Endocrine Abstracts

Patients with GC excess (Cushing’s syndrome) develop central obesity, insulin resistance and hepatic steatosis. The A-ring reductases (5α-reductase type 1 (5αR1) and 2 (5αR2)) generate dihydrotestosterone from testosterone, but importantly also inactivate cortisol and are highly expressed in human liver. We propose that 5αR may regulate GC exposure and therefore may modulate metabolic phenotype in human liver.

Primary human hepatocytes and the C3A human hepatoma cell line were incubated with cortisol (0–1000 nM), alone or in combination with the selective 5αR2 inhibitor, Finasteride (500 nM) or non-selective inhibitor, Dutasteride (500 nM) for 24 h. In addition, C3A cells (which express 5αR1, but not 5αR2), were transfected with a plasmid containing either WT, or inactivated mutant (R246Q) 5αR2. The functional impact of these manipulations was assessed through real-time PCR based gene expression, enzyme activity assays using both gas and liquid chromatography/mass spectrometry and functional assessments of de novo lipogenesis (DNL).

Cortisol decreased DNL in a dose-dependent manner (e.g. 85.66.6% (100 nM), 73.57.9% (250 nM), 55.045.6% (1000 nM), P<0.05). 5αR2 over-expression increased DHT generation and cortisol clearance and in the absence of cortisol, did not alter rates of DNL. However, in the presence of cortisol, 5αR2 restored DNL to levels observed in untreated controls (e.g. 61.9±7.6% (cortisol) vs 103.8±8.8% (5αR2+cortisol), P<0.05, control=100%). Complementary experiments using the R246Q 5αR2 construct did not alter cortisol-mediated suppression of DNL. Furthermore, both Finasteride and Dutasteride augmented the action of cortisol to supress DNL in primary cultures of human hepatocytes (e.g. 88.3±5.3 vs 76.9±5.2%, cortisol vs cortisol+finasteride, P=0.05).

We have demonstrated that manipulation of 5αR activity can regulate metabolic phenotype in human liver. Further clinical studies are now warranted, but this may have significant clinical implications for those patients with mutations in 5αR2 and those prescribed 5αR inhibitors.