The Effect And Mechanism Of Rad GTPase On Insulin Signaling In Adipose Tissue And Steletal Muscle Of Mice

Objective In this study,we aimed to investigate the effect of Rad(Rasassociated with diabetes)GTPase on insulin signaling in adipose tissue and skeletal muscle to explore its possible mechanism.Methods1.Rad GTPase knockout mice were used as an experimental model,and littermate wildtype mice were used as the control group.All experiments were started with 8-week-old male mice.Glucose tolerance test(GTT)and insulin tolerance test(ITT)were performed on chow diet or high-fat diet(HFD)mice,respectively.The body weight changes in the HFD group were observed and measured once every month.The mice were anatomically examined to measure fat pads in different locations after three months of feeding.2.We injected insulin or vehicle control(saline)to the wildtype and Rad GTPase knockout mice fed with HFD for 3 months.The adipose tissues and skeletal muscles in wildtype and Rad GTPase knockout mice were harvested at 10 min after insulin or vehicle injection for Western-blotting analyses.Results1.The results of GTT and ITT tests suggest:(a)when compared to wildtype control mice,the Rad GTPase knockout mice showed insulin resistance and impaired glucose tolerance with chow diet,suggesting a prediabetic condition of these mice.(b)One bonus injection insulin to wildtype mice significantly reduced the blood glucose level,but the Rad GPTase knockout mice showed less response to insulin injection,indicating insulin resistance of Rad GTPase knockout mice fed with HFD for 3 months.Peritoneal injection of glucose induced higher glucose levels in blood of Rad GTPase knockout mice than that of wildtype mice,further demonstration of impaired glucose tolerance in mice of Rad GTPase deficiency.2.Through the observation of body weight changes and the measurement of fat pads in these mice fed with HFD,we found that Rad GTPase knockout mice have larger body weight than wild-type mice after 3-month HFD feeding,and fat tissue was greater at every site in Rad GTPase knockout mice than those of wildtype mice.3.Western-blotting analyses documented that Rad GTPase deficiency did not affect insulin signaling in both skeletal muscle and adipose tissue.4.Western-blotting analyses demostrated that Rad GTPase defiecincy increased JNK signaling in adipose tissue,which may leads to insulin resistance of Rad GTPase knockout mice.ConclusionRad GTPase is a mediator that enhances insulin signaling in adipose tissue through reducing JNK signaling.