Blood flow, lipid oxidation, and muscle glycogen synthesis after glycogen depletion by strenuous exercise

• Published in: Medicine and science in sports and exercise Vol. 29; no. 7; p. 874
• Main Authors: Tuominen, J A, Peltonen, J E, Koivisto, V A
• Format: Journal Article
• Language: English
• Published: United States 01.07.1997
• Subjects: Adult; Exercise - physiology; Exercise Test; Forearm - physiology; Glucose - metabolism; Glycogen - metabolism; Glycogen Synthase - physiology; Humans; Insulin; Leg - physiology; Lipid Metabolism; Male; Muscle, Skeletal - blood supply; Muscle, Skeletal - physiology; Oxidation-Reduction; Regional Blood Flow
• ISSN: 0195-9131
• DOI: 10.1097/00005768-199707000-00006

We studied the interrelationship between blood flow, glycogen synthesis, and glucose and lipid utilization in 14 healthy men. A 4-h euglycemic insulin clamp with indirect calorimetry and muscle biopsies were done after a glycogen depletion (exercise) and after a resting day (control). In spite of the exercise induced decrease in leg muscle glycogen content (28% in the basal state, 22% after hyperinsulinemia, P < 0.05 in both as compared with the control study), basal or insulin stimulated glycogen synthase activity remained unchanged. In the basal state, glucose oxidation was 54% lower (P < 0.001) and lipid oxidation 108% higher (P < 0.001) after the glycogen depletion as compared with that in the control study. During the post-depletion insulin clamp, the glucose oxidation rate was 17% lower (P < 0.02) and lipid oxidation 169% higher (P < 0.01), while the whole body total glucose disposal was similar in both studies. Baseline forearm blood flow was similar and increased equally by over 40% during both insulin clamp studies (P < 0.05). Basal glucose extraction after glycogen depletion study was one third of that in the control study (P < 0.05). Both basal and insulin stimulated leg muscle glycogen content correlated inversely with basal forearm blood flow (r = -0.69, P < 0.01 and r = -0.82, P < 0.001, respectively) and basal lipid oxidation (r = -0.54, P < 0.05 and r = -0.64, P < 0.01, respectively) after glycogen depletion. Basal glycogen synthase fractional activity correlated positively with forearm blood flow (r = 0.78, P < 0.001) and forearm glucose uptake (r = 0.71, P < 0.05) during the insulin infusion. 1) the unchanged insulin sensitivity in the face of glycogen depletion is probably a result of increased lipid oxidation, and 2) blood flow is related inversely to muscle glycogen content and directly to glycogen synthase activity.