INS and type 2 diabetes mellitus: Coplanar PCBs dose-dependently impair glucose and insulin tolerance in LF-fed mice in an AhR-dependent manner. We defined dose-dependent effects of two coplanar PCBs (PCB-77 and PCB-126)—both of which are prevalent in the environment (McFarland and Clarke 1989) and/or linked to T2D (Carpenter 2008; Everett et al. 2007)—on glucose and insulin tolerance in LF-fed mice.