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

Overexpression of LOX-1 in hepatocytes protects vascular smooth muscle cells from phenotype transformation and wire injury induced carotid neoatherosclerosis through ALOX15

Neoatherosclerosis (NA), the main pathological basis of late stent failure, is the main limitation of interventional therapy. However, the specific pathogenesis and treatment remain unclear. In vivo, NA model was established by carotid wire injury and high-fat feeding in ApoE-/- mice. Oxidized low-density lipoprotein receptor-1/lectin-like oxidized low-density lipoprotein receptor-1 (OLR1/LOX-1), a specific receptor for oxidized low-density lipoprotein (ox-LDL), was specifically ectopically overexpressed in hepatocytes by portal vein injection of adeno-associated serotype 8 (AAV8)-thyroid binding globulin (TBG)-Olr1 and the protective effect against NA was examined. In vitro, LOX-1 was overexpressed on HHL5 using lentivirus (LV)-OLR1 and the vascular smooth muscle cells (VSMCs)-HHL5 indirect co-culture system was established to examine its protective effect on VSMCs and the molecular mechanism. Functionally, we found that specific ectopic overexpression of LOX-1 by hepatocytes competitively engulfed and metabolized ox-LDL, alleviating its resulting phenotypic transformation of VSMCs including migration, downregulation of contractile shape markers (smooth muscle α-actin (SMαA) and smooth muscle-22α (SM22α)), and upregulation of proliferative/migratory shape markers (osteopontin (OPN) and Vimentin) as well as foaminess and apoptosis, thereby alleviating NA, which independent of low-density lipoprotein (LDL) lowering treatment (evolocumab, a monoclonal antibody to proprotein convertase subtilisin/kexin type 9 (PCSK9)). Mechanistically, we found that overexpression of LOX-1 in hepatocytes competitively engulfed and metabolized ox-LDL through upregulation of arachidonate-15-lipoxygenase (ALOX15), which further upregulated scavenger receptor class B type I (SRBI) and ATP-binding cassette transporter A1 (ABCA1). In conclusion, the overexpression of LOX-1 in liver protects VSMCs from phenotypic transformation and wire injury induced carotid neoatherosclerosis through ALOX15.

Association of exposures to serum terpenes with the prevalence of dyslipidemia: a population-based analysis

This study sought to examine hitherto unresearched relationships between serum terpenes and the prevalence of dyslipidemia. Serum terpenes such as limonene, α-pinene, and β-pinene from the 2013-2014 National Health and Nutrition Examination Survey (NHANES) were used as independent variables in this cross-sectional study. Continuous lipid variables included total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), non-HDL-C, triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), residual cholesterol (RC), and apolipoprotein B (Apo B). Binary lipid variables (elevated TC, ≥5.18 mmol/L; lowered HDL-C, <1.04 mmol/L in men, and <1.30 mmol/L in women; elevated non-HDL-C, ≥4.2 mmol/L; elevated TG, ≥1.7 mmol/L; elevated LDL-C, ≥3.37 mmol/L; elevated RC, ≥1.0 mmol/L; and elevated Apo B, ≥1.3 g/L) suggest dyslipidemia. The relationships between the mixture of serum terpenes with lipid variables were investigated using weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR). The study for TC, HDL-C, and non-HDL-C included a total of 1,528 people, whereas the analysis for TG, LDL-C, RC, and Apo B comprised 714 participants. The mean age of the overall participants was 47.69 years, and 48.77% were male. We found that tertiles of serum terpene were positively associated with binary (elevated TC, non-HDL-C, TG, LDL-C, RC, Apo B, and lowered HDL-C) and continuous (TC, non-HDL-C, TG, LDL-C, RC, and Apo B, but not HDL-C) serum lipid variables. WQS regression and BKMR analysis revealed that the mixture of serum terpenes was linked with the prevalence of dyslipidemia. According to our data, the prevalence of dyslipidemia was correlated with serum concentrations of three terpenes both separately and collectively.

Can improvement in hormonal and energy balance reverse cardiovascular risk factors in athletes with amenorrhea?

Female athletes display a high prevalence of hypothalamic amenorrhea as a result of energy imbalance. In these athletes with amenorrhea, decreased luteinizing hormone/follicule-stimulating hormone secretion leads to deficiency in endogenous estrogen. The severe estrogen deficiency in these athletes may increase cardiovascular risk similar to that in postmenopausal women. This review discusses the potential cardiovascular risk factors in athletes with amenorrhea as a result of hypoestrogenism, which include endothelial dysfunction and unfavorable lipid profiles. We also consider the potential to reverse the cardiovascular risk by restoring energy or hormonal imbalance along the reproductive axis in athletes with amenorrhea.

Emerging role of 12/15-Lipoxygenase (ALOX15) in human pathologies

12/15-lipoxygenase (12/15-LOX) is an enzyme, which oxidizes polyunsaturated fatty acids, particularly omega-6 and -3 fatty acids, to generate a number of bioactive lipid metabolites. A large number of studies have revealed the importance of 12/15-LOX role in oxidative and inflammatory responses. The in vitro studies have demonstrated the ability of 12/15-LOX metabolites in the expression of various genes and production of cytokine related to inflammation and resolution of inflammation. The studies with the use of knockout and transgenic animals for 12/15-LOX have further shown its involvement in the pathogenesis of a variety of human diseases, including cardiovascular, renal, neurological and metabolic disorders. This review summarizes our current knowledge on the role of 12/15-LOX in inflammation and various human diseases.

Hypertriglyceridemia and adverse outcomes during pregnancy

Introducción. Durante el embarazo, los niveles séricos de triglicéridos maternos aumentan como un mecanismo de adaptación fisiológica para suplir las necesidades del feto en desarrollo. Pese a que el incremento excesivo se ha asociado a preeclampsia, macrosomía y parto pretérmino, no se han establecido de manera contundente los niveles a partir de los cuales se deben tomar medidas en cada trimestre para prevenir complicaciones.Objetivo. Hacer una revisión sobre fisiopatología, efectos en madre e hijo, valores esperados en cada trimestre e intervenciones terapéuticas en hipertrigliceridemia gestacional.Materiales y métodos. Se realizó una revisión con la búsqueda de artículos en las bases de datos ScienceDirect, PubMed, Scopus, LILACS, Cochrane y SciELO con los términos: Pregnancy; Hypertriglyceridemia; Maternal-Fetal Exchange; Fetal Development; Pregnancy Complications y sus equivalentes en español.Resultados. Se encontraron 59 artículos que cumplieron los criterios de búsqueda y daban respuesta a los objetivos.Conclusiones. El número limitado y la gran variabilidad de los datos indican la necesidad de realizar más investigaciones que establezcan los rangos de normalidad de los triglicéridos durante los tres trimestres del embarazo y así determinar riesgos e intervenciones eficaces antes de la gestación y reducir la morbimortalidad materno-infantil.

Abnormal lipoprotein oxylipins in metabolic syndrome and partial correction by omega-3 fatty acids

Metabolic syndrome (MetSyn) is characterized by chronic inflammation which mediates the associated high risk for cardiovascular and other diseases. Oxylipins are a superclass of lipid mediators with potent bioactivities in inflammation, vascular biology, and more. While their role as locally produced agents is appreciated, most oxylipins in plasma are found in lipoproteins suggesting defective regulation of inflammation could be mediated by the elevated VLDL and low HDL levels characteristic of MetSyn. Our objective was to compare the oxylipin composition of VLDL, LDL, and HDL in 14 optimally healthy individuals and 31 MetSyn patients, and then to determine the effects of treating MetSyn subjects with 4g/day of prescription omega-3 fatty acids (P-OM3) on lipoprotein oxylipin profiles. We compared oxylipin compositions of healthy (14) and MetSyn (31) subjects followed by randomization and assignment to 4g/d P-OM3 for 16 weeks using LC/MS/MS. Compared to healthy subjects, MetSyn is characterized by abnormalities of (1) pro-inflammatory, arachidonate-derived oxylipins from the lipoxygenase pathway in HDL; and (2) oxylipins mostly not derived from arachidonate in VLDL. P-OM3 treatment corrected many components of these abnormalities, reducing the burden of inflammatory mediators within peripherally circulating lipoproteins that could interfere with, or enhance, local effectors of inflammatory stress. We conclude that MetSyn is associated with a disruption of lipoprotein oxylipin patterns consistent with greater inflammatory stress, and the partial correction of these dysoxylipinemias by treatment with omega-3 fatty acids could explain some of their beneficial effects.

Low Levels of High-Density Lipoprotein Cholesterol Do Not Predict the Incidence of Type 2 Diabetes in an Iranian High-Risk Population: The Isfahan Diabetes Prevention Study

OBJECTIVES

To evaluate the ability of low-level fasting high-density lipoprotein cholesterol (HDLC) to predict the incidence of type 2 diabetes (T2D) in an Iranian high-risk population.

METHODS

Seven-year follow-up data (n = 1,775) in non-diabetic first-degree relatives (FDR) of consecutive patients with T2D aged 30-70 years were analyzed. The primary outcome was the diagnosis of T2D based on repeated oral glucose tolerance test (OGTT). We used Cox proportional hazard models to estimate the hazard ratio (HR) for the incidence of T2D across quartiles of HDLC, and plotted a receiver operating characteristic (ROC) curve to assess discrimination.

RESULTS

The highest quartile compared with the lowest quartile of HDLC was associated with T2D in age- and gender-adjusted models (HR: 0.83, 95% CI: 0.73-0.95). Further adjustment for fasting plasma glucose and cholesterol attenuated the association for T2D incidence (HR: 0.93, 95% CI: 0.80-1.08). The area under the ROC curve for HDLC was 54.1% (95% CI: 50.2-58.0).

CONCLUSIONS

HDLC level was a weak predictor of T2D in an Iranian high-risk population, independent of age and gender.

Time-resolved cellular effects induced by TcdA from Clostridium difficile

RATIONALE

The anaerobe Clostridium difficile is a common pathogen that causes infection of the colon leading to diarrhea or pseudomembranous colitis. Its major virulence factors are toxin A (TcdA) and toxin B (TcdB), which specifically inactivate small GTPases by glucosylation leading to reorganization of the cytoskeleton and finally to cell death. In the present work a quantitative proteome analysis using the isotope-coded protein label (ICPL) approach was conducted to investigate proteome changes in the colon cell line Caco-2 after treatment with recombinant wild-type TcdA (rTcdA-wt) or a glucosyltransferase-deficient mutant TcdA (rTcdA-mut).

METHODS

Proteins from crude cell lysates or cellular subfractions were identified by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). Two time points (5 h, 24 h) of toxin treatment were analyzed and about 4000 proteins were identified in each case.

RESULTS

After 5 h treatment with rTcdA-wt, 150 proteins had a significantly altered abundance; rTcdA-mut caused regulation of 50 proteins at this time point. After 24 h treatment with rTcdA-wt changes in abundance of 61 proteins were observed, but no changes in protein abundance were detected after 24 h if cells were treated with rTcdA-mut. TcdA affected several proteins involved in signaling events, cytoskeleton and cell-cell contact organization, translation, and metabolic processes. The ICPL-dependent quantification was verified by label-free targeted MS techniques based on multiple reaction monitoring (MRM) and triple quadrupole mass spectrometry.

CONCLUSIONS

LC/MS-based proteome analyses and the ICPL approach revealed comprehensive and reproducible proteome date and provided new insights into the cellular effects of clostridial glucosylating toxins (CGT).

Serum high-density lipoprotein cholesterol and progression to arterial stiffness in middle-aged and elderly Chinese

BACKGROUND AND AIMS

Low high-density lipoprotein cholesterol (HDL-c) is a risk factor for cardiovascular disease. Brachial-ankle pulse wave velocity (baPWV) is an indicator of arterial stiffness, which is recognized as a predictor of cardiovascular disease. The aim of this study was to investigate the association between HDL-c and baPWV among middle-aged and elderly Chinese.

METHODS

A total number of 1133 Chinese (430 men, 703 women) aged from 50 to 90 years old were recruited from Shanghai downtown district. The baPWV and major cardiovascular risk factors of the participants were measured.

RESULTS

Serum HDL-c was negatively correlated with baPWV (r = -0.143, P < 0.001) after adjustment for age and gender. Multivariate linear regression analysis demonstrated that age (P < 0.001), systolic blood pressure (P < 0.001), HDL-c (P < 0.001), smoking (P = 0.001), BMI (P = 0.002), fasting plasma glucose (P = 0.004), and white blood cell (P = 0.005) were independently associated with baPWV. After multiple adjustments, participants in the highest quartile of HDL-c had an odds ratio of 0.442 (95% CI 0.268-0.729) for developing high arterial stiffness compared with participants in the lowest quartile. The association remained significant after further adjustment for major cardiovascular risk factors.

CONCLUSION

HDL-c has an independent protective effect on arterial stiffness in middle-aged and elderly Chinese. Early detection of HDL-c level is important in high risk populations with arterial stiffness. Increasing HDL-c level may be an attractive therapeutic target for the prevention of arterial function and subsequent disease.

Knockdown of scavenger receptor class B type I reduces prostate specific antigen secretion and viability of prostate cancer cells

BACKGROUND

Scavenger Receptor Class B Type I (SR-BI) facilitates influx of cholesterol to the cell from lipoproteins in the circulation. This influx of cholesterol may be important for many cellular functions, including synthesis of androgens. Castration-resistant prostate cancer tumors are able to synthesize androgens de novo in order to supplement the loss of exogenous sources often induced by androgen deprivation therapy. Silencing of SR-BI may impact the ability of prostate cancer cells, particularly those of castration-resistant state, to maintain the intracellular supply of androgens by removing a supply of cholesterol.

METHODS

SR-BI expression was knocked down using small interfering RNA in LNCaP and C4-2 cells. The effect of down-regulation of SR-BI on PSA production, cell toxicity, and cell viability was measured in both cell types. In addition, compensatory cholesterol synthesis activity was measured using the radiolabeled precursor, (14) C-acetate.

RESULTS

SR-BI protein expression is higher basally in C4-2 cells than LNCaP cells. Silencing of SR-BI expression to greater than 85% reduced PSA production in LNCaP and C4-2 SRBI-KD cells by 55% and 58% compared to negative control cells, respectively. SR-BI-KD C4-2 cells demonstrated significantly reduced cell viability (>25%) compared the NC cells.

CONCLUSIONS

The down-regulation of SR-BI significantly impacts PSA production of prostate cancer cells, as well as the viability of C4-2 cells in the presence and absence of HDL. This may indicate a deficiency in cholesterol availability to the androgen synthesis pathway or may implicate a role for SR-BI in prostate cancer signal transduction pathways.

Fluoride in low concentration modifies expression and activity of 15 lipoxygenase in human PBMC differentiated monocyte/macrophage

Epidemiological and experimental evidences demonstrate positive correlation between environmental and occupational fluoride exposure and risk to various cardio-respiratory disorders. That fore we decided to examine the effect of fluorides on activity and expression of 15LOX enzyme which is implicated in biosynthesis of inflammatory mediators. Expression of 15LOX-1 and -2 enzymes mRNA and protein was analyzed using RT PCT and immunoblotting methods respectively whereas HPLC method was used to measure the levels of 15 lipoxygenases end products. Additionally AA and LA concentration in cells was measured using GC method. We observed that fluoride in small concentration may significantly decrease activity of 15LOX-1 and -2 in human PBMC macrophages and then concentration of its end products: 15-HETE, 12-HETE and 9+13-HODE, what may cause development of inflammation through the cholesterol arrest into the macrophages and its differentiation to foam cell. Noted by our team overexpression of the 15LOX-1 enzyme in macrophages after addition of lowest fluoride concentrations (1 and 3 μM) may be aimed at fighting inflammation development and excessive intracellular lipid accumulation. But highest fluoride concentrations (6 and 10 μM) added to cell culture slowly declined expression of this enzyme probably because of developing inflammation. Additional 15LOX-2 expression in macrophages after fluoride addition was low in 1 and 3 μM concentrations, but increased significantly after 10 μM fluoride addition what may suggest developing acute inflammation, because 15LOX-2 is associated to increased local hypoxia. This study indicated that even in small concentrations fluorides changes the amounts and activity of 15 LOX-1 and -2 enzymes taking part in the development of inflammatory process.

High-density lipoprotein levels and 10-year cardiovascular risk in HIV-1-infected patients

We aimed to determine the contribution of high-density lipoprotein cholesterol (HDL-c) to cardiovascular disease (CVD) risk in a cohort of HIV-infected patients. The contribution of CVD risk factors to the predicted CVD risk was assessed. We estimated the degree of reclassification of CVD risk if HDL-c concentration was increased in all patients by 20 and 40%, respectively. After age, HDL-c contributed most to the overall cardiovascular risk. Increasing HDL-c by 20% and 40% reclassified six and 12 patients to lower CVD risk groups, respectively. In this cohort, HDL-c contributed more to cardiovascular risk than smoking, total cholesterol, systolic blood pressure (SBP) and sex.

Functional and pathological roles of the 12- and 15-lipoxygenases

The 12/15-lipoxygenase enzymes react with fatty acids producing active lipid metabolites that are involved in a number of significant disease states. The latter include type 1 and type 2 diabetes (and associated complications), cardiovascular disease, hypertension, renal disease, and the neurological conditions Alzheimer's disease and Parkinson's disease. A number of elegant studies over the last thirty years have contributed to unraveling the role that lipoxygenases play in chronic inflammation. The development of animal models with targeted gene deletions has led to a better understanding of the role that lipoxygenases play in various conditions. Selective inhibitors of the different lipoxygenase isoforms are an active area of investigation, and will be both an important research tool and a promising therapeutic target for treating a wide spectrum of human diseases.

Partial filling affinity capillary electrophoresis with cationic poly(vinylpyrrolidone)-based copolymer coatings for studies on human lipoprotein-steroid interactions

Human plasma lipoproteins have strong hydrophobic interactions with steroids and their fatty acyl derivatives such as estradiol fatty acyl esters. In this work, affinity capillary electrophoresis with the partial filling technique was applied to study the hydrophobic interactions between lipoproteins, which are nanometer-sized particles, and nonconjugated steroids. The capillaries were first rinsed with one of two novel poly(vinylpyrrolidone) (PVP)-based cationic copolymers that were strongly adsorbed onto the fused-silica surface via electrostatic interactions. This surface treatment greatly suppressed the adsorption of lipoproteins. Low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particles were then employed in the coated capillaries as pseudostationary phase in the partial filling mode. The changes in corrected migration times of steroids increased linearly with the filling time of the lipoproteins. The affinity constants between the steroids and lipoproteins were calculated, and the most hydrophobic steroid studied, progesterone, had stronger affinity than testosterone or androstenedione toward both LDL and HDL. Affinity between steroids and LDL was stronger than that between steroids and HDL. Interactions between the steroids and lipoproteins were mainly nonspecific with particle lipid components, whereas some were site specific with the apolipoproteins. The developed technique has great potential for determination of the affinity of various compounds toward lipoproteins.

ABCA1 expression and statins: inhibitory effect in peripheral blood mononuclear cells

The ATP-binding cassette transporter A1 (ABCA1) has an essential role in the formation of nascent high-density lipoprotein particles and also participates in the cholesterol efflux from macrophages in the artery wall. Several substances, such as statins, or even gene variants are able to modulate ABCA1 expression. There is strong evidence that statin treatment downregulates the ABCA1 expression in nonloaded macrophages. Interestingly, in cholesterol-loaded macrophages, which are more relevant to atherogenesis, this effect is lost. We observed an inhibitory effect of atorvastatin in peripheral blood mononuclear cells of hypercholesterolemic individuals. Moreover, in these individuals, the ABCA1 -14C>T polymorphism was associated with high baseline gene-expression levels. Other studies are needed to evaluate how relevant these findings are to the formation of arterial foam cells in vivo.

Vascular risk factors and cognitive function among 3763 participants in the Hypertension in the Very Elderly Trial (HYVET): a cross-sectional analysis

BACKGROUND

It is well known that the global population is aging and that those over the age of 80 are the fastest growing part of this expansion. Also known is that prevalence of hypertension and cognitive decline both increase with increasing age.

METHOD

The Hypertension in the Very Elderly Trial (HYVET) was a double blind placebo-controlled trial of antihypertensive treatment (indapamide SR 1.5 mg +/- perindopril 2-4 mg) and recruited only those hypertensives who were aged 80 or over and were without a diagnosis of dementia at baseline. Systolic blood pressure had to be in the range 160-199 mmHg and diastolic pressure <110 mmHg. Cognitive function was assessed at baseline using the Mini-mental State Examination prior to randomization into the trial. Also collected at baseline was information relating to sociodemographic, clinical, cardiovascular and biochemical factors which may impact upon cognitive function. This paper reports on the baseline cognitive function data from the HYVET trial and its relationship to these factors.

RESULTS

The mean age of the 3763 HYVET participants who had full cognitive function data at baseline was 83.6 years; 60 percent were female. The median MMSE score at baseline was 26 and, in multivariate analyses, higher at younger age, with male gender, higher educational level, having higher creatinine, higher total cholesterol and lower high-density lipoprotein cholesterol.

CONCLUSIONS

This is the first such study to examine a large number of very elderly hypertensives and it shows some similar patterns to those seen in younger elderly groups.

Carnitine palmitoyltransferase IA polymorphism P479L is common in Greenland Inuit and is associated with elevated plasma apolipoprotein A-I

Carnitine palmitoyltransferase IA, encoded by CPT1A, is a key regulator of fatty acid metabolism. Previously, a loss-of-function mutation, namely, c.1436 C-->T (p.P479L), was reported in CPT1A in the homozygous state in Canadian aboriginal male with presumed CPT1A deficiency. To determine the population frequency of this variant, we determined CPT1A p.P479L genotypes in 1111 Greenland Inuit. Associations between genotype and variation in plasma total cholesterol, triglycerides, LDL, HDL, apolipoprotein (apo) B, and apoA-I was also investigated. We found the L479 allele occurs at a high frequency in this sample (0.73), while it was completely absent in 285 nonaboriginal samples. This suggests that the original proband's symptoms were not likely due to the CPT1A p.P479L mutation because it is very common in Inuit and because symptoms suggesting CPT1A deficiency have not been reported in any carrier subsequently studied. However, CPT1A p.P479L was associated with elevated plasma HDL and apoA-I levels. The association with increased levels of HDL and apoA-I suggest that the polymorphism might protect against atherosclerosis.

Unmet Medical Needs and the Role of Pharmaceutical Companies

Rising health care costs have been prioritized in the budget planning of all Western countries. Rising R&D costs of up to $800 million per marketed new pharmaceutical have dramatically reduced the approval of new chemical entities (NCEs). Globalization of diseases like AIDS and SARS has had a definite impact on the economic situation not only in the Western world, but also in developing countries, especially for AIDS in Africa and SARS in Asia. The World Health Organization (WHO) is calling for free anti-tuberculosis (TB) drugs to be made available to people living with human immunodeficiency virus (HIV). The spread between unmet medical need in large indications (e.g. Alzheimer's disease) and in niche indications (e.g. Huntington disease) and the economic burden to create a blockbuster ($1 billion sales within one year after launch) has created a marketing-driven clinical development of new chemical entities. A paradigm shift has occurred by which developing a new innovative drug by documenting shortterm efficacy, quality and safety rather than long-term efficacy and emphasizing pharma-covilliglance including considerations of health economy within the medical environment a shift that has fundamentally changed and challenged the pharmaceutical industry.

Effect of fenofibrate therapy on paraoxonase1 status in patients with low HDL-C levels

OBJECTIVES

We evaluated the effect of micro-coated fenofibrate on lipid parameters, high sensitivity C-reactive protein and paraoxonase1 levels in dyslipidemic patients with low high-density lipoproteins levels. In addition, the effects of the paraoxonase1 polymorphisms on lipid and paraoxonase1 responses to fenofibrate therapy were examined.

METHODS

A total of 61 dyslipidemic patients with low high-density lipoproteins levels were recruited into this study to receive micro-coated fenofibrate (160 mg/day) for 12 weeks. Lipid parameters, C-reactive protein, paraoxonase1 concentration and activity were measured at baseline and after 6 and 12 weeks of fenofibrate treatment. Four polymorphisms in both the coding (L55M and Q192R) and regulatory regions (T-108C and G-909C) of human paraoxonase1 were also quantified.

RESULTS

Micro-coated fenofibrate significantly decreased total cholesterol, triglycerides, non-high-density lipoprotein cholesterol, oxidized low-density lipoprotein and apolipoprotein-B levels after 6 and 12 weeks (all p<0.001). While high-density lipoprotein and apolipoprotein AI levels were significantly increased by 14.7% and 6.9%, respectively, after 6 weeks and by 17.3% and 7.2%, respectively, after 12 weeks (all p<0.01). There were no significant differences in the mean of low-density lipoprotein and C-reactive protein after fenofibrate treatment. There were significant increases in paraoxonase1 concentration and activity by 7.7% and 5.7% after 6 weeks and by 14.6% and 10.1% after 12 weeks, respectively (all p<0.01). After micro-coated fenofibrate therapy, a significantly positive correlation between the change in high-density lipoprotein and the changes in paraoxonase1 concentration and activity was observed (p=0.001). On the other hand, the changes in paraoxonase1 activity were significantly and negatively correlated with the changes in triglycerides (p=0.007). The therapeutic response of lipid parameters to micro-coated fenofibrate was independent of paraoxonase1 polymorphisms. However, paraoxonase1 Q192R and T-108C polymorphisms significantly affected the increase in paraoxonase1 activity (the highest increase in 192QQ and -108TT) and paraoxonase1 concentration (the highest increase in -108TT).

CONCLUSION

Lipid-modifying therapy with micro-coated fenofibrate in patients with low high-density lipoprotein levels not only reduced atherogenic lipids (total cholesterol, triglycerides, oxidized low-density lipoprotein and apolipoprotein-B) and increased atheroprotective lipids but also increased paraoxonase1 concentration and activity. Increasing paraoxonase1 levels by fenofibrate may play an important role in decreasing low-density lipoprotein oxidation.

Effects of ABCA1 SNPs, including the C-105T novel variant, on serum lipids of Brazilian individuals

BACKGROUND

ABCA1 plays an important role in HDL metabolism. Single nucleotide polymorphisms (SNPs) in ABCA1 gene were associated with variation in plasma HDL-c.

METHODS

The effect of the ABCA1 SNPs C-14T, R219K and of a novel variant C-105T on serum lipids was investigated in 367 unrelated Brazilian individuals (224 hypercholesterolemic and 143 normolipidemic). The relation between ABCA1 SNPs and the lipid-lowering response to atorvastatin (10 mg/day/4 weeks) was also evaluated in 141 hypercholesterolemic (HC) individuals. The polymorphisms were detected by PCR-RFLP and confirmed by DNA sequencing.

RESULTS

Linkage disequilibrium was found between the SNPs C-105T and C-14T in the HC group. HC individuals carrying -105CT/TT genotypes had higher serum HDL-c and lower triglyceride and VLDL-c concentrations as well as lower TG/HDL-c ratio compared to the -105CC carriers (p<0.05). The R219K SNP was associated with reduced serum triglyceride, VLDL-c and TG/HDL-c ratio in the HC group (p<0.05), and with an increased serum apoAI in NL individuals. The effects of ABCA1 SNPs on basal serum lipids of HC individuals were not modified by atorvastatin treatment.

CONCLUSIONS

The ABCA1 SNPs R219K and C-105T were associated with a less atherogenic lipid profile but not with the lowering-cholesterol response to atorvastatin in a Brazilian population.

High-density lipoprotein cholesterol and residual cardiometabolic risk in metabolic syndrome

It has long been recognized that elevated levels of low-density lipoprotein cholesterol (LDL-C) increase the risk of cardiovascular disease (CVD) and that pharmacologic therapy to decrease LDL-C significantly reduces cardiovascular events. Despite the effectiveness of statins for CVD risk reduction, even optimal LDL-lowering therapy alone fails to avert approximately 60% to 70% of CVD cases, and the incidence of CVD mortality continues to grow. A low plasma concentration of high-density lipoprotein cholesterol (HDL-C) is also associated with increased risk of CVD and is 1 component of metabolic syndrome, a cluster of interrelated CVD risk factors. HDL stimulates reverse cholesterol transport from the peripheral tissues to the liver for removal from the body, prevents deleterious effects of LDL on endothelial function, acts as an antioxidant, and also possesses anti-inflammatory, antithrombotic, and antiapoptotic effects. Some of the treatments that increase HDL-C concentrations have been shown to reduce atheroma volume and may prevent the formation of new atherosclerotic lesions, thereby reducing the risk of CVD. For these reasons, increasing HDL-C concentrations has become a potentially attractive therapeutic target for individuals who are at increased risk of CVD, including those with metabolic syndrome. Traditional strategies to increase HDL-C include the use of niacin, statins, and fibric acid derivatives. Pharmacotherapies that have recently been developed and are currently being evaluated include inhibition of the enzyme cholesteryl ester transfer protein (CETP) and antagonism of the endocannabinoid CB1 receptor. Initial studies of CETP inhibitors suggest that these agents may markedly increase HDL-C concentrations. Clinical trials with rimonabant, a CB1 receptor antagonist, have demonstrated significant weight loss as well as increased HDL-C levels and reduced triglyceride levels.

Coating of open tubular capillaries with discoidal and spherical high-density lipoprotein particles in electrochromatography

A new method was developed for the coating of fused-silica capillaries with human high-density lipoproteins (HDLs) for use in electrochromatography. The HDL particles used for the coating differed in particle shape and composition. Both discoidal and spherical particles formed a monolayer on the inner silica wall as confirmed by atomic force microscopy. The effect of coating conditions, such as HDL concentration and coating time, was investigated with spherical HDL particles. Examination of the influence of pH on the coating stability also allowed the determination of pI values for the HDL particles attached to the capillary wall. The pI values for spherical and discoidal HDL particles were close to 5.0. The repeatabilities of the EOF mobility and the retention factors of the uncharged steroid hormones used as model compounds were exploited in the evaluation of the coating stability. The optimal coating was achieved with 0.1 mg/mL HDL protein and 50 min flushing with coating solution followed by 15 min standing time. Electrochromatography with HDL-coated open tubular capillaries offers a new tool for the study of HDL particle structure and transformations.

Human high-density lipoprotein particles prevent activation of the JNK pathway induced by human oxidised low-density lipoprotein particles in pancreatic beta cells

AIMS/HYPOTHESIS

We explored the potential adverse effects of pro-atherogenic oxidised LDL-cholesterol particles on beta cell function.

MATERIALS AND METHODS

Isolated human and rat islets and different insulin-secreting cell lines were incubated with human oxidised LDL with or without HDL particles. The insulin level was monitored by ELISA, real-time PCR and a rat insulin promoter construct linked to luciferase gene reporter. Cell apoptosis was determined by scoring cells displaying pycnotic nuclei.

RESULTS

Prolonged incubation with human oxidised LDL particles led to a reduction in preproinsulin expression levels, whereas the insulin level was preserved in the presence of native LDL-cholesterol. The loss of insulin production occurred at the transcriptional levels and was associated with an increase in activator protein-1 transcriptional activity. The rise in activator protein-1 activity resulted from activation of c-Jun N-terminal kinases (JNK, now known as mitogen-activated protein kinase 8 [MAPK8]) due to a subsequent decrease in islet-brain 1 (IB1; now known as MAPK8 interacting protein 1) levels. Consistent with the pro-apoptotic role of the JNK pathway, oxidised LDL also induced a twofold increase in the rate of beta cell apoptosis. Treatment of the cells with JNK inhibitor peptides or HDL countered the effects mediated by oxidised LDL.

CONCLUSIONS/INTERPRETATION

These data provide strong evidence that oxidised LDL particles exert deleterious effects in the progression of beta cell failure in diabetes and that these effects can be countered by HDL particles.

Endothelial and leukocyte adhesion molecules in primary hypertriglyceridemia

Hypertriglyceridemia is known to be associated to functional impairment of the endothelium and, consequently, to higher risk of atherosclerosis. Nevertheless, some crucial steps in the development of the atherosclerotic plaque are still unknown in primary hypertriglyceridemia. The aim of the present study was to explore the expression of soluble and leukocyte-associated cell adhesion molecules in a group of patients with primary hypertriglyceridemia, both including (n=50) and excluding (n=24) subjects with metabolic syndrome, in comparison with control normotriglyceridemic individuals (n=30). Lipid profile, CETP activity, HDL and VLDL chemical composition were evaluated. Soluble (VCAM-1, ICAM-1 and E-selectin) and leukocyte cell adhesion molecules (CD18, CD49d and CD54) were measured by enzyme-linked immunosorbent assay and flow cytometry, respectively. Patients with primary hypertriglyceridemia as compared with control subjects showed significantly higher VCAM-1 (15.6+/-4.5 ng/ml versus 13.9+/-3.8 ng/ml, respectively; p<0.05) and ICAM-1 (16.9+/-3.1 ng/ml versus 15.2+/-3.2 ng/ml, respectively; p<0.05). Regarding leukocyte cell adhesion molecules, significant increases were also detected in monocyte CD18 (398+/-180 versus 332+/-136 arbitrary units, respectively; p<0.05) and CD54 (49+/-14 versus 42+/-12 arbitrary units, respectively; p<0.05), and lymphocyte CD18 (122+/-53 versus 101+/-33 arbitrary units, respectively; p<0.05). ICAM-1 plasma levels, as well as monocyte CD18 and CD54, and lymphocyte CD18 persisted elevated even if patients with metabolic syndrome were discarded among those with hypertriglyceridemia. The increase in circulating and leukocyte cell adhesion molecules in primary hypertriglyceridemic patients would highlight the inflammatory process which is a key event in atherogenesis.

Compositional protein analysis of high density lipoproteins in hypercholesterolemia by shotgun LC-MS/MS and probabilistic peptide scoring

A protein of a biological sample is usually quantified by immunological techniques based on antibodies. Mass spectrometry offers alternative approaches that are not dependent on antibody affinity and avidity, protein isoforms, quaternary structures, or steric hindrance of antibody-antigen recognition in case of multiprotein complexes. One approach is the use of stable isotope-labeled internal standards; another is the direct exploitation of mass spectrometric signals recorded by LC-MS/MS analysis of protein digests. Here we assessed the peptide match score summation index based on probabilistic peptide scores calculated by the PHENYX protein identification engine for absolute protein quantification in accordance with the protein abundance index as proposed by Mann and co-workers (Rappsilber, J., Ryder, U., Lamond, A. I., and Mann, M. (2002) Large-scale proteomic analysis of the human spliceosome. Genome Res. 12, 1231-1245). Using synthetic protein mixtures, we demonstrated that this approach works well, although proteins can have different response factors. Applied to high density lipoproteins (HDLs), this new approach compared favorably to alternative protein quantitation methods like UV detection of protein peaks separated by capillary electrophoresis or quantitation of protein spots on SDS-PAGE. We compared the protein composition of a well defined HDL density class isolated from plasma of seven hypercholesterolemia subjects having low or high HDL cholesterol with HDL from nine normolipidemia subjects. The quantitative protein patterns distinguished individuals according to the corresponding concentration and distribution of cholesterol from serum lipid measurements of the same samples and revealed that hypercholesterolemia in unrelated individuals is the result of different deficiencies. The presented approach is complementary to HDL lipid analysis; does not rely on complicated sample treatment, e.g. chemical reactions, or antibodies; and can be used for projective clinical studies of larger patient groups.

Effect of eicosapentaenoic/docosahexaenoic fatty acids and soluble fibers on blood lipids of individuals classified into different levels of lipidemia

OBJECTIVE

This study evaluated the effect of a formulation containing eicosapentaenoic acid and docosahexaenoic acid combined with soluble fibers (beta-glucan and guar gum) on fasting blood lipids used as coronary heart disease biomarkers of individuals classified into different levels of lipidemia by multivariate techniques.

METHODS

Serum total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triacylglycerol, plasma glucose concentrations, body mass index, age, and waist circumference were determined in 99 healthy volunteers. Three clusters or subgroups were identified according to coronary heart disease risk levels. Within each cluster, individuals were randomly assigned to one of four experimental groups, with each group receiving samples of a functional formulation containing 460 mg of omega-3 polyunsaturated fatty acids and/or 580 mg of soluble fibers, and placebo to be consumed in one bottle per day (200 mL) for 6 wk.

RESULTS

No significant changes were observed for triacylglycerol (P = 0.281) and total cholesterol (P = 0.082) concentrations across the three subgroups. Soluble dietary fibers improved the sensory quality of the formulation containing eicosapentaenoic acid and docosahexaenoic acid. The efficiency of cluster analysis to discriminate individuals in subgroups was confirmed by one-way analysis of variance (P < 0.003).

CONCLUSION

The omega-3 polyunsaturated fatty acid supplementation equivalent to fish consumed 2.5 to 3 times per week by a functional food-containing soluble dietary fiber showed no beneficial result in terms of changes in blood lipids in individuals classified according to different levels of lipidemia. Small numbers of patients in each cluster and possibly the low dose of fish oil and soluble dietary fibers used in this study may have also contributed to the lack of these differences. Multivariate techniques proved to be a very efficient tool to solve the heterogeneity problem usually observed in human designs and to evaluate the results within subgroups categorized by n variables extracted from the same population.

Lipoprotein distribution and biological variation of 24S- and 27-hydroxycholesterol in healthy volunteers

24S- and 27-hydroxycholesterol are obligatory intermediates of cholesterol catabolism and play an important role in the maintenance of whole-body cholesterol homeostasis. Using an HPLC-MS method for oxysterol quantification, the distribution of esterified and unesterified oxysterols in lipoprotein subfractions as well as the influence of daytime, food intake and menstrual cycle on oxysterol concentrations were investigated in healthy volunteers. Moreover, reference intervals for 24S- and 27-hydroxycholesterol in plasma as well as the corresponding levels for 27-hydroxycholesterol in the HDL subfraction were established in 100 healthy volunteers. Both circulating oxysterols are mainly transported in association with HDL and LDL--primarily in the esterified form. No significant diurnal changes and no variations during menstrual cycle of either absolute or cholesterol-related plasma levels were detected. In contrast to 24S-hydroxycholesterol in plasma and 27-hydroxycholesterol in the HDL subfraction, the 95% reference intervals of 27-hydroxycholesterol both in plasma and the non-HDL subfraction were higher in males than in females. The concentrations of 27-hydroxycholesterol in plasma and the non-HDL subfraction showed strong positive correlations with the concentrations of cholesterol, non-HDL cholesterol and triglycerides. Our data on the lipoprotein distribution of oxysterols as well as on their intra- and inter-individual variation set the stage for future clinical studies.

Current understanding of the role of high-density lipoproteins in atherosclerosis and senescence

Numerous epidemiologic and interventional studies revealed that high-density lipoprotein (HDL) is an important risk factor for coronary heart disease. There are several well documented HDL functions that may account for the antiatherogenic effects of this lipoprotein. The best recognized of these is the capacity of HDL to transport cholesterol from the periphery to the liver, and thereby prevent cholesterol deposition in the arterial wall. Further properties of HDL that may also be antiatherogenic include its potent anti oxidative and anti-inflammatory action. In addition, HDL seems to be involved in processes related to senescence at both the cellular and whole-organism level. Both protein components of HDL (such as apolipoprotein A-I) and its lipid components (such as, lysosphingolipids) appear to mediate the antiatherogenic and anti-aging effects of HDL. The purpose of this review is to summarize the novel functions of HDL that may protect from atherosclerosis and senescence.

New insights into the biogenesis of human high-density lipoproteins

PURPOSE OF REVIEW

The interest for the human HDL system was recently revived by the identification of the ABCA1 as a critical component in the formation and maintenance of plasma HDL levels. The present review focuses on recent progress in our understanding of the basic mechanisms underlying HDL biogenesis pathways.

RECENT FINDINGS

Several novel mechanisms governing ABCA1/apoA-I interactions have recently been identified: apolipoprotein A-I activates ABCA1 phosphorylation through the cAMP/protein kinase A-dependent pathway; the majority of ABCA1 exists as a tetramer in human living cell, supporting the concept that the homotetrameric ABCA1 complex constitutes the minimum functional unit for the formation of nascent HDL particles; apolipoprotein A-I has been shown to have a recycling retroendocytic pathway with uptake and resecretion of the lipidated nascent HDL particles by the cell, most likely through the ABCA1 transporter pathway; there is evidence that the speciation of nascent HDL into pre-beta and alpha-HDL is linked to specific cell lines, and occurs by both ABCA1-dependent and independent pathways.

SUMMARY

The fundamental mechanisms underlying the biogenesis, speciation and maturation of HDL remain complex and not well understood. Understanding the mechanisms governing HDL genesis at the cellular level could provide novel insights into the human atheroprotective system in health and disease.

Lipoproteins and mitogen-activated protein kinase signaling: a role in atherogenesis?

PURPOSE OF REVIEW

Lipoproteins play a critical role in the development of atherosclerosis, which might result partly from their capacity to induce specific intracellular signaling pathways. The goal of this review is to summarize the signaling properties of lipoproteins, in particular, their capacity to induce activation of mitogen-activated protein kinase pathways and the resulting modulation of cellular responses in blood vessel cells.

RECENT FINDINGS

Lipoproteins activate the extracellular signal-regulated kinase and p38 mitogen-activated protein kinase pathways in all blood vessel cell types. This may require lipoprotein docking to scavenger receptor B1, allowing transfer of cholesterol and sphingosine-1-phosphate to plasma membranes. Subsequent propagation of the signals probably requires the stimulation of G protein-coupled receptors, followed by the transactivation of receptor tyrosine kinases. Lipoprotein-induced extracellular signal-regulated kinase activity favors cell proliferation, whereas lipoprotein-induced p38 mitogen-activated protein kinase activity leads to cell hyperplasia and promotes cell migration. Some signaling pathways and cellular effects induced by lipoproteins have been observed in atherosclerotic plaques and therefore represent potential targets for the development of anti-atherosclerotic drugs.

SUMMARY

The main blood vessel cell types have the capacity to activate protein kinase pathways in the presence of lipoproteins. This induces cell proliferation, hyperplasia and migration, known to be dysregulated in atherosclerotic lesions.

Apolipoprotein A-I activates Cdc42 signaling through the ABCA1 transporter

It has been suggested that the signal transduction initiated by apolipoprotein A-I (apoA-I) activates key proteins involved in cholesterol efflux. ABCA1 serves as a binding partner for apoA-I, but its participation in apoA-I-induced signaling remains uncertain. We show that the exposure of human fibroblasts to ABCA1 ligands (apolipoproteins and amphipathic helical peptides) results in the generation of intracellular signals, including activation of the small G-protein Cdc42, protein kinases (PAK-1 and p54JNK), and actin polymerization. ApoA-I-induced signaling was abrogated by glyburide, an inhibitor of the ABC transporter family, and in fibroblasts from patients with Tangier disease, which do not express ABCA1. Conversely, induction of ABCA1 expression with the liver X receptor agonist, T0901317, and the retinoid X receptor agonist, R0264456, potentiated apoA-I-induced signaling. Similar effects were observed in HEK293 cells overexpressing ABCA1-green fluorescent protein (GFP) fusion protein, but not ABCA1-GFP (K939M), which fails to hydrolyze ATP, or a nonfunctional ABCA1-GFP with a truncated C terminus. We further found that Cdc42 coimmunoprecipitates with ABCA1 in ABCA1-GFP-expressing HEK293 cells exposed to apoA-I but not in cells expressing ABCA1 mutants. We conclude that ABCA1 transduces signals from apoA-I by complexing and activating Cdc42 and downstream kinases and, therefore, acts as a full apoA-I receptor.

Male hormonal contraception: a safe option?

Hormonal male contraception is based on the administration of testosterone alone or more likely with a progestogen. Testosterone has been used for several decades for the treatment of male hypogonadism, with an excellent safety record. Use as part of a contraceptive regimen by healthy people for prolonged periods will necessitate careful re-examination of safety issues. Although potential male contraceptive regimens have been investigated for many years, there have been mostly small-scale studies unable to assess safety. This is now changing, with larger studies of regimens underway. This, and the increasing involvement of the pharmaceutical industry, means that much more data will shortly be forthcoming and it is hoped that this will also provide valuable information relevant to normal male health. The main areas of interest are the cardiovascular system and the prostate, but bone health and body composition are also important, as are behavioral and psychologic aspects. The development of this field also allows the investigation of potential health benefits, which may be related to the use of synthetic androgens with tissue-selective metabolism or action.

Atheroprotective Effects of High-Density Lipoprotein-Associated Lysosphingolipids

Numerous epidemiological studies document an inverse relationship between plasma high-density lipoprotein (HDL) levels and the extent of atherosclerotic disease. The atheroprotective effects of HDL are more and more often seen in conjunction with the ability of HDL to restrict proinflammatory processes and thereby to carry out cytoprotection and organoprotection. Lysosphingolipids such as sphingosine 1 phosphate, sphingosylphosphorylcholine, and lysosulfatide are biologically active compounds that have recently been found to be associated with HDL particles. An increasing body of evidence suggests that several anti-inflammatory effects exerted by HDL can be attributed to the presence of lysosphingolipids in this lipoprotein fraction. In this review, we discuss the latest developments concerning the potential atheroprotective role of HDL-associated lysosphingolipids.

The CAG Repeat Polymorphism in the Androgen Receptor Gene Is Associated with HDL-Cholesterol but Not with Coronary Atherosclerosis or Myocardial Infarction

Background: Age-adjusted morbidity and mortality rates from coronary heart disease (CHD) are higher in men than in women. Androgens are suspected to be responsible for the male disadvantage. The genomic effect of androgens is mediated by the androgen receptor (AR), which has a polymorphic CAG repeat in exon 1. The number of repeats is inversely related to the transcriptional activity of the AR on target genes.

Methods: We investigated the association of this CAG repeat polymorphism with CHD and myocardial infarction (MI) in 2 independent case–control studies involving 544 Caucasian men.

Results: The number of CAG repeats in the AR gene correlated significantly with HDL-cholesterol (HDL-C) in controls (r = 0.21; P = 0.015). This effect was independent of triglycerides, body mass index, alcohol intake, smoking, and age in a multiple regression model (R2 = 50%). Despite decreased HDL-C, lower CAG repeat numbers were not associated with increased risk for CHD (odds ratio = 0.82; 95% confidence interval, 0.50–1.36; P = 0.44) or MI in carriers of AR genes with lower CAG repeat numbers (odds ratio = 0.72; 95% confidence interval, 0.37–1.39; P = 0.33).

Conclusions: Shorter, more androgenic AR alleles with fewer CAG repeats are associated with lower HDL-C, but not with an increased risk for CHD or MI, which argues against a detrimental androgen effect on cardiovascular risk under physiologic conditions.

Prevalence of aspirin resistance measured by PFA-100

BACKGROUND

Aspirin protects from cardiovascular events. However, a number of patients who take this drug suffer events, probably due to aspirin resistance. Our objective was to determine the prevalence of aspirin resistance in patients taking this drug and to test if resistance is related to different variables.

METHODS

Platelet function was studied in 113 patients (90 men) aged 63+/-9 (80 with stable ischaemic heart disease) who took aspirin (100 to 300 mg/day). By a platelet function analyzer, called PFA-100, the epinephrine closure time was studied. We also analysed the possible relationship between epinephrine closure time and the following variables: total cholesterol, LDL, HDL cholesterol, total/HDL cholesterol, triglycerides, lipoprotein(a), and C reactive protein. The possible association between aspirin resistance (epinephrine closure time <161 s) and different variables was also analyzed with the SPSS statistical package. Results are expressed in median (interquartile range).

RESULTS

Aspirin resistance was found in 32% of cases. Ischaemic heart disease, smoking habit, and treatment with statins were associated with a significantly greater percent of resistance (p=0.049, 0.009, and 0.043, respectively). Patients with aspirin resistance had higher levels of total/HDL cholesterol: 4.46 (3.76-5.55) vs. 3.97 (3.20-4.75) (p = 0.023); and lipoprotein(a): 57.2 (24.8-85.0) mg/dl vs. 13.1 (3.7-38.0) mg/dl (p = 0.007).

CONCLUSIONS

Aspirin resistance is frequent and easily detected by PFA-100. It occurs more frequently in smokers. A mild association is found with ischaemic heart disease, some lipids, and treatment with statins. Our results support the applicability of this method to clinical practice.

Current understanding of the metabolism and biological actions of HDL

PURPOSE OF REVIEW

A low concentration of HDL-cholesterol is an important risk factor for coronary heart disease. The purpose of this review is to summarize the novel functions of HDL that may protect not only from atherosclerosis, but also from inflammation-induced organ damage.

RECENT FINDINGS

HDL interacts with several cellular receptors and lipid transporters. The interactions of HDL or apolipoprotein A-I with the scavenger receptor BI or adenosine triphosphate binding cassette transporters A1, G1 and G4 induce cholesterol efflux. Apolipoproteins and enzymes carried by HDL exert antioxidative functions. Some oxidative modifications of apolipoprotein A-I, for example of tyrosine residues, may however interfere with anti-atherosclerotic activities. The interactions of HDL and lysosphingolipids therein with scavenger receptor BI and sphingolipid receptors, respectively, elicit signals activating the protein kinase Akt, which in turn is a regulator of apoptosis in beta, endothelial and smooth muscle cells as well as a regulator of nitric oxide production and adhesion molecule expression in endothelial cells. Other signal transduction cascades are also elicited by HDL, some of which induce cholesterol efflux or activate mitogen-activated protein kinases.

SUMMARY

Properties with respect to cytokine production, lipid oxidation, cholesterol efflux and reverse cholesterol transport make HDL a protective agent and thus an interesting therapeutic target in atherosclerosis and inflammation-induced organ damage.

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).

Hormone therapy and mortality during a 14-year follow-up of 14 324 Norwegian women

OBJECTIVES

We evaluated mortality from cardiovascular disease (CVD), coronary heart disease (CHD) and all causes in relation to use of any hormone therapy (HT) and HT with oestradiol and norethisterone or levonorgestrel.

DESIGN

Population-based cohort study.

SETTING AND SUBJECTS

Women in three Norwegian counties were invited to a health survey in 1985-88 and 82.8% participated. In all 14 324 post- or perimenopausal women aged 35-62 years, including 702 HT users with a mean age of 48.8 years, were followed for 14 years.

RESULTS

Women using HT had mortality from all causes and CVD comparable with that of nonusers. The relative risk (RRs) for CVD mortality amongst all women were 0.69 (95% CI: 0.35-1.33) for users of HT, and 0.96 (95% CI: 0.43-2.17) for users of HT with norethisterone or levonorgestrel. Amongst women free of self-reported cardiovascular health problems at baseline all-cause, CVD and CHD mortality tended to be lower amongst users of HT whilst HT use was linked with increased mortality amongst women with cardiovascular health problems.

CONCLUSIONS

In this cohort of women around the usual age of menopause all-cause or CVD mortality amongst users of HT, most often oestradiol combined with norethisterone or levonorgestrel, was not markedly different from that of nonusers. Early CHD events amongst HT users prior to the baseline survey, together with selective inclusion of healthy subjects, may in part explain protective effects of HT on CHD reported from previous observational studies.

Treating low HDL—From bench to bedside

The inverse relationship between the plasma high-density lipoprotein cholesterol (HDL-C) and the risk of coronary heart disease (CHD) is well recognized in the general population. However, the development of effective therapeutics targeting HDL continues to be challenging, which is due in part to the heterogeneity of its structure and composition and the complexity of its metabolism. In this paper, we review a number of recent advances in our understanding of HDL metabolism and its role in atherogenesis. We discuss the HDL-C raising effect of a selected number of currently available lipid-modifying drugs and on a selected number of novel HDL-targeted therapeutic strategies under development.

Pharmacologic elevation of high-density lipoproteins: recent insights on mechanism of action and atherosclerosis protection

PURPOSE OF REVIEW

Despite the best efforts in reduction of low-density lipoprotein cholesterol, most cardiovascular events are not being prevented. Because high-density lipoprotein (HDL) promotes reverse cholesterol transport and other antiatherogenic effects, interventions aimed at raising HDL cholesterol or mimicking its beneficial effects may greatly improve treatment and prevention of cardiovascular disease. This article reviews the antiatherogenic effects of HDL, recent insights into the mechanisms of action of currently available, and emerging HDL-based therapies.

RECENT FINDINGS

New insights into the basic science of HDL function and metabolism (such as the discovery of beta-chain ATP synthase as a hepatic catabolic HDL receptor) are further characterizing the importance of HDL in atheroprotection and identifying novel targets of drug development. Nicotinic acid, fibrates, statins, and thiazolidinediones not only increase HDL cholesterol but also alter HDL subpopulation size and composition. Furthermore, these drugs promote direct antiatherogenic effects of HDL (antioxidation, anti-inflammation, antithrombotic effects, endothelial stabilization). Emerging HDL-raising therapies (such as cholesteryl ester transfer protein inhibitors and 1,2-dimyristoyl-sn-glycero-phosphocholine) and novel interventions that mimic HDL's beneficial effects (such as apolipoprotein AImilano and apolipoprotein AI mimetic peptides) are proving beneficial in animal and human studies.

SUMMARY

An understanding of the atheroprotective mechanisms of HDL is essential for the rational use of currently available drugs and directed development of new drugs. Increasing total HDL cholesterol may not be as important as increasing the functional properties of HDL. Cardiovascular disease treatment and prevention can be improved by combining current low-density lipoprotein-based strategies with effective HDL-based interventions.

High density lipoproteins in the intersection of diabetes mellitus, inflammation and cardiovascular disease

PURPOSE OF REVIEW

Low HDL-cholesterol, diabetes mellitus and elevated C-reactive protein as well as various inflammatory diseases are risk factors for coronary heart disease. Both diabetes mellitus and inflammation decrease HDL-cholesterol. We summarize recent findings on the mechanisms underlying low HDL-cholesterol in diabetes and inflammation, as well as on novel functions of HDL that may protect not only from atherosclerosis but also from diabetes mellitus and inflammation-induced organ damage.

RECENT FINDINGS

Elevated levels of non-esterified fatty acids and disturbed insulin action contribute to low HDL-cholesterol in diabetes mellitus by modifying lipolysis, apolipoprotein A-I production, as well as the activities of adenosine triphosphate-binding cassette transporter A1 and lipid transfer. Inflammation causes low HDL-cholesterol by increasing the activities of endothelial lipase and soluble phospholipase A2 and by replacing apolipoprotein A-I in HDL with serum amyloid A. HDL and lysosphingolipids therein have been identified as activators of the protein kinase Akt, which in turn is a regulator of apoptosis in beta-cells, endothelial cells, and smooth muscle cells, as well as a regulator of nitric oxide production and adhesion molecule expression in endothelial cells.

SUMMARY

The protective properties of HDL in cytokine production, lipid oxidation, cholesterol efflux and reverse cholesterol transport make HDL a protective agent in inflammation-induced organ damage including diabetes mellitus. However, inflammation and diabetes cause a decrease in HDL-cholesterol concentrations and impair HDL function, placing HDL into the centre of a vicious cycle that may escalate into diabetes mellitus, inflammation-induced organ damage and atherosclerosis.