The importance of paraoxonase 1 activity in chronic kidney disease

Paraoxonase 1 (PON1) is one of the most significant antioxidative enzymes associated with high-density lipoprotein (HDL). It has been proved that is involved in the pathogenesis of many diseases including chronic kidney disease (CKD). The association between PON1 and CKD seems to be mutual, such that the disease produces a significant decrease in PON1 activity levels, while the genetics of PON1 may affect the risk of susceptibility to CKD. Recent studies reveal that the decrease in serum PON1 activity observed in non-dialyzed and dialyzed CKD patients as well as in renal transplant (RT) patients is linked to an increased vulnerability to atherosclerosis. We intend to summarize current literature concerning PON1 activity in CKD, highlighting on the main determinants of PON1 activity, its association with oxidative stress, the impact of its genetic polymorphism on the disease development, the effect of drugs and nutritional state. Furthermore, evidence supporting the implication of reduced PON1 activity in the incident of cardiovascular disease in CKD patients, is also examined. It appears that despite the lack of standardization of PON1 activity measurement, PON1 remains a valuable biomarker for the researchers through the last decades, which contributes to the assessment of the antioxidant status having prognostic benefit on adverse clinical outcomes at various stages and etiologies of kidney disease.

Paraoxonase 1 concerning dyslipidaemia, cardiovascular diseases, and mortality in haemodialysis patients

Paraoxonase 1 (PON1) is known for preventing atherosclerosis through lipid-modifying features, antioxidant activity, anti-inflammatory, anti-apoptosis, anti-thrombosis, and anti-adhesion properties. Uremic patients requiring haemodialysis (HD) are especially prone to atherosclerosis and its complications. We analysed the PON1 gene (PON1) polymorphisms and serum PON1 (paraoxonase) activity concerning dyslipidaemia and related cardiovascular diseases and mortality to show how they associate under uremic conditions modified by maintenance HD treatment. The rs662 AA + AG (OR 1.76, 95%CI 1.10-2.80, P = 0.018), rs854560 TT (OR 1.48, 95%CI 1.04-2.11, P = 0.031), and rs854560 AT + TT (OR 1.28, 95%CI 1.01-1.63, P = 0.040) contributed to the prevalence of atherogenic dyslipidaemia diagnosed by the triglyceride (TG)/HDL-cholesterol ratio ≥ 3.8. The normalized serum PON1 activity positively correlated with atherogenic dyslipidaemia (ẞ 0.67 ± 0.25, P = 0.008). The PON1 rs854560 allele T was involved in the higher prevalence of ischemic cerebral stroke (OR 1.38, 1.02-1.85, P = 0.034). The PON1 rs705379 TT genotype contributed to cardiovascular (HR 1.27, 95% CI 1.03-1.57, P = 0.025) and cardiac (HR 1.34, 95% CI 1.05-1.71, P = 0.018) mortality. All P-values were obtained in multiple regression analyses, including clinical variables. Multifaceted associations of PON1 with dyslipidaemia, ischemic cerebral stroke, and cardiovascular mortality in HD patients provide arguments for the consideration of PON1 and its protein product as therapeutic targets in the prevention of atherosclerosis and its complications in uremic patients.

Paraoxonase 1 gene polymorphisms concerning non-insulin-dependent diabetes mellitus nephropathy in hemodialysis patients

AIMS

Data on involvement of paraoxonase 1 gene (PON1) in non-insulin-dependent diabetes mellitus (NIDDM) nephropathy are scarce. We investigated PON1 polymorphisms concerning end-stage NIDDM nephropathy and atherosclerotic complications in NIDDM nephropathy patients treated with hemodialysis (HD).

METHODS

In NIDDM nephropathy (n = 402) and non-diabetic (n = 998) HD subjects, we obtained PON1 polymorphisms by HRM analysis (rs662) or predesigned TaqMan SNV Genotyping Assay (rs854560, rs705379).

RESULTS

Only PON1 rs705379 was associated with end-stage NIDDM nephropathy in the recessive (OR 1.451, 95% CI 1.104-1.906, P = 0.009) and additive (OR 1.398, 95%CI 1.009-1.936, P = 0.046) inheritance modes. NIDDM nephropathy patients bearing the rs854560 T allele were at higher risk for ischemic cerebral stroke (OR 2.087, 95%CI 1.145-3.801, P = 0.016). In non-diabetic patients but not NIDDM nephropathy subjects, atherogenic dyslipidemia corresponded with PON1 rs662 A allele and PON1 rs854560 TT homozygosity.

CONCLUSIONS

In HD patients, NIDDM nephropathy correlates with the TT genotype of PON1 rs705379. The rs854560 T allele indicates a higher risk for atherosclerotic diseases in NIDDM nephropathy subjects. The T alleles of both PON1 SNVs are known as low expression variants downregulated serum PON1 activity. An increase of diminished PON1 activity may be a target in the prevention of NIDDM nephropathy and NIDDM atherosclerotic complications.

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.

Long Pentraxin 3 as a Broader Biomarker for Multiple Risk Factors in End-Stage Renal Disease: Association with All-Cause Mortality

Persistent inflammation in end-stage renal disease (ESRD) patients is known to underlie the progression of chronic kidney disease and to be associated with multiple risk factors including malnutrition, atherosclerosis, and cardiovascular disease (CVD). The acute-phase protein pentraxin 3 (PTX3) has a proven potential as a local inflammatory biomarker, but its clinical utility in ESRD remains unclear. Circulating levels of PTX3 and classical inflammatory mediators, including the clinical prototypical C-reactive protein (CRP), were assessed in 246 ESRD patients on dialysis and analysed in relation to the lipid profile, adipokine levels, and nutritional, cardiac, and renal fibrosis markers. Occurrence of deaths was recorded for the following year. Contrarily to the classical inflammatory markers, PTX3 levels were negatively correlated with nutritional markers and associated with a less atherogenic lipid profile. Levels of the cardiac and renal fibrosis markers and of the oxidized LDL/LDL-C ratio were found to be independent determinants of PTX3 concentration. When comparing inflammatory mediators, the increase in the PTX3 levels was the only predictor of all-cause mortality in dialysis patients in a survival model adjusted to all markers under study, other than the inflammatory ones, besides common confounding factors in dialysis. Data support the clinical applicability of PTX3 as a broader inflammatory biomarker than the classical ones, presenting a close association with inflammation, malnutrition, CVD, and renal fibrosis and a great potential to predict all-cause mortality in dialysis patients. The pleiotropic character of PTX3 may be of clinical relevance, and it could be targeted to ameliorate the high morbidity and mortality associated with ESRD.

The effect of divalent metal chelators and cadmium on serum phosphotriesterase, lactonase and arylesterase activities of paraoxonase 1

Paraoxonase 1 (PON1) is calcium dependent enzyme involved in many functions in human body. PON1 is synthesized in the liver and secreted to the bloodstream where bounds high-density lipoproteins (HDL). Association of PON1 with HDL increases the enzyme stability and biological activities. PON1 have three different activities: phosphotriesterase, lactonase and arylesterase. Until now there is now commercial available kits to determine these three PON1 activities. Also there is no date about stability of PON1 in serum after storage condition. We have elaborated the optimal conditions for determination of PON1 activities in serum using manual procedure as well as the best storage temperature of human serum for determination of PON1 activities. We have also confirmed that PON1 in serum is associated with HDL. Additionally we have investigated the effect of D-penicillamine, ethylenediaminetetraacetic acid and cadmium chloride on PON1 activities in human serum. D-penicillamine and ethylenediaminetetraacetic acid in therapeutic doses as well as cadmium chloride in toxic doses decrease PON1 activities in human serum when compared to non-treated serum. D-penicillamine as metal chelator inhibits much stronger PON1 activities than ethylenediaminetetraacetic acid.

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-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.

Dynamic interplay between metabolic syndrome and immunity

Obesity and its co-morbidities as metabolic syndrome, type 2 diabetes mellitus and cardiovascular diseases are major health problems worldwide. Several reports indicated that nutrient excess and metabolic syndrome are linked with altered immune response. Indeed, metabolic syndrome is characterized by insulin resistance and chronic low-grade inflammation, which conditions are the consequences of the complex interaction between adipocytes and immune cells. Enlarged white adipose tissue is infiltrated by immune cells and secretes various bioactive substances, like adipokines, cytokines and other inflammatory mediators. Due to its special architecture in which metabolic and immune cells are in intimate proximity, metabolic and immunologic pathways are closely integrated in adipose tissue. With the contribution of altered gut microbiota, adipokines and cytokines modulate insulin signaling and immune response leading to adipose tissue inflammation and systemic insulin resistance. In this chapter, we focus on the cellular and molecular mechanisms that lead to impaired insulin sensitivity and chronic low-grade inflammation in obesity. We also detail the potential role of adipokines and immune cells in this deleterious process, and the concerns of vaccination in metabolic syndrome. Finally, we address the links between obesity and gut microbiota as an emerging new field of interest, and scratch the surface of potential therapeutic opportunities.