TGFB1 and obesity due to melanocortin 4 receptor deficiency: A potential correlation between obesity and hepatic leptin resistance noted by the elevated serum leptin levels in the HFHF group led to the failure of leptin to stimulate hepatic lipid turnover45,46; this failure induces IR and steatosis, which further develops hepatic fibrosis because leptin plays a proinflammatory role in mediating procollagen I, TGF-β1, and TNF-α expression47.