title: Insulin sensitivity, vascular function, and iron stores in voluntary blood donors.
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.
  
  
  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.
authors.affiliation: Section of Cardiovascular Medicine, Department of Internal Medicine, Yale School of Medicine, 135 College St., New Haven, CT 06510, USA.
authors.forename: Haoyi
authors.initials: H
authors.lastname: Zheng
authors.forename: Milan
authors.initials: M
authors.lastname: Patel
authors.forename: Ritchard
authors.initials: R
authors.lastname: Cable
authors.forename: Lawrence
authors.initials: L
authors.lastname: Young
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Katz
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D001782:Blood Donors; D003430:Cross-Sectional Studies; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007501:Iron / Q000097:blood*; D008875:Middle Aged; D014654:Vascular Patency / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology*
chemical_list: D015415:Biomarkers; D007328:Insulin; D007501:Iron