Plasma kinetics of a cholesterol-rich emulsion in subjects with or without coronary artery disease

Identifying Metabolomic Profiles of Insulinemic Dietary Patterns

The food-based empirical dietary index for hyperinsulinemia (EDIH) score assesses the insulinemic potential of diet. This cross-sectional study evaluated associations between EDIH scores from food frequency questionnaires with c-peptide concentrations and with 448 metabolites, from fasting plasma samples, in multivariable linear regression analyses. Metabolites were measured with liquid chromatography tandem mass spectroscopy. Using a robust two-stage study design, discovery of metabolite associations was conducted among 1109 Women's Health Initiative (WHI) Hormone Therapy (HT) trial participants and results replicated in an independent dataset of 810 WHI Observational Study (OS) participants. In both discovery and replication datasets, statistical significance was based on the false-discovery rate adjusted P < 0.05. In the multivariable-adjusted analyses, EDIH was significantly associated with c-peptide concentrations among 919 women (HT & OS) with c-peptide data. On average, c-peptide concentrations were 18% higher (95% CI, 6%, 32%; P-trend < 0.0001) in EDIH quintile 5 compared to quintile 1. Twenty-six metabolites were significantly associated with EDIH in the discovery dataset, and 19 of these were replicated in the validation dataset. Nine metabolites were found to decrease in abundance with increasing EDIH scores and included: C14:0 CE, C16:1 CE, C18:1 CE, C18:3 CE, C20:3 CE, C20:5 CE, C36:1 PS plasmalogen, trigonelline, and eicosapentanoate, whereas the 10 metabolites observed to increase with increasing EDIH scores were: C18:2 SM, C36:3 DAG, C36:4 DAG-A, C51:3 TAG, C52:3 TAG, C52:4, TAG, C54:3 TAG, C54:4 TAG, C54:6 TAG, and C10:2 carnitine. Cholesteryl esters, phospholipids, acylglycerols, and acylcarnitines may constitute circulating metabolites that are associated with insulinemic dietary patterns.

Esterification of HDL-cholesterol is Decreased in Diabetes Mellitus and CAD and Enhanced Following Treatment with Statins

Background:

The main goal of using statins is to reduce the level of plasma cholesterol, meanwhile they have a wide spectrum of actions.

Objectives:

To identify the effect of statins on fractional cholesterol esterification (FCE) as well as the complete profile of lipids and (apo)lipoproteins.

Design and methods:

In an age and sex matched case-control study, 400 subjects who were referred for coronary angiography were divided into two groups according using statins.

Results:

Total cholesterol was decreased significantly following treatment with statins (165.6 ± 38.0 mg/dL vs. 205.3 ± 48.4, p≤0.001). About 90% of the reduction was occurred in nonHDL and 10% in HDL fraction. Reduction of nonHDL cholesterol (125.2 ± 35.2 mg/dL vs. 162.8 ± 45.2, p≤0.001) occurred on both unesterified (52.4 ± 21.5 mg/dL vs. 65.2 ± 25.5, p≤0.001) and esterified cholesterol (74.7 ± 27.3 mg/dL vs. 96.6 ± 34.1, p≤0.001). But the decrease in HDL cholesterol (40.4 ± 10.0 mg/dL vs. 42.3 ± 9.9, p≤0.079) happened exclusively in unesterified fraction (10.9 ± 3.4 vs. 15.2 ± 5.1, p≤0.001) and was counterbalanced with a significant increase in esterified portion (29.5 ± 8.2 mg/dL vs. 27.2 ± 9.5, p≤0.020). The ratio of esterified- per total- cholesterol in HDL was 67.5 ± 8.1% in the control group and was decreased to 58.0 ± 14.9% (p≤0.01) in diabetes and CAD and increased to 73.5 ± 6.9 (p≤0.01) after using statins.

Conclusions:

The results suggest that the percent of esterified cholesterol in HDL fraction is decreased in diabetes and CAD patients and increased by using statins.

The Ratio of Unesterified/esterified Cholesterol is the Major Determinant of Atherogenicity of Lipoprotein Fractions

Background

The hypothesis is proposed that the atherogenicity of lipoporotein fractions is correlated with the content of unesterified cholesterol.

Objectives

To evaluate the role and prognostic values of unesterified and esterified cholesterol in lipoprotein fractions for coronary artery disease (CAD).

Design and methods

The study population consisted of 400 patients who were divided to CAD controls and cases according to the data of coronary angiography. Fractional cholesterol esterification (FCE) as well as the complete profile of lipids and (apo)lipoproteins were determined.

Results

Total cholesterol was increased significantly in CAD patients (196.3 ± 52.3 mg/dL vs. 185.7 ± 48.0, p≤ 0.049) and the increment occurred totally in unesterified portion (77.2 ± 28.4 mg/dL vs. 71.1 ± 24.4, p≤ 0.031). HDL cholesterol showed a significant decrease in CAD group (39.9 ± 9.5 mg/dL vs. 44.6 ± 10.5, p≤ 0.001), but the decrement occurred wholly in the esterified portion (26.2 ± 9.2 mg/dL vs. 31.1 ± 8.1, p≤ 0.001). NonHDL cholesterol was increased significantly in CAD group (156.8 ± 48.3 mg/dL vs. 140.3 ± 43.6, p≤ 0.001), and the changes occurred in both un- and esterified portions. FCE in HDL was diminished significantly in CAD patients (64.8 ± 13.9% vs. 69.3 ± 7.9, p≤ 0.01). In multivariate logistic regression analysis, unesterified cholesterol in NonHDL (UeNonHDLc) and esterified cholesterol in HDL (EsHDLc) excluded total cholesterol and HDLc respectively from the regression equation. In ROC analysis, the ratio of UeNonHDLc/EsHDLc was the strongest predictor for CAD among cholesterol subfractions.

Conclusions

The results confirm that UeNonHDLc is atherogenic and EsHDLc is antiatherogenic and are independent risk factors for CAD.

Atherogenic Impact of Lecithin-Cholesterol Acyltransferase and Its Relation to Cholesterol Esterification Rate in HDL (FERHDL) and AIP [log(TG/HDL-C)] Biomarkers: The Butterfly Effect?

The atherogenic impact and functional capacity of LCAT was studied and discussed over a half century. This review aims to clarify the key points that may affect the final decision on whether LCAT is an anti-atherogenic or atherogenic factor. There are three main processes involving the efflux of free cholesterol from peripheral cells, LCAT action in intravascular pool where cholesterol esterification rate is under the control of HDL, LDL and VLDL subpopulations, and finally the destination of newly produced cholesteryl esters either to the catabolism in liver or to a futile cycle with apoB lipoproteins. The functionality of LCAT substantially depends on its mass together with the composition of the phospholipid bilayer as well as the saturation and the length of fatty acyls and other effectors about which we know yet nothing. Over the years, LCAT puzzle has been significantly supplemented but yet not so satisfactory as to enable how to manipulate LCAT in order to prevent cardiometabolic events. It reminds the butterfly effect when only a moderate change in the process of transformation free cholesterol to cholesteryl esters may cause a crucial turn in the intended target. On the other hand, two biomarkers – FERHDL (fractional esterification rate in HDL) and AIP [log(TG/HDL-C)] can offer a benefit to identify the risk of cardiovascular disease (CVD). They both reflect the rate of cholesterol esterification by LCAT and the composition of lipoprotein subpopulations that controls this rate. In clinical practice, AIP can be calculated from the routine lipid profile with help of AIP calculator www.biomed.cas.cz/fgu/aip/calculator.php.

Alterations in lipid transfers to HDL associated with the presence of coronary artery disease in patients with type 2 diabetes mellitus

Background

We previously showed that unesterified-cholesterol transfer to high-density lipoprotein (HDL), a crucial step in cholesterol esterification and role in reverse cholesterol transport, was diminished in non-diabetic patients with coronary artery disease (CAD). The aim was to investigate whether, in patients with type 2 diabetes mellitus (T2DM), the occurrence of CAD was also associated with alterations in lipid transfers and other parameters of plasma lipid metabolism.

Methods

Seventy-nine T2DM with CAD and 76 T2DM without CAD, confirmed by cineangiography, paired for sex, age (40–80 years), BMI and without statin use, were studied. In vitro transfer of four lipids to HDL was performed by incubating plasma of each patient with a donor emulsion containing radioactive lipids during 1 h at 37 °C. Lipids transferred to HDL were measured after chemical precipitation of non-HDL fractions and the emulsion. Results are expressed as % of total radioactivity of each lipid in HDL.

Results

In T2DM + CAD, LDL-cholesterol and apo B were higher than in T2DM. T2DM + CAD also showed diminished transfer to HDL of unesterified cholesterol (T2DM + CAD = 7.6 ± 1.2; T2DM = 8.2 ± 1.5 %, p < 0.01) and of cholesteryl-esters (4.0 ± 0.6 vs 4.3 ± 0.7, p < 0.01). Unesterified cholesterol in the non-HDL serum fraction was higher in T2DM + CAD (0.93 ± 0.20 vs 0.85 ± 0.15, p = 0.02) and CETP concentration was diminished (2.1 ± 1.0 vs 2.5 ± 1.1, p = 0.02). Lecithin-cholesterol acyltransferase activity, HDL size and lipid composition were equal.

Conclusion

Reduction in T2DM + CAD of cholesterol transfer to HDL may impair cholesterol esterification and reverse cholesterol transport and altogether with simultaneous increased plasma unesterified cholesterol may facilitate CAD development in T2DM.

Transfer of lipids to high-density lipoprotein (HDL) is altered in patients with familial hypercholesterolemia

OBJECTIVE

In familial hypercholesterolemia (FH), the metabolism and anti-atherogenic functions of HDL can be affected by the continuous interactions with excess LDL amounts. Here, lipid transfers to HDL, an important step for HDL intravascular metabolism and for HDL role in reverse cholesterol transport (RCT) were investigated in FH patients.

METHODS

Seventy-one FH patients (39 ± 15 years, LDL-cholesterol=274 ± 101; HDL-cholesterol=50 ± 14 mg/dl) and 66 normolipidemic subjects (NL) (38 ± 11 years, LDL-cholesterol=105 ± 27; HDL-cholesterol=52 ± 12 mg/dl) were studied. In vitro, lipid transfers were evaluated by incubation of plasma samples (37°C, 1h) with a donor lipid nanoemulsion labeled with 3H-triglycerides (TG) and 14C-unesterified cholesterol (UC) or with 3H-cholesteryl ester (EC) and 14C-phospholipids (PL). Radioactivity was counted at the HDL fraction after chemical precipitation of apolipoprotein (apo) B-containing lipoproteins and the nanoemulsion. Data are % of total radioactivity measured in the HDL fraction.

RESULTS

Transfer of UC to HDL was lower in FH than in NL (5.6 ± 2.1 vs 6.7 ± 2.0%, p=0.0005) whereas TG (5.5 ± 3.1 vs 3.7 ± 0.9%, p=0.018) and PL (20.9 ± 4.6 vs 18.2 ± 3.7 %, p=0.023) transfers were higher in FH. EC transfer was equal. By multivariate analysis, transfers of all four lipids correlated with HDL-cholesterol and with apo A-I.

CONCLUSION

FH elicited marked changes in three of the four tested lipid transfers to HDL. The entry of UC into HDL for subsequent esterification is an important driving force for RCT and reduction of UC transfer to HDL was previously associated to precocious coronary heart disease. Therefore, in FH, HDL functions can be lessened, which can also contribute to atherogenesis.

Lipoprotein metabolism in patients with type 1 diabetes under intensive insulin treatment

Background

Type 1 diabetes (T1DM) is frequently accompanied by dyslipidemia related with insulin-dependent steps of the intravascular lipoprotein metabolism. T1DM dyslipidemia may predispose to precocious cardiovascular disease and the lipid status in T1DM under intensive insulin treatment has not been sufficiently explored. The aim was to investigate the plasma lipids and the metabolism of LDL and HDL in insulin-treated T1DM patients with high glycemic levels.

Methods

Sixteen male patients with T1DM (26 ± 7 yrs) with glycated hemoglobin >7%, and 15 control subjects (28 ± 6 yrs) were injected with a lipid nanoemulsion (LDE) resembling LDL and labeled with ¹⁴C-cholesteryl ester and ³H-free-cholesterol for determination of fractional clearance rates (FCR, in h^-1) and cholesterol esterification kinetics. Transfer of labeled lipids from LDE to HDL was assayed in vitro.

Results

LDL-cholesterol (83 ± 15 vs 100 ± 29 mg/dl, p=0.08) tended to be lower in T1DM than in controls; HDL-cholesterol and triglycerides were equal. LDE marker ¹⁴C-cholesteryl ester was removed faster from plasma in T1DM patients than in controls (FCR=0.059 ± 0.022 vs 0.039 ± 0.022h-1, p=0.019), which may account for their lower LDL-cholesterol levels. Cholesterol esterification kinetics and transfer of non-esterified and esterified cholesterol, phospholipids and triglycerides from LDE to HDL were also equal.

Conclusion

T1DM patients under intensive insulin treatment but with poor glycemic control had lower LDL-cholesterol with higher LDE plasma clearance, indicating that LDL plasma removal was even more efficient than in controls. Furthermore, HDL-cholesterol and triglycerides, cholesterol esterification and transfer of lipids to HDL, an important step in reverse cholesterol transport, were all normal. Coexistence of high glycemia levels with normal intravascular lipid metabolism may be related to differences in exogenous insulin bioavailabity and different insulin mechanisms of action on glucose and lipids. Those findings may have important implications for prevention of macrovascular disease by intensive insulin treatment.

Removal from the plasma of the free and esterified forms of cholesterol and transfer of lipids to HDL in type 2 diabetes mellitus patients

BACKGROUND

The aim was to investigate new markers for type 2 diabetes (T2DM) dyslipidemia related with LDL and HDL metabolism. Removal from plasma of free and esterified cholesterol transported in LDL and the transfer of lipids to HDL are important aspects of the lipoprotein intravascular metabolism. The plasma kinetics (fractional clearance rate, FCR) and transfers of lipids to HDL were explored in T2DM patients and controls, using as tool a nanoemulsion that mimics LDL lipid structure (LDE).

RESULTS

14C- cholesteryl ester FCR of the nanoemulsion was greater in T2DM than in controls (0.07 ± 0.02 vs. 0.05 ± 0.01 h-1, p = 0.02) indicating that LDE was removed faster, but FCR 3 H- cholesterol was equal in both groups. Esterification rates of LDE free-cholesterol were equal. Cholesteryl ester and triglyceride transfer from LDE to HDL was greater in T2DM (4.2 ± 0.8 vs. 3.5 ± 0.7%, p = 0.03 and 6.8 ± 1.6% vs. 5.0 ± 1.1, p = 0.03, respectively). Phospholipid and free cholesterol transfers were not different.

CONCLUSIONS

The kinetics of free and esterified cholesterol tended to be independent in T2DM patients and the lipid transfers to HDL were also disturbed. These novel findings may be related with pathophysiological mechanisms of diabetic macrovascular disease.

Plasma kinetics of an LDL-like nanoemulsion and lipid transfer to HDL in subjects with glucose intolerance

OBJECTIVE

Glucose intolerance is frequently associated with an altered plasma lipid profile and increased cardiovascular disease risk. Nonetheless, lipid metabolism is scarcely studied in normolipidemic glucose-intolerant patients. The aim of this study was to investigate whether important lipid metabolic parameters, such as the kinetics of LDL free and esterified cholesterol and the transfer of lipids to HDL, are altered in glucose-intolerant patients with normal plasma lipids.

METHODS

Fourteen glucose-intolerant patients and 15 control patients were studied; none of the patients had cardiovascular disease manifestations, and they were paired for age, sex, race and co-morbidities. A nanoemulsion resembling a LDL lipid composition (LDE) labeled with 14C-cholesteryl ester and ³H-free cholesterol was intravenously injected, and blood samples were collected over a 24-h period to determine the fractional clearance rate of the labels by compartmental analysis. The transfer of free and esterified cholesterol, triglycerides and phospholipids from the LDE to HDL was measured by the incubation of the LDE with plasma and radioactivity counting of the supernatant after chemical precipitation of non-HDL fractions.

RESULTS

The levels of LDL, non-HDL and HDL cholesterol, triglycerides, apo A1 and apo B were equal in both groups. The 14C-esterified cholesterol fractional clearance rate was not different between glucose-intolerant and control patients, but the ³H-free-cholesterol fractional clearance rate was greater in glucose-intolerant patients than in control patients. The lipid transfer to HDL was equal in both groups.

CONCLUSION

In these glucose-intolerant patients with normal plasma lipids, a faster removal of LDE free cholesterol was the only lipid metabolic alteration detected in our study. This finding suggests that the dissociation of free cholesterol from lipoprotein particles occurs in normolipidemic glucose intolerance and may participate in atherogenic signaling.

Resistance training changes LDL metabolism in normolipidemic subjects: a study with a nanoemulsion mimetic of LDL

OBJECTIVE

To evaluate the effects of resistance training (RT) on the metabolism of an LDL-like nanoemulsion and on lipid transfer to HDL, an important step of HDL metabolism.

METHODS

LDL-like nanoemulsion plasma kinetics was studied in 15 healthy men under regular RT for 1-4 years (age = 25 ± 5 years, VO(2)peak = 50 ± 6 mL/kg/min) and in 15 healthy sedentary men (28 ± 7 years, VO(2)peak = 35 ± 9 mL/kg/min). LDL-like nanoemulsion labeled with (14)C-cholesteryl-ester and (3)H-free-cholesterol was injected intravenously, plasma samples were collected over 24-h to determine decay curves and fractional clearance rates (FCR). Lipid transfer to HDL was determined in vitro by incubating of plasma samples with nanoemulsions (lipid donors) labeled with radioactive free-cholesterol, cholesteryl-ester, triacylglycerols and phospholipids. HDL size, paraoxonase-1 activity and oxidized LDL levels were also determined.

RESULTS

The two groups showed similar LDL and HDL-cholesterol and triacylglycerols, but oxidized LDL was lower in RT (30 ± 9 vs. 61 ± 19 U/L, p = 0.0005). In RT, the nanoemulsion (14)C-cholesteryl-ester was removed twice as fast than in sedentary individuals (FCR: 0.068 ± 0.023 vs. 0.037 ± 0.028, p = 0.002), as well as (3)H-free-cholesterol (0.041 ± 0.025 vs. 0.022 ± 0.023, p = 0.04). While both nanoemulsion labels were removed at the same rate in sedentary individuals, RT (3)H-free-cholesterol was removed slower than (14)C-cholesteryl-ester (p = 0.005). HDL size, paraoxonase 1 and the transfer rates to HDL of the four lipids were the same in both groups.

CONCLUSIONS

RT accelerated the clearance of LDL-like nanoemulsion, which probably accounts for the oxidized LDL levels reduction in RT. RT also changed the balance of free and esterified cholesterol FCR's. However, RT had no effect on HDL metabolism related parameters.

Impact of high cholesterol intake on tissue cholesterol content and lipid transfers to high-density lipoprotein

OBJECTIVE

Esterified cholesterol is the storage form of cholesterol in the organism. High-density lipoprotein (HDL), where free cholesterol is transferred from other lipoproteins and tissues, is the main esterification site in plasma. The aim of this study was to investigate how high cholesterol intake changes free/esterified ratios of cholesterol in the plasma, aorta, liver and lipid transfers to HDL.

METHODS

Twenty male Golden Syrian hamsters fed 0.5% cholesterol for 15 wk and 19 controls without cholesterol feeding were sacrificed to determine serum lipids, transfer proteins (cholesteryl ester transfer protein and phospholipid transfer protein), and amount of free and esterified cholesterol in the aorta and liver. In vitro transfer of radioactive free and esterified cholesterol, phospholipids, and triacylglycerols to HDL was performed by incubating whole plasma with an artificial nanoemulsion used as a lipid donor and measuring radioactivity in the HDL fraction after chemical precipitation of non-HDL fractions and of the nanoemulsion.

RESULTS

Compared with controls, cholesterol-fed animals showed a 137% increase in non-HDL plasma fraction and a 61% increase in HDL (P < 0.001). The esterified/free cholesterol ratio in non-HDL and HDL fractions did not change. In the aorta, free cholesterol increased 55% and the esterified/free ratio (0.2) decreased. Cholesterol accumulation in the liver was several-fold greater and esterified/free increased (1.3). Cholesterol feeding pronouncedly increased the transfer of free and esterified cholesterol, phospholipids, and triacylglycerols to HDL and cholesteryl ester transfer protein and phospholipid transfer protein activities.

CONCLUSIONS

Free cholesterol is cytotoxic and less stable than esterified cholesterol, and the present data on how the organism responds to high cholesterol intake with respect to esterified/free ratios in the plasma, aorta, liver, and lipid transfers to HDL may have physiopathologic implications.

Exercise training accelerates the removal from plasma of LDL-like nanoemulsion in moderately hypercholesterolemic subjects

OBJECTIVE

Exercise training improves plasma lipid profile and diminishes risk of coronary heart disease. Previously, we showed that training increases LDL plasma clearance, as tested by an artificial LDL-like nanoemulsion method, presumably by increasing LDL receptor activity. In this study, we investigated whether training could also improve LDL clearance in hypercholesterolemic subjects (HCh) that are exposed to increased risk of cardiovascular events.

METHODS

Twenty sedentary HCh and 20 normolipidemic (NL) sedentary volunteers were divided into four groups: 12 HCh submitted to 4-month training program, 8 HCh with no exercise program, 12 NL submitted to 4-month training and 8 NL with no exercise program. An LDL-like nanoemulsion labeled with (14)C-cholesteryl ester was injected intravenously into all subjects and plasma samples were collected during 24 h after injection to determine the fractional clearance rate (FCR, in h(-1)) by compartmental analysis. The study was performed on the first and on the last day of the 4-month study period.

RESULTS

In both, trained HCh and NL groups, training increased nanoemulsion FCR by 36% (0.0443+/-0.0126; 0.0602+/-0.0187, p=0.0187 and 0.0503+/-0.0203; 0.0686+/-0.0216, p=0.0827, respectively). After training, LDL cholesterol diminished in both HCh and NL groups. In HCh, but not in NL group, LDL susceptibility to oxidation decreased, but oxidized LDL was unchanged. In both non-trained groups FCR was the same for the last and the 4-month previous evaluation.

CONCLUSION

In HCh, exercise training increased the removal of LDL as tested by the nanoemulsion, and this probably accounted for decreased LDL cholesterol and diminished LDL susceptibility to oxidation.

Enhanced removal from the plasma of LDL-like nanoemulsion cholesteryl ester in trained men compared with sedentary healthy men

The objective of this study was to evaluate the effects of exercise training on plasma removal of a cholesterol-rich nanoemulsion (LDE) that mimics low-density lipoprotein (LDL) lipid structure and binds to LDL receptors. LDE-derived cholesteryl ester plasma kinetics was studied in 24 exercise-trained and 20 sedentary male subjects. LDE labeled with [14C]cholesteryl ester was injected intravenously, and plasma samples were collected over a 24-h period to determine radioisotope decay curves. LDL cholesterol concentration was similar in both groups. Fractional clearance rate (FCR) of the nanoemulsion label was greater in the exercise-trained group compared with the sedentary group (0.138 ± 0.152 and 0.0261 ± 0.023 h−1, respectively). A positive correlation was found ( r = 0.60, P < 0.01) between FCR and peak O2consumption in trained subjects. Circulating oxidized LDL levels were lower in trained subjects compared with the sedentary group (9.0 ± 2.0 and 16.0 ± 3.0 mU/l). LDE was also injected into control and LDL receptor gene knockout mice submitted and not submitted to training. Muscle LDE uptake percentage was increased in the trained mice compared with the untrained mice (1.1 ± 0.8 and 0.2 ± 0.1, respectively, P < 0.0001) in the control group but not in the knockout animals, indicating that the LDL receptor is involved in the increased uptake elicited by exercise. These results show that exercise training increases LDE plasma removal, which in turn suggests that it also increases LDL receptors or LDL receptor activity.

Chloroquine increases low-density lipoprotein removal from plasma in systemic lupus patients

Low-density lipoprotein (LDL) pathway in systemic lupus erythematosus (SLE) patients taking chloroquine diphosphate (CDP) was evaluated through the kinetic behavior of a radioactive cholesterol-rich nanoemulsion (LDE) that resembles the LDL lipidic structure. LDE was labeled with (14)C-cholesteryl ester ((14)C-CE), then IV injected in inactive female SLE patients: 10 taking CDP (CDP), 10 without therapy (NO THERAPY); and 10 normal subjects (CONTROL). Groups were age-matched and followed rigorous selection criteria of conditions that interfere in the lipid profile. Blood samples were collected in pre-established intervals after infusion for radioactivity measurement. Fasting lipoproteins were determined in the beginning of kinetic studies. Fractional clearance rate (FCR) of (14)C-CE was significantly different in the three groups (P = 0.03). In fact, a greater FCR of (14)C-CE was observed in CDP compared to NO THERAPY (0.076 +/- 0.037 versus 0.046 +/- 0.021 h(-1); P < 0.05) and to CONTROL (0.0516 +/- 0.0125 h(-1); P < 0.05). Accordingly, a significant lower total and LDL cholesterol were observed in CDP (156 +/- 16 and 88 +/- 16 mg/dl) compared to NO THERAPY (174 +/- 15 and 108 +/- 17 mg/dl; P < 0.05) and to CONTROL (200 +/- 24 and 118 +/- 23 mg/dl; P < 0.05). In contrast, no difference in (FCR) of (14)C-CE of NO THERAPY and CONTROL groups was observed. This is the first in vivo demonstration that LDE removal by LDL receptor from plasma is increased in SLE patients taking CDP with a consequent beneficial decrease in LDL-c levels.

Deposition of free cholesterol in the blood vessels of patients with coronary artery disease: a possible novel mechanism for atherogenesis

A cholesterol-rich nanoemulsion (LDE) that mimics the composition of low-density lipoprotein (LDL) acquires apoE in the plasma and is taken-up by the cells by LDL receptors. In this study, to verify whether free cholesterol (FC) and the cholesteryl ester (CE) components of LDL are taken-up differently by the vessels. LDE labeled with (3)H-cholesterol and (14)C-cholesteryl oleate was injected into 20 coronary artery disease patients 24 h before a scheduled myocardial coronary artery bypass grafting. The plasma kinetics of both radiolabels was determined from plasma samples collected over 24 h, and fragments of vessels discarded during surgery were collected and analyzed for radioactivity. LDE FC was removed faster than CE. The radioactive counting of LDE CE was greater than that of LDE FC in the blood, but the uptake of FC was markedly greater than that of CE in all fragments: fivefold greater in the aorta (p = 0.04), fourfold greater in the internal thoracic artery (p = 0.03), tenfold greater in the saphenous vein (p = 0.01) and threefold in the radial artery (p = 0.05). In conclusion, the greater removal from plasma of FC compared with CE and the remarkably greater vessel tissue uptake of FC compared with CE suggests that, in the plasma, FC dissociates from the nanoemulsion particles and precipitates in the vessels. Considering LDE as an artificial nanoemulsion model for LDL, our results suggest that dissociation of FC from lipoprotein particles and deposition in the vessel wall may play a role as an independent mechanism in atherogenesis.

High cholesterol intake modifies chylomicron metabolism in normolipidemic young men

Whether the consumption of egg yolk, which has a very high cholesterol content without excess saturated fats, has deleterious effects on lipid metabolism is controversial. Absorbed dietary cholesterol enters the bloodstream as chylomicrons, but the effects of regular consumption of large amounts of cholesterol on the metabolism of this lipoprotein have not been explored even though the accumulation of chylomicron remnants is associated with coronary artery disease (CAD). We investigated the effects of high dietary cholesterol on chylomicron metabolism in normolipidemic, healthy young men. The plasma kinetics of a chylomicron-like emulsion, doubly-labeled with 14C-cholesteryl ester (14C-CE) and 3H-triolein (3H-TG) were assessed in 25 men (17-22 y old, BMI 24.1 +/- 3.4 kg/m2). One group (n = 13) consumed 174 +/- 41 mg cholesterol/d and no egg yolk. The other group (n = 12) consumed 3 whole eggs/d for a total cholesterol intake of 804 +/- 40 mg/d. The nutritional composition of diets was the same for both groups, including total lipids and saturated fat, which comprised 25 and 7%, respectively, of energy intake. Serum LDL and HDL cholesterol and apoprotein B concentrations were higher in the group consuming the high-cholesterol diet (P < 0.05), but serum triacylglycerol, apo AI, and lipoprotein (a) did not differ between the 2 groups. The fractional clearance rate (FCR) of the 14C-CE emulsion, obtained by compartmental analysis, was 52% slower in the high-cholesterol than in the low-cholesterol group (P < 0.001); the 3H-TG FCR did not differ between the groups. Finally, we concluded that high cholesterol intakes increase the residence time of chylomicron remnants, as indicated by the 14C-CE kinetics, which may have undesirable effects related to the development of CAD.

Plasma kinetics of a cholesterol-rich microemulsion (LDE) in patients with Hodgkin's and non-Hodgkin's lymphoma and a preliminary study on the toxicity of etoposide associated with LDE

BACKGROUND

Neoplastic diseases are often associated with low plasma low-density lipoprotein (LDL) cholesterol and diminished LDL clearance due to upregulation in cancer cells of the receptors that internalize the lipoprotein. Thus, it is possible to use LDL or cholesterol-rich microemulsions (LDE) that bind to LDL receptors as carriers of antineoplastic agents to concentrate those drugs into cancer tissues. Our aim was to determine whether LDL cholesterol concentration plus LDE increased clearance occur in lymphomas.

PATIENTS AND METHODS

The LDE labeled with [(3) H]-cholesteryl oleate was injected into four Hodgkin's and 12 non-Hodgkin's lymphoma patients and into 16 healthy control subjects and the LDE plasma residence time (RT) was determined from sequential plasma samples. Two volunteers with relapsed/refractory lymphoma were treated with 300 mg/m(2) body surface etoposide associated with LDE in six cycles at 3-week intervals.

RESULTS

The LDL cholesterol was lower in lymphoma patients than in controls (94+/-52 and 115+/-16 mg/dL, p=0.0362, respectively). The LDE RT was 49% smaller in lymphoma patients than in controls (RT=21.9 and 45.7 h; p=0.0134), with positive correlation between RT and LDL cholesterol. LDE-etoposide showed no considerable toxicity in all cycles in the two treated patients and the disease remained stable during the treatment.

CONCLUSIONS

Our results suggest that lymphomas overexpress LDL receptors that make room for using LDE as drug-targeting vehicle and that the LDE-etoposide preparation is suitable for patient use.

Plasma kinetics of free and esterified cholesterol in familial hypercholesterolemia: Effects of simvastatin

The objective of this study was to evaluate the kinetics of both free and esterified forms of cholesterol contained in a emulsion that binds to LDL receptors (LDE) in subjects with heterozygous familial hypercholesterolemia (FH), and the same subjects under the effects of high-dose simvastatin treatment, as compared with a control normolipidemic group (NL). Twenty-one FH patients (44.0 +/- 13.0 yr, 12 females, LDL cholesterol levels 6.93 +/- 1.60 mmol/L) and 22 normolipidemic patients (44.0 +/- 15.0, 10 females, LDL cholesterol levels 3.15 +/- 0.62 mmol/L) were injected intravenously with 14C-cholesteryl ester and 3H-cholesterol. FH patients were also evaluated after 2 mon of 40 or 80 mg/d simvastatin treatment, and plasma samples were collected over 24 h to determine the residence time (RT, in h) of both LDE labels, expressed as the median (25%; 75%). The RT of both 14C-cholesteryl ester and 3H-cholesterol were greater in FH than in NL [FH: 36.0 (20.5; 1191.0), NL: 17.0 (12.0-62.5), P = 0.015; and FH: 52.0 (30.0; 1515.0); NL 20.5 (14.0-30.0) P < 0.0001]. Treatment reduced LDL cholesterol by 36% (P < 0.0001), RT of 14C-cholesteryl ester by 49% (P = 0.0029 vs. baseline), and 3H-cholesterol RT by 44% (P = 0.019 vs. baseline). After treatment, the RT values of 14C-cholesteryl ester in the FH group approached the NL values (P = 0.58), but the RT of 3H-cholesterol was still greater than those for the NL group (P = 0.01). The removal of LDE cholesteryl esters and free cholesterol was delayed in FH patients. Treatment with a high dose of simvastatin normalized the removal of cholesterol esters but not the removal of free cholesterol.

Effects in post-menopausal women of transdermal estrogen associated with progestin upon the removal from the plasma of a microemulsion that resembles low-density lipoprotein (LDL)

OBJECTIVE

To evaluate the effects of transdermal estradiol and medroxyprogesterone acetate (MPA) treatment on the removal from the plasma of a cholesterol-rich microemulsion (LDE) that roughly resembles low-density lipoprotein (LDL) structure and that binds to LDL receptors.

METHODS

Ten healthy post-menopausal women were studied before and after 3-month treatment with transdermal estradiol in the following dosages administered every 3.5 days: 25, 50, 50, 100, 100, 50, 50 and 25 microg. From the 15th to the 21st day and from the 22nd to the 28th day of estrogen treatment, respectively, 10 and 5 mg q.d. MPA per oral were associated to the transdermal estrogen. The emulsion labeled with 14C-cholesteryl oleate was injected after 12 h fasting and its fractional catabolic rate (FCR) was calculated from the plasma decaying curves of the isotope.

RESULTS

Treatment reduced LDL-cholesterol levels by 8% only (149.0 +/- 36.0 mg/dl, 138.0 +/- 27.0 mg/dl; P = 0.046), but the FCR of LDE expressed in medians (25%; 75%) increased from 0.0054 (0.003; 0.052) h(-1) to 0.021 (0.009; 0.10) h(-1), P = 0.002.

CONCLUSION

The association used in this study so as to mimic the increasing-decreasing pattern of the hormonal ovarian production reduced modestly LDL-cholesterol levels but pronouncedly increased the lipoprotein removal as tested by LDE FCR.

Plasma kinetics of a cholesterol-rich microemulsion in subjects with heterozygous beta-thalassemia

Patients with beta-thalassemia trait have been reported to present lower plasma concentrations of low-density lipoprotein (LDL) and lower frequencies of acute myocardial infarction than normal subjects. In this study, the metabolism of LDL was tested in 12 patients with heterozygous beta-thalassemia trait (HBT) and 13 healthy subjects without the disease by determining the plasma kinetics of an artificially made cholesterol-rich microemulsion (LDE) that mimics the LDL metabolism and binds to LDL receptors. The emulsion was labeled with 14C-cholesterol ester and injected intravenously into the subjects. Blood samples were drawn at regular intervals over 24 hr to determine the plasma decay curve of the emulsion radioactive label and to estimate its plasma fractional clearance rate (FCR, in hr(-1)). FCR of the 14C-cholesterol ester was greater in HBT compared to controls (0.0631 +/- 0.0178 hr(-1) and 0.0501 +/- 0.0094 hr(-1), respectively; mean +/- SD, P = 0.022). No differences were found regarding LDL cholesterol plasma concentration between the two groups, but apolipoprotein B concentration was lower in HBT than in control subjects (80 +/- 44 and 96 +/- 14, respectively; mean +/- SD, P = 0.026). Our results show that LDE FCR is increased in HBT, indicating that LDL clearance is increased in patients with beta-thalassemia trait possibly due to the increased proliferation in the bone marrow of erythroid precursors.

Cholesterol improves the utilization of parenteral lipid emulsions

Lipid emulsions have become an indispensable component of parenteral nutrition. Commercially available emulsions mostly have an identical composition of triglycerides (from plant oils) and egg-yolk phospholipids as emulsifier. Previous attempts to improve the composition of lipid emulsions have focused mainly on the triglyceride moiety. In the first fundamental modification of a lipid emulsion since their broader introduction into clinical medicine, we included free cholesterol in a lipid emulsion. We evaluated elimination and hydrolysis of triglycerides and lipid oxidation (by indirect calorimetry) in 10 healthy male normolipemic volunteers, comparing a conventional lipid emulsion (20% triglycerides) with an otherwise identical emulsion with the addition of 4 g/l free cholesterol. The rise in plasma triglycerides was mitigated during infusion of the cholesterol-enriched solution (323.8 +/- 27.5 vs. 202.0 +/- 18.9 mg.dL-1, p < 0.001), plasma half-life was reduced (41.6 +/- 5.4 vs. 29.3 +/- 5.1 min, p < 0.05), and total-body clearance was enhanced (0.96 +/- 0.1 vs. 1.52 +/- 0.2 ml.b.w.(.)min-1, p < 0.02). The rise in plasma free fatty acids (400.7 +/- 39.0 vs. 532.2 +/- 64.0 mumol.L-1; p < 0.02) and ketone bodies (beta-hydroxybutyrate) (151.6 +/- 37.0 vs. 226.3 +/- 33.01 mumol.L-1; p < 0.02) was augmented. Increases in plasma insulin and glucagon were less pronounced (p < 0.05). The fall in respiratory quotient was greater and the fraction of lipid oxidation as a percentage of total energy expenditure was increased (66.2% +/- 6.0 vs. 70.9% +/- 6.3, p < 0.05) during infusion of the modified solution. No impairment of gas exchange or other side effects were observed. Taken together these results indicate that the elimination of a cholesterol-supplemented lipid emulsion is accelerated, triglyceride hydrolysis is enhanced, and lipid oxidation is augmented. Thus, addition of cholesterol to a lipid emulsion might not only present a means of providing cholesterol in parenteral nutrition but also help to reshape artificial lipid particles to a more chylomicron-resembling composition and improve lipid utilization.