TGFB1 and obesity due to melanocortin 4 receptor deficiency: Our data indicate that macrophage-derived Tgfβ1 promotes Aldh1a1 in brown adipocytes, which is consistent with recent findings demonstrating that Aldh1a1 is exclusively expressed in mature adipocytes and that its loss has been associated with increased brown-adipocyte function.49 In conclusion, our findings underscore the role of LAMs in the expansion of BAT, which contributes to the transition of BAT from its functional state to a WAT-like phenotype during obesity.