Sleep deprivation and diet affect human GH gene expression in transgenic mice in vivo

Abstract

Human (h) growth hormone (GH) production studies are largely li mited to effects on secretion. How pituitary hGH gene (hGH-N/GH1) expression is regulated is important in our understanding of the role hGH plays in physiology and disease. Here we assess for the first time the effect of sleep deprivation (SD) and high-fat diet (HFD) on hGH-N expression in vivo using partially humanized 171hGH/CS transgenic (TG) mice, and attempted to elucidate a role for DNA methylation. Activation of hGH-N expression requires interactions between promoter and upstream locus control region (LCR) sequences incl uding pituitary-specific hypersensitive site (HS) I/II. Both SD and diet affect hGH secre tion, but the effect of SD on hGH-N expression is unknown. Mice fed a HFD or regular chow diet for 3 days underwent SD (or no SD) for 6 h at Zeitgeber time (ZT) 3. Serum and pituitaries were assessed over 24 h at 6-h intervals beginning at ZT 14. SD and HFD caused sig nificant changes in serum corticosterone and insulin, as well as hGH and circadian clock-related gene RNA levels. No clear association between DNA methylation and the negative e ffects of SD or diet on hGH RNA levels was observed. However, a correlation with increased methylation at a CpG (cytosine paired with a guanine) in a putative E-box within the hGH LCR HS II was suggested in situ. Methylation at this site also increased BMAL1/CLOCK-related n uclear protein binding in vitro. These observations support an effect of SD on hGH synthesis at the level of gene expression.

Keywords

• sleep deprivation
• high-fat diet
• dna methylation
• human growth hormone