In both the eNOS-knockout mice and the wild-type mice fed an HFD during the 12 weeks of our study period, obesity, insulin resistance, dyslipidemia and high serum leptin levels were observed, although these markers were comparable between the eNOS-knockout and the wild-type mice fed an HFD, with the exception of the serum cholesterol level. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.