Expression of C/EBP alpha, beta and delta in fetal and postnatal subcutaneous adipose tissue

The C/EBP (CCAAT/enhancer binding protein) family of transcription factors (C/EBP alpha, beta, and delta) has been implicated in the development and the metabolic regulation of adipocytes from in vitro studies, yet the function of these factors, particularly CEBP beta and delta, in vivo has not been characterized. To assess the role of these factors in vivo, subcutaneous adipose, tissue from fetal and postnatal pigs was examined for C/EBP alpha, beta, and delta expression in developing and mature adipocytes. Western blot analysis of fetal adipose tissue showed a progressive increase of C/EBP alpha expression in 50, 75 and 95 day old fetuses. C/EBP beta and delta proteins were not observed in fetal adipose tissue. These results were confirmed with immunohistochemical studies of fetal adipose showing enhanced C/EBP alpha expression in the nuclei of adipocytes and cells closely associated with adipose cell clusters from 75 and 95 day old fetuses. For the same tissues only light background staining with no differential enhancement was found for C/EBP beta and delta. In postnatal adipose tissue C/EBP alpha and C/EBP beta protein were expressed in both 8 day old postnatal and mature (180 day) pigs. C/EBP delta reactive products were found in postnatal tissues however, their molecular weights were lower than that found in fetal pig liver. Our data suggest that adipose cell terminal differentiation proceeds in the pig fetus without the expression of C/EBP beta and delta and that these factors may have a more important role in fully differentiated adipose cells in postnatal tissue.