Association between serum concentrations of persistent organic pollutants and insulin resistance among nondiabetic adults

OBJECTIVE - We reported strong relations between serum concentrations of persistent organic pollutants (POPs), especially organochlorine (OC) pesticides or nondioxin-like polychlorinated biphenyls (PCBs), and prevalence of diabetes in a US population with background exposure to POPS. Here, we investigated POPS and insulin resistance, a frequent pathogenic precursor of type 2 diabetes. RESEARCH DESIGN AND METHODS - Serum POPS and homeostasis model assessment of insulin resistance (HOMA-IR) were investigated cross-sectionally in 749 nondiabetic participants aged >= 20 years. Nineteen POPS in five subclasses were selected, detectable in >= 60% of participants. RESULTS - Among subclasses, OC pesticides were most strongly associated with HOMA-IR. Adjusted geometric means of HOMA were 3.27, 3.36, 3.48, and 3.85 (P for trend < 0.01) across quartiles of OC pesticides. The relationship strengthened with increasing HOMA-IR percentile: adjusted odds ratios comparing the highest versus lowest POPS quartile were 1.8 for being >= 50th percentile of HOMA-IR, 4.4 for being >= 75th percentile, and 7.5 for being >= 90th percentile. Associations with elevated HOMA-IR appeared to be specific to oxychlordane and trans-nonachlor but also were found for two nondioxin-like PCBs. No HOMA-IR associations were seen in the other three POP subclasses. The association between OC pesticides and HOMA IR teneded to strengthen as waist circumference increased, with no apparent association. in the lowest quartile of OC pesticide concentrations. CONCLUSIONS - These findings, coupled with those concerning diabetes prevalence, suggest that OC pesticides and nondioxin-like PCBs may be associated with type 2 diabetes risk by increasing insulin resistance, and POPS may interact with obesity to increase the risk of type 2 diabetes.