Effects Of Bariatric Surgery On The Metabolism And Gut Microbiota In A Hyperuricemic Rat Model

Backgroud Hyperuricemia and gout are two kinds of metabolic diseases that seriously harm people's health and reduce their living standards.In recent years,with the improvement of people's living standards,the lifestyle of high protein and high fructose diet has caused a significant increase in the incidence of hyperuricemia and gout.Hyperuricemia is not only the cause of gout and urate nephropathy,but a large number of studies have shown that hyperuricemia is closely related to obesity,lipid disorders,type 2 diabetes,non-alcoholic fatty liver disease and cardiovascular disease.For the treatment of hyperuricemia,the main treatment measures include improving the lifestyle and reducing the serum uric acid level,but the effect is not good.With the development of weight loss surgery,some metabolic diseases such as obesity and type 2 diabetes mellitus have significantly improved glucose metabolism after bariatric surgery.At the same time,the serum uric acid level of obese patients after weight reduction surgery has also been reduced to some degrees.But these studies are mainly from clinical observation,whether there is a causal association between hyperuricemia and these diseases as well as the specific mechanism of bariatric surgery reduces serum uric acid level is still controversial.Therefore,in this experiment,firstly,we establish hyperuricemia rat model at the first part,with dynamic observation of changes in lipid metabolism and intestinal flora in the process of establishing models of hyperuricemia in rats,and at the second part,through the observation of effects of bariatric surgery on glucose and lipid metabolism in rats with hyperuricemia and changes of intestinal flora to explore its related mechanism.In this experiment,the two parts of the study are briefly introduced.Part I Dynamic alteration of metabolism and gut microbiota in the process of the development of hyperuricemic rat modelObjective : The main objective of this study was to explore the evolutionary changes of serum uric acid and alteration of metabolism of glycolipids and gut microbiota in hyperuricemic rat model.Method: Thirty eight-week-old Wistar rats were randomly divided into two groups: model group and control group.The model group were fed on 10% yeast-rich food ad libitum and orally administered adenine and potassium oxonate once a day for 3 weeks.The control group were fed on standard food(laboratory standard chow)and intragastrical administration of saline simultaneously.During the establishment of hyperuricemic rat model every week,five rats of each group were sacrificed.Before killing the rats,fecal sample were sampled and stored in-80? condition and the gut microbiota of fecal samples were analyzed by 16 S r RNA gene pyrosequencing and analyzed using Quantitative Insights into Microbial Ecology(QIIME)to characterize the alteration of abundance and diversity of gut microbiota.Blood samples were obtained by puncturing abdominal aorta and after centrifuging the serum samples,then the index of glycolipid metabolism examined.Result:During the establishment of hyperuricemic rat model,compared with control group,serum uric acid,creatinine and blood urea nitrogen levels,fasting plasma glucose,fasting insulin levels were significantly increased in the model group,and the insulin resistance index calculated by HOMA-IR in the model group was much higher than that in control group.In addition,we revealed that the model group was abnormally imbalanced in the metabolism of lipids profile.Serum tryglyceride,total cholestoral,very low density lipoprotein-cholestoral(VLDL-c)in the model group gradually increased and significantly higher than that in the control group,while serum high density lipoprotein-cholestoral(HDLc)was significantly decreased compared with control group.Gut microbiota was analyzed by 16 S r RNA pyrosequencing and principal coodinate analysis(PCo A)based on unweighted unifrace showed that the model group and control group was separately clustered.Microbial annotation of gut microflora showed that the relative abundance of a probiotics lactobacillus and butyrate-producing bacteria Ruminococcus spp.and Roseburia spp.was siginificantly reduced,while was enriched in the phylum Proteobacteria and species Escherichia coli and Bacteroides fragilis.Pearson association analysis showed that the abundance of Entorococcus(r=0.43,P=0.02)and Escherichia(r=0.37,P=0.048)was positively associated with serum uric acid,while the abundance of Prevotella(r=-0.32,P=0.03)and Anaerovibrio(r=-0.36,P=0.02)was negatively associated with serum uric acid.Although the richness of Roseburia(r=-0.28,P=0.14)and Ruminococcus(r=-0.32,P=0.1)showed slightly negative association with serum uric acid,the significance was not remarkable.Conclusion:During the establishment of hyperuricemic rat model,metabolism of glucose and lipids were imbalanced,furthermore,changes of gut microbiota was found during that process,we speculated that hyperuricemia might be associated with dysbiosis of gut microbiota.Part II Metabolic effects and alteration of gut microbiota after Roux-en-Y gastric bypass and sleeve gastrectomy in hyperuricemic rat modelObjective: To investigate the effects of Roux-en-Y gastric bypass(RYGB)and sleeve gastrectomy(SG)on metabolism of serum uric acid,glucose,lipid profiles and alteration of gut microbiota in hyperuricemic rat model,and by observing the alteration of serum LPS,IL-6,TNF-?and XO to explore the related mechanism.Method: Fourty eight-week-old Wistar rats were randomly divided into two groups: model group and control group.The model group were fed on 10% yeast-rich food ad libitum and orally administered adenine and potassium oxonate once a day for 3 weeks.The control group were fed on standard food(laboratory standard chow)and intragastrical administration of saline simultaneously.Three weeks later,the model group was randomized three subgroups: Sham,SG and RYGB group(each group has 10 rats).Subsequently,the above three groups were received different operational procedures respectively.Body weight,amounts of food intake were measured before and every two weeks after surgery.Pre-and post-operative surgical serum uric acid(SUA),blood urea nitrogen(BUN)and creatinine(Cr),fasting glucose,insulin,HOMA-IR and lipid profiles were determined.Serum LPS,IL-6,TNF-? and XO were measured by Elisa kit.8 weeks after surgery,fecal samples of rats were obtained to analyze microbial 16 S r RNA gene to charaterize the changes of diversity and compositional constructure of gut microbiota in different groups.Result: Before the surgery,no significant difference for body weight was observed among the four groups(control 331.6±8.70 g vs.sham 332.42±13.57 g vs.SG 341.57±13.63 g vs.RYGB 336.83±14.92 g,respectively;all the P values>0.05).Postoperatively,at 2,4,6 and8 week,the difference of body weight between sham group and control group was not significant.But body weight of SG and RYGB group was much lower than those in sham and control groups with remarkable significance.Preoperatively,there was no significant difference among the four groups of the amounts of food intake(control 25.08±0.67 g vs.sham 25.74±0.65 g vs.SG 25.21±0.84 g vs.26.26±0.66g;all the P values>0.05).After the surgery,at week 2,4,6 and 8 week,the amounts of food intake between sham group and control group showed no statistically difference.However,SG group and RYGB group greatly lowered the amounts of food intake compared with sham and control groups.More importantly,we found that the effects of reduced food intake in RYGB group was more obvious than that in SG group.Three weeks later after the establishing the hyperuricemic rat model,compared with control group,serum uric acid of model group significantly increased with significantly statistical differentiation(145.59±6.37ummol/L vs.195.86±12.78ummol/L;P<0.001).After the surgical procedures,serum uric acid of sham,SG and RYGB groups were not statistically different at 2 week.During 4,6 and 8 week after surgery,although serum uric acid of sham group remained to be increase,the decreasing trends of SG and RYGB were significant.The difference between SG and RYGB groups for serum uric acid was not statistically significant.Postoperatively,the changing trends of serum BUN and Cr in SG and RYGB groups was similar to the changing trend of serum uric acid.For the glucose metabolic indecies,before the surgery,fasting blood glucose levels of the 3experimental groups were higher than that in control group(sham 7.17±0.64mmol/L,SG7.14±1.11mmol/L,RYGB 7.46±0.65mmol/L vs.control 5.16±0.74mmol/L;all the P value<0.001).After surgery,at week 2,no statistical differences were observed among the sham,SG and RYGB groups.During the observing stages,at 4,6 and 8 week,SG and RYGB groups significantly reduced fasting blood glucose level compared with sham group with statistical difference.The difference between SG and RYGB groups for fasting blood glucose changes was not significant at different points.Preoperatively,fasting insulin concentration of the 3 experimental groups significantly increased compared with control group(sham14.18±0.65 m U/L,SG14.18±0.53 m U/L,RYGB 14.04±0.46 m U/L vs.control10.38±0.62 m U/L;all the P value<0.001).After the surgery,at week 2,4,6 and 8 week,SG and RYGB group significantly lowered fasting insulin concentration compared with sham group.For the insulin resistance index calculated by HOMA-IR,we observed that before the surgery,HOMA-IR value of the three experimental groups were higher than that in control group(sham 2.25±0.16,SG 2.33±0.16,RYGB 2.30±0.60 vs.Control 1.52±0.11;all the P value<0.001).After surgery,during the observed stages at 2,4,6 and 8 week,HOMA-IR value of SG and RYGB groups was lower thant that in sham group,with significant difference,but HOMA-IR value of SG and RYGB was not significant difference.For the lipid metabolism,before the surgery,compared with control group,serum triglyceride level among the three experimental groups remarkably increased with statistical difference(sham1.67±0.11mmol/L,SG 1.72±0.09mmol/L,RYGB 1.72±0.17mmol/L vs.Control 0.89±0.16mmol/L;all the P value<0.001).After the surgery,at 4,6 and 8 week,SG and RYGB group significantly reduced serum triglyceride compared with sham group.From the beginning of week 6,serum triglyceride level of SG group slowly increased and at the end of observing stage,serum level of triglyceride even significantly higher than RYGB group but still lower than that in sham group.Before the surgery,serum total cholesterol levels among the three experimental groups were higher than that in the control group(sham 2.43±0.28mmol/L,SG 2.41±0.30mmol/L,RYGB 2.43±0.22mmol/L vs.Control1.56±0.26mmol/L;all the P values<0.001).Postoperatively,since the beginning of week4,serum total cholesterol level of SG group was significant lower than that in sham group,but RYGB group significantly lowered serum total cholesterol level compared with sham group since the beginning of week 6 and sustained to week 8.As to the inflammatory index,before the surgery,serum LPS,IL-6,TNF-? and XO among the three experimental groups were significantly increased compared with control group,the results are as follows: LPS(sham 0.63±0.04EU/L,SG 0.61±0.06EU/L,RYGB 0.63±0.07 vs.control0.26±0.04EU/L;all the P<0.001);IL-6(sham 17.80±1.0ng/L,SG 17.90±0.92ng/L,RYGB 17.93±0.93ng/L vs.control 10.02±0.63ng/L;all the P<0.001);TNF-?(sham36.98±0.92ng/d L,SG 36.48±0.80ng/d L,RYGB 36.83±0.91 vs.control 24.42ng/d L;all the P<0.001);XO(sham 13.70±0.57U/L,SG 13.94±0.35U/L,RYGB 13.83±0.53U/L vs.control 8.61±0.43U/L;all the P<0.001)?Postoperatively,compared with sham group,the effects of SG surgery on serum LPS,IL-6,TNF-?and XO levels were less,but RYGB surgery significantly reduced serum inflammatory biomarkers.After the surgery,RYGB was more enriched in the relative abundance of Proteobacteria than that in the SG group.Compared with sham group,RYGB and SG surgery significantly resulted in the increase in the relative abundance of Verrucomicrobia and Akkermansia_muciniphila,while remarkably reduced the relative abundance of and Escherichia_coli.Conclusion: RYGB and SG surgery significantly reduced the body weight,amounts of food intake and serum uric acid and improved the imbalance of metabolism of glucose and lipid profiles of hyperuricemic rat.Mechanically,RYGB and SG surgery might reduce serum uric acid by decreasing LPS,IL-6,TNF-? and XO concentrations and increase the excretion of uric acid by improving insulin resistance as well as the weight loss by reduced food intake.