Oxidative inactivation of lactonase activity of purified human paraoxonase 1 (PON1)

Sex Difference Impacts on the Relationship between Paraoxonase-1 (PON1) and Type 2 Diabetes

Type-2 diabetes (T2D) and its cardiovascular complications are related to sex. Increasing evidence suggests that paraoxonase 1 (PON1) activity, an antioxidant enzyme bound to high-density lipoproteins (HDL), is implicated in the onset and clinical progression of T2D. Since we previously showed that PON1 is a sexual dimorphic protein, we now investigated whether sex might impact the relationship between PON1 and this chronic disease. To address this aim, we assessed PON1 activity in the sera of 778 patients, including controls (women, n = 383; men, n = 198) and diabetics (women, n = 79; men = 118). PON1 activity decreased in both women and men with T2D compared with controls (p < 0.05 and p > 0.001, respectively), but the change was 50% larger in the female cohort. In line with this result, the enzyme activity was associated with serum glucose level only in women (r = -0.160, p = 0.002). Notably, only within this gender category, lower PON1 activity was independently associated with increased odds of being diabetic (odds ratio (95% Confidence interval: 2.162 (1.075-5.678)). In conclusion, our study suggests that PON1-deficiency in T2D is a gender-specific phenomenon, with women being more affected than men. This could contribute to the partial loss of female cardiovascular advantage associated with T2D.

Crosstalk Between Adipokines and Paraoxonase 1: A New Potential Axis Linking Oxidative Stress and Inflammation

Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated protein that endows its carrier with (lipo-)lactonase-dependent antioxidative features. Low levels of PON1 activity have been observed in association with obesity, a major risk factor for cardiovascular disease (CVD). Considering the well-recognized atheroprotective role of PON1, exogenous/endogenous factors that might modulate its levels/activity are raising great interest. Since adipokines represent a molecular link between obesity and CVD, we here explored the possible impact of these substances on PON1 activity/expression. The levels of interleukin (IL)-6, IL-8, tumor necrosis factor alpha, monocyte chemoattractant protein-1, hepatocyte growth factor, resistin, leptin, and adiponectin were measured along with arylesterase, paraoxonase, and lactonase activities of PON1 in 107 postmenopausal women. Moreover, the direct effect of resistin on PON1 expression was evaluated in vitro. Multivariate analysis revealed that only resistin was significantly and inversely correlated with PON1-lactonase activities (r = −0.346, p < 0.001) regardless of confounding factors such as age or HDL-cholesterol. It is worth noting that no statistical link was found between adipokine and arylesterase or paraoxonase, the two promiscuous activities of PON1. Notably, resistin down-regulated PON1 expression occurred in hepatocellular carcinoma cultures. Our study suggests that resistin might be a negative modulator of PON1 expression and anti-oxidative activity.

Increased PON lactonase activity in morbidly obese patients is associated with impaired lipid profile

AIMS

The paraoxonase-1 (PON1) enzyme could play an important role in the anti-oxidant capacity of high-density lipoprotein. However, there are no studies which analyse the evolution of the three activities of PON1 (PON arylesterase, PON paraoxonase and PON lactonase) after Roux-en-Y Gastric Bypass (RYGB) in morbidly obese subjects. We analysed the association of PON concentration and activities with the evolution of morbidly obese subjects who underwent RYGB, and its relationship with biochemical variables and different atherogenic indices.

METHODS

Twenty-seven non-obese and 82 morbidly obese subjects were studied before and 6 months after RYGB.

RESULTS

Before RYGB, morbidly obese subjects had a lower PON1 concentration (P < 0.05) and higher PON lactonase activity (P < 0.001) than non-obese subjects, with no differences in PON arylesterase and PON paraoxonase activities. After RYGB, PON1 concentration (P < 0.05) and PON lactonase activity (P < 0.001) decreased with regard to the presurgery state. PON lactonase activity correlated with the atherogenic index of plasma before (r = 0.19, P = 0.047) and after RYGB (r = 0.27, P = 0.035). In different multiple lineal regression analysis models, presurgery PON lactonase activity was associated with total cholesterol (β = 0.909, P < 0.001), LDL (β = 0.632, P = 0.006) and DBP (β = 0.230, P = 0.030) (R²  = 0.295), postsurgery PON lactonase activity was associated with esterified cholesterol (β = 0.362, P = 0.011) (R²  = 0.131), and the change (Δ) in PON lactonase activity after RYGB was associated with Δesterified cholesterol (β = 0.304, P = 0.030) (R²  = 0.093).

CONCLUSIONS

PON lactonase activity is associated with the presence of morbid obesity and with an impaired lipid profile. All associations found could indicate the relationship between PON lactonase activity and the development of atherosclerosis.

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.

Toxic effects of methamidophos on paraoxonase 1 activity and on rat kidney and liver and ameliorating effects of alpha-tocopherol

The role of alpha-tocopherol on nephrotoxicity and hepatotoxicity induced by methamidophos (MT) was investigated in wistar rats. Animals were given via gavage, for four weeks, a low dose of MT (MT1), a high dose of MT (MT2), vitamin E (200 mg/kg of bw) or both MT2 plus vitamin E (Vit E) and control group was given distillate water. MT treatment resulted in a significant decrease in the body weight of MT2-treated group. Moreover, MT-treated groups had significantly lower butyrylcholinesterase (p < 0.01) and paraoxonase 1 (PON1) activities compared with the control group (p < 0.05). However, MT2-treated group had significantly higher alkaline phosphatase activity compared with untreated rats (p < 0.05). Both MT-treated groups had significantly higher urea (p < 0.01) and uric acid levels (p < 0.05) compared with the control group. However, significant low uric acid level (p < 0.05) was noted in MT2 plus vit E-treated rats compared with MT2-treated group. Histopathological changes in organ tissues were observed in both MT-treated groups and MT2 plus vit E-treated rats. However, the damage was reduced in MT2 plus vit E-treated rats. Therefore, this study deduces that alpha-tocopherol administration may ameliorate the adverse effects of subacute exposure to MT on rat liver and kidney and this antioxidant can protect PON1 from oxidative stress induced by this organophosphorus pesticide. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 842-854, 2016.

Anti-apolipoprotein A-1 autoantibodies as risk biomarker for cardiovascular diseases in type 2 diabetes mellitus

OBJECTIVE

Anti-Apolipoprotein A-1 autoantibodies (anti-ApoA-1 IgG) represent an emerging prognostic cardiovascular marker in patients with myocardial infarction or autoimmune diseases associated with high thrombotic events. The aim of this work is to investigate the incidence of anti-apoA-1 autoantibodies in type 2 diabetes (T2DM) patients with and without CVD and to study potential association with disease risk and its effect on plasma lipid parameters.

METHODS

Qualitative determination of anti-apoA-1 IgG was assayed in sera from 302 subjects classified into T2DM patients (n=102), T2DM+CVD (n=112) and healthy controls (n=88).

RESULTS

The incidence of anti-apoA-1 IgG was significantly higher among CVD patients (35.7%) than T2DM patients (8.8%) or control subjects (6.1%), p<0.0001. A significant association with CVD was identified (p<0.0001) and subjects who were positive for anti-apoA-1 IgG were at 8.5 times increased risk to develop CVD when compared to controls. Diabetic patients who were positive for the antibodies showed 5.7 times increased CVD risk. ROC analysis indicated anti-apoA-1 IgG as a risk biomarker for CVD in T2DM patients with an AUC value of 0.76, sensitivity of 35.7% and specificity of 91.2%. Studying the effect on lipid parameters, anti-apoA-1 IgG associated with significantly higher serum concentrations of TC and non-HDL-C in all groups and with higher concentrations of LDL-C in diabetic patients and higher TC/HDL-C ratio in CVD patients.

CONCLUSION

Our results indicate that anti-apoA-1 IgG is a cardiovascular risk biomarker in T2DM patients.

Paraoxonase 1 activity and phenotype distribution in premenopausal and postmenopausal women

Introduction

Postmenopausal women have higher risk of cardiovascular disease. One of the contributing factors could be reduced activity of anti-atherogenic enzyme paraoxonase 1 (PON1). The aim of this study was to examine differences in the lipid status, paraoxonase and arylesterase PON1 activities and PON1 phenotype in women with regular menstrual cycle and in postmenopausal women.

Materials and methods:

The study included 51 women in reproductive age (25 in follicular and 26 in luteal phase of the menstrual cycle) and 23 women in postmenopause. Lipid parameters in sera were determined using original reagents and according to manufacturer protocol. PON1 activity in serum was assessed by spectrophotometric method with substrates: paraoxon and phenylacetate. PON1 phenotype was determined by double substrate method.

Results:

Compared to the women in follicular and luteal phase, postmenopausal women have significantly higher concentration of triglyceride [0.9 (0.7–1.3), 0.7 (0.6–1.0) vs. 1.5 (0.9–1.7) mmol/L; P = 0.002], cholesterol [5.10 (4.78–6.10), 5.05 (4.70–5.40) vs. 6.30 (5.73–7.23) mmol/L; P < 0.001], LDL [3.00 (2.56–3.63), 3.00 (2.70–3.70) vs. 3.90 (3.23–4.50) mmol/L; P < 0.001], and apolipoprotein B [0.88 (0.75–1.00), 0.79 (0.68–1.00) vs. 1.07 (0.90–1.24) mmol/L; P = 0.002]. PON1 basal [104 (66–260), 106 (63–250) vs. 93 (71–165) U/L; P = 0.847] and salt-stimulated paraoxonase activity [210 (131–462), 211 (120–442) vs. 180 (139–296) U/L; P = 0.857] as well as arylesterase activity [74 (63–82), 70 (54–91) vs. 70 (60–81) kU/L; P = 0.906] and PON1 phenotype (P = 0.810) were not different in the study groups.

Conclusion:

There are no differences in PON1 activity and PON1 phenotype between women with regular menstrual cycle and postmenopausal women.

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 lactonase activity, inflammation and antioxidant status in plasma of patients with type 1 diabetes mellitus

OBJECTIVES

To investigate paraoxonase-1 (PON1) lactonase activity, myeloperoxidase (MPO) activity (as a marker of inflammation) and antioxidant status in plasma of patients with type 1 diabetes mellitus.

METHODS

Whole blood and plasma samples were collected from patients with diabetes and healthy control subjects. PON1 lactonase and MPO activities and total antioxidant capacity (TEAC) were determined in plasma. Glycosylated haemoglobin (HbA1c) was quantified in whole blood.

RESULTS

Plasma PON1 lactonase and MPO activities were significantly higher and TEAC was significantly lower in patients with diabetes (n = 18) compared with healthy control subjects (n = 20). There were significant positive correlations between PON1 lactonase activity and MPO activity and HbA1c level, and plasma MPO and HbA1c. There were significant negative correlations between PON1 lactonase activity and TEAC, and MPO activity and TEAC.

CONCLUSIONS

Increased lactonase activity may inefficiently compensate for the high level of chronic inflammation and low antioxidant capacity in the plasma of patients with type 1 diabetes mellitus.

Dietary fatty acid intake is associated with paraoxonase 1 activity in a cohort-based analysis of 1,548 subjects

BACKGROUND

Paraoxonase 1 (PON1) is a cardioprotective, HDL-associated glycoprotein enzyme with broad substrate specificity. Our previous work found associations between dietary cholesterol and vitamin C with PON1 activity. The goal of this study was to determine the effect of specific dietary fatty acid (DFA) intake on PON1 activity.

METHODS

1,548 participants with paraoxonase activity measures completed the Harvard Standardized Food Frequency Questionnaire to determine their daily nutrient intake over the past year. Eight saturated, 3 monounsaturated, and 6 polyunsaturated DFAs were measured by the questionnaire. To reduce the number of observations tested, only specific fatty acids that were not highly correlated (r < 0.8) with other DFAs or that were representative of other DFAs through high correlation within each respective group (saturated, monounsaturated, or polyunsaturated) were retained for analysis. Six specific DFA intakes - myristic acid (14 carbon atoms, no double bonds - 14:0), oleic acid (18:1), gadoleic acid (20:1), α-linolenic acid (18:3), arachidonic acid (20:4), and eicosapentaenoic acid (20:5) - were carried forward to stepwise linear regression, which evaluated the effect of each specific DFA on covariate-adjusted PON1 enzyme activity.

RESULTS

Four of the 6 tested DFA intakes - myristic acid (p = 0.038), gadoleic acid (p = 6.68 × 10(-7)), arachidonic acid (p = 0.0007), and eicosapentaenoic acid (p = 0.013) - were independently associated with covariate-adjusted PON1 enzyme activity. Myristic acid, a saturated fat, and gadoleic acid, a monounsaturated fat, were both positively associated with PON1 activity. Both of the tested polyunsaturated fats, arachidonic acid and eicosapentaenoic acid, were negatively associated with PON1 activity.

CONCLUSIONS

This study presents the largest cohort-based analysis of the relationship between dietary lipids and PON1 enzyme activity. Further research is necessary to elucidate and understand the specific biological mechanisms, whether direct or regulatory, through which DFAs affect PON1 activity.

Serum paraoxonase 1 activity is associated with fatty acid composition of high density lipoprotein

Introduction. Cardioprotective effect of high density lipoprotein (HDL) is, in part, dependent on its related enzyme, paraoxonase 1 (PON1). Fatty acid composition of HDL could affect its size and structure. On the other hand, PON1 activity is directly related to the structure of HDL. This study was designed to investigate the association between serum PON1 activity and fatty acid composition of HDL in healthy men. Methods. One hundred and forty healthy men participated in this research. HDL was separated by sequential ultracentrifugation, and its fatty acid composition was analyzed by gas chromatography. PON1 activity was measured spectrophotometrically using paraxon as substrate. Results. Serum PON1 activity was directly correlated with the amount of stearic acid and dihomo-gamma-linolenic acid (DGLA). PON1/HDL-C was directly correlated with the amount of miristic acid, stearic acid, and DGLA and was inversely correlated with total amount of ω6 fatty acids of HDL. Conclusion. The fatty acid composition of HDL could affect the activity of its associated enzyme, PON1. As dietary fats are the major determinants of serum lipids and lipoprotein composition, consuming some special dietary fatty acids may improve the activity of PON1 and thereby have beneficial effects on health.

Paraoxonase 1 activities, regulation, and interactions with atherosclerotic lesion

PURPOSE OF REVIEW

Improving serum levels of HDL and its subfractions, as well as, oxidative/inflammatory properties has become a fundamental aim in today's atherosclerosis research. Efforts to reach this goal are paralleled by achievements in drug development toward decreasing serum LDL levels and oxidative status.

RECENT FINDINGS

Paraoxonase1 (PON1) is an HDL-associated enzyme that is deemed responsible for many of the HDL's antiatherogenic and cardioprotective characteristics. PON1 is highly sensitive to variations in its milieu, and endogenous compounds (fatty acids, phospholipids), nutritional ingredients (flavonoids and other antioxidants), and environmental elements (reactive nitrogen and oxygen species, metals, surfactants), significantly affect the enzyme's activities. PON1 was shown to be responsible for some of the HDL antiatherogenic characteristics such as HDL-mediated cholesterol efflux from macrophages, and the inhibition of LDL oxidation.

SUMMARY

The present review summarizes the recent literature related to various elements in PON1's milieu that regulate its activities, with an emphasis on its interrelation with components of the human carotid atherosclerotic lesion (plaque) which are in constant contact with circulating HDL-associated PON1.

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.

Regulation of hepatic paraoxonase-1 expression

Serum paraoxonase-1 (PON1) is a member of the paraoxonases family (PON1, PON2, and PON3). PON1 is synthesized and secreted by the liver, and in circulation it is associated with HDL. PON1 has antioxidative properties, which are associated with the enzyme's capability to decrease oxidative stress in atherosclerotic lesions and to attenuate atherosclerosis development. Epidemiological evidence demonstrates that low PON1 activity is associated with increased risk of cardiovascular events and cardiovascular disease and is an independent risk factor for coronary artery disease. Therefore, pharmacological modulation of PON1 activity or PON1 gene expression could constitute a useful approach for preventing atherosclerosis. A primary determinant of serum PON1 levels is the availability of the enzyme for release by the liver, the principal site of PON1 production. Together with the enzyme secretion rate, enzymatic turnover, and protein stability, the level of PON1 gene expression is a major determinant of PON1 status. This paper summarizes recent progress in understanding the regulation of PON1 expression in hepatocytes.

Lipid peroxidation and paraoxonase-1 activity in celiac disease

Paraoxonase-1 (PON1) plays an antioxidant and anti-inflammatory role. Aim of the study was to investigate the alteration of paraoxonase-1 activity in celiac disease (CD), an intestinal disorder characterized by toxic injury exerted by gluten peptides. Activities of PON1, levels of biochemical markers of lipid peroxidation and total antioxidant capacity were evaluated in serum obtained from 27 celiac patients (11 at diagnosis, 16 treated with gluten free diet) and 25 healthy subjects. Moreover, the serum susceptibility of Cu²⁺-induced lipid peroxidation was investigated in controls and patients. The results showed a lower PON1 activity in serum of both groups of celiac patients with respect to control subjects. PON1 activity in CD was related with markers of disease severity and was negatively correlated with the levels of lipid hydroperoxide and with the susceptibility of serum to lipid peroxidation induced in vitro by metal ions. The alteration of PON1 activity and markers of lipid peroxidation realized at lower extent in patients who were on a gluten-free diet.

Human carotid lesion linoleic acid hydroperoxide inhibits paraoxonase 1 (PON1) activity via reaction with PON1 free sulfhydryl cysteine 284

Paraoxonase 1 (PON1) is an HDL-associated lactonase with antiatherogenic properties. These include dampening the oxidation properties of human carotid lesion lipid extract (LLE), which in turn inactivates the enzyme. The aims of this study were to identify the PON1 inhibitor in LLE and explore the mechanism of inhibition. LLE inhibited both recombinant PON1 and HDL-PON1 lactonase activity in a dose- and time-dependent manner. Addition of antioxidants or electrophiles to LLE did not prevent PON1 inhibition. LLE was unable to inhibit a PON1 mutant lacking Cys284, whereas it did inhibit all other PON1 mutants tested. The inhibitor in the LLE was identified as linoleic acid hydroperoxide (LA-OOH) and inhibition was specific to this hydroperoxide. During its inhibition, PON1 acted like a peroxidase enzyme, reducing LA-OOH to LA-hydroxide via its Cys284. A similar reaction occurred with external thiols, such as DDT or cysteine, which also prevented PON1 inhibition and restored enzyme activity after inhibition. Thus, the antiatherogenic properties of HDL could be, at least in part, related to the sulfhydryl-reducing characteristics of its associated PON1, which are further protected and recycled by the sulfhydryl amino acid cysteine.