Remodeling of the sperm epigenome by lifestyle factors before conception could account for altered metabolism in the next generation offspring. Here, we hypothesized that endurance training changes the epigenome of human spermatozoa. Using small RNA (sRNA) sequencing and reduced representation bisulfite sequencing (RRBS), we, respectively, investigated sRNA expression and DNA methylation in pure fractions of motile spermatozoa collected from young healthy individuals before, after 6 weeks of endurance training and after 3 months without exercise. Expression of 8 PIWI interacting RNA were changed by exercise training. RRBS analysis revealed 330 differentially methylated regions (DMRs) after training and 303 DMRs after the detraining period, which were, in both conditions, enriched at close vicinity of transcription start sites. Ontology analysis of genes located at proximity of DMRs returned terms related to neurological function at the trained state and, to a much lesser extent, at the detrained state. Our study reveal that short-term endurance training induces marked remodeling of the sperm epigenome, and identify genes related to the development of the central nervous system as potential hot spots for epigenetic variation upon environmental stress.Electronic supplementary materialThe online version of this article (10.1186/s13148-018-0446-7) contains supplementary material, which is available to authorized users.

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Exercising at different times of day elicits different effects on exercise performance and metabolic health. However, the specific signals driving the observed time-of-day specific effects of exercise have not been fully identified. r Exercise influences the skeletal muscle circadian clock, although the relative contribution of muscle contraction and extracellular signals is unknown. r Here, we show that contraction acutely increases the expression of the core circadian clock gene Period Circadian Regulator 2 (Per2) and phase-shifts Per2 rhythmicity in muscle cells. This contraction effect on core clock genes is mediated through a calcium-dependant mechanism; r The results obtained in the present study suggest that a proportion of the ability of exercise to entrain the skeletal muscle clock is driven directly by muscle contraction. Contraction interventions may be used to mimic some time-of-day specific effects of exercise on metabolism and muscle performance.

Exercise training triggers numerous positive adaptations through the regulation of genes controlling muscle structure and function. Epigenetic modifications, including DNA methylation, participate in transcriptional activation by allowing the recruitment of the transcription machinery to gene promoters. Exercise induces dynamic DNA demethylation at gene promoters; however, the contribution of the demethylation precursor hydroxymethylcytosine is unknown. Given the evanescent nature of hydroxymethylcytosine, a muscle contraction model that allows for the collection of samples that are repeatedly stimulated over time is required to determine whether contraction-induced demethylation is preceded by changes in the hydroxymethylcytosine level. Here, we established an acute skeletal muscle contraction model to mimic the effects of acute exercise on gene expression. We used this model to investigate the effect of muscle contraction on DNA demethylation and hydroxymethylation. First, we performed an acute exercise study in healthy humans to identify an exercise-responsive gene that we could study in culture. We identified the nuclear receptor subfamily 4 group A member 3 (Nr4a3) gene with the highest fold-expression increase after acute exercise. We then refined an electrical pulse stimulation (EPS) protocol that could induce expression of the Nr4a3 gene in C2C12 myotubes. Using targeted bisulfite sequencing, we found that in response to EPS, a region of the Nr4a3 promoter is rapidly demethylated at 60 min and re-methylated at 120 min. Of interest, hydroxymethylation of the differentially methylated region of Nr4a3 promoter after EPS was elevated immediately after EPS, with lowest levels reached at 60 min after EPS. In conclusion, we have established a cell culture-based protocol to mimic the acute transcriptional responses to exercise. Furthermore, we provide insight into the mechanism by which the exercise-responsive gene Nr4a3 is demethylated after muscle contraction.

Chronic hyperglycemia is associated with low response to aerobic exercise training in rodent models and humans, including reduced aerobic exercise capacity and impaired oxidative remodeling in skeletal muscle. Here, we investigated whether glucose lowering with the sodium glucose cotransporter-2 inhibitor (SGLT2i), canagliflozin (Cana; 30 mg/kg/day), could restore exercise training response in a model of hyperglycemia (low dose streptozotocin; STZ). Cana effectively prevented increased blood glucose in STZ-treated mice. After 6 weeks of voluntary wheel running, Cana-treated mice displayed improvements in aerobic exercise capacity, higher capillary density in striated muscle, and a more oxidative fiber-type in skeletal muscle. In contrast, these responses were blunted or absent in STZ mice. Recent work implicates glucose-induced accumulation of skeletal muscle extracellular matrix (ECM) and hyper-activation of JNK/SMAD2 mechanical signaling as potential mechanisms underlying poor exercise response. In line with this, muscle ECM accretion was prevented by Cana in STZ-treated mice. JNK/SMAD2 signaling with acute exercise was 2-fold higher in STZ compared to Control but was normalized by Cana. In human participants, ECM accumulation was associated with increased JNK signaling, low VO2peak and impaired metabolic health (siOGTT). These data demonstrate that hyperglycemia-associated impairments in exercise adaptation can be ameliorated by co-therapy with SGLT2i.

Exercise training improves skeletal muscle function, notably through tissue regeneration by muscle stem cells. Here, we hypothesized that exercise training reprograms the epigenome of muscle cell, which could account for better muscle function. Genome-wide DNA methylation of myotube cultures established from middle-aged obese men before and after endurance exercise training identified a differentially methylated region (DMR) located downstream of Gremlin 1 (GREM1), which was associated with increased GREM1 expression. GREM1 expression was lower in muscle satellite cells from obese, compared to lean mice, and exercise training restored GREM1 levels to those of control animals. We show that GREM1 regulates muscle differentiation through the negative control of satellite cell self-renewal, and that GREM1 controls muscle lineage commitment and lipid oxidation through the AMPK pathway. Our study identifies novel functions of GREM1 and reveals an epigenetic mechanism by which exercise training reprograms muscle stem cells to improve skeletal muscle function.

■ AbstractOBJECTIVES: Diabetes and exercise training have been shown to involve interleukin 6 (IL-6) signaling in muscle. However, the relationship between the actions of these two stimuli on muscle IL-6 and their downstream components is still unknown. Thus, the effect of endurance training on the key components of muscle IL-6 signaling transduction was investigated in a rat model of type 2 diabetes. METHODS: Diabetes was induced by streptozotocin (STZ) in male Wistar rats fed a high-fat diet, with normal rats acting as controls. The animals were left to conduct their normal activities or assigned to endurance training in a treadmill. At the end of 8 weeks, blood biochemical profiles, exercise performance, muscle oxidative capacity, glucose transporter 4 (GLUT4) protein distribution, and expressions of IL-6 and its downstream proteins were determined. RESULTS: Blood biochemical profiles of the diabetic rats were altered compared to normal rats, whereas endurance training improved blood chemistry and exercise performance. It also increased muscle oxidative capacity, and promoted GLUT4 subcellular localization to the membrane in muscles. Furthermore, protein expression of IL-6 receptor (IL-6Rα) was increased in both normal and diabetic rats after endurance training, but no significant changes in IL-6, phosphorylated signal transducer and activator of transcription 3 (p-STAT3), or suppressor of cytokine signaling 3 (SOC3) were observed in muscles of normal and diabetic rats. CONCLUSIONS: IL-6 signaling pathway mediating muscle response to endurance training was conserved in type 2 diabetes. There was no link between training-induced IL-6 downstream targets in skeletal muscles and IL-6-induced type 2 diabetes.

Hyperglycemia is associated with lower aerobic exercise capacity (VO2peak) in humans and rodent models. We tested whether reducing blood glucose levels with a dietary intervention can restore VO2peak in hyperglycemic mice. Male and female CD-1 mice were injected with low dose streptozotocin (STZ) to induce moderate hyperglycemia (>200 mg/dL). Hyperglycemic mice were randomized to receive a standard diet (STZ-CHOW) or a ketogenic diet (STZ-KETO). KETO significantly reduced blood glucose in STZ-treated mice. Next, both groups underwent similar volumes of exercise training by voluntary wheel running, or remained sedentary for 8 wks. In males, VO2peak during maximal exercise testing was similar in sedentary mice, regardless of diet. However, with training, VO2peak was significantly improved in STZ-KETO, but not STZ-CHOW males (see Figure). In females, KETO significantly increased VO2peak in sedentary mice, with no additional increase in response to training. Improved VO2peak with KETO in females was associated with a 50% increase in skeletal muscle mitochondrial ATP synthase protein. In contrast, ATP synthase was not regulated by diet in males. Our data demonstrate that a ketogenic diet can improve VO2peak in mice with hyperglycemia. In males, improved VO2peak with KETO was exercise-dependent, while in females, the beneficial effects of KETO on VO2peak and mitochondrial content were exercise-independent. Disclosure P.Pattamaprapanont: None. M.Formato: None. R.Nogueira soares: None. S.J.Lessard: None.