Monica Gomaraschi

Endothelial Protection by High-Density Lipoproteins. From Bench to Bedside

Abstract—There are several potential mechanisms by which HDLs protect against the development of vascular disease. One relates to the unique ability of these lipoproteins to remove cholesterol from the arterial wall. Another is the ability of HDL to prevent and eventually correct endothelial dysfunction, a key variable in the pathogenesis of atherosclerosis and its complications. HDLs help maintain endothelial integrity, facilitate vascular relaxation, inhibit blood cell adhesion to vascular endothelium, reduce platelet aggregability and coagulation, and may favor fibrinolysis. These functions of HDLs complement their activity in arterial cholesterol removal by providing an excellent rationale for favorably influencing pathological processes underlying a variety of clinical conditions, such as accelerated atherosclerosis, acute coronary syndromes, and restenosis after coronary angioplasty, through a chronic or acute elevation of plasma HDL concentration.

Endothelial Protection by High-Density Lipoproteins

Abstract—There are several potential mechanisms by which HDLs protect against the development of vascular disease. One relates to the unique ability of these lipoproteins to remove cholesterol from the arterial wall. Another is the ability of HDL to prevent and eventually correct endothelial dysfunction, a key variable in the pathogenesis of atherosclerosis and its complications. HDLs help maintain endothelial integrity, facilitate vascular relaxation, inhibit blood cell adhesion to vascular endothelium, reduce platelet aggregability and coagulation, and may favor fibrinolysis. These functions of HDLs complement their activity in arterial cholesterol removal by providing an excellent rationale for favorably influencing pathological processes underlying a variety of clinical conditions, such as accelerated atherosclerosis, acute coronary syndromes, and restenosis after coronary angioplasty, through a chronic or acute elevation of plasma HDL concentration.

Genetic lecithin:cholesterol acyltransferase deficiency and cardiovascular disease

The lecithin:cholesterol acyltransferase (LCAT) enzyme is responsible for the synthesis of cholesteryl esters in human plasma and plays a critical role in high density lipoprotein (HDL) metabolism. Genetic LCAT deficiency is a rare metabolic disorder characterized by low HDL cholesterol levels. This paper reviews the genetic and biochemical features of LCAT deficiency, highlighting the absence of enhanced preclinical atherosclerosis in carriers, despite the remarkably low HDL cholesterol.

A unique protease-sensitive high density lipoprotein particle containing the apolipoprotein A-I(Milano) dimer effectively promotes ATP-binding Cassette A1-mediated cell cholesterol efflux

Carriers of the apolipoprotein A-IMilano (A-IM) variant present with severe reductions of plasma HDL levels, not associated with premature coronary heart disease (CHD). Sera from 14 A-IM carriers and matched controls were compared for their ability to promote ABCA1-driven cholesterol efflux from J774 macrophages and human fibroblasts. When both cell types are stimulated to express ABCA1, the efflux of cholesterol through this pathway is greater with A-IM than control sera (3.4 ± 1.0% versus 2.3 ± 1.0% in macrophages; 5.2 ± 2.4% versus 1.9 ± 0.1% in fibroblasts). A-IM and control sera are instead equally effective in removing cholesterol from unstimulated cells and from fibroblasts not expressing ABCA1. The A-IM sera contain normal amounts of apoA-I-containing preβ-HDL and varying concentrations of a unique small HDL particle containing a single molecule of the A-IM dimer; chymase treatment of serum degrades both particles and abolishes ABCA1-mediated cholesterol efflux. The serum content of chymase-sensitive HDL correlates strongly and significantly with ABCA1-mediated cholesterol efflux (r = 0.542, p = 0.004). The enhanced capacity of A-IM serum for ABCA1 cholesterol efflux is thus explained by the combined occurrence in serum of normal amounts of apoA-I-containing preβ-HDL, together with a unique protease-sensitive, small HDL particle containing the A-IM dimer, both effective in removing cell cholesterol via ABCA1.

Anti-inflammatory and cardioprotective activities of synthetic high-density lipoprotein containing apolipoprotein A-I mimetic peptides.

Apolipoprotein A-I (apoA-I) mimetic peptides may represent an alternative to apoA-I for large-scale production of synthetic high-density lipoproteins (sHDL) as a therapeutic agent. In this study, the cardioprotective activity of sHDL made with either L37pA peptide or its d-stereoisomer, D37pA, was compared to sHDL made with apoA-I. The peptides were reconstituted with palmitoyl-oleoyl-phosphatidylcholine, which yielded sHDL particles comparable to apoA-I sHDL in diameter, molecular weight, and α-helical content. Pretreatment of endothelial cells with either peptide sHDL reduced tumor necrosis factor α-stimulated vascular cell adhesion molecule-1 expression to the same extent as apoA-I sHDL. In an isolated rat heart model of ischemia/reperfusion (I/R) injury, L37pA and D37pA sHDL significantly reduced postischemic cardiac contractile dysfunction compared to the saline control, as indicated by a 49.7 ± 6.4% (L37pA; P < 0.001) and 53.0 ± 9.1% (D37pA; P < 0.001) increase of left ventricular-developed pressure (LVDP) after reperfusion and by a 45.4 ± 3.4% (L37pA; P < 0.001) and 49.6 ± 2.6% (D37pA; P < 0.001) decrease of creatine kinase (CK) release. These effects were similar to the 51.3 ± 3.0% (P < 0.001) increase of LVDP and 51.3 ± 3.0 (P < 0.001) reduction of CK release induced by apoA-I sHDL. Consistent with their cardioprotective effects, all three types of sHDL particles mediated an approximate 20% (P < 0.001) reduction of cardiac tumor necrosis factor α (TNFα) content and stimulated an approximate 35% (P < 0.05) increase in postischemic release of prostacyclin. In summary, L37pA and D37pA peptides can form sHDL particles that retain a similar level of protective activity as apoA-I sHDL on the endothelium and the heart; thus, apoA-I mimetic peptides may be useful therapeutic agents for the prevention of cardiac I/R injury.

Hypocholesterolaemic effects of lupin protein and pea protein/fibre combinations in moderately hypercholesterolaemic individuals.

The present study was aimed to evaluate the effect of plant proteins (lupin protein or pea protein) and their combinations with soluble fibres (oat fibre or apple pectin) on plasma total and LDL-cholesterol levels. A randomised, double-blind, parallel group design was followed: after a 4-week run-in period, participants were randomised into seven treatment groups, each consisting of twenty-five participants. Each group consumed two bars containing specific protein/fibre combinations: the reference group consumed casein+cellulose; the second and third groups consumed bars containing lupin or pea proteins+cellulose; the fourth and fifth groups consumed bars containing casein and oat fibre or apple pectin; the sixth group and seventh group received bars containing combinations of pea protein and oat fibre or apple pectin, respectively. Bars containing lupin protein+cellulose ( - 116 mg/l, - 4·2%), casein+apple pectin ( - 152 mg/l, - 5·3%), pea protein+oat fibre ( - 135 mg/l, - 4·7%) or pea protein+apple pectin ( - 168 mg/l, - 6·4%) resulted in significant reductions of total cholesterol levels (P<0·05), whereas no cholesterol changes were observed in the subjects consuming the bars containing casein+cellulose, casein+oat fibre or pea protein+cellulose. The present study shows the hypocholesterolaemic activity and potential clinical benefits of consuming lupin protein or combinations of pea protein and a soluble fibre, such as oat fibre or apple pectin.

Macrophage, But Not Systemic, Apolipoprotein E Is Necessary for Macrophage Reverse Cholesterol Transport In Vivo

Objective—To assess the role of apolipoprotein (apo) E in macrophage reverse cholesterol transport (RCT) in vivo. Methods and Results—ApoE exerts an antiatherosclerotic activity by regulating lipoprotein metabolism and promoting cell cholesterol efflux. We discriminated between macrophage and systemic apoE contribution using an assay of macrophage RCT in mice. The complete absence of apoE lead to an overall impairment of the process and, similarly, the absence of apoE exclusively in macrophages resulted in the reduction of cholesterol mobilization from macrophages to plasma, liver, and feces. Conversely, expression of apoE in macrophages is sufficient to promote normal RCT even in apoE-deficient mice. The mechanisms accounting for these results were investigated by evaluating the first step of RCT (ie, cholesterol efflux from cells). Macrophages isolated from apoE-deficient mice showed a reduced ability to release cholesterol into the culture medium, whereas the apoB-depleted plasma from apoE-deficient and healthy mice possessed a similar capacity to promote cellular lipid release from cultured macrophages. Conclusion—Our data demonstrate, for the first time to our knowledge, that apoE significantly contributes to macrophage RCT in vivo and that this role is fully attributable to apoE expressed in macrophages.

Nutraceutical approach to moderate cardiometabolic risk: results of a randomized, double-blind and crossover study with Armolipid Plus.

BACKGROUND Primary cardiovascular prevention may be achieved by lifestyle/nutrition improvements and specific drugs, although a relevant role is now emerging for specific functional foods and nutraceuticals. OBJECTIVES The aim of this study was to evaluate the usefulness of a nutraceutical multitarget approach in subjects with moderate cardiovascular risk and to compare it with pravastatin treatment. SUBJECTS Thirty patients with moderate dyslipidemia and metabolic syndrome (according to the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults) were included in an 8-week randomized, double-blind crossover study and took either placebo or a nutraceutical combination that contained red yeast rice extract, berberine, policosanol, astaxanthin, coenzyme Q10, and folic acid (Armolipid Plus). Subsequently, they were subjected to another 8-week treatment with pravastatin 10 mg/d. This dosage was selected on the basis of its expected -20% efficacy in reducing low-density lipoprotein-cholesterol. RESULTS Treatment with Armolipid Plus led to a significant reduction of total cholesterol (-12.8%) and low-density lipoprotein-cholesterol (-21.1%), similar to pravastatin (-16% and -22.6%, respectively), and an increase of high-density lipoprotein-cholesterol (4.8%). Armolipid Plus improved the leptin-to-adiponectin ratio, whereas adiponectin levels were unchanged. CONCLUSIONS These results indicate that this nutraceutical approach shows a lipid-lowering activity comparable to pravastatin treatment. Hence, it may be a safe and useful option, especially in conditions of moderate cardiovascular risk, in which a pharmacologic intervention may not be appropriate.

Normal Vascular Function Despite Low Levels of High-Density Lipoprotein Cholesterol in Carriers of the Apolipoprotein A-I Milano Mutant

Background— Carriers of the apolipoprotein A-IMilano (apoA-IM) mutant have very low plasma high-density lipoprotein cholesterol (HDL-C) levels but do not show any history of premature cardiovascular disease or any evidence of preclinical vascular disease. HDL is believed to prevent the development of vascular dysfunction, which may well contribute to HDL-mediated atheroprotection. Whether the low HDL level of apoA-IM carriers is associated with impaired vascular function is presently unknown. Methods and Results— The vascular response to reactive hyperemia, assessed by measuring postischemic increase in forearm arterial compliance, and the plasma concentration of soluble cell adhesion molecules were evaluated in 21 adult apoA-IM carriers, 21 age- and gender-matched nonaffected relatives (control subjects), and 21 healthy subjects with low HDL-C (low-HDL subjects). The average plasma HDL-C and apoA-I levels of apoA-IM carriers were remarkably lower than those of control subjects and significantly lower than those of low-HDL subjects. The postischemic increase in forearm arterial compliance in the apoA-IM carriers was 2-fold greater than in low-HDL subjects and remarkably similar to that of control subjects. Plasma soluble cell adhesion molecule levels were similar in apoA-IM carriers and control subjects but were greater in low-HDL subjects. When incubated with endothelial cells, HDL isolated from apoA-IM carriers was more effective than HDL from control and low-HDL subjects in stimulating endothelial nitric oxide synthase expression and activation and in downregulating tumor necrosis factor-&agr;–induced expression of vascular cell adhesion molecule-1. Conclusions— Despite their very low HDL levels, apoA-IM carriers do not display typical features of impaired vascular function because of an improved activity of apoA-IM HDL in maintaining endothelial cell homeostasis.

Plasma lecithin: cholesterol acyltransferase and carotid intima-media thickness in European individuals at high cardiovascular risk

Lecithin:cholesterol acyltransferase (LCAT) is the enzyme responsible for cholesterol esterification in plasma. LCAT is a major factor in HDL remodeling and metabolism, and it has long been believed to play a critical role in macrophage reverse cholesterol transport (RCT). The effect of LCAT on human atherogenesis is still controversial. In the present study, the plasma LCAT concentration was measured in all subjects (n = 540) not on drug treatment at the time of enrollment in the multicenter, longitudinal, observational IMPROVE study. Mean and maximum intima-media thickness (IMT) of the whole carotid tree was measured by B-mode ultrasonography in all subjects. In the entire cohort, LCAT quartiles were not associated with carotid mean and maximum IMT (P for trend 0.95 and 0.18, respectively), also after adjustment for age, gender, HDL-cholesterol (HDL-C), and triglycerides. No association between carotid IMT and LCAT quartiles was observed in men (P=0.30 and P=0.99 for mean and maximum IMT, respectively), whereas carotid IMT increased with LCAT quartiles in women (P for trend 0.14 and 0.019 for mean and maximum IMT, respectively). The present findings support the concept that LCAT is not required for an efficient reverse cholesterol transport and that a low plasma LCAT concentration and activity is not associated with increased atherosclerosis.