The Regulation of BRN3B in Adipocytes by Glucose and Insulin

Abstract

Obesity is the inappropriate accumulation of excess fat stored in the adipocytes of the adipose tissue. Understanding the molecular mechanisms that regulate the process of the preadipocyte to adipocyte conversion, adipogenesis, is crucial when trying to design treatments for the disease. Known transcription factors, such as Peroxisome proliferator-activated receptor y (PPARy), play an essential role in preadipocytes differentiation into adipocytes. However, more recently novel nuclear receptors such as, Brn-3b (or POU4F2, second transcription factor in the fourth class of POU family), have been shown to be expressed in adipose tissue, but their link with adipogenesis is yet to be established. 3T3-L1s, a murine adipocyte cell-line, was used to investigate Brn3b gene expression during adipogenesis in high and low glucose conditions, in the presence and absence of dexamethasone, and compared to PPARy gene expression. Two experiements with high glucose were performed one in the presence of dexamethasone and the other without dexamethasone. A third experiement was conducted using low glucose with dexamethsone. RNA extracted from cells at different time intervals was converted to cDNA before being analyzed by qPCR. Morphological examination of the cells confirmed the requirement of high glucose concentrations for cells to differentiate into adipocytes. There was significant increase in PPARy gene expression during adipogenesis of cells grown in high glucose concentration in presence or absence of dexamethasone. However, no detectable expression of Brn-3b was apparent in either the preadipocytes or the adipocytes, under any of the experimental conditions studied. These results suggest that the expression of Brn-3b in adipose tissue derives from the non-adipocyte cells of the tissue, such as neuronal, endothelial, monocytic or epthelial.