Montserrat Pérez-Cuellar

Aggregated Electronegative Low Density Lipoprotein in Human Plasma Shows a High Tendency toward Phospholipolysis and Particle Fusion

Aggregation and fusion of lipoproteins trigger subendothelial retention of cholesterol, promoting atherosclerosis. The tendency of a lipoprotein to form fused particles is considered to be related to its atherogenic potential. We aimed to isolate and characterize aggregated and nonaggregated subfractions of LDL from human plasma, paying special attention to particle fusion mechanisms. Aggregated LDL was almost exclusively found in electronegative LDL (LDL(−)), a minor modified LDL subfraction, but not in native LDL (LDL(+)). The main difference between aggregated (agLDL(−)) and nonaggregated LDL(−) (nagLDL(−)) was a 6-fold increased phospholipase C-like activity in agLDL(−). agLDL(−) promoted the aggregation of LDL(+) and nagLDL(−). Lipoprotein fusion induced by α-chymotrypsin proteolysis was monitored by NMR and visualized by transmission electron microscopy. Particle fusion kinetics was much faster in agLDL(−) than in nagLDL(−) or LDL(+). NMR and chromatographic analysis revealed a rapid and massive phospholipid degradation in agLDL(−) but not in nagLDL(−) or LDL(+). Choline-containing phospholipids were extensively degraded, and ceramide, diacylglycerol, monoacylglycerol, and phosphorylcholine were the main products generated, suggesting the involvement of phospholipase C-like activity. The properties of agLDL(−) suggest that this subfraction plays a major role in atherogenesis by triggering lipoprotein fusion and cholesterol accumulation in the arterial wall.

Bariatric surgery in morbidly obese patients improves the atherogenic qualitative properties of the plasma lipoproteins

OBJECTIVE The purpose of this study was to evaluate the effect of weight loss induced in morbidly obese subjects by Roux-en-Y gastric bypass bariatric surgery on the atherogenic features of their plasma lipoproteins. METHODS Twenty-one morbidly obese subjects undergoing bariatric surgery were followed up for up to 1 year after surgery. Plasma and lipoproteins were assayed for chemical composition and lipoprotein-associated phospholipase A2 (Lp-PLA2) activity. Lipoprotein size was assessed by non-denaturing polyacrylamide gradient gel electrophoresis, and oxidised LDL by ELISA. Liver samples were assayed for mRNA abundance of oxidative markers. RESULTS Lipid profile analysis revealed a reduction in the plasma concentrations of cholesterol and triglycerides, which were mainly associated with a significant reduction in the plasma concentration of circulating apoB-containing lipoproteins rather than with changes in their relative chemical composition. All patients displayed a pattern A phenotype of LDL subfractions and a relative increase in the antiatherogenic plasma HDL-2 subfraction (>2-fold; P < 0.001). The switch towards predominantly larger HDL particles was due to an increase in their relative cholesteryl ester content. Excess weight loss also led to a significant decrease in the plasma concentration of oxidised LDL (∼-25%; P < 0.01) and in the total Lp-PLA2 activity. Interestingly, the decrease in plasma Lp-PLA2 was mainly attributed to a decrease in the apoB-containing lipoprotein-bound Lp-PLA2. CONCLUSION Our data indicate that the weight loss induced by bariatric surgery ameliorates the atherogenicity of plasma lipoproteins by reducing the apoB-containing Lp-PLA2 activity and oxidised LDL, as well as increasing the HDL-2 subfraction.

Clusterin/apolipoprotein J binds to aggregated LDL in human plasma and plays a protective role against LDL aggregation

Clusterin/apolipoprotein J (apoJ) is an extracellular chaperone involved in the quality control system against protein aggregation. A minor part of apoJ is transported in blood bound to LDLs, but its function is unknown. Our aim was to determine the role of apoJ bound to LDLs. Total LDL from human plasma was fractionated into native LDL [LDL(+)] and electronegative LDL [LDL(‐)]. The latter was separated into nonaggregated [nagLDL(‐)] and aggregated LDL(‐)[agLDL (‐)]. The content of apoJ was 6‐fold higher in LDL(‐) than in LDL(+) and 7‐fold higher in agLDL(‐) than in nagLDL(‐). The proportion of LDL particles containing apoJ (LDL/J+) was 3‐fold lower in LDL(+) than in LDL(‐). LDL/J+ particles shared several characteristics with agLDL(‐), including increased negative charge and aggregation. apoJ‐depleted particles (LDL/J‐) showed increased susceptibility to aggregation, whether spontaneous or induced by proteolysis or lipolysis, as was revealed by turbidimetric analysis, gel filtration chromatography, lipoprotein precipitation, native gradient gel electrophoresis, circular dichroism, and transmission electronic microscopy. The addition of purified apoJ to total LDL also prevented its aggregation induced by proteolysis or lipolysis. These findings point to apoJ as a key modulator of LDL aggregation and reveal a putative new therapeutic strategy against atherosclerosis.—Martínez‐Bujidos, M., Rull, A., González‐Cura, B., Pérez‐Cuéllar, M., Montoliu‐Gaya, L., Villegas, S., Ordóñez‐Llanos, J., Sénchez‐Quesada, J. L. Clusterin/apolipoprotein J binds to aggregated LDL in human plasma and plays a protective role against LDL aggregation. FASEB J. 29, 1688‐1700 (2015). www.fasebj.org

Hypoxia worsens the impact of intracellular triglyceride accumulation promoted by electronegative low-density lipoprotein in cardiomyocytes by impairing perilipin 5 upregulation

Plasma lipoproteins are a source of lipids for the heart, and the proportion of electronegative low density lipoprotein [LDL(-)] is elevated in cardiometabolic diseases. Perilipin 5 (Plin5) is a crucial protein for lipid droplet management in the heart. Our aim was to assess the effect of LDL(-) on intracellular lipid content and Plin5 levels in cardiomyocytes and to determine whether these effects were influenced by hypoxia. HL-1 cardiomyocytes were exposed to native LDL [LDL(+)], LDL(-), and LDL(+) enriched in non-esterified fatty acids (NEFA) by phospholipase A2 (PLA2)-mediated lipolysis [PLA2-LDL(+)] or by NEFA loading [NEFA-LDL(+)] under normoxia or hypoxia. LDL(-), PLA2-LDL(+) and NEFA-LDL(+) raised the intracellular NEFA and triglyceride (TG) content of normoxic cardiomyocytes. Plin5 was moderately upregulated by LDL(+) but more highly upregulated by LDL(-), PLA2-LDL(+) and NEFA-LDL(+) in normoxic cardiomyocytes. Hypoxia enhanced the effect of LDL(-), PLA2-LDL(+) and NEFA-LDL(+) on intracellular TG and NEFA concentrations but, in contrast, counteracted the upregulatory effect of these LDLs on Plin5. Fluorescence microscopy experiments showed that hypoxic cardiomyocytes exposed to LDL(-), PLA2-LDL(+) and NEFA-LDL(+) have an increased production of reactive oxygen species (ROS). By treating hypoxic cardiomyocytes with WY-14643 (PPARα agonist), Plin5 remained high. In this situation, LDL(-) failed to enhance intracellular NEFA concentration and ROS production. In conclusion, these results show that Plin5 deficiency in hypoxic cardiomyocytes exposed to LDL(-) dramatically increases the levels of unpacked NEFA and ROS.

sST2 levels are associated with all‐cause mortality in anticoagulated patients with atrial fibrillation

Atrial fibrillation (AF) is associated with high morbidity and mortality, even despite the use of oral anticoagulation (OAC). Soluble suppression of tumorigenicity‐2 (sST2) is a member of the interleukin‐1 receptor family [interleukin‐1 receptor‐like 1 (IL1RL1)], which has been associated with an increased risk of mortality and morbidity in heart failure or acute coronary syndrome. We assessed the predictive value of sST2 levels in an unselected ‘real‐world’ cohort of anticoagulated AF patients.

Soluble LRP1 is an independent biomarker of epicardial fat volume in patients with type 1 diabetes mellitus

Epicardial adipose tissue (EAT) is a metabolically active tissue intimately associated with metabolic syndrome and cardiovascular disease. Quantification of EAT volume is an interesting clinical tool for the evaluation of cardiometabolic disease. Nevertheless, current methodology presents serious disadvantages. The soluble form of the receptor LRP1 (sLRP1) is a non-invasive biomarker of EAT in general population. Here, we analysed the potential of circulating sLRP1 as biomarker of EAT volume in patients with type 1 diabetes mellitus (T1DM). The study included a well-characterized cohort of T1DM patients without clinical cardiovascular disease (N = 73). EAT volume was assessed by a multidetector computed tomography (MDCT). sLRP1 and panel of inflammatory and endocrine mediators were measured using commercially available ELISA. EAT volume showed a direct association with circulating sLRP1 (β = 0.398, P = 0.001) in univariate linear regression analysis. This association was higher than that observed for other potential inflammatory and endocrine biomarkers. Using multivariate linear regression analyses, we demonstrated that the association between EAT volume and circulating sLRP1 was independent of potential confounding factors, including age, sex, body mass index, CRP, HbA1c and LDL-C (P < 0.050 for all multivariate linear regression models). In conclusion, sLRP1 is an independent biomarker of EAT in T1DM patients.

Thermal stability of human plasma electronegative low-density lipoprotein: A paradoxical behavior of low-density lipoprotein aggregation.

Low-density lipoprotein (LDL) aggregation is central in triggering atherogenesis. A minor fraction of electronegative plasma LDL, termed LDL(-), plays a special role in atherogenesis. To better understand this role, we analyzed the kinetics of aggregation, fusion and disintegration of human LDL and its fractions, LDL(+) and LDL(-). Thermal denaturation of LDL was monitored by spectroscopy and electron microscopy. Initially, LDL(-) aggregated and fused faster than LDL(+), but later the order reversed. Most LDL(+) disintegrated and precipitated upon prolonged heating. In contrast, LDL(-) partially retained lipoprotein morphology and formed soluble aggregates. Biochemical analysis of all fractions showed no significant degradation of major lipids, mild phospholipid oxidation, and an increase in non-esterified fatty acid (NEFA) upon thermal denaturation. The main baseline difference between LDL subfractions was higher content of NEFA in LDL(-). Since NEFA promote lipoprotein fusion, increased NEFA content can explain rapid initial aggregation and fusion of LDL(-) but not its resistance to extensive disintegration. Partial hydrolysis of apoB upon heating was similar in LDL subfractions, suggesting that minor proteins importantly modulate LDL disintegration. Unlike LDL(+), LDL(-) contains small amounts of apoA-I and apoJ. Addition of exogenous apoA-I to LDL(+) hampered lipoprotein aggregation, fusion and precipitation, while depletion of endogenous apoJ had an opposite effect. Therefore, the initial rapid aggregation of LDL(-) is apparently counterbalanced by the stabilizing effects of minor proteins such as apoA-I and apoJ. These results help identify key determinants for LDL aggregation, fusion and coalescence into lipid droplets in vivo.

ATRIAL MYOCARDIAL INFARCTION INDUCED DURING ELECTIVE PERCUTANEOUS CORONARY INTERVENTION

Accidental occlusion of atrial coronary artery branches during percutaneous coronary intervention (PCI) may lead to atrial myocardial infarction, but this complication has not been systematically analyzed. This study aimed to prospectively characterize the incidence and consequences of atrial branch