The Effect Of Zinc Deficiency On Diabetic Nephropathy And Its Relative Mechanism

Diabetic nephropathy is one of the most serious complications of diabetes,is also the leading cause of death in diabetes. Its main pathological basis isglomerular basement membrane thickening and extracellular matrix accumula-tion. In the process of diabetic nephropathy progress, many factors involved inthe extracellular matrix accumulation. It includes:(1) the oxidative ornitration material (ROS or RNS) induced by diabetes cause the damage of renalcells;(2) the glomerular inflammation leads to a large accumulation ofinflammation factors, such as intercellular adhesion molecule-1(ICAM-1),Plasminogen activator inhibitor-1(PAI-1), transforming growth factor-β(TGF-β) and connective tissue growth factor (CTGF);(3) the imbalance ofsynthesis and degradation of mesangial matrix components, such as synthesisincreasing, degradation reducing or both existing. In the process of the matrixsynthesis, CTGF played a key role. In addition, some extracellular matrixcomponents, such as fibronectin (FN) and collagen IV (Col IV) was alsoinvolved in the renal fibrosis of diabetes.Zinc, as one of necessary trace elements, has a lot of biological function.Among them, participating in the normal structure, secretion, and function ofinsulin; antioxidation or inducing other antioxidant factor to resist oxidativedamage and anti-inflammatory, play a vital role in maintaining the stability ofthe internal environment.In diabetes, it always exists zinc deficiency. The two main reasons are theincreasing of urine zinc and disabsorption of gastrointestin induced byhyperglycemia in diabetes. The low level of zinc can cause abnormalconduction of insulin postreceptor, which will reduce the glucose tolerance.Zinc is the essential factor of a variety of antioxidant enzymes including Nrf2. Therefore, zinc deficiency will lead to the dysfunction of these enzymes, andaccentated the oxidative damage induced by diabetes. But, it is unknown thatthe specific role and the relative mechanism of zinc deficiency on oxidativedamage, inflammation, and fibrosis of diabetic nephropathy. So we make thefollowing experiment:We treat the FVB mice with low dose of STZ continuous5times to buildsuccessfully diabetes animal model. According to relevant literature reports,zinc specific chelator TPEN is injected daily intraperitoneal4months in orderto establish the zinc deficiency state in diabetes. Through Naphthol AS-DChloroacetate esterase assay, immune fluorescence, Western blot, atomicabsorption spectrometry and special staining, PAS to detect the level ofinflammation: inflammatory cell infiltrates into kidney, the expression ofinflammation index ICAM-1and PAI-1; Oxidative damage: the expression ofoxidative damage index3-NT and nitration damage index4-HNE; Fibrosisaspects: the expression of fibrosis indices CTGF, immunofluorescence stainingof CollagenIV and kidney special pathological dyeing PAS.At the same time, high glucose and palmitat are used to treat human renalproximal tubular epithelial cells, which can mimic the intemal environment ofhyperglycemia and hyperlipidaemia in diabetes. Then the special zinc chelator,TPEN, is used to remove zinc, either intercellular or intracellular, and zincchloride is applied to supplement zinc. The expression and function ofanti-oxidatiion factor Nrf2are detected to confirm the relative mechanismwhich zinc deficiency enhance the oxidative damage in diabetic nephropathy.Through the in vivo animal experiment above, we find:1. Zinc deficiency didn't affect the level of blood glucose, the ratio ofkidney and body weight.2. The level of zinc is reduced by TPEN injection both in control anddiabetes groups. 3. Zinc deficiency increases the infiltration of inflammatory cells andenhances the expression of inflammation index ICAM-1and PAI-1.4. Zinc deficiency accentated the expression of oxidative damage index3-NT and nitration damage index4-HNE.5. Through PAS staining, zinc deficiency aggravates the glomerulosc-lerosis of diabetic nephropathy. The expression of fibrosis index CTGF and theaccumulation of Collagen IV in glomeruli and kidney tubules are all increasing.Through the in vitro experiment of treating human renal proximal tubulecells, we get the result:1. TPEN remove zinc either intercellular or intracellular.2. High glucose and high palmitat increase the expression of inflammationindex PAI-1.3, Under high glucose, the expression of PAI-1and CTGF increase withthe increasing of TPEN concentration.4. TPEN enhance the expression of PAI-1induced by high glucose andhigh palmitat; furthermore, the zinc chloride reduce the expression of PAI-1induced by TPEN.5. High glucose and high palmitat lower the expression of anti-oxidationfactor Nrf2and it's nuclear translocation.6. Under high glucose and high palmitat, the expression of anti-oxidationfactor Nrf2and it's nuclear translocation are lessened by TPEN and recoveredby zinc chloride.7. Under high glucose and high palmitat, the expression of Nrf2downstream factor NQO1decreases. TPEN accentated the decreasing and Zincsupplementation recover this decreasing.According to the above experimental results, we draw the followingconclusion:1. zinc deficiency enhance the inflammation of diabetic nephro-pathy;2. zinc deficiency enhance the oxidative damage of diabetic nephropathy; 3. zinc deficiency enhance the fibrosis of diabetic nephropathy;4.one mechan-ism of zinc deficiency attentated the oxidative damage is the decreasingexpressionof Nrf2and it's function.