Osamu Hirashima

Hyperglycemia Rapidly Suppresses Flow-Mediated Endothelium- Dependent Vasodilation of Brachial Artery

OBJECTIVES We examined whether endothelial dysfunction occurs when acute hyperglycemia is induced by oral glucose loading. BACKGROUND Endothelial dysfunction has been shown to occur in patients with diabetes mellitus (DM), and chronic hyperglycemia is implicated as a cause of endothelial dysfunction. However, in many patients with Type 2 DM and in those with impaired glucose tolerance (IGT), fasting blood glucose may be within normal limits, and hyperglycemia occurred only post-prandially. METHODS With ultrasound technique, we measured flow-mediated endothelium-dependent vasodilation during oral glucose tolerance test in 58 subjects: (17 patients with normal glucose tolerance [NGT], 24 with IGT, and 17 with type 2 DM). In addition, we measured the levels of thiobarbituric acid reactive substances (TBARS) and nitrite/nitrate. RESULTS Flow-mediated vasodilation decreased after glucose loading (NGT: 7.53+/-0.40, 4.24+/-0.28 and 6.35+/-0.40, in fasting, at 1- and 2-h, respectively, IGT: 6.50+/-0.48, 1.40+/-0.41** and 4.00+/-0.47*, respectively; DM: 4.77+/-0.37, 1.35+/-0.38** and 1.29+/-0.29%**, respectively; *p < 0.01 vs. fasting, **p < 0.005 vs. fasting). The TBARS concentration increased in parallel with plasma glucose level in each group (NGT: 1.43+/-0.07, 2.03+/-0.12 and 1.80+/-0.12, respectively; IGT: 1.65+/-0.11, 2.46+/-0.12** and 1.94+/-0.08*, respectively; DM: 1.73+/-0.07, 2.34+/-0.08** and 2.47+/-0.09** nmol/ml, respectively; *p < 0.05 vs. fasting, **p < 0.01 vs. fasting). Glucose loading did not change nitrite/nitrate concentration in any of the groups. CONCLUSIONS Hyperglycemia in response to oral glucose loading rapidly suppresses endothelium-dependent vasodilation, probably through increased production of oxygen-derived free radicals. These findings strongly suggest that prolonged and repeated post-prandial hyperglycemia may play an important role in the development and progression of atherosclerosis.

Vitamin E administration improves impairment of endothelium-dependent vasodilation in patients with coronary spastic angina

OBJECTIVES We examined the effects of oral administration of vitamin E, an antioxidant, on endothelium-dependent vasodilation in patients with coronary spastic angina. BACKGROUND We have recently reported that endothelium-dependent vasodilation is impaired in patients with coronary spastic angina (CSA). Furthermore, it is known that oxidative stress may play an important role in the impairment of endothelium-dependent vasodilation in cardiovascular diseases. METHODS With the ultrasound technique, flow-dependent vasodilation of the brachial arteries during reactive hyperemia was examined before and after treatment for a month with either oral administration of vitamin E (alpha-tocopherol acetate, 300 mg/day) or placebo, which is randomly assigned, in patients with CSA (n=60). RESULTS Before treatment, patients with CSA had impaired flow-dependent vasodilation, lower plasma levels of alpha-tocopherol and higher plasma levels of thiobarbituric acid reactive substances (TBARS), as compared with age- and sex-matched control subjects (n=60) (flow-dependent vasodilation: 3.1+/-1.8 vs. 7.1+/-2.5%, p < 0.001; alpha-tocopherol levels: 8.9+/-1.8 vs. 10.8+/-1.8 microg/ml, p < 0.001). In patients with CSA, treatment with vitamin E restored flow-dependent vasodilation (3.1+/-1.7 vs. 8.3+/-2.0%, p < 0.001), and this improvement was associated with the decreases in plasma TBARS levels and anginal attacks. CONCLUSIONS The results indicate that vitamin E treatment improved endothelium-dependent vasodilation and decreased plasma TBARS levels in patients with CSA. Thus, increased oxidative stress may contribute to endothelial dysfunction and anginal attacks in patients with CSA.

Deficiency in nitric oxide bioactivity in epicardial coronary arteries of cigarette smokers

OBJECTIVES This study sought to examine nitric oxide-mediated regulation of epicardial coronary arterial tone in cigarette smokers. BACKGROUND Cigarette smoking is a major risk factor for coronary artery disease and is highly prevalent in patients with coronary spastic angina. Long-term exposure to cigarette smoking has been recently reported to suppress endothelium-dependent arterial relaxation in vivo humans. METHODS Responses of epicardial coronary artery diameter to single or combined infusion of acetylcholine and NG-monomethyl-L-arginine (L-NMMA) into the left main coronary artery were examined in 11 current smokers and 17 nonsmokers using quantitative coronary angiography. RESULTS Acetylcholine dilated one-third of the proximal segments and most of the distal segments of coronary arteries in nonsmokers, whereas it constricted most of the proximal and distal segments in smokers. L-NMMA decreased the basal diameter of coronary arteries in nonsmokers but had minimal effect on the basal diameter in smokers. L-NMMA abolished the dilator response to acetylcholine in the coronary arteries of nonsmokers but had minimal effect on the constrictor response to acetylcholine in the arteries of smokers. The dilator response to nitroglycerin was significantly increased in the coronary arteries of smokers compared with in those of nonsmokers. The constrictor response to L-NMMA at rest was significantly correlated with the dilator response to nitroglycerin and with the diameter changes to acetylcholine in both smokers and nonsmokers. CONCLUSIONS Nitric oxide bioactivity at rest and at acetylcholine-stimulated conditions in smokers was decreased, leading to the supersensitivity of the artery to the dilator effect of nitroglycerin as well as the constrictor effect of acetylcholine in smokers. Cigarette smoking affects nitric oxide-mediated regulation of coronary artery tone.

Vitamin C attenuates abnormal vasomotor reactivity in spasm coronary arteries in patients with coronary spastic angina

OBJECTIVES This study sought to examine effect of vitamin C, an antioxidant, on the abnormal vasomotor reactivity in spasm coronary arteries. BACKGROUND Oxygen free radicals generated in the arterial walls have been shown to cause endothelial vasomotor dysfunction. METHODS Responses of the epicardial arterial diameters of the left coronary arteries to the intracoronary infusion of acetylcholine (ACh) (10 and 50 microg/min) were measured by quantitative coronary angiography before and during combined intracoronary infusion of vitamin C (10 mg/min) or saline as a placebo in 32 patients with coronary spastic angina and in 34 control subjects. RESULTS Vitamin C infusion suppressed the constrictor response of the epicardial diameter to ACh in spasm coronary arteries but had no significant effect in the control coronary arteries (percent change in distal diameter in response to 10 microg/min of ACh [constriction (-), dilation (+), mean +/- SEM] before vitamin C: -8.2 +/- 2.9% in spasm arteries, +8.4 +/- 2.9%* in control arteries; during vitamin C: +0.2 +/- 3.8%* in spasm arteries, +7.2 +/- 1.3%* in control arteries [*p < 0.01 vs. spasm arteries before vitamin CI). The coronary sinus-arterial difference in plasma thiobarbituric acid reactive substances during ACh infusion, an indicator of lipid peroxidation in coronary circulation, was higher in patients with coronary spastic angina than in control subjects (p < 0.01) but was suppressed in patients with coronary spastic angina to comparable levels in control subjects by combined infusion of vitamin C. Saline infusion had no effect. CONCLUSIONS The results indicate that vitamin C attenuates vasomotor dysfunction in epicardial coronary arteries in patients with coronary spastic angina. Oxygen free radicals may at least in part play a role in the abnormal coronary vasomotor reactivity in response to ACh in spasm coronary arteries.

Improvement of endothelial function and Insulin sensitivity with Vitamin C in patients with coronary spastic angina: Possible role of reactive oxygen species

OBJECTIVES This study was designed to examine the effect of antioxidant supplementation on the endothelial function and insulin sensitivity in patients with coronary spastic angina (CSA). BACKGROUND Insulin resistance may play a key role in coronary heart disease, and there is a possible link between acetylcholine-induced coronary vasoconstriction and hyperinsulinemia in patients with CSA. Endothelial dysfunction is present in the systemic arteries in CSA patients, and reactive oxygen species may cause inactivation of nitric oxide in these patients. METHODS We measured flow-mediated dilation of the brachial artery using ultrasound technique in 22 patients with CSA and 20 control subjects. We also evaluated glucose tolerance using a 75-g oral glucose tolerance test and insulin sensitivity using steady-state plasma glucose (SSPG) methods in the same patients. RESULTS The incidence of impaired glucose tolerance was higher in the CSA group than in the control group. Vitamin C infusion augmented flow-mediated dilation and decreased SSPG levels in the CSA group (from 3.27 +/- 0.77% to 7.00 +/- 0.59% [p < 0.001 by analysis of variance (ANOVA)] and from 177.3 +/- 13.3 to 143.1 +/- 14.9 mg/dl [p = 0.047 by ANOVA], respectively) but not in the control group (from 6.47 +/- 0.66% to 6.80 +/- 0.60% and from 119.8 +/- 11.7 mg/dl to 118.1 +/- 11.3 mg/dl, respectively). The steady-state plasma insulin levels were not affected by vitamin C infusion in either group. CONCLUSIONS Vitamin C improves both endothelial function and insulin sensitivity in patients with CSA. Thus, reactive oxygen species and/or decreased nitric oxide bioactivity may play an important role in the genesis of both endothelial dysfunction and insulin resistance in patients with CSA.

Endothelium-dependent vasodilation in the brachial artery is impaired in smokers: effect of vitamin C

Cigarette smoking has been shown to cause endothelial dysfunction. To examine the effects of vitamin C and cigarette smoking on endothelium-dependent vasodilation, we measured the lumen diameter and flow velocity of the brachial arteries at rest, during reactive hyperemia following transient arterial occlusion, and after sublingual nitroglycerin (0.3 mg) in smokers (n = 20) and nonsmokers (n = 20) with high-resolution ultrasound after infusion of saline or saline plus vitamin C (10 mg/min for 20 min). We also performed the same study in smokers (n = 15) before and 10 min after cigarette smoking. In addition, we measured the serum levels of vitamin C and the plasma levels of thiobarbituric acid-reactive substances (TBARS) as an index of lipid peroxidation. The smokers had lower vitamin C levels, higher TBARS levels, and showed impairment of flow-dependent vasodilation (5.3 +/- 1.9 vs. 9.2 +/- 1.5%, P < 0.0001) compared with nonsmokers. Vitamin C administration improved the impairment of flow-dependent vasodilation (5.3 +/- 1.9 to 9.0 +/- 3.2%, P < 0.001) and decreased TBARS in smokers but not in nonsmokers. Furthermore, cigarette smoking acutely worsened the impairment of flow-dependent vasodilation (5.4 +/- 1.8 to 1.5 +/- 1.3%, P < 0.01) and increased TBARS. We conclude that 1) endothelium-dependent vasodilation in the brachial arteries is impaired in smokers and this impairment is improved by vitamin C administration in association with a decrease in TBARS and 2) cigarette smoking produces acute impairment of endothelium-dependent vasodilation in smokers in association with an increase in TBARS.Cigarette smoking has been shown to cause endothelial dysfunction. To examine the effects of vitamin C and cigarette smoking on endothelium-dependent vasodilation, we measured the lumen diameter and flow velocity of the brachial arteries at rest, during reactive hyperemia following transient arterial occlusion, and after sublingual nitroglycerin (0.3 mg) in smokers ( n = 20) and nonsmokers ( n = 20) with high-resolution ultrasound after infusion of saline or saline plus vitamin C (10 mg/min for 20 min). We also performed the same study in smokers ( n = 15) before and 10 min after cigarette smoking. In addition, we measured the serum levels of vitamin C and the plasma levels of thiobarbituric acid-reactive substances (TBARS) as an index of lipid peroxidation. The smokers had lower vitamin C levels, higher TBARS levels, and showed impairment of flow-dependent vasodilation (5.3 ± 1.9 vs. 9.2 ± 1.5%, P < 0.0001) compared with nonsmokers. Vitamin C administration improved the impairment of flow-dependent vasodilation (5.3 ± 1.9 to 9.0 ± 3.2%, P < 0.001) and decreased TBARS in smokers but not in nonsmokers. Furthermore, cigarette smoking acutely worsened the impairment of flow-dependent vasodilation (5.4 ± 1.8 to 1.5 ± 1.3%, P < 0.01) and increased TBARS. We conclude that 1) endothelium-dependent vasodilation in the brachial arteries is impaired in smokers and this impairment is improved by vitamin C administration in association with a decrease in TBARS and 2) cigarette smoking produces acute impairment of endothelium-dependent vasodilation in smokers in association with an increase in TBARS.

Intracoronary Infusion of Reduced Glutathione Improves Endothelial Vasomotor Response to Acetylcholine in Human Coronary Circulation

BACKGROUND Oxygen free radicals have been shown to cause endothelial vasomotor dysfunction. This study examined the effect of reduced glutathione (GSH), an antioxidant, on human coronary circulation. METHODS AND RESULTS Responses of epicardial diameter and blood flow of the left anterior descending coronary artery to intracoronary infusion of acetylcholine (ACh, 50 microg/min) were measured by quantitative coronary angiography and Doppler flow-wire technique, respectively, before and during combined intracoronary infusion of GSH (50 mg/min) or saline in 26 subjects with no significant coronary stenosis. GSH infusion suppressed the constrictor response of epicardial diameter to ACh and enhanced the increase in blood flow response to ACh. Furthermore, GSH potentiated the coronary dilator effect of nitroglycerin. A beneficial effect of GSH on the epicardial diameter response to ACh was observed in a subgroup of subjects with > or = 1 coronary risk factors but not in a subgroup without risk factors. Saline infusion did not have any effects. CONCLUSIONS The results indicate that GSH improved coronary endothelial vasomotor function, particularly in subjects with coronary risk factors, and it potentiated the vasodilator effect of nitroglycerin in human coronary arteries.

Gender difference in improvement of endothelium-dependent vasodilation after estrogen supplementation.

OBJECTIVES We examined whether there is a gender difference in the improvement of endothelium-dependent vasodilation after estrogen supplementation. BACKGROUND Estrogen therapy reduces the risk of cardiovascular events in postmenopausal women, and the augmented release of endothelium-derived nitric oxide (NO) by estrogens has been suggested to be one of the mechanisms for the cardioprotective effects of estrogen. METHODS With ultrasound technique, we measured the diameter and blood flow of the brachial artery at rest, during reactive hyperemia after transient occlusion and after nitroglycerin administration before and after estradiol supplementation in 15 postmenopausal women (mean 63 years) and in 15 men matched for age and risk factors for atherosclerosis. RESULTS Estradiol supplementation augmented the flow-mediated vasodilation and serum level of nitrite/nitrate (metabolites of NO) in women (respectively, from mean +/- SEM of 8.0 +/- 0.6% to 12.9 +/- 0.6% [p < 0.01 by analysis of variance (ANOVA)] and from 64.9 +/- 8.7 to 93.7 +/- 9.4 mumol/liter [p < 0.05 by ANOVA]) but not in men (respectively, from 8.1 +/- 0.6% to 8.3 +/- 0.7% and from 57.8 +/- 6.7 to 60.8 +/- 5.4 mumol/liter). The increases in blood flow during reactive hyperemia and in diameter after nitroglycerin administration were not affected by estradiol supplementation in either men or women. CONCLUSIONS Estradiol supplementation improves endothelium-dependent vasodilation in women, probably because of augmented NO production/release, but not in men. Thus, there may be gender differences in the effects of estrogen therapy on endothelial functions and NO production/release.

Nitric Oxide-Mediated Flow-Dependent Dilation Is Impaired in Coronary Arteries in Patients With Coronary Spastic Angina

OBJECTIVES This study sought to examine whether flow-dependent dilation is impaired at the site of coronary artery spasm in patients with coronary spastic angina. BACKGROUND Physiologic stimuli such as exercise and exposure to cold have been shown to cause an increase in coronary blood flow, leading to flow-dependent dilation of coronary arteries in normal subjects, but cause coronary constriction in patients with coronary spastic angina. METHODS A maximal increase in blood flow was induced selectively in the left anterior descending coronary artery (LAD) by infusion of adenosine through a Doppler flow catheter tip in the midportion of the LAD in 10 patients with coronary spastic angina, all with angiographically demonstrated spasm of the LAD, and in 11 control patients. Coronary artery diameter at the proximal site of the LAD (exposed to increased flow but not to adenosine) was measured by quantitative angiography. RESULTS Flow-dependent dilation of the proximal LAD was found to be less in spasm arteries than in control arteries. Infusion of NG-monomethyl-L-arginine (L-NMMA) in the proximal LAD suppressed flow-dependent dilation in control arteries but had no significant effect on spasm arteries. The dilator response to nitroglycerin was not impaired in spasm coronary arteries. CONCLUSIONS Our results indicate that flow-dependent coronary dilation is impaired in spasm arteries, partly due to a deficiency in endothelial nitric oxide bioactivity, which in turn may contribute to the increase in coronary tone during physiologic stimuli in patients with coronary spastic angina.

Serial Changes in Plasma Levels of Soluble P-Selectin in Patients With Acute Myocardial Infarction ☆

The present study examines whether an acute inflammatory response occurs during acute myocardial infarction (AMI) by measuring soluble P-selectin levels. We examined plasma soluble P-selectin levels in 16 consecutive patients with AMI, in 15 patients with angina, and in 13 control subjects with chest pain but normal coronary arteries and no coronary spasm. In patients with AMI, blood samples were obtained immediately after admission and at 1, 4, 24, and 48 hours, and 1 week after initiation of reperfusion therapy. The plasma soluble P-selectin levels were significantly higher in the AMI group on admission than in the other 2 groups (83 +/- 13 ng/ml, p < 0.01). The plasma soluble P-selectin levels at baseline were not significantly different between the angina and control groups (28 +/- 4 vs 24 +/- 5 ng/ml, p = NS). Plasma soluble P-selectin levels reached their peak significantly at 4 hours after initiation of the reperfusion therapy in patients with AMI. The peak level was significantly higher than the level on admission (115 +/- 17 vs 83 +/- 13 ng/ml, p < 0.05). The plasma soluble P-selectin levels were higher in the AMI group than in the angina and control groups over the time course (p < 0.01). Our data indicate that the plasma soluble P-selectin levels are increased in patients with AMI, and that the levels are increases after reperfusion therapy more than before reperfusion. We suggest that the increase in the plasma soluble P-selectin levels may be caused by the activation of endothelial cells and platelets after myocardial ischemia and reperfusion during AMI.