Effects of metabolic stress and exercise on skeletal muscle structure and function

Introduction Obesity and diabetes induce structural and metabolic disturbances in insulin-sensitive tissues. Furthermore, physical exercise is one of the most prescribed lifestyle modifications to counteract these disturbances. However, comparisons of metabolic effects between different exercise modalities in an obesity context are scarce and require further investigation. Aims To investigate the metabolic effect of two isocaloric training programs: moderate-intensity endurance (END) or high intensity interval training (HIIT), in a mouse model of diet-induced obesity using a preventive and a treatment approach; and to investigate the effect of long-term diabetes and obesity on the skeletal muscle extracellular matrix (ECM). Methods Three different animal experiments were designed to achieve the aims of this thesis. 1) 72 male C57BL/6 mice were fed with standard CHOW or high-fat diet (HFD) for 10 weeks; simultaneously they underwent one of two different isocaloric exercise programs, constant-moderate (END) or high-intensity interval training (HIIT) for the same 10 weeks. 2) 72 male C57BL/6 mice were fed with standard CHOW or HFD for 10 weeks; then they underwent END or HIIT for another 10 weeks. In the third experiment, 51 male C57BL/6 mice were fed with standard CHOW or HFD for 15 weeks; then in a subset of each dietary group diabetes was induced. Subsequently, dietary intervention was continued for another 15 weeks. Results From a preventive perspective, END and HIIT induced similar metabolic benefits in HFD mice, however, only END normalized glucose metabolism markers. In already obese and insulin resistant mice, HIIT induced a better metabolic effect in quadriceps (skeletal muscle) and subcutaneous adipose tissue, whereas specific benefits were seen in the liver after END. Regarding the muscle ECM, diabetes induced a fibrotic profile. In contrast, HFD alone induced a dysregulation in ECM regulators. Conclusions Different exercise prescriptions exert differential metabolic benefits in high-fat fed mice. END induced greater desirable metabolic benefits in a preventive context, whereas HIIT appears to give greater efficacy in already obese and insulin-resistant mice. Future research should aim to explore the mechanisms behind these differential effects of exercise

Constant-Moderate and High-Intensity Interval Training Have Differential Benefits on Insulin Sensitive Tissues in High-Fat Fed Mice

In a mouse model of diet-induced obesity, this study determined if two exercise prescriptions with equivalent time and distance covered, [constant-moderate endurance (END) and high intensity interval training (HIIT)], exert differential metabolic benefits on insulin sensitive tissues. Male 10 week old C57BL/6 mice were fed a high fat diet (HFD; 45% kcal fat) ad libitum for 10 weeks and for a further 10 weeks they underwent END or HIIT training (3 × 40 min sessions/wk). Untrained HFD and chow-fed mice acted as controls. At 30 weeks of age, mice were sacrificed and quadriceps muscle, subcutaneous adipose tissue (SAT) and liver were excised. Neither END nor HIIT altered body weight or composition in HFD mice. In quadriceps, HFD decreased high-molecular weight adiponectin protein, which was normalized by END and HIIT. In contrast, HIIT but not END reversed the HFD-driven decrease in the adiponectin receptor 1 (AdipoR1). In SAT, both programs tended to decrease collagen VI protein (p = 0.07–0.08) in HFD, whereas only HIIT induced an increase in the mRNA (3-fold vs. HFD untrained) and protein (2-fold vs. HFD untrained) of UCP1. In liver, only END reversed collagen I accumulation seen in HFD untrained mice. Our results suggest that HIIT may promote better systemic metabolic changes, compared to END, which may be the result of the normalization of muscle AdipoR1 and increased UCP1 seen in SAT. However, END was more effective in normalizing liver changes, suggesting differential metabolic effects of END and HIIT in different tissues during obesity

Physiological relevance of aerobic exercise training for the preparation of bariatric surgery candidates

Bariatric surgery is popular among clinicians to treat obesity because of its high impact on body weight reduction. However, the fast rate of weight loss has several consequences, such as loss of muscle mass and strength, and functional capacity. Therefore, preoperative interventions are needed to secure the surgery’s success, where physical exercise could be an effective intervention. Nevertheless, the most effective preoperative exercise prescription, along with its potential post-surgical carry-over effects, is still unclear. Recent studies have highlighted that exercise programs that differ, for instance, in intensity, induce differential metabolic benefits, that seem to be tissue-specific. This might be clinically relevant since it has been described that obesity-related metabolic impairments are not stereotypical in humans. This brief review analyses some tissue-specific disturbances derived from obesity, and how aerobic exercise programs, particularly high-intensity interval training and moderate-intensity constant training could elicit differential benefits, particularly in candidates to undergo bariatric surgery.La cirugía bariátrica es popular para el tratamiento de la obesidad debido a su alto impacto sobre la reducción del peso corporal. Sin embargo, esta acelerada pérdida de peso tiene variadas consecuencias, tales como el descenso de masa y fuerza muscular, así como de la capacidad funcional. Por tanto, el manejo preoperatorio es necesario para asegurar el éxito quirúrgico, dentro de las cuales el ejercicio físico ocupa un lugar importante. No obstante, se desconoce la prescripción del ejercicio más efectiva en esta población, así como los potenciales efectos que puedan perdurar posterior a la cirugía. Estudios recientes destacan que programas de ejercicio que difieren, por ejemplo, en intensidad, inducen beneficios metabólicos diferenciales, los cuales parecer ser tejido-dependientes. Esto puede ser clínicamente relevante, considerando que las alteraciones metabólicas asociadas a obesidad no son estereotípicas en humanos. Esta breve revisión analiza algunas alteraciones derivadas de obesidad, las cuales se presentan de forma específica en diferentes tejidos, y además como diferentes programas de ejercicio aeróbico, tales como el interválico de alta intensidad como el de intensidad moderada y constante podrían provocar beneficios diferenciales, particularmente en candidatos a cirugía bariátrica.Sociedad Argentina de Fisiologí

Effect of high-intensity interval training on glycemic control in adults with type 1 diabetes and overweight or obesity : a randomized controlled trial with partial crossover

To study the effect of 12 weeks of high-intensity interval training (HIIT) on glycemic control in adults with type 1 diabetes and overweight or obesity. RESEARCH DESIGN AND METHODS Thirty inactive adults with type 1 diabetes who had BMI ≥25 kg/m2 and HbA1c ≥7.5% were randomized to 12 weeks of either HIIT exercise intervention consisting of 4 x 4-min HIIT (85–95% peak heart rate) performed thrice weekly or usual care control. In a partial crossover design, the control group subsequently performed the 12-week HIIT intervention. The primary end point was the change in HbA1c from baseline to 12 weeks. Glycemic and cardiometabolic outcomes were measured at 0, 12, and 24 weeks. RESULTS Participants were aged 44 ± 10 years with diabetes duration 19 ± 11 years and BMI 30.1 ± 3.1 kg/m2. HbA1c decreased from 8.63 ± 0.66% at baseline to 8.10 ± 1.04% at 12 weeks in the HIIT intervention group (P = 0.01); however, this change was not significantly different from the control group (HIIT-0.53 ± 0.61%, control-0.14 ± 0.48%, P = 0.08). In participants who undertook at least 50% of the prescribed HIIT intervention, the HbA1c reduction was significantly greater than control (HIIT-0.64 ± 0.64% [n = 9], control-0.14 ± 0.48% [n = 15], P = 0.04). There were no differences in insulin dose, hypoglycemia on continuous glucose monitoring, blood pressure, blood lipids, body weight, or body composition between groups. CONCLUSIONS Overall, there was no significant reduction in HbA1c with a 12-week HIIT intervention in adults with type 1 diabetes. However, glycemic control may improve for people who undertake HIIT with greater adherence