Protective Effects Of Elabela On Diabetic Nephropathy And Its Possible Mechanism

Aims:To observe whether Elabela(ELA)can improve human kidney proximal tubular cell(HK-2)injury induced by high glucose,and to study the effect and related mechanism of ELA on kidney injury in spontaneous type 2 diabetes db/db mice.Methods:Human renal tubular epithelial cells(HK-2 cells)were randomly divided into three groups(n=6):normal glucose groups(5.5mmol/L,NG groups),high glucose groups(30.0mmol/L,HG groups),and high glucose with ELA treatment groups(25.0mmol/L+1umol/L ELA,HG+ELA groups).High glucose medium was used for 72h to establish high glucose model.The levels of fibronectin(FN)and type Ⅳcollagen(Col-Ⅳ)in each group were examined by Western blot.Then in vivo experiment:Sixteen eight-week-old male db/db mice were intraperitoneally injected with ELA(5mg·kg-1·day-1)or equivalent normal saline(n=8)for 8 weeks.Eight agematched male db/m mice received equivalent normal saline injection as normal control.At the end of the experiment,blood samples and urine samples were obtained for HbA1c and urinary albumin/creatinine(ACR)measurements.Immunohistochemistry was used to observe the expression of ELA.Histopathological changes in kidney tissue were observed by HE staining and Masson staining.The levels of collagen type Ⅳ(ColⅣ)and transforming growth factor-β1(TGF-β1)as well as Yes-associated protein(YAP)phosphorylation in kidney tissue were examined by western blot.Results:The expression levels of FN and Col-IV proteins in HK-2 cells exposed to high glucose were significantly higher than NG groups(0.43±0.06 vs 0.25±0.07,0.48±0.12 vs 0.20±0.00,all P<0.05).The protein expression levels of FN and Col-Ⅳin HG+ELA groups were lower than those in HG groups(0.24±0.02 vs 0.43±0.06,0.22±0.02 vs 0.48±0.12,all P<0.05).Immunohistochemistry showed that ELA expression was decreased in the renal tissue of db/db mice compared with db/m mice(P<0.05).After ELA treatment,ACR and blood pressure were markedly decreased in db/db mice(P<0.05),without significant changes in the body weight and HbA1c.Renal tubular epithelial cells edema,basement membrane thickening,and increased collagen fiber in db/db were improved by ELA administration.Compared with db/m mice,the levels of TGF-β1 and Col-IV expression as well as YAP phosphorylation were significantly increased in renal tissue of db/db mice(0.98±0.08 vs 0.68±0.10,1.10±0.14 vs 0.51±0.08,3.38±0.72 vs 0.81±0.13,all P<0.05),which were downregulated after ELA administration(0.80±0.06,0.51±0.05,2.21±0.22,all P<0.05).Conclusions:ELA may reduce high-glucose induced HK-2 cells fibrosis and improve the renal injury of db/db mice by regulating the signaling pathway of YAP,thereby delaying the development of diabetic nephropathy.