Effect And Mechanism Of Sleeve Gastrectomy With Bypass Of Proximal Small Intestine On Glucose Metabolism

Part I:Effect of sleeve gastrectomy with bypass of proximal smallintestine on glucose metabolismBackgroundThe prevalence of diabetes mellitus(DM)is increasing year by year worldwide in recent years,and DM has become one of the most important chronic non-communicable diseases threatening human health.A growing number of observational studies and randomized controlled trials have shown that bariatric/metabolic surgery,when used specifically to treat diabetes,promotes dramatic and durable glycemic control.Sleeve gastrectomy(SG)and Roux-en-Y gastric bypass(RYGB)are currently the most commonly performed bariatric/metabolic surgical procedures.Although bariatric/metabolic surgeries can provide satisfactory diabetes control,uncontrolled diabetes and postsurgical relapse have been reported in some patients.Associated risk factors include longer preoperative duration of diabetes,preoperative insulin use,weight regain,less weight loss,poor compliance,and postoperative high-calorie diet.To strengthen the effect of SG on diabetes,pioneer surgeons have combined various novel procedures with SG,involving surgeries of different parts of the small intestine and other non-surgical interventions.These procedures,collectively referred to as SG-plus procedures.SG plus duodenojejunal bypass(SG-DJB)is based on the intestinal bypass design concept of RYGB,small intestinal surgery was added to SG.SG-DJB was initially performed in a porcine model and was reported in 2008,and used to treat obesity with T2DM.We compared SG-DJB with SG in a previous animal study and found similar improvements in diabetes on Goto-Kakizaki diabetic rats.However,later clinical studies consistently showed that SG-DJB was superior to SG in promoting diabetes remission,A possible reason for this discrepancy is that both SG and SG-DJB provide good diabetes control,and that the effect is so quick and durable in diabetic animalsthat the superiority of SG-DJB is not obvious.It was found that high-fat diet(HFD)could act as an independent adverse factor to affect the hypoglycemic effect of surgery,thus inducing postoperative diabetes recurrence in T2DM rats.Therefore,we added a HFD postoperatively in this study to disrupt the improvement in diabetes after SG-DJB and SG-JJB.In addition to SG-DJB,we also studied SG plus jejunoj ejunal bypass(SG-JJB)to clarify the role of proximal intestinal bypass in "SG+" surgery.Objective:The aim of this study was to compare the effect of glucose metabolism after SG with bypass of proximal small intestine and SG alone under a postoperative adverse diet for diabetes remission in a high-fat diet(HFD)/streptozotocin(STZ)-induced diabetic rat model.MethodsThe HFD/STZ-induced diabetic rats were randomly divided into a sham surgery,SG,SG-DJB and SG-JJB groups(n=10 in each group).All surgeries were performed under general anesthesia with 10%chloral hydrate solution(3 mg/kg,injected intraperitoneally)after preoperative preparation.After surgery,the rats in each group were continuously fed the same HFD as preoperatively,after 3 to 5 days of low-residue diet.Body weight,food intake,and fasting blood glucose(FBG)were measured once per week for the first 2 weeks after surgery and then twice per week untl the end of the study.OGTT was performed at baseline and at 2,8,and 16 weeks postoperatively.In addition,homeostasis model assessment of insulin resistance(HOMA-IR),hepatic function indices,fasting lipid profiles and ghrelin,and secretion of glucagon-like peptide-1(GLP-1)and insulin after glucose gavage were measured at 2 and 16 weeks postoperatively.Results1.Body weight and food intake:Compared with the sham group.the body weight of rats in the other 3 groups was significantly lower from 4 weeks postoperatively and food intake was significantly lower from 2 weeks postoperatively.There were no significant differences in weight loss or food intake among the 3 surgery groups during the observation period.2.FBG:SG,SG-DJB,and SG-JJB groups had significantly lower FBG levels than those in the sham group from 1 week postoperatively.Mean FBG of the SG group was significantly higher than that of the SG-DJB group from 12 weeks postoperatively and was higher than that of the SG-JJB group from 14 weeks postoperatively.There were no significant differences in FBG between the SG-DJB and SG-JJB groups within the 16-week observation period after surgery.3.OGTT:Two weeks postoperatively,the AUCOGTT of the SG,SG-DJB,and SG-JJB groups were lower than that of the sham group;this difference remained until the end of the study.Compared with the SG group,the DJB-SG and JJB-SG groups had lower AUCOGTT at 16 weeks postoperatively.The AUCoOGTT of the SG,SG-DJB,and SG-JJB groups were significantly higher at 16 weeks than at 2 weeks postoperatively.There was no significant difference between SG-DJB and SG-JJB groups at any time after surgerY.4.insulin resistance index:Compared with the sham group,the SG,SG-DJB,and SG-JJB groups had lower HOMA-TR values at 2 weeks postoperatively.At 16 weeks postoperatively,the SG-DJB and SG-JJB groups continued to have lower values than the sham group.However,there was no significant difference between the sham and SG groups.HOMA-iR in the SG,SG-DJB,and SG-JJB groups were significantly higher at 16 weeks than at 2 weeks postoperatively.There were no significant differences among the SG,SG-DJB,and SG-JJB groups at either time point5.Glucose-stimulated insulin secretion:At 2 weeks postoperatively,there were no differences among groups in serum insulin concentrations during fasting or in response to glucose Gavage.However,the insulin secretion levels of the SG,SG-DJB,and SG-JJB groups were higher than those of the sham group at 16 weeks postoperatively.No significant difference was observed in insulin secretion among the SG,SG-DJB,and SG-JJB groups.6.GLP-1 and ghrelin secretion:The SG.SG-DJB,and SG-JJB groups secreted more GLP-1 after glucose gavage and lower fasting serum total ghrelin levels than the sham group at 2 and 16 weeks postoperatively.GLP-1 secretion levels in the SG-DJB and SG-JJB groups were higher than that in the SG group at 16 weeks postoperatively.There was no difference in GLP-1 secretion between the SG-DJB and SG-JJB groups and ghrelin levels among the SG,SG-DJB,and SG-JJB groups after surgery.7.Liver function and lipid profiles:Serum ALT and AST of rats in the three surgery groups were lower than those in the sham group at 16 weeks postoperatively,but not at 2 weeks postoperatively.At 2 weeks postoperatively.fasting triglycerides and NEFA levels of rats in the SG,SG-DJB,and SG-JJB groups were lower than those in the sham group.These differences lasted until 16 weeks postoperatively.Serum fasting cholesterol of rats in the three surgery groups were lower than those in the sham group at 116 weeks postoperatively.Conclusions1.The present animal study revealed that SG,SG-DJB,SG-JJB have significant hypoglycemic effects,and SG-DJB and SG-JJB provided better diabetes control than SG alone under the interference of a postoperative HFD.2.SG-DJB and SG-JJB has a better long-term effect in improving insulin sensitivity,indicating that the improvement and worsening of insulin sensitivity was associated with diabetes remission and HFD-induced diabetes relapse after surgery.3.Duodenal exclusion was not essential in SG-plus procedures.Compared with these SG plus duodenal switch/bypass procedures,SG-JJB keeps the duodenum intact and is less invasive and technically easier.Our results should be confirmed with further clinical studies.Part Ⅱ:Mechanism of sleeve gastrectomy with bypass of proximalsmall intestine on glucose metabolismBackgroundT2DM is a kind of chronic non-infectious disease caused by combined action of environmental and genetic factors.The onset of T2DM is insidious,and its pathogenesis is still unclear,but insulin resistance and dysfunction in its secretion by pancreatic βcell are the pathogenesis basis of T2DM.In the early stage of T2DM,insulin resistance leads to decreased glucose uptake and utilization in the body.At this time,pancreatic βcell secretes more insulin compensatorily,leading to hyperinsulinemia for maintaining stable blood glucose level.When insulin secretion is insufficient to compensate for the increase of blood glucose level caused by insulin resistance,the blood glucose exceeds the normal range,leading to the occurrence of T2DM.Recent studies have found that chronic low-grade inflammation in the body plays an important role in the occurrence and development of insulin resistance and T2DM,and increased lipopolysaccharide(LPS)in the circulation is the main proinflammatory factor resulting in chronic low-grade inflammation in the T2DM.A large number of studies have shown that HFD can affect the expression level of intestinal tight junction protein,and also favors changes in intestinal microenvironment,including intestinal flora,triggering intestinal inflammation,impairing intestinal barrier function and increasing intestinal permeability,then leading to increase of circulatory LPS level.When the increase of LPS entering the circulation causes excessive release of nonspecific inflammatory factors such as TNF-α,which further interferes with insulin receptor substrate(IRS)and phosphatidylinositol-3-kinase(PI3-K)signaling and reduces insulin sensitivity,which is one of the maj or molecular mechanisms of insulin r-esistance.In recent years,bariatric/metabolic surgery has gradually become one of the hot issues in the research of treatment of T2DM,and global researchers have conducted in-depth research on its therapeutic mechanism.yet the mechanism remains unclear.The researchers found that bariatric/metabolic surgery can significantly reduce serum LPS levels in obese and T2DM patients,and alleviate chronic inflammation.The decrease in serum LPS level may attribute to the improvement of intestinal flora and the repair of intestinal barrier function.At present,there are abundant studies on intestinal flora,but few studies on intestinal barrier function.Further studies are needed focusing on the changes of intestinal barrier function after SG surgery alone and SG with bypass of proximal intestinal and influence on enhancing the hypoglycemic effect.Due to the possibility of "blind loop syndrome" in SG-JJB surgery,which may affect the evaluation of intestinal barrier function,we will conduct a separate study on JJB surgery in another subject.SG-DJB is relatively mature and has wider clinical application,which can reflect the mechanism of bypass of proximal intestinal in increasing the hypoglycemic effect of SG surgery.Therefore,in this part of the study,we only focused on the comparison between SG-DJB and SG surgery.Objective:The purpose of this study was to compare the effect of SG-DJB)and SG alone on intestinal barrier function and intestinal permeability,and their role of improving glucose metabolism in T2DM rats under adverse dietary disturbance.MethodsIn this study,urine,serum and terminal ileum specimens of SHAM,SG and SG-DJB groups were retained in the part I.The lactulose and mannitol molecular probe methodwas used to evaluate the intestinal permeability,and urine was retained at baseline andat 8,and 16 weeks postoperatively as required.The content of lactulose and mannitol in urine was quantitatively detected by High Performance Liquid Chromatography(HPLC),and then the ratio of lactulose and mannitol excretion rate was calculated.The expression levels of Occludin,claudin-1 and claudin-3 proteins were detected by immunohistochemistry and Western Blot,and serum LPS,TNF-a and GLP-2 were detected by ELISA kit.Results1.Intestinal permeability:The lactulose and mannitol molecular probe method was used to evaluate the intestinal permeability at baseline and 8,and 16 weeks postoperatively by comparing the ratio of lactulose and mannitol excretion rates(L/M).Compared with the sham group,the SG and SG-DJB groups had lower L/M ratios at 8 weeks postoperatively.At 1 6 weeks postoperatively,the SG-DJB groups continued to have lower ratio than the sham group.However,there was no significant difference between the sham and SG groups.There were no significant differences among the SG and SG-DJB at any time point.2.Expression of tight junction protein in intestinal epithelial cells:Rats in the sham,SG and SG-DJB groups were sacrificed at 16 weeks postoperatively,and the terminal ileum was retained for immunohistochemical and Western Blot experiments.The positive expressions of Occludin,claudin-1 and claudin-3 proteins in SG and SG-DJB groups were higher than sham group.And the positive expressions of Occludin and claudin-1 proteins in SG-DJB group was higher than those in SG group,but the positive expressions of claudin-3 proteins in SG and SG-DJB groups were not significantly different.Western Blot results in each group were similar to those of immunohistochemistry.3.Levels of serum LPS:The serum LPS level of SG-DJB group was significantly lower than those of sham and SG groups.There was no significant difference in serum LPS levels between SG and sham groups.4.Levels of serum TNF-a:The serum TNF-a level of SG-DJB group was significantly lower than that of sham group.There were no significant differences in serum TNF-a levels between SG and sham groups,also between SG and SG-DJB groups.5.Levels of serum GLP-2:Serum GLP-2 level of SG-DJB group was significantly higher than those of sham and SG groups,and serum GLP-2 level of SG group was also significantly higher than that of SHAM group.Conclusions1.Under continuous high-fat diet after surgery,changes in intestinal permeability and chronic inflammation may be related to improvement and deterioration of insulin sensitivity after SG surgery2.Combined DJB surgery can significantly increase secretion of GLP-2 after SG surgery,up-regulate the expression intestinal epithelial cells and repair intestinal barrier function damaged by HFD,thus alleviate chronic inflammatory state.