Background: Endothelial dysfunction, a precursor of vascular disease, begins early in type 1 diabetes mellitus and is associated with folate status.
Methods: A randomized, double-blind, placebo-controlled study of folate (5 mg daily) and vitamin B6 (100 mg daily) in 124 children with type 1 diabetes determined the immediate and 8-week effects of these vitamins, alone and in combination, on endothelial function. Endothelial function, assessed as flow-mediated dilation and glyceryltrinitrate-induced dilation with high-resolution ultrasound of the brachial artery, was measured at baseline, at 2 and 4 hours after the first dose (n = 35), and at 4 and 8 weeks of treatment (n = 122).
Results: Flow-mediated dilation normalized in all treatment groups. From baseline to 8 weeks, flow-mediated dilation improved with folate from 2.6% +/- 4.3% (mean +/- SD) to 9.7% +/- 6.0%, with vitamin B6 from 3.5% +/- 4.0% to 8.3% +/- 4.2%, and with folate/vitamin B6 from 2.8% +/- 3.5% to 10.5% +/- 4.4%. This improvement in flow-mediated dilation occurred within 2 hours and was maintained at 8 weeks for each treatment. Flow-mediated dilation in the placebo group, and glyceryltrinitrate-induced dilation in all groups, did not change. Increases in serum folate, red cell folate, and serum vitamin B6 levels related to increases in flow-mediated dilation. Improvement in flow-mediated dilation was independent of changes in total plasma homocyst(e)ine, glucose, hemoglobin A1c, and high-sensitivity C-reactive protein levels. Baseline red cell folate levels and baseline diastolic blood pressure were related inversely to improvement in flow-mediated dilation. Serum triglyceride and low-density lipoprotein cholesterol inversely related to baseline flow-mediated dilation.
Conclusions: High-dose folate and vitamin B6 normalized endothelial dysfunction in children with type 1 diabetes. This effect was maintained over 8 weeks, with no additional benefit from combination treatment.