Associations of organochlorine pesticides and polychlorinated biphenyls in visceral vs. subcutaneous adipose tissue with type 2 diabetes and insulin resistance

Background exposure to organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs) has been linked to type 2 diabetes. As OC pesticides and PCBs mainly accumulate in adipose tissue and there are physiological and clinical differences between visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT), we explored if there were associations of OC pesticides and PCBs in VAT or SAT with type 2 diabetes and insulin resistance. Participants were 50 patients with or without type 2 diabetes who underwent surgery for either cancer or benign liver or gallbladder lesions. We analyzed 14 OC pesticides and 22 PCB congeners in both VAT and SAT. Insulin resistance was estimated using homeostasis model assessment (HOMA). Although concentrations of OC pesticides and PCBs were strongly correlated between VAT and SAT, absolute concentrations differed substantially between them. In particular, concentrations of all PCBs were consistently about 5-10 times higher in VAT than SAT, but these patterns were independent of diabetes status. Some OC pesticides or PCBs, such as dichlorodiphenyltrichloroethanes (DDTs), chlordanes, and PCBs with 5 or less chlorides showed significant associations with diabetes or insulin resistance. For example, when tertiles of concentration-based summary measures were used, adjusted ORs were 1.0, 2.3, and 9.0 (P trend = 0.02) for DDTs in VAT and 1.0, 2.1, and 5.7 (P trend = 0.08) for PCBs with 5 or less chlorides. This study generally confirmed previous findings using serum concentrations. It would be useful to study pharmacodynamics of POPs in VAT and SAT further.