Role Of Brown Adipose Tissue In Exendin-4 Combating Nephropathy In Diabetic Mice

BackgroundAfter entering twenty-first Century,the prevalence of diabetes is on the rise.Diabetes and related acute and chronic complications will not only have a serious impact on the quality of life and production capacity of the patient,but also cause a heavy burden onthe family and society beeause ofmedical expernses.Diabetic kidney disease(DKD)is one of the common and serious chronic microvascular complications of diabetes.The pathogenesis of diabetic nephropathy is very complex and has not yet been fully clarified.The methods for treating diabetic nephropathy include strict control of blood sugar and blood pressure,the use of renin-angiotensin-aldosterone system inhibitors,taking lipid-lowering drugs and so on,as well as the improvement of life style,but these treatments can only delay but fail to block the progress of DKD.Therefore,further exploration of the pathogenesis of DKD and the search for new therapeutic targets have become hot spots and difficult points in medical research.Exendin-4,a glucagon like peptide receptor agonist,has been found to protect the kidney from the role of Exendin-4 in protecting the islet cells,reducing blood sugar and reducing weight.In recent years,the increase in the content or activity of brown adipose tissue BAT in the body can reduce insulin resistance and inflammation in the body.At the same time,BAT is a multifunctional endocrine organ,secreting a variety of adipokines involved in the regulation of systemic metabolism,including the regulation of renal metabolism.Previous studies in this research group have shown that brown fat transplantation can also improve nephropathy and reduce urinary albumin in type 2 diabetic mice.Domestic studies have shown that Exendin-4 can enhance BAT metabolism and promote the differentiation of brown adipocytes in vitro.However,foreign studies on the browning of Exendin-4 adipose tissue are not consistent.In our previous study,we also found that Exendin-4 had no significant effect on the differentiation of cultured brown adipocytes.It is not clear whether Exendin-4 can improve diabetic nephropathy or renal protection that is independent of BAT through BAT.Therefore,the role of Exendin-4 intervention and brown fat removal to explore the role of BAT in the intervention of Exendin-4 in diabetic nephropathy in mice.ObjectiveTo investigate the role of brown adipose tissue in Exendin-4 combating nephropathy in diabetic miceMethod47 5-6 weeks male C57BL/6J mice were randomly divided into 8 rats of normal control(Control)group,39 diabetic(DM)group,normal control group and diabetic nephropathy group mice(HFD*4w+stz+HFD*4w).After ninth weeks of successful modeling,they were divided into groups and dried.Group DM was randomly divided into diabetes control group(DM-con),diabetes Exendin-4 intervention group(DM+E4),diabetic brown fat removal group(DM+Exc),diabetic brown fat removal and Exendin-4 intervention group(DM+Exc+E4),9-10 rats in each group.During the experiment,the mental state and activity of mice were observed.Body weight,food intake and random blood glucose were measured every week.Metabolic cage was used to collect urine for 24 hours.After 8 weeks of admmistration,the nice were killed after eighteenth weeks of pentobarbital sodium anaesthesia.The blood,kidney and fat tissue of the mice were collected,and some of them were quickly put into liquid nitrogen and stored at-80 C fridge,and some of them were fixed in 4%neutral formalin.The changes of blood glucose,body weight,low density lipoprotein,high-density lipoprotein and triglyceride were observed.The RT-PCR method was used to detect the mRNA expression of FN,TGF-β1 and COL1 in the renal cortex of mice.The ELISA method was used to determine the morphological changes of renal tissue in mice with 24h albuminuria and 8-OHdG content.PAS and Masson staining.Statistical analysisThe data were expressed with mean standard deviation,and the SPSS 19 statistical software was used to deal with the data.Compare the use of multiple samples were One-Way ANOVA,homogeneity of variance data for multiple comparisons using the LSD method,homogeneity of variance data approximate variance analysis using Welch method,using Dunnett s T3 multiple comparison method,P<0.05 was considered statistically significant difference.ResultsExendin-4 could reduce the blood glucose level of type 2 diabetic mice,but did not achieve significant statistical difference.Whether BAT was removed or not,Exendin-4 significantly reduced triglyceride level in type 2 diabetic mice.Exendin-4 can significantly reduce the blood LDL-c level of BAT mice with type 2 diabetes.Exendin-4 can significantly reduce urinary albumin and 8-OHdG levels in type 2 diabetic mice,and delay the progression of nephropathy.BAT removal increased renal fibrosis in type 2 diabetic mice,but there was a significant statistical difference in COL1 expression.No matter whether or not to remove BAT,Exendin-4 intervention could significantly reduce the index of renal fibrosis in type 2 diabetic mice.ConclusionsExendin-4 can significantly reduce triglyceride level in type 2 diabetic mice,reduce urinary albumin,improve renal fibrosis and delay progression of diabetic nephropathy.The renal protective effect of Exendin-4 on diabetes may not depend on BAT.