The Protective Effects And Mechanisms Of Aqueous Extract Of Se-enriched Auricularia Auricular On Mice With Diabetic Kidney Damage

Objective: Diabetic kidney damage is one of the most common and important complications of diabetes.The aim of the present study was to investigate the protective effects of aqueous extract of Se-enriched A.Auricularia(AESAA)on diabetes-induced kidney damage in mice and explore the molecular mechanisms of underlying its actions,compared with aqueous extract of A.Auricularia(AEAA).Methods:(1)The methods of water extraction and freeze drying were used to prepare AESAA and AEAA samples,and ICP-MS method was used to determine the selenium content of AESAA and AEAA.(2)The DPPH radical,hydroxyl radical,superoxide radical scavenging capacity and reducing power test were ultilized to evaluate the antioxidant ability of AESAA in vitro.(3)B57C/6J mice were selected to establish a mouse model of type 2 diabetes by high-fat diet(HFD)combined with a single injection of streptozotocin(STZ).The dose of AESAA was designed according to the maximum human tolerance to selenium.(4)After 8-week orally administration,the mice were sacrificed.The oral glucose tolerance test(OGTT)in diabetic mice was performed.The changes of serum lipid,urea nitrogen,creatinine and uric acid in diabetic mice were examined.HE staining was performed to evaluate the effect of AESAA on the pathological morphology of kidney in mice.(5)To study the effect of AESAA on oxidative stress in diabetic mice,the GSH-Px,CAT activities and the MDA content in serum and kidney of diabetic mice were determined.(6)The contents of the inflammatory cytokines Tumor necrosis factor-?(TNF-?),interleukin-6(IL-6)and interleukin-1(IL-1?)in the serum and kidney were determined by ELISA method to evaluate the anti-inflammatory effect of AESAA.(7)The protein expression of RAGE,p-Erk,p-JNK,p-P38 and p-NF-?B in kidney were detected by western blot.The expression of RAGE in kidney was further confirmed by immunohistochemistry.Results:(1)AESAA and AEAA samples were prepared successfully.It was found that the selenium content in AESAA was 31.79 mg/kg,which was much higher than the selenium content(4.4 mg/kg)in AEAA.(2)Among the four antioxidant system,the antioxidant capacity of AESAA was significantly higher than AEAA in the same concentration,in which AESAA exhibited stronger scavenging ability to DPPH radical and hydroxyl radical and the scavenging rates are 66.85% and 64.69%,respectively.(3)The type 2 diabetic mouse model was established successfully.(4)AESAA decreased glucose level and improved oral glucose tolerance of diabetic mice;AESAA treatments significantly reduced serum cholesterol(TC),triglycerides(TG)and low-density lipoprotein cholesterol(LDL-C)levels,elevated high density lipoprotein cholesterol(HDL-C)levels,indicating the effective improvement of AESAA on lipid disorder in diabetic mice;In addition,AESAA improved the pathological damage of kidney and exhibited an markedly reduction in serum urea nitrogen(BUN),creatinine(Cr)and uric acid(UA)levels of diabetic mice.(5)The results showed that AESAA significantly increased the GSH-Px,CAT activities and decreased the MDA content in serum and kidney of diabetic mice,suggesting that AESAA could improve oxidative stress induced by high glucose in diabetic mice.(6)AESAA decreased the levels of inflammatory factorsTNF-?,IL-1? and IL-6 in serum and kidney of diabetic mice.(7)Western blot and immunohistochemistry showed that AESAA reduced the expression of RAGE,p-Erk,p-JNK,p-P38 and p-NF-?B in the kidney of diabetic mice.Conclusion: These results indicated that AESAA can alleviate diabetes-induced kidney damage in mice by improving oxidative stress and suppressing inflammation,which was modulated by RAGE/MAPK/NF-?B signaling pathway.