We investigated whether post-exercise capsinoids (CSN) supplementation could enhance muscle glycogen resynthesis via GLUT4/Akt expressions in human skeletal muscle. Nine male college students (aged 21.4±0.2 years, BMI 21.9±1.3 kg/m2, VO2max 47.1±1.8 ml/kg/min) participated in this crossover designed study, and completed a 60-min cycling exercise at 70% VO2max. Immediately after exercise, participants consumed high-carbohydrate diet (2 g carb/kg bodyweight) with CSN (12 mg, single dosage) or placebo. Biopsied muscle samples (vastus lateralis) were obtained immediately (0h) and 3h after exercise. Blood and expired gas samples were collected before and after exercise. We found oral CSN supplementation immediately after exercise was unable to enhance glycogen resynthesis in exercised human skeletal muscle. Despite, CSN could alter the energy reliance on fat oxidation during post-exercise recovery, based on gaseous exchange measurement (NEFA and glycerol). We further identified no significant differences in postprandial glucose/insulin area under curve in both trials. Western blot data showed no significant response of p-Akt/Akt ratio with CSN during post-exercise recovery. Inconsistent with glycogen levels, muscle GLUT4 expression was significantly elevated at 3h in CSN trial. Our findings emphasize the necessity of further evidences to confirm the ergogenic properties of CSN in connection with glycogen recovery in exercised human skeletal muscle.

Rho guanosine triphosphatases (GTPases) are key regulators in a number of cellular functions, including actin cytoskeleton remodeling and vesicle traffic. Traditionally, Rho GTPases are studied because of their function in cell migration and cancer, while their roles in metabolism are less documented. However, emerging evidence implicates Rho GTPases as regulators of processes of crucial importance for maintaining metabolic homeostasis. Thus, the time is now ripe for reviewing Rho GTPases in the context of metabolic health. Rho GTPase-mediated key processes include the release of insulin from pancreatic β-cells, glucose uptake into skeletal muscle and adipose tissue, and muscle mass regulation. Through the current review, we cast light on the important role of Rho GTPases in skeletal muscle, adipose tissue, and the pancreas and mechanisms by which Rho GTPases act to regulate glucose metabolism in health and disease. We also describe challenges and goals for future research.