Glucocorticoids and the Differentiation of Porcine Preadipocytes4

Abstract

The function of glucocorticoids in the differentiation of porcine preadipocytes was examined. Stromal-vascular cell cultures (containing preadipocytes) derived from adipose tissue of the perirenal, ham and shoulder regions of neonatal pigs were incubated in the presence of hydrocortisone at 0 to 100 ng/ml medium. Perirenal cells did not respond to hydrocortisone with an increase in enzyme expression, nor did they demonstrate growth characteristics similar to those of cultures derived from the ham or shoulder. Cultures from the shoulder and ham regions demonstrated dose-responsive increases in enzymatic expression to hydrocortisone. Enzymatic responses by cultures derived from the ham region were lower than responses by cultures from the shoulder region as measured by changes in the activities of sn-glycerol-3-phosphate dehydrogenase and lipoprotein lipase. Addition of insulin to the medium did not produce a synergistic effect with glucocorticoid on differentiation as determined by these enzymatic parameters. However, [14C]glucose metabolism by the cells in culture was synergistically increased by insulin and glucocorticoid supplementation of the medium. The ability of hydrocortisone to induce differentiation of porcine preadipocytes in vitro suggests that the changes that occur in plasma glucocorticoid concentrations during late gestation may play an important role in the rapid development of s.c. adipose tissue in the fetal pig. Secondly, the differences in culture characteristics and hormone responses of cells derived from different locations of adipose tissue formation indicate that differences may exist in the regulation of the growth and development of preadipocytes from different anatomical locations.

Prolonged dietary treatment with conjugated linoleic acid stimulates porcine muscle peroxisome proliferator activated receptor gamma and glutamine-fructose aminotransferase gene expression in vivo

“…The conflicting increase in intramuscular fat deposits and associated reduction in subcutaneous fat deposits in CLA-fed animals may be due to differences in PPAR expression and adipocyte cellular development between the two fat locations (Brun & Spiegelman 1997, Grindflek et al 1998, Valmaseda et al 1999. Intramuscular fat and muscle tissue have a higher percentage of s-v stem cells and preadipocytes than subcutaneous fat (Ramsay et al 1989, May et al 1994. It has also been demonstrated in vitro that s-v cells, fibroblasts and newborn mouse muscle stem cells can be induced to differentiate into preadipocytes and to express adipocyte-specific genes such as AFABP, by treating them with PPAR activators such as thiazolidinedione drugs (Lehmann et al 1995, Teboul et al 1995.…”

Preadipocyte Recruitment in Stromal Vascular Cultures After Depletion of Committed Preadipocytes by Immunocytotoxicity

“…No one has initiated DEX treatment at seeding or before confluence, i.e., during the proliferation phase in porcine S-V cultures. Replication either directly or indirectly reduces the capability of preadipocytes to differentiate in s-V cultures (8,12,28), whereas DEX generally antagonized cell proliferation in S-V cultures (20,22,34). Studies of cell lines indicate that preadipocyte differentiation may be coupled with growth arrest (2,24,25,26).…”

Characterization of sgk, a novel member of the serine/threonine protein kinase gene family which is transcriptionally induced by glucocorticoids and serum.

“…Glucocorticoid hormones play a fundamental role in the control of homeostasis, differentiation, and development in animal tissues (8,10,15,29,35). These steroids exert their regulatory effects through intracellular receptors which act as potent transcriptional activators of genes that possess glucocorticoid response elements (GREs) (reviewed in references 3 and 11).…”