Simvastatin therapy reduces prooxidant-antioxidant balance: results of a placebo-controlled cross-over trial.

Abstract

Oxidative stress is thought to play an important role in atherogenesis. The statin group of cholesterol-lowering drugs have been shown to reduce cardiovascular events and possess antioxidant properties. We aimed to assess the effects of simvastatin on a novel measure of prooxidant-antioxidant balance (PAB) in dyslipidemic patients. The PAB assay can measure the prooxidant burden and the antioxidant capacity simultaneously in one assay, thereby giving a redox index. We treated 102 dyslipidemic individuals with simvastatin, or a placebo in a double-blind, cross-over, placebo-controlled trial. PAB values were measured before and after each treatment period. Seventy-seven subjects completed the study. We found that statin therapy was associated with a significant reduction in PAB values (P < 0.001). This effect appeared to be independent of the cholesterol-lowering effects of statins. We conclude that serum PAB values are decreased by simvastatin therapy. Regarding previous reports on the elevation of PAB in conditions associated with oxidative stress, the PAB assay, along with other markers of oxidative stress, may be applied to estimate the extent of oxidative stress in patients, assessment of the antioxidative efficacy of medication such as statins and perhaps also for the identification of those individuals who need antioxidant therapy.

Full text

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ORIGINAL ARTICLE
Simvastatin Therapy Reduces Prooxidant-Antioxidant Balance:
Results of a Placebo-Controlled Cross-Over Trial
Seyyed M. R. Parizadeh•Mahmoud R. Azarpazhooh•Mohsen Moohebati•
Mohsen Nematy•Majid Ghayour-Mobarhan•Shima Tavallaie•Amir A. Rahsepar•
Maral Amini•Amirhossein Sahebkar•Maryam Mohammadi•Gordon A. A. Ferns
Received: 16 March 2010/Accepted: 10 December 2010/Published online: 5 January 2011
? AOCS 2011
Abstract
role in atherogenesis. The statin group of cholesterol-
lowering drugs have been shown to reduce cardiovascular
events and possess antioxidant properties. We aimed to
assess the effects of simvastatin on a novel measure of
prooxidant–antioxidant balance (PAB) in dyslipidemic
patients. The PAB assay can measure the prooxidant bur-
den and the antioxidant capacity simultaneously in one
assay, thereby giving a redox index. We treated 102
dyslipidemic individuals with simvastatin, or a placebo in
a double-blind, cross-over, placebo-controlled trial. PAB
values were measured before and after each treatment
period. Seventy-seven subjects completed the study. We
found that statin therapy was associated with a significant
reduction in PAB values (P\0.001). This effect appeared
to be independent of the cholesterol-lowering effects of
statins. We conclude that serum PAB values are decreased
by simvastatin therapy. Regarding previous reports on the
elevation of PAB in conditions associated with oxidative
Oxidative stress is thought to play an important
stress, the PAB assay, along with other markers of oxida-
tive stress, may be applied to estimate the extent of oxi-
dative stress in patients, assessment of the antioxidative
efficacy of medication such as statins and perhaps also for
the identification of those individuals who need antioxidant
therapy.
Keywords
balance (PAB) ? Dyslipidemia
Simvastatin ? Prooxidant–antioxidant
Abbreviations
BMI
CVD
eNOS
FBS
HDL-C
HMG-CoA
LDL-C
NADPH
Body mass index
Cardiovascular disease
Endothelial nitric oxide synthase
Fasting blood sugar
High-density lipoprotein cholesterol
3-Hydroxy-3-methylglutaryl-coenzyme A
Low density lipoprotein cholesterol
Nicotinamideadeninedinucleotidephosphate
S. M. R. Parizadeh
Department of Biochemistry and Nutrition, Faculty of Medicine,
Mashhad University of Medical Sciences, Mashhad, Iran
S. M. R. Parizadeh
Biochemistry and Nutrition Research Center,
Avicenna (Bu-Ali) Research Institute,
Mashhad University of Medical Sciences, Mashhad, Iran
M. Moohebati ? M. Nematy ? M. Ghayour-Mobarhan ?
S. Tavallaie ? A. A. Rahsepar ? A. Sahebkar ? M. Mohammadi
Cardiovascular Research Center,
Avicenna (Bu-Ali) Research Institute,
Mashhad University of Medical Sciences, Mashhad, Iran
M. R. Azarpazhooh ? A. A. Rahsepar
Department of Neurology, Faculty of Medicine,
Mashhad University of Medical Sciences, Mashhad, Iran
M. Moohebati
Department of Cardiology, Faculty of Medicine,
Mashhad University of Medical Sciences, Mashhad, Iran
M. Nematy ? M. Ghayour-Mobarhan (&)
Department of Nutrition, Faculty of Medicine,
Mashhad University of Medical Sciences, Mashhad, Iran
e-mail: ghayourm@mums.ac.ir
M. Amini
Young Researchers Club, Mashhad Islamic Azad University,
Mashhad, Iran
G. A. A. Ferns
Institute for Science and Technology in Medicine,
University of Keele, Guy Hilton Research Centre,
Thornburrow Drive, Stoke on Trent, Staffordshire ST4 7QB, UK
123
Lipids (2011) 46:333–340
DOI 10.1007/s11745-010-3517-x

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NF-jBNuclear factor kappa-light-chain-enhancer of
activated B cells
Nitric oxide
Oxidized low density lipoprotein cholesterol
Prooxidant–antioxidant balance
Reactive oxygen species
Statistical analysis software
Standard deviation
Total cholesterol
Triglycerides
3,30,5,50-Tetramethylbenzidine
NO
ox-LDL
PAB
ROS
SAS
SD
TC
TG
TMB
Introduction
Oxidative stress is an imbalance between the production of
pro-oxidants and antioxidant defenses in favor of pro-oxi-
dants. Oxidative stress is usually related to the increased
formation of reactive oxygen species (ROS), and is thought
to play an important role in the pathogenesis of cardio-
vascular disease (CVD) and its complications. Recently
oxidative stress [1] and inflammation [2] have been pro-
posed to be significant risk factors for CVD, and the lipid
oxidation hypothesis provides one mechanism by which
oxidative stress may be implicated [3].
It is also suggested that oxidative stress may be a strong
and independent prognostic predictor of cardiovascular
events [4].
Low density lipoprotein cholesterol (LDL-C) has been
associated with several pro-atherothrombotic processes
through the development of endothelial dysfunction,
inflammation and foam cell formation [5]. Indeed, indi-
viduals with relatively normal LDL levels but high expo-
sure to oxidative stress such as those with hypertension [6],
are at increased risk of developing CVD via the formation
of pro-inflammatory and pro-atherogenic molecules asso-
ciated with the formation of oxidized-LDL (ox-LDL).
Ox-LDL has been shown to accumulate in the arterial wall
and this is associated with the development of endothelial
dysfunction [7, 8]. Thus, reduction in plasma levels of LDL
and ox-LDL may represent a useful approach for pre-
venting from atherosclerotic diseases.
Statins are a group of lipid-lowering agents which block
the rate limiting step in cholesterol biosynthesis, the con-
versionof3-hydroxy-3-methylglutaryl-coenzyme
(HMG-CoA) to mevalonic acid. The LDL-cholesterol
lowering property of statins is associated with a reduction
of cardiovascular endpoints including definite coronary
events (specified as nonfatal myocardial infarction or death
from coronary heart disease), definite nonfatal myocardial
infarctions; death from definite plus suspected coronary
A
heart disease and death from all cardiovascular causes [9].
However, it has been argued that the benefits obtained with
statin therapy in patients with a wide range of cholesterol
levels may be due to their ‘‘pleiotropic’’ non-cholesterol-
lowering effects. These pleiotropic effects of statins
include: improving endothelial function, decreasing oxi-
dative stress (by lowering ROS production and increasing
the resistance of LDL-C to oxidation), inhibiting platelet
adhesion, reducing inflammation, and enhancing the sta-
bility of atherosclerotic plaques [10].
Until now, many methods have been developed that can
separately determine the total pro-oxidant and antioxidant
capacities and are therefore hard, time consuming, expen-
sive, and imprecise. We have recently used a simple, rapid
and inexpensive method [11] to measure the PAB directly,
by using 3,30,5,50-tetramethylbenzidine (TMB) and two
different kinds of reaction, an enzymatic reaction where the
chromogen TMB is oxidized to a colored cation by perox-
ides, and a chemical reaction in which the colored TMB
cationisreducedtoacolorlesscompoundbyantioxidants.A
redoxindexistherebyderived fromthesetworeactions.The
assay hasbeencalibratedagainstthe mostsignificant known
oxidants and antioxidants and its response has been found to
bealineardecreaseagainstantioxidantsandalinearincrease
againstoxidants.Themethodwasalso,validatedindepthby
other known oxidative stress markers [11]. In this study, we
aimedtoevaluatetheeffectofsimvastatinonPABvaluesby
a modified PAB assay [12] in a randomized, double blind,
cross-over trial in dyslipidemic patients.
Methods
Subjects
One hundred and two men and women, aged 20–88 who
were not originally taking lipid-lowering agents were
recruited from the lipid clinics at the Qaem hospital,
Mashhad, Iran. In addition to a history of not taking statins,
other inclusion criteria were any of the following condi-
tions (based on the NCEP-ATP III guidelines [13]): (1)
patients with\2 risk factors (except diabetes mellitus) for
coronary heart disease (CHD) and 160 mg/dL\LDL-
C\190 mg/dL, or (2) patients with C2 risk factors
(except diabetes mellitus) for coronary heart disease
(CHD) and 130 mg/dL\LDL-C\160 mg/dL. Cardio-
vascular risk factors were defined as age [65 years,
hypertension (defined as taking any anti-hypertensive
medication; or systolic blood pressure C140 mmHg or
diastolic blood pressure C90 mmHg), diabetes mellitus
(defined as fasting blood sugar (FBS) C 126 mg/dL),
positive family history of CVD, smoking, male sex and
obesity [defined as body mass index (BMI) C 30 kg/m2].
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The exclusion criteria were; malignancy or history of
malignancy, infections, connective tissue disorders or
treatment with immunomodulatory drugs (e.g. corticoste-
roids), liver or renal disease, leukocytosis (white blood cell
count [10,000 109/L), thrombocytosis (platelet count
[450,000 109/L) and anemia (hematocrit \40%). Each
subject gave informed written consent to participate in the
study, which had previously been approved by the Mash-
had University of Medical Science Ethics Committee. In
addition, subjects were advised to continue their normal
medication schedule.
Study Design
This study was designed as a randomized, double blind,
cross-over trial in which each patient received simvastatin
or a placebo and then crossed over to the alternate regimen.
Each treatment period was 30 days and there was a 2-week
washout interval in between the regimens. The dose of
simvastatin and all other medication remained unchanged
during the experimental period, and the patients were
advised not to change their lifestyle during the study. At
the first visit, patients were randomized for one of two
treatment regimens, 51 patients were provided with sim-
vastatin 40 mg/day for 30 days and other 51 patients
received a placebo (simply prepared by filling empty cap-
sules—which were matched for size and color with sim-
vastatin capsules—with starch instead of simvastatin) for
30 days. After another 2-week wash-out period, patients
crossed over to the other form of treatment.
Anthropometric Measurements
Anthropometric parameters including weight, height, and
BMI were measured. Weight was measured with the sub-
jects dressed in light clothing after an overnight fasting
using a standard scale. BMI was calculated as weight (kg)
divided by height squared (m2).
Blood Sampling
Blood samples were collected four times for each subject
(before and after starting each period). Blood samples for
laboratory assays were obtained on the day of sampling
after 12 h of fasting. Following venipuncture, blood sam-
ples were collected in Vacutainer?tubes and centrifuged at
10,000g for 15 min at 4 ?C. After separation, aliquots of
serum were frozen at -80 ?C until analysis.
Routine Biochemical Analysis
A full fasted lipid profile comprising total cholesterol, tri-
glycerides, high-density lipoprotein cholesterol (HDL-C)
and LDL-C was determined for each subject. Serum lipid
and FBS concentrations were measured enzymatically with
the use of commercial kits.
Chemicals
TMB powder (3,30,5,50-tetramethylbenzidine, Fluka), per-
oxidase enzyme (Applichem: 230 U/mg, A3791,0005,
Darmstadt, Germany), chloramine T trihydrate (Appli-
chem: A4331, Darmstadt, Germany), hydrogen peroxide
(30%) (Merck). These chemicals and all the other reagents
used were reagent grade and were prepared in double
distilled water.
Prooxidant–Antioxidant Balance (PAB) Assay
A modified PAB assay was applied based on a previously
described method [11, 12]. The standard solutions were
prepared by mixing varying proportions (0–100%) of
250 lM hydrogen peroxide with 3 mM uric acid (in
10 mM NaOH). TMB powder (60 mg) was dissolved in
10 mL DMSO. For preparation of the TMB cation, 400 lL
of the TMB/DMSO solution was added to 20 mL of acetate
buffer (0.05 M buffer, pH 4.5), and then 70 lL of fresh
chloramine T (100 mM) solution was added to this 20 mL.
The solution was mixed well and incubated for 2 h at room
temperature in a dark place. Then 25 U of peroxidase
enzyme solution was added to 20 mL of TMB cation
solution, dispensed in 1 mL and stored at -20 ?C. In order
to prepare the TMB solution 200 lL of TMB/DMSO was
added to 10 mL of acetate buffer (0.05 M buffer, pH 5.8)
and the working solution was prepared by mixing 1 mL
TMB cation with 10 mL of TMB solution. This working
solution was incubated for 2 min at room temperature in a
dark place and used immediately. Ten microliters of each
sample, standard or blank (distilled water) were mixed with
200 lL of working solution in each well of a 96-well plate,
which was then incubated in a dark place at 37 ?C for
12 min. At the end of the incubation time, 100 lL of 2 N
HCl was added to each well, and the optical density (OD)
was measured in an ELISA reader at 450 nm with a ref-
erence wavelength of 620 or 570 nm. A standard curve was
provided from the values relative to the standard samples.
The values of the PAB are expressed in arbitrary units, this
is the percentage of hydrogen peroxide in the standard
solution. The values of the unknown samples were then
calculated based on the values obtained from the above
standard curve.
Statistical Analysis
Values were expressed as means ± SD or, in the case of
non-normally distributed data, as median and inter-quartile
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range. The comparison between pre and post treatments
was done using the paired t test or the Wilcoxon signed
rank test. Data obtained from independent variables ana-
lyzed using Student’s t test (for those with normal distri-
bution) or Mann–Whitney U test (for those without normal
distribution). Categorical data were compared using v2test.
Correlations between changes in serum PAB and LDL-C
levels were assessed using the Pearson correlation coeffi-
cient. Mixed model analysis of variance for 2 9 2 cross-
over studies were fitted when assumption for normality
were met. All analysis were performed with the Statistical
Analysis Software (SAS version 8). A two-sided P value of
\0.05 was considered statistically significant.
Results
From 102 subjects who entered our study, 25 (24.5%) did
not complete the study, leading to a final sample size of 77
(78.18%). The reasons for drop-outs were non-compliance
with the study protocol (n = 21), drug intolerance (n = 2)
and moving to anothercity (n = 2) (Fig. 1). To rule out the
possibility of a carryover effect from one treatment period
to the other treatment period, we compared baseline values
before the first treatment period to those before the second
treatment period. No significant difference was found in the
analysis (P[0.05). The mean age and BMI of subjects
were 46.61 ± 13.95 and 29.94 ± 6.08, respectively, with
72.1% being female. The prevalence of smoking, diabetes
mellitus and hypertension were 7.0, 14.0 and 9.3%,
respectively.
Effect of Administration of Simvastatin Versus Placebo
on Weight, BMI and FBS
FBS was not significantly affected by simvastatin nor by
the placebo (P[0.05). However, mean baseline values for
BMI and weight were significantly different between the
first and second periods of treatment (P = 0.019 and
P = 0.003, respectively) (Table 1).
Assessed for eligibility
(n=114)
Did not meet inclusion criteria
(n=12)
Non-compliance with study protocol
(n=1)
Moving to another city (n = 1)
Allocated to intervention
(n = 51)
Non-compliance with study protocol
(n = 3)
rug intolerance (n = 2) D
Allocated to intervention
(n = 51)
Allocation
Follow-up of the
first period
Enrollment
Randomized
Follow-up of the
second period
Non-compliance with study protocol
(n = 6)
Movinng to another city (n = 1)
Non-compliance with study protocol
(n = 11)
Analyzed (n = 38)
Analyzed (n = 39)
Analysis
Wash-out
period
Fig. 1 Flow chart of the trial
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Effect of Administration of Simvastatin Versus Placebo
on Lipid Parameters
As expected, total cholesterol, LDL-C and triglycerides
were reduced significantly after 4-weeks of treatment
with simvastatin (P\0.001). However, HDL-C did not
change significantly with either treatment (P[0.05)
(Table 1).
Effect of Administration of Simvastatin Versus Placebo
on PAB Values
Treatment with simvastatin 40 mg/day for 4 weeks caused
a statistically significant reduction in the mean PAB values
(P\0.001) (Fig. 2).
Correlation Between Changes in PAB Values
with Changes in LDL-C Levels
Statistical analysis showed that there was no significant
correlation between changes in PAB values and serum
LDL-C levels in any of the periods, neither in the placebo-
statin nor in the statin-placebo group (P[0.05, Table 2).
The only exception was a significant correlation between
PAB changes and serum total cholesterol changes in the
placebo-statin group (P\0.05, Table 2).
Discussion
In the present study we found that simvastatin therapy for
4 weeks caused a statistically significant reduction in mean
PAB values, showing that statin therapy may be associated
with a reduction in levels of oxidative stress. Our finding
confirms the results of other studies evaluating the effect of
statins on plasma measures of oxidation status. Fluvastatin
therapy was found to reduce superoxide radical generation
Table 1 Effect of simvastatin and placebo therapy in two groups of subjects
Study groupsFirst
Pre treatment
Period
Post treatment
Second
Pre treatment
Period
Post treatment
Period effecta
Treatment
effect (S vs. P)
FBS (mg/dl) Statin–placebo86.46 ± 19.52 85.58 ± 17.12 81.28 ± 15.83 81.09 ± 13.65(P[0.05)(P[0.05)
Placebo–statin 104.36 ± 47.61101.71 ± 45.86 103.5 ± 45.55 99.10 ± 33.28
Weight (kg)Statin–placebo 71.59 ± 22.02 72.42 ± 19.2473.80 ± 18.6075.27 ± 18.55(P = 0.003)(P[0.05)
Placebo–statin78.04 ± 16.6377.17 ± 16.30 76.99 ± 15.5076.71 ± 16.41
BMI (kg/m2)Statin–placebo28.83 ± 6.18 28.30 ± 6.1928.95 ± 5.9029.09 ± 5.91(P = 0.019)(P[0.05)
Placebo–statin31.12 ± 6.4130.83 ± 6.3630.33 ± 7.41 31.25 ± 6.04
TC (mg/dl) Statin–placebo203.02 ± 36.11152.48 ± 41.60 181.69 ± 30.65182.38 ± 37.64(P[0.05)(P\0.001)
Placebo–statin193.32 ± 39.65191.06 ± 38.04194.85 ± 37.75160.37 ± 60.81
LDL-C (mg/dl)Statin–placebo131.44 ± 28.4687.35 ± 35.01119.75 ± 26.44121.09 ± 23.86(P[0.05)(P\0.001)
Placebo–statin118.38 ± 30.48115.22 ± 35.03121.75 ± 28.2592.50 ± 46.48
HDL-C (mg/dl)Statin–placebo44.08 ± 10.8043.31 ± 12.1940.36 ± 13.3441.79 ± 14.97(P[0.05)(P[0.05)
Placebo–statin42.40 ± 11.92 42.64 ± 13.3244.55 ± 12.42 45.96 ± 14.58
TG (mg/dl)Statin–placebo137.23 ± 65.07118.87 ± 57.20 128.11 ± 58.17126.54 ± 59.14 (P[0.05)(P\0.001)
Placebo–statin156.00 ± 84.11 151.35 ± 76.98 156.65 ± 93.07132.37 ± 93.13
Values are expressed as means ± SD for normally distributed data and median and interquartile range. Statin-placebo group took statin at first,
while placebo-statin group received statin following placebo
BMI body mass index, FBS fasting blood sugar, TC total cholesterol, HDL high-density lipoprotein, LDL low-density lipoprotein, TG triglyc-
erides, PAB prooxidant–antioxidant balance
aDefined as comparison of mean values between the first and second periods
Statin-Placebo Placebo-Statin
0
50
100
150
First period baseline
First period final
Second period baseline
Second period final
PAB (AU)
Fig. 2 Effect of simvastatin versus placebo on serum PAB values.
Period effect: P[0.05; treatment effect: P\0.001
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and the susceptibility of LDL to oxidation in cholesterol-
fed rabbits [14]. Moreover, simvastatin was reported to
lower superoxide generation in human macrophages [15].
Furthermore, oxidative stress of different patients has been
shown to decrease after treatment with atorvastatin, sim-
vastatin, pravastatin, fluvastatin, and lovastatin [16–18]. In
addition, treatment with these statins was followed by a
prolonged lag time of LDL oxidation [19–21]. Statin
therapy also causes a significant reduction in plasma levels
of ox-LDL [17] and it has also been reported that in
hypercholesterolemia or mixed type hyperlipidemia, ator-
vastatin can increase total plasma antioxidant status, lead-
ing to a lower LDL oxidation capacity [19].
There appear to be several mechanisms whereby statins
may reduce oxidative stress. Apart from their hypocho-
lesterolemic effects and the subsequent reduction of oxi-
dation substrate, statins are known to exert radical
scavenging activity and decrease the generation and release
of ROS through different mechanism such as inhibition of
Rac1GTPase and NADPH-oxidase [22].
Nicotinamide adenine dinucleotide phosphate (NADPH)
oxidases are as one of the important sources of superoxide
in human coronary artery, and their activities have been
reported to be increased in patients with CVD [23]. Statins
have been reported to reduce NADPH dependant super-
oxide formation by monocyte-derived cell lines in culture
[24]. Atorvastatin has been reported to inhibit angiotensin
II-induced superoxide formation by NADPH oxidase in
rats in vivo [25]. Statin therapy has been also suggested to
inhibit ox-LDL induced NADPH oxidase expression and
superoxide anion formation [26]. The anti-inflammatory
properties of statins make them able to inhibit macrophage
growth and foam cell formation stimulated with ox-LDL
[27], leading to a reduction in influx of inflammatory cells,
which consecutively results in a decreased release of ROS
and the LDL oxidation.
Statins may also act as an antioxidant via different
mechanisms, for instance, there are some reports, though
not consistent, indicating that statins are able to increase
the activity and/or expression of antioxidant enzymes such
as catalase, paraoxonase and glutathione peroxidase, while
decreasing those of NADPH oxidase [28–31]. It is also
reported that statins can increase the release of NO [32],
and also several statins have the ability to increase eNOS
expression in the blood vessels of treated animals [33],
resulting in the restoration of endothelial function. More-
over, atorvastatin has been reported to increase paraoxon-
ase activity and decrease the enhanced cellular uptake of
ox-LDL of monocytes differentiating into macrophages
[34]. Finally some statin metabolites are considered to
possess antioxidant properties and prevent lipid peroxida-
tion [35] (Fig. 3).
In our study, we did not find a significant correlation
between changes in PAB values with changes in serum
levels of LDL-C, implying that antioxidant activity of
statins may be at least partly due to other pleiotropic
properties rather than just lipid-lowering effects of these
drugs. It is suggested that the underlying cholesterol
independent effects relates to the inhibition of isoprenoid
intermediates of the cholesterol synthesis pathway [36].
The aforementioned studies together with the findings of
the present study support the notion that oxidative stress
could be used as a significant risk predictor in the athero-
sclerotic process. Statins have pleiotropic properties as
endothelial protective, anti-inflammatory, and antioxida-
tive agents, and suggest that other markers such as
Table 2 Correlations between changes in serum PAB and LDL-C
levels
LDL-C Total cholesterol
rprp
Placebo–statin
First period 0.197
[0.05
[0.05
0.335
\0.05
[0.05Second period0.005-0.016
Statin–placebo
First period0.050
[0.05
[0.05
0.031
[0.05
[0.05Second period-0.356-0.360
Correlations were assessed using the Pearson correlation coefficient
PAB prooxidant–antioxidant balance
Fig. 3 Some antioxidant mechanisms of statins. Statins inhibit the
assembly of NAD(P)H oxidase in both vascular cells and phagocytes,
thus preventing the formation of superoxide (O2
arrows associated with gene expression indicate upregulation of
expression of antioxidant enzymes (eNOS and catalase) and down-
regulation of oxidants (NAD[P]H components and cyclooxygenase-
2). Permission from Drugs of Today [41] [Drugs of Today
2004;40(12):975–989. Copyright ? 2004 Prous Science, S.A. All
rights reserved.]
?2). Bi-directional
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C-reactive protein, oxidative biomarkers and isoprenoid
intermediates might be used in conjunction with serum
cholesterol levels to assess the therapeutic benefits of statin
therapy better.
In previous studies using the PAB assay, it was reported
to be elevated in a number of conditions associated with
oxidative stress including diabetes mellitus [11], coronary
artery disease [12], acute coronary syndrome [37], exfo-
liative glaucoma [38], and stroke [39]. PAB values have
been also reported to decrease following antioxidant vita-
mins (E and C) [11] and selenium consumption [40]. The
PAB assay may be useful as a CVD risk predictor [12, 37]
and could help to identify patients with higher oxidative
stress in order to introduce interventions for the prevention
of vascular disease earlier. In the present study, we showed
that this assay may serve as a useful method to assess the
effect of statin therapy in CVD, indicating that the PAB
assay, along with other known markers of oxidative stress,
may be used to estimate the extent of oxidative stress in
high-risk groups, identify subjects who need antioxidant
therapy, and evaluate the antioxidative efficacy of different
supplements and medications. Finally, further clinical
research is required based on a larger healthy population,
as well as on various physiological and pathological states
associated with oxidative stress, and by multiple labora-
tories in order to substantiate the potency of the assay to
become a clinical laboratory test.
Study Limitations
The present study had several limitations. First, 25 subjects
did not complete the study due to non-compliance with the
study protocol or drug intolerance. Second, simvastatin was
administered at a dose of 40 mg/day for a limited period
(30 days), and longer term studies are necessary to show
that this effect is sustained. Finally, using several doses of
statins could have been useful to determine whether the
observed effects of simvastatin are dose-dependent and
whether higher doses exert more dramatic effects.
Acknowledgments
their family members who volunteered to participate in this study.
This work was financially supported by the Iran National Science
Foundation and Mashhad University of Medical Science (MUMS),
Mashhad, Iran.
We are particularly grateful to the patients and
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