Improved method for making nondenaturing composite gradient gels for the electrophoretic separation of lipoproteins

HDL Subclasses and the Distribution of Paraoxonase-1 Activity in Patients with ST-Segment Elevation Acute Myocardial Infarction

The aim of this multicentric study was to assess the impacts of oxidative stress, inflammation, and the presence of small, dense, low-density lipoproteins (sdLDL) on the antioxidative function of high-density lipoprotein (HDL) subclasses and the distribution of paraoxonase-1 (PON1) activity within HDL in patients with ST-segment elevation acute myocardial infarction (STEMI). In 69 STEMI patients and 67 healthy control subjects, the lipoproteins' subclasses were separated using polyacrylamide gradient (3-31%) gel electrophoresis. The relative proportion of sdLDL and each HDL subclass was evaluated by measuring the areas under the peaks of densitometric scans. The distribution of the relative proportion of PON1 activity within the HDL subclasses (pPON1 within HDL) was estimated using the zymogram method. The STEMI patients had significantly lower proportions of HDL2a and HDL3a subclasses (p = 0.001 and p < 0.001, respectively) and lower pPON1 within HDL3b (p = 0.006), as well as higher proportions of HDL3b and HDL3c subclasses (p = 0.013 and p < 0.001, respectively) and higher pPON1 within HDL2 than the controls. Independent positive associations between sdLDL and pPON1 within HDL3a and between malondialdehyde (MDA) and pPON1 within HDL2b were shown in the STEMI group. The increased oxidative stress and increased proportion of sdLDL in STEMI are closely related to the compromised antioxidative function of small HDL3 particles and the altered pPON1 within HDL.

Overweight and obesity in polycystic ovary syndrome: association with inflammation, oxidative stress and dyslipidaemia

Polycystic ovary syndrome (PCOS) is associated with altered lipid profile and increased small, dense LDL particles (sdLDL). Considering that paraoxonase 1 (PON1) is an antioxidative enzyme located on HDL particles, the aim of this study was to investigate the connection between oxidative stress (OS) and PON1 activity with lipoprotein subclasses in PCOS depending on obesity. In 115 PCOS patients, lipoprotein subclasses distributions were determined by gradient gel electrophoresis. OS status was assessed by total oxidative status (TOS), advanced oxidation protein products, malondialdehyde (MDA), prooxidant-antioxidant balance (PAB), total antioxidative status (TAS) and superoxide dismutase (SOD) and PON1 activity. Overweight/obese PCOS patients (n 55) had increased OS compared with normal weight patients (n 60). In addition, overweight/obese group had lower HDL size and higher proportion of HDL 3a subclasses (P < 0·05). PAB was in negative correlation with HDL 2a (P < 0·001), whereas MDA and SOD correlated positively with HDL 3 subclasses (P < 0·05). Serum PON1 activity was positively associated with proportions of PON1 activity on HDL 2b (P < 0·05) and 2a (P < 0·01), but negatively with the proportion on HDL 3 particles (P < 0·01). LDL B phenotype patients had increased TAS, SOD and PON1 activity on HDL 2b, but decreased PON1 activity on HDL 3 subclasses. OS is associated with altered lipoprotein subclasses distribution in PCOS patients. Obesity in PCOS affects the profile of HDL subclasses, reflected through the reduced proportion of PON1 activity on HDL 3 subclasses in the presence of sdLDL particles.

Antioxidant status in hypertensive disorders of pregnancy

Objective: Pregnancy can be associated with maternal hypertension leading to possible complications in pregnancy outcome. Antioxidant status may be proned to changes during pregnancy with hypertension. The aim of our study was to estimate antioxidant status through high-risk pregnancies.Methods: Seventy-nine pregnant women with high-risk for preeclampsia development were included and 46 of them developed some hypertensive disorder in pregnancy. Superoxide-dismutase (SOD) and paraoxonase 1 (PON1) activities and relative proportion of PON1 activiity on different HDL subclasses were determined in 1^st, 2^nd, and 3^rd trimester and prior to delivery.Results: SOD activity was significantly lower in 2^nd and 3^rd trimesters when compared to 1^st trimester (P˂0.001) whereas PON1 activity was significantly higher in 3^rd than in 1^st trimester (P˂0.05) in group of hypertensive women. This group had significantly higher SOD and PON1 activities and relative proportion of PON1 on HDL_3c subclasses in the 1^st trimester, significantly increased PON1 in the 3^rd trimester and prior to delivery and significantly higher PON1 activity on HDL_3c subclasses (P˂0.05) than nonhypertensive group. In 1^st trimester and prior to delivery, total PON1 activity and relative proportion of PON1 on HDL_3c subclasses exhibited significant ability to mark out hypertension in pregnancy (P˂0.05).Conclusions: SOD activity decreased whereas total PON1 activity increased during pregnancy with hypertension. Pregnant women with hypertension had higher activities of PON1 and SOD and relative proportion of PON1 on HDL_3c subclasses than nonhypertensive ones. PON1 activity and relative proportion of PON1 on HDL_3c subclasses exhibited significant association with hypertension in pregnancy.

Increased Oxidized High-Density Lipoprotein/High-Density Lipoprotein-Cholesterol Ratio as a Potential Indicator of Disturbed Metabolic Health in Overweight and Obese Individuals

BACKGROUND

We evaluated the qualitative characteristics of high-density lipoprotein (HDL) particles in metabolically healthy and unhealthy overweight and obese subjects.

METHODS

The study involved 115 subject individuals classified as metabolically healthy and unhealthy, as in overweight and obese groups. Commercial enzyme-linked immunosorbent assay (ELISA) kits were used to measure oxidized HDL (OxHDL) and serum amyloid A (SAA) concentrations. Lipoprotein subfractions were separated using nondenaturing gradient gel electrophoresis.

RESULTS

An independent association was shown between increased OxHDL/HDL-cholesterol ratio and the occurrence of metabolically unhealthy phenotype in the overweight and obese groups. The OxHDL/HDL-cholesterol ratio showed excellent and acceptable diagnostic accuracy in determination of metabolic health phenotypes (overweight group, AUC = 0.881; obese group, AUC = 0.765). Accumulation of smaller HDL particles in metabolically unhealthy subjects was verified by lipoprotein subfraction analysis. SAA concentrations did not differ significantly between phenotypes.

CONCLUSIONS

Increased OxHDL/HDL-cholesterol ratio may be a potential indicator of disturbed metabolic health in overweight and obese individuals.

Association of acute Babesia canis infection and serum lipid, lipoprotein, and apoprotein concentrations in dogs

BACKGROUND

Babesia canis infection induces a marked acute phase response (APR) that might be associated with alteration in lipid and lipoprotein metabolism and disease prognosis.

HYPOTHESIS

Dogs with B. canis-induced APR develop dyslipidemia with altered lipoprotein concentration and morphology.

ANIMALS

Twenty-nine client-owned dogs with acute B. canis infection and 10 clinically healthy control dogs.

METHODS

Observational cross-sectional study. Serum amyloid A (SAA) was measured using ELISA. Cholesterol, phospholipids, and triglycerides were determined biochemically. Lipoproteins were separated using agarose gel electrophoresis. Lipoprotein diameter was assessed by polyacrylamide gradient gel electrophoresis; correlation with ApoA-1 (radioimmunoassay) and SAA was determined.

RESULTS

Dogs with B. canis infection had a marked APR (median SAA, 168.3 μg/mL; range, 98.1-716.2 μg/mL) compared with controls (3.2 μg/mL, 2.0-4.2 μg/mL) (P < .001). Dogs with B. canis infection had significantly lower median cholesterol (4.79 mmol/L, 1.89-7.64 mmol/L versus 6.15 mmol/L, 4.2-7.4 mmol/L) (P = .02), phospholipid (4.64 mmol/L, 2.6-6.6 mmol/L versus 5.72 mmol/L, 4.68-7.0 mmol/L) (P = .02), and α-lipoproteins (77.5%, 27.7%-93.5% versus 89.2%, 75.1%-93.5%) (P = .04), and higher ApoA-1 (1.36 U, 0.8-2.56 U versus 0.95 U, 0.73-1.54 U) concentrations (P = .02). Serum amyloid A correlated with high-density lipoproteins (HDLs) diameter (rho = .43; P = .03) and ApoA-1 (rho = .63, P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Major changes associated with B. canis-induced APR in dogs are related to concentration, composition, and morphology of HDL particles pointing to an altered reverse cholesterol transport. Parallel ApoA-1 and SAA concentration increase is a unique still unexplained pathophysiological finding.

The NOAEL Metformin Dose Is Ineffective against Metabolic Disruption Induced by Chronic Cadmium Exposure in Wistar Rats

Previous studies have proposed that cadmium (Cd) is a metabolic disruptor, which is associated with insulin resistance, metabolic syndrome, and diabetes. This metal is not considered by international agencies for the study of metabolic diseases. In this study, we investigate the effect of metformin on Cd-exposed Wistar rats at a lowest-observed-adverse-effect level (LOAEL) dose (32.5 ppm) in drinking water. Metabolic complications in the rats exposed to Cd were dysglycemia, insulin resistance, dyslipidemia, dyslipoproteinemia, and imbalance in triglyceride and glycogen storage in the liver, muscle, heart, kidney, and adipose tissue. Meanwhile, rats treated orally with a No-observable-adverse-effect level (NOAEL) dose of metformin (200 mg/kg/day) showed mild improvement on serum lipids, but not on glucose tolerance; in tissues, glycogen storage was improved, but lipid storage was ineffective. In conclusion, metformin as a first-line pharmacological therapy must take into consideration the origin and duration of metabolic disruption, because in this work the NOAEL dose of metformin (200 mg/kg/day) showed a limited efficiency in the metabolic disruption caused by chronic Cd exposure.

Activity of paraoxonase 1 (PON1) on HDL2 and HDL3 subclasses in renal disease

INTRODUCTION

Cardiovascular complications, as the main cause of mortality in renal patients, are followed with altered lipoproteins composition. Considering that paraoxonase-1 (PON1) is an anti-oxidative enzyme located mainly on HDL particles, the current study has aim to investigate whether failure of kidney function leads to changes in the distribution of PON1 activity between different HDL subclasses.

MATERIALS AND METHODS

In 77 renal patients (21 chronic kidney disease (CKD) and 56 end stage renal disease (ESRD) patients on dialysis) and 20 healthy subjects PON1 activity on HDL₂ and HDL₃ subclasses was determined by zymogram method that combines gradient gel electrophoresis separation of HDL subclasses and measurement of PON1 activity in the same gel.

RESULTS

Serum paraoxonase (p<0.01) and arylesterase activity (p<0.001) of PON1 as well as its concentration (p<0.01) were significantly lower in CKD and ESRD patients compared to controls. Relative proportion of HDL₃ subclasses was higher in ESRD patients than in healthy participants, while HDL₂ subclasses was significantly decreased in CKD (p<0.05) and ESRD (p<0.001) patients, as compared to controls. Furthermore, control subjects had higher PON1 activity on HDL₂ (CKD and ESRD patients p<0.001) and HDL₃ (CKD p<0.05; ESRD patients p<0.001) subclasses in comparison with the both patients groups. Also, significant negative correlation was found between paraoxonase activity of PON1 in serum and creatinine concentration (ρ=-0.373, p<0.01).

CONCLUSIONS

This study showed that altered HDL subclasses distribution, changed PON1 activities on different HDL subclasses as well as diminished anti-oxidative protection could be important factors in atherosclerosis development in CKD and ESRD patients.

Associations of lipoprotein subclasses and oxidative stress status in pulmonary and pulmonary plus extrapulmonary sarcoidosis

Background: Sarcoidosis is an inflammatory disease with pulmonary and extrapulmonary manifestations. In such pathologic conditions, increased oxidative stress and rearrangement of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) may occur. Objective: This study evaluated association of oxidative stress and lipoprotein subclasses in severe forms of pulmonary and pulmonary plus extrapulmonary sarcoidosis. Methods: Lipid parameters, LDL and HDL subclass distributions, high-sensitivity C-reactive protein (hsCRP), serum amyloid A (SAA), paraoxonase 1 (PON1), malondialdehyde (MDA), total-oxidant status (TOS), sulfhydryl (SH) groups, pro-oxidant anti-oxidant balance (PAB) were determined in 77 patients (53 isolated pulmonary and 24 pulmonary plus extrapulmonary) and 139 controls. Results: Both pulmonary and extrapulmonary sarcoidosis patients had significantly higher levels of triglycerides and TOS (P<0.05) and more LDL II, LDL III, LDL IVA particles (P<0.01), but lower HDL size, SH groups (P<0.001), PON1 activity and less LDL I subclasses (P<0.05) than controls. In isolated pulmonary disease, HDL-cholesterol (P<0.01) was significantly lower whereas proportions of HDL 3a and PAB were significantly higher (P<0.05) when compared with the control group. PON1 was significantly higher in pulmonary than in combined pulmonary-extrapulmonary disease (P<0.05). In pulmonary sarcoidosis, TOS and PON1 correlated significantly with small-sized HDL particles (P<0.05). Conclusions: Both patient groups were characterized by adverse lipoprotein profile and elevated oxidative stress. In isolated pulmonary group significant associations of oxidative stress and HDL particles distribution was demonstrated. Pulmonary sarcoidosis was associated with higher PON1 activity and rearrangement of LDL particles did not depend on disease localization. (Sarcoidosis Vasc Diffuse Lung Dis 2018; 35: 198-205).

Relationship Between the Apolipoprotein E Genotype and LDL Particle Size in Patients With Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is associated with dyslipidemia and increased cardiovascular risk. We assessed the effects of apolipoprotein E ( APOE) genotype on low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particle size and lipid subclasses (separated by gradient gel electrophoresis) in patients with OSA. Stable patients (n = 181) prospectively recruited underwent full polysomnography. Both LDL particle size and LDL I proportion were reduced from ∊3∊3 homozygotes to ∊2 carriers and to ∊4 carriers (analysis of variance: P = .024; P = .040, respectively); carriers of the ∊4 allele of the APOE genotype had significantly lower LDL particle size and LDL I proportion compared to ∊3∊3 homozygotes ( P < .05 for both comparisons). Insulin resistance increased from patients with no OSA to those with mild–moderate and to those with severe OSA ( P < .001). In multivariate analysis, LDL size was independently predicted by APOE genotype, male gender, and the presence of metabolic syndrome (MetS; P = .001, P = .020, P = .027, respectively). The HDL particle size was not affected by APOE genotype. Our data demonstrate that both the ∊4 APOE genotype and MetS are independently related to smaller LDL size in patients with OSA.

Distribution of low-density lipoprotein and high-density lipoprotein subclasses in patients with sarcoidosis

CONTEXT

Systemic inflammatory diseases are associated with proatherogenic lipoprotein profile, but there is a lack of information regarding overall distributions of lipoprotein subclasses in sarcoidosis.

OBJECTIVE

To investigate whether patients with sarcoidosis have altered distributions of plasma low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particles.

DESIGN

Seventy-seven patients with biopsy-proven sarcoidosis (29 with acute and 48 with chronic sarcoidosis) treated with corticosteroids and 77 age- and sex-matched controls were included in the study. Low-density lipoprotein and HDL subclasses were determined by gradient gel electrophoresis, while inflammatory markers and lipid parameters were measured by standard laboratory methods.

RESULTS

Compared to controls, patients had fewer LDL I subclasses (P < .001), but more LDL II and III (P < .001) subclasses. This pattern was evident in both acute and chronic disease groups. Patients also had smaller HDL size (P < .001) and higher proportions of HDL 2a (P = .006) and 3a particles (P = .004). Patients with chronic sarcoidosis had smaller LDL size than those with acute disease (P = .02) and higher proportions of HDL 3a subclasses (P = .04) than controls. In acute sarcoidosis, relative proportions of LDL and HDL particles were associated with levels of inflammatory markers, whereas in chronic disease an association with concentrations of serum lipid parameters was found.

CONCLUSIONS

The obtained results demonstrate adverse lipoprotein subfraction profile in sarcoidosis with sustained alterations during disease course. Evaluation of LDL and HDL particles may be helpful in identifying patients with higher cardiovascular risk, at least for prolonged corticosteroid therapy due to chronic disease course.

Characteristics of low-density and high-density lipoprotein subclasses in pediatric renal transplant recipients

Renal transplant recipients often suffer from dyslipidemia which is one of the principal risk factors for cardiovascular disease. This study sought to determine characteristics of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles and their associations with carotid intima-media thickness (cIMT) in a group of pediatric renal transplant recipients. We also examined the influence of immunosuppressive therapy on measured LDL and HDL particle characteristics. HDL size and subclass distribution were determined using gradient gel electrophoresis, while concentrations of small, dense LDL (sdLDL)-cholesterol (sdLDL-C) and sdLDL-apolipoprotein B (sdLDL-apoB) using heparin-magnesium precipitation method in 21 renal transplant recipients and 32 controls. Renal transplant recipients had less HDL 2b (P < 0.001), but more HDL 3a (P < 0.01) and 3b (P < 0.001) subclasses. They also had increased sdLDL-C (P < 0.01) and sdLDL-apoB (P < 0.05) levels. The proportion of the HDL 3b subclasses was a significant predictor of increased cIMT (P < 0.05). Patients treated with cyclosporine had significantly higher sdLDL-C and sdLDL-apoB concentrations (P < 0.05) when compared with those on tacrolimus therapy. Pediatric renal transplant recipients have impaired distribution of HDL and LDL particles. Changes in the proportion of small-sized HDL particles are significantly associated with cIMT. Advanced lipid testing might be useful in evaluating the effects of immunosuppressive therapy.

Cox proportional hazard model analysis of survival in end-stage renal disease patients with small-sized high-density lipoprotein particles

OBJECTIVE

Dyslipidemia is commonly seen in patients with end-stage renal disease (ESRD). This prospective study investigates whether small-sized high-density lipoprotein (HDL) particles alone or in combination with high sensitivity C-reactive protein (hsCRP) are independent determinants of ESRD mortality.

DESIGN AND METHODS

We performed 36 months follow-up study in 122 haemodialysis (HD) patients. HDL size and subclass distribution were determined by gradient gel electrophoresis. Baseline characteristics of the patients were evaluated for the prediction of mortality.

RESULTS

Cox regressions analysis showed that patients with small-sized HDL particles had 2.8-fold higher risk of lethal outcome (P<0.05). Concomitant presence of small-sized HDL particles and increased hsCRP concentration were significantly associated with reduced survival rate (HR=3.907; P<0.05). Observed relationships persisted after adjustment for serum lipid and lipoprotein concentrations.

CONCLUSIONS

Our results indicate that small-sized HDL particles alone and combined with elevated hsCRP concentrations are independent predictors of reduced survival in HD patients.

Effects of diet on genetic regulation of lipoprotein metabolism in baboons

Several measures of lipoprotein phenotype are significant predictors of cardiovascular risk. Although such lipoprotein phenotypes are under strong genetic control, it is not clear to what extent they are controlled by the same - and by different - genes and whether these relationships may be altered in different dietary environments. Therefore, we measured six lipoprotein traits (three LDL traits - LDLC and apoB concentrations and LDL size - and three HDL traits - HDLC and apoA1 concentrations and HDL size) on each of three diets differing in level of fat and cholesterol. In bivariate analyses, all but two metabolically related trait pairs were genetically correlated, though none were completely correlated, implying additive genetic effects by both pleiotropic and unique genes. In comparing genetic correlations for the same pair of traits across diet, we detected evidence of diet effects on genetic control of these metabolically related traits; specifically, increasing level of dietary cholesterol was associated with a significant decrease in the genetic correlation of apoA1 with HDL size, and a significant increase in the genetic correlations of LDL size with LDLC and apoB. The results suggest a complex network of genes affecting lipoprotein metabolism: the genes may exert both unique and pleiotropic effects; the genes may exert detectable effects in many or only in specific dietary environments.

Effects of rosuvastatin on electronegative LDL as characterized by capillary isotachophoresis: the ROSARY Study

Electronegative LDL, a charge-modified LDL (cm-LDL) subfraction that is more negatively charged than normal LDL, has been shown to be inflammatory. We previously showed that pravastatin and simvastatin reduced the electronegative LDL subfraction, fast-migrating LDL (fLDL), as analyzed by capillary isotachophoresis (cITP). The present study examined the effects of rosuvastatin on the more electronegative LDL subfraction, very-fast-migrating LDL (vfLDL), and small, dense charge-modified LDL (sd-cm-LDL) subfractions. Patients with hypercholesterolemia or those who were being treated with statins (n = 81) were treated with or switched to 2.5 mg/d rosuvastatin for 3 months. Rosuvastatin treatment effectively reduced cITP cm-LDL subfractions of LDL (vfLDL and fLDL) or sdLDL (sd-vfLDL and sd-fLDL), which were closely related to each other but were different from the normal subfraction of LDL [slow-migrating LDL (sLDL)] or sdLDL (sd-sLDL) in their relation to the levels of remnant-like particle cholesterol (RLP-C), apolipoprotein (apo) C-II, and apoE. The percent changes in cm-LDL or sd-cm-LDL caused by rosuvastatin were correlated with those in the particle concentrations of LDL or sdLDL measured as LDL-apoB or sdLDL-apoB and the levels of HDL-C, RLP-C, apoC-II, and apoE. In conclusion, rosuvastatin effectively reduced both the vfLDL subfraction and sd-cm-LDL subfractions as analyzed by cITP.

Does simultaneous determination of LDL and HDL particle size improve prediction of coronary artery disease risk?

BACKGROUND

Alterations in plasma lipoprotein subclass distribution affect the risk for coronary artery disease (CAD). However, it is unclear whether the determination of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) phenotypes may or may not improve the ability to predict CAD development.

METHODS

Polyacrylamide gradient (3-31%) gel electrophoresis was used to simultaneously determine size and distribution of lipoprotein subclasses in 181 CAD patients and 178 controls.

RESULTS

Mean LDL and HDL subclass sizes were significantly smaller in patients than in controls (p < 0.001). Multivariate logistic regression analysis showed that small dense LDL particles were independent CAD risk predictors (OR = 2.867, p < 0.01), even when adjusted for other traditional risk factors, while small HDL particles lost their significance after adjustment (OR = 2.071, p = 0.054). The area under the ROC curve for LDL (0.671) and HDL (0.643) particle size measurement demonstrated low clinical accuracy when compared to the combination of traditional lipid risk factor measurements.

CONCLUSIONS

CAD is associated with the predominance of smaller LDL and HDL particles. However, simultaneous determination of these two lipoprotein phenotypes provides no additional power in discriminating CAD and non-CAD subjects, beyond that obtained by the traditional risk factors.

Vitamin E dietary supplementation significantly affects multiple risk factors for cardiovascular disease in baboons

BACKGROUND

Oxidative stress is a widely accepted risk factor for cardiovascular disease (CVD), but the CVD benefit of dietary antioxidants, such as vitamin E, is controversial.

OBJECTIVE

Therefore, we have investigated, in the baboon model, the effects of dietary vitamin E supplementation on risk factors for CVD.

DESIGN

Pedigreed baboons (n = 251) were fed 2 atherogenic diets, high in fat and cholesterol, that differed in vitamin E concentrations. After 7 wk on each diet, blood samples were taken, and a panel of CVD risk factor traits (ie, indicators of lipoprotein metabolism and oxidative stress) were measured.

RESULTS

Vitamin E supplementation caused significantly higher total antioxidant status (TAS) and lower oxidized LDL as expected. In addition, vitamin E caused 2 paradoxical effects on HDL metabolism: higher apolipoprotein A-I (apo A-I) concentrations and lower HDL sizes. We calculated a difference (Delta) variable for each trait as the value on the high-vitamin E diet minus that on the low-vitamin E diet and determined that several HDL concentration Delta variables were significantly correlated with Delta TAS, but only one, Delta apo A-I, was independently correlated. Genetic analyses showed that 2 Delta variables, Delta paraoxonase and Delta HDL(2), were significantly heritable, but that neither Delta TAS nor Delta apo A-I were heritable.

CONCLUSIONS

Thus, our data show that dietary vitamin E improves TAS and LDL quality. They also show 2 apparently paradoxical effects on HDL metabolism: lower HDL(2), which is mediated by genes, and higher apo A-I, which is not. These effects have contrasting associations with CVD risk and may help account for the mixed results from clinical trials of dietary vitamin E.

Effects of reconstituted HDL on charge-based LDL subfractions as characterized by capillary isotachophoresis

Modified LDL in human plasma including small, dense LDL (sdLDL) and oxidized LDL carries a more negative charge than unmodified LDL and is atherogenic. We examined the effects of apolipoprotein A-I (apoA-I)/POPC discs on charge-based LDL subfractions as determined by capillary isotachophoresis (cITP). Three normal healthy subjects and seven patients with metabolic disorders were included in the study. LDL in human plasma was separated into two major subfractions, fast- and slow-migrating LDL (fLDL and sLDL), by cITP. Normal LDL was characterized by low fLDL, and mildly oxidized LDL in vitro and mildly modified LDL in human plasma were characterized by increased fLDL. Moderately oxidized LDL in vitro and moderately modified LDL in a patient with hypertriglyceridemia and HDL deficiency were characterized by both increased fLDL and a new LDL subfraction with a faster mobility than fLDL [very-fast-migrating LDL as determined by cITP (vfLDL)]. cITP LDL subfractions with faster electrophoretic mobility (fLDL vs. sLDL, vfLDL vs. fLDL) were associated with an increased content of sdLDL. Incubation of a plasma fraction with d>1.019 g/ml (depleted of triglyceride-rich lipoproteins) in the presence of apoA-I/POPC discs at 37 degrees C greatly decreased vfLDL and fLDL but increased sLDL. Incubation of whole plasma from patients with an altered distribution of cITP LDL subfractions in the presence of apoA-I/POPC discs also greatly decreased fLDL but increased sLDL. ApoA-I/POPC discs decreased the cITP fLDL level, the free cholesterol concentration, and platelet-activating factor acetylhydrolase activity in the sdLDL subclasses (d=1.040-1.063 g/ml) and increased the size of LDL. ApoA-I/POPC discs reduced charge-modified LDL in human plasma by remodeling cITP fLDL into sLDL subfractions.

Polyacrylamide gradient gel electrophoresis of lipoprotein subclasses

High-density (HDL), low-density (LDL), and very-low-density (VLDL) lipoproteins are heterogeneous cholesterol-containing particles that differ in their metabolism, environmental interactions, and association with disease. Several protocols use polyacrylamide gradient gel electrophoresis (GGE) to separate these major lipoproteins into known subclasses. This article provides a brief history of the discovery of lipoprotein heterogeneity and an overview of relevant lipoprotein metabolism, highlighting the importance of the subclasses in the context of their metabolic origins, fates, and clinical implications. Various techniques using polyacrylamide GGE to assess HDL and LDL heterogeneity are described, and how the genetic and environmental determinations of HDL and LDL affect lipoprotein size heterogeneity and the implications for cardiovascular disease are outlined.