Oral

Background: 
Non-alcoholic fatty liver disease (NAFLD) has become the leading cause of chronic liver disease in children population due to obesity epidemic. However, there is no specific drug approved for NAFLD treatment. Chinese tea has been shown to have the function to prevent the progression of NAFLD through extracellular vesicles (EVs). However, the mechanism of tea-derived extracellular vesicles (TDEVs) on NAFLD is not known. We aim to investigate the role of TDEVs on pediatric NAFLD. 

Methods: 
HepG2 cell model of NAFLD was established by oil induction and then treated with different doses of functional TDEVs (100uM, low-dose group; and 200uM, high-dose group). The fat droplets in HepG2 cell was assessed by Oil red staining. The triglyceride (TG) and interleukin 6 (IL-6) levels were evaluated by Enzyme‑linked immunosorbent assay (ELISA). The mRNA expressions of MTTP gene and proteins were detected by qPCR and Westen Bloting respectively. DNA methylation of MTTP gene promoters was analyzed by bisulfite genomic sequencing.

Results: 
Smaller fat droplets, a less level of TG and a higher level of IL-6 were found in HepG2 cells treated by TDEVs than in control cells. There was a decrease in mRNA of MTTP in low-dose group compared with control group, and a further decrease in high-dose group. The protein expression of MTTP showed the same trend with mRNA. The DNA methylation of MTTP in model group was significantly increased compared to control group (P>0.05). However, the methylation of MTTP was overtly decreased in low-dose group compared to the model group (P<0.05), which was further decreased in high-dosage group.

Conclusion: 
The results of this study indicates that tea-derived extracellular vesicles improves NAFLD by reduction of MTTP gene methylation in HepG2 cell.