Insulin Sensitivity, Vascular Function, and Iron Stores in Voluntary Blood Donors

doi:10.2337/dc07-0748

Insulin Sensitivity, Vascular Function, and Iron Stores in Voluntary Blood Donors

¹Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
²American Red Cross Blood Services, Farmington, Connecticut, and Dedham, Massachusetts

Address correspondence and reprint requests to Stuart D. Katz, MD, Yale School of Medicine, 135 College St., Suite 301, New Haven, CT 06510. E-mail: stuart.katz{at}yale.edu

Abstract

OBJECTIVE— Reduced iron stores after blood donation are associated with improved vascular function and decreased cardiovascular risk. We sought to determine whether iron-dependent changes in glucose metabolism may contribute to improved vascular function in blood donors.

RESEARCH DESIGN AND METHODS— We conducted a prospective cross-sectional study in 21 high-frequency blood donors (more than eight donations in the last 2 years) and 21 low-frequency blood donors (one to two donations in the last 2 years) aged 50–75 years. Serum markers of iron stores, whole-body insulin sensitivity index (WBISI) during oral glucose tolerance testing, and flow-mediated dilation in the brachial artery were determined in all subjects.

RESULTS— Serum ferritin was decreased (median values 23 vs. 36 ng/ml, P < 0.05) and flow-mediated dilation in the brachial artery was increased (median values 5.9 vs. 5.3%, P < 0.05) in high-frequency donors compared with low-frequency donors, respectively, but WBISI (median values 4.8 vs. 4.7) and related measures of glucose tolerance did not differ between groups. Flow-mediated dilation significantly decreased at 1 h after oral glucose loading in both groups, but the decrease in flow-mediated dilation at 1 h did not differ between high- and low-frequency donors.

CONCLUSIONS— High-frequency blood donation reduced serum ferritin and increased flow-mediated dilation compared with low-frequency donation but did not improve insulin sensitivity or protect the vascular endothelium from the adverse effects of acute hyperglycemia after oral glucose loading. These findings suggest that the mechanisms linking blood donation to improved vascular function are not likely related to changes in glucose metabolism.

Footnotes

Published ahead of print at http://care.diabetesjournals.org on 13 July 2007. DOI: 10.2337/dc07-0748.

A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

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 July 10, 2007.
- Received April 17, 2007.
DIABETES CARE