Intervention of tripterygium wilfordii polyglucosideson on the toll like receptor4-mediated immune and inflammatory signaling pathway of liver in diabetic rats

Abstract

Objective To investigate protective effects of tripterygium wilfordiipoly glucosides (TWP)on the toll like receptor 4(TLR4)-mediated immune and inflammatory signaling pathway on type 2 diabetes fatty liver disease and elucidate the possible involved mechanisms. Methods Seventy-five healthy male Sprague Dawley rats, aged 4-5 weeks and weighed (161±9) g, were divided to normal control group (NC,n=15) and high-fat diet group(n=60) by random number table method. Type 2 diabetes model was induced with 8-week high-fat diet followed by low-dose streptozocin(STZ) injection(30 mg/kg). The diabetic rats were randomly assigned to four groups: diabetes mellitus group (DM,n=11), low-dose TWP (1 mg·kg-1·d-1, DM+TL,n=10), medium-dose TWP(3 mg·kg-1·d-1,DM+TM,n=13), and high-dose TWP (6 mg·kg-1·d-1,DM+ TH,n=11). Treatment was given by gavage once daily for 8 weeks.We analyzed the liver histopathological change, and the gene and protein expression of TLR4 and nuclear factor-κB(NF-κB) by real time PCR and Western blotting, and the levels of serum downstream inflammatory factors interleukin 1β(IL-1β) and tumor necrosis factor α(TNF-α) by ELISA.The significance of the data obtained was evaluated using analysis of variance (ANOVA). Results (1)Compared to the normal control group,diabetic rats were found to have obvious steatohepatitis and inflammatory cell infiltration. TWP-treated diabetic rats showed reduced hepatic inflammation in different levels. (2)TLR4 and NF-κB mRNA and protein expression in the hepatic tissue in the DM group were significantly increased, compared with those in the NC group(7.02±1.45 vs 1.05±0.18, 8.91±1.59 vs 1.04±0.25, 2.31±0.17 vs 1, 2.84±0.38 vs 1, respectively,t=7.157-16.540, allP<0.05). The expression of TLR4 and NF-κB mRNA and protein showed different significantly between groups (F= 12.992-60.578,P<0.05 all above), and was decreased in TWP treatment groups in a dose-dependent manner (t=2.264-7.223, all P<0.05).(3)Serum IL-1β and TNF-α in different groups showed different significantly (F=57.717,42.992,P<0.05 all above).Serum IL-1β and TNF-α in DM group were significantly increased, compared with those in the NC group(t=14.669,10.327,P<0.05 all above) and were decreased in TM and TH group (t=3.663-4.924,P<0.05 all above). Conclusions TWP treatment may delay the progression of diabetic non-alcohol fatty liver disease via inhibition of TLR4/NF-κB signaling cascade pathway, and its downstream inflammatory effectors. Key words: Diabetes mellitus, type 2; Tripterygium wilfordii polyglucosides; Inflammation; Toll like receptor4; Liver