Asymptomatic individuals with high HDL-C levels overexpress ABCA1 and ABCG1 and present miR-33a dysregulation in peripheral blood mononuclear cells.

Considering the growing knowledge and perspectives on microRNAs (miRNAs) that control high-density lipoprotein cholesterol (HDL-C) levels and metabolism, this study aimed at evaluating whether hsa-miR-33a and hsa-miR-128a are differentially expressed in peripheral blood mononuclear cells from asymptomatic individuals with low and high HDL-C, as well as at investigating the potential relationships with ATP binding cassete transporter A1 (ABCA1) expression, cholesterol efflux capacity and other parameters related with reverse cholesterol transport. In addition, the associations with cardiovascular risk were investigated by carotid-intima media thickness (cIMT). Asymptomatic volunteers of both genders (n=51) were classified according to HDL-C (mg/dL) in hypoalphalipoproteinemics (hypo, HDL-C ≤3 9), hyperalphalipoproteinemics (hyper, HDL-C ≥ 68) and controls (CTL, HDL-C ≥ 40<68). cIMT, lipids, lipoproteins, HDL size and volume, C reactive protein and insulin were determined, as well as the activities of several proteins and enzymes related to HDL metabolism. In a subgroup of 19 volunteers the cellular cholesterol efflux and HDL composition were determined. Total RNA was extracted from peripheral blood mononuclear cells for relative quantification experiments. Hypo volunteers presented significantly higher levels of triglycerides, VLDL-C and insulin; in addition, HDL size and volume decreased when compared with CTL and hyper. Regarding gene expression analysis, the hyper group presented a decrease of 72% in hsa-miR-33a and higher mRNA expression of ABCA1 and ABCG1 when compared with CTL. No significant differences in hsa-miR-128a expression, cholesterol efflux, cIMT or plaques were found. Further studies are necessary to elucidate the mechanisms underlying the complex miRNA network, regulating cellular cholesterol homeostasis in humans and its clinical repercussions.

Reference values for high-density lipoprotein particle size and volume by dynamic light scattering in a Brazilian population sample and their relationships with metabolic parameters.

BACKGROUND: Current data indicate that the size of high-density lipoprotein (HDL) may be considered an important marker for cardiovascular disease risk. We established reference values of mean HDL size and volume in an asymptomatic representative Brazilian population sample (n=590) and their associations with metabolic parameters by gender. METHODS: Size and volume were determined in HDL isolated from plasma by polyethyleneglycol precipitation of apoB-containing lipoproteins and measured using the dynamic light scattering (DLS) technique. RESULTS: Although the gender and age distributions agreed with other studies, the mean HDL size reference value was slightly lower than in some other populations. Both HDL size and volume were influenced by gender and varied according to age. HDL size was associated with age and HDL-C (total population); non- white ethnicity and CETP inversely (females); HDL-C and PLTP mass (males). On the other hand, HDL volume was determined only by HDL-C (total population and in both genders) and by PLTP mass (males). CONCLUSIONS: The reference values for mean HDL size and volume using the DLS technique were established in an asymptomatic and representative Brazilian population sample, as well as their related metabolic factors. HDL-C was a major determinant of HDL size and volume, which were differently modulated in females and in males.

Association between ABCG1 polymorphism rs1893590 and high-density lipoprotein (HDL) in an asymptomatic Brazilian population.

ATP binding cassette transporter G1 (ABCG1) promotes lipidation of nascent high-density lipoprotein (HDL) particles, acting as an intracellular transporter. SNP rs1893590 (c.-204A > C) of ABCG1 gene has been previously studied and reported as functional over plasma HDL-C and lipoprotein lipase activity. This study aimed to investigate the relationships of SNP rs1893590 with plasma lipids and lipoproteins in a large Brazilian population. Were selected 654 asymptomatic and normolipidemic volunteers from both genders. Clinical and anthropometrical data were taken and blood samples were drawn after 12 h fasting. Plasma lipids and lipoproteins, as well as HDL particle size and volume were determined. Genomic DNA was isolated for SNP rs1893590 detection by TaqMan(®) OpenArray(®) Real-Time PCR Plataform (Applied Biosystems). Mann-Whitney U, Chi square and two-way ANOVA were the used statistical tests. No significant differences were found in the comparison analyses between the allele groups for all studied parameters. Conversely, significant interactions were observed between SNP and age over plasma HDL-C, were volunteers under 60 years with AA genotype had increased HDL-C (p = 0.048). Similar results were observed in the group with body mass index (BMI) < 25 kg/m(2), where volunteers with AA genotype had higher HDL-C levels (p = 0.0034), plus an increased HDL particle size (p = 0.01). These findings indicate that SNP rs1893590 of ABCG1 has a significant impact over HDL-C under asymptomatic clinical conditions in an age and BMI dependent way.

Arterial tissue and plasma concentration of enzymatic-driven oxysterols are associated with severe peripheral atherosclerotic disease and systemic inflammatory activity.

INTRODUCTION: Cholesterol undergoes oxidation via both enzymatic stress- and free radical-mediated mechanisms, generating a wide range of oxysterols. In contrast to oxidative stress-driven metabolites, enzymatic stress-derived oxysterols are scarcely studied in their association with atherosclerotic disease in humans. METHODS: 24S-hydroxycholesterol (24S-HC), 25-hydroxycholesterol (25-HC), and 27-hydroxycholesterol (27-HC) were assessed in plasma and arteries with atherosclerotic plaques from 10 patients (54-84 years) with severe peripheral artery disease (PAD) as well as arteries free of atherosclerotic plaques from 13 individuals (45-78 years, controls). RESULTS: Plasma 25-HC was higher in PAD individuals than in controls (6.3[2] vs. 3.9[1.9] ng/mgCol; p = 0.004). 24S-HC and 27-HC levels were, respectively, five- and 20-fold higher in the arterial tissue of PAD individuals than in those of the controls (p = 0.016 and p = 0.001). Plasma C-reactive protein correlated with plasma 24-HC (r = 0.51; p = 0.010), 25-HC (r = 0.75; p < 0.001), 27-HC (r = 0.48; p = 0.015), and with tissue 24S-HC (r = 0.4; p = 0.041) and 27-HC (r = 0.46; p = 0.023). CONCLUSION: Arterial intima accumulation of 27-HC and 24S-HC is associated with advanced atherosclerotic disease and systemic inflammatory activity in individuals with severe PAD.

Early Carotid Atherosclerosis and Hepatic Lipase-514 C/T Polymorphism: A Study in Hyperalphalipoproteinemic Individuals / Aterosclerosis carotídea subclínica y el polimorfsmo HL-514 C/T de la lipasa hepática: un estudio en individuos hiperalfalipoproteinémicos

Objective: Hepatic lipase (HL) is involved in the metabolism of several lipoproteins and has a key role in reverse cholesterol transport and atherosclerosis. The aim of this study was to evaluate the effects of HL -514C/T polymorphism on sub-clinical and established carotid atherosclerotic in hyperalphalipoproteinemic and control individuals. Methods: One hundred and sixty nine asymptomatic individuals (aged 47 ± 16 years), 71 hyperalphalipopro-teinemic (Hyper-A, HDL-C = 68mg/dL) and 98 controls (CTL, HDL-C< 68mg/dL) were selected by clinical and laboratory evaluations. Lipids and lipoproteins were measured by enzymatic methods. HL activity was measured in post-heparin plasma by a radiometric assay and HL-514C/T genotypes were analyzed by PCR. Carotid intima-media thickness (cIMT) was measured by Doppler ultrasonography. Results: No differences in HL -514C/T genotype frequencies were observed between the groups. HL -514C/T polymorphism did not contribute to variations in cIMT or atherosclerotic lesion frequencies in Hyper-A and controls. Furthermore, no interactions between HL-514C/T polymorphism and cIMT or atherosclerotic lesions were found. Conclusions: In hyperalphalipoproteinemic individuals the -514C/T polymorphism is not associated with significant variations in HDL-Cholesterol concentrations. Besides, it has no repercussions on carotid atherosclerosis, although hepatic lipase activity is significantly reduced. No financial conflicts of interest exist.

Objetivo: La Lipasa Hepática (HL) está implicada en el metabolismo de las lipoproteínas distintas y desempeña un papel en el transporte inverso del colesterol y la aterosclerosis. El objetivo de este estudio fue evaluar los efectos del polimorfismo HL-514 C/T en la aterosclerosis carotídea subclínica en los individuos e hiperalfalipoproteinémicos y controles establecidos. Métodos: Ciento sesenta y nueve sujetos asintomáticos (edad 47 ± 16 años), 71 hiperalfalipoproteinémicos (Hyper-A, HDL-C = 68mg/dL) y 98 controles (CTL, HDL-C <68mg/dL) fueron seleccionados por evaluaciones clínicas y de laboratorio. Lípidos y lipoproteínas se midieron por métodos enzimáticos. La actividad de la HL se midió en plasma después de la heparina por el método radiométrico, y los genotipos HL-514C/T se analizaron por PCR. El Grosor íntimo-medial carotídeo (cIMT) se midió mediante ecografía. Resultados: No hubo diferencias en las frecuencias de los genotipos HL-514 C/T se observó entre los grupos. Polimorfismo HL-514 C/T no ha contribuido a los cambios en cIMT o la frecuencia de las lesiones ateroscleróticas en Hyper-A y los controles. Por otra parte, no hay interacción entre el polimorfismo HL-514 C/T y cIMT ni fueron halladas lesiones ateroscleróticas. Conclusiones: El polimorfismo HL -514 C/T no está asociado con cambios significativos en el colesterol HDL en hiperalfalipoproteinémicos particulares y no tiene efecto en la arteriosclerosis carotídea a pesar de que la actividad de la HL ha sido reducida significativamente. Los autores declaran no poseer conflictos de interés.

Early Carotid Atherosclerosis and Hepatic Lipase-514 C/T Polymorphism: A Study in Hyperalphalipoproteinemic Individuals / Aterosclerosis carotídea subclínica y el polimorfsmo HL-514 C/T de la lipasa hepática: un estudio en individuos hiperalfalipoproteinémicos

Objective: Hepatic lipase (HL) is involved in the metabolism of several lipoproteins and has a key role in reverse cholesterol transport and atherosclerosis. The aim of this study was to evaluate the effects of HL -514C/T polymorphism on sub-clinical and established carotid atherosclerotic in hyperalphalipoproteinemic and control individuals. Methods: One hundred and sixty nine asymptomatic individuals (aged 47 ± 16 years), 71 hyperalphalipopro-teinemic (Hyper-A, HDL-C = 68mg/dL) and 98 controls (CTL, HDL-C< 68mg/dL) were selected by clinical and laboratory evaluations. Lipids and lipoproteins were measured by enzymatic methods. HL activity was measured in post-heparin plasma by a radiometric assay and HL-514C/T genotypes were analyzed by PCR. Carotid intima-media thickness (cIMT) was measured by Doppler ultrasonography. Results: No differences in HL -514C/T genotype frequencies were observed between the groups. HL -514C/T polymorphism did not contribute to variations in cIMT or atherosclerotic lesion frequencies in Hyper-A and controls. Furthermore, no interactions between HL-514C/T polymorphism and cIMT or atherosclerotic lesions were found. Conclusions: In hyperalphalipoproteinemic individuals the -514C/T polymorphism is not associated with significant variations in HDL-Cholesterol concentrations. Besides, it has no repercussions on carotid atherosclerosis, although hepatic lipase activity is significantly reduced. No financial conflicts of interest exist.(AU)

Objetivo: La Lipasa Hepática (HL) está implicada en el metabolismo de las lipoproteínas distintas y desempeña un papel en el transporte inverso del colesterol y la aterosclerosis. El objetivo de este estudio fue evaluar los efectos del polimorfismo HL-514 C/T en la aterosclerosis carotídea subclínica en los individuos e hiperalfalipoproteinémicos y controles establecidos. Métodos: Ciento sesenta y nueve sujetos asintomáticos (edad 47 ± 16 años), 71 hiperalfalipoproteinémicos (Hyper-A, HDL-C = 68mg/dL) y 98 controles (CTL, HDL-C <68mg/dL) fueron seleccionados por evaluaciones clínicas y de laboratorio. Lípidos y lipoproteínas se midieron por métodos enzimáticos. La actividad de la HL se midió en plasma después de la heparina por el método radiométrico, y los genotipos HL-514C/T se analizaron por PCR. El Grosor íntimo-medial carotídeo (cIMT) se midió mediante ecografía. Resultados: No hubo diferencias en las frecuencias de los genotipos HL-514 C/T se observó entre los grupos. Polimorfismo HL-514 C/T no ha contribuido a los cambios en cIMT o la frecuencia de las lesiones ateroscleróticas en Hyper-A y los controles. Por otra parte, no hay interacción entre el polimorfismo HL-514 C/T y cIMT ni fueron halladas lesiones ateroscleróticas. Conclusiones: El polimorfismo HL -514 C/T no está asociado con cambios significativos en el colesterol HDL en hiperalfalipoproteinémicos particulares y no tiene efecto en la arteriosclerosis carotídea a pesar de que la actividad de la HL ha sido reducida significativamente. Los autores declaran no poseer conflictos de interés.(AU)

Does plasma HDL-C concentration interact with whole-body cholesterol metabolism?

This review examines the interactions between plasma high density lipoprotein (HDL) metabolism and whole-body cholesterol economy. More specifically, this review addresses three questions: 1) does plasma HDL-C concentration correlate with the parameters of whole-body cholesterol metabolism? 2) Do variations in cholesterol metabolism interfere with plasma HDL-C concentrations? 3) Are the markers of cholesterol synthesis and intestinal absorption specifically under the control of plasma HDL? The following answers were provided to each question, respectively: 1) plasma HDL influences whole-body cholesterol synthesis rate but the evidence that HDL modifies the total amount of cholesterol absorbed by the intestine is not clearly supported by present investigations; 2) there are suggestions that changes in whole body cholesterol metabolism rates do not interfere with plasma HDL-C concentrations; 3) markers of cholesterol synthesis and absorption may specifically be controlled by plasma HDL-C concentrations regarding the genetic causes of extremely low HDL-C concentrations, although within the general population plasma HDL-C concentration is likely ascribed to insulin resistance or diabetes mellitus.

HDL-C concentration is related to markers of absorption and of cholesterol synthesis: Study in subjects with low vs. high HDL-C.

BACKGROUND: The antiatherogenic functions of high density lipoprotein (HDL-C) include its role in reverse cholesterol transport, but to what extent the concentration of HDL-C interferes with the whole-body cholesterol metabolism is unknown. Therefore, we measured markers of body cholesterol synthesis (desmosterol and lathosterol) and of intestinal cholesterol absorption (campesterol and ß-sitosterol) in healthy subjects that differ according to their plasma HDL-C concentrations. METHODS: Healthy participants presented either low HDL-C (< 40 mg/dl, n=33, 17 male and 16 female) or high HDL-C (> 60 mg/dl, n=33, 17 male and 16 female), BMI< 30 kg/m², were paired according to age and gender, without secondary factors that might interfere with their plasma lipid concentrations. Plasma concentrations of non-cholesterol sterols were measured by the combined GC-MS analysis. RESULTS: Plasma desmosterol did not differ between the two groups; however, as compared with the high HDL-C participants, the low HDL-C participants presented higher concentration of lathosterol and lower concentration of the intestinal cholesterol absorption markers campesterol and ß-sitosterol. CONCLUSION: Plasma concentrations of HDL, and not the activities of LCAT and CETP that regulate the reverse cholesterol transport system, correlate with plasma sterol markers of intestinal cholesterol absorption directly, and of cholesterol synthesis reciprocally.

Protective modulation of carotid atherosclerosis in hyperalphalipoproteinemic individuals.

To determine whether hyperalphalipoproteinemia modifies carotid intima-media thickness (cIMT) and/or influences the relationship of clinical and biochemical parameters with cIMT. This study was conducted on 169 asymptomatic individuals, classified as hyperalphalipoproteinemic (Hyper-A) (Hyper-A, n = 71, HDL-C > or =68 mg/dL) and controls (CTL) (CTL, n = 98, HDL-C >32 and <68 mg/dL). Enzymatic, nephelometric and ultracentrifugation methods were used for biochemical determinations. Hepatic lipase (HL), lipoprotein lipase (LPL), cholesteryl ester transfer protein (CETP) and phospholipids transfer protein (PLTP) activities were measured by radiometric exogenous methods. The prevalence of dyslipidemia, hypertension, smoking, sedentariness, postmenopausal women, coronary artery disease (CAD) and familial history of CAD were determined. High resolution beta-mode carotid ultrassonography was performed. The Hyper-A group was older and had higher frequencies of hypercholesterolemia (40%), hypertension (31%), sedentariness (37%) and postmenopausal women (1%). In Hyper-A individuals, the mean cIMT after adjustment for age and gender was similar between the groups (0.85 +/- 0.24 mm Hyper-A versus 0.69 +/- 0.17 mm CTL). In multivariate models, age was a significant predictor of cIMT in Hyper-A (R (2) = 0.04, p < or = 0.001), independently of other clinical or biochemical factors. In contrast to CTL, where age (R (2) = 0.63 p < or = 0.001), male sex (R (2) = 0.03, p < or = 0.001), blood pressure (R (2) = 0.006, p < or = 0.001) and HDL-C (R (2) = 0.02, p < 0.022) accounted for the cIMT variations. Despite an increased prevalence of cardiovascular risk factors in Hyper-A and resistance of carotid thickness to modulation by metabolic and anthropometric factors (except age), the similarity in cIMT between Hyper-A and healthy individuals emphasizes the atheroprotective effects of HDL.

Determinants of serum lipoprotein(a) concentration in normolipidaemic individuals without clinical atherosclerosis.

BACKGROUND: Lipoprotein(a) (Lp(a)) is an independent risk factor for coronary artery diseases. The main objective of this work was to evaluate the determinants of plasma Lp(a) concentrations in normolipidaemic individuals. METHODS: Immunonephelometric quantification of Lp(a) was made in 177 volunteers. A multivariate analysis was employed to verify the influence of clinical and biochemical parameters on plasma Lp(a) concentration. RESULTS: The serum Lp(a) concentration in this population ranged from 0.7 to 40 nmol/L. The Lp(a) predictors were: sex (female), HDL2 triglyceride (negative) and LDL-cholesterol (positive). CONCLUSIONS: The modulation of plasma Lp(a) concentration in this study points to pro-atherogenic lipoprotein associations.

Atherosclerosis in aged mice over-expressing the reverse cholesterol transport genes.

We determined whether over-expression of one of the three genes involved in reverse cholesterol transport, apolipoprotein (apo) AI, lecithin-cholesterol acyl transferase (LCAT) and cholesteryl ester transfer protein (CETP), or of their combinations influenced the development of diet-induced atherosclerosis. Eight genotypic groups of mice were studied (AI, LCAT, CETP, LCAT/AI, CETP/AI, LCAT/CETP, LCAT/AI/CETP, and non-transgenic) after four months on an atherogenic diet. The extent of atherosclerosis was assessed by morphometric analysis of lipid-stained areas in the aortic roots. The relative influence (R2) of genotype, sex, total cholesterol, and its main sub-fraction levels on atherosclerotic lesion size was determined by multiple linear regression analysis. Whereas apo AI (R2 = 0.22, P < 0.001) and CETP (R2 = 0.13, P < 0.01) expression reduced lesion size, the LCAT (R2 = 0.16, P < 0.005) and LCAT/AI (R2 = 0.13, P < 0.003) genotypes had the opposite effect. Logistic regression analysis revealed that the risk of developing atherosclerotic lesions greater than the 50th percentile was 4.3-fold lower for the apo AI transgenic mice than for non-transgenic mice, and was 3.0-fold lower for male than for female mice. These results show that apo AI overexpression decreased the risk of developing large atherosclerotic lesions but was not sufficient to reduce the atherogenic effect of LCAT when both transgenes were co-expressed. On the other hand, CETP expression was sufficient to eliminate the deleterious effect of LCAT and LCAT/AI overexpression. Therefore, increasing each step of the reverse cholesterol transport per se does not necessarily imply protection against atherosclerosis while CETP expression can change specific atherogenic scenarios.

Atherosclerosis in aged mice over-expressing the reverse cholesterol transport genes

We determined whether over-expression of one of the three genes involved in reverse cholesterol transport, apolipoprotein (apo) AI, lecithin-cholesterol acyl transferase (LCAT) and cholesteryl ester transfer protein (CETP), or of their combinations influenced the development of diet-induced atherosclerosis. Eight genotypic groups of mice were studied (AI, LCAT, CETP, LCAT/AI, CETP/AI, LCAT/CETP, LCAT/AI/CETP, and non-transgenic) after four months on an atherogenic diet. The extent of atherosclerosis was assessed by morphometric analysis of lipid-stained areas in the aortic roots. The relative influence (R²) of genotype, sex, total cholesterol, and its main sub-fraction levels on atherosclerotic lesion size was determined by multiple linear regression analysis. Whereas apo AI (R² = 0.22, P < 0.001) and CETP (R² = 0.13, P < 0.01) expression reduced lesion size, the LCAT (R² = 0.16, P < 0.005) and LCAT/AI (R² = 0.13, P < 0.003) genotypes had the opposite effect. Logistic regression analysis revealed that the risk of developing atherosclerotic lesions greater than the 50th percentile was 4.3-fold lower for the apo AI transgenic mice than for non-transgenic mice, and was 3.0-fold lower for male than for female mice. These results show that apo AI overexpression decreased the risk of developing large atherosclerotic lesions but was not sufficient to reduce the atherogenic effect of LCAT when both transgenes were co-expressed. On the other hand, CETP expression was sufficient to eliminate the deleterious effect of LCAT and LCAT/AI overexpression. Therefore, increasing each step of the reverse cholesterol transport per se does not necessarily imply protection against atherosclerosis while CETP expression can change specific athero genic scenarios.

Sex differences in risk factors for coronary heart disease: a study in a Brazilian population.

BACKGROUND: In Brazil coronary heart disease (CHD) constitutes the most important cause of death in both sexes in all the regions of the country and interestingly, the difference between the sexes in the CHD mortality rates is one of the smallest in the world because of high rates among women. Since a question has been raised about whether or how the incidence of several CHD risk factors differs between the sexes in Brazil the prevalence of various risk factors for CHD such as high blood cholesterol, diabetes mellitus, hypertension, obesity, sedentary lifestyle and cigarette smoking was compared between the sexes in a Brazilian population; also the relationships between blood cholesterol and the other risk factors were evaluated. RESULTS: The population presented high frequencies of all the risk factors evaluated. High blood cholesterol (CHOL) and hypertension were more prevalent among women as compared to men. Hypertension, diabetes and smoking showed equal or higher prevalence in women in pre-menopausal ages as compared to men. Obesity and physical inactivity were equally prevalent in both sexes respectively in the postmenopausal age group and at all ages. CHOL was associated with BMI, sex, age, hypertension and physical inactivity. CONCLUSIONS: In this population the high prevalence of the CHD risk factors indicated that there is an urgent need for its control; the higher or equal prevalences of several risk factors in women could in part explain the high rates of mortality from CHD in females as compared to males.

Acute in vivo chylomicron metabolism and postalimentary lipoprotein alterations in normolipidemic male smokers.

Increased postprandial lipemia has been stated as one of the mechanisms responsible for atherogenesis in smokers. We measured the postalimentary lipid response and the in vivo intravascular delipidation index of an artificial chylomicron emulsion in healthy adult smokers and controls. The blood was collected in the fasting state immediately after the smokers smoked one cigarette. The lipemia was measured 2, 4, 6 and 8 h postalimentarily in smokers (S, n = 8) and in non-smoking controls (C, n = 8) and the chylomicron metabolism rate was measured 2, 4, 6, 8, 12, 16, 20, 24 and 30 min after the injection of an artificial emulsion to S (n = 10) and to C (n = 10). The lipoproteins were isolated in the fasting period and 4 h after the fatty meal and their chemical composition in cholesterol, triglycerides, phospholipids and protein was determined. Smokers showed an increased lipolysis percentage value (mean +/- S.E.M.) of the artificial chylomicron (39.1 +/- 3.1) compared to controls (26.5 +/- 3.3) and higher levels of HDL(2)-PL: 28.4 +/- 4.3 (S) versus 16.2 +/- 2.0 (C) mg/dl (mean +/- S.E.M.). In conclusion, the oral fat tolerance was not altered in smokers but an upregulation of the rate of metabolism of the TG-rich lipoproteins was elicited immediately after smoking one cigarette.

Plasma lipases and lipid transfer proteins increase phospholipid but not free cholesterol transfer from lipid emulsion to high density lipoproteins.

BACKGROUND: Plasma lipases and lipid transfer proteins are involved in the generation and speciation of high density lipoproteins. In this study we have examined the influence of plasma lipases and lipid transfer protein activities on the transfer of free cholesterol (FC) and phospholipids (PL) from lipid emulsion to human, rat and mouse lipoproteins. The effect of the lipases was verified by incubation of labeled (3H-FC,14C-PL) triglyceride rich emulsion with human plasma (control, post-heparin and post-heparin plus lipase inhibitor), rat plasma (control and post-heparin) and by the injection of the labeled lipid emulsion into control and heparinized functionally hepatectomized rats. RESULTS: In vitro, the lipase enriched plasma stimulated significantly the transfer of 14C-PL from emulsion to high density lipoprotein (p<0.001) but did not modify the transfer of 3H-FC. In hepatectomized rats, heparin stimulation of intravascular lipolysis increased the plasma removal of 14C-PL and the amount of 14C-PL found in the low density lipoprotein density fraction but not in the high density lipoprotein density fraction. The in vitro and in vivo experiments showed that free cholesterol and phospholipids were transferred from lipid emulsion to plasma lipoproteins independently from each other. The incubation of human plasma, control and control plus monoclonal antibody anti-cholesteryl ester transfer protein (CETP), with 14C-PL emulsion showed that CETP increases 14C-PL transfer to human HDL, since its partial inhibition by the anti-CETP antibody reduced significantly the 14C-PL transfer (p<0.05). However, comparing the nontransgenic (no CETP activity) with the CETP transgenic mouse plasma, no effect of CETP on the 14C-PL distribution in mice lipoproteins was observed. CONCLUSIONS: It is concluded that: 1-intravascular lipases stimulate phospholipid transfer protein mediated phospholipid transfer, but not free cholesterol, from triglyceride rich particles to human high density lipoproteins and rat low density lipoproteins and high density lipoproteins; 2-free cholesterol and phospholipids are transferred from triglyceride rich particles to plasma lipoproteins by distinct mechanisms, and 3 - CETP also contributes to phospholipid transfer activity in human plasma but not in transgenic mice plasma, a species which has high levels of the specific phospholipid transfer protein activity.

Origin of cholesterol transported in intestinal lymph: studies in patients with filarial chyluria.

In subjects fed a cholesterol-free diet there are three possible sources of intestinal lymph cholesterol: a) mucosal synthesis; b) absorption of endogenous (biliary) cholesterol; and c) transudation of plasma lipoproteins into the lacteals of the intestinal wall. To test these possibilities, the extent of transudation was measured by means of [3H]beta-sitosterol administered intravenously as a marker. Absorption of biliary cholesterol was reduced by oral administration of beta-sitosterol (9 g/day), and mucosal synthesis of cholesterol was evaluated by comparisons of plasma/lymph [14C]cholesterol specific activity ratios after intravenous administration of a single dose of labeled cholesterol. Studies were carried out on six patients with filarial chyluria. In five patients fed a cholesterol-free diet the results indicated that lymph cholesterol was largely derived by transudation of plasma lipoproteins into the lacteals from the intestinal blood supply, without contribution from de novo mucosal synthesis or from absorption of endogenous cholesterol. The intestinal lymph of one patient fed cholesterol (2 g/day) contained cholesterol originating mostly from plasma transudation and from dietary absorption, with little contribution from absorbed endogenous cholesterol. In all experiments the larger part of the cholesterol transported away from the intestine in the lymph was carried in chylomicrons, even though it had its origin in plasma lipoproteins.