New Insights Into the Role of Lipoprotein(a)-Associated Lipoprotein-Associated Phospholipase A 2 in Atherosclerosis and Cardiovascular Disease

Anti-inflammatory therapies for atherosclerosis

The view of atherosclerosis as an inflammatory disease has emerged from observations of immune activation and inflammatory signalling in human atherosclerotic lesions, from the definition of inflammatory biomarkers as independent risk factors for cardiovascular events, and from evidence of low-density lipoprotein-induced immune activation. Studies in animal models of hyperlipidaemia have also supported the beneficial effects of countering inflammation to delay atherosclerosis progression. Specific inflammatory pathways with relevance to human diseases have been identified, and inhibitors of these pathways are either already in use for the treatment of other diseases, or are under development and evaluation. These include 'classic' drugs (such as allopurinol, colchicine, and methotrexate), biologic therapies (for example tumour necrosis factor inhibitors and IL-1 neutralization), as well as targeting of lipid mediators (such as phospholipase inhibitors and antileukotrienes) or intracellular pathways (inhibition of NADPH oxidase, p38 mitogen-activated protein kinase, or phosphodiesterase). The evidence supporting the use of anti-inflammatory therapies for atherosclerosis is mainly based on either observational or small interventional studies evaluating surrogate markers of disease activity. Nevertheless, these data are crucial to understand the role of inflammation in atherosclerosis, and to design randomized controlled studies to evaluate the effect of specific anti-inflammatory strategies on cardiovascular outcomes.

Lipoprotein-associated phospholipase A2 and arterial stiffness evaluation in patients with inflammatory bowel diseases

BACKGROUND AND AIMS

The association between inflammatory bowel diseases (IBD) and cardiovascular disease (CVD) remains equivocal. Arterial stiffness, as assessed by pulse wave velocity (PWV), and lipoprotein-associated phospholipase A2 (Lp-PLA2) are surrogates of CVD risk.

AIM

The aim of this study was to assess carotid-femoral PWV and Lp-PLA2 in patients with IBD without history of CVD.

METHODS

Established CVD risk factors, IBD characteristics, PWV and Lp-PLA2 activity were assessed in 44 patients with IBD, 29 with Crohn's disease (CD) and 15 with ulcerative colitis (UC), and 44 matched controls.

RESULTS

IBD patients had lower total and low density lipoprotein cholesterol (LDL-C) levels. There was no difference in PWV between patients and controls (6.8 vs. 6.4m/s), but patients with CD had higher PWV compared to those with UC (7 vs. 6.3m/s; p=0.044), and to controls. Smoking rates were significantly higher among CD patients. Factors associated with PWV were age, mean arterial pressure and smoking. Lp-PLA2 activity was significantly lower in patients with IBD (46.8 vs. 53.9 nmol/mL/min; p=0.011). There was no difference in Lp-PLA2 between CD and UC patients. LDL-C was the only significant predictor of Lp-PLA2.

CONCLUSIONS

Our study showed lower Lp-PLA2 activity in patients with IBD compared with controls, reflecting lower LDL-C in the former. There was no difference in PWV between the two groups. Arterial stiffness was higher in patients with CD, which is likely related to higher smoking rates. These findings challenge a possible association between IBD and CVD, but further studies are required.

Simultaneous quantitation and size characterization of apolipoprotein(a) by ultra-performance liquid chromatography/mass spectrometry

RATIONALE

Apolipoprotein(a) is a polymorphic glycoprotein covalently bound to apoB100 in Lp(a) particles and has been described to be both atherogenic and prothrombotic, although its exact mechanism of action is not well defined. Apolipoprotein(a) is routinely measured by immunoassays. Unfortunately, the accuracy of the measurement can be affected by the apolipoprotein(a) size (number of kringles) polymorphism in Lp(a) particles. Here we describe an ultra-performance liquid chromatography/mass spectrometry (UPLC/MS) assay that is capable of measuring apolipoprotein(a) concentrations while simultaneously determining the number of kringles present per protein.

METHODS

Plasma samples were diluted and proteins de-lipidated with deoxycholate prior to tryptic digestion. Distinct tryptic peptides from different regions of apolipoprotein(a) were measured to determine both concentration and the number of kringles present per protein. Separation and quantitation of tryptic peptides is carried out at 700 μL/min using a 1.7 µm C18 column (2.1 × 100 mm) coupled to a Thermo Vantage triple quadrupole (QQQ) mass spectrometer with a heated electrospray ionization (HESI) source.

RESULTS

This method was compared to established methods for measuring concentration (monoclonal antibody based ELISA) and size (gel-electrophoresis) using 80 plasma samples proved by NWLRL. The slope and r(2) value for the correlation of concentrations were determined to be 0.96 and 0.98, demonstrating excellent agreement of absolute values between the UPLC/MS and ELISA methods. As measured by UPLC/MS, the average kringle number or size is smaller than determined by the electrophoretic method.

CONCLUSIONS

A single UPLC/MS method was developed capable of measuring apolipoprotein(a) concentration and size (by measuring the number of kringles per protein). This assay passes criteria required for 'fit for purpose' assays including sensitivity, intra and interday reproducibility and freeze/thaw stability. While the agreement between UPLC/MS and ELISA is excellent for concentration and may provide researchers with additional tools for studying apolipoprotein(a), the dissimilarities between UPLC/MS and the electrophoretic method may also be exploited for understanding apolipoprotein(a) structure and function.

Lipoprotein-associated phospholipase A2 regulates macrophage apoptosis via the Akt and caspase-7 pathways

AIM

Mutations in lipoprotein-associated phospholipase A2 (Lp-PLA2) are related to atherosclerosis. However, the molecular effects of Lp-PLA2 on atherosclerosis have not been fully investigated. Therefore, this study attempted to elucidate this issue.

METHODS

Monocytes were isolated from randomly selected healthy male volunteers according to each Lp-PLA2 genotype (wild-type Lp-PLA2 [Lp-PLA2 (V/V)], the heterozygous V279F mutation [LpPLA2 (V/F)] and the homozygous V279F mutation [Lp-PLA2 (F/F)]) and differentiated into macrophages. The level of apoptosis in the macrophages following incubation without serum was measured using the annexin V/propidium iodide double staining method, and the underlying mechanisms were further examined using a culture cell line.

RESULTS

The average plasma Lp-PLA2 concentration [Lp-PLA2 (V/V): 129.4 ng/mL, Lp-PLA2 (V/F): 70.7 ng/mL, Lp-PLA2 (F/F): 0.4 ng/mL] and activity [Lp-PLA2 (V/V): 164.3 nmol/min/mL, LpPLA2 (V/F): 100.9 nmol/min/mL, Lp-PLA2 (F/F): 11.6 nmol/min/mL] were significantly different between each genotype, although the basic clinical characteristics were similar. The percentage of apoptotic cells was significantly higher among the Lp-PLA2 (F/F) macrophages compared with that observed in the Lp-PLA2 (V/V) macrophages. This induction of apoptosis was independent of the actions of acetylated low-density lipoproteins. In addition, the transfection of the expression plasmid of V279F mutant Lp-PLA2 into Cos-7 cells or monocyte/macrophage-like U937 cells promoted apoptosis. The knockdown of Lp-PLA2 also increased the number of apoptotic cells. Among the cells expressing mutant Lp-PLA2, the caspase-7 activity was increased, while the activated Akt level was decreased.

CONCLUSIONS

The V279F mutation of Lp-PLA2 positively regulates the induction of apoptosis in macrophages and Cos-7 cells. An increase in the caspase-7 activity and a reduction in the activated Akt level are likely to be involved in this phenomenon.

Baseline elevated Lp-PLA2 is associated with increased risk for re-stenosis after stent placement

Background

Lipoprotein associated phospholipase A2 (Lp-PLA2) is a novel biomarker for cardiovascular risk prediction. Whether increased Lp-PLA2 level is associated with re-stenosis after stent-placement is unclear.

Methods

Totally 326 participants eligible for stent-placement were enrolled and divided into two groups according to baseline Lp-PLA2 levels (named normal and elevated groups). Baseline characteristics and clinical outcomes were compared between normal and elevated groups. The relationships between Lp-PLA2 and other risk factors with re-stenosis were evaluated.

Results

Only the between-group difference of Lp-PLA2 was significant (123.2 ± 33.6 ng/mL vs 336.8 ± 85.4 ng/mL, P < 0.001) while other demographic and clinical characteristics between these two groups were comparable. Approximately 55.1% and 58.5% of participants in normal and elevated groups presented with acute coronary syndrome, and the percentage of tri-vessels stenoses was significantly higher in elevated group (40.8% vs 32.1%, P = 0.016). Nearly 96.0% and 94.0% of participants in normal and elevated Lp-PLA2 groups were placed with drug-eluting stents, and the others were with bare-metal stents. After 1 year’s follow-up, the incidence of clinical end-points was comparable (13.3% vs 15.4%, P = 0.172). Nevertheless, the incidence of re-stenosis was marginally higher in elevated Lp-PLA2 group (8.5% versus 4.6%, P = 0.047). With multivariate analysis, after adjustment for other risk factors, Lp-PLA2 remained an independent predictor for re-stenosis with a hazard ratio of 1.140. No synergistic effect between Lp-PLA2 and other risk factors for re-stenosis was found.

Conclusion

Increased Lp-PLA2 level is associated with an increased risk of re-stenosis. Lp-PLA2 assessment may be useful in predicting subjects who are at increased risk for re-stenosis.

Lipoprotein-associated phospholipase A2 and AGEs are associated with cardiovascular risk factors in women with history of gestational diabetes mellitus

OBJECTIVE

Although most women with gestational diabetes mellitus (GDM) return to normal glucose tolerance after delivery, they have increased risk of cardiometabolic diseases. This study aimed to evaluate the relationships between plasma levels of Lp-pla2 and AGEs and cardiometabolic risk factors in women with GDM.

METHODS

190 women with GDM (cases) and 80 healthy women (controls) were enrolled. Demographic and clinical data were collected and analyzed about 2 years after the delivery.

RESULTS

Of the 190 cases, 19 (10%), 38 (20%) and 10 (5%) had type 2 diabetes mellitus, metabolic syndrome and hypertension after delivery, respectively. There were significant differences in variables between cases and controls: Lp-pla2 (pg/mL) 1991.5 ± 905.3 versus 1527.0 ± 799.8; AGEs (ng/mL) 403.0 ± 208.6 versus 321.8 ± 150.3. The plasma Lp-pla2 and AGEs levels were positively correlated with metabolic indexes in women with previous GDM.

CONCLUSION

Women with GDM have increased risk of cardiometabolic disease. AGEs and Lp-pla2 could be utilized as novel biomarkers to identify at an early stage of women with increased risk of metabolic and cardiovascular disease.

10-Dehydrogingerdione raises HDL-cholesterol through a CETP inhibition and wards off oxidation and inflammation in dyslipidemic rabbits

OBJECTIVE

To investigate the CETP suppression by 10-dehydrogingerdione, a compound in Zingiber officinale, and its effect on the progression of atherosclerosis in dyslipidemic rabbits and the underlying oxidative and inflammatory consequences.

METHODS

Twenty-four New Zealand male rabbits were fed either a normal diet or an atherogenic diet. The rabbits on the atherogenic diet received treatments of atorvastatin or 10-dehydrogingerdione and placebo concurrently (n = 6/group). Blood samples were collected after three and six weeks for biochemical analysis.

RESULTS

10-Dehydrogingerdione-treated rabbits showed a significant improvement in serum lipids especially HDL-C in a time-dependant manner. This effect was correlated to its ability to lower CETP. Lp(a), ox-LDL, hsCRP, homocysteine and MMP9 decreased significantly in both 10-dehydrogingerdione- and atorvastatin-treated rabbits compared with placebo (p < 0.001). Lp(a) achieved normal values by both treatments, while homocysteine did not reach normal values by either treatments. Conversely, MMP9 returned below normal values by 10-dehydrogingerdione (p < 0.001), hsCRP and ox-LDL were slightly below normal values (hsCRP: p < 0.001; ox-LDL: p < 0.001 and p < 0.05 in 10-dehydrogingerdione and atorvastatin groups, respectively). The effect achieved by 10-dehydrogingerdione was similar to that of atorvastatin on hsCRP and Lp(a). However, 10-dehydrogingerdione exerted better effect than atorvastatin on homocysteine, MMP9 (p < 0.001) and ox-LDL (p < 0.05).

CONCLUSIONS

In a rabbit dyslipidemic model, 10-dehydrogingerdione lowers LDL-C and raises HDL-C by suppressing CETP; an effect that modulates inflammatory and oxidative risk factors of CVD. These findings suggested that the naturally occurring 10-dehydrogingerdione might be a potential CETP inhibitor for the treatment of atherosclerosis and residual risk in CVD.

Lipoprotein(a): a promising marker for residual cardiovascular risk assessment

Atherosclerotic cardiovascular diseases (CVD) are still the leading cause of morbidity and mortality worldwide, although optimal medical therapy has been prescribed for primary and secondary preventions. Residual cardiovascular risk for some population groups is still considerably high although target low density lipoprotein-cholesterol (LDL-C) level has been achieved. During the past few decades, compelling pieces of evidence from clinical trials and meta-analyses consistently illustrate that lipoprotein(a) (Lp(a)) is a significant risk factor for atherosclerosis and CVD due to its proatherogenic and prothrombotic features. However, the lack of effective medication for Lp(a) reduction significantly hampers randomized, prospective, and controlled trials conducting. Based on previous findings, for patients with LDL-C in normal range, Lp(a) may be a useful marker for identifying and evaluating the residual cardiovascular risk, and aggressively lowering LDL-C level than current guidelines' recommendation may be reasonable for patients with particularly high Lp(a) level.

Correlation between plasma lipoprotein-associated phospholipase A2 and peripheral arterial disease

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is a recently identified and potentially useful plasma biomarker for cardiovascular diseases. However, its role in peripheral arterial disease (PAD) remains unclear. The objective of this study was to assess the independent association of Lp-PLA₂ and other inflammatory markers with the reduced ankle-brachial blood pressure index (ABI), a marker of PAD. We performed a cross-sectional study in 982 individuals aged ≥40 years who were recruited from the First Affiliated Hospital of Zhengzhou University. PAD was defined as an ABI <0.9 in at least one leg. The individuals were further divided into two groups, 145 with PAD and 837 without PAD. Following adjustment for traditional cardiovascular risk factors, the odds ratios of PAD when comparing the highest to the lowest quartiles were 3.24 (95% CI, 1.68–3.94) for Lp-PLA₂, 2.14 (95% CI, 1.07–3.11) for homocysteine, 1.93 (95% CI, 1.02–4.01) for fibrinogen, 2.26 (95% CI, 1.32–5.74) for apolipoprotein B and 1.3 (95% CI, 0.75–2.49) for high-sensitivity C-reactive protein (hsCRP). When Lp-PLA₂ and inflammatory markers were simultaneously included in the full model, the corresponding odds ratios were 1.81 (95% CI, 1.14–3.68) for Lp-PLA₂, 1.15 (95% CI, 0.49–2.69) for homocysteine, 1.21 (95% CI, 0.88–5.57) for fibrinogen, 0.98 (95% CI, 0.51–3.85) for apolipoprotein B and 1.23 (95% CI, 1.12–3.51) for hsCRP. Lp-PLA₂ levels were significantly and independently associated with PAD following adjustment for other inflammatory markers. These findings reflect the potential role of circulating Lp-PLA₂ as a marker of atherosclerosis.

Lipoprotein(a) and risk of coronary, cerebrovascular, and peripheral artery disease: the EPIC-Norfolk prospective population study

OBJECTIVE

Although the association between circulating levels of lipoprotein(a) [Lp(a)] and risk of coronary artery disease (CAD) and stroke is well established, its role in risk of peripheral arterial disease (PAD) remains unclear. Here, we examine the association between Lp(a) levels and PAD in a large prospective cohort. To contextualize these findings, we also examined the association between Lp(a) levels and risk of stroke and CAD and studied the role of low-density lipoprotein as an effect modifier of Lp(a)-associated cardiovascular risk.

METHODS AND RESULTS

Lp(a) levels were measured in apparently healthy participants in the European Prospective Investigation of Cancer (EPIC)-Norfolk cohort. Cox regression was used to quantify the association between Lp(a) levels and risk of PAD, stroke, and CAD outcomes. During 212 981 person-years at risk, a total of 2365 CAD, 284 ischemic stroke, and 596 PAD events occurred in 18 720 participants. Lp(a) was associated with PAD and CAD outcomes but not with ischemic stroke (hazard ratio per 2.7-fold increase in Lp(a) of 1.37, 95% CI 1.25-1.50, 1.13, 95% CI 1.04-1.22 and 0.91, 95% CI 0.79-1.03, respectively). Low-density lipoprotein cholesterol levels did not modify these associations.

CONCLUSIONS

Lp(a) levels were associated with future PAD and CAD events. The association between Lp(a) and cardiovascular disease was not modified by low-density lipoprotein cholesterol levels.

Emerging therapeutic agents to lower lipoprotein (a) levels

PURPOSE OF REVIEW

Recent epidemiological and genetic studies have suggested that lipoprotein (a) [Lp(a)] is a causal mediator of cardiovascular disease (CVD). There is now interest in evaluating Lp(a) as a therapeutic target. This review will summarize emerging therapeutic agents to lower Lp(a).

RECENT FINDINGS

Apheresis is the most efficacious method to lower Lp(a). Currently, there are no approved drugs to specifically lower Lp(a). However, recent data has demonstrated that Lp(a) can be significantly lowered, along with reductions in other apolipoprotein B-100 (apoB) containing lipoproteins, with antisense oligonucleotides to apoB, monoclonal antibodies to proprotein convertase subtilisin/kexin type 9, cholesterol ester transfer protein inhibitors, and thyromimetics. The farnesoid X receptor/fibroblast growth factor axis and interleukin-6 also influence Lp(a) levels and may be targets of therapy. Finally, specific apolipoprotein (a) [apo(a)] inhibitors apo(a) have been developed and reduce apo(a) mRNA and protein levels up to 86% without significantly affecting other lipoproteins.

SUMMARY

Lp(a) remains the last major lipoprotein disorder without any specific therapy. With the strong and accumulating data on its role as a causal risk factor for CVD, a rationale exists to develop novel agents to reduce Lp(a) and test the hypothesis that this will lead to reduced CVD events.

Effect of improving glycemic control in patients with type 2 diabetes mellitus on low-density lipoprotein size, electronegative low-density lipoprotein and lipoprotein-associated phospholipase A2 distribution

The aim of this study was to determine the effect of intensified hypoglycemic therapy in patients with type 2 diabetes mellitus on the distribution of lipoprotein-associated phospholipase A2 (Lp-PLA2) activity between high-density lipoprotein and low-density lipoprotein (LDL) and its relation with the lipid profile and other qualitative properties of LDL. Forty-two patients with type 2 diabetes on the basis of poor glycemic control and normal or near normal LDL cholesterol were recruited. Lifestyle counseling and pharmacologic hypoglycemic therapy were intensified to improve glycemic control, but lipid-lowering therapy was unchanged. At 4 ± 2 months, glycosylated hemoglobin had decreased by a mean of 2.1%, but the only effect on the lipid profile were statistically significant decreases in nonesterified fatty acids and apolipoprotein B concentration. LDL size increased and the proportion of electronegative LDL decreased significantly. In parallel, total Lp-PLA2 activity decreased significantly, promoting a redistribution of Lp-PLA2 activity toward a higher proportion in high-density lipoprotein. Improvements in glycemic control led to more marked changes in Lp-PLA2 activity and distribution in patients with diabetes who had not received previous lipid-lowering therapy. In conclusion, optimizing glycemic control in patients with type 2 diabetes promotes atheroprotective changes, including larger LDL size, decreased electronegative LDL, and a higher proportion of Lp-PLA2 activity in high-density lipoprotein.

Acute impact of apheresis on oxidized phospholipids in patients with familial hypercholesterolemia

We measured oxidized phospholipids (OxPL), lipoprotein (a) [Lp(a)], and lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) pre- and postapheresis in 18 patients with familial hypercholesterolemia (FH) and with low(∼10 mg/dl; range 10-11 mg/dl), intermediate (∼50 mg/dl; range 30-61 mg/dl), or high (>100 mg/dl; range 78-128 mg/dl) Lp(a) levels. By using enzymatic and immunoassays, the content of OxPL and Lp-PLA(2) mass and activity were quantitated in lipoprotein density fractions plated in microtiter wells, as well as directly on apoB-100, Lp(a), and apoA-I immunocaptured within each fraction (i.e., OxPL/apoB and Lp-PLA(2)/apoB). In whole fractions, OxPL was primarily detected in the Lp(a)-containing fractions, whereas Lp-PLA(2) was primarily detected in the small, dense LDL and light Lp(a) range. In lipoprotein capture assays, OxPL/apoB and OxPL/apo(a) increased proportionally with increasing Lp(a) levels. Lp-PLA(2)/apoB and Lp-PLA(2)/apoA-I levels were highest in the low Lp(a) group but decreased proportionally with increasing Lp(a) levels. Lp-PLA(2)/apo(a) was lowest in patients with low Lp(a) levels and increased proportionally with increasing Lp(a) levels. Apheresis significantly reduced levels of OxPL and Lp-PLA(2) on apoB and Lp(a) (50-75%), particularly in patients with intermediate and high Lp(a) levels. In contrast, apheresis increased Lp-PLA(2)-specific activity (activity/mass ratio) in buoyant LDL fractions. The impact of apheresis on Lp(a), OxPL, and Lp-PLA(2) provides insights into its therapeutic benefits beyond lowering apoB-containing lipoproteins.

LDL lowering in peripheral arterial disease: are there benefits beyond reducing cardiovascular morbidity and mortality?

Peripheral arterial disease affecting the lower extremities is associated with increased mortality due to cardiovascular events and reduced functional capacity due to claudication. There is abundant evidence to support the role of lipid lowering with statins in preventing cardiovascular events in patients with peripheral arterial disease. Over the last 10 years, multiple studies have been designed to test the theory that LDL C lowering with statins could result in improved exercise performance in patients with peripheral arterial disease. However, this remains an active area of investigation to better understand how the pleiotropic effects of statins could lead to enhanced functional capacity for patients with claudication. Furthermore, new insights into the complex pathophysiology of claudication may help us to understand the potential role of lipid lowering therapy in alleviating exercise induced symptoms.

Lipoprotein-associated phospholipase A(2) mass and activity and risk of cardiovascular disease in a population with high prevalences of obesity and diabetes: the Strong Heart Study

OBJECTIVE

To investigate the association of lipoprotein-associated phospholipase A(2) (LpPLA(2)) mass and activity with incident cardiovascular disease (CVD) in a population with high prevalences of insulin resistance and diabetes, conditions for which epidemiological data remain sparse.

RESEARCH DESIGN AND METHODS

We conducted a nested, case-control study (n = 1,008) within a population-based cohort of American Indians. Case subjects were defined by incidence of first-ever CVD up to 10 years later. Control subjects comprised participants free of CVD events during the follow-up period who were frequency matched to case subjects by age, sex, and diabetes status. LpPLA(2) mass and activity were measured using commercially available assays.

RESULTS

LpPLA(2) mass and activity were moderately correlated with each other (r = 0.30), but only LpPLA(2) activity exhibited moderate correlations with lipid fractions. After extensive adjustment for covariates, both LpPLA(2) measures were significantly associated with incident CVD, but the relationship was inverse for LpPLA(2) mass (highest versus lowest tertile, relative risk [RR] 0.55 [95% CI 0.39-0.79]) and positive for LpPLA(2) activity (highest versus lowest tertile, 1.65 [1.12-2.42]). These associations were similar when participants with and without diabetes were examined separately.

CONCLUSIONS

In this population-based cohort enriched with dysmetabolic phenotypes, LpPLA(2) mass and activity showed divergent associations with CVD. The inverse relationship for LpPLA(2) mass is contrary to observations from predominantly nondiabetic populations and will require independent replication. Whether this finding relates to redistribution of LpPLA(2) to lipoprotein classes where it is less atherogenic or reflects incomplete measurement of LpPLA(2) mass associated with altered lipoprotein composition in insulin resistance warrants further investigation.

Lipoprotein(a): more interesting than ever after 50 years

PURPOSE OF REVIEW

Lipoprotein(a) [Lp(a)] is a risk factor for cardiovascular disease; we highlight the most recent research initiatives that have sought to define Lp(a)-dependent pathogenicity as well as pharmacologic approaches to lowering Lp(a).

RECENT FINDINGS

Recent large-scale meta-analyses have confirmed elevated Lp(a) concentrations to be a moderate but consistent prospective coronary heart disease (CHD) risk factor. The Mendelian randomization approach has also associated LPA variants with Lp(a) concentration and CHD risk. Discoveries linking Lp(a) to oxidized phospholipid burden have implicated a proinflammatory role for Lp(a) hinting at a new mechanism underlying the association with CHD risk, which adds to previous atherogenic and thrombogenic mechanisms. Most existing Lp(a)-lowering drug treatments almost always show simultaneous effects on other lipoproteins, making it difficult to assign any clinical outcome specifically to the effects of Lp(a) lowering. Early experiments with antisense oligonucleotides targeting apolipoprotein(a) mRNA seem to indicate the pleiotropic effects of Lp(a) reduction on LDL and HDL in mice. The mechanism linking Lp(a) concentration with concentrations of other blood lipids remains unknown but may provide an insight into Lp(a) metabolism.

SUMMARY

Despite the wealth of epidemiologic evidence supporting Lp(a) concentration as a CHD risk factor, the lack of a definitive functional mechanism involving an Lp(a)-dependent pathway in CHD pathogenesis has limited the potential clinical connotation of Lp(a). However, the application of novel technologies to the long-standing mysteries of Lp(a) biology seems to provide the opportunity for expanding our understanding of Lp(a) and its complex role in cardiovascular health.

Simvastatin reduces lipoprotein-associated phospholipase A2 in lipopolysaccharide-stimulated human monocyte-derived macrophages through inhibition of the mevalonate-geranylgeranyl pyrophosphate-RhoA-p38 mitogen-activated protein kinase pathway

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), which is produced primarily by macrophages and is predominately found in the blood and in atherosclerotic plaques, represents a potentially promising target for combating atherosclerosis. Although statins are known to decrease the levels and activity of circulating and plaque Lp-PLA(2) during atherosclerosis, little is known regarding the mechanisms underlying inhibition of Lp-PLA(2) by statins. Therefore, the aim of this study was to explore the molecular mechanisms responsible for inhibition of Lp-PLA(2) by statins. Our results showed that treatment with simvastatin inhibited lipopolysaccharide (LPS)-induced increases in Lp-PLA(2) expression and secreted activity in human monocyte–derived macrophages in a dose- and time-dependent manner. These effects could be reversed by treatment with mevalonate or geranylgeranyl pyrophosphate (GGPP), but not by treatment with squalene or farnesyl pyrophosphate. Treatment with the Rho inhibitor C3 exoenzyme also inhibited LPS-induced increases in Lp-PLA(2) expression and secreted activity, mimicking the effects of simvastatin. In addition, treatment with simvastatin blocked LPS-induced activation of RhoA, which could be abolished by treatment with GGPP. Inhibition of p38 mitogen-activated protein kinase (MAPK), but not extracellular signal regulated kinase 1/2 or Jun N-terminal kinase, suppressed LPS-induced increases in Lp-PLA(2) expression and secreted activity, similar to the effects of simvastatin. Treatment of human monocyte–derived macrophages with either simvastatin or C3 exoenzyme prevented LPS-induced activation of p38 MAPK, which could be abolished by treatment with GGPP. Together, these results suggest that simvastatin reduces Lp-PLA(2) expression and secreted activity in LPS-stimulated human monocyte–derived macrophages through the inhibition of the mevalonate–GGPP–RhoA-p38 MAPK pathway. These observations provide novel evidence that statins have pleiotropic effects and suggest that inhibition of Lp-PLA(2) via this mechanism may account, at least in part, for the clinical benefit of statins in combating atherosclerosis.

Phospholipase A2 enzymes, high-dose atorvastatin, and prediction of ischemic events after acute coronary syndromes

BACKGROUND

Secretory phospholipase A2 (sPLA(2)) and lipoprotein-associated phospholipase A2 (Lp-PLA(2)) are enzyme biomarkers of increased cardiovascular risk and targets of emerging therapeutic agents. Their relationship to cardiovascular events in the setting of high-dose statin therapy compared with placebo in patients with acute coronary syndrome is not known.

METHODS AND RESULTS

sPLA(2) and Lp-PLA(2) mass and activity were measured in 2587 patients in the Myocardial Ischemia Reduction With Acute Cholesterol Lowering (MIRACL) trial at baseline and after 16 weeks of treatment with atorvastatin 80 mg/d or placebo. Baseline levels of sPLA(2) and Lp-PLA(2) mass and activity were not associated with the primary efficacy measure of the trial of death, myocardial infarction, or unstable angina. However, in the overall cohort, baseline sPLA(2) mass predicted risk of death after multivariable adjustment (hazard ratio for 2-fold increase, 1.30; 95% confidence interval, 1.09-1.56; P=0.004). This association remained significant when examined separately in the placebo group but not in the atorvastatin group. Compared with placebo, atorvastatin reduced median sPLA(2) mass (-32.1% versus -23.1%), sPLA(2) activity (-29.5% versus -19.2%), Lp-PLA(2) mass (-35.8% versus -6.2%), and Lp-PLA(2) activity (-24.3% versus 5.4%; P<0.001 for all). Atorvastatin reduced the hazard of death associated with elevated sPLA(2) mass and activity by ≈50%.

CONCLUSIONS

sPLA(2) mass independently predicts death during a 16-week period after acute coronary syndrome. High-dose atorvastatin significantly reduces sPLA(2) and Lp-PLA(2) mass and activity after acute coronary syndrome and mitigates the risk of death associated with sPLA(2) mass. Atorvastatin may exert antiinflammatory effects on phospholipases that contribute to its therapeutic benefit after acute coronary syndrome.

Phospholipases: an overview

Phospholipids are present in all living organisms. They are a major component of all biological membranes, along with glycolipids and cholesterol. Enzymes aimed at cleaving the various bonds in phospholipids, namely phospholipases, are consequently widespread in nature, playing very diverse roles from aggression in snake venom to signal transduction, lipid mediators production, and digestion in humans. Although all phospholipases target phospholipids as substrates, they vary in the site of action on the phospholipids molecules, physiological function, mode of action, and their regulation. Significant studies on phospholipases characterization, physiological role, and industrial potential have been conducted worldwide. Some of them have been directed for biotechnological advances, such as gene discovery and functional enhancement by protein engineering. Others reported phospholipases as virulence factors and major causes of pathophysiological effects. In this introductory chapter, we provide brief details of different phospholipases.

Antiphospholipid antibodies and atherosclerosis: insights from rheumatoid arthritis--a five-year follow-up study

OBJECTIVES

Life expectancy in rheumatoid arthritis (RA) patients is reduced by 3-10 years, probably due to cerebrovascular and cardiovascular diseases associated with atherosclerosis. In the present study, we wanted to verify if previously reported IgA anti-beta 2-glycoprotein I (2GPI) antibodies possibly represented an independent risk factor for atherosclerosis in RA patients during a longer period of follow up.

METHODS

The follow-up study (after 5.5 years) comprised all initially included patients and controls (premenopausal women, non-diabetic, normotensive at the start of the study), except for two RA patients (one died and one not available). The same clinical, laboratory and ultrasound assessments were performed.

RESULTS

Patients and controls were divided into three categories: Intima-media thickness (IMT) progressors, plaque progressors, IMT and plaque progressors. In controls, 55% represented IMT progressors and 5% IMT and plaque progressors. No statistically significant differences were detected comparing the progressors with delta (Δ=difference between follow-up and baseline study for each group in a time span of 5.5 years) LDL cholesterol, homocysteine and IgA anti-β2GPI. In patients, there were 48.5% IMT progressors, 5.8% plaque progressors and 19.1% IMT and plaque progressors. The progression was statistically significant associated with the levels of Δ homocysteine and Δ apolipoprotein B but not with LDL cholesterol and IgA anti-β2GPI.

CONCLUSIONS

The follow-up study showed advanced atherosclerosis in RA patients compared to sex and age matched controls. However, we were not able to confirm our initial impression that IgA anti-β2GPI might represent an independent risk factor for atherosclerosis.

No effect of Implanon® on inflammatory cardiovascular parameters

OBJECTIVE

Recently, we found decreased levels of C-reactive protein (CRP) during use of the low-dosed contraceptive implant Implanon®. To further elucidate, whether this finding might be a sign for a lower inflammatory reaction and is associated with changes in levels of other cytokines, we investigated the effect of this implant on interleukin-6 (IL-6) and adiponectin. Plasma lipids and sex hormone levels have been shown to interact with the investigated parameters in vivo and in vitro. Therefore these parameters were measured as well.

DESIGN

Prospective case-control study.

SETTING

Family-planning centre, University hospital.

SUBJECTS

Thirty-six non-smoking women with regular cycles.

INTERVENTIONS

Blood samples for the measurements were taken in the early follicular phase of the cycle in both groups. A second sample was taken 12 weeks after Implanon insertion or in the controls during the early follicular phase of cycle 4.

RESULTS

Implanon did not cause significant changes in IL-6, adiponectin or lipoprotein (Lp)(a). At baseline, there was a significant positive correlation between IL-6 and CRP and a negative correlation between adiponectin and CRP.

CONCLUSION

We did not observe a negative impact of Implanon on risk markers for atherosclerotic disease such as IL-6, adiponectin, and Lp(a). These data are reassuring for clinicians who prescribe progestagen-only preparations as first choice contraceptives in females with cardiovascular risk factors.

Differential associations of serum amyloid A and pentraxin-3 with allele-specific lipoprotein(a) levels in African Americans and Caucasians

Lipoprotein(a) [Lp(a)] is a cardiovascular disease (CVD) risk factor, where inflammation impacts levels differentially across ethnicity. We investigated the effect of systemic [serum amyloid A (SAA)] and vascular [pentraxin-3 (PTX-3)] inflammation on Lp(a) levels across different apolipoprotein(a) [apo(a)] sizes in a biethnic population. Lp(a) and allele-specific apo(a) levels, apo(a) sizes, SAA, and PTX-3 levels were determined in 336 Caucasians and 224 African Americans. We dichotomized subjects into 2 groups using the respective median SAA (29.8 and 41.5 mg/dL for Caucasians and African Americans, respectively) or PTX-3 levels (1.6 and 1.1 ng/mL for Caucasians and African Americans, respectively). Among African Americans, but not in Caucasians, Lp(a) levels were increased (146 vs 117 nmol/L, P = 0.024) in the high versus low SAA group. No difference was observed across PTX-3 groups. Furthermore, among African Americans with smaller (<26 K4 repeats) apo(a) sizes, allele-specific apo(a) levels (111 vs 79 nmol/L, P = 0.020) were increased in the high versus low SAA group. Again, no difference was observed for PTX-3. We did not find any significant associations between allele-specific apo(a) and SAA or PTX-3 levels among Caucasians with smaller (<26 K4) apo(a) sizes. In conclusion, increased levels of SAA, but not PTX-3, were associated significantly with higher Lp(a) levels for smaller (<26 K4) apo(a) sizes in African Americans. Our results implicate that a proinflammatory stimulus may result in an increased cardiovascular risk through a selective increase in Lp(a) levels among African Americans who carry a smaller apo(a) size.

Combinations of ezetimibe with nonstatin drug regimens affecting lipid metabolism

In this article we discuss the available data on the effects of combined therapy of ezetimibe with agents affecting lipid metabolism other than statins. We consider studies evaluating the effects of combined therapy of ezetimibe with bile acid sequestrants, fenofibrate, niacin, n-3 fatty acids, plant sterols, orlistat, metformin, acarbose and glitazones. Combination of ezetimibe with bile acid sequestrants (especially colesevelam) was shown to have additional effects on lipid parameters in patients with hyperlipidemia. Combination of ezetimibe with fenofibrate may be a good approach to improve the overall lipid profile of patients with mixed hyperlipidemia. The addition of ezetimibe to niacin-based therapy can be useful for high-risk patients with dyslipidemia who are not achieving their assigned treatment goals. For patients who cannot tolerate statins there are useful combinations of ezetimibe with other drugs affecting lipid metabolism. These combinations improve many metabolic parameters, but more trials should be carried out to reach more robust conclusions about their effects on cardiovascular disease prevention.

Fenofibrate plus simvastatin (fixed-dose combination) for the treatment of dyslipidaemia

INTRODUCTION

Statin use results in a significant reduction of cardiovascular disease (CVD) risk. However, patients still have residual CVD risk, even if they are receiving optimal statin treatment.

AREAS COVERED

This review, based on a Pubmed/Scopus search, discusses the available evidence regarding the use of a fixed-dose fenofibrate plus simvastatin combination. This combination is useful for patients with mixed dyslipidaemia because it improves the overall lipoprotein profile. Although in clinical trials the rate of adverse events was not significantly greater than monotherapy, patients who receive combination treatment should be monitored carefully. Furthermore, in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) Study, this combination did not result in a significant reduction of CVD events compared with simvastatin monotherapy. However, a possible benefit in this trial was observed in the subgroup of patients with high triglyceride and low high-density lipoprotein cholesterol levels.

EXPERT OPINION

The fixed-dose fenofibrate plus simvastatin combination treatment produces additive results and is safe when patients are properly monitored. Existing evidence appears to support the addition of fenofibrate to simvastatin treatment for the reduction of residual CVD risk in patients with atherogenic dyslipidaemia. However, this combination did not lead to better clinical outcomes in the absence of dyslipidaemia.

Lipoprotein(a) levels, apo(a) isoform size, and coronary heart disease risk in the Framingham Offspring Study

The aim of this study was to assess the independent contributions of plasma levels of lipoprotein(a) (Lp(a)), Lp(a) cholesterol, and of apo(a) isoform size to prospective coronary heart disease (CHD) risk. Plasma Lp(a) and Lp(a) cholesterol levels, and apo(a) isoform size were measured at examination cycle 5 in subjects participating in the Framingham Offspring Study who were free of CHD. After a mean follow-up of 12.3 years, 98 men and 47 women developed new CHD events. In multivariate analysis, the hazard ratio of CHD was approximately two-fold greater in men in the upper tertile of plasma Lp(a) levels, relative to those in the bottom tertile (P < 0.002). The apo(a) isoform size contributed only modestly to the association between Lp(a) and CHD and was not an independent predictor of CHD. In multivariate analysis, Lp(a) cholesterol was not significantly associated with CHD risk in men. In women, no association between Lp(a) and CHD risk was observed. Elevated plasma Lp(a) levels are a significant and independent predictor of CHD risk in men. The assessment of apo(a) isoform size in this cohort does not add significant information about CHD risk. In addition, the cholesterol content in Lp(a) is not a significant predictor of CHD risk.

Plasma lipoprotein-associated phospholipase A2 in patients with metabolic syndrome and carotid atherosclerosis

Background

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is a recently identified and potentially useful plasma biomarker for cardiovascular and atherosclerotic diseases. However, the correlation between the Lp-PLA₂ activity and carotid atherosclerosis remains poorly investigated in patients with metabolic syndrome (MetS). The present study aimed to evaluate the potential role of Lp-PLA₂ as a comprehensive marker of metabolic syndrome in individuals with and without carotid atherosclerosis.

Methods

We documented 118 consecutive patients with MetS and 70 age- and sex-matched healthy subjects served as controls. The patients were further divided into two groups: 39 with carotid plaques and 79 without carotid plaques to elucidate the influence of Lp-PLA₂ on carotid atherosclerosis. The plasma Lp-PLA₂ activity was measured by using ELISA method and carotid intimal-media thickness (IMT) was performed by ultrasound in all participants.

Results

Lp-PLA₂ activity was significantly increased in MetS subgroups when compared with controls, and was higher in patients with carotid plaques than those without plaques (P < 0.05). Furthermore, we found that significant difference in Lp-PLA₂ was obtained between patients with three and four disorders of metabolic syndrome (P < 0.01). Age (β = 0.183, P = 0.029), LDL-cholesterol (β = 0.401, P = 0.000) and waist-hip ratio (β = 0.410, P = 0.000) emerged as significant and independent determinants of Lp-PLA₂ activity. Multiple stepwise regression analysis revealed that LDL-cholesterol (β = 0.309, P = 0.000), systolic blood pressure (β = 0.322, P = 0.002) and age (β = 0.235, P = 0.007) significantly correlated with max IMT, and Lp-PLA₂ was not an independent predictor for carotid IMT.

Conclusions

Lp-PLA₂ may be a modulating factor for carotid IMT via age and LDL-cholesterol, not independent predictor in the pathophysiological process of carotid atherosclerosis in patients with MetS.

Recent progress in phospholipase A₂ research: from cells to animals to humans

Mammalian genomes encode genes for more than 30 phospholipase A₂s (PLA₂s) or related enzymes, which are subdivided into several classes including low-molecular-weight secreted PLA₂s (sPLA₂s), Ca²+-dependent cytosolic PLA₂s (cPLA₂s), Ca²+-independent PLA₂s (iPLA₂s), platelet-activating factor acetylhydrolases (PAF-AHs), lysosomal PLA₂s, and a recently identified adipose-specific PLA. Of these, the intracellular cPLA₂ and iPLA₂ families and the extracellular sPLA₂ family are recognized as the "big three". From a general viewpoint, cPLA₂α (the prototypic cPLA₂ plays a major role in the initiation of arachidonic acid metabolism, the iPLA₂ family contributes to membrane homeostasis and energy metabolism, and the sPLA₂ family affects various biological events by modulating the extracellular phospholipid milieus. The cPLA₂ family evolved along with eicosanoid receptors when vertebrates first appeared, whereas the diverse branching of the iPLA₂ and sPLA₂ families during earlier eukaryote development suggests that they play fundamental roles in life-related processes. During the past decade, data concerning the unexplored roles of various PLA₂ enzymes in pathophysiology have emerged on the basis of studies using knockout and transgenic mice, the use of specific inhibitors, and information obtained from analysis of human diseases caused by mutations in PLA₂ genes. This review focuses on current understanding of the emerging biological functions of PLA₂s and related enzymes.

Pathological aspects of lipid peroxidation

Lipid peroxidation (LPO) product accumulation in human tissues is a major cause of tissular and cellular dysfunction that plays a major role in ageing and most age-related and oxidative stress-related diseases. The current evidence for the implication of LPO in pathological processes is discussed in this review. New data and literature review are provided evaluating the role of LPO in the pathophysiology of ageing and classically oxidative stress-linked diseases, such as neurodegenerative diseases, diabetes and atherosclerosis (the main cause of cardiovascular complications). Striking evidences implicating LPO in foetal vascular dysfunction occurring in pre-eclampsia, in renal and liver diseases, as well as their role as cause and consequence to cancer development are addressed.

Lipoprotein(a) as a cardiovascular risk factor: current status

AIMS

The aims of the study were, first, to critically evaluate lipoprotein(a) [Lp(a)] as a cardiovascular risk factor and, second, to advise on screening for elevated plasma Lp(a), on desirable levels, and on therapeutic strategies.

METHODS AND RESULTS

The robust and specific association between elevated Lp(a) levels and increased cardiovascular disease (CVD)/coronary heart disease (CHD) risk, together with recent genetic findings, indicates that elevated Lp(a), like elevated LDL-cholesterol, is causally related to premature CVD/CHD. The association is continuous without a threshold or dependence on LDL- or non-HDL-cholesterol levels. Mechanistically, elevated Lp(a) levels may either induce a prothrombotic/anti-fibrinolytic effect as apolipoprotein(a) resembles both plasminogen and plasmin but has no fibrinolytic activity, or may accelerate atherosclerosis because, like LDL, the Lp(a) particle is cholesterol-rich, or both. We advise that Lp(a) be measured once, using an isoform-insensitive assay, in subjects at intermediate or high CVD/CHD risk with premature CVD, familial hypercholesterolaemia, a family history of premature CVD and/or elevated Lp(a), recurrent CVD despite statin treatment, ≥3% 10-year risk of fatal CVD according to European guidelines, and/or ≥10% 10-year risk of fatal + non-fatal CHD according to US guidelines. As a secondary priority after LDL-cholesterol reduction, we recommend a desirable level for Lp(a) <80th percentile (less than ∼50 mg/dL). Treatment should primarily be niacin 1-3 g/day, as a meta-analysis of randomized, controlled intervention trials demonstrates reduced CVD by niacin treatment. In extreme cases, LDL-apheresis is efficacious in removing Lp(a).

CONCLUSION

We recommend screening for elevated Lp(a) in those at intermediate or high CVD/CHD risk, a desirable level <50 mg/dL as a function of global cardiovascular risk, and use of niacin for Lp(a) and CVD/CHD risk reduction.

Recent developments with lipoprotein-associated phospholipase A2 inhibitors

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is a calcium-independent phospholipase A(2) enzyme secreted by leukocytes and associated with circulating low-density lipoprotein and macrophages in atherosclerotic plaques. Until recently, the biological role of Lp-PLA(2) in atherosclerosis was controversial, but now the preponderance of evidence demonstrates a proatherogenic role of this enzyme. Lp-PLA(2) generates two proinflammatory mediators, lysophosphatidylcholine and oxidized nonesterified fatty acids, which play a major role in the development of atherosclerotic lesions and formation of a necrotic core, leading to more vulnerable plaques. These findings have opened the door to a potential novel therapeutic target, selective inhibition of Lp-LPA(2). Recently, both animal models and human studies have shown that selective inhibition of Lp-PLA(2) reduces plasma Lp-PLA(2) activity, plaque area, and necrotic core area. This article reviews the most recent developments with Lp-PLA(2) inhibitors.

Darapladib: an emerging therapy for atherosclerosis

Despite a reduction in cardiovascular risk conferred by therapies that modify circulating lipids, a need remains for novel treatments to further decrease the occurrence of complications of atherosclerotic cardiovascular diseases. Lipoprotein-associated phospholipase-A2 is an important regulator of lipid metabolism and inflammation that circulates with lipoprotein particles and is carried into the arterial wall with low-density lipoprotein particles during the progression of atherosclerosis. Within the vessel wall, lipoprotein-associated phospholipase-A2 releases small molecules that stimulate macrophage recruitment and evolution to foam cells, leading to plaque vulnerability. Epidemiologic studies demonstrate that elevated circulating levels of lipoprotein-associated phospholipase-A2 predict an increased risk of myocardial infarction and stroke, whereas histologic examination of diseased human coronary arteries reveals intense presence of the enzyme in atherosclerotic plaques that are prone to rupture. These considerations suggest lipoprotein-associated phospholipase-A2 as a promising therapeutic target, and a specific inhibitor, darapladib, has been under development for this application. This review summarizes the completed preclinical and early phase clinical studies that underlie two recently commenced phase III clinical trials that will investigate the efficacy and safety of darapladib in nearly 13,000 individuals with coronary heart disease. When completed, these trials should provide important insights into the utility of darapladib to reduce myocardial infarction, stroke and cardiovascular death.

Lipoprotein(a), inflammation, and peripheral arterial disease in a community-based sample of older men and women (the InCHIANTI study)

Lipoprotein(a) (Lp[a]) may represent an independent risk factor for peripheral arterial disease of the lower limbs (LL-PAD), but prospective data are scant. We estimated the association between baseline Lp(a) with prevalent and incident LL-PAD in older subjects from the InCHIANTI Study. LL-PAD, defined as an ankle-brachial index <0.90, was assessed at baseline and over a 6-year follow-up in a sample of 1,002 Italian subjects 60 to 96 years of age. Plasma Lp(a) and potential traditional and novel cardiovascular risk factors (including a score based on relevant inflammatory markers) were entered in multivariable models to assess their association with prevalent and incident LL-PAD. At baseline, Lp(a) concentration was directly related to the number of increased inflammatory markers (p <0.05). There were 125 (12.5%) prevalent cases of LL-PAD and 57 (8.3%) incident cases. After adjustment for potential confounders, participants in the highest quartile of the Lp(a) distribution (>/=32.9 mg/dl) were more likely to have LL-PAD compared to those in the lowest quartile (odds ratio [OR] 1.83, 95% confidence interval [CI] 1.01 to 3.33). The association was stronger (OR 3.80, 95% CI 1.50 to 9.61) if LL-PAD was defined by harder criteria, namely an ankle-brachial index <0.70. Compared to subjects in the lowest Lp(a) quartile, those in the highest quartile showed a somewhat increased risk of incident LL-PAD (lowest quartile 7.7%, highest quartile 10.8%), but the association was not statistically significant (OR 1.52, 95% CI 0.71 to 3.22). In conclusion, Lp(a) is an independent LL-PAD correlate in the cross-sectional evaluation, but further prospective studies in larger populations, with longer follow-up and more definite LL-PAD ranking, might be needed to establish a longitudinal association.

Association of Lp-PLA(2) activity with allele-specific Lp(a) levels in a bi-ethnic population

OBJECTIVES

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) and lipoprotein(a) [Lp(a)] have been implicated as cardiovascular disease risk factors, and are differentially regulated across ethnicity. We investigated the association between Lp-PLA(2) activity and allele-specific apolipoprotein(a) [apo(a)] levels in a bi-ethnic population.

METHODS

Lp-PLA(2) activity, Lp(a) and allele-specific apo(a) levels were determined in 224 African Americans and 336 Caucasians.

RESULTS

Lp-PLA(2) activity level was higher among Caucasians compared to African Americans (173 + or - 41 nmol/min/ml vs. 141 + or - 39 nmol/min/ml, P<0.001), and positively associated with Lp(a), total and LDL cholesterol, triglyceride, apolipoprotein B-100, and negatively with HDL cholesterol levels in both ethnic groups. The association between Lp-PLA(2) activity and Lp(a) was stronger among African Americans compared to Caucasians (R=0.238, beta(1)=3.48, vs. R=0.111, beta(1)=1.93, respectively). The Lp-PLA(2) activity level was significantly associated with allele-specific apo(a) levels for smaller (<26 K4 repeats) apo(a) sizes in both ethnic groups (P=0.015 for African Americans, P=0.038 for Caucasians). In contrast, for larger (>26 K4 repeats) apo(a) sizes, high Lp-PLA(2) activity levels were associated with higher allele-specific apo(a) levels in African Americans (P=0.009), but not in Caucasians.

CONCLUSION

The association between Lp-PLA(2) activity and allele-specific apo(a) levels differs across African American-Caucasian ethnicity.

Darapladib

IMPORTANCE OF THE FIELD

Atherosclerosis is an inflammatory-immune mediated disease process. Plaque rupture is responsible for the clinical events of ischemic death, myocardial infarction, acute coronary syndromes and ischemic strokes. Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) seems to play a major role in the development of such high-risk lesions, in both the coronary and carotid arteries. Darapladib is a selective inhibitor of Lp-PLA(2).

AREAS COVERED IN THIS REVIEW

An overview of darapladib by reviewing the studies (1990 - 2009) that have provided the rationale for the development of darapladib; and a discussion of its potential merit as a new therapeutic drug to target high-risk atherosclerosis.

WHAT THE READER WILL GAIN

The reader should gain an understanding of the importance of inflammation during atherogenesis as well as of the biology of Lp-PLA(2) and its proatherogenic role. Additional insights will be gained into the role of selective inhibitors of Lp-PLA(2) as new therapeutic agents.

TAKE HOME MESSAGE

Darapladib is a selective inhibitor of Lp-PLA(2) and represents a new class of therapeutic agents that target inflammation to treat high-risk atherosclerosis.