Prolonged antioxidant vitamin E and /or C supplementation could be effective to improve endothelial function in non-obese T2DM subjects
Controversy exists among trials assessing whether prolonged antioxidant vitamin supplementation improves endothelial function in type 2 diabetes mellitus ( T2DM ) subjects .
The aim of this study was to systematic ally review and quantify the effect of antioxidant vitamin supplementation on endothelial function in T2DM subjects .
Vitamin C improves endothelium-dependent vasodilation in patients with non-insulin-dependent diabetes mellitus.
Endothelium-dependent vasodilation is impaired in humans with diabetes mellitus . Inactivation of endothelium-derived nitric oxide by oxygen-derived free radicals contributes to abnormal vascular reactivity in experimental models of diabetes . To determine whether this observation is relevant to humans , we tested the hypothesis that the antioxidant , vitamin C , could improve endothelium-dependent vasodilation in forearm resistance vessels of patients with non-insulin-dependent diabetes mellitus . We studied 10 diabetic subjects and 10 age-matched , nondiabetic control subjects .  Forearm blood flow was determined by venous occlusion plethysmography . Endothelium-dependent vasodilation was assessed by intraarterial infusion of methacholine ( 0.3 - 10 micrograms/min ) . Endothelium-independent vasodilation was measured by intraarterial infusion of nitroprusside ( 0.3 - 10 micrograms/min ) and verapamil ( 10 - 300 micrograms/min ) . Forearm blood flow dose-response curves were determined for each drug before and during concomitant intraarterial administration of vitamin C ( 24 mg/min ) . In diabetic subjects , endothelium-dependent vasodilation to methacholine was augmented by simultaneous infusion of vitamin C ( P = 0.002 ) ; in contrast , endothelium-independent vasodilation to nitroprusside and to verapamil were not affected by concomitant infusion of vitamin C ( P = 0.9 and P = 0.4 , respectively ) . In nondiabetic subjects , vitamin C administration did not alter endothelium-dependent vasodilation ( P = 0.8 ) . We conclude that endothelial dysfunction in forearm resistance vessels of patients with non-insulin-dependent diabetes mellitus can be improved by administration of the antioxidant , vitamin C. These findings support the hypothesis that nitric oxide inactivation by oxygen-derived free radicals contributes to abnormal vascular reactivity in diabetes
Prolonged antioxidant vitamin E and /or C supplementation could be effective to improve endothelial function in non-obese T2DM subjects
Controversy exists among trials assessing whether prolonged antioxidant vitamin supplementation improves endothelial function in type 2 diabetes mellitus ( T2DM ) subjects .
The aim of this study was to systematic ally review and quantify the effect of antioxidant vitamin supplementation on endothelial function in T2DM subjects .