Expression of insulin-like growth factor-I (IGF-I) and IGF-binding proteins during adipogenesis

Endocrinology. 1994 Nov;135(5):1863-8. doi: 10.1210/endo.135.5.7525256.

Abstract

Insulin-like growth factor-I (IGF-I) stimulates the differentiation of preadipocytes, but the expression of IGF-I and IGF-binding proteins (IGFBPs) during the course of adipogenesis has not been investigated. Using two in vitro models, primary mouse preadipocytes and the 3T3-L1 preadipocyte cell line stimulated to differentiate with IGF-I, we studied IGF and IGFBP expression before and during differentiation. Primary preadipocyte cultures expressed IGF-I, IGFBP-2, and IGFBP-4 messenger RNAs (mRNAs), and conditioned medium (CM) contained IGFBP-3 [approximately 46,000 mol wt (M(r))], IGFBP-4 (24,000 M(r)), and a 30,000 M(r) IGFBP identified by immunoblot as IGFBP-2. During differentiation, an additional approximately 34,000 M(r) form of IGFBP-2 was predominant, but IGFBP-2 mRNA decreased, suggesting that a mechanism other than steady state mRNA levels is regulating protein abundance in CM. Like primary cultures, undifferentiated 3T3-L1 cells expressed IGFBP-4 mRNA, but insignificant levels of IGF-I and IGFBP-2 mRNAs. 3T3-L1 cell CM contained IGFBP-3 and IGFBP-4, and with the addition of IGF-I, a 30,000 M(r) IGFBP was also present. This IGFBP was not recognized by antiserum to IGFBP-1, -2, -4, -5, or -6. During differentiation of 3T3-L1 cells, an approximately 34,000 M(r) form of IGFBP-2 was also present in CM. In summary, primary cultures of mouse preadipocytes and 3T3-L1 cells express similar IGFBPs during IGF-I-stimulated adipogenesis. The presence of a larger isoform of IGFBP-2 in a differentiation-dependent manner and a potentially novel IGFBP in response to IGF-I suggests that these IGFBPs may be important in modulating IGF-I action in adipogenesis.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adipocytes / chemistry*
  • Adipocytes / cytology*
  • Adipocytes / metabolism
  • Adipose Tissue / chemistry*
  • Adipose Tissue / cytology*
  • Adipose Tissue / metabolism
  • Animals
  • Blotting, Northern
  • Carrier Proteins / analysis*
  • Carrier Proteins / genetics
  • Carrier Proteins / physiology*
  • Cell Differentiation / physiology
  • Cell Division / physiology
  • Cell Line
  • Insulin-Like Growth Factor Binding Protein 1
  • Insulin-Like Growth Factor Binding Protein 2
  • Insulin-Like Growth Factor Binding Protein 4
  • Insulin-Like Growth Factor Binding Proteins
  • Insulin-Like Growth Factor I / analysis*
  • Insulin-Like Growth Factor I / genetics
  • Insulin-Like Growth Factor I / physiology*
  • Mice
  • Polymerase Chain Reaction
  • RNA, Messenger / analysis
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Stem Cells / chemistry*
  • Stem Cells / cytology*
  • Stem Cells / metabolism

Substances

  • Carrier Proteins
  • Insulin-Like Growth Factor Binding Protein 1
  • Insulin-Like Growth Factor Binding Protein 2
  • Insulin-Like Growth Factor Binding Protein 4
  • Insulin-Like Growth Factor Binding Proteins
  • RNA, Messenger
  • Insulin-Like Growth Factor I