title: Effects of Dietary Crude Protein Levels and Cysteamine Supplementation on Protein Synthetic and Degradative Signaling in Skeletal Muscle of Finishing Pigs.
abstract: Dietary protein levels and cysteamine (CS) supplementation can affect growth performance and protein metabolism of pigs. However, the influence of dietary protein intake on the growth response of CS-treated pigs is unclear, and the mechanisms involved in protein metabolism remain unknown. Hence, we investigated the interactions between dietary protein levels and CS supplementation and the effects of dietary crude protein levels and CS supplementation on protein synthetic and degradative signaling in skeletal muscle of finishing pigs. One hundred twenty barrows (65.84 ± 0.61 kg) were allocated to a 2 × 2 factorial arrangement with five replicates of six pigs each. The primary variations were dietary crude protein (CP) levels (14% or 10%) and CS supplemental levels (0 or 700 mg/kg). The low-protein (LP) diets (10% CP) were supplemented with enough essential amino acids (EAA) to meet the NRC AA requirements of pigs and maintain the balanced supply of eight EAA including lysine, methionine, threonine, tryptophan, valine, phenylalanine, isoleucine, and leucine. After 41 days, 10 pigs per treatment were slaughtered. We found that LP diets supplemented with EAA resulted in decreased concentrations of plasma somatostatin (SS) (P<0.01) and plasma urea nitrogen (PUN) (P<0.001), while dietary protein levels did not affect other traits. However, CS supplementation increased the average daily gain (P<0.001) and lean percentage (P<0.05), and decreased the feed conversion ratio (P<0.05) and back fat (P<0.05). CS supplementation also increased the concentrations of plasma insulin-like growth factor 1 (IGF-1) (P<0.001), and reduced the concentrations of leptin, SS, and PUN (P<0.001). Increased mRNA abundance of Akt1 and IGF-1 signaling (P<0.001) and decreased mRNA abundance of Forkhead Box O (FOXO) 4 (P<0.01) and muscle atrophy F-box (P<0.001) were observed in pigs receiving CS. Additionally, CS supplementation increased the protein levels for the phosphorylated mammalian target of rapamycin (mTOR), eIF-4E binding protein 1, and ribosomal protein S6 kinase 1 (P<0.001). There were no interactions between dietary protein levels and CS supplementation for all traits. In conclusion, dietary protein levels and CS supplementation influenced growth and protein metabolism through independent mechanisms in pigs. In addition, LP diets supplemented with EAA did not affect growth performance and other traits except the concentrations of SS and PUN probably through maintenance of protein synthesis and degradation signaling. Moreover, CS supplementation improved growth performance by increasing plasma IGF-1 concentrations possibly through alterations of mTOR and Akt/FOXO signaling pathways in skeletal muscle of finishing pigs.
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhou
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Jiaolong
authors.initials: J
authors.lastname: Li
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Yiqiu
authors.initials: Y
authors.lastname: Luo
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Bolin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Shen
authors.initials: S
authors.lastname: Xing
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Yuping
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: College of Animal Science and Technology, Jilin Agricultural University, Changchun, 130118, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
authors.affiliation: College of Animal Science and Technology, Key Laboratory of Animal Origin Food Production and Safety Guarantee of Jiangsu Province, Synergetic Innovation Center of Food Safety and Nutrition, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Guanghong
authors.initials: G
authors.lastname: Zhou
mesh_terms: D000601:Amino Acids, Essential / Q000378:metabolism; D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D003543:Cysteamine / Q000378:metabolism*; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000378:metabolism*; D019587:Dietary Supplements; D015870:Gene Expression; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism*; D014176:Protein Biosynthesis; D059748:Proteolysis; D012333:RNA, Messenger / Q000378:metabolism; D034421:Sus scrofa; D013552:Swine; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D000601:Amino Acids, Essential; D004044:Dietary Proteins; D012333:RNA, Messenger; D003543:Cysteamine; D007334:Insulin-Like Growth Factor I; D058570:TOR Serine-Threonine Kinases