Submitted to: General and Comparative Endocrinology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/4/2003
Publication Date: 8/1/2003
Citation: Hausman, G.J. Dexamethasone induced preadipocyte recruitment and expression of CCAAT/enhancing protein alpha and peroxisome proliferator activated receptor-gamma proteins in porcine stromal-vascular (S-V) cell cultures obtanained before and after the onset of fetal adipogenesis. General and Comparative Endocrinology. 2003. v. 133. p. 61-70. Interpretive Summary: Glucocorticoids induce fat cell development and upregulate expression of key DNA binding proteins that regulate fat cell gene expression in cultures of fat cell precursors from young pigs. However, the influence of these DNA binding proteins on the initiation of fat cell development is obscured since expression of these proteins is very high before fat cells develop in cultures of pig fat cell precursors. Glucocorticoids have little to no influence on expression of these proteins in cultures of fat cell precursors from fetal pigs. However, the capability of glucocorticoids to induce expression of one of these proteins develops with age and is coincidental with fat cell development. Expression of this DNA binding protein may initiate hormone regulation of fat cell development in the pig. Further study is necessary to examine potential relationships between fat deposition in pigs and the expression of this DNA binding protein.
Technical Abstract: The present study examined the influence of dexamethasone (DEX) treatment on preadipocyte recruitment and expression of transcription factor proteins in adipose tissue stromal- vascular (S-V) cell cultures from 50 and 75 day old pig fetuses and young pigs. C/EBPalpha ,C/EBPdelta and PPARgamma immunoreactive cells had evenly reactive nuclei and unreactive nucleoli. DEX recruited many more preadipocytes in 75 day than in 50 day fetal S-V cultures. However, DEX did not increase the number of differentiated preadipocytes (lipid + , C/EBP alpha+ ) in 50 day S-V cultures and only slightly increased this number in 75 day fetal S-V cultures. In fetal cultures,extensive, precocious increases in C/EBPalpha expression (number of reactive cells) by day three were followed by extensive decreases in expression. However, PPARgamma expression was not expressed precociously since preadipocyte lipid accretion and PPARgamma immunoreactivity were strongly linked in fetal and pig S-V cultures. Nevertheless, all cells with lipid in fetal S-V cultures were C/EBPalpha and PPARgamma reactive. DEX increases preadipocyte differentiation in pig S-V cultures and in this study DEX increased PPARgamm expression to a much greater degree in pig than in fetal S-V cultures. These studies suggest that restricted adipogenesis in the pig fetus is attributable to limited DEX induced PPARgamma expression.