Effects of GHRP-2 and Cysteamine Administration on Growth Performance, Somatotropic Axis Hormone and Muscle Protein Deposition in Yaks (Bos grunniens) with Growth Retardation

PLoS One. 2016 Feb 19;11(2):e0149461. doi: 10.1371/journal.pone.0149461. eCollection 2016.

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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Body Weight / drug effects
  • Cattle / growth & development*
  • Cysteamine / pharmacology*
  • Female
  • Growth Disorders / drug therapy
  • Growth Disorders / veterinary*
  • Growth Hormone / blood
  • Growth Hormone-Releasing Hormone / blood
  • Insulin-Like Growth Factor I / metabolism*
  • Muscle Proteins / metabolism
  • Muscle, Skeletal / drug effects*
  • Muscle, Skeletal / metabolism
  • Oligopeptides / pharmacology*
  • Somatostatin / blood

Substances

  • Muscle Proteins
  • Oligopeptides
  • Somatostatin
  • Cysteamine
  • Insulin-Like Growth Factor I
  • Growth Hormone
  • Growth Hormone-Releasing Hormone
  • growth hormone-releasing peptide-2

Grants and funding

This study was supported by China Agriculuture (Beef Cattle/Yak) Research System (CARS-38) (http://www.beefsys.com/) and Efficiently Special Key Technologies of Converting Grass to Livestock in Qinghai-Tibet Plateau Community (201203008). ZW received the funding. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.