PPARG and obesity due to melanocortin 4 receptor deficiency: Furthermore, neuronal PPARγ knockout mice (which lack the factor in neurons of both the PNS and CNS) have a distinct metabolic phenotype, being resistant to both diet-induced obesity and the insulin-sensitizing effects of TZDs [20], suggesting a possible role for PPARγ signaling in PNS or CNS neurons in metabolic homeostasis.