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

<b><i>Objective</i></b><i>:</i> 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.<b><i>Methods</i></b><i>:</i> 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.<b><i>Result</i></b><i>:</i> 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 tRNA^LeuTAA, tRNA^CysGCA, tRNA^GluCTC, tRNA^IleGAT, tRNA^MetCAT, and tRNA^SerAGA 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.<b><i>Conclusion</i></b><i>:</i> 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.