METTL3 exacerbates insulin resistance in hepatocytes by regulating m6A modification of cytochrome P450 2B6.

Background: Insulin resistance (IR) in hepatocytes endangers human health, and frequently results in the development of non-alcoholic fatty liver disease (NAFLD). Research on m⁶A methylation of RNA molecules has gained popularity in recent years; however, the molecular mechanisms regulating the processes of m⁶A modification and IR are not known. The cytochrome P450 (CYP450) enzyme system, which is mainly found in the liver, is associated with the pathogenesis of NAFLD. However, few studies have been conducted on CYP450 related m⁶A methylation. Here, we investigated the role of the methyltransferase METTL3 in exacerbating IR in hepatocytes, mainly focusing on the regulation of m⁶A modifications in CYP2B6.

Methods and results: Analysis using dot blot and epitranscriptomic chips revealed that the m⁶A modification pattern of the transcriptome in high-fat diet (HFD)-induced fatty liver and free fatty acid (FFA)-induced fatty hepatocytes showed significant changes. CYP450 family members, especially Cyp2b10, whose homolog in humans is CYP2B6, led to a noticeable increase in m⁶A levels in HFD-induced mice livers. Application of the METTL3 methyltransferase inhibitor, STM2457, increased the level of insulin sensitivity in hepatocytes. We then analyzed the role of METTL3 in regulating m⁶A modification of CYP2B6 in hepatocytes. METTL3 regulated the m⁶A modification of CYP2B6, and a positive correlation was found between the levels of CYP2B6 translation and m⁶A modifications. Furthermore, interference with METTL3 expression and exposure to STM2457 inhibited METTL3 activity, which in turn interfered with the phosphorylated insulin receptor substrate (pIRS)-glucose transporter 2 (GLUT2) insulin signaling pathway; overexpression of CYP2B6 hindered IRS phosphorylation and translocation of GLUT2 to membranes, which ultimately exacerbated IR.

Conclusion: These findings offer unique insights into the role that METTL3-mediated m⁶A modifications of CYP2B6 play in regulating insulin sensitivity in hepatocytes and provide key information for the development of strategies to induce m⁶A modifications for the clinical treatment of NAFLD.