Abstract
Dietary protein intake is important for skeletal muscle protein synthesis. In this study, we investigated the differential effect of protein sources on hypertrophy of plantaris muscle induced by surgical ablation of gastrocnemius and soleus muscles. Six-week old mice were fed diets containing caseinate, whey, or soy as protein sources for 2 weeks. Plantaris muscle hypertrophy was induced by a unilateral ablation of synergistic muscles after a week. Food intake of soy protein-fed mice was higher than that of caseinate and whey-fed mice, resulting in higher body and fat weights. Plantaris muscle weight in sham-operated mice was not different across the groups. Overload-operated plantaris muscle weight and increased ratio of overloaded muscle to sham-operated muscle weights were higher in caseinate-fed mice than in whey- and soy protein-fed mice, suggesting caseinate as a promising protein source for muscle hypertrophy.
Highlights
Skeletal muscles play important roles in extending healthy life expectancy
We showed that the type of protein source affects functionally overloaded muscle hypertrophy, whereas there is no effect on sham-operated muscle weight
Induced higher muscle hypertrophy compared to whey and soy proteins, indicating that caseinate intake, as a daily protein source, may lead to muscle hypertrophy in a long-term intake/exercise model compared to whey and soy protein intake
Summary
Skeletal muscles play important roles in extending healthy life expectancy. Reduction of muscle mass and strength with aging is considered to be one of the major causes of disability in older people [1]. Dietary whey protein has been reported to be more capable of supporting muscle protein synthesis than soy protein in a clinical study [12]. Kanda et al had reported that FSR, after exercise and administration of whey protein, is similar to that after caseinate administration, and seems to be higher than that after soy protein administration, statistical analysis could not be performed [13]. Peak FSR, under no-exercise condition, is reported to be different between whey protein and soy protein (45 min and 90 min, respectively) [14]. These reports convey the effects of intake of a single intake of protein source.
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