BackgroundThis study investigated the effect of fermented milk supplementation on glucose metabolism associated with muscle damage after acute exercise in humans.MethodsEighteen healthy young men participated in each of the three trials of the study: rest, exercise with placebo, and exercise with fermented milk. In the exercise trials, subjects carried out resistance exercise consisting of five sets of leg and bench presses at 70–100% 12 repetition maximum. Examination beverage (fermented milk or placebo) was taken before and after exercise in double-blind method. On the following day, we conducted an analysis of respiratory metabolic performance, blood collection, and evaluation of muscle soreness.ResultsMuscle soreness was significantly suppressed by the consumption of fermented milk compared with placebo (placebo, 14.2 ± 1.2 score vs. fermented milk, 12.6 ± 1.1 score, p < 0.05). Serum creatine phosphokinase was significantly increased by exercise, but this increase showed a tendency of suppression after the consumption of fermented milk. Exercise significantly decreased the respiratory quotient (rest, 0.88 ± 0.01 vs. placebo, 0.84 ± 0.02, p < 0.05), although this decrease was negated by the consumption of fermented milk (0.88 ± 0.01, p < 0.05). Furthermore, exercise significantly reduced the absorption capacity of serum oxygen radical (rest, 6.9 ± 0.4 μmol TE/g vs. placebo, 6.0 ± 0.3 μmol TE/g, p < 0.05), although this reduction was not observed with the consumption of fermented milk (6.2 ± 0.3 μmol TE/g).ConclusionThese results suggest that fermented milk supplementation improves glucose metabolism and alleviates the effects of muscle soreness after high-intensity exercise, possibly associated with the regulation of antioxidant capacity.

During exercise, the energy consumed in muscle tissue is mainly supplied by carbohydrates (CHO) and fats. In regard to health promotion and athletic sports, it is important to regulate the metabolism of these two substrates. Fats are supplied by meals, and also by adipose tissues, but CHO must be acquired from meals before exercise because little is stored as glycogen in the liver or muscle tissue. Previous studies have been conducted on the ergogenic effects of CHO feeding before exercise (1-10). It was reported that CHO solution (such as glucose and maltodextrin) feeding before exercise can improve exercise performance through enhanced endurance exercise capacity (2,4,5,10). Moreover, it was also reported that CHO mixed meal feeding before exercise can improve endurance exercise capacity (7,9,11).The intake of CHO elevates the secretion of insulin from the pancreas into the blood. Glucose and insulin in plasma reach a peak approximately 30 min after the ingestion of CHO and thereafter gradually decrease to the basal level. Insulin facilitates glucose uptake into skeletal muscle cells via the translocation of glucose transporter 4 (GLUT4) and then increases CHO oxidation. On the other hand, insulin prevents fat oxidation in muscle tissue by inhibition of lipoprotein lipase activity (12). Hyperinsulinemia tends to supply energy with a predominance of CHO over fats as the energy source in the initial period during exercise (7). Previous studies have shown, by examining timing of carbohydrate intake before exercise, that a shorter time from intake to exercise increases blood glucose and insulin levels at the start of exercise and these factors gradually decrease after the start of exercise (9, 10). Moreover, Chryssanthopoulos et al. (5) have reported that glucose intake at 30 min before exercise causes a rapid reduction of blood glucose after the beginning of exercise. On the other hand, Coyle et al. (13) have shown that carbohydrate utilization during exercise is higher under the condition of meal intake at 4 h before exercise compared with the fasting condition. Therefore, regardless of the timing of carbohydrate intake, it is likely that carbohydrate intake before exercise promotes its utilization as a major energy Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Hangi-cho, Shimogamo, Sakyo-ku, Kyoto, Kyoto 606-8522, Japan (Received June 5, 2013) Summary Although the intake of carbohydrates is important for the supplementation of energy substrate utilized during exercise, fat oxidation is possibly prevented by an elevation of insulin, and whether or not the timing of the intake of meals affects energy metabolism during exercise has not been clarified. The purpose of this study was to investigate the effect of the timing of the intake of meals taken at different times before exercise on the carbohydrate and fat metabolism during aerobic exercise. The subjects were eight young trained athletes who performed cycling exercise at the lactate threshold (LT) intensity for 60 min. They performe...

To study the mechanism of hyperinsulinism and glucose intolerance in liver disease, insulin removal rate by liver and muscle, glucose uptake by muscle and insulin secretion from pancreas were measured using the perfusion in rats with injured liver induced by carbon tetrachloride (liver injury rat). In the perfused liver, insulin removal rate of liver injury rat decreased to 62% of that of normal rat, but it did not alter in the perfused muscle. Insulin response to arginine by the perfused pancreas of liver injury rat was similar to that of normal rat. Before insulin infusion, glucose uptake by the perfused muscle was similar in liver injury rat and normal rat. In contrast, during insulin infusion, glucose uptake by the perfused muscle was 1.5 times higher in liver injury rat than in normal rat. These results suggested that the peripheral hyperinsulinism was solely due to decreased hepatic insulin degradation, but not hypersecretion of insulin from pancreas and furthermore, might suggest that the insulin resistance was related to appearance of biologically inactive endogenous insulin, because of exogenous insulin completely acting on peripheral target tissue.