Secretion of insulin-like growth factor (IGF)-I and -II and IGF binding proteins (IGFBPs) in fetal stromal-vascular (S-V) cell cultures obtained before and after the onset of adipogenesis in vivo.
The present study examined the influence of dexamethasone (DEX) treatment on preadipocyte differentiation and insulin-like growth factor binding protein (IGFBP) secretion in stromal-vascular (S-V) cell cultures established from subcutaneous adipose tissue obtained from nine 75 day and four 50 day pig fetuses. Cultures of S-V cells from four young pigs (5-7 days old) were also studied. Each fetal S-V cell culture represented 1 pool of S-V cells/dam. Cultures were seeded and plated in 10% FBS from day 0-3 and treated with insulin (ITS) + 10 nM DEX from day 3-6 (late DEX treatment). Alternatively, cultures were seeded and plated in 10% FBS + 80 nM DEX from day 0-3 and treated with insulin alone from day 3-6 (early DEX treatment). Conditioned media was collected on day 6 of culture after 3 days of conditioning, and prepared for subsequent 125I-IGF-I ligand blot analysis for IGFBPs and RIA for IGF-I and IGF-II. Early and late DEX increased (P<0.05) preadipocyte (AD-3+) recruitment but only early DEX increased preadipocyte differentiation (lipid + and C/EBP alpha+) by day 6 in S-V cultures from 75 day fetuses. Levels of IGFBP-2, IGFBP-4, IGF-I and IGF-II in media conditioned by 75 day fetal S-V cultures were not influenced by late DEX. However, late DEX reduced levels of 29 kDa IGFBPs and markedly increased (P<0.05) IGFBP-3 levels in 75 day S-V media. Late DEX also markedly increased (P<0.05) IGFBP-3 levels in 50 day S-V media but had little influence on other IGFBPs. Early DEX treatment increased (P<0.05) IGFBP-4 levels in 75 day S-V media but had little to no influence on levels of IGF-I, IGF-II and other IGFBPs. These studies indicate that IGFBP-4 may regulate local metabolism during preadipocyte differentiation, whereas IGFBP-3 may antagonize preadipocyte differentiation by targeting IGF-I away from differentiating cells and towards growing cells.
Hausman
G J
GJ
USDA-ARS, R.B. Russell Agricultural Research Center, Animal Physiology Research Unit, Athens, GA 30604-5677, USA.
Richardson
R L
RL
Simmen
F A
FA
D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000273:Adipose Tissue / Q000098:blood supply / Q000196:embryology; D000818:Animals; D001808:Blood Vessels / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D003907:Dexamethasone / Q000494:pharmacology; D005865:Gestational Age; D007150:Immunohistochemistry; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000378:metabolism; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D034421:Sus scrofa
D017077:Culture Media, Conditioned; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018974:Insulin-Like Growth Factor Binding Protein 4; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D003907:Dexamethasone