Epigallocatechin gallate targets FTO and inhibits adipogenesis in an mRNA m6A-YTHDF2-dependent manner

Background/objective: N-6-methyladenosine (m(6)A) modification of mRNA plays a role in regulating adipogenesis. However, its underlying mechanism remains largely unknown. Epigallocatechin gallate (EGCG), the most abundant catechin in green tea, plays a critical role in anti-obesity and anti-adipogenesis. Methods: High-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (HPLC-QqQ-MS/MS) was performed to determine the m(6)A levels in 3T3-L1 preadipocytes. The effects of EGCG on the m(6)A levels in specific genes were determined by methylated RNA immunoprecipitation coupled with quantitative real-time PCR (meRIP-qPCR). Several adipogenesis makers and cell cycle genes were analyzed by quantitative real-time PCR (qPCR) and western blotting. Lipid accumulation was evaluated by oil red O staining. All measurements were performed at least for three times. Results: Here we showed that EGCG inhibited adipogenesis by blocking the mitotic clonal expansion (MCE) at the early stage of adipocyte differentiation. Exposing 3T3-L1 cells to EGCG reduced the expression of fat mass and obesityassociated (FTO) protein, an m(6)A demethylase, which led to increased overall levels of RNA m(6)A methylation. Cyclin A2 (CCNA2) and cyclin dependent kinase 2 (CDK2) play vital roles in MCE. The m(6)A levels of CCNA2 and CDK2 mRNA were dramatically enhanced by EGCG. Interestingly, EGCG increased the expression of YTH N-6-methyladenosine RNA binding protein 2 (YTHDF2), which recognized and decayed methylated mRNAs, resulting in decreased protein levels of CCNA2 and CDK2. As a result, MCE was blocked and adipogenesis was inhibited. FTO overexpression and YTHDF2 knockdown in 3T3-L1 cells significantly increased CCNA2 and CDK2 protein levels and ameliorated the EGCG-induced adipogenesis inhibition. Thus, m(6)A-dependent CCNA2 and CDK2 expressions mediated by FTO and YTHDF2 contributed to EGCG-induced adipogenesis inhibition. Conclusion: Our findings provide mechanistic insights into how m(6)A is involved in the EGCG regulation of adipogenesis and shed light on its anti-obesity effect.