The effects of lipid-lowering therapy on paraoxonase activities and their relationships with the oxidant???antioxidant system in patients with dyslipidemia

A prospective study to assess the role of paraoxonase 1 genotype and phenotype on the lipid-lowering and antioxidant activity of statins

Human paraoxonase 1 (PON1) enzyme protects against atherosclerosis by preventing low-density lipoprotein from oxidative modification. Upregulation of PON1 enzymatic activity is suggested to contribute to atheroprotective potential of statins. Glutamine (Q) to arginine (R) at site 192 and leucine (L) to methionine (M) substitution at site 55 polymorphisms influence the PON1 activity. The study assessed the role of PON1 polymorphisms on lipid-lowering and PON1-modulating activity of statins in a Western Indian cohort of patients with dyslipidemia. Lipid profile and PON1 activity were determined at baseline and 3 months after initiation of statin treatment. PON1 genotypes (QQ, QR, RR; LL, LM, and MM) were determined by PCR-RFLP. Paraoxon was used as a substrate for assessing PON1 activity by spectrophotometry. A total of 140 statin-naïve patients were enrolled; of them, 116 were available for final analysis. Fifty-seven (50%) had QQ, 39 (35%) had QR, and 17 (15%) had RR genotypes. Seventy-six (67%) patients had LL, 35 (31%) had LM, and 2 (2%) had MM genotypes. We observed no impact of PON1 polymorphisms on lipid parameters posttreatment. A significant increase was observed in the serum PON1 activity from a median (range) of 47.92 U/L (9.03-181.25) to 72.22 U/L (7.64-244.44) (P < 0.05) following statin treatment, which was independent from high-density lipoprotein (HDL) concentration. This increase was significantly greater in QQ compared to QR and RR genotypes (P = 0.01). To conclude, the important antioxidant properties of statins are exerted via the rise in serum PON1 activity, independent of HDL cholesterol concentrations. The increase was greater in individuals with QQ genotype. Future large-scale studies will validate the premise that QQ homozygotes see added benefits from statin treatment compared to R carriers. In the meantime, PON1 enzymatic activity remains an important marker to be measured while assessing pleotropic effects of statins in CAD.

Mutual Influences between Nitric Oxide and Paraoxonase 1

One of the best consolidated paradigms in vascular pharmacology is that an uncontrolled excess of oxidizing chemical species causes tissue damage and loss of function in the endothelial and subendothelial layers. The fact that high-density lipoproteins play an important role in preventing such an imbalance is integrated into that concept, for which the expression and activity of paraoxonases is certainly crucial. The term paraoxonase (aryldialkyl phosphatase, EC 3.1.8.1) encompasses at least three distinct isoforms, with a wide variation in substrate affinity, cell and fluid localization, and biased expression of polymorphism. The purpose of this review is to determine the interactions that paraoxonase 1 has with nitric oxide synthase, its reaction product, nitric oxide (nitrogen monoxide, NO), and its derived reactive species generated in an oxidative medium, with a special focus on its pathological implications.

Effect of statin treatment on circulating malondialdehyde concentrations: a systematic review and meta-analysis

Background

The effect of statins on oxidative stress markers, such as malondialdehyde (MDA), is still a matter of debate. We sought to address this issue by conducting a systematic review and meta-analysis of published data on the effect of statin treatment on systemic MDA concentrations.

Methods

A literature search was conducted on MEDLINE/PubMed, ISI Web of Sciences and Scopus. Data were pooled using a random-effects model.

Results

A total of 35 studies assessing MDA concentrations before and after statin treatment in 1512 participants (mean age 53.6 years, 48.7% males) were identified. Extreme between-study heterogeneity was observed (I² = 96.0%, p < 0.001). Pooled standardized mean difference (SMD) showed a significant reduction in plasma MDA concentrations after treatment (SMD = -1.47 µmol/l, 95% confidence interval = -1.89 to -1.05 μmol/l; p < 0.001). Similarly, a subgroup analysis of 10 studies that also included a placebo group showed a significant reduction in plasma MDA concentrations with statins (-1.03 μmol/l, 95% confidence interval = -1.52 to -0.29 μmol/l; p = 0.036).

Conclusions

This systematic review and meta-analysis showed that statin treatment significantly reduces systemic MDA concentrations. However, the results should be interpreted with caution because of extreme between-study heterogeneity, which warrants further intervention studies.

Therapeutic effect of simvastatin on DMBA-induced breast cancer in mice

Preclinical studies have shown positive effects of statins against specific cancers. This study aimed to determine the therapeutic effect of simvastatin in 12-dimethylbenz(a)anthracene (DMBA)-induced breast cancer. Female albino mice were divided into two groups, with or without DMBA administration. After tumor appearance, DMBA-treated group was further divided into four groups (D1-D4) as control (D1), treated with simvastatin at 80 and 40 mg/kg/day, orally (D2 and D3) and tamoxifen (50 mg/kg/day, orally) treated group (D4). After 4 weeks, animals were sacrificed, serum samples were collected and tumors were dissected for histopathological study and determination of selected parameters. The tumor marker carcinoma antigen 15-3 (CA15-3), oxidative stress parameters and prostaglandin E2 (PGE2) levels were analyzed in serum and tumors in experimental groups. Tamoxifen and high dose of simvastatin improved parameters of mammary carcinogenesis including mean tumor volume, body weight and percent of mortality as compared to mice with breast tumors without treatment (D1). Additionally, simvastatin usage increased total antioxidant capacity (TAC) level, paraoxonase 1 (PON1) activity in serum and decreased total oxidant status (TOS) and malondialdehyde (MDA) levels in tumors similar to tamoxifen. No significant decrease was found in serum CA 15-3 and tumor PGE2 levels in simvastatin and tamoxifen treated groups as compared to D1 group. These data suggest that simvastatin has anticancer effects which are relatively similar to that of tamoxifen in an animal model of breast cancer.

Serum Endocan Levels are Associated With Paraoxonase 1 Concentration in Patients With Chronic Kidney Disease

Endocan is a soluble proteoglycan released by the vascular endothelium. The increase of its serum levels is associated with inflammation, endothelial dysfunction and cardiovascular events in patients with chronic kidney disease (CKD). We studied the association of serum endocan with the lipid profile of 105 CKD patients with dyslipidemia, divided in two groups, non-dialyzed (CKD, N = 57) and hemodialysis (HD, N = 48) in comparison with 30 normal controls (NC). We also analyzed endocan in relation with the concentration of two serum HDL-linked members of the paraoxonase (PON) family, PON1 and PON3, which have been previously found to have antiatherogenic properties. The results showed that endocan levels were significantly higher in HD patients than in CKD patients (P < 0.001) and NC (P < 0.001). PON1 was significantly decreased only in HD patients compared to NC (P < 0.001), whereas PON3 was significantly increased in both patient groups (P < 0.001). Endocan levels were significantly and positively correlated with total cholesterol and LDL-C in CKD and additionally were negatively correlated with HDL-C in HD group. PON1 levels were significantly correlated with endocan in both groups, while no correlation was observed for PON3 in either group. Multiple regression analysis between endocan and the above lipid parameters in the total of patients revealed that endocan was independently associated only with PON1 (β = -0.513, P = 0.002). It is concluded that the increase of serum endocan levels in patients with CKD may be associated with the decrease of PON1 concentration, irrespective of lipid alterations produced by atherosclerosis development.

Ameliorative effect of statin therapy on oxidative damage in heart tissue of hypercholesterolemic rabbits

The aim of this study was to investigate the effects of a high-cholesterol diet in the presence and absence of statin on Cu-Zn-superoxide dismutase (Cu,Zn-SOD), malondialdehyde (MDA), protein carbonyl (PCO), and nitric oxide (NO) of blood and heart tissue, the antioxidant activity of serum paraoxonase-1 (PON-1), and on the blood lipid profile of rabbits. The animals were divided into four groups each of which included 10 rabbits. Rabbits in group 1 received a regular rabbit chow diet (normal diet) for 8 weeks; those in group 2 received atorvastatin (0.3 mg atorvastatin per day/kg body weight) for 8 weeks; those in group 3 received high-cholesterol diet for 8 weeks; and those in group 4 received high-cholesterol diet for 4 weeks, a high-cholesterol diet + atorvastatin (0.3 mg atorvastatin per day/kg body weight) for 8 weeks. The parameters were measured by spectrophotometric methods. As expected, the atherogenic diet caused a pronounced increase in lipid profile (not HDL) parameters. Rabbits in group 3 showed higher PCO, MDA, and NO levels in circulating and heart tissue compared to the rabbits in group 1. Atorvastatin has prevented or limited LDL oxidation and has showed constitutively beneficial effects in group 4. Increased LDL-C, PCO, MDA, and NO levels leading to decreasing PON-1 activity thus create a predisposition to atherogenesis in this model. But atorvastatin administration partly ameliorated oxidative damage in heart injury of hypercholesterolemic rabbits. Atorvastatin which functions as a potent antioxidant agent may inhibit this LDL-C oxidation by increasing PON-1 activity in atherogenesis.

Antioxidant and lipid-regulating effects of probucol combined with atorvastatin in patients with acute coronary syndrome

OBJECTIVE

To investigate the effects of probucol combined with atorvastatin on the serum oxidation index and lipid levels in patients diagnosed with acute coronary syndrome (ACS).

METHODS

We randomly assigned 126 ACS patients (77 males and 49 females) to the control group (atorvastatin 20 mg/day, n=62) or the treatment group (atorvastatin 20 mg/day and probucol 750 mg/day, n=64). All the patients were followed up for 12 weeks. As oxidization indices, we measured the serum levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), oxidized LDL (ox-LDL), and paraoxonase-1 (PON1) before and after treatment. We also monitored the adverse effects of the drugs during the treatment.

RESULTS

At baseline, there were no obvious differences (P>0.05) between the two groups (including age, gender, etc.). After 12 weeks of treatment, the ox-LDL levels in the treatment group were significantly lower while PON1 levels were significantly higher than those in the control group. There were no statistically significant difference between the two groups with respect to the side effects (P<0.05).

CONCLUSIONS

The combined use of atorvastatin and probucol in ACS patients could reduce ox-LDL expression and increase PON1 expression more effectively than use atorvastatin alone.

Lipid-lowering efficacy of atorvastatin

BACKGROUND

This represents the first update of this review, which was published in 2012. Atorvastatin is one of the most widely prescribed drugs and the most widely prescribed statin in the world. It is therefore important to know the dose-related magnitude of effect of atorvastatin on blood lipids.

OBJECTIVES

Primary objective To quantify the effects of various doses of atorvastatin on serum total cholesterol, low-density lipoprotein (LDL)-cholesterol, high-density lipoprotein (HDL)-cholesterol and triglycerides in individuals with and without evidence of cardiovascular disease. The primary focus of this review was determination of the mean per cent change from baseline of LDL-cholesterol. Secondary objectives • To quantify the variability of effects of various doses of atorvastatin.• To quantify withdrawals due to adverse effects (WDAEs) in placebo-controlled randomised controlled trials (RCTs).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 11, 2013), MEDLINE (1966 to December Week 2 2013), EMBASE (1980 to December Week 2 2013), Web of Science (1899 to December Week 2 2013) and BIOSIS Previews (1969 to December Week 2 2013). We applied no language restrictions.

SELECTION CRITERIA

Randomised controlled and uncontrolled before-and-after trials evaluating the dose response of different fixed doses of atorvastatin on blood lipids over a duration of three to 12 weeks.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility criteria for studies to be included and extracted data. We collected information on withdrawals due to adverse effects from placebo-controlled trials.

MAIN RESULTS

In this update, we found an additional 42 trials and added them to the original 254 studies. The update consists of 296 trials that evaluated dose-related efficacy of atorvastatin in 38,817 participants. Included are 242 before-and-after trials and 54 placebo-controlled RCTs. Log dose-response data from both trial designs revealed linear dose-related effects on blood total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides. The Summary of findings table 1 documents the effect of atorvastatin on LDL-cholesterol over the dose range of 10 to 80 mg/d, which is the range for which this systematic review acquired the greatest quantity of data. Over this range, blood LDL-cholesterol is decreased by 37.1% to 51.7% (Summary of findings table 1). The slope of dose-related effects on cholesterol and LDL-cholesterol was similar for atorvastatin and rosuvastatin, but rosuvastatin is about three-fold more potent. Subgroup analyses suggested that the atorvastatin effect was greater in females than in males and was greater in non-familial than in familial hypercholesterolaemia. Risk of bias for the outcome of withdrawals due to adverse effects (WDAEs) was high, but the mostly unclear risk of bias was judged unlikely to affect lipid measurements. Withdrawals due to adverse effects were not statistically significantly different between atorvastatin and placebo groups in these short-term trials (risk ratio 0.98, 95% confidence interval 0.68 to 1.40).

AUTHORS' CONCLUSIONS

This update resulted in no change to the main conclusions of the review but significantly increases the strength of the evidence. Studies show that atorvastatin decreases blood total cholesterol and LDL-cholesterol in a linear dose-related manner over the commonly prescribed dose range. New findings include that atorvastatin is more than three-fold less potent than rosuvastatin, and that the cholesterol-lowering effects of atorvastatin are greater in females than in males and greater in non-familial than in familial hypercholesterolaemia. This review update does not provide a good estimate of the incidence of harms associated with atorvastatin because included trials were of short duration and adverse effects were not reported in 37% of placebo-controlled trials.

Comparison of the effects of escitalopram and atorvastatin on diet-induced atherosclerosis in rats

Atherosclerosis is one of the most common disorders among the elderly. Depression may be associated with the development of atherosclerosis. Thus, the aim of this study is to evaluate and compare the effects of escitalopram (a selective serotonin reuptake inhibitor) with atorvastatin (a well known antihyperlipidemic drug) on high fat diet induced atherosclerosis in rats. The results of this study showed that the administration of either escitalopram or atorvastatin for 6 weeks was associated with a significant decrease in serum levels of total cholesterol, triglycerides, low density lipoproteins, very low density lipoproteins, and serum malondialdehyde, and a significant increase in high density lipoproteins when compared with the atherosclerosis model group. Histopathological examination of the aortas from the test rats revealed significant regression of atherosclerotic changes, together with a significant decrease in vascular cell adhesion molecule-1 (VCAM-1) expression in the media of both the escitalopram group and the atorvastatin group when compared with the atherosclerosis model group. This study has shown that escitalopram reduced atherosclerotic changes, thus its use as an antidepressant in elderly patients should be considered.

Implication of low HDL-c levels in patients with average LDL-c levels: a focus on oxidized LDL, large HDL subpopulation, and adiponectin

To evaluate the impact of low levels of high density lipoprotein cholesterol (HDL-c) on patients with LDL-c average levels, focusing on oxidative, lipidic, and inflammatory profiles. Patients with cardiovascular risk factors (n = 169) and control subjects (n = 73) were divided into 2 subgroups, one of normal HDL-c and the other of low HDL-c levels. The following data was analyzed: BP, BMI, waist circumference and serum glucose Total-c, TGs, LDL-c, oxidized LDL, total HDL-c and subpopulations (small, intermediate, and large), paraoxonase-1 (PON1) activity, hsCRP, uric acid, TNF-α, adiponectin, VEGF, and iCAM1. In the control subgroup with low HDL-c levels, significantly higher values of BP and TGs and lower values of PON1 activity and adiponectin were found, versus control normal HDL-c subgroup. However, differences in patients' subgroups were clearly more pronounced. Indeed, low HDL-c subgroup presented increased HbA1c, TGs, non-HDL-c, Ox-LDL, hsCRP, VEGF, and small HDL-c and reduced adiponectin and large HDL. In addition, Ox-LDL, large-HDL-c, and adiponectin presented interesting correlations with classical and nonclassical markers, mainly in the normal HDL-c patients' subgroup. In conclusion, despite LDL-c average levels, low HDL-c concentrations seem to be associated with a poor cardiometabolic profile in a population with cardiovascular risk factors, which is better evidenced by traditional and nontraditional CV biomarkers, including Ox-LDL, large HDL-c, and adiponectin.

Implications of serum paraoxonase activity in obesity, diabetes mellitus, and dyslipidemia

Human serum paraoxonase 1 (PON1) is an enzyme with esterase activity, and is physically bound to high-density lipoproteins (HDL). It plays a key role in the action of HDL toward protection of lipoprotein and biological membrane against oxidative damage. It may have a protective role against atherosclerosis by virtue of its action on hydrolyzing lipid peroxides and preventing accumulation of phospholipids in oxidized low-density lipoprotein (LDL). PON1 is hypothesized to be an indicator of the risk of atherosclerosis and coronary artery disease development. Numerous studies have implicated PON1 activity in relation to various endocrine disorders. The current article reviews the clinical perspectives of PON1 activity with regards to obesity, diabetes mellitus with its complications, and dyslipidemia.

Lipid lowering efficacy of atorvastatin

BACKGROUND

Atorvastatin is one of the most widely prescribed drugs and the most widely prescribed statin in the world. It is therefore important to know the dose-related magnitude of effect of atorvastatin on blood lipids.

OBJECTIVES

To quantify the dose-related effects of atorvastatin on blood lipids and withdrawals due to adverse effects (WDAE).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library Issue 4, 2011, MEDLINE (1966 to November 2011), EMBASE (1980 to November 2011), ISI Web of Science (1899 to November 2011) and BIOSIS Previews (1969 to November 2011). No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled and uncontrolled before-and-after trials evaluating the dose response of different fixed doses of atorvastatin on blood lipids over a duration of 3 to 12 weeks.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. WDAE information was collected from the placebo-controlled trials.

MAIN RESULTS

Two hundred fifty-four trials evaluated the dose-related efficacy of atorvastatin in 33,505 participants. Log dose-response data revealed linear dose-related effects on blood total cholesterol, low-density lipoprotein (LDL)-cholesterol and triglycerides. Combining all the trials using the generic inverse variance fixed-effect model for doses of 10 to 80 mg/day resulted in decreases of 36% to 53% for LDL-cholesterol. There was no significant dose-related effects of atorvastatin on blood high-density lipoprotein (HDL)-cholesterol. WDAE were not statistically different between atorvastatin and placebo for these short-term trials (risk ratio 0.99; 95% confidence interval 0.68 to 1.45).

AUTHORS' CONCLUSIONS

Blood total cholesterol, LDL-cholesterol and triglyceride lowering effect of atorvastatin was dependent on dose. Log dose-response data was linear over the commonly prescribed dose range. Manufacturer-recommended atorvastatin doses of 10 to 80 mg/day resulted in 36% to 53% decreases of LDL-cholesterol. The review did not provide a good estimate of the incidence of harms associated with atorvastatin because of the short duration of the trials and the lack of reporting of adverse effects in 37% of the placebo-controlled trials.

Additional Common Polymorphisms in the PON Gene Cluster Predict PON1 Activity but Not Vascular Disease

Background. Paraoxonase 1 (PON1) enzymatic activity has been consistently predictive of cardiovascular disease, while the genotypes at the four functional polymorphisms at PON1 have not. The goal of this study was to identify additional variation at the PON gene cluster that improved prediction of PON1 activity and determine if these variants predict carotid artery disease (CAAD). Methods. We considered 1,328 males in a CAAD cohort. 51 tagging single-nucleotide polymorphisms (tag SNPs) across the PON cluster were evaluated to determine their effects on PON1 activity and CAAD status. Results. Six SNPs (four in PON1 and one each in PON2/3) predicted PON1 arylesterase (AREase) activity, in addition to the four previously known functional SNPs. In total, the 10 SNPs explained 30.1% of AREase activity, 5% of which was attributable to the six identified predictive SNPs. We replicate rs854567 prediction of 2.3% of AREase variance, the effects of rs3917510, and a PON3 haplotype that includes rs2375005. While AREase activity strongly predicted CAAD, none of the 10 SNPs predicting AREase predicted CAAD. Conclusions. This study identifies new genetic variants that predict additional PON1 AREase activity. Identification of SNPs associated with PON1 activity is required when evaluating the many phenotypes associated with genetic variation near PON1.

Naringenin is an inhibitor of human serum paraoxonase (PON1): an in vitro study

BACKGROUND

Inhibition studies on PON1 as an organophosphate-hydrolyzing and atheroprotective enzyme could be useful in elucidating the function of PON1. This study is aimed at examining the in vitro effects of the flavonoid naringenin on PON1 activity in human serum and purified enzyme.

METHODS

The inhibition kinetics of the interaction of naringenin with human PON1 in serum and purified enzyme was determined spectrophotometrically using paraoxon and phenylacetate as the substrates.

RESULTS

Naringenin could be introduced as an effective inhibitor on purified human PON1 activity for phenylacetate as the substrate with an IC(50) value of 10 µM. Paraoxonase and arylesterase activities of PON1, in the serum assay, were also inhibited by naringenin with IC(50) values of 37.9 and 34.6 µM, respectively. PON1, according to acompetitive-type inhibition pattern, was inhibited by naringenin with K(i) constant of 14.5 µM for serum paraoxonase activity. The results were compared with a known inhibitor of PON1, 2-hydroxyquinoline. We believe (to our knowledge) that this is the first reported study for kinetic parameters of PON1 inhibition by naringenin.

CONCLUSIONS

Lipophilic property appears to be an important feature of the structure in evaluating the inhibitor potential. Comparison of our findings and other authors showed that the induction of PON1 gene by naringenin and its inhibitory effects on the enzyme protein are probably two different mechanisms by which the flavonoid affects PON1. The in vitro data reported in this study could be useful in the development of structure-activity relationship for PON1 inhibition.

Effects of combining simvastatin with rosiglitazone on inflammation, oxidant stress and ambulatory blood pressure in patients with the metabolic syndrome: the SIROCO study

AIM

Individually, statins and thiazolidinediones (TZDs) show positive effects on atherosclerosis progression in cellular and animal models as well as patients with diabetes; however, their combined effects have not been studied. This study examines the effects of simvastatin combined with rosiglitazone on vascular inflammation, oxidant stress, ambulatory blood pressure (BP) and other atherosclerotic factors in patients with the metabolic syndrome.

METHODS

This is a randomized, double blind, placebo-controlled study in 53 subjects with the metabolic syndrome. Participants were randomized to simvastatin 40 mg/day plus placebo vs. simvastatin 40 mg/day plus rosiglitazone 4 mg/day for 6 months. The primary endpoint was the between-group difference in high-sensitivity C-reactive protein (hs-CRP) and secondary variables including urinary isoprostanes, serum malondialdehyde (MDA), ambulatory BP, adiponectin, and lipid and glycaemic profiles.

RESULTS

At study end, the group randomized to the simvastatin/rosiglitazone combination had a greater reduction in hs-CRP of 1.33 mg/dl, (p = 0.029) and showed a trend for a greater reduction in urinary isoprostane (-39%), (p = 0.056) compared to simvastatin/placebo group. Changes in MDA levels did not differed between groups (p = 0.81). 24-h systolic blood pressure (SBP) also showed a 4.5 mmHg reduction at 6 months (p = 0.06). Adiponectin levels increased by 3.91 µg/ml in the combination group over placebo, (p = 0.03) and blood glucose decreased in combination group vs. placebo.

CONCLUSION

Our data show that patients with the metabolic syndrome given a statin/TZD combination manifest greater reductions in markers of vascular inflammation and oxidant stress, 24-h ambulatory BP and increases in adiponectin as well as improved glycaemic indices.

Effect of atorvastatin therapy on oxidant-antioxidant status and atherosclerotic plaque formation

Background:

The aim of this study was to determine the oxidant–antioxidant status and lipid peroxidation products, as well as paraoxonase and atherosclerotic plaque formation, in a hypercholesterolemic atherosclerosis rabbit model to investigate the effects of atorvastatin in the atherosclerotic process.

Methods:

Forty male New Zealand rabbits were divided into four groups, ie, a control group receiving standard pellets, a group receiving atorvastatin therapy, a hypercholesterolemic group receiving an atherogenic diet, and a group receiving both an atherogenic diet and atorvastatin.

Results:

The atherogenic diet increased the levels of low-density lipoprotein (LDL) thiobarbituric acid reactive substances (1.84 vs 3.79 nmol/mg protein) and LDL-conjugated diene (147 vs 318 μmol/mg protein) after induction of oxidation by Cu²⁺, despite an increase of superoxide dismutase activity. Treatment with atorvastatin limited LDL oxidation significantly (LDL thiobarbituric acid reactive substances 2.19 nmol/mg protein, LDL-conjugated diene 222 μmol/mg protein). Paraoxonase, which prevents LDL oxidation and inactivates LDL-derived oxidized phospholipids, showed a pronounced decrease in the group receiving the atherogenic diet (110 U/L to 28 U/L), and atorvastatin treatment increased paraoxonase activity. Histological examination of arcus aorta tissues from the hypercholesterolemic group showed abundant plaque formation surrounding and obstructing the lumen, whereas treatment with atorvastatin prevented or limited plaque formation, keeping the plaque thin and localized.

Conclusion:

Atorvastatin has dramatic antiatherosclerotic effects, part of which seems to be due to the antioxidant features of the parent drug and/or its metabolites, favoring inhibition of LDL oxidation.

Effect of HDL composition and particle size on the resistance of HDL to the oxidation

Objectives

To study the resistance of HDL particles to direct oxidation in respect to the distribution of HDL particles.

Design and Methods

We studied HDL composition, subclass distribution, and the kinetics of CuSO₄-induced oxidation of total HDL and HDL₃ in vitro in 36 low-HDL-C subjects and in 41 control subjects with normal HDL-C.

Results

The resistance of HDL₃ to oxidation, as assessed from the propagation rate was significantly higher than that of total HDL. The propagation rate and diene formation during HDL oxidation in vitro was attenuated in HDL derived from low-HDL-C subjects. Propagation rate and maximal diene formation during total HDL oxidation correlated significantly with HDL mean particle size. The propagation rate of total HDL oxidation in vitro displayed a significant positive association with HDL₂ particle mass and HDL mean particle size by multiple regression analyses.

Conclusions

These observations highlight that the distribution of HDL subpopulations has important implications for the potential of HDL as an anti-oxidant source.

Modulating effect of atorvastatin on paraoxonase 1 activity in type 2 diabetic Egyptian patients with or without nephropathy

The aim of this study was to investigate the modulating effect of atorvastatin on serum paraoxonase 1 enzyme (PON1) activity in type 2 diabetic Egyptian patients with or without nephropathy. The present study was carried out on the following groups: control group, which consisted of 30 healthy persons; Group I, which consisted of 20 type 2 diabetic patients without nephropathy; and Group II, which consisted of 20 type 2 diabetic patients with nephropathy. All the patients selected were under an antidiabetic regimen of insulin, and patients receiving antihypertensive agents were excluded from the follow-up study to avoid drug interaction fallacies. Twenty-two patients (15 without nephropathy and seven with nephropathy) received atorvastatin in individually adjusted oral dosage (range 10-20 mg) once per day for 12 weeks. All cases were subjected to thorough clinical examination and history taking and measurement of serum levels of PON1 activity, malondialdehyde (MDA), glutathione reductase activity, fasting glucose, total cholesterol, triglycerides, high-density lipoprotein (HDL), low-density lipoprotein (LDL), urea, and creatinine. Urine samples were collected for determination of proteinuria. The obtained results showed that PON1 activity and HDL significantly decreased and fasting glucose significantly increased in Group I and Group II when compared to the control group, with significant difference in their levels between Group II and Group I. MDA, total cholesterol, and LDL levels significantly increased and glutathione reductase activity significantly decreased in Group I and Group II when compared to the control group. Urea, creatinine, and proteinuria levels showed significant increase in Group II when compared to the control group and Group I, with nonsignificant difference between control group and Group I. Atorvastatin therapy caused a significant increase in PON1 activity, and serum levels of MDA and glutathione reductase activity were significantly decreased and increased, respectively. Also, total cholesterol, triglyceride and LDL-cholesterol levels were significantly reduced with a significant increase in HDL-cholesterol levels. There was a significant modest reduction in serum urea and creatinine levels as well as in proteinuria level. Fasting glucose level was significantly reduced under the antidiabetic regimen of insulin through the follow-up period. PON1 activity showed a significant negative correlation with glucose and LDL, and a significant positive correlation with HDL in all the studied groups. It could be concluded that atorvastatin with its pleiotropic effects could provide optimal therapeutic intervention to control not only dyslipidemia, but also oxidative stress status with consequent improvement in the course of type 2 diabetes and diabetic nephropathy. More specifically, restoration of PON1 activity by atorvastatin opens a window to investigate other drugs that could provide a new adjuvant therapeutic line for better control of diabetes and diabetic nephropathy. Further research is also recommended to study the distribution of PON1 genetic polymorphism among the Egyptian population to explain the variability in its activity and its relationship with other factors that associate diabetes and its complications.

Single intravenous injection of plasmid DNA encoding human paraoxonase-1 inhibits hyperlipidemia in rats

Paraoxonase-1 (PON1, EC 3.1.8.1) is a high-density lipoprotein (HDL)-associated antioxidant enzyme, and its activity correlates negatively with the level of plasma low-density lipoprotein cholesterol (LDL-C) and triglyceridemia (TG). In this study, we examined the therapeutic effect of plasmid DNA containing the human PON1 gene (pcDNA/PON1) in hyperlipidemic model rats. The rats were fed a high-fat and high-cholesterol diet for 25 days to produce a hyperlipidemic animal model. Single intravenous injection of pcDNA/PON1 into model rats prevented dyslipidemia and hepatic lipid accumulation. The mechanisms of pcDNA/PON1 in treating hyperlipidemia were associated with increases of serum antioxidant PON1 and SOD activities, and with reduction of the levels of total cholesterol (TC), LDL-C and TG. The results suggest the potential therapeutic effect of pcDNA/PON1 on hyperlipidemia.

Benefits and difficulties in measuring HDL subfractions and human paraoxonase-1 activity during statin treatment

Dyslipidaemia including decreased high density lipoprotein cholesterol concentration is one of several factors that have been implicated in increased cardiovascular risk. Since their introduction in the 1980s, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have emerged as the one of the best-selling class of medications to date, with numerous trials demonstrating powerful efficacy in preventing cardiovascular diseases. Although statins have been shown to modestly raise or not alter HDL-cholesterol, their effect on HDL subfractions and on HDL-associated enzymes including human paraoxonase-1 (PON1) has not yet been fully explored. This review summarizes the currently available data on the effect of statins on HDL subfractions and on PON1 activity with a particular emphasis on the clinical relevance of these effects. Moreover, methodological problems of HDL subfraction and PON1 activity determinations are also discussed.

Amyotrophic lateral sclerosis-like conditions in possible association with cholesterol-lowering drugs: an analysis of patient reports to the University of California, San Diego (UCSD) Statin Effects Study

BACKGROUND

While cases of amyotrophic lateral sclerosis (ALS) or ALS-like conditions have arisen in apparent association with HMG-CoA reductase inhibitors ('statins') and/or other lipid-lowering drugs (collectively termed 'statins' in this paper for brevity), additional information is needed to understand whether the connection may be causal. The University of California, San Diego (UCSD) Statin Effects Study is a patient-targeted adverse event surveillance project focused on lipid-lowering agents, whose aim is to capitalize on patient reporting to further define characteristics and natural history of statin adverse effects (AEs), and to ascertain whether a patient-targeted surveillance system might lead to presumptive identification of previously unrecognized AEs. ALS was a candidate 'new' AE identified through this process. The aim of the analysis presented here was to examine characteristics and natural history of reported statin-associated ALS-like conditions with attention to factors that may bear on the issue of causality.

METHODS

For the present analysis, we focused on cases of statin-associated ALS that were reported to our study group prior to publication of a possible statin-ALS association. Of 35 identified subjects who had contacted the UCSD Statin Effects Study group to report ALS or an ALS-like condition, 18 could not be reached (e.g. contact information was no longer valid). Six were unable to participate (e.g. due to progression of their disease). Of the 11 who could be contacted and were able to participate, one declined to give informed consent. The remaining ten, with either a formal or probable diagnosis of ALS in the context of progressive muscle wasting/weakness arising in association with lipid-lowering drug therapy, completed a mail or phone survey eliciting information about ALS symptom onset and change in association with drug use/modification and development of statin-associated AEs. We reviewed findings in the context of literature on statin antioxidant/pro-oxidant balance, as well as ALS mechanisms involving oxidative stress and mitochondrial dysfunction.

RESULTS

All ten subjects reported amelioration of symptoms with drug discontinuation and/or onset or exacerbation of symptoms with drug change, rechallenge or dose increase. Three subjects initiated coenzyme Q10 supplementation; all reported initial benefit. All subjects reportedly developed statin AEs (not indicative of ALS) prior to ALS symptom onset, strongly disproportionate to expectation (p < 0.001). Since this reflects induction of pro-oxidant effects from statins, these findings lend weight to a literature-supported mechanism by which induction by statins of oxidative stress with amplification of mitochondrial dysfunction, arising in a vulnerable subgroup, may propel mechanisms underlying both AEs and, more rarely, ALS.

CONCLUSION

A theoretical foundation and preliminary clinical observations suggest that statins (and other lipid-lowering drugs) may rarely be associated with ALS in vulnerable individuals in whom pro-oxidant effects of statins predominate. Our observations have explanatory relevance extending to ALS causes that are not statin associated and to statin-associated neurodegenerative conditions that are not ALS. They suggest means for identification of a possible vulnerable subgroup. Indeed whether statins may, in contrast, confer ALS protection when antioxidant effects predominate merits examination.

The antiatherogenic function of HDL is impaired in hyperhomocysteinemic subjects

High plasma homocysteine concentrations have been associated with increased risk of cardiovascular disease, whereas plasma HDL concentration is inversely correlated to such disorders. We hypothesized that hyperhomocysteinemic subjects may have dysfunctional HDL. We therefore investigated the ability of serum from hyperhomocysteinemic male and female subjects (n = 10) and control subjects (n = 10) to induce cholesterol efflux and to inhibit release of inflammatory mediators from human umbilical vein endothelial cell. We found that serum from hyperhomocysteinemic subjects had impaired ability to induce cholesterol efflux from lipid-loaded macrophages compared with healthy controls. HDL from those with markedly raised homocysteine concentrations had a reduced antiinflammatory effect in tumor necrosis factor-alpha-activated endothelial cells with an attenuated suppressive effect on interleukin-6 growth-related oncogene-alpha release. Also, the activity of paraoxonase in serum, a multifunctional enzyme with antioxidative effects in relation to the function of HDL, was significantly reduced in hyperhomocysteinemic subjects, in particular those with markedly raised homocysteine concentration. Our findings suggest that hyperhomocysteinemic individuals have dysfunctional HDL particles with attenuated antiatherogenic activity and may represent a novel explanation for the increased risk of cardiovascular events in these individuals.

Effect of Statins on Serum Apolipoprotein J and Paraoxonase-1 Levels in Patients With Ischemic Heart Disease Undergoing Coronary Angiography

It has been proposed that apolipoprotein J (apo J) and paraoxonase-1 (PON1) correlate with the extent and severity of ischemic heart disease (IHD). This article compares apo J and PON1 serum concentrations, PON1 activity, and the apo J/PON1 ratio in 138 IHD patients (64 statins users and 74 statin nonusers) referred for angiography and possible percutaneous coronary intervention. The effect of statin treatment on apo J and PON1 concentrations, PON1 activity, and the degree of coronary artery stenosis were evaluated. In both groups, apo J levels were increased, whereas PON1 concentration and activity decreased. IHD patients on statins had significantly lower apo J concentration and higher PON1 concentration and activity. Patients on statins had less coronary artery stenosis. High apo J levels, low PON1 levels, low PON1 activity, and a high apo J/PON1 ratio were associated with IHD. Statin treatment reverses these changes, probably by multiple beneficial actions.

Relation of serum total antioxidant status with metabolic risk factors in Korean adults

The purpose of the present study was to examine the relation of total antioxidant status (TAS) to metabolic risk factors in Korean adults. Anthropometric measures, blood pressure, serum lipids and fasting glucose were determined in 406 men and women. TAS was measured by using commercially available Randox kit. Serum TAS was significantly positively correlated with body weight (p=0.004), body mass index (BMI) (p=0.033), waist circumference (p=0.017), total cholesterol (p=0.038) and triglyceride (TG) (p<0.001). The mean TAS of hypertriglyceridemic subjects (TG ≥150 mg/dl) was significantly higher than that of subjects whose TG was lower than 150 mg/dl (p=0.001). When central obesity, TG, high density lipoprotein cholesterol, fasting glucose and blood pressure were considered as metabolic risk factors, TAS was shown to be elevated with increased number of metabolic risk factors (p=0.004). The positive association between TAS and a number of metabolic risk factors suggests that increased TAS may not always indicate one's healthier condition. In order to help understand TAS as a marker of total antioxidant capacity in humans with various metabolic conditions, it is needed to clarify the factors affecting TAS in relation to changes in metabolic risk factors.

Paraoxonase and arylesterase activities in patients with cardiac syndrome X, and their relationship with oxidative stress markers

OBJECTIVES

Paraoxonase-1 is a high-density lipoprotein-associated enzyme with three activities, which are paraoxonase, arylesterase and dyazoxonase. Paraoxonase-1 was shown to decrease in patients with cardiovascular diseases. We aimed to examine serum paraoxonase and arylesterase activities, and their relation with oxidative stress markers such as lipid hydroperoxide and total antioxidant status in patients with cardiac syndrome X.

METHODS

Forty-one consecutive patients with cardiac syndrome X (CSX group), 33 consecutive patients without cardiac syndrome X (non-cardiac syndrome X group) and 20 healthy volunteers as control group were taken into the study. Serum paraoxonase and arylesterase activities were measured spectrophotometrically. Lipid hydroperoxide levels were measured by ferrous oxidation with xylenol orange assay. Total antioxidant status was determined using an automated measurement method.

RESULTS

Basal paraoxonase, salt-stimulated paraoxonase and arylesterase activities were significantly lower in patients with cardiac syndrome X than those of the non-cardiac syndrome X and control groups (P<0.001, for both). Moreover, lipid hydroperoxide was found at high level, and total antioxidant status was found at low level in patients with cardiac syndrome X than control and non-cardiac syndrome X groups (P<0.001, for all). In patients with cardiac syndrome X, in multiple linear regression analysis, both paraoxonase and arylesterase activities were independently correlated with lipid hydroperoxide levels (P=0.001, P=0.003, respectively), and also arylesterase activity was independently correlated with magnitude of ST depression (P=0.002).

CONCLUSION

Reduced paraoxonase and arylesterase activities and total antioxidant status levels and enhanced lipid hydroperoxide levels in patients with cardiac syndrome X might indicate increased oxidative stress that can play a role in pathogenesis of cardiac syndrome X.

Effect of rosuvastatin versus atorvastatin treatment on paraoxonase-1 activity in men with established cardiovascular disease and a low HDL-cholesterol

OBJECTIVE

Paraoxonase-1 (PON-1) is a high-density lipoprotein (HDL) associated enzyme involved in the protective mechanisms of HDL. Our aim was to compare the effect of treatment with rosuvastatin and atorvastatin on serum PON-1 activity.

METHODS

We performed a prespecified prospective study in 68 patients, part of a larger, multicentre randomized study--RADAR (Rosuvastatin and Atorvastatin in different Dosages And Reverse cholesterol transport). Patients aged 40-80 years, all men, with established cardiovascular disease and high-density lipoprotein cholesterol (HDL-C) < 1.0 mmol/L (< 40 mg/dL) entered a 6-week dietary run-in period before receiving treatment with rosuvastatin 10 mg or atorvastatin 20 mg daily for 6-weeks. Doses were increased after 6 weeks to rosuvastatin 20 mg or atorvastatin 40 mg and after 12 weeks to rosuvastatin 40 mg or atorvastatin 80 mg daily. Serum PON-1 activity and lipid profile were determined at baseline, 6 and 18 weeks.

RESULTS

After 18 weeks, the rosuvastatin arm showed a significant increase of PON-1 activity (6.39 U/L, p = 0.02) whereas this was not observed in the atorvastatin arm (1.84 U/L, p = 0.77). The difference between groups did not reach significance (p = 0.11). Both rosuvastatin and atorvastatin resulted in significant (p = 0.0001) and similar increases in HDL-C after 6 weeks [0.06 mmol/L (2.32 mg/dL) vs. 0.05 mmol/L (1.93 mg/dL)] and after 18 weeks [0.10 mmol/L (3.87 mg/dL) vs. 0.10 mmol/L (3.87 mg/dL)].

CONCLUSIONS

Rosuvastatin treatment resulted in a significant increment of serum PON-1 activity with increasing dose while this was not observed with atorvastatin.

Effects of atorvastatin therapy on hypercholesterolemic rabbits with respect to oxidative stress, nitric oxide pathway and homocysteine

Hypercholesterolemia is characterized with changes in lipid profile, nitric oxide pathway and oxidative stress markers. This study is designed to evaluate the effects of hypercholesterolemic diet and atorvastatin therapy on oxidative stress, lipid peroxide and thiobarbituric acid reactive substances (TBARS), NO pathway markers, nitric oxide(NO) and asymmetric dimethylarginine (ADMA), homocysteine, and paraoxonase activity (PON1) in rabbits. Twenty rabbits fed with high-cholesterol diet for 8 weeks were randomly divided into 2 groups on the fourth week of the hypercholesterolemic diet. First group was fed with high-cholesterol diet alone, whereas the second group with the same cholesterol diet plus atorvastatin (0.3 mg/kg/day) for 4 weeks. High-cholesterol diet increased total cholesterol, low density lipoprotein (LDL-C), high density lipoprotein (HDL-C), ADMA, TBARS and lipid peroxide levels and reduced PON1 activity and NO levels in rabbits. Four weeks of atorvastatin therapy significantly increased HDL-C, PON1 activity and reduced LDL-C, TBARS and lipid peroxide concentrations. Atorvastatin therapy is beneficial in decreasing oxidative stress related with hypercholesterolemia, mainly affecting lipid profile and PON1 activity.

Paraoxonase and arylesterase activities in coronary artery disease

BACKGROUND

Paraoxonase-1 is an enzyme with three activities which are inversely related to cardiovascular diseases. Accordingly, the aim of the study was to investigate the paraoxonase, arylesterase activities and oxidative/anti-oxidative status in coronary artery disease (CAD) and their correlation with the extent of CAD.

MATERIALS AND METHODS

Study populations of 193 patients with angiographically documented CAD, 83 patients with normal coronary angiograms (NCAD) and 55 healthy volunteers were included in the study. The patients with CAD were divided into three categories according to the number of diseased coronaries. Also, a Gensini score was calculated for each patient. Serum paraoxonase and arylesterase activities were measured spectrophotometrically. Oxidative and anti-oxidative status was evaluated by measuring serum lipid hydroperoxide (LOOH), total anti-oxidant status (TAS) and free sulfhydryl groups (-SH = total thiol). Lipid parameters were determined by routine laboratory methods.

RESULTS

Serum paraoxonase and arylesterase activities, TAS and -SH levels were lower in the CAD group compared with the NCAD group and control group (P < 0.05, all). Serum LOOH levels of the CAD group were greater than those in both the control and NCAD groups (P < 0.05). The major decreases in paraoxonase, arylesterase activities, -SH and TAS levels and the major increase in LOOH levels were observed in the 3-vessels disease group. In multiple linear regression analysis, the Gensini score was independently correlated with paraoxonase activity (beta = -0.469, P < 0.001), -SH levels (beta = -0.232, P < 0.001), HDL levels and history of diabetes.

CONCLUSIONS

Both paraoxonase activity and -SH levels are independently associated with the presence and extent of CAD. Reduced paraoxonase activity and -SH levels may play a role in the severity of coronary atherosclerosis.

Inverse correlation of serum paraoxonase and homocysteine thiolactonase activities and antioxidant capacity of high-density lipoprotein with the severity of cardiovascular disease in persons with type 2 diabetes mellitus

Atherosclerotic risk is increased in diabetes partly because of increased plasma levels of the oxidized low-density lipoprotein and homocysteine, 2 independent and important cardiovascular disease (CVD) risk factors. Paraoxonase (PON) is a multifunctional antioxidant enzyme component of high-density lipoprotein (HDL), which can protect against low-density lipoprotein (LDL) oxidation. It also exhibits homocysteine thiolactonase (HCTL) activity that detoxifies homocysteine thiolactone, which can damage proteins by homocysteinylation of the lysine residues, thus leading to atherosclerosis. We conducted a cross-sectional study to correlate PON-1, HCTL activities, and the lag time of LDL oxidation in 15 healthy control subjects and in 55 subjects with type 2 diabetes mellitus with different degrees of CVD. Compared with healthy controls and diabetic subjects without evidence of overt CVD, we not only found 47% (P < .005) decrease in PON-1 activity, but also for the first time, 30% (P = .019) decrease in HCTL activity in subjects with a prior coronary artery bypass surgery. There was corresponding decreased effectiveness of HDLs from diabetic groups (with and without CVD) in protecting against LDL oxidation. Moreover, the PON-1 activity was significantly inversely correlated to the extent of intracoronary lesions determined at catheterization (ie, a high Gensini score). These decreases in PON-1 and HCTL activity were not due to any bias in preferential distribution of low-activity QQ homozygotes in the diabetic groups compared with the control group because QQ allele was equally distributed in all the experimental groups, whereas RR allele tended to increase in the diabetic subjects with coronary artery bypass surgery compared with the other groups. Therefore, clinical intervention to restore the impaired antiatherogenic activities of HDL should be considered an important goal in the treatment of persons with diabetes.

Traditional risk factor assessment does not capture the extent of cardiovascular risk in systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is associated with accelerated atherosclerosis. However, the degree of endothelial dysfunction and its relationship to traditional and novel cardiovascular risk factors have not been examined in SLE.

METHODS

In a case-control design, 35 patients with clinically stable SLE and 35 control subjects matched for age, sex, body mass index and smoking status were studied. Arterial elasticity, lipid profile, homocysteine, measures of inflammation and oxidative stress were determined.

RESULTS

Among traditional vascular risk factors, there was a nonsignificant trend towards lower blood pressure in the control subjects, whereas low-density lipoprotein (LDL) cholesterol levels were significantly lower in the SLE group (2.5 vs 3.3 mmol/L, P < 0.001). Patients with SLE had significantly lower small artery elasticity (SAE; 4.9 vs 7.0 ml/mmHg x 100, P < 0.001) and higher plasma homocysteine (11.4 vs 8.3 mmol/L, P = 0.002) than control subjects. Levels of serum sVCAM-1 (614 vs 494 ng/mL, P = 0.002), oxidized LDL (144 vs 97, P < 0.001) and CD40 ligand (4385 vs 1373 pg/ml, P = 0.001) were significantly higher in SLE. Oxidized LDL levels, older age at SLE diagnosis and higher disease damage scores correlated inversely with SAE but not traditional risk factors.

CONCLUSION

Impaired endothelial function as shown by decreased SAE, and an adverse profile of novel proatherogenic and prothrombotic vascular disease risk factors were prevalent in clinically quiescent SLE. These findings show the vulnerability of patients with SLE for atherosclerosis, and emphasize that assessments based on traditional risk factors alone may be inadequate.

Paraoxonases and cardiovascular diseases: pharmacological and nutritional influences

PURPOSE OF REVIEW

To summarize the new articles published in the last year on paraoxonases, including their expression in cardiovascular diseases, and regulation by pharmacological and nutritional means.

RECENT FINDINGS

The elucidation of the crystal structure of the paraoxonase 1 (PON1) gene, obtained by directed evolution, shows that it consists of a six-bladed beta-propeller with a unique active site. PON1 is present in HDL but also in lipoprotein-deficient serum, in VLDL and in chylomicrons. PON1 protects lipids in lipoproteins, in macrophages and in erythrocytes from oxidation. Cellular PON2 and PON3 were also shown to reduce oxidative stress. Beyond its antioxidative properties, PON1 possesses additional antiatherogenic properties against macrophage foam cell formation: attenuation of cholesterol and oxidized lipids influx, inhibition of macrophage cholesterol biosynthesis and stimulation of macrophage cholesterol efflux. The PON1 gene is regulated by Sp1 and protein kinase C, whereas the PON2 gene in macrophages is regulated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. PON1 activity and mass are both reduced in cardiovascular diseases and the hypocholesterolemic drugs, statins, increase serum PON1 activity (by reducing oxidative stress, or by upregulating hepatic PON1 expression). Expression of cellular PON2, like PON1, was upregulated by statins. Nutritional antioxidants, such as polyphenols, increase PON1 mRNA expression and activity, by an aryl hydrocarbon receptor-dependent mechanism.

SUMMARY

The elucidation of PON1 structure and its active center has enabled a better understanding of its mechanism of action, including its physio-pathological substrate(s). Some drugs and nutrients including dietary antioxidants and polyphenols considerably increase the activities of paraoxonases which, in turn, can reduce oxidative stress and atherosclerosis development.

Paraoxonase-1 (PON-1) genotype and activity and in vivo oxidized plasma low-density lipoprotein in Type II diabetes

The HDL (high-density lipoprotein)-associated enzyme PON (paraoxonase)-1 protects LDL (low-density lipoprotein) from oxidative modification in vitro, although it is unknown if this anti-atherogenic action occurs in vivo. In a cross-sectional study of 58 Type II diabetic subjects and 50 controls, we examined the fasting plasma LDL basal conjugated diene concentration [a direct measurement of circulating oxLDL (oxidatively modified LDL)], lipoprotein particle size by NMR spectroscopy, PON-1 polymorphisms (coding region polymorphisms Q192R and L55M, and gene promoter polymorphisms −108C/T and −162G/A), PON activity (with paraoxon or phenyl acetate as the substrates) and dietary antioxidant intake. Plasma oxLDL concentrations were higher in Type II diabetic patients (males, P=0.048; females, P=0.009) and unrelated to NMR lipoprotein size, PON-1 polymorphisms or PON activity (with paraoxon as the substrate) in any group. In men with Type II diabetes, however, there was a direct relationship between oxLDL concentrations and PON activity (with phenyl acetate as the substrate; r=0.611, P=0.0001) and an atherogenic NMR lipid profile in those who were PON-1 55LL homozygotes. Circulating oxLDL concentrations in vivo were unrelated to PON-1 genotypes or activity, except in male Type II diabetics where there was a direct association between PON activity (with phenyl acetate as the substrate) and oxLDL levels. These in vivo data contrast with in vitro data, and may be due to confounding by dietary fat intake. Male Type II diabetic subjects with PON-1 55LL homozygosity have an atherogenic NMR lipid profile independent of LDL oxidation. These data do not support an in vivo action of PON on LDL oxidation.