Prevention of coronary heart disease by raising high-density lipoprotein cholesterol?

Dietary Fishmeal Can Be Partially Replaced with Non-Grain Compound Proteins through Evaluating the Growth, Biochemical Indexes, and Muscle Quality in Marine Teleost Trachinotus ovatus

In the context of human food shortages, the incorporation of non-grain feedstuff in fish feed deserves more research attention. Here, the feasibility and appropriate ratio of non-grain compound protein (NGCP, containing bovine bone meal, dephenolized cottonseed protein, and blood cell meal) for dietary fishmeal (FM) replacement were explored in golden pompano (Trachinotus ovatus). Four isonitrogenous (45%) and isolipidic (12%) diets (Control, 25NGP, 50NGP, and 75NGP) were prepared. Control contained 24% FM, whereas the FM content of 25NGP, 50NGP, and 75NGP was 18%, 12%, and 6%, respectively, representing a 25%, 50%, and 75% replacement of FM in Control by NGCP. Juvenile golden pompano (initial weight: 9.71 ± 0.04 g) were fed the four diets for 65 days in sea cages. There was no significant difference between the 25NGP and Control groups in terms of weight gain, weight gain rate, and specific growth rate; contents of crude protein, crude lipid, moisture, and ash in muscle and whole fish; muscle textural properties including hardness, chewiness, gumminess, tenderness, springiness, and cohesiveness; and serum biochemical indexes including total protein, albumin, blood urea nitrogen, HDL cholesterol, total cholesterol, and triglycerides. However, the golden pompano in 50NGP and 75NGP experienced nutritional stress, and thus some indicators were negatively affected. In addition, compared to the Control group, the expression levels of genes related to protein metabolism (mtor, s6k1, and 4e-bp1) and lipid metabolism (pparγ, fas, srebp1, and acc1) of the 25NGP group showed no significant difference, but the 4e-bp1 and pparγ of the 75NGP group were significantly upregulated and downregulated, respectively (p < 0.05), which may explain the decline in fish growth performance and muscle quality after 75% FM was replaced by NGCP. The results suggest that at least 25% FM of Control can be replaced by NGCP, achieving a dietary FM content of as low as 18%; however, the replacement of more than 50% of the dietary FM negatively affects the growth and muscle quality of golden pompano.

Highly effective lipid-lowering therapy on local vascular stiffness and symptoms of chronic heart failure in patients with postinfarction cardiosclerosis

Objective. To study the effect of achieving the target level of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL–C) on the parameters of local vascular stiffness and the development of chronic heart failure (CHF) in patients with ST-elevation myocardial infarction (STEMI).

Design and methods. The study included 80 patients with myocardial infarction with ST segment elevation (STEMI) aged 35 to 65 years. On the 7–9th day of STEMI, at the 24th and 48th weeks of treatment with atorvastatin 40–80 mg clinical symptoms of heart failure were analyzed, the lipid profile and brain natriuretic peptide (BNP) were determined. Ultrasound of the common carotid arteries using high-frequency RF signal technology was performed. Depending on the effectiveness of treatment with atorvastatin, patients were retrospectively divided into 2 groups: 40 people who reached the target level of LDL–C (highly effective therapy, HET) and 37 patients who did not reach the target level of LDL–C (relatively effective therapy, RET).

Results. In patients who reached the target LDL–С level, the initial BNP values were 115,2 pg/ml, with the regression by 34,5 % at follow-up (p = 0,03). There was no significant change in the RET group. In the HET group, a decrease in IMT, an improvement in distensibility parameters, a decrease in local PWV and stiffness index of common carotid arteries, were found. Based on the 6-minute walk test, only patients in HET group showed an increase in exercise tolerance after 24th week (p = 0,04). Also, individuals who did not reach the target LDL–С level, showed a decrease in the quality of life 27,4 % (p = 0,03). Patients in the HET group showed no negative dynamics.

Conclusion. We showed that at the long-term follow-up after STEMI, the achievement of the target LDL cholesterol values was accompanied by a significant improvement in the parameters of local rigidity of the main arteries, and a decrease in BNP level, as well as by more favorable course of CHF.

High-density lipoprotein ameliorates palmitic acid-induced lipotoxicity and oxidative dysfunction in H9c2 cardiomyoblast cells via ROS suppression

Background

High levels circulating saturated fatty acids are associated with diabetes, obesity and hyperlipidemia. In heart, the accumulation of saturated fatty acids has been determined to play a role in the development of heart failure and diabetic cardiomyopathy. High-density lipoprotein (HDL) has been reported to possess key atheroprotective biological properties, including cellular cholesterol efflux capacity, anti-oxidative and anti-inflammatory activities. However, the underlying mechanisms are still largely unknown. Therefore, the aim of the present study is to test whether HDL could protect palmitic acid (PA)-induced cardiomyocyte injury and explore the possible mechanisms.

Results

H9c2 cells were pretreated with HDL (50–100 μg/ml) for 2 h followed by PA (0.5 mM) for indicated time period. Our results showed that HDL inhibited PA-induced cell death in a dose-dependent manner. Moreover, HDL rescued PA-induced ROS generation and the phosphorylation of JNK which in turn activated NF-κB-mediated inflammatory proteins expressions. We also found that PA impaired the balance of BCL₂ family proteins, destabilized mitochondrial membrane potential, and triggered subsequent cytochrome c release into the cytosol and activation of caspase 3. These detrimental effects were ameliorated by HDL treatment.

Conclusion

PA-induced ROS accumulation and results in cardiomyocyte apoptosis and inflammation. However, HDL attenuated PA-induced lipotoxicity and oxidative dysfunction via ROS suppression. These results may provide insight into a possible molecular mechanism underlying HDL suppression of the free fatty acid-induced cardiomyocyte apoptosis.

Non-fasting High-Density Lipoprotein Is Associated With White Matter Microstructure in Healthy Older Adults

A growing body of evidence indicates that biomarkers of cardiovascular risk may be related to cerebral health. However, little is known about the role that non-fasting lipoproteins play in assessing age-related declines in a cerebral biomarker sensitive to vascular compromise, white matter (WM) microstructure. High-density lipoprotein cholesterol (HDL-C) is atheroprotective and low-density lipoprotein cholesterol (LDL-C) is a major atherogenic lipoprotein. This study explored the relationships between non-fasting levels of cholesterol and WM microstructure in healthy older adults. A voxelwise and region of interest approach was used to determine the relationship between cholesterol and fractional anisotropy (FA). Participants included 87 older adults between the ages of 59 and 77 (mean age = 65.5 years, SD = 3.9). Results indicated that higher HDL-C was associated with higher FA in diffuse regions of the brain when controlling for age, sex, and body mass index (BMI). HDL-C was also positively associated with FA in the corpus callosum and fornix. No relationship was observed between LDL-C and FA. Findings suggest that a modifiable lifestyle variable associated with cardiovascular health may help to preserve cerebral WM.

High-density lipoprotein cholesterol as a therapeutic target for residual risk in patients with acute coronary syndrome

Objective

The current guideline recommends lowering low-density lipoprotein cholesterol (LDL-C) for the primary management of dyslipidemia in patients at high-risk of cardiovascular events. Patients who have achieved LDL-C levels below the recommended targets may still experience cardiovascular events, suggesting additional therapeutic targets beyond LDL-C. The aim of this study was to investigate whether high-density lipoprotein cholesterol (HDL-C) levels had an impact on plaque stabilization in patients with acute coronary syndrome (ACS).

Methods

This study consisted of 90 ACS patients with untreated dyslipidemia. In optical coherence tomography (OCT) analysis, a plaque with fibrous cap thickness ≦160 μm was defined as a high-risk plaque. We registered one high-risk plaque per one patient by baseline OCT imaging, and then administrated high-intensity statin. Based on the follow-up OCT results, patients whose registered plaque was no longer high-risk plaque were classified into a responder group and the remains into a non-responder group.

Results

No differences were observed in the baseline LDL-C and HDL-C levels between the two groups. Reduction of LDL-C levels (δ LDL-C: −53 ± 21 mg/dL vs. −42 ± 29 mg/dL, p = 0.036) and increase of HDL-C levels (δ HDL-C: 2.5 ± 5.9 mg/dL vs. −0.3 ± 6.7 mg/dL, p = 0.039) were greater in the responder group. On multivariate logistic regression analysis, δ LDL-C levels (OR: 0.956, 95% CI: 0.921–0.993; p = 0.020) and δ HDL-C levels (OR: 1.143; 95% CI: 1.005–1.300, p = 0.041) were independent contributors for plaque stabilization.

Conclusions

Increase of HDL-C levels is associated with plaque stabilization in patients with ACS. HDL-C could be a therapeutic target for residual risk management.

Combined effects of shear stress and glucose on the morphology, actin filaments, and VE-cadherin of endothelial cells in vitro

Objective

The purpose of the present study was to analyze the effects of glucose and shear stress on the morphology and density of endothelial cells, actin filamen, and the expression of VE-cadherin.

Methods

After confluency of endothelial cells (3–4 days), 22 mM of d-glucose was administered for 7 days. Endothelial cells were exposed to shear stress of 10 dyne/cm² for varied durations of 5, 8, 12, and 15 min. Morphology of ECs was observed using an inverted microscope before and after shear stress exposure. VE-cadherin and actin filament were analyzed immunohistochemically.

Results

Exposure to high glucose induces more shrinkage and the cell density decreased at 15 min. High glucose reduced actin filaments and the more globular ones, especially around the nuclei. There was a decline in VE-cadherin scores with significant differences between treatments with 5 mM and 22 mM of glucose.

Conclusion

Combination exposure of shear stress and high glucose changes morphology, reduces actin filament and VE-cadherin, of endothelial cells.

Structure-function relationships in reconstituted HDL: Focus on antioxidative activity and cholesterol efflux capacity

AIMS

High-density lipoprotein (HDL) contains multiple components that endow it with biological activities. Apolipoprotein A-I (apoA-I) and surface phospholipids contribute to these activities; however, structure-function relationships in HDL particles remain incompletely characterised.

METHODS

Reconstituted HDLs (rHDLs) were prepared from apoA-I and soy phosphatidylcholine (PC) at molar ratios of 1:50, 1:100 and 1:150. Oxidative status of apoA-I was varied using controlled oxidation of Met112 residue. HDL-mediated inactivation of PC hydroperoxides (PCOOH) derived from mildly pre-oxidized low-density lipoprotein (LDL) was evaluated by HPLC with chemiluminescent detection in HDL+LDL mixtures and re-isolated LDL. Cellular cholesterol efflux was characterised in RAW264.7 macrophages.

RESULTS

rHDL inactivated LDL-derived PCOOH in a dose- and time-dependent manner. The capacity of rHDL to both inactivate PCOOH and efflux cholesterol via ATP-binding cassette transporter A1 (ABCA1) increased with increasing apoA-I/PC ratio proportionally to the apoA-I content in rHDL. Controlled oxidation of apoA-I Met112 gradually decreased PCOOH-inactivating capacity of rHDL but increased ABCA1-mediated cellular cholesterol efflux.

CONCLUSIONS

Increasing apoA-I content in rHDL enhanced its antioxidative activity towards oxidized LDL and cholesterol efflux capacity via ABCA1, whereas oxidation of apoA-I Met112 decreased the antioxidative activity but increased the cholesterol efflux. These findings provide important considerations in the design of future HDL therapeutics. Non-standard abbreviations and acronyms: AAPH, 2,2'-azobis(-amidinopropane) dihydrochloride; ABCA1, ATP-binding cassette transporter A1; apoA-I, apolipoprotein A-I; BHT, butylated hydroxytoluene; CV, cardiovascular; EDTA, ethylenediaminetetraacetic acid; HDL-C, high-density lipoprotein cholesterol; LOOH, lipid hydroperoxides; Met(O), methionine sulfoxide; Met112, methionine 112 residue; Met86, methionine 86 residue; oxLDL, oxidized low-density lipoprotein; PBS, phosphate-buffered saline; PC, phosphatidylcholine; PL, phospholipid; PCOOH, phosphatidylcholine hydroperoxide; PLOOH, phospholipid hydroperoxide.

Coleus forskohlii Extract Supplementation in Conjunction with a Hypocaloric Diet Reduces the Risk Factors of Metabolic Syndrome in Overweight and Obese Subjects: A Randomized Controlled Trial

Limited studies have shown that Coleus forskohlii extract may aid in weight management. This randomized, double blind placebo-controlled clinical study assessed the effects of supplementation with C. forskohlii extract on key markers of obesity and metabolic parameters in overweight and obese individuals. Thirty participants completed the trial and they were randomly assigned to receive either 250 mg of C. forskohlii extract (n = 15) or a placebo twice daily for 12 weeks. All participants were advised to follow a hypocaloric diet throughout the study. Body weight, body mass index (BMI), waist and hip circumference, and waist to hip ratio, were monitored fortnightly. Dietary intake was assessed at the baseline and weeks 4, 8 and 12. Appetite was assessed using visual analogue scales and blood samples were analyzed for plasma lipids, ghrelin, leptin, glucose and insulin at the baseline and end of the intervention. Significant reductions to waist and hip circumference (p = 0.02; p = 0.01, respectively) were recorded in both experimental and placebo groups after the 12 week intervention. Furthermore, high density lipoprotein-cholesterol (HDL-C) was significantly increased (p = 0.01) in both groups. The experimental group showed a favorable improvement in insulin concentration and insulin resistance (p = 0.001; 0.01 respectively) compared to the placebo group. These findings suggest that C. forskohlii extract in conjunction with a hypocaloric diet may be useful in the management of metabolic risk factors.

Association of high density lipoprotein with platelet to lymphocyte and neutrophil to lymphocyte ratios in coronary artery disease patients

Background. We aimed to evaluate a relationship between platelet-lymphocyte ratio (PLR) and neutrophil-lymphocyte ratio (NLR) with high density lipoprotein (HDL) cholesterol levels in coronary artery disease (CAD) patients. Methods. A total of 354 patients with angiographically confirmed coronary blockages were enrolled in the study. Hematological indices and lipid profiling data of all the patients were collected. Results. We have observed significant association between HDL and PLR (P = 0.008) and NLR (P = 0.009); however no significant relationship was obtained with HDL and isolated platelet (P = 0.488), neutrophil (P = 0.407), and lymphocyte (P = 0.952) counts in CAD patients. The association was subjected to gender specific variation as in males PLR (P = 0.024) and NLR (P = 0.03) were highly elevated in low HDL patients, whereas in females the elevation could not reach the statistically significant level. The PLR (217.47 versus 190.3; P = 0.01) and NLR (6.33 versus 5.10; P = 0.01) were significantly higher among the patients with acute coronary syndrome. In young patients the PLR (P = 0.007) and NLR (P = 0.001) were inversely associated with HDL, whereas in older population only NLR (P = 0.05) had showed a significant association. Conclusion. We conclude that PLR and NLR are significantly elevated in CAD patients having low HDL levels.

Zanthoxylum piperitum DC ethanol extract suppresses fat accumulation in adipocytes and high fat diet-induced obese mice by regulating adipogenesis

This study was conducted to determine the anti-obesity effects of Zanthoxylum piperitum DC fruit ethanol extract (ZPE) in 3T3-L1 adipocytes and obese mice fed a high-fat diet. We evaluated the influence of the addition of ZPE to a high-fat diet on body weight, adipose tissue weight, serum and hepatic lipids in C57BL/6 mice. In addition, adipogenic gene expression was determined by Western blot and real-time reverse transcription-PCR analysis. We assessed the effect of ZPE on 3T3-L1 preadipocyte differentiation. ZPE reduced weight gain, white adipose tissue mass, and serum triglyceride and cholesterol levels (p<0.05) in high-fat diet-fed C57BL/6 mice. ZPE decreased lipid accumulation and PPARγ, C/EBPα, SREBP-1, and FAS protein and mRNA levels in the liver. ZPE inhibited in vitro adipocyte differentiation in a dose-dependent manner and significantly attenuated adipogenic transcription factors, such as PPARγ, C/EBPα, and SREBP-1 in 3T3L1 cells. These findings suggest that Z. piperitum DC exerts an anti-obesity effect by inhibiting adipogenesis through the downregulation of genes involved in the adipogenesis pathway.

Relationship between concentration difference of different density lipoproteins and shear stress in atherosclerosis

Previous research has observed concentration polarization in LDL and HDL in the arterial system. However, there is no report that links this concentration polarization to the development of vascular atherosclerosis (AS). Therefore, the purpose of this study is to establish the relationship between concentration difference of LDL and HDL and shear stress using a carotid bifurcation vascular model. PTFE was employed to create the carotid bifurcation model. Endothelial cells were coated on the inner wall of the graft. In a recirculation system, HDL and LDL concentration were measured under two different ICA flow velocities at 5 different locations within our model. We report the following: (1) LDL and HDL concentration difference was observed in both high flow and low flow environments; (2) the degree of LDL and HDL concentration polarization varied depending of high flow and low flow environment; (3) absolute values of concentration difference between LDL and HDL at the inner wall surface decreased with the increase in shear stress when shear stress was more than 1.5 Pa. This variation trend would be more pronounced if shear stress were less than 0.5 Pa. Our study suggests that under the action of shear stress, concentration differences of LDL or HDL create a disturbance in the balance of atherogenic factors and anti-As factors, resulting in the occurrence of AS.

The safety, pharmacokinetics, and effects of LGD-4033, a novel nonsteroidal oral, selective androgen receptor modulator, in healthy young men

BACKGROUND

Concerns about potential adverse effects of testosterone on prostate have motivated the development of selective androgen receptor modulators that display tissue-selective activation of androgenic signaling. LGD-4033, a novel nonsteroidal, oral selective androgen receptor modulator, binds androgen receptor with high affinity and selectivity. Objectives. To evaluate the safety, tolerability, pharmacokinetics, and effects of ascending doses of LGD-4033 administered daily for 21 days on lean body mass, muscle strength, stair-climbing power, and sex hormones.

METHODS

In this placebo-controlled study, 76 healthy men (21-50 years) were randomized to placebo or 0.1, 0.3, or 1.0 mg LGD-4033 daily for 21 days. Blood counts, chemistries, lipids, prostate-specific antigen, electrocardiogram, hormones, lean and fat mass, and muscle strength were measured during and for 5 weeks after intervention.

RESULTS

LGD-4033 was well tolerated. There were no drug-related serious adverse events. Frequency of adverse events was similar between active and placebo groups. Hemoglobin, prostate-specific antigen, aspartate aminotransferase, alanine aminotransferase, or QT intervals did not change significantly at any dose. LGD-4033 had a long elimination half-life and dose-proportional accumulation upon multiple dosing. LGD-4033 administration was associated with dose-dependent suppression of total testosterone, sex hormone-binding globulin, high density lipoprotein cholesterol, and triglyceride levels. follicle-stimulating hormone and free testosterone showed significant suppression at 1.0-mg dose only. Lean body mass increased dose dependently, but fat mass did not change significantly. Hormone levels and lipids returned to baseline after treatment discontinuation.

CONCLUSIONS

LGD-4033 was safe, had favorable pharmacokinetic profile, and increased lean body mass even during this short period without change in prostate-specific antigen. Longer randomized trials should evaluate its efficacy in improving physical function and health outcomes in select populations.

Pleiotropic effects on subclasses of HDL, adiposity, and glucose metabolism in adult Alaskan Eskimos

The aim of this study was to analyze the heritability and the presence of pleiotropic effects on subfractions of high-density lipoproteins (HDLs) as measured by nuclear magnetic resonance (NMR), parameters for adiposity, and glucose metabolism in adult Alaskan Eskimos. The present family study included 1,214 adult Alaskan Eskimos (537 male/677 female). Body weight, height, circumferences, selected skinfolds, and blood pressure were measured in all participants. Blood samples were collected under fasting conditions for the isolation of plasma. Glucose, insulin, subclasses and size of lipoproteins, triglycerides, total, and HDL cholesterol and lipoprotein (a) were measured in plasma. HbA1c was measured in total blood. Univariate and bivariate quantitative genetic analyses were conducted between HDL subclasses and size and the anthropometric and biochemical measures using the variance decomposition approach. Variation in all the analyzed traits exhibits a significant genetic component. Heritabilities ranged between 0.18 +/- 0.11 for LDL(2) (intermediate) and 0.89 +/- 0.07 for small HDL. No common genetic effects were found on the HDL subclasses (small, intermediate, and large). Small HDL particles were genetically correlated with LDL particles and HbA1c. Negative genetic correlations were observed between intermediate and large HDL subfractions, HDL size and measures of adiposity, and LDL and parameters for glucose metabolism (HbA1, insulin). These observations confirm the presence of possible pleiotropic effects on HDL, adiposity, and cardiovascular risk factors and provide novel insight on the relationship between HDL subclasses, adiposity, and glucose regulation.

Concentration polarization of high-density lipoprotein and its relation with shear stress in an in vitro model

The purpose of this study was to determine the concentration polarization of high-density lipoprotein (HDL) at the surface of the carotid artery under conditions of steady flow and to establish its relationship with shear stress using an in vitro vascular simulation model of carotid bifurcation. Shear stress, HDL concentration at the surface, and the ratio of HDL concentration at the surface to concentration in bulk flow were measured at different locations within the model under high-speed (1.451 m/s) and low-speed (0.559 m/s) flow. HDL showed concentration polarization at the surface of the carotid artery model, particularly in the internal carotid artery sinus. With decreasing flow velocity, the shear stress at the surface also decreased, and HDL concentration polarization increased. The concentration polarization of HDL was negatively and strongly correlated with shear stress at both low- (r = −0.872, P < .001) and high-speed flow (r = −0.592, P = .0018).

A one-year randomized double-blind, multicentre study to evaluate the effects of an oestrogen-reduced, continuous combined hormone replacement therapy preparation containing 1 mg oestradiol valerate and 2 mg dienogest on metabolism in postmenopausal women

OBJECTIVES

To evaluate the impact of an oestrogen-reduced, continuous combined hormone replacement therapy preparation containing 1 mg oestradiol valerate (1EV) and 2 mg dienogest (2DNG) on metabolism.

METHODS

In a randomized double-blind study, 1EV/2DNG was compared with a reference preparation containing 1 mg 17Beta-oestradiol and 0.5 mg norethisterone acetate (E2/NETA). For the primary variable, i.e. the ratio of HDL cholesterol (week 52 to baseline), at least 98 case evaluations were planned. Secondary variables were other lipid parameters, haemostasis factors and carbohydrate metabolism.

RESULTS

After 1 year of treatment, the mean HDL cholesterol levels had decreased by 4.5 +/- 14.8% in the 1EV/2DNG group and by 6.1 +/- 13.9% in the E2/NETA group (treatment difference NS). The ratio of HDL cholesterol (week 52 to baseline) was 0.944 for 1EV/2DNG and 0.929 for E2/NETA (geometric means). The primary efficacy variable, the ratio of the geometric means of the two treatments (1EV/2DNG/E2/NETA) was 1.016, with a lower one-sided 95% confidence limit of 0.973, which was clearly above the prespecified non-inferiority bound of 0.85 (p-value < 0.001). HDL2 cholesterol increased by 0.3 +/- 34.4% (1EV/2DNG) and decreased by 6.2 +/- 34.3% (E2/NETA; treatment difference NS); HDL3 cholesterol decreased by 4.4 +/- 19.9% (1EV/2DNG) and 8.2 +/- 17.7% (E2/NETA; treatment difference NS). Changes in the haemostasis and carbohydrate variables were very similar in both treatment groups.

CONCLUSION

This study provides evidence that a new oestrogen-reduced HRT preparation containing 1 mg oestradiol valerate and 2 mg dienogest has no major impact on lipid variables. Minimal changes were seen in haemostatic and carbohydrate variables.

The GGN and CAG repeat polymorphisms in the exon-1 of the androgen receptor gene are, respectively, associated with insulin resistance in men and with dyslipidemia in women

The human androgen receptor (AR) gene possesses two trinucleotide repeats of CAG and GGN in exon-1. The GGN repeat affects the amount of AR protein translated, while the CAG repeat affects the efficiency of AR transcriptionaly. In this study, we have genotyped these polymorphic tracts in a representative sample of 557 Caucasian adult individuals (314 women and 243 men) from the Canary Islands, Spain (the ENCA Study), and investigated their association with fasting serum levels of lipids, glucose and insulin. The number of CAG repeats in women (expressed as the average length of the two alleles) was inversely correlated with serum levels of LDL-cholesterol (Spearman rho=-0.179; P<0.01). Women with an average number of CAG repeats in the upper tertile showed significantly lower levels of LDL-cholesterol than those grouped in the lower and middle tertile, after adjusting for age, body mass index, waist-to-hip ratio, smoking and alcohol drinking. The number of GGN repeats in men was correlated with fasting insulin levels (Spearman rho=-0.206; P<0.01), the homeostasis model assessment of insulin resistance (HOMA-IR; Spearman rho=-0.230; P<0.01) and the McAuley index of insulin sensitivity (Spearman rho=0.194; P<0.01). Men with a number of GGN repeats in the upper tertile showed lower levels of insulin and HOMA and a higher level of the McAuley index than those grouped in the lower and middle tertile, after adjusting for the variables listed above. These results support the hypothesis that the longer alleles of the CAG and GGN polymorphisms in the exon-1 of the AR gene, indicative of lower androgenic signaling, respectively protect women from developing dyslipemia and men from developing insulin resistance.

Combination therapy with an HMG-CoA reductase inhibitor and a fibric acid derivative: a critical review of potential benefits and drawbacks

It has been clearly shown that lowering low density lipoprotein-cholesterol (LDL-C) [most often with an HMG-CoA reductase inhibitor] decreases the risk of a cardiovascular event. However, this risk reduction was, at most, 35% in clinical trials, meaning that many events could not be prevented. Moreover, reaching target lipid values as recommended by the current guidelines is often difficult, mainly in high-risk situations such as secondary prevention or type 2 diabetes mellitus. As the two main classes of lipid-lowering drugs (HMG-CoA reductase inhibitors and fibric acid derivatives) have complementary effects on lipid parameters, it seems logical to combine both treatments particularly in patients with combined hyperlipidemia. In fact, combination therapy with an HMG-CoA reductase inhibitor and a fibric acid derivative induces a further decrease in LDL-C levels compared with monotherapy and improves other lipid values such as high density lipoprotein-cholesterol (HDL-C) and triglyceride (TG) levels. Unfortunately, there are currently no available randomized, prospective clinical data on the reduction of the incidence of cardiovascular events with such a combination. This is mainly because the use of HMG-CoA reductase inhibitor and fibric acid derivative combinations was initially described as dangerous. It is true that such a combination increases the risk of muscle toxicity that already exists with monotherapy. Muscle toxicity can eventually lead to life-threatening rhabdomyolysis and some precautions of use are required; however, the risk seems actually lower than what has been initially reported. The use of combined therapy with an HMG-CoA reductase inhibitor and a fibric acid derivative requires the respect of some rules such as avoiding the prescription in patients with concomitant conditions like renal failure and avoiding the use of gemfibrozil as a fibric acid derivative in such a combination. It is now imperative to design clinical trials to determine the clinical efficacy and precise safety of this combined treatment especially in patients with abnormalities in every parameter of the lipid triad (LDL, HDL and TG) and a high vascular risk such as patients with type 2 diabetes mellitus.

Pharmacologic management of isolated low high-density lipoprotein syndrome

High-density lipoprotein (HDL) cholesterol is a heterogeneous group of lipoproteins exhibiting a variety of properties like prostacyclin production stimulation, decrease in platelet aggregation, endothelial cell apoptosis inhibition, and low-density lipoprotein oxidation blockade. Epidemiologic studies have shown an inverse relation between HDL cholesterol levels and cardiovascular risk. Low HDL cholesterol is associated with increased risk for myocardial infarction, stroke, sudden death, peripheral artery disease, and postangioplasty restenosis. In contrast, high HDL levels are associated with longevity and protection against atherosclerotic disease development. Given the evolving epidemic of obesity, diabetes mellitus, and metabolic syndrome, the prevalence of low HDL will continue to rise. In the United States, low HDL is present in 35% of men, 15% of women, and approximately 63% of patients with coronary artery disease. Data extracted from the Framingham study highlight that 1-mg increase in HDL levels decreases by 2% to 3% the risk of cardiovascular disease. There is no doubt regarding clinical importance about isolated low HDL, but relatively few clinicians consider a direct therapeutic intervention of this dyslipidemia. In this sense, lifestyle measures should be the first-line strategy to manage low HDL levels. On the other hand, pharmacologic options include niacin, fibrates, and statins. Fibrates appear to reduce risk preferentially in patients with low HDL with metabolic syndrome, whereas statins reduce risk across all levels of HDL. Torcetrapib, a cholesteryl esters transfer protein inhibitor, represented a hope to raise this lipoprotein; however, all clinical trials on this drug had ceased after ILLUMINATE, RADIANCE and ERASE trials had recorded an increase in mortality, rates of myocardial infarction, angina, and heart failure. In the near future, drugs as beta-glucans, Apo-A1 mimetic peptides, and ACAT inhibitors, are the new promises to treat this condition.

[New trends in lipidology: the increasing role of HDL-cholesterol]

Previous epidemiological studies have demonstrated the low level of high-density lipoprotein (HDL) cholesterol as an independent risk factor for cardiovascular diseases, the increase of which is one of the cornerstones of preventive cardiovascular care. In addition to its major role in reverse cholesterol transport, HDL-C has other biological activities that may contribute to its protective effects against atherosclerosis. These include antioxidant, anti-inflammatory, antithrombotic/profibrinolytic and vasoprotective effects. Current guidelines recommend aggressive lifestyle modifications, niacin, fibrate, statin or a combination of these to increase HDL-cholesterol levels. In addition, several novel HDL-based therapeutic strategies have been or are currently being tested. These include newer formulations of nicotinic acid/receptor agonists, CETP inhibitors, cannabinoid-1 receptor antagonists, PPAR agonists, liver X receptor/farnesoid X receptor agonists, and apoA-I and/or phospholipid-derived therapies. In this article previous clinical trials, epidemiological observations, basic science studies and the most important trials of novel agents are reviewed.

Surrogate markers for atherosclerosis in overweight subjects with atherogenic dyslipidemia: the GEMS project

Metabolic syndrome is a constellation of major risk factors for cardiovascular disease. In affected individuals with this syndrome, the independent contribution of low high-density lipoprotein-cholesterol and increased triglyceride levels to the development of atherosclerosis remains to be clarified. We assessed the relationship between these 2 parameters and several surrogate markers for atherosclerosis. One hundred and twenty overweight cases, defined as having high-density lipoprotein-cholesterol (<or=25 age- and gender-specific percentile in general population) and high triglyceride values (>or=75 percentile) were compared with 120 discordant overweight controls defined on lipid values (high-density lipoprotein-cholesterol >or=50 percentile and triglycerides <or=50 percentile). Case-control pairs were matched for age and gender. Carotid and femoral arteries were examined to determine carotid intima-media thickness and the presence of atherosclerotic plaque(s). Endothelial function was assessed by laser Doppler flowmetry in the skin microvasculature. Daytime ambulatory blood pressure monitoring was performed for each subject. Cases had higher prevalence of atherosclerotic plaques (mean 1.50 +/- 0.15 vs 0.80 +/- 0.15, P < .001), increased carotid intima-media thickness (mean 0.66 +/- 0.15 vs 0.61 +/- 0.15, P < .01), and a significantly reduced temperature-induced and postischemic endothelial vasodilation compared with controls. In conclusion, low high-density lipoprotein-cholesterol and high triglycerides levels are major contributors to peripheral atherosclerosis and are associated with an increase in intima-media thickness and impaired microvascular endothelial function in overweight individuals.

Effect of obesity on high-density lipoprotein metabolism

Reduced levels of high-density lipoproteins (HDL) in non-obese and obese states are associated with increased risk for the development of coronary artery disease. Therefore, it is imperative to determine the mechanisms responsible for reduced HDL in obese states and, conversely, to examine therapies aimed at increasing HDL levels in these individuals. This paper examines the multiple causes for reduced HDL in obese states and the effect of exercise and diet--two non-pharmacologic therapies--on HDL metabolism in humans. In general, the concentration of HDL-cholesterol is adversely altered in obesity, with HDL-cholesterol levels associated with both the degree and distribution of obesity. More specifically, intra-abdominal visceral fat deposition is an important negative correlate of HDL-cholesterol. The specific subfractions of HDL that are altered in obese states include the HDL2, apolipoprotein A-I, and pre-beta1 subfractions. Decreased HDL levels in obesity have been attributed to both an enhancement in the uptake of HDL2 by adipocytes and an increase in the catabolism of apolipoprotein A-I on HDL particles. In addition, there is a decrease in the conversion of the pre-beta1 subfraction, the initial acceptor of cholesterol from peripheral cells, to pre-beta2 particles. Conversely, as a means of reversing the decrease in HDL levels in obesity, sustained weight loss is an effective method. More specifically, weight loss achieved through exercise is more effective at raising HDL levels than dieting. Exercise mediates positive effects on HDL levels at least partly through changes in enzymes of HDL metabolism. Increased lipid transfer to HDL by lipoprotein lipase and reduced HDL clearance by hepatic triglyceride lipase as a result of endurance training are two important mechanisms for increases in HDL observed from exercise.

Increasing apoA-I production as a target for CHD risk reduction

Dyslipidemia leading to coronary heart diseases (CHD) enables venues to prevent or treat CHD by other strategies than only lowering serum LDL cholesterol (LDL-C) concentrations, which is currently the most frequently targeted change. Unlike LDL-C, elevated high-density lipoprotein cholesterol (HDL-C) concentrations may protect against the development of CHD as demonstrated in numerous large-scale epidemiological studies. In this review we describe that besides elevating serum HDL-C concentrations by increasing alpha-HDL particles, approaches to elevate HDL-C concentrations by increasing pre-beta HDL particle concentrations seems more attractive. Besides infusion of apoA-I(Milano), using apoA-I mimetics, or delipidation of alpha-HDL particles, elevating de novo apoA-I production may be a suitable target to functionally increase pre-beta HDL particle concentrations. Therefore, a detailed description of the molecular pathways underlying apoA-I synthesis and secretion, completed with an overview of known effects of pharmacological and nutritional compounds on apoA-I synthesis will be presented. This knowledge may ultimately be applied in developing dietary intervention strategies to elevate apoA-I production and serum HDL-C concentrations and consequently lower CHD risk.

High-density lipoprotein-associated 17beta-estradiol fatty acyl ester uptake by Fu5AH hepatoma cells: implications of the roles of scavenger receptor class B, type I and the low-density lipoprotein receptor

17beta-estradiol (E2) fatty acyl esters naturally incorporate into high-density lipoprotein (HDL). The objective was to elucidate mechanisms involved in HDL-associated E2 cellular uptake and to determine the intracellular distribution of E2 and its fatty acyl esters (E2-FAE) after uptake. [3H]E2 or [3H] cholesterol was incubated with human serum for 24 h to allow for fatty acyl esterification. Total-HDL containing [3H]E2-FAE or [3H]cholesterol esters was isolated by sequential density ultracentrifugation and then incubated with Fu5AH rat hepatoma cells for various time points. Cellular uptake was determined by intracellular radioactivity as a percentage of total radioactivity. Chemical inhibition of scavenger receptor class B, type I and low-density lipoprotein (LDL) receptor competition assays were performed to determine cellular uptake mechanisms. Compared to HDL-[3H]cholesterol, cellular uptake of HDL-[3H]E2 occurred at an initially rapid rate. SR-BI inhibition resulted in a decrease in HDL-E2 uptake and LDL impaired this uptake in a concentration-dependent manner. Accordingly, pretreatment of cells with BLT-1 combined with LDL addition significantly attenuated HDL-E2 uptake. HDL-E2-FAE was hydrolyzed into free E2 with the maximum at 24 h. Fu5AH cells facilitate HDL-E2 uptake by at least SR-BI and LDL receptor pathways and intracellular hydrolysis of E2-FAE into free E2 ensues.

Relationship between apolipoproteins and the alteration of HDL subclasses in hyperlipidemic subjects

BACKGROUND

To elucidate the relationship between the apolipoproteins, especially apoA-I and the alteration of HDL subclasses in hyperlipidemic, HTC and HTG subjects.

METHODS

ApoA-I contents of plasma HDL subclasses were quantitated by two-dimensional gel electrophoresis coupled with immunodetection in 233 normolipidemic subjects and 312 hyperlipidemic subjects (132 HTC and 180 HTG subjects). Making use of the mean +/-1 SD of apoA-I levels, we further subdivided normolipidemic, hyperlipidemic, HTC and HTG subjects into 3 subgroups, respectively.

RESULTS

Subjects in the middle and low apoA-I subgroups had decreased HDL-C and apoA-I while increased TG, apoB100, apoCII, apoCIII and apoE concentrations. With the reduction of apoA-I concentrations, the apoA-I contents of all HDL subclasses decreased successively and significantly. The relative percentage of small-sized HDL increased significantly while those of large-sized HDL(2a), HDL(2b) decreased significantly in hyperlipidemic, especially in HTG group. Multiple liner regression result revealed that apoA-I was positively and significantly correlated with all HDL subclasses and apoA-I level influenced the distribution of HDL subclasses powerfully in hyperlipidemic subjects.

CONCLUSIONS

Both the rate and efficiency of RCT might be weakened more seriously in hyperlipidemic, especially in HTG subjects with low apoA-I levels. ApoA-I level might be a powerful factor correlated with the distributions of HDL subclasses.

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.

Statins induce S1P1 receptors and enhance endothelial nitric oxide production in response to high-density lipoproteins

BACKGROUND AND PURPOSE

Sphingosine 1-phosphate (S1P) is a serum-borne naturally occurring sphingolipid, specifically enriched in high-density lipoprotein (HDL) fractions. S1P binds to G-protein-coupled S1P1 receptors to activate endothelial NO synthase (eNOS) in vascular endothelial cells. We explored whether and how statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, modulate expression of S1P1 receptors and endothelial responses for subsequent stimulation with S1P or with HDL.

EXPERIMENTAL APPROACH

Protein expression and phosphorylation and mRNA expression in cultured bovine aortic endothelial cells (BAEC) were determined using immunoblots and reverse transcription PCR analyses, respectively. NO synthesis was assessed as nitrite production.

KEY RESULTS

Stimulation of BAEC with pitavastatin or atorvastatin led to significant increases in S1P1-receptors, at levels of protein and mRNA, in a dose-dependent manner. When BAEC were treated with pitavastatin prior to stimulation with S1P or with normal human HDL, phosphorylation and activation of eNOS evoked by S1P or by HDL was enhanced. These effects of statins were counteracted by L-mevalonate and were mimicked by an inhibitor of geranylgeranyl transferase I, suggesting that inhibition of HMG-CoA reductase activity and subsequent decreases in protein geranylgeranylation may contribute to these actions of statins. Specific knock down of S1P1 receptors by small interfering RNA led to attenuation of eNOS responses to HDL.

CONCLUSIONS AND IMPLICATIONS

Statins induce S1P1 receptors and potentiate responses of endothelial cells to HDL-associated sphingolipids, identifying a novel aspect of the pleiotropic actions of statins through which they may exert NO-dependent vascular protective effects.

Britt C, G. Wilson J, O. Milliken N, G. Binz J, C. Lobe D, R. Oliver W, C. Lewis M, M. Ignar D. The Effect of PPARalpha, PPARdelta, PPARgamma, and PPARpan Agonists on Body Weight, Body Mass, and Serum Lipid Profiles in Diet-Induced Obese AKR/J Mice

Activation of peroxisome proliferator-activated receptor (PPAR) alpha, delta, and gamma subtypes increases expression of genes involved in fatty acid transport and oxidation and alters adiposity in animal models of obesity and type-2 diabetes. PPARpan agonists which activate all three receptor subtypes have antidiabetic activity in animal models without the weight gain associated with selective PPARgamma agonists. Herein we report the effects of selective PPAR agonists (GW9578, a PPARalpha agonist, GW0742, a PPARdelta agonist, GW7845, a PPARgamma agonist), combination of PPARalpha and delta agonists, and PPARpan (PPARalpha/gamma/delta) activators (GW4148 or GW9135) on body weight (BW), body composition, food consumption, fatty acid oxidation, and serum chemistry of diet-induced obese AKR/J mice. PPARalpha or PPARdelta agonist treatment induced a slight decrease in fat mass (FM) while a PPARgamma agonist increased BW and FM commensurate with increased food consumption. The reduction in BW and food intake after cotreatment with PPARalpha and delta agonists appeared to be synergistic. GW4148, a PPARpan agonist, induced a significant and sustained reduction in BW and FM similar to an efficacious dose of rimonabant, an antiobesity compound. GW9135, a PPARpan agonist with weak activity at PPARdelta, induced weight loss initially followed by rebound weight gain reaching vehicle control levels by the end of the experiment. We conclude that PPARalpha and PPARdelta activations are critical to effective weight loss induction. These results suggest that the PPARpan compounds may be expected to maintain the beneficial insulin sensitization effects of a PPARgamma agonist while either maintaining weight or producing weight loss.

Relationship between plasma HDL subclasses distribution and lipoprotein lipase gene HindIII polymorphism in hyperlipidemia

BACKGROUND

Different high-density lipoprotein (HDL) subclasses have distinct but interrelated metabolic functions. HDL directly influences the atherogenic process, and changes in HDL subclasses distribution may be related to the incidence and prevalence of atherosclerosis. Lipoprotein lipase (LPL) is an important enzyme for hydrolysis of triglyceride-rich lipoproteins, and its activity is positively correlated with the plasma HDL cholesterol level. LPL gene HindIII polymorphism has been found associated with variations in lipid levels, but the impact on HDL subclasses distribution is less clearly established.

METHODS

The relative apolipoprotein (apo) A-I contents (% apoA-I) of plasma HDL subclasses were determined by two-dimensional gel electrophoresis coupled with immunodetection and LPL gene HindIII polymorphism was assayed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 173 hyperlipidemic and 155 normolipidemic subjects.

RESULTS

The frequencies of 495TT genotype and allele T were the highest both in the hyperlipidemic and control groups. Compared with the control group, the frequency of 495TT genotype was higher, while the frequencies of 495TG and 495GG genotypes were significantly lower (P<0.05) in the hyperlipidemic group. Two-dimensional gel electrophoresis and immunodetection showed that HDL subclasses distribution was altered in hyperlipidemia, and had a general shift toward smaller size. Compared with the control group, the hyperlipidemic group had significantly higher relative apoA-I contents of prebeta1-HDL, prebeta2-HDL, HDL3b and HDL3a (P<0.05) and lower HDL2a and HDL2b levels (P<0.001). In the hyperlipidemic group, allele T carriers' frequency was higher than that in the control group (P<0.05), and the genotype of 495TT showed higher levels of plasma TG, apoB100, TG/HDL-C ratio, relative apoA-I contents of prebeta1-HDL, HDL3b and lower HDL2a, HDL2b compared with that of the 495GG genotype subgroup (P<0.05). In the control group, the genotype of 495TT had higher plasma TG, HDL3c and lower HDL2a compared with that of 495GG subgroup (P<0.05).

CONCLUSIONS

The 495TT genotype of LPL gene HindIII polymorphism was associated with changes of HDL subclasses distribution in Chinese population with hyperlipidemia. The particle size of HDL shifted toward smaller, which, in turn, indicated that RCT might be weakened and HDL maturation might be abnormal in hyperlipidemic subjects with 495TT genotype.

Myeloperoxidase-mediated oxidation of high-density lipoproteins: Fingerprints of newly recognized potential proatherogenic lipoproteins

Substantial evidence supports the notion that oxidative processes participate in the pathogenesis of atherosclerotic heart disease. Major evidence for myeloperoxidase (MPO) as enzymatic catalyst for oxidative modification of lipoproteins in the artery wall has been suggested in numerous studies performed with low-density lipoprotein. In contrast to low-density lipoprotein, plasma levels of high-density lipoprotein (HDL)-cholesterol and apoAI, the major apolipoprotein of HDL, inversely correlate with the risk of developing coronary artery disease. These antiatherosclerotic effects are attributed mainly to HDL's capacity to transport excess cholesterol from arterial wall cells to the liver during 'reverse cholesterol transport'. There is now strong evidence that HDL is a selective in vivo target for MPO-catalyzed oxidation impairing the cardioprotective and antiinflammatory capacity of this antiatherogenic lipoprotein. MPO is enzymatically active in human lesion material and was found to be associated with HDL extracted from human atheroma. MPO-catalyzed oxidation products are highly enriched in circulating HDL from individuals with cardiovascular disease where MPO concentrations are also increased. The oxidative potential of MPO involves an array of intermediate-generated reactive oxygen and reactive nitrogen species and the ability of MPO to generate chlorinating oxidants-in particular hypochlorous acid/hypochlorite-under physiological conditions is a unique and defining activity for this enzyme. All these MPO-generated reactive products may affect structure and function of HDL as well as the activity of HDL-associated enzymes involved in conversion and remodeling of the lipoprotein particle, and represent clinically useful markers for atherosclerosis.

Molecular aspects of atherogenesis: new insights and unsolved questions

The development of atherosclerotic disease results from the interaction between environment and genetic make up. A key factor in atherogenesis is the oxidative modification of lipids, which is involved in the recruitment of mononuclear leukocytes to the arterial intima--a process regulated by several groups of adhesion molecules and cytokines. Activated leukocytes, as well as endothelial mitochondria, can produce reactive oxygen species (ROS) that are associated with endothelial dysfunction, a cause of reduced nitric oxide (NO) bioactivity and further ROS production. Peroxisome proliferator-activated receptors (PPAR) and liver X receptors (LXR) are nuclear receptors significantly involved in the control of lipid metabolism, inflammation and insulin sensitivity. Also, an emerging role has been suggested for G protein coupled receptors and for the small Ras and Rho GTPases in the regulation of the expression of endothelial NO synthase (eNOS) and of tissue factor, which are involved in thrombus formation and modulation of vascular tone. Further, the interactions among eNOS, cholesterol, oxidated LDL and caveola membranes are probably involved in some molecular changes observed in vascular diseases. Despite the relevance of oxidative processes in atherogenesis, anti-oxidants have failed to significantly improve atherosclerosis (ATS) prevention, while statins have proved to be the most successful drugs.

Stimulation of liver-directed cholesterol flux in mice by novel N-acetylgalactosamine-terminated glycolipids with high affinity for the asialoglycoprotein receptor

OBJECTIVE

Interventions that promote liver-directed cholesterol flux can suppress atherosclerosis, as demonstrated for scavenger receptor-BI overexpression in hypercholesterolemic mice. In analogy, we speculate that increasing lipoprotein flux to the liver via the asialoglycoprotein receptor (ASGPr) may be of therapeutic value in hypercholesterolemia.

METHODS AND RESULTS

A bifunctional glycolipid (LCO-Tyr-GalNAc3) with a high-nanomolar affinity for the ASGPr (inhibition constant 2.1+/-0.2 nmol/L) was synthesized that showed rapid association with lipoproteins on incubation with serum. Prior incubation of LCO-Tyr-GalNAc3 with radiolabeled low-density lipoprotein or high-density lipoprotein (0.5 microg/microg of protein) resulted in a dramatic induction of the liver uptake of these lipoproteins when injected intravenously into mice (70+/-3% and 78+/-1%, respectively, of the injected dose at 10 minutes of low-density lipoprotein and high-density lipoprotein), as mediated by the ASGPr on hepatocytes. Intravenously injected LCO-Tyr-GalNAc3 quantitatively incorporated into serum lipoproteins and evoked a strong and persistent (> or =48 hour) cholesterol-lowering effect in normolipidemic mice (37+/-2% at 6 hours) and hyperlipidemic apoE(-/-) mice (32+/-2% at 6 hours). The glycolipid was also effective on subcutaneous administration.

CONCLUSIONS

LCO-Tyr-GalNAc3 is very effective in promoting cholesterol uptake by hepatocytes and, thus, may be a promising alternative for the treatment of those hyperlipidemic patients who do not respond sufficiently to conventional cholesterol-lowering therapies.

Relationship between plasma HDL subclasses distribution and apoA-I gene polymorphisms

BACKGROUND

It is generally accepted that apolipoprotein (apo) A-I is the dominant structural apolipoprotein of HDL particles and different HDL subclasses have distinct but interrelated metabolic functions. HDL is known to directly affect the atherogenic process hence changes in HDL subclasses distribution may be related to the incidence and prevalence of atherosclerosis.

METHODS

The ApoA-I contents (mg/l) of plasma HDL subclasses were determined by 2-dimensional gel electrophoresis coupled with immunodetection and apoA-I genotypes were assayed by PCR-RFLP in 307 Chinese subjects (169 males, 138 females).

RESULTS

The G/G and C/C genotypes were the most frequent at -78 bp and +83 bp of apoA-I gene, respectively. There were no significant differences in the frequencies of rare A allele at -78 bp and rare T allele at +83 bp between males and females. Compared with the G/G carriers, G/A and A/A carriers had significantly higher plasma concentrations of TG, apoC-II, apoC-III, apoA-I contents of prebeta(1)-HDL, HDL(3a) and TG/HDL-C ratio. And in addition, A/A carriers had significantly lower apoA-I contents of HDL(2a) and HDL(2b). Females had increased plasma concentrations of apoA-I, HDL-C, apoA-I contents of HDL(2a) and HDL(2b) while decreased apoA-I contents of prebeta(1)-HDL, HDL(3b) and TG/HDL-C ratio as compared to males carrying the same genotype. No significant differences were demonstrated on the concentrations of plasma lipids, lipoproteins, apolipoproteins and apoA-I contents of plasma HDL subclasses between the C/C and C/T subjects.

CONCLUSION

The G/A polymorphism at -78 bp of apoA-I gene was associated with changes of HDL subclasses distribution. There was a general shift towards smaller-sized HDL, which, in turn, indicated that reverse cholesterol transport (RCT) might be weakened and HDL maturation might be abnormal in the subjects with G/A mutation.

Relationship between plasma lipid concentrations and HDL subclasses

BACKGROUND

It is generally accepted that different high-density lipoprotein (HDL) subclasses have distinct but interrelated metabolic functions. HDL is known to directly influence the atherogenic process and changes in HDL subclasses distribution may be related to the incidence and prevalence of atherosclerosis.

METHODS

Apo-AI contents(mg/l) of plasma HDL subclasses were determined by 2-dimensional gel electrophoresis coupled with immunodetection for apo-AI. Four hundred forty-two Chinese adults subjects aged 33 to 78 years were assigned to different groups according to the third Report of NCEP (ATP III) guidelines. The subjects were first divided into 2 groups, normal and high TG, then further classified by plasma TC, HDL-C and LDL-C concentrations. The subjects were also divided into TC desirable and TC high groups.

RESULTS

Apo-A contents of prebeta(1)-HDL were higher while HDL(2b) were lower in high TG subjects vs. the corresponding normal TG subjects according to plasma TC and LDL-C concentrations. With the increase of plasma TC concentrations, apo-AI contents of prebeta(1)-HDL were significantly higher in high TC subgroup vs. TC desirable subgroup in normal TG subjects. With the decrease of HDL-C concentrations, apo-AI contents of HDL(2b) tended to decrease in normal TG subjects. And, with the increases of LDL-C concentration, in normal TG subjects, apo-AI contents of prebeta(1)-HDL and HDL(3b) were significantly higher and those of HDL(2b) were significantly lower in very high LDL-C subgroup vs. LDL-C optimal subgroup. On the other hand, apo-AI contents of prebeta(1)-HDL and HDL(3a) were significantly higher, while HDL(2a) and HDL(2b) were significantly lower in high TG and very high TG subgroup vs. normal TG subgroup within either TC desirable or TC high subjects. In a multivariate linear regression model, TG and TC concentrations were all associated independently and positively with high prebeta(1)-HDL; however, HDL-C were inversely associated with high prebeta(1)-HDL. And TG and TC concentrations were all associated independently and negatively with low HDL(2b), but HDL-C and apo-AI were positively associated with low HDL(2b).

CONCLUSIONS

With the increase of plasma TG, TC, LDL-C or the decrease of plasma HDL-C concentrations, there was a general shift toward smaller-sized HDL, which, in turn, indicates that reverse cholesterol transport might be weakened and HDL maturation might be abnormal. Plasma TG concentration is a more important factor than TC concentration on the changes of HDL subclass distribution. Moreover, when TG is normal and HDL-C decreased, large-size HDL particles tended to decrease.

Modulation of high-density lipoprotein cholesterol metabolism and reverse cholesterol transport

Low high-density lipoprotein (HDL)-cholesterol (C) is an important risk factor for coronary heart disease. In vitro, HDL exerts several potentially anti-atherogenic effects including reverse cholesterol transport (RCT) from peripheral cells to the liver. Hence, raising HDL-C has become an interesting target for anti-atherosclerotic drug therapy. Levels of HDL-C and the composition of HDL subclasses in plasma are regulated by apolipoproteins, lipolytic enzymes, lipid transfer proteins, receptors, and cellular transporters. The interplay of these factors leads to RCT and determines the composition and thereby the anti-atherogenic properties of HDL. Recent findings suggest that the mechanism of HDL modification rather than a sole increase in HDL-C determines the efficacy of anti-atherosclerotic drug therapy. In several controlled and prospective intervention studies, patients with low HDL-C and additional risk factors benefited from treatment with fibrates or statins. However, in only some of the fibrate trials was prevention of coronary events in patients with low HDL-C and hypertriglyceridaemia related to an increase in HDL-C. This may be because currently available drugs increase HDL-C levels only moderately and because HDL levels per se do not necessarily correlate with the functionality of HDL. However, several novel targets to modify RCT have emerged from the recent understanding of HDL synthesis, maturation and catabolism. The four major targets for an anti-atherogenic strategy in HDL metabolism include stimulation of apoA-I synthesis and secretion, the stimulation of ABCA1 expression, the inhibition of cholesterol ester transfer protein, and the up-regulation of scavenger receptor BI. These and other modulations of HDL metabolism are thought to result in improved RCT making them attractive targets for the development of new regimens of anti-atherogenic drug therapy.

Risk factors for atherosclerotic vascular disease

Several controlled interventional trials have shown the benefit of anti-hypertensive and hypolipidaemic drugs for the prevention of coronary heart disease (CHD). International guidelines for the prevention of CHD agree in their recommendations for tertiary prevention and recommend lowering the blood pressure to below 140 mm/90 mm Hg and low density lipoprotein (LDL)-cholesterol to below 2.6 mmol/l in patients with manifest CHD. Novel recommendations for secondary prevention are focused on the treatment of the pre-symptomatic high-risk patient with an estimated CHD morbidity risk of higher than 20% per 10 years or an estimated CHD mortality risk of higher than 5% per 10 years. For the calculation of this risk, the physician must record the following risk factors: sex, age, family history of premature myocardial infarction, smoking, diabetes, blood pressure, total cholesterol, LDL-cholesterol, high-density lipoprotein (HDL)-cholesterol, and triglyceride. This information allows the absolute risk of myocardial infarction to be computed by using scores or algorithms which have been deduced from results of epidemiological studies. To improve risk prediction and to identify new targets for intervention, novel risk factors are sought. High plasma levels of C-reactive protein has been shown to improve the prognostic value of global risk estimates obtained by the combination of conventional risk factors and may influence treatment decisions in patients with intermediate global cardiovascular risk (CHD morbidity risk of 10%-20% per 10 years or CHD mortality risk of 2%-5% per 10 years).

Lipid and non-lipid effects of statins

Long- and short-term trials with the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have demonstrated significant reductions in cardiovascular events in patients with and without history of coronary heart disease. Statins are well-established low-density lipoprotein (LDL)-lowering agents, but their clinical benefit is believed to result from a number of lipid and non-lipid effects beyond LDL lowering, including a rise in plasma high-density lipoprotein levels. Beyond improving the lipid profile, statins have additional non-lipid effects including benefit on endothelial function, inflammatory mediators, intima-media thickening, prothombotic factors that ultimately result in plaque stabilization. These effects arise through the inhibition of several mevalonate-derived metabolites other than cholesterol itself, which are involved in the control of different cellular functions. Although statins represent the gold standard in the prevention and treatment of coronary heart disease, combination therapy with other lipid-lowering drugs, as well as novel therapeutic indications, may increase their therapeutic potential.

Dyslipidemia in visceral obesity: mechanisms, implications, and therapy

Visceral obesity is frequently associated with high plasma triglycerides and low plasma high density lipoprotein-cholesterol (HDL-C), and with high plasma concentrations of apolipoprotein B (apoB)-containing lipoproteins. Atherogenic dyslipidemia in these patients may be caused by a combination of overproduction of very low density lipoprotein (VLDL) apoB-100, decreased catabolism of apoB-containing particles, and increased catabolism of HDL-apoA-I particles. These abnormalities may be consequent on a global metabolic effect of insulin resistance. Weight reduction, increased physical activity, and moderate alcohol intake are first-line therapies to improve lipid abnormalities in visceral obesity. These lifestyle changes can effectively reduce plasma triglycerides and low density lipoprotein-cholesterol (LDL-C), and raise HDL-C. Kinetic studies show that in visceral obesity, weight loss reduces VLDL-apoB secretion and reciprocally upregulates LDL-apoB catabolism, probably owing to reduced visceral fat mass, enhanced insulin sensitivity and decreased hepatic lipogenesis. Adjunctive pharmacologic treatments, such as HMG-CoA reductase inhibitors, fibric acid derivatives, niacin (nicotinic acid), or fish oils, may often be required to further correct the dyslipidemia. Therapeutic improvements in lipid and lipoprotein profiles in visceral obesity can be achieved by several mechanisms of action, including decreased secretion and increased catabolism of apoB, as well as increased secretion and decreased catabolism of apoA-I. Clinical trials have provided evidence supporting the use of HMG-CoA reductase inhibitors and fibric acid derivatives to treat dyslipidemia in patients with visceral obesity, insulin resistance and type 2 diabetes mellitus. Since drug monotherapy may not adequately optimize dyslipoproteinemia, dual pharmacotherapy may be required, such as HMG-CoA reductase inhibitor/fibric acid derivative, HMG-CoA reductase inhibitor/niacin and HMG-CoA reductase inhibitor/fish oils combinations. Newer therapies, such as cholesterol absorption inhibitors, cholesteryl ester transfer protein antagonists and insulin sensitizers, could also be employed alone or in combination with other agents to optimize treatment. The basis for a multiple approach to correcting dyslipoproteinemia in visceral obesity and the metabolic syndrome relies on understanding the mechanisms of action of the individual therapeutic components.

Synthesis of cinnamic acid derivatives and their inhibitory effects on LDL-oxidation, acyl-CoA:cholesterol acyltransferase-1 and -2 activity, and decrease of HDL-particle size

A series of cinnamic acid derivatives were synthesized and their biological abilities on lipoprotein metabolism were examined. Among the tested compounds, 4-hydroxycinnamic acid (l-phenylalanine methyl ester) amide (1) and 3,4-dihydroxyhydrocinammic acid (l-aspartic acid dibenzyl ester) amide (2) inhibited human acyl-CoA:cholesterol acyltransferase-1 and -2 activities with apparent IC(50) around 60 and 95 microM, respectively. Compounds 1 and 2 also served as an antioxidant against copper mediated low-density lipoproteins (LDL) oxidation with apparent IC(50)=52 and 3 microM, compound 1 and 2, respectively. Additionally, decrease of HDL-particle size under presence of LDL was inhibited by the 1 at 307 microM of final concentration. Treatment of the 1 or 2 did not influence normal growth of RAW264.7 without detectable cytotoxic activity from a cell viability test. These results suggest that the new cinnamic acid derivatives possess useful biological activity as an anti-atherosclerotic agent with inhibition of cellular cholesterol storage and transport by the both ACAT, inhibition of LDL-oxidation, HDL particle size rearrangement.

Biology: risk factor modification by OCs and HRT lipids and lipoproteins

The many effects that the oestrogens and progestagens used in oral contraceptive (OC) and postmenopausal hormone replacement therapies (HRTs) have on lipoprotein metabolism are of importance because of the involvement of lipoproteins in endothelial damage and arterial occlusion. Lipoproteins promoting endothelial damage include: low density lipoprotein (LDL), particularly the small dense subfraction (sdLDL), remnants of very low density lipoprotein (VLDL) and chylomicron metabolism, and lipoprotein (a). High density lipoprotein (HDL) has pleiotropic effects that prevent or alleviate endothelial damage. Orally administered oestrogens increase hepatic triglyceride synthesis and VLDL secretion and increase the proportion of sdLDL. Oestrogens increase the rates of elimination of LDL, VLDL remnants and chylomicrons, suppress the synthesis of key enzymes of lipoprotein metabolism, hepatic and lipoprotein lipase, and increase synthesis of the principal apoprotein of HDL, apoAI. In general, progestagens oppose these effects according to type and dose. In OC and HRT users, this leads to a range of different lipoprotein profiles, which may differ from those evaluated with respect to vascular disease risk in population studies. Accumulating evidence suggests that the clinical implications of steroid induced changes in the lipoprotein profile will need to be evaluated independently of population-based evidence.

Fatty acids induce increased granulocyte macrophage-colony stimulating factor secretion through protein kinase C-activation in THP-1 macrophages

Insulin resistance and type 2 diabetes are associated with elevated circulating levels of nonesterified FA (NEFA) and lipoprotein remnants. The dyslipidemia is an important contributor to the excess arterial disease associated with insulin resistance and type 2 diabetes, but the mechanisms involved are elusive. In the present study we examined the effect of NEFA on macrophages. For this purpose, we utilized human macrophages, prepared by treating THP-1 monocytes with phorbol ester. We found that albumin-bound NEFA at physiological levels increase the secretion of granulocyte macrophage-colony stimulating factor (GM-CSF) by the THP-1 macrophages in a dose-dependent manner. The effect was registered as an increase in mRNA, and the amount of GM-CSF secreted correlated with the accumulation of TAG and DAG in the cell. The NEFA-induced rise in GM-CSF appeared to be mediated by activation of protein kinase C, probably acting on extracellular signal-regulated kinases 1 and 2 and being calcium dependent. We speculate that increased secretion of GM-CSF by resident macrophages in the intima exposed chronically to high levels of NEFA, such as those present in insulin resistance, may contribute to a proatherogenic response of arterial cells.

Inhibition of cholesteryl ester transfer protein increases serum apolipoprotein (apo) A-I levels by increasing the synthesis of apo A-I in rabbits

BACKGROUND

Inhibition of cholesteryl ester transfer protein (CETP) is an effective way to increase HDL levels in animals and humans. The effects of a CETP inhibitor, JTT-705, on the in vivo kinetics of apolipoprotein (apo) A-I and apo A-I gene expression in the liver and intestine were investigated.

METHODS

Japanese White rabbits were randomly fed normal rabbit chow LRC-4 (n=10, control) or a food admixture of LRC-4 and 0.75% JTT-705 (n=10, treated) for 7 months. An in vivo kinetics study of apo A-I was performed by injecting rabbit 125I-apo A-I, and apo A-I mRNA levels were quantified by RT-PCR.

RESULTS

JTT-705 significantly inhibited CETP activities, increased serum levels of HDL-cholesterol (C), HDL2-C, HDL-phospholipid, and apo A-I, and decreased HDL-triglyceride levels. The synthetic rate of apo A-I was higher in the treated rabbits than in control rabbits (13.7 +/- 2.6 versus 9.5 +/- 1.3 mg/kg per day, P < 0.05), while the fractional catabolic rate was similar in the two groups. JTT-705 increased apo A-I mRNA levels in the liver without affecting those in the intestine.

CONCLUSION

Inhibition of CETP activity by JTT-705 increases HDL levels by increasing the synthesis of apo A-I, suggesting that it could be a promising therapeutic approach for atherosclerosis.

Low high-density lipoprotein cholesterol: physiological background, clinical importance and drug treatment

Low high-density lipoprotein (HDL) cholesterol is an important risk factor for coronary heart disease (CHD). In vitro, HDL exerts several potentially anti-atherogenic activities. HDLs mediate the reverse cholesterol transport (RCT) from peripheral cells to the liver, inhibit oxidation of low-density lipoprotein (LDL), adhesion of monocytes to the endothelium, apoptosis of vascular endothelial and smooth muscle cells and platelet activation, and stimulate the endothelial secretion of vasoactive substances as well as smooth muscle cell proliferation. Hence, raising HDL-cholesterol levels has become an interesting target for anti-atherosclerotic drug therapy. Levels of HDL cholesterol and the composition of HDL subclasses in plasma are regulated by apolipoproteins, lipolytic enzymes, lipid transfer proteins, receptors and cellular transporters. The interplay of these factors leads to RCT and determines the composition and, thereby, the anti-atherogenic properties of HDL. Several inborn errors of metabolism, as well as genetic animal models, are characterised by both elevated HDL cholesterol and increased rather than decreased cardiovascular risk. These findings suggest that the mechanism of HDL modification rather than simply increasing HDL cholesterol determine the efficacy of anti-atherosclerotic drug therapy. In several controlled and prospective intervention studies, patients with low HDL cholesterol and additional risk factors benefited from treatment with fibric acid derivatives (fibrates) or HMG-CoA reductase inhibitors (statins). However, only in some trials was prevention of coronary events in patients with low HDL cholesterol and hypertriglyceridaemia related to an increase in HDL cholesterol. We discuss the clinical and metabolic effects of fibrates, statins, nicotinic acid and sex steroids, and present novel therapeutic strategies that show promise in modifying HDL metabolism. In conclusion, HDL-cholesterol levels increase only moderately after treatment with currently available drugs and do not necessarily correlate with the functionality of HDL. Therefore, the anti-atherosclerotic therapy of high-risk cardiovascular patients should currently be focused on the correction of other risk factors present besides low HDL cholesterol. However, modification of HDL metabolism and improvement of RCT remain an attractive target for the development of new regimens of anti-atherogenic drug therapy.

Testosterone and atherosclerosis

Hypoandrogenemia in men and hyperandrogenemia in women are associated with increased risk of coronary artery disease but also with visceral obesity, insulin resistance, low high-density lipoprotein (HDL) cholesterol, elevated triglycerides, low-density lipoprotein (LDL) cholesterol and plasminogen activator inhibitor (PAI-1). These gender differences and confounders render the precise role of endogenous androgens in atherosclerosis unclear. Exogenous androgens, on the other hand, induce both apparently beneficial and deleterious effects on cardiovascular risk factors by decreasing serum levels of HDL-C, PAI-1 (apparently deleterious), Lp(a), fibrinogen, insulin, leptin and visceral fat mass (apparently beneficial) in men as well as women. However, androgen-induced declines in circulating HDL-C should not automatically be assumed to be pro-atherogenic, since it may reflect accelerated reverse cholesterol transport instead.Short-term application of supraphysiological doses of exogenous T can reduce the severity and frequency of angina pectoris and improve the electrocardiographic signs of myocardial ischaemia; long-term effects have not been investigated. Nonetheless, interpretations of the effects of pharmacological doses of androgens on arterial compliance and flow-mediated dilatation in particular must be treated with circumspection also because at physiological concentrations, beneficial, neutral, and detrimental effects on vascular reactivity can be observed.Testosterone exerts 'pro-atherogenic' effects on macrophage function by facilitating the uptake of modified lipoproteins and an 'anti-atherogenic' effect by stimulating efflux of cellular cholesterol to HDL. In the majority of animal experiments, exogenous testosterone exerted neutral or beneficial effects on the development of atherosclerosis. In conclusion, the overall effect of administration of testosterone on cardiovascular-disease risk is difficult to assess because androgens have such an extraordinary array of effects in vivo. When dealing with a complex multifactorial condition such as CAD, it is premature to assume that clinical benefits can be derived from manipulation of the sex steroid milieu - even when these assumptions are based on biologically plausible mechanisms or, indeed, on cross-sectional risk-factor observational data. Neither needs the therapeutic use of testosterone in men be restricted by concerns regarding cardiovascular side effects.

Reverse cholesterol transport, high density lipoproteins and HDL cholesterol: recent data

Unlike LDL cholesterol, which is a major cardiovascular risk factor, HDL cholesterol plays an important anti-atherogenic role through reverse cholesterol transport from peripheral cells to the liver. Some recent biochemical and epidemiological data shed light on this key function. In the hereditary Tangier disease with disseminated lipid storage, the main biochemical feature is a dramatically low level of HDL cholesterol. Different mutations in the ATP-binding cassette transporter A1 (ABCA1) gene have been recently described, which interfere with cellular cholesterol efflux. This results in low HDL plasma level, and defective reverse cholesterol transport to the liver. Moreover, selective hepatic uptake of HDL cholesteryl esters by SR-B1, a class B scavenger receptor, also plays a key role. In the follow-up of the PROCAM Study, the relative risk of coronary events is high in a cluster of patients with increased total cholesterol/HDL-cholesterol ratio. In the prospective secondary prevention VA-HIT study, the relative risk of coronary events in patients with low HDL cholesterol levels is decreased of 22% with a treatment by gemfibrozil. If the present available range of drugs targeted at increasing HDL cholesterol levels is rather narrow, future therapies will be encouraging, especially with agonists of PPARs.