Poor vitamin C status is associated with increased carotid intima-media thickness, decreased microvascular function, and delayed myocardial repolarization in young patients with type 1 diabetes

Abstract

Background: Vascular endothelial dysfunction, accelerated thickening of arterial intima, and changes in ventricular repolarization contribute to increased cardiovascular morbidity in type 1 diabetes (T1D). Although vitamin C has important antioxidant functions and increased oxidative stress is a central mechanism of cardiovascular dysfunction in T1D, the relation between vitamin C and the cardiovascular system in young diabetic patients has not been investigated. Objective: In a cohort of young patients with T1D, we investigated the relation of plasma concentrations of vitamin C with indexes of vascular function and structure and duration of the QT interval corrected for heart rate (QTc). Design: Carotid artery intima-media thickness, cutaneous microvascular function, and duration of the QTc interval were measured in 59 patients (mean age: 17 y; range: 10-22 y) with T1D (diabetes duration: 3-20 y). Plasma vitamin C was analyzed by HPLC with coulometric detection. Results: Carotid artery intima-media thickness and duration of the QTc interval were higher in patients in the lowest tertile of vitamin C than in those in the highest tertile (P < 0.05 for both). The cutaneous microvascular response to acetylcholine was lower (P = 0.003) in the lowest tertile group than in the highest tertile group, but the response to sodium nitroprusside was not significantly different between these 2 groups. All differences remained significant after adjustment for age, sex, diabetes duration, body mass index, and glycated hemoglobin. Conclusions: In this relatively small-scale cross-sectional study of young patients with T1D, lower plasma concentrations of vitamin C seem to be associated with adverse changes in the microcirculation, peripheral arteries, and ventricular repolarization. Large-scale prospective studies are needed to confirm these results and to clarify the underlying mechanisms. © 2009 American Society for Nutrition.