Glycyrrhiza uralensis root extract ameliorates high glucose-induced renal proximal tubular fibrosis by attenuating tubular epithelial-myofibroblast transdifferentiation by targeting TGF-beta 1/Smad/Stat3 pathway

Growing evidences indicate that high glucose toxicity-associated fibrotic effects play a pivotal role in diabetic nephropathy (DN). Tubular epithelial-myofibroblast transdifferentiation is a major hallmark of renal fibrosis event under diabetic stress. Roots of Glycyrrhiza uralensis (Radix glycyrrhizae) used as a sweetener and traditional Chinese medicine possess high potential for renal protection. In this study, a cell model for high glucose (HG) injury with HK-2 renal proximal tubular epithelial cell line and a type-II-diabetes model with Apoe(em1/Narl)/Narl mice was established and the beneficial effects of aqueous R. glycyrrhizae extract (RGE) was investigated. RGE-induced regulation on the high glucose-induced excessive production of TGF-beta 1 and the Smad/Stat3 mechanisms of renal fibrosis were determined. HK-2 cells were challenged with 45 mM of high glucose for 48 hr. Following high glucose challenge, the cells were treated with 0.5, 1, and 1.5 mg/ml concentrations of RGE. The effect of RGE on DN was determined using high fructose diet-induced type-II-diabetes in Apoe(em1/Narl)/Narl mice models. Our results showed that RGE suppressed the expression of HG-induced TGF beta signaling and associated fibrosis mechanism better than the pharmacological drug acarbose. These data suggest that RGE as a potential herbal supplement in attenuating fibrosis-associated diabetic nephropathy and a potential agent in diabetes treatments.