Protein expression in pectoral skeletal muscle of chickens as influenced by dietary methionine.

Effects of dietary methionine (Met) on pectoralis muscle development and the effect that Met as a nutritional substrate has on protein expression of skeletal muscle cells of pectoralis muscle of chickens were evaluated in this study. Broiler chickens received a common pretest diet up to 21 d of age and were subsequently fed either a low (LM) or high Met (HM) diet (0.41 vs. 0.51% of diet) from 21 to 42 d of age. Dietary deficiency was shown in vivo judging by the depression in breast meat weight and yield when broilers were fed the LM diet. Global protein expression was analyzed by quantitative high-performance liquid chromatography nanospray ionization tandem mass spectrometry. Up- and downregulated proteins were analyzed via Ingenuity Pathways Analysis to identify the metabolic pathways affected. Four canonical pathways related to muscle development were identified as being differentially regulated between LM- and HM-fed chickens. These pathways included the citrate cycle and calcium, actin cytoskeleton, and clathrin-mediated endocytosis signaling. The HM diet may have allowed for increased muscle growth by an increased availability of nutrients to muscle cells. Although the Met supplementation was associated with enhanced breast muscle growth, contraction fiber concentrations in muscles decreased and were associated with a lower calcium transportation rate and sensitivity and with a lower energy supply. It is further suggested that increased muscle protein deposition, that was induced by Met supplementation, may have been largely due to sarcoplasmic rather myofibrillar hypertrophy.