Journal of Clinical Endocrinology & Metabolism, Vol 81, 4379-4384, Copyright © 1996 by Endocrine Society

ARTICLES

Effect of short-term fasting on free/dissociable insulin-like growth factor I concentrations in normal human serum

A Bereket, TA Wilson, SL Blethen, J Fan, RA Frost, MC Gelato and CH Lang
Division of Pediatric Endocrinology, State University of New York School of Medicine, Stony Brook 11794, USA.

A small portion of circulating insulin-like growth factor I (IGF-I) is detected in the free or readily dissociable state, which is thought to be the metabolically active form. The amount of free/dissociable IGF-I in serum is dependent on a complex interplay between the production rate and the concentrations of IGF-I and IGF-binding proteins (IGFBPs). IGF availability is also influenced by posttranslational changes in IGFBPs that affect the affinity of IGFBPs for IGF-I. In the present study, we examined whether a short term fast (approximately 12 h) alters the serum concentration of free/dissociable IGF-I, and whether these changes are associated with alterations in IGFBP-1 and the proteolysis status of IGFBP-3. Circulating free/dissociable IGF-I concentrations, as assessed by a two-site immunoradiometric assay, did not differ between fasting and 4 h after a morning meal (1.48 +/- 0.07 vs. 1.50 +/- 0.07 microgram/L, respectively). Likewise, free/dissociable IGF-I levels measured by RIA after separation by centrifugal ultrafiltration were not different between the two groups (1.43 +/- 0.14 vs. 1.38 +/- 0.18 microgram/L, respectively). IGF-I bioactivity, as measured by thymidine incorporation by fibroblasts, did not differ in fasting and 4-h postprandial sera. There was no difference in IGFBP-3 and total acid-ethanol-extractable IGF-I concentrations in serum from fasted and fed subjects. In contrast, the concentration of IGFBP-1 in the serum was increased approximately 5- fold in the fasted state compared to fed values. IGFBP-1 existed in a highly phosphorylated form under fasting conditions. There was no change in IGFBP-3 proteolysis assessed either in vivo or in vitro between the fasting and fed states. The results indicate that a physiologically relevant short term overnight fast does not alter the circulating levels of free/dissociable IGF-I despite a marked elevation in IGFBP-1.

This article has been cited by other articles:

				G. Venkatasubramanian, S. Chittiprol, N. Neelakantachar, M. N. Naveen, J. Thirthall, B. N. Gangadhar, and K. T. Shetty Insulin and Insulin-Like Growth Factor-1 Abnormalities in Antipsychotic-Naive Schizophrenia Am J Psychiatry, October 1, 2007; 164(10): 1557 - 1560. [Abstract] [Full Text] [PDF]

				E. M. N. Bannink, J. van Doorn, P. G. H. Mulder, and A. C. S. Hokken-Koelega Free/Dissociable Insulin-Like Growth Factor (IGF)-I, Not Total IGF-I, Correlates with Growth Response during Growth Hormone Treatment in Children Born Small for Gestational Age J. Clin. Endocrinol. Metab., August 1, 2007; 92(8): 2992 - 3000. [Abstract] [Full Text] [PDF]

				J.-W. Chen, M. F Nielsen, A. Caumo, H. Vilstrup, J. S. Christiansen, and J. Frystyk Changes in bioactive IGF-I and IGF-binding protein-1 during an oral glucose tolerance test in patients with liver cirrhosis. Eur. J. Endocrinol., August 1, 2006; 155(2): 285 - 292. [Abstract] [Full Text] [PDF]

				L. E. L. Katz, D. D. DeLeon, H. Zhao, and A. F. Jawad Free and Total Insulin-Like Growth Factor (IGF)-I Levels Decline during Fasting: Relationships with Insulin and IGF-Binding Protein-1 J. Clin. Endocrinol. Metab., June 1, 2002; 87(6): 2978 - 2983. [Abstract] [Full Text] [PDF]

				C. H. Lang, X. Liu, G. J. Nystrom, and R. A. Frost Acute response of IGF-I and IGF binding proteins induced by thermal injury Am J Physiol Endocrinol Metab, June 1, 2000; 278(6): E1087 - E1096. [Abstract] [Full Text] [PDF]

				H. J. H. M. T. van Dessel, P. D. K. Lee, G. Faessen, B. C. J. M. Fauser, and L. C. Giudice Elevated Serum Levels of Free Insulin-Like Growth Factor I in Polycystic Ovary Syndrome J. Clin. Endocrinol. Metab., September 1, 1999; 84(9): 3030 - 3035. [Abstract] [Full Text]

				C. Camacho-Hübner, K. A. Woods, F. Miraki-Moud, P. C. Hindmarsh, A. J. Clark, Y. Hansson, A. Johnston, R. C. Baxter, and M. O. Savage Effects of Recombinant Human Insulin-Like Growth Factor I (IGF-I) Therapy on the Growth Hormone-IGF System of a Patient with a Partial IGF-I Gene Deletion J. Clin. Endocrinol. Metab., May 1, 1999; 84(5): 1611 - 1616. [Abstract] [Full Text]

				D. W Johnson, H. J Saunders, M. J Field, and C. A Pollock Role of insulin-like growth factor binding proteins in human post-nephrectomy proximal tubule cells J. Physiol., April 15, 1998; 508(2): 587 - 595. [Abstract] [Full Text] [PDF]

				R. A. Frost, C. H. Lang, and M. C. Gelato Transient Exposure of Human Myoblasts to Tumor Necrosis Factor-{alpha} Inhibits Serum and Insulin-Like Growth Factor-I Stimulated Protein Synthesis Endocrinology, October 1, 1997; 138(10): 4153 - 4159. [Abstract] [Full Text] [PDF]

				J. Frystyk, T. Grofte, C. Skjarbak, and H. Orskov The Effect of Oral Glucose on Serum Free Insulin-Like Growth Factor-I and -II in Healthy Adults J. Clin. Endocrinol. Metab., September 1, 1997; 82(9): 3124 - 3127. [Abstract] [Full Text] [PDF]

				B. L. G. Nyomba, L. Berard, and L. J. Murphy Free Insulin-Like Growth Factor I (IGF-I) in Healthy Subjects: Relationship with IGF-Binding Proteins and Insulin Sensitivity J. Clin. Endocrinol. Metab., July 1, 1997; 82(7): 2177 - 2181. [Abstract] [Full Text] [PDF]

				P. D. K. Lee, S. K. Durham, V. Martinez, O. Vasconez, D. R. Powell, and J. Guevara-Aguirre Kinetics of Insulin-Like Growth Factor (IGF) and IGF-Binding Protein Responses to a Single Dose of Growth Hormone J. Clin. Endocrinol. Metab., July 1, 1997; 82(7): 2266 - 2274. [Abstract] [Full Text] [PDF]