Tea extracellular vesicles attenuates NAFLD via reducing TG levels by inhibited MTTP gene methylation

Abstract Background: Therapeutic effect of traditional medicines for nonalcoholic fatty liver disease (NAFLD) is far from satisfactory. Tea has been shown to have efficacy in preventing NAFLD. We hypothesized that tea derived extracellular vesicles (TDEVs) may attenuate NAFLD. Methods: Extracellular vesicles (EVs) were isolated from fresh tea. High Performance Liquid Chromatography (HPLC) was used to detect the epigallocatechin-3-gallate (EGCG)in TDEVs. Oleic acid-induced HepG2 cells were treated with different doses of TDEVs. Oil red O staining and fluorescent staining were used to analyze TDEVs efficacy in NAFLD HepG2 cell model. Enzyme‑linked immunosorbent assay (ELISA) was applied to evaluate the levels of triglycerides (TG) and interleukin 6 (IL-6). Q-PCR technique was used to detect the mRNA expressions of MTTP, and Western Blotting was applied to evaluate their protein expressions. Bisulfite genomic sequencing was used to analyze the level of DNA methylation within the promoter of MTTP gene. Results: The concentrations of EGCG in TDEVs was 1.031 ± 0.044 mg/ml, equivalent to 5.6 mg/100 g/FW. Oil red O staining and fluorescent staining demonstrated TDEVs absorbed by HepG2 cells contributed to oil droplets decomposition and a consequential decrease in TG and IL-6 levels. Q-PCR and Western Blotting showed an upregulation in MTTP gene expression by TDEVs. Bisulfite genomic sequencing analysis revealed a reduction in the methylation level of MTTP gene in TDEVs groups. Conclusion: The results of this study indicated that TDEVs attenuated NAFLD via reducing TG level by inhibition of MTTP gene methylation in NAFLD cell model.