Retention of apolipoprotein (apo)B and apoE-containing lipoproteins by extracellular vascular proteoglycans is critical in atherogenesis. Moreover, high circulating apoC-III levels are associated with increased atherosclerosis risk. To test whether apoC-III content of apoB-containing lipoproteins affects their ability to bind to the vascular proteoglycan biglycan, we evaluated the impact of apoC-III on the interaction of [(35)S]SO(4)-biglycan derived from cultured arterial smooth muscle cells with lipoproteins obtained from individuals across a spectrum of lipid concentrations. The extent of biglycan binding correlated positively with apoC-III levels within VLDL (r = 0.78, P < 0.01), IDL (r = 0.67, P < 0.01), and LDL (r = 0.52, P < 0.05). Moreover, the biglycan binding of VLDL, IDL, and LDL was reduced after depletion of apoC-III-containing lipoprotein particles in plasma by anti-apoC-III immunoaffinity chromatography. Since apoC-III does not bind biglycan directly, enhanced biglycan binding may result from a conformational change associated with increased apo C-III content by which apoB and/or apoE become more accessible to proteoglycans. This may be an intrinsic property of lipoproteins, since exogenous apoC-III enrichment of LDL and VLDL did not increase binding. ApoC-III content may thus be a marker for lipoproteins characterized as having an increased ability to bind proteoglycans.

The epsilon 4 allele of the apolipoprotein E gene (ApoE) is associated with an increased risk for sporadic and some familial forms of Alzheimer's disease (AD) but the precise mechanism of pathogenesis is unknown. ApoE is a ligand for at least three receptors in the central nervous system, low density lipoprotein receptor (LDL-R), very low density lipoprotein receptor VLDL-R and low density lipoprotein-like receptor (LRP). We have tested for association between these receptors and dementia of the Alzheimer's type (DAT) in a clinically based sample of Caucasian cases and age-matched controls. In contrast to findings in a Japanese cohort we detected no association between DAT and a polymorphism in the VLDL-R gene. No association was detected with the LDL-R gene. We observed a possible association between the 87 allele of a polymorphism within the LRP gene and DAT which remained significant after correction for multiple testing. When the effects of known risk factors for AD such as ApoE epsilon 4 were applied, the effect of LRP no longer reached conventional levels of statistical significance. Nevertheless, LRP is a plausible candidate gene and we may be observing a minor risk factor that will require further examination in other large independent samples to assess whether it truly modifies susceptibility to DAT.

The influence of adrenalectomy and dexamethasone on hepatic free fatty acid metabolism was studied in isolated perfused livers from male rats. Adrenalectomy 1 week prior to perfusion did not affect uptake of oleate, output of triglyceride, or rate of ketogenesis compared to sham-operated match-fed controls. Livers from dexamethasone-treated rats (0-2 mg/kg per day for 7 days) removed less oleate from the perfusate, esterified more to total and very low density lipoprotein (VLDL) triglyceride, and oxidized less to ketone bodies, compared to match fed controls; additional studies with [1-(14)C]oleate confirmed these findings. The output of glucose by livers from dexamethasone-treated rats was also stimulated. The output of VLDL triglyceride was correlated with output of total perfusate triglyceride (r = 0.77, P < 0.001). Prior to perfusion, dexamethasone livers accumulated more triglyceride than did control livers. Adrenalectomy did not affect the concentration of plasma free fatty acid or blood ketones and glucose; however, the plasma concentration of triglyceride was elevated. Dexamethasone increased the concentration of plasma free fatty acid, total triglyceride, and VLDL protein, triglyceride, phospholipid, and free cholesterol. No changes were observed in the concentration or composition of plasma low density lipoprotein (LDL) lipids. The concentration of plasma high density lipoprotein (HDL) protein and lipid, and plasma apoA-I, tended to increase; the ratio of total HDL cholesterol to LDL cholesterol was elevated with dexamethasone treatment. These observations suggest that augmented synthesis and secretion of VLDL triglyceride contribute to glucocorticoid-induced hyper-triglyceridemia.-Cole, T. G., H. G. Wilcox, and M. Heimberg. Effects of adrenalectomy and dexamethasone on hepatic lipid metabolism.

A group of 33 mildly hypercholesterolemic men were stratified into three groups on diets closely matched except for the polyunsaturated fatty acid supplement. The first group received 14 g/day of linoleic acid (safflower oil); the second group, 9 g of alpha-linolenic acid (linseed oil); and the third group, 3.8 g of n-3 fatty acids (fish oil). Only fish oil lowered plasma triglycerides (by 24% at 6 weeks, p less than 0.05 compared to safflower oil). Very low density lipoprotein (VLDL) apoprotein (apo) B, triglyceride, and cholesterol all fell significantly with the fish-oil diet (p less than 0.01). Low density lipoprotein (LDL) cholesterol fell by 0.18 and 0.10 mmol/l, respectively, with the safflower-oil and linseed-oil diets, but rose by 0.24 mmol/l with the fish-oil diet (p less than 0.05). There was a strong correlation between the changes in VLDL triglyceride and LDL cholesterol with the fish-oil diet (r = -0.84, p less than 0.002). High density lipoprotein (HDL) cholesterol fell slightly in all three groups (p less than 0.02 with the linseed-oil diet only). However, the apo A-I/A-II ratio rose by 5% (p less than 0.05), and the HDL2/HDL3 protein ratio increased by 28% with the fish-oil diet (p less than 0.005). Fish oil reduced the capacity for transfer of cholesteryl ester between LDL and HDL by 23% (p less than 0.02 compared to baseline), reduced plasma lecithin:cholesterol acyltransferase activity by 21% (p less than 0.05), and reduced maximal stimulated thromboxane production by 9% (p less than 0.05). Thus fish oil produced three potentially beneficial changes: significant decreases in VLDL concentration and in thromboxane production and an increase in the HDL2/HDL3 ratio. The increase in the average HDL particle size probably reflected reduced cholesteryl ester acceptor capacity within the smaller pool of VLDL, as well as the decline in lipid transfer activity in plasma involving transfer protein itself, LDL, and HDL.

The effects of low-dose short-term corticosteroids on plasma lipid and lipoprotein cholesterol was measured in 23 subjects who received prednisone for active rheumatic disease. After 1 month, plasma cholesterol increased from 195 to 219 mg/dl (P less than 0.001), and high density lipoprotein cholesterol (HDL-C) from 52 to 70 mg/dl (P less than 0.001). Mean plasma triglyceride (TG) and low density lipoprotein cholesterol (LDL-C) did not show a significant change. There was a wide variation in individual response of plasma lipid values to corticosteroid treatment. There was also a strong relationship between change in plasma total cholesterol and change in LDL-C (r = 0.86) (P less than 0.001), and change in TG (r = 0.39, P less than 0.01), but not in HDL-C. Thus, short-term, low-dose corticosteroids markedly affect plasma lipid levels. In most subjects there is an increase in HDL-C; however, an increase in total cholesterol may be indicative of a change in VLDL-C and LDL-C as well.

The purpose of this study was to report the relationship between fat distribution, physical activity (PA), and cardiovascular disease (CVD) risk factors. Percent fat, computed tomography intra-abdominal adipose tissue (IAF), anthropometrics, Baecke activity questionnaire, and CVD risk (blood pressure, cholesterol, HDL, HDL2, HDL3, IDL, LDL, VLDL, and triglycerides) were evaluated in 137 men 30-71 yr old. IAF was consistently more highly related to CVD risk than other fat distribution variables including percent fat and waist:hip ratio (r = 0.3-0.45). IAF was significantly related to CVD risk after adjusting for other fat distribution variables. With the exception of the sum of biceps, triceps, thigh, and calf skinfolds (peripheral skinfolds), which was negatively related to CVD risk, no other fat distribution variable had consistent significant partial correlations with CVD risk. PA was related to IAF after adjusting for peripheral skinfolds, but PA was not related to peripheral skinfolds after adjusting for IAF, indicating more active men have relatively low IAF. IAF was related to CVD risk after adjusting for PA, but PA was not related to CVD risk after adjusting for IAF. These results indicate that IAF is directly related to CVD risk while the lower CVD risk found with more active men is more directly related to the low IAF found in more active men.

BACKGROUND

The measurement of triglyceride (TG)-rich particles after an oral fat challenge has been used to provide a measure of risk for coronary artery disease independent of the fasting plasma triglyceride concentration. The analytical "gold standard" for measuring TG-rich lipoproteins uses density gradient ultracentrifugation; however, this technique is labor-intensive. Because of our need to perform numerous postprandial analyses of TG-rich lipoproteins for a large interventional study (Genetics of Lipid Lowering Drugs and Diet Network), we evaluated the use of nuclear magnetic resonance (NMR) spectroscopy for measuring TG-rich particles.

METHODS

EDTA-blood samples were obtained 0, 3.5, 6, and 8 h after ingestion of an oral fat meal (89% of calories from fat) in 20 apparently healthy individuals. The plasma TG concentrations of chylomicron and chylomicron remnant/VLDL fractions were analyzed by ultracentrifugation and NMR spectroscopy.

RESULTS

Comparison of all values (n = 78) by ultracentrifugation (x) and NMR (y) produced a linear regression equation of y = 0.979x - 0.035 mmol/L (R(2) = 0.90) for chylomicrons and y = 1.398x + 0.067 mmol/L (R(2) = 0.96) for the fraction containing chylomicron remnants and VLDL. Postprandial response of chylomicrons and chylomicron remnant/VLDL was similar, with maximum response occurring between 3.5 to 6 h regardless of method of measurement.

CONCLUSIONS

Chylomicron and chylomicron remnant/VLDL fraction measurements obtained by NMR have a high degree of correlation with results produced by ultracentrifugation. NMR may therefore be suitable as an alternative method for the measurement of postprandial TG-rich lipoproteins in individuals consuming a high-fat meal.

VLDL receptor (VLDL-R) is a novel member of the LDL receptor gene family with distinct tissue distribution and function. It binds and internalizes VLDL particles and is primarily expressed in skeletal muscle, heart, brain and adipose tissue, which use fatty acids for energy production or storage. CRF is associated with elevated serum triglyceride and VLDL concentrations and depressed VLDL and chylomicron clearance. We have recently shown marked down-regulation of lipoprotein lipase expression in CRF. This study was conducted to test the hypothesis that VLDL-R expression may be similarly depressed in CRF. To this end, VLDL-R mRNA (Northern blot) and protein mass (Western blot) of skeletal muscle (soleus) and heart were measured in male Sprague-Dawley rats six weeks after 5/6 nephrectomy (CRF group) or sham operation (NL group). A group of erythropoietin (EPO)-treated (150 U/kg twice weekly) CRF animals was included to determine the possible effect of EPO-deficiency anemia (EPO-CRF group). Subgroups of animals were studied at weeks 1, 3 and 6. The CRF group showed a fivefold increase in plasma triglyceride concentration. This was associated with an impressive fourfold reduction in heart and skeletal muscle VLDL-R mRNA and protein mass. VLDL-R mRNA levels in the heart and skeletal muscle were directly related to creatinine clearance and inversely related to serum triglyceride and VLDL concentrations. EPO therapy led to a mild improvement in CRF hypertriglyceridemia but failed to improve VLDL-R expression. Thus, the rise in plasma triglyceride and VLDL concentrations in CRF animals was associated with marked down-regulation of VLDL-R expression. Down-regulation of VLDL-R expression, shown here for the first time, reveals another facet of disturbed lipid metabolism in CRF.

Levels of plasma very low density lipoprotein (VLDL) and low density lipoprotein (LDL) constituents increase with age. In an attempt to further define the mechanisms responsible for these changes, kinetic studies of VLDL and LDL apolipoprotein (apo) B-100 were carried out in 19 normolipidemic male subjects with plasma total cholesterol and triglyceride levels below the 90th percentile whose ages ranged from 24 to 73 years. Subjects were maintained on standardized diets consisting of 47-49% of calories as carbohydrate, 15% protein, and 36-40% fat (15-17% saturated, 15-17% monounsaturated, 6% polyunsaturated) with 150 mg cholesterol/1000 kcal. At the end of the diet period, the metabolism of apoB-100 within VLDL, intermediate density lipoprotein (IDL), and LDL was studied in the fed state using a primed-constant infusion of [2H3]leucine. Data were fit to a multicompartmental model to determine residence times and production rates of apoB-100 in each fraction. There were significant positive correlations between age and VLDL, IDL, and LDL apoB-100 concentrations (r = 0.50, 0.62, and 0.69; P = 0.03, 0.004, and 0.001, respectively). There was a positive correlation between age and the production rate of VLDL apoB-100 (r = 0.50, P = 0.03), but there was no significant relationship between age and either IDL or LDL apoB-100 production rates. Age was also positively correlated with the residence time of LDL apoB-100 (r = 0.68 P = 0.001). Our data suggest that the age-associated increase in VLDL apoB-100 is due to an increased production rate of this constituent, whereas the age-associated increase in LDL apoB-100 is due to an increased residence time of these particles in plasma.

OBJECTIVE

Phospholipids (PLs) are increasingly recognized as key molecules with potential diagnostic value in acute inflammation, CVD and atherosclerosis. We introduce a pioneer mass spectrometry (MS)-based approach aiming to investigate the relationship of specific plasma PL-subsets with atherogenic blood parameters in young patients with familial hyperlipidemia representing high-CVD-risk groups.

METHODS

Plasma of carefully phenotyped FH and FCH patients as well as normolipidemic subjects (age 13 ± 5 years, n = 20) was used. Clinical parameters were assessed using standard laboratory techniques and lipids were subjected to a direct targeted monitoring using LC-ESI-SRM- and MALDI-QIT-TOF-MS/MS, respectively. Statistical analysis was performed to evaluate correlations between PL data and the clinical parameters.

RESULTS

Most characteristically significant differences of SM/PC and PC/LPC ratios and positive correlations between SM vs. LDL-C (r = 0.946; p = 0.004) and LPC vs. VLDL-C (r = 0.669; p = 0.218) were observed in FH in contrast to the other study groups. OxPC levels were found in the range of ∼2-20 μmol/L with predominance of short-chain aldehydic species (e.g. SOVPC). A positive correlation of OxPCs with IMT (r = 0.952; p = 0.052) and HDL-C (r = 0.893; p = 0.016) but negative correlation with OxLDL (r = -0.910; p = 0.096) was observed.

CONCLUSIONS

Our study was a first attempt to use a MALDI-QIT-TOF-MS/MS based clinical lipidomics approach to investigate atherogenic dyslipidemia in young patients with familial hyperlipidemia. This technique represents a promising platform for clinical screening of lipid biomarkers in the future.

OBJECTIVE

Serum paraoxonase (PON) is a calcium-dependent esterase that is known to contribute to the antioxidant protection conferred by high-density lipoprotein (HDL) on low-density lipoprotein (LDL) oxidation. Serum PON activity was shown to be reduced in patients with diseases such as myocardial infarction, diabetes mellitus, etc in comparison to healthy subjects. However, the relation of serum PON levels to cancer is still not known. So, we intended to measure serum PON, HDL, LDL and very low-density lipoprotein (VLDL) levels and to investigate the relation of serum PON to plasma lipoproteins in the patients with gastric cancer.

METHODS

We measured serum PON, HDL, LDL and VLDL levels in 20 patients with gastric cancer and in 20 age-and gender-matched healthy controls. We investigated the relationship between PON and HDL, PON and LDL, and PON and VLDL.

RESULTS

Serum HDL levels were lower in the patients than in controls (33.10 +/- 7.75 mg/dL, and 47.30 +/- 6.65 mg/dL, respectively) (p<0.0001). Serum VLDL levels were lower in the patients than in controls (21.65 +/- 6.92 mg/dL, and 33.10 +/- 6.09 mg/dL, respectively) (p<0.0001). Serum LDL levels measured in the patients were not significantly different from those of the controls. Serum PON levels were lower in the patients than in controls (67.10 +/- 17.92 U/L, and 87.50 +/- 23.39 U/L, respectively) and there was a positive correlation between serum PON and HDL levels (r: 0.52, p<0.05).

CONCLUSIONS

We concluded that the patients with gastric cancer had low serum PON, HDL, and VLDL levels compared to healthy controls. The importance of PON as a predictive risk factor for cancer should be assessed in future studies.

Lp(a) is a major inherited risk factor for premature atherosclerosis. The mechanism of Lp(a) atherogenicity has not been elucidated, but likely involves both its ability to interfere with plasminogen activation and its atherogenic potential as a lipoprotein particle after receptor-mediated uptake. We demonstrate that Lp(a) stimulates production of vascular cell adhesion molecule 1 (VCAM-1) and E-selectin in cultured human coronary artery endothelial cells (HCAEC). This effect resulted from a rise in intracellular free calcium induced by Lp(a) and could be inhibited by the intracellular calcium chelator, BAPTA/AM. The involvement of the LDL and VLDL receptors in Lp(a) activation of HCAEC were ruled out since Lp(a) induction of adhesion molecules was not prevented by an antibody (IgGC7) to the LDL receptor or by receptor-activating protein, an antagonist of ligand binding to the VLDL receptor. Addition of alpha2-macroglobulin as well as treatment with heparinase, chondroitinase ABC, and sodium chlorate did not decrease levels of VCAM-1 and E-selectin stimulated by Lp(a), suggesting that neither the low density lipoprotein receptor-related protein nor cell-surface proteoglycans are involved in Lp(a)-induced adhesion molecule production. Neither does the binding site on HCAEC responsible for adhesion molecule production by Lp(a) appear to involve plasminogen receptors, as levels of VCAM-1 and E-selectin were not significantly decreased by the addition of glu-plasminogen, the lysine analog epsilon-aminocaproic acid, or by trans-4-(aminomethyl)-cyclohexanecarboxymethylic acid (tranexamic acid), which acts by binding to the lysine binding sites carried on the kringle structures in plasminogen. In contrast, recombinant apolipoprotein (a) [r-apo(a)] competed with Lp(a) and attenuated the expression of VCAM-1 and E-selectin. In summary, we have identified a calcium-dependent interaction of Lp(a) with HCAEC capable of inducing potent surface expression of VCAM-1 and E-selectin that does not appear to involve any of the known potential Lp(a) binding sites. Because leukocyte recruitment to the vessel wall appears to represent one of the important early events in atherogenesis, this newly described endothelial cell-activating effect of Lp(a) places it at a crucial juncture in the initiation of atherogenic disease and may lead to a better understanding of the role of Lp(a) in the vascular biology of atherosclerosis.

The autoimmune MRL/lpr mouse strain, a model for systemic lupus erythematosus, exhibited an unusual plasma lipoprotein profile, suggesting a possible interaction of autoimmune disease and lipoprotein metabolism. In an effort to examine the genetic basis of such interactions, and to study their relationship to atherogenesis, we performed a quantitative trait locus analysis using a total of 272 (MRL/lprxBALB/cJ) second generation (F2) intercross mice. These mice were examined for levels of total plasma cholesterol, HDL cholesterol, VLDL and LDL cholesterol, unesterified cholesterol, autoantibodies, and aortic fatty streak lesions. Using a genome scan approach, we identified 4 quantitative trait loci controlling plasma lipoprotein levels on chromosomes (Chrs) 5, 8, 15, and 19. The locus on Chr 15 exhibited lod scores of 11.1 for total cholesterol and 6.7 for VLDL and LDL cholesterol in mice fed an atherogenic diet, and it contains a candidate gene, the sterol regulatory element binding protein-2. The locus on Chr 5 exhibited lod scores of 3.8 for total cholesterol and 4.1 for unesterified cholesterol in mice fed an atherogenic diet, and this locus has been observed in 2 previous studies. The locus on Chr 8 exhibited a lod score of 3.1 for unesterified cholesterol in mice fed a chow diet. This locus contains the lecithin-cholesterol acyltransferase gene, and decreased activity of the enzyme in the MRL strain suggests that this gene underlies the quantitative-trait locus. The locus on Chr 19 exhibited a lod score of 8.4 for HDL cholesterol and includes the Fas gene, which is mutated in MRL/lpr mice and is primarily responsible for the autoimmune phenotype in this cross. That the Fas gene is responsible for the HDL quantitative-trait loci is supported by the finding that autoantibody levels were strongly correlated with HDL cholesterol levels (rho=-0.37, P<0.0001) among the F2 mice. HDL cholesterol levels were in turn significantly associated with aortic fatty streak lesions among the F2 mice (rho=-0.17, P=0.006). Further, there was a threshold effect of autoantibody levels on the development of fatty streak lesions (rho=0.45, P=0.004 for 42 F2 mice with anti-dsDNA Ab over 0.5 OD). Our results support the concept that the high prevalence of coronary artery disease in systemic lupus erythematosus is due in part to a reduction of HDL cholesterol levels resulting from the autoimmune disease.

OBJECTIVE

Serum paraoxonase (PON) is a calcium-dependent esterase that is known to contribute to the antioxidant protection conferred by high-density lipoprotein (HDL) on low-density lipoprotein (LDL) oxidation. Serum PON activity was shown to be reduced in patients with diseases such as myocardial infarction, diabetes mellitus, etc in comparison to healthy subjects. However, the relation of serum PON levels to cancer is still not known. So, we intended to measure serum PON, HDL, LDL and very low-density lipoprotein (VLDL) levels and to investigate the relation of serum PON to plasma lipoproteins in the patients with pancreatic cancer.

METHODS

We measured serum PON, HDL, LDL, and VLDL levels in 20 patients with pancreatic cancer and in 20 age-and gender-matched healthy controls. We investigated the relationship between PON and HDL, PON and LDL, and PON and VLDL.

RESULTS

Serum HDL levels were lower in the patients than in controls (40.21 +/- 13.82 mg/dL, and 47.30 +/- 6.65 mg/dL, respectively) (p<0.05). Serum LDL and VLDL levels measured in the patient group were not significantly different from those of the control group. Serum PON levels were lower in the patients than in controls (61.57 +/- 22.44 U/L, and 87.50 +/- 23.39 U/L, respectively) (p<0.005). There was a positive correlation between serum PON and HDL levels (r: 0.69, p<0.05).

CONCLUSIONS

We concluded that the patients with pancreatic cancer had low PON and HDL levels compared to healthy controls. The importance of PON as a predictive risk factor for cancer should be assessed in future studies.

A specific isoform of apolipoprotein E has been associated with the accelerated rate of disease expression of sporadic Alzheimer's disease (AD) and late-onset familial AD (FAD). An earlier age at onset has also been demonstrated in familial AD patients with mutations in the amyloid precursor protein (APP) gene (APP717 and APP670/671)13 carrying the APOE epsilon-4 allele compared to those who do not, but not in familial AD patients with APP692 or 693 mutations, or in chromosome 14-linked familial AD patients. Hypothesizing that receptors for apoE-containing lipoproteins act as a potential risk factor for AD, we performed an association study using a polymorphic triplet (CGG) repeat in the gene for the VLDL receptor (VLDL-R), a receptor for apoE-containing lipoproteins. The frequency of the 5-repeat allele was significantly higher in all of the Japanese sporadic AD patients (P < 0.02) than in the Japanese controls. Moreover, the odds ratio was significantly increased in the AD patients homozygous for the 5-repeat allele (OR = 2.1, 95% CI = [1.1-4.2]). Multiple logistic regression analysis reveals that the relative risk conferred by the presence of two copies of the 5-repeat allele and at least one copy of the APOE epsilon-4 allele is 8.7 (95% CI = [2.9-25.8]). Our results suggest that the VLDL-R gene is a susceptibility gene for AD.

The relationship between risk factors for CHD such as physical activity, cardiovascular fitness, subcutaneous body fat, dietary intake characteristics, age, and sex with the blood lipid profile was examined in 39 boys and 58 girls aged 10-15 yr. In boys, a high level of physical activity was related to higher concentrations of HDL-C (r = 0.32, P < 0.05), as well as to lower concentrations of VLDL-C, total triglycerides (TG), and the ratio of total cholesterol (TC) to HDL-C (r = -0.42; -0.40, both P < 0.01; and -0.37, P < 0.05). A high sum of 10 skinfolds (sigma 10SF) was related to a higher ratio of TC/HDL-C (r = 0.35; P < 0.05). In girls, physical activity was positively related to HDL-C (r = 0.29; P < 0.05). The sigma 10SF showed a negative association with Apo A-I and HDL-C (r = -0.26, -0.29, both P < 0.05) and a positive association with apolipoprotein B (Apo B) (r = 0.28, P < 0.05). Cardiovascular fitness was not significantly related to any of the blood lipid concentrations, in either boys or girls. Intake of saturated fats and dietary cholesterol was positively related to TC levels in boys, but the associations failed to reach statistical significance (r = 0.34 and r = 0.31, P>> 0.05) due to the small sample size (N = 32).(ABSTRACT TRUNCATED AT 250 WORDS)

The primary determinants of hepatic uptake of long chain fatty acids have been considered to be the plasma concentrations of fatty acid and albumin, with little or no intrinsic control by the hepatocyte itself. However, recent studies of liver cell suspensions have shown that in immature, adult, castrated, and hormone-treated rats, sex steroids exert striking effects on [(14)C]oleate uptake and utilization (which were significantly increased by estradiol and diminished by testosterone). To determine whether these observed sex differences in fatty acid uptake also were present in the intact liver, single-pass [(14)C]oleate uptake was measured in isolated perfused livers. Livers from sexually mature female and male rats were perfused single-pass with albumin-bound [(14)C]oleate in Krebs-Ringer bicarbonate buffer. Net uptake, calculated as the product of the transhepatic difference in (14)C-labeled fatty acid concentration and perfusate flow rate, reached a steady-state within 1 min and remained constant throughout the 10-min perfusion period. At 0.17 mM [(14)C]oleate and 0.15 mM albumin, extraction fraction and net uptake of [(14)C]oleate per gram liver were more than twice as great in females as in male livers (0.33 +/- 0.03 versus 0.15 +/- 0.02, P < 0.001; and 218 +/- 22 versus 101 +/- 15 nmol/g liver, P < 0.01, with parallel differences in [(14)C]oleate total utilization and incorporation into triglycerides. Significant differences in uptake also were observed at higher [(14)C]oleate concentrations (0.34 and 0.68 mM). Under all conditions, oxidation of [(14)C]oleate in female liver equaled or exceeded that in male liver, indicating that the increased incorporation into triglycerides and other glycerolipids was not simply the result of differences in the distribution of [(14)C]oleate among cellular metabolic pathways. These studies demonstrate that in the intact liver, as in isolated hepatocytes, there are profound sex differences in the uptake of long chain fatty acids. This difference may account in part for the observed sex steroid effects on hepatic triglyceride biosynthesis and VLDL production. The mechanism of these uptake differences remains to be determined.-Kushlan, M. C., J. L. Gollan, W-L. Ma, and R. K. Ockner. Sex differences in hepatic uptake of long chain fatty acids in single-pass perfused rat liver.

A specific, precise, and sensitive double-antibody radioimmunoassay for the measurement of human apolipoprotein CII (apoCII) was developed. ApoCII was labeled with (125)I (chloramine-T) and monospecific antibody was raised in rabbits. No appreciable cross-reactivity with apolipoproteins CI, CIII, AI, AII, low density lipoproteins, and lipoprotein-free plasma was observed. Lipoproteins containing apoCII displaced the standard curve in parallel. ApoCII measurement was not affected by pretreatment of plasma with tetramethylurea, ethanol-diethyl ether, or heating. Mean (+/-SE) plasma-immunoreactive apoCII in 47 normotriglyceridemic subjects was 51.8+/-3.2 mug/ml, generally comparable with previous estimates of its concentration by other methods. ApoCII levels in 9 subjects with type IIB lipoprotein pattern, 14 with the type IV lipoprotein pattern, and 5 with type V lipoprotein pattern were respectively, 89.9+/-4.6, 85.4+/-6.9, 132.8+/-21.0 mug/ml, all higher than normals (P < 0.001). Plasma apoCII and triglyceride concentrations correlated in normo- and hypertriglyceridemics (r = 0.36 and 0.58, P < 0.05). Plasma triglycerides correlated inversely with the fraction of total apoCII in very low density lipoprotein (VLDL)-free plasma (r = -0.75, P < 0.01). There was no correlation between plasma apoCII and high density lipoprotein cholesterol. In normotriglyceridemics, VLDL apoCII levels correlated with in vitro lipoprotein lipase (LPL) activator activities (r = 0.89, P < 0.01). In hypertriglyceridemic subjects the mean concentrations of apoCII per milligrams VLDL protein, LPL activator activity per milligrams VLDL protein, and LPL activator activity per micrograms VLDL apoCII were all lower than in normotriglyceridemics, P < 0.05. As plasma triglycerides and apoCII increase, apoCII is redistributed from high density lipoprotein to VLDL. However, the amount of apoCII per milligram VLDL protein and its LPL activator potency per milligram VLDL protein are reduced. These factors may contribute to impaired VLDL catabolism.

In order to study the lipoprotein pattern in diabetes mellitus, plasma lipoproteins were isolated by rate zonal centrifugation in 12 control subjects (median fasting blood glucose level: 80 mg/dl (range: 74-86)), 14 diabetic patients treated by diet alone 104 mg/dl (76-153), 27 patients treated by diet plus insulin (180 mg/dl (106-404)), and 32 patients treated by diet plus sulphonylurea [178 mg/dl (103-361)]. No significant differences of median relative body weight existed between the four groups. Neither the diabetic group on diet alone nor the insulin-treated group differed significantly from control subjects with respect to lipid and lipoprotein concentrations. Diabetics treated with diet plus sulphonylurea, however, differed significantly from the control group with regard to the following parameters (median and range); plasma triglycerides (210 [75-620) mg/dl; p less than 0.01)] and intermediate density lipoproteins (65 (10-338) mg/dl; p less than 0.05)) were higher; low density lipoproteins (236 (82-418) mg/dl; p less than 0.05)) and high density lipoproteins2 (HDL2) [51 (12-121) mg/dl; p less than 0.01)] concentrations were lower. When data from all 85 studied individuals were analysed together, significant positive correlations were observed between fasting blood glucose and plasma triglyceride concentration (r = 0.28, p less than 0.01), and between fasting blood glucose and plasma very low density lipoproteins (VLDL) (r = 0.23, p less than 0.05). A negative correlation was found between blood glucose and plasma HDL2 (r = -0.29, p less than 0.01). In addition, VLDL correlated negatively with HDL2 (r = -0.89, p less than 0.001) but not with plasma HDL3 concentration. It is concluded that the deranged lipoprotein metabolism in diabetes mellitus may be better controlled by insulin than by sulphonylureas.

The hypocholesterolemic and anti-atherogenic properties of sulfamic acid ((2,4,6-tris (1-methylethyl) phenyl) acetyl) 2,6-bis(1-methylethyl) phenyl ester, the ACAT inhibitor, CI-1011, was tested in 120 male F1B hamsters fed a hypercholesterolemic chow-based diet containing 10%, coconut oil and 0.05% cholesterol plus: (i) no drug treatment (HCD); (ii) 3 mg/kg per day (HCD+3): (iii)10 mg/kg per day (HCD+10); (iv) 30 mg/kg per day (HCD+30) of CI-1011; or (v) 500 mg/kg per day of cholestyramine (CSTY). Plasma samples were collected at 8 and 10 weeks for measurement of total cholesterol (TC), very low-density lipoprotein cholesterol (VLDL-C), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG). For the progression studies, animals were euthanized after 10 weeks for aortic fatty streak area and hepatic cholesterol analysis. For the regression study, a cohort of the HCD was treated with 30 mg/kg per day of CI-1011 (regression) for an additional 8 weeks. The HCD+3, HCD+10, HCD+30 and CSTY lowered plasma TC (25, 32, 34 and 32%, respectively), VLDL-C (62, 74, 71 and 75%, respectively), LDL-C (25, 38, 47 and 46%, respectively) and TG (48, 47, 42 and 45%, respectively). All treatments resulted in a significant lowering of aortic fatty streak area (68, 86, 93 and 94%, respectively) and reduction in hepatic cholesteryl esters (57, 65, 67 and 70%, respectively). Regression of aortic fatty streak area was 90% after 8 weeks of HCD+30 treatment. Also during the regression phase, plasma TC, LDL-C and TG were lowered 23, 33 and 47%, respectively, as well as, hepatic cholesteryl esters (76%). Significant correlations between plasma LDL-C concentration and aortic fatty streak area (r=0.62, P < 0.004) in the HCD+10 group, suggest that CI-1101 altered aortic lipid infiltration primarily by its effect on plasma lipids. However the 30 mg/kg per day dose of CI-1011 which additionally reduced aortic fatty streak area by 51% relative to the 10 mg/kg per day dose was only associated with a 14% further decrease in plasma LDL-C. Finally the 10-fold regression of aortic fatty streak area was associated with only a 35% reduction in plasma LDL-C. These exceptions to the lipid-lesion relationship raise the possibility of additional effects of CI-1011, which may occur independent of or in concert with lipoprotein cholesterol lowering. It is concluded that in hypercholesterolemic hamsters, CI-1011 is approximately 50 times more potent than cholestyramine in cholesterol-lowering, reduction and regression of aortic fatty streak area.

BACKGROUND

Although LDL cholesterol (LDL-C) is generally accepted to be a major risk factor for progression of atherosclerosis, the traditional measurement of LDL-C includes measurement of IDL. Little is known about the relationship between IDL and progression of atherosclerosis. Therefore, we investigated the association of plasma lipoprotein subclasses with progression of preintrusive carotid artery atherosclerosis in the Monitored Atherosclerosis Regression Study (MARS).

RESULTS

MARS was a randomized, double-blind, placebo-controlled serial arterial imaging trial conducted in subjects 37 to 67 years old with angiographically defined coronary artery disease. Analytical ultracentrifugation was used to determine lipoprotein subclasses, including LDL (Sf 0 to 12), IDL (Sf 12 to 20), VLDL (Sf 20 to 400), and HDL (F1.20 0 to 9) in 188 subjects. Subjects were randomized to a cholesterol-lowering diet plus placebo or lovastatin 80 mg/d. The outcome measure, the annual progression rate of the distal common carotid artery far wall intima-media thickness determined by high resolution B-mode ultrasonography, was determined at baseline and every 6 months on trial. When the major apolipoprotein B-containing lipoproteins were measured independently, IDL (r=.21, P<.005) but not VLDL (r=-.09, P=.24) or LDL (r=.09, P=.26) was associated with the progression of carotid artery intimamedia thickness.

CONCLUSIONS

These data provide further evidence for the role of triglyceride-rich lipoproteins in the progression of atherosclerosis and support the evidence that indicates that the risk of atherosclerosis attributable to LDL-C may in part be the result of lipoproteins in the IDL fraction (Sf 12 to 20) that is included within the traditional measurements of LDL-C.

Heart-healthy dietary recommendations include decreasing the intake of saturated fatty acids (SFA). However, the relative benefit of replacing SFA with monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), or carbohydrates (CARB) is still being debated. We have used two mouse models of atherosclerosis, low density lipoprotein receptor-deficient (LDLRKO) and apolipoprotein E-deficient (apoEKO) mice to measure the effects of four isocaloric diets enriched with either SFA, MUFA, PUFA, or CARB on atherosclerotic lesion area and lipoprotein levels. In LDLRKO mice, compared with the SFA diet, the MUFA and CARB diets significantly increased atherosclerosis in both sexes, but the PUFA diet had no effect. The MUFA and CARB diets also increased very low density lipoprotein-cholesterol (VLDL-C) and LDL-cholesterol (LDL-C) in males and VLDL-C levels in females. Analysis of data from LDLRKO mice on all diets showed that atherosclerotic lesion area correlated positively with VLDL-C levels (males: r = 0.47, P < 0.005; females: r = 0.52, P < 0.001). In contrast, in apoEKO mice there were no significant dietary effects on atherosclerosis in either sex. Compared with the SFA diet, the CARB diet significantly decreased VLDL-C in males and the MUFA, PUFA, and CARB diets decreased VLDL-C and the CARB diet decreased LDL-C in females. In summary, in LDLRKO mice the replacement of dietary SFA by either MUFA or CARB causes a proportionate increase in both atherosclerotic lesion area and VLDL-C. There were no significant dietary effects on atherosclerotic lesion area in apoEKO mice. These results are surprising and suggest that, depending on the underlying genotype, dietary MUFA and CARB can actually increase atherosclerosis susceptibility, probably by raising VLDL-C levels through a non-LDL receptor, apoE-dependent pathway.

OBJECTIVE

Cigarette smoking is a recognized risk factor for cardiovascular diseases and has been implicated in the pathogenesis of atherosclerosis. Platelet adhesiveness and aggregation increases as a result of smoking. Cigarette smoking modifies haemostatic parameters via thrombosis with a consequently higher rate of cardiovascular events, but smoking-induced alterations of platelet membrane fluidity and other changes have not been studied.

METHODS

Thirty experimental and control subjects (mean age 35+/-8) were selected for the study. Experimental subjects had smoked 10+/-2 cigarettes per day for 7-10 years. The plasma lipid profile, platelet carbonyls, sulfhydryl groups, Na(+)/k(+)-ATPase activity, fluidity using a fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH), total cholesterol and phospholipids as well individual phospholipids were determined.

RESULTS

Increases in the platelet membrane cholesterol phospholipid (C/P) ratio, phosphotidylethanolamine, phosphotidylserine with decreased phosphotidylcholine, Na(+)/k(+)-ATPase activity, fluidity and no significant change in phosphotidylinositol and sphingomylein, as well as increases in plasma total cholesterol, LDL-cholesterol, protein carbonyls with decreased HDL-cholesterol and sulfhydryl groups were observed in cigarette smokers. Platelet membrane total phospholipids were positively correlated with plasma LDL-cholesterol (r=0.568) and VLDL-cholesterol (r=0.614) in cigarette smokers.

CONCLUSIONS

Increased plasma LDL-cholesterol, VLDL-cholesterol and total cholesterol might have resulted in the increased C/P ratio and decreased platelet membrane fluidity of cigarette smokers.

Alterations in plasma high density lipoproteins (HDL) were studied in thirty-eight male chronic alcoholics. Twenty-four (63%) of the patients had increased HDL protein (measured immunochemically) and twenty-five (66%) had increased HDL cholesterol (determined after polyanion precipitation of very low density lipoproteins (VLDL) and low density lipoproteins (LDL)). A statistically significant correlation was found between HDL protein and HDL cholesterol (r = 0.39). gamma-Glutamyltransferase (GT) was elevated in eighteen (47%) of the alcoholics. No significant correlations were found between GT and HDL protein or HDL cholesterol. The increase in HDL, as studied by rate zonal ultracentrifugation, was heterogeneous with changes in the HDL2 as well as HDL3 subfractions. It is suggested that determination of HDL total cholesterol, in combination with GT, may represent a valuable and sensitive test for detection of alcoholism.