Retinol-Binding Protein 4 and Insulin Resistance in Polycystic Ovary Syndrome

  1. Samantha K. Hutchison, MBBS12,
  2. Cheryce Harrison, BBNSC13,
  3. Nigel Stepto, PHD34,
  4. Caroline Meyer, PHD2 and
  5. Helena J. Teede, PHD12
  1. 1Jean Hailes Foundation Research Group, Monash University Institute of Health Services Research, Melbourne, Australia
  2. 2Diabetes Unit, Southern Health, Melbourne, Australia
  3. 3Department of Physiology, Monash University, Melbourne, Australia
  4. 4School of Human Movement, Recreation and Performance, Victoria University, Melbourne, Australia
  1. Corresponding author: Professor Helena Teede, helena.teede{at}med.monash.edu.au

Abstract

OBJECTIVE—Polycystic ovary syndrome (PCOS) is an insulin-resistant state with insulin resistance being an established therapeutic target; however, measurement of insulin resistance remains challenging. We aimed to 1) determine serum retinol-binding protein 4 (RBP4) levels (purported to reflect insulin resistance) in women with PCOS and control subjects, 2) examine the relationship of RBP4 to conventional markers of insulin resistance, and 3) examine RBP4 changes with interventions modulating insulin resistance in overweight women with PCOS.

RESEARCH DESIGN AND METHODS—At baseline, 38 overweight women (BMI >27 kg/m2) with PCOS and 17 weight-matched control subjects were compared. Women with PCOS were then randomly assigned to 6 months of a higher-dose oral contraceptive pill (OCP) (35 μg ethinyl estradiol/2 mg cyproterone acetate) or metformin (1 g b.i.d.). Outcome measures were insulin resistance (total insulin area under the curve) on an oral glucose tolerance test, RBP4, and metabolic/inflammatory markers.

RESULTS—Overweight women with PCOS were more insulin resistant than control subjects, yet RBP4 levels were not different in women with PCOS versus those in control subjects (35.4 ± 4.3 vs. 28.9 ± 3.1 μg/ml, P = 0.36). RBP4 correlated with cholesterol and triglycerides but not with insulin resistance. Metformin improved insulin resistance by 35%, whereas the OCP worsened insulin resistance by 33%. However, RBP4 increased nonsignificantly in both groups (43.7 ± 6.3 vs. 42.6 ± 5.5 μg/ml, P = 0.92).

CONCLUSIONS—Overweight women with PCOS were more insulin resistant than control subjects, but this finding was not reflected by RBP4 levels. RBP4 correlated with lipid levels but not with insulin resistance markers. RBP4 levels did not change when insulin resistance was reduced by metformin or increased by the OCP. These data suggest that RBP4 is not a useful marker of insulin resistance in PCOS but may reflect other metabolic features of this condition.

Footnotes

  • Published ahead of print at http://care.diabetesjournals.org on 4 April 2008.

    Clinical trial reg. no. ISRCTN51367236, clinicaltrials.gov.

    Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details.

    The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Accepted April 1, 2008.
    • Received December 9, 2007.
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  1. Published online before print April 4, 2008, doi: 10.2337/dc07-2265 Diabetes Care July 2008 vol. 31 no. 7 1427-1432
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