Pre-exercise casein peptide supplementation enhances endurance training-induced mitochondrial enzyme activity in slow twitch muscle, but not fast twitch muscle of high fat diet-fed mice

Abstract

To establish an efficient method of enhancing mitochondrial biogenesis, we investigated the effect of casein peptide supplementation. The aim of this study was to examine whether oral casein peptide ingestion enhances exercise-induced mitochondrial adaptation in high fat diet-induced obese diabetes mice. Mice received either casein peptide or water (0.2 mg/g body weight, 7 times/week) and were subjected to treadmill running (20–25 m/min × 60 min, 5 times/week for 6 weeks) 30 min later. In plantaris muscle (higher proportion of fast-twitch muscle fibers), casein peptide treatment did not impact mitochondrial adaptation. However, in soleus muscle (higher proportion of slow-twitch muscle fibers) and heart, casein peptide supplementation with exercise increased mitochondrial enzyme activity (citrate synthase and β-hydroxyacyl CoA dehydrogenase activity). To clarify the mechanisms underlying mitochondrial adaptation enhancement, we investigated the acute effects of pre-exercise casein peptide ingestion on the phosphorylation status of cellular signaling cascades associated with mitochondrial adaptations. We observed that casein peptide ingestion boosted exercise-induced AMPK phosphorylation in soleus, but not plantaris muscle. Thus, our present investigation suggested that casein peptide ingestion enhanced exercise-induced mitochondrial adaptation in slow twitch muscle, but not fast twitch muscle in high fat diet-induced obese-diabetes mice.

Keywords

• casein peptide supplementation
• mitochondrial adaptation
• fiber type
• endurance training