Marked reductions in bioactive insulin-like growth factor I (IGF-I) during hemodialysis

OBJECTIVE: Hemodialysis (HD) patients lose lean body mass, even when they are adequately dialysed. One reason may be a decreased activity of the IGF-system. However, data on changes in bioactive IGF-I during HD are sparse.

DESIGN: Ten stable, non-diabetic HD patients were studied with 30 min intervals during a scheduled HD, with blood sampling before (-15 and 0 min), during (4 h) and after (1 h) the session. Patients were fasted for at least 6 h before and during the study. Arterial and venous blood was sampled for determination of IGF-I bioactivity, free and total IGF-I and IGF-II, IGF binding protein-1 (IGFBP-1), IGFBP-1 complexed IGF-I and IGFBP-2.

RESULTS: Total IGF-I and -II decreased marginally (<12%) at the very end of the study (P<0.05). By contrast, at 3 h free and bioactive IGF-I had declined by approximately 35% and 50%, respectively, and levels remained suppressed for the rest of the study (P<0.05). Concomitantly, IGFBP-1 and IGFBP-1:IGF-I complex formation increased 5.0-fold and 2.6-fold, respectively (P<0.05). By contrast, IGFBP-2 did not increase as a result of HD. No major differences between arterial and venous concentrations were observed.

CONCLUSION: Despite marginal reductions in total IGF-I and -II, bioactive and free IGF-I declined markedly during and after HD. This is likely a consequence of the increase in IGFBP-1, sequestering free IGF-I, and reducing bioactive IGF-I. Based on the present data we hypothesize that the catabolism induced by HD is in part related to the observed reductions in bioactive IGF-I.