Serum levels of human growth hormone (hGH) vary considerably over a 24-hour period, in line with human behaviours. The impact of sleep duration on serum hGH has been documented, but specific transcriptional activation of GH has proved difficult to examine. This leaves questions regarding the mechanistic regulation of hGH expression in response to behaviour unanswered.

Jarmasz and colleagues have attempted to delineate the interactions between sleep and dietary regimens and the transcriptional control of hGH. The group used partially humanised transgenic 171hGH/CS mice, containing a single copy of the hGH gene. CD-1 mice were fed standard chow or a high fat diet as well as being subjected to sleep deprivation protocols. The dietary regimen was unable to alter expression of circadian genes in wild type mice, whilst stress of acute sleep deprivation did change circadian expression. This demonstrates the uncoupling of dietary challenge from sleep deprivation. Additionally, for the first time, this study shows sleep deprivation to negatively impact hGH transcript levels in the pituitary.

The work suggests DNA methylation of the hGH gene as a putative mechanism for this regulation.

Read the full article in Endocrine Connections 9 1135−1147