Protective Effect And Mechanism Of Liraglutide On The Kidney Of Diabetic Rats

?Content?Diabetes mellitus(DM)is a chronic metabolic disorder characterized by hyperglycemia caused by a combination of genetic and environmental factors.Its incidence has increased year by year and has become a global public health problem that seriously affects people's health.Diabetic nephropathy(DN)is one of most common chronic complications of diabetes and the leading cause of end-stage renal disease.The pathogenesis of diabetic nephropathy is still unclear.However,there are no known therapies currently available that can treat the progressive lesion of glomerular histology and loss of renal function in DN.DN has led to a series of serious health problems and caused great harm to the health of the population.Liraglutide,a synthetic glucagon-like peptide-1 receptor(GLP-1R)agonist,has been recently used in the patients with diabetes mellitus.Recently,GLP-1R has been found in extra-pancreatic tissues such as kidney,heart,nervous system,and vascular endothelium.GLP-1 analogues has renal protection in diabetic animals,but the specific mechanism is not clear.For instance,GLP-1 analogue liraglutide was shown to decrease transforming growth factor-?(TGF-?)expression through the protein kinase A(PKA)signaling pathway,and delay the progression of DN.Exendin-4 was reported to ameliorate inflammatory response through GLP-1receptor and reduce renal damage.Therefore,in the present study,rats with streptozotocin(STZ)-induced Type 1 diabetes model were treated with subcutaneous injections of liraglutide for 8 weeks.The basic physiological indexes,renal function changes,renal cortical protein(Col-IV,GLP-1R,cAMP,PKA,p-PKA),renal cortical inflammatory factors(IL-6,TNF-?),Fibrosis factors(CTGF,TGF-?)and cyclic adenosine monophosphate(cAMP)protein kinase A(PKA)signaling pathway-related proteins.Will be test to investigate the protective effect and mechanism of liraglutide on early kidney injury in STZ-induced diabetic rats.?Research purposes?1.Determine that liraglutide ameliorates renal injury in STZ induced diabetic rats.2.Investigate that liraglutide ameliorate inflammatory response through the protein kinase A(PKA)signaling pathway,and decreases ECM protein abundance.?Method?1.SPF grade SD male rats were treated with a single intraperitoneal injection of 65mg/Kg of STZ to produce Type 1 diabetes model.The rats with were fasting blood glucose?16.7mmol/L after 72 hours of intraperitoneal injection were diagnosed as DM.Twenty rats were randomly divided into diabetic group(DM group)and liraglutide group(DML group),with 10 rats in each group.The other 10 normal rats in the same batch were selected as the control group(NC group).2.The successful diabetic rat model in the liraglutide group received liraglutide 200 ug/kg subcutaneously,q12 h,and adjusted the dose of liraglutide weekly according to body weight.Diabetes group and control group were given subcutaneous injection of equal volume of normal saline.3.The fasting blood glucose and body weight of each group were monitored every weekend.After 8 weeks of drug intervention,the kidney weight,kidney hypertrophy index(kidney weight/body weight),serum urea nitrogen,serum creatinine,24 h urinary protein,urinary protein/creatinine ratio were measured.Renal cortical interleukin-6(IL-6),tumor necrosis factor alpha(TNF-?),connective tissue growth factor(CTGF),and transforming growth factor beta(TGF-?)mRNA were detected by real-time quantitative PCR(RT q-PCR)mRNA expression level.Western blotting(WB)was used to detect the expression of collagen IV(Col-IV),GLP-1R and cAMP/PKA signaling-related proteins,and HE and PAS staining were used to observe renal pathological changes.?Result?1.Compared with the NC group,the DM group showed significant polydipsia,polyuria,decreased activity,mental wilting,unresponsiveness,and pubic hairiness.The symptoms in the DML group were less than those in the DM group.2.The fasting blood glucose of DM group and DML group was significantly higher than that of NC group(p<0.05),but there was no significant difference in fasting blood glucose between DM group and DML group(p>0.05).3.There was no significant difference in body weight between the DM group and the DML group after the model formation(p>0.05),but it was significantly lighter than the NC group(p<0.05).4.The kidney weight and kidney hypertrophy index of DM group were significantly higher than that of NC group(p<0.05),while the above indexes of DML group were significantly lower than DM group(p<0.05).5.The serum urea nitrogen,serum creatinine,24 h urinary protein and urinary protein /creatinine ratio in the DM group were significantly higher than those in the NC group(p<0.05),while the above indexes in the DML group were significantly lower than those in the DM group(p<0.05).6.HE and PAS staining of kidney tissue showed that the DM group showed a larger glomerular volume,increased cells,mesangial cell proliferation,mesangial area widening,and some vacuolar degeneration of renal tubules.Tubulointerstitial inflammatory cell infiltration,partial renal tubular epithelial cell degeneration,brush border detachment;DML group was less than DM group lesions,glomerular cells slightly increased,mesangial cell proliferation was reduced,mesangial area widened.7.The expression of Col-IV protein in DM group was significantly higher than that in NC group(p<0.05),while that in DML group was significantly lower than that in DM group(p<0.05).8.The expressions of IL-6,TNF-? and fibrosis factors CTGF and TGF-? in DM group were significantly higher than those in NC group(p<0.05),while theabove indexes in DML group were significantly lower than those in DM group(p<0.05).9.The expression of GLP-1R protein in DM group was significantly lower than that in NC group(p<0.05),while that in DML group was significantly higher than that in DM group(p<0.05).10.The expressions of cAMP and p-PKA protein and the ratio of p-PKA/PKA in DM group were significantly lower than those in NC group(p<0.05),while the above indexes in DML group were significantly higher than those in DM group(p<0.05).?Conclusion?1.Besides hypoglycemic effect,Liraglutide ameliorates renal injury in STZ induced Type 1 diabetic rats,indicated by decreases in urinary protein excretion,serum creatinine and blood urea nitrogen levels,renal hypertrophy index,mesangial matrix expansion,and Col-IV protein accumulation in kidney.2.By binding with GLP-1R,liraglutide may activate the cAMP/PKA pathway and inhibit the expression of renal cortical proinflammatory cytokines IL-6,TNF-?and fibrogenic factors CTGF,TGF-? mRNA,so as to reduce the proliferation of mesangial matrix and exert a protective effect on the kidney.