Light, but not heavy alcohol drinking, stimulates paraoxonase by upregulating liver mRNA in rats and humans

The Role of Polyphenols in Modulating PON1 Activity Regarding Endothelial Dysfunction and Atherosclerosis

The incidence and prevalence of cardiovascular diseases are still rising. The principal mechanism that drives them is atherosclerosis, an affection given by dyslipidemia and a pro-inflammatory state. Paraoxonase enzymes have a protective role due to their ability to contribute to antioxidant and anti-inflammatory pathways, especially paraoxonase 1 (PON1). PON1 binds with HDL (high-density lipoprotein), and high serum levels lead to a protective state against dyslipidemia, cardiovascular diseases, diabetes, stroke, nonalcoholic fatty liver disease, and many others. Modulating PON1 expression might be a treatment objective with significant results in limiting the prevalence of atherosclerosis. Lifestyle including diet and exercise can raise its levels, and some beneficial plants have been found to influence PON1 levels; therefore, more studies on herbal components are needed. Our purpose is to highlight the principal roles of Praoxonase 1, its implications in dyslipidemia, cardiovascular diseases, stroke, and other diseases, and to emphasize plants that can modulate PON1 expression, targeting the potential of some flavonoids that could be introduced as supplements in our diet and to validate the hypothesis that flavonoids have any effects regarding PON1 function.

Modulatory Effect of Lifestyle-Related, Environmental and Genetic Factors on Paraoxonase-1 Activity: A Review

Paraoxonase-1 (PON1) is a calcium-dependent, HDL-bound serum hydrolase active toward a wide variety of substrates. PON1 displays three types of activities, among which lactonase, paraoxonase, arylesterase and phosphotriesterase can be distinguished. Not only is this enzyme a major organophosphate compound detoxifier, but it is also an important constituent of the cellular antioxidant system and has anti-inflammatory and antiatherogenic functions. The concentration and activity of PON1 is highly variable among individuals, and these differences can be both of genetic origin and be a subject of epigenetic regulation. Owing to the fact that, in recent decades, the exposure of humans to an increasing number of different xenobiotics has been continuously rising, the issues concerning the role and activity of PON1 shall be reconsidered with particular attention to growing pharmaceuticals intake, dietary habits and environmental awareness. In the following manuscript, the current state of knowledge concerning the influence of certain modifiable and unmodifiable factors, including smoking, alcohol intake, gender, age and genotype variation on PON1 activity, along with pathways through which these could interfere with the enzyme's protective functions, is presented and discussed. Since exposure to certain xenobiotics plays a key role in PON1 activity, the influence of organophosphates, heavy metals and several pharmaceutical agents is also specified.

Effect of Carotenoids on Paraoxonase-1 Activity and Gene Expression

Paraoxonase 1 (PON1) is an antioxidant enzyme attached to HDL with an anti-atherogenic potential. It protects LDL and HDL from lipid peroxidation. The enzyme is sensitive to various modulating factors, such as genetic polymorphisms as well as pharmacological, dietary (including carotenoids), and lifestyle interventions. Carotenoids are nutritional pigments with antioxidant activity. The aim of this review was to gather evidence on their effect on the modulation of PON1 activity and gene expression. Carotenoids administered as naturally occurring nutritional mixtures may present a synergistic beneficial effect on PON1 status. The effect of carotenoids on the enzyme depends on age, ethnicity, gender, diet, and PON1 genetic variation. Carotenoids, especially astaxanthin, β-carotene, and lycopene, increase PON1 activity. This effect may be explained by their ability to quench singlet oxygen and scavenge free radicals. β-carotene and lycopene were additionally shown to upregulate PON1 gene expression. The putative mechanisms of such regulation involve PON1 CpG-rich region methylation, Ca(2+)/calmodulin-dependent kinase II (CaMKKII) pathway induction, and upregulation via steroid regulatory element-binding protein-2 (SREBP-2). More detailed and extensive research on the mechanisms of PON1 modulation by carotenoids may lead to the development of new targeted therapies for cardiovascular diseases.

Moderate alcohol consumption and lipoprotein subfractions: a systematic review of intervention and observational studies

CONTEXT

Moderate alcohol consumption is associated with decreased risk of cardiovascular disease (CVD) and improvement in cardiovascular risk markers, including lipoproteins and lipoprotein subfractions.

OBJECTIVE

To systematically review the relationship between moderate alcohol intake, lipoprotein subfractions, and related mechanisms.

DATA SOURCES

Following PRISMA, all human and ex vivo studies with an alcohol intake up to 60 g/d were included from 8 databases.

DATA EXTRACTION

A total of 17 478 studies were screened, and data were extracted from 37 intervention and 77 observational studies.

RESULTS

Alcohol intake was positively associated with all HDL subfractions. A few studies found lower levels of small LDLs, increased average LDL particle size, and nonlinear relationships to apolipoprotein B-containing lipoproteins. Cholesterol efflux capacity and paraoxonase activity were consistently increased. Several studies had unclear or high risk of bias, and heterogeneous laboratory methods restricted comparability between studies.

CONCLUSIONS

Up to 60 g/d alcohol can cause changes in lipoprotein subfractions and related mechanisms that could influence cardiovascular health.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. 98955.

Environmental Factors Modifying HDL Functionality

BACKGROUND

Currently, it has been recognized that High-Density Lipoproteins (HDL) functionality plays a much more essential role in protection from atherosclerosis than circulating HDL-cholesterol (HDL-C) levels per se. Cholesterol efflux from macrophages to HDL, cholesterol efflux capacity (CEC) has been shown to be a key metric of HDL functionality. Thus, quantitative assessment of CEC may be an important tool for the evaluation of HDL functionality, as improvement of HDL function may lead to a reduction of the risk for Cardiovascular disease (CVD).

INTRODUCTION

Although the cardioprotective action of HDLs is exerted mainly through their involvement in the reverse cholesterol transport (RCT) pathway, HDLs also have important anti-inflammatory, antioxidant, antiaggregatory and anticoagulant properties that contribute to their favorable cardiovascular effects. Certain genetic, pathophysiologic, disease states and environmental conditions may influence the cardioprotective effects of HDL either by inducing modifications in lipidome and/or protein composition or in the enzymes responsible for HDL metabolism. On the other hand, certain healthy habits or pharmacologic interventions may actually favorably affect HDL functionality.

METHOD

The present review discusses the effects of environmental factors, including obesity, smoking, alcohol consumption, dietary habits, various pharmacologic interventions, as well as aerobic exercise, on HDL functionality.

RESULT

Experimental and clinical studies or pharmacological interventions support the impact of these environmental factors in the modification of HDL functionality, although the mechanisms that are mediated are poorly understood.

CONCLUSION

Further research should be conducted to unreal the underlying mechanisms of these environmental factors and to identify new pharmacologic interventions, capable of enhancing CEC, improving HDL functionality and potentially improving cardiovascular risk.

The effect of curcumin and exercise rehabilitation on liver paraoxonase-1 and NF-kβ gene expression in the rat induced by forced drinking of ethanol

Aim of the study

Binge ethanol drinking causes liver damage and decreased paraoxonase-1 (PON-1) gene expression. On the other hand, regular physical activity and curcumin consumption as non-invasive interventions can have liver protective effects through enhancing antioxidant defense, and improving PON-1 and NF-kβ (nuclear factor kappa B) gene expression. The aim of this study was to investigate the interactive effect of exercise rehabilitation and curcumin consumption on hepatocyte damage as well as NF-kβ and PON-1 gene expression in rats.

Material and methods

Fifty-six male Wistar rats were randomly selected and equally divided into seven groups: dextrose-control (Dext-Con), ethanol-control (Eth-Con), ethanol-saline (Eth-sal), ethanol-DMSO (Eth-DMSO), ethanol-curcumin (Eth-Cur), ethanol-swimming training (Eth-SWT) and ethanol-SWT + curcumin (Eth-SWT + Cur). After four days of the binge drinking protocol followed by six days of quitting, the interventions of SWT and curcumin (50 mg/kg) were employed for 14 days. Afterwards, the rats’ liver tissues were collected and sent to the laboratory for biochemical assays.

Results

The interaction of SWT and curcumin caused an increase in PON-1 gene expression (p = 0.02). In addition, curcumin consumption (p = 0.003) and its interaction with SWT (p = 0.004) resulted in a reduction in NF-kβ gene expression. Also, liver tissue damage was observed in the Eth-Con group compared to other groups.

Conclusions

The combination of curcumin and SWT may be used to reduce the side effects of binge ethanol drinking and improve recovery in the quitting period.

Paraoxonase 1 and atherosclerosis-related diseases

A direct and an indirect relationship between paraoxonase 1 (PON1) and atherosclerosis exists. Given PON1's physical location within high-density lipoprotein (HDL) particles and its recognized enzyme activity, it is certainly reasonable to suggest that PON1 facilitates the antiatherogenic nature of HDL particles. PON1 also plays a role in regulating reverse cholesterol transport, antioxidative, anti-inflammatory, antiapoptotic, vasodilative, and antithrombotic activities and several endothelial cell functions. HDL dysfunctionality is a more recent issue and seems to be centered on pathological conditions affecting HDL structure and size profiles. This review is focused on the role of PON1 status in different atherosclerosis-related diseases that we have studied over the last twenty years (coronary heart disease, acute ischemic stroke, diabetes mellitus type 2, end-stage renal disease, chronic obstructive pulmonary disease, and sarcoidosis) with the aim to determine the true value of PON1 as a biomarker. The role of PON1 in cancer is also covered, as risk factors and mechanisms underlying both atherosclerosis and cancer share common features.

Relationship between internal and external factors and the activity of PON1

Paraoxonase 1 (PON1) is an A-esterase calcium-dependent enzyme that is associated with high-density lipoprotein (HDL) and capable of hydrolyzing a wide variety of substrates, including organophosphate (OP) pesticides. The PON1 phenotype can be modulated by multiple internal and external factors, thereby affecting the catalytic capacity of the enzyme. The aim of this study was to evaluate factors that could modulate PON1 activity in a sample occupationally exposed to pesticides. A cross-sectional, descriptive, and analytical study was carried out with 240 workers. The participants were stratified according to their level of pesticide exposure as reference, moderate-exposure, and high-exposure groups. PON1 activities (arylesterase/AREase, CMPAase, and ssPONase (salt-stimulated)) were determined by spectrophotometry, and the Q192R and L55MPON1 genotypes by real-time PCR. The most frequent genotypes were heterozygous (QR) and homozygous (LL) for PON1Q192R and PON1L55M polymorphisms, respectively. The internal factors associated with the activity of PON1 were the PON1 genotypes (55 and 192) and biochemical parameters related to the lipid profile, in contrast, various external factors related to diet and harmful habits as well as with exposure to pesticides were associated with the activity of PON1. However, using a multivariate mixed ordinal regression model, we found a significant reduction of ssPONase activity in the high-exposure group compared with the reference group only in haplotypes QQLL and RRLL.

Effects of Moderate Ethanol Consumption on Lipid Metabolism and Inflammation Through Regulation of Gene Expression in Rats

Aims

Epidemiological studies and experimental data from rodent models have reported a non-linear relationship between consumption of alcohol and cardiovascular disease (CVD) risk that suggests that light-to-moderate drinking as opposed to excessive consumption may provide some cardiovascular benefits. The present study examined potential mechanisms by which moderate alcohol consumption may provide a protective effect against CVD.

Short summary

Wistar rats exposed for 3 months to a 20% ethanol intermittent-access voluntary drinking paradigm displayed a reduction in epididymal fat, blood glucose and non-HDL and total cholesterol. These effects were accompanied by decreased expression of Hmgcr, Srebp-2, Cox-2 and RelA, indicating downregulation of genes involved in cholesterol synthesis and inflammation.

Methods

Twenty-four male Wistar rats voluntarily consumed a 20% v/v ethanol solution on alternate days for 13 weeks (ethanol-treated) or were given access to water alone (non-ethanol-exposed control).

Results

There was no difference in body weight gain between the two groups, however, epididymal fat weight was lower in ethanol-fed rats (P = 0.030). Blood glucose, total cholesterol, non-high-density lipoprotein (HDL) and oxidized low-density lipoprotein (LDL) levels were lower in the ethanol group compared to controls (P < 0.05). There was a significant reduction in the expression of hydroxymethylglutaryl-coenzyme A reductase and sterol regulatory element-binding protein-2 in ethanol-treated rats (P < 0.05), suggesting that ethanol may have lowered cholesterol levels via downregulation of genes involved in cholesterol synthesis. Paraoxonase-1, which is associated with inhibition of LDL cholesterol oxidation, was upregulated in the ethanol group (P = 0.029). Ethanol-treated rats exhibited significantly lower levels of high-mobility box group protein 1 (P ≤ 0.05). Cyclooxygenase-2 and RelA gene expression were significantly lower in ethanol-treated rats (P < 0.05), indicating possible anti-inflammatory effects.

Conclusions

These findings suggest that moderate ethanol consumption may potentially contribute to improved cardiovascular outcomes by reducing body fat, improving blood cholesterol and blood glucose, and modulation of gene expression involved in inflammation and/or cholesterol synthesis.

Why Should Psychiatrists and Neuroscientists Worry about Paraoxonase 1?

BACKGROUND

Nitro-oxidative stress (NOS) has been implicated in the pathophysiology of psychiatric disorders. The activity of the polymorphic antioxidant enzyme paraoxonase 1 (PON1) is altered in diseases where NOS is involved. PON1 activity may be estimated using different substrates some of which are influenced by PON1 polymorphisms.

OBJECTIVES

1) to review the association between PON1 activities and psychiatric diseases using a standardized PON1 substrate terminology in order to offer a state-of-the-art review; and 2) to review the efficacy of different strategies (nutrition, drugs, lifestyle) to enhance PON1 activities.

METHODS

The PubMed database was searched using the terms paraoxonase 1 and psychiatric diseases. Moreover, the database was also searched for clinical trials investigating strategies to enhance PON1 activity.

RESULTS

The studies support decreased PON1 activity as determined using phenylacetate (i.e., arylesterase or AREase) as a substrate, in depression, bipolar disorder, generalized anxiety disorder (GAD) and schizophrenia, especially in antipsychotic-free patients. PON1 activity as determined with paraoxon (i.e., POase activity) yields more controversial results, which can be explained by the lack of adjustment for the Q192R polymorphism. The few clinical trials investigating the influence of nutritional, lifestyle and drugs on PON1 activities in the general population suggest that some polyphenols, oleic acid, Mediterranean diet, no smoking, being physically active and statins may be effective strategies that increase PON1 activity.

CONCLUSION

Lowered PON1 activities appear to be a key component in the ongoing NOS processes that accompany affective disorders, GAD and schizophrenia. Treatments increasing attenuated PON1 activity could possibly be new drug targets for treating these disorders.

Serum paraoxonase-1 activity is associated with light to moderate alcohol consumption: the PREVEND cohort study

Background

Paraoxonase-1 (PON-1) is a high-density lipoprotein (HDL)-associated enzyme with antioxidative properties, which may protect against the development of cardiovascular disease. Alcohol consumption increases HDL cholesterol, but the extent to which alcohol consumption gives rise to higher serum PON-1 activity is uncertain.

Objective

In a population-based study, we determined the relation of serum PON-1 activity with alcohol consumption when taking account of HDL cholesterol and apolipoprotein A-I (apoA-I), its major apolipoprotein.

Design

A cross-sectional study was performed in 8224 participants of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) cohort. Alcohol consumption was categorized as 1) no/rarely (25.3%); 2) 0.1-10 g/d (49.3%); 3) 10-30 g/d (20.1%); and 4) >30 g/d (5.2%) with 1 drink equivalent to 10 g alcohol. Serum PON-1 activity was measured as its arylesterase activity (phenyl acetate as substrate).

Results

Median serum PON-1 activity was 50.8, 53.1, 54.4, and 55.7 U/L in the 4 categories of alcohol consumption, respectively (P < 0.001). Its increase paralleled the increments in HDL cholesterol and apoA-I. Notably, there was no further increase in PON-1 activity, HDL cholesterol, and apoA-I when alcohol consumption was increased from 10-30 g/d to >30 g/d. Multivariable linear regression analysis demonstrated that PON-1 activity was related to alcohol consumption independently from clinical covariates, high sensitivity C-reactive protein, and lipid concentrations, including HDL cholesterol (P < 0.001 for each category of alcohol consumption with no alcohol consumption as the reference category). Notably, as inferred from standardized β-coefficients, there was no difference in PON-1 activity between 10-30 g alcohol/d and >30 g alcohol/d.

Conclusions

Alcohol consumption is associated with an increase in serum PON-1 activity, but its effect seems to reach a plateau with alcohol consumption of 10-30 g/d.

Consumption of orange fermented beverage improves antioxidant status and reduces peroxidation lipid and inflammatory markers in healthy humans

BACKGROUND

Alcoholic fermentation of fruits has generated novel products with high concentrations of bioactive compounds and moderate alcohol content. The aim of this study was to evaluate the potential effect on cardiovascular risk factors of the regular consumption by healthy humans of a beverage obtained by alcoholic fermentation and pasteurization of orange juice.

RESULTS

Thirty healthy volunteers were enrolled in a randomized controlled study. The experimental group (n = 15) drank 500 mL orange beverage (OB) per day for 2 weeks (intervention phase), followed by a 3-week washout phase. Blood samples were collected at baseline (E-T0) and at the end of the intervention (E-T1) and washout (E-T2) phases. Controls (n = 15) did not consume OB during a 2-week period. OB intake significantly increased oxygen radical absorbance capacity (43.9%) and reduced uric acid (-8.9%), catalase (CAT) (-23.2%), thiobarbituric acid reactive substances (TBARS) (-30.2%) and C-reactive protein (-2.1%) (E-T1 vs. E-T0). These effects may represent longer-term benefits, given the decreased uric acid (-8.9%), CAT (-34.6%), TBARS (-48.4%) and oxidized low-density lipoprotein (-23.9%) values recorded after the washout phase (E-T2 vs. E-T0).

CONCLUSION

The regular consumption of OB improved antioxidant status and decreased inflammation state, lipid peroxidation and uric acid levels. Thus OB may protect the cardiovascular system in healthy humans and be considered a novel functional beverage. © 2017 Society of Chemical Industry.

Paraoxonases: metabolic role and pharmacological projection

Atherosclerosis is one of the leading causes of death in Western countries, with high-density lipoproteins (HDL) playing an important protective role due to their ability to inhibit oxidation of low-density lipoproteins (LDL), thus relieving vascular subendothelial damage. One of the proteins constituting HDL particles is paraoxonase-1 (PON1), an enzyme able to hydrolyze aryl esters, lactones, and organophosphates. Other closely related paraoxonases are designated as PON2, which is a protein localized inside many different kinds of cells, and PON3, not only present in HDL but also in mitochondria and endoplasmic reticulum, as well. Given that the amount and the activity of PON1 in human serum are significantly lower in people suffering from cardiovascular diseases, enhancing both parameters might contribute to their treatment and prevention. One of the physiologically interesting substrates for the abovementioned hydrolytic cleavage is homocysteine thiolactone (HTL), an atherothrombotic active form of homocysteine. Although it was therefore postulated that PON1 would participate in preventing the HTL-mediated lipid peroxidation, some attention is recently paid to other enzymes, like biphenyl hydrolase-like protein, that seem to more selectively involved in lowering this risk factor. The aim of this paper is to elucidate the role of paraoxonases, especially PON1, by reviewing the latest studies in order to understand both its physiological role and modulation by drugs, nutrients, and plant extracts.

European versus Asian differences for the associations between paraoxonase-1 genetic polymorphisms and susceptibility to type 2 diabetes mellitus

Many studies have examined the associations between paraoxonase‐1 (PON1) genetic polymorphisms (Q192R, rs662 and L55M, rs854560) and the susceptibility to type 2 diabetes mellitus (T2DM) across different ethnic populations. However, the evidence for the associations remains inconclusive. In this study, we performed a meta‐analysis to clarify the association of the two PON1 variants with T2DM risk. We carried out a systematic search of PubMed, Embase, CNKI and Wanfang databases for studies published before June 2017. The pooled odds ratios (ORs) for the association and their corresponding 95% confidence intervals (CIs) were calculated by a random‐ or fixed‐effect model. A total of 50 eligible studies, including 34 and 16 studies were identified for the PON1 Q192R (rs662) and L55M (rs854560) polymorphism, respectively. As for the PON1 Q192R polymorphism, the 192R allele was a susceptible factor of T2DM in the South or East Asian population (OR > 1, P < 0.05) but represented a protective factor of T2DM in European population (OR = 0.66, 95% CI = 0.45–0.98) under a heterozygous genetic model. With regard to the PON1 L55M polymorphism, significant protective effects of the 55M allele on T2DM under the heterozygous (OR = 0.77, 95% CI = 0.61–0.97) and dominant (OR = 0.80, 95% CI = 0.65–0.99) genetic models were found in the European population, while no significant associations in the Asian populations under all genetic models (P > 0.05). In summary, by a comprehensive meta‐analysis, our results firmly indicated that distinct effects of PON1 genetic polymorphisms existed in the risk of T2DM across different ethnic backgrounds.

The role of paraoxonase in cancer

The paraoxonase (PON) gene family includes three proteins, PON1, PON2 and PON3. PON1 and PON3 are both associated with high-density lipoprotein (HDL) particles and exert anti-oxidant and anti-inflammatory properties. PON2 and PON3 are intracellular enzymes which modulate mitochondrial superoxide anion production and endoplasmic reticulum (ER) stress-induced apoptosis. The pleiotropic roles exerted by PONs have been mainly investigated in cardiovascular and neurodegenerative diseases. In recent years, overexpression of PON2 and PON3 has been observed in cancer cells and it has been proposed that both enzymes could be involved in tumor survival and stress resistance. Moreover, a lower activity of serum PON1 has been reported in cancer patients. This review summarizes literature data on the role of PONs in human cancers and their potential role as a target for antitumor drugs.

Alterations in serum paraoxonase-1 activity and lipid profile in chronic alcoholic patients infected with Strongyloides stercoralis

The objective of this study was to investigate paraoxonase-1 (PON1) activity, cortisol levels, and the lipid profile in the sera of alcoholic and non-alcoholic Strongyloides stercoralis-infected and uninfected individuals in a sample of 276 individuals attended at the National Health System in Salvador, Bahia, Brazil. The activity of PON1 was measured by the Beltowski method, serum lipids, and cortisol levels using commercial kits. PON1 activity was low in both alcoholic and non-alcoholic individuals infected with S. stercoralis. A positive correlation was observed between PON1 activity and cortisol concentration in alcoholic individuals who were not infected with S. stercoralis; whereas a negative correlation occurred in S. stercoralis-infected nonalcoholic individuals. The levels of triglycerides, LDL-C, and VLDL-C in S. stercoralis-infected alcoholic individuals were significantly lower than in uninfected alcoholic individuals. The high level of HDL-C and the low level of LDL-C, VLDL, triglycerides and PON1 activity in alcoholic patients infected with S. stercoralis evidenced an anti-atherogenic pattern.

Association of paraoxonase 1 (PON1) gene polymorphisms and concentration with essential hypertension

Human serum paraoxonase 1 (PON1) is carried by high-density lipoprotein in blood circulation and is shown to be effective in preventing oxidized phospholipids carried by low-density lipoprotein particles, thus it acts as an antioxidant. Polymorphism in this gene has been investigated for many metabolic diseases, but it is not thought to be a genetic risk factor for essential hypertension. The aim of this study was to determine whether there was an association between PON1 gene polymorphisms and concentration with essential hypertension. The study population was comprised of 100 patients with essential hypertension and 100 healthy controls. One promoter region [C(-108)T] and two coding region (Q192R and L55M) polymorphisms in the PON1 gene were genotyped in individuals by using the TaqMan assay. Plasma PON1 concentration in all volunteers was also measured spectrophotometrically by the enzyme-linked immunosorbent assay method. The genotype and allele frequencies of the PON1 C(-108)T polymorphism showed significant differences between the essential hypertensive and control groups (CT vs. CC: p<0.001; T allele vs. C allele: p<0.001). There was no significant difference for the PON1 L55M polymorphism between the groups, while the heterozygote genotype of the PON1 Q192R polymorphism showed significant difference (p = 0.03). The PON1 concentration was also found to be significantly lower in hypertensive patients (p < 0.001). Decline in the level of PON1 gene may be one of the main factors in the development of essential hypertension, and the PON1 C(-108)T polymorphism may have a prognostic value in the patients with essential hypertension.

Impact of Dyrk1A level on alcohol metabolism

Alcoholic liver diseases arise from complex phenotypes involving many genetic factors. It is quite common to find hyperhomocysteinemia in chronic alcoholic liver diseases, mainly due to deregulation of hepatic homocysteine metabolism. Dyrk1A, involved in homocysteine metabolism at different crossroads, is decreased in liver of hyperhomocysteinemic mice. Here, we hypothesized that Dyrk1A contributes to alcohol-induced hepatic impairment in mice. Control, hyperhomocysteinemic and mice overexpressing Dyrk1A were fed using a Lieber-DeCarli liquid diet with or without ethanol (5% v/v ethanol) for one month, and liver histological examination and liver biochemical function tests were performed. Plasma alanine aminotransferase and homocysteine levels were significantly decreased in mice overexpressing Dyrk1A compared to control mice with or without alcohol administration. On the contrary, the mean plasma alanine aminotransferase and homocysteine levels were significantly higher in hyperhomocysteinemic mice than that of control mice after alcohol administration. Paraoxonase 1 and CYP2E1, two phase I xenobiotic metabolizing enzymes, were found increased in the three groups of mice after alcohol administration. However, NQO1, a phase II enzyme, was only found increased in hyperhomocysteinemic mice after alcohol exposure, suggesting a greater effect of alcohol in liver of hyperhomocysteinemic mice. We observed positive correlations between hepatic alcohol dehydrogenase activity, Dyrk1A and ADH4 protein levels. Importantly, a deleterious effect of alcohol consumption on hepatic Dyrk1A protein level was found. Our study reveals on the one hand a role of Dyrk1A in ethanol metabolism and on the other hand a deleterious effect of alcohol administration on hepatic Dyrk1A level.

Alcohol consumption and prevalence of erectile dysfunction in Japanese patients with type 2 diabetes mellitus: Baseline data from the Dogo Study

Diabetes mellitus and heavy alcohol consumption are both associated with vascular disease, a category that includes erectile dysfunction (ED). However, the association between alcohol consumption and ED among patients with type 2 diabetes mellitus remains unclear. The aim of the present multicenter cross-sectional study was to investigate the relationship between drinking frequency, weekly alcohol consumption, daily alcohol consumption, and ED among Japanese patients with type 2 diabetes mellitus. Study subjects were 340 male Japanese patients with type 2 diabetes mellitus, aged 19-70 years, who had undergone blood tests at our institutions. A self-administered questionnaire was used to collect information on the variables under study. ED was defined as present when a subject had a Sexual Health Inventory for Men score <8. Adjustment was made for age, body mass index, duration of type 2 diabetes mellitus, current smoking, hypertension, dyslipidemia, glycated hemoglobin, stroke, coronary artery disease, diabetic retinopathy, diabetic nephropathy, and diabetic neuropathy. The prevalence of ED was 43.2% (147/340). The frequency of alcohol consumption and weekly alcohol consumption were independently inversely associated with ED (p for trend p = 0.001 and 0.004, respectively). The relationship between daily alcohol consumption and ED was an inverted J-shaped curve: alcohol consumption of less than 60 g, but not 60 g or more, per day was independently related to a lower prevalence of ED (p for quadratic trend = 0.003). In Japanese men with type 2 diabetes mellitus, an inverted J-shaped relationship between daily alcohol consumption and ED was observed, while frequency of alcohol consumption and weekly alcohol consumption were significantly inversely associated with ED.

Association between alcohol consumption and serum paraoxonase and arylesterase activities: a cross-sectional study within the Bavarian population

High alcohol consumption is an important risk factor for chronic disease and liver degeneration. Paraoxonase (PON1) and arylesterase (AE) are functions of the enzyme paraoxonase, which is synthesised by the liver. Paraoxonase circulates in plasma bound to HDL and hydrolyses lipid peroxides, protecting lipoproteins against oxidative modification. It has been shown that excessive alcohol consumption leads to a reduction of serum PON1 and AE activities; however, studies investigating the association with low and moderate alcohol consumption are scarce. We investigated the cross-sectional association between alcohol consumption and serum activities of PON1 and AE using data from the population-based Bavarian Food Consumption Survey II survey. PON1 and AE activities were quantified in serum samples of 566 male and female study participants (aged 18-80 years), and dietary intake including alcohol consumption was estimated from three 24-h dietary recalls. The association between alcohol consumption and PON1 and AE activities was analysed using linear regression, adjusted for age, sex and socio-economic status. There was no strong association between alcohol consumption and enzymatic activities of PON1 and AE in the Bavarian population. PON1 activity was seen to be lowest in non-drinkers (0 g/d) and highest in people who consumed 15·1-30 g of alcohol/d. AE activity increased across alcohol consumption categories, with a mean maximum difference of 14 U/ml (P for linear trend 0·04). These associations were attenuated after adjustment for blood concentrations of HDL. The results of this study do not support the hypothesis that alcohol consumption is related to important alterations in PON1 and AE activities.

Protective Role of Dietary Curcumin in the Prevention of the Oxidative Stress Induced by Chronic Alcohol with respect to Hepatic Injury and Antiatherogenic Markers

Curcumin, an antioxidant compound found in Asian spices, was evaluated for its protective effects against ethanol-induced hepatosteatosis, liver injury, antiatherogenic markers, and antioxidant status in rats fed with Lieber-deCarli low menhaden (2.7% of total calories from ω-3 polyunsaturated fatty acids (PUFA)) and Lieber-deCarli high menhaden (13.8% of total calories from ω-3 PUFA) alcohol-liquid (5%) diets supplemented with or without curcumin (150 mg/kg/day) for 8 weeks. Treatment with curcumin protected against high ω-3 PUFA and ethanol-induced hepatosteatosis and increase in liver injury markers, alanine aminotransferase, and aspartate aminotransferase. Curcumin upregulated paraoxonase 1 (PON1) mRNA and caused significant increase in serum PON1 and homocysteine thiolactonase activities as compared to high ω-3 PUFA and ethanol group. Moreover, treatment with curcumin protected against ethanol-induced oxidative stress by increasing the antioxidant glutathione and decreasing the lipid peroxidation adduct 4-hydroxynonenal. These results strongly suggest that chronic ethanol in combination with high ω-3 PUFA exacerbated hepatosteatosis and liver injury and adversely decreases antiatherogenic markers due to increased oxidative stress and depletion of glutathione. Curcumin supplementation significantly prevented these deleterious actions of chronic ethanol and high ω-3 PUFA. Therefore, we conclude that curcumin may have therapeutic potential to protect against chronic alcohol-induced liver injury and atherosclerosis.

The impact of environmental and biological factors on paraoxonase 1 and γ-glutamyltranspeptydase activities in the blood of smelters

Disorders of paraoxonase and γ-glutamyltranspeptydase activities can induce development of the atherosclerotic process. The aim of the study was to examine the effect of occupational exposure to heavy metals, tobacco smoke and alcohol consumption on the activities of paraoxonase and γ-glutamyltranspeptydase as well as glutathione concentration. We have observed reduced paraoxonase activity and higher γ-glutamyltranspeptydase activity in serum of smelters when compared to control groups. In the blood of smoking smelters was demonstrated a negative correlation between paraoxonase activity and BMI value as well as between paraoxonase activity and tobacco smoke and consumption of 40% alcohol. Also, negative correlation was found for the activity of paraoxonase and glutathione concentration as well as γ-glutamyltranspeptydase activity. Higher γ-glutamyltranspeptydase activity and lower paraoxonase activity in the serum of smelters exposed to heavy metals and tobacco smoke can cause disorders in functioning of the body.

Paraoxonase (PON1) polymorphisms Q192R and L55M are not associated with human longevity: A meta-analysis

BACKGROUND

Genetic mutations in the paraoxonase 1 (PON1) encoding gene have been considered to affect mortality and of these the functional promoter region polymorphisms Q192R and L55M are among the most widely studied.

OBJECTIVE

The aim of this study was to determine whether the Q192R and L55M polymorphisms of PON1 can increase susceptibility to longevity. A meta-analysis was performed to obtain a comprehensive estimation of the association between Q192R and L55M and longevity in long-lived individuals (LLIs) aged 80 years or more.

MATERIAL AND METHODS

A search was carried out in the PubMed database (from January 2001 to May 2014) to obtain data on the role of PON1 polymorphisms in longevity and a pooled odds ratio (OR) with a 95% confidence interval (CI) was used to assess the associations.

RESULTS

The meta-analysis was based on 9 studies of PON1 Q192R and 5 studies of PON1 L55M that covered a total of 5086 LLIs and 4494 controls. Overall, significantly increased risks were not observed for either Q192R or L55M. The results of the statistical calculations were as follows: R vs. Q (additive model): OR = 1.080, 95% CI = 0.989-1.179, p = 0.088 and RR + RQ vs. QQ (dominant model): OR = 1.099, 95% CI = 0.975-1.240, p = 0.124; M vs. L (additive model): OR = 0.946, 95% CI = 0.862-1.039, p = 0.245 and MM + ML vs. LL (dominant model): OR = 0.951, 95% CI = 0.836-1.081, p = 0.442 for Q192R and L55M, respectively. The results did not change with an age cut-off among the LLIs of ≥ 93 years.

CONCLUSION

No evidence that the Q192R and L55M polymorphisms of PON1 impacted on the probability of reaching extreme ages was found although this cannot be completely ruled out; however, the possibility of population-specific effects due to the influence of and interaction between different genes or environmental factors could not be ruled out.

HDL and lifestyle interventions

The main lifestyle interventions to modify serum HDL cholesterol include physical exercise, weight loss with either caloric restriction or specific dietary approaches, and smoking cessation. Moderate alcohol consumption can be permitted in some cases. However, as these interventions exert multiple effects, it is often difficult to discern which is responsible for improvement in HDL outcomes. It is particularly noteworthy that recent data questions the use of HDL cholesterol as a risk factor and therapeutic target since randomised interventions and Mendelian randomisation studies failed to provide evidence for such an approach. Therefore, these current data should be considered when reading and interpreting this review. Further studies are needed to document the effect of lifestyle changes on HDL structure-function and health.

A snapshot of the hepatic transcriptome: ad libitum alcohol intake suppresses expression of cholesterol synthesis genes in alcohol-preferring (P) rats

Research is uncovering the genetic and biochemical effects of consuming large quantities of alcohol. One prime example is the J- or U-shaped relationship between the levels of alcohol consumption and the risk of atherosclerotic cardiovascular disease. Moderate alcohol consumption in humans (about 30 g ethanol/d) is associated with reduced risk of coronary heart disease, while abstinence and heavier alcohol intake is linked to increased risk. However, the hepatic consequences of moderate alcohol drinking are largely unknown. Previous data from alcohol-preferring (P) rats showed that chronic consumption does not produce significant hepatic steatosis in this well-established model. Therefore, free-choice alcohol drinking in P rats may mimic low risk or nonhazardous drinking in humans, and chronic exposure in P animals can illuminate the molecular underpinnings of free-choice drinking in the liver. To address this gap, we captured the global, steady-state liver transcriptome following a 23 week free-choice, moderate alcohol consumption regimen (∼ 7.43 g ethanol/kg/day) in inbred alcohol-preferring (iP10a) rats. Chronic consumption led to down-regulation of nine genes in the cholesterol biosynthesis pathway, including HMG-CoA reductase, the rate-limiting step for cholesterol synthesis. These findings corroborate our phenotypic analyses, which indicate that this paradigm produced animals whose hepatic triglyceride levels, cholesterol levels and liver histology were indistinguishable from controls. These findings explain, at least in part, the J- or U-shaped relationship between cardiovascular risk and alcohol intake, and provide outstanding candidates for future studies aimed at understanding the mechanisms that underlie the salutary cardiovascular benefits of chronic low risk and nonhazardous alcohol intake.

Association of serum paraoxonase concentration with serum lipid levels and bone mineral density measurements in early postmenopausal women

OBJECTIVE

To determine the association of serum paraoxonase concentration with serum lipid levels and bone mineral density in early postmenopausal Turkish women.

DESIGN

One hundred healthy postmenopausal women were included in a cross-sectional study in a University hospital clinic. Blood was drawn from women who had bone mineral density (BMD) measurements during routine visits. BMD of the lumbar vertebrae was measured by dual-energy X-ray absorptiometry. The serum paraoxonase concentration and serum lipid levels were measured. Women were divided into two groups: those with normal lumbar vertebrae BMD and those with osteopenic lumbar vertebrae. Serum paraoxonase concentration was compared between the groups. The correlation between serum paraoxonase concentration and bone mass parameters was performed using Pearson's test.

RESULTS

The paraoxonase concentration in the osteopenic group was significantly lower than in the group with normal lumbar vertebrae BMD. The paraoxonase concentration was moderately correlated with total cholesterol, low density lipoprotein cholesterol and triglyceride levels among early postmenopausal Turkish women.

CONCLUSIONS

Early postmenopausal women with osteopenic lumbar vertebrae have significantly lower paraoxonase concentration than those with normal lumbar vertebrae BMD. Further studies are needed to clarify the associations between the osteoporosis risk factors and paraoxonase concentration during late postmenopausal years.

Effects of dietary components on high-density lipoprotein measures in a cohort of 1,566 participants

Background

Recent data suggest that an increased level of high-density lipoprotein cholesterol (HDL-C) is not causally protective against heart disease, shifting focus to other sub-phenotypes of HDL. Prior work on the effects of dietary intakes has focused largely on HDL-C. The goal of this study was to identify the dietary intakes that affect HDL-related measures: HDL-C, HDL-2, HDL-3, and apoA1 using data from a carotid artery disease case–control cohort.

Methods

A subset of 1,566 participants with extensive lipid phenotype data completed the Harvard Standardized Food Frequency Questionnaire to determine their daily micronutrient intake over the past year. Stepwise linear regression was used to separately evaluate the effects of dietary covariates on adjusted levels of HDL-C, HDL-2, HDL-3, and apoA1.

Results

Dietary folate intake was positively associated with HDL-C (p = 0.007), HDL-2 (p = 0.0011), HDL-3 (p = 0.0022), and apoA1 (p = 0.001). Alcohol intake and myristic acid (14:0), a saturated fat, were each significantly associated with increased levels of all HDL-related measures studied. Dietary carbohydrate and iron intake were significantly associated with decreased levels of all HDL-related measures. Magnesium intake was positively associated with HDL-C, HDL-2, and HDL-3 levels, but not apoA1 levels, while vitamin C was only associated with apoA1 levels. Dietary fiber and protein intake were both associated with HDL-3 levels alone.

Conclusions

This study is the first to report that dietary folate intake is associated with HDL-C, HDL-2, HDL-3, and apoA1 levels in humans. We further identify numerous dietary intake associations with apoA1, HDL-2, and HDL-3 levels. Given the shifting focus away from HDL-C, these data will prove valuable for future epidemiologic investigation of the role of diet and multiple HDL phenotypes in heart disease.

Paraoxonases function as unique protectors against cardiovascular diseases and diabetes: Updated experimental and clinical data

Paraoxonase (PON) refers to a family of three enzymes, namely PON1, PON2, and PON3. PON1 and PON3 are found in circulation bound to high-density lipoprotein, whereas PON2 is an intracellular protein. PON1 was first discovered as an enzyme to hydrolyze the organophosphate pesticide paraoxon, an activity that both PON2 and PON3 lack. All three PON enzymes are able to degrade oxidized lipids and protect against oxidative stress. PON enzymes also act to suppress inflammation. Animal studies show a critical role for PON enzymes, especially PON1 in protecting against cardiovascular diseases and related disorders, including diabetes and metabolic syndrome. In line with the findings in experimental animals, accumulating evidence from clinical research also indicates that PON enzymes function as potential protectors in human cardiovascular diseases and related disorders. Identification of PON enzymes as important players in cardiovascular health will facilitate the development of novel preventive and therapeutic modalities targeting PON enzymes to combat cardiovascular diseases and related disorders, which collectively constitute the chief contributors to the global burden of disease. This review describes the biochemical properties and molecular regulation of PON and summarizes the major recent findings on the functions of PON in protecting against cardiovascular diseases and related disorders.

Paraoxonases and chemokine (C-C motif) ligand-2 in noncommunicable diseases

Oxidative stress and inflammation underpin most diseases; their mechanisms are inextricably linked. Chronic inflammation is associated with oxidation, anti-inflammatory cascades are linked to decreased oxidation, increased oxidative stress triggers inflammation, and redox balance inhibits the inflammatory cellular response. Whether or not oxidative stress and inflammation represent the cause or consequence of cellular pathology, they contribute significantly to the pathogenesis of noncommunicable diseases (NCD). The incidence of obesity and other related metabolic disturbances are increasing, as are age-related diseases due to a progressively aging population. Relationships between oxidative stress, inflammatory signaling, and metabolism are, in the broad sense of energy transformation, being increasingly recognized as part of the problem in NCD. In this chapter, we summarize the pathologic consequences of an imbalance between circulating and cellular paraoxonases, the system for scavenging excessive reactive oxygen species and circulating chemokines. They act as inducers of migration and infiltration of immune cells in target tissues as well as in the pathogenesis of disease that perturbs normal metabolic function. This disruption involves pathways controlling lipid and glucose homeostasis as well as metabolically driven chronic inflammatory states that encompass several response pathways. Dysfunction in the endoplasmic reticulum and/or mitochondria represents an important feature of chronic disease linked to oxidation and inflammation seen as self-reinforcing in NCD. Therefore, correct management requires a thorough understanding of these relationships and precise interpretation of laboratory test results.

Pharmacogenetics of paraoxonase activity: elucidating the role of high-density lipoprotein in disease

PON1 is a key component of high-density lipoproteins (HDLs) and is at least partially responsible for HDL's antioxidant/atheroprotective properties. PON1 is also associated with numerous human diseases, including cardiovascular disease, Parkinson's disease and cancer. In addition, PON1 metabolizes a broad variety of substrates, including toxic organophosphorous compounds, statin adducts, glucocorticoids, the likely atherogenic L-homocysteine thiolactone and the quorum-sensing factor of Pseudomonas aeruginosa. Numerous cardiovascular and antidiabetic pharmacologic agents, dietary macronutrients, lifestyle factors and antioxidant supplements affect PON1 expression and enzyme activity levels. Owing to the importance of PON1 to HDL function and its individual association with diverse human diseases, pharmacogenomic interactions between PON1 and the various factors that alter its expression and activity may represent an important therapeutic target for future investigation.

Paraoxonase 1 and oxidative stress in paediatric non-alcoholic steatohepatitis

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) in children is a significant public health concern. Oxidative stress is an important component in the pathophysiology of NASH. Several enzymatic antioxidant mechanisms protect the liver from oxidative injury. Examination of the expression of these enzymes in NASH livers may provide insight on the roles for these antioxidant mechanisms in the pathophysiology of NASH.

METHODS

The mRNA expression of catalase, glutathione peroxidase 1 (GPX1), glutathione reductase (GSR), paraoxonase 1 (PON1) and other reactive oxygen species-related genes was evaluated by microarray and quantitative real-time PCR analyses. The PON1 protein levels were evaluated in liver and serum by Western blot analyses. Serum enzymatic activities of GPX, GSR and PON1 (paraoxonase and arylesterase activities) were examined.

RESULTS

NASH livers exhibited elevated mRNA expression of catalase and PON1, but not GPX1 or GSR. No difference in serum GPX or GSR activity was detected between NASH patients and controls. Elevated expression of PON1 mRNA and protein was detected in NASH livers, but serum PON1 protein and activities were not elevated.

CONCLUSIONS

Elevated expression of catalase and PON1 suggests protective roles for these antioxidants in NASH livers. Given the importance of oxidative stress in the pathophysiology of NASH, future studies focusing on these enzymes could identify important targets for therapeutic or preventive interventions for NASH patients.

Paraoxonases: ancient substrate hunters and their evolving role in ischemic heart disease

Interest in the role of paraoxonases (PON) in cardiovascular research has increased substantially over the past two decades. These multifaceted and pleiotropic enzymes are encoded by three highly conserved genes (PON1, PON2, and PON3) located on chromosome 7q21.3-22.1. Phylogenetic analysis suggests that PON2 is the ancient gene from which PON1 and PON3 arose via gene duplication. Although PON are primarily lactonases with overlapping, but distinct specificities, their physiologic substrates remain poorly characterized. The most interesting characteristic of PON, however, is their multifunctional roles in various biochemical pathways. These include protection against oxidative damage and lipid peroxidation, contribution to innate immunity, detoxification of reactive molecules, bioactivation of drugs, modulation of endoplasmic reticulum stress, and regulation of cell proliferation/apoptosis. In general, PON appear as "hunters" of old and new substrates often involved in athero- and thrombogenesis. Although reduced PON activity appears associated with increased cardiovascular risk, the correlation between PON genotype and ischemic heart disease remains controversial. In this review, we examine the biochemical pathways impacted by these unique enzymes and investigate the potential use of PON as diagnostic tools and their impact on development of future therapeutic strategies.

CYP2E1, oxidative stress, post-translational modifications and lipid metabolism

Chronic alcohol-mediated down-regulation of hepatic ST6Gal1 gene leads to defective glycosylation of lipid-carrying apolipoproteins such as apo E and apo J, resulting in defective VLDL assembly and intracellular lipid and lipoprotein transport, which in turn is responsible for alcoholic hepatosteatosis and ALD. The mechanism of ethanol action involves thedepletion of a unique RNA binding protein that specifically interacts with its 3'-UTR region of ST6Gal1 mRNA resulting in its destabilization and consequent appearance of asialoconjugates as alcohol biomarkers. With respect to ETOH effects on Cardio-Vascular Diseases, we conclude that CYP2E1 and ETOH mediated oxidative stress significantly down regulates not only the hepatic PON1 gene expression, but also serum PON1 and HCTLase activities accompanied by depletion of hepatic GSH, the endogenous antioxidant. These results strongly implicate the susceptibility of PON1 to increased ROS production. In contrast, betaine seems to be both hepatoprotective and atheroprotective by reducing hepatosteatosis and restoring not only liver GSH that quenches free radicals, but also the antiatherogenic PON1 gene expression and activity.

Dietary cholesterol increases paraoxonase 1 enzyme activity

HDL-associated paraoxonase 1 (PON1) activity has been consistently associated with cardiovascular and other diseases. Vitamins C and E intake have previously been positively associated with PON1 in a subset of the Carotid Lesion Epidemiology and Risk (CLEAR) cohort. The goal of this study was to replicate these findings and determine whether other nutrient intake affected PON1 activity. To predict nutrient and mineral intake values, 1,402 subjects completed a standardized food frequency survey of their dietary habits over the past year. Stepwise regression was used to evaluate dietary and covariate effects on PON1 arylesterase activity. Five dietary components, cholesterol (P < 2.0 × 10(-16)), alcohol (P = 8.51 × 10(-8)), vitamin C (P = 7.97 × 10(-5)), iron (P = 0.0026), and folic acid (0.037) were independently predictive of PON1 activity. Dietary cholesterol was positively associated and predicted 5.5% of PON1 activity, second in variance explained. This study presents a novel finding of dietary cholesterol, iron, and folic acid predicting PON1 activity in humans and confirms prior reported associations, including that with vitamin C. Identifying and understanding environmental factors that affect PON1 activity is necessary to understand its role and that of HDL in human disease.

Paraoxonase 1 (PON1) C/T-108 association with longitudinal mean arterial blood pressure

BACKGROUND

Blood pressure is a complex quantitative trait with a strong genetic component. In this study, we leveraged the Veterans Affairs electronic medical record system to explore the relationship between Paraoxonase 1 (PON1)-108 C/T (rs705379) and mean arterial blood pressure (MAP).

METHODS

Outpatient blood pressure data over an approximate 8-year period was collected from the Veterans Affairs Hypertensive Cohort (N = 1,302). Association between genotype and longitudinal MAP was further explored using a random effects model controlling for age, ancestry, renal function, and other determinants of blood pressure. To control for population stratification, principal component groupings based on ancestry informative markers in this dataset were included as covariates (in addition to self-identified ancestry). Data from the African American Study of Kidney Disease and Hypertension (AASK, N = 857) was used to confirm significant findings in an independent cohort.

RESULTS

There was a significant interaction between PON1-108 C/T genotype and follow-up age group. At a younger age (<50 years), there was an estimated 2.53 mm Hg (95% confidence interval: 1.06, 4.00) increase in MAP with each additional C-allele. At the older age groups, there were no significant associations between PON1-108 C/T genotype and MAP. Using data from the AASK trial, the C-allele at PON1-108 C/T was significantly associated with a higher MAP (P = 0.005) but only among younger participants (<54 years).

CONCLUSIONS

The PON1-108 polymorphism may be associated with MAP in an age-dependent manner.

Is alcohol beneficial or harmful for cardioprotection?

While the effects of chronic ethanol consumption on liver have been well studied and documented, its effect on the cardiovascular system is bimodal. Thus, moderate drinking in many population studies is related to lower prevalence of coronary artery disease (CAD). In contrast, heavy drinking correlates with higher prevalence of CAD. In several other studies of cardiovascular mortalities, abstainers and heavy drinkers are at higher risk than light or moderate drinkers. The composite of this disparate relation in several population studies of cardiovascular mortality has been a "U-" or "J-"shaped curve. Apart from its ability to eliminate cholesterol from the intima of the arteries by reverse cholesterol transport, another major mechanism by which HDL may have this cardioprotective property is by virtue of the ability of its component enzyme paraoxonase1 (PON1) to inhibit LDL oxidation and/or inactivate OxLDL. Therefore, PON1 plays a central role in the disposal of OxLDL and thus is antiatherogenic. Furthermore, PON1 is a multifunctional antioxidant enzyme that can also detoxify the homocysteine metabolite, homocysteine thiolactone (HTL), which can pathologically cause protein damage by homocysteinylation of the lysine residues, thereby leading to atherosclerosis. We demonstrated that moderate alcohol up regulates liver PON1 gene expression and serum activity, whereas heavy alcohol consumption had the opposite effects in both animal models and in humans. The increase in PON1 activity in light drinkers was not due to preferential distribution of high PON1 genotype in this group. It is well known that wine consumption in several countries shows a remarkable inverse correlation to local rates of CAD mortality. Significantly, apart from its alcohol content, red wine also has polyphenols such as quercetin and resveratrol that are also known to have cardioprotective effects. We have shown that quercetin also up regulates PON1 gene in rats and in human liver cells. The action of quercetin seems to be mediated via the active form of the nuclear lipogenic transcription factor, sterol-regulatory element-binding protein 2 (SREBP2) that is translocated from endoplasmic reticulum to the nucleus. However, the mechanism of action of ethanol-mediated up-regulation of PON1 gene remains to be elucidated. We conclude that both moderate ethanol and quercetin, the two major components of red wine, exhibit cardioprotective properties via the up-regulation of the antiatherogenic gene PON1.

Paraoxonase 1 (PON1) as a genetic determinant of susceptibility to organophosphate toxicity

Paraoxonase (PON1) is an A-esterase capable of hydrolyzing the active metabolites (oxons) of a number of organophosphorus (OP) insecticides such as parathion, diazinon and chlorpyrifos. PON1 activity is highest in liver and in plasma. Human PON1 displays two polymorphisms in the coding region (Q192R and L55M) and several polymorphisms in the promoter and the 3'-UTR regions. The Q192R polymorphism imparts differential catalytic activity toward some OP substrates, while the polymorphism at position -108 (C/T) is the major contributor of differences in the levels of PON1 expression. Both contribute to determining an individual's PON1 "status". Animal studies have shown that PON1 is an important determinant of OP toxicity. Administration of exogenous PON1 to rats or mice protects them from the toxicity of specific OPs. PON1 knockout mice display a high sensitivity to the toxicity of diazoxon and chlorpyrifos oxon, but not of paraoxon. In vitro catalytic efficiencies of purified PON192 alloforms for hydrolysis of specific oxon substrates accurately predict the degree of in vivo protection afforded by each isoform. Evidence is slowly emerging that a low PON1 status may increase susceptibility to OP toxicity in humans. Low PON1 activity may also contribute to the developmental toxicity and neurotoxicity of OPs, as shown by animal and human studies.

Hormonal and chemical regulation of paraoxonases in mice

In humans and rodents, paraoxonase (PON/Pon) 1 expression and activity in livers and serum are higher in females than in males, and some drugs increase paraoxonase's expression. However, the underlining mechanisms of gender-divergent expression and chemical regulation of Pon1 remain largely unknown. The present study determined the regulatory mechanisms contributing to gender-divergent and chemically altered Pon expression in mouse livers. Pon1 mRNA was much more abundant in the livers of mice than other tissues, with higher levels in female livers than male livers at mRNA and protein levels. Pon2 mRNA was ubiquitously expressed in mouse tissues, but minimally in mouse liver. Pon3 mRNA was most abundant in mouse lung and liver and less abundant in other tissues. Pon1 mRNA was lowest in fetal liver, markedly increased at parturition, and remained relatively constant thereafter. Pon2 and Pon3 mRNA are highly expressed in fetal liver and decreased after birth. Male-pattern growth hormone (GH) administration in hypophysectomized and lit/lit mice decreased Pon1 expression. Sex hormones and female-pattern GH administration had no effect on Pon1 expression, indicating the importance of male-pattern GH in regulating Pon1. Aryl hydrocarbon receptor, pregnane X receptor, and NF-E2-related factor activators had no effect on Pon1 mRNA. A constitutive androstane receptor (CAR) activator decreased Pon1 expression in wild-type but not CAR-null mice. In conclusion, Pon1 mRNA was most abundant in adult mouse livers, whereas Pon2 and Pon3 mRNAs were most abundant in fetal mouse livers. Female-predominant Pon1 expression in mouse livers is caused by the inhibitory effects of male-pattern GH secretion, and CAR activation decreases Pon1 expression.

The human paraoxonase gene cluster as a target in the treatment of atherosclerosis

The paraoxonase (PON) gene cluster contains three adjacent gene members, PON1, PON2, and PON3. Originating from the same fungus lactonase precursor, all of the three PON genes share high sequence identity and a similar β propeller protein structure. PON1 and PON3 are primarily expressed in the liver and secreted into the serum upon expression, whereas PON2 is ubiquitously expressed and remains inside the cell. Each PON member has high catalytic activity toward corresponding artificial organophosphate, and all exhibit activities to lactones. Therefore, all three members of the family are regarded as lactonases. Under physiological conditions, they act to degrade metabolites of polyunsaturated fatty acids and homocysteine (Hcy) thiolactone, among other compounds. By detoxifying both oxidized low-density lipoprotein and Hcy thiolactone, PONs protect against atherosclerosis and coronary artery diseases, as has been illustrated by many types of in vitro and in vivo experimental evidence. Clinical observations focusing on gene polymorphisms also indicate that PON1, PON2, and PON3 are protective against coronary artery disease. Many other conditions, such as diabetes, metabolic syndrome, and aging, have been shown to relate to PONs. The abundance and/or activity of PONs can be regulated by lipoproteins and their metabolites, biological macromolecules, pharmacological treatments, dietary factors, and lifestyle. In conclusion, both previous results and ongoing studies provide evidence, making the PON cluster a prospective target for the treatment of atherosclerosis.

Interrelationships between paraoxonase-1 and monocyte chemoattractant protein-1 in the regulation of hepatic inflammation

Oxidative stress and inflammation play a central role in the onset and development of liver diseases irrespective of the agent causing the hepatic impairment. The monocyte chemoattractant protein-1 is intimately involved in the inflammatory reaction and is directly correlated with the degree of hepatic inflammation in patients with chronic liver disease. Recent studies showed that hepatic paraoxonase-1 may counteract the production of the monocyte chemoattractant protein-1, thus playing an anti-inflammatory role. The current review summarises experiments suggesting how paraoxonase-1 activity and expression are altered in liver diseases, and their relationships with the monocyte chemoattractant protein-1 and inflammation.

Determinants of paraoxonase activity in healthy adults

SCOPE

Paraoxonase-1 (PON-1), associated with HDL, is regarded as anti-atherogenic, attributed to its ability to hydrolyze oxidized lipids. Here, the impact of PON and apolipoprotein E genotypes, age, alcohol and HDL-cholesterol (HDL-C) on PON activity is examined.

METHODS AND RESULTS

In total, 104 healthy UK adults participated in the study, with basal (PONA) and stimulated (PONB) PON-1 activities and arylesterase activity determined in these individuals. In univariate and correlation analysis age, HDL-C, alcohol intake and both PON genotypes were significantly associated with PONA and PONB activities (p<0.05). However, in the standard linear regression model, which explained 69% of the variability in both PONA (p<0.001) and PONB activities (p<0.001) only PON Q192R genotype emerged as a significant independent determinant, with four to fivefold higher levels in the RR versus wild-type QQ genotype groups. For PON arylesterase, HDL-C (p=0.030), apolipoprotein E (p=0.023) and PON Q192R (p=0.002) and PON L55M (p=0.002) genotypes collectively explained 14% of the total variability in the regression model.

CONCLUSION

Our results indicate that PON genotypes are stronger determinants of PON activity relative to the other potential modulators assessed. The relative impact of dietary components on PON activities remains to be established.

Paraoxonase-1 genetic polymorphisms and susceptibility to DNA damage in workers occupationally exposed to organophosphate pesticides

Human paraoxonase 1 (PON1) is a lipoprotein-associated enzyme involved in the detoxification of organophosphate pesticides (OPs) by hydrolyzing the bioactive oxons. Polymorphisms of the PON1 gene are responsible for variation in the expression and catalytic activity of PON1 enzyme. In the present study, we have determined (a) the prevalence of two common PON1 polymorphisms, (b) the activity of PON1 and acetylcholinesterase enzymes, and (c) the influence of PON1 genotypes and phenotypes variation on DNA damage in workers exposed to OPs. We examined 230 subjects including 115 workers exposed to OPs and an equal number of normal healthy controls. The results revealed that PON1 activity toward paraoxon (179.19±39.36 vs. 241.52±42.32nmol/min/ml in controls) and phenylacetate (112.74±17.37 vs. 134.28±25.49μmol/min/ml in controls) was significantly lower in workers than in control subjects (p<0.001). No significant difference was observed in the distribution of genotypes and allelic frequencies of PON1(192)QR (Gln/Arg) and PON1(55)LM (Leu/Met) in workers and control subjects (p>0.05). The PON1 activity toward paraoxonase was found to be significantly higher in the R/R (Arg/Arg) genotypes than Q/R (Gln/Arg) and lowest in Q/Q (Gln/Gln) genotypes in both workers and control subjects (p<0.001). For PON1(55)LM (Leu/Met), PON1 activity toward paraoxonase was observed to be higher in individuals with L/L (Leu/Leu) genotypes and lowest in individuals with M/M (Met/Met) genotypes in both groups (p<0.001). No influence of PON1 genotypes and phenotypes was seen on the activity of acetylcholinesterase and arylesterase. The DNA damage was observed to be significantly higher in workers than in control subjects (p<0.05). Further, the individuals who showed least paraoxonase activity i.e., those with (Q/Q [Gln/Gln] and M/M [Met/Met]) genotypes showed significantly higher DNA damage compared to other isoforms in workers exposed to OPs (p<0.05). The results indicate that the individuals with PON1 Q/Q and M/M genotypes are more susceptible toward genotoxicity. In conclusion, the study suggests wide variation in enzyme activities and DNA damage due to polymorphisms in PON1 gene, which might have an important role in the identification of individual risk factors in workers occupationally exposed to OPs.