Effect of Atorvastatin on Paraoxonase Activity in Patients with Hyperlipidemia
Jeevan K. Shetty,
Paraoxonase is high density lipoprotein associated enzyme which
prevents the oxidation of low density lipoprotein. In the present study
we evaluated the effect of atorvastatin on serum paraoxonase levels in
south Indian population with hyperlipidemia. The study was conducted on
59 newly diagnosed hyperlipidemic patients and 41 healthy controls. Hyperlipidemic
patients were divided into two groups, group 1-before treatment and group
2-three months after receiving 10 mg atorvastatin daily. Serum paraoxonase
and lipid profile were estimated in both cases and controls. Serum paraoxonase
activity and high density lipoprotein levels were lower and total cholesterol,
triglycerides and low density lipoproteins were high in hyperlipidemics
compared to controls (p<0.01). Serum paraoxonase activity and high
density lipoproteins levels were increased and total cholesterol, triglycerides
and low density lipoprotein levels were decreased significantly in group
2 cases compared to group 1 cases (p<0.01). Serum paraoxonase correlated
positively with high density lipoprotein (R = 0.347, p<0.01). Atorvastatin
apart from favorably improving lipid profile, also improves paraoxonase
activity significantly, this may suggest anti-atherogenic role of statins
along with their antilipidemic function.
South Asians especially Indians show at increased risk for atherosclerosis
and premature coronary heart disease (Sarkar and Madhsudhan, 2006). Hyperlipidemia
is highly prevalent in Indian population and known to contribute towards
increased mortality and morbidity related to cardiovascular and cerebrovascular
disorders (Mackness and Durrington, 2003). Several antilipidemic drugs
are in use which improves lipid profile favorably thus decreasing the
rate of mortality and morbidity. Recently antilipidemic drugs like fenofibrates
shown improvement in paraoxonase activity along with favorable improvement
in lipid profile (Paragh et al., 2003). Serum paraoxonase is a
calcium dependent high density lipoprotein associated esterase that is
known to catalyze the hydrolysis of organophosphates. Serum paraoxonase
is known to prevent protein oxidation by preventing homocysteinylation
of protein (James et al., 2000) Paraoxonase decreases low density
lipoprotein oxidation by its peroxidase activity and by preventing homocysteinylation
of Apo B 100 (Aviram et al., 1998). Mackness et al. (1991)
showed reduced paraoxonase activity in patients with hyperlipidemia. In
the present study, we studied the activity of serum paraoxonase in south
Indian population with hyperlipidemia and effect of atorvastatin on serum
MATERIALS AND METHODS
The study was carried out on 59 newly diagnosed hyperlipidemics not associated
with any systemic disease and 41 healthy controls. Mean age and sex of
patients was 46±6 years and 48 males/11 females and that of controls
was 42±7 years and 30 males/11 females, respectively. Informed
consent was taken from all subjects involved and the study was approved
by institutional review board. Hyperlipidemic patients were recruited
from Kasturba Medical College hospital; who came for routine health check
up. We have excluded all the cases with diabetes mellitus, chronic renal
failure on conservative management or on hemodialysis and any other inflammatory
conditions. We have included all those diagnosed with hyperlipidemia for
the first time with or without associated conditions like hypertension
or atherosclerosis related medical disorders. The paraoxonase activity
was estimated at the time of diagnosis. All the hyperlipidemic subjects
were treated with 10 mg of atorvastatin daily for the period of three
months and advised to take low cholesterol diet. After three months, follow
up was done and the lipid profile and paraoxonase activity was estimated.
The hyperlipidemic patients were divided into two groups, group 1-cases
at the time of diagnosis and group 2-cases three months after treatment
with 10 mg atorvastatin daily.
Under aseptic conditions blood samples (5 mL) were drawn into plain vacutainers
from ante-cubital veins of controls and cases. The collected blood was
allowed to clot for 30 min and then centrifuged at 2000 g for 15 min for
clear separation of serum. All assays were performed immediately after
serum was separated.
Special chemical paraoxone was obtained from Sigma chemicals, St Louis,
MO, USA. All other reagents were of analytical grade. Paraoxonase was
estimated spectrophotometrically by the method described elsewhere with
minimal modifications. Briefly, the assay mixture consists of 500 μL
of 2.2 mM Paraoxone substrate in 0.1 M tris-HCl buffer, pH 8.0 containing
2 mM CaCl2 and 50 μL of fresh serum specimen. The absorbance
was monitored at 405 nm at 25°C. One unit (IU) of Paraoxonase activity
is defined as 1 μmol of p-nitrophenol formed per min per liter at
25°C and activity was expressed as U L-1 of serum (Schiavon
et al., 1996).
Fasting lipid profile was estimated by enzymatic kinetic assay method
using automated analyzer, Hitachi model 912. Total cholesterol estimation
was done by cholesterol oxidase method; HDL cholesterol was estimated
by same method after precipitating the LDL, VLDL and Chylomicrons (Allain,
1974). Triglycerides were estimated by enzymatic mixture containing lipoprotein
lipase, glycerol kinase and glycerol-3-phosphate oxidase and peroxidase
(McGowan, 1983). Low density lipoprotein levels were calculated by using
The results were expressed as mean±Standard Deviation (SD). A p-value
of <0.05 was considered statistically significant. Analysis of Variance
(ANOVA) was used to compare mean values. Pearson correlation was applied
to correlate between the parameters.
RESULTS AND DISCUSSION
As shown in the Table 1, serum total cholesterol,
triglycerides, low density lipoprotein were elevated (p<0.01) and high
density lipoprotein and paraoxonase levels were significantly low (p<0.01)
in group 1 cases compared to healthy controls. There was significant decrease
in total cholesterol, triglycerides, low density lipoprotein (p<0.01)
and increase in high density lipoprotein (p<0.01) in group 2 cases
compared to group 1 cases. Serum paraoxonase activity improved significantly
in group 2 cases compared (p<0.01). There was positive correlation
between high density cholesterol and paraoxonase activity in group 2 cases
(R = 0.347, p<0.01) (Fig. 1).
||Serum paraoxonase and lipid profile parameters in healthy controls,
cases before treatment (group 1) and three months after treatment
|Values were expressed mean±SD, *: p<0.01 compared
to healthy controls, **: p<0.01 compared to group 1 cases
||Serum paraoxonase activity (U L-1) in health control
and hyperilidemic patients before and after treatment (1) healthy
control, (2) hyperlipidemics before treatment and (3) hyperlipidemics
three month after treatment
||Correlation between paraoxonase and high density lipoprotein three
months after treatment with atorvastatin
In present study we found significant decrease in paraoxonase activity
in hyperlipidemia patients. This decrease in paraoxonase activity may
be associated with decrease in levels of high density lipoproteins, as
this enzyme is associated with high density lipoproteins. Thus decrease
in paraoxonase activity and increase in low density lipoproteins in hyperlipidemia
may be favorable for atherogenesis process, thus predisposing them for
premature coronary artery disease. The exact mechanism of anti-atherogenic
function of high density lipoproteins and its associated components is
not clear at present but the role of high density lipoprotein associated
paraoxonase activity in this process is increasingly stressed in recent
times (Watson et al., 1995).
Statins, a 3-hydroxy methyl glutaryl Coenzyme A reductase inhibitors
are drugs of choice in different types of hyperlipidemia especially their
role in favorably improving lipid profile. In our study, atorvastatin
apart from favorably improving the lipid profile, it also improved the
activity of paraoxonase (Fig. 1). This improvement in
paraoxonase activity correlated positively with increased high density
lipoproteins level (Fig. 2). Previous authors found
improvement of paraoxonase activity with fenofibrates (Paragh et al.,
2003). The improvement in paraoxonase activity by fenofibrates was due
to induction of paraoxonase 1 gene promoter activation by fibrates (Gouedadr
et al., 2003). We found improvement in paraoxonase activity on
treatment with atorvastatin for three months in hyperlipidemic patients
and it may implicates the role of statins in improving the paraoxonase
activity and there by decreasing the rate of atrherogenesis in this population.
However, long term follow-up studies are required to know the outcome
of such treatment and it also requires specially designed study to understand
the molecular mechanisms of statin in improving paraoxonase activity.
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