Numerous studies have reported that post-exercise ingestion of carbohydrates with protein supplementation can enhance glycogen recovery. However, few reports have focused on the degrees of degradation of the ingested proteins due to post-exercise glycogen resynthesis. Accordingly, the aim of this study was to clarify the effects of differences in protein degradation on muscle glycogen recovery. Male seven-week-old C57BL/6J mice performed a single bout of 60-min treadmill running exercise and were then orally administered glucose (Glu; 1.5 mg/g body weight (BW)), glucose with casein peptide (Glu + Pep; 1.5 + 0.5 mg/g BW) or its constituent amino acid mixture (Glu + AA; 1.5 + 0.5 mg/g BW). At 120 min after supplementation, the soleus muscle glycogen content in the Glu and Glu + AA groups was significantly higher than that immediately after exercise; however, no such difference was observed in the Glu + Pep group. Blood substrate concentration and insulin signaling did not differ among the three groups. Furthermore, energy expenditure during the recovery period in the Glu + Pep group was significantly higher than that in the Glu and Glu + AA groups. These findings suggest that post-exercise co-ingestion of glucose and casein peptide might delay glycogen resynthesis, at least in part through increased energy expenditure caused by casein peptide ingestion.
Background Few studies have evaluated differences in the curd-forming ability of casein on gastric volume and content directly after ingestion in humans. Objectives This study evaluated the time course of gastric volume and curd conditions in the stomach after protein ingestion. Methods This was an open-labeled, randomized crossover trial. Ten healthy men (age: 33.4 ± 7.3 y; body mass index: 21.9 ± 0.9 kg/m2) received 350 g of three isonitrogenous and isocaloric protein drinks containing 30 g of micellar casein (MCN), sodium caseinate (SCN), or whey protein concentrate (WPC). The gastric antrum cross-sectional area (CSA) and curd in the stomach were measured using ultrasonography within 5 h after ingestion. The differences between test foods were tested using the MIXED model and post-hoc tests using Fisher's protected least significant difference. Results The incremental area under the curve of the gastric antrum CSA after MCN ingestion was 1.3-fold and 1.5-fold higher than that after the ingestion of SCN and WPC, respectively (both P < 0.05), but not different between SCN and WPC. The number of participants with curds of ≥ 20 mm with a high echogenicity clot observed in the stomach within 5 h after MCN ingestion was significantly greater than that after the ingestion of other proteins (n = 9 for MCN, n = 2 for SCN, and n = 0 for WPC, both P < 0.01). The regression line slopes on total plasma amino acid concentration and gastric antrum CSA were significantly different between the participants with and without curds. Conclusion In contrast to SCN and WPC, MCN ingestion resulted in slow kinetics of gastric antrum CSA. Differences in curd formation in the stomach affect gastric emptying and plasma amino acid absorption kinetics after casein ingestion in healthy men. This trial was registered as UMIN000038388 (https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000043746).
BackgroundSkeletal muscle atrophy is caused by a variety of diseases and conditions. In particular, skeletal muscle atrophy in the elderly contributes to a loss of independence with advanced age and increases the risk of falling. However, the effect of food consumed on a daily basis on skeletal muscle atrophy has been the focus of little research. In this study, the effects of dietary supplementation with shiikuwasha extract or grape extract on dexamethasone-induced skeletal muscle atrophy were evaluated in aged rats.MethodsAged male rats (15-month-old) were fed a diet supplemented with either 1 % shiikuwasha extract or 1 % grape extract for 19 days. During the last 5 days of the feeding period, rats were injected with dexamethasone to induce muscle atrophy.ResultsBody weight and hind-limb muscle weight were significantly decreased by dexamethasone treatment. The supplementation of shiikuwasha extract showed no effect on body weight loss, but markedly attenuated tibialis anterior muscle weight loss induced by dexamethasone. On the other hand, grape extract did not affect muscle weight loss. Furthermore, shiikuwasha extract significantly reduced dexamethasone-induced expression of atrogin-1 and MuRF1 mRNA, but did not reduce LC3B-II protein levels.ConclusionThese results suggest that shiikuwasha extract may partially inhibit the activation of the ubiquitin–proteasome system and may consequently attenuate skeletal muscle atrophy induced by dexamethasone in aged rats.
In post-stroke hemiparesis patients, the skeletal muscle mass decrease rapidly with the histological degradation. We investigated the effect of nutritional supplementation with whey protein and vitamin D on the muscle mass and muscle quality, in post-stroke convalescent rehabilitation patients in a randomized, single-blinded, placebo-controlled trial. Fifty patients were randomly assigned to two groups; HP group received supplemental jelly (100 kcal; whey protein 10 g; vitamin D 20 μg) twice a day throughout up to 16-week period, the control group received placebo jelly. Cross-sectional area (CSA) of thigh muscle, skeletal muscle index (SMI), muscle strength, activity of daily living (ADL), and some nutritional indicators in blood were measured. Although no significant difference was observed in CSA and SMI between the groups, fat infiltration into the thighs muscle was singnificantly lower in the HP group. There were no significant difference in muscle strength and ADL between the groups. Blood urea nitrogen and serum 25(OH)D at endpoint were significantly higher in the HP group but physiological normal ranges. Supplementation with whey protein and vitamin D in post-stroke patients led to suppression of fat infiltration into the muscle. Long-term follow-up studies are needed to verify whether this nutritional intervention provides substantial benefits for the prognosis of stroke survivors.
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