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

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

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 (8 donations in last 2 years) and 21 low-frequency blood donors (1-2 donations in last 2 years) aged 50-75 years. Serum markers of iron stores, whole body insulin sensitivity index 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 when compared with low-frequency donors, but whole body insulin sensitivity index (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 hour after oral glucose loading in both groups, but the decrease in flow-mediated dilation at 1 hour did not differ between high-frequency and low-frequency donors.

Conclusions:High-frequency blood donation reduced serum ferritin and increased flow-mediated dilation when compared with low-frequency donation, but did not improve insulin sensitivity nor 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.

High-frequency blood donation was associated with reduced iron stores and improved vascular function when compared with low-frequency blood donors, but measures of insulin sensitivity did not differ between groups. These findings suggest that the mechanisms linking blood donation to improved vascular function are not related to changes in glucose metabolism.

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