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 irondependent 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 Ͻ 0.05) and flow-mediated dilation in the brachial artery was increased (median values 5.9 vs. 5.3%, P Ͻ 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. Diabetes Care 30:2685-2689, 2007I ron is a prooxidant cofactor that has been proposed to be associated with increased risk of cardiovascular events in humans (1,2). Chronic reduction in iron stores in response to frequent blood donation is associated with improved vascular function in the brachial artery and biochemical evidence of decreased oxidative stress (3). In a randomized trial of patients with peripheral vascular disease, reduction of iron stores with serial phlebotomy decreased mortality compared with conventional therapy in the subjects in the youngest age quartile (aged 43-61 years) (4).A potential mechanistic link between iron stores, vascular function, and cardiovascular risk may be related to irondependent effects on glucose metabolism (5,6). Diabetes is a well-recognized modifiable cardiovascular risk factor associated with increased serum ferritin levels and evidence of vascular endothelial dysfunction (7,8). Iron overload is associated with decreased insulin production, increased insulin resistance, and increased risk of diabetes (5,6). We hypothesized that improved vascular function associated with reduction in iron stores after blood donation might be partly attributable to improved insulin sensitivity. To test this hypothesis, we assessed insulin sensitivity during an oral glucose tolerance...

Relationship between blood donors' iron status and their age, body mass index and donation frequency

“…9 Likewise, many investigations have evaluated the impact of blood donation frequency per year on SF levels, and have reported that ferritin concentrations diminished markedly with increased blood donations. 8,[19][20][21][22] In contrast to our findings regarding Hb levels, no correlation was observed between levels of Hb and donation frequency in male blood donors in some other studies. 15,20,21,23 The difference between the present study and these other relevant investigations may be explained by differences in the baseline Hb values, sensitivity and specificity of laboratory measurements, minimum donation interval, age range, food patterns and ethnic types of the participants in these surveys.…”

“…Unlike our study, it has also been shown that indicators of iron status other than SF do not present contrasts between frequent and infrequent blood donors. 22 In our study, the minimum Hb cutoff for blood donation found that the Hb levels of multi-time donors did not notably contrast with those of donors who were giving blood for the first time. 25 Likewise, concordant with our results, other studies found that the SF levels in male donors had a negative significant relationship with the number of donations.…”

A review of potential metabolic etiologies of the observed association between red meat consumption and development of type 2 diabetes mellitus

“…Increased insulin sensitivity and decreased insulin secretion were observed in blood donors compared with non-donors [90]. Decreased serum ferritin in highly frequent blood donors (≥8 per 2 years) was associated with increased flow-mediated dilation, in comparison with infrequent donors (1-2 per 2 years), but no improvement of insulin sensitivity was observed [91]. Ten healthy blood donors receiving 4-weekly phlebotomy (500 ml) showed significantly reduced insulin and glucose by 39% and 19% respectively in an OGTT.…”

Dietary Intake and Serum and Hair Concentrations of Minerals and their Relationship with Serum Lipids and Glucose Levels in Hypertensive and Obese Patients with Insulin Resistance

“…In a 3-year prospective analysis, ferritin and transferrin levels were associated with hyperinsulinemia and hyperglycemia [35]. In the other study, blood donation was simultaneously associated with increased insulin sensitivity and decreased iron stores in healthy people [36], whereas, Zheng et al [37] showed that the mechanisms linking blood donation to improved vascular function were not related to changes in glucose metabolism.…”