The effect of statin therapy on plasma high-density lipoprotein cholesterol levels is modified by paraoxonase-1 in patients with familial hypercholesterolaemia

Sphingosine 1-Phosphate and Apolipoprotein M Levels and Their Correlations with Inflammatory Biomarkers in Patients with Untreated Familial Hypercholesterolemia

High-density lipoprotein (HDL)-bound apolipoprotein M/sphingosine 1-phosphate (ApoM/S1P) complex in cardiovascular diseases serves as a bridge between HDL and endothelial cells, maintaining a healthy endothelial barrier. To date, S1P and ApoM in patients with untreated heterozygous familial hypercholesterolemia (HeFH) have not been extensively studied. Eighty-one untreated patients with HeFH and 32 healthy control subjects were included in this study. Serum S1P, ApoM, sCD40L, sICAM-1, sVCAM-1, oxLDL, and TNFα concentrations were determined by ELISA. PON1 activities were measured spectrophotometrically. Lipoprotein subfractions were detected by Lipoprint. We diagnosed FH using the Dutch Lipid Clinic Network criteria. Significantly higher serum S1P and ApoM levels were found in HeFH patients compared to controls. S1P negatively correlated with large HDL and positively with small HDL subfractions in HeFH patients and the whole study population. S1P showed significant positive correlations with sCD40L and MMP-9 levels and PON1 arylesterase activity, while we found significant negative correlation between sVCAM-1 and S1P in HeFH patients. A backward stepwise multiple regression analysis showed that the best predictors of serum S1P were large HDL subfraction and arylesterase activity. Higher S1P and ApoM levels and their correlations with HDL subfractions and inflammatory markers in HeFH patients implied their possible role in endothelial protection.

Familial Hypercholesterolemia: Do HDL Play a Role?

Cardiovascular disease (CVD) in heterozygous familial hypercholesterolemia (HeFH), the most frequent monogenic disorder of human metabolism, is largely driven by low-density lipoprotein (LDL) cholesterol concentrations. Since the CVD rate differs considerably in this population, beyond the lifetime LDL cholesterol vascular accumulation, other classical risk factors are involved in the high cardiovascular risk of HeFH. Among other lipoprotein disturbances, alterations in the phenotype and functionality of high-density lipoproteins (HDL) have been described in HeFH patients, contributing to the presence and severity of CVD. In fact, HDL are the first defensive barrier against the burden of high LDL cholesterol levels owing to their contribution to reverse cholesterol transport as well as their antioxidant and anti-inflammatory properties, among others. In this context, the present narrative review aimed to focus on quantitative and qualitative abnormalities in HDL particles in HeFH, encompassing metabolic, genetic and epigenetic aspects.

Familial Hypercholesterolemia: New Horizons for Diagnosis and Effective Management

Familial hypercholesterolemia (FH) is a common genetic cause of premature cardiovascular disease (CVD). The reported prevalence rates for both heterozygous FH (HeFH) and homozygous FH (HoFH) vary significantly, and this can be attributed, at least in part, to the variable diagnostic criteria used across different populations. Due to lack of consistent data, new global registries and unified guidelines are being formed, which are expected to advance current knowledge and improve the care of FH patients. This review presents a comprehensive overview of the pathophysiology, epidemiology, manifestations, and pharmacological treatment of FH, whilst summarizing the up-to-date relevant recommendations and guidelines. Ongoing research in FH seems promising and novel therapies are expected to be introduced in clinical practice in order to compliment or even substitute current treatment options, aiming for better lipid-lowering effects, fewer side effects, and improved clinical outcomes.

Systematic review and meta-analysis deciphering the impact of fibrates on paraoxonase-1 status

OBJECTIVE

A significant residual cardiovascular risk is consistently observed in patients treated with statins. A combined treatment with fibrates reduces cardiovascular events in very high-risk patients. Because this is apparently unconnected to an improvement in lipid-related outcomes we hypothesized that the cardioprotective effects of fibrates might be associated with an improvement in paraoxonase-1 (PON1) status.

METHOD

The search for existing evidence, using the Medline, Scopus and Cochrane databases, was systematic and followed the PRISMA statement without restrictions on publication date. We excluded non-clinical and observational studies and we extracted data on baseline and post-treatment values of serum PON1 activity and other measurements of PON1 status.

RESULTS

Nine studies (including 12 treatment arms) in patients with hyperlipidemia, diabetes or metabolic syndrome treated with fibrates, alone or in combination with statins, were included to synthesize results. A meta-analysis of the data using a random-effects model revealed a significant increase in serum PON1 activity following fibrate therapy (WMD: 15.64U/L, 95% CI: 6.94, 24.34, p<0.001), an effect that was robust and not sensitive to any particular study. Subgroup analysis indicated differences in the effect size among types of fibrates and that PON1 alterations were associated with high-density lipoprotein cholesterol changes following fibrate therapy.

CONCLUSIONS

Results indicate a significant PON1-enhancing effect of fibrates. Whether this effect is associated with a clinical benefit, although likely, remains to be further investigated.

Clinical and genetic association of serum paraoxonase and arylesterase activities with cardiovascular risk

OBJECTIVE

Diminished serum paraoxonase and arylesterase activities (measures of paraoxonase-1 [PON-1] function) in humans have been linked to heightened systemic oxidative stress and atherosclerosis risk. The clinical prognostic use of measuring distinct PON-1 activities has not been established, and the genetic determinants of PON-1 activities are not known.

METHODS AND RESULTS

We established analytically robust high-throughput assays for serum paraoxonase and arylesterase activities and measured these in 3668 stable subjects undergoing elective coronary angiography without acute coronary syndrome and were prospectively followed for major adverse cardiovascular events (MACE= death, myocardial infarction, stroke) over 3 years. Low serum arylesterase and paraoxonase activities were both associated with increased risk for MACE, with arylesterase activity showing greatest prognostic value (quartile 4 versus quartile 1; hazard ratio 2.63; 95% CI, 1.97-3.50; P<0.01). Arylesterase remained significant after adjusting for traditional risk factors, C-reactive protein, and creatinine clearance (hazard ratio, 2.20; 95% CI, 1.60-3.02; P<0.01), predicted future development of MACE in both primary and secondary prevention populations, and reclassified risk categories incrementally to traditional clinical variables. A genome-wide association study identified distinct single nucleotide polymorphisms within the PON-1 gene that were highly significantly associated with serum paraoxonase (1.18×10(-303)) or arylesterase (4.99×10(-116)) activity but these variants were not associated with either 3-year MACE risk in an angiographic cohort (n=2136) or history of either coronary artery disease or myocardial infarction in the Coronary Artery Disease Genome-Wide Replication and Meta-Analysis consortium (n≈80 000 subjects).

CONCLUSIONS

Diminished serum arylesterase activity, but not the genetic determinants of PON-1 functional measures, provides incremental prognostic value and clinical reclassification of stable subjects at risk of developing MACE.

Paraoxonase variants relate to 10-year risk in coronary artery disease: impact of a high-density lipoprotein-bound antioxidant in secondary prevention

OBJECTIVES

We investigated the effects of paraoxonase (PON)-1 variants on long-term clinical outcome in patients with coronary artery disease (CAD).

BACKGROUND

PON-1 is a potential therapeutic target to further reduce cardiovascular risk because it is a detoxifying esterase with antioxidant properties. The PON-1 knockout models result in higher susceptibility to atherosclerosis, and PON activity contributes to cardiovascular risk in humans. Human gene variants determine PON activity; however, the impact of these variants on recurrent cardiovascular events in vascular disease is as of yet unknown.

METHODS

We conducted a 10-year follow-up study of 793 CAD patients in the REGRESS (REgression GRowth Evaluation Statin Study) trial cohort, using nationwide registries. Genotypes were obtained of 2 PON-1 isotypes (L55M, rs854560, and Q192R, rs662), which were previously associated with PON activity. Absolute and relative risks by genotype were estimated using Kaplan-Meier and proportional hazards analyses.

RESULTS

Carriership of the PON-1 glutamine isotype at codon 192 and methionine at codon 55 was associated with a higher risk of death due to ischemic heart disease. Hazard ratios per allele copy were 1.71 (95% confidence interval: 1.0 to 2.8, p=0.03) for the glutamine isotype at codon 192 and 1.56 (95% confidence interval: 1.1 to 2.3, p=0.03) for methionine at codon 55. Both isotypes had previously been related to lower PON activity. No effect was observed on all-cause mortality.

CONCLUSIONS

PON-1 gene variants influence the 10-year risk of fatal complications from CAD in male patients, despite no effect on all-cause mortality. These long-term findings confirm functional data on PON-1 activity, emphasize the relevance of this pathway in vascular disease, and enforce its putative role as a target to modify and estimate cardiovascular risk.

Atorvastatin effect on the distribution of high-density lipoprotein subfractions and human paraoxonase activity

Human serum paraoxonase-1 (PON1) protects lipoproteins against oxidation by hydrolyzing lipid peroxides in oxidized low-density lipoprotein (LDL); therefore, it may protect against atherosclerosis. Changes in the ratio of high-density lipoprotein (HDL) subfractions may alter the stability and the antioxidant capacity of PON1. The aim of the study was to examine the effect of atorvastatin treatment on the distribution of HDL subfractions, LDL size, cholesteryl ester transfer protein (CETP), lecithin-cholesterol acyltransferase (LCAT), and PON1 activity. In all, 33 patients with type IIa and IIb hypercholesterolemia were involved in the study. LDL sizes and HDL subfractions were determined by gradient gel electrophoresis. CETP, LCAT, and PON1 activities were measured spectrophotometrically. Three months of treatment with atorvastatin 20 mg daily significantly increased the HDL3 (+8.13%) and decreased the HDL2a and HDL2b subfractions (-1.57% and -6.55%, respectively). The mean LDL size was significantly increased (+3.29%). The level of oxidized LDL was significantly decreased (-46.0%). The PON1 activity was augmented by the atorvastatin treatment (+5.0%). The CETP activity positively correlated with the HDL2b level and negatively correlated with the HDL3 and HDL2a levels. Atorvastatin alters the HDL subfractions, which may improve its antiatherogenic effect via enhancement of the PON1 activity.

Effect of paraoxonase 1 polymorphisms on the response of lipids and lipoprotein-associated enzymes to treatment with fluvastatin

BACKGROUND

Decreased paraoxonase 1 (PON1) and increased total serum lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) activities are suggested to be risk factors for vascular disease. Common PON1 genetic polymorphisms (Q192R and L55M) significantly affect PON1 activity and may also influence high-density lipoprotein (HDL)-associated Lp-PLA(2) activity. However, little is known about the possible effect of PON1 common genetic polymorphisms on the response of lipids as well as PON1 and Lp-PLA(2) activities to treatment with statins.

METHODS

Two hundred two hypercholesterolemic patients were treated with fluvastatin 40 mg/day. Fasting serum lipids, Q192R and L55M PON1 polymorphisms as well as PON1 and Lp-PLA(2) (total serum and HDL-associated) activities were determined before and after 6 months of treatment.

RESULTS

Fluvastatin treatment did not affect HDL-cholesterol or apolipoprotein (apo) AI but resulted in significant decreases in total cholesterol, triglycerides, low-density lipoprotein-cholesterol, apo B and apo E, as well as total serum Lp-PLA(2) activity. In contrast, PON1 activity significantly increased. None of these changes was influenced by Q192R or L55M PON1 polymorphisms. Overall, HDL-Lp-PLA(2) did not change but L55M polymorphism significantly influenced its response to fluvastatin. Specifically, LL homozygotes experienced a significant increase, while M carriers (LM or MM) experienced a non-significant decrease in HDL-Lp-PLA(2) activity (p = 0.030 between groups).

CONCLUSIONS

Q192R and L55M PON1 polymorphisms did not affect the response of lipids, PON1 and total serum Lp-PLA(2) to treatment with a statin. However, L55M PON1 polymorphism significantly modulated the response of HDL-Lp-PLA(2). It should be noted that this is an association study and therefore provides no proof but only indication that PON1 may also exert Lp-PLA(2) activity in HDL.