title: Refeeding and insulin regulate S6K1 activity in chicken skeletal muscles.
abstract: Broiler chickens are characterized by fast muscle growth and high protein deposition, most likely subsequent to a high protein synthesis. However, the regulation of protein synthesis in chicken muscle is still unknown. In contrast, it has been clearly demonstrated in mammals that S6K1 is a key regulator of protein synthesis. In the present study, S6K1 was characterized in both pectoralis and gastrocnemius muscles in chickens. A 133-bp fragment of chicken S6K1 cDNA had 84% identity to mammalian S6K1. We investigated in vivo the effects of refeeding and insulin treatment after 16 h starvation. S6K1 enzyme activity was significantly increased in both pectoralis and gastrocnemius muscles by refeeding (two- to threefold greater than in food-deprived chickens, P < 0.05). Optimal activation occurred 30 min after refeeding following 16 h starvation. S6K1 activation was associated with its phosphorylation on serine and Thr 389 residues, which occurred within the first 5 min of refeeding. S6K1 was also significantly stimulated in both pectoralis and gastrocnemius muscles after a single insulin injection (nine- to 12-fold greater than in control chickens, P < 0.001). Our results indicate that S6K1 is expressed in chickens muscles and activated by refeeding and insulin treatment.
authors.affiliation: Régulation du métabolisme des oiseaux, Station de Recherches Avicoles, Institut National de la Recherche Agronomique, Centre de Tours-Nouzilly, Nouzilly, France.
authors.forename: Karine
authors.initials: K
authors.lastname: Bigot
authors.forename: Mohammed
authors.initials: M
authors.lastname: Taouis
authors.forename: Sophie
authors.initials: S
authors.lastname: Tesseraud
mesh_terms: D000818:Animals; D001786:Blood Glucose; D002645:Chickens; D004435:Eating; D007328:Insulin / Q000097:blood* / Q000494:pharmacology; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism*; D010766:Phosphorylation; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D009124:Muscle Proteins; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C448959:ribosomal protein S6 kinase, 70kD, polypeptide 2