Energy homeostasis targets chromosomal reconfiguration of the human GH1 locus
Hana Vakili, … , Yan Jin, Peter A. Cattini
Hana Vakili, … , Yan Jin, Peter A. Cattini
Published October 8, 2014
Citation Information: J Clin Invest. 2014;124(11):5002-5012. https://doi.org/10.1172/JCI77126.
View: Text | PDF
Research Article Endocrinology

Energy homeostasis targets chromosomal reconfiguration of the human GH1 locus

Abstract

Levels of pituitary growth hormone (GH), a metabolic homeostatic factor with strong lipolytic activity, are decreased in obese individuals. GH declines prior to the onset of weight gain in response to excess caloric intake and hyperinsulinemia; however, the mechanism by which GH is reduced is not clear. We used transgenic mice expressing the human GH (hGH) gene, GH1, to assess the effect of high caloric intake on expression as well as the local chromosome structure of the intact GH1 locus. Animals exposed to 3 days of high caloric intake exhibited hyperinsulinemia without hyperglycemia and a decrease in both hGH synthesis and secretion, but no difference in endogenous production of murine GH. Efficient GH1 expression requires a long-range intrachromosomal interaction between remote enhancer sequences and the proximal promoter region through “looping” of intervening chromatin. High caloric intake disrupted this interaction and decreased both histone H3/H4 hyperacetylation and RNA polymerase II occupancy at the GH1 promoter. Incorporation of physical activity muted the effects of excess caloric intake on insulin levels, GH1 promoter hyperacetylation, chromosomal architecture, and expression. These results indicate that energy homeostasis alters postnatal hGH synthesis through dynamic changes in the 3-dimensional chromatin structure of the GH1 locus, including structures required for cell type specificity during development.

Authors

Hana Vakili, Yan Jin, Peter A. Cattini

×

Figure 10

The HFD-induced reduction of RNA pol II–GH1 promoter association is blunted by addition of physical activity.

Options: View larger image (or click on image) Download as PowerPoint
The HFD-induced reduction of RNA pol II–GH1 promoter association is blun...
ChIP assay of (A and C) RNA pol II and (B and D) Ser5-pRNA pol II, as indicators of the transcription complex at the GH1 promoter and transcriptional initiation/elongation, in 171hGH/CS-TG mice fed HFD or LFD for 3 days, without (A and B) or with (C and D) incorporation of physical activity (swimming). Binding events were calculated by qPCR based on signals obtained from the immunoprecipitated/input DNA amplification, using specific primers for the GH1 promoter and Untr6 control. Results (mean ± SEM) are expressed relative to LFD group Untr6 value (arbitrarily set to 1). Significance was assessed by 1-way ANOVA with Bonferroni post-test (n = 3–6). *P < 0.05, **P < 0.01.