(11-07-09) 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.



Odermarsky M, Lykkesfeldt J, Liuba P.
Division of Pediatric Cardiology, Department of Pediatrics, Lund University Hospital, Lund, Sweden, and the Department of Disease Biology, Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark.

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 (QT(c)). DESIGN: Carotid artery intima-media thickness, cutaneous microvascular function, and duration of the QT(c) 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 QT(c) 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.

Source: Am J Clin Nutr. 2009 Jun 24.

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