The Effects Of Green Tea Polyphenols On Renal Function And Autophagy Flux Of Rats In Three Dietary Patterns

Objective: Epidemiological and experimental studies revealed that Western dietary pattern contributes to chronic kidney disease,whereas dietary restriction(DR)or dietary polyphenols like green tea polyphenols(GTPs)can ameliorate the progression of kidney injury.This study aimed to observe the effects of GTPs on renal function and autophagy flux in three dietary patterns as well investigate the renal protective effects of GTPs and explore the underneath mechanism.Methods: In vivo,sixty Wistar rats were randomly divided into 6 groups: standard diet(STD),DR,high-fat diet(HFD),and three diets plus 200 mg/kg(BW)·d GTPs,respectively.After 18 weeks,rats were transferred to metabolic cages for 24 h urine collection and sacrificed to collect blood and tissues.Blood glucose and lipids,serum cystatin C,urinary N-acetyl-β-D-glucosaminidase activity,and creatinine were detected by kits.Autophagy-lysomeme related protein(Beclin-1,LC3-II,p62,cathepsin B,cathepsin D and LAMP-1),AMPK and p-AMPK were determined by Western Blot.In vitro,human proximal tubular epithelial cells(HK-2)were cultured in medium containing epigallocatechin-3-gallate(EGCG),palmitic acid(PA)and EGCG with PA,respectively.The autophagy related protein LC3-II,p62,Beclin-1,AMP-activated protein kinase(AMPK)and p-AMPK were determined by Western Blot after these treatment.Results:(1)HFD group exhibited renal injuries by increased serum cystatin C level and urinary N-acetyl-β-D-glucosaminidase activity,which can be ameliorated byGTPs.A significantly increase in Ccr and a decrease in urinary NAG was shown in rats fed on DR with or without GTPs compared to STD.No significant differences were observed in the levels of these three biomarkers between STD+GTPs and STD rats.(2)HFD significantly increased the expression of LC3-II,Beclin-1,p62 and LAMP-1decreased cathepsin B expression compared to STD group.And decreased p62/SQSTM1 expression was detected in HFD+GTPs rats compared to HFD group.Compared to STD group,the protein expression of LC3-II in the kidneys was significantly increased in DR and DR+GTPs,and protein expression of Beclin-1 was increased in DR;besides,the expression of LC3-II was increased and p62/SQSTM1 was significantly decreased in STD+GTPs.(3)Phosphorylation of AMPK was significantly decreased in HFD;GTPs significantly increased the expression of AMPK phosphorylation in the kidney of HFD rats.Phosphorylation of AMPK was increased in DR and STD+GTPs compared to STD group.(4)In vivo,EGCG increased LC3-II expression in a dose-dependent manner while did not alter p62 expression.PA treatment increased the protein expression of LC3-II and p62.PA did not further increased LC3-II accumulation when treated with bafilomycin A1.Co-treatment with EGCG increased expression of LC3-II and reduced the expression of p62 compared to PA-BSA treatment alone.(5)PA induced a decreased in phosphorylation of AMPK,which was improved by EGCGConclusions: GTPs mimic the effects of DR to induce autophagy and exert renal protective effect by alleviating HFD-induced autophagy suppression.