Pharmacological modulation of RORα controls the fat browning, adaptive thermogenesis and body weight in mice.

Beiging is an attractive therapeutic strategy to fight against obesity and its side metabolic complications. The loss of function of the nuclear transcription factor RORa has been related to a lean phenotype with higher thermogenesis in sg/sg mice lacking this protein. Here we show that pharmacological modulation of RORa activity exerts reciprocal and cell-autonomous effect on UCP1 expression ex vivo, in cellulo and in vivo. The RORa inverse-agonist SR3335 up-regulated UCP1 expression in brown and subcutaneous white adipose tissue (scWAT) explants of WT mice, while the RORa agonist SR1078 had the opposite effect. We confirmed the reciprocal action of these synthetic RORa ligands on gene expression, mitochondrial mass and uncoupled oxygen consumption rate in cultured murine and human adipocytes. Time-course analysis revealed stepwise variation in gene expression, first of TLE3, an inhibitor of the thermogenic program, followed by a reciprocal effect on PRDM16 and UCP1. Finally, RORa ligands were shown to be useful tools to modulate in vivo UCP1 expression in scWAT with associated changes in this fat depot mass. SR3335 and SR1078 provoked opposite effects on the WT mice body weight, but without any effect on sg/sg mice. This slimming effect of SR3335 was related to an increased adaptive thermogenesis of the mice, as assessed by the rectal temperature of cold-stressed mice and induction of UCP1 in scWAT, as well as by indirect calorimetry in presence or not of a b3 adrenoreceptor agonist. These data confirmed that RORa ligands could be useful tools to modulate thermogenesis and energy homeostasis.