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

OBJECTIVE: Brown adipose tissue activation is a potential anti-obesity strategy. N(7)-methylguanosine (m(7)G) modification is a novel RNA epigenetic modification, but its role in adipose metabolism remains unexplored. METHODS: Male mice were fed a high-fat diet (HFD), followed by PCR array screening. Gain-of-function experiments and TRAC-seq were employed to explore WDR4 function. RESULT: A Mouse Epigenetic Modification Enzymes PCR Array revealed that WDR4 expression showed the most pronounced downregulation in HFD mice. Overexpression of WDR4 in 3T3-L1 cells and primary adipocytes 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 and bafilomycin A1 attenuated WDR4-induced adipocyte browning. WDR4 overexpression enhanced translational activity and reshaped the tRNA m(7)G methylome in 3T3-L1 adipocytes, specifically induced 38 unique tRNA m(7)G modification sites, and increasing cleavage scores of multiple tRNAs. GSE229240 dataset revealed that WDR4 mutation significantly reduced translation efficiency of 195 genes enriched in the TGF-β signalling , including BMP8B. Knockdown of BMP8B partially counteracted WDR4-mediated mitophagy. CONCLUSION: WDR4 promotes adipocyte browning by enhancing BMP8B translation through tRNA m(7)G modification, revealing a novel m(7)G epitranscriptomic mechanism with therapeutic potential for obesity.