Effects of high-fat diet on fatty acid metabolism, expression and activity of acetyl-coenzyme A carboxylase in skeletal muscle in aged rats / 中华老年医学杂志

ABSTRACT

Objective To investigate the effects of high-fat diet on fatty acid metabolism, expression and activity of acetyl coenzyme A carboxylase (ACC) in skeletal muscle in rats. Methods Male Wistar rats aged 22-24 months were randomly divided into old control (OC) group and high-fat diet (HF) group. Male Wistar rats aged 4-5 months were selected as young control (YC) group. The rats in OC and YC groups were fed with basic diet, and the rats in HF group received high-fat diet. Insulin sensitivity was evaluated by hyperinsulinemic-euglycemic clamp technique. Skeletal muscle triglyceride was extracted and measured by an automated biochemistry analyzer. Long-chain acetyl coenzyme A (LCACoAs) were extracted from muscle and measured by a fluorospectrophotometer. Protein expressions of ACC and P-ACC were measured using SDS-PAGE and Western blot techniques. Results (1)Fasting blood glucose (FBG), fasting insulin (FINS) and free fatty acid were higher in OC group than in YC group and they increased significantly in HF group. Triglyceride (TG) and total cholesterol (TO levels were also elevated after high-fat feeding. (2)Glucose infusion rates (GIR) were reduced in OC group than in YC group, and decreased significantly after high-fat feeding. GIR was lower at the end of the 8th week than at the end of the 4th week in HF group. (3) Compared with YC group, skeletal muscle triglyceride and LCACoAs increased in OC group and increased significantly in HF group. (4)No alterations of protein levels of ACC in skeletal muscle were detected among three groups (P>0.05). The protein levels of P-ACC in skeletal muscle were lower in OC group, and much lower in HF group than in YC group (P<0.05 or P<0.01). Conclusions Compared with young rats, abnormal fatty acid metabolism and insulin resistance always exist in aged rats. High-fat feeding results in a significant increase in lipid content in skeletal muscle. Alterations of ACC activity may contribute to fat accumulation in skeletal muscle and insulin resistance.