Vascular endothelium and inflammatory process, in patients with combined Type 2 diabetes mellitus and coronary atherosclerosis: the effects of vitamin C

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Abstract
Aims Type 2 diabetes mellitus (DM) and coronary artery disease (CAD) are both associated with endothelial dysfunction and elevated oxidative and inflammatory state. We examined the effect of vitamin C on endothelial function and levels of soluble vascular cell adhesion molecule (sVCAM‐1), interleukin‐6 (IL‐6) and tumour necrosis factor (TNF‐α), in DM patients with or without CAD and in non‐diabetic subjects. Methods Thirty‐seven patients with DM + CAD, 17 patients with DM without CAD and 21 non‐diabetic subjects were divided into groups receiving vitamin C 2 g/day or no anti‐oxidant for 4 weeks. Forearm blood flow was determined using venous occlusion gauge‐strain plethysmography. Forearm vasodilatory response to reactive hyperemia was considered as index of endothelium‐dependent dilation. Results Baseline levels of IL‐6 and TNF‐α were significantly higher in patients with DM + CAD compared with patients with DM (P < 0.01) or non‐diabetic subjects (P < 0.01). IL‐6 and TNF‐α levels were also higher in DM compared with non‐diabetic subjects (P < 0.05). sVCAM‐1 levels were lower in non‐diabetic controls compared with DM + CAD (P < 0.05) or DM (P < 0.05). Reactive hyperaemia was higher in non‐diabetic controls compared with DM + CAD (P < 0.001) or DM (P < 0.001). Vitamin C significantly increased reactive hyperaemia only in the DM + CAD group, while it had no effect on serum levels of sVCAM‐1, TNF‐α and IL‐6 in any of the groups. Conclusions Type 2 diabetes mellitus is associated with impaired endothelial function and increased levels of TNF‐α, IL‐6 and sVCAM‐1, especially in patients with DM and CAD. Vitamin C significantly increased forearm vasodilatory response to reactive hyperaemia only in patients with combined DM and CAD.