Nocturnal blood glucose and IGFBP-1 changes in type 1 diabetes: Differences in the dawn phenomenon between insulin regimens.

ABSTRACT

OBJECTIVE: Insulin-like growth factor binding protein-1 (IGFBP-1) is known to regulate the bioavailability of insulin-like growth factor (IGF) and the levels of IGFBP-1 are increased in the morning in patients with type 1 diabetes mellitus. We investigated the nocturnal fluctuations of glucose, IGFBP-1, and free IGF-1 levels with three insulin regimens. RESEARCH DESIGN AND METHODS: Forty-eight type 1 diabetes patients were divided into three groups according to their basal insulin therapy (continuous subcutaneous insulin infusion [CSII], insulin glargine, NPH insulin). Blood samples were obtained every 2 h between 2 300 h and 0700 h to measure plasma glucose, IGFBP-1 and free IGF-1 levels. RESULTS: The dawn phenomenon was more frequent with NPH (62.1%) than with glargine (16.6%, p<0.05) and CSII (14.3%, p<0.05). In the NPH group, the serum IGFBP-1 levels were markedly increased from 21.0+/-3.6 ng/ml at 2 300 h to 200.3+/-21.8 ng/ml at 0700 h and free IGF-1 levels were inversely decreased; these changes were partially suppressed in the CSII and glargine groups. CONCLUSIONS: The use of insulin regimens that provide sufficient insulin levels in the early morning can suppress the dawn phenomenon, leading to improved glycemic control. The increase in circulating IGFBP-1 in the morning, as a result of waning of insulin action, lowers free IGF-1 levels and may cause insulin resistance.