Relationship of polychlorinated biphenyls with type 2 diabetes and hypertension.

Diabetes and hypertension are important contributors to morbidity and mortality worldwide. Both of these conditions are caused by some combination of genetic and environmental factors which may include exposure to persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs). Studies have shown an association between elevated serum PCBs and the metabolic syndrome, insulin sensitivity and insulin secretion. Cross-sectional studies have shown associations between diabetes or hypertension and certain PCB congeners or classes, while those same studies show no association between diabetes or hypertension and several other PCB congeners. In animal and human cell studies, various PCBs and dioxins appear to alter glucose and insulin metabolism. These studies specifically show effects on the glucose transporter (GLUT-4) gene and protein; insulin-like growth factor binding protein-1 (IGFBP-1); nuclear transcription factor kappa B (NFkB); tumor necrosis factor alpha (TNF-alpha); and insulin production. There are a few longitudinal studies examining the association of diabetes or hypertension and PCBs with no consensus conclusion. Some longitudinal studies have found there to be an association, others have not and a gender difference has also been noted. Prospective studies are needed to determine if PCBs and other POPs contribute to development of diabetes and hypertension.