AHR and obesity due to melanocortin 4 receptor deficiency: Because obesity has been reported to increase the total body burden of lipophilic PCBs (Brown and Lawton 1984; Fukano and Doguchi 1977; McFarland and Clarke 1989), we examined effects of adipocyte AhR deficiency on the development of HF diet–induced obesity and glucose homeostasis in mice of each genotype administered VEH or PCB-77.