Age-related serum levels of insulin like growth factor-I, -II and IGF-binding protein 3 following myocardial infarction

Aging retards the repair process by decreasing hormone secretion from the s omatotrophic axis, which plays a major role in tissue reconstruction after injury. The aim of this study was to determine the effect of aging on serum insulin-like growth factor-I (IGF-I), IGF-II and IGF-binding protein-3 (IG FBP-3) levels following myocardial infarction (MI). For four consecutive da ys, we monitored the variation of serum IGF-I, IGF-II and IGFBP-3 concentra tions in 26 patients aged 19-71 years who were diagnosed with MI. Serum IGF -I, IGF-II and IGFBP-3 were measured daily by double antibody radioimmunoas say. Daily serum IGF-I concentrations showed a significant negative correla tion with age (r = -0.528, P < 0.001). Total serum IGF-I was significantly (P = 0.002) higher in the younger age group (patients under 50 years) compa red to the older group (50 years and over); 206 +/- 16 ng/ml vs 136 +/- 12 ng/ml. During this investigation, younger patients (under 50 years) showed no significant daily variations in IGF-I levels compared to older patients (50 years and over) who presented a significant decline (P = 0.012). Total serum IGF-II in both groups decreased significantly with time. Total serum IGFBP-3 in the younger age group was significantly higher (P = 0.046) than in the older age group (3.42 +/- 0.18 mu g/ml vs 2.95 +/- 0.13 mu g/ml). MI patients in both groups showed significantly lower IGF-I and IGF-II (IGFs) with higher IGFBP-3 compared to age- and sex-adjusted levels of normal adu lts (controls). The present results confirm that age and cardiac condition affect IGFs and IGFBP-3 levels. We are inclined to believe that older patie nts with a cardiac condition are less able to maintain their blood IGF-I le vels during the recovery period compared to younger patients. Given the bio logical impact of IGF-I on regeneration, this could explain why older patie nts take longer to recover and heal poorly in comparison to younger patient s. (C) 2000 Harcourt Publishers Ltd.