Endocrine Abstracts

Excessive glucocorticoid exposure has been implicated in the pathogenesis of obesity and the metabolic syndrome. The in vivo conversion of inactive to active glucocorticoids is catalysed by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), requiring NADPH as a cofactor. Hexose-6-phosphate dehydrogenase (H6PDH) is co-localised with 11β-HSD1 in the lumen of the endoplasmic reticulum and controls local NADPH availability. Thus H6PDH plays an important role in the directionality of 11β-HSD1 and the activation of glucocorticoids. While various regulators of 11β-HSD1 have been identified, little is currently known about the regulation of H6PDH. This study aimed to assess changes in H6PDH gene expression after the administration of a variety of treatments, using a human fetal liver cell line (WRL-68). Following 24 h serum starvation, confluent cells were treated with a range of concentrations of dexamethasone (1–1000 nM), testosterone (0.1–10 μg/ml) or estradiol (0.1–10 μg/ml) for 8 or 24 h. RNA was extracted from the cells to measure H6PDH mRNA expression by real-time PCR, and Western Blots and H6PDH activity assays were utilised to assess protein expression levels. Increasing concentrations of dexamethasone (>250 nM) resulted in a dose-dependent increase in H6PDH mRNA (fold change 36.9±14.1, P<0.006, n=4). This effect was seen at 8 and 24 hours of culture (fold change: 59.5±3.2 (8 h) vs 11.0±0.2 (24 h); P<0.004). H6PDH protein expression also increased in a dose-dependent manner. Upregulation of H6PDH mRNA also occurred following treatment with testosterone (fold change: control 1.0±0.0, 0.1 μg/ml 1.1±0.03, 1.0 μg/ml 2.3±0.12, 10 μg/ml 3.5±0.03; P<0.001, n=2) and estradiol (fold change: control 1.0±0.0, 0.1μg/ml 0.6±0.08, 1.0 μg/ml 1.2±0.05, 10 μg/ml 5.1±0.49; P<0.05, n=2). Glucocorticoids and sex hormones appear to play a role in the regulation of H6PDH within liver. This regulation of H6PDH could have implications for the pathology of the metabolic syndrome.