Differential regulation of protein synthesis by skeletal muscle type in chickens.

In mammalian skeletal muscles, protein synthesis rates vary according to fiber types. We herein demonstrated differences in the regulatory mechanism underlying the protein synthesis in the pectoralis major (a glycolytic twitch muscle), adductor superficialis (an oxidative twitch muscle), and adductor profound (a tonic muscle) muscles of 14-day-old chickens. Under ad libitum feeding conditions, protein synthesis is significantly higher in the adductor superficialis muscle than in the pectoralis major muscle, suggesting that protein synthesis is upregulated in oxidative muscles in chickens, similar to that in mammals.

The IGF-1/Akt/S6 pathway and expressions of glycolytic myosin heavy chain isoforms are upregulated in chicken skeletal muscle during the first week after hatching.

Skeletal muscle mass is an important trait in the animal industry. We previously reported an age-dependent downregulation of the insulin-like growth factor 1 (IGF-1)/Akt/S6 pathway, major protein synthesis pathway, in chicken breast muscle after 1 week of age, despite a continuous increase of breast muscle weight. Myosin heavy chain (HC), a major protein in muscle fiber, has several isoforms depending on chicken skeletal muscle types.

Differential regulation of the expression of lipid metabolism-related genes with skeletal muscle type in growing chickens.

The regulatory mechanisms of carbohydrate and lipid metabolism are known to differ among skeletal muscle types in mammals. For example, glycolytic muscles prefer glucose as an energy source, whereas oxidative muscles prefer fatty acids (FA). We herein demonstrated differences in the expression of genes involved in carbohydrate and lipid metabolism in the pectoralis major (a glycolytic twitch muscle), adductor superficialis (an oxidative twitch muscle), and adductor profound (a tonic muscle) of 14-day-old chicks.