Volume 2, Number 7: July 1999

Long-Term Ascorbic Administration Reverses Endothelial Vasomotor Dysfunction in Patients with Coronary Artery Disease

  Comparison of antiplatelet activity of microencapsulated aspirin 162.5 mg (Caspac XL), with enteric coated aspirin 75 mg and 150 mg in patients with atherosclerosis.

  Lipophilic antioxidants in blood plasma as markers of atherosclerosis: the role of alpha-carotene and gamma-tocopherol.

   Atherosclerosis and inflammation. Patterns of cytokine regulation in patients with peripheral arterial disease

Long-Term Ascorbic Acid Administration Reverses Endothelial Vasomotor Dysfunction in Patients With Coronary Artery Disease

Reference:Circulation 1999;99:3234-3240.

Background—Loss of endothelium-derived nitric oxide (EDNO) contributes to the clinical expression of coronary artery disease (CAD). Increased oxidative stress has been linked to impaired endothelial vasomotor function in atherosclerosis, and recent studies demonstrated that short-term ascorbic acid treatment improves endothelial function.

Methods and Results—In a randomized, double-blind, placebo-controlled study, we examined the effects of single-dose (2 g PO) and long-term (500 mg/d) ascorbic acid treatment on EDNO-dependent flow-mediated dilation of the brachial artery in patients with angiographically established CAD. Flow-mediated dilation was examined by high-resolution vascular ultrasound at baseline, 2 hours
after the single dose, and 30 days after long-term treatment in 46 patients with CAD. Flow-mediated dilation improved from 6.6±3.5% to 10.1±5.2% after single-dose treatment, and the effect was sustained after long-term treatment (9.0±3.7%), whereas flow-mediated dilation was 8.6±4.7% at baseline and remained unchanged after single-dose (7.8±4.4%) and long-term (7.9±4.5%) treatment with placebo (P=0.005 by repeated-measures ANOVA). Plasma ascorbic acid concentrations increased from 41.4±12.9 to 115.9±34.2 µmol/L after single-dose treatment and to 95.0±36.1 µmol/L after long-term treatment (P<0.001).

Conclusions—In patients with CAD, long-term ascorbic acid treatment has a sustained beneficial effect on EDNO action. Because endothelial dysfunction may contribute to the pathogenesis of cardiovascular events, this study indicates that ascorbic acid treatment may benefit patients with CAD.  

Reference: Br J Clin Pharmacol 1999 Jul;48(1):57-62.

AIMS: A new formulation, low dose microencapsulated aspirin, permits slow absorption of aspirin and
presystemic acetylation of platelet cyclo-oxygenase within the portal circulation, potentially avoiding
deleterious effects on gastric and systemic prostaglandin synthesis. The objective of this study was to
determine whether the administration of microencapsulated aspirin was as effective as enteric coated
(EC) aspirin as an inhibitor of platelet function in patients with atherosclerosis. METHODS: One hundred
and four patients were enrolled and randomised after a run in period of at least 14 days on aspirin EC 75
mg (day 0), to receive either microencapsulated aspirin 162.5 mg (n=34), aspirin EC 150 mg (n=36) or
continue on aspirin EC 75 mg (n=34) for 28 days. Serum thromboxane B2 and collagen-induced platelet
aggregation and release of 5-hydroxytryptamine (EC50 values) were measured on days 0 and 28.
Aggregation/release EC50s were then repeated in the presence of a large dose of aspirin added in vitro
to determine the EC50 at the maximum level of platelet inhibition. RESULTS: Median thromboxane B2
levels were low after 14 days run-in therapy with aspirin EC 75 mg, but significant further reductions were
seen on day 28 in patients randomised to microencapsulated aspirin 162.5 mg (P=0.0368) and aspirin
EC 150 mg (P=0.0004) compared with those remaining on aspirin EC 75 mg. Median EC50 s on day 28
showed small but significant increases from baseline (day 0) in aggregation in patients randomised to
microencapsulated aspirin 162.5 mg (0.62-0.85, P=0.0482) and in both aggregation and release in
patients randomised to aspirin EC 150 mg (0.95-1.20, P=0.0002, 8.4-11.7, P<0.0001, respectively)
signifying enhanced antiplatelet activity. No changes were seen in patients continuing on aspirin EC 75
mg. Results following addition of high dose aspirin in vitro suggest that mechanisms other than
thromboxane synthesis may be operative in the long term effects of microencapsulated aspirin 162.5 mg
and aspirin EC 150 mg over aspirin EC 75 mg. CONCLUSIONS: The results show good inhibition of
thromboxane B2 synthesis and subsequent platelet activity by all preparations of aspirin, although both
microencapsulated aspirin 162.5 mg and aspirin EC 150 mg are slightly more effective than aspirin EC 75 mg. A randomised trial is now required to determine whether microencapsulated aspirin is associated with  fewer gastric side-effects. 

Lipophilic antioxidants in blood plasma as markers of atherosclerosis: the role of alpha-carotene and gamma-tocopherol.

Reference: Atherosclerosis 1999 May;144(1):117-22.

Oxidative theory of atherosclerosis implies that plasma levels of lipophilic antioxidants might serve as
indicators of lipoprotein oxidation in the arterial wall and as markers of the development of atherosclerosis.
However, it is unknown whether the measurement of plasma antioxidants is able to reflect atherogenesis
or its risk. In order to assess whether the levels of lipophilic antioxidants in human plasma can discriminate  between subjects with and without atherosclerosis, we measured the lipophilic antioxidants
alpha-tocopherol, gamma-tocopherol, alpha-carotene, beta-carotene and ubiquinol-10 in plasma of 34
patients with coronary heart disease (CHD) and in 40 control subjects. We found that alpha-carotene and
gamma-tocopherol were significantly lower in plasma of CHD patients compared to controls. This
decrease was significantly independent of whether the antioxidants were expressed as its absolute
amounts in plasma (P < 0.001 for alpha-carotene, and P = 0.001 for gamma-tocopherol) or normalized to
plasma lipids (P < 0.001 for both). In contrast, beta-carotene was only lower in plasma of CHD patients in
comparison to controls, when normalized to the lipids (P = 0.02). Independent contributions of different
parameters to the variation in these plasma antioxidants were estimated using multiple regression
approach. The analysis showed that both the decrease in alpha-carotene and the decrease in
gamma-tocopherol were significantly associated only with the presence of CHD (P < 0.001 for each
regression), while the decrease in beta-carotene was significantly related to the presence of
hyperlipidaemia (P < 0.001). In striking contrast, no decrease in plasma alpha-tocopherol and ubiquinol-10  was detected in the patient group independently of how these antioxidants were expressed. These data  suggest that plasma levels of alpha-carotene and gamma-tocopherol may represent markers of  atherosclerosis in humans. Measuring these antioxidants may be of clinical importance as a practical
approach to assess atherogenesis and/or its risk.

Reference: Atherosclerosis 1999;145(1):51-60

Inflammatory phenomena at sites of atherosclerotic plaques are increasingly thought to be major
determinants of the progression and clinical outcome of atherosclerotic disease. Therefore, attention is
being paid to systemic markers/mediators which may reflect the inflammatory activity in the plaques.
This study evaluates the pattern of the main proinflammatory cytokines tumor necrosis factor- (TNF),
interleukin-1 (IL-1), and interleukin-6 (IL-6), their soluble receptors/antagonist, and a variety of
inflammatory markers, in patients with peripheral arterial disease (PAD). Eight patients with PAD
suffering from claudicatio intermittens (CI), eight with critical limb ischemia (CLI) and eight controls (C)
were studied. Blood samples were collected at baseline in all groups and, for C and CI, immediately
after and 4 h after a 30-min treadmill test. Baseline: no differences in cytokine plasma levels were
detected among the three groups. In contrast, soluble receptors of TNF (type I and II) and of IL-6, and
IL-1 receptor antagonist (IL-1ra) were increased in CI and CLI patients, as compared to C. Of note,
IL-1ra correlated with the occurrence and stage of the disease in a highly significant proportion of the
patients, reaching a predictive value for the disease of P<0.0001. The opposite trend was observed for
the soluble receptor of IL-1. Notably, in the patients no alterations could be found in white blood cell
counts, expression of CD11c adherence molecule by circulating monocytes or, in vitro, O2- release from
zymosan-activated neutrophils. Moreover, plasma levels of platelet activating factor (PAF), of neutrophil
elastase and of the acute phase reactants C-reactive protein (CRP) and 1-acid glycoprotein were not
found to be significantly altered. In contrast, the acute-phase proteins 1-antitrypsin (1AT) and
haptoglobin (HG) were found to be increased. Effect of treadmill: IL-1 and TNF remained at baseline
levels following exercise, and IL-6 dropped to undetectable levels. Among cytokine antagonists, again
the most relevant changes concerned the IL-1ra, which was significantly increased immediately after the
treadmill test, both in CI and C, and returned to baseline levels after 4 h. In contrast, soluble TNF, IL-1
  and IL-6 receptors, PAF, and the other markers of leukocyte activation were not found to be altered.
Soluble TNF and IL-6 receptors were shown to inhibit the biological effects of their ligands. Similarly,
IL-1ra and the acute phase proteins 1AT and HG have been reported to exert anti-inflammatory
functions. The increased plasma levels of these agents, together with low levels of inflammatory
cytokines and other pro-inflammatory mediators such as PAF and 1-acid glycoprotein, appear to draw
an undescribed picture, so far, of upregulation of a composite systemic anti-inflammatory mechanism in
atherosclerotic patients. IL-1ra appears to be a reliable marker of the state of activation of this
mechanism. These results may provide a basis for developing new insights into the pathogenesis of the
atherosclerotic disease.