Exposure of perfluorononanoic acid suppresses the hepatic insulin signal pathway and increases serum glucose in rats

Abstract

Exposure to perfluorononanoic acid (PFNA), an increasingly persistent organic pollutant that has been detected in abiotic and biotic matrices, has been demonstrated to cause hepatotoxicity in animals. However, the effects of PFNA on hepatic glucose metabolism have not been fully characterized. In this study, male rats were exposed to 0, 0.2, 1 or 5mg/kg/d PFNA for 14 days to explore the specific effect of PFNA on hepatic glycometabolism and its underlying mechanisms. The results showed that administration of 5mg/kg/d PFNA significantly increased serum glucose and hepatic glycogen in rats. Quantitative real-time PCR analysis showed that PFNA exposure changed the expression levels of several genes related to hepatic glucose metabolism, such as the glucose-6-phosphatase (G6PC) gene and the glucose transporter 2 (GLUT2) gene, which were upregulated, and the glucokinase (GCK) gene and the phosphoinositide-3-kinase, catalytic, alpha polypeptide (PI3Kca) gene, which were decreased. The protein expression levels of phospho-insulin receptor 1(IRS1), phospho-PI3K, phospho-AKT and phospho-phosphoinositide-dependent kinase 1 (PDK1) were decreased in the livers of rats that received 5mg/kg/d PFNA. The expression of phospho-glycogen synthase kinase-3 beta (GSK3β, Ser 9) was increased, which explains the augment of hepatic glycogen. Significant increases in hydrogen peroxide (H2O2) and malondialdehyde (MDA) were found in the livers of 5mg/kg/d PFNA-treated rats. Thus, exposure to PFNA disordered glucose metabolism via inhibiting hepatic insulin signal pathway, accelerating the output of glucose and increasing glycogen synthesis in the rat liver. Furthermore, the oxidative stress induced by PFNA may be involved in this process.