Stephanie A. Amiel

Circadian variation of GH-independent IGF-binding protein in diabetes mellitus and its relationship to insulin. A new role for insulin?

Evidence is accumulating that a non‐GH dependent insulin‐like growth factor‐binding protein (IGF‐BP) is not only a carrier protein but also has an active role in the growth process.

Suppression of endogenous insulin secretion regulates the rapid rise of insulin-like growth factor binding protein (IGFBP)-1 levels following acute hypoglycaemia

OBJECTIVES Recent animal studies have suggested that insulin‐like growth factor binding protein (IGFBP)‐1 may regulate the insulin‐like actions of the circulating IGFs. In man, IGFBP‐1 levels change rapidly with nutritional status and are inversely related to changes in insulin. In‐vitro studies have shown that both insulin and glucose independently regulate IGFBP‐1 secretion in an inverse manner. A rapid rise of serum IGFBP‐1 levels following insulin‐induced hypoglycaemia suggested that glucose or glucose availability, rather than insulin, may be the major regulator of IGFBP‐1.

INSULIN-DEPENDENCE OF THE SMALL IGF-BINDING PROTEIN (IGF-SBP)

Publisher Summary This chapter describes the insulin-dependence of the small IGF-binding protein (IGF-SBP). Evidence is accumulating that the IGF-SBP may be an important acute modulator of IGF activity. The relationship within individuals was examined in profiles of IGF-SBP and insulin measured over 12 or 24 h periods in 14 normal subjects and in 11 adolescents with diabetes mellitus. In 5 of the diabetics overnight profiles were repeated with euglycaemia maintained with a glucose clamp. The relationship between individuals was studied in a cross-sectional study of 116 normal subjects in whom fasting levels of IGF-SBP and insulin were measured. IGF-SBP was measured with a specific RIA. The IGF-SBP was shown to be closely inversely related to insulin in both normals and subjects with diabetes mellitus. In the diabetics IGF-SBP levels were generally high consistent with the insulin deficiency. Very high concentrations were observed in poorly controlled subjects, although a simple relationship with the level of acute metabolic control could not be established. In puberty the rise in IGF-I is accompanied by a rise in insulin and a fall in IGF-SBP.