Promyelocytic leukemia inhibits adipogenesis, and loss of promyelocytic leukemia results in fat accumulation in mice

Abstract

The function of the tumor suppressor promyelocytic leukemia (PML) protein is disrupted in promyelocytic leukemia. PML has been reported to function as a negative regulator of mTOR (mammalian target of rapamycin) and nuclear Akt under some conditions. mTOR and Akt pathways regulate a diverse array of pathways, including those that control insulin signaling, energy metabolism, growth, cellular survival, and lifespan. Although the PML-mTOR/Akt link suggests that PML may have metabolic functions in the whole organism, very little is known about the metabolic functions of PML. Here we report that PML−/−mice did not show any significant metabolic defects. There was no impairment in the mTOR/Akt or AMPK signaling in white adipose tissue, liver, or muscle. However, despite having normal food intake and activity levels, PML−/−mice gained body weight faster and had more fat mass, particularly subcutaneous fat mass, in the diet-induced obesity model. Using in vitro adipogenesis models, we discovered that PML is a suppressor of adipogenesis. PML expression decreased during adipogenesis and was undetectable in fully differentiated adipocytes. Loss of PML increased expression of the adipogenic transcription factors CCAAT/enhancer binding protein-α and peroxisome proliferator-activated receptor-γ. We found that the Sirt1-NCor-SMRT corepressor complex, which represses pparg transcription, does not bind to the pparg promoter efficiently upon PML depletion. On the basis of these findings, we propose that PML is a negative regulator of the adipogenic transcription factors and that, in times of energy excess, PML may limit fat accumulation by suppressing the differentiation of preadipocytes into adipocytes.