Abstract: Objective To measure the changes of gastric inhibitory polypeptide (GIP) of the  diabetic rats before and after  gastric bypass surgery (GBP) and to discuss the possible mechanism of GBP  in treatment of type 2 diabetes mellitus.Methods The animal models with diabetes mellitus were established in 40 eight weeks old Wistar rats by intraperitoneal injection with STZ，then all the rats were randomly divided into control,diet control,sham operation and operation groups.The rats in control group took food freely,the rats in diet control group were controlled  with  food intake at 15 g/d,the rats in sham operation group  underwent in situ anastomosis after GBP,and the rats in operation group  received GBP.Results Compared with before operation  the fasting and postprandial plasma glucose levels in operation group 4 and 8 weeks after operation were significantly lower than those in the other 3 groups at the corresponding time points(P<0.01);the mean fasting and postprandial serum insulin levels were  significantly higher than those in the other groups at the corresponding time points (P<0.01 ).Compared with before operation,the serum GIP levels in operation group 4 and 8 weeks after operation were   decreased significantly ( P<0.01), and the fasting and postprandial serum GIP levels in operation group were significantly lower than those in the other groups at the corresponding time points (P<0.01).1 week after operation,the average intakes in operation group and sham operation group were decreased and then increased.The average intake in operation group was decreased again from the second postoperative week and was less than those in  sham operation group and control group till the experiment ended (P＜0.05).Compared with before operation,the body mass of the rats in operation group,shame operation group and diet control group were decreased significantly 1 week after operation (P＜0.05).Conclusion The blood glucose and the serum GIP levels of the diabetic rats after GBP are decreased,and its mechanism  may be related to  decreasing  GIP secretion and lifting the peripheral tissue insulin resistance.

Key words: diabetes mellitus,type 2, gastric bypass, gastric inhibitory polypeptide