Sexually dimorphic role of constitutive androstane receptor in the regulation of endocrine and metabolic homeostasis

The constitutive androstane receptor (CAR) is a transcription factor involved in detoxification through regulating expression of xenobiotic-metabolizing enzymes. Highly expressed in the liver, it is important in protecting the organism against exogenous and endogenous toxic molecules such as bile acids and bilirubin and in the catabolism of thyroid and steroid hormones. A role has also been assigned to CAR in the regulation of energy metabolism, although related mechanisms have been studied primarily in males and in physiopathological conditions. Here, we compared the impact of CAR deficiency on energy homeostasis regulation between male and female mice in a normal physiological context. Large-scale gene expression analysis in 16-week-old animals revealed significant sexual dimorphism in the hepatic transcriptome of CAR-/- mice. Thirty-six WT or CAR-/- males and 36 WT or CAR-/- females were housed in the laboratory animal room (23 ± 2 ºC) and segregated in 2 groupes each including 18 mice. One groupe of WT and CAR-/- males and females was sacrified at the age of 16 weeks. An other group containing the same animals was followed for 68 weeks. Body weight was monitored throughout the experiment, and glucose tolerance and insulin sensitivity tests were performed. At death, blood, liver, epididymal adipose tissue (WAT) were collected and serum biochemical parameters were measured. Liver were analyzed for fatty acid content, histology. Hepatic gene expression studies were performed on the 16 week-old mice by microarray . Gene expression profiles were performed on 6 liver samples per group at the GeT‐TRiX facility (GénoToul, Génopole Toulouse Midi-Pyrénées) using Agilent Sureprint G3 Mouse GE v2 microarrays (8x60K, design 074809) following the manufacturer's instructions. For each sample, Cyanine-3 (Cy3) labeled cRNA was prepared from 200 ng of total RNA using the One-Color Quick Amp Labeling kit (Agilent) according to the manufacturer's instructions, followed by Agencourt RNAClean XP (Agencourt Bioscience Corporation, Beverly, Massachusetts). Dye incorporation and cRNA yield were checked using Dropsense™ 96 UV/VIS droplet reader (Trinean, Belgium). 600 ng of Cy3-labelled cRNA were hybridized on the microarray slides following the manufacturer’s instructions. Immediately after washing, the slides were scanned on Agilent G2505C Microarray Scanner using Agilent Scan Control A.8.5.1 software and fluorescence signal extracted using Agilent Feature Extraction software v10.10.1.1 with default parameters. Microarray data were analyzed using R (www.r-project.org, R v. 3.1.2), using Bioconductor packages (www.bioconductor.org, v 3.0, as described in GEO accession GSE. Raw data (median signal intensity) were filtered, log2 transformed and normalized using quantile method3