Changes in the size and electrophoretic mobility of HDL subpopulation particles in chronic kidney disease.

BACKGROUND: High-density lipoprotein (HDL) is a heterogeneous group of particles with anti-atherogenic properties whose metabolism is alterated in chronic kidney disease (CKD). The aim of this study was to evaluate the particle size and mobility of HDL subpopulations in non-dialysis CKD patients. METHODS: The study involved 42 non-dialysis CKD patients (stages 3a-4) and 18 control subjects. HDL was separated by non-denaturing two-dimensional polyacrylamide gradient gel electrophoresis (2D-PAGGE) and eight HDL subpopulations; preß1, preß2a-c, and α1-4 were distinguished. The size and electrophoretic mobility of HDL subpopulation particles were compared between the groups, and a regression analysis was conducted. RESULTS: In CKD patients, the mean sizes of α-HDL and preß2-HDL particles were significantly lower compared to the control group (8.42 ± 0.32 nm vs. 8.64 ± 0.26 nm, p = 0.014; 11.45 ± 0.51 vs. 12.34 ± 0.78 nm, p = 0.003, respectively). The electrophoretic mobility of preß2-HDL relative to α-HDL was significantly higher in CKD patients compared to the control group (Rf 0.65 ± 0.06 vs. 0.53 ± 0.10, p = 0.002). The size and mobility of HDL subpopulations correlated with eGFR values (p < 0.01). These relationships remained statistically significant after adjusting for age, gender, statin treatment, apolipoprotein AI, total cholesterol, and triglyceride levels. DISCUSSION: CKD affects the size and mobility of HDL particles, which can be related to HDL dysfunction. The magnitude of HDL size and mobility changes depended on CKD stage and differed for individual HDL subpopulations, which indicates that some stages of HDL metabolism may be more affected by the presence of chronic kidney disease.

The Differential Effects of HDL Subpopulations on Lipoprotein Lipase (LPL)-Mediated VLDL Catabolism.

High-density lipoprotein (HDL) subpopulations functional assessment is more relevant for HDL anti-atherogenic activity than cholesterol level. The aim of the study was to assess the impact of HDL-2 and HDL-3 on lipoprotein lipase (LPL)-mediated very-low-density lipoprotein (VLDL) catabolism related to hypertriglyceridemia development. VLDL and HDLs were isolated from serum by ultracentrifugation. VLDL was incubated with LPL in the absence and presence of total HDL or HDL subpopulations. Next, VLDL remnants were separated, and their composition and electrophoretic mobility was assessed. Both HDL subpopulations increased the efficiency of triglyceride lipolysis and apolipoprotein CII and CIII removal from VLDL up to ~90%. HDL-3 exerted significantly greater impact than HDL-2 on apolipoprotein E (43% vs. 18%, p < 0.001), free cholesterol (26% vs. 18%, p < 0.05) and phospholipids (53% vs. 43%, p < 0.05) removal from VLDL and VLDL remnant electrophoretic mobility (0.18 vs. 0.20, p < 0.01). A greater release of these components was also observed in the presence of total HDL with a low HDL-2/HDL-3 cholesterol ratio. Both HDL subpopulations affect VLDL composition during lipolysis, but HDL-3 exhibited a greater effect on this process. Altered composition of HDL related to significant changes in the distribution between HDL-2 and HDL-3 can influence the VLDL remnant features, affecting atherosclerosis progression.

Decreased Efficiency of Very-Low-Density Lipoprotein Lipolysis Is Linked to Both Hypertriglyceridemia and Hypercholesterolemia, but It Can Be Counteracted by High-Density Lipoprotein.

Impaired triglyceride-rich lipoprotein plasma catabolism is considered the most important factor for hypertriglyceridemia development. The aim of this study was to evaluate the impact of hypercholesterolemia and hypertriglyceridemia on the efficiency of lipoprotein lipase (LPL)-mediated very-low-density lipoprotein (VLDL)-triglyceride lipolysis and the role of high-density lipoprotein (HDL) in this process. Subjects with no history of cardiovascular disease (CVD) and untreated with lipid-lowering agents were recruited into the study and divided into normolipidemic, hypercholesterolemic, and hyperlipidemic groups. VLDL was isolated from serum and incubated with LPL in the absence or presence of HDL. For the hypercholesterolemic and hyperlipidemic groups, a significantly lower percentage of hydrolyzed VLDL-triglyceride was achieved compared to the normolipidemic group (p < 0.01). HDL enhanced the lipolysis efficiency in the hypercholesterolemic and hyperlipidemic groups on average by ~7% (p < 0.001). The lowest electrophoretic mobility of the VLDL remnants indicating the most effective lipolysis was obtained in the normolipidemic group (p < 0.05). HDL presence significantly reduced the electrophoretic mobility of the VLDL remnants for the hypercholesterolemic and hyperlipidemic groups (p < 0.05). The results of our study indicate that VLDL obtained from hypercholesterolemic and hyperlipidemic subjects are more resistant to lipolysis and are additional evidence of the need for early implementation of hypocholesterolemic treatment, already in asymptomatic CVD subjects.

Non-HDL-C/TG ratio indicates significant underestimation of calculated low-density lipoprotein cholesterol (LDL-C) better than TG level: a study on the reliability of mathematical formulas used for LDL-C estimation.

OBJECTIVES: Low-density lipoprotein cholesterol (LDL-C) is the main laboratory parameter used for the management of cardiovascular disease. The aim of this study was to compare measured LDL-C with LDL-C as calculated by the Friedewald, Martin/Hopkins, Vujovic, and Sampson formulas with regard to triglyceride (TG), LDL-C and non-high-density lipoprotein cholesterol (non-HDL-C)/TG ratio. METHODS: The 1,209 calculated LDL-C results were compared with LDL-C measured using ultracentrifugation-precipitation (first study) and direct (second study) methods. The Passing-Bablok regression was applied to compare the methods. The percentage difference between calculated and measured LDL-C (total error) and the number of results exceeding the total error goal of 12% were established. RESULTS: There was good correlation between the measurement and calculation methods (r 0.962-0.985). The median total error ranged from -2.7%/+1.4% (first/second study) for Vujovic formula to -6.7%/-4.3% for Friedewald formula. The numbers of underestimated results exceeding the total error goal of 12% were 67 (Vujovic), 134 (Martin/Hopkins), 157 (Samspon), and 239 (Friedewald). Less than 7% of those results were obtained for samples with TG >4.5 mmol/L. From 57% (Martin/Hopkins) to 81% (Vujovic) of underestimated results were obtained for samples with a non-HDL-C/TG ratio of <2.4. CONCLUSIONS: The Martin/Hopkins, Vujovic and Sampson formulas appear to be more accurate than the Friedewald formula. To minimize the number of significantly underestimated LDL-C results, we propose the implementation of risk categories according to non-HDL-C/TG ratio and suggest that for samples with a non-HDL-C/TG ratio of <1.2, the LDL-C level should not be calculated but measured independently from TG level.

The effect of Cistus incanus herbal tea supplementation on oxidative stress markers and lipid profile in healthy adults.

BACKGROUND: Oxidative stress and dyslipidemia play a critical role in the development of cardiovascular disease (CVD). Regular intake of polyphenol-rich diets is associated with a reduced risk of CVDs. METHODS: The present study was a pilot study with 24 healthy volunteers and was designed to determine if a 12-week administration of Cistus incanus herbal tea, containing phenolic acids and flavonoids, reduces cardiovascular risk factors including oxidative stress and dyslipidemia in healthy adults. Phenolic compounds profile and antibacterial activity of Cistus incanus infusion were also measured. RESULTS: Herbal infusion led to improvement in lipid profile by increase (D4%, p = 0.033) high-density lipoprotein cholesterol concentration and decrease triglyceride (D14%, p = 0.013) concentrations. In addition, the Cistus incanus diet was associated with decreased serum concentrations of malondialdehyde (D16%, p < 0.01) and advanced oxidation protein products (D18%, p < 0.001). CONCLUSIONS: Cistus incanus administration decreases cardiovascular risk factors including oxidative stress and dyslipidemia and this action supports the idea of using Cistus incanus tea on a daily basis as an effective dietary component for prevention of atherosclerotic CVD.

Detection of Lipoprotein X (LpX): A challenge in patients with severe hypercholesterolaemia.

BACKGROUND: Lipoprotein X (LpX) is an abnormal lipoprotein fraction, which can be detected in patients with severe hypercholesterolaemia and cholestatic liver disease. LpX is composed largely of phospholipid and free cholesterol, with small amounts of triglyceride, cholesteryl ester and protein. There are no widely available methods for direct measurement of LpX in routine laboratory practice. We present the heterogeneity of clinical and laboratory manifestations of the presence of LpX, a phenomenon which hinders LpX detection. METHODS: The study was conducted on a 26-year-old female after liver transplantation (LTx) with severely elevated total cholesterol (TC) of 38 mmol/L and increased cholestatic liver enzymes. TC, free cholesterol (FC), cholesteryl esters (CE), triglycerides, phospholipids, HDL-C, LDL-C, and apolipoproteins AI and B were measured. TC/apoB and FC:CE ratios were calculated. Lipoprotein electrophoresis was performed using a commercially available kit and laboratory-prepared agarose gel. RESULTS: Commercially available electrophoresis failed to demonstrate the presence of LpX. Laboratory-prepared gel clearly revealed the presence of lipoproteins with γ mobility, characteristic of LpX. The TC/apoB ratio was elevated and the CE level was reduced, confirming the presence of LpX. Regular lipoprotein apheresis was applied as the method of choice in LpX disease and a bridge to reLTx due to chronic liver insufficiency. CONCLUSIONS: The detection of LpX is crucial as it may influence the method of treatment. As routinely available biochemical laboratory tests do not always indicate the presence of LpX, in severe hypercholesterolaemia with cholestasis, any discrepancy between electrophoresis and biochemical tests should raise suspicions of LpX disease.

Plasma Levels of Preß1-HDL Are Significantly Elevated in Non-Dialyzed Patients with Advanced Stages of Chronic Kidney Disease.

In chronic kidney disease (CKD), the level of high-density lipoprotein (HDL) decreases markedly, but there is no strong inverse relationship between HDL-cholesterol (HDL-C) and cardiovascular diseases. This indicates that not only the HDL-C level, but also the other quantitative changes in the HDL particles can influence the protective functionality of these particles, and can play a key role in the increase of cardiovascular risk in CKD patients. The aim of the present study was the evaluation of the parameters that may give additional information about the HDL particles in the course of progressing CKD. For this purpose, we analyzed the concentrations of HDL containing apolipoprotein A-I without apolipoprotein A-II (LpA-I), preß1-HDL, and myeloperoxidase (MPO), and the activity of paraoxonase-1 (PON-1) in 68 patients at various stages of CKD. The concentration of HDL cholesterol, MPO, PON-1, and lecithin-cholesterol acyltransferase (LCAT) activity were similar in all of the analyzed stages of CKD. We did not notice significant changes in the LpA-I concentrations in the following stages of CKD (3a CKD stage: 57 ± 19; 3b CKD stage: 54 ± 15; 4 CKD stage: 52 ± 14; p = 0.49). We found, however, that the preß1-HDL concentration and preß1-HDL/LpA-I ratio increased along with the progress of CKD, and were inversely correlated with the estimated glomerular filtration rate (eGFR), even after adjusting for age, gender, triacylglycerols (TAG), HDL cholesterol, and statin therapy (ß = -0.41, p < 0.001; ß = -0.33, p = 0.001, respectively). Our results support the earlier hypothesis that kidney disease leads to the modification of HDL particles, and show that the preß1-HDL concentration is significantly elevated in non-dialyzed patients with advanced stages of CKD.

Progression of Chronic Kidney Disease Affects HDL Impact on Lipoprotein Lipase (LPL)-Mediated VLDL Lipolysis Efficiency.

BACKGROUND/AIMS: Hypertriglyceridaemia (HTG) and reduction and dysfunction of high density lipoprotein (HDL) are common lipid disturbances in chronic kidney disease (CKD). HTG in CKD is caused mainly by the decreased efficiency of lipoprotein lipase (LPL)-mediated very low density lipoprotein triglyceride (VLDL-TG) lipolysis. It has not been clarified whether HDL dysfunction in CKD contributes directly to HTG development; thus, the aim of this study was to assess the impact of CKD progression on the ability of HDL to enhance LPL-mediated VLDL-TG lipolysis efficiency. METHODS: VLDL was isolated from non-dialysis patients in CKD stages 3 and 4 and from non-CKD patients. The VLDL was incubated with LPL at the constant LPL:VLDL-TG ratio, in the absence or presence of HDL. After incubation, the VLDL was separated and the percentage (%) of hydrolyzed TG was calculated. RESULTS: HDL presence increased the lipolysis efficiency of VLDL isolated from CKD and non-CKD patients, for the VLDL-TG> 50 mg/dl. Its effect was dependent on the VLDL-TG and HDL-cholesterol concentrations in the reaction mixtures: the higher the concentrations of VLDL-TG and HDL-cholesterol, the greater the effect. The positive impact of HDL on VLDL lipolysis was modified by CKD progression: the percentage of lipolyzed VLDL-TG in the presence of HDL decreased with a reduction in eGFR (r=0.43, p=0.009), and for patients with stage 4 CKD, no positive impact of HDL on lipolysis was observed. The percentage of lipolyzed TG correlated negatively with apoE and apoCs content in VLDL, and positively with HDL-apoCII, as well as with VLDL and HDL apoCII/ apoCIII ratios. The progression of CKD was associated with unfavourable changes in VLDL and HDL composition; apoE and apoCs levels increased in VLDL with a decrease in eGFR whereas the HDL-cholesterol level decreased. CONCLUSION: The progression of CKD affects lipoprotein composition and properties, and modulates the positive impact of HDL on VLDL lipolysis efficiency. In CKD patients, HDL deficiency and dysfunction can directly affect hypertriglyceridaemia development.

HDL subpopulations containing apoA-I without apoA-II (LpA-I) in patients with angiographically proven coronary artery disease.

BACKGROUND: High density lipoproteins (HDL) can be divided into two metabolically distinct fractions, one containing apolipoprotein (Apo) A-I but not ApoA-II [apolipoprotein A-I; lipoprotein (Lp) A-I] and the other containing both ApoA-I and ApoA-II (LpA-I/A-II). LpA-I fraction which, seeming to be more cardioprotective than LpA-I/A-II particles, is itself heterogeneous. Preß1-HDL is a minor subfraction of LpA-I and the initial acceptor of cellular cholesterol in the process of reverse cholesterol transport. The aim of the study was to determine the usefulness of the determination of LpA-I fractions as indicators for the atherosclerotic process. METHODS: The study included 112 patients with angiographically-documented coronary artery disease (CAD+) and 51 patients with negative results of coronary angiography (CAD-). We evaluated LpA-I concentration in serum in HDL2 and HDL3 fractions as well as Preß1-HDL concentration. Furthermore, we analyzed the association of the assessed parameters with the extent and severity of CAD assessed by Gensini score. RESULTS: CAD+ patients were characterized by a lower concentration of serum LpA-I by 19%, LpA-I in HDL2 by 26%, higher level of Preß1-HDL by 27%, and elevated Preß1-HDL/LpA-I values by 62%. Univariate correlation analysis indicated that serum LpA-I and HDL-cholesterol concentrations were negatively correlated with Gensini score (R=-0.279; p=0.002, R=-0.227; p=0.016, respectively) whereas Preß1-HDL/LpA-I values were positively correlated with the severity of CAD (R=0.529; p<0.001). In multiple linear regression, after adjusting for age, gender, preexisting hypertension, diabetes, and statin therapy, only the Preß1-HDL/LpA-I values remained an independent determinant of atherosclerosis severity (ß=-0.499; p<0.001). CONCLUSIONS: Our results show a lower level of LpA-I and higher concentration of Preß1-HDL in the CAD+ patients compared to the CAD- group. We suggest that the distribution of LpA-I is different in CAD and the Preß1-HDL/LpA-I ratio may have additional value in assessing anti-atherogenic potential of HDL particles and it is likely to become a clinically valuable indicator of atherosclerosis development.

Impact of phosphatidylcholine liposomes on the compositional changes of VLDL during lipoprotein lipase (LPL)-mediated lipolysis.

Lipoprotein lipase (LPL)-mediated triacylglycerol (TAG) hydrolysis in very low density lipoprotein (VLDL) is accompanied by the release of surface material containing phospholipids (PL), free cholesterol (FC) and apolipoproteins, E (apoE) and Cs (apoCII, apoCIII). The released molecules are accepted by high density lipoprotein (HDL), and new HDL-sized apoE-containing particles are also generated. A decrease in the number of HDL particles or abnormalities in their structure is associated with unfavourable changes in the features of VLDL remnants. Phosphatidylcholine liposomes (PC-L) can also act as acceptors of surface material components released from lipoproteins. Thus, the aim of this study was to assess the impact of liposomes on compositional changes of VLDL during its LPL-mediated lipolysis. VLDL isolated from human sera was incubated with LPL (LPL:VLDLTAG; 24 µg/ml:90 mg/dl) and/or PC-L (VLDLPL:PC-LPL; 1:30 weight ratio). After incubation (2h, 37 °C) VLDL was separated from other reaction products, and VLDL lipid and apolipoprotein content were analysed. Newly generated HDL-sized apoE-containing lipoproteins were separated by two-dimensional non-denaturing gradient gel electrophoresis (2D-PAGGE). The reaction of VLDL with PC-L in the presence or absence of LPL significantly affected the VLDL composition. The ratio of core (TAG+cholesteryl ester) to surface (PL+FC) lipids in VLDL decreased 1.8-fold with PC-L, 1.2-fold with LPL and 3-fold with PC-L+LPL. The reaction with PC-L and PC-L+LPL caused a 3.7-fold and 3.2-fold decrease of apoCs/apoE average weight ratio, respectively. Compositional changes in VLDL under the influence of PC-L were accompanied by an increase in the efficiency of VLDL lipolysis and the generation of apoE-containing HDL-sized particles, heterogeneous in size (from ∼ 9 to ∼ 18.8 nm) and mobility (γ and preß). We conclude that PL-rich particles, similarly to HDL, promote the release of surface material components from VLDL during LPL-mediated lipolysis and positively influence VLDL features which can facilitate VLDL metabolism. Such PC-L activity may impact on its antiatherogenic properties.

Impact of plant-based diet on lipid risk factors for atherosclerosis.

BACKGROUND: The aim of the study was to investigate the effect of a vegan diet on the serum lipid profile with particular regard to the parameters characterizing the high-density lipoprotein (HDL) fractions in subjects without subclinical atherosclerosis, measured by carotid Doppler ultrasonography. METHODS AND RESULTS: Forty-two 23 to 38 year old subjects (21 omnivores and 21 vegans) participated in the study. Compared to the omnivores, the vegan subjects were characterized by lower parameters of lipid profile: total cholesterol (p < 0.001), low-density lipoprotein (LDL)-cholesterol (p < 0.001), non-HDL-cholesterol (p < 0.001), apolipoprotein B (apoB) (p < 0.001) and phospholipids (p < 0.01). Concentration of HDL-cholesterol was apparently similar between groups. Furthermore, the parameters which characterize HDL particles (con-centration of apolipoproteins AI [apoAI] and AII, HDL-phospholipids, LpAI fraction and pre-b1-HDL fraction) were not significantly different between omnivore and vegan subjects. The apoB/apoAI ratio in vegans was lower than in omnivores (p < 0.01). There was no difference between serum concentration of triacylglycerols between omnivores and vegans. The activity of paraoxonase-1 and 8-iso-prostaglandin F2a concentration were also not different between the study groups. CONCLUSIONS: We suggest that a vegan diet may have a beneficial effect on serum lipid profile and cardiovascular protection, but it is not associated with changes in HDL composition.

PON-1 Activity and Plasma 8-Isoprostane Concentration in Patients with Angiographically Proven Coronary Artery Disease.

The aim of the study was to estimate association of the extent of angiographically proven coronary artery disease (CAD) with plasma 8-isoprostane F2 (8-iso-PGF2α) levels as a reliable marker of lipid peroxidation and serum activity of paraoxonase-1, which demonstrates the ability to protect against lipid oxidation. The study included 105 patients with angiographically documented CAD (CAD+) and 45 patients with negative results of coronary angiography (CAD-). Compared to the control group CAD+ patients were characterized by increased 8-iso-PGF2α levels (P = 0.007) and reduced activity of PON-1 towards paraoxon (PONase, P = 0.002) and phenyl acetate (AREase, P = 0.037). Univariate correlation analysis indicated that 8-iso-PGF2α concentrations were positively associated with the severity of CAD as evaluated by the Gensini score (R = 0.41, P < 0.001) while PONase activity (R = -0.26, P < 0.05) and AREase activity (R = -0.23, P < 0.05) were inversely correlated with CAD severity. PONase activity and 8-iso-PGF2α concentration remained independent determinant of atherosclerosis severity in multiple linear regression after adjusting for age, gender, smoking habits, hypertension, type 2 diabetes, statin therapy, and HDL-C and TAG concentration (ß coefficients -0.267; P < 0.05 and 0.368; P < 0.001, resp.). The results suggest that PON-1 activity and 8-iso-PGF2α concentration are associated with the presence and extent of coronary stenosis and may be considered additional markers of coronary artery disease.

Interaction between VLDL and phosphatidylcholine liposomes generates new γ-LpE-like particles.

One of the subfractions of HDL involved in reverse cholesterol transport is γ-LpE. It has been assumed that, like preß-LpAI, it can be generated during the interaction between phosphatidylcholine liposomes and lipoproteins and can contribute to more efficient cholesterol efflux after the introduction of liposomes to plasma. However, there has been no evidence concerning what the sources of these particles in plasma might be. Here, we determined whether the interaction of phosphatidylcholine liposomes with VLDL and the subsequent conversions of particles could be a source of new γ-LpE particles. We found that the interaction between liposomes and VLDL affected its lipid and protein composition. The content of phospholipids increased (~96 %) while the content of free cholesterol and apolipoprotein E decreased in VLDL during the reaction with liposomes (~100 and ~24 %, respectively). New particles which did not contain apolipoprotein B were generated. Heterogeneous HDL-sized populations of particles were generated, containing phospholipids and apolipoprotein E as the sole apolipoprotein, with densities from 1.063 to 1.21 g/ml, either with γ-mobility on agarose gel and Stokes diameters from 8.58 to 22.07 nm or with preß-mobility and Stokes diameters from 9.9 to 21.08 nm. The obtained results contribute to the understanding of changes in lipoproteins under the influence of phosphatidylcholine liposomes, showing the formation of new (γ-LpE)-like and (preß-LpE)-like particles, similar in mobility and size to plasma HDL-LpE. These newly generated particles can claim a share of the antiatherogenic effects of liposomes, observed in studies both in vitro and in vivo.