Low plasma concentrations of vitamin C are associated with adverse changes in the microcirculation, peripheral arteries, and ventricular repolarization in young people with Type 1 diabetes, Swedish researchers report.

Enhanced oxidative stress plays a key role in the development of vascular complications in Type 1 diabetes. It has been suggested that antioxidants such as vitamin C may protect against cardiovascular disease (CVD) by reducing this process.

Petru Liuba (Lund University Hospital, Sweden) and co-workers investigated the relation between plasma concentrations of vitamin C and changes in vascular function and structure and myocardial repolarization in a cohort of young patients with Type 1 diabetes.

The 59 participants, recruited from a diabetes outpatient clinic, were aged 10 to 22 years and had a mean duration of diabetes of 9 years. Patients with a family history of major CVD risk factors other than diabetes were excluded.

Carotid artery intima-media thickness (IMT) was measured using ultrasound, cutaneous microvascular function with a laser Doppler multifiber probe during transdermal iontophoresis of acetylcholine and sodium nitroprusside, and duration of the QTc interval (ventricular repolarization) by electrocardiogram.

Plasma vitamin C was analyzed by high performance liquid chromatography with coulometric detection and the patients were grouped into three plasma vitamin C tertiles: low (14.0 to 49.0 µmol/l), middle (above 49.0 to 84.0 µmol/l), and high (above 84.0 to 119 µmol/l).

Writing in the American Journal of Clinical Nutrition, the authors report that carotid IMT was significantly greater in the lowest vitamin C tertile compared with the highest.

The cutaneous microvascular response to acetylcholine was significantly lower in the lowest tertile group than in the highest tertile group, but there was no difference in the response to sodium nitroprusside between vitamin C tertiles.

The QTc interval was significantly greater in the lowest vitamin C tertile than in the highest. Prolongation of the QTc interval is a significant predictor of adverse cardiovascular prognosis in patients with Type 1 diabetes.

Differences in all measures remained significant after adjustment for baseline variables.

“Poor vitamin C status is associated with increased carotid artery IMT, decreased microvascular function, and delayed myocardial repolarization in young patients with Type 1 diabetes,” conclude the authors.

“Large-scale prospective studies are needed to confirm these results and to clarify the underlying mechanisms,” they add.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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