Insulin-like growth factor binding protein-1 as glucose regulator in adolescent boys with type 1 diabetes

Abstract

The aim of the present study was to investigate whether the diurnal variability of B-Glucose is dependent on GH, IGF-I and IGFBP-I levels, apart from insulin, and if there is any difference between Tanner stages 3 and 5. Five boys in Tanner stage 3 and 6 boys in stage 5 with type 1 diabetes were included. Blood was continuously collected from a cubital vein for 24 h. S-Insulin, S-GH, S-IGF-I and S-IGFBP-1 were analysed. B-Glucose was analysed hourly at bedside. One week before and 1 wk after the 24-h study period the participants performed self-monitoring of blood glucose (SMBG) during normal physiologic conditions. In the 24-h profile of B-Glucose, insulin, IGFBP-I and GH, we found a significant positive correlation between B-Glucose and log IGFBP-1 (r=0.5, p= 0.005) and an inverse correlation to insulin (r=-0.5, p= 0.004) but no correlation to logGH (r=-0.04, p= 0.831). In multiple regression analysis, B-Glucose was still significantly correlated to log IGFBP-1, when adjusting for insulin and GH, in Tanner stage 5. We found a difference between Tanner stages 3 and 5 in the variability of B-Glucose over a longer period during normal daily activity (p= 0.02), but not over the 24-h study period. Conclusion: We have demonstrated in type 1 diabetes adolescent boys a relationship between simultaneously measured blood-glucose and IGFBP-1 levels independent of the insulin and GH levels, suggesting that the free fraction of IGF-I influences the glucose metabolism.