Effects Of Aerobic Exercise And Dietary Intervention On LKB1/AMPK Pathway In Islets Of IR Rat

Objective: In this research,we build an insulin-resistant rat model through high fat diet feeding.After observation of influence of long-term aerobic exercise and dietary intervention on LKB1/AMPK signaling pathway in islets of insulin-resistant rats,the research intends to demonstrate the regulation mechanism of aerobic exercise and dietary intervention improving insulin resistance.Methods: 100 male 7w-old SD rats were randomly divided into normal diet group(N)and high fat diet group(HFD).After feeding the subjects for 10 w,their body weight,fasting blood glucose(FBG),fasting insulin(FINS)and glucose tolerance test(IPGTT)were measured to guarantee the success of IR rat model.IR rats were randomly divided into four groups: IRHC group(high fat diet),IRHE group(high fat diet + exercise),IRNC group(normal diet)and IRNE group(normal diet + exercise);normal rats were randomly divided into NC group(normal diet)and NE group(normal diet + exercise).Exercise intervention group exercised on treadmill 20m/min,0%,60min/d,5d/w)for 8w.After exercise intervention,their body weight,body composition and IPGTT were measured.24 hours after ending of exercise,FBG,FINS,fasting C-peptide,TC and TG contents were measured through blood test;then islets were taken to do the following test: AMPK? and p-AMPK?Thr172 were measured by immunohistochemical method;the protein expressions of AMPK?,p-AMPK?Thr172,PDX-1,GLUT2,GCK,SNAP25,KIR6.2,and Pax-6 were detected by Western Blot.Results: After 10w's high fat diet feeding,IR rats were successfully modeled.In IRHC group(long-time high fat diet feeding rats),insulin resistance occurred along with obesity,dyslipidemia and impaired glucose tolerance,and in islets,the protein expressions of PDX-1 and SNAP25 were significantly increased,while the protein expressions of LKB1,p-AMPK?Thr172,AMPK,GLUT2,GCK,KIR6.2,Pax-6 were decreased significantly.After 8w's aerobic exercise,obesity,insulin resistance,dyslipidemia and impaired glucose tolerance were significantly improved in IRHE group,but the related protein expression in islets did not change significantly.After 8w's dietary intervention,obesity,insulin resistance,dyslipidemia and impaired glucose tolerance were significantly improved in IRNC group,and in islets,the protein expressions of LKB1,p-AMPK?Thr172,AMPK?,GLUT2,GCK,KIR6.2 and Pax-6 were significantly increased,but the protein expressions of PDX-1 and SNAP25 were significantly decreased.After 8w's aerobic exercise combined with dietary intervention,obesity,insulin resistance,dyslipidemia and impaired glucose tolerance were more significantly improved in IRNE group,and in islets,the protein expressions of LKB1,p-AMPK?Thr172,GCK,KIR6.2 and Pax-6 were significantly improved,while the protein expressions of PDX-1 and SNAP25 were decreased significantly.Conclusions:(1)Long-term high-fat diet could reduce the protein expressions of GLUT2 and GCK,which led to impaired glucose sensitivity in islets,decreased the protein expressions of LKB1/AMPK and KIR6.2,increased the protein expressions of PDX-1 and SNAP25 and promoted insulin synthesis and basal secretion to compensate for peripheral IR.(2)Long-term aerobic exercise could improve IR,but had no significant effect on the protein expressions of LKB1/AMPK,PDX-1,Pax-6,KIR6.2,SNAP25,GLUT2 or GCK in islets,indicating that exercise improved IR but may not directly by improving islets' function.(3)The restoration of normal diet could improve IR,which could improve impaired glucose sensitivity in islets by increasing the expressions of GLUT2 and GCK,increase the expressions of LKB1/AMPK,KIR6.2 as well as Pax-6,and decrease insulin synthesis and basal secretion by and decreasing the expressions of PDX-1 and SNAP25 to improve the function of islets.