LEP and obesity due to melanocortin 4 receptor deficiency: Furthermore, the serum levels of BBDEs were found to be positively associated with the expression of obesity biomarkers in subcutaneous and visceral adipose tissue, such as leptin, adiponectin, tumor necrosis factor α (TNFα), and PPARγ, implying that exposure to these pollutants may contribute to the development of obesity in humans [59].