Effect of ingested whey protein hydrolysate on gene expression profiles compared to an identical composition of amino acid mixture in rat skeletal muscle

We have previously showed that whey protein hydrolysate (WPH) causes a greater increase in muscle protein synthesis than an identical composition of amino acids mixture does. The present study was conducted to investigate a comparative effect of WPH on gene expression. Male Sprague-Dawley rats subjected to a 2-h swimming exercise were administered either a carbohydrate-amino acid diet or a carbohydrate-WPH diet immediately after exercise. One hour after exercise, epitrochlearis muscle mRNA was sampled and subjected to DNA microarray analysis. As a result, ingestion of WPH altered 189 genes in considering the false discovery rate. Among the upregulated genes, 8 Gene Ontology (GO) terms were enriched, which included key elements in muscle repair after exercise such as Cd24, Ccl2, Ccl7 and Cxcl1. On the other hand, 9 GO terms were enriched in the gene sets downregulated by ingestion of WPH and these GO terms fell into 2 clusters, regulation of ATPase activity, and immune response. Furthermore, we found that WPH activate the 2 upstream proteins, extracellular signal-regulated kinase 1/2 (ERK1/2) and hypoxia-inducible factor-1 (HIF-1), which may act as key factors for regulation of gene expression. These results suggest that ingestion of WPH, compared to an identical composition of amino acid mixture, induces greater changes in the after-exercise gene expression profile via activation of the proteins, ERK1/2 and HIF-1.

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Kanda A, Ishijima T, Shinozaki F, Nakayama K, Fukasawa T, Nakai Y, Abe K, Kawahata K, Ikegami S