title: Effects of GHRP-2 and Cysteamine Administration on Growth Performance, Somatotropic Axis Hormone and Muscle Protein Deposition in Yaks (Bos grunniens) with Growth Retardation.
abstract: The objective of this study was to investigate the effects of growth hormone-releasing peptide-2 (GHRP-2) and cysteamine (CS) administration on growth performance in yaks with growth retardation and try to elucidate its regulatory mechanisms. Trial 1, thirty-six 1-year-old Qinghai high plateau yaks (body weight 38-83.2 kg) were randomly chosen for body weight and jugular blood samples collection. The relationship between body weight and serum GHRH (P < 0.05, R = 0.45), GH (P < 0.05, R = 0.47), IGF-1 (P < 0.05, R = 0.62) was significantly correlated in yaks colonies with lighter body weights. Trial 2, fifteen 1-year-old Qinghai high plateau yaks with growth retardation (average body weight 54.8 ± 8.24 kg) were randomly selected and assigned to negative control group (NG), GHRP-2 injection group (GG) and cysteamine feeding group (CG), with 5 yaks per group. Another five 1-year-old Qinghai high plateau yaks with normal growth performance (average body weight 75.3 ± 2.43 kg) were selected as positive control group (PG). The average daily gain (ADG) of the GG and CG were significantly higher than those in the PG and NG (P < 0.05). Both GHRP-2 and CS administration significantly enhanced the myofiber diameter and area of skeletal muscle (P<0.05). GHRP-2 significantly enhanced the serum GH and IGF-1 levels (P < 0.05), and up-regulated GHR, IGF-1 and IGF-1R mRNA expression in the liver and skeletal muscle (P < 0.05), enhanced the mRNA expression of PI3K, AKt and mTOR in the skeletal muscle (P<0.05). CS significantly reduced the serum SS levels and the hypothalamus SS mRNA expression (P < 0.05), and enhanced GHR and IGF-1 mRNA expression in the liver (P < 0.05), decreased the mRNA expression of muscle atrophy F-box (Atrogin-1) and muscle ring finger 1 (MuRF1) mRNA (P < 0.05).
  
  
  CONCLUSIONS
  Growth retardation in yaks was primarily due to somatotropic axis hormones secretion deficiency. Both GHRP-2 and CS administration can accelerate growth performance and GH, IGF-1 secretion in yaks with growth retardation. GHRP-2 enhanced muscle protein deposition mainly by up-regulated the protein synthesis pathways, whereas CS worked mainly by down-regulated the ubiquitin-proteasome pathway.
authors.affiliation: Institute of Animal Nutrition, Sichuan Agricultural University, Key Laboratory of Low Carbon Culture and Safety Production in Cattle in Sichuan, Chengdu, Sichuan, P.R. China.
authors.forename: Rui
authors.initials: R
authors.lastname: Hu
authors.affiliation: Institute of Animal Nutrition, Sichuan Agricultural University, Key Laboratory of Low Carbon Culture and Safety Production in Cattle in Sichuan, Chengdu, Sichuan, P.R. China.
authors.forename: Zhisheng
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institute of Animal Nutrition, Sichuan Agricultural University, Key Laboratory of Low Carbon Culture and Safety Production in Cattle in Sichuan, Chengdu, Sichuan, P.R. China.
authors.forename: Quanhui
authors.initials: Q
authors.lastname: Peng
authors.affiliation: Institute of Animal Nutrition, Sichuan Agricultural University, Key Laboratory of Low Carbon Culture and Safety Production in Cattle in Sichuan, Chengdu, Sichuan, P.R. China.
authors.forename: Huawei
authors.initials: H
authors.lastname: Zou
authors.affiliation: Institute of Animal Nutrition, Sichuan Agricultural University, Key Laboratory of Low Carbon Culture and Safety Production in Cattle in Sichuan, Chengdu, Sichuan, P.R. China.
authors.forename: Hongze
authors.initials: H
authors.lastname: Wang
authors.affiliation: Institute of Animal Nutrition, Sichuan Agricultural University, Key Laboratory of Low Carbon Culture and Safety Production in Cattle in Sichuan, Chengdu, Sichuan, P.R. China.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Yu
authors.affiliation: Institute of Animal Nutrition, Sichuan Agricultural University, Key Laboratory of Low Carbon Culture and Safety Production in Cattle in Sichuan, Chengdu, Sichuan, P.R. China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Jing
authors.affiliation: Institute of Animal Genetics and Breeding, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, Sichuan, P.R. China.
authors.forename: Yixin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Animal Science and Technology, State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing, P.R. China.
authors.forename: Binghai
authors.initials: B
authors.lastname: Cao
authors.affiliation: Animal Husbandry and Veterinary Institute, Haibei, Qinghai, P.R. China.
authors.forename: Shanke
authors.initials: S
authors.lastname: Bao
authors.affiliation: Ningxia Xiahua Muslim Food Co. Ltd., Zhongwei, Ningxia, P.R. China.
authors.forename: Wenhua
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Animal Husbandry and Veterinary Institute, Haibei, Qinghai, P.R. China.
authors.forename: Suonan
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Animal Husbandry and Veterinary Institute, Haibei, Qinghai, P.R. China.
authors.forename: Hanzhong
authors.initials: H
authors.lastname: Ji
authors.affiliation: Animal Husbandry and Veterinary Institute, Haibei, Qinghai, P.R. China.
authors.forename: Xiangying
authors.initials: X
authors.lastname: Kong
authors.affiliation: Ningxia Xiahua Muslim Food Co. Ltd., Zhongwei, Ningxia, P.R. China.
authors.forename: Quanxi
authors.initials: Q
authors.lastname: Niu
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002417:Cattle / Q000254:growth & development*; D003543:Cysteamine / Q000494:pharmacology*; D005260:Female; D006130:Growth Disorders / Q000188:drug therapy / Q000662:veterinary*; D013006:Growth Hormone / Q000097:blood; D013007:Growth Hormone-Releasing Hormone / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology*; D013004:Somatostatin / Q000097:blood
chemical_list: D009124:Muscle Proteins; D009842:Oligopeptides; D013004:Somatostatin; D003543:Cysteamine; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; C091874:growth hormone-releasing peptide-2