Daily Variations in Dietary Lysine Content Alter the Expression of Genes Related to Proteolysis in Chicken Pectoralis major Muscle

Abstract

Amino acids are known to be anabolic factors that affect protein metabolism, but the response of animals to daily amino acid changes is little understood. We aimed to test the effects of feeding birds with alternations of diets varying in lysine content on the expression of genes related to proteolysis in chicken muscle. Cyclic feeding programs with 2 diets, each given for 24 h during 48-h cycles, were carried out from 10 d of age. Three programs were used: 1) control treatment with continuous distribution of a complete diet containing standard medium lysine level (ML; 11.9 g/kg); 2) alternation of diets with high (HL) and low (LL) lysine levels; 3) alternation of ML and LL diets, where LL = 70%, ML = 100%, HL = 130% of standard lysine level. The Pectoralis major muscles were sampled after 2 wk of cyclic feeding. Measurements included the expression patterns of 6 genes involved in proteolysis, and mammalian target of rapamycin and Forkhead box-O transcription factor (FoxO) signaling. Cathepsin B, m-calpain, and E3 ubiquitin ligases Muscle Ring Finger-1 and Muscle Atrophy F box were significantly overexpressed in chickens transiently fed the LL diet, whereas the mRNA levels of 20S proteasome C2 subunit and ubiquitin remained unchanged. Modifications of E3 ubiquitin ligase expression can be partly explained by significant changes in FoxO phosphorylation with cyclic dietary treatments. Our results suggest timing-sensitive regulation of proteolysis in chicken muscle according to dietary treatment and a high metabolism capacity to compensate for changes in amino acid supply, which might be used for nutritional purposes.