Fatty acid-derived lipid mediators and blood platelet aggregation

Plasma lipids are dysregulated preceding diagnosis of preeclampsia or delivery of a growth restricted infant

BACKGROUND

Lipids serve as multifunctional metabolites that have important implications for the pregnant mother and developing fetus. Abnormalities in lipids have emerged as potential risk factors for pregnancy diseases, such as preeclampsia and fetal growth restriction. The aim of this study was to assess the potential of lipid metabolites for detection of late-onset preeclampsia and fetal growth restriction.

METHODS

We used a case-cohort of 144 maternal plasma samples at 36 weeks' gestation from patients before the diagnosis of late-onset preeclampsia (n = 22), delivery of a fetal growth restricted infant (n = 55, defined as <5th birthweight centile), gestation-matched controls (n = 72). We performed liquid chromatography-tandem mass spectrometry (LC-QQQ) -based targeted lipidomics to identify 421 lipids, and fitted logistic regression models for each lipid, correcting for maternal age, BMI, smoking, and gestational diabetes.

FINDINGS

Phosphatidylinositol 32:1 (AUC = 0.81) and cholesterol ester 17:1 (AUC = 0.71) best predicted the risk of developing preeclampsia or delivering a fetal growth restricted infant, respectively. Five times repeated five-fold cross validation demonstrated the lipids alone did not out-perform existing protein biomarkers, soluble tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) for the prediction of preeclampsia or fetal growth restriction. However, lipids combined with sFlt-1 and PlGF measurements improved disease prediction.

INTERPRETATION

This study successfully identified 421 lipids in maternal plasma collected at 36 weeks' gestation from participants who later developed preeclampsia or delivered a fetal growth restricted infant. Our results suggest the predictive capacity of lipid measurements for gestational disorders holds the potential to improve non-invasive assessment of maternal and fetal health.

FUNDING

This study was funded by a grant from National Health and Medical Research Council.

A Phytoprostane from Gracilaria longissima Increases Platelet Activation, Platelet Adhesion to Leukocytes and Endothelial Cell Migration by Potential Binding to EP3 Prostaglandin Receptor

Plant phytoprostanes (PhytoPs) are lipid oxidative stress mediators that share structural similarities with mammal prostaglandins (PGs). They have been demonstrated to modulate inflammatory processes mediated by prostaglandins. The present study aims to test the effects of the most abundant oxylipin from Gracilaria longissima, ent-9-D1t-Phytoprostane (9-D1t-PhytoP), on platelet activation and vascular cells as well as clarify possible interactions with platelets and the endothelial EP3 receptor Platelet and monocyte activation was assessed by flow cytometry in the presence of purified 9-D1t-PhytoP. Cell migration was studied using the human Ea.hy926 cell line by performing a scratch wound healing assay. The RNA expression of inflammatory markers was evaluated by RT-PCR under inflammatory conditions. Blind docking consensus was applied to the study of the interactions of selected ligands against the EP3 receptor protein. The 9D1t-PhytoP exerts several pharmacological effects; these include prothrombotic and wound-healing properties. In endothelial cells, 9D1t-PhytP mimics the migration stimulus of PGE₂. Computational analysis revealed that 9D1t-PhytP forms a stable complex with the hydrophobic pocket of the EP3 receptor by interaction with the same residues as misoprostol and prostaglandin E₂ (PGE₂), thus supporting its potential as an EP3 agonist. The potential to form procoagulant platelets and the higher endothelial migration rate of the 9-D1t-PhytoP, together with its capability to interact with PGE₂ main target receptor in platelets suggest herein that this oxylipin could be a strong candidate for pharmaceutical research from a multitarget perspective.

Evidence showing lipotoxicity worsens outcomes in covid-19 patients and insights about the underlying mechanisms

We compared three hospitalized patient cohorts and conducted mechanistic studies to determine if lipotoxicity worsens COVID-19. Cohort-1 (n = 30) compared COVID-19 patients dismissed home to those requiring intensive-care unit (ICU) transfer. Cohort-2 (n = 116) compared critically ill ICU patients with and without COVID-19. Cohort-3 (n = 3969) studied hypoalbuminemia and hypocalcemia’s impact on COVID-19 mortality. Patients requiring ICU transfer had higher serum albumin unbound linoleic acid (LA). Unbound fatty acids and LA were elevated in ICU transfers, COVID-19 ICU patients and ICU non-survivors. COVID-19 ICU patients (cohort-2) had greater serum lipase, damage-associated molecular patterns (DAMPs), cytokines, hypocalcemia, hypoalbuminemia, organ failure and thrombotic events. Hypocalcemia and hypoalbuminemia independently associated with COVID-19 mortality in cohort-3. Experimentally, LA reacted with albumin, calcium and induced hypocalcemia, hypoalbuminemia in mice. Endothelial cells took up unbound LA, which depolarized their mitochondria. In mice, unbound LA increased DAMPs, cytokines, causing endothelial injury, organ failure and thrombosis. Therefore, excessive unbound LA in the circulation may worsen COVID-19 outcomes.

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Three cohorts of hospitalized COVID-19 patients with different severities were studied

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Severe COVID-19 increased serum linoleic acid (LA) and unbound fatty acid levels

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Endothelial cell uptake of unbound LA dose-dependently depolarized mitochondria

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Unbound LA increased cytokines, endothelial injury, organ failure and thrombosis

Ontogeny of circulating lipid metabolism in pregnancy and early childhood: a longitudinal population study

Background: There is mounting evidence that in utero and early life exposures may predispose an individual to metabolic disorders in later life; and dysregulation of lipid metabolism is critical in such outcomes. However, there is limited knowledge about lipid metabolism and factors causing lipid dysregulation in early life that could result in adverse health outcomes in later life. We studied the effect of antenatal factors such as gestational age, birth weight and mode of birth on lipid metabolism at birth; changes in the circulating lipidome in the first four years of life and the effect of breastfeeding in the first year of life. From this study, we aim to generate a framework for deeper understanding into factors effecting lipid metabolism in early life, to provide early interventions for those at risk of developing metabolic disorders including cardiovascular diseases.

Methods and findings: We performed comprehensive lipid profiling of 1074 mother-child dyads in the Barwon Infant Study (BIS), a population based pre-birth cohort and measured 776 distinct lipid species across 42 lipid classes using ultra high-performance liquid chromatography (UHPLC). We measured lipids in 1032 maternal serum samples at 28 weeks' gestation, 893 cord serum samples at birth, 793, 735, and 511 plasma samples at six, twelve months, and four years, respectively. The lipidome differed between mother and newborn and changed markedly with increasing child's age. Cord serum was enriched with long chain poly-unsaturated fatty acids (LC-PUFAs), and corresponding cholesteryl esters relative to the maternal serum. Alkenylphosphatidylethanolamine species containing LC-PUFAs increased with child's age, whereas the corresponding lysophospholipids and triglycerides decreased. We performed regression analyses to investigate the associations of cord serum lipid species with antenatal factors: gestational age, birth weight, mode of birth and duration of labor. Majority of the cord serum lipids were strongly associated with gestational age and birth weight, with most lipids showing opposing associations. Each mode of birth showed an independent association with cord serum lipids. Breastfeeding had a significant impact on the plasma lipidome in the first year of life, with upto 17-fold increases in a few species of alkyldiaclylglycerols at 6 months of age.

Conclusions: This study sheds light on lipid metabolism in infancy and early childhood and provide a framework to define the relationship between lipid metabolism and health outcomes in early childhood.

Funding Statement: This work was supported by the A*STAR-NHMRC joint call funding (1711624031).

Eicosanoid blood vessel regulation in physiological and pathological states

Arachidonic acid can be metabolized in blood vessels by three primary enzymatic pathways; cyclooxygenase (COX), lipoxygenase (LO), and cytochrome P450 (CYP). These eicosanoid metabolites can influence endothelial and vascular smooth muscle cell function. COX metabolites can cause endothelium-dependent dilation or constriction. Prostaglandin I2 (PGI2) and thromboxane (TXA2) act on their respective receptors exerting opposing actions with regard to vascular tone and platelet aggregation. LO metabolites also influence vascular tone. The 12-LO metabolite 12S-hydroxyeicosatrienoic acid (12S-HETE) is a vasoconstrictor whereas the 15-LO metabolite 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA) is an endothelial-dependent hyperpolarizing factor (EDHF). CYP enzymes produce two types of eicosanoid products: EDHF vasodilator epoxyeicosatrienoic acids (EETs) and the vasoconstrictor 20-HETE. The less-studied cross-metabolites generated from arachidonic acid metabolism by multiple pathways can also impact vascular function. Likewise, COX, LO, and CYP vascular eicosanoids interact with paracrine and hormonal factors such as the renin-angiotensin system and endothelin-1 (ET-1) to maintain vascular homeostasis. Imbalances in endothelial and vascular smooth muscle cell COX, LO, and CYP metabolites in metabolic and cardiovascular diseases result in vascular dysfunction. Restoring the vascular balance of eicosanoids by genetic or pharmacological means can improve vascular function in metabolic and cardiovascular diseases. Nevertheless, future research is necessary to achieve a more complete understanding of how COX, LO, CYP, and cross-metabolites regulate vascular function in physiological and pathological states.

Platelet lipidome: Dismantling the "Trojan horse" in the bloodstream

The platelet-lipid chapter in the story of atherothrombosis is an old one, recapitulated and revised in many contexts. For decades several stimulating facets have been added to it, both unraveling and increasing the perplexity of platelet-lipid interplay and its pathophysiological consequences. The recent paradigm shift in our perspective has evolved with lipidomic analysis of the intraplatelet compartment and platelet releasate. These investigations have disclosed that platelets are in constant interaction with circulatory lipids, often reflected in their lipid repertoire. In addition, they offer a shielded intracellular space for oxidative lipid metabolism generating "toxic" metabolites that escape degradation by plasma lipases and antioxidant defense, circulate undetected by conventional plasma lipid profile, and deposited at atherosclerotic lesions or thrombus. Lipidomics divulges this silent invader in platelet vehicles, thereby providing potential biomarkers of pathologic manifestations and therapeutic targets to be exploited, which is surmised in this review.

The importance of blood platelet lipid signaling in thrombosis and in sepsis

Blood platelets are the first line of defense against hemorrhages and are also strongly involved in the processes of arterial thrombosis, a leading cause of death worldwide. Besides their well-established roles in hemostasis, vascular wall repair and thrombosis, platelets are now recognized as important players in other processes such as inflammation, healing, lymphangiogenesis, neoangiogenesis or cancer. Evidence is accumulating they are key effector cells in immune and inflammatory responses to host infection. To perform their different functions platelets express a wide variety of membrane receptors triggering specific intracellular signaling pathways and largely use lipid signaling systems. Lipid metabolism is highly active in stimulated platelets including the phosphoinositide metabolism with the phospholipase C (PLC) and the phosphoinositide 3-kinase (PI3K) pathways but also other enzymatic systems producing phosphatidic acid, lysophosphatidic acid, platelet activating factor, sphingosine 1-phosphate and a number of eicosanoids. While several of these bioactive lipids regulate intracellular platelet signaling mechanisms others are released by activated platelets acting as autocrine and/or paracrine factors modulating neighboring cells such as endothelial and immune cells. These bioactive lipids have been shown to play important roles in hemostasis and thrombosis but also in vessel integrity and dynamics, inflammation, tissue remodeling and wound healing. In this review, we will discuss some important aspects of platelet lipid signaling in thrombosis and during sepsis that is an important cause of death in intensive care unit. We will particularly focus on the implication of the different isoforms of PI3Ks and on the generation of eicosanoids released by activated platelets.

Shotgun lipidomics in substantiating lipid peroxidation in redox biology: Methods and applications

Multi-dimensional mass spectrometry-based shotgun lipidomics (MDMS-SL) has made profound advances for comprehensive analysis of cellular lipids. It represents one of the most powerful tools in analyzing lipids directly from lipid extracts of biological samples. It enables the analysis of nearly 50 lipid classes and thousands of individual lipid species with high accuracy/precision. The redox imbalance causes oxidative stress, resulting in lipid peroxidation, and alterations in lipid metabolism and homeostasis. Some lipid classes such as oxidized fatty acids, 4-hydroxyalkenal species, and plasmalogen are sensitive to oxidative stress or generated corresponding to redox imbalance. Therefore, accurate assessment of these lipid classes can provide not only the redox states, but also molecular insights into the pathogenesis of diseases. This review focuses on the advances of MDMS-SL in analysis of these lipid classes and molecular species, and summarizes their recent representative applications in biomedical/biological research. We believe that MDMS-SL can make great contributions to redox biology through substantiating the aberrant lipid metabolism, signaling, trafficking, and homeostasis under oxidative stress-related condition.

Module-based association analysis for omics data with network structure

Module-based analysis (MBA) aims to evaluate the effect of a group of biological elements sharing common features, such as SNPs in the same gene or metabolites in the same pathways, and has become an attractive alternative to traditional single bio-element approaches. Because bio-elements regulate and interact with each other as part of network, incorporating network structure information can more precisely model the biological effects, enhance the ability to detect true associations, and facilitate our understanding of the underlying biological mechanisms. However, most MBA methods ignore the network structure information, which depicts the interaction and regulation relationship among basic functional units in biology system. We construct the connectivity kernel and the topology kernel to capture the relationship among bio-elements in a module, and use a kernel machine framework to evaluate the joint effect of bio-elements. Our proposed kernel machine approach directly incorporates network structure so to enhance the study efficiency; it can assess interactions among modules, account covariates, and is computational efficient. Through simulation studies and real data application, we demonstrate that the proposed network-based methods can have markedly better power than the approaches ignoring network information under a range of scenarios.

Anti-platelet activity of water dispersible curcuminoids in rat platelets

Curcuminoids are active principle of turmeric with plethora of health beneficial properties. In this study, we have evaluated for the first time the effect of water dispersible curcuminoids on rat platelet aggregation. Curcuminoids (10-30 µg/mL) significantly inhibited platelet aggregation induced by agonists viz., collagen, ADP and arachidonic acid. Curcuminoids were found to be two-fold more potent than curcumin in inhibiting platelet aggregation. Intracellular curcuminoid concentration was relatively higher than curcumin in rat platelets. Curcuminoids significantly attenuated thromboxane A2 , serotonin levels in rat platelets which play an important role in platelet aggregation. Curcuminoid treatment increased nitric oxide (NO) levels in platelets treated with agonists. Curcuminoids inhibited free radicals such as superoxide anion released from activated platelets, which ultimately inhibits platelet aggregation. Further, curcuminoids inhibited 12-lipoxygenase activity and formation of 12-hydroperoxyeicosatetraenoic acid (12-HPETE) in activated rat platelets which regulates platelet aggregation. The results suggest that curcuminoids have remarkable anti-platelet activity by modulating multiple mechanisms involved in platelet aggregation. Thus curcuminoids may have a therapeutic potential to prevent platelet activation related disorders.

Treatment of dyslipidemia in allogeneic hematopoietic stem cell transplant patients

As survival rates in allogeneic hematopoietic stem cell transplantation (HSCT) continue to improve, attention to long-term complications, including cardiovascular disease, becomes a major concern. Cardiovascular disease and dyslipidemia are a common, yet often overlooked occurrence post-HSCT that results in significant morbidity and mortality. Also, increasing evidence shows that several anti-hyperlipidemia medications, the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors in particular, may have a role in modulating graft-versus-host disease (GVHD). However, factors such as drug-drug interactions, adverse effect profiles, and the relative efficacy in lowering cholesterol and triglyceride levels must be taken into account when choosing safe and effective lipid-lowering therapy in this setting. This review seeks to provide guidance to the clinician in the management of dyslipidemia in the allogeneic HSCT population, taking into account the recently published American College of Cardiology/American Heart Association guidelines on hyperlipidemia management, special considerations in this challenging population, and the evidence for each agent's potential role in modulating GVHD.

Dietary manipulation of platelet function

Activated platelets contribute to plaque formation within blood vessels in the early and late stages of atherogenesis, and therefore they have been proposed as risk factor for cardiovascular disease. Anti-platelet drugs, such as aspirin, are now the most prescribed pharmacological treatment in Europe. Certain dietary bioactives also beneficially affect platelet function, and with less side effects, albeit that effects are generally more subtle. Therefore, consumption of dietary bioactives could play a role in the prevention of atherothrombotic vascular disease. Here we review the efficacy of dietary treatment strategies, especially those involving certain dietary fatty acids and polyphenols, to modulate platelet function in healthy subjects or in patients with cardiovascular disease. Variation in study populations, small study sizes and lack of comparability between methods to assess platelet function currently limit robust evidence on the efficacy of dietary bioactives in healthy subjects or specific patient groups. Also, limited knowledge of the metabolism of dietary bioactives, and therefore of the bioavailability of bioactive ingredients, restricts our ability to identify the most effective dietary regimes to improve platelet function. Implementation of uniform point-of-care tests to assess platelet function, and enhanced knowledge of the efficacy by which specific dietary compounds and their metabolites affect platelet function, may enable the identification of functional anti-platelet ingredients that are eligible for a health claim, or combined treatment strategies, including both pharmacological anti-platelet treatment as well as dietary intervention, to tackle atherothrombotic vascular disease.

Plasma and serum lipidomics of healthy white adults shows characteristic profiles by subjects' gender and age

Blood is a commonly used biofluid for biomarker discovery. Although blood lipid metabolites are considered to be potential biomarker candidates, their fundamental properties are not well characterized. We aimed to (1) investigate the matrix type (serum vs. plasma) that may be preferable for lipid biomarker exploration, (2) elucidate age- and gender-associated differences in lipid metabolite levels, and (3) examine the stability of lipid metabolites in matrix samples subjected to repeated freeze-thaw cycles. Using liquid chromatography-mass spectrometry, we performed lipidomic analyses for fasting plasma and serum samples for four groups (15 subjects/group) of young and elderly (25-34 and 55-64 years old, respectively) males and females and for an additional aliquot of samples from young males, which were subjected to repeated freeze-thaw cycles. Lysophosphatidylcholine and diacylglycerol levels were higher in serum than in plasma samples, suggesting that the clotting process influences serum lipid metabolite levels. Gender-associated differences highlighted that the levels of many sphingomyelin species were significantly higher in females than in males, irrespective of age and matrix (plasma and serum). Age-associated differences were more prominent in females than in males, and in both matrices, levels of many triacylglycerols were significantly higher in elderly females than in young females. Plasma and serum levels of most lipid metabolites were reduced by freeze-thawing. Our results indicate that plasma is an optimal matrix for exploring lipid biomarkers because it represents the original properties of an individual's blood sample. In addition, the levels of some blood lipid species of healthy adults showed gender- and age-associated differences; thus, this should be considered during biomarker exploration and its application in diagnostics. Our fundamental findings on sample selection and handling procedures for measuring blood lipid metabolites is important for ensuring the quality of biomarkers identified and its qualification process.

The emerging role of oxylipins in thrombosis and diabetes

The prevalence of cardiovascular disease (CVD), the leading cause of death in the US, is predicted to increase due to the shift in age of the general population and increase in CVD risk factors such as obesity and diabetes. New therapies are required to decrease the prevalence of CVD risk factors (obesity and diabetes) as well as reduce atherothrombosis, the major cause of CVD related mortality. Oxylipins, bioactive metabolites derived from the oxygenation of polyunsaturated fatty acids, play a role in the progression of CVD risk factors and thrombosis. Aspirin, a cyclooxygenase-1 inhibitor, decreases atherothrombotic associated mortality by 25%. These potent effects of aspirin have shown the utility of modulating oxylipin signaling pathways to decrease CVD mortality. The role of many oxylipins in the progression of CVD, however, is still uncertain or controversial. An increased understanding of the role oxylipins play in CVD risk factors and thrombosis could lead to new therapies to decrease the prevalence of CVD and its associated mortality.

A novel class of fungal lipoxygenases

Lipoxygenases (LOXs) are well-studied enzymes in plants and mammals. However, fungal LOXs are less studied. In this study, we have compared fungal LOX protein sequences to all known characterized LOXs. For this, a script was written using Shell commands to extract sequences from the NCBI database and to align the sequences obtained using Multiple Sequence Comparison by Log-Expectation. We constructed a phylogenetic tree with the use of Quicktree to visualize the relation of fungal LOXs towards other LOXs. These sequences were analyzed with respect to the signal sequence, C-terminal amino acid, the stereochemistry of the formed oxylipin, and the metal ion cofactor usage. This study shows fungal LOXs are divided into two groups, the Ile- and the Val-groups. The Ile-group has a conserved WRYAK sequence that appears to be characteristic for fungal LOXs and has as a C-terminal amino acid Ile. The Val-group has a highly conserved WL-L/F-AK sequence that is also found in LOXs of plant and animal origin. We found that fungal LOXs with this conserved sequence have a Val at the C-terminus in contrast to other LOXs of fungal origin. Also, these LOXs have signal sequences implying these LOXs will be expressed extracellularly. Our results show that in this group, in addition to the Gaeumannomyces graminis and the Magnaporthe salvinii LOXs, the Aspergillus fumigatus LOX uses manganese as a cofactor.

Plasma and serum from nonfasting men and women differ in their lipidomic profiles

Biomarkers will play important roles in disease diagnosis, drug development, and the proper use of drugs. Blood is considered the best biofluid for biomarker research because it is easy to access and a wealth of data are available. However, previous studies revealed that several ionic metabolites showed different levels (including presence or absence) in plasma and serum. Thus, attention should be paid to selecting the best biofluid for biomarker exploration. Many lipid molecules have biological significance and thus would be candidate biomarkers. However, no comprehensive study revealing differences in lipid metabolite levels between plasma and serum has been undertaken. Furthermore, gender differences have not been reported. To clarify the difference in the levels of lipid metabolites between human plasma and serum from both genders, we performed lipid metabolomic analysis using liquid chromatography-mass spectrometry-based systems for phospholipids (PLs), lysoPLs, sphingomyelins, ceramides and oxidative fatty acids. Our results revealed that most of the lipid metabolites were present at similar levels in plasma and serum and in males and females. However, several oxidative fatty acid metabolites showed differences. Of the metabolites related to clotting processes, three showed higher levels in serum than in plasma, and three were detected only in serum. Furthermore, four metabolites were present at different levels between males and females, and two were detected only in males. Thus, attention should be paid to the selection of plasma or serum when utilizing these lipid metabolites as biomarkers.

Characterization of platelet aminophospholipid externalization reveals fatty acids as molecular determinants that regulate coagulation

Aminophospholipid (APL) trafficking across the plasma membrane is a key event in cell activation, apoptosis, and aging and is required for clearance of dying cells and coagulation. Currently the phospholipid molecular species externalized are unknown. Using a lipidomic method, we show that thrombin, collagen, or ionophore-activated human platelets externalize two phosphatidylserines (PSs) and five phosphatidylethanolamines (PEs). Four percent of the total cellular PE/PS pool (∼300 ng/2 × 10(8) cells, thrombin), is externalized via calcium mobilization and protease-activated receptors-1 and -4, and 48% is contained in microparticles. Apoptosis and energy depletion (aging) externalized the same APLs in a calcium-dependent manner, and all stimuli externalized oxidized phospholipids, termed hydroxyeicosatetraenoic acid-PEs. Transmembrane protein-16F (TMEM-16F), the protein mutated in Scott syndrome, was required for PE/PS externalization during thrombin activation and energy depletion, but not apoptosis. Platelet-specific APLs optimally supported tissue factor-dependent coagulation in human plasma, vs. APL with longer or shorter fatty acyl chains. This finding demonstrates fatty acids as molecular determinants of APL that regulate hemostasis. Thus, the molecular species of externalized APL during platelet activation, apoptosis, and energy depletion were characterized, and their ability to support coagulation revealed. The findings have therapeutic implications for bleeding disorders and transfusion therapy. The assay could be applied to other cell events characterized by APL externalization, including cell division and vesiculation.

New families of bioactive oxidized phospholipids generated by immune cells: identification and signaling actions

Phospholipids are of critical importance in mammalian cell biology, both through providing a permeability barrier and acting as substrates for synthesis of lipid mediators. Recently, several new families of bioactive lipids were identified that form through the enzymatic oxidation of membrane phospholipids in circulating innate immune cells and platelets. These comprise eicosanoids attached to phosphatidylethanolamine and phosphatidylcholine and form within 2-5 minutes of cell activation by pathophysiologic agonists, via the coordinated action of receptors and enzymes. In this review, we summarize what is currently known regarding their structures, mechanisms of formation, cell biology, and signaling actions. We show that phospholipid oxidation by acutely activated immune cells is a controlled event, and we propose a central role in regulating membrane biology and innate immune function during health and disease. We also review the mass spectrometry methods used for identification of the lipids and describe how these approaches can be used for discovery of new lipid mediators in complex biologic samples.

Fatty acids in cardiovascular health and disease: a comprehensive update

Research dating back to the 1950s reported an association between the consumption of saturated fatty acids (SFAs) and risk of coronary heart disease. Recent epidemiological evidence, however, challenges these findings. It is well accepted that the consumption of SFAs increases low-density lipoprotein cholesterol (LDL-C), whereas carbohydrates, monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) do not. High-density lipoprotein (HDL)-C increases with SFA intake. Among individuals who are insulin resistant, a low-fat, high-carbohydrate diet typically has an adverse effect on lipid profiles (in addition to decreasing HDL-C, it also increases triglyceride and LDL particle concentrations). Consequently, a moderate fat diet in which unsaturated fatty acids replace SFAs and carbohydrates are not augmented is advised to lower LDL-C; compared with a low-fat diet, a moderate-fat diet will lower triglycerides and increase HDL-C. Now, there is some new evidence that is questioning the health benefits of even MUFAs and PUFAs. In addition, in a few recent studies investigators have also failed to demonstrate expected cardiovascular benefits of marine-derived omega-3 fatty acids. To clarify the clinical pros and cons of dietary fats, the National Lipid Association held a fatty acid symposium at the 2011 National Lipid Association Scientific Sessions. During these sessions, the science regarding the effects of different fatty acid classes on coronary heart disease risk was reviewed.

Why and How Meet n-3 PUFA Dietary Recommendations?

Obesity and the metabolic syndrome are systemic inflammatory diseases reaching epidemic proportions. Contemporary changes in human nutrition occurred characterized by increased consumption of fat and of vegetable oils rich in n-6 polyunsaturated fatty acids (PUFAs) together with decrease in n-3 PUFA-rich foods, resulting in an n-6/n-3 ratio of 10–20/1 in Western diet for a ratio around 1/1 in the diet of our ancestors. The literature provides compelling evidence for the health benefit of n-3 PUFA consumption on inflammation and metabolic syndrome prevention and treatment. Such evidence led to the establishment of comprehensive recommendations. However, we show here that, both in collective catering proposed to children and in hospital diet, it is not straightforward to meet such recommendations. Willingness of governments to institute changes, with accountable decisions on catering, nutritional education, and food processing, is required to face our neglected responsibility in promoting balanced diet and consumption of foods rich in essential nutrients in the general population.

Thrombin-activated human platelets acutely generate oxidized docosahexaenoic-acid-containing phospholipids via 12-lipoxygenase

Arachidonate-containing oxidized phospholipids are acutely generated by 12-LOX (12-lipoxygenase) in agonist-activated platelets. In the present study, formation of structurally related lipids by oxidation of DHA (docosahexaenoic acid)-containing phospholipids is demonstrated using lipidomic approaches. Precursor scanning reverse-phase LC (liquid chromatography)-MS/MS (tandem MS) identified a new family of lipids that comprise phospholipid-esterified HDOHE (hydroxydocosahexaenoic acid). Two diacyl and two plasmalogen PEs (phosphatidylethanolamines) containing predominantly the 14-HDOHE positional isomer (18:0p/14-HDOHE-PE, 18:0a/14-HDOHE-PE, 16:0a/14-HDOHE-PE and 16:0p/14-HDOHE-PE) were structurally characterized using MS/MS and by comparison with biogenic standards. An involvement of 12-LOX was indicated as purified recombinant human 12-LOX also generated the 14-HDOHE isomer from DHA. Pharmacological studies using inhibitors and recombinant platelet 12-LOX indicate that they form via esterification of newly formed non-esterified HDOHE. HDOHE-PEs formed at significant rates (2-4 ng/4×10(7) cells) within 2-180 min of thrombin stimulation, and their formation was blocked by calcium chelation. In summary, a new family of oxidized phospholipid was identified in thrombin-activated human platelets.