Circulating levels of proprotein convertase subtilisin/kexin type 9 (PCSK9) are associated with monocyte subsets in patients with stable coronary artery disease.

BACKGROUND: Proprotein convertase subtilisin/kexin type-9 (PCSK9) is an enzyme promoting the degradation of low-density lipoprotein receptors (LDL-R) in hepatocytes. Inhibition of PCSK9 has emerged as a novel target for lipid-lowering therapy. Monocytes are crucially involved in the pathogenesis of atherosclerosis and can be divided into three subsets. OBJECTIVE: The aim of this study was to examine whether circulating levels of PCSK9 are associated with monocyte subsets. METHODS: We included 69 patients with stable coronary artery disease. PCSK9 levels were measured and monocyte subsets were assessed by flow cytometry and divided into classical monocytes (CD14++CD16-; CM), intermediate monocytes (CD14++CD16+; IM) and non-classical monocytes (CD14+CD16++; NCM). RESULTS: Mean age was 64 years and 80% of patients were male. Patients on statin treatment (n = 55) showed higher PCSK9-levels (245.4 (206.0-305.5) ng/mL) as opposed to those without statin treatment (186.1 (162.3-275.4) ng/mL; p = 0.05). In patients on statin treatment, CM correlated with circulating PCSK9 levels (R = 0.29; p = 0.04), while NCM showed an inverse correlation with PCSK9 levels (R = -0.33; p = 0.02). Patients with PCSK9 levels above the median showed a significantly higher proportion of CM as compared to patients with PCSK9 below the median (83.5 IQR 79.2-86.7 vs. 80.4, IQR 76.5-85.2%; p = 0.05). Conversely, PCSK9 levels >median were associated with a significantly lower proportion of NCM as compared to those with PCSK9

Small dense LDL - an important part of the atherogenic lipoprotein profile in individuals with impaired metabolism of lipoproteins. Comparison of two analytical procedures.

OBJECTIVES: To compare two different analytical methods for determination of small dense LDL and to determine a share of corresponding and non-corresponding (inconsistent) results METHODS: In the group of 104 hyperlipidemic patients and 20 healthy individuals of the control group we analysed the total cholesterol and triglycerides by enzymatic CHOD PAP method (Roche Diagnostics, Germany) in EDTA-K2 plasma. Small dense LDL (sdLDL) were quantified by the electrophoretic method for lipoprotein analysis on polyacrylamide gel (PAG) (Lipoprint LDL System, Quantimetrix, CA, USA) and simultaneously, the small dense LDL concentrations in the indentical samples were analysed by an enzymatic method LDL-EX ´Seiken´(Randox, England). RESULTS: In 31 patients we found the discrepancy in the sdLDL levels using the two different procedures. Out of them, 24 patients tested by enzymatic method ´SEIKEN´ had higher sdLDL values (more than 0.9 mmol/l) compared to the Lipoprint LDL results, which identified normal sdLDL values in the same samples (in 23% of tested patients). In 7 patients out of the 31 tested patients with discrepant sdLDL values, the Lipoprint LDL identified increased values of plasma sdLDL (more than 0.155 mmol/l), while the enzymatic LDL-EX Seiken did not find an increased concentration of sdLDL (in 7% of tested patients). In the control group a discrepancy in the sdLDL results between the two tested analytical methods was not found. CONCLUSION: The concentration of sdLDL in plasma lipoprotein spectrum obtained by two different laboratory procedures was analysed, compared, evaluated and 70% identical corresponding results have been confirmed.

Monocyte subset distribution in patients with stable atherosclerosis and elevated levels of lipoprotein(a).

BACKGROUND: Lipoprotein(a) (Lp(a)) is a proatherogenic plasma lipoprotein currently established as an independent risk factor for the development of atherosclerotic disease and as a predictor for acute thrombotic complications. In addition, Lp(a) is the major carrier of proinflammatory oxidized phospholipids (OxPL). Today, atherosclerosis is considered to be an inflammatory disease of the vessel wall in which monocytes and monocyte-derived macrophages are crucially involved. Circulating monocytes can be divided according to their surface expression pattern of CD14 and CD16 into at least 3 subsets with distinct inflammatory and atherogenic potential. OBJECTIVE: The aim of this study was to examine whether elevated levels of Lp(a) and OxPL on apolipoprotein B-100-containing lipoproteins (OxPL/apoB) are associated with changes in monocyte subset distribution. METHODS: We included 90 patients with stable coronary artery disease. Lp(a) and OxPL/apoB were measured, and monocyte subsets were identified as classical monocytes (CMs; CD14++CD16-), intermediate monocytes (IMs; CD14++CD16+), and nonclassical monocytes (NCMs; CD14+CD16++) by flow cytometry. RESULTS: In patients with elevated levels of Lp(a) (>50 mg/dL), monocyte subset distribution was skewed toward an increase in the proportion of IM (7.0 ± 3.8% vs 5.2 ± 3.0%; P = .026), whereas CM (82.6 ± 6.5% vs 82.0 ± 6.8%; P = .73) and NCM (10.5 ± 5.3 vs 12.8 ± 6.0; P = .10) were not significantly different. This association was independent of clinical risk factors, choice of statin treatment regime, and inflammatory markers. In addition, OxPL/apoB was higher in patients with elevated Lp(a) and correlated with IM but not CM and NCM. CONCLUSIONS: In conclusion, we provide a potential link between elevated levels of Lp(a) and a proatherogenic distribution of monocyte subtypes in patients with stable atherosclerotic disease.

Impaired antioxidant HDL function is associated with premature myocardial infarction.

BACKGROUND: There is growing evidence that the predictive value of HDL cholesterol levels for cardiovascular risk stratification is limited in patients with coronary artery disease (CAD). HDL function seems to be a more sensitive surrogate of cardiovascular risk estimation than simple serum levels. Therefore, we aimed to assess whether impaired antioxidant HDL function is involved in the development of premature acute myocardial infarction (AMI). METHODS: In this multicentre case-control study, we compared the antioxidant function of HDL, measured by the HDL inflammatory index (HII), and HDL particle size in 184 patients comprising 92 patients with AMI at a very young age (≤40 years of age) and 92 age- and gender-matched controls. RESULTS: Antioxidant capacities of HDL were significantly impaired in the acute phase of AMI (HII of 1·50 [IQR 1·10-1·74] vs. 0·56 [IQR 0·41-0·86] in controls, P < 0·001 as well as in the chronic stable phase 1 year after the event (HII of 0·85 [IQR 0·72-1·03] vs. 0·56 [IQR 0·41-0·86], P < 0·001) compared to controls. Moreover, HDL function in the stable phase remained significantly associated with premature MI in adjusted logistic regression analysis with an OR of 2·24 per SD increase of HII (95% CI 1·28-3·91; P = 0·005). Analyses of HDL size revealed a significant correlation between all HDL subfractions and HDL function in controls, whereas this correlation was lost for large and intermediate HDL in AMI patients. CONCLUSION: Impaired antioxidant function of HDL is independently associated with the development of premature AMI. The maintenance of HDL function might evolve into a significant therapeutic target, especially in patients with premature CAD.

Association of small dense LDL serum levels and circulating monocyte subsets in stable coronary artery disease.

OBJECTIVE: Atherosclerosis is considered to be an inflammatory disease in which monocytes and monocyte-derived macrophages play a key role. Circulating monocytes can be divided into three distinct subtypes, namely in classical monocytes (CM; CD14++CD16-), intermediate monocytes (IM; CD14++CD16+) and non-classical monocytes (NCM; CD14+CD16++). Low density lipoprotein particles are heterogeneous in size and density, with small, dense LDL (sdLDL) crucially implicated in atherogenesis. The aim of this study was to examine whether monocyte subsets are associated with sdLDL serum levels. METHODS: We included 90 patients with angiographically documented stable coronary artery disease and determined monocyte subtypes by flow cytometry. sdLDL was measured by an electrophoresis method on polyacrylamide gel. RESULTS: Patients with sdLDL levels in the highest tertile (sdLDL≥4mg/dL;T3) showed the highest levels of pro-inflammatory NCM (15.2±7% vs. 11.4±6% and 10.9±4%, respectively; p<0.01) when compared with patients in the middle (sdLDL=2-3mg/dL;T2) and lowest tertile (sdLDL=0-1mg/dL;T1). Furthermore, patients in the highest sdLDL tertile showed lower CM levels than patients in the middle and lowest tertile (79.2±8% vs. 83.9±7% and 82.7±5%; p<0.01 for T3 vs. T2+T1). Levels of IM were not related to sdLDL levels (5.6±4% vs. 4.6±3% vs. 6.4±3% for T3, T2 and T1, respectively). In contrast to monocyte subset distribution, levels of circulating pro- and anti-inflammatory markers were not associated with sdLDL levels. CONCLUSION: The atherogenic lipoprotein fraction sdLDL is associated with an increase of NCM and a decrease of CM. This could be a new link between lipid metabolism dysregulation, innate immunity and atherosclerosis.

Small high-density lipoprotein is associated with monocyte subsets in stable coronary artery disease.

OBJECTIVE: High-density lipoprotein (HDL) particles are heterogeneous in structure and function and the role of HDL subfractions in atherogenesis is not well understood. It has been suggested that small HDL may be dysfunctional in patients with coronary artery disease (CAD). Monocytes are considered to play a key role in atherosclerotic diseases. Circulating monocytes can be divided into three subtypes according to their surface expression of CD14 and CD16. Our aim was to examine whether monocyte subsets are associated with HDL subfractions in patients with atherosclerosis. METHODS: We included 90 patients with angiographically stable CAD. Monocyte subsets were defined as classical monocytes (CD14++CD16-; CM), intermediate monocytes (CD14++CD16+; IM) and non-classical monocytes (CD14+CD16++; NCM). HDL subfractions were measured by electrophoresis on polyacrylamide gel. RESULTS: Serum levels of small HDL correlated with circulating pro-inflammatory NCM and showed an inverse relationship to circulating CM independently from other lipid parameters, risk factors, inflammatory parameters or statin treatment regime, respectively. IM were not associated with small HDL. In particular, patients with small HDL levels in the highest tertile showed dramatically increased levels of NCM (14.7 ± 7% vs. 10.7 ± 5% and 10.8 ± 5%; p = 0.006) and a decreased proportion of CM (79.3 ± 7% vs. 83.7 ± 6% and 83.9 ± 6%; p = 0.004) compared to patients in the two lower tertiles. In contrast, intermediate HDL, large HDL and total HDL were not associated with monocyte subset distribution. CONCLUSION: Small HDL levels are associated with pro-inflammatory NCM and inversely correlated with CM. This may suggest that small HDL could have dysfunctional anti-inflammatory properties in patients with established CAD.

Lipoprotein Lp(a) in lipoprotein spectrum indentified by Lipoprint LDL system.

OBJECTIVE: Identification of lipoprotein subfractions in lipoprotein profile by Lipoprint LDL system, where a lipoprotein(a), an independent risk factor for the development of cardiovascular disease, migrates with. The concentration of lipoprotein(a) in serum over 0.3 g/l increases the risk of athero-thrombosis and a brain stroke. The persons with increased levels of lipoprotein(a) and contemporarily increased cholesterol level in serum, are at increased risk of the inception of cardiovascular or cerebrovascular event even 3-times. PATIENTS AND METHODS: In a general group of subjects with increased serum concentration of lipoprotein(a) a lipoprotein profile analysis was performed. The general group of subjects was divided into two groups: subgroup with the lipoprotein(a) concentration in the range between 0.3-0.8 g/l and a subgroup with the lipoprotein(a) concentration over 0.8 g/l, to learn if the lipoprotein(a) particles of different serum concentration and different size do not migrate in different positions of the lipoprotein spectrum. For the analysis of serum lipoproteins an innovated electrophoresis method on polyacrylamide gel (PAG) - Lipoprint LDL system USA, was used. Lipids: a total cholesterol and triglycerides in serum were analysed by an enzymatic method CHOD PAP (Roche Diagnostics, FRG), lipoprotein(a) was analysed by an immuno-nephelometric method (Roche Diagnostics, FRG). RESULTS: In the Lipoprint LDL system using a polyacrylamide gel (PAG) for the lipoprotein separation, lipoprotein(a) migrates in the position IDL2-IDL3. In the band of IDL2 a high Lp(a) values can be identified, when the increment of IDL2 subfraction is over the value of 0.015 g/l, i.e. 15 mg/dl (reference range for IDL2) and when the increment of IDL3 subfraction is over the value of 25 mg/dl, i.e. 0.025 g/l (reference range for IDL3). CONCLUSIONS: A clear contribution of new method is: identification of the lipoprotein subpopulations where the lipoprotein(a) migrates with different migration position for the mild increased lipoprotein(a) concentration and high lipoprotein(a) concentration in serum was not confirmed.

Relative importance of different lipid risk factors for the development of myocardial infarction at a very young age (≤ 40 years of age).

BACKGROUND: Low-density lipoprotein (LDL) cholesterol lowering has been established as one of the principal targets in preventive cardiology. Recently, assessment of LDL particle size and number as well as other lipid moieties has been presented as a more reliable method to quantify atherogenicity of the lipoprotein fractions. Thus, it was our aim to assess the influence of different lipoprotein fractions on premature myocardial infarction (≤ 40 years of age). METHODS AND RESULTS: We enrolled 302 patients into our multicentre case-control study, including 102 patients with myocardial infarction and 200 age-, gender- and centre-matched controls. The LDL and HDL Lipoprint System were used for lipid subfraction quantification. The lipid risk factors most strongly associated with premature acute myocardial infarction (AMI) in the adjusted model were non-HDL C (OR 5·02, 95% CI 2·75-9·15, P-value = 0·001), LDL-C (OR 4·35, 95% CI 2·5-7·57, P-value = 0·001), VLDL-C (OR 3·66, 95% CI 2·14-6·28, P-value = 0·001), large IDL-C (OR 3·15, 95% CI 1·94-5·12, P-value = 0·001), large LDL-C (OR 3·67, 95% CI 2·19-6·15, P-value = 0·001) and intermediate LDL-C (OR 1·96, 95% CI 1·25-3·06, P-value = 0·003). In contrast, small dense LDL was not significantly associated with premature myocardial infarction. CONCLUSION: Non-HDL cholesterol is most strongly associated with premature coronary artery disease and could serve as preferred risk predictor and therapeutic target in this young patient population (≤ 40 years). Besides, VLDL, LDL-C, large LDL, intermediate LDL and large IDL were significantly associated with premature myocardial infarction. Furthermore, our data suggest that risk prediction using small dense LDL particles might not be useful in young AMI survivors.

HDL subfractions analysis: a new laboratory diagnostic assay for patients with cardiovascular diseases and dyslipoproteinemia.

OBJECTIVE: The HDL family forms a protective part of plasma lipoproteins. It consists of large HDL, intermediate HDL, and small HDL subclasses. The large HDL and intermediate HDL subclasses are considered anti-atherogenic parts of the HDL family. The atherogenicity of the small HDL subclass is currently the subject of much discussion. In the patient group with the diagnosis of cardiovascular disease (arterial hypertension, coronary heart disease) and in individuals with a non-atherogenic hypercholesterolemia, a type of lipoprotein profile (either a non-atherogenic phenotype A, or an atherogenic phenotype B) was identified, and a concentration of small dense LDL (sdLDL) was analyzed. The aim of this study was to identify the major representative of the HDL subclasses in the individuals with cardiovascular diseases, who had an atherogenic lipoprotein phenotype B, and in the individuals with the diagnosis of non-atherogenic hyper-betalipoproteinemia LDL1,2, who had a non-atherogenic lipoprotein phenotype A. METHODS: Identification of the specific lipoprotein phenotype and a quantitative analysis of small dense LDL was performed by an electrophoresis method on polyacrylamide gel (PAG), using the Lipoprint LDL system. For a quantitative analysis of HDL subclasses, i.e., large HDL, intermediatete HDL, and small HDL, in subjects with newly diagnosed cardiovascular diseases (arterial hypertension and coronary heart disease), and in subjects with a non-atherogenic hypercholesterolemia (hyper-betalipoproteinemia LDL1,2), we used an innovative electrophoresis method on polyacrylamide gel (PAG), the Lipoprint HDL system. With regard to lipids, total cholesterol and triglycerides in plasma were analyzed by an enzymatic CHOD PAP method. A control group consisted of a group of healthy normolipidemic volunteers without signs of clinically manifested impairment of the cardiovascular system. RESULTS: In the patient group with the diagnosis of arterial hypertension (p<0.0002) and coronary heart disease (p<0.0001), (both are classified as cardiovascular diseases), the large HDL subclass was significantly decreased and the small HDL subclass was increased (p<0.0001). The concentration of the intermediate HDL subclass did not differ from that of the control group. These results were in accordance with an atherogenic lipoprotein phenotype B in individuals with the diagnosis of cardiovascular diseases, where, using a Lipoprint LDL analysis, a high concentration of atherogenic small dense LDL (p<0.0001) was found. Thus, it seems that the small HDL subclass represents an atherogenic part of the HDL family. Conversely, an increased concentration of total HDL (p<0.0001), large HDL (p<0.005), and intermediate HDL subclasses (p<0.0001) was found in a group of subjects with a non-atherogenic hyper-betalipoproteinemia LDL1,2.The concentration of the small HDL subclass did not differ from that of the control group. In this non-atherogenic lipoprotein profile, only traces of atherogenic small dense LDL were identified. CONCLUSIONS: The advantages of this new method includes: (i) Identification of ten HDL subfractions with Lipoprint HDL analysis (large HDL1-3, intermediate HDL 4-7, and small HDL 8-10) . (ii) Discovery of a high concentration of small HDL in plasma lipoproteins in patients with cardovascular diseases with an atherogenic lipoprotein phenotype B, confirms that the atherogenic subclass of HDL family is attributable to small HDL. (iii) Presence of a low concentration of small HDL in non-atherogenic hypercholesterolemia also confirms the atherogenic characteristics of the small HDL subclass per se. (iv) Presence of small dense LDL is definitive to diagnose an atherogenic lipoprotein profile. It is valid for hyperlipidemia and for normolipidemia as well.

Hyper-betalipoproteinemia LDL 1,2: a newly identified nonatherogenic hypercholesterolemia in a group of hypercholesterolemic subjects.

OBJECTIVE: The identification of a non-atherogenic and an atherogenic lipoprotein profile, non-athero phenotype A vs. athero phenotype B, in a group of hypercholesterolemic subjects reveals newly discovered non-atherogenic hypercholesterolemia. Individuals with this type of hypercholesterolemia, or hyper-betalipoproteinemia LDL1,2, are probably not at increased risk to develop a premature atherothrombosis or a sudden cardiovascular event. Examined individuals with hyper-betalipoproteinemia LDL1,2 were divided into two subgroups: individuals under 40 years of age, and older individuals between 46 and 71 years of age. Subjects in the under 40 years of age group did not have any apparent clinical or laboratory-proven impairment of the cardiovascular system. The older subjects with hyper-betalipoproteinemia and a non-atherogenic lipoprotein profile had only mild signs of clinically irrelevant aortic valve sclerosis. METHODS: A quantitative analysis of the lipoprotein spectrum in plasma in a group of hypercholesterolemic subjects was performed. An innovative electrophoresis method on polyacrylamide gel (PAG) was used for the analysis of plasma lipoproteins and for the identification of atherogenic vs. non-atherogenic lipoproteins in plasma. With regard to lipids, total cholesterol and triglycerides in plasma were analyzed with an enzymatic CHOD PAP method (Roche Diagnostics, FRG). A new parameter, the score for anti-atherogenic Risk (SAAR), was calculated as the ratio between non-atherogenic to atherogenic plasma lipoproteins in the examined subjects. RESULTS: There was a high concentration of LDL1, and LDL2 subfractions (p<0.0001), and an extremely low concentration of LDL3-7 (p<0.0001) in the non-atherogenic lipoprotein profile of hyper-betalipoproteinemia LDL1,2 compared to the control group. Higher concentrations (p<0.0001) of lipids and lipoproteins in the non-atherogenic hypercholesterolemia, compared to the control group, were also found. The hyper-betalipoproteinemia LDL1,2 was also characterized by high SAAR values. There was found a higher concentration of HDL large and HDL intermediate subfractions in hypercholesterolemic subjects. CONCLUSIONS: The advantages of this new diagnostic method include: (i) identification of the existence of a non-atherogenic hyper-betalipoproteinemia LDL1,2 in examined hypercholesterolemic subjects with untreated hypercholesterolemia (ii) introduction of a new risk measure, the score for anti-atherogenic risk (SAAR), for the estimation of atherogenic/anti-atherogenic risk. (iii) the presence of small dense LDL in plasma is decisive for the declaration of an atherogenic lipoprotein profile. It is valid for hyperlipidemia and for normolipidemia as well.