Effect Of Roux-en-Y Gastric Bypass On Beta-cell Mass In Obese Rats

Objective: To investigate the effect of Roux-en-Y gastric bypass(RYGB)on ? cell mass in obese rats and to understand the potential mechanism for improving glycemic control after RYGB.Thus the study may offer a theory basis for bariatric surgery treating obese patients with diabetes.Methods:(1)Forty SD rats were randomly chosen and fed with a western high fat diet(HFD),and the other six rats fed with normal chow diet(NCD)were used as controls.After 16 weeks feeding,RYGB or a sham operation(SHAM group)was performed on obese rats of which body weight was 20% more than those in NCD group.(2)The number of rats in NCD group,HFD group,RYGB group and SHAM group were 6,6,10 and 6 respectively.Body weight was recorded before and after surgery.(3)At 6 weeks after surgery,intraperitoneal glucose tolerance test(GTT)was performed,blood insulin and C-peptide levels were measued at fasting and 30 minutes after glucose administration,HOME-IR index was calculated to evaluated insulin sensitivity.(4)At 8 weeks after surgery,total fat mass,epididymal fat mass and pancreas tissue mass were determined.Fasting plasma GLP-1 levels were measured with ELISA.Morphological analyses of pancreas and ?-cells mass were examined with immunohistochemical staining and immunofluorescence analysis respectively.Results:(1)The number of rats in each group was 6.Compared with rats in NCD group,rats in HFD group had higher body weight,epididymal fat mass and total fat mass(P<0.05).In contrast,rats in RYGB group had lower body weight,epididymal fat mass and total fat mass than that in HFD and SHAM groups(P<0.05).(2)A high-fat diet feeding induced impaired glucose tolerance and insulin resistance in HFD rats.After surgery,rats in RYGB group showed enhanced ? cell function,reflected in improved glucose control,lower fasting insulin levels,as well as higher insulin and C-peptide levels 30 minutes after glucose administration(P<0.05).HOME-IR index also decreased after RYGB.(3)In the NCD and RYGB rats,abundant insulin staining was observed in the images of the pancreatic tissue.In the HFD and SHAM rats,the insulin-stained areas were sparse and markedly reduced in size.(4)Compared with rats in HFD and SHAM groups,the ratio of pancreas weight to body weight,relative b-cell area,b-cell mass and thenumber of islets increased in rats underwent RYGB(P<0.05).It showed no significant difference in mean size of individual b-cell and mean islet size among different groups(P(29)0.05).(5)Fasting GLP-1 levels were significantly higher in RYGB rats in comparison with that in HFD and SHAM groups(P<0.05).Conclusion:(1)HFD induced early obesity,impaired glucose tolerance and decreased insulin sensitivity.(2)RYGB can significantly improve glucose tolerance and ? cell function in obese rats,which is in part due to the increased ? cell mass and islet number postoperatively.