Effects of Prior High-Intensity Exercise on Glucose Metabolism in Normal and Insulin-resistant Men

Abstract

The effects of prior high-intensity cycle exercise (85% VO2 max) to muscular exhaustion on basal and insulin-stimulated glucose metabolism were studied in obese, insulin-resistant, and normal subjects. Six obese (30.4% fat) and six lean (14.5% fat) adult males underwent two separate, two-level hyperinsulinemic-euglycemic clamp studies (100-min infusions at 40 and 400 mU/m2/min), with and without exercise 12 h earlier. Carbohydrate oxidation was estimated by indirect calorimetry using a ventilated hood system, and endogenous glucose production by D-(3-3H)-glucose infusion. Glycogen content and glycogen synthase activity (GS %l) were measured in vastus lateralis muscle biopsies before and at the end of each insulin clamp procedure. After exercise, the obese and lean subjects had comparably low muscle glycogen concentrations (0.10 versus 0.08 mg/g protein, respectively), and equal activation of muscle GS activity (54.4 versus 45.3 GS %l, respectively). In the obese subjects, insulin-stimulated glucose disposal was increased significantly, but not totally corrected to normal. In both groups there was a comparable increase in nonoxidative glucose disposal (NOGD), whereas glucose oxidation was decreased and lipid oxidation was increased. Thus, the major effect of prior exercise was to increase insulin-stimulated glucose disposal in the obese subjects and to alter the pathways of glucose metabolism to favor NOGD and decrease glucose oxidation. No correlation was found between the exercise-induced increase in GS %l and NOGD, except in the normal subjects during maximal insulin stimulation. Thus, glycogen synthase activity does not appear to be rate-limiting for NOGD at physiologic insulin concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-Term Moderate Weight Loss and Resistance Training Do Not Affect Insulin-Stimulated Glucose Disposal in Postmenopausal Women

“…As reported by Mikines et al (43), one single session of aerobic exercise increased insulin action for up to 48 h after the exercise, with no remaining effect observed after 5 days. Various investigators have also demonstrated that one session of aerobic or resistance exercise and 1 week of vigorous aerobic exercise also decreases the insulin response to a glucose challenge when the measurements were made 24 h after the last exercise session (21,41,42,44). However, the results of this study do not contradict the importance of exercise as a therapeutic tool in the management of glucose metabolism in obese and insulinresistant individuals.…”

“…One major methodological difference is that metabolic parameters were reassessed 24 h after the last exercise session in those studies, whereas glucose disposal was measured 72 h after resistance training in the current study. There is evidence to show that the time of metabolic reevaluation is important when considering the effect of acute or training exercise on glucose metabolism (41)(42)(43). As reported by Mikines et al (43), one single session of aerobic exercise increased insulin action for up to 48 h after the exercise, with no remaining effect observed after 5 days.…”

Exercise training increases insulin-stimulated glucose disposal and GLUT4 (SLC2A4) protein content in patients with type 2 diabetes

“…Thus, exercise has been considered to have positive effects on whole-body glucose homeostasis, and it has been suggested that these effects on metabolism bypass defects in insulin signalling in type 2 diabetes [6]. In insulin-resistant humans, whole-body glucose disposal was increased between 12 and 48 h after an acute bout of exercise in some [33,34], but not all [2] studies. Here we report that whole-body insulin-mediated glucose disposal was unaltered in obese non-diabetic and obese type 2 diabetic subjects 16 h after 1 h of cycle ergometer exercise performed at 75% VO 2peak .…”

Role and Management of Exercise in Diabetes Mellitus

“…Hepatic glycogen stores recover at a slower rate. When studied 12-14 h after high-intensity cycle exercise, glucose oxidation and turnover rates are lower than in the nonexercised state and FFA oxidation rates are increased (56). In response to insulin infusion, total glucose disposal is increased only slightly, but there is a marked change in the metabolic pathways of glucose metabolism.…”

“…After glycogen-depleting exercise, glucose oxidation rates are decreased and nonoxidative glucose disposal, presumably representing primarily glycogen synthesis, is markedly increased. Thus, part of the increased insulin sensitivity and glucose utilization after exercise is related to the resynthesis of depleted muscle glycogen stores (56,57).…”