High Density Lipoprotein Free Cholesterol Research Articles

Correction of Familial LCAT Deficiency by AAV-hLCAT Prevents Renal Injury and Atherosclerosis in Hamsters-Brief Report.

[Figure: see text].

HDL Particle Size and Functionality Comparison between Patients with and without Confirmed Acute Myocardial Infarction.

Introduction Cardiovascular diseases (CVDs) continue to be the most common cause of death worldwide, and acute myocardial infarction (AMI) is noteworthy due to its great magnitude. Objectives This study was carried out to evaluate the structure (molecular and particle size) and functionality of high-density lipoprotein (HDL) shortly after AMI, in the presence of acute inflammatory response. Casuistic and Methods A cross-sectional, observational study was conducted between January 2015 and August 2016, with a total convenient sample of 85 patients. The patients' data were segregated according to the Registry of Acute Myocardial Infarction (REAMI), with 45 confirmed AMI patients. The study groups consisted of patients from both sexes, older than 35 years, presented to the Hospital São Rafael (HSR) initially with AMI clinical symptoms. In addition, 40 nonischemic control patients (CPs), without AMI symptomatology, and according to previous inclusion criteria, were selected for convenience in an outpatient care unit. The HDL particle size was measured by laser light scattering (LLS), after separation of HDL from apoB-rich lipoproteins. The paraoxonase-1 (PON-1) activity was determined in a spectrophotometer by using paraoxon as a substrate. The other laboratory marker information, secondary data, was obtained in the laboratory system. Results The HDL particle size, free cholesterol, and hs-CRP analysis showed significant differences when compared between REAMI and CP groups (p < 0.0001, p=0.007, and p < 0.0001; two-tailed unpaired t-test, respectively). Regarding paraoxonase, the data comparison between REAMI and CP groups was also significantly different (p < 0.0067; two-tailed unpaired t-test). Conclusion Despite an important current database on the HDL cholesterol role, our study provides relevant complementary information about the HDL particle susceptibility to the inflammation following AMI. The HDL particles' quantitative and functional attributes should be measured as markers of HDL functionality.

Lipoprotein subfractions by nuclear magnetic resonance are associated with tumor characteristics in breast cancer.

BackgroundHigh-Density Lipoprotein (HDL)-cholesterol, has been associated with breast cancer development, but the association is under debate, and whether lipoprotein subfractions is associated with breast tumor characteristics remains unclear.MethodsAmong 56 women with newly diagnosed invasive breast cancer stage I/II, aged 35–75 years, pre-surgery overnight fasting serum concentrations of lipids were assessed, and body mass index (BMI) was measured. All breast tumors were immunohistochemically examined in the surgical specimen. Serum metabolomics of lipoprotein subfractions and their contents of cholesterol, free cholesterol, phospholipids, apolipoprotein-A1 and apolipoprotein-A2, were assessed using nuclear magnetic resonance. Principal component analysis, partial least square analysis, and uni- and multivariable linear regression models were used to study whether lipoprotein subfractions were associated with breast cancer tumor characteristics.ResultsThe breast cancer patients had following means: age at diagnosis: 55.1 years; BMI: 25.1 kg/m2; total-Cholesterol: 5.74 mmol/L; HDL-Cholesterol: 1.78 mmol/L; Low-Density Lipoprotein (LDL)-Cholesterol: 3.45 mmol/L; triglycerides: 1.18 mmol/L. The mean tumor size was 16.4 mm, and the mean Ki67 hotspot index was 26.5 %. Most (93 %) of the patients had estrogen receptor (ER) positive tumors (≥1 % ER+), and 82 % had progesterone receptor (PgR) positive tumors (≥10 % PgR+). Several HDL subfraction contents were strongly associated with PgR expression: Apolipoprotein-A1 (β 0.46, CI 0.22–0.69, p < 0.001), HDL cholesterol (β 0.95, CI 0.51–1.39, p < 0.001), HDL free cholesterol (β 2.88, CI 1.28–4.48, p = 0.001), HDL phospholipids (β 0.70, CI 0.36–1.04, p < 0.001). Similar results were observed for the subfractions of HDL1-3. We observed inverse associations between HDL phospholipids and Ki67 (β -0.25, p = 0.008), and in particular between HDL1’s contents of cholesterol, phospholipids, apolipoprotein-A1, apolipoprotein-A2 and Ki67. No association was observed between lipoproteins and ER expression.ConclusionOur findings hypothesize associations between different lipoprotein subfractions, and PgR expression, and Ki 67 % in breast tumors. These findings may have clinical implications, but require confirmation in larger studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12944-016-0225-4) contains supplementary material, which is available to authorized users.

A simple and precise method for direct measurement of fractional esterification rate of high density lipoprotein cholesterol by high performance liquid chromatography

The relationship between fractional cholesterol esterification rate in plasma or serum high-density lipoprotein (HDL) (FER(HDL)) and lipoprotein subfractions and other cardiovascular disease (CVD) risk factors has been demonstrated. However, the current method for measuring FER(HDL) requires fresh serum samples and radioactive labeling of the samples, making it impractical for use in clinical laboratories. In this study, we developed a simple and precise HPLC method for the measurement of FER(HDL). Correlations between FER(HDL) and CVD risk factors were evaluated in 119 healthy volunteers. Fasting blood samples were collected and serum was isolated within 2 h. Serum HDL was prepared by precipitation of apolipoprotein B (apoB)-containing lipoproteins with dextran sulfate and magnesium chloride. HDL fractions were divided into two aliquots and incubated at 0°C and 37°C, respectively, for 1 h. Free cholesterol in the HDL fractions was analyzed by HPLC. FER(HDL) was calculated as the percent decrease of free cholesterol during incubation. The esterification reaction of HDL free cholesterol was not linear, but the measured FER(HDL) was stable when serum samples were stored at room temperature for <4 h, or at 4°C for <24 h. The intra-assay and total CVs for FER(HDL) measurements were 1.0%-2.1% and 1.6%-3.8%, respectively. Results of 119 healthy volunteers showed that FER(HDL) was positively correlated with age, BMI, blood pressure, total cholesterol (TC), triglyceride (TG) and small dense low-density lipoprotein-cholesterol (LDLb-C), and negatively correlated with HDL-C and HDL2-C. FER(HDL) has shown to be a predictor of HDL and LDL subfraction distributions. This method is simple, non-radioactive and precise and will be useful in prediction of lipoprotein subfraction distributions and in clinical assessment of CVD risks.

Cooperation between hepatic cholesteryl ester hydrolase and scavenger receptor BI for hydrolysis of HDL-CE

Liver is the sole organ responsible for the final elimination of cholesterol from the body either as biliary cholesterol or bile acids. High density lipoprotein (HDL)-derived cholesterol is the major source of biliary sterols and represents a mechanism for the removal of cholesterol from peripheral tissues including artery wall-associated macrophage foam cells. Via selective uptake through scavenger receptor BI (SR-BI), HDL-cholesterol is thought to be directly secreted into bile, and HDL cholesteryl esters (HDL-CEs) enter the hepatic metabolic pool and need to be hydrolyzed prior to conversion to bile acids. However, the identity of hepatic CE hydrolase (CEH) as well as the role of SR-BI in bile acid synthesis remains elusive. In this study we examined the role of human hepatic CEH (CES1) in facilitating hydrolysis of SR-BI-delivered HDL-CEs. Over-expression of CEH led to increased hydrolysis of HDL-[³H]CE in primary hepatocytes and SR-BI expression was required for this process. Intracellular CEH associated with BODIPY-CE delivered by selective uptake via SR-BI. CEH and SR-BI expression enhanced the movement of [³H]label from HDL-[³H]CE to bile acids in vitro and in vivo. Taken together, these studies demonstrate that SR-BI-delivered HDL-CEs are hydrolyzed by hepatic CEH and utilized for bile acid synthesis.

TheSrb1+1050TAllele Is Associated with Metabolic Syndrome in Children but Not with Cholesteryl Ester Plasma Concentrations of High-Density Lipoprotein Subclasses

Low cholesterol and phospholipid plasma levels of some high-density lipoprotein (HDL) subclasses have been described in children with metabolic syndrome. Scavenger receptor class B type I (SR-BI) has been proposed to be at the origin of such HDL alterations because of its key role on cholesteryl esters-HDL metabolism. However, the possible contribution of SR-BI has not been specifically explored in this kind of patients. Plasma lipid concentrations of HDL subclasses, i.e., triglycerides (TG), phosphatidylcholine (Ph), free cholesterol (FC), and total cholesterol (TC), were determined by enzymatic staining on polyacrylamide gradient gels (PAGE) in 39 pediatric patients with metabolic syndrome and 65 children as controls. Cholesteryl esters were estimated by the difference between TC and FC. Proteins of HDL subclasses were also stained for the assessment of the relative size distribution of HDL. For statistical analysis, the study population was grouped by Srb1 +1050C-->T polymorphism (rs5888) as carriers or noncarriers of the T allele, and data were corrected by metabolic syndrome status. The Srb1 +1050T allele was associated with metabolic syndrome [odds ratio (OR)=2.18 (1.12-4.22), P=0.02]. Plasma TG corresponding to HDL3a, as well as the relative proportion of this HDL subclass, were slightly higher in carriers of the T allele as compared to CC homozygous subjects. Cholesteryl esters plasma concentrations of all HDL subclasses were comparable between T allele carriers and noncarriers after correction by metabolic syndrome status. Srb1 +1050T was associated with metabolic syndrome, but T carrier subjects did not show important differences concerning HDL subclasses as compared to noncarriers.

Early Atherosclerosis in Obese Juveniles Is Associated with Low Serum Levels of Adiponectin

There is growing evidence that adiponectin, the most abundant adipocytokine of adipose tissue cells, plays a crucial role in advanced atherosclerosis. The objective of the study was to evaluate the role of adiponectin in early atherosclerosis. One hundred forty obese juveniles (mean age, 13.5 +/- 4.4 yr) and 100 age-matched, healthy, normal-weight controls from the STYrian Juvenile Obesity Study were investigated. We measured adipocytokines, inflammatory biomarkers, parameters of insulin resistance, and lipid subfractions. Intima-media thickness (IMT) of common carotid arteries was determined by ultrasonography. Furthermore, lipometric measurements were performed in obese juveniles to determine the topographic distribution of sc adipose tissue (SAT). Compared with controls, the group of obese juveniles exhibited a significantly increased IMT (P < 0.001) and elevated high-sensitive C-reactive protein (P < 0.001), indicating early stages of atherosclerosis. Serum levels of adiponectin were highly significantly negatively correlated with carotid IMT, even after controlling for common cardiovascular risk factors (P < 0.001; r = -0.34). Furthermore, adiponectin was positively correlated with high-density lipoprotein-free cholesterol and serum apolipoprotein-A1 and negatively with triglycerides, insulin resistance, uric acid, and serum transaminases. By a multiple regression analysis, adiponectin was shown to be the strongest predictive variable for carotid IMT. Finally, adiponectin was found positively correlated with SAT thickness of the rear and inner thigh in boys and negatively with the SAT thickness of the neck in girls. In summary, our study describes an influence of SAT topography on adiponectin serum levels and provides first evidence that incipient atherosclerosis is associated with low serum levels of this adipocytokine.

Stability of serum total and high density lipoprotein cholesterol during whole blood incubation examined by high performance liquid chromatography

目的 检查全血贮存对血清总胆固醇(TC)和高密度脂蛋白胆固醇(HDLC)的影响,并探讨其可能机制.方法建立高效液相色谱(HPLC)方法,测定不同个体全血样品经不同温育后血清TC、总游离胆固醇(TFC)、HDLC和高密度脂蛋白游离胆固醇(HDLFC),计算有关参数或指标并做统计分析.结果建立的HPLC方法平均批内变异系数0.22 %～0.51 %;全血温育造成血清TC和HDLC变化(平均0.6 %～2.1 %和2.0 %～4.1 %),有些个体变化明显(TC >±3 %,HDLC>±5 %).结论建立血清TC、TFC、HDLC和HDLFC的精密测定方法;血清TC和HDLC在不同条件下的全血贮存中,受血清体积变化、血细胞-脂蛋白间胆固醇交换或转移等许多复杂因素的影响而发生变化;血脂测定标本应尽量减少不必要的贮存。

Enhancement of Scavenger Receptor Class B Type I-mediated Selective Cholesteryl Ester Uptake fromapoA-I−/− High Density Lipoprotein (HDL) by Apolipoprotein A-I Requires HDL Reorganization by Lecithin Cholesterol Acyltransferase

The severe depletion of cholesteryl ester (CE) in adrenocortical cells of apoA-I(-/-) mice suggests that apolipoprotein (apo) A-I plays an important role in the high density lipoprotein (HDL) CE selective uptake process mediated by scavenger receptor BI (SR-BI) in vivo. A recent study showed that apoA-I(-/-) HDL binds to SR-BI with the same affinity as apoA-I(+/+) HDL, but apoA-I(-/-) HDL has a decreased V(max) for CE transfer from the HDL particle to adrenal cells. The present study was designed to determine the basis for the reduced selective uptake of CE from apoA-I(-/-) HDL. Variations in apoA-I(-/-) HDL particle diameter, free cholesterol or phospholipid content, or the apoE or apoA-II content of apoA-I(-/-) HDL had little effect on HDL CE selective uptake into Y1-BS1 adrenal cells. Lecithin cholesterol acyltransferase treatment alone or addition of apoA-I to apoA-I(-/-) HDL alone also had little effect. However, addition of apoA-I to apoA-I(-/-) HDL in the presence of lecithin cholesterol acyltransferase reorganized the large heterogeneous apoA-I(-/-) HDL to a more discrete particle with enhanced CE selective uptake activity. These results show a unique role for apoA-I in HDL CE selective uptake that is distinct from its role as a ligand for HDL binding to SR-BI. These data suggest that the conformation of apoA-I at the HDL surface is important for the efficient transfer of CE to the cell.

Hepatic Scavenger Receptor BI Promotes Rapid Clearance of High Density Lipoprotein Free Cholesterol and Its Transport into Bile

The clearance of free cholesterol from plasma lipoproteins by tissues is of major quantitative importance, but it is not known whether this is passive or receptor-mediated. Based on our finding that scavenger receptor BI (SR-BI) promotes free cholesterol (FC) exchange between high density lipoprotein (HDL) and cells, we tested whether SR-BI would effect FC movement in vivo using [(14)C]FC- and [(3)H]cholesteryl ester (CE)-labeled HDL in mice with increased (SR-BI transgenic (Tg)) or decreased (SR-BI attenuated (att)) hepatic SR-BI expression. The initial clearance of HDL FC was increased in SR-BI Tg mice by 72% and decreased in SR-BI att mice by 53%, but was unchanged in apoA-I knockout mice compared with wild-type mice. Transfer of FC to non-HDL and esterification of FC were minor and could not explain differences. The hepatic uptake of FC was increased in SR-BI Tg mice by 34% and decreased in SR-BI att mice by 22%. CE clearance and uptake gave similar results, but with much slower rates. The uptake of HDL FC and CE by SR-BI Tg primary hepatocytes was increased by 2.2- and 2.6-fold (1-h incubation), respectively, compared with control hepatocytes. In SR-BI Tg mice, the initial biliary secretion of [(14)C]FC was markedly increased, whereas increased [(3)H]FC appeared after a slight delay. Thus, in the mouse, a major portion of the clearance of HDL FC from plasma is mediated by SR-BI.

Delayed increase in high density lipoprotein-phospholipids after ingestion of a fat load in normolipidemic patients with coronary artery disease

We studied the effect of a single oral fat load, supplemented with retinyl palmitate (RP), on high density lipoprotein (HDL) lipids in six normolipidemic men with coronary artery disease (CAD) and in six age- and lipid-matched controls. All subjects were selected from a study group which underwent the same protocol 2 years earlier. Post-prandial total plasma lipids, plasma RP levels, and HDL lipids were evaluated at 2-h intervals up till 10 h after the meal. In most subjects the post-prandial response of plasma triglyceride (TG) and plasma RP was identical in the first and second tests. Following the fat load, control subjects showed no change in HDL total cholesterol (TC) or HDL cholesteryl ester (CE) and showed an increase in HDL-TG. CAD subjects however showed a decrease in HDL-TC and HDL-CE and an increase in HDL-TG, similar to the increase in control subjects. In control subjects an increase in HDL phospholipid (PL) was apparent between 0 and 8 h after the fat load. By contrast, in CAD subjects the increase in HDL-PL was only found after as long as 6 h. The magnitude of the post-prandial response of HDL-PL measured during the test was significantly lower in the CAD group. The effects of the fat load on HDL free cholesterol (FC) were similar to the changes in HDL-PL. These data support the hypothesis that PL and FC released during the degradation of chylomicrons as surface remnants are taken up by HDL. This process is clearly delayed in normolipidemic CAD subjects compared with controls. The data suggest that differences in the post-prandial response to an oral fat load in normolipidemic CAD patients and control subjects are not confined to the clearance of TG-rich lipoproteins, but also involve a difference in the uptake of chylomicron surface material by HDL.

Cholesteryl Ester Transfer Protein Mediates Selective Uptake of High Density Lipoprotein Cholesteryl Esters by Human Adipose Tissue

We have determined the role of cholesteryl ester transfer protein (CETP) in selective uptake of high density lipoprotein (HDL)-derived cholesteryl esters (CE) by human adipose tissue, using organ culture or collagenase-digested adipocytes. Incubation of the fresh tissue fragments with HDL containing [3H]CE or 125I-apoprotein (apo) A-I resulted in significant uptake of HDL-CE-derived label. Addition of recombinant CETP (rCETP) increased CE uptake in a dose-response fashion. In contrast, little association of 125I-apoA-I with adipose tissue was noted, and addition of rCETP did not alter apoA-I uptake or degradation. Incubation of adipose tissue with TP2, an anti-CETP monoclonal antibody, which inhibits neutral lipid transfer, markedly reduced selective uptake of HDL-CE. Studies using human adipocytes isolated by collagenase digestion also demonstrated selective uptake of HDL-CE and enhancement of this process by rCETP. To confirm that the association of HDL-CE-derived radioactivity with adipose tissue was not due to neutral lipid exchange between adipocytes and HDL, we measured changes in HDL composition following incubation of HDL and rCETP with isolated adipocytes. A decrease in HDL-CE concentration in the medium was observed, an effect which was markedly attenuated when incubations were carried out in the presence of monoclonal antibody TP2. Furthermore, the decrease in HDL-CE was accompanied by an increase in HDL free cholesterol, likely representing efflux of adipocyte cholesterol to HDL. There were no significant changes in phospholipid, apoA-I, or apoA-II in the medium following incubation with adipocytes. These data demonstrate a novel and important role for CETP in selective uptake of HDL-cholesteryl esters by human adipocytes and suggest that this pathway may be of quantitative physiological significance in HDL remodeling and adipocyte cholesterol accumulation.

Higher high density lipoprotein cholesterol associated with moderate alcohol consumption is not related to altered plasma lecithin: cholesterol acyltransferase and lipid transfer protein activity levels

Lecithin:cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) are important factors involved in HDL metabolism. Altered plasma activity levels of these factors could play a role in the increase in high density lipoprotein (HDL) cholesterol associated with moderate alcohol consumption. We measured plasma LCAT, CETP and PLTP activities with exogenous substrate assays, as well as lipoproteins and HDL lipids in 6 alcohol-abstaining men, 18 matched men who used ⪯ 1 and 18 men who used > 1 alcohol-containing drinks per day. Plasma cholesterol and triglycerides were similar in the three groups. HDL total cholesterol, HDL cholesteryl ester, HDL free cholesterol and HDL triglycerides were higher in the alcohol drinkers compared to the abstainers (all P < 0.05). No differences in plasma LCAT, CETP and PLTP activity levels were observed between the three groups. Analysis of covariance also demonstrated that the use of alcohol was associated with higher HDL cholesterol ( P < 0.04), whereas plasma LCAT, CETP and PLTP activity levels were not related to alcohol consumption. Furthermore, HDL cholesteryl ester was positively associated with LCAT activity ( P < 0.001), PLTP activity ( P < 0.01) and alcohol intake ( P < 0.04) and negatively with plasma triglycerides ( P < 0.001) and CETP activity ( P < 0.03), indicating that alcohol influenced HDL cholesteryl ester independently from these biochemical parameters. The higher HDL cholesterol associated with moderate alcohol consumption is, therefore, unlikely to be caused by an effect on plasma LCAT, CETP or PLTP activity levels.

Analysis of high density lipoproteins by a modified gradient gel electrophoresis method.

A high resolution electrophoretic method has been developed to separate plasma high density lipoprotein (HDL) particles by size using 4-30% polyacrylamide agarose (PAA) gradient gels, Sudan black B staining, and laser densitometry. Fourteen distinct HDL bands were observed with HDL-1 being designated as the largest particle and HDL-14 as the smallest particle. HDL-1 was similar in size to ferritin (Stokes diameter 12.2 nm), HDL-8 to catalase (9.2 nm), and HDL-13 to lactate dehydrogenase (8.1 nm). HDL-1 to HDL-7 were found within the density range of HDL2b (d 1.063-1.10 g/ml), HDL-8 to HDL-10 within HDL2a (d 1.10-1.125 g/ml), and HDL-11 to HDL-14 within HDL3 (d 1.125-1.21 g/ml). On immunoblotting, apolipoprotein A-I (apoA-I) was found in all HDL bands examined, being most prominent in HDL-6, 11, and 12. ApoA-II was not detected in HDL bands 1-5, but was present in all other HDL bands and was most prominent in HDL-9. ApoE was detected mainly in HDL bands 1-7, and was observed in only trace amounts in other bands. Lp A-I isolated by immunoaffinity column chromatography from the plasma of five subjects contained five subspecies (HDL-5, 6, and 11-13), while Lp A-I/A-II also had five subspecies (HDL-8, 9, and 11-13) in these subjects. In normal subjects (n = 57) four or five HDL bands were generally observed, with HDL-9, 11, and 12 being the most frequently observed. Mean HDL particle score (method of sizing based on scanning densitometry, where low score indicates large size and high score indicates small size) was significantly correlated (P < 0.001) with the concentrations of HDL cholesterol (r = -0.796), HDL free cholesterol (r = -0.780), HDL cholesteryl ester (r = -0.683), HDL phospholipid (r = -0.663), HDL apoA-I (r = -0.577), and HDL protein (r = -0.459), but not with HDL triglyceride (r = 0.069). In addition, HDL particle score was significantly correlated (P < 0.05) with HDL total mass (r = -0.649), HDL free cholesterol content (% of total mass, r = -0.608), HDL triglyceride content (r = 0.415), HDL phospholipid content (r = -0.359), and HDL protein content (r = 0.295), but not with HDL cholesteryl ester content (r = -0.219) or HDL apoA-I content (r = 0.183).(ABSTRACT TRUNCATED AT 400 WORDS)

Free cholesterol concentrations in the high-density lipoprotein subfraction-3 as a risk indicator in patients with angiographically documented coronary artery disease

The pathophysiology of plasma lipoprotein metabolism has long been linked to coronary artery disease (CAD). The present study evaluated the association between plasma lipoprotein lipid and apolipoprotein (apo) components and CAD in a group of 80 consecutive Caucasian patients undergoing coronary angiography. Coronary cineangiography was carried out using the Judkins technique and the lesions quantified by calculating a coronary artery lesion score (CALS). Very low- and low-density lipoproteins (VLDL and LDL) were separated by ultracentrifugation, and high-density lipoprotein (HDL) and HDL subfraction-3 (HDL3) isolated by a differential precipitation procedure. Apo A-I, A-II, and B were assayed by endpoint laser nephelometry using specific antibodies. Total cholesterol, free cholesterol, and fatty acid concentrations were measured by gas-liquid chromatography, and lecithin: cholesterol acyltransferase (LCAT) activity by the decrease in the concentration of free cholesterol. On the basis of the presence of CAD, the 80 patients were divided into two groups: 52 (65%) with CAD (mean CALS = 7.8) and 28 (35%) without CAD (zero CALS). The lipoprotein fraction that most clearly differentiated the groups was HDL cholesterol concentration, with a mean +/- SEM value of 36.5 +/- 1.5 mg/dl for those with CAD and 45.1 +/- 2.1 mg/dl for those without (P < 0.01). The mean HDL3 cholesterol concentration was 29.9 +/- 1.2 mg/dl for patients with CAD and 37.4 +/- 1.8 mg/dl for those without (P < 0.001). These differences in HDL cholesterol and HDL3 cholesterol were mainly caused by differences in the free cholesterol component, with a mean HDL free cholesterol level of 10.8 +/- 1.1 and 16.1 +/- 1.4 mg/dl (P < 0.01), and a mean HDL3 free cholesterol level of 7.6 +/- 0.6 and 11.9 +/- 0.8 mg/dl (P < 0.001) in patients with and without CAD, respectively. Plasma LCAT activity was decreased in patients with CAD (P < 0.05), as were the apo A-I and A-II concentrations in both the HDL (P < 0.001) and HDL3 (P < 0.001) fractions. No significant association was found between CAD and HDL2 cholesterol or plasma total cholesterol, LDL cholesterol, or VLDL cholesterol concentrations. A stepwise discriminant analysis revealed that HDL3 free cholesterol was the only variable selected. Using HDL3 free cholesterol as a screening variable for CAD (cutoff 10.55 mg/dl), the sensitivity for CAD was 87% and the specificity for non-CAD 67%. The positive and negative predictive values of HDL3 free cholesterol were 82 and 75%, respectively. We have shown that the concentrations of HDL cholesterol and HDL3 most clearly differentiated between patients with and without CAD.

Role of elevated lecithin: Cholesterol acyltransferase and cholesteryl ester transfer protein activities in abnormal lipoproteins from proteinuric patients

Lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) are key factors in the esterification of free cholesterol, and the distribution of cholesteryl ester among lipoproteins in plasma. Alterations in these processes may play a role in the lipoprotein abnormalities associated with glomerular proteinuria. The activities of LCAT and CETP were measured using excess exogenous substrate assays in nine patients with nephrotic-range proteinuria and in 18 matched controls. The proteinuria-lowering effect of four weeks of angiotensin converting enzyme (ACE) inhibition with enalapril was also studied. Plasma very low lipoprotein and low density lipoprotein (VLDL and LDL) cholesterol, triacylglycerol and apolipoprotein B levels were significantly elevated in the patients compared with controls. High density lipoprotein (HDL) total cholesterol, free cholesterol, cholesteryl ester and the free cholesterol/cholesteryl ester ratio in HDL were lower. Total plasma apolipoprotein A1 was normal. Plasma LCAT and CETP activities were elevated in the patients by 30% (P < 0.01) and by 39% (P < 0.01), respectively, and were both inversely related to serum albumin. VLDL and LDL cholesterol levels were positively related to LCAT and CETP activities, whereas the HDL free cholesterol content was inversely related to LCAT activity. ACE inhibition resulted in a 40% reduction of proteinuria, a partial normalization of LCAT activity, and a decrease in VLDL and LDL cholesterol. In conclusion, elevated activities of LCAT and CETP may provide a mechanism that contributes to the low proportion of cholesterol in HDL relative to that in VLDL and LDL, as well as to the compositional changes of HDL seen in glomerular proteinuria.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of cellular and lipoprotein cholesterol contents on the flux of cholesterol between fibroblasts and high density lipoprotein.

Previous studies indicate that free cholesterol moves passively between high density lipoprotein (HDL) and cell plasma membranes by uncatalyzed diffusion of cholesterol molecules in the extracellular aqueous phase. By this mechanism, the rate constants for free cholesterol influx (Cli) and efflux (ke) should not be very sensitive to the free cholesterol content of cells or HDL. Thus, at a given HDL concentration, the unidirectional influx and efflux of cholesterol mass (Fi, Fe) should be proportional to the cholesterol content of HDL and cells, respectively, and net efflux of cholesterol mass (Fe-Fi greater than 0) should occur when either cells are enriched with cholesterol or HDL is depleted of cholesterol. We have examined the influence of cell and HDL free cholesterol contents on the bidirectional flux of free cholesterol between HDL and human fibroblasts and also attempted to detect some dependence of flux on the binding of HDL to the cells. In the range of HDL concentrations from 1 to 1000 micrograms of protein/ml, ke for cell free cholesterol approximately doubled for every 10-fold increase in HDL concentration, reaching 0.04 h-1 at 1000 micrograms of HDL/ml. ke and Cli were not influenced by the doubling of fibroblast free cholesterol content (from 31 +/- 5 to 62 +/- 13 micrograms of cholesterol/mg of protein). There was an approximate exchange of cholesterol between HDL and the unenriched fibroblasts (e.g. at [HDL] = 100 micrograms/ml, Fe and Fi = 3.2 and 3.0 micrograms of cholesterol/[4 h.mg of cell protein], respectively). In contrast, there was substantial net efflux from the enriched cells (at [HDL] = 100 micrograms/ml, Fe and Fi = 5.5 and 3.1 micrograms of cholesterol/[4 h.mg of cell protein], respectively). The rate constants for cholesterol flux were not influenced by changing the free cholesterol content of HDL, so that there was net efflux of cell cholesterol in the presence of cholesterol-depleted HDL and net influx from cholesterol-rich HDL. The Kd of HDL binding to fibroblasts was reduced from 1.7 to 0.9 micrograms/ml by the enrichment of the cells with free cholesterol; this increase in affinity for HDL was not reflected in enhanced rate constants for cholesterol flux. The inhibition of specific HDL binding by treatment of the lipoprotein with dimethyl suberimidate did not affect cholesterol flux using either control or cholesterol-rich cells at any HDL concentration in the range 1-1000 micrograms/ml. The above results are consistent with the concept that net movement of free cholesterol between cells and HDL occurs by passive, mass-action effects.(ABSTRACT TRUNCATED AT 400 WORDS)

Enzymic determination of the free cholesterol fraction of high-density lipoprotein in plasma with use of 2,4,6-tribromo-3-hydroxybenzoic acid.

A highly sensitive enzymic colorimetric reagent is described for determination of the free cholesterol fraction of high-density lipoprotein (HDL), which represents about 20% of the total cholesterol content of this lipoprotein. For greater sensitivity with respect to cholesterol, I used 2,4,6-tribromo-3-hydroxybenzoic acid instead of phenol in the cholesterol oxidase/peroxidase/4-aminoantipyrine reagent system. This allows determination of the free cholesterol fraction of HDL isolates prepared with polyethylene glycol 6000, a method for precipitating beta-lipoprotein that involves a twofold dilution of plasma. The reagent, adapted for use with a Cobas-Bio centrifugal analyzer, results in between-run and within-run CVs of less than 3% and a linearity to at least 400 mg of HDL free cholesterol per liter. Comparison with results by Trinder's cholesterol method, which measures cholest-4-en-3-one at 232 nm, showed good correlation (r = 0.9829, slope 1.0001, and y-intercept +2.4797 mg/L). With the manual procedure for HDL free cholesterol, between-batch and within-batch CVs were less than 5%, and results correlated well with those by the automated method (r = 0.9975, slope 0.9839, and y-intercept +2.4327 mg/L). The mean (and SD) HDL free cholesterol for 123 men was 96.8 (30.6) mg/L and for 122 women 136.4 (36.8) mg/L, indicating a distinct sex-related difference, similar to that found for HDL total cholesterol. HDL free cholesterol in plasma may therefore be a potential new predictor of coronary heart disease.

Different cholesterol fractions, LCAT activity and lipid peroxides in the serum of children whose parents had early coronary heart disease

Children whose parents had early coronary heart disease were investigated for lipid abnormalities. In order to assess high risk parameters and the efficacy of the applied care, serum total cholesterol (TC), total triglyceride (TT), total free cholesterol (FC) high density lipoprotein cholesterol (HDLC), high density lipoprotein free cholesterol (HDLFC), lipid peroxide (LP) levels, and lecithin: cholesterol acyl transferase (LCAT) activity were measured. Compared to a group of control children, the offspring of high risk subjects had increased TC, FC, and LP levels and decreased HDLC levels. After one year of preventative care all parameters normalized except the high FC level and elevated LCAT activity. The measurement of serum FC and LP levels seems to be a useful method for the determination of true high risk. The LCAT activity may show the efficacy of the dietary treatment.

High density lipoprotein free cholesterol and other lipids in coronary heart disease.

The cholesterol and choline-containing phospholipid fractions of high density lipoproteins (HDL) were determined in healthy males and in male patients with coronary heart disease (CHD) to ascertain which HDL parameter or combined parameters possess the greatest discriminative power. The free cholesterol fraction (HDL-fc) was found to be the most significant discriminator between controls and males with CHD, the mean levels (+/- SEM) being 6.6 (+/- 0.9) and 4.4 (+/- 0.6) mg/dl, respectively. Classification of CHD patients and controls using one-variable discriminant function analysis (DFA) yielded an error rate of 27% for plasma HDL-fc. Two-variable DFA using both the HDL esterified cholesterol levels and the HDL-fc levels of controls and patients reduced the error rate to 11%. The results obtained in this study indicate a possible role for HDL-fc as a predictor of CHD risk.