Protective Effect And Mechanism Of GLP-1 On Diabetes Mellitus Complicated With Chronic Colitis

Background:The epidemic of chronic diseases such as diabetes,obesity,cardiovascular disease and inflammatory bowel disease poses a major threat to global health currently.Diabetes Mellitus characterized by dysregulation of glucose metabolism caused by absolute or relative insulin deficiency,is a complex chronic disease.The global incidence of diabetes increases year by year,with a total prevalence in 20-79 year olds in 2021 was estimated to be 10.5%(536.6 million patients).The global diabetes data released by IDF estimated that there would be 783.2 million diabetic patients until 2045.It is often accompanied by various comorbidities and long-term complications,including cardiovascular disease,retinopathy,nephropathy,and neurological disease,which have attracted attention.In addition,some new comorbidities such as COVID-19,pulmonary fibrosis,and intestinal diseases are becoming more common.The hospitalization rate and risk of infectious are higher in patients with diabetes complicated with ulcerative colitis.Inflammatory Bowel Disease consists of Crohn's disease and ulcerative colitis,ulcerative Colitis(UC)is an immune-mediated chronic inflammatory bowel disease characterized by persistent superficial inflammation of the colon.The etiology of the UC has not yet been confirmed and is generally believed that environmental,genetic and microbial factors may be involved together.In worldwide,the growing incidence and prevalence of UC aggravate the economic load.The summary incidence rate of UC is 1.18 per 100,000 person in China.The higher utilization of 5ASA compounds in patients with milder disease may cause hyperglycemia especially in IBD-DM patients.Dehydration,electrolyte imbalance,sepsis,and parenteral nutrition caused by UC,which are significant risk factors for hyperosmolar hyperglycemia status and diabetic ketoacidosis,the typical complications of diabetes.Diabetes and UC are chronic systemic diseases concerned with chronic inflammation,dysbiosis,impaired immune function,and risk of infection.With the development of genomics and metabolomics,research on the pathophysiology and gene mutations of diabetes and ulcerative colitis has provided evidence of genetic or epigenetic predisposition for comorbidity of DM and IBD.It is clearly that diabetes coexist with UC has epidemiological,pathogenetic,clinical,and therapeutic implications.Glucagon-like peptide-1(GLP-1)is a multifaceted hormone,mainly secreted by ileum and colon cells after stimulation.Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion,decrease of gastric emptying,inhibition of food intake,increase of natriuresis and diuresis,and modulation of?-cell proliferation,and reduce body weight,becoming an effective drug in the treatment of diabetes.More and more studies have shown that GLP-1 can play a beneficial role in improving Alzheimer's disease,cardiovascular disease,chronic kidney disease,non-alcoholic fatty liver disease,asthma and intestinal mucositis through decreasing inflammation and apoptosis,alleviating oxidative stress and regulating intestinal microbes.However,the role and molecular mechanism of GLP-1 in diabetic patients with chronic colitis is still unclear.In conclusion,this study explored the protective effect and possible molecular mechanism of GLP-1 on diabetes complicated with chronic colitis at both animal and cellular levels,aims to provide a safe,economical and small side effects strategy for diabetic patients with chronic colitis.It has a good application prospect to reduce the economic burden of clinical patients,reduce adverse drug events and drug incompatibilities,and maintain a better healthy condition,which is expected to become a new choice for the treatment of diabetic companied with ulcers colitis.Objects:To explore the protective effect and mechanism of GLP-1 on diabetes combined with chronic colitis.Methods:1.Study on the anti-inflammatory effect of GLP-1 in diabetic mice with chronic colitis(1)A mouse model of diabetes mellitus combined with chronic colitis was established,supplemented different dose of GLP-1 in the treatment groups.We observed the general state,blood glucose,body weight change and fecal status of the diabetic mice with chronic colitis.Immunohistochemical staining was used to evaluate the histopathological damage of colon tissue.We revealed the level of neutrophil infiltration by MPO test.ELISA was used to test the secretion levels of inflammatory cytokines IL-1?,IL-6 and TNF-?.Western Blot was used to detect the expression of AKT/NF-?B and MAPK pathway related proteins.(2)Cellular experiments confirmed the anti-inflammatory effect and mechanism of GLP-1.High-concentration glucose combined with lipopolysaccharide stimulated Caco2 cells to mimic the intestinal environment of diabetes.The appropriate concentration of GLP-1 was selected by CCK8 experiment,and the m RNA expression level of TNF-?,IL-1?and IL-6 was tested by q RT-PCR.AKT/NF-?B and MAPK pathway proteins were detected by Western Blot.2.Effects of GLP-1 on intestinal tight junction protein expressionThe levels of tight junction proteins ZO-1,Occludin and Claudin-3expression related to intestinal barrier integrity were detected by immunofluorescence and Western Blot,respectively.3.Effects of GLP-1 on intestinal microfloraColon contents of mice were collected,and the changes of intestinal microflora of mice were analyzed by 16s RNA high-throughput sequencing,and the changes of intestinal microflora composition richness and diversity after GLP-1 treatment were analyzed,as well as the correlation with inflammatory factors.Results:1.We tested the fasting blood glucose of Maf A^-/-diabetic mice exceed 11.1mmol/L,and the model group animals were treated with 2%(w/v)DSS drinking water.Compared with the control group,the diabetes complicated with chronic colitis mouse model were slightly dispirited,activity reduced,sparse stool,occult blood and hematochezia,loss of weight and a significant increase in DAI,the mouse model was successfully established.2.Supplement of GLP-1 decreased blood glucose,ameliorated the weight loss,intestinal bleeding and other general states,increased the length of colon,and improved the pathological injury of intestinal tissue in the animal models.3.Compared with the diabetes complicated with chronic colitis mouse model group,supplement of GLP-1 down-regulated MPO activity and decreased secretion of pro-inflammatory cytokines TNF-?,IL-1?,and IL-6 in intestinal tissues,also inhibited the activation of AKT/NF-?B and MAPK signaling pathways in colon tissues.4.GLP-1 reduced the m RNA expression of pro-inflammatory cytokines such as TNF-?,IL-1?,and IL-6 and inhibited the phosphorylation of AKT/NF-?B and MAPK signaling pathway related proteins in Caco2 cells.5.GLP-1 up-regulated the level of intestinal tight junction proteins ZO-1,Occludin and Claudin-3 to maintain the integrity of the intestinal epithelial barrier.6.According to 16s RNA sequencing analysis of mice fecal,GLP-1regulated the structure of intestinal flora especially increased the relative abundance of beneficial bacteria coriobacteriia,Lachnospiraceae,Parasutterella and Ruminiclostridium whereas decreased the relative abundance of bacteroids and bacillus.Sperman correlation analysis showed that the increased Lachnospiraceae and coriobacteriia was negatively correlated with IL-1?,IL-6 and TNF-?,while the bacteroids was positively correlated with the above inflammatory cytokines.Conclusion:1.GLP-1 showed a protective effect on diabetes combined with chronic colitis,decreased blood glucose and alleviated glucotoxicity,reduced the expression levels of inflammatory factors TNF-?,IL-1?,and IL-6 by regulating AKT/NF-?B and MAPK signaling pathways,which could alleviate intestinal inflammatory injury.2.GLP-1 promoted intestinal tight junction protein expression,which could help enhance intestinal epithelial integrity.3.GLP-1 increased the abundance of beneficial bacteria and the diversity of microbial flora,and the increasing of the beneficial bacteria was negatively correlated with the inflammatory factors IL-1?,IL-6 and TNF-?,suggested that GLP-1 could effectively ameliorate diabetes combined with chronic colitis damage by promoting gut microecology.