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.

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Low-intensity exercise on the day of meal intake, particular after intake, can prevent the elevation of postprandial triglyceride concentration in healthy young subjects.

Improvement of glucose metabolism in the skeletal muscle has a key role in exercise performance and prevention of metabolic diseases. In our previous study, we showed that intake of milk casein hydrolysate improves glucose metabolism in humans, but the mechanism of action was not elucidated. In this study, we aimed to investigate the mechanism of action of milk casein hydrolysate and its derived peptides on glucose uptake and glucose metabolic signalling in cultured skeletal muscle cells. Differentiated C2C12 myotubes were used for the experiments. The differentiated cells were incubated with milk casein hydrolysate, valine-proline-proline and isoleucine-proline-proline. Subsequently, the rate of 2-deoxy-glucose uptake and the phosphorylation levels of insulin-dependent and-independent signalling factors were examined. We found that the rate of 2-deoxy-glucose uptake in both milk casein hydrolysate and isoleucine-proline-proline-treated cells was higher than that in the control cells. Immunoblotting assays showed that the phosphorylation levels of AMP-activated protein kinase, a rate-limiting factor in insulin-independent signalling, and of liver kinase B1, an upstream factor of AMP-activated protein kinase, in both milk casein hydrolysate and isoleucine-proline-proline-treated cells were higher than those in the control cells. Such significant effects were not observed after treatment with valineproline-proline. Moreover, the insulin-dependent signalling was not significantly affected under the different conditions. The findings of our study suggest that milk casein hydrolysate enhances glucose uptake by activating insulin-independent AMPactivated protein kinase signalling in skeletal muscle cells, which might be mediated by a milk casein hydrolysate-derived peptide, namely, isoleucine-proline-proline.

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PurposeWe investigated the effect of Katsura-uri (Japanese pickling melon; Cucumis melo var. conomon) on energy metabolism during exercise in human and animal studies.MethodsEight healthy men (mean age, 21.4 ± 0.7 years) participated in a single-blind, crossover study. Thirty minutes after ingesting the Katsura-uri drink or placebo drink, they exercised on a cycle ergometer at 40% maximal heart rate for 30 min. Respiratory gas analysis was performed during exercise to examine oxygen consumption and substrate utilization. Blood biochemical parameters were evaluated during exercise. In the animal study, the effect of methylthioacetic acid (MTA), a Katsura-uri derived component was examined in mice. Immediately after running at 25 m/min for 30 min, biochemical parameters in the hind limb muscle and blood of mice were measured.ResultsOxygen consumption during exercise was higher in the Katsura-uri condition (19.8 ± 3.5 mL/kg/min) than the placebo condition (18.6 ± 3.0 mL/kg/min) (P < 0.05). The elevation of blood lactate was lower in the Katsura-uri condition (1.7 ± 0.4 mM) than the placebo condition (2.2 ± 0.6 mM) 15 min after beginning exercise (P < 0.05). There was a higher positive correlation between lactate concentration and carbohydrate oxidation during exercise in the Katsura-uri condition (R2 = 0.86) compared to the placebo condition (R2 = 0.47). The decrease in intermuscular pH and the increase in blood lactate following exercise were prevented by MTA supplementation (250 ppm) with significant differences in the MTA-supplemented group compared to the control group.ConclusionsThese results suggest that the ingestion of Katsura-uri and/or MTA improves glucose metabolism and acidification in skeletal muscles during exercise in human and animal studies.

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Low birth weight has been reported as a risk factor for non-communicable diseases, which can be caused by metabolic dysfunction. Here, we conducted a retrospective study to define the correlation between birth weight and present physical characteristics/fitness in Japanese university students, by gender. The subjects were from among 1,333 healthy university students. They carried out a self-administered questionnaire on birth weight, physical characteristics, and exercise habits, and 8 types of physical fitness tests. We excluded data from subjects that lacked information in their questionnaire and those who were not a full-term single birth. Finally, data of 378 participants (28.4% of all subjects, 116 males and 262 females) were analyzed. We categorized the participants into lower and higher birth weight groups, based on the overall median value calculated for birth weight. The lower birth weight group of males demonstrated lower grip strength; however, there was no significant association after adjustment for height, weight, and exercise habits. The lower birth weight group of females showed higher scores on the 50-meter running test even after the adjustment for physical characteristics and exercise habits. These results suggest that lower birth weight males had a lower grip strength, which was strongly associated with their physical size. In contrast, higher sprint performance was shown to be independent of physical size in lower birth weight females.