Effects of aging on serological and hepatic morphological changes in rats with non-alcoholic fatty liver disease

Objective To investigate and analyze serological and hepatic morphological changes in aged rats with non-alcoholic fatty liver disease(NAFLD)by establishing NAFLD model with SD rats at different months of age. Methods Male SD rats were randomly divided into four groups according to age: the aged model group(18-months-old), the aged control group(18-months-old), the young model group(2-months-old)and the young control group(2-months-old), with 12 rats in each group.Rats in the model groups and the control groups were fed a 45% high-fat diet and a normal diet, respectively, for eight weeks.Serum biochemical indexes and the insulin index were measured.Hepatic histological changes were evaluated under a light microscope following HE staining and Oil red staining. Results The body and liver weights of the rats increased with age, and the average rate of weight growth and liver wet weight of the model groups were higher than those of their corresponding control groups(P<0.01). Levels of serum alanine aminotransferase(ALT), triglycerides(TG), cholesterol(CHOL), glucose(GLU), fasting insulin(FINS)and homeostatic model assessment of insulin resistance(HOMA-IR)in the aged model group were higher than those in the corresponding control group and of the young model group(P<0.05). Under the light microscope, hepatic cells stained with HE and Oil red showed diffuse swelling and were full of lipid vacuoles in the model groups.In the aged model group, hepatic cells were characterized by macrovesicular steatosis with focal necrosis. Conclusions Clear hyperlipemia, hyperglycemia and hyperinsulinemia can be seen in a NAFLD model induced by short-term high-fat feeding.Insulin resistance and decreased insulin sensitivity are more significant in aged rats with NAFLD. Key words: Fatty liver; Insulin resistance; Aging