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KMID : 1134820000290030493
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Journal of the Korean Society of Food Science and Nutrition
2000 Volume.29 No. 3 p.493 ~ p.499
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Changes in Serum Insulin - Like Growth Factor Binding Protein - 5 of Osteopenia
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Kim Young
Nam Tak-Jeong
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Abstract
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Insulin-like growth factor (IGF)-I and II are important mitogenic and anabolic peptides and are thought to be involved in regulating the proliferation and differentiation of a number of cell types in vitro and in vivo. IGFs exist in serum and other biological fluids, as complexes bound to a family of structually related proteins, termed IGF-binding proteins (IGFBPs). A family of structually related IGFBPs, different from the IGF receptors, is believed to be involved in the modulation of IGF action in different tissues, including bone tissue. Of the several IGFBPs, stimulatory IGFBP-5, which has a strong affinity for hydroxyapatite, is the major IGFBP stored in human bone. In this study, I investigated the changes of IGFBP-5 in serum from osteopenia patients. The amounts of IGFBP-5 in osteopenia were reduced when they were compared with normal standards. These changes were activated by IGFBP-5 proteases. IGFBP- 5 protease that cleaves IGFBP-5 in osteopenia serum had properties which were serine protease and metalloprotease, because EDTA and 1,10-phenanthroline (both are metalloprotease inhibitors), aprotinin, heparine, heparine cofactor 2 (HC2), and heparine＋HC2 (those are serine protease inhibitors) had inhibitory activities. IGF-I, IGF-II and insulin showed no inhibitory effects on the IGFBP-5 proteases. Gelatin zymography showed that 66 kDa and 97 kDa bands were identified in normal standards, and 69 kDa band was identified in osteopenias.
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KEYWORD
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insulin-like growth factors (IGFs), IGF binding protein-5, osteopenia
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