Insulin-like growth factor binding protein 3 in inflammatory bowel disease

Epithelial cell growth regulation has been reported to be altered in inflammatory bowel disease (IBD) patients. The cell growth regulatory factor, insulin-like growth factor binding protein 3 (IGFBP-3), may be partly responsible for this phenomenon. So far, IGFBP-3 levels have been assessed as values of total protein, which is a sum of bioactive intact 43- to 45-kDa protein and its inactive proteolytic cleavage fragments. We aimed to assess the levels of intact IGFBP-3 and its cleaving protease MMP-9 in IBD. Patients with IBD and controls were included. Total plasma IGFBP-3 concentration was measured in ELISA. Western blot analysis, which distinguishes between intact and cleaved IGFBP-3, was performed in order to determine the ratio of intact to total protein; this ratio was used to calculate the concentration of intact IGFBP-3. The profile of plasma proteases was evaluated in zymography and MMP-9 levels were determined in ELISA. The concentration of intact IGFBP-3 was significantly decreased in patients with moderate to severe IBD activity compared to those in remission or controls. Of note, a dramatic depletion of intact IGFBP-3 was found in 7.4% of patients with IBD. Zymography revealed that the dominant gelatinase was the pro-form of MMP-9. However, no differences in MMP-9 levels were noted between those with active disease and controls. The level of intact IGFBP-3 is decreased in IBD patients with moderate to severe disease activity. This decrease may be linked to altered IGFBP-3 production or to increased cleavage by proteases other than MMP-9.