Glucocorticoids Affect 24 h Clock Genes Expression in Human Adipose Tissue Explant Cultures

<div><h3>Aims</h3><p>to examine firstly whether <em>CLOCK</em> exhibits a circadian expression in human visceral (V) and subcutaneous (S) adipose tissue (AT) <em>in vitro</em> as compared with <em>BMAL1</em> and <em>PER2,</em> and secondly to investigate the possible effect of the glucocorticoid analogue dexamethasone (DEX) on positive and negative clock genes expression.</p> <h3>Subjects and Methods</h3><p>VAT and SAT biopsies were obtained from morbid obese women (body mass index≥40 kg/m²) (n = 6). In order to investigate rhythmic expression pattern of clock genes and the effect of DEX on <em>CLOCK</em>, <em>PER2</em> and <em>BMAL1</em> expression, control AT (without DEX) and AT explants treated with DEX (2 hours) were cultured during 24 h and gene expression was analyzed at the following times: 10:00 h, 14:00 h, 18:00 h, 22:00 h, 02:00 h and 06:00 h, using qRT-PCR.</p> <h3>Results</h3><p><em>CLOCK</em>, <em>BMAL1</em> and <em>PER2</em> expression exhibited circadian patterns in both VAT and SAT explants that were adjusted to a typical 24 h sinusoidal curve. <em>PER2</em> expression (negative element) was in antiphase with respect to <em>CLOCK</em> and in phase with <em>BMAL1</em> expression (both positive elements) in the SAT (situation not present in VAT). A marked effect of DEX exposure on both positive and negative clock genes expression patterns was observed. Indeed, DEX treatment modified the rhythmicity pattern towards altered patterns with a period lower than 24 hours in all genes and in both tissues.</p> <h3>Conclusions</h3><p>24 h patterns in <em>CLOCK</em> and <em>BMAL1</em> (positive clock elements) and <em>PER2</em> (negative element) mRNA levels were observed in human adipose explants. These patterns were altered by dexamethasone exposure.</p>