Endocrine Abstracts

Recent data showed the existence of a specific adipocyte population composed of ‘brite’ cells in white adipose tissue (WAT), characterized by a peculiar gene expression pattern including PRDM16. Despite showing a low basal UCP1 expression, these cells display higher UCP1 expression when stimulated. In view of the involvement of the endocannabinoid system in energy homeostasis, the aim of our work is to establish whether the CB1 receptor could be a target for brown phenotype induction in vivo.

We analyzed UCP1 and PRDM16 mRNA expression by QT-RTPCR in brown adipose tissue (BAT), white subcutaneous inguinal (scWAT) and visceral epididymal (eWAT) adipose tissues, obtained from CB1KO (CBN) and Rimonabant-treated (10 mg/kg per day i.p., 4 weeks) mice vs respective controls (CT), undergoing standard diet (SD) or high-fat diet (HFD) from the 8th to 20th week of age. In CT mice, HFD significantly stimulates UCP1 mRNA in all adipose depots (eWAT P<0.001; scWAT and BAT P<0.01) when compared to SD mice, whereas PRDM16 expression is increased only in eWAT depot (P<0.05), suggesting a tissue-specific gene expression response induced by HFD. We observed constant and similar gene expression modulation in CBN and Rimonabant treated animals. Comparing CT and CBN/Rimonabant mice, relevant changes in gene expression were found in scWAT where CB1 signaling inhibition induced a strong increase in UCP1 expression (P<0.01) regardless of diet type, whereas CB1 blockade induced PRDM16 increase (P<0.05) only in HFD condition. These data, together with the finding of the sole increase of CB1 expression in HFD vs SD in scWAT (P<0.01), strengthen the hypothesis that CB1 receptor antagonization may modulate brown-cell recruitment mechanisms on specific WAT depots. Further studies are underway to complete the characterization of the gene expression pattern of these putative ‘brite’ cells.