Influence of siRNA-mediated PPARγ Gene Knockdown on Insulin Resistance Induced by Myocardial

Objective To observe the influenece of siRNA-mediated PPARγ gene knockdown on insulin resistance induced by myocardial ischemia-reperfusion in adult rats. Method The targeting PPARγ siRNA was synthesized. The myocardial cells of adult rats were isolated and cultured. They were divided into four groups: IRI group, siRNA-PPARγ group, empty group and blank control group. Two groups of rat cardiac cells were transfected with PPARγ-targeting siRNA (siRNA-PPARγ group), or empty small interfering RNA (NC group), respectively. Real-time quantitive PCR was performed to detect the mRNA levels of PPARγ and GLUT-4. PPARγ protein expression level was determined with Western blot test. The uptake rate of glucose was determined by the isotope tracer method. Result The PPARγ mRNA and protein expression of IRI group were significantly higher than those in blank control group (P<0.05). The PPARγ mRNA and protein expression of siRNA-PPARγ group were significantly less than those in blank control and IRI group (P<0.01). There was no significant difference in the PPARγ mRNA and protein expression between the blank group and IRI group. The mRNA expression of GLUT-4 in blank control was no significant difference at each time point. The mRNA expression of GLUT-4 in IRI group was significantly less at 0 min, but increased gradually over the following time point. Finally, The mRNA expression of GLUT-4 in IRI group restored the same level as blank control. There was no significant difference in the GLUT-4 mRNA expression between the empty group and IRI group. The GLUT-4 mRNA expression in siRNA-PPARγ group was significantly less than that in IRI group or NC group (P<0.05), and recovered more slowly than IRI group. After given insulin, The uptake rate of glucose in siRNA-PPARγ group was significantly less at each time point compared with those in IRI group (P<0.05), declined by 49.78%, 38.94%, 18.61%, 11.54% at 0 min, 15 min, 1 h,2 h, respectively. At 6 h time point, the uptake rate of glucose in siRNA-PPARγ group reached the same level as IRI group. There was no significant difference was observed in the uptake rate of glucose between the empty group and IRI group. Conclusion The siRNA-mediated PPARγ gene knockdown may enhance the myocardial insulin resistance. The molecular mechanisms that trigger myocardial cell insulin resistance might because the silence of PPARγ expression decreasing the expression of GLUT-4 and decline its transportation from cytoplasm to membrane.