Plasma IGF-1 binding proteins in lean and obese non-diabetic subjects.
Obese patients have markedly increased plasma insulin concentrations indicating insulin resistance. In contrast, plasma IGF-1 concentrations are little affected. Since the biological effects of IGF-1, including several insulin-like actions, appear to be modulated by serum carrier proteins, alterations of IGF-1 binding proteins were investigated in the serum of lean healthy individuals, and of obese patients with normal glucose tolerance. Obese patients had increased fasting plasma insulin and decreased plasma h-GH concentrations, compared to lean controls. IGF-1 concentrations were similar in both groups. Serum IGF-1 binding proteins were separated by polyacrylamide gel electrophoresis under non-reducing conditions, electroblotted onto a nitrocellulose sheet, and quantified by ligand blot with 125I IGF-1 and autoradiography. IGF-1 binding proteins of apparent molecular weight 42 kDa, 39 kDa, 35 kDa, 30 kDa and 24 kDa were observed. Obese patients had a level of IGF-1 binding proteins of 35 kDa which was decreased to 40 +/- 25% (s.d.) of control values. This 35 kDa protein corresponds to IGF-BP2, which may be involved in glucose homeostasis. It is concluded that alterations of IGF-1 binding proteins are present in obesity and may have consequences for glucose metabolism.
Tappy
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Institut de Physiologie, Université de Lausanne, Switzerland.
Jan
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C
Temler
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D000328:Adult; D001345:Autoradiography; D002352:Carrier Proteins / Q000097:blood*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D013006:Growth Hormone / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1; D008297:Male; D008970:Molecular Weight; D009765:Obesity / Q000097:blood*
D002352:Carrier Proteins; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D013006:Growth Hormone