REGULATION OF INSULIN-LIKE GROWTH-FACTOR BINDING PROTEIN-1 (IGFBP-1) IN INSULIN-DEPENDENT DIABETES-MELLITUS - EFFECTS OF HYPERGLYCEMIA AND INSULIN

The aim of the present study was to characterize the effect of 44 h of hyperglycaemia on diurnal levels of insulin-like growth factor bindin g protein-1 (IGFBP-1), insulin-like growth factor-1 (IGF-1), growth ho rmone (GH) and glucagon in 7 well-controlled subjects with insulin-dep endent diabetes mellitus (IDDM). Hyperglycaemia (similar to 15 mmol/l) was induced by a glucose infusion, while the degree of insulinisation was similar to that of a corresponding period with near normoglycaemi a (similar to 6.9 mmol/l). Hyperglycaemia for 44 h did not alter the n ormal diurnal IGFBP-1 levels when the degree of insulinisation was unc hanged, The diurnal secretion pattern of IGFBP-1 was preserved in both genders and without any difference between the control and hyperglyca emic periods. However, the IGFBP-1 levels were increased in these IDDM subjects despite a peripheral hyperinsulinemia. An inverse correlatio n was found between IGFBP-1 and peripheral insulin levels both during periods of rapid changes in IGFBP-1 and insulin concentrations (i.e. m orning hours) as well as during the total 24-h sampling period. Total IGF-1 levels were low, but no further decrease was seen after 24 h of hyperglycaemia in the presence of unchanged insulin levels. In conclus ion, the present study clearly shows that the increased IGFBP-1 level seen during poor metabolic control in IDDM is not caused by hyperglyca emia. Glucose levels per se do not influence either total IGF-1 or IGF BP-1 concentrations in well-insulinised diabetic patients.