| Objective: High-fat feed C57BL/6 mice to induce animal model of insulin resistance, then carried out program of aerobic exercise intervention, observe the changes of mitochondrial uncoupling protien 3 expression ,mitochondrial respiratory function, free fatty acid content in skeleton muscle. Explore role of UCP3 in mechanism of IR occurance and in the aerobic exercise prevent IR.Methods: 1)Creating mouse model of insulin resistance: First, 80 male, 8-week old C57BL/6 mice were divide into normal chow group and high-fat diet group randomly, fed by normal and high fat diet respectively. 8 weeks later, The normal chow group was randomly divided into normal chow diet contorl (NC) and normal chow exercise group (NE), meanwhile mice from high fat diet groups which have insulin resistance continued to be fed with high-fat diet and randomly divided into high-fat diet control (HC) and high-fat diet exercise training group (HE) during the subsequent 8-week period. 2) Exercise protocol: Exercise training consisted of motorized treadmill running for 1 hour/day, 5days/week at an intensity of 75%VO2max. 3) Measurement of Indicators: after 8-week exercise, measured fasting blood glucose concentration, fasting serum insulin level, mitochondrial respiratory state 3 and state 4 and ATP synthesis enzyme activity. Detected content of FFA, UCP3 and GLUT4 expression in skeletal muscle. observe lipid desposition with Oil red O stain skeletal muscle. Results: 1) Changes of FBG and FINs:The FBG and FINs were altered significantly by either high fat diet or aerobic exercise. 2) Changes in mitochondrial respiratory function: HC compared with NC, mitochondrial state 4 respiration of mice skeletal muscle was significantly higher (p<0.05), state 3 respiration and respiratory control ratio (RCR) were significantly lower (p<0.01). NE and HE compared with respective control groups, state 3 and RCR were significantly increased (p<0.01). 3) Mitochondrial ATP synthesis enzyme activity: ATP synthesis enzyme activity was increased by high-fat feeding (p<0.01) but were decreased by exercise training (p<0.05). 4) The expression of UCP3 mRNA and protien: we found UCP3 mRNA level of HC group was increased by 41.78% than NC group (p<0.01), similarly UCP3 protien level was increased by 69.47% (p<0.01). Two exercise groups were decreased significantly in mRNA and protien. 5) The expression of GLUT4 mRNA and protien: The expression of GLUT4 mRNA and protien were significantly decreased in HC group compared to NC group (espectively decreased 49% and 42.71%, p<0.01). The expression of GLUT4 mRNA and protien of HE group were espectively increased by 40% and 36.9% than HC group. 6) Free fatty acid content: HC group were significantly higher than in skeletal muscle free fatty acid NC group (p<0.01). The exercise group was significantly lower than the control group (p<0.01). 7)Correlation analysis: RCR and UCP3 protien were significantly negative correlation, UCP3 protien and FFA and State 4 were significantly positive correlation. 8) Lipid desposition : Oil red staining, we found lipid desposition in HC was more than NC. Conclusion:1) High-fat can induce IR accomponied higher HOMA-IR and lipid accumulation. 2) Long term high-fat load increase state 4 respiration, induce uncoupling of respiratory chain, reduced RCR, respiratory function was reduced in the mitochondria of mice skeletal muscle; Up-regulation of UCP3 is maybe induced by elevation of FFA, be related to compensatory increase in FFA metabolism, fight IR occurrence and development.3)Long-term aerobic training can reduce skeletal muscle mitochondria state 4 respiration in the IR mice, increased coupling of mitochondrial energy conversion and improve mitochondrial respiratory function; Down-regulation of UCP3 expression reflect the adaptability of skeletal muscle mitochondrial function to accelerate the glucose and lipid metabolism rate under high-fat, delay the occurrence and development of IR. |
PDF Full Text Request