The circulating IGF system and its relationship with 24-h glucose regulation and insulin sensitivity in healthy subjects

Clinical Endocrinology
J FrystykHans Ørskov

Abstract

It has been suggested that circulating free IGF-I participates in glucose homeostasis and that IGFBP-1 reflects changes in insulin sensitivity. To study this further, we examined 10 healthy, nonobese subjects under standardized conditions for 24 h with and without an intravenous infusion of glucose, the latter in order to augment insulin sensitivity. Serum was collected every 2 h for analysis of free and total IGFs, IGFBP-1, - 2 and - 3 and the acid labile subunit (ALS). Insulin sensitivity was estimated at the end of each 24-h study period by use of the hyperinsulinaemic euglycaemic clamp technique. Glucose infusion resulted in mild hyperglycaemia (P < 0.0001), a reduction in IGFBP-1 by approximately 40% (P < 0.0003), and increased insulin and C-peptide levels (P < 0.0001). Glucose infusion also increased insulin sensitivity (P < 0.003). However, despite the reduction in IGFBP-1, glucose infusion did not increase free IGF-I over the control level, and free IGF-II was slightly reduced (P < 0.02). Irrespective of glucose infusion, free IGF-I and -II remained stable during daytime (i.e. they were unresponsive to meal-related changes in plasma glucose), but both free fractions decreased during the night, reaching nadir at 04.00 h....Continue Reading

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Citations

Mar 26, 2008·European Journal of Endocrinology·S B CatrinaK Brismar
Oct 6, 2004·Expert Opinion on Investigational Drugs·Maria B GrantRobert N Mames
Oct 12, 2007·Growth Hormone & IGF Research : Official Journal of the Growth Hormone Research Society and the International IGF Research Society·Damien P BelobrajdicIan W Saunders
Sep 1, 2004·Growth Hormone & IGF Research : Official Journal of the Growth Hormone Research Society and the International IGF Research Society·Jan Frystyk
Sep 24, 2004·Clinical Nutrition : Official Journal of the European Society of Parenteral and Enteral Nutrition·Christopher J ScarlettRoss C Smith
Oct 13, 2009·Growth Hormone & IGF Research : Official Journal of the Growth Hormone Research Society and the International IGF Research Society·Jan FrystykDavid R Clemmons
May 24, 2007·International Journal of Cancer. Journal International Du Cancer·Gertraud MaskarinecRudolph Kaaks
Apr 6, 2004·Medicine and Science in Sports and Exercise·Jeff S Volek

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