Several mechanisms through which POPs, predominantly dioxin-like chemicals, could affect diabetes incidence have been investigated, including hyperinsulinemia, antagonism of peroxisome proliferator-activated receptor-γ (PPAR-γ) expression, induction of tumor necrosis factor-α (TNF-α), auto-immunity, and alterations in steroid metabolism. The gene discussed is PPARG; the disease is diabetes mellitus.