사람의 섬유아세포에서 Glucose 농도가 Insulin-like Growth Factor Binding Protein-5의 발현에 미치는 영향

Abstract

사람의 섬유아세포인 GM10에서 glucose 농도에 따른 IGFBP-5의 존재와 발현에 미치는 영향을 살펴보고 당뇨병과 관련된 in vitro model system으로서의 활용 가능성을 검토하고자 하였다. 섬유아세포인 GM10 세포를 시용하여 glu-cose 배양 조건에 따른 IGFBP-5의 존재와 발현에 미치는 영향을 살펴보았다. 그 결과, IGFBP-5의 단백질 수준은 고농도 glucose 배양 조건에서 증가하였으나, IGFBP-5 mRNA 발현에는 아무런 영향을 나타내지 않았다. IGFBP-5 protease 활성은 고농도 glucose 배양 조건에서 높았다. IGF- I 과 인슐 린은 IGFBP-5 protease 활성에 관여하는 것으로 보여지며, GM10 세포에 있어서 IGFBP-5의 분해에는 serine protease 뿐만 아니라 metalloprotease가 관여하는 것으로 나타났다. 또한, gelatin zymography를 통한 protease 활성은 고농도 glucose 배양 조건에서 크게 나타났으며, 시간 의존적으로 증가하였다. 본 연구 결과를 바탕으로 IGFs와 같은 세포 성장인자에 대한 연구는 세포수준의 당뇨병과 관련된 in vitro model system이 가능하리라고 여겨지며 더 많은 연구가 진행되어야 할 것으로 보인다. Insulin-like growth factor-I (IGF-I) and IGF-II have structure like insulin. In contrast to insulin, however, the bioavaility of IGFs is modulated by the IGF-binding protein (IGFBPs). Each of IGFBPs was different with molecular masses, biological characteristics, and immunological properties.. Human fibroblasts secrete IGFBPs that can modify IGF-I action. In diabetes mellitus, the most study of IGF systems have been investigated in insulin-dependent diabetes mellitus, non-insulin-dependent diabetes mellitus, and streptozotocin-in-duced animals in vivo. Recently, a little research regarding the IGFs system has been proposed in por-tion of cell in vitro. In this study, effects of low or high glucose condition on IGFBP-5 in GM10 was investigated. By western blotting analysis, IGFBP-5 level decreased in cells cultured at high glucose, but IGFBP-5 level of mRNA didn't change. IGFBP-5 protease that cleaves IGFBP-5 in conditioned me-dium had was inhibited by EDTA and heparin, like serine protease and metalloprotease. Furthermore, the protease activity was increased in high glucose cultivated condition. In results of gelatin zymog-raphy, molecular weight of proteolytic metalloenzymes was indentified 69-kDa and protease activity was increased in time-dependent manner. Although the mechanism has yet to be determined, IGFBP-5 proteolysis in GM10 cells cultured with high glucose may increase effects of IGFs to decrease the glu-cose level through dissociation of IGFs from IGFBPs. Therefore, we suggest that IGF- I and IGFBPs could be potential models in study of pathophysiology such as diabetes mellitus.