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Effect of ascorbic acid treatment on conduit vessel endothelial dysfunction in patients with hypertension
S J Duffy1, N Gokce, M Holbrook
1Evans Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Insights
Oral ascorbic acid therapy did not improve endothelial function in hypertensive patients. This study found no reversal of conduit vessel endothelial dysfunction with ascorbic acid treatment, suggesting further research into resistance vessels is needed.
Area of Science:
- Cardiovascular Medicine
- Vascular Biology
- Nutritional Science
Background:
- Hypertension is linked to low plasma ascorbic acid and impaired endothelial function.
- Vascular oxidative stress is implicated in hypertension and endothelial dysfunction.
- Previous research indicated chronic oral ascorbic acid lowers blood pressure in hypertensive individuals.
Purpose of the Study:
- To investigate the effect of acute and chronic ascorbic acid treatment on endothelial vasomotor function in hypertensive patients.
- To determine if ascorbic acid improves brachial artery flow-mediated dilation, an indicator of endothelial function.
Main Methods:
- A randomized, double-blind, placebo-controlled study involving 39 hypertensive patients.
- Assessed brachial artery flow-mediated dilation after acute (2 g) and chronic (500 mg/day for 1 month) ascorbic acid administration.
- Compared results with normotensive controls and measured plasma ascorbic acid levels.
Main Results:
- Hypertensive patients exhibited impaired endothelium-dependent, flow-mediated dilation compared to controls.
- Ascorbic acid treatment significantly increased plasma ascorbic acid levels.
- Neither acute nor chronic ascorbic acid therapy improved brachial artery flow-mediated dilation or nitroglycerin-mediated dilation.
Conclusions:
- Conduit vessel endothelial dysfunction associated with hypertension is not reversed by acute or chronic oral ascorbic acid.
- Further investigation is warranted to explore ascorbic acid's effects on resistance vessel vasomotor function.
Abstract:
Hypertension is associated with low plasma ascorbic acid levels and impaired endothelial function. Recent evidence suggests that increased vascular oxidative stress contributes to the pathophysiology of endothelial dysfunction and hypertension. We recently showed that chronic oral ascorbic acid therapy lowers blood pressure in hypertensive patients. We hypothesized that it would also improve endothelial vasomotor function. In a randomized, double-blind, placebo-controlled study, we examined the effect of acute (2 g po) and chronic (500 mg/day for 1 mo) ascorbic acid treatment on brachial artery flow-mediated dilation in 39 patients with hypertension. Compared with 82 age- and gender-matched normotensive controls, these patients had impaired endothelium-dependent, flow-mediated dilation of the brachial artery [8.9 +/- 6.1 vs. 11.2 +/- 5.7% (SD), P < 0.04]. After therapy, plasma ascorbic acid concentrations increased acutely from 50 +/- 12 to 149 +/- 51 micromol/l and were maintained at 99 +/- 33 micromol/l with chronic treatment (both P < 0.001). As previously reported, chronic ascorbic acid therapy reduced systolic and mean blood pressure in these patients. However, acute or chronic ascorbic acid treatment had no effect on brachial artery endothelium-dependent, flow-mediated dilation or on endothelium-independent, nitroglycerin-mediated dilation. These results demonstrate that conduit vessel endothelial dysfunction secondary to hypertension is not reversed by acute or chronic treatment with oral ascorbic acid. The effects of this treatment on resistance vessel vasomotor function warrant further investigation.