OBJECTIVEThe prevalence of non-alcoholic fatty liver disease (NAFLD) has markedly increased. Insulin resistance has been implicated in the pathogenesis of NAFLD. This study was aimed at observing the relationship between insulin resistance and NAFLD, and evaluating the role of pioglitazone (PGZ) acting as insulin-sensitizing agents in the prevention and treatment of rat fatty liver induced by high fat feeding.

METHODSThe rats were separated randomly into 6 groups: model group I were fed high fat diet for 8 weeks, PGZ prevention group were given PGZ 4 mg/(kg.d) simultaneously, while control group I were fed normal food for 8 weeks; model group II were fed high fat diet for 16 weeks, PGZ treatment group were given PGZ 4 mg/(kg.d) orally simultaneous with high fat diet for 8 weeks after high fat feeding for 8 weeks, control group II were fed normal food for 16 weeks. The rats were sacrificed after 8 weeks and 16 weeks respectively. Liver weight, body weight, serum activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), tumor necrosis factor alpha (TNF-alpha), fasting blood glucose (FBG), fasting plasma insulin (FINS), HOMA (homeostasis model assessment) insulin resistance index (HOMA-IR), and the liver histology of rats of all groups were assayed.

RESULTSAfter 8 weeks, the liver in model group I showed typical steatosis, accompanied with mild to moderate lobular inflammatory cell infiltration, liver indexes and serum levels of ALT, AST, ALP, TNF-alpha were significantly increased (P<0.05) compared with control group I. Whereas, the degree of hepatic injury was attenuated in PGZ prevention group, liver indexes and serum levels of ALT, ALP were significantly decreased (P<0.05) compared with model group I. After 16 weeks, notable steatosis, and lobular inflammation were observed in model group II rat liver, while the degree of hepatic injury was attenuated in the PGZ treatment group. Liver index, serum levels of ALT, AST, ALP, FINS and HOMA-IR were significantly increased (P<0.05) in model group II compared with control group II. Whereas, in PGZ treatment group, serum levels of AST and FINS showed decreasing tendency, liver indexes, serum levels of ALT, ALP, TNF-alpha and HOMA-IR were significantly decreased compared with model group II.

CONCLUSIONInsulin resistance plays a role in the pathogenesis of NAFLD in rats. Pioglitazone can attenuate insulin resistance and biochemical and histological injury in high fat-induced fatty liver in rats.