Non-transferrin-bound iron is associated with biomarkers of oxidative stress, inflammation and endothelial dysfunction in type 2 diabetes

AimsTo investigate the association between circulating non-transferrin-bound iron [NTBI], and markers of oxidative stress, endothelial function and inflammation in subjects with type 2 diabetes and non-diabetic subjects with varying degrees of obesity.MethodsPlasma NTBI was measured by HPLC, together with total iron, iron-binding capacity, transferrin saturation and soluble transferrin receptor, together with total and reduced ascorbate, malondialdehyde [MDA], E-selectin and high-sensitivity c-reactive protein [hs-CRP] in groups of 28 subjects with type 2 diabetes, 28 non-obese controls and 17 obese non-diabetic subjects.ResultsLevels of NTBI were higher than controls in the diabetes group, but the total serum iron levels were lower. MDA levels were higher than controls in both the diabetes and obese groups, and this was associated with higher levels of oxidised ascorbate. hs-CRP levels were higher in both the diabetes and obese groups, and E-selectin was significantly higher in the diabetes group. There were strong positive correlations between HbA1c levels and NTBI [P < 0.01], HbA1c and E-selectin [P < 0.001] and NTBI and E-selectin [P < 0.02] in the diabetes group.ConclusionThese results support the hypothesis that iron-mediated oxidative stress may be a mechanism linking poor glycaemic control with vascular dysfunction in type 2 diabetes.