Cajanonic acid A regulates the ratio of Th17/Treg via inhibition of expression of IL-6 and TGF-β in insulin-resistant HepG2 cells

Background: The objectives of the present study are to investigate whether cajanonic acid A (CAA) can reduce insulin resistance (IR) in HepG2 cells and to gain a preliminary understanding of the mechanisms underlying this effect. Methods: Following induction of IR in HepG2 cells, we tested the regulatory effect of CAA on glucose consumption and evaluated hepatocyte production of IL-6, TGF-β, and key molecules in the insulin transduction pathway. A transwell co-culturing system was used to assess the effect of CAA on IR in HepG2 cells during the differentiation of CD4(+) T cells by calculating the ratio of (Th17)/regulatory T cell (Treg). We evaluated the effect of CAA on the expression of IL-17RC cells and HepG2 cell apoptosis by immunofluorescence and flow cytometry assay. Results: CAA improved dexamethasone-induced reduction in glucose consumption in HepG2 cells, inhibited hepatocyte production of IL-6 and TGF-β, increased the expression of IL-17RC cell, and increased cellular apoptosis in insulin-resistant HepG2 cells. When co-cultured with CD4(+) T cells, insulin-resistant HepG2 cells induced a decrease in the ratio of Th17/Treg, but CAA dampened the effect. Application of IL-6 and TGF-β, together with CAA, reversed the effect of CAA on insulin-resistant HepG2 cells. Overexpression of IL17R, however, counteracted the effect of IL-6 neutralizing antibody within the culture system. Conclusion: CAA can regulate the ratio of Th17/Treg by mediating the expression of IL-6 and TGF-β in insulin-resistant HepG2 cells.