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Vitamin C

October 2006

Effects of vitamin C on intracoronary L-arginine dependent coronary vasodilatation in patients with stable angina.

OBJECTIVE: To assess the effects of intravenous vitamin C administration on the vasomotor responses to intracoronary L-arginine infusion in epicardial coronary arteries. METHODS: 28 patients with coronary artery disease and stable angina were enrolled in the study. Eight patients received intracoronary infusions of 150 micromol/min L-arginine before and after intravenous infusion of vitamin C, 10 patients received intracoronary infusions of 150 micromol/min L-arginine before and after intravenous infusion of normal saline, and 10 patients received intracoronary normal saline before and after intravenous infusion of vitamin C. The diameter of proximal and distal coronary artery segments was measured by quantitative angiography. RESULTS: Infusion of L-arginine caused significant dilatation of both proximal (4.87 (0.96)%, p < 0.01 v normal saline) and distal (6.33 (1.38)%, p < 0.01 v normal saline) coronary segments. Co-infusion of vitamin C and L-arginine dilated proximal coronary segments by 8.68 (1.40)% (p < 0.01 v normal saline, p < 0.01 v L-arginine) and distal segments by 13.07 (2.15)% (p < 0.01 v normal saline, p < 0.01 v L-arginine). Intravenous infusion of vitamin C caused a borderline increase in proximal and distal coronary segment diameters (1.93 (0.76)% and 2.09 (1.28)%, respectively, not significant). CONCLUSIONS: L-arginine dependent coronary segment vasodilatation was augmented by the antioxidant vitamin C in patients with coronary artery disease. Thus, vitamin C may have beneficial effects on nitric oxide bioavailability induced by L-arginine.

Heart. 2005 Oct;91(10):1319-23

Vitamin C-induced activation of phospholipase D in lung microvascular endothelial cells: Regulation by MAP kinases.

Our earlier studies have shown that vitamin C at pharmacological doses (mM) induces loss of redox-dependent viability in bovine lung microvascular endothelial cells (BLMVECs) that is mediated by oxidative stress. Therefore, here, we investigated the vitamin C-induced activation of the lipid signaling enzyme, phospholipase D (PLD) in BLMVECs. Monolayer cultures of BLMVECs were treated with vitamin C (0-10 mM) for different time periods (0-2 h) and the activity of PLD was determined. Vitamin C induced activation of PLD in BLMVECs in a time- and dose-dependent fashion that was significantly attenuated by antioxidants, p38 mitogen-activated protein kinase (p38 MAPK)-specific inhibitor (SB203580), extracellular signal-regulated protein kinase (ERK)-specific inhibitor (PD98059), and transient transfection of cells with dominant-negative (DN)-p38 MAPK and DN-ERK1/ERK2. Vitamin C also induced phosphorylation and enhanced the activities of p38 MAPK and ERK in BLMVECs in a time-dependent fashion. It was also evident that vitamin C induced translocation of PLD(1) and PLD(2), association of p38 MAPK and ERK with PLD(1) and PLD(2), threonine phosphorylation of PLD(1) and PLD(2) and SB203580- and PD98059-inhibitable threonine phosphorylation of PLD(1) in BLMVECs. Transient transfection of BLMVECs with DN-p38 MAPK and DN-ERK1/ERK2 resulted in marked attenuation of vitamin C-induced phosphorylation of threonine in PLD(1) and PLD(2). We, for the first time, showed that vitamin C at pharmacological doses, activated PLD in the lung microvascular ECs through oxidative stress and MAPK activation.

Cell Signal. 2006 Sep;18(9):1396-407

Antioxidant effects of combined vitamins C and E in acute myocardial infarction. The randomized, double-blind, placebo controlled, multicenter pilot Myocardial Infarction and VITamins (MIVIT) trial.

AIMS: There is a large body of evidence that reactive oxygen species (ROS) produced during myocardial ischemia and reperfusion play a crucial role in myocardial damage and endothelial dysfunction. The MIVIT pilot trial was designed to test the effects of antioxidant vitamins C and E on the clinical outcome of patients with AMI. METHODS and RESULTS: In this randomized, double-blind, multicenter trial, 800 patients (mean age 62) with AMI were randomly allocated to receive, on top of routine medication, one of two treatments: vitamin C (1000 mg/12 h infusion) followed by 1200 mg/24 h orally and vitamin E (600 mg/24 h) or matching placebo for 30 days. Primary end point (composite of in-hospital cardiac mortality, non-fatal new myocardial infarction, VT/VF/asystole, shock/pulmonary edema) occurred less frequently in patients treated with antioxidants (55 [14%] vs 75 [19%], OR 0.82 [95% CI, 0.68-1.00], p=0.048). CONCLUSIONS: This randomized pilot trial shows that supplementation with antioxidant vitamins is safe and seems to positively influence the clinical outcome of patients with AMI. A larger study is warranted to provide further evidence of this promising and inexpensive regimen.

Kardiol Pol. 2005 Apr;62(4):344-50

Ascorbic acid (vitamin C) and iloprost attenuate the lung injury caused by ischemia/reperfusion of the lower extremities of rats.

The objectives of this study were to compare the protective effects of ascorbic acid and iloprost on lung injury caused by ischemia reperfusion (I/R) of the lower extremities of rats. Wistar albino rats (n = 34) were divided into five groups. In the I/R group (n = 6), the aorta was cross-clamped for 3 hr, followed by 1 hr of reperfusion. In the vitamin C group (n = 8), animals were pretreated with 100 mg/kg ascorbic acid via the left jugular vein before aortic cross-clamping. In the iloprost group (n = 8), animals were pretreated with 20 ng/(kg x min) iloprost by constant intravenous infusion via the left jugular venous cannula. In the sham group (n = 6), the abdomen was left open at the same period and a juguler venous line was established. In the control group (n = 6), lungs were removed and blood samples taken immediately after sternotomy. No treatment was given in this group. After both lungs were removed, biochemical parameters were measured and histopathological evaluation was made. Although the arterial blood pO2 and HCO3 levels were statistically significantly high in both the vitamin C and iloprost groups compared to the I/R group, plasma malondialdehyde (MDA) levels were significantly low. Meanwhile, the MDA levels in the lung tissue were significantly low in the vitamin C group compared to the I/R group. The MDA level in the lung tissue in the iloprost group was also low compared to the I/R group, but it was not statistically significant. The lungs of the I/R group displayed intense interstitial leukocytic infiltration in histopathological examination compared to the other groups. Pretreatment of animals with iloprost and vitamin C significantly decreased the pulmonary injury characterized by decreased plasma leukocyte sequestration. The results suggest that both vitamin C and iloprost are useful agents for attenuating the lung injury caused by increased oxidative stress and neutrophil accumulation after a period of I/R of the lower extremities.

Ann Vasc Surg. 2006 Jan;20(1):49-55

Oral vitamin C administration reduces early recurrence rates after electrical cardioversion of persistent atrial fibrillation and attenuates associated inflammation.

BACKGROUND: Inflammation and oxidative stress have been recently implicated in the pathophysiology of atrial fibrillation (AF). The aim of this study was to examine the potential benefit of vitamin C on the early recurrence rates and on inflammatory indices after successful cardioversion of persistent AF, as well as to investigate the time course of changes in these indices post-cardioversion. METHODS: We prospectively studied 44 consecutive patients after successful electrical cardioversion of persistent AF. All patients received standard treatment and were randomised in one to one fashion to either oral vitamin C administration or no additional therapy. We followed-up the patients for 7 days performing successive measurements of white blood cell (WBC) count, C-reactive protein (CRP), fibrinogen, and ferritin levels. RESULTS: One week after successful cardioversion, AF recurred in 4.5% of patients in the vitamin C group and in 36.3% of patients in the control group (p=0.024). Compared to baseline values, inflammatory indices decreased after cardioversion in patients receiving vitamin C but did not change significantly in the control group. A significant variance was found in the serial measurements of WBC counts (F=5.86, p=0.001) and of fibrinogen levels (F=4.10, p=0.0084) in the two groups. In the vitamin C group CRP levels were lower on the seventh day (p<0.05). CRP and fibrinogen levels were higher in patients who relapsed into AF compared to patients who maintained sinus rhythm (F=2.77, p=0.044 and F=3.51, p=0.017, respectively). CONCLUSIONS: These findings suggest that vitamin C reduces the early recurrence rates after cardioversion of persistent AF and attenuates the associated low-level inflammation. These effects indicate that therapeutic approaches targeting at inflammation and oxidative stress may exert favourable effects on atrial electrical remodeling.

Int J Cardiol. 2005 Jul 10;102(2):321-6

The relationship between potency of oxidative stress and severity of dilated cardiomyopathy.

BACKGROUND: It has been suggested that oxidative stress may have a role in the etiopathogenesis of congestive heart failure. OBJECTIVES: To investigate and compare the oxidative-antioxidative status and oxidative stress index (OSI) of patients with idiopathic dilated cardiomyopathy (IDC) with those of healthy volunteers, and to determine the relationship between total antioxidant capacity (TAC) and ejection fraction (EF). METHODS: Twenty-eight patients with IDC and 24 control subjects were enrolled in the study. Antioxidative status was evaluated by measuring the TAC and the vitamin C and thiol levels in the plasma. Oxidative status was evaluated by measuring the total peroxide level. The per cent ratio of TAC to total peroxide level was accepted as the OSI. EF was measured using Simpson’s method. RESULTS: TAC and vitamin C and thiol levels of plasma were found to be significantly lower in patients with IDC than in control subjects (P < 0.001). In contrast, total peroxide levels and OSIs were significantly higher in patients with IDC than in control subjects (P = 0.002 and P = 0.002, respectively). An important positive correlation was found between TAC and EF (r = 0.772; P < 0.001). On the other hand, significant negative correlations were found between EF and OSI and between EF and total peroxide levels in patients. CONCLUSIONS: Oxidants are increased and antioxidants are decreased in patients with IDC; as a result, the oxidative-antioxidative balance is shifted to the oxidative side. There is a significant correlation between the potency of oxidative stress and the severity of IDC. It is believed that supplementation of antioxidants in the treatment of IDC may be helpful to these patients.

Can J Cardiol. 2005 Aug;21(10):851-5