UCP1 and obesity due to melanocortin 4 receptor deficiency: Deletion of Mettl3 driven by the Ucp1 promoter severely impairs the maturation of BAT by reducing m6A peaks and the expression of Prdm16, Pparγ, and Ucp1. This significantly reduces BAT-mediated adaptive thermogenesis and promotes high-fat diet-induced obesity and systemic insulin resistance (110).