Obesity and insulin resistance developed at around 12 weeks, histopathological features of NASH could be detected from 16 weeks, while expression of Cyp2c and Cyp3a, pregnane X receptor (PXR) and peroxisome proliferator-activated receptor-gamma coactivator-1alpha mRNA are elevated at 28-weeks of age [8,13]. The gene discussed is CYP3A4; the disease is obesity due to melanocortin 4 receptor deficiency.