Insulin regulation of insulin-like growth factor binding protein-1 in obese and nonobese humans

Cheryl A. Conover, Phillip Lee, Jill A. Kanaley, Jay T. Clarkson, Michael D. Jensen

Research output: Contribution to journalArticle

200 Citations (Scopus)

Abstract

Insulin is the principal regulator of hepatic insulin-like growth factor binding protein-1 (IGFBP-1) production, mediating the rapid decrease in plasma IGFBP-1 in response to nutritional intake. In this study, we defined IGFBP-1 regulation by insulin in upper and lower body obesity, conditions associated with insulin resistance and chronic hyperinsulinemia. Overnight postabsorptive IGFBP-1 levels in obese and nonobese women showed an inverse, nonlinear relationship with plasma insulin concentrations. Maximum suppression of IGFBP-1 was seen at 70-90 pmol/L plasma insulin. Both groups of obese women had mean fasting plasma insulin concentrations above this threshold level and, consequently, markedly suppressed IGFBP-1 levels. To assess the dynamics of insulin regulated IGFBP-1, 10 obese and 8 nonobese women were studied during sequential saline infusion (0-90 min), hyperinsulinemia (insulin infusion; 90-210 min) and hypoinsulinemia (somatostatin + GH infusion; 210-330 min). Insulin infusion rapidly decreased plasma IGFBP-1 levels in nonobese subjects (60% decrease in 2 h), but had little or no further suppressive effect in obese subjects. Complete insulin withdrawal resulted in a significant rise in plasma IGFBP-1 concentrations in all subjects, but the response was blunted in obese compared to nonobese groups. In contrast to plasma IGFBP-1, IGF-I concentrations did not vary during hyper- and hypoinsulinemic infusion periods and were not significantly different between groups. Basal GH levels were significantly higher in nonobese when compared to obese women, but did not change with infusions. In conclusion, low IGFBP-1 levels in obesity are related to elevated insulin levels which are, in turn, related to body fat distribution and insulin resistance. The chronically depressed levels of IGFBP-1 may promote IGF bioactivity as well as its feedback regulation of GH secretion, thus contributing to the metabolic and mitogenic consequences of obesity. In addition, our findings imply that hepatic insulin sensitivity in terms of IGFBP-1 production is preserved despite peripheral insulin resistance in obesity.

Original languageEnglish (US)
Pages (from-to)1355-1360
Number of pages6
JournalJournal of Clinical Endocrinology and Metabolism
Volume74
Issue number6
StatePublished - Jun 1992
Externally publishedYes

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Insulin-Like Growth Factor Binding Protein 1
Insulin
Plasmas
Insulin Resistance
Obesity
Hyperinsulinism
Body Fat Distribution
Liver
Somatostatin
Insulin-Like Growth Factor I
Vascular Resistance
Bioactivity

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology, Diabetes and Metabolism

Cite this

Insulin regulation of insulin-like growth factor binding protein-1 in obese and nonobese humans. / Conover, Cheryl A.; Lee, Phillip; Kanaley, Jill A.; Clarkson, Jay T.; Jensen, Michael D.

In: Journal of Clinical Endocrinology and Metabolism, Vol. 74, No. 6, 06.1992, p. 1355-1360.

Research output: Contribution to journalArticle

Conover, Cheryl A. ; Lee, Phillip ; Kanaley, Jill A. ; Clarkson, Jay T. ; Jensen, Michael D. / Insulin regulation of insulin-like growth factor binding protein-1 in obese and nonobese humans. In: Journal of Clinical Endocrinology and Metabolism. 1992 ; Vol. 74, No. 6. pp. 1355-1360.
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