| Objective: Although bariatric surgery is one of the most effective methods to treat obesity and related metabolic syndrome,the mechanism of its action is still not completely clear.The present studies show that as the component of the cell walls of gram-negative bacteria,the enterogenous lipopolysaccharide(lipopolysaccharide,LPS)plays an important role in fat chyle absorption and insulin resistance.This study aims to explore the mechanism involved by detecting the metabolic changes and internal distribution of the LPS contained in rat enterogenous gram-negative bacterium during preoperative and postoperative period of sleeve gastrectomy.Methods : 1)Grouping: 80 Six-week old male rats: surgical group(n=20),sham operation group(n=20)and practice group(n=30)were fed high fat diet,the control group(n=10)were standard diet.All rats were fed for 8 weeks without dietary restriction.The weight,body length and glucose tolerance and insulin resistance level were measured after 8 weeks.Rats in surgical group were performed sleeve gastrectomy.Residual gastric volume refers to clinical standard.According to the execution time postoperative,they were divided into 1 week group(n=5),2 weeks group(n=5),3 weeks group(n=5)and 4 weeks group(n=5).Rats in sham operation group were performed exploratory Laparotomy,whose grouping coincides with surgical group.2)Operation quality evaluation and learning curve: Operation time and intraoperative blood loss were used to evaluate the quality of surgery and draw learning curve in order to analysis the cause of operative death.3)Weight curve: Rats weight of surgical group and sham operation group were measured once for two days after operation to draw weight curve and do statistical analysis.4)Gram stain of rats faeces: Faeces of rats from surgical group and sham operation group were selected randomly both preoperatively and 4-week postoperatively,which were used to analysis the proportion of the gram-positive bacterium and gramnegative bacterium.5)Serum levels of LPS: Rats' blood in surgical group and sham operation group were collected regularly both before and post operation to measure serum levels of LPS by Rat LPS Enzyme-linked immunoassay.6)Distribution of LPS in rat liver and abdominal fat: In surgical group and sham operation group,100 mg tissues of liver,mesentery fat,perirenal fat and epididymal fat were picked and grinded for tissue homogenate with normal saline when rats were executed to quantify the LPS contained in these tissues by Rat LPS Enzyme-linked immunoassay.7)Glucose tolerance test and insulin resistance in rats: Glucose tolerance tests and insulin resistance level tests were performed in each group both preoperatively and postoperatively.Results: 1)Rats in surgical group weight 31.38% more than the control group.Rats in sham operation group weight 29.74% more than the control group;Body length,the level of glucose tolerance and insulin resistance level of high fat diet rats all showed difference with the control group(p<0.0001).2)Operation time is the most important factor of survival rate of rats.Rats died due to the overlong operation time make up 31.82% of all dead rats.3)The weight of rats both from surgical group and sham operation group decreased after operation,but the weight of rats in sham operation group rebound gradually,even more heavier than preoperative.Oppositely,the weight of rats in surgical group decreased progressively and then stabilized,which showed difference with sham operation group(p<0.0001).4)In random oil microscopic view,the proportion of gram-positive bacteria of surgical group were increased compared with sham operation group(p<0.0001).On the contrary,the proportion of gram-negative bacteria of surgical group were reduced(p<0.0001).5)Rats' serum level of LPS shows no significant difference between surgical group and sham operation group before operation(p=0.5226),while two groups both demonstrate an upward trend after operation.Then the rats' serum level of LPS in operation group declined obviously,however,the rats' serum level of LPS in sham operation group climbed up higher than preoperative levels.Differences between the two groups have statistical significance.Also,serum levels of LPS in the two groups have significant linear correlation with contemporaneous body weight(p=0.0004).6)The level of LPS in liver shows no significant difference between surgical group and sham operation group in each measurement point(operation group p=0.1548,sham operation group p=0.7595).The level of LPS in mesentery fat,perirenal fat and epididymal fat shows a trend of gradient decrease with time,while LPS of sham operation group is not closely related to time.At the 28 th day after operation,the level of LPS in abdominal fat significantly decreased compared with sham operation group(perirenal fat p=0.0002,epididymal fat p<0.0001,mesentery fat p=0.0101).7)The glucose tolerance levels and HOMA IR of rats in surgical group significantly decreased in 28 days after operation(p<0.0001),while these index in sham operation group obviously elevated(glucose tolerance p=0.0156,HOMA IR p=0.0003).The difference has statistical significance(p<0.0001).Conclusion: 1)There is a close relationship between their LPS and body weight after sleeve gastrectomy of obese rats.The change of LPS may be one of the reasons why body weight changed.2)After sleeve gastrectomy of obese rats,accompanied the decrease of LPS and body weight,glucose tolerance and insulin sensitivity are also improved. |
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