Oxidative Stress And Flow-Mediated Dilation During Incremental Handgrip Exercise In Multiple Sclerosis

BACKGROUND: In Multiple Sclerosis (MS), a disease with a known inflammatory etiology, regular exercise enhances functional capacity. However, the impact of inflammation and oxidative stress on vascular function during exercise in patients with MS remains unknown. PURPOSE: To examine the effect of oxidative stress on exercise-induced brachial artery (BA) vasodilation in patients diagnosed with MS compared to healthy controls. METHODS: In a balanced double blind, placebo controlled design, 9 female patients with relapsing-remitting (RR) MS (49 ± 3 yrs) and 8 female controls (47 ± 4 yrs) ingested either a placebo or antioxidant cocktail (AOC (Vitamins C, E + lipoic acid)) prior to handgrip exercise (2, 4, 6, 8 kg at 0.5 Hz). Doppler ultrasound was used to examine exercise-induced BA vasodilation during the two conditions. Venous blood was analyzed for C-reactive protein (CRP), thiobarbituric acid reactive substances (TBARS), the ferric reducing ability of plasma (FRAP), and superoxide dismutase (SOD). RESULTS: Baseline CRP (2.3 ± 0.9 (MS); 2.1 ± 1.0 mg/L), TBARS (2.7 ± 0.2 (MS); 2.2 ± 0.2 μmol/L), FRAP (870 ± 18 (MS); 782 ± 100 mmol/L), SOD (12 ± 1.8 (MS); 14.5 ± 1.0 μ/ml), BA diameter (3.6 ± 0.1 (MS); 3.6 ± 0.2 mm), and blood flow (37 ± 5.2 (MS); 37 ± 5.3 ml/min) were not different between MS patients and controls. The AOC evoked a 16 ± 7% and 19 ± 4% increase in FRAP, 36 ± 16% and 18 ± 5% increase in SOD, and 4 ± 6% and -4 ± 19% change in TBARS (MS and controls, respectively). BA diameter progressively increased with greater workload in both groups, however this response was attenuated in the MS patients (5 ± 1.3% (MS); 14 ± 6.3%). The AOC ameliorated this deficit in vasodilation, resulting in an 8 ± 2.5% dilation in the MS patients and an 11 ± 3.5% dilation in the controls. Both blood flow and shear rates were unaffected in either group by the AOC. CONCLUSIONS: Despite a lack of clear evidence of elevated baseline systemic inflammation or oxidative stress, the acutely improved vascular function associated with the AOC in these patients with RR MS and not the controls suggests a negative role for oxidative stress in terms of vascular function during exercise in this population.