| Background and purpose:The structural imbalance of intestinal flora has been proved by more and more studies in the pathogenesis of abnormal glucose metabolism including type 2diabetes.High-fat and high-calorie food processed at high temperature is the main source of dietary advanced glycation end products(AGEs).It is estimated that part of the intake of AGEs is not absorbed in the intestinal tract,which may be metabolized by the microorganism in the intestinal lumen,thus affecting the composition of intestinal microorganisms.Most dietary fiber can not be digested and absorbed through the upper digestive tract,but can be fermented by intestinal flora in the colon and promote the growth of beneficial bacteria.Therefore,the purpose of this study is to provide direct evidence and comprehensive understanding of whether patients with abnormal glucose metabolism can reduce the risk of diabetes by reducing dietary AGEs intake or supplementing dietary fiber to change the composition and function of intestinal microorganisms through metagenomics and metabonomic analysis.Methods:In this study,oral glucose tolerance test and screening questionnaires were conducted on people with high risk factors of diabetes in community hospitals.60 subjects with abnormal glucose metabolism who met the inclusion and exclusion criteria were included(49 prediabetes and 11 suspected diabetes).They were randomly divided into three groups: low dietary AGEs(LAGEs)group,whole grains(W)group,and usual care(U)group.The general data,the dietary questionnaires and physical examination of the subjects were recorded,the blood of the subjects were collected for biochemical test and non-targeted metabonomic analysis,and the feces of the subjects were collected for metagenomic analysis.The correlation between the results of serum metabonomics and intestinal metagenomics was analyzed.Results:1.Clinical results:(1).After 6 months intervention,a total of 53 subjects(17 subjects in LAGEs group,18 subjects in W group and 18 subjects in U group)completed follow-up.The rates of normal glucose metabolism in LAGEs group,W group and U group were76.5%,61.1% and 38.9%,respectively,with statistical difference(P <0.05).After 6month,the diabetes progression rate in LAGEs group,W group and U group were5.9%,5.6% and 11.1%,respectively,and there was no statistical difference(P >0.05).(2).There was no significant change in fasting blood glucose(FPG)in the three groups after intervention,but postprandial 2-hour blood glucose(PBG)decreased significantly in three groups after intervention(P<0.05).Hb A1 c did not change significantly in LAGEs group,but increased significantly in W group and U group after intervention(P<0.05).Fasting insulin(Fins)and HOMA-IR in W group were significantly lower than in U group after intervention(P<0.05).Postprandial insulin(Pins)in LAGEs group and U group decreased significantly after intervention(P<0.05),but there was no significant decrease in W group.(3).There was no significant change in total cholesterol(TC),low density lipoprotein(LDL)and high density lipoprotein(HDL)between the three groups after intervention.Triglyceride(TG)decreased significantly after intervention in LAGEs group(P<0.05).There were no statistical changes in waist circumference,hip circumference,body mass index,blood pressure and body weight among the three groups after intervention,but LAGEs group lost 5.8% of weight after intervention.(4).There was no significant difference in dietary guidelines compliance and energy intake among the three groups.The common adverse effects after dietary fiber supplementation were increased stool frequency,abdominal distension,increased exhaust and loss of appetite.2.The result of serum non-targeted metabonomics and metagenomics analysis of intestinal flora(1).Through the supervised orthogonal partial least square discriminant analysis(OPLS-DA)model,the three groups of samples could be significantly distinguished in the positive and negative ion mode after intervention,indicating that the three dietary interventions changed the content of serum metabolism in subjects with abnormal glucose metabolism.(2).Principal coordinate analysis(PCo A)based on Bray Curtis distance showed that intestinal microorganisms in LAGEs group were significantly far away after intervention,while intestinal microorganisms in W group and U group were not significantly separated after intervention.The results showed that LAGEs diet regulated the intestinal flora structure of subjects with abnormal glucose metabolism,while the intestinal microbial diversity of W or U diet did not change significantly.The functional annotations of metagenomics suggested that the three dietary interventions regulated the composition of intestinal flora and caused functional changes.For example,LAGEs diet up-regulated glycosaminoglycan degradation,aminoacyl-t RNA biosynthesis and down-regulated fatty acid degradation,ketone body synthesis and degradation,glycerolipid metabolism and other pathways.W diet up-regulated riboflavin metabolism.U diet down-regulated C5-branched dibasic acid metabolism,ubiquinone and other terpenoid-quinone biosynthesis and fatty acid degradation pathways.(3).LAGEs diet up-regulated the contents of 6 metabolites such as L-ascorbic acid,ascorbic acid,alanine-isoleucine and alanine-leucine,and down-regulated the contents of 33 metabolites such as phosphatidylcholine(PC),lysophosphatidylcholine(LPC),lysophosphatidylethanolamine(Lysope),choline,thromboxane B2(TXB2),epoxyeicosatrienoic acid(EETs),glycine-valine,L-glutamic acid and L-aspartic acid.Differential metabolites were mainly concentrated in alanine,aspartic acid and glutamic acid metabolism,vitamin B6 metabolism,ascorbic acid and uronic acid metabolism and fatty acid synthesis metabolism.The correlation analysis between metabonomics and metagenomics showed that PC,LPC,Lysope,L-aspartic acid and L-glutamic acid were positively correlated with Enterobacter cloacae,Enterobacter kobe,Klebsiella pneumoniae,Klebsiella aerogene and Klebsiella variicola.(4).W diet up-regulated the contents of 27 metabolites such as alanine-isoleucine,sphingomyelin,phosphoethanolamine,4 PCs,palmitoylethanolamide,hypoxanthine and inosine,and down-regulated the contents of 13 metabolites such as EETs,TXB2,2 PCs,glycine-valine,fatty acid hydroxyl fatty acid and L-cysteine.The differential metabolites were mainly enriched in phenylalanine metabolism,D-arginine and D-ornithine metabolism,arginine and proline metabolism and purine metabolism.The correlation analysis between metabonomics and metagenomics showed that TXB2,PC(4:0/18:5),fatty acid hydroxyl fatty acid and2-hydroxyglutaric acid were positively correlated with Klebsiella variicola and Klebsiella quasipneumoniae.Conclusion:1.Reducing dietary AGEs intake,supplementing dietary fiber or usual care could reduce significantly PBG and Pins in different degrees.However,reducing dietary AGEs intake had more advantages in returning to normal glucose metabolism and reducing TG,while dietary fiber supplementation had more advantages in improving insulin resistance.2.Reducing dietary AGEs intake could increase the diversity of intestinal flora and decrease the contents of serum metabolites such as PC,LPC,Lysope,L-aspartic acid and L-glutamic acid in subjects with abnormal glucose metabolism.Reducing dietary AGEs intake participated in glycerol phospholipid metabolism and amino acid metabolism by down-regulating the relative abundance of Enterobacter cloacae,Enterobacter kobe,Klebsiella pneumoniae,Klebsiella aerogene and Klebsiella variicola,thus regulating glycolipid metabolism.3.Supplementing dietary fiber did not significantly change the diversity of intestinal flora in subjects with abnormal glucose metabolism,but decreased the contents of serum metabolites such as TXB2,PC,fatty acid hydroxyl fatty acids and2-hydroxyglutaric acid.Supplementing dietary fiber participated in glycerol phospholipid metabolism by down-regulating the relative abundance of Klebsiella variicola and Klebsiella pneumoniae,thus regulating glycerolipid metabolism. |
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