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

The aim of the present study was to investigate whether the diurnal variabi lity of B-Glucose is dependent on GH, IGF-I and IGFBP-1 levels, apart from insulin, and if there is any difference between Tanner stages 3 and 5. Five boys in Tanner stage 3 and 6 buys in stage 5 with type 1 diabetes were inc luded. Blood was continuously collected from a cubital vein for 24 h. S-Ins ulin, S-GH, S-IGF-I and S-IGFBP-1 were analysed. B-Glucose was analysed hou rly at bedside. One week before and 1 wk after the 24-h study period the pa rticipants performed self-monitoring of blood glucose (SMBG) during normal physiologic conditions. In the 24-h profile of B-Glucose, insulin, IGFBP-1 and GH, we found a significant positive correlation between B-Glucose and l og 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 mul tiple 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 relat ionship between Simultaneously measured blood-glucose and IGFBP-1 levels in dependent of the insulin and GH levels, suggesting that the free fraction o f IGF-I influences the glucose metabolism.