Explored To The Mechanism Of Lycium Barbarum Polysaccharide In Improving Prediabetes By Regulating Duodenal Contraction

Objective Prediabetes,the stage of blood glucose level above the normal value but below the threshold of diabetes,is the main transition stage to the development of diabetes,but its pathogenesis remain unclear.Emerging evidence suggest that the gut can sense changes of glucose and then send the signal to the hypothalamus which regulates the utilization of blood glucose in peripheral tissues.However,patients with hyperglycemia have a hypercontractility of duodenum.When the abnormal contraction occurs,an abnormal signal is transmitted from the intestine to the hypothalamus,resulting insulin resistance and constant hyperglycemia.At present,it is not known whether Lycium barbarum polysaccharide(LBP)has any effect on the signal transmitted from the gut to the hypothalamus.In our study,we used the prediabetic mouse model and examined the amplitude and frequency of duodenal contraction detected by the biological signal acquisition and processing system to explore the ability of LBP to regulate duodenal hypercontractility in prediabetic mice,and also preliminary investigate the mechanism of LBP improving prediabetic mice.Methods Thirty-five C57/6J mice(9 weeks of age)were divided into 5 groups: normal group,model group,low-dose LBP group(50 mg/kg),medium-dose LBP group(100 mg/kg)and highdose LBP group(150 mg/mg),with 7 mice in each group.The normal group was fed standard diet,and the other groups were fed high-fat diet.The intervention period was 12 weeks.After the experiment,the serum TC,TG,HDL-C and LDL-C levels were determined by biochemical method.Serum insulin expression was detected by enzyme-linked immunosorbent assay.The amplitude and frequency of duodenal contraction were detected by BL-420 N biological signal acquisition and processing system.The expression levels of n NOS in hypothalamus and GLUT4 in muscle were detected by immunofluorescence staining.The composition of gut microbiota were detected by16 S r DNA high-throughput sequencing and their metabolites were detected by liquid chromatography and mass spectrometry.Then,gut microbiota clearance by antibodies was performed to determine whether LBP regulates duodenal hypercontractility by intestinal flora in prediabetic mice.By testing the content of short-chain fatty acids which is metabolized by intestinal bacteria,we can be certain whether short-chain fatty acids play a key role in the regulation of duodenal hypercontraction in prediabetic mice by LBP.Results(1)The supplementation of LBP on prediabetic mice reduced the body weight and epididymal fat content of mice,reduced the level of fasting blood glucose,promoted insulin release,improved glucose tolerance,and reduced TC and LDL-C levels(all P< 0.05).(2)Compared with the model group,the supplementation of LBP could reduce the amplitude of duodenal contraction(P < 0.05),but had no significant effect on the frequency of duodenal contraction.In addition,LBP can increase the level of n NOS in hypothalamus and GLUT4 in soleus muscle.(3)Through the analysis of intestinal flora,we found that the intestinal flora of mice showed obvious clustering in each group,and the intestinal flora of mice showed a trend of separation between groups.By genus level analysis,the relative abundance of Akkermansia and Lachnospiraceae_NK4A136_group increased after the supplementation of LBP.After intestinal bacteria clearance,LBP had no improvement effect on prediabetic mice.(4)Acetic acid decreased body weight,epididymal fat content,fasting blood glucose and insulin release in prediabetic mice(P < 0.05).Acetic acid could reduce the amplitude of duodenal contraction(P < 0.05),but had no significant effect on the frequency of duodenal contraction.Conclusions With the supplementation of LBP,the intestinal microenvironment of prediabetic mice can be improved and the production of acetic acid can be promoted.Then,acetic acid may bind to short-chain fatty acid receptors which are on the surface of intestinal neurons,thus improving the hypercontractility of duodenum in prediabetic mice.Thereby,the signal from intestine is sent to the hypothalamus which promotes the utilization of glucose in peripheral tissues by the release of NO.