Pre‐exercise casein hydrolysate ingestion activates AMP‐activated protein kinase signaling pathway in slow muscle fibers but not in fast fibers

Abstract

AimsThe aim of this study was to clarify the effect of casein hydrolysate ingestion on intracellular signal transduction pathway at rest or after exercise in skeletal muscle.MethodsEight weeks old male ICR mice were used and ingested either water or casein hydrolysate (0.2 mg/g BW) in this experiment. [Experiment 1: at rest] Mice were randomly divided into control group (CON) and casein hydrolysate ingestion group (CH). After ingestion, blood samples were collected from tail vein of mice (0, 15, 30, 45, 60 min). [Experiment 2: exercise] Mice were randomly divided into exercise group (Ex) and casein hydrolysate ingestion exercise group (CH+Ex). Mice were subjected to treadmill running (20 m/min, 60 min) 30 min after ingestion and blood samples were collected from tail vein of mice. Blood branched‐chain amino acid (BCAA) concentrations and AMP‐activated protein kinase (AMPK) phosphorylation were measured as intracellular signal transduction pathway.Results[Experiment 1] Positive main effects of casein hydrolysate on blood BCAA concentrations were observed (p<0.05). The phosphorylation status of AMPK showed no significant differences between the two groups. [Experiment 2] In plantaris muscle, the phosphorylation status of AMPK showed no significant differences between the two groups as with the case at rest. In contrast, in soleus muscle, the phosphorylation status of AMPK in CH+Ex group was significantly higher than that in Ex (p<0.05).ConclusionPre‐exercise casein hydrolysate ingestion activates AMP‐activated protein kinase signaling pathway in slow muscle fibers but not in fast fibers.