are protein-bound regions of repetitive nucleotide sequences (TTAGGG) at the end of human chromosomes, and their length is a marker of cellular aging. Intrauterine growth restriction is associated with shorter blood cell telomeres at birth and individuals with type 2 diabetes have shorter telomeres. Individuals with a low birth weight (LBW) have an increased risk of metabolic disease and type 2 diabetes. Therefore, we aimed to investigate the relationship between birth weight and telomere length and the association between birth weight, telomere length and cardiometabolic phenotype in adulthood. Young, healthy men with LBW (n = 55) and normal birth weight (NBW) (n = 65) were examined including blood pressure, blood samples and body composition. Leukocyte telomere length was determined using a high-throughput qPCR method. The LBW men were more insulin resistant as determined by the HOMA-IR index. There was no difference in telomere length between LBW and NBW subjects. When adjusting for birth weight and cohort effect, significant negative associations between telomere length and fasting glucose (P = 0.003) and HbA1c (P = 0.0008) were found. In conclusion, no significant difference in telomere length was found between LBW and NBW men. The telomere length was negatively associated with glucose concentrations and HbA1c levels within the normal non-diabetic range independent of birth weight.

Leukocyte and Skeletal Muscle Telomere Length and Body Composition in Monozygotic Twin Pairs Discordant for Long-term Hormone Replacement Therapy

Estrogen-based hormone replacement therapy (HRT) may be associated with deceleration of cellular aging. We investigated whether long-term HRT has effects on leukocyte (LTL) or mean and minimum skeletal muscle telomere length (SMTL) in a design that controls for genotype and childhood environment. Associations between telomeres, body composition, and physical performance were also examined. Eleven monozygotic twin pairs (age 57.6 ± 1.8 years) discordant for HRT were studied. Mean duration of HRT use was 7.3 ± 3.7 years in the user sister, while their co-twins had never used HRT. LTL was measured by qPCR and SMTLs by southern blot. Body and muscle composition were estimated by bioimpedance and computed tomography, respectively. Physical performance was measured by jumping height and grip strength. HRT users and non-users did not differ in LTL or mean or minimum SMTL. Within-pair correlations were high in LTL (r = 0.69, p = .020) and in mean (r = 0.74, p = .014) and minimum SMTL (r = 0.88, p = .001). Body composition and performance were better in users than non-users. In analyses of individuals, LTL was associated with BMI (r 2 = 0.30, p = .030), percentage total body (r 2 = 0.43, p = .014), and thigh (r 2 = 0.55, p = .004) fat, while minimum SMTL was associated with fat-free mass (r 2 = 0.27, p = .020) and thigh muscle area (r 2 = 0.42, p = .016). We found no associations between HRT use and telomere length. Longer LTLs were associated with lower total and regional fat, while longer minimum SMTLs were associated with higher fat-free mass and greater thigh muscle area. This suggests that telomeres measured from different tissues may have different associations with measures of body composition.

Role of telomeres and associated maintenance genes in Type 2 Diabetes Mellitus: A review

Type 2 Diabetes Mellitus (T2DM), a multifactorial complex disorder, is emerging as a major cause of morbidity, mortality and socio-economic burden across the world. Despite huge efforts in understanding genetics of T2DM, only ∼10% of the genetic factors have been identified so far. Telomere attrition, a natural phenomenon has recently emerged in understanding the pathophysiology of T2DM. It has been indicated that Telomeres and associated pathways might be the critical components in the disease etiology, though the mechanism(s) involved are not clear. Recent Genome Wide (GWAS) and Candidate Gene Case-Control Association Studies have also indicated an association of Telomere and associated pathways related genes with T2DM. Single Nucleotide Polymorphisms (SNPs) in the telomere maintenance genes: TERT, TERC, TNKS, CSNK2A2, TEP1, ACD, TRF1 and TRF2, have shown strong association with telomere attrition in T2DM and its pathophysiology, in these studies. However, the assessment has been made within limited ethnicities (Caucasians, Han Chinese cohort and Punjabi Sikhs from South Asia), warranting the study of such associations in different ethnic groups. Here, we propose the possible mechanisms, in the light of existing knowledge, to understand the association of T2DM with telomeres and associated pathways.

A short leucocyte telomere length is associated with development of insulin resistance

AIMS/HYPOTHESIS

A number of studies have shown that leucocyte telomere length (LTL) is inversely associated with insulin resistance and type 2 diabetes mellitus. The aim of the present longitudinal cohort study, utilising a twin design, was to assess whether shorter LTL predicts insulin resistance or is a consequence thereof.

METHODS

Participants were recruited between 1997 and 2000 through the population-based national Danish Twin Registry to participate in the GEMINAKAR study, a longitudinal evaluation of metabolic disorders and cardiovascular risk factors. Baseline and follow-up measurements of LTL and insulin resistance over an average of 12 years were performed in a subset of the Registry consisting of 338 (184 monozygotic and 154 dizygotic) same-sex twin pairs.

RESULTS

Age at baseline examination was 37.4 ± 9.6 (mean ± SD) years. Baseline insulin resistance was not associated with age-dependent changes in LTL (attrition) over the follow-up period, whereas baseline LTL was associated with changes in insulin resistance during this period. The shorter the LTL at baseline, the more pronounced was the increase in insulin resistance over the follow-up period (p < 0.001); this effect was additive to that of BMI. The co-twin with the shorter baseline LTL displayed higher insulin resistance at follow-up than the co-twin with the longer LTL.

CONCLUSIONS/INTERPRETATION

These findings suggest that individuals with short LTL are more likely to develop insulin resistance later in life. By contrast, presence of insulin resistance does not accelerate LTL attrition.

Movement-Based Behaviors and Leukocyte Telomere Length among US Adults

INTRODUCTION

Short leukocyte telomere length (LTL) has become a hallmark characteristic of aging. Some, but not all, evidence suggests that physical activity (PA) may play an important role in attenuating age-related diseases and may provide a protective effect for telomeres. The purpose of this study was to examine the association between PA and LTL in a national sample of US adults from the National Health and Nutrition Examination Survey.

METHODS

National Health and Nutrition Examination Survey data from 1999 to 2002 (n = 6503; 20-84 yr) were used. Four self-report questions related to movement-based behaviors (MBB) were assessed. The four MBB included whether individuals participated in moderate-intensity PA, vigorous-intensity PA, walking/cycling for transportation, and muscle-strengthening activities. An MBB index variable was created by summing the number of MBB an individual engaged in (range, 0-4).

RESULTS

A clear dose-response relation was observed between MBB and LTL; across the LTL tertiles, respectively, the mean numbers of MBB were 1.18, 1.44, and 1.54 (Ptrend < 0.001). After adjustments (including age) and compared with those engaging in 0 MBB, those engaging in 1, 2, 3, and 4 MBB, respectively, had a 3% (P = 0.84), 24% (P = 0.02), 29% (P = 0.04), and 52% (P = 0.004) reduced odds of being in the lowest (vs highest) tertile of LTL; MBB was not associated with being in the middle (vs highest) tertile of LTL.

CONCLUSIONS

Greater engagement in MBB was associated with reduced odds of being in the lowest LTL tertile.

Skeletal muscle ceramide species in men with abdominal obesity

BACKGROUND

Obesity is a risk factor for diabetes and its consequences, including accelerated ageing and mortality. The underlying factor could be accumulation of certain lipid moieties, such as ceramides (CER) and diacylgycerol (DAG) within muscle tissue, which are known to promote insulin resistance (IR), induce inflammation and oxidative injury, ultimately altering muscle function.

AIM

First, to study the relationship between body composition and age (independent variables) with skeletal muscle accumulation of lipid species, oxidative injury and strength. Second, to analyze the relationship between muscle tissue metabolites and insulin resistance, inflammation and lymphocyte telomere length, the latter as an indicator of ageing.

METHODOLOGY

The sample included 56 healthy sedentary males, scheduled for inguinal hernia surgery, aged 27 to 80 y. Each individual was subject to anthropometric measurements, body composition assessment through radiologic densitometry (DEXA), measurement of handgrip and quadriceps strength, serum biochemical parameters (lipoproteins, creatinine, high sensitivity C reactive protein [hsCRP], fasting and post glucose insulin and glucose concentrations for calculation of IR through the Matsuda and HOMA-IR indexes), and extraction of peripheral leukocytes for measurement of telomere length. During the surgical procedure, a sample of muscle tissue was obtained (anterior abdominal oblique) in order to measure CER and DAG (and sub species according to chain length and saturation) by mass spectrometry, 4 hydroxy-2-nonenal adducts (4-HNE) using electron microscopy immunohistochemistry, and carboxymethyl-lisine (CML) by immunohistochemistry, the latter as indicators of oxidative stress (OS).

RESULTS

Body mass index (BMI) of twenty six individuals was > 25 k/m2, while BMI of 7 was > 30 k/m2. Overweight/obese individuals, did not exhibit differences in skeletal muscle lipid metabolites, however total CER and specific long chain CER sub-species (20 and 22 carbon) increased significantly among individuals with a central fat distribution (n = 14) as well as in glucose intolerant subjects (n =23). A negative association was found between mononuclear leukocyte telomere length and 20 and 22 carbon CER (rho = - 0.4 and -0.5 0 p < 0.05). Muscle strength was not associated with any of the measured muscle metabolites or markers of OS. A multiple regression analysis accepted central abdominal fat and telomere length as significant predictors of CER (R2 = 0.28).

CONCLUSIONS

An association was found between accumulation of specific ceramide species in muscle tissue and abdominal obesity, glucose intolerance and shortening of leukocyte telomeres, although not with muscle oxidative injury or dysfunction.

The influence of the telomere-telomerase system on diabetes mellitus and its vascular complications

INTRODUCTION

The telomere-telomerase system plays an important role in the pathogenesis and disease progression of diabetes mellitus as well as in its vascular complications. Recent studies suggest that telomere shortening and abnormal telomerase activity occur in patients with diabetes mellitus, and targeting the telomere-telomerase system has become a prospective treatment for diabetes mellitus and its vascular complications. This review highlights the significance of the telomere-telomerase system and supports its role as a possible therapeutic target for patients with diabetes mellitus and its vascular complications Areas covered: This review covers the advances in understanding the telomere-telomerase system over the last 30 years and its significance in diabetes mellitus. In addition, it provides knowledge regarding the significance of the telomere-telomerase system in diabetes mellitus and its vascular complications as well as its role and mechanisms in oxidative stress, cell therapy and antioxidant activity Expert opinion: The telomere-telomerase system may be a potential therapeutic target that can protect against DNA damage and apoptosis in patients with diabetes mellitus and its vascular complications. DNA damage and apoptosis are associated with oxidative stress and are involved in the dysfunction of pancreatic β cells, insulin resistance, and its vascular complications. Abnormalities in the telomere-telomerase system may be associated with diabetes mellitus and its vascular complications. Therapies targeting telomere-telomerase system, telomerase reverse transcriptase transfection and alterative telomere lengthening must be identified before gene therapy can commence.

Telomeres and human health

Telomeres are the tips of chromosomes and consist of proteins and hexanucleotide tandem repeats of DNA. The DNA repeats are shortened at each mitotic division of normal cells, and the telomere length chronicles how many divisions the cell has undergone. Thus, telomere length is a marker of fundamental biological pathways. It has been possible to measure telomere length for more than 20 years, and it has been established that telomere length is associated with age, sex and lifestyle factors. Here, the current knowledge of telomere length as a biomarker of disease susceptibility and mortality will be reviewed. In addition, technical difficulties and the reasons why measurement of telomeres has still not been introduced into routine clinical practice will be discussed. Findings from recent studies conducted in many thousands of individuals indicate that telomere length is not-or at best only marginally-independently associated with risk of common disorders such as cardiovascular, pulmonary and neoplastic diseases. However, in sufficiently powered studies, short telomeres are repeatedly and independently found to be associated with increased risk of early death in the general population or in subsets of individuals. This indicates that measurement of telomeres could be a valuable prognostic biomarker in many clinical settings. However, whether short telomeres are a causal factor for or simply a marker of increased risk of early death must be determined. Finally, how Mendelian randomization studies could clarify this issue, and which clinical studies might be carried out to refine this very promising biomarker for routine clinical use will be considered.

Consumption of a low glycaemic index diet in late life extends lifespan of Balb/c mice with differential effects on DNA damage

BACKGROUND

Caloric restriction is known to extend the lifespan of all organisms in which it has been tested. Consequently, current research is investigating the role of various foods to improve health and lifespan. The role of various diets has received less attention however, and in some cases may have more capacity to improve health and longevity than specific foods alone. We examined the benefits to longevity of a low glycaemic index (GI) diet in aged Balb/c mice and examined markers of oxidative stress and subsequent effects on telomere dynamics.

RESULTS

In an aged population of mice, a low GI diet extended average lifespan by 12%, improved glucose tolerance and had impressive effects on amelioration of oxidative damage to DNA in white blood cells. Telomere length in quadriceps muscle showed no improvement in the dieted group, nor was telomerase reactivated.

CONCLUSION

The beneficial effects of a low GI diet are evident from the current study and although the impact to telomere dynamics late in life is minimal, we expect that earlier intervention with a low GI diet would provide significant improvement in health and longevity with associated effects to telomere homeostasis.

Telomere length and long-term endurance exercise: does exercise training affect biological age? A pilot study

Background

Telomeres are potential markers of mitotic cellular age and are associated with physical ageing process. Long-term endurance training and higher aerobic exercise capacity (VO_2max) are associated with improved survival, and dynamic effects of exercise are evident with ageing. However, the association of telomere length with exercise training and VO_2max has so far been inconsistent. Our aim was to assess whether muscle telomere length is associated with endurance exercise training and VO_2max in younger and older people.

Methods

Twenty men; 10 young (22–27 years) and 10 old (66–77 years), were studied in this cross-sectional study. Five out of 10 young adults and 5 out of 10 older were endurance athletes, while other halves were exercising at a medium level of activity. Mean telomere length was measured as telomere/single copy gene-ratio (T/S-ratio) using quantitative real time polymerase chain reaction. VO_2max was measured directly running on a treadmill.

Results

Older endurance trained athletes had longer telomere length compared with older people with medium activity levels (T/S ratio 1.12±0.1 vs. 0.92±0.2, p = 0.04). Telomere length of young endurance trained athletes was not different than young non-athletes (1.47±0.2 vs. 1.33±0.1, p = 0.12). Overall, there was a positive association between T/S ratio and VO_2max (r = 0.70, p = 0.001). Among endurance trained athletes, we found a strong correlation between VO_2max and T/S ratio (r = 0.78, p = 0.02). However, corresponding association among non-athlete participants was relatively weak (r = 0.58, p = 0.09).

Conclusion

Our data suggest that VO_2max is positively associated with telomere length, and we found that long-term endurance exercise training may provide a protective effect on muscle telomere length in older people.