Study of factors influencing the decreased HDL associated PON1 activity with aging

The use of serum paraoxonase-1 to assess inflammation in horses with colitis serum paraoxonase-1 in horses with colitis

BACKGROUND

Paraoxonase-1 (PON-1) has been suggested as a marker of inflammation and oxidative stress in horses and could potentially be used for prognostication in horses with colitis.

OBJECTIVES

Assessment of PON-1 in horses with colitis and comparison of two methods.

METHODS

Serum PON-1 was measured by two methods (paraoxon and p-nitrophenyl acetate) in 161 horses with colitis and 57 controls. Follow-up samples obtained during hospitalization were available from 106 horses with colitis. The two methods were compared.

RESULTS

Serum PON-1 was significantly lower in horses with colitis than in healthy horses (P < .0001 for both methods) as well as in nonsurvivors compared with survivors (P = .0141 [paraoxon-based method] and P < .0001 [p-nitrophenyl acetate-based method]), but with marked overlap between groups. PON-1 activity did not change parallel to a change in inflammatory status in response to treatment when assessed at admission and in up to seven follow-up samples. Admission PON-1 activity could not reliably classify horses as survivors or nonsurvivors, with sensitivity and specificity ranging between 53.1% and 72.9%. Results from the two methods were comparable.

CONCLUSIONS

Both methods reliably measured serum PON-1 activity. Significant differences in PON-1 activity were found between healthy horses and horses with colitis and between survivors and nonsurvivors. However, PON-1 activity varied considerably within groups. Both the proposed reference intervals as well as alternative cutoff values resulted in suboptimal diagnostic and prognostic performance, and the use of serum PON-1 in horses with colitis thus seems to add little to existing diagnostic and prognostic markers.

High-Density Lipoprotein Metabolism and Function in Cardiovascular Diseases: What about Aging and Diet Effects?

Cardiovascular diseases (CVDs) have become the leading global cause of mortality, prompting a heightened focus on identifying precise indicators for their assessment and treatment. In this perspective, the plasma levels of HDL have emerged as a pivotal focus, given the demonstrable correlation between plasma levels and cardiovascular events, rendering them a noteworthy biomarker. However, it is crucial to acknowledge that HDLs, while intricate, are not presently a direct therapeutic target, necessitating a more nuanced understanding of their dynamic remodeling throughout their life cycle. HDLs exhibit several anti-atherosclerotic properties that define their functionality. This functionality of HDLs, which is independent of their concentration, may be impaired in certain risk factors for CVD. Moreover, because HDLs are dynamic parameters, in which HDL particles present different atheroprotective properties, it remains difficult to interpret the association between HDL level and CVD risk. Besides the antioxidant and anti-inflammatory activities of HDLs, their capacity to mediate cholesterol efflux, a key metric of HDL functionality, represents the main anti-atherosclerotic property of HDL. In this review, we will discuss the HDL components and HDL structure that may affect their functionality and we will review the mechanism by which HDL mediates cholesterol efflux. We will give a brief examination of the effects of aging and diet on HDL structure and function.

Dietary proteins modulate high-density lipoprotein characteristics in a sex-specific way in Apoe-deficient mice

OBJECTIVES

The type and amount of dietary protein have become a topic of renewed interest, considering their involvement in several diseases. However, little attention has been devoted to the effect of avian proteins despite their wide human consumption. In a previous study, we saw that compared with soybean protein, the consumption of avian proteins, depending on sex, resulted in similar or lower atherosclerosis with a higher paraoxonase 1 activity, an antioxidant enzyme carried by high-density lipoproteins (HDL). This suggests that under these conditions, the HDL lipoproteins may undergo important changes. The aim of this research was to study the influence of soybean, chicken, and turkey proteins on the characteristics of HDL.

METHODS

Male and female Apoe-deficient mice were fed purified Western diets based on the AIN-93 diet, differing only in the protein source, for 12 wk. After this period, blood and liver samples were taken for analysis of HDL composition and hepatic expression of genes related to HDL metabolism (Abca1, Lcat, Pltp, Pon1, and Scarb1). Depending on sex, these genes define a different network of interactions. Females consuming the turkey protein-containing diet showed decreased atherosclerotic foci, which can be due to larger very-low-density lipoproteins (VLDLs) calculated by molar ratio triacylglycerols/VLDL cholesterol and higher expression of Lcat. In contrast, in males, a higher ratio of paraoxonase1 to apolipoprotein A1 decreased the oxidative status of the different lipoproteins, and augmented Abca1 expression was observed.

CONCLUSIONS

The source of protein has an effect on the development of atherosclerosis depending on sex by modifying HDL characteristics and the expression of genes involved in their properties.

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.

Lower paraoxonase 1 paraoxonase activity is associated with a worse prognosis in patients with non-ST-segment elevation myocardial infarction in long-term follow-up

BACKGROUND

Acute coronary syndrome (ACS) is one of the main manifestations of coronary artery disease, with a higher prevalence and worst prognosis. Oxidative stress is important in atherosclerosis and ACS, and paraoxonase 1 (PON1) is directly related to reducing the effects of oxidative stress on lipoproteins. The present study evaluated the prognostic value of PON1 activity in patients with non-ST-segment elevation ACS [non-ST-segment elevation myocardial infarction (NSTEMI) and unstable angina (UA)], included in the ERICO study.

METHODS

PON1 paraoxonase activity was determined in serum samples from 485 patients collected on admission. The prognostic value in the follow-up of up to 5 years was evaluated according to cutoff points established by tertiles. Kaplan-Meier curves and Cox regression were used for the analysis of all-cause mortality and cardiovascular mortality.

RESULTS

The sample consisted mainly of elderly patients with a high frequency of cardiovascular risk factors. At follow-up of up to 5 years, there were 126 deaths from all causes (80 deaths from CVD). The lowest tertile of PON1 paraoxonase activity was associated with a higher risk of death in patients with NSTEMI, but not in patients with UA.

CONCLUSION

PON1 paraoxonase activity has potential prognostic value in patients with NSTEMI.

Expression of PON1, PON2, PON3 and MPO Genes in Patients with Depressive Disorders

Background: Taking into account the role of oxidative stress in neurodegeneration, we sought to evaluate the expression of genes for select enzymes with antioxidant properties (paraoxonases PON1, PON2 and PON3 and myeloperoxidase MPO) at the mRNA and protein levels in patients with depressive disorders. We further sought to determine the impact of oxidative stress in the etiopathogenesis of this group of mood disorders. Methods: A total of 290 subjects (190 depressed patients, 100 healthy controls) took part in the study. Sociodemographic and clinical data were collected. The severity of depressive symptoms was assessed using the Hamilton Depression Rating Scale (HDRS). Venous blood was collected. RT-PCR was used to assess gene expression at the mRNA level, while enzyme-linked immunosorbent assay (ELISA) was used to assess gene expression at the protein level. Results: The expression of the PON2 and PON3 genes at the protein level was significantly higher in depressive patients than in healthy controls. mRNA expression of the PON1, PON2 and PON3 genes was slightly higher in patients with depressive disorders than in the control group, however, this relationship was not statistically significant. On the other hand, the expression of the MPO gene at both mRNA and protein levels was significantly lower in patients with depressive disorder than in the control group. Conclusions: Our results are not in agreement with many studies on enzymes involved in maintaining oxidative balance. Our findings may not support the utility of paraoxonases (PON) or myeloperoxidase (MPO) as promising biomarker candidates of depression pending larger and well controlled studies.

Paraoxonase-1 Facilitates PRRSV Replication by Interacting with Viral Nonstructural Protein-9 and Inhibiting Type I Interferon Pathway

Paraoxonase-1 (PON1), an esterase with specifically paraoxonase activity, has been proven to be involved in inflammation and infection. Porcine reproductive and respiratory syndrome virus (PRRSV) is still a major concern in pigs and causes severe economic losses to the swine industry worldwide. In this study, the role of PON1 was investigated in porcine alveolar macrophages (PAMs) during PRRSV infection. The results showed that PRRSV replication downregulated PON1, and the knockdown of PON1 significantly decreased PRRSV replication. Similarly, PON1 overexpression could enhance PRRSV replication. Interestingly, we observed that PON1 interacted with PRRSV nonstructural protein 9 (Nsp9), the RNA-dependent RNA polymerase, and the knockdown of PON1 lowered the RNA binding ability of Nsp9, suggesting that PON1 can facilitate Nsp9 function in viral replication. In addition, the knockdown of PON1 expression led to the amplification of type I interferon (IFN) genes and vice versa. In summary, our data demonstrate that PON1 facilitates PRRSV replication by interacting with Nsp9 and inhibiting the type I IFN signaling pathway. Hence, PON1 may be an additional component of the anti-PRRSV defenses.

The Relationship between Cancer and Paraoxonase 1

Extensive research has been carried out to understand and elucidate the mechanisms of paraoxonase 1 (PON1) in the development of diseases including cancer, cardiovascular diseases, neurological diseases, and inflammatory diseases. This review focuses on the relationship between PON1 and cancer. The data suggest that PON1, oxidative stress, chronic inflammation, and cancer are closely linked. Certainly, the gene expression of PON1 will remain challenging to study. Therefore, targeting PON1, redox-sensitive pathways, and transcription factors promise prevention and therapy in the development of several diseases, including cancer.

HDL Composition, Heart Failure, and Its Comorbidities

Although research on high-density lipoprotein (HDL) has historically focused on atherosclerotic coronary disease, there exists untapped potential of HDL biology for the treatment of heart failure. Anti-oxidant, anti-inflammatory, and endothelial protective properties of HDL could impact heart failure pathogenesis. HDL-associated proteins such as apolipoprotein A-I and M may have significant therapeutic effects on the myocardium, in part by modulating signal transduction pathways and sphingosine-1-phosphate biology. Furthermore, because heart failure is a complex syndrome characterized by multiple comorbidities, there are complex interactions between heart failure, its comorbidities, and lipoprotein homeostatic mechanisms. In this review, we will discuss the effects of heart failure and associated comorbidities on HDL, explore potential cardioprotective properties of HDL, and review novel HDL therapeutic targets in heart failure.

The Removal of Time-Concentration Data Points from Progress Curves Improves the Determination of Km: The Example of Paraoxonase 1

Several approaches for determining an enzyme's kinetic parameter K_m (Michaelis constant) from progress curves have been developed in recent decades. In the present article, we compare different approaches on a set of experimental measurements of lactonase activity of paraoxonase 1 (PON1): (1) a differential-equation-based Michaelis-Menten (MM) reaction model in the program Dynafit; (2) an integrated MM rate equation, based on an approximation of the Lambert W function, in the program GraphPad Prism; (3) various techniques based on initial rates; and (4) the novel program "iFIT", based on a method that removes data points outside the area of maximum curvature from the progress curve, before analysis with the integrated MM rate equation. We concluded that the integrated MM rate equation alone does not determine kinetic parameters precisely enough; however, when coupled with a method that removes data points (e.g., iFIT), it is highly precise. The results of iFIT are comparable to the results of Dynafit and outperform those of the approach with initial rates or with fitting the entire progress curve in GraphPad Prism; however, iFIT is simpler to use and does not require inputting a reaction mechanism. Removing unnecessary points from progress curves and focusing on the area around the maximum curvature is highly advised for all researchers determining K_m values from progress curves.

High-density lipoproteins and immune response: A review

High-density lipoproteins (HDLs) are heterogeneous lipoproteins that modify their composition and functionality depending on physiological or pathological conditions. The main roles of HDL are cholesterol efflux, and anti-inflammatory and antioxidant functions. These functions can be compromised under pathological conditions. HDLs play a role in the immune system as anti-inflammatory molecules but when inflammation occurs, HDLs change their composition and carry pro-inflammatory cargo. Hence, many molecular intermediates that influence inflammatory microenvironments and cell signaling pathways can modulate HDLs structural modification and function. This review provides a comprehensive assessment of the importance of HDL composition and anti-inflammatory function in the onset and progression of atherosclerotic cardiovascular diseases. On the other hand, immune cell activation during progression of atheroma plaque formation can be influenced by HDLs through HDL-derived cholesterol depletion from lipid rafts and through HDL interaction with HDL receptors expressed on T and B lymphocytes. Cholesterol efflux is mediated by HDL receptors located in lipid rafts in peripheral cells, which undergo membrane structural modifications, and interferes with subsequent molecules interactions or intracellular signaling cascades. Regarding antigen-presentation cells such as macrophages or dendritic cells, HDL function may then modulate lymphocytes activation in immune response. Our review also contributes to the understanding of the effects exerted by HDLs in signal transduction associated to our immune cell population during chronic diseases progression.

Good Cholesterol Gone Bad? HDL and COVID-19

The transmissible respiratory disease COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected millions of people worldwide since its first reported outbreak in December of 2019 in Wuhan, China. Since then, multiple studies have shown an inverse correlation between the levels of high-density lipoprotein (HDL) particles and the severity of COVID-19, with low HDL levels being associated with an increased risk of severe outcomes. Some studies revealed that HDL binds to SARS-CoV-2 particles via the virus's spike protein and, under certain conditions, such as low HDL particle concentrations, it facilitates SARS-CoV-2 binding to angiotensin-converting enzyme 2 (ACE2) and infection of host cells. Other studies, however, reported that HDL suppressed SARS-CoV-2 infection. In both cases, the ability of HDL to enhance or suppress virus infection appears to be dependent on the expression of the HDL receptor, namely, the Scavenger Receptor Class B type 1 (SR-B1), in the target cells. SR-B1 and HDL represent crucial mediators of cholesterol metabolism. Herein, we review the complex role of HDL and SR-B1 in SARS-CoV-2-induced disease. We also review recent advances in our understanding of HDL structure, properties, and function during SARS-CoV-2 infection and the resulting COVID-19 disease.

Role of Paraoxonase1 in the Regulation of High-Density Lipoprotein Functionality and in Cardiovascular Protection

Significance: Human paraoxonase (PON) is a member of the gene family that includes paraoxonase 1 (PON1), PON2, and PON3. PON is known for its capacity to hydrolyze a wide range of substrates, including organophosphorus compounds, nerve gases, and aromatic carboxylic acid esters. Recent Advances: Several studies have highlighted the involvement of PON, particularly PON1, in the modulation of the capacity of high-density lipoprotein (HDL) to protect against the atherosclerosis process and its clinical manifestations. PON1 exhibits antioxidant and anti-inflammatory activities and may be involved in the regulation of the principal antiatherogenic activity of HDL, that is, the regulation of the reverse cholesterol transport process. Critical Issues: Although epidemiological studies have shown that there is an inverse relationship between HDL levels and cardiovascular risk, several studies have emphasized the importance of HDL functionality in protecting against cardiovascular diseases (CVD). Given that PON1 is involved in several atheroprotective functions of HDL, the aim of this article is to review the existing literature on PON1 and to discuss the principal mechanisms by which PON1 may exert its different activities. Future Directions: The elucidation of the mechanisms by which PON1 modulates the functionality of HDL as well as the identification of the interventions that stimulate PON1 activity and/or increase its plasma concentration would make it possible to propose new strategies to prevent CVD. Antioxid. Redox Signal. 34, 191-200.

Ovarian stimulated cycles reduce protection of follicular fluid against free radicals

Controlled ovarian hyperstimulation cycle with exogenous gonadotropins (COH) is associated with clinical complications. The aim of this work was to determine whether COH alters the physiological antioxidant status of follicular fluid in women with no reproductive dysfunction, compared to the natural cycle (NC). In this longitudinal study, forty-one women (oocyte donors) consecutively underwent NC and COH. Follicular fluid was collected at oocyte retrieval and different redox biomarkers were determined: total antioxidant activity (TAA), oxygen radical absorbance capacity (ORAC), nitric oxide, α- and γ-tocopherol, the fatty acid composition, activities of superoxide dismutase, catalase, total and Se-dependent glutathione peroxidases, and the antioxidant paraoxonase (PON) family. Results showed that TAA (1.70 ± 0.03 mM versus 1.86 ± 0.03 mM, p < 0.05), α-tocopherol (4.37 ± 0.26 μM versus 5.74 ± 0.30 μM, p < 0.05), PON1 paraoxonase (245 ± 24 nmol/min/ml versus 272 ± 27 nmol/min/ml, p < 0.05), PON1 arylesterase (87.2 ± 4.6 μmol/min/ml versus 99.3 ± 4.8 μmol/min/ml, p < 0.05), and PON3 simvastatinase (13.48 ± 0.52 nmol/min/ml versus 16.29 ± 0.72 nmol/min/ml, p < 0.001) were significantly lower in COH versus NC. Fatty acids from COH were more saturated, increasing palmitate and decreasing the n-6 and total polyunsaturated fatty acids (PUFAs). Docosahexaenoic acid also increased (p < 0.05). Results suggest that COH could lead to premature ovarian aging and provide new insights into the possible prevention of the adverse effects of ovarian hyperstimulation by directing therapeutic applications to the maintenance of the redox balance and fatty acid status, with special attention to paraoxonase proteins and docosahexaenoic acid.

Circulating Lactonase Activity but Not Protein Level of PON-1 Predicts Adverse Outcomes in Subjects with Chronic Kidney Disease

The burden of cardiovascular disease and death in chronic kidney disease (CKD) outpaces that of the other diseases and is not adequately described by traditional risk factors alone. Diminished activity of paraoxonase (PON)-1 is associated with increased oxidant stress, a common feature underlying the pathogenesis of CKD. We aimed to assess the prognostic value of circulating PON-1 protein and PON lactonase activity on adverse clinical outcomes across various stages and etiologies of CKD. Circulating PON-1 protein levels and PON lactonase activity were measured simultaneously in patients with CKD as well as a cohort of apparently healthy non-CKD subjects. Both circulating PON-1 protein levels and PON lactonase activity were significantly lower in CKD patients compared to the non-CKD subjects. Similarly, across all stages of CKD, circulating PON-1 protein and PON lactonase activity were significantly lower in patients with CKD compared to the non-CKD controls. Circulating PON lactonase activity, but not protein levels, predicted future adverse clinical outcomes, even after adjustment for traditional risk factors. The combination of lower circulating protein levels and higher activity within the CKD subjects were associated with the best survival outcomes. These findings demonstrate that diminished circulating PON lactonase activity, but not protein levels, predicts higher risk of future adverse clinical outcomes in patients with CKD.

Antibiotics Used in Patients after Surgery and Effects of Human Serum Paraoxonase-I (PON1) Enzyme Activity

Background:

Paraoxonase (PON; arilesterase, [EC 3.1.8.1]) is an enzyme from the group arilesterases (ARE). This enzyme is capable of hydrolyzing paraoxone which is the active metabolite of parathion, an organic phosphorus insecticide. PON activity was found to be low in individuals prone to development of atherosclerosis such as diabetes, familial hypercholesterolemia and kidney disorders. It was noted that PON enzyme activity decreases in relation to age increase in adults. PON enzyme activity is approximately half of that in newborns and premature babies. Approximately one year after birth, it reaches the adult level. It can be said that PON1 has significant role on living organisms. For this reason, many studies on interactions of PON-drugs are needed. </P><P> Objective: In this article, our aim is to investigate in vitro effects of four pharmaceutically active agents (fosfomycin, cefuroxime axetil, cefaclor monohydrate, and cefixime) which are often used in patients after surgery on human serum paraoxanase-I (PON1) enzyme activity.

Methods:

In this article, we purify paraoxonase-I enzyme from human serum by using ammonium sulfate precipitation (in the range of 60-80%), ion exchange and gel filtration chromatography. We use electrophoresis to check the purity of the enzyme. We investigate the paraoxonase activity of the enzyme at 412 nm the inhibition effects of the active substances. Paraoxone is used as the substrate. Activity measurements arw made at different inhibitor concentrations related to inhibitor studies and % Activity- [I] graphs are drawn for drug active substances. Lineweaver-Burk graphics are used to determine the Ki constants. Finally, to determine the types of inhibition we interpret these graphs.

Results:

The active agents used after surgery decreased the PON1 enzyme activity. They showed different inhibition mechanism. The inhibition mechanism of fosfomycin and cefaclor monohydrate was noncompetitive, cefixime was uncompetitive and cefuroxime axetil was a competitive inhibitor. The IC50 values for fosfomycin, cefuroxime axetil, cefaclor monohydrate, and cefixime were calculated to be 31.5 mM, 1.03 mM, 4.18 mM and 0.781 mM, respectively, and the Ki constants were determined to be 27.98 ± 12.25 mM, 2.20 ± 0.22 mM, 4.81 ± 2.25 mM and 1.12 ± 0.32 mM, respectively. The IC50 and Ki values showed that cefixime active agent has the maximum inhibition.

Conclusion:

In this study, we have detected that cefuroxime axetil inhibited competitively in vitro paraoxonase activity of this enzyme. According to this information, we thought that cefuroxime axetil linked to the active site of the enzyme. Fosfomycin and cefaclor monohydrate can be attached with amino acids out of the active site of the enzyme because they inhibit enzyme noncompetitively. Cefixime can be attached only to the enzyme-substrate complex because it inhibits enzyme uncompetitively.

Paraoxonase (PON)-1: a brief overview on genetics, structure, polymorphisms and clinical relevance

Paraoxonase-1 (PON1) is a high-density lipoprotein-associated esterase and is speculated to play a role in several human diseases including diabetes mellitus and atherosclerosis. Low PON1 activity has been associated with increased risk of major cardiovascular events, therefore a variety of studies have been conducted to establish the cardioprotective properties and clinical relevance of PON1. The major aim of this review was to highlight the important studies and to subsequently assess if PON1 has clinical relevance. A review of the literature showed that there is currently insufficient data to suggest that PON1 has clinical relevance. It is our opinion that robust studies are required to clarify the clinical relevance of PON1.

A case-control study: The association of serum paraoxonase 1 activity and concentration with the development of type 2 diabetes mellitus

BACKGROUND

A longitudinal study assessed serum paraoxonase 1 (PON1) activity and concentration as affected by age and as associated with the development of type 2 diabetes (T2D). PON1's recently established physiological function is the hydrolysis of lipolactones in oxidized LDL particles.

METHODS

Serum samples and clinical data collected and stored at different time points over a 20-year interval in the Air Force Health Study were analysed. PON1 activity and concentration and C-reactive protein concentration in samples from the same individuals 20 years apart were compared using a paired t test (n = 159). A case-control study design and multivariable logistic regression analysis assessed the association of PON1's activity and concentration with the subsequent development of T2D (n = 222 and α = 0.10).

RESULTS

No difference with age was found in PON1 activity assessed using 3 substrates, paraoxon (P = 0.897), phenyl acetate (P = 0.994), and dihydrocoumarin (P = 0.505), or PON1 serum concentration (P = 0.357). C-reactive protein concentration increased 0.7 mg/L (P = 0.004) over the 20-year interval. Lower PON1 activity assayed with phenyl acetate (P = 0.015, OR = 1.25 per 1000 U/L decrease) was associated with an increased risk of developing T2D as was a lower PON1 serum concentration (P = 0.004, OR = 1.72 per 2 μmol/L decrease). PON1 activity assayed with paraoxon (P = 0.681) or dihydrocoumarin (P = 0.136) was not associated with the development of T2D.

CONCLUSIONS

Lower PON1 activity and concentration were associated with an increased risk of developing T2D when adjusted for many of the common risk markers for T2D previously identified. Thus, PON1 may have merit as a biomarker for the development of T2D.

The role of paraoxonase 1 in regulating high-density lipoprotein functionality during aging

Pharmacological interventions to increase the concentration of high-density lipoprotein (HDL) have led to disappointing results and have contributed to the emergence of the concept of HDL functionality. The anti-atherogenic activity of HDLs can be explained by their functionality or quality. The capacity of HDLs to maintain cellular cholesterol homeostasis and to transport cholesterol from peripheral cells to the liver for elimination is one of their principal anti-atherogenic activities. However, HDLs possess several other attributes that contribute to their protective effect against cardiovascular diseases. HDL functionality is regulated by various proteins and lipids making up HDL particles. However, several studies investigated the role of paraoxonase 1 (PON1) and suggest a significant role of this protein in the regulation of the functionality of HDLs. Moreover, research on PON1 attracted much interest following several studies indicating that it is involved in cardiovascular protection. However, the mechanisms by which PON1 exerts these effects remain to be elucidated.

Advanced glycation end products affect cholesterol homeostasis by impairing ABCA1 expression on macrophages

Reverse cholesterol transport (RCT), which is intimately linked to high-density lipoproteins (HDLs), plays a key role in cholesterol homeostasis and the prevention of atherosclerosis. The goal of the present study was to investigate the effect of aging and advanced glycation end products (AGEs) on RCT as well as on other factors that may affect the antiatherogenic property of HDLs. The transfer of macrophage-derived cholesterol to the plasma and liver and then to the feces for elimination was significantly lower in aged mice than in young mice. Chronic injection of d -galactose (D-gal) or AGEs also significantly reduced RCT (65.3% reduction in [³H]cholesterol levels in the plasma of D-gal-treated mice after 48 h compared with control mice, P < 0.01). The injection of both D-gal and aminoguanidine hydrochloride increased [³H]cholesterol levels in the plasma, although the levels were lower than those of control mice. The in vitro incubation of HDLs with dicarbonyl compounds increased the carbonyl and conjugated diene content of HDLs and significantly reduced PON1 paraoxonase activity (87.4% lower than control HDLs, P < 0.0001). Treating J774A.1 macrophages with glycated fetal bovine serum increased carbonyl formation (39.5% increase, P < 0.003) and reduced ABCA1 protein expression and the capacity of macrophages to liberate cholesterol (69.1% decrease, P < 0.0001). Our results showed, for the first time, that RCT is altered with aging and that AGEs contribute significantly to this alteration.

The effect of passive and active exposure to tobacco smoke on lipid profile parameters and the activity of certain membrane enzymes in the blood of women in the first trimester of pregnancy

The effect of tobacco smoke on lipid peroxidation, the lipid profile and membrane-bound enzymatic activity in the first trimester of pregnancy was investigated. In the plasma of women with active exposure to tobacco smoke, we have found increased lipid peroxidation and higher total concentrations of cholesterol, triglycerides and low-density lipoproteins in the blood, as well as a decreased concentration of high-density lipoproteins. A higher concentration of low-density lipoproteins and a lower concentration of high-density lipoproteins were also found in the plasma of passive smokers. In contrast, women who smoked before pregnancy had only a higher low-density lipoprotein concentration. In the group of active and passive smoking women, lower arylesterase and phosphotriesterase activities of paraoxonase were observed, while the lactonase activity of paraoxonase decreased only in the group of active smoking women. In women with active exposure to tobacco smoke, a higher activity level of alanine aminopeptidase and γ-glutamyltransferase in the plasma was found. It is important to monitor the lipid profile during pregnancy, especially when exposure to tobacco smoke occurs.

Paraoxonase activities in human follicular fluid: role in follicular maturation

The paraoxonases (PONs) are antioxidant enzymes associated with beneficial effects against several diseases and some exposures. Little is known, however, about the role of PONs in human reproduction. This work was conducted to investigate whether any association existed between the activities of the PON enzymes (1, 2, and 3) with the follicular size and fertility parameters in assisted reproduction. The study included 100 subfertile women (patients) and 55 proven fertile women (oocyte donors), all undergoing an ovarian stimulation cycle. Follicular fluid from small (diameter <12 mm) and large (diameter ≥18 mm) follicles was collected from each woman. The PONs were quantified in follicular fluid by immunoblotting. PON1 arylesterase and paraoxonase, PON2 methyl paraoxonase and PON3 simvastatinase activities from both donors and patients were significantly higher (P < 0.001) in follicular fluid from large follicles compared with small ones. In large follicles, PON3 activity was significantly higher (P < 0.01) in donors compared with patients. Follicular fluid PON1 arylesterase and paraoxonase activity was positively correlated with the number of retrieved oocytes in donors. This study shows an increase in the activities of PONs with follicle size, thus providing indirect evidence for the role of PONs in follicle maturation.

Human paraoxonase 1 overexpression in mice stimulates HDL cholesterol efflux and reverse cholesterol transport

This study was aimed to investigate the effect of human PON1 overexpression in mice on cholesterol efflux and reverse cholesterol transport. PON1 overexpression in PON1-Tg mice induced a significant 3-fold (p<0.0001) increase in plasma paraoxonase activity and a significant ~30% (p<0.0001) increase in the capacity of HDL to mediate cholesterol efflux from J774 macrophages compared to wild-type mice. It also caused a significant 4-fold increase (p<0.0001) in the capacity of macrophages to transfer cholesterol to apoA-1, a significant 2-fold (p<0.0003) increase in ABCA1 mRNA and protein expression, and a significant increase in the expression of PPARγ (p<0.0003 and p<0.04, respectively) and LXRα (p<0.0001 and p<0.01, respectively) mRNA and protein compared to macrophages from wild-type mice. Moreover, transfection of J774 macrophages with human PON1 also increased ABCA1, PPARγ and LXRα protein expression and stimulates macrophages cholesterol efflux to apo A1. In vivo measurements showed that the overexpression of PON1 significantly increases the fecal elimination of macrophage-derived cholesterol in PON1-Tg mice. Overall, our results suggested that the overexpression of PON1 in mice may contribute to the regulation of the cholesterol homeostasis by improving the capacity of HDL to mediate cholesterol efflux and by stimulating reverse cholesterol transport.

Reconstituted high-density lipoproteins promote wound repair and blood flow recovery in response to ischemia in aged mice

BACKGROUND

The average population age is increasing and the incidence of age-related vascular complications is rising in parallel. Impaired wound healing and disordered ischemia-mediated angiogenesis are key contributors to age-impaired vascular complications that can lead to amputation. High-density lipoproteins (HDL) have vasculo-protective properties and augment ischemia-driven angiogenesis in young animals. We aimed to determine the effect of reconstituted HDL (rHDL) on aged mice in a murine wound healing model and the hindlimb ischemia (HLI) model.

METHODS

Murine wound healing model-24-month-old aged mice received topical application of rHDL (50 μg/wound/day) or PBS (vehicle control) for 10 days following wounding. Murine HLI model-Femoral artery ligation was performed on 24-month-old mice. Mice received rHDL (40 mg/kg) or PBS, intravenously, on alternate days, 1 week pre-surgery and up to 21 days post ligation. For both models, blood flow perfusion was determined using laser Doppler perfusion imaging. Mice were sacrificed at 10 (wound healing) or 21 (HLI) days post-surgery and tissues were collected for histological and gene analyses.

RESULTS

Daily topical application of rHDL increased the rate of wound closure by Day 7 post-wounding (25 %, p < 0.05). Wound blood perfusion, a marker of angiogenesis, was elevated in rHDL treated wounds (Days 4-10 by 22-25 %, p < 0.05). In addition, rHDL increased wound capillary density by 52.6 %. In the HLI model, rHDL infusions augmented blood flow recovery in ischemic limbs (Day 18 by 50 % and Day 21 by 88 %, p < 0.05) and prevented tissue necrosis and toe loss. Assessment of capillary density in ischemic hindlimb sections found a 90 % increase in rHDL infused animals. In vitro studies in fibroblasts isolated from aged mice found that incubation with rHDL was able to significantly increase the key pro-angiogenic mediator vascular endothelial growth factor (VEGF) protein (25 %, p < 0.05).

CONCLUSION

rHDL can promote wound healing and wound angiogenesis, and blood flow recovery in response to ischemia in aged mice. Mechanistically, this is likely to be via an increase in VEGF. This highlights a potential role for HDL in the therapeutic modulation of age-impaired vascular complications.

The role of protein oxidation and DNA damage in elderly hypertension

INTRODUCTION

This study aimed to evaluate the role of protein oxidation and DNA damage in the elderly hypertensive (HT) patients.

MATERIALS AND METHODS

This study consisted of four groups: two elderly groups with 30 HT patients and 30 normotensive healthy volunteers, and two young groups with 30 HT patients and 30 normotensive healthy volunteers. Plasma total thiol (T-SH), advanced oxidation protein products (AOPPs), protein carbonyl (PCO), ischemia modified albumin (IMA), urine 8-hydroxy-2'-deoxyguanosine (8-OHdG), and prooxidant-antioxidant balance (PAB) levels were measured.

RESULTS

In the elderly HT group AOPPs, PCO, 8-OHdG, and PAB were significantly higher than the elderly control group. In the young HT group T-SH levels were significantly lower and the other oxidative stress parameters were significantly higher than the young control group. In the elderly control group AOPPs, PCO, IMA, 8-OHdG and PAB were significantly higher than the young control group. T-SH was significantly lower in the elderly control than the young control group. In the elderly HT group, T-SH levels were significantly lower and AOPPs, PCO, IMA, 8-OHdG, and PAB levels were significantly higher than the young HT group.

CONCLUSION

Protein and DNA cell damage occurs by oxidation of free radicals throughout life. Our study supports the view that these radicals may be responsible for the development of hypertension with aging process. Urine 8-OHdG levels can be used as a marker for oxidative DNA damage in the elderly hypertensive patients. Finally, our results suggest that oxidative stress may influence both the development and progression of hypertension and aging.

Paraoxonase-1 and adipokines: Potential links between obesity and atherosclerosis

Oxidative stress and chronic low-grade inflammation are major characteristics of obesity-related disorders. The dominance of pro-oxidant and pro-inflammatory mechanisms triggers insulin resistance and enhances the progression of atherosclerosis. Discovered first as an esterase that hydrolyze organophosphates, human paraoxonase-1 is bound to high-density lipoprotein and inhibits the oxidation of lipoproteins and reduces the degree of inflammation, hence it is considered to act against atherosclerosis. In contrast, the majority of the adipokines secreted from the enlarged white adipose tissue promote the atherosclerotic process; and altered adipokine secretion is now regarded as one of the major contributors of increased cardiovascular morbidity and mortality in obesity. In this review, we detail the correlations between paraoxonase-1 and some selected adipokines, namely leptin, adiponectin and chemerin. Adipokine imbalance leads to decreased paraoxonase-1 activity that results in enhanced atherosclerosis; therefore, altered adipokine secretion may be predictive of cardiovascular complications in obesity. As an active organ secreting biological active substances, white adipose tissue may also act as a "fine-tuner" of immune and endocrine actions attenuating or enhancing reactions triggered by pathogens, inflammation and metabolic stimuli; and obesity, as a chronic noxious state may perturb the proper functioning of this fine-tuning process. Further investigations are of major importance to elucidate the associations between adipokines and paraoxonase-1 and to establish accurate interventions against obesity-related disorders.

Biomarkers of lipid peroxidation related to hypertension in aging

The aim of this clinical study was to evaluate the influence of aging on the levels of lipid peroxidation (quantified as thiobarbituric acid-reactive substances (TBARS) content), lipid hydroperoxide (LOOH), hexanoyl lysine (HEL), 8-iso-prostaglandin F2α (8-iso-PGF2α) and total antioxidant capacity (TAC), and determine their relationships to the demographic and cardiovascular risk factors in elderly hypertensive (HT) patients. This study consisted of four groups: two elderly groups with 30 HT patients (11 males, 19 females) and 30 normotensive healthy volunteers (15 males, 15 females), and two young groups with 30 HT patients (13 males, 17 females) and 30 normotensive healthy volunteers (12 males, 18 females). In the elderly control group, the TBARS, LOOH, HEL and 8-iso-PGF2α levels, and the carotid intima media thickness (CIMT) were significantly higher than in the young control group. The TBARS, LOOH, HEL and 8-iso-PGF2α levels and the CIMT measurements were significantly higher in the elderly HT group than in the young HT group. In addition, the TAC levels were significantly lower in the elderly and young HT groups than in the elderly and young control groups. The CIMT was significantly positively correlated with TBARS (r=0.40, P<0.001), HEL (r= 0.30, P=0.001), LOOH (r= 0.44, P<0.001) and 8-iso-PGF2α (r= 0.32, P<0.001) in all of the HT groups. It seems that in elderly patients, the LOOH and TBARS are better biomarkers of lipid peroxidation in hypertension in terms of sensitivity. In all of the HT groups, 8-iso-PGF2α had the highest sensitivity. Hypertension is associated with lipid peroxidation due to an impaired oxidant/antioxidant status. Increased lipid peroxidation and decreased antioxidants with aging indicate that peroxidative damage further increases with higher blood pressure and the aging process.

Association of Paraoxonase 1 Gene Polymorphisms With the Risk of Hepatitis B Virus-related Liver Diseases in a Guangxi Population: A Case-control Study

Paraoxonase 1 (PON1), a liver-induced glycoprotein enzyme responsible for antioxidant defense against reactive oxygen species and anti-inflammatory, has been linked to various cancers. The objective of this study was to explore the association of PON1 rs662 and rs705382 with the risk of chronic hepatitis B (CHB), hepatitis B virus-related liver cirrhosis (LC), and hepatocellular carcinoma (HCC) in patients living in the Guangxi region of southern China. The PON1 rs662 and rs705382 single-nucleotide polymorphisms (SNPs) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 99 CHB patients, 84 LC patients, 258 HCC patients, and 221 healthy controls.Significant associations with CHB risk were observed for the rs705382 SNP after adjusting for sex, age, ethnicity, smoking, alcohol consumption, and body mass index. When stratified by sex and age, this positive association was significantly strengthened among men and individuals over 40 years old. Moreover, a decreased risk of LC was associated with the rs705382 CG and the combined GG + CG genotypes among women, with borderline statistical significance. In haplotype analyses, the haplotype GA was associated with a 1.68-fold increase in the risk of HCC.Our results showed that the PON1 rs705382 SNP might be a risk factor for CHB in Guangxi populations.

Total oxidative stress, paraoxonase and arylesterase levels at patients with pseudoexfoliation syndrome and pseudoexfoliative glaucoma

AIM

To investigate the oxidative stress status of the aqueous humor and serum of patients with pseudoexfoliation (PEX) syndrome and pseudoexfoliative glaucoma (PEG) and to measure paraoxonase (PON) and arylesterase (ARE) levels.

METHODS

A total of 78 patients were enrolled in the study, with 26 patients in each separate group. The patients were divided into three groups: the first group entailed PEX syndrome patients, while the second group consisted of patients with PEG and the third group involved patients with no additional systemic diseases, other than the diagnosis of cataract as control. Total oxidative stress (TOS), total antioxidant capacity (TAC), PON, and ARE levels in aqueous humor and serum were measured.

RESULTS

TAC, PON and arylesterase levels in aqueous humor and serum of the PEX syndrome and PEG patients were significantly decreased compared with control group (P<0.05). TOS values were higher in patients with PEX syndrome and PEG than controls (P<0.05). TAC, PON and ARE levels of aqueous humor did not differ significantly between the PEX syndrome and PEG groups.

CONCLUSION

These findings are potentially of significance and add to the growing body of evidence for oxidative stress in PEX syndrome and PEG. Decreased antioxidant defense and increased oxidative stress system may play an important role in the pathogenesis of PEX syndrome and PEG.

Small Dense Low Density Lipoprotein Cholesterol, Paraoxonase 1 and Lipid Profile in Postmenopausal Women: Quality or Quantity?

BACKGROUND AND AIMS

Atherosclerosis, the root cause of cardiovascular disease (CVD), has a number of risk factors-some modifiable and some not. CVD increases in women particularly during the postmenopausal period. Small dense low-density lipoprotein (sdLDL), a subclass of LDL, is an important determinant of atherosclerosis in postmenopausal women. Paraoxonase1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme that prevents oxidative modifications in LDL and HDL. With this background, we studied the sdLDL-C, PON1 and lipid profile in postmenopausal women to compare between quality and quantity of LDL.

METHODS

We studied 80 pre- and postmenopausal women (40/group). The following parameters were studied: lipid profile, sdLDL-C and PON1 levels. With proper statistical tools the correlation between these parameters was studied.

RESULTS

Postmenopausal women, in comparison with premenopausal women, have significantly increased levels of serum triglycerides and sdLDL-C and very-low-density lipoprotein cholesterol (VLDL-C) and significantly decreased levels of HDL-C and PON1. PON1 activity was negatively correlated with age, TC, TG, LDL-C and sdLDL-C (r = -0.574, -0.119, -0.226, -0.473 and -0.455, respectively) and positively correlated with HDL-C (r = 0.368), whereas sdLDL-C was positively correlated with age, TC, TG, LDL-C (r = 0.633, 0.485, 0.561 and 0.705, respectively) and negatively with HDL-C (r = -0.235). Stepwise multiple regression analysis demonstrated HDL-C and menopausal status as the best determinant for PON1 (R(2) = 0.320, p < 0.05) and menopausal status, LDL-C, TG, and TC were the best determinants for sdLDL-C (R(2) = 0.606, p < 0.05).

CONCLUSION

The results of the present study suggest quality, i.e., sdLDL-C, is more important than only LDL-C levels. Similarly, decrease in PON1 and increase in sdLDL-C go hand in hand. This shows that antioxidant capacity is compromised with a qualitative downfall in lipoproteins in postmenopausal women.

Association between Paraoxonase 1 (PON1) Polymorphisms and the Risk of Acute Coronary Syndrome in a North African Population

The purpose of the present study was to investigate the distribution of PON1 Q192R and L55M polymorphisms and activities in a North African population and to determine their association with cardiovascular complications. The prevalence of the QQ, QR, RR, LL, LM, and MM genotypes in the study population was 55.4%, 34.09%, 9.83%, 41.97%, 48.20%, and 9.83% respectively. The Q, R, L, and M alleles had a gene frequency of 0.755, 0.245, 0.67, and 0.33, respectively. The PON1 192 RR genotype was significantly more prevalent among ACS patients than among healthy subjects. There was a 4.33-fold increase in the risk of ACS in subjects presenting the PON1 192 RR genotype compared to those with the QQ genotype (OR=4.33; 95% CI=1.27–17.7). There was a significantly different distribution of PON1 L55M in the ACS patient groups (UA, STEMI, NSTEMI). Moreover, individuals presenting the PON1 55MM genotype present a higher risk for ACS than those with LL genotype (OR=3.69; 95% CI=1.61–11.80). Paraoxonase activities were significantly lower in coronary patients than in healthy subjects. The decrease in PON1 activity was inversely correlated with the number of concomitant risk factors for CVD (r=0.57, p<0.0001). The results of the present study suggested that the PON1 R and M alleles may play a role in the pathogenesis of cardiac ischemia in our North African population and that a decrease in PON1 activity may be a valuable marker for monitoring the development of the atherosclerosis process and the associated cardiovascular complications.

APOL1 G1 genotype modifies the association between HDLC and kidney function in African Americans

Background

Despite evidence of an association between variants at the apolipoprotein L1 gene (APOL1) locus and a spectrum of related kidney diseases, underlying biological mechanisms remain unknown. An earlier preliminary study published by our group showed that an APOL1 variant (rs73885319) modified the association between high-density lipoprotein cholesterol (HDLC) and estimated glomerular filtration rate (eGFR) in African Americans. To further understand this relationship, we evaluated the interaction in two additional large cohorts of African Americans for a total of 3,592 unrelated individuals from the Howard University Family Study (HUFS), the Natural History of APOL1-Associated Nephropathy Study (NHAAN), and the Atherosclerosis Risk in Communities Study (ARIC). The association between HDLC and eGFR was determined using linear mixed models, and the interaction between rs73885319 genotype and HDLC was evaluated using a multiplicative term.

Results

Among individuals homozygous for the risk genotype, a strong inverse HDLC-eGFR association was observed, with a positive association in others (p for the interaction of the rs73885319 × HDLC =0.0001). The interaction was similar in HUFS and NHAAN, and attenuated in ARIC. Given that ARIC participants were older, we investigated an age effect; age was a significant modifier of the observed interaction. When older individuals were excluded, the interaction in ARIC was similar to that in the other studies.

Conclusions

Based on these findings, it is clear that the relationship between HDLC and eGFR is strongly influenced by the APOL1 rs73885319 kidney risk genotype. Moreover, the degree to which this variant modifies the association may depend on the age of the individual. More detailed physiological studies are warranted to understand how rs73885319 may affect the relationship between HDLC and eGFR in individuals with and without disease and across the lifespan.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1645-7) contains supplementary material, which is available to authorized users.

PON1 and Mediterranean Diet

The Mediterranean diet has been proven to be highly effective in the prevention of cardiovascular diseases. Paraoxonase 1 (PON1) has been implicated in the development of those conditions, especially atherosclerosis. The present work describes a systematic review of current evidence supporting the influence of Mediterranean diet and its constituents on this enzyme. Despite the differential response of some genetic polymorphisms, the Mediterranean diet has been shown to exert a protective action on this enzyme. Extra virgin olive oil, the main source of fat, has been particularly effective in increasing PON1 activity, an action that could be due to low saturated fatty acid intake, oleic acid enrichment of phospholipids present in high-density lipoproteins that favor the activity, and increasing hepatic PON1 mRNA and protein expressions induced by minor components present in this oil. Other Mediterranean diet constituents, such as nuts, fruits and vegetables, have been effective in modulating the activity of the enzyme, pomegranate and its compounds being the best characterized items. Ongoing research on compounds isolated from all these natural products, mainly phenolic compounds and carotenoids, indicates that some of them are particularly effective, and this may enhance the use of nutraceuticals and functional foods capable of potentiating PON1 activity.

Human paraoxonase-1 (PON1): Gene structure and expression, promiscuous activities and multiple physiological roles

Human PON1 is a HDL-associated lipolactonase capable of preventing LDL and cell membrane oxidation and is therefore considered to be atheroprotective. PON1 contributes to the antioxidative function of HDL and reductions in HDL-PON1 activity, prevalent in a wide variety of diseases with an inflammatory component, are believed to lead to dysfunctional HDL which can promote inflammation and atherosclerosis. However, PON1 is multifunctional and may contribute to other HDL functions such as in innate immunity, preventing infection by quorum sensing gram negative bacteria by destroying acyl lactone mediators of quorum sensing, and putative new roles in cancer development and the promotion of healthy ageing. In this review we explore the physiological roles of PON1 in disease development, as well as PON1 gene and protein structure, promiscuous activities and the roles of SNPs and ethnicity in determining PON1 activity.

Low HDL cholesterol but not high LDL cholesterol is independently associated with subclinical coronary atherosclerosis in healthy octogenarians

AIM OF THE STUDY

Although low-density lipoprotein cholesterol (LDL-C) has been consistently demonstrated a predictor of atherosclerotic disease in a large spectrum of clinical settings, among individuals aged of 80 years or older this concept is uncertain. This study was evaluated in a carefully selected population if the association between LDL-C and coronary atherosclerotic burden remains significant in the very elderly.

METHODS

Individuals aged of 80 years or older (n = 208) who spontaneously sought primary prevention care and have never manifested cardiovascular disease, malnutrition, neoplastic or consumptive disease were enrolled for a cross-sectional analysis. Medical evaluation, anthropometric measurements, blood tests and cardiac computed tomography were obtained.

RESULTS

In analyses adjusted for age, gender, diabetes, systolic and diastolic blood pressure, smoking and statin therapy, no association was found between coronary calcium score (CCS) and LDL-C [1.79 (0.75-4.29)]. There was no association between triglycerides and CCS. The association between high-density lipoprotein cholesterol (HDL-C) and CCS was significant and robust in unadjusted [0.32 (0.15-0.67)] as well as in the fully adjusted analysis [0.34 (0.15-0.75)].

CONCLUSION

The present study confirms in a healthy cohort of individuals aged of 80 years or more that while the association between LDL-C and coronary atherosclerosis weakens with aging, the opposite occurs with the levels of HDL-C.

Paraoxonase 1 activity and level of antibodies directed against oxidized low density lipoproteins in a group of an elderly population in Poland - PolSenior study

The aim of this study was to assess two factors influencing the amount of oxidized LDL-paraoxonase 1 (PON1) activity and the level of anti-oxidized LDL antibodies (anti-ox LDL) in a large group of elderly individuals in Poland. The effects of cognitive status, hypertension and metabolic syndrome and of selected serum lipids and inflammation indicators on PON1 activity and anti-ox LDL level were also examined. The investigated population consisted of 3154 individuals aged 65 and more - participants of the population-based PolSenior project. PON1 arylesterase activity was determined spectrophotometrically, anti-ox-LDL antibodies using ELISA method. PON1 activity significantly decreased with advancing age, was lower in males than in females and decreased in persons with impaired cognition. Individuals with hypertension and high lipid levels showed higher PON1 activity. Lower PON1 activity was related to higher level of inflammation indicators - hsCRP and IL-6. The significant association of PON1 activity with age, HDL-C, LDL-C, sex and IL-6 was confirmed in multivariate analysis. Anti-ox LDL antibodies level was significantly higher in the two oldest subgroups of males. It was significantly lower in males than in females. It was decreased in persons with higher serum triglycerides. No relationship of anti-ox LDL level with cognition, hypertension, metabolic syndrome, inflammation indicators and serum lipid levels was observed. In some persons very high levels of anti-ox LDL were stated, most frequently in the oldest persons, particularly in men.

CONCLUSION

Both investigated antioxidant factors - PON1 activity and anti-ox LDL level, could play an important role in aging.

Onion extract (Allium cepa L.), quercetin and catechin up-regulate paraoxonase 1 activity with concomitant protection against low-density lipoprotein oxidation in male Wistar rats subjected to oxidative stress

BACKGROUND

Paraoxonase 1 (PON1) protects the oxidative modification of low-density lipoprotein (LDL) and is a major anti-atherosclerotic protein component of high-density lipoprotein. We explored the effect of onion extract and flavonoids (quercetin and catechin) in the regulation of PON1 expression and correlating with oxidised LDL levels in male Wistar rats subjected to mercuric chloride (HgCl₂) induced oxidative insult. Rats were divided into eight groups: Control, Experimental (HgCl₂), Experimental + onion/catechin/quercetin, Positive control (Normal + onion/catechin/quercetin). Treatment continued for 4 weeks.

RESULTS

PON1 activity and radical scavenging activity decreased in the Experimental group (P < 0.001) with increased susceptibility of LDL for oxidation and plasma malondialdehyde levels (P < 0.001). Onion extract significantly attenuated the adverse effects of HgCl₂ by up-regulating PON1 activity (P < 0.05), radical scavenging activity (P < 0.01), and protected against LDL oxidation (P < 0.001) and lipid peroxidation (P < 0.01). Similar effects were observed with quercetin and to a lesser extent with catechin.

CONCLUSIONS

The findings may explain the anti-atherosclerotic effect of onion and also foods containing quercetin and catechins.

Alteration of HDL functionality and PON1 activities in acute coronary syndrome patients

OBJECTIVE

The functionality of HDL has been suggested as an important factor in the prevention of cardiovascular and coronary artery diseases. The objective of the present study was to investigate the functionality of HDL and the factors that may affect the anti-atherogenic properties of HDL in ACS patients.

METHODS AND RESULTS

One hundred healthy subjects and 205 ACS patients were recruited. HDL functionality was evaluated by measuring their capacity to mediate cholesterol efflux from J774 macrophages. Oxidative stress status was determined by measuring plasma malondialdehyde (MDA), protein carbonyl, and vitamin E levels by HPLC. The PON1 Q192R polymorphism status and PON1 paraoxonase and arylesterase activities of the healthy subjects and ACS patients were also determined. The HDL of ACS patients displayed a limited capacity to mediate cholesterol efflux, especially via the ABCA1-pathway. MDA (7.06±0.29 μM) and protein carbonyl (9.29±0.26 μM) levels were significantly higher in ACS patients than in healthy subjects (2.29±0.21 μM and 3.07±0.17 μM, respectively, p<0.0001), while α- and γ-tocopherol (vitamin E) levels in ACS patients were 8-fold (p<0.001) and 2-fold (p<0.05) lower than in healthy subjects. Paraoxonase, arylesterase and HDL-corrected PON1 activities (PON1 activity/HDL ratio) were significantly lower in ACS patients. Logistic regression analyses showed that high PON1 paraoxonase and arylesterase activities had a significant protective effect (OR=0.413, CI 0.289-0.590, p<0.001; OR=0.232 CI 0.107-0.499, p<0.001, respectively) even when adjusted for HDL level, age, BMI, and PON1 polymorphism.

CONCLUSION

The results of the present study showed that the functionality of HDL is impaired in ACS patients and that the impairment may be due to oxidative stress and an alteration of PON1 activities.

Serum paraoxonase/arylesterase activity and oxidative stress status in children with metabolic syndrome

OBJECTIVE

This study aimed to measure paraoxonase/arylesterase activities and to evaluate the total oxidant and antioxidant capacities in obese children and in children with metabolic syndrome (MetS).

METHODS

A total of 151 children of comparable ages (13.23±1.96 years, 13.45±1.85 years and 13.95±1.31 years) were enrolled in the study. Forty of these were children with MetS, 55 were obese and 56 were healthy controls. Diagnosis of the MetS was made according to International Diabetes Federation criteria. Paraoxonase/arylesterase activities were evaluated by using paraoxon and phenylacetate substrates. Total oxidant status (TOS) and total antioxidant status (TAS) were measured and oxidative stress index (OSI) was estimated by calculation.

RESULTS

High levels of paraoxonase were detected in the obese group, whereas high levels of arylesterase were detected in both MetS and obese groups. Higher values for TOS, TAS and OSI were found in the MetS group (p<0.05).

CONCLUSION

Higher values of mean TOS and OSI in the MetS group than those in the control groups indicate that these parameters may be indicators of future risks such as atherosclerosis in patients with MetS.

Paraoxonase 1 polymorphisms within a Mississippi USA population as possible biomarkers of enzyme activities associated with disease susceptibility

Paraoxonase (PON1) hydrolyzes paraoxon (PO) and diazoxon (DZO), active metabolites of insecticides parathion and diazinon. The PON1 gene has single nucleotide polymorphisms (SNPs) including a codon 192 arginine (R) to glutamine (Q) and methionine (M) to leucine (L) at codon 55. Hydrolysis of PO (POase), DZO (DZOase), dihydrocoumarin (lactonase), and phenyl acetate (arylesterase) were evaluated for associations with race, gender, age, and PON1 55/192 SNP genotypes. Variables were analyzed both individually and in combination. QQ individuals had higher lactonase (p < 0.001) than RR individuals. This might partially explain why predominantly RR African Americans have higher rates of coronary disease than predominantly QQ Caucasians. Significant (p < 0.001) differences in arylesterase were seen among genotypes with QQ and MM lowest whereas RR and LL were highest. This opposes the prevailing belief that arylesterase is unaffected by genotype and suggests that this activity cannot be used to quantify PON1 protein.