Effects of Anoectochilus formosanus Hayata on TNF-α induced insulin resistance FL83B cells

Anoectochilus formosanus Hayata (Orchidaceac) is an indigenous and valuable Taiwanese medicinal plant which usually used as a folk medicine for liver fibrosis, diabetes and treatment of cardiovascular diseases. Although, studies have pointed out that it possesses antidiabetic properties, not much study in cell culture has been conducted. The main purpose of this study was to investigate the anti-insulin resistance effects of three different extracts (hot water extract, distilled water and ethanol (50:50, v/v) extract and ethanol extract) from leaf, stem and root of A. formosanus Hayata towards mouse normal liver cells (FL83B) which induced by using tumor necrosis factor-α (TNF-α). In this study, DPPH antioxidant activity, total phenolic content and carbohydrate analysis were carried out to estimate the chemical content of different extracts from leaves, stems and roots of A. formosanus. Yet, hot water extract from the root showed relatively higher total phenolic content and carbohydrate content than the other extracts. Meanwhile, the cytotoxicity of different part of the plant was also evaluated by using MTT ((3-(4,5-Dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide) assay. Hot water extracted from root at concentration of 0.125 mg/mL showed no toxicity towards the mouse liver normal cell line FL83B. Additionally, in order to investigate effects of extracts on restoration of insulin resistant FL83B cells, the cells were co-treated with 40 ng/mL of TNF-α and different extract from A. formosanus for 12 hours. Then the cells was incubated at 37 °C water bath for 1 hour with a fluorescent D-glucose analog 2- [N-(7-nitrobenz-2-oxa-1,3- diazol-4-yl) amino]-2deoxy-D-glucose (2-NBDG) followed by flow cytometric detection of fluorescence produced by the cells. The results showed that water extract from the root displayed higher glucose uptake ability as compared to control group. Furthermore, the glucose uptake ability of FL83B cells increased as increased the concentration of hot water extract from root. In conclusion, hot water extract from root of A. formosanus Hayata significantly improved insulin sensitivity in the TNF-α induced FL83B cells.