Diabetes Helped and Weight Loss Foiled by PCBs
Exposure to persistent organic pollutants such as polychlorinated biphenyls (PCBs) has been linked to the development of type 2 diabetes, and a recent study in mice helps explain why.
To help understand why PCBs increases risk of type 2 diabetes, the effects of a PCB-containing diet (diet is one of the major sources of human exposure) on inflammation and glucose and insulin tolerance was investigated in mice. The effects were studied in both lean and obese mice fed a low-fat or high-fat diet respectively.
In the mice fed a low-fat diet, PCBs increased adipose expression of tumor necrosis factor alpha (TNF-α) and significantly impaired glucose and insulin tolerance for up to two weeks after exposure. The high-fat diet mice did not experience the same effects despite having double the concentration of PCBs in their adipose tissue, however when moved on to a weight loss phase they developed impaired glucose and insulin tolerance, while the control mice improved.
Overall, these findings suggest that PCBs may impair glucose tolerance by concentrating in adipose tissue and increasing local expression of TNF-α. Furthermore, obesity may acutely protect against the harmful effects of PCB exposure, but bioaccumulation of PCBs in fat stores may mitigate beneficial effects of weight loss.
Baker NA, Karounos M, English V, et al. Coplanar polychlorinated biphenyls impair glucose homeostasis in lean C57BL/6 mice and mitigate beneficial effects of weight loss on glucose homeostasis in obese mice. Environ Health Perspect. 2013 Jan;121(1):105-10.