| Diabetes mellitus(DM)is a common disease with a rapidly increasing incidence worldwide.There is a direct correlation between high blood glucose levels and microvascular complications.Studies have confirmed that long-term hyperglycemia leads to the development and progression of various microvascular complications,including diabetic nephropathy(DN).The pathological manifestations of diabetic nephropathy are from the initial glomerular,mesangial,matrix hypertrophy,and gradually progress to glomerulosclerosis and even fibrosis.Although the exact pathogenesis of DN is still unknown,studies indicate that DN might be due to the interactions between multiple factors including metabolism,inflammation,hemodynamics,and heredity.In recent years,more and more scientists focus on studying inflammatory factors in the pathogenesis of DN.Some studies shown that in DN cases macrophages and T cells aggregate at the glomerular and interstitial sites,even early stage of diabetes.There was a positive correlation between glomerulosclerosis index and the severity of macrophage infiltration.The increase of inflammatory factors can enhance the accumulation of macrophages in the kidney tissue,which eventually leads to thicken the glomerular basement membrane and worsen renal damage.Metformin is the first-line drug for the treatment of diabetes.In the past,metformin was considered to have nephrotoxicity and should not be used in patients with renal diseases.The latest medical guidelines at home and abroad point out that metformin can be safety used in patients with early and mid-stage DN.In recent years,researchers have found that metformin has a protective effect on DN,but the specific mechanism is unclear yet.In order to understand the mechanism of metformin on the inflammatory response in DN rats and the protective mechanism of metformin to DN,in this study we examined the expression of monocyte chemoattractant protein-1(MCP-1)and intercellular adhesion molecule-1(ICAM-1)in the kidney tissue of DN rats before and after metformin treatment.We also investigated the effect of metformin on fasting blood glucose,24 h urinary protein and renal function.Our studies might be provide useful theoretical suggestion on the treatment of DN.We establish an animal model of DN using rats and observe the fasting blood glucose,HbA1 c,renal function and 24 h urinary protein levels,as well as the expression levels of MCP-1 and ICAM-1 in each group of rats.We also investigated the metformin treatment after the above changes in the indicators,and then to study the mechanism of metformin on DN inflammatory response.MethodsWe selected 30 SPF healthy male Sprague-Dawley(SD)rats,Ten of them were randomly selected as the normal controls,The rest SD rats were used for generating DN rats by giving a single low-dose injection of streptozotocin in the rats' right lower abdomen.The successful DN rats were randomly divided into untreated group and metformin treated group.The rats in the treated group were administrated with metformin daily(150 mg/kg),and the other two groups were given equal doses of normal saline for 8 weeks.In the 8 weeks,the mental status and weight of all rats were measured.After 24 weeks,Daily urine volume was collected to measure 24 h urinary protein excretion rate at the end of the experiment.The blood was collected after euthanizing the rats for the examination of kidney weight,blood glucose,HbA1 c and renal function.The renal tissues of each group were subjected to special pathological staining,and the pathological changes of the kidneys were observed under light microscope.Immunohistochemistry and western blot were used to measured the expression of MCP-1 and ICAM-1 in renal tissues;Real-time PCR was used to detect the expression of MCP-1 and ICAM-1 mRNA in renal tissues.Results1.Basic conditions of rats in each group: Rats in the control group survived well with normal movement.The DN rats perferred to excessively drink and eat and showed polyuria.Those rats became extremely thin with much less movement.After treatment with metformin,the physical conditions were improved in those rats.Compared with the normal control group,the untreated DN rats had significantly decrease of the body weight(P<0.01),the increased of kidney weight(P<0.01),and the kidney coefficient increased(P<0.01).The body weight of treated rats was decreased compared with the control animals(P<0.01)but was significantly increased compared to the untreated DN rats(P<0.01).We also found that the increase of the kidney weight and the kidney coefficient in treated rats compared to the normal controls(P<0.01)but decreased to some extent compared with the untreated DN rats(P<0.01);2.Biochemical indicators of the rats: Our study indicates that RBG,HbA1 c,BUN,SCr and 24 h urinary albumin levels in DN group were significantly higher(P<0.01)compared with the normal control rats.However,after the treatment with metformin,those biochemical indicators decreased significantly(P<0.01)compared to the untreated animals;3.Renal histopathological changes: We examined the pathological features of kidney tissue.In the untreated DN rats,we found that the lobulated renal bodies and a large number of collagen fibers in the glomeruli.We also observed severe hyperplasia of the mesangial cells,and thickening basement membrane,and a large number of inflammatory cells in the tubulointerstitium.The tubular tubules showed vacuolar degeneration,loose cytoplasm,and tubular lumen enlargement.There is a large amount of protein tube formation in the cavity.After the treatment of metformin,we found that the improvement of the pathological changes of glomerular mesangial cells and renal interstitium compared with DN rats;4.Metformin alleviates renal inflammation in DN rats: The expression levels of MCP-1,ICAM-1 protein and nucleic acid in the renal tissue of the DN were higher than the normal control rats(P<0.01).And the expression levels of MCP-1,ICAM-1 protein and nucleic acid in the renal tissue of the treatment with metformin were decreased than the untreated DN rats(P<0.05).Conclusion1.Metformin can improve the pathological morphology of diabetic nephropathies in rat kidney,protect renal function,reduce 24-hour urinary protein excretion,and protect the kidney of diabetic rats.2.Metformin can reduce the expression of MCP-1 and ICAM-1 in renal tissues,improving the inflammatory in renal tissues,thereby improving renal fibrosis and delaying the progression of diabetic nephropathy. |
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