Determinants of plasma HDL concentrations and reverse cholesterol transport

Azelastine a potent antihistamine agent, as hypolipidemic and modulator for aortic calcification in diabetic hyperlipidemic rats model

AIM

Our study aimed to illustrate the effect of the antihistaminic drug azelastine on aortic calcification in diabetic hyperlipidemic (DH) rats along with the underlying molecular mechanism.

METHODS

Twenty-four male albino Wistar rats were categorised into four groups. One group received normal rodent chow (normal group), while the other groups were rendered diabetic and hyperlipidemic; one received no drugs and served as a positive control while the other two groups received either azelastine (4 mg/kg) or 10-dehydrogingerdione (10 mg/kg) orally and daily for 8 weeks.

RESULTS

Azelastine significantly reduced blood glucose, HbA1c and serum ALP, OCN, downregulated apo B, improved the lipid profile (LDL-c decrease and HDL-c increase), attenuated calcium deposition and aortic calcification as compared to control group. 10-DHGD showed comparatively lower effect.

CONCLUSION

Anti-calcifying effect of azelastine might be related to upregulation of apo A (HDL-c) and downregulation of apo B mRNA expression indeed good modulator of aortic calcification.

IMPACT STATEMENT

Many studies have indicated that high-density lipoprotein-cholesterol (HDL-c) is inversely correlated with atherosclerotic plaque progression and could reduce cardiovascular disease risk. An anti-calcifying effect of HDL-c has been reported and targeting this lipoprotein may therefore be a valuable approach to vascular calcification control. Azelastine is a selective H1 antagonist that was identified to increase mRNA expression of apolipoprotein A. This encouraged us to investigate the effect of azelastine on lipid profile and markers of aortic calcification in DH rats. Our findings showed that azelastine ameliorated aortic calcification and increased apoA expression along with a decline in apo B. This may represent the underlying mechanism while the histopathological findings offered a significant support to the collected biochemical data.

Fat and Protein Combat Triggers Immunological Weapons of Innate and Adaptive Immune Systems to Launch Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD) is the second-most common neurodegenerative disease in the world, affecting up to 10 million people. This disease mainly happens due to the loss of dopaminergic neurons accountable for memory and motor function. Partial glucocerebrosidase enzyme deficiency and the resultant excess accumulation of glycosphingolipids and alpha-synuclein (α-syn) aggregation have been linked to predominant risk factors that lead to neurodegeneration and memory and motor defects in PD, with known and unknown causes. An increasing body of evidence uncovers the role of several other lipids and their association with α-syn aggregation, which activates the innate and adaptive immune system and sparks brain inflammation in PD. Here, we review the emerging role of a number of lipids, i.e., triglyceride (TG), diglycerides (DG), glycerophosphoethanolamines (GPE), polyunsaturated fatty acids (PUFA), sphingolipids, gangliosides, glycerophospholipids (GPL), and cholesterols, and their connection with α-syn aggregation as well as the induction of innate and adaptive immune reactions that trigger neuroinflammation in PD.

Sensitive Morphological Characterization of Oriented High-Density Lipoprotein Nanoparticles Using 31 P NMR Spectroscopy

The biological function of high-density lipoprotein (HDL) nanoparticles, the so-called good cholesterol that is associated with a low risk of heart disease, depends on their composition, morphology, and size. The morphology of HDL particles composed of apolipoproteins, lipids and cholesterol is routinely visualised by transmission electron microscopy (TEM), but higher-resolution tools are needed to observe more subtle structural differences between particles of different composition. Here, reconstituted HDL formulations are oriented on glass substrates and solid-state 31 P NMR spectroscopy is shown to be highly sensitive to the surface curvature of the lipid headgroups. The spectra report potentially functionally important differences in the morphology of different HDL preparations that are not detected by TEM. This method provides new morphological insights into HDL comprising a naturally occurring apolipoprotein A-I mutant, which may be linked to its atheroprotective properties, and holds promise as a future research tool in the clinical analysis of plasma HDL.

Investigation of the impact of birth by cesarean section on fetal and maternal metabolism

PURPOSE

Elective cesarean section (CS) was related to long-term adverse health effects in the offspring, but little is known about underlying mechanisms. Our study investigates the metabolic changes in both maternal and cord blood associated with CS in comparison to vaginal delivery (VD) to explore potential causal pathways.

METHODS

Samples obtained from PREOBE study participants were subjected to LC-MS/MS-targeted metabolomics comprising > 200 metabolites.

RESULTS

Elective CS showed an impact on both maternal and cord blood metabolomes. In maternal blood, the CS group showed lower levels of phospholipids (PL), principally ether-linked phosphatidylcholines (aaPC), pyruvic acid, branched chain keto-acids (BCKA), and other gluconeogenic substrates, but since the CS group showed different HDL levels in comparison to the VD group, we could not exclude contribution of the latter in the findings. In cord blood, the most remarkable finding in the CS group was the high levels of Cys; conversely, the lower levels of non-esterified fatty acids (NEFA), some tricarboxylic acid (TCA) cycle metabolites, gluconeogenic substrates, markers of β-oxidation, and the sum of hexoses were lower in CS-born babies in addition to tendentially lower levels of PL.

CONCLUSIONS

We speculate that lower levels of maternal and fetal corticosteroids in CS, due to less stressful condition, cause metabolic perturbations at birth initiating future negative health outcomes. This further supports the early programming hypothesis.

Current Therapies Focused on High-Density Lipoproteins Associated with Cardiovascular Disease

High-density lipoproteins (HDL) comprise a heterogeneous family of lipoprotein particles divided into subclasses that are determined by density, size and surface charge as well as protein composition. Epidemiological studies have suggested an inverse correlation between High-density lipoprotein-cholesterol (HDL-C) levels and the risk of cardiovascular diseases and atherosclerosis. HDLs promote reverse cholesterol transport (RCT) and have several atheroprotective functions such as anti-inflammation, anti-thrombosis, and anti-oxidation. HDLs are considered to be atheroprotective because they are associated in serum with paraoxonases (PONs) which protect HDL from oxidation. Polyphenol consumption reduces the risk of chronic diseases in humans. Polyphenols increase the binding of HDL to PON1, increasing the catalytic activity of PON1. This review summarizes the evidence currently available regarding pharmacological and alternative treatments aimed at improving the functionality of HDL-C. Information on the effectiveness of the treatments has contributed to the understanding of the molecular mechanisms that regulate plasma levels of HDL-C, thereby promoting the development of more effective treatment of cardiovascular diseases. For that purpose, Scopus and Medline databases were searched to identify the publications investigating the impact of current therapies focused on high-density lipoproteins.

Metabolomic and transcriptomic profiling of hepatocellular carcinomas in Hras12V transgenic mice

Activation of the Ras/MAPK pathway is prevalently involved in the occurrence and development of hepatocellular carcinoma (HCC). However, its effects on the deregulated cellular metabolic processes involved in HCC in vivo remain unknown. In this study, a mouse model of HCC induced by hepatocyte-specific expression of the Hras12V oncogene was investigated using an integrative analysis of metabolomics and transcriptomics data. Consistent with the phenotype of abundant lipid droplets in HCC, the lipid biosynthesis in HCC was significantly enhanced by (1) a sufficient supply of acetyl-CoA from enhanced glycolysis and citrate shuttle activity; (2) a sufficient supply of NADPH from enhanced pentose phosphate pathway (PPP) activity; (3) upregulation of key enzymes associated with lipid biosynthesis; and (4) downregulation of key enzymes associated with bile acid biosynthesis. In addition, glutathione (GSH) was significantly elevated, which may result from a sufficient supply of 5-oxoproline and L-glutamate as well as an enhanced reduction in the process of GSSG being turned into GSH by NADPH. The high level of GSH along with elevated Bcl2 and Ucp2 expression may contribute to a normal level of reactive oxygen species (ROS) in HCC. In conclusion, our results suggest that the lipid metabolism, glycolysis, PPP, tricarboxylic acid (TCA) cycle, citrate shuttle activity, bile acid synthesis, and redox homeostasis in the HCC induced by ras oncogene are significantly perturbed, and these altered metabolic processes may play crucial roles in the carcinogenesis, development, and pathological characteristics of HCC.

Impact of cholesterol on disease progression

Cholesterol-rich microdomains (also called lipid rafts), where platforms for signaling are provided and thought to be associated with microbe-induced pathogenesis and lead to cancer progression. After treatment of cells with cholesterol disrupting or usurping agents, raft-associated proteins and lipids can be dissociated, and this renders the cell structure nonfunctional and therefore mitigates disease severity. This review focuses on the role of cholesterol in disease progression including cancer development and infectious diseases. Understanding the molecular mechanisms of cholesterol in these diseases may provide insight into the development of novel strategies for controlling these diseases in clinical scenarios.

CETP TaqIB genotype modifies the association between alcohol and coronary heart disease: the INTERGENE case-control study

Alcohol consumption at moderate levels has been associated with decreased risk of coronary heart disease (CHD). However, the cardio-protective effect of alcohol may be restricted to subjects with a particular genotype of the cholesteryl ester transfer protein (CETP) polymorphism. There is evidence for this from one study in men, but the finding has not been confirmed since. The present study specifically re-examines the potential modification of the association between alcohol consumption and CHD by the CETP TaqIB (rs708272) polymorphism in a sample including both men and women. The INTERGENE case-control study consists of 618 patients with CHD and 2921 control subjects, of whom 19% were homozygous for the CETP TaqIB B2 allele. Alcohol consumption was categorized into sex-specific tertiles of ethanol intake, with non-drinkers constituting a separate category. Logistic regression was used to determine the association between CHD with genotype, ethanol intake, and their interaction. Participants with intermediate ethanol intake (2nd tertile) had lower risk of CHD than those with low ethanol intake (odds ratio [OR] = 0.65; 95% confidence interval [CI] 0.50-0.85). The strongest protective association was seen in the CETP TaqIB B2 homozygotes for intermediate vs. low ethanol intake (odds ratio OR = 0.21; 95% CI 0.10-0.44). The interaction between ethanol intake and genotype was statistically significant (p = 0.008), and of similar size in men and women though significant only in men (p = 0.01). The effect modification could not be explained by differences in lifestyle, socioeconomics, or alcohol-related biological variables such as HDL-cholesterol. Our study is the first to replicate previous findings of an effect modification in men. It gives only suggestive results for women, possibly due to the small number of female cases (n = 165). The prevented fraction for the favorable combination of genotype and alcohol consumption is about 6%, a value suggesting that the cardio-protective effect of moderate alcohol consumption applies only to a small segment of the general population.

Celastrol suppresses obesity process via increasing antioxidant capacity and improving lipid metabolism

High fat diet, as an important risk factor, plays a pivotal role in atherosclerotic process. Celastrol is one of the active triterpenoid compounds with antioxidative and anti-inflammatory characters. The aims of this study were to evaluate the effect of celastrol on weight, blood lipid and oxidative injury induced by high fat emulsion, and investigate its potential pharmacological mechanisms. Male Sprague-Dawley rats were fed with high fat emulsion for 6 wk to mimic high fat mediated oxidative injury. The effects of celastrol on weight and blood lipid were evaluated, and its mechanisms were disclosed by applying western blot, ELISA and assay kits. Long-term consumption of high fat emulsion could significantly increase weight by enhancing total cholesterol (TC), triacylglycerol (TG), apolipoprotein B (Apo B), low-density lipoprotein cholesterol (LDL-c) levels, attenuating ATP-binding cassette transporter A1 (ABCA1) expression, and decreasing the levels of high-density lipoprotein cholesterol (HDL-c) and apolipoprotein A-I (Apo A-I), and inhibit antioxidant enzymes activities, improve nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. Comparing with model group, celastrol was able to effectively suppress weight and attenuate high fat mediated oxidative injury by improving ABCA1 expression, reducing the levels of TC, TG, LDL-c and Apo B in plasma, and increasing antioxidant enzymes activities and inhibiting NADPH oxidase activity, and decreasing the serum levels of Malondialdehyde (MDA) and reactive oxygen species in dose-dependent way. These data demonstrated that celastrol was able to effectively suppress weight and alleviate high-fat mediated cardiovascular injury via mitigating oxidative stress and improving lipid metabolism.

Emerging therapeutic strategies to enhance HDL function

Epidemiologic studies indicate a strong inverse correlation between plasma levels of high-density lipoproteins (HDL) and cardiovascular disease (CVD). The most relevant cardioprotective mechanism mediated by HDL is thought to be reverse cholesterol transport (RCT). New insights in HDL biology and RCT have allowed the development of promising agents aimed to increase HDL function and promote atherosclerosis regression. In this regard, apo-AI analogs and CETP inhibitors dalcetrapib and anacetrapib have aroused a great interest and opened new expectations in the treatment of CVD.

Adiponectin and lipid profiles compared with insulins in relation to early growth of British South Asian and European children: the Manchester children's growth and vascular health study

CONTEXT

Adiponectin, high-density lipoprotein cholesterol (HDL-C) and insulin concentrations may be important in the pathophysiology of cardiovascular disease.

OBJECTIVE

We tested the hypothesis that serum adiponectin rather than insulin differs from early life, between South Asians and Europeans, with a potentially key role in excess cardiovascular risk characteristic of adult South Asians.

DESIGN AND PARTICIPANTS

We conducted a longitudinal study of 215 British-born children of European (n = 138) and South Asian (n = 77) origin, from birth to 3 yr.

MAIN OUTCOME MEASURE

Serum adiponectin, insulin, proinsulin and HDL-C concentrations were assessed in relation to ethnic group and growth in anthropometric variables from 0-3 yr of age.

RESULTS

Serum adiponectin was lower in South Asian children, despite their smaller size, notable at age 3-6 months (9.5 vs. 11.8 mg/liter; P = 0.04), with no ethnic differences in serum lipids or insulin or proinsulin. In mixed-effects longitudinal models for HDL-C, determinants were adiponectin (P = 0.034), age (P < 0.001), and body mass index (P < 0.001) but not ethnicity. None of these or growth variables affected either insulin or proinsulin. In a fully adjusted mixed-effects longitudinal model including age, sex, insulin, and proinsulin, the independent determinants of serum adiponectin were height [21.3 (95% confidence interval = 31.7-10.8 cm lower, for every 1 mmol/liter increase in adiponectin, P < 0.001], HDL-C [2.8 (1.3-4.2) mmol/liter higher, P < 0.0001], body mass index (lower, P = 0.03), and South Asian ethnicity (lower, P = 0.01).

CONCLUSIONS

These British South Asian-origin infants have lower serum adiponectin but no differences in HDL-C or insulin molecules. In South Asians, factors affecting adiponectin metabolism in early life, rather than insulin resistance, likely determine later excess cardiovascular risk.

Biliary sterol secretion is required for functional in vivo reverse cholesterol transport in mice

BACKGROUND & AIMS

High-density lipoproteins (HDLs) protect against atherosclerotic cardiovascular disease, mainly by promoting reverse cholesterol transport (RCT). Biliary sterol secretion supposedly represents the final step in RCT, but the relevance of this pathway has not been explored. We tested the dependency of RCT on functional biliary sterol secretion.

METHODS

Macrophage-to-feces RCT was studied in mice with abolished (bile duct ligation) or decreased biliary sterol secretion (adenosine triphosphate binding cassette transporter B4 (Abcb4)-/- mice, with and without administration of a liver X receptor [LXR] agonist) after intraperitoneal injection of (3)H-cholesterol-loaded primary macrophage foam cells from mice. Fecal tracer excretion and also fecal mass sterol excretion were measured. Metabolism and tissue uptake of HDL cholesteryl ester was assessed with HDL kinetic studies.

RESULTS

Bile-duct ligation completely abolished RCT from (3)H-cholesterol-loaded macrophages to feces (P < .001). In Abcb4-/- mice lacking biliary cholesterol secretion, RCT was decreased markedly; fecal (3)H-tracer excretion was almost absent within neutral sterols (P < .001) and reduced within bile acids (P < .05). LXR activation stimulated RCT in wild-type (5.5-fold; P < .001) but not Abcb4-/- mice, whereas mass fecal sterol excretion increased similarly in both models (P < .05). Kinetic studies revealed minimal uptake of HDL cholesteryl ester by the intestine, which decreased on LXR activation (P < .05).

CONCLUSIONS

Functional RCT depends on biliary sterol secretion; there is no compensatory increase in RCT via bile acids. The stimulating effect of LXR agonists on RCT requires biliary cholesterol secretion. These results have implications for therapies against atherosclerotic cardiovascular disease targeting the RCT pathway.

A new framework for reverse cholesterol transport: Non-biliary contributions to reverse cholesterol transport

Reduction of low-density lipoprotein-cholesterol through statin therapy has only modestly decreased coronary heart disease (CHD)-associated mortality in developed countries, which has prompted the search for alternative therapeutic strategies for CHD. Major efforts are now focused on therapies that augment high-density lipoprotein (HDL)-mediated reverse cholesterol transport (RCT), and ultimately increase the fecal disposal of cholesterol. The process of RCT has long been thought to simply involve HDL-mediated delivery of peripheral cholesterol to the liver for biliary excretion out of the body. However, recent studies have revealed a novel pathway for RCT that does not rely on biliary secretion. This non-biliary pathway rather involves the direct excretion of cholesterol by the proximal small intestine. Compared to RCT therapies that augment biliary sterol loss, modulation of non-biliary fecal sterol loss through the intestine is a much more attractive therapeutic strategy, given that excessive biliary cholesterol secretion can promote gallstone formation. However, we are at an early stage in understanding the molecular mechanisms regulating the non-biliary pathway for RCT, and much additional work is required in order to effectively target this pathway for CHD prevention. The purpose of this review is to discuss our current understanding of biliary and non-biliary contributions to RCT with particular emphasis on the possibility of targeting the intestine as an inducible cholesterol secretory organ.

Biliary cholesterol secretion: More than a simple ABC

Biliary cholesterol secretion is a process important for 2 major disease complexes, atherosclerotic cardiovascular disease and cholesterol gallstone disease. With respect to cardiovascular disease, biliary cholesterol secretion is regarded as the final step for the elimination of cholesterol originating from cholesterol-laden macrophage foam cells in the vessel wall in a pathway named reverse cholesterol transport. On the other hand, cholesterol hypersecretion into the bile is considered the main pathophysiological determinant of cholesterol gallstone formation. This review summarizes current knowledge on the origins of cholesterol secreted into the bile as well as the relevant processes and transporters involved. Next to the established ATP-binding cassette (ABC) transporters mediating the biliary secretion of bile acids (ABCB11), phospholipids (ABCB4) and cholesterol (ABCG5/G8), special attention is given to emerging proteins that modulate or mediate biliary cholesterol secretion. In this regard, the potential impact of the phosphatidylserine flippase ATPase class I type 8B member 1, the Niemann Pick C1-like protein 1 that mediates cholesterol absorption and the high density lipoprotein cholesterol uptake receptor, scavenger receptor class B type I, is discussed.

Dysfunctional high-density lipoprotein and atherosclerosis

High-density lipoprotein (HDL) is well established as a negative risk factor for the development of atherosclerosis. Epidemiologic, pathologic, and experimental studies have demonstrated a role for HDL in protection from coronary artery disease. HDL has been demonstrated to reduce the risk from atherosclerosis by multiple pathophysiologic mechanisms. Low-density lipoprotein is a metabolic end product that can be recognized and cleared by specific hepatic receptors with excretion into the bile. However, low-density lipoprotein may also be scavenged in the periphery by the monocyte-macrophage system, with subsequent generation of lipid-laden foam cells. HDL may reduce the atherosclerotic burden by multiple potential mechanisms. HDL can interact with the foam cell to remove cholesterol via receptor-mediated binding, passive diffusion, and alteration of intracellular cholesterol trafficking by ATP binding cassettes. The process of reverse cholesterol transport is a major mechanism by which HDL can remove cholesterol from the periphery, allowing it to be cleared by the liver and then excreted into the bile. However, HDL exhibits multiple additional potential beneficial physiologic effects. Endothelial function and repair is potentiated by HDL. Normal HDL has significant anti-inflammatory and antioxidant activity. Prostacyclin production and improvement in fibrinolytic balance is also attributed to normally functioning HDL. HDL is also intimately related to the metabolism of other circulating lipoproteins. However, multiple clinical studies have identified individuals with a significant atherosclerotic burden despite normal or elevated levels of HDL cholesterol. Clinical conditions associated with inflammation and oxidative stress have adversely altered the normal functions of HDL. Clinical assays have been developed to assess the functionality of HDL. Dysfunctional HDL may be returned to normal by diet, exercise, degree of fat intake, and pharmacologic approaches. Orally active mimetic proteins are in development and have shown clinical promise.

Adding monounsaturated fatty acids to a dietary portfolio of cholesterol-lowering foods in hypercholesterolemia

BACKGROUND

Higher intake of monounsaturated fat may raise high-density lipoprotein (HDL) cholesterol without raising low-density lipoprotein (LDL) cholesterol. We tested whether increasing the monounsaturated fat content of a diet proven effective for lowering LDL cholesterol (dietary portfolio) also modified other risk factors for cardiovascular disease, specifically by increasing HDL cholesterol, lowering serum triglyceride and further reducing the ratio of total to HDL cholesterol.

METHODS

Twenty-four patients with hyperlipidemia consumed a therapeutic diet very low in saturated fat for one month and were then randomly assigned to a dietary portfolio low or high in monounsaturated fatty acid for another month. We supplied participants' food for the two-month period. Calorie intake was based on Harris-Benedict estimates for energy requirements.

RESULTS

For patients who consumed the dietary portfolio high in monounsaturated fat, HDL cholesterol rose, whereas for those consuming the dietary portfolio low in monounsaturated fat, HDL cholesterol did not change. The 12.5% treatment difference was significant (0.12 mmol/L, 95% confidence interval [CI] 0.05 to 0.21, p = 0.003). The ratio of total to HDL cholesterol was reduced by 6.5% with the diet high in monounsaturated fat relative to the diet low in monounsaturated fat (-0.28, 95% CI -0.59 to -0.04, p = 0.025). Patients consuming the diet high in monounsaturated fat also had significantly higher concentrations of apolipoprotein AI, and their C-reactive protein was significantly lower. No treatment differences were seen for triglycerides, other lipids or body weight, and mean weight loss was similar for the diets high in monounsaturated fat (-0.8 kg) and low in monounsaturated fat (-1.2 kg).

INTERPRETATION

Monounsaturated fat increased the effectiveness of a cholesterol-lowering dietary portfolio, despite statin-like reductions in LDL cholesterol. The potential benefits for cardiovascular risk were achieved through increases in HDL cholesterol, further reductions in the ratio of total to HDL cholesterol and reductions in C-reactive protein. (ClinicalTrials.gov trial register no. NCT00430430.).

Influence of N-terminal helix bundle stability on the lipid-binding properties of human apolipoprotein A-I

As the principal component of high-density lipoprotein (HDL), apolipoprotein (apo) A-I plays essential roles in lipid transport and metabolism. Because of its intrinsic conformational plasticity and flexibility, the molecular details of the tertiary structure of lipid-free apoA-I have not been fully elucidated. Previously, we demonstrated that the stability of the N-terminal helix bundle structure is modulated by proline substitution at the most hydrophobic region (residues around Y18) in the N-terminal domain. Here we examine the effect of proline substitution at S55 located in another relatively hydrophobic region compared to most of the helix bundle domain to elucidate the influences on the helix bundle structure and lipid interaction. Fluorescence measurements revealed that the S55P mutation had a modest effect on the stability of the bundle structure, indicating that residues around S55 are not pivotally involved in the helix bundle formation, in contrast to the insertion of proline at position 18. Although truncation of the C-terminal domain (Δ190-243) diminishes the lipid binding of apoA-I molecule, the mutation S55P in addition to the C-terminal truncation (S55P/Δ190-243) restored the lipid binding, suggesting that the S55P mutation causes a partial unfolding of the helix bundle to facilitate lipid binding. Furthermore, additional proline substitution at Y18 (Y18P/S55P/Δ190-243), which leads to a drastic unfolding of the helix bundle structure, yielded a greater lipid binding ability. Thus, proline substitutions in the N-terminal domain of apoA-I that destabilized the helix bundle promoted lipid solubilization. These results suggest that not only the hydrophobic C-terminal helical domain but also the stability of the N-terminal helix bundle in apoA-I are important modulators of the spontaneous solubilization of membrane lipids by apoA-I, a process that leads to the generation of nascent HDL particles.

Effect of increasing doses of Rosuvastatin and Atorvastatin on apolipoproteins, enzymes and lipid transfer proteins involved in lipoprotein metabolism and inflammatory parameters

This paper contains detailed results of a sub-population of the prospective randomized RADAR (Rosuvastatin and Atorvastatin in different Dosages And Reverse cholesterol transport) study.

OBJECTIVE

Statin treatment results in substantially decreased incidence of cardiovascular events but the exact pathophysiological mechanism of their beneficial effect is yet unclear. We aimed to examine the effects of up-titrated doses of two widely used statins (atorvastatin (ATOR) and rosuvastatin (ROSU)) on parameters involved in lipoprotein metabolism, in patients with low high density lipoprotein cholesterol values (HDL-C).

RESEARCH DESIGN AND METHODS

In this RADAR substudy, 80 patients, aged 40-80 years, with known cardiovascular disease and low HDL-C (<1.0 mmol/l), were randomized to receive, after an initial 6 week dietary run-in phase, either ATOR 20 mg (n = 41) or ROSU 10 mg (n = 39). The doses were up-titrated (in 6 week intervals) to 80 mg of ATOR or 40 mg of ROSU at 12 weeks. Serum lipoproteins and lipoprotein metabolism parameters were measured at baseline and at 6 and 18 weeks of follow up.

RESULTS

Both statins significantly reduced total cholesterol (TChol) and non-HDL-C values with ROSU being more effective for the doses studied (p < 0.05). No statistically significant effect on HDL-C was observed for either statin. Apolipoproteins (apo) B, CI, CIII, AV and E were significantly reduced in both groups (p < 0.05), while the ratio of HDL particles containing both apoAI and apoAII (LpAI-AII) over HDL containing apoAI alone (LpAI) was changed for both statins with the decrease of LpAI being more prominent in the ATOR group (p = 0.028). Cholesterol ester transfer protein (CETP) mass and activity, phospholipid transfer protein (PLTP) activity and lipoprotein-associated phospholipase A2 (Lp-PLA2) mass and activity were all significantly reduced in both treatment groups over the follow-up period (p < 0.001). ATOR displayed a more prominent decrease of PLTP activity compared to ROSU (p = 0.043), while ROSU displayed a more prominent decrease of Lp-PLA2 activity compared to ATOR (p = 0.04). Both statins effectively reduced, in a dose-dependent way, high sensitivity C-reactive protein values over time, while no effect on the levels of circulating inter cellular adhesion molecule 1 (cICAM-1) was observed.

CONCLUSIONS

The effects of statin treatment extend further and beyond a mere TChol and LDL cholesterol reduction, as demonstrated by the aforementioned alterations of lipoproteins, enzymes and lipid transfer proteins involved in lipoprotein metabolism and pro-atherogenic and inflammatory molecules. ROSU and ATOR displayed a similar pattern of effect on lipid metabolism with discrete differences in the magnitude of this effect in certain variables. Despite the limitations of small population size and lack of clinical end points, reported data provide an insight for the possible pathophysiological mechanisms implicated in the effect of increasing dosages of different statin treatments.

Composition, structure and substrate properties of reconstituted discoidal HDL with apolipoprotein A-I and cholesteryl ester

To investigate the influence of lipid unsaturation and neutral lipid on the maturation of high density lipoproteins, the discoidal complexes of apoA-I, phosphatidylcholine and cholesteryl ester (CE) were prepared. Saturated dipalmitoylphosphatidylcholine (DPPC) and unsaturated palmitoyllinoleoylphosphatidylcholine (PLPC), palmitoyloleoylphosphatidylcholine (POPC), and fluorescent probe cholesteryl 1-pyrenedecanoate (CPD) that forms in a diffusion- and concentration-dependent manner short-lived dimer of unexcited and excited molecules (excimer) were used. The apoA-I/DPPC/CPD complexes were heterogeneous by size, composition and probe location. CPD molecules incorporated more efficiently into larger complexes and accumulated in a central part of the discs. The apoA-I/POPC(PLPC)/CPD were also heterogeneous, however, probe molecules distributed preferentially into smaller complexes and accumulated at disc periphery. The kinetics of CPD transfer by recombinant cholesteryl ester transfer protein (CETP) to human plasma LDL is well described by two-exponential decay, the fast component with a shorter transfer time being more populated in PLPC compared to DPPC complexes. The presence of CE molecules in discoidal HDL results in particle heterogeneity. ApoA-I influences the CETP activity modulating the properties of apolipoprotein-phospholipid interface. This may include CE molecules accumulation in the boundary lipid in unsaturated phosphatidylcholine and cluster formation in the bulk bilayer in saturated phosphatidylcholine.

High-density lipoprotein metabolism and the human embryo

BACKGROUND

High-density lipoprotein (HDL) appears to be the dominant lipoprotein particle in human follicular fluid (FF). The reported anti-atherogenic properties of HDL have been attributed in part to reverse cholesterol transport. The discoveries of the scavenger receptor class B type I (SR-BI) and the ATP-binding cassette A1 lipid (ABCA1) transporter have generated studies aimed at unraveling the pathways of HDL biogenesis, remodeling and catabolism. The production of SR-BI and ABCA1 knockout mice as well as other lipoprotein metabolism-associated mutants has resulted in reduced or absent fertility, leading us to postulate the existence of a human hepatic-ovarian HDL-associated axis of fertility. Here, we review an evolving literature on the role of HDL metabolism on mammalian fertility and oocyte development.

METHODS

An extensive online search was conducted of published articles relevant to the section topics discussed. All relevant English language articles contained in Pubmed/Medline, with no specific time frame for publication, were considered for this narrative review. Cardiovascular literature was highly cited due to the wealth of relevant knowledge on HDL metabolism, and the dearth thereof in the reproductive field.

RESULTS

Various vertebrate models demonstrate a role for HDL in embryo development and fertility. In our clinical studies, FF levels of HDL cholesterol and apolipoprotein AI levels were negatively associated with embryo fragmentation, but not with embryo cell cleavage rate. However, the HDL component, paraoxonase 1 arylesterase activity, was positively associated with embryo cell cleavage rate.

CONCLUSIONS

HDL contributes to intra-follicular cholesterol homeostasis which appears to be important for successful oocyte and embryo development.

Combined hepatic lipase -514C/T and cholesteryl ester transfer protein I405V polymorphisms are associated with the risk of coronary artery disease

Hepatic lipase (LIPC) and cholesteryl ester transfer protein (CETP) are important components of high-density lipoprotein (HDL) metabolism and reverse cholesterol transport. Therefore, their genes are promising candidate genes for cardiovascular disease. The aim of the present study was to investigate whether combined LIPC -514C/T and CETP I405V polymorphisms correlate with angiographically documented coronary artery disease (CAD). Genotyping was performed in 317 patients who underwent clinically indicated coronary angiography. The patients were classified with significantly diseased arteries if one or more coronary arteries had a stenosis >50% and with minimally diseased arteries if there was no significant stenosis (<40%) in any artery. There were no significant associations of individual polymorphisms with the risk of significant CAD. In a multivariate logistic regression analysis including cardiovascular risk factors, simultaneous presence of both LIPC -514T and CETP 405V alleles was an independent predictor of significantly diseased arteries (odds ratio = 2.04; p = 0.022). This association was not significant in women with combined genotype who had the highest HDL-cholesterol. In conclusion, the combined T allele of LIPC -514C/T and V allele of CETP I405V are associated with the risk of CAD. Further, the higher HDL-cholesterol and female gender may reduce the effect of combined genotype on CAD risk.

The potential influence of genetic variants in genes along bile acid and bile metabolic pathway on blood cholesterol levels in the population

The liver is currently known to be the major organ to eliminate excess cholesterol from our body. It accomplishes this function in two ways: conversion of cholesterol molecules into bile acids (BAs) and secretion of unesterified cholesterol molecules into bile. BAs are synthesized in the hepatocytes, secreted into bile and delivered to the lumen of the small intestine where they act as detergents to facilitate absorption of fats and fat-soluble vitamins. About 95% of BAs are recovered in the ileum during each cycle of the enterohepatic circulation. Five percent are lost and replaced by newly synthesized BAs, which amounts to approximately 500 mg/day in adult humans. In contrast to the efficiency of the BAs' enterohepatic circulation, 50% of the 1000 mg of cholesterol secreted daily into bile is lost in feces. It is known that rare human mutations in certain genes in bile acid and bile metabolic pathway influence blood cholesterol levels. With the recent success of genome-wide association studies, we are convinced that common genetic variants also play a role in the genetic architecture of plasma lipid traits. In this review, we summarized the current state of knowledge about genetic variations in bile acid and bile metabolic pathway, and assessed their impact on blood cholesterol levels and cholesterol metabolic kinetics in the population.

Impaired serum capacity to induce cholesterol efflux is associated with endothelial dysfunction in type 2 diabetes mellitus

OBJECTIVE

Reverse cholesterol transport (RCT) plays a protective role against atherosclerosis and cholesterol efflux from cells is an early step in the RCT pathway. We investigated whether the capacity of serum to induce cholesterol efflux was associated with endothelial dysfunction in type 2 diabetes.

METHODS

Endothelium-dependent and -independent vasodilation of the brachial artery was measured by high-resolution vascular ultrasound and serum cholesterol efflux capacity was determined by measuring the transfer of [3H]cholesterol from Fu5AH cells to serum in 137 patients with type 2 diabetes and 75 controls.

RESULTS

Serum cholesterol efflux capacity was lower in diabetic patients than in the controls (13.6+/-2.5% vs. 14.6+/-3.4%, respectively, p=0.02), and both endothelium-dependent vasodilation (4.9+/-2.2% vs. 8.8+/-4.1%, respectively, p<0.01) and endothelium-independent vasodilation were impaired (13.4+/-4.3% vs. 16.3+/-5.5%. respectively, p<0.01). Endothelium-dependent vasodilation correlated with serum cholesterol efflux capacity (r=0.26, p=0.003) in diabetic patients and controls (r=0.24, p=0.037). On general linear model analysis, the presence of diabetes, brachial artery diameter and serum cholesterol efflux capacity were significant independent determinants of endothelium-dependent vasodilation.

CONCLUSION

Impaired serum cholesterol efflux capacity was associated with endothelial dysfunction independent of other cardiovascular risk factors.

Regulation of bile acid and cholesterol metabolism by PPARs

Bile acids are amphipathic molecules synthesized from cholesterol in the liver. Bile acid synthesis is a major pathway for hepatic cholesterol catabolism. Bile acid synthesis generates bile flow which is important for biliary secretion of free cholesterol, endogenous metabolites, and xenobiotics. Bile acids are biological detergents that facilitate intestinal absorption of lipids and fat-soluble vitamins. Recent studies suggest that bile acids are important metabolic regulators of lipid, glucose, and energy homeostasis. Agonists of peroxisome proliferator-activated receptors (PPARα, PPARγ, PPARδ) regulate lipoprotein metabolism, fatty acid oxidation, glucose homeostasis and inflammation, and therefore are used as anti-diabetic drugs for treatment of dyslipidemia and insulin insistence. Recent studies have shown that activation of PPARα alters bile acid synthesis, conjugation, and transport, and also cholesterol synthesis, absorption and reverse cholesterol transport. This review will focus on the roles of PPARs in the regulation of pathways in bile acid and cholesterol homeostasis, and the therapeutic implications of using PPAR agonists for the treatment of metabolic syndrome.

Sex-associated effect of CETP and LPL polymorphisms on postprandial lipids in familial hypercholesterolaemia

Background

This study assessed the gender-specific influence of the cholesteryl ester transfer protein (TaqIB, I405V) and lipoprotein lipase (S447X) polymorphisms on the response to an oral fat tolerance test in heterozygotes for familial hypercholesterolaemia.

Methods

We selected and genotyped 80 men and postmenopausal women heterozygous for familial hypercholesterolaemia (main group) as well as 11 healthy control subjects. Patients were subgrouped based on their response to oral fat tolerance test. The oral fat tolerance test was defined as pathological when postprandial triglyceride concentration was higher than the highest triglyceride concentration observed in healthy subjects (220 mg/dl) at any time (2, 4, 6 or 8 h).

Results

In the pathological subgroup, men had significantly higher incremental area under the curve after oral fat tolerance test than postmenopausal women. Furthermore, multivariate analysis revealed a gender association of TaqIB and I405V influence on postprandial lipaemia in this subgroup.

Conclusion

In conclusion, it seems that gender and TaqIB polymorphism of the cholesteryl ester transfer protein gene were both associated with the distribution of triglyceride values after oral fat tolerance test, only in subjects with a pathological response to oral fat tolerance test. Specifically, men carrying the B2 allele of the TaqIB polymorphism showed a higher postprandial triglyceride peak and a delayed return to basal values compared with women carrying B2. However, further investigations in larger populations are required to replicate and confirm these findings.

Deletion of single amino acid E235 affects the structure and lipid interaction of human apolipoprotein A-I C-terminal peptides

The C-terminal domain of apolipoprotein (apo) A-I plays an important role in lipid binding. ApoA-I Nichinan, a naturally occurring human apoA-I variant with a deletion of E235 located in the C-terminus, is associated with low high-density lipoprotein (HDL) cholesterolemia. In the present study, a series of variant peptides corresponding to residues 220-241 of human apoA-I were examined to clarify the influences of E235 deletion (DeltaE235) on the structure and lipid interaction of the C-terminal region. NMR studies demonstrated that in trifluoroethanol, apoA-I 220-241/DeltaE235 peptide forms the alpha-helical structure similar to wild-type (WT) peptide. Circular dichroism measurements revealed that the interaction with phospholipid vesicles induced structural changes from random coil to alpha-helix both in apoA-I 220-241 WT and E235A, a variant with a negative charge ablation, peptides. These peptides also showed abilities to form HDL-like particles through microsolubilization of phospholipid vesicles, indicating that the negative charge ablation in E235 has no effect on the lipid interaction. By contrast, neither lipid binding-induced alpha-helix formation nor microsolubilization of vesicles were observed in apoA-I 220-241/DeltaE235 and L230P, a helix-breaking variant, peptides. In addition, fluorescence measurements showed that tryptophan fluorescence intensity of apoA-I 220-241/F225W greatly increased upon lipid binding, while only a little increase was observed for the corresponding DeltaE235 variant. Taken together, these results suggest that the deletion of E235 causes defective lipid binding of apoA-I Nichinan because of the impaired helix-forming ability of the C-terminal residues.

Novel roles of hepatic lipase and phospholipid transfer protein in VLDL as well as HDL metabolism

OBJECTIVE

Elevated plasma phospholipid transfer protein (PLTP) expression may increase atherosclerosis in mice by reducing plasma HDL and increasing hepatic VLDL secretion. Hepatic lipase (HL) is a lipolytic enzyme involved in several aspects of the same pathways of lipoprotein metabolism. We investigated whether the effects of elevated PLTP activity are compromised by HL deficiency.

METHODS AND RESULTS

HL deficient mice were crossbred with PLTP transgenic (PLTPtg) mice and studied in the fasted state. Plasma triglycerides were decreased in HL deficiency, explained by reduced hepatic triglyceride secretion. In PLTPtg mice, a redistribution of HL activity between plasma and tissue was evident and plasma triglycerides were also decreased. HL deficiency mitigated or even abolished the stimulatory effect of elevated PLTP activity on hepatic triglyceride secretion. HL deficiency had a modest incremental effect on plasma HDL, which remained present in PLTP transgenic/HL(-/-) mice, thereby partially compensating the decrease in HDL caused by elevation of PLTP activity. HDL decay experiments showed that the fractional turnover rate of HDL cholesteryl esters was delayed in HL deficient mice, increased in PLTPtg mice and intermediate in PLTPtg mice in an HL(-/-) background.

CONCLUSIONS

HL affects hepatic VLDL. Elevated PLTP activity lowers plasma HDL-cholesterol by stimulating the plasma turnover and hepatic uptake of HDL cholesteryl esters. HL is not required for the increase in hepatic triglyceride secretion or for the lowering of HDL-cholesterol induced by PLTP overexpression.

Reverse cholesterol transport in type 2 diabetes mellitus

High-density lipoprotein (HDL) plays an important protective role against atherosclerosis, and the anti-atherogenic properties of HDL include the promotion of cellular cholesterol efflux and reverse cholesterol transport (RCT), as well as antioxidant, anti-inflammatory and anticoagulant effects. RCT is a complex pathway, which transports cholesterol from peripheral cells and tissues to the liver for its metabolism and biliary excretion. The major steps in the RCT pathway include the efflux of free cholesterol mediated by cholesterol transporters from cells to the main extracellular acceptor HDL, the conversion of free cholesterol to cholesteryl esters and the subsequent removal of cholesteryl ester in HDL by the liver. The efficiency of RCT is influenced by the mobilization of cellular lipids for efflux and the intravascular remodelling and kinetics of HDL metabolism. Despite the increased cardiovascular risk in people with type 2 diabetes, current knowledge on RCT in diabetes is limited. In this article, abnormalities in RCT in type 2 diabetes mellitus and therapeutic strategies targeting HDL and RCT will be reviewed.

Hepatic SR-BI, not endothelial lipase, expression determines biliary cholesterol secretion in mice

High density lipoprotein cholesterol is thought to represent a preferred source of sterols secreted into bile following hepatic uptake by scavenger receptor class B type I (SR-BI). The present study aimed to determine the metabolic effects of an endothelial lipase (EL)-mediated stimulation of HDL cholesterol uptake on liver lipid metabolism and biliary cholesterol secretion in wild-type, SR-BI knockout, and SR-BI overexpressing mice. In each model, injection of an EL expressing adenovirus decreased plasma HDL cholesterol (P < 0.001) whereas hepatic cholesterol content increased (P < 0.05), translating into decreased expression of sterol-regulatory element binding protein 2 (SREBP2) and its target genes HMG-CoA reductase and LDL receptor (each P < 0.01). Biliary cholesterol secretion was dependent on hepatic SR-BI expression, being decreased in SR-BI knockouts (P < 0.001) and increased following hepatic SR-BI overexpression (P < 0.001). However, in each model, biliary secretion of cholesterol, bile acids, and phospholipids as well as fecal bile acid and neutral sterol content, remained unchanged in response to EL overexpression. Importantly, hepatic ABCG5/G8 expression did not correlate with biliary cholesterol secretion rates under these conditions. These results demonstrate that an acute decrease of plasma HDL cholesterol levels by overexpressing EL increases hepatic cholesterol content but leaves biliary sterol secretion unaltered. Instead, biliary cholesterol secretion rates are related to the hepatic expression level of SR-BI. These data stress the importance of SR-BI for biliary cholesterol secretion and might have relevance for concepts of reverse cholesterol transport.

Independent protein-profiling studies show a decrease in apolipoprotein A1 levels in schizophrenia CSF, brain and peripheral tissues

Although some insights into the etiology of schizophrenia have been gained, an understanding of the illness at the molecular level remains elusive. Recent advances in proteomic profiling offer great promise for the discovery of markers underlying pathophysiology of diseases. In the present study, we employed two high-throughput proteomic techniques together with traditional methods to investigate cerebrospinal fluid (CSF), brain and peripheral tissues (liver, red blood cells and serum) of schizophrenia patients in an attempt to identify peripheral/surrogate disease markers. The cohorts used to investigate each tissue were largely independent, although some CSF and serum samples were collected from the same patient. To address the major confounding factor of antipsychotic drug treatment, we also included a large cohort of first-onset drug-naive patients. Apolipoprotein A1 (apoA1) showed a significant decrease in expression in schizophrenia patients compared to controls in all five tissues examined. Specifically, using SELDI-TOF mass spectrometry, apoA1 was found decreased in CSF from schizophrenia patients (-35%, P=0.00001) and, using 2D-DIGE, apoA1 was also found downregulated in liver (-30%, P=0.02) and RBCs (-60%, P=0.003). Furthermore, we found a significant reduction of apoA1 in sera of first-onset drug-naive schizophrenia patients using enzyme-linked immunosorbent assay (-18%, P=0.00008) and in two investigations of post-mortem brain tissue using western blot analysis (-35%, P=0.05; -51%, P=0.05). These results show that apoA1 is consistently downregulated in the central nervous system as well as peripheral tissues of schizophrenia patients and may be linked to the underlying disease mechanism.

Lipids including cholesteryl linoleate and cholesteryl arachidonate contribute to the inherent antibacterial activity of human nasal fluid

Mucosal surfaces provide first-line defense against microbial invasion through their complex secretions. The antimicrobial activities of proteins in these secretions have been well delineated, but the contributions of lipids to mucosal defense have not been defined. We found that normal human nasal fluid contains all major lipid classes (in micrograms per milliliter), as well as lipoproteins and apolipoprotein A-I. The predominant less polar lipids were myristic, palmitic, palmitoleic, stearic, oleic, and linoleic acid, cholesterol, and cholesteryl palmitate, cholesteryl linoleate, and cholesteryl arachidonate. Normal human bronchioepithelial cell secretions exhibited a similar lipid composition. Removal of less-polar lipids significantly decreased the inherent antibacterial activity of nasal fluid against Pseudomonas aeruginosa, which was in part restored after replenishing the lipids. Furthermore, lipids extracted from nasal fluid exerted direct antibacterial activity in synergism with the antimicrobial human neutrophil peptide HNP-2 and liposomal formulations of cholesteryl linoleate and cholesteryl arachidonate were active against P. aeruginosa at physiological concentrations as found in nasal fluid and exerted inhibitory activity against other Gram-negative and Gram-positive bacteria. These data suggest that host-derived lipids contribute to mucosal defense. The emerging concept of host-derived antimicrobial lipids unveils novel roads to a better understanding of the immunology of infectious diseases.

Cellular cholesterol efflux to serum is impaired in diabetic nephropathy

BACKGROUND

Cholesterol efflux from cells is an early step of reverse cholesterol transport (RCT) and the capacity of serum to induce cellular cholesterol efflux has recently been shown to be an independent predictor of coronary artery atherosclerosis. Our aim is to evaluate the capacity of serum to induce ATP-binding cassette transporter A1 (ABCA1) and scavenger receptor class B type I (SR-BI) mediated cholesterol efflux in type 2 diabetic patients with nephropathy.

METHODS

Diabetic patients were recruited according to their urinary albumin excretion rate (normoalbuminuria, microalbuminuria and proteinuria) with 20 subjects in each group and compared with 20 age-matched controls. The ability of the serum to induce cholesterol efflux was measured using a cell culture system.

RESULTS

Serum capacity to induce ABCA1-mediated cholesterol efflux was decreased in patients with microalbuminuria or proteinuria (p < 0.05) whereas SR-BI-mediated cholesterol efflux was impaired in all three groups of diabetic patients (p < 0.05). Plasma high-density lipoprotein (HDL) cholesterol and apoAI were reduced in all groups of diabetic patients, but pre-beta-HDL was only significantly decreased in those with microalbuminuria or proteinuria. Serum advanced glycation end products (AGEs) were significantly increased in diabetic patients with microalbuminuria or proteinuria. Serum AGEs and pre-beta-HDL were the significant independent determinants of ABCA1-mediated cholesterol efflux, whereas plasma HDL and log (creatinine) were the significant determinants of SR-BI-mediated cholesterol efflux.

CONCLUSION

The capacity of serum to induce ABCA1- and SR-BI-mediated cholesterol efflux was impaired in diabetic patients with incipient or overt nephropathy. These abnormalities may contribute to the accelerated development of atherosclerotic vascular disease in these patients.

High density lipoprotein cholesterol: an evolving target of therapy in the management of cardiovascular disease

Since the pioneering work of John Gofman in the 1950s, our understanding of high density lipoprotein cholesterol (HDL-C) and its relationship to coronary heart disease (CHD) has grown substantially. Numerous clinical trials since the Framingham Study in 1977 have demonstrated an inverse relationship between HDL-C and one’s risk of developing CHD. Over the past two decades, preclinical research has gained further insight into the nature of HDL-C metabolism, specifically regarding the ability of HDL-C to promote reverse cholesterol transport (RCT). Recent attempts to harness HDL’s ability to enhance RCT have revealed the complexity of HDL-C metabolism. This review provides a detailed update on HDL-C as an evolving therapeutic target in the management of cardiovascular disease.

Multiple actions of high-density lipoprotein

PURPOSE OF REVIEW

The most accepted property of high-density lipoprotein is reverse cholesterol transport. However, other beneficial actions may contribute to the antiatherogenic role of high-density lipoprotein. This review addresses the action of high-density lipoprotein beyond reverse cholesterol transport.

RECENT FINDINGS

High-density lipoprotein cholesterol levels are inversely associated with coronary heart disease and other forms of vascular disease. Apart from transferring excess cholesterol to the liver, high-density lipoprotein exhibits favorable effects on oxidation, inflammation, thrombosis and endothelial function. Some of these actions are at least in part attributed to high-density lipoprotein-associated enzymes, such as paraoxonase and platelet-activating factor acetylhydrolase. However, high-density lipoprotein can become dysfunctional and proatherogenic under certain circumstances.

SUMMARY

Current data suggest that high-density lipoprotein possesses various properties beyond reverse cholesterol transport. However, many issues on the exact role of high-density lipoprotein remain unknown. Future research is needed.

Enhanced nitrosative stress during Trypanosoma cruzi infection causes nitrotyrosine modification of host proteins: implications in Chagas' disease

Oxidative/nitrosative stress may be important in the pathology of Chagas' disease. Experimental animals infected by Trypanosoma cruzi showed an early rise in myocardial and peripheral protein-3-nitrotyrosine (3NT) and protein-carbonyl formation that persisted during the chronic stage of disease. In comparison, experimental chronic ethanol-induced cardiomyopathy was slow to develop and presented with a moderate increase in oxidative stress and minimal to no nitrosative stress after long-term alcohol feeding of animals. The oxidative stress in both chagasic animals and animals with ethanol-induced cardiomyopathy correlated with the persistence of reactive oxygen species-producing inflammatory intermediates. Protein-3NT formation in T. cruzi-infected animals was associated with enhanced nitric oxide expression (inferred by nitrite/nitrate levels) and myeloperoxidase activity, suggesting that both peroxynitrite- and myeloperoxidase-mediated pathways contribute to increased protein nitration in Chagas' disease. We used one- and two-dimensional gel electrophoresis and Western blot analysis to identify disease-specific plasma proteins that were 3NT-modified in T. cruzi-infected animals. Nitrated protein spots (56 in total) were sequenced by matrix-assisted laser desorption ionization/time of flight mass spectrometry and liquid chromatography-tandem mass spectrometry and identified by a homology search of public databases. Clustering of 3NT-modified proteins according to their functional characteristics revealed that the nitration of immunoglobulins, apolipoprotein isoforms, and other proteins might perturb their functions and be important in the pathology of Chagas' disease. We also showed that nitrated peptides derived from titin and alpha-actin were released into the plasma of patients with Chagas' disease. Such modified proteins may be useful biomarkers of Chagas' disease.

Determinants of leukocyte adenosine triphosphate-binding cassette transporter G1 gene expression in type 2 diabetes mellitus

Cellular cholesterol efflux is regulated by cholesterol transporters including adenosine triphosphate-binding cassette transporter A1 (ABCA1), ABCG1, and scavenger receptor class B type I (SR-BI). We have investigated whether the expression of these transporters is affected by type 2 diabetes mellitus and the association with glycemic indexes and oxidized low-density lipoprotein (oxLDL). Messenger RNA of ABCA1, ABCG1, and SR-BI in peripheral monocytes was measured in 30 diabetic patients and 30 matched controls. Plasma oxLDL and advanced glycation end products (AGEs) were assayed by enzyme-linked immunosorbent assay. Cellular cholesterol efflux from monocytes to serum was determined in a subgroup chosen randomly. The expression of ABCG1 was decreased in diabetic patients (P < .05), whereas the levels of ABCA1 and SR-BI were comparable between the 2 groups. Fasting glucose, hemoglobin A(1c), AGEs, and oxLDL were all significantly increased in diabetic patients. There was an inverse correlation between serum AGEs and ABCG1 (r = -0.44, P < .05) that remained significant after adjusting for potential confounding factors. No associations between fasting glucose, hemoglobin A(1c), plasma lipids, or oxLDL and the expression of ABCG1, ABCA1, or SR-BI were found. Cholesterol efflux from monocytes to standard serum or autologous serum was significantly impaired in diabetic patients, and the reduction in efflux to autologous serum correlated with the expression of ABCG1 (r = 0.60, P < .05). The expression of ABCG1 in monocytes is reduced in type 2 diabetes mellitus and is partly related to serum AGEs concentration. The reduction in ABCG1 is associated with impairment in cholesterol efflux and may contribute to accelerated foam cell formation in diabetic patients.

The specific amino acid sequence between helices 7 and 8 influences the binding specificity of human apolipoprotein A-I for high density lipoprotein (HDL) subclasses: a potential for HDL preferential generation

Humans have two major high density lipoprotein (HDL) sub-fractions, HDL(2) and HDL(3), whereas mice have a monodisperse HDL profile. Epidemiological evidence has suggested that HDL(2) is more atheroprotective; however, currently there is no direct experimental evidence to support this postulate. The amino acid sequence of apoA-I is a primary determinant of HDL subclass formation. The majority of the alpha-helical repeats in human apoA-I are proline-punctuated. A notable exception is the boundary between helices 7 and 8, which is located in the transitional segment between the stable N-terminal domain and the C-terminal hydrophobic domain. In this study we ask whether the substitution of a proline-containing sequence (PCS) separating other helices in human apoA-I for the non-proline-containing sequence (NPCS) between helices 7 and 8 (residues 184-190) influences HDL subclass association. The human apoA-I mutant with PCS2 replacing NPCS preferentially bound to HDL(2). In contrast, the mutant where PCS3 replaced NPCS preferentially associated with HDL(3). Thus, the specific amino acid sequence between helices 7 and 8 influences HDL subclass association. The wild-type and mutant proteins exhibited similar physicochemical properties except that the two mutants displayed greater lipid-associated stability versus wild-type human apoA-I. These results focus new attention on the influence of the boundary between helices 7 and 8 on the properties of apoA-I. The expression of these mutants in mice may result in the preferential generation of HDL(2) or HDL(3) and allow us to examine experimentally the anti-atherogenicity of the HDL subclasses.

The strengths and limitations of the apoB/apoA-I ratio to predict the risk of vascular disease: a Hegelian analysis

The levels of pro- and antiatherogenic lipoproteins are the most important risk factors for vascular disease, and there is now compelling evidence that the apolipoprotein (apo) B/apoA-I ratio is a better index of the likelihood of vascular events than any of the corresponding cholesterol indices: the total cholesterol/high-density lipoprotein cholesterol (HDL-C) ratio, non-HDL-C/HDL-C ratio, or low-density lipoprotein cholesterol (LDL-C)/HDL-C ratio. But are there any restrictions on the application of the apoB/apoA-I ratio to clinical practice? This article suggests that the answer is yes. Based on the available biologic and epidemiologic data, the relation between risk and apoB is continuous, whereas at the extremes of HDL concentration in plasma the relation to risk is not certain. Moreover, LDL plays a causal role in atherogenesis whereas HDL plays a contingent role. Appreciating these distinctions should allow appropriate use of the apoB/apoA-I ratio as a simple, single, summary index of the lipoprotein-related risk of vascular disease.

Efficient coupling of transducin to monomeric rhodopsin in a phospholipid bilayer

G protein-coupled receptors (GPCRs) are seven transmembrane domain proteins that transduce extracellular signals across the plasma membrane and couple to the heterotrimeric family of G proteins. Like most intrinsic membrane proteins, GPCRs are capable of oligomerization, the function of which has only been established for a few different receptor systems. One challenge in understanding the function of oligomers relates to the inability to separate monomeric and oligomeric receptor complexes in membrane environments. Here we report the reconstitution of bovine rhodopsin, a GPCR expressed in the retina, into an apolipoprotein A-I phospholipid particle, derived from high density lipoprotein (HDL). We demonstrate that rhodopsin, when incorporated into these 10 nm reconstituted HDL (rHDL) particles, is monomeric and functional. Rhodopsin.rHDL maintains the appropriate spectral properties with respect to photoactivation and formation of the active form, metarhodopsin II. Additionally, the kinetics of metarhodopsin II decay is similar between rhodopsin in native membranes and rhodopsin in rHDL particles. Photoactivation of monomeric rhodopsin.rHDL also results in the rapid activation of transducin, at a rate that is comparable with that found in native rod outer segments and 20-fold faster than rhodopsin in detergent micelles. These data suggest that monomeric rhodopsin is the minimal functional unit in G protein activation and that oligomerization is not absolutely required for this process.

The effect of NeOpuntia on blood lipid parameters--risk factors for the metabolic syndrome (syndrome X)

Metabolic syndrome (syndrome X) causes millions of cardiovascular complications and premature deaths every year. The aim of this study was to evaluate the effects of NeOpuntia, patented, dehydrated, Opuntia ficus-indica leaves, on blood lipid parameters and metabolic syndrome. Opuntia ficus-indica leaves are traditionally consumed as a vegetable. Participants in this monocentric, randomized, placebocontrolled, double-blind, 6-wk study were 68 women, ages 20 to 55 y, with metabolic syndrome and a body mass index between 25 and 40. Fifty-nine subjects completed the study according to the study plan. All volunteers followed wellbalanced diets with controlled lipid input. NeOpuntia or placebo capsules were taken at a dosage of 1.6 g per meal. All 5 syndrome X criteria were measured on days 0, 14, and 42, including low-density lipoprotein cholesterol (LDL-C), highdensity lipoprotein cholesterol (HDL-C), and triglyceride levels. For the 42 females above 45 y of age, we show a significant increase in HDL-C levels with NeOpuntia and a tendency toward decreased triglyceride levels. At the same time, there was a decrease in HDL-C levels with placebo. Overall, for the entire study population, similar but less pronounced tendencies were demonstrated. Forty-two females taking NeOpuntia with no additional hypolipemic treatment, had a pronounced reduction in LDL cholesterol, especially after day 14. At the study end, 39% of the NeOpuntia group, but only 8% of the placebo group, were no longer diagnosed with metabolic syndrome. Our results indicate an advantage of using NeOpuntia in dietary supplements and functional foods because of improvement of blood lipid parameters associated with cardiovascular risks.

Mapping the structural transition in an amyloidogenic apolipoprotein A-I

The single amino acid mutation G26R in human apolipoprotein A-I (apoA-IIOWA) leads to the formation of beta-secondary structure rich amyloid fibrils in vivo. Here we show that full-length apoA-IIOWA has a decreased lipid-binding capability, an increased amino-terminal sensitivity to protease, and a propensity to form annular protofibrils visible by electron microscopy. The molecular basis for the conversion of apolipoprotein A-I to a proamyloidogenic form was examined by electron paramagnetic resonance spectroscopy. Our recent findings [Lagerstedt, J. O., Budamagunta, M. S., Oda, M. N., and Voss, J. C. (2007) J. Biol. Chem. 282, 9143-9149] indicate that Gly26 in the native apoprotein separates a preceding beta-strand structure (residues 20-25) from a downstream largely alpha-helical region. The current study demonstrates that the G26R variant promotes a structural transition of positions 27-56 to a mixture of coil and beta-strand secondary structure. Microscopy and staining by amyloidophilic dyes suggest that this alteration extends throughout the protein within 1 week of incubation in vitro, leading to insoluble aggregates of distinct morphology. The severe consequences of the Iowa mutation likely arise from the combination of losing the contribution of the native Gly residue in terminating beta-strand propagation and the promotion of beta-structure when an Arg is introduced adjacent to the succeeding residue of identical charge and size, Arg27.

In Vivo Reverse Cholesterol Transport From Macrophages Lacking ABCA1 Expression Is Impaired

BACKGROUND

ATP-binding cassette transporter A1 (ABCA1) is a key mediator of cholesterol efflux to apoA-I in cholesterol loaded macrophages, a first step of reverse cholesterol transport (RCT) in vivo. Macrophage specific abca1 inactivation or overexpression, respectively, accelerated or suppressed the development of atherosclerosis in mouse models. However, it is yet to be established that the ABCA1 effect is related to specific changes in RCT from the macrophages in vivo.

METHODS AND RESULTS

one marrow-derived macrophages from abca1-/- or abca1+/- mice were labeled with 3H-cholesterol-AcLDL or 3H-cholesterol-LDL and injected into abca1+/+ abca1+/- or abca1-/- mice. When injected into abca1+/+ mice, return of 3H-cholesterol from labeled abca1-/- macrophages to serum, liver, bile, and feces was reduced by 50% (P=0.01) compared with control. When labeled wild-type macrophages were injected into abca1-/- mice, as compared with wild-type mice, the return of 3H-cholesterol to serum, liver, bile, and feces was also reduced.

CONCLUSIONS

ABCA1 expression in macrophages contributes significantly to in vivo macrophage RCT. The important residual RCT observed from abca1-/- macrophages highlight the functionality of transporters that efflux to HDL.