Sleeve Gastrectomy Model In Diet-induced Obese Sprague-Dawley Rat

Objective: Sleeve gastrectomy has the same efficacy in resolution of T2DM as the classic by pass operation and animal model is the best method for elucidating the mechanism. Although animal model for sleeve gastrectomy (SG) were reported by domestic and foreign researcher, some technical details were not described and still there were reports of regain of body after surgery. The objective of our experiment is to develope a long-term weight loss animal model for SG in DIO (diet-induced obesity) Sprague-Dawley (SD) rats by surgical technique more similar to the standard human surgical approach of laparoscopic sleeve gastrectomy (LSG) and providing a better platform for further investigating metabolic and hormonal parameters related to SG improvement of type 2 diabetes mellitus.Methods: (1) analysis of learning curve and evaluation of sleeve gastrectomy in DIO rats: 26 male SD (6-week-old) rats were fed with high-fat diet for 4 weeks, developing DIO rats model and 15 male SD (6-week-old) rats were divided randomly in three groups following the sequence of operation time. The first group was 6 rats and the second and the third group were respectively 10 rats. All rats underwent SG. The establishments of the residual volume of the stomach are determined by a sterile Foley urethral catheter (#10F/3.3mm) as Bougie tube and the division of the antrum 8mm proximal to the pylorus. The body weight was recorded daily after operation. Peripheral blood concentrations of total ghrelin in all of subjects were measured before operation and on the 7th day, 14th day and 28th day after operation by ELISA. (2) modification of sleeve gastrectomy model: 9 DIO rats were divided randomly in two groups. Six rats of them underwent SG as the sleeve gastrectomy group (SGG) and the other three rats underwent a laparotomy and stomach manipulation as the sham operative group (SOG). The establishments of the residual volume of the stomach were modified. A sterile Foley urethral catheter (#8F/2.7mm) was used and the beginning of gastric resection was 5mm proximal to the pylorus. The body weight was recorded daily before and after operation. Average caloric intake of rats was tested weekly. Peripheral blood concentrations of total ghrelin were the same.Results: (1) 14 rats survived among 26 rats after operation. Operative duration, blood loss and mortality in third group were fewer than the second and the third group. Average weight of rats regained to the preoperative level on the 14th days after surgery. The plasma ghrelin level declined after operation, but began to go up on 7 days after operation and reached to preoperative level on the 28th days.(2) All animals survived through the experiment. The weights of the rats in SOG began to rise on the average fifth postoperative days (POD). At the end of the experiment, the mean weight (487.43±10.12g) of the SOG was distinctly higher than the mean one (467.00±8.43g) of the same group on the day before surgery. However, weight loss was achieved obviously in the SGG, which reached a maximum on the eighth POD. Following that time point, the average weight of the SGG got to rise slowly but was still lower (420.08±18.61g) than preoperative levels (471.77±17.89g) at all time till the end of experiment. The difference between two group had statistical significance (P=0.000).(3) Average caloric intake of rats in SGG was lower than that of SOG after operation. In the fouth postoperative week, average caloric intake of SGG (22.1±3.26g) fell 17.60% compared with average one of SOG (26.8±1.46g).The difference between two group had no statistical significance (P=0.121).(4) SGG showed a strikingly decrease trend in ghrelin level after intervention. The preoperative ghrelin concentration inperipheral blood was 1595.05±14.42 pg/ml and the postoperative level was 1316.80±14.74pg/ml, decreased with 17.44%. The ghrelin level of rats in SOG had no significant change throughout the experiment. The difference between two group had statistical significance (P=0.000).Conclusion: We have established some technical details of sleeve gastrectomy in DIO rats including a stent with a caliber of 2.7mm, starting the resection point 5mm away from pylorus and finishing it by His angle and remove the fundus totally. The body weigh loss process and post-operative ghrelin change are similar to those observed in human research. This model can be used for the further study elucidating the mechanism of resolution of T2DM following sleeve gastrectomy.