RARγ and TRβ expressions are decreased in PBMC and SWAT of obese subjects in weight gain

In order to evaluate the expression of nuclear receptors at the peripheral level in obese subjects, messenger RNA (mRNA) levels of different isoforms of retinoic acid receptor (RAR), triiodothyronine (TR), and peroxisome proliferator-activated receptor (PPAR) were determined and compared in peripheral mononuclear blood cells (PBMC) and subcutaneous white adipose tissue (SWAT). Twelve lean subjects and 68 obese subjects divided into weight gain (WG), weight-stable (WS), and weight loss (WL) groups were studied. Nuclear receptor mRNA levels were assessed in PBMC and SWAT using a quantitative real-time reverse transcription polymerase chain reaction method. mRNA levels of RARγ were significantly lower in PBMC of obese subjects (WG −19%, WS −30%, and WL −24.7%) as in SWAT of WG (−50%). Lower mRNA levels of TRβ were observed in PBMC and SWAT of WG (−50.7% and −28%, respectively) just as for TRα in PBMC of WG (−19%). In contrast, retinoid X receptors α (RXRα) and RARα mRNA levels were higher in PBMC of obese subjects (+53% and +54.5% in WG, +56% and +67% in WS, and +68% and +49.7% in WL, respectively), while expression of RXRα was lower in SWAT of WG (−24.5%). As for PPARγ, its mRNA level was significantly higher in PBMC of WG subjects (+34%) while its expression was not modified in SWAT, contrary to the PPARγ2 isoform which was significantly higher. These data show that in both adipose tissue and blood compartment of obese subjects, expressions of RARγ and TRβ were downregulated. Thus, we suggest that the expression in PBMC of obese subjects may constitute new cellular indicators of nuclear receptor retinoid and thyroid status.