Regulation of Insulin-Like Growth Factor Binding Protein-I During the 24-Hour Metabolic Clock and in Response to Hypoinsulinemia Induced by Fasting and Sandostatin in Normal Women
Objective: To establish the relation of insulin-like growth factor-I (IGF-I) and IGF-binding protein-1 (IGFBP-1) with 24-hour metabolic excursions in normal healthy women and in response to acute interruption of metabolic homeostasis by hypoinsulinemia. Methods: Hourly blood samples during the 24-ho...
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Veröffentlicht in: | Journal of the Society for Gynecologic Investigation 1995-01, Vol.2 (1), p.38-44 |
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Sprache: | eng |
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Zusammenfassung: | Objective:
To establish the relation of insulin-like growth factor-I (IGF-I) and IGF-binding protein-1 (IGFBP-1) with 24-hour metabolic excursions in normal healthy women and in response to acute interruption of metabolic homeostasis by hypoinsulinemia.
Methods:
Hourly blood samples during the 24-hour metabolic clock were obtained from seven normally cyclin women. Uniform dietary composition (50% carbohydrate, 35% fat, and 15% protein) and timing of meals (8 AM, 12 PM, and 6 PM) were prescribed. Daytime hypoinsulinemia was induced by omitting meals and by Sandostain (100 μg) administration. Changes in serum levels of glucose, insulin, cortisol, IGF-I, and IGFBP-1 were measured.
Results:
The diurnal pattern of serum IGFBP-1 levels during the 24-hour metabolic clock was characterized by a rapid fall during the feeding phase of the day and a progressive 3.5-fold rise during nocturnal fasting; IGF-I levels were unchanged. Changes in IGFBP-1 levels were in parallel to those of cortisol and were inversely related to increases in glucose (80%) and insulin (tenfold) levels after each meal and to their decline during nocturnal fasting. Daytime fasting and administration of Sandostatin were accompanied by rapid and sustained increases in IGFBP-1 when insulin levels declined to 54 ± 20 pmol/L.
Conclusions:
With constant levels of IGF-I, the diurnal rhythm of IGFBP-1 may subserve a physiologic function by coordinating insulin and IGF-I action with substrate availability. Fluctuations of insulin levels during the 24-hour metabolic clock in normal women appear to sere as a signal, with an inhibitory effect on IGFBP-1 production when levels are above 70 pmol/L and a stimulatory effect at levels below 70 pmol/L. These findings provide a basis for future investigations in woman with nutritionally related reproductive disorders. |
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ISSN: | 1071-5576 1556-7117 |
DOI: | 10.1177/107155769500200108 |