Insulin-like growth factor (IGF)-I and IGF-binding protein-3 serum levels in relapsing-remitting and secondary progressive multiple sclerosis patients

Abstract

Insulin-like growth factor (IGF)-I has a role in remyelination, and insulin-like growth factor-binding protein-3 (IGFBP-3) might reduce its bioavailability. A role of IGFBP-3 in multiple sclerosis (MS) progression was hypothesized in patients with primary progressive (PP) MS. To evaluate serum levels of IGF-I and IGFBP-3 in patients with relapsing-remitting (RR) and secondary progressive (SP) MS and their correlations with disease activity and progression. Sixty-three (41 RR and 22 SP) 'naive' MS patients and 60 age-matched healthy controls were enrolled. Patients were assessed through clinical [Expanded Disability Status Scale (EDSS), Multiple Sclerosis Severity Scale (MSSS), number of relapses] and laboratory investigations. IGF-I and IGFBP-3 were measured by ELISA. Levels of IGF-I and IGFBP-3 were similar in the two MS groups. IGFBP-3 levels were higher in patients with MS than in controls (P < 0.001), with a reduction in IGF-I/BP3 ratio (P < 0.001). Patients showing IGFBP-3 levels higher than 2SD of the normal population had a higher EDSS (mean EDSS 3.7 vs. 2.8, P = 0.021). MSSS was not related to IGF-I or IGFBP-3 serum levels. Our patients showed high IGFBP-3 serum levels respect to controls and higher serum levels were associated with a higher EDSS, despite of comparable disease duration. Therefore, MS and higher disability seem to be associated with a reduction in bioavailability of IGF-I. MSSS score was not related to IGFBP-3 levels, suggesting that IGFBP-3 might not have the pathogenetic role previously suggested for PP MS, in the mechanism of progression in the SP form of disease.