Familiality of triglyceride and LPL response to exercise training: the HERITAGE study

The HERITAGE Family Study: A Review of the Effects of Exercise Training on Cardiometabolic Health, with Insights into Molecular Transducers

The aim of the HERITAGE Family Study was to investigate individual differences in response to a standardized endurance exercise program, the role of familial aggregation, and the genetics of response levels of cardiorespiratory fitness and cardiovascular disease and diabetes risk factors. Here we summarize the findings and their potential implications for cardiometabolic health and cardiorespiratory fitness. It begins with overviews of background and planning, recruitment, testing and exercise program protocol, quality control measures, and other relevant organizational issues. A summary of findings is then provided on cardiorespiratory fitness, exercise hemodynamics, insulin and glucose metabolism, lipid and lipoprotein profiles, adiposity and abdominal visceral fat, blood levels of steroids and other hormones, markers of oxidative stress, skeletal muscle morphology and metabolic indicators, and resting metabolic rate. These summaries document the extent of the individual differences in response to a standardized and fully monitored endurance exercise program and document the importance of familial aggregation and heritability level for exercise response traits. Findings from genomic markers, muscle gene expression studies, and proteomic and metabolomics explorations are reviewed, along with lessons learned from a bioinformatics-driven analysis pipeline. The new opportunities being pursued in integrative -omics and physiology have extended considerably the expected life of HERITAGE and are being discussed in relation to the original conceptual model of the study.

Nicotinamide riboside-A missing piece in the puzzle of exercise therapy for older adults?

Maintaining physical mobility is important for preventing age-related comorbidities in older adults. Endurance and resistance training prevent mobility loss in aging, but exercise alone does not always achieve the expected improvements in physical and cardiopulmonary function. Recent preclinical evidence suggests that a reason for the variability in exercise training responses may be the age-related dysregulation of the nicotinamide adenine dinucleotide (NAD+) metabolome. NAD+ is an essential enzymatic cofactor in energetic and signaling pathways. Endogenous NAD+ pool is lower in several chronic and degenerative diseases (e.g., cardiovascular diseases, Alzheimer's and Parkinson's diseases, muscular dystrophies), and also in aging. Exercise requires a higher energy expenditure than a resting state, thus a state of NAD+ insufficiency with reduced energy metabolism, could result in an inadequate exercise response. Recently, the NAD+ precursor nicotinamide riboside (NR), a vitamin B3 derivate, showed an ability to improve NAD+ metabolome homeostasis, restoring energy metabolism and cellular function in various organs in animals. NR has also been tested in older humans and is considered safe, but the effects of NR supplementation alone on physical performance are unclear. The purpose of this review is to examine the preclinical and clinical evidence on the effect of NR supplementation strategies alone and in combination with physical activity on mobility and skeletal muscle and cardiovascular function.

Precision exercise medicine: understanding exercise response variability

There is evidence from human twin and family studies as well as mouse and rat selection experiments that there are considerable interindividual differences in the response of cardiorespiratory fitness (CRF) and other cardiometabolic traits to a given exercise programme dose. We developed this consensus statement on exercise response variability following a symposium dedicated to this topic. There is strong evidence from both animal and human studies that exercise training doses lead to variable responses. A genetic component contributes to exercise training response variability.

In this consensus statement, we (1) briefly review the literature on exercise response variability and the various sources of variations in CRF response to an exercise programme, (2) introduce the key research designs and corresponding statistical models with an emphasis on randomised controlled designs with or without multiple pretests and post-tests, crossover designs and repeated measures designs, (3) discuss advantages and disadvantages of multiple methods of categorising exercise response levels—a topic that is of particular interest for personalised exercise medicine and (4) outline approaches that may identify determinants and modifiers of CRF exercise response. We also summarise gaps in knowledge and recommend future research to better understand exercise response variability.

MicroRNAs associated with exercise and diet: a systematic review

MicroRNAs are posttranscriptional regulators of gene expression. MicroRNAs reflect individual biologic adaptation to exposures in the environment. As such, measurement of circulating microRNAs presents an opportunity to evaluate biologic changes associated with behavioral interventions (i.e., exercise, diet) for weight loss. The aim of this study was to perform a systematic review of the literature to summarize what is known about circulating microRNAs associated with exercise, diet, and weight loss. We performed a systematic review of three scientific databases. We included studies reporting on circulating microRNAs associated with exercise, diet, and weight loss in humans. Of 1,219 studies identified in our comprehensive database search, 14 were selected for inclusion. Twelve reported on microRNAs associated with exercise, and two reported on microRNAs associated with diet and weight loss. The majority of studies used a quasiexperimental, cross-sectional design. There were numerous differences in the type and intensity of exercise and dietary interventions, the biologic source of microRNAs, and the methodological approaches used quantitate microRNAs. Data from several studies support an association between circulating microRNAs and exercise. The evidence for an association between circulating microRNAs and diet is weaker because of a small number of studies. Additional research is needed to validate previous observations using methodologically rigorous approaches to microRNA quantitation to determine the specific circulating microRNA signatures associated with behavioral approaches to weight loss. Future directions include longitudinal studies to determine if circulating microRNAs are predictive of response to behavioral interventions.

Polygenic risk for hypertriglyceridemia is attenuated in Japanese men with high fitness levels

High cardiorespiratory fitness (CRF) is associated with a reduced risk for dyslipidemia; however, blood lipid levels are also affected by individual genetic variations. We performed a cross-sectional study to determine whether CRF modifies polygenic risk for dyslipidemia. Serum levels of triglycerides (TG), LDL cholesterol (LDL-C), and HDL cholesterol (HDL-C) were measured in 170 Japanese men (age 20–79 yr). CRF was assessed by measuring maximal oxygen uptake (V̇o2max), and subjects were divided into low-fitness and high-fitness groups according to the reference V̇o2max value for health promotion in Japan. We analyzed 19 single nucleotide polymorphisms (SNPs) associated with TG, LDL-C, or HDL-C levels. Based on these SNPs, we calculated three genetic risk scores (GRSs: TG-GRS, LDL-GRS, and HDL-GRS), and subjects were divided into low, middle, and high groups according to the tertile for each GRS. Serum TG levels of low-fitness individuals were higher in the high and middle TG-GRS groups than in the low TG-GRS group ( P < 0.01 and P < 0.05, respectively), whereas no differences were detected in the TG levels of high-fitness individuals among the TG-GRS groups. In contrast, the high LDL-GRS group had higher LDL-C levels than did the low LDL-GRS group, and HDL-C levels were lower in the high HDL-GRS group than in the low HDL-GRS group regardless of the fitness level ( P < 0.05). These results suggest that high CRF attenuates polygenic risk for hypertriglyceridemia; however, high CRF may not modify the polygenic risk associated with high LDL-C and low HDL-C levels in Japanese men.

Adverse metabolic response to regular exercise: is it a rare or common occurrence?

Background

Individuals differ in the response to regular exercise. Whether there are people who experience adverse changes in cardiovascular and diabetes risk factors has never been addressed.

Methodology/Principal Findings

An adverse response is defined as an exercise-induced change that worsens a risk factor beyond measurement error and expected day-to-day variation. Sixty subjects were measured three times over a period of three weeks, and variation in resting systolic blood pressure (SBP) and in fasting plasma HDL-cholesterol (HDL-C), triglycerides (TG), and insulin (FI) was quantified. The technical error (TE) defined as the within-subject standard deviation derived from these measurements was computed. An adverse response for a given risk factor was defined as a change that was at least two TEs away from no change but in an adverse direction. Thus an adverse response was recorded if an increase reached 10 mm Hg or more for SBP, 0.42 mmol/L or more for TG, or 24 pmol/L or more for FI or if a decrease reached 0.12 mmol/L or more for HDL-C. Completers from six exercise studies were used in the present analysis: Whites (N = 473) and Blacks (N = 250) from the HERITAGE Family Study; Whites and Blacks from DREW (N = 326), from INFLAME (N = 70), and from STRRIDE (N = 303); and Whites from a University of Maryland cohort (N = 160) and from a University of Jyvaskyla study (N = 105), for a total of 1,687 men and women. Using the above definitions, 126 subjects (8.4%) had an adverse change in FI. Numbers of adverse responders reached 12.2% for SBP, 10.4% for TG, and 13.3% for HDL-C. About 7% of participants experienced adverse responses in two or more risk factors.

Conclusions/Significance

Adverse responses to regular exercise in cardiovascular and diabetes risk factors occur. Identifying the predictors of such unwarranted responses and how to prevent them will provide the foundation for personalized exercise prescription.

Do genetic variations alter the effects of exercise training on cardiovascular disease and can we identify the candidate variants now or in the future?

Cardiovascular disease (CVD) and CVD risk factors are highly heritable, and numerous lines of evidence indicate they have a strong genetic basis. While there is nothing known about the interactive effects of genetics and exercise training on CVD itself, there is at least some literature addressing their interactive effect on CVD risk factors. There is some evidence indicating that CVD risk factor responses to exercise training are also heritable and, thus, may have a genetic basis. While roughly 100 studies have reported significant effects of genetic variants on CVD risk factor responses to exercise training, no definitive conclusions can be generated at the present time, because of the lack of consistent and replicated results and the small sample sizes evident in most studies. There is some evidence supporting “possible” candidate genes that may affect these responses to exercise training: APO E and CETP for plasma lipoprotein-lipid profiles; eNOS, ACE, EDN1, and GNB3 for blood pressure; PPARG for type 2 diabetes phenotypes; and FTO and BAR genes for obesity-related phenotypes. However, while genotyping technologies and statistical methods are advancing rapidly, the primary limitation in this field is the need to generate what in terms of exercise intervention studies would be almost incomprehensible sample sizes. Most recent diabetes, obesity, and blood pressure genetic studies have utilized populations of 10,000–250,000 subjects, which result in the necessary statistical power to detect the magnitude of effects that would probably be expected for the impact of an individual gene on CVD risk factor responses to exercise training. Thus at this time it is difficult to see how this field will advance in the future to the point where robust, consistent, and replicated data are available to address these issues. However, the results of recent large-scale genomewide association studies for baseline CVD risk factors may drive future hypothesis-driven exercise training intervention studies in smaller populations addressing the impact of specific genetic variants on well-defined physiological phenotypes.