[12], [29], [30] Although the several phenotypes are shared by both mouse models (e.g. obesity and insulin resistance), ob/ob mouse model differs from db/db model such that leptin-deficiency was shown to be specifically associated with severe early-onset obesity in obese humans [6]. The metabolic alterations and gender variations observed in ob/ob mice, compared with B6 mice, are discussed below. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.