WDR4-mediate tRNA m7G modification to promote mitophagy and browning of white adipose tissue for ameliorating obesity

Objective: Brown adipose tissue activation has emerged as a potential therapeutic strategy in obesity due to its ability to enhance energy expenditure. N7-methylguanosine (m7G) modifications is a novel RNA epigenetic modification, but its role in adipose tissue metabolism and obesity remains unexplored.Methods: A high-fat diet (HFD) was administered to establish obesity mice model, followed by PCR array analysis. Gain-of-function experiments and TRAC-seq were employed to explore the functional role of WDR4.Result: A Mouse EpigeneticModification Enzymes PCR Array revealed that WDR4 expression showed the most pronounced downregulation in HFD mice. Overexpression of WDR4 in 3T3-L1 cells significantly increased UCP1 expression and suppressed lipid droplet formation, and enhanced mitophagy as evidenced by mitochondrial ultrastructure, autophagic vesicles, and LC3 expression. Suppression of mitophagy using 3-MA attenuated WDR4-induced above adipocyte browning. WDR4 overexpression reshaped the tRNA m7G methylome in 3T3-L1 adipocytes, specific induced 38 unique tRNA m7G modification sites, and the cleavage scores of tRNALeuTAA, tRNACysGCA, tRNAGluCTC, tRNAIleGAT, tRNAMetCAT, and tRNASerAGA were markedly elevated. GSE229240 dataset revealed that WDR4 mutation significantly reduced translation efficiency of 195 genes in 3T3-L1 adipocytes, these genes were enriched in TGF-β signaling pathway, including BMP8B. Translation efficiency of BMP8B which had codons decoded by tRNA m7G modification was enhanced by WDR4 overexpression.Conclusion: WDR4 promotes mitophagy by enhancing BMP8B translation through tRNA m7G modification, thereby promoting adipocyte browning. These findings reveal a novel m7G epitranscriptomic mechanism linking to mitophagy and provide a potential therapeutic target for obesity.