Association of glutathione peroxidase activity with insulin resistance and dietary fat intake during normal pregnancy.

Glutathione peroxidase (GPx) is one of the most important antioxidant enzymes in humans. We studied the relationship between erythrocyte GPx activity and fasting serum insulin, plasma glucose, and C-peptide, estimates of insulin resistance from the homeostasis model of assessment as well as dietary fat intake in 408 normotensive nondiabetic pregnant women from Camden, NJ. GPx activity and the metabolic parameters were determined at entry to care (16 wk of pregnancy) and during the third trimester. GPx activity and the levels of insulin resistance increased significantly between entry and the third trimester. Statistically significant associations, all positive, were observed between GPx activity and fasting insulin (beta = 0.009, P < 0.001), glucose (beta = 0.975, P < 0.05), C-peptide (beta = 1.537, P < 0.01), and insulin resistance from the homeostasis model of assessment (beta = 0.209, P < 0.01). Dietary intakes of fat and polyunsaturated fatty acids were positively correlated with GPx activity as well. African Americans had significantly higher GPx activity, dietary fat, and polyunsaturated fatty acid intake than Hispanics and Caucasians. In conclusion, we demonstrated that normal pregnancy is associated with increased GPx activity and insulin resistance. There are ethnic differences in antioxidant response and dietary fat intake. Our findings suggest a potential link among antioxidant defenses, insulin resistance, and dietary fat intake.