Atheroprotective mechanisms of HDL

Human endothelial progenitor cells internalize high-density lipoprotein

Endothelial progenitor cells (EPCs) originate either directly from hematopoietic stem cells or from a subpopulation of monocytes. Controversial views about intracellular lipid traffic prompted us to analyze the uptake of human high density lipoprotein (HDL), and HDL-cholesterol in human monocytic EPCs. Fluorescence and electron microscopy were used to investigate distribution and intracellular trafficking of HDL and its associated cholesterol using fluorescent surrogates (bodipy-cholesterol and bodipy-cholesteryl oleate), cytochemical labels and fluorochromes including horseradish peroxidase and Alexa Fluor® 568. Uptake and intracellular transport of HDL were demonstrated after internalization periods from 0.5 to 4 hours. In case of HDL-Alexa Fluor® 568, bodipy-cholesterol and bodipy-cholesteryl oleate, a photooxidation method was carried out. HDL-specific reaction products were present in invaginations of the plasma membrane at each time of treatment within endocytic vesicles, in multivesicular bodies and at longer periods of uptake, also in lysosomes. Some HDL-positive endosomes were arranged in form of "strings of pearl"- like structures. HDL-positive multivesicular bodies exhibited intensive staining of limiting and vesicular membranes. Multivesicular bodies of HDL-Alexa Fluor® 568-treated EPCs showed multilamellar intra-vacuolar membranes. At all periods of treatment, labeled endocytic vesicles and organelles were apparent close to the cell surface and in perinuclear areas around the Golgi apparatus. No HDL-related particles could be demonstrated close to its cisterns. Electron tomographic reconstructions showed an accumulation of HDL-containing endosomes close to the trans-Golgi-network. HDL-derived bodipy-cholesterol was localized in endosomal vesicles, multivesicular bodies, lysosomes and in many of the stacked Golgi cisternae and the trans-Golgi-network Internalized HDL-derived bodipy-cholesteryl oleate was channeled into the lysosomal intraellular pathway and accumulated prominently in all parts of the Golgi apparatus and in lipid droplets. Subsequently, also the RER and mitochondria were involved. These studies demonstrated the different intracellular pathway of HDL-derived bodipy-cholesterol and HDL-derived bodipy-cholesteryl oleate by EPCs, with concomitant.

Statin treatment improves plasma lipid levels but not HDL subclass distribution in patients undergoing percutaneous coronary intervention

Despite the established efficacy of statin therapy, the risk of cardiovascular events remains high in many patients. We examined high-density lipoprotein (HDL) subclass distribution profiles among statin-treated coronary heart disease (CHD) patients undergoing percutaneous coronary intervention (PCI). Plasma HDL subclasses were measured in 85 patients with established CHD and quantified by two-dimensional gel electrophoresis and immunoblotting. In CHD patients with statin treatment, the mean value of total cholesterol (TC) reached the desirable level and the triacylglycerol level (TAG) was borderline high. Moreover, low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), apolipoproteinA-I, and apolipoproteinB-100 levels in these patients resembled those in normolipidemic healthy subjects. The HDL subclass did not show a normal distribution and was characterized by the lower large-sized HDL(2b) contents and higher contents of small-sized preβ₁-HDL in CHD patients, compared to those in normolipidemic control subjects. Multiple stepwise regression analysis revealed that the severity of coronary stenosis, determined by the Gensini Score, was significantly and independently predicted by HDL(2b) and HDL(3b). Statin therapy was effective in modifying plasma lipids levels, but not adequate as a monotherapy to normalize the HDL subclass distribution phenotype of patients with CHD undergoing PCI. The HDL subclass distribution may aid in risk stratification, especially in patients with CHD and therapeutic LDL-C and HDL-C levels.

HDL inflammation and atherosclerosis: current and future perspectives

The role of high-density lipoprotein (HDL) in the genesis and evolution of cardiovascular disease is a topical and interesting issue. Reduced HDL concentrations appear to be unable to efficiently eliminate the cholesterol excess at the vascular wall level, contributing to the onset of the inflammatory response that typically occurs in the pathogenesis of atherosclerosis from its earliest stages. In the last decade, many studies have explored the possibility of reducing cardiovascular risk through modulation of HDL levels, glimpsing new fascinating therapeutic horizons. This review summarizes recent findings on HDL and cardiovascular disease, mainly with an educational objective, considering the biochemical, cellular and molecular aspects of these particles.

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.

Harnessing a physiologic mechanism for siRNA delivery with mimetic lipoprotein particles

Therapeutics based on RNA interference (RNAi) have emerged as a potential new class of drugs for treating human disease by silencing the target messenger RNA (mRNA), thereby reducing levels of the corresponding pathogenic protein. The major challenge for RNAi therapeutics is the development of safe delivery vehicles for small interfering RNAs (siRNAs). We previously showed that cholesterol-conjugated siRNAs (chol-siRNA) associate with plasma lipoprotein particles and distribute primarily to the liver after systemic administration to mice. We further demonstrated enhancement of silencing by administration of chol-siRNA pre-associated with isolated high-density lipoprotein (HDL) or low-density lipoprotein (LDL). In this study, we investigated mimetic lipoprotein particle prepared from recombinant apolipoprotein A1 (apoA) and apolipoprotein E3 (apoE) as a delivery vehicle for chol-siRNAs. We show that apoE-containing particle (E-lip) is highly effective in functional delivery of chol-siRNA to mouse liver. E-lip delivery was found to be considerably more potent than apoA-containing particle (A-lip). Furthermore, E-lip–mediated delivery was not significantly affected by high endogenous levels of plasma LDL. These results demonstrate that E-lip has substantial potential as delivery vehicles for lipophilic conjugates of siRNAs.

CNR1 genotype influences HDL-cholesterol response to change in dietary fat intake

BACKGROUND

Success in further reducing the burden of cardiovascular disease (CVD) is threatened by the increasing prevalence of obesity-related atherogenic dyslipidemia. HDL-cholesterol (HDL-C) level is inversely correlated with CVD risk; each 1 mg/dl decrease in HDL-C is associated with a 6% reduction in risk. We previously showed that a common CNR1 haplotype, H3 (frequency 20%), is protective against the reduction in HDL-C that typically accompanies weight gain. In the present study, we extend that observation by reporting the effect of CNR1 haplotype on HDL-C response to modification of dietary fat intake in weight maintenance and weight loss.

METHODS

Six haplotype tagging SNPs that cover the CNR1 gene locus were genotyped in 590 adults of varying body mass index (cohort 1 is 411 males with BMI 18.5-30.0 kg/m(2); cohort 2 is 71 females with BMI18.5-30.0 kg/m(2); and cohort 3 is 108 females with BMI 30-39.9 kg/m(2)). Dietary intakes were modified so that fat intake in the "high fat" condition was 15-20% greater than in the "low fat" condition, and lipid profiles were compared between carriers versus noncarriers for each of the five commonly observed CNR1 haplotypes (H1-H5).

RESULTS

In normal to overweight subjects on eucaloric diets, the H3 haplotype was significantly associated with short-term high fat diet induced changes in HDL-C level in females (carriers 5.9 mg/dl>noncarriers, p = 0.007). The H3 haplotype was also significantly associated with HDL-C level after 16 weeks on high fat calorie restricted diet in obese females (carriers 6.8 mg/dl>noncarriers, p = 0.009).

CONCLUSION

Variability within the CNR1 gene locus contributes to gender-related differences in the HDL-cholesterol response to change in dietary fat intake. Functional characterization of this relationship in vitro may offer insights that potentially yield therapeutic guidance targeting dietary macronutrient composition, a direction much needed in the current epidemic of obesity.

High-density lipoprotein subclasses and their relationship to cardiovascular disease

OBJECTIVE

To assess the clinical utility of measuring high-density lipoprotein (HDL) subfractions to assess coronary heart disease (CHD) risk.

METHODS

Literature review of 80 published investigations.

RESULTS

Measurements of HDL2b by gradient gel electrophoresis provided more consistent evidence of CHD risk than measurement of HDL2 cholesterol. Five of the seven studies that compared the extent or progression of atherosclerosis with gradient gel electrophoresis estimates of HDL subclasses (71%) assigned statistical significance to HDL2b. Ten of the 11 case-control comparisons (91%) reported lower HDL2b in cases. In contrast, of the 16 association studies relating HDL2 cholesterol and HDL3 cholesterol to extent of disease, five reported no significant relationships with either subfraction, two reported significant relationships with both HDL2 and HDL3 cholesterol, four reported significant relationships with HDL2 but not HDL3 cholesterol, and five reported relationships with HDL3 but not HDL2 cholesterol. Forty-five percent of the case-control comparisons reported that both HDL2 cholesterol and HDL3 cholesterol were significantly lower in cases than controls, 17% failed to find significance for either subfraction, and the remainder reported significantly lower values in cases for HDL2 cholesterol only (26%) or HDL3 cholesterol only (11%). On average, the case-control differences were similar for HDL2 (-0.12 ± 0.01 mmol/L) and HDL3 cholesterol (-0.10 ± 0.02 mmol/L), although relative to controls, the percent reduction was twice as great for HDL2 (-25.7 ± 2.9%) than HDL3 cholesterol (-12.1 ± 1.5%). Eight prospective studies were identified and four reported that both HDL2 and HDL3 predicted lower risk for CHD, one reported reductions in risk for HDL2 but not HDL3 cholesterol, and three reported reductions in risk for HDL3 but not HDL2 cholesterol. None of the prospective studies show that measurements of HDL cholesterol subfractions improve the identification of persons at risk.

CONCLUSIONS

HDL2 and HDL3 cholesterol do not distinguish cardioprotective differences between HDL subclasses. More extensive characterization of HDL particles by one or two dimensional gel electrophoresis, ion mobility, or ultracentrifugation may provide more specific information about CHD risk than the measurement of HDL cholesterol, HDL3 cholesterol, or HDL2 cholesterol.

Carriers of lecithin cholesterol acyltransferase gene mutations have accelerated atherogenesis as assessed by carotid 3.0-T magnetic resonance imaging [corrected]

OBJECTIVES

The aim of this study was to investigate the role of reduced lecithin: cholesterol acyltransferase (LCAT) function on atherogenesis using 3.0-T carotid magnetic resonance imaging (MRI) and B-mode ultrasound.

BACKGROUND

The role of low high-density lipoprotein cholesterol as a causal factor in atherogenesis has recently been questioned. LCAT plays a key role in high-density lipoprotein cholesterol metabolism.

METHODS

Carotid 3.0-T MRI and B-mode ultrasound measurements were performed in 40 carriers of LCAT gene mutations and 40 controls, matched for age. Patients with cardiovascular disease were excluded.

RESULTS

Carriers had 31% lower LCAT activity levels and 38% decreased high-density lipoprotein cholesterol levels (both p < 0.001 vs. controls). Carriers presented with a 10% higher normalized wall index (0.34 ± 0.07 vs. 0.31 ± 0.04, p = 0.002), a 22% higher mean wall area (17.3 ± 8.5 mm(2) vs. 14.2 ± 4.1 mm(2), p = 0.01), and a 22% higher total wall volume (1,039 ± 508 mm(3) vs. 851 ± 247 mm(3), p = 0.01 vs. controls) as measured by MRI. The prevalence (20 vs. 5, p = 0.002) and the total volume (102 mm(3) vs. 3 mm(3)) of atherosclerotic plaque components on MRI relating to lipid-rich tissue or calcification were also higher in carriers than in controls. All differences retained significance after adjustment for age, sex, blood pressure, low-density lipoprotein cholesterol, body mass index, smoking, and family history of cardiovascular disease. Common carotid intima-media thickness measured with ultrasound was increased in carriers by 12.5% (0.72 ± 0.33 mm vs. 0.64 ± 0.15 mm, p = 0.14).

CONCLUSIONS

Carriers of LCAT gene mutations exhibit increased carotid atherosclerosis, indicating an increased risk of cardiovascular disease. The present findings imply that increasing LCAT activity may be an attractive target in cardiovascular prevention strategies.

Identification of dehydroxytrichostatin A as a novel up-regulator of the ATP-binding cassette transporter A1 (ABCA1)

The ATP-binding cassette transporter A1 (ABCA1) mediates the cellular efflux of excess cholesterol and phospholipids to lipid-poor apolipoprotein A-I (apoA-I). ABCA1 plays an important role in high-density lipoprotein (HDL) biogenesis and reverse cholesterol transport. By using a cell-based screening model for the ABCA1 up-regulator and column chromatography, an active compound, 9179B, was isolated. Through analysis of its NMR data, 9179B was identified as dehydroxytrichostatin A. We found that 9179B increased the transcription of ABCA1 in a cell-based reporter assay, with an EC₅₀ value of 2.65 μM. 9179B up-regulated ABCA1 expression at both mRNA and protein levels in HepG2 and RAW264.7 cells. It also up-regulated the expression of scavenger receptor class B type I (SR-BI) as well as the uptake of DiI-HDL in RAW264.7 cells. This compound stimulated ApoA-I-mediated cellular cholesterol efflux from RAW 264.7 cells. We further found that 9179B was a potent histone deacetylase (HDAC) inhibitor with an IC₅₀ value of 0.08 μM. Reporter gene assays showed that the regulation of ABCA1 transcription by 9179B was mainly mediated by the −171/−75 bp promoter region. Together, our results indicate that 9179B is an ABCA1 up-regulator and dehydroxytrichostatin A may be a novel anti-atherogenic compound.

Effects of apple cider vinegars produced with different techniques on blood lipids in high-cholesterol-fed rats

Red delicious apples were used to produce natural apple cider with and without inclusion of maceration. Traditional surface and industrial submersion methods were then applied to make vinegar from apple ciders. Apple cider vinegar samples produced with inclusion of maceration in the surface method had the highest total phenolic content, chlorogenic acid, ORAC, and TEAC levels. Cholesterol and apple vinegar samples were administered using oral gavage to all groups of rats except the control group. Apple cider vinegars, regardless of the production method, decreased triglyceride and VLDL levels in all groups when compared to animals on high-cholesterol diets without vinegar supplementation. Apple cider vinegars increased total cholesterol and HDL and LDL cholesterol levels and decreased liver function tests when compared to animals on a high-cholesterol diet without vinegar supplementation. A high-cholesterol diet resulted in hepatic steatosis. VSBM and VSB groups significantly decreased steatosis.

Hypolipidaemic and hypoglycaemic effects of total flavonoids from seed residues of Hippophae rhamnoides L. in mice fed a high-fat diet

BACKGROUND

The present study was designed to investigate the hypolipidaemic and hypoglycaemic effects of total flavonoids from seed residues of Hippophae rhamnoides L. (FSH) in a high-fat diet fed mouse model. Consumption of a high-fat diet (HFD) for 4 weeks caused a significant rise of serum total cholesterol in mice. These hypercholesterolaemic mice then were orally administrated with different doses of FSH (50, 100 and 150 mg kg⁻¹ body weight) and simvastatin (20 mg kg⁻¹ body weight) for another 12 weeks under continuous HFD feeding.

RESULTS

FSH administration markedly reduced total mouse body, liver, and epididymal fat pad weights. Serum total cholesterol and low density of lipoprotein-cholesterol levels were also significantly decreased by FSH treatment. Additionally, FSH significantly lowered total cholesterol and triglyceride concentrations in liver, and the results were corroborated by transmission electron microscope findings. The rise in serum glucose was significantly suppressed by FSH treatment while improving impaired glucose tolerance.

CONCLUSION

These results suggest that FSH possesses hypolipidaemic and hypoglycaemic properties in mice fed a high-fat diet and could be developed as a supplement in healthcare foods and drugs.

Expression and recovery of biologically active recombinant Apolipoprotein AI(Milano) from transgenic safflower (Carthamus tinctorius) seeds

Apolipoprotein AI Milano (ApoAI(Milano) ) was expressed as a fusion protein in transgenic safflower seeds. High levels of expression corresponding to 7 g of ApoAI(Milano) per kilogram of seed have been identified in a line selected for commercialization. The ApoAI(Milano) fusion protein was extracted from seed using an oilbody-based process and matured in vitro prior to final purification. This yielded a Des-1,2-ApoAI(Milano) product which was confirmed by biochemical characterization including immunoreactivity against ApoAI antibodies, isoelectric point, N-terminal sequencing and electrospray mass spectrometry. Purified Des-1,2-ApoAI(Milano) readily associated with dimyristoylphosphatidylcholine in clearance assays comparable to Human ApoAI. Its biological activity was assessed by cholesterol efflux assays using Des-1,2-ApoAI(Milano) :1-palmitoyl-2-oleoyl phosphatidylcholine complexes in vitro and in vivo. This study has established that high levels of biologically functional ApoAI(Milano) can be produced using a plant-based expression system.

The role of ATP-binding-cassette-transporter-A1 (ABCA1) gene polymorphism on coronary artery disease risk

ATP-binding cassette transporter A1 (ABCA1) plays a pivotal role in intracellular cholesterol removal and exerts a protective effect against atherosclerosis. The role of genetic factors in susceptibility to coronary artery disease (CAD) is not clear. The aim of this study was to evaluate for the first time the possible association between R219K gene polymorphism and coronary artery disease in an Iranian adult population. A total of 207 consecutive patients with CAD (group A) and 94 patients without CAD (group B) were studied. We determined the presence of the R219K variant in the ABCA1 gene by polymerase chain reaction (PCR) and restriction analysis in 301 patients with and without CAD. The distribution of genotypes among the 2 groups was significantly different (P=0.009). In univariate analysis (with genotype AA as reference), the GG genotype was associated with a significantly increased risk of CAD (P=0.002; odds ratio [OR]=2.761; 95% confidence interval [CI]=1.418-5.374), but the GA genotype did not show a significant association (P=0.234) (data not shown). A multivariate logistic regression analysis (using sex as clinically significant variable, and using age, diabetes mellitus, low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein [HDL], smoking, body mass index [BMI], and genotype as statistically significant variables) was used to determine independent associations and adjusted ORs. The GG genotype (compared with the AA genotype) was an independent predictor of CAD (OR=2.856, 95% CI=1.307-6.241; P=0.009), followed by BMI (P=0.034; OR=1.100; 95% CI=1.007-1.200). The GG genotype in the ABCA1 gene is independently associated with CAD in Iranian patients.

Impaired anti-inflammatory function of apolipoprotein A-II concentrations predicts metabolic syndrome and diabetes at 4 years follow-up in elderly Turks

BACKGROUND

We evaluated prospectively the predictive value of serum apolipoprotein (apo) A-II, the second major apolipoprotein of high-density lipoprotein (HDL), for cardiometabolic risk in Turkish adults showing abnormalities in other proteins that normally confer protection.

METHODS

Determinants of apoA-II and its associations with coronary heart disease (CHD), metabolic syndrome (MetS) and diabetes were investigated at 4 years follow-up in 193 elderly men and women.

RESULTS

ApoA-II concentrations at baseline, in addition to being significantly related to HDL-cholesterol, were directly associated with complement C3 in multivariate linear regression analyses comprising nine variables. Following adjustment for gender, age and HDL-cholesterol (>30/>33 g/L, in men and women, respectively), low serum apoA-II concentrations predicted incident MetS [relative risk (RR) 3.5 (95% CI 1.4; 8.6)] and type 2 diabetes [RR 4.5 (95% CI 1.3; 15.6)] in both genders at an increment of 1 SD. Increased apoA-II values were not associated with prevalent or incident CHD, and tended to be marginally atheroprotective only in males.

CONCLUSIONS

Serum apoA-II concentrations confer risk for MetS and diabetes and exhibit evidence of anti-inflammatory properties among Turks. These findings support the effects seen for several other HDL protein constituents. This finding may explain the increased cardiometabolic risk among Turks.

Antihyperlipidaemic activity of swertiamarin, a secoiridoid glycoside in poloxamer-407-induced hyperlipidaemic rats

We have investigated antihyperlipidaemic effect of swertiamarin (50 mg/kg, oral once) isolated from the perennial herb Enicostemma littorale Blume in poloxamer 407 (P-407)-induced hyperlipidaemic rats. Rats were made hyperlipidaemic by intraperitoneal administration of P-407 (400 mg/kg). Serum lipid levels such as total cholesterol, triglycerides and low-density lipoprotein cholesterol increased significantly (P < 0.001) compared with normal control rats. All these changes were significantly prevented in the rats treated with swertiamarin. Serum high-density lipoprotein (HDL) cholesterol was found to be reduced in the P-407 control rats. However, administration of swertiamarin significantly (P < 0.01) increased HDL levels and it showed a significant lipid-lowering effect, as well as a high antiatherogenic potential. Overall swertiamarin is an effective lipid-lowering lead compound and can be useful for preventing atherosclerosis.

OSBPL10, a novel candidate gene for high triglyceride trait in dyslipidemic Finnish subjects, regulates cellular lipid metabolism

Analysis of variants in three genes encoding oxysterol-binding protein (OSBP) homologues (OSBPL2, OSBPL9, OSBPL10) in Finnish families with familial low high-density lipoprotein (HDL) levels (N = 426) or familial combined hyperlipidemia (N = 684) revealed suggestive linkage of OSBPL10 single-nucleotide polymorphisms (SNPs) with extreme end high triglyceride (TG; >90th percentile) trait. Prompted by this initial finding, we carried out association analysis in a metabolic syndrome subcohort (Genmets) of Health2000 examination survey (N = 2,138), revealing association of multiple OSBPL10 SNPs with high serum TG levels (>95th percentile). To investigate whether OSBPL10 could be the gene underlying the observed linkage and association, we carried out functional experiments in the human hepatoma cell line Huh7. Silencing of OSBPL10 increased the incorporation of [(3)H]acetate into cholesterol and both [(3)H]acetate and [(3)H]oleate into triglycerides and enhanced the accumulation of secreted apolipoprotein B100 in growth medium, suggesting that the encoded protein ORP10 suppresses hepatic lipogenesis and very-low-density lipoprotein production. ORP10 was shown to associate dynamically with microtubules, consistent with its involvement in intracellular transport or organelle positioning. The data introduces OSBPL10 as a gene whose variation may contribute to high triglyceride levels in dyslipidemic Finnish subjects and provides evidence for ORP10 as a regulator of cellular lipid metabolism.

Meal replacement with mixed rice is more effective than white rice in weight control, while improving antioxidant enzyme activity in obese women

The physiologic consequences of using white rice or mixed rice were evaluated in overweight Korean women (body mass index > or = 25 kg/m(2)) over a period of 6 weeks. Forty women between 20 and 35 years of age were randomly divided into 2 groups who consumed 1 of 2 low-energy meal replacements containing either white rice (WR group) or mixture of brown rice and black rice (BRBL group). The subjects were not allowed to have any food other than the low-energy meal replacement 3 times a day and snacks provided by the researcher. The changes in anthropometric indices and blood parameters such as lipid levels and antioxidant activities were measured every 3 weeks during the dietary intervention. The subjects showed a significant reduction in weight, body mass index, and body fat (%) during the experimental period, with the BRBL group exhibiting levels of all 3 parameters significantly lower than those of the WR group (P < .05). The levels of total cholesterol and triacylglycerols decreased gradually and significantly after intervention in both groups, with no significant difference between groups. High-density lipoprotein cholesterol was significantly elevated in the BRBL group but not in the WR group. Superoxide dismutase activity was not affected by dietary intervention, but glutathione peroxidase activity in the BRBL group was higher than in the WR group, and the level of thiobarbituric acid-reactive substance was lower in the BRBL group compared to the WR group. In conclusion, meal replacement with mixed rice was superior to replacement with white rice in weight control, improving antioxidant enzyme activity, and as such, should be recommended for diet therapy in obese women.

Apolipoprotein A-IV, a putative satiety/antiatherogenic factor, rises after gastric bypass

Roux-en-Y gastric bypass surgery (RYGBP) leads to improvements in satiety and obesity-related comorbidities. The mechanism(s) underlying these improvements are not known but may be revealed in part by discovery proteomics. Therefore, fasting plasma was collected from 12 subjects (mean BMI >45) during RYGBP and during a second procedure approximately 17 months later. Body weight, obesity-related comorbidities, and medication use were decreased after RYGBP. Mass spectrometry-based proteomic analysis was performed on a subset of seven samples using isobaric isotope-coded affinity tags (four plex iTRAQ). Initial proteomic analysis (n = 7) quantified and identified hundreds of plasma proteins. Manual inspection of the data revealed a 2.6 +/- 0.5-fold increase in apolipoprotein A-IV (apo A-IV, gene designation: APOA4), a approximately 46-kDa glycoprotein synthesized mainly in the bypassed small bowel and liver after RYGBP. The change in apo A-IV was significantly greater than other apolipoproteins. Immunoblot analysis of the full longitudinal sample set (n = 12) indicated even higher increases (8.3 +/- 0.2 fold) in apo A-IV. Thus iTRAQ may underestimate the changes in protein concentrations compared to western blotting of apo A-IV. Apo A-IV inhibits gastric emptying and serves as a satiety factor whose synthesis and secretion are increased by the ingestion of dietary fat. It also possesses anti-inflammatory and antiatherogenic properties. Based on these functions, we speculate changes in apo A-IV may contribute to weight loss as well as the improvements in inflammation and cardiovascular disease after RYGBP. In addition, the findings provide evidence validating the use of iTRAQ proteomics in discovery-based studies of post-RYGBP improvements in obesity-related medical comorbidities.

Beneficial effects of curcumin on hyperlipidemia and insulin resistance in high-fat-fed hamsters

This study investigated the effect of curcumin (0.05-g/100-g diet) supplementation on a high-fat diet (10% coconut oil, 0.2% cholesterol, wt/wt) fed to hamsters, one of the rodent species that are most closely related to humans in lipid metabolism. Curcumin significantly lowered the levels of free fatty acid, total cholesterol, triglyceride, and leptin and the homeostasis model assessment of insulin resistance index, whereas it elevated the levels of high-density lipoprotein cholesterol and apolipoprotein (apo) A-I and paraoxonase activity in plasma, compared with the control group. The levels of hepatic cholesterol and triglyceride were also lower in the curcumin group than in the control group. In the liver, fatty acid beta-oxidation activity was significantly higher in the curcumin group than in the control group, whereas fatty acid synthase, 3-hydroxy-3-methylglutaryl coenzyme A reductase, and acyl coenzyme A:cholesterol acyltransferase activities were significantly lower. Curcumin significantly lowered the lipid peroxide levels in the erythrocyte and liver compared with the control group. These results indicate that curcumin exhibits an obvious hypolipidemic effect by increasing plasma paraoxonase activity, ratios of high-density lipoprotein cholesterol to total cholesterol and of apo A-I to apo B, and hepatic fatty acid oxidation activity with simultaneous inhibition of hepatic fatty acid and cholesterol biosynthesis in high-fat-fed hamsters.

[Atherosclerotic risk factors associated with cardiorespiratory fitness and BMI in adolescents]

Previous research has demonstrated high prevalence of atherosclerotic risk factors in adolescents; however, the associate factors related to its onset are unclear. Therefore, the objective of this study was to relate inadequate blood pressure levels, total cholesterol (TC), HDL-C, LDL-C and triglycerides (TG) with different VO2máx and BMI levels in a sample of 249 adolescents, aged between 12 to 16 years old. For VO2máx prediction, the 20 meters test was used. The BMI was calculated using the body mass/heigh(2) equation. The considerate inadequate levels were: blood pressure > or =90th percentile; total cholesterol > or =150 mg/dL; LDL-C > or = 100 mg/dL, TG > or =100 mg/dL and HDL-C <45 mg/dL. Logistic regression was used as statistical procedures, with p<0.05. For the boys, significant associations were observed between the low VO2máx with TC (OR 4.33; IC=1.23-15.20) and TG (OR=4.88; IC=1.15-20.79) and between overweight and TG (OR=4.33; IC=1.42-13.21). After BMI correction, the males subjects with low VO2máx maintained their significant associations with TC (OR=5.73; IC=1.52-21.58) and TG (OR=3.81; IC=1.86-16.94). The evidences in this study suggested an inverse relationship of the cardiorespiratory fitness with TC and TG for boys, independently of the BMI.

Comparison of hypolipidemic activity of synthetic gallic acid-linoleic acid ester with mixture of gallic acid and linoleic acid, gallic acid, and linoleic acid on high-fat diet induced obesity in C57BL/6 Cr Slc mice

Hyperlipidemia is the major risk factors of heart disease such as atherosclerosis, stroke, and death. In the present study, we studied the effect of gallic acid (GA), linoleic acid (LA), mixture of GA and LA (MGL), and chemically synthesized gallic acid-linoleic acid ester (octadeca-9,12-dienyl-3,4,5-trihydroxybenzoate, GLE) on the ability to ameliorate hyperlipidemia in C57BL/6 mice fed a high-fat diet (HFD). GLE, GA, LA, and MGL were mixed with HFD and the composition of the test compounds were 1% of the diet for 7 weeks. After 7 weeks, the average body weight of ND and GLE groups was lower than that of HFD group (P<0.05). The liver weight of mice decreased (P<0.05) in all treatment groups relative to HFD fed group. The plasma lipids such as triglyceride and LDL-cholesterol were found to be decreased (P<0.05) in GLE, GA, LA, and MGL fed mice when compared to that of HFD fed mice. But high-density lipoprotein (HDL) cholesterol increased (P<0.05) in HFD and GLE fed mice when compared to that of ND fed mice. The hepatic accumulation of fat droplets of GA, LA, GLE, and MGL group showed considerably lower than that of HFD group. Adipose histology showed that GLE supplementation was found to be more effective in decreasing the size of adipocyte relative to those of other treatment groups. In conclusion, the supplementation of synthetic GLE from gallic acid and linoleic acid ester may have a potential hypolipidemic effect on mice fed high-fat diet. Further studies are required to prove GLE as a hypolipidemic agent.

Hypolipidemic effects of Citrus bergamia Risso et Poiteau juice in rats fed a hypercholesterolemic diet

Citrus bergamia Risso et Poiteau fruits have been traditionally utilized, in Calabria (Italy), as a popular remedy for their hypolipidemic properties. C. bergamia juice total phenol content (2474.35+/-38 microg/mL) was evaluated by the Folin-Ciocalteu method; moreover, HPLC analysis led to the identification of naringin (520 ppm), neoeriocitrin (370 ppm), and neohesperidin (310 ppm). The present study was designed to investigate the hypolipidemic effects of C. bergamia juice and its protective effect on liver of hyperlipidemic rats. Chronic administration of C. bergamia (1 mL/rat/day) provoked a significant reduction in serum cholesterol, triglycerides, and low-density lipoprotein (LDL) levels and an increase in high-density lipoprotein (HDL) levels; moreover, histopathological observations showed, in rats submitted to C. bergamia treatment, a protection of hepatic parenchyma. In addition, fecal neutral sterols and fecal bile acid excretion was found to be increased after C. bergamia treatment. These results suggest that the hypocholesterolemic effect of C. bergamia may be mediated by the increase in fecal neutral sterols and total bile acids excretion. In addition to the hypolipidemic effect, the juice shows radical scavenging activity in the diphenylpicrylhydrazyl (DPPH) test; probably the two effects are related. These observations suggest that the positive intake of C. bergamia may reduce the risk of some cardiovascular diseases through its radical scavenging function and hypocholesterolemic action.

Mechanisms and optimization of in vivo delivery of lipophilic siRNAs

Cholesterol-conjugated siRNAs can silence gene expression in vivo. Here we synthesize a variety of lipophilic siRNAs and use them to elucidate the requirements for siRNA delivery in vivo. We show that conjugation to bile acids and long-chain fatty acids, in addition to cholesterol, mediates siRNA uptake into cells and gene silencing in vivo. Efficient and selective uptake of these siRNA conjugates depends on interactions with lipoprotein particles, lipoprotein receptors and transmembrane proteins. High-density lipoprotein (HDL) directs siRNA delivery into liver, gut, kidney and steroidogenic organs, whereas low-density lipoprotein (LDL) targets siRNA primarily to the liver. LDL-receptor expression is essential for siRNA delivery by LDL particles, and SR-BI receptor expression is required for uptake of HDL-bound siRNAs. Cellular uptake also requires the mammalian homolog of the Caenorhabditis elegans transmembrane protein Sid1. Our results demonstrate that conjugation to lipophilic molecules enables effective siRNA uptake through a common mechanism that can be exploited to optimize therapeutic siRNA delivery.

Common ABCA1 variants, HDL levels, and cellular cholesterol efflux in subjects with familial low HDL

HDL promotes cholesterol efflux from peripheral cells via ABCA1 in the first step of reverse cholesterol transport (RCT). We investigated whether the early steps of RCT were disturbed in subjects with familial low HDL and an increased risk for early atherosclerosis. Cholesterol efflux from monocyte-derived macrophages to lipid-free apolipoprotein A-I (apoA-I; %) was measured in 22 patients with familial low HDL without Tangier disease mutations and in 21 healthy controls. In addition, we defined the different alleles of ABCA1 using single-nucleotide polymorphism haplotypes and measured ABCA1 and ABCG1 mRNA transcript levels in cholesterol-loaded macrophages. Similar ABCA1-mediated cholesterol efflux levels were observed for macrophages derived from control subjects and from low-HDL subjects. However, when efflux of cholesterol was estimated as cholesterol efflux to apoA-I (%)/relative ABCA1 mRNA expression level, cholesterol removal was significantly (P = 0.001) lower in the low-HDL group. Cholesterol-loaded macrophages from low-HDL subjects showed significantly increased levels of ABCA1 mRNA but not of ABCG1 mRNA and were more often carriers of the rare ABCA1 alleles L158 and R219K. These results suggest that defective ABCA1 function in cholesterol-loaded macrophages is one potential contributor to the impaired RCT process and the increased coronary heart disease risk in subjects with familial low HDL.

Dietary myristic acid modifies the HDL-cholesterol concentration and liver scavenger receptor BI expression in the hamster

The influence of myristic acid in a narrow physiological range (0·5 to 2·4 % of total dietary energy) on the plasma and hepatic cholesterol metabolism was investigated in the hamster. The hamsters were fed on a diet containing 12·5 g fat/100 g and 0·05 g cholesterol/100 g with 0·5 % myristic acid (LA diet) for 3 weeks (pre-period). During the following 3 weeks (test period), they were divided into four dietary groups with 0·5 % (LA), 1·2 % (LM), 1·8 % (ML) or 2·4 % (M) myristic acid. Finally, half the hamsters in each group were again fed the LA diet for another 3 weeks (post-period). At the end of the test period, the hepatic expression of the scavenger receptor BI (SR-BI) was lower in the LM, ML and M groups than in the LA group whereas the hepatic cholesteryl ester concentration was higher. Cholesterol 7α hydroxylase activity was lower in the ML and M groups than in the LA and LM groups while the sterol 27 hydroxylase and 3-hydroxy-3-methyl glutaryl coenzyme A reductase activities were not modulated by dietary myristic acid. This is the first time a negative correlation has been observed between the HDL-cholesterol concentration and the hepatic mass of SR-BI (r-0·69;P<0·0001) under physiological conditions. An inverse linear regression was also shown between SR-BI and the percentage of myristic acid in the diet (r-0·75;P<0·0001). The hepatic mass of SR-BI in the M group had increased at the end of the post-period compared with the test-period values. The present investigation shows that myristic acid modulates HDL-cholesterol via a regulation of the SR-BI expression.

Association of heterozygous familial hypercholesterolemia with smaller HDL particle size

Small, dense HDL particles have been associated with factors known to increase the risk of cardiovascular disease, such as obesity, hypertriglyceridemia, small dense LDL particles, decreased HDL-cholesterol levels and increased apoA-I fractional catabolic rate from plasma. In order to assess the potential contribution of HDL particle size to atherosclerosis in heterozygous familial hypercholesterolemia (FH), we examined the electrophoretic characteristics of HDL particles in a large cohort of well defined FH heterozygotes and controls. A total of 259 FH heterozygotes and 208 controls participated in the study. FH subjects were carriers of one of the nine French Canadian mutations in the LDL receptor gene. All subjects were apoE3 homozygotes. HDL particles were characterized by non-denaturing polyacrylamide gradient gel electrophoresis following a 6-week lipid-lowering drug-free baseline period. The integrated HDL size was significantly smaller in the FH group compared to controls (FH=87.3+/-5.2 Angstroms versus controls=91.6+/-4.9 Angstroms, P<0.0001). In each groups, men had smaller HDL particles than women. Multiple regression linear analyses showed that the FH/Control status accounted for 20.3% of the variance in the integrated HDL size. These results suggest that the FH/control status was independently associated with variations in HDL particle size and that these variations could contribute to the development of premature atherosclerosis in these patients.

High density lipoprotein subfractions: isolation, composition, and their duplicitous role in oxidation

The plasma HDLs represent a major class of cholesterol-transporting lipoprotein that can be divided into two distinct subfractions, HDL(2) and HDL(3), by ultracentrifugation. Existing methods for the subfractionation of HDL requires lengthy ultracentrifugations, making them unappealing for large-scale studies. We describe a method that subfractionates HDL from plasma in only 6 h, representing a substantial decrease in total isolation time. The subfractions so isolated were assessed for a variety of lipid and protein components, in addition to their susceptibility to oxidation, both alone and in combination with VLDL and LDL. We report for the first time a prooxidant role for HDL during VLDL oxidation, in which HDL donates preformed hydroperoxides to VLDL in a cholesteryl ester transfer protein (CETP)-dependent process. Examination of the participation of HDL in LDL oxidation has reinforced its classic role as a potent antioxidant. Furthermore, we have also implicated the second major HDL-associated enzyme, LCAT, in these processes, whereby it acts as a potent prooxidant during VLDL oxidation but as an antioxidant during LDL oxidation. Thus, we have identified a potentially duplicitous role for HDL in the pathogenesis of atherosclerosis, attributable to both CETP and LCAT.

Effect of probucol on HDL metabolism and class B type I scavenger receptor (SR-BI) expression in the liver of hypercholesterolemic rabbits

BACKGROUND

Scavenger receptor class B type I (SR-BI) is a major receptor for high-density lipoproteins (HDL) in the liver. Overexpression of SR-BI attenuated experimental atherosclerosis in murine models, concomitant with a reduction in plasma HDL-cholesterol levels. Probucol is known to be a potent hypolipidemic drug to regress xanthoma formation and carotid atherosclerosis in conjunction with a marked reduction in HDL-cholesterol levels. However, the mechanism by which probucol affects atherosclerosis is not completely understood, and the effect of probucol on the expression of SR-BI was controversial. The aim of this study was to know the effect of probucol on HDL metabolism and SR-BI expression in the liver.

METHODS

Sixteen rabbits fed with high cholesterol diet for 8 weeks were randomly divided into two groups: (1) high cholesterol group (n = 8): maintained high cholesterol diet for 6 weeks; (2) probucol group (n = 8): the same cholesterol diet plus 1% probucol for 6 weeks. Control group (n = 8) was fed with normal diet for 14 weeks. The classical in situ two steps perfusion of the liver with collagenase IV was used to isolate the parenchymal hepatocytes. The selective uptake of HDL by hepatocytes was performed using the double radiolabelled HDL. Immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) were used to evaluate SR-BI expression in the liver.

RESULTS

Compared with control group, rabbits fed with high cholesterol diet showed higher levels of serum total cholesterol (TC), low-density lipoprotein (LDL) cholesterol and HDL-C, all of which were significantly reduced by probucol treatment. The selective uptake of HDL CEs in probucol group (249.68 +/- 60.13 ng/mg cell protein) was about two folds higher as compared with the control group (122.47 +/- 54.06 ng/mg cell protein, P < 0.01) and high cholesterol group (104.92 +/- 47.91 ng/mg cell protein, P < 0.01), but it could not be reproduced in vitro. The expression of SR-BI were significantly decreased in the high cholesterol group (0.48 +/- 0.06) as compared with control group (0.65 +/- 0.06, P < 0.01). Probucol increased SR-BI expression (0.68 +/- 0.06, P < 0.01) as compared with high cholesterol group. The expression of SR-BI was positively associated with the selective CEs uptake (r = 0.47, P = 0.032).

CONCLUSIONS

Probucol up-regulates SR-BI expression and enhance the uptake of HDL CEs by hepatocytes, which may help us to understand the anti-atherogenic properties and the HDL-C-lowering effect of probucol.

Alterations of high-density lipoprotein subclasses in hypercholesterolemia and combined hyperlipidemia

BACKGROUND

Alterations in plasma lipid levels can influence the composition, content, and distribution of plasma lipoprotein subclasses that effect atherosclerosis risk. Hypercholesterolemia and combined hyperlipidemia are common forms of atherogenic dyslipoproteinemia. This study evaluates the alterations of high-density lipoprotein (HDL) subclasses in hypercholesterolemic and combined hyperlipidemic subjects.

METHODS

Apolipoprotein A-I contents of plasma HDL subclasses were quantitated by 2-dimensional gel electrophoresis in 242 normolipidemic subjects, 66 hypercholesterolemic subjects and 59 combined hyperlipidemic subjects.

RESULTS

Compared with the normolipidemic subjects, apolipoprotein A-I contents of small-sized pre-beta1-HDL, HDL3c, HDL3b and HDL3a were significantly higher in both hypercholesterolemic subjects (p<.01, p<.05, p<.01 and p<.05, respectively) and combined hyperlipidemic subjects (p<.01, p<.05, p<.01 and p<.01, respectively). In contrast, apolipoprotein A-I contents of large-sized HDL2a and HDL2b were significantly lower in hypercholesterolemic subjects (p<.05 and p<.01, respectively) as well as combined hyperlipidemic subjects (p<.01 and p<.01, respectively). In addition, pre-beta1-HDL increased significantly (p<.05) while HDL2a and HDL2b decreased significantly (p<.05 and p<.01, respectively) in combined hyperlipidemic group versus hypercholesterolemic subjects. With the elevation of triglyceride levels, pre-beta1-HDL, and HDL3a increased successively, however, HDL2a and HDL2b decreased successively in subjects with total cholesterol levels greater than 240 mg/dl.

CONCLUSIONS

The particle size of HDL shifted towards smaller size in hypercholesterolemic subjects, and that the shift was more prominent in combined hyperlipidemic subjects. The alternations mentioned above indicate that HDL maturation might be abnormal, and reverse cholesterol transport (RCT) might be weakened.

Efflux of cholesterol and phospholipids derived from the haemoglobin-lipid adduct in human red blood cells into plasma

OBJECTIVE

The interior of red blood cells (RBCs) contains a variable amount of cholesterol and phospholipids bound to haemoglobin (Hb). This current study was devised to determine if this pool of lipids (termed Hb-Ch) was available for exchange with plasma lipoproteins.

DESIGN AND METHODS

We studied the in vitro efflux of lipids from human RBCs into fasting plasma in men with either low (control group) or high Hb-Ch (study group).

RESULTS

When plasma was incubated with a two-fold excess of autologous RBCs the plasma cholesterol level increased due to a decrease in the level of cholesterol from the RBC membrane (in the control group) and due to a decrease in the level of cholesterol both from the RBC membrane and the Hb-Ch fraction (in the study group). The loss of Hb-Ch-derived phospholipids during lipid efflux was roughly equal to that of Hb-Ch-derived cholesterol. The loss of RBC cholesterol into plasma high-density lipoproteins (HDL) was more pronounced in our study group and correlated with the loss of cholesterol from Hb-Ch.

CONCLUSION

The Hb-Ch adduct significantly contributes to the lipid efflux from RBCs into plasma. The majority of cholesterol released from Hb-Ch appears in the plasma HDL fraction suggesting that Hb-Ch may play a role in reverse cholesterol transport in vivo.

Newly developed reconstituted high-density lipoprotein containing sphingosine-1-phosphate induces endothelial tube formation

Reconstituted high-density lipoprotein (rHDL) has been shown to produce a rapid regression of atherosclerosis in animal models and humans. Sphingosine-1-phosphate (S1P), which is a bioactive lipid in HDL, plays a role in mitogenesis, endothelial cell motility, and cell survival, as well as organization and differentiation into a vessel. In this study, we examined the direct role of a newly developed rHDL, [POPC(1-palmitoyl-2-oleoyl phosphatidylcholine)/S1P/apolipoproteinA-I(A-I)]rHDL containing S1P in tube formation in endothelial cells (ECs) as well as cholesterol efflux in macrophage. The effect of (POPC/S1P/A-I)rHDL on cholesterol efflux in macrophage was similar to that of conventional rHDL, (POPC/A-I)rHDL. In addition, (POPC/S1P/A-I)rHDL induced EC proliferation through the activation of phospho-Akt and phospho-extracellular-signal-regulated kinases (p-ERK) 1/2 and EC tube formation, and this effect was blocked by inhibitors of Akt, ERK and endothelial nitric-oxide synthase (eNOS). In addition, (POPC/S1P/A-I)rHDL-induced p-ERK1/2 activation and EC tube formation can be mainly attributed to S1P-stimulated signaling through S1P2 and S1P3 as determined by an anti-sense strategy. In conclusion, (POPC/S1P/A-I)rHDL induces cholesterol efflux independently of S1P but has additional S1P-mediated effects on EC tube formation mediated by Akt/ERK/NO through S1P2 and S1P3. In the future, these new discs may be useful for the treatment of atherosclerotic and ischemic cardiovascular disease, such as acute coronary syndrome and atherosclerosis obliterans.

Functionally defective high-density lipoprotein: a new therapeutic target at the crossroads of dyslipidemia, inflammation, and atherosclerosis

High-density lipoproteins (HDL) possess key atheroprotective biological properties, including cellular cholesterol efflux capacity, and anti-oxidative and anti-inflammatory activities. Plasma HDL particles are highly heterogeneous in physicochemical properties, metabolism, and biological activity. Within the circulating HDL particle population, small, dense HDL particles display elevated cellular cholesterol efflux capacity, afford potent protection of atherogenic low-density lipoprotein against oxidative stress and attenuate inflammation. The antiatherogenic properties of HDL can, however be compromised in metabolic diseases associated with accelerated atherosclerosis. Indeed, metabolic syndrome and type 2 diabetes are characterized not only by elevated cardiovascular risk and by low HDL-cholesterol (HDL-C) levels but also by defective HDL function. Functional HDL deficiency is intimately associated with alterations in intravascular HDL metabolism and structure. Indeed, formation of HDL particles with attenuated antiatherogenic activity is mechanistically related to core lipid enrichment in triglycerides and cholesteryl ester depletion, altered apolipoprotein A-I (apoA-I) conformation, replacement of apoA-I by serum amyloid A, and covalent modification of HDL protein components by oxidation and glycation. Deficient HDL function and subnormal HDL-C levels may act synergistically to accelerate atherosclerosis in metabolic disease. Therapeutic normalization of attenuated antiatherogenic HDL function in terms of both particle number and quality of HDL particles is the target of innovative pharmacological approaches to HDL raising, including inhibition of cholesteryl ester transfer protein, enhanced lipidation of apoA-I with nicotinic acid and infusion of reconstituted HDL or apoA-I mimetics. A preferential increase in circulating concentrations of HDL particles possessing normalized antiatherogenic activity is therefore a promising therapeutic strategy for the treatment of common metabolic diseases featuring dyslipidemia, inflammation, and premature atherosclerosis.

Variations on a gene: rare and common variants in ABCA1 and their impact on HDL cholesterol levels and atherosclerosis

Cholesterol and its metabolites play a variety of essential roles in living systems. Virtually all animal cells require cholesterol, which they acquire through synthesis or uptake, but only the liver can degrade cholesterol. The ABCA1 gene product regulates the rate-controlling step in the removal of cellular cholesterol: the efflux of cellular cholesterol and phospholipids to an apolipoprotein acceptor. Mutations in ABCA1, as seen in Tangier disease, result in accumulation of cellular cholesterol, reduced plasma high-density lipoprotein cholesterol, and increased risk for coronary artery disease. To date, more than 100 coding variants have been identified in ABCA1, and these variants result in a broad spectrum of biochemical and clinical phenotypes. Here we review genetic variation in ABCA1 and its critical role in cholesterol metabolism and atherosclerosis in the general population.