Long-term oral exposure to bisphenol A induces glucose intolerance and insulin resistance

Abstract

Bisphenol A (BPA) is a widely used endocrine disruptor. Recent epidemiologic results have suggestedanassociationbetween exposure toBPAandcardiovascular disease, type 2 diabetes, and obesity.We investigated the in vivo effects of long-term oral exposure to BPA on insulin resistance and glucose intolerance. In the present study, 4- to 6-week-old male mice on a high-fat diet (HFD)were treated with 50 μg/kg body weight per day of BPAorally for 12 weeks. Long-termoral exposure to BPA along with an HFD for 12 weeks inducedglucose intolerance in growingmale mice. Intraperitoneal glucose tolerance tests showed that the mice that received an HFD and BPA exhibited a significantly larger area under the curve than did those that received an HFD only (119.9±16.8 vs 97.9±18.2 mM/min, P=0.027). Bodyweight, percentage of white adipose tissue, and percentage of body fat did not differ between the two groups of mice. However, treatment with BPA reduced Akt phosphorylation at position Thr308 and GSK3β phosphorylation at position Ser9 in skeletal muscle. BPA tended to decrease serum adiponectin levels and to increase serum interleukin 6 and tumor necrosis factor α, although these findings were not statistically significant. Treatment with BPA did not induce any detrimental changes in the islet area or morphology or the insulin content of β cells. In conclusion, long-term oral exposure to BPA induced glucose intolerance and insulin resistance in growing mice. Decreased Akt phosphorylation in skeletal muscle by way of altered serum adipocytokine levels might be one mechanism by which BPA induces glucose intolerance.