Effects of exercises on the lipid metabolism and expression of PPAR-α mRNA in skeletal muscles of ApoE knockout mice

Abstract

Objective To observe the influence of exercises on the mRNA expression of peroxisome proliferator-activated receptor (PPAR-α) and its target genes of acyl-CoA oxidase (ACO),Enoyl-CoA-hydratase and 3-hydroxyacyl-CoA-dehydrogenase (EHHADH) in the skeletal muscles in insulin-resistance mice to develop a way to improve the lipid metabolism.Methods Twenty male ApoE knockout mice were randomly divided into two groups,the high-fat diet group (group HFD) and the exercise training group (group Ex).The HFD group were fed with highfat diet,while the Ex group were fed in the same way,with additionally swimming training.And ten healthy male C57BL/6j mice were chosen as the control group(group ND).After 12 weeks of intervention,the serum lipid,blood glucose and insulin levels were determined,and homeostasis model assessment insulin resistance index (Homa-IRI) was calculated.The bilateral gastrocnemiuses were cut to be observed under a transmission electron microscope,and the mRNA expression of PPAR-α,ACO and EHHADH in skeletal muscle were measured using reverse transcription polymerase chain reaction(RT-PCR).Results The transmission electron microscope showed that the sarcolemma edema,mitochondrial swelling,as well as focal myocytolysis and edema within myofibrils were observed in the HFD group.The total cholesterol,low-density lipoprotein cholesterol,free fatty acid,fasting glucose,insulin and HomaIRI of the HFD group were significantly higher than the control group (P ＜ 0.05),while the mRNA expression of PPAR-α,ACO and EHHADH was significantly deceased than the latter(P ＜ 0.05).After swimming,the abovementioned pathological changes disappeared.The serum lipid of the Ex group were significantly lower (P ＜ 0.05),while HDL was significantly higher (P ＜ 0.05).And fasting insulin,glucose and HOMA-IR of the Ex group were significantly lower (P ＜ 0.05),while the mRNA expression of the above in the Ex group were significantly increased (P ＜0.05).Conclusion Swimming training could improve insulin resistance and metabolic disorder of lipid of ApoE knockout mice.The possible mechanisms may be through up-regulating the expression of PPAR-α,which in turn stimulates the expression of ACO and EHHADH mRNA to strengthen fatty acid β-oxidation. Key words: Exercises; Insulin resistance; Peroxisome proliferators-activated receptor alpha; acyl-CoA oxidase; Enoyl-CoA-hydratase and 3-hydroxyacyl-CoA-dehydrogenase