BDNF and obesity due to melanocortin 4 receptor deficiency: Importantly, this BDNF polymorphism is weakly associated with obesity, though brain-specific conditional BDNF knockout mice exhibit typical symptoms of obesity (hyperglycemia, hyperleptinemia, high cholesterol, and hyperinsulinemia) due to abnormal appetite regulation controlled by both neuropeptide Y (NPY) and pro-opiomelanocortin (POMC) neurons in the hypothalamus (104).