FAS and obesity due to melanocortin 4 receptor deficiency: It was recently reported that SREBPs are essential for hepatic steatosis in dietary and genetic rodent models of obesity [28], suggesting that a high level of SREBP-1c in high-fat diet-induced obese rats up-regulates the expression of FAS and ACC1 and subsequently increases lipid synthesis, which may be associated with increased insulin levels in obese rats.