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

Paraoxonase-2 agonist vutiglabridin promotes autophagy activation and mitochondrial function to alleviate non-alcoholic steatohepatitis

BACKGROUND AND PURPOSE

Only limited therapeutic agents have been developed for non-alcoholic steatohepatitis (NASH). Glabridin, a promising anti-obesity candidate, has only limited druggability due to its low in vivo chemical stability and bioavailability. Therefore, we developed vutiglabridin (VUTI), which is based on a glabridin backbone, and investigated its mechanism of action in treating NASH in animal models.

EXPERIMENTAL APPROACH

Anti-NASH effects of VUTI were determined in in vitro fatty liver models, spheroids of primary human hepatocytes and L02 normal liver cell lines. To identify VUTI possible cellular target/s, biotin-labelled VUTI was synthesized and underwent chemical proteomic analysis. Further, the evaluation of VUTI therapeutic efficacy was carried out using an amylin-NASH and high-fat (HF) diet-induced obese (DIO) mouse models. This was carried out using transcriptomic, lipidomic and proteomic analyses of the livers from the amylin-NASH mouse model.

KEY RESULTS

VUTI treatment markedly reduces hepatic steatosis, fibrosis and inflammation by promoting lipid catabolism, activating autophagy and improving mitochondrial dysfunction, all of which are hallmarks of effective NASH treatment. The cellular target of VUTI was identified as paraoxonase 2 (PON2), a newly proposed protein target for the treatment of NASH, VUTI enhanced PON2 activity. The results using PON2 knockdown cells demonstrated that PON2 is important for VUTI- activation of autophagy, promoting mitochondrial function, decreasing oxidative stress and alleviating lipid accumulation under lipotoxic condition.

CONCLUSION AND IMPLICATIONS

Our data demonstrated that VUTI is a promising therapeutic for NASH. Targeting PON2 may be important for improving liver function in various immune-metabolic diseases including NASH.

Biomarkers of Oxidative Stress Tethered to Cardiovascular Diseases

Cardiovascular disease (CVD) is a broad term that incorporated a group of conditions that affect the blood vessels and the heart. CVD is a foremost cause of fatalities around the world. Multiple pathophysiological mechanisms are involved in CVD; however, oxidative stress plays a vital role in generating reactive oxygen species (ROS). Oxidative stress occurs when the concentration of oxidants exceeds the potency of antioxidants within the body while producing reactive nitrogen species (RNS). ROS generated by oxidative stress disrupts cell signaling, DNA damage, lipids, and proteins, thereby resulting in inflammation and apoptosis. Mitochondria is the primary source of ROS production within cells. Increased ROS production reduces nitric oxide (NO) bioavailability, which elevates vasoconstriction within the arteries and contributes to the development of hypertension. ROS production has also been linked to the development of atherosclerotic plaque. Antioxidants can decrease oxidative stress in the body; however, various therapeutic drugs have been designed to treat oxidative stress damage due to CVD. The present review provides a detailed narrative of the oxidative stress and ROS generation with a primary focus on the oxidative stress biomarker and its association with CVD. We have also discussed the complex relationship between inflammation and endothelial dysfunction in CVD as well as oxidative stress-induced obesity in CVD. Finally, we discussed the role of antioxidants in reducing oxidative stress in CVD.

The Activity and Polymorphism of the PON1 in Patients with Chronic Liver Disease: a Systematic Review and Meta-analysis

BACKGROUND

Liver diseases are among the ten deadliest diseases in the world. Measuring PON1 is a test to assess the degree of liver disorder. There are several preliminary studies on the rate of PON1 activity in people with liver disease, and there are differences between the results of these studies; therefore, the aim of this research work is to determine the level of PON1 activity in people with liver disease using meta-analysis.

METHOD

The study searched to select articles that were published electronically from 2002 to 2020, in national and international databases of SID, MagIran, Embase, ScienceDirect, Scopus, PubMed, and Web of Science (WoS).

RESULTS

Among the articles included in the meta-analysis, the samples in the case (patients) and control groups were 807 and 2276, respectively. The mean activity of PON1 in individuals with liver disease in the case and control groups were 142.06 ± 7.7 and 272.19 ± 39.6, respectively, and this was statistically significant (P < 0.05). The mean difference analysis highlights a difference of - 2.75 ± 0.48 between the patient and control groups, indicating that liver disease significantly reduces PON1 activity.

CONCLUSION

The results of this study demonstrate that the polynomorphism of the PON1 is associated with an increased risk of liver disease, with lower levels of PON1 activity in people with liver disease than in healthy patients and this decrease was more in patients with liver cirrhosis than in other liver diseases. Given the importance of this gene's activity, studies such as this could provide a promising path for better drug design and treatment in future.

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.

Biochemical indices of oxidative stress and inflammation in the evaluation of peripheral artery disease

BACKGROUND

The aims of this study were: (1) to investigate changes in indices of oxidative stress and inflammation in the evaluation of peripheral artery disease (PAD); (2) to compare the diagnostic efficacy of these parameters with that of classical clinical laboratory routine parameters.

DESIGN AND METHODS

We studied 115 patients with PAD and 300 healthy volunteers.

RESULTS

PAD patients had significantly increased circulating concentrations of F2-isoprostanes, protein carbonyls, chemokine (C-C motif) ligand 2 (CCL2), high-sensitivity C-reactive protein (hs-CRP), β-2-microglobulin (B2M), and decreased paraoxonase-1 (PON1) levels. When patients were classified according to the Fontaine score, we observed important increases in plasma F2-isoprostanes and CCL2 that appeared in milder stages of the disease, and remained so at similar levels in more advanced stages; almost no overlapping with the control group was noted. Receiver operating characteristics analysis comparing patients and controls revealed that the areas under the curve for F2-isoprostanes and CCL2 approached unity [0.999 (0.998-1.000) and 0.993 (0.985-1.000)], respectively, and significantly higher to those of the other measured parameters.

CONCLUSION

Our data suggest that F2-isoprostanes and CCL2 measurements may be useful tools for the diagnosis of PAD.

Low protective PON1 lactonase activity in an Arab population with high rates of coronary heart disease and diabetes

BACKGROUND

Recent studies showing that high density lipoproteins (HDL) can effect plaque regression indicate that recent trial failures do not exclude an atheroprotective role of HDL. Instead, they highlight differences between HDL function and measured HDL-cholesterol (HDL-C). PON1 is one key functional activity of HDL. Urban Palestinians have lower HDL-C and a higher incidence and mortality of coronary heart disease than those of Israelis. We hypothesized that the cardioprotective PON1 lactonase and arylesterase activities and PON1 functional genotype may differ between Palestinians and Israelis.

METHODS

We measured PON1 activities in a cross-sectional population-based study of Palestinian (n=960) and Israeli (n=694) residents in Jerusalem, 1654 participants in all.

RESULTS

Palestinians had high prevalences of obesity and diabetes and low mean concentrations of HDL-cholesterol (0.97 mmol/l in men and 1.19 mmol/l in women). Lactonase and arylesterase activities were lower by 10.8% (p=1.2∗10(-14)) and 2.7% (p<0.0005), respectively, in Palestinians as compared to Israelis. The functional genotype distribution, demonstrated by plotting paraoxonase vs lactonase activities, showed a modest between-group difference (p=0.024), with 12.1% RR in Palestinian Arabs vs 8.4% in Israeli Jews, but no overall difference in allele frequencies. Lactonase correlated inversely with age (Spearman's rho=-.156), weakly with BMI (-.059), positively with HDL-C (.173) and non-HDL-C (.103), but was not associated with triglycerides or fasting glucose. Palestinians showed consistently lower lactonase activity in logistic regression models adjusted for multiple covariates and for functional genotype (odds ratios of 1.81 and 1.98, respectively, for the lower fifth vs the upper 4 fifths of lactonase activity p<0.0001).

CONCLUSION

We showed a lower physiologically-significant lactonase PON1 activity in an Arab population, a finding consistent with the high cardiovascular and diabetes risk of Palestinians.

Human paraoxonase 1 as a pharmacologic agent: limitations and perspectives

Human PON1 (h-PON1) is a multifaceted enzyme and can hydrolyze (and inactivate) a wide range of substrates. The enzyme shows anti-inflammatory, antioxidative, antiatherogenic, ant-diabetic, antimicrobial, and organophosphate (OP)-detoxifying properties. However, there are certain limitations regarding large-scale production and use of h-PON1 as a therapeutic candidate. These include difficulties in producing recombinant h-PON1 (rh-PON1) using microbial expression system, low hydrolytic activity of wild-type h-PON1 towards certain substrates, and low storage stability of the purified enzyme. This review summarizes the work done in our laboratory to address these limitations. Our results show that (a) optimized polynucleotide sequence encoding rh-PON1 can express the protein in an active form in E. coli and can be used to generate variant of the enzyme having enhanced hydrolytic activity, (b) in vitro refolding of rh-PON1 enzyme can dramatically increase the yield of an active enzyme, (c) common excipients can be used to stabilize purified rh-PON1 enzyme when stored under different storage conditions, and (d) variants of rh-PON1 enzyme impart significant protection against OP-poisoning in human blood (ex vivo) and mouse (in vivo) model of OP-poisoning. The rh-PON1 variants and their process of production discussed here will help to develop h-PON1 as a therapeutic candidate.

Treatment with omega-3 fatty acid ethyl-ester alters fatty acid composition of lipoproteins in overweight or obese adults with insulin resistance

INTRODUCTION

The effects of dietary fatty acid supplementation on lipoprotein fatty acid composition have rarely been described.

PATIENTS AND METHODS

Sixty-one overweight and obese adults with dyslipidemia and insulin resistance were randomized to placebo, 2g/day extended-release nicotinic acid (ERN), 4g/day prescription omega-3 fatty acid ethyl ester (P-OM3), or combination therapy for 16 weeks. Lipoprotein fatty acid composition was analyzed by gas chromatography pre- and post-treatment.

RESULTS

Treatment with P-OM3 or combination, but not ERN, increased proportions of eicosapentaenoic acid, docosahexaenoic acid, and docosapentaenoic acid, and reduced those for arachidonic acid in all lipoprotein fractions, with greatest impact in the high-density lipoprotein fraction. P-OM3-induced changes in eicosapentaenoic acid within low-density lipoproteins and very low-density lipoproteins were associated with beneficial effects on mean arterial pressure and pulse pressure.

CONCLUSIONS

P-OM3 supplementation, with or without ERN, was associated with differentially altered lipoprotein fatty acid composition and improved blood pressure parameters.