Serum free IGF-I during a hyperinsulinemic clamp following 3 days of administration of IGF-I vs. saline

J. Frystyk, M. Hussain, C. Skjærbæk, O. Schmitz, J. S. Christiansen, E. R. Froesch, H. Ørskov

Research output: Contribution to journalArticle

Abstract

In a randomized crossover study in eight healthy subjects, we compared the effect of 3 days of continuous subcutaneous administration of insulin- like growth factor I (IGF-I; 10 μg · kg-1 · h-1) and saline of fasting serum levels of free IGF-I, total (extractable) IGF-I, and IGF-binding protein (IGFBP)-1 and -3. On the 3rd day a hyperinsulinemic (euglycemic and hypoglycemic) clamp was performed. When preclamp (baseline) levels were compared after 3 days, IGF-I administration had increased total IGF-I from 225 ± 21 (means ± SE) to 1,003 ± 46 μg/l (P < 0.0001), free IGF-I from 0.5 ± 0.2 to 10.4 ± 1.7 μg/l (P < 0.001), IGFBP-3 from 2,908 ± 148 to 3,591 ± 179 μg/l (P < 0.01), and IGFBP-I from 7.6 ± 3.8 to 19.6 ± 2.5 μg/l (P < 0.01). During the clamp, levels of free IGF-I increased gradually from baseline to 1.0 ± 0.3 μg/l (saline; P < 0.01) and to 19.6 ± 4.7 μg/l (IGF-I; P < 0.005). Concomitantly, levels of IGFBP-1 decreased gradually from baseline to 4.1 ± 2.3 μg/l (saline; P < 0.0005) and to 4.6 ± 1.8 μg/l (IGF-I; P < 0.0001). Total IGF-I exhibited minor changes only during the clamp (P < 0.05), and the IGFBP-3 was unchanged. In conclusion, administration of IGF-I increased total IGF-I about fourfold, whereas free IGF-I increased 20-fold. Noteworthily, in both situations a further twofold increase in free IGF-I was observed during the hyperinsulinemic clamp, concomitant with a decrease in IGFBP-1. This supports the hypothesis that IGFBP-1 is important in the short-term regulation of free IGF-I in vivo.

Original languageEnglish (US)
Pages (from-to)E507-E513
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume273
Issue number3 36-3
StatePublished - Sep 1 1997
Externally publishedYes

    Fingerprint

Keywords

  • Insulin-like growth factor I
  • Insulin-like growth factor- binding protein-1
  • Insulin-like growth factor-binding protein-3
  • Recombinant human insulin-like growth factor I
  • Ultrafiltration

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

Cite this

Frystyk, J., Hussain, M., Skjærbæk, C., Schmitz, O., Christiansen, J. S., Froesch, E. R., & Ørskov, H. (1997). Serum free IGF-I during a hyperinsulinemic clamp following 3 days of administration of IGF-I vs. saline. American Journal of Physiology - Endocrinology and Metabolism, 273(3 36-3), E507-E513.