The aim of the present study was to examine the impact of obesity on pancreatic expression of these mitochondrial proteins (cytochrome P450 27 A1/sterol 27-hydroxylase (Cyp27A1), ADX, ADXR, StARD1, TSPO, LXRα) in the Zucker (fa/fa) rodent model of genetic obesity and their function in regulation of cholesterol efflux and insulin release in BRIN-BD11 insulinoma cells. The gene discussed is CYP27A1; the disease is obesity due to melanocortin 4 receptor deficiency.