Dual activity of serum lipoprotein-associated phospholipase A(2) yielding positive and inverse associations with cardiometabolic risk

Age- and Sex-Specific Association between Lipoprotein-Related Phospholipase A2 and Cardiometabolic Risk Factors

(1) Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a risk factor for predicting cardiovascular diseases. Metabolic syndrome is characterized by a state of chronic inflammation that is related to an increased risk of cardiovascular events and death. In the present study, we aimed to analyze the correlation between cardiometabolic risk factors and Lp-PLA2 levels. (2) We collected the related retrospective medical data of Chinese adults, of which 3983 were men and 2836 were women (aged ≥ 18 years), who underwent health check-ups, and discussed the sex and age-related differences. (3) Data analysis showed that Lp-PLA2 was significantly related to lipoproteins and glutamic pyruvic transaminase (GPT), and that a linear trend was observed with increasing Lp-PLA2 levels for all ages and sexes. However, fasting glucose was significantly related to Lp-PLA2 only in the younger population. The two obesity-related parameters (waist-to-height ratio and waist circumference) also had a greater correlation with Lp-PLA2 levels in the younger groups; however, the correlation weakened in the elderly population. Meanwhile, the correlation between mean arterial pressure and creatinine level and Lp-PLA2 was significant only in younger men. (4) The results show that the expression patterns of Lp-PLA2 differ between sexes and across age groups.

Lipoprotein-associated phospholipase A₂ activity is increased in patients with definite familial hypercholesterolemia compared with other forms of hypercholesterolemia

BACKGROUND AND AIM

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) plays a key role in atherosclerosis development. It is considered a marker of increased risk of cardiovascular disease (CVD) and plaque vulnerability. Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated plasma levels of low-density lipoprotein cholesterol and a higher prevalence of early CVD. Our aim was to evaluate the differences in Lp-PLA₂ activity in a population of hypercholesterolemic patients with and without definite FH.

METHODS AND RESULTS

Hypercholesterolemic patients were consecutively recruited. Definite FH was defined according to Dutch Lipid Clinic Network criteria ≥8. All patients underwent routine clinical examination and biological assessments and Lp-PLA₂ activity was measured in blood samples. Among 469 patients, 118 had a definite diagnosis of FH. Lp-PLA₂ activity was significantly higher in definite FH patients compared to non-definite FH patients (206.5 ± 54.5 vs. 180.8 ± 48.4 nmol/min/mL, p < 0.0001). Lp-PLA₂ positively correlated with total cholesterol, LDL-C and apolipoprotein B and negatively with HDL-C and apolipoprotein A-1. In multivariate analysis, definite FH diagnosis, LDL-C, HDL-C and statin treatment remained correlates of Lp-PLA₂ independently of systolic blood pressure.

CONCLUSIONS

Lp-PLA₂ activity was higher in definite FH than in non-definite FH patients independently of LDL-C levels and statin treatment. These results highlight the particular phenotype of FH subjects among hypercholesterolemic patients. As increased Lp-PLA₂ activity suggests, FH patients exhibit higher arterial inflammation that may contribute to their high cardiovascular risk. Our results reinforce the potential beneficial role of statins pleiotropic effects and the need for proper identification and treatment of FH patients.

Lipoprotein-associated phospholipase A2 activity in obese adolescents with and without type 2 diabetes

Lipoprotein-associated phospholipase A2 (Lp-PLA2) was identified as a strong predictor for cardiovascular events. Furthermore, it is highly associated with obesity. The role of Lp-PLA2 in diabetes mellitus is controversial and analyses, especially in adolescents with type 2 diabetes (T2D), are missing. Therefore, we compared Lp-PLA2 activity between two obese age-, sex-, and BMI-matched cohorts of adolescents with and without T2D. Relationships between Lp-PLA2 activity and age, BMI, hemoglobin A1c, lipids, and adipokines were evaluated. Lp-PLA2 activity was analyzed in serum of 72 obese adolescents without T2D (mean age 15.2 ± 1.6 years) and in 65 obese adolescents with T2D (mean age 15.5 ± 1.8 years). Clinical data were obtained from the Diabetes-Patienten-Verlaufsdokumentation (DPV) registry. Surprisingly, obese adolescents with T2D had lower levels of Lp-PLA2 activity than obese children without T2D (160.2 ± 45.0 versus 180.9 ± 35.6 nmol/min/ml, p = 0.003), but this decrease could only be detected in male (158.8 ± 45.3 versus 190.8 ± 31.3 nmol/min/ml, p < 0.001) and not in female adolescents (162.1 ± 45.5 versus 167.7 ± 37.1 nmol/min/ml, p = 0.60). In multiple linear regression analysis, differences in Lp-PLA2 activity between cohorts remained large and significant (ß-coefficient: -31.60, 95% confidence interval [-49.27;-13.93], p < 0.001). Furthermore, Lp-PLA2 activity was positively associated with BMI (ß-coefficient: 2.04 [0.68;3.40], p = 0.004) and negatively associated with the adipokines leptin (ß-coefficient: -0.53 [-0.89;-0.17], p = 0.004) and adiponectin (ß-coefficient: -3.06, [-5.63;-0.48], p = 0.02). Elevated mean glucose concentrations in adolescents with T2D were not associated with an increase but with a decrease of Lp-PLA2 activity. Hence, in young patients with T2D the Lp-PLA2 activity as a risk predictor for cardiovascular events needs further investigation.

Modified risk associations of lipoproteins and apolipoproteins by chronic low-grade inflammation

INTRODUCTION

Lipoproteins and the apolipoproteins (apo) that they carry are major determinants of cardiovascular diseases (CVD) as well as metabolic, renal and inflammatory chronic disorders either directly or through mediation of risk factors. The notion that elevated low-density lipoprotein cholesterol (LDL-C) and apoB levels are related to the acquisition of CVD and, high-density lipoprotein cholesterol (HDL-C) and apoA-I indicate protection against CVD has been challenged in the past decade. Advanced age, adiposity, ethnicity or impaired glucose intolerance rendered autoimmune activation in an environment of pro-inflammatory state/oxidative stress and may disrupt the linear risk association between lipoproteins. Areas covered: This review summarizes the modified risk associations of lipoproteins and apolipoprotein by an environment of chronic systemic low-grade inflammation with special emphasis on the non-linear relationship of lipoprotein(a) [Lp(a)], a biomarker of renewed interest in cardiometabolic risk. Expert commentary: It seems that autoimmune activation in an environment of pro-inflammatory state/oxidative stress not only disrupts the linear risk association between lipoproteins, but also may cause interference in immunoassays. Hence, methodological improvement in immunoassays and much further research focusing on population segments susceptible to a pro-inflammatory state is necessary for further advances in knowledge.

Cardiovascular risk assessment and screening in diabetes

Diabetes used to be considered as a coronary heart disease equivalence and universally classified high cardiovascular risk population. However increasing epidemiological evidence now indicates the heterogeneity of risk among the diabetic patients and imposes animportance of stratifying those with relative low-risk from high-risk ones. Despite the existing risk assessment tools, current cardivoascualr disease prevention guidelines fail to provide more detailed stratification strategies for patient with diabetes and expose them to either overtreatment or undertreatment. On the other hand, various screening modality, including novel biomarkers and subclinical asthrosclerosis scanning, including coronary calcium scanning, carotid intima-media thickness, myocardial perfusion imaging and coronary computed tomography angiography, have provided very promising usage is risk stratification. With better developed test techniques and more extensive evidence, these modalities may serve in standardized screening algorithm to improve the cardiovascular risk assessment of patients with diabetes and better instruct their individualized preventive therapy.

Rheumatoid factor mediates excess serum lipoprotein(a) for independent association with type 2 diabetes in men

OBJECTIVE

The potential association of rheumatoid factor (RF) and lipoprotein (Lp)(a) levels, as well as with the likelihood of type 2 diabetes and hypertension, needs exploring.

METHODS

Cross-sectional associations were sought in this unselected and population-based 1539-adult cohort (age 58.8±10.6 years). RF was assayed nephelometrically. Multiple logistic regression analyses were used for covariates of RF positivity and for the latter's association with diabetes and hypertension.

RESULTS

RF-positive individuals were older, fewer current smokers, had significantly lower fasting triglycerides (by 13%), higher fibrinogen, and tended to higher sex hormone-binding globulin (SHBG) levels. Whereas, women had a similar risk profile irrespective of RF status, RF-positive men had significantly higher Lp(a). In contrast to Lp(a) being positively correlated with SHBG in RF-negative subjects (r=0.08; p=0.007), an inverse correlation existed in seropositive individuals (r=-0.32, p=0.011), suggesting the interplay of an immune complex. In regression analyses, RF positivity was associated with Lp(a) in men but not in women, [OR 1.53 (1.19; 1.96)], independent of age, SHBG, and C-reactive protein (CRP). RF positivity was further associated with diabetes [OR 1.98 (95% CI 1.11; 3.52)] in the whole sample, additively to waist circumference and CRP, major determinants of diabetes. RF-positive subjects were not significantly associated independently with hypertension.

CONCLUSION

Autoimmune activation linked to Lp(a) is mediated by the autoantibody RF in contributing to the development of type 2 diabetes.

Association of traditional risk factors with coronary artery disease in nonagenarians: the primary role of hypertension

BACKGROUND

Previous studies have shown different relationships between traditional cardiovascular risk factors for coronary artery disease (CAD) in very elderly people. Although new associations with CAD have been reported, there is also evidence of the possibility of new therapeutic strategies for the treatment or prevention of CAD.

DESIGN

This article retrospectively examines the possible association of traditional cardiovascular risk factors with CAD in very elderly people aged >90 years. This study represents the hypothesis that the elderly aged >90 years have a different cardiovascular profile with respect to CAD than patients <90 years old.

METHODS

Data on all patients aged >90 years who received a cardiac catheterization were collected from hospital charts from the Department of Internal Medicine, Saarland University Medical Center, Germany, within the study period of 2004-2013. The cardiovascular risk profiles were compared in patients aged >90 years with and without CAD after cardiac catheterization.

RESULTS

One hundred and six out of 67,976 (0.2%, mean age 91.6±1.8 years, 40 female [37.7%]; 95% confidence interval [CI]: 0.1-0.2), and out of a total of 114 of the very elderly patients, were found to have CAD. From the results of this study, the author could establish only a causal relationship between hypertension and CAD in very elderly people (P=0.005). At best, this is just an association with a higher risk of CAD in this age group. Several studies with similar outcomes are needed to establish causality.

CONCLUSION

This study could find no link between CAD and traditional risk factors, except for hypertension.

Unexpected inverse relationship between impaired glucose metabolism and lipoprotein-associated phospholipase A2 activity in patients with stable vascular disease

BACKGROUND

Elevated lipoprotein-associated phospholipase A2 activity (aLp-PLA2) is associated with increased risk of cardiovascular events. In patients with stable atherovascular disease, we aimed to investigate whether impaired glucose metabolism might be associated with higher risk of elevated aLp-PLA2.

METHODS

We conducted a cross-sectional study in 825 stable patients after acute coronary syndrome, coronary revascularization or after first ischemic stroke (Czech part of EUROASPIRE III surveys). We measured aLp-PLA2 using diaDexus commercial kit.

RESULTS

In multiple step-wise regression analysis, the aLp-PLA2 was significantly positively associated with male gender, current smoking, LDL cholesterol and metabolic syndrome and negatively with statin treatment, body mass index and LDL/apoB ratio. After adjustment for these confounders, we observed an inverse relationship between aLp-PLA2 and fasting glycemia [β coefficient -2.18 (p<0.0001)] or glycated hemoglobin A1c (HbA1c) [β coefficient -5.89 (p<0.0001)]. Moreover, we found a positive association between aLp-PLA2 and pancreatic β cell function [β coefficient +0.10 (p<0.0001)], but not with an insulin sensitivity.

CONCLUSION

In present study, we cannot confirm any additive risk of impaired glucose metabolism in terms of increased activity of Lp-PLA2. On the contrary, presence of inadequately controlled diabetes mellitus was independently associated with lower risk of elevated aLp-PLA2 .

Impact of the LDL subfraction phenotype on Lp-PLA2 distribution, LDL modification and HDL composition in type 2 diabetes

Background

Qualitative alterations of lipoproteins underlie the high incidence of atherosclerosis in diabetes. The objective of this study was to assess the impact of low-density lipoprotein (LDL) subfraction phenotype on the qualitative characteristics of LDL and high-density lipoprotein (HDL) in patients with type 2 diabetes.

Methods

One hundred twenty two patients with type 2 diabetes in poor glycemic control and 54 healthy subjects were included in the study. Patients were classified according to their LDL subfraction phenotype. Seventy-seven patients presented phenotype A whereas 45 had phenotype B. All control subjects showed phenotype A. Several forms of modified LDL, HDL composition and the activity and distribution of lipoprotein-associated phospholipase A2 (Lp-PLA2) were analyzed.

Results

Oxidized LDL, glycated LDL and electronegative LDL were increased in both groups of patients compared with the control group. Patients with phenotype B had increased oxidized LDL and glycated LDL concentration than patients with phenotype A. HDL composition was abnormal in patients with diabetes, being these abnormalities more marked in patients with phenotype B. Total Lp-PLA2 activity was higher in phenotype B than in phenotype A or in control subjects. The distribution of Lp-PLA2 between HDL and apoB-containing lipoproteins differed in patients with phenotype A and phenotype B, with higher activity associated to apoB-containing lipoproteins in the latter.

Conclusions

The presence of LDL subfraction phenotype B is associated with increased oxidized LDL, glycated LDL and Lp-PLA2 activity associated to apoB-containing lipoproteins, as well as with abnormal HDL composition.