362-OR: Divergent Roles of METTL14-Mediated m6A in Regulating Brown and White Adipose Tissue Transcriptomes and Systemic Metabolism

N⁶-methyladenosine (m⁶A) is among the most abundant post-transcriptional modifications in mRNA, yet its precise cell-type-specific roles in orchestrating gene expression programs remain elusive. Although brown and white adipocytes are both considered fat cells, their unique properties underscore the importance of context-specific post-transcriptional regulation for whole-body metabolism. Here, we provide the first evidence that m⁶A methyltransferase-like 14 (METTL14) differentially regulates transcriptomes in brown and white adipose tissue (BAT and WAT), leading to divergent metabolic outcomes. We found that human brown and white adipocytes (hBAT and hWAT) display markedly distinct m⁶A landscapes; besides, in insulin-resistant humans and mice, METTL14 expression differs significantly between the fat depots in the context of correlation with insulin sensitivity. Mettl14-knockout in BAT via Ucp1-cre promotes secretion of specific prostaglandins and improved peripheral insulin sensitivity in mice. Conversely, Mettl14-deficiency in WAT via Adipoq-cre triggers white adipocyte apoptosis, lipodystrophy, and systemic insulin resistance. Integration of m⁶A-seq and RNA-seq profiling revealed strikingly distinct transcriptomes and m⁶A methylomes in Mettl14-deficient BAT versus Mettl14-deficient WAT. More specifically, upregulated prostaglandin biosynthesis pathways were enriched in Mettl14-deficient BAT, and TNF-associated and apoptotic pathways were activated in Mettl14-deficient WAT. Using stable METTL14-knockout hBAT or hWAT cell lines, we report that METTL14-mediated m⁶A negatively regulates gene expression of PTGES2, CBR1, and PGC1a in hBAT, and TRAIL, TNFR1, RIP, and DFFA in hWAT by promoting mRNA decay. These data shed light on the ability of m⁶A to impact metabolism in a cell-type-specific manner with implications for influencing the pathophysiology of metabolic diseases.