Oleic acid inhibits cholesteryl esterase and cholesterol utilization for testosterone synthesis in mouse Leydig cells

We have observed that nonesterified fatty acids (NEFA) inhibit testosterone synthesis in response to luteinizing hormone (LH) in mouse Leydig cells, possibly by affecting cholesterol utilization or endogenous concentrations. We have now studied the influence of oleic acid (OA) on the cellular content of cholesterol, hydrolysis of cholesterol esters, and steroidogenesis in isolated mouse Leydig cells. OA (700 micromol/L added with fatty acid-free [FAF] albumin, 3 g/dL) significantly (P<.025) reduced testosterone production in response to LH (10 ng/mL), total cholesterol concentrations of Leydig cells and the culture medium, and cholesteryl esterase activity in the cytosol and mitochondria. We also studied the effects of OA on steroidogenesis and cellular cholesterol concentrations after treatments to increase cellular cholesterol. OA at lower concentrations (5 micromol/L with albumin, 0.1 g/dL) or low-density lipoprotein ([LDL] 4 micrograms protein/mL) increased cellular cholesterol (P<.01) without affecting basal steroidogenesis. These treatments failed to reverse the inhibitory (P<.05) effect of OA on testosterone synthesis following LH stimulation, but did significantly (P<.01) increase cellular cholesterol. In summary, OA appears to inhibit testosterone synthesis by inhibiting cholesteryl esterase activity.