Effects And Mechanisms Of Peroxisome Proliferator-Activated Receptor Gamma 1 DeSUMOylation On Insulin Resistance Induced By High Fat Diet In Mice

Objective: The purpose of this study was to investigate the effect of SERP1 mediated de SUMOylation of PPARγ1 on the vascular insulin resistance in C57BL/6mice induced by hyperglycemia and high fat stress and its underlying mechanisms.Methods: Our study was divided into four groups: control group(Ctrl),insulin resistance group(IR),IR+ negative control group(Vehicle),and IR+SENP1overexpression group(Ad-SENP1).C57BL/6 mice weighing approximately 15-20 g were selected for a high-fat diet,and obese models were established successfully after90 days.Five obese mice were injected with negative empty adenoviruses via tail veins as the Vehicle group.In addition,five Ad-SENP1 overexpressing adenoviruses were injected as the Ad-SENP1 group.30 days later,mice were sacrificed by anaesthesia,serum,thoracic aorta,and abdominal aorta were then selected for subsequent experiments.Finally,the following indicators were tested: 1)mouse morphological parameters such as Length,Weight,and Lee’s index;2)mouse serum insulin(FINS),triglyceride(TG),total cholesterol(TCH),etc.;3)the levels of by SENP1 were detected by Western blotting and the SUMO-1 levels of PPARγ1 were tested via Immunocoprecipitation(Co-IP);4)the levels of NO and Ang II in serum;5)the levels of methane dicarboxylic aldehyde(MDA)and manganese superoxide dismutase(SOD-Mn)in serum;6)western blotting detected the levels of IKK,IKK-pS176,the interaction between IKK and PIAS1 was detected by Co-IP,and the expression level of PI3K/AKT/eNOS in insulin signaling pathway was detected by western blotting.7)the endothelium-dependent vasodilation effect of thoracic aorta was detected by Powerlab system.Results:(1)De SUMOlyation of PPARγ1K77 can improve the insulin resistance of mice and its blood vessels under the stimulation of high glucose and high fat.The results showed that the level of PPARγ1 SUMO-1 in Ad-SENP1 group significantly decreased compared with that in Vehicle group.The level of PPARγ1 SUMO-1 in Ad-SENP1 group increased significantly.In additions,the level of NO increased71%compared with that in Vehicle group,while the level of Ang II decreased89%compared with that in Vehicle group in Ad-SENP1 group.Those results indicate that over-expression of SENP1 could lead to De SUMOylation-1 of PPARγ1K77 site and finally improve the insulin resistance state of mice and its vascular which induced by high glucose and high fat.(2)Effects of PPARγ1K77 De SUMOylation-1 on insulin resistance of vascular endothelial cells induced by high glucose and high fat.Western blotting results show that the level of IKK-pS176 in Ad-SENP1 group was down-regulated obviously.Immunoprecipitation results show that the interaction between Ike and PIAS1 was also weakened.Another western blotting results show that devitalization of PPARγ1K77 could relieve the inhibition of PI3K/AKT/eNOS signal pathway induced by high glucose and high fat stress.Conclusion: Overexpression of SENP1 leads to the de SUMOylation of PPARγ1.De SUMOylation of PPARγ1 can improve insulin resistance in the whole body and blood vessels induced by high glucose and high fat,and its mechanism may be related to the decrease of IKK-pS176 activity,the weakening of the interaction between IKK and PIAS1 and the suppression of PI3K/Akt/eNOS signaling pathway.