title: Skeletal muscle growth hormone receptor signaling regulates basal, but not fasting-induced, lipid oxidation.
abstract: BACKGROUND
  Growth hormone (GH) stimulates whole-body lipid oxidation, but its regulation of muscle lipid oxidation is not clearly defined. Mice with a skeletal muscle-specific knockout of the GH receptor (mGHRKO model) are protected from high fat diet (HFD)-induced insulin resistance and display increased whole-body carbohydrate utilization. In this study we used the mGRHKO mice to investigate the role of muscle GHR signaling on lipid oxidation under regular chow (RC)- and HFD- fed conditions, and in response to fasting.
  
  
  RESULTS
  Expression of lipid oxidation genes was analyzed by real-time PCR in the muscles of RC- and HFD- fed mice, and after 24 h fasting in the HFD-fed mice. Expression of lipid oxidation genes was lower in the muscles of the mGHRKO mice relative to the controls, irrespective of diet. However, in response to 24 h fasting, the HFD-fed mGHRKO mice displayed up-regulation of lipid oxidation genes similar to the fasted controls. When subjected to treadmill running challenge, the HFD-fed mGHRKO mice demonstrated increased whole-body lipid utilization. Additionally, under fasted conditions, the adipose tissue of the mGHRKO mice displayed increased lipolysis as compared to both the fed mGHRKO as well as the fasted control mice.
  
  
  CONCLUSIONS
  Our data show that muscle GHR signaling regulates basal lipid oxidation, but not the induction of lipid oxidation in response to fasting. We further demonstrate that muscle GHR signaling is involved in muscle-adipose tissue cross-talk; however the mechanisms mediating this remain to be elucidated.
authors.affiliation: Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine, Mount Sinai School of Medicine, New York, New York, United States of America.
authors.forename: Archana
authors.initials: A
authors.lastname: Vijayakumar
authors.forename: YingJie
authors.initials: Y
authors.lastname: Wu
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Buffin
authors.forename: Xiaosong
authors.initials: X
authors.lastname: Li
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Gordon
authors.forename: Shoshana
authors.initials: S
authors.lastname: Yakar
authors.forename: Derek
authors.initials: D
authors.lastname: LeRoith
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D059305:Diet, High-Fat; D005215:Fasting; D005786:Gene Expression Regulation; D050356:Lipid Metabolism / Q000235:genetics; D008066:Lipolysis; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008931:Mitochondria, Muscle / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D010805:Physical Conditioning, Animal; D011986:Receptors, Somatotropin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D011986:Receptors, Somatotropin