Mathematical evaluation of methods for estimation of the concentration of the major lipid components of human serum lipoproteins.

The concentration of total cholesterol and triglycerides in the three major lipoprotein classes of human serum was measured in 136 men, randomly selected from an industrial population, by a quantitative method of lipoprotein electrophoresis on agarose gel and of fractions separated by preparative ultracentrifugation. Correlation coefficients for the two estimates were 0.98 for triglycerides in very low-density lipoproteins, 0.93 for total cholesterol in low-density lipoproteins, and 0.75 for total cholesterol in high-density lipoproteins. Data obtained form the analyses of the ultracentrifugal fractions were used to develop regression equations that predict the concentrations of total cholesterol and triglycerides in the lipoprotein classes from their concentrations in whole serum. These equations take into account the inverse curvilinear relationship between total cholesterol in high-density lipoproteins and serum tiriglyceride concentration. When applied to a separate sample of 530 men, the predicted values for triglycerides in very low-density lipoproteins and total cholesterol in low-density lipoproteins correlated as well with ultracentrifugal values as did the electrophoretic estimates. However, for total cholesterol in high-density lipoproteins, the electrophoretic method was superior. Similar regression equations were developed from ultracentrifugal lipoprotein analyses in 158 women from the same industrial population. Although the concentration of total cholesterol in the low-density lipoproteins estimated by both electrophoresis and the regression equations agreed closely in most cases with the ultracentrifugal values, errors exceeded 10% with sufficient frequency to limit the value of the estimates for this purpose. In both men and women, the ratio of total cholesterol to triglycerides in high-density lipoproteins was a hyperbolic function of serum triglyceride concentration, suggesting that cholesteryl esters in the core of this lipoprotein are progressively replaced by triglycerides as the concentration of triglycerides in very low-density lipoproteins increases. This altered composition of nonpolar lipids accounts, at least in part, for the reduction of cholesterol in high-density lipoproteins in hyperlipemic individuals.     

Low density lipoprotein apheresis by membrane differential filtration (cascade filtration).

Membrane differential filtration (MDF) is an apheresis technique with which atherogenic lipoproteins can be eliminated from plasma on the basis of particle size. In 52 patients (REMUKAST Study, 1,702 treatments), low density lipoprotein (LDL) cholesterol was decreased by 61%, high density lipoprotein (HDL) cholesterol by 42%, and fibrinogen by 54%. Our own results in 3 patients show decreases of 62%, 31%, and 59%, respectively; lipoprotein (a) (Lp[a]) was reduced by 58%. The elimination of atherogenic lipoproteins was accompanied by a loss of macromolecules (IgM: 55%, IgG: 27%, alpha 2-macroglobulin: 49%) resulting in improved hemorrheologic parameters. Although HDL is eliminated with each apheresis session, pretreatment concentrations of HDL cholesterol increased by 24% during regular apheresis for 1 year (26 patients, REMUKAST Study). However, preapheresis concentrations of other macroglobulins such as immunoglobulins remained decreased compared to concentrations obtained before the first apheresis session (IgM: 34%, IgG: 23%, and IgA: 16%). We conclude that MDF apheresis is an effective method to lower elevated concentrations of atherogenic lipoproteins. The concomitant loss of other macromolecules transiently improves hemorrheology but demands a close monitoring of immunoglobulin concentrations as a safety parameter.     

Simultaneous determination of serum cholesterol in high- and low-density lipoproteins with use of heparin, Ca2+, and an anion-exchange resin.

Cholesterol concentrations in serum high-density and low-density lipoproteins are simultaneously determined simply, specifically, and rapidly by use of the precipitation method with heparin, Ca2+, and an anion-exchange resin. The isolation of lipoproteins is reproducible, selective, and complete, as judged by electrophoresis on polyacrylamide gel and by immunoelectrophoresis, with use of samples with very-low-density lipoprotein triglyceride concentrations of less than 3.5 g/liter. The precision of the present method is as good (CV, 2.8-3.1%) as that for the method used by the U.S. Lipid Research Clinics (CV 2.0-3.2%). The present method and the heparin-Mn2+ method of the Clinics gave results that agreed reasonably well (for low-density-lipoprotein cholesterol r = 0.935, P less than 0.001; for high-density-lipoprotein cholesterol r = 0.837, P less than 0.001). we also describe the relations between high- or low-density lipoprotein cholesterol and total cholesterol, and between cholesterol concentrations in these two lipoprotein classes.     

Alterations in lipoprotein composition in peritoneal dialysis patients.

OBJECTIVE: Dyslipidemia is common among patients with end-stage renal disease, whether treated by hemodialysis (HD) or peritoneal dialysis (PD). To better understand the specific lipoprotein abnormalities in PD patients, we measured the lipid and apolipoprotein (Apo) composition of the four major classes of plasma lipoproteins in PD patients, HD patients, and healthy control subjects: very low density (VLDL), intermediate density (IDL), low density (LDL), and high density lipoproteins (HDL). DESIGN: Fasting plasma samples were obtained from 15 nondiabetic PD patients, 15 nondiabetic HD patients, and 16 healthy control subjects, all from a cross section of patients and subjects in the region of G?teborg, Sweden. Lipoproteins were isolated by preparative ultracentrifugation, and lipid and apolipoprotein concentrations were measured by gas chromatography and electroimmunoassay, respectively. RESULTS: Alterations in lipoprotein composition were apparent in all four lipoprotein density classes from PD and HD patients. VLDL contained a significantly higher concentration of ApoCIII in both HD and PD patients, and an elevation of free cholesterol, triglyceride, ApoB, ApoCII, and ApoE in PD patients. IDL from both PD and HD patients contained an excess of free and esterified cholesterol and triglyceride and significantly elevated levels of ApoB, ApoCII, ApoCIII, and ApoE. LDL had a higher concentration of ApoB in PD patients and elevated triglyceride and ApoCIII in both PD and HD patients. HDL isolated from PD patients had lower free cholesterol and ApoAI levels compared to control subjects, but these were not significantly different from HD patients. CONCLUSIONS: An increase in lipid and apolipoprotein mass in IDL, and an enrichment of ApoCIII in VLDL, IDL, and LDL were observed in both HD and PD patients. The predominant alteration in lipoprotein composition distinguishing PD patients from HD patients was an elevation of ApoB in LDL. Further study of these alterations in lipoprotein composition in PD patients will be helpful in understanding the underlying causes of dyslipidemia and, ultimately, to the selection of hypolipidemic drugs or other treatments to reduce the cardiovascular risks associated with dyslipidemia in these patients.     

Effect of simvastatin on the apparent size of LDL particles in patients with type IIB hyperlipoproteinemia.

After 15 weeks of simvastatin therapy (20 mg/day), low density lipoprotein particle size in sera of 16 patients with type IIb hyperlipoproteinemia increased significantly from 233 +/- 5.0 A to 237 +/- 7.0 A (P less than 0.05), analyzed by 2-16% polyacrylamide gradient gel electrophoresis. Under simvastatin therapy the concentrations of total cholesterol, total triglyceride, very low density lipoprotein cholesterol and triglyceride, low density lipoprotein cholesterol and apolipoprotein B in serum fell significantly by 30%, 30%, 43%, 28%, 36% and 26%, respectively, and the concentration of high density lipoprotein cholesterol rose significantly by 14%. The changes of low density lipoprotein particle size induced by simvastatin therapy were correlated best with the changes of very low density lipoprotein triglyceride concentration (r2 = 0.438, P less than 0.01). Our results suggest that simvastatin therapy, additionally to a reduction of the serum cholesterol concentration, increases low density lipoprotein particle size which may contribute to reduction of the risk of coronary heart disease in patients with type IIb hyperlipoproteinemia.     

Component analysis of HPLC profiles of unique lipoprotein subclass cholesterols for detection of coronary artery disease

BACKGROUND: Patients with coronary artery disease (CAD) are known to have several lipoprotein abnormalities. We examined plasma cholesterol concentrations of major lipoproteins and their subclasses, using a gel permeation HPLC, to establish an association between a lipoprotein subclass pattern and the presence of CAD. METHODS: We performed a simple and fully automated HPLC, followed by mathematical treatment on chromatograms, for measuring cholesterol concentrations of major lipoproteins and their subclasses in 62 male patients (45 with CAD and 17 controls without CAD) who underwent cardiac catheterization. RESULTS: For major lipoprotein classes, the patient group had a significantly (P<0.05) higher LDL-cholesterol (LDL-C) and lower HDL-cholesterol (HDL-C), but no difference in VLDL-cholesterol (VLDL-C) concentrations. For lipoprotein subclasses, the patient group had a significantly higher small VLDL-C (mean particle diameter of 31.3 nm, P<0.001), small LDL-C (23.0 nm, P<0.05), and very small LDL-C (16.7-20.7 nm, P<0.001), but a significantly lower large HDL-C (12.1 nm, P<0.001) concentrations. Combined variables of "small VLDL-C+small LDL-C+very small LDL-C-large HDL-C" differentiated the patient from the control group more clearly than single-subclass measurements or calculated traditional lipid markers. CONCLUSIONS: These results suggest the usefulness of multiple and simultaneous subclass analysis of proatherogenic and antiatherogenic lipoproteins and indicate that HPLC and its component analysis can be used for easy detection and evaluation of abnormal distribution of lipoprotein subclasses associated with CAD.     

Hypertriglyceridemia in pregnancy does not contribute to the enhanced formation of remnant lipoprotein particles

BACKGROUND: During pregnancy, serum cholesterol (TC) and triglyceride (TG) concentrations are known to increase significantly, but whether remnant lipoprotein particles (RLP) increase has not been shown. METHODS: We compared lipid profiles in 22 healthy pregnant women to 31 healthy nonpregnant women and 24 patients with diabetes mellitus (DM), by measuring cholesterol and TG concentrations in major lipoprotein classes after HPLC separation and immunoseparation of RLP. RESULTS: Serum TG and TC concentrations were significantly higher in the pregnant group than in the healthy control or DM groups. Cholesterol and TG concentrations of all major lipoprotein classes were also significantly higher in the pregnant group than the control and DM groups, except for VLDL-TG in the DM group. RLP-C and RLP-TG concentrations were significantly higher in the pregnant group (8.7 mg/dl and 25.4 mg/dl on average) than the control group (2.4 mg/dl and 5.7 mg/dl), but not different from the DM group (8.8 mg/dl and 24.1 mg/dl). RLP-TG to RLP-C ratios were similar among the three groups and correlated with the VLDL-TG to VLDL-C ratio. The percentages of RLP-C in VLDL-C and RLP-TG in VLDL-TG in the pregnant group (15.9% and 15.7%) were significantly lower than those of the control (48.5% and 35.6%) and the DM (32.7% and 20.8%) groups. CONCLUSIONS: RLP increased moderately during gestation with the increase in VLDL and TG, but the percentage of RLP in VLDL was significantly lower in the pregnant women compared with the control and DM patients, suggesting that hypertriglyceridemia in pregnancy is not primarily due to an increase in the atherogenic RLP.     

Effects of bezafibrate on HDL2/HDL3 ratio in postmenopausal hypertriglyceridemic women

The short-term effects of bezafibrate on high-density lipoprotein cholesterol quality and triglyceride-rich lipoprotein metabolism in 186 postmenopausal hypertriglyceridemic women were investigated. Patients were randomized to an untreated group and to bezafibrate (400 mg/d) for 6 months. Fasting lipid concentrations, high-density lipoprotein 2, and high-density lipoprotein 3 levels were measured at baseline and after 3 and 6 months. At 3 months, bezafibrate had significantly decreased mean serum triglycerides and remnant-like particle cholesterol levels (105.7 +/- 43.4 mg/dL and 5.33 +/- 2.1 mg/dL, P < .001, respectively) from baseline values (232.5 +/- 63.9 mg/dL and 9.69 +/- 3.8 mg/dL, respectively). It also maintained lower total cholesterol, low-density lipoprotein cholesterol, triglycerides, and remnant-like particle cholesterol concentrations to 6 months. After 3 months, it significantly increased mean serum high-density lipoprotein cholesterol (55.1 +/- 14.7 vs 64.8 +/- 12.1 mg/dL; P < .0001) and maintained higher high-density lipoprotein cholesterol at 6 months. The high-density lipoprotein 2-high-density lipoprotein 3 ratio was decreased after 3 months of therapy with bezafibrate (2.13 +/- 0.68) from the baseline (2.42 +/- 0.71) (P < .01).     

Lipoprotein profiles in plasma and interstitial fluid analyzed with an automated gel-filtration system

BACKGROUND: High-quality methods for lipoprotein characterization are warranted in studies on various metabolic diseases. MATERIALS AND METHODS: An automated system for size-exclusion chromatography (SEC) of lipoproteins using commercially available components is described. Cholesterol or triglyceride content in separated lipoproteins from plasma and interstitial fluid (IF) was continuously determined on-line using microlitre sample volumes. RESULTS: The lipoprotein assay showed a good concordance with the classic ultra-centrifugation/precipitation technique using fresh or frozen samples. Determination of lipoproteins in IF obtained from vacuum-induced skin blisters from 18 healthy subjects revealed that very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL) cholesterol levels were 18%, 19% and 25%, respectively, of concomitant plasma concentrations. The size-exclusion chromatography (SEC) system also allows for triglyceride determination on-line and it could be shown that the system is advantageous for an accurate determination of triglycerides in conditions when there are high levels of glycerol, e.g. in mice and in patients with hyperglycerolaemia (pseudo-hypertriglyceridaemia). CONCLUSIONS: The described system should be of value in studies where detailed lipoprotein analysis is warranted and particularly when significant sample series with small volumes are available. Our data also suggest that there is a 4-5.5-fold concentration gradient between plasma and IF for the three major plasma lipoproteins.     

Studies on the turnover of triglyceride and esterified cholesterol in subjects with the nephrotic syndrome

Factors involved in the hyperlipidemia of nephrosis have been studied in seven patients. The turnover of triglyceride was measured in plasma very low density lipoproteins after the injection of glycerol-(14)C. The turnover of esterified cholesterol was measured in whole plasma and in very low density lipoproteins after the injection of mevalonic acid-2-(3)H.Urine protein loss was found to be significantly correlated with the plasma concentrations of triglyceride and free cholesterol, suggesting that increasing loss of protein is associated with the formation of larger lipoproteins. Lactescent plasmas were found in the subjects with the greatest protein loss.The turnover rate of triglyceride tended to be higher among subjects with higher than with lower triglyceride concentrations and was on the average higher than among six normotriglyceridemic subjects. However, there was also evidence for decreased clearance of glyceride from plasma. The hypertriglyceridemia of nephrosis appeared to reflect both increased formation of glyceride and decreased removal of glyceride from plasma.The turnover of esterified cholesterol was significantly higher in whole plasma of nephrotic subjects than in normocholesterolemic nonnephrotic patients. Esterified cholesterol turnover in very low density lipoproteins was raised in the two subjects in whom a major part of total esterified cholesterol was carried in this lipoprotein fraction.These studies were repeated in one subject after remission was induced. The cessation of urinary loss of protein was associated with reductions in the concentrations and turnover of triglyceride and esterified cholesterol.The increased turnover of plasma lipids in nephrosis may reflect the general increase in the formation of protein.     

Radioimmunoassay studies of human apolipoprotein E.

This report describes the development and first applications of a sensitive and specific double antibody radioimmunoassay for human apoplipoprotein E (apoE). ApoE was purified from the very low density lipoproteins of hypertriglyceridemic patients by heparin-agarose affinity chromatography, DEAE-cellulose chromatography, and preparative polyacrylamide gel electrophoresis. The purified apoprotein had an amino acid composition characteristic of apoE and resulted in the production of monospecific antisera when injected into rabbits. The radioimmunoassay, which was carried out in the presence of 5 mM sodium decyl sulfate, had a working range of 0.8-12 ng. The withinassay coefficient of variation was 9% and the coefficient of variation for systematic between-assay variability was 3%. Prior delipidation of samples with organic solvents did not alter their immunoreactivity. In 26 normal volunteers, the mean plasma apoE concentration was 36 +/- 13 microgram/ml. Hyperlipidemic patients (n = 68) had higher mean apoE levels. A single patient with type III hyperlipoproteinemia had a plasma apoE level of 664 microgram/ml. The plasma apoE level was independently related to plasma cholesterol and triglyceride levels in a population of 108 normal and nonchylomicronemic hyperlipidemic patients. The multiple correlation coefficient for this relationship was 0.73. Thus, variation in plasma cholesterol and triglyceride concentrations described 53% of the variation in apoE concentrations in this population. The lipoprotein distribution of apoE was investigated by agarose column chromatography and ultracentrifugation of plasma. Agarose column chromatography demonstrated that all or nearly all plasma apoE is associated with lipoproteins. In plasma from normal volunteers and hypercholesterolemic patients, apoE was found in two discrete lipoprotein classes: very low density lipoproteins and a set of lipoprotein particles with size and density characteristics similar to HDL2. In hypertriglyceridemic patients, nearly all apoE was associated with the triglyceride-rich lipoproteins.     

Lipoprotein fractionation by a precipitation method. A simple quantitative procedure.

A method is described for quantitation of the three major classes of serum lipoproteins. After precipitation of very low density lipoprotein (VLDL) using sodium dodecyl sulphate, the cholesterol and triglyceride content of this lipoprotein class is directly measured. In a second aliquot serum high density lipoprotein (HDL) lipids are measured after precipitation of VLDL and low density lipoprotein (LDL). LDL cholesterol and triglyceride contents are calculated by difference. The procedure requires 2 ml serum, and sensitivity is adequate to permit lipoprotein analyses on umbilical cord serum. Close agreement is observed between this precipitation method and preparative ultracentrifugation.     

The biochemical composition and metabolism of lipoproteins in type V hyperlipoproteinaemia.

The biochemical composition of lipoproteins in Type V hyperlipoproteinaemia was investigated with special reference to apolipoprotein-B. The in vivo metabolism of protein-labelled low density lipoprotein was also studied in five such patients (3 diabetic, 2 obese subjects). In association with pathologically elevated plasma levels of chylomicrons and very low density lipoproteins, low density lipoprotein concentration was significantly reduced. The proportions of triglyceride to apo-B and triglyceride to cholesterol were significantly increased in all lipoprotein classes, while the proportion of cholesterol to apo-B was significantly reduced. Disappearance of chylomicronaemia with treatment was associated with a prompt increase in low density lipoprotein concentration. The reduced low density lipoprotein concentration was accompanied by an accelerated fractional turnover rate, and by an absolute turnover rate which was subnormal. These results were interpreted as reduced synthesis of low density lipoprotein apoprotein and as a possible block in the conversion of very low density lipoprotein to low density lipoprotein in some Type V patients.     

Differing associations of lipid and lipoprotein disturbances with the macrovascular and microvascular complications of type 1 diabetes.

OBJECTIVE: Cardiovascular disease (CVD) is increased in patients with type 1 diabetes, but lipid and lipoprotein patterns remain favorable. In contrast, nephropathy is associated with an adverse distribution. We compared the associations and predictive power of lipid and lipoprotein disturbances with these complications. RESEARCH DESIGN AND METHODS: A nested case-control study from the EURODIAB cohort of 140 case subjects with evidence of at least one complication and 84 control subjects with no complications were analyzed. Conventional and unconventional lipid and lipoprotein fractions, including apolipoprotein (apo)-A1, lipoprotein (Lp)-A1, LpA1/A2, apoB, and LDL particle size were measured centrally. RESULTS: CVD was only associated with increased LDL cholesterol (3.6 vs. 3.0 mmol/l, P = 0.02). In contrast, albuminuria was associated with elevated cholesterol, triglyceride, LDL, and apoB and with diminished LDL particle size. No disturbances in HDL and related lipoproteins were noted. In normoalbuminuric patients, CVD was not associated with any significant changes in lipids. CVD in macroalbuminuric patients was associated with increased triglyceride level (2.37 vs. 1.07 mmol/l, P = 0.001; P = 0.02 for CVD/albuminuria interaction) and LDL cholesterol (5.4 vs. 3.3 mmol/l, P = 0.005; P = 0.004 for interaction). Independent associations were observed for total cholesterol and for LDL particle size and albuminuria. CONCLUSIONS: Abnormalities in lipid and lipoprotein disturbances are more closely related to albuminuria than to CVD in patients with type 1 diabetes. Measurement of conventional parameters provide sufficient risk information. ApoB and LDL particle size offer limited extra information. HDL metabolism remains undisturbed in the presence of complications. These changes reflect associations with glycemic control, which is the key to understanding lipid and lipoprotein disturbances.     

Multiple Changes in Apoprotein B Containing Lipoproteins after Ethanol Withdrawal in Alcoholic Men

The plasma concentrations and chemical compositions of the apolipoprotein B containing lipoproteins (VLDL, IDL and LDL) were studied in 29 male alcoholic subjects at the end of a drinking period and in 17 healthy controls. No difference was found in the concentrations of plasma total cholesterol and triglyceride between the alcoholics and the controls, whereas plasma HDL cholesterol and VLDL triglycerides were 90% and 73%, respectively, higher in the alcoholics. The VLDL cholesterol: triglyceride ratio was reduced by 32%, whereas VLDL protein:cholesterol and phospho-lipid: cholesterol ratios were increased by 36% and 46%, respectively. IDL mass and protein concentrations, and particularly the fractional cholesteryl ester content of IDL tended to be low in the alcoholics. The plasma concentrations of all the LDL components except triglycerides were reduced in the alcoholics, resulting in a lower LDL cholesterol: triglyceride ratio. During the four day abstinence, when the lipoprotein values were followed in 15 alcoholic subjects, the abnormalities in VLDL composition and LDL plasma concentrations changed towards the values of the controls. In six alcoholic subjects who volunteered for LDL kinetic studies the fractional catabolic rate for LDL particles isolated immediately after the drinking period and seven days later were the same. These studies suggest that the alterations in all the apoB containing lipoproteins may contribute to the delayed progression of atherosclerosis observed in alcohol users.     

Familial apolipoprotein AI and apolipoprotein CIII deficiency. Subclass distribution,composition, and morphology of lipoproteins in a disorder associated with premature atherosclerosis.

Lipoprotein classes isolated from the plasma of two patients with apolipoprotein AI (apo AI) and apolipoprotein CIII (apo CIII) deficiency were characterized and compared with those of healthy, age- and sex-matched controls. The plasma triglyceride values for patients 1 and 2 were 31 and 51 mg/dl, respectively, and their cholesterol values were 130 and 122 mg/dl, respectively; the patients, however, had no measurable high density lipoprotein (HDL)-cholesterol. Analytic ultracentrifugation showed that patients'' S degrees f 0-20 lipoproteins possess a single peak with S degrees f rates of 7.4 and 7.6 for patients 1 and 2, respectively, which is similar to that of the controls. The concentration of low density lipoprotein (LDL) (S degrees f 0-12) particles, although within normal range (331 and 343 mg/dl for patients 1 and 2, respectively), was 35% greater than that of controls. Intermediate density lipoproteins (IDL) and very low density lipoproteins (VLDL) (S degrees f 20-400) were extremely low in the patients. HDL in the patients had a calculated mass of 15.4 and 11.8 mg/dl for patients 1 and 2, respectively. No HDL could be detected by analytic ultracentrifugation, but polyacrylamide gradient gel electrophoresis (gge) revealed that patients possessed two major HDL subclasses: (HDL2b)gge at 11.0 nm and (HDL3b)gge at 7.8 nm. The major peak in the controls, (HDL3a)gge, was lacking in the patients. Gradient gel analysis of LDL indicated that patients'' LDL possessed two peaks: a major one at 27 nm and a minor one at 26 nm. The electron microscopic structure of patients'' lipoprotein fractions was indistinguishable from controls. Patients'' HDL were spherical and contained a cholesteryl ester core, which suggests that lecithin/cholesterol acyltransferase was functional in the absence of apo AI. The effects of postprandial lipemia (100-g fat meal) were studied in patient 1. The major changes were the appearance of a 33-nm particle in the LDL density region of 1.036-1.041 g/ml and the presence of discoidal particles (12% of total particles) in the HDL region. The latter suggests that transformation of discs to spheres may be delayed in the patient. The simultaneous deficiency of apo AI and apo CIII suggests a dual defect in lipoprotein metabolism: one in triglyceride-rich lipoproteins and the other in HDL. The absence of apo CIII may result in accelerated catabolism of triglyceride-rich particles and an increased rate of LDL formation. Additionally, absence of apo CIII would favor rapid uptake of apo E-containing remnants by liver and peripheral cells. Excess cellular cholesterol would not be removed by the reverse cholesterol transport mechanism since HDL levels are exceedingly low and thus premature atherosclerosis occurs.     

Multiple changes in apoprotein B containing lipoproteins after ethanol withdrawal in alcoholic men

The plasma concentrations and chemical compositions of the apolipoprotein B containing lipoproteins (VLDL, IDL and LDL) were studied in 29 male alcoholic subjects at the end of a drinking period and in 17 healthy controls. No difference was found in the concentrations of plasma total cholesterol and triglyceride between the alcoholics and the controls, whereas plasma HDL cholesterol and VLDL triglycerides were 90% and 73%, respectively, higher in the alcoholics. The VLDL cholesterol:triglyceride ratio was reduced by 32%, whereas VLDL protein:cholesterol and phospholipid:cholesterol ratios were increased by 36% and 46%, respectively. IDL mass and protein concentrations, and particularly the fractional cholesteryl ester content of IDL tended to be low in the alcoholics. The plasma concentrations of all the LDL components except triglycerides were reduced in the alcoholics, resulting in a lower LDL cholesterol:triglyceride ratio. During the four day abstinence, when the lipoprotein values were followed in 15 alcoholic subjects, the abnormalities in VLDL composition and LDL plasma concentrations changed towards the values of the controls. In six alcoholic subjects who volunteered for LDL kinetic studies the fractional catabolic rate for LDL particles isolated immediately after the drinking period and seven days later were the same. These studies suggest that the alterations in all the apoB containing lipoproteins may contribute to the delayed progression of atherosclerosis observed in alcohol users.     

Estrogen-induced gallstone formation in males. Relation to changes in serum and biliary lipids during hormonal treatment of prostatic carcinoma.

To assess if and by which mechanisms pharmacological estrogen treatment induces gallstone disease, we examined patients with recently diagnosed prostatic cancer randomly allocated to estrogen therapy (n = 37) or orchidectomy (n = 35). According to gallbladder ultrasonography, after 1 yr new gallstones had developed in 5 of 28 estrogen-treated patients, compared with 0 of 26 orchidectomized patients (P = 0.03). Estrogen therapy for 3 mo increased the relative concentration of cholesterol and cholesterol saturation of bile by approximately 30% (n = 10). Serum LDL cholesterol was reduced by approximately 40%, and its relative change related inversely to that of bile cholesterol (Rs = -0.77). There were no changes in biliary or serum lipids after orchidectomy (n = 9). Secretion rates of biliary lipids were measured with a duodenal perfusion technique. Patients on chronic estrogen therapy (n = 5) had approximately 40% higher biliary excretion rates of cholesterol than age-matched controls (n = 7). Phospholipid secretion was also higher, but no difference in bile acid secretion was found. We conclude that an increased hepatic secretion of cholesterol results in increased cholesterol saturation of bile and an enhanced rate of gallstone formation during estrogen treatment. The changes in bile cholesterol seem to be related to the induced changes in serum lipoprotein metabolism.     

Gemfibrozil treatment potentiates oxidative resistance of high-density lipoprotein in hypertriglyceridemic patients

BACKGROUND: Studies suggest that both oxidized low and high density lipoprotein (LDL and HDL) play a role in the pathogenesis of atherosclerosis. Gemfibrozil is widely used and is reported to increase cholesterol of LDL and HDL in hypertriglyceridemic patients. The aim of this study was to investigate the effect of gemfibrozil treatment on the oxidative status of lipoprotein particles in Fredrickson phenotype IV hypertriglyceridemic patients. METHODS: Twenty-two patients, aged 38-64 years, with fasting plasma triglyceride concentrations between 2.90 and 8.97 mmol L(-1), were recruited and were given gemfibrozil 300 mg three times daily for 12 weeks. Venous blood samples were collected before gemfibrozil treatment, after 4, 8, or 12 weeks of treatment, and 4 weeks after termination of treatment, and used to analyse the plasma lipid profile, isolate lipoproteins, and analyse the chemical composition and in vitro oxidation of lipoprotein particles. RESULTS: Gemfibrozil treatment resulted in a decrease in plasma total triglyceride levels and the triglyceride content of all lipoproteins. Plasma total cholesterol levels were decreased as a result of a decrease in very low density lipoprotein (VLDL) cholesterol levels. A slight increase in LDL cholesterol levels was observed, whereas the thiobarbituric acid-reactive substances (TBARS) of LDL were decreased and the lag and peak time of LDL to oxidation were unchanged and maximal diene production was decreased. Plasma HDL cholesterol levels, the surface-to-core ratio of HDL particles, and the resistance of HDL to oxidation were increased. CONCLUSION: The decreased TBARS and diene production of LDL, increased HDL cholesterol levels, and increased resistance of HDL to oxidation may, in part, explain why gemfibrozil treatment was found to be generally beneficial in terms of protection against coronary heart disease.     

Lipid composition and lipopolysaccharide binding capacity of lipoproteins in plasma and lymph of patients with systemic inflammatory response syndrome and multiple organ failure

BACKGROUND: Lipopolysaccharide (LPS), the major glycolipid component of Gram-negative bacterial outer membranes, is a potent endotoxin responsible for many of the directly or indirectly induced symptoms of infection. Lipoproteins (in particular, high-density lipoproteins) sequester LPS, thereby acting as a humoral detoxification mechanism. PATIENTS: Differences in the lipoprotein composition in human plasma and lymph of a control patient group (n = 5) without systemic inflammatory response syndrome (non-SIRS/MOF) and patients with SIRS and multiple organ failure (MOF, n = 9) were studied. The LPS binding capacity of the lipoproteins in SIRS/MOF and non-SIRS/MOF patients was investigated by rechallenge of the plasma and lymph with fluorescently labeled LPS ex vivo. The lipoprotein composition was analyzed using immunochemical techniques and high-performance gel permeation chromatography. RESULTS: In the non-SIRS/MOF patient group, plasma and lymph levels of apolipoprotein A-I (600 and 450 mg/L, respectively), apolipoprotein B (440 and 280 mg/L, respectively), total cholesterol (2.88 and 1.05 mM, respectively), and total triglycerides (0.67 and 0.97 mM, respectively) were observed. In the SIRS/MOF group, a decrease of apolipoprotein A-I (-55% in plasma and lymph), a decrease of apolipoprotein B (-43% in plasma and -38% in lymph), and a decrease of total cholesterol levels (-54% in plasma and -37% in lymph) were demonstrated. However, the triglyceride levels in the SIRS/MOF group showed a 30% increase in plasma and a 47% decrease in lymph compared with the non-SIRS/MOF patients. In SIRS/MOF patients, a 2.8-fold increase in plasma and a 1.8-fold increase in lymph of the LPS low-density lipoprotein/high-density lipoprotein ratio was observed, indicating that the relative LPS binding capacity of the lipoproteins in the SIRS/MOF patient group showed a trend to be shifted mainly toward low-density lipoproteins. Furthermore, in plasma and lymph of four SIRS/MOF patients, a novel cholesterol-containing high-density lipoprotein-like particle was found that barely had LPS binding capacity (<5%). CONCLUSIONS: In the SIRS/MOF patients, the changes in lipoprotein composition in lymph are a reflection of those in plasma, except for the triglyceride levels. In comparison with the non-SIRS/MOF patients, the SIRS/MOF patients show a shifted LPS binding capacity of high-density lipoproteins toward low-density lipoproteins in plasma and in lymph. Moreover, in plasma and lymph, novel cholesterol-containing particles, resembling high-density lipoprotein, were identified in the SIRS/MOF patient group.