Phospholipase A(2) enzymes in metabolic and cardiovascular diseases

Transcriptomic analysis of diabetic kidney disease and neuropathy in mouse models of type 1 and type 2 diabetes

Diabetic kidney disease (DKD) and diabetic peripheral neuropathy (DPN) are common complications of type 1 (T1D) and type 2 (T2D) diabetes. However, the mechanisms underlying pathogenesis of these complications are unclear. In this study, we optimized a streptozotocin-induced db/+ murine model of T1D and compared it to our established db/db T2D mouse model of the same C57BLKS/J background. Glomeruli and sciatic nerve transcriptomic data from T1D and T2D mice were analyzed by self-organizing map and differential gene expression analysis. Consistent with prior literature, pathways related to immune function and inflammation were dysregulated in both complications in T1D and T2D mice. Gene-level analysis identified a high degree of concordance in shared differentially expressed genes (DEGs) in both complications and across diabetes type when using mice from the same cohort and genetic background. As we have previously shown a low concordance of shared DEGs in DPN when using mice from different cohorts and genetic backgrounds, this suggests that genetic background may influence diabetic complications. Collectively, these findings support the role of inflammation and indicate that genetic background is important in complications of both T1D and T2D.

Association of lipid composition and unsaturated fatty acids of VLDL with atrial remodeling in metabolic syndrome

Subjects with metabolic syndrome (MetS) commonly have atrial remodeling, which indicates a risk for atrial fibrillation. This study determined MetS-related changes in lipid components in very-low-density lipoprotein (VLDL), which has been shown to cause atrial remodeling, the effect of statins on these changes, and the correlation between atrial remodeling and VLDL lipid compositions. Blood samples were collected from 12 non-MetS and 27 sex- and age-matched MetS subjects. Fourteen patients with MetS (MetS-off statin) discontinued statin therapy 14 days before the study, while the remaining 13 remained on it (MetS-on statin). The VLDLs were isolated and processed for mass-based lipid profiling. Lipidomic analyses were performed and associated with atrial remodeling markers measured using standard echocardiography and electrocardiography. Compared with the VLDL components of the non-MetS group, glucosyl/galactosyl ceramide, lyso-phosphatidylcholine, lyso-phosphatidylethanolamine, and triglycerides were enriched in the MetS-off statin group. Statin therapy attenuated all abnormally abundant lipid classes in MetS, except for triglycerides. In addition, lyso-phosphatidylcholine, lyso-phosphatidylethanolamine, and triglycerides were significantly correlated with atrial dilatation, and the latter two were also correlated with the PR interval. Enrichment of double bonds, which indicate unsaturated fatty acids, was also significantly correlated with atrial remodeling and P-wave duration. This study suggests that the pathological lipid payload of MetS-VLDL may contribute to atrial remodeling in patients.

Role of Enterocyte Enpp2 and Autotaxin in Regulating Lipopolysaccharide Levels, Systemic Inflammation and Atherosclerosis

Conversion of lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA) by autotaxin, a secreted phospholipase D, is a major pathway for producing LPA. We previously reported that feeding Ldlr^-/- mice standard mouse chow supplemented with unsaturated LPA or LPC qualitatively mimicked the dyslipidemia and atherosclerosis induced by feeding a Western diet (WD). Here we report that adding unsaturated LPA to standard mouse chow also increased the content of reactive oxygen species (ROS) and oxidized phospholipids (OxPL) in jejunum mucus. To determine the role of intestinal autotaxin, enterocyte specific Ldlr^-/-/Enpp2 knockout (iKO) mice were generated. In control mice, the WD increased enterocyte Enpp2 expression and raised autotaxin levels. Ex vivo, addition of OxPL to jejunum from Ldlr^-/- mice on a chow diet induced expression of Enpp2. In control mice, the WD raised OxPL levels in jejunum mucus, and decreased gene expression in enterocytes for a number of peptides and proteins that affect antimicrobial activity. On the WD, the control mice developed elevated levels of LPS in jejunum mucus and plasma, with increased dyslipidemia and increased atherosclerosis. All of these changes were reduced in the iKO mice. We conclude that the WD increases the formation of intestinal OxPL, which i) induce enterocyte Enpp2 and autotaxin resulting in higher enterocyte LPA levels; that ii) contribute to the formation of ROS that help to maintain the high OxPL levels; iii) decrease intestinal antimicrobial activity; and iv) raise plasma LPS levels that promote systemic inflammation and enhance atherosclerosis.

Decoding the transcriptome of calcified atherosclerotic plaque at single-cell resolution

Atherogenesis involves an interplay of inflammation, tissue remodeling and cellular transdifferentiation (CTD), making it especially difficult to precisely delineate its pathophysiology. Here we use single-cell RNA sequencing and systems-biology approaches to analyze the transcriptional profiles of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) in calcified atherosclerotic core (AC) plaques and patient-matched proximal adjacent (PA) portions of carotid artery tissue from patients undergoing carotid endarterectomy. Our results reveal an anatomic distinction whereby PA cells express inflammatory mediators, while cells expressing matrix-secreting genes occupy a majority of the AC region. Systems biology analysis indicates that inflammation in PA ECs and VSMCs may be driven by TNFa signaling. Furthermore, we identify POSTN, SPP1 and IBSP in AC VSMCs, and ITLN1, SCX and S100A4 in AC ECs as possible candidate drivers of CTD in the atherosclerotic core. These results establish an anatomic framework for atherogenesis which forms the basis for exploration of a site-specific strategy for disruption of disease progression.

Single-cell RNA sequencing and systems biology are used to profile the human vascular cell populations in calcified atherosclerotic core plaques from carotid endarterectomy samples, showing an anatomic distinction between gene expression of inflammatory versus matrix-secreting factors.

Phospholipase A2, a nonnegligible enzyme superfamily in gastrointestinal diseases

Gastrointestinal tract is important for digestion, absorption, detoxification and immunity. Gastrointestinal diseases are mainly caused by the imbalance of protective and attacking factors in gastrointestinal mucosa, which can seriously harm human health. Phospholipase A₂ (PLA₂) is a large family closely involved in lipid metabolism and is found in almost all human cells. A growing number of studies have revealed that its metabolites are deeply implicated in various inflammatory pathways and also regulates the maintenance of numerous biological events such as dietary digestion, membrane remodeling, barrier action, and host immunity. In addition to their phospholipase activity, some members of the superfamily also have other catalytic activities. Based on the in-depth effects of phospholipase A2 on bioactive lipid metabolism and inflammatory cytokines, PLA₂ and its metabolites are likely to be involved in the pathogenesis, development or prevention of gastrointestinal diseases. Therefore, this review will focus on the physiological and pathogenic roles of several important PLA₂ enzymes in the gastrointestinal tract, and reveals the potential of PLA₂ as a therapeutic target for gastrointestinal diseases.

Peroxiredoxins as Potential Targets for Cardiovascular Disease

Increased oxidative stress (OS) is considered a common etiology in the pathogenesis of cardiovascular disease (CVD). Therefore, the precise regulation of reactive oxygen species (ROS) in cardiovascular cells is essential to maintain normal physiological functions. Numerous regulators of cellular homeostasis are reportedly influenced by ROS. Hydrogen peroxide (H₂O₂), as an endogenous ROS in aerobic cells, is a toxic substance that can induce OS. However, many studies conducted over the past two decades have provided substantial evidence that H₂O₂ acts as a diffusible intracellular signaling messenger. Antioxidant enzymes, including superoxide dismutases, catalase, glutathione peroxidases, and peroxiredoxins (Prdxs), maintain the balance of ROS levels against augmentation of ROS production during the pathogenesis of CVD. Especially, Prdxs are regulatory sensors of transduced intracellular signals. The intracellular abundance of Prdxs that specifically react with H₂O₂ act as regulatory proteins. In this review, we focus on the role of Prdxs in the regulation of ROS-induced pathological changes in the development of CVD.

Analysis of the uterine lumen in fertility-classified heifers: I. Glucose, prostaglandins, and lipids†

Survival and growth of the bovine conceptus (embryo and associated extraembryonic membranes) are dependent on endometrial secretions or histotroph found in the uterine lumen. Previously, serial embryo transfer was used to classify heifers as high fertile (HF), subfertile (SF), or infertile (IF). Here, we investigated specific histotroph components [glucose, prostaglandins (PGs), and lipids] in the uterine lumen of day 17 pregnant and open fertility-classified heifers. Concentrations of glucose in the uterine lumen were increased by pregnancy but did not differ among fertility-classified heifers. Differences in expression of genes encoding glucose transporters and involved with glycolysis and gluconeogenesis were observed between conceptuses collected from HF and SF heifers. In the uterine lumen, PGE2 and PGF2α were increased by pregnancy, and HF heifers had higher concentrations of PGE2, PGF2α, and 6-keto-PFG1α than SF heifers. Differences were found in expression of genes regulating PG signaling, arachidonic acid metabolism, and peroxisome proliferator-activated receptor signaling among conceptuses and endometrium from fertility-classified heifers. Lipidomics was conducted exclusively in samples from HF heifers, and phosphatidylcholine was the main lipid class that increased in the uterine lumen by pregnancy. Expression of several lipid metabolism genes differed between HF and SF conceptuses, and a number of fatty acids were differentially abundant in the uterine lumen of pregnant HF and SF heifers. These results support the ideas that uterine luminal histotroph impacts conceptus survival and programs its development and is a facet of dysregulated conceptus-endometrial interactions that result in loss of the conceptus in SF cattle during the implantation period of pregnancy establishment.

Lipid Receptor G2A-Mediated Signal Pathway Plays a Critical Role in Inflammatory Response by Promoting Classical Macrophage Activation

Macrophage polarization is a dynamic and integral process in tissue inflammation and remodeling. In this study, we describe that lipoprotein-associated phospholipase A₂ (Lp-PLA₂) plays an important role in controlling inflammatory macrophage (M1) polarization in rodent experimental autoimmune encephalomyelitis (EAE) and in monocytes from multiple sclerosis (MS) patients. Specific inhibition of Lp-PLA₂ led to an ameliorated EAE via markedly decreased inflammatory and demyelinating property of M1. The effects of Lp-PLA₂ on M1 function were mediated by lysophosphatidylcholine, a bioactive product of oxidized lipids hydrolyzed by Lp-PLA₂ through JAK2-independent activation of STAT5 and upregulation of IRF5. This process was directed by the G2A receptor, which was only found in differentiated M1 or monocytes from MS patients. M1 polarization could be inhibited by a G2A neutralizing Ab, which led to an inhibited disease in rat EAE. In addition, G2A-deficient rats showed an ameliorated EAE and an inhibited autoimmune response. This study has revealed a mechanism by which lipid metabolites control macrophage activation and function, modification of which could lead to a new therapeutic approach for MS and other inflammatory disorders.

A new trick for an old dog? Myocardial-specific roles for prostaglandins as mediators of ischemic injury and repair

The small lipid-derived paracrine signaling molecules known as prostaglandins have been recognized for their ability to modulate many facets of cardiovascular physiology since their initial discovery more than 85 years ago. Although the role of prostaglandins in the vasculature has gained significant attention across time, a handful of historical studies have also directly implicated the cardiomyocyte in both prostaglandin synthesis and release. Recently, our understanding of how prostaglandin receptor modulation impacts and contributes to myocardial structure and function has gained attention while leaving most other components of myocardial prostaglandin metabolism and signaling unexplored. This mini-review highlights both the key historical studies that underpin modern prostaglandin research in the heart, while concurrently presenting the latest findings related to how prostaglandin metabolism and signaling impact myocardial injury and repair.

Metabolomics Insights into Oleate-Induced Disorders of Phospholipid Metabolism in Macrophages

BACKGROUND

Diet-induced disordered phospholipid metabolism and disturbed macrophage metabolism contribute to the pathogenesis of metabolic diseases. However, the effects of oleate, a main dietary fatty acid, on macrophage phospholipid metabolism are unclear.

OBJECTIVES

We aimed to discover oleate-induced disorders of macrophage phospholipid metabolism and potential therapeutic targets for treating diet-related metabolic diseases.

METHODS

RAW 264.7 cells were exposed to 65 μg oleate/mL, within the blood concentration range of humans and mice, to trigger disorders of phospholipid metabolism. Meanwhile, WY-14643 and pioglitazone, 2 drugs widely used for treating metabolic diseases, were employed to prevent oleate-induced disorders of macrophage phospholipid metabolism. Subsequently, an untargeted metabolomics approach based on liquid chromatography-mass spectrometry was used to discover relevant metabolic disorders and potential therapeutic targets.

RESULTS

We showed that 196 metabolites involved in phospholipid metabolism were altered upon oleate treatment and interventions of WY-14643 and pioglitazone (P < 0.05, 2-tailed Mann-Whitney U test). Notably, most lysophospholipids were decreased, whereas most phospholipids were increased in oleate-treated macrophages. Phosphatidylethanolamines accumulated most among phospholipids, and their acyl chain polyunsaturation increased in oleate-treated macrophages. Additionally, saturated fatty acids were decreased, whereas polyunsaturated fatty acids were increased in oleate-treated macrophages. Furthermore, changes in phosphatidylglycerols, phosphatidylinositols, cardiolipins, phosphatidates, lysophosphatidylglycerols, and acylcarnitines in oleate-treated macrophages could be attenuated or even abolished by WY-14643 and/or pioglitazone treatment.

CONCLUSIONS

Oleate induced accumulation of various phospholipids, increased acyl chain polyunsaturation of phosphatidylethanolamines, and decreased lysophospholipids in RAW 264.7 macrophages. This study suggests macrophage phospholipid and fatty acid metabolism as potential therapeutic targets for intervening diet-related metabolic diseases.

The phospholipase A2 family's role in metabolic diseases: Focus on skeletal muscle

The prevalence of obesity and type 2 diabetes has increased substantially in recent years creating a global health burden. In obesity, skeletal muscle, the main tissue responsible for insulin-mediated glucose uptake, exhibits dysregulation of insulin signaling, glucose uptake, lipid metabolism, and mitochondrial function, thus, promoting type 2 diabetes. The phospholipase A2 (PLA2) enzyme family mediates lipid signaling and membrane remodeling and may play an important role in metabolic disorders such as obesity, diabetes, hyperlipidemia, and fatty liver disease. The PLA2 family consists of 16 members clustered in four groups. PLA2s hydrolyze the sn-2 ester bond of phospholipids generating free fatty acids and lysophospholipids. Differential tissue and subcellular PLA2 expression patterns and the abundance of distinct fatty acyl groups in the target phospholipid determine the impact of individual family members on metabolic functions and, potentially, diseases. Here, we update the current knowledge of the role of the PLA2 family in skeletal muscle, with a view to their potential for therapeutic targeting in metabolic diseases.

The correlation between lipoprotein associated phospholipase A2 and central overweight status

OBJECTIVE

Being overweight is associated with an increased risk of diabetes mellitus, hypertension, and cardiovascular disease. Lipoprotein-associated phospholipase A2 (Lp-PLA2) can independently predict the risk of cardiovascular disease. This study is aimed to investigate whether Lp-PLA2 was associated with an overweight status.

METHODS

This was a cross-sectional study that enrolled 3760 Chinese adults (age, 18-50 years) who underwent medical examination department of Xiamen Chang-Gung Hospital (XCGH) from 2018 to 2020. To explore the distribution of overweight classifications in the Chinese population, we evaluated the correlation of the overweight status with Lp-PLA2, after correcting for possible influencing factors.

RESULTS

The Lp-PLA2 level was greater in male than in female subjects (p < 0.001). Subjects with a central overweight status had a greater Lp-PLA2 level than those with normal weight and a peripheral overweight status, in both male and female cohorts. The Lp-PLA2 level was significantly greater in those with additional comorbidities (namely diabetes mellitus (DM), hypertension (HTN), overweight, and metabolic syndrome (MetS)). The age-adjusted and LDL-adjusted Lp-PLA2 level also was significantly higher in the DM (+) and HTN (-) subgroups than in the DM (-), HTN (-), DM (-), and HTN (+) subgroups.

CONCLUSION

Lp-PLA2 is associated with sex, central overweight status, diabetes, hypertension, and MetS in adults aged < 50 years and the age-adjusted and LDL-adjusted Lp-PLA2 was significantly higher in the DM (+) and HTN (-) subgroups than in the DM (-) and HTN (-) and DM (-) and HTN (+) subgroups.

A Representative GIIA Phospholipase A2 Activates Preadipocytes to Produce Inflammatory Mediators Implicated in Obesity Development

Adipose tissue secretes proinflammatory mediators which promote systemic and adipose tissue inflammation seen in obesity. Group IIA (GIIA)-secreted phospholipase A₂ (sPLA₂) enzymes are found to be elevated in plasma and adipose tissue from obese patients and are active during inflammation, generating proinflammatory mediators, including prostaglandin E₂ (PGE₂). PGE₂ exerts anti-lipolytic actions and increases triacylglycerol levels in adipose tissue. However, the inflammatory actions of GIIA sPLA₂s in adipose tissue cells and mechanisms leading to increased PGE₂ levels in these cells are unclear. This study investigates the ability of a representative GIIA sPLA₂, MT-III, to activate proinflammatory responses in preadipocytes, focusing on the biosynthesis of prostaglandins, adipocytokines and mechanisms involved in these effects. Our results showed that MT-III induced biosynthesis of PGE₂, PGI₂, MCP-1, IL-6 and gene expression of leptin and adiponectin in preadipocytes. The MT-III-induced PGE₂ biosynthesis was dependent on cytosolic PLA₂ (cPLA₂)-α, cyclooxygenases (COX)-1 and COX-2 pathways and regulated by a positive loop via the EP₄ receptor. Moreover, MT-III upregulated COX-2 and microsomal prostaglandin synthase (mPGES)-1 protein expression. MCP-1 biosynthesis induced by MT-III was dependent on the EP4 receptor, while IL-6 biosynthesis was dependent on EP3 receptor engagement by PGE₂. These data highlight preadipocytes as targets for GIIA sPLA₂s and provide insight into the roles played by this group of sPLA₂s in obesity.

The effects of oxidative stress on the development of atherosclerosis

Atherosclerosis is a cardiovascular disease (CVD) known widely world wide. Several hypothesizes are suggested to be involved in the narrowing of arteries during process of atherogenesis. The oxidative modification hypothesis is related to oxidative and anti-oxidative imbalance and is the most investigated. The aim of this study was to review the role of oxidative stress in atherosclerosis. Furthermore, it describes the roles of oxidative/anti-oxidative enzymes and compounds in the macromolecular and lipoprotein modifications and in triggering inflammatory events. The reactive oxygen (ROS) and reactive nitrogen species (RNS) are the most important endogenous sources produced by non-enzymatic and enzymatic [myeloperoxidase (MPO), nicotinamide adenine dinucleotide phosphate (NADH) oxidase and lipoxygenase (LO)] reactions that may be balanced with anti-oxidative compounds [glutathione (GSH), polyphenols and vitamins] and enzymes [glutathione peroxidase (Gpx), peroxiredoxins (Prdx), superoxide dismutase (SOD) and paraoxonase (PON)]. However, the oxidative and anti-oxidative imbalance causes the involvement of cellular proliferation and migration signaling pathways and macrophage polarization leads to the formation of atherogenic plaques. On the other hand, the immune occurrences and the changes in extra cellular matrix remodeling can develop atherosclerosis process.

The Impact of 6-month Micronutrient Supplementation on Viral, Immunological, and Mental Health Profile of a Cohort of Highly Active Antiretroviral Therapy-Naive HIV-Positive Patients in Northern Nigeria

Background:

HIV is a chronic disease with inflammatory reactions involving numerous elements of the immune system, resulting in an increased risk for other physical and psychiatric morbidities. Micronutrients, some of which possess anti-inflammatory properties, may help prevent the development of psychological disorders such as anxiety and depression in people living with HIV disease.

Objectives:

This study examined the profile of viral load, CD4 cell count, C-reactive protein, anxiety, and depression among highly active antiretroviral therapy (HAART)-naive HIV-positive patients receiving micronutrient supplementation over a 6-month period.

Materials and Methods:

A total of ninety HAART-naïve HIV-infected patients completed the Hospital Anxiety Depression Scale. Their blood samples were taken for serum viral load, CD4 cell count, and C-reactive protein at baseline. They all received a micronutrient supplement for 6 months, and 68 participants who remained in treatment at 6 months were reassessed with the same parameters.

Results:

After 6 months of micronutrient supplementation, the participants were found to have statistically significantly lower mean scores on the anxiety (t-test = 2.970, P = 0.003) and depression (t-test = 3.843, P = 0.001) subscales. They also had statistically significantly lower median CD4 cell count (P = 0.00) and C-reactive protein serum measures (P = 0.04). The median viral load decreased although the difference was not statistically significant.

Conclusion:

Micronutrient supplementation may reduce inflammatory reactions, anxiety, and depression in HAART-naive HIV-infected persons.

Polyunsaturated Phospholipid Modified Membrane Degradation Catalyzed by a Secreted Phospholipase A2

To optimize the compositions of the lipid-based nanomedicine and to advance understanding of the roles of polyunsaturated phospholipids in biological membranes, this study examined the effects of polyunsaturated phospholipids on the degradation of giant unilamellar vesicles catalyzed by a secreted phospholipase A2 (sPLA₂) using fluorescence microscopy. Molecular interfacial packing, interaction, and degradation of the films containing various mixing ratios of saturated and polyunsaturated phospholipids were quantified using a Langmuir trough integrated with synchrotron X-ray surface scattering techniques. It was found that a high molar fraction (0.63 and above) of polyunsaturated phospholipids not only enhanced the rate of sPLA₂-catalyzed vesicle degradation but also changed the vesicle deformation process and degradation product morphology. Hydrolysis of the saturated phospholipids generated highly ordered liquid crystal domains, which was reduced or prohibited by the presence of the polyunsaturated phospholipids in the reactant film.

Small-molecule inhibitors as potential therapeutics and as tools to understand the role of phospholipases A2

Phospholipase A2 (PLA2) enzymes are involved in various inflammatory pathological conditions including arthritis, cardiovascular and autoimmune diseases. The regulation of their catalytic activity is of high importance and a great effort has been devoted in developing synthetic inhibitors. We summarize the most important small-molecule synthetic PLA2 inhibitors developed to target each one of the four major types of human PLA2 (cytosolic cPLA2, calcium-independent iPLA2, secreted sPLA2, and lipoprotein-associated LpPLA2). We discuss recent applications of inhibitors to understand the role of each PLA2 type and their therapeutic potential. Potent and selective PLA2 inhibitors have been developed. Although some of them have been evaluated in clinical trials, none reached the market yet. Apart from their importance as potential medicinal agents, PLA2 inhibitors are excellent tools to unveil the role that each PLA2 type plays in cells and in vivo. Modern medicinal chemistry approaches are expected to generate improved PLA2 inhibitors as new agents to treat inflammatory diseases.

Genome-wide DNA methylation profiling of human diabetic peripheral neuropathy in subjects with type 2 diabetes mellitus

DNA methylation is an epigenetic mechanism important for the regulation of gene expression, which plays a vital role in the interaction between genetic and environmental factors. Aberrant epigenetic changes are implicated in the pathogenesis of diabetes and diabetic complications, but the role of DNA methylation in diabetic peripheral neuropathy (DPN) is not well understood. Therefore, our aim in this study was to explore the role of DNA methylation in the progression of DPN in type 2 diabetes. We compared genome-wide DNA methylation profiles of human sural nerve biopsies from subjects with stable or improving nerve fibre counts to biopsies from subjects with progressive loss of nerve fibres. Nerve fibre counts were determined by comparing myelinated nerve fibre densities between an initial and repeat biopsy separated by 52 weeks. Subjects with significant nerve regeneration (regenerators) and subjects with significant nerve degeneration (degenerators) represent the two extreme DPN phenotypes. Using reduced representation bisulfite sequencing, we identified 3,460 differentially methylated CpG dinucleotides between the two groups. The genes associated with differentially methylated CpGs were highly enriched in biological processes that have previously been implicated in DPN such as nervous system development, neuron development, and axon guidance, as well as glycerophospholipid metabolism and mitogen-activated protein kinase (MAPK) signalling. These findings are the first to provide a comprehensive analysis of DNA methylation profiling in human sural nerves of subjects with DPN and suggest that epigenetic regulation has an important role in the progression of this prevalent diabetic complication.

Molecular interactions of phospholipid monolayers with a model phospholipase

The intrinsic overexpression of secretory phospholipase A2 (sPLA2) in various pro-inflammatory diseases and cancers has the potential to be exploited as a therapeutic strategy for diagnostics and treatment. To explore this potential and advance our knowledge of the role of sPLA2 in related diseases, it is necessary to systematically investigate the molecular interaction of the enzyme with lipids. By employing a Langmuir trough integrated with X-ray reflectivity and grazing incidence X-ray diffraction techniques, this study examined the molecular packing structure of 1,2-palmitoyl-sn-glycero-3-phosphocholine (DPPC) films before and after enzyme adsorption and enzyme-catalyzed degradation. Molecular interaction of sPLA2 (from bee venom) with the DPPC monolayer exhibited Ca2+ dependence. DPPC molecules at the interface without Ca2+ retained a monolayer organization; upon adsorption of sPLA2 to the monolayer the packing became tighter. In contrast, sPLA2-catalyzed degradation of DPPC occurred in the presence of Ca2+, leading to disruption of the ordered monolayer structure of DPPC. The interfacial film became a mixture of highly ordered multilayer domains of palmitic acid (PA) and loosely packed monolayer phase of 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (lysoPC) that potentially contained the remaining un-degraded DPPC. The redistribution of lipid degradation products into the third dimension, which produced multilayer PA domains, damaged the structural integrity of the original lipid layer and may explain the bursting of liposomes observed in other studies after a latency period of mixing liposomes with sPLA2. A quantitative understanding of the lipid packing and lipid-enzyme interaction provides an intuitive means of designing and optimizing lipid-related drug delivery systems.

Anti-inflammatory therapy for cardiovascular disease

Chronic subclinical inflammation is a central process in the pathogenesis of cardiovascular disease (CVD) and it has been linked with both the initiation and progression of atherosclerosis. Several pro-inflammatory cytokines, such as the C-reactive protein (CRP), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) have been described as independent risk factors for coronary heart disease and promoters of atherogenesis. Thus, extensive research is being conducted to assess the role of anti-inflammatory therapy in the primary and secondary prevention of CVD. Our review aims to provide the clinical and scientific data pertaining to the effects of different anti-inflammatory agents administered in patients with CVD.

Pancreatic and mucosal enzymes in choline phospholipid digestion

The digestion of choline phospholipids is important for choline homeostasis, lipid signaling, postprandial lipid and energy metabolism, and interaction with intestinal bacteria. The digestion is mediated by the combined action of pancreatic and mucosal enzymes. In the proximal small intestine, hydrolysis of phosphatidylcholine (PC) to 1-lyso-PC and free fatty acid (FFA) by the pancreatic phospholipase A₂ IB coincides with the digestion of the dietary triacylglycerols by lipases, but part of the PC digestion is extended and must be mediated by other enzymes as the jejunoileal brush-border phospholipase B/lipase and mucosal secreted phospholipase A₂ X. Absorbed 1-lyso-PC is partitioned in the mucosal cells between degradation and reacylation into chyle PC. Reutilization of choline for hepatic bile PC synthesis, and the reacylation of 1-lyso-PC into chylomicron PC by the lyso-PC-acyl-CoA-acyltransferase 3 are important features of choline recycling and postprandial lipid metabolism. The role of mucosal enzymes is emphasized by sphingomyelin (SM) being sequentially hydrolyzed by brush-border alkaline sphingomyelinase (alk-SMase) and neutral ceramidase to sphingosine and FFA, which are well absorbed. Ceramide and sphingosine-1-phosphate are generated and are both metabolic intermediates and important lipid messengers. Alk-SMase has anti-inflammatory effects that counteract gut inflammation and tumorigenesis. These may be mediated by multiple mechanisms including generation of sphingolipid metabolites and suppression of autotaxin induction and lyso-phosphatidic acid formation. Here we summarize current knowledge on the roles of pancreatic and mucosal enzymes in PC and SM digestion, and its implications in intestinal and liver diseases, bacterial choline metabolism in the gut, and cholesterol absorption.

Discovery, fine-mapping, and conditional analyses of genetic variants associated with C-reactive protein in multiethnic populations using the Metabochip in the Population Architecture using Genomics and Epidemiology (PAGE) study

C-reactive protein (CRP) is a circulating biomarker indicative of systemic inflammation. We aimed to evaluate genetic associations with CRP levels among non-European-ancestry populations through discovery, fine-mapping and conditional analyses. A total of 30 503 non-European-ancestry participants from 6 studies participating in the Population Architecture using Genomics and Epidemiology study had serum high-sensitivity CRP measurements and ∼200 000 single nucleotide polymorphisms (SNPs) genotyped on the Metabochip. We evaluated the association between each SNP and log-transformed CRP levels using multivariate linear regression, with additive genetic models adjusted for age, sex, the first four principal components of genetic ancestry, and study-specific factors. Differential linkage disequilibrium patterns between race/ethnicity groups were used to fine-map regions associated with CRP levels. Conditional analyses evaluated for multiple independent signals within genetic regions. One hundred and sixty-three unique variants in 12 loci in overall or race/ethnicity-stratified Metabochip-wide scans reached a Bonferroni-corrected P-value <2.5E-7. Three loci have no (HACL1, OLFML2B) or only limited (PLA2G6) previous associations with CRP levels. Six loci had different top hits in race/ethnicity-specific versus overall analyses. Fine-mapping refined the signal in six loci, particularly in HNF1A. Conditional analyses provided evidence for secondary signals in LEPR, IL1RN and HNF1A, and for multiple independent signals in CRP and APOE. We identified novel variants and loci associated with CRP levels, generalized known CRP associations to a multiethnic study population, refined association signals at several loci and found evidence for multiple independent signals at several well-known loci. This study demonstrates the benefit of conducting inclusive genetic association studies in large multiethnic populations.

New quinoxalinone inhibitors targeting secreted phospholipase A2 and α-glucosidase

Elevated blood glucose and increased activities of secreted phospholipase A2 (sPLA2) are strongly linked to coronary heart disease. In this report, our goal was to develop small heterocyclic compound that inhibit sPLA2. The title compounds were also tested against α-glucosidase and α-amylase. This array of enzymes was selected due to their implication in blood glucose regulation and diabetic cardiovascular complications. Therefore, two distinct series of quinoxalinone derivatives were synthesised; 3-[N'-(substituted-benzylidene)-hydrazino]-1H-quinoxalin-2-ones 3a-f and 1-(substituted-phenyl)-5H-[1,2,4]triazolo[4,3-a]quinoxalin-4-ones 4a-f. Four compounds showed promising enzyme inhibitory effect, compounds 3f and 4b-d potently inhibited the catalytic activities of all of the studied proinflammatory sPLA2. Compound 3e inhibited α-glucosidase (IC50 = 9.99 ± 0.18 µM); which is comparable to quercetin (IC50 = 9.93 ± 0.66 µM), a known inhibitor of this enzyme. Unfortunately, all compounds showed weak activity against α-amylase (IC50 > 200 µM). Structure-based molecular modelling tools were utilised to rationalise the SAR compared to co-crystal structures with sPLA2-GX as well as α-glucosidase. This report introduces novel compounds with dual activities on biochemically unrelated enzymes mutually involved in diabetes and its complications.

Weighted gene co-expression network analysis of expression data of monozygotic twins identifies specific modules and hub genes related to BMI

Background

The therapeutic management of obesity is challenging, hence further elucidating the underlying mechanisms of obesity development and identifying new diagnostic biomarkers and therapeutic targets are urgent and necessary. Here, we performed differential gene expression analysis and weighted gene co-expression network analysis (WGCNA) to identify significant genes and specific modules related to BMI based on gene expression profile data of 7 discordant monozygotic twins.

Results

In the differential gene expression analysis, it appeared that 32 differentially expressed genes (DEGs) were with a trend of up-regulation in twins with higher BMI when compared to their siblings. Categories of positive regulation of nitric-oxide synthase biosynthetic process, positive regulation of NF-kappa B import into nucleus, and peroxidase activity were significantly enriched within GO database and NF-kappa B signaling pathway within KEGG database. DEGs of NAMPT, TLR9, PTGS2, HBD, and PCSK1N might be associated with obesity. In the WGCNA, among the total 20 distinct co-expression modules identified, coral1 module (68 genes) had the strongest positive correlation with BMI (r = 0.56, P = 0.04) and disease status (r = 0.56, P = 0.04). Categories of positive regulation of phospholipase activity, high-density lipoprotein particle clearance, chylomicron remnant clearance, reverse cholesterol transport, intermediate-density lipoprotein particle, chylomicron, low-density lipoprotein particle, very-low-density lipoprotein particle, voltage-gated potassium channel complex, cholesterol transporter activity, and neuropeptide hormone activity were significantly enriched within GO database for this module. And alcoholism and cell adhesion molecules pathways were significantly enriched within KEGG database. Several hub genes, such as GAL, ASB9, NPPB, TBX2, IL17C, APOE, ABCG4, and APOC2 were also identified. The module eigengene of saddlebrown module (212 genes) was also significantly correlated with BMI (r = 0.56, P = 0.04), and hub genes of KCNN1 and AQP10 were differentially expressed.

Conclusion

We identified significant genes and specific modules potentially related to BMI based on the gene expression profile data of monozygotic twins. The findings may help further elucidate the underlying mechanisms of obesity development and provide novel insights to research potential gene biomarkers and signaling pathways for obesity treatment. Further analysis and validation of the findings reported here are important and necessary when more sample size is acquired.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4257-6) contains supplementary material, which is available to authorized users.

Intestinal phospholipid and lysophospholipid metabolism in cardiometabolic disease

PURPOSE OF REVIEW

Phospholipids are major constituents in the intestinal lumen after meal consumption. This article highlights current literature suggesting the contributory role of intestinal phospholipid metabolism toward cardiometabolic disease manifestation.

RECENT FINDINGS

Group 1b phospholipase A2 (PLA2g1b) catalyzes phospholipid hydrolysis in the intestinal lumen. The digestive product lysophospholipid, particularly lysophosphatidylcholine (LPC), has a direct role in mediating chylomicron assembly and secretion. The LPC in the digestive tract is further catabolized into lysophosphatidic acid and choline via autotaxin-mediated and autotaxin-independent mechanisms. The LPC and lysophosphatidic acid absorbed through the digestive tract and transported to the plasma directly promote systemic inflammation and cell dysfunction, leading to increased risk of cardiovascular disease and obesity/diabetes. The choline moiety generated in the digestive tract can also be used by gut bacteria to generate trimethylamine, which is subsequently transported to the liver and oxidized into trimethylamine-N-oxide that also enhances atherosclerosis and cardiovascular abnormalities.

SUMMARY

Products of phospholipid metabolism in the intestine through PLA2g1b and autotaxin-mediated pathways directly contribute to cardiometabolic diseases through multiple mechanisms. The implication of these studies is that therapeutic inhibition of PLA2g1b and autotaxin in the digestive tract may be a viable approach for cardiovascular and metabolic disease intervention.

Systems Pharmacology Dissection of the Integrated Treatment for Cardiovascular and Gastrointestinal Disorders by Traditional Chinese Medicine

Though cardiovascular diseases (CVDs) and gastrointestinal disorders (GIDs) are different diseases associated with different organs, they are highly correlated clinically. Importantly, in Traditional Chinese Medicine (TCM), similar treatment strategies have been applied in both diseases. However, the etiological mechanisms underlying them remain unclear. Here, an integrated systems pharmacology approach is presented for illustrating the molecular correlations between CVDs and GIDs. Firstly, we identified pairs of genes that are associated with CVDs and GIDs and found that these genes are functionally related. Then, the association between 115 heart meridian (HM) herbs and 163 stomach meridian (SM) herbs and their combination application in Chinese patent medicine was investigated, implying that both CVDs and GIDs can be treated by the same strategy. Exemplified by a classical formula Sanhe Decoration (SHD) treating chronic gastritis, we applied systems-based analysis to introduce a drug-target-pathway-organ network that clarifies mechanisms of different diseases being treated by the same strategy. The results indicate that SHD regulated several pathological processes involved in both CVDs and GIDs. We experimentally confirmed the predictions implied by the effect of SHD for myocardial ischemia. The systems pharmacology suggests a novel integrated strategy for rational drug development for complex associated diseases.

Role of Sphingolipids in Infant Gut Health and Immunity

Sphingomyelin (SM), glycosphingolipids, and gangliosides are important polar lipids in the milk fat globule membrane but are not found in standard milk replacement formulas. Because digestion and absorption of SM and glycosphingolipids generate the bioactive metabolites ceramide, sphingosine, and sphingosine-1-phosphate (S1P), and because intact gangliosides may have beneficial effects in the gut, this may be important for gut integrity and immune maturation in the neonate. The brush border enzymes that hydrolyze milk SM, alkaline sphingomyelinase (nucleotide phosphodiesterase pyrophosphatase 7), and neutral ceramidase are expressed at birth in both term and preterm infants. Released sphingosine is absorbed, phosphorylated to S1P, and converted to palmitic acid via S1P-lyase in the gut mucosa. Hypothetically, S1P also may be released from absorptive cells and exert important paracrine actions favoring epithelial integrity and renewal, as well as immune function, including secretory IgA production and migration of T lymphocyte subpopulations. Gluco-, galacto-, and lactosylceramide are hydrolyzed to ceramide by lactase-phlorizin hydrolase, which also hydrolyzes lactose. Gangliosides may adhere to the brush border and is internalized, modified, and possibly transported into blood, and may exert protective functions by their interactions with bacteria, bacterial toxins, and the brush border.

Metabolic regulation by secreted phospholipase A2

Within the phospholipase A₂ (PLA₂) superfamily that hydrolyzes phospholipids to yield fatty acids and lysophospholipids, the secreted PLA₂ (sPLA₂) enzymes comprise the largest family that contains 11 isoforms in mammals. Individual sPLA₂s exhibit unique distributions and specific enzymatic properties, suggesting their distinct biological roles. While sPLA₂s have long been implicated in inflammation and atherosclerosis, it has become evident that they are involved in diverse biological events through lipid mediator-dependent or mediator-independent processes in a given microenvironment. In recent years, new biological aspects of sPLA₂s have been revealed using their transgenic and knockout mouse models in combination with mass spectrometric lipidomics to unveil their target substrates and products in vivo. In this review, we summarize our current knowledge of the roles of sPLA₂s in metabolic disorders including obesity, hepatic steatosis, diabetes, insulin resistance, and adipose tissue inflammation.

Tg6F ameliorates the increase in oxidized phospholipids in the jejunum of mice fed unsaturated LysoPC or WD

Mouse chow supplemented with lysophosphatidylcholine with oleic acid at sn-1 and a hydroxyl group at sn-2 (LysoPC 18:1) increased LysoPC 18:1 in tissue of the jejunum of LDL receptor (LDLR)-null mice by 8.9 ± 1.7-fold compared with chow alone. Western diet (WD) contained dramatically less phosphatidylcholine 18:1 or LysoPC 18:1 compared with chow, but feeding WD increased LysoPC 18:1 in the jejunum by 7.5 ± 1.4-fold compared with chow. Feeding LysoPC 18:1 or feeding WD increased oxidized phospholipids in the jejunum by 5.2 ± 3.0-fold or 8.6 ± 2.2-fold, respectively, in LDLR-null mice (P < 0.0004), and 2.6 ± 1.5-fold or 2.4 ± 0.92-fold, respectively, in WT C57BL/6J mice (P < 0.0001). Adding 0.06% by weight of a concentrate of transgenic tomatoes expressing the 6F peptide (Tg6F) decreased LysoPC 18:1 in the jejunum of LDLR-null mice on both diets (P < 0.0001), and prevented the increase in oxidized phospholipids in the jejunum in LDLR-null and WT mice on both diets (P < 0.008). Tg6F decreased inflammatory cells in the villi of the jejunum, decreased dyslipidemia, and decreased systemic inflammation in LDLR-null and WT mice on both diets. We conclude that Tg6F reduces diet-induced inflammation by reducing the content of unsaturated LysoPC and oxidized phospholipids in the jejunum of mice.

Development of a potent 2-oxoamide inhibitor of secreted phospholipase A2 guided by molecular docking calculations and molecular dynamics simulations

Inhibition of group IIA secreted phospholipase A2 (GIIA sPLA2) has been an important objective for medicinal chemists. We have previously shown that inhibitors incorporating the 2-oxoamide functionality may inhibit human and mouse GIIA sPLA2s. Herein, the development of new potent inhibitors by molecular docking calculations using the structure of the known inhibitor 7 as scaffold, are described. Synthesis and biological evaluation of the new compounds revealed that the long chain 2-oxoamide based on (S)-valine GK241 led to improved activity (IC50=143 nM and 68 nM against human and mouse GIIA sPLA2, respectively). In addition, molecular dynamics simulations were employed to shed light on GK241 potent and selective inhibitory activity.

Progesterone-induced Acrosome Exocytosis Requires Sequential Involvement of Calcium-independent Phospholipase A2β (iPLA2β) and Group X Secreted Phospholipase A2 (sPLA2)

Phospholipase A2 (PLA2) activity has been shown to be involved in the sperm acrosome reaction (AR), but the molecular identity of PLA2 isoforms has remained elusive. Here, we have tested the role of two intracellular (iPLA2β and cytosolic PLA2α) and one secreted (group X) PLA2s in spontaneous and progesterone (P4)-induced AR by using a set of specific inhibitors and knock-out mice. iPLA2β is critical for spontaneous AR, whereas both iPLA2β and group X secreted PLA2 are involved in P4-induced AR. Cytosolic PLA2α is dispensable in both types of AR. P4-induced AR spreads over 30 min in the mouse, and kinetic analyses suggest the presence of different sperm subpopulations, using distinct PLA2 pathways to achieve AR. At low P4 concentration (2 μm), sperm undergoing early AR (0-5 min post-P4) rely on iPLA2β, whereas sperm undergoing late AR (20-30 min post-P4) rely on group X secreted PLA2. Moreover, the role of PLA2s in AR depends on P4 concentration, with the PLA2s being key actors at low physiological P4 concentrations (≤2 μm) but not at higher P4 concentrations (~10 μm).

Modulation of C-reactive protein and plasma omega-6 fatty acid levels by phospholipase A2 gene polymorphisms following a 6-week supplementation with fish oil

This clinical trial investigated the impact of a six-week supplementation with fish oil and single nucleotide polymorphisms (SNPs) in PLA2G4A and PLA2G6 genes on total omega-6 fatty acid (n-6 FA) levels in plasma phospholipids (PL) and plasma C-reactive protein (CRP) levels in 191 subjects. Interaction effects between SNPs and supplementation modulated total n-6 FAs and CRP levels in both men and women. Associations between SNPs and total n-6 FA levels and between SNPs and CRP levels were identified in men, independently of supplementation. Supplementation decreased total n-6 FAs without affecting plasma CRP levels. Changes in CRP levels correlated positively with changes in total n-6 FAs in men (r=0.25 p=0.01), but not in women. In conclusion, total n-6 FA levels in plasma PL and plasma CRP levels are modulated by SNPs within PLA2G4A and PLA2G6 genes alone or in combination with fish oil supplementation.

Virtual analysis of structurally diverse synthetic analogs as inhibitors of snake venom secretory phospholipase A2

Due to the toxic pathophysiological role of snake venom phospholipase A2 (PLA2 ), its compelling limitations to anti-venom therapy in humans and the need for alternative therapy foster considerable pharmacological interest towards search of PLA2 specific inhibitors. In this study, an integrated approach involving homology modeling, molecular dynamics and molecular docking studies on VRV-PL-V (Vipera russellii venom phospholipase A2 fraction-V) belonging to Group II-B secretory PLA2 from Daboia russelli pulchella is carried out in order to study the structure-based inhibitor design. The accuracy of the model was validated using multiple computational approaches. The molecular docking study of this protein was undertaken using different classes of experimentally proven, structurally diverse synthetic inhibitors of secretory PLA2 whose selection is based on IC50 value that ranges from 25 μM to 100 μM. Estimation of protein-ligand contacts by docking analysis sheds light on the importance of His 47 and Asp 48 within the VRV-PL-V binding pocket as key residue for hydrogen bond interaction with ligands. Our virtual analysis revealed that compounds with different scaffold binds to the same active site region. ADME analysis was also further performed to filter and identify the best potential specific inhibitor against VRV-PL-V. Additionally, the e-pharmacophore was generated for the best potential specific inhibitor against VRV-PL-V and reported here. The present study should therefore play a guiding role in the experimental design of VRV-PL-V inhibitors that may provide better therapeutic molecular models for PLA2 recognition and anti-ophidian activity.

Orai3 Surface Accumulation and Calcium Entry Evoked by Vascular Endothelial Growth Factor

Supplemental Digital Content is available in the text.

Vascular endothelial growth factor (VEGF) acts, in part, by triggering calcium ion (Ca²⁺) entry. Here, we sought understanding of a Synta66-resistant Ca²⁺ entry pathway activated by VEGF.

Calcium-independent phospholipases A2 and their roles in biological processes and diseases

Among the family of phospholipases A2 (PLA2s) are the Ca(2+)-independent PLA2s (iPLA2s) and they are designated group VI iPLA2s. In relation to secretory and cytosolic PLA2s, the iPLA2s are more recently described and details of their expression and roles in biological functions are rapidly emerging. The iPLA2s or patatin-like phospholipases (PNPLAs) are intracellular enzymes that do not require Ca(2+) for activity, and contain lipase (GXSXG) and nucleotide-binding (GXGXXG) consensus sequences. Though nine PNPLAs have been recognized, PNPLA8 (membrane-associated iPLA2γ) and PNPLA9 (cytosol-associated iPLA2β) are the most widely studied and understood. The iPLA2s manifest a variety of activities in addition to phospholipase, are ubiquitously expressed, and participate in a multitude of biological processes, including fat catabolism, cell differentiation, maintenance of mitochondrial integrity, phospholipid remodeling, cell proliferation, signal transduction, and cell death. As might be expected, increased or decreased expression of iPLA2s can have profound effects on the metabolic state, CNS function, cardiovascular performance, and cell survival; therefore, dysregulation of iPLA2s can be a critical factor in the development of many diseases. This review is aimed at providing a general framework of the current understanding of the iPLA2s and discussion of the potential mechanisms of action of the iPLA2s and related involved lipid mediators.

Association between polymorphisms in phospholipase A2 genes and the plasma triglyceride response to an n-3 PUFA supplementation: a clinical trial

BACKGROUND

Fish oil-derived long-chain omega-3 (n-3) polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), reduce plasma triglyceride (TG) levels. Genetic factors such as single-nucleotide polymorphisms (SNPs) found in genes involved in metabolic pathways of n-3 PUFA could be responsible for well-recognized heterogeneity in plasma TG response to n-3 PUFA supplementation. Previous studies have shown that genes in the glycerophospholipid metabolism such as phospholipase A2 (PLA2) group II, IV, and VI, demonstrate changes in their expression levels in peripheral blood mononuclear cells (PBMCs) after n-3 PUFA supplementation.

METHODS

A total of 208 subjects consumed 3 g/day of n-3 PUFA for 6 weeks. Plasma lipids were measured before and after the supplementation period. Five SNPs in PLA2G2A, six in PLA2G2C, eight in PLA2G2D, six in PLA2G2F, 22 in PLA2G4A, five in PLA2G6, and nine in PLA2G7 were genotyped. The MIXED Procedure for repeated measures adjusted for age, sex, BMI, and energy intake was used in order to test whether the genotype, supplementation or interaction (genotype by supplementation) were associated with plasma TG levels.

RESULTS

The n-3 PUFA supplementation had an independent effect on plasma TG levels. Genotype effects on plasma TG levels were observed for rs2301475 in PLA2G2C, rs818571 in PLA2G2F, and rs1569480 in PLA2G4A. Genotype x supplementation interaction effects on plasma TG levels were observed for rs1805018 in PLA2G7 as well as for rs10752979, rs10737277, rs7540602, and rs3820185 in PLA2G4A.

CONCLUSION

These results suggest that, SNPs in PLA2 genes may influence plasma TG levels during a supplementation with n-3 PUFA. This trial was registered at clinicaltrials.gov as NCT01343342.

Source and role of intestinally derived lysophosphatidic acid in dyslipidemia and atherosclerosis

We previously reported that i) a Western diet increased levels of unsaturated lysophosphatidic acid (LPA) in small intestine and plasma of LDL receptor null (LDLR(-/-)) mice, and ii) supplementing standard mouse chow with unsaturated (but not saturated) LPA produced dyslipidemia and inflammation. Here we report that supplementing chow with unsaturated (but not saturated) LPA resulted in aortic atherosclerosis, which was ameliorated by adding transgenic 6F tomatoes. Supplementing chow with lysophosphatidylcholine (LysoPC) 18:1 (but not LysoPC 18:0) resulted in dyslipidemia similar to that seen on adding LPA 18:1 to chow. PF8380 (a specific inhibitor of autotaxin) significantly ameliorated the LysoPC 18:1-induced dyslipidemia. Supplementing chow with LysoPC 18:1 dramatically increased the levels of unsaturated LPA species in small intestine, liver, and plasma, and the increase was significantly ameliorated by PF8380 indicating that the conversion of LysoPC 18:1 to LPA 18:1 was autotaxin dependent. Adding LysoPC 18:0 to chow increased levels of LPA 18:0 in small intestine, liver, and plasma but was not altered by PF8380 indicating that conversion of LysoPC 18:0 to LPA 18:0 was autotaxin independent. We conclude that i) intestinally derived unsaturated (but not saturated) LPA can cause atherosclerosis in LDLR(-/-) mice, and ii) autotaxin mediates the conversion of unsaturated (but not saturated) LysoPC to LPA.

Phospholipase A2 - nexus of aging, oxidative stress, neuronal excitability, and functional decline of the aging nervous system? Insights from a snail model system of neuronal aging and age-associated memory impairment

The aging brain undergoes a range of changes varying from subtle structural and physiological changes causing only minor functional decline under healthy normal aging conditions, to severe cognitive or neurological impairment associated with extensive loss of neurons and circuits due to age-associated neurodegenerative disease conditions. Understanding how biological aging processes affect the brain and how they contribute to the onset and progress of age-associated neurodegenerative diseases is a core research goal in contemporary neuroscience. This review focuses on the idea that changes in intrinsic neuronal electrical excitability associated with (per)oxidation of membrane lipids and activation of phospholipase A₂ (PLA₂) enzymes are an important mechanism of learning and memory failure under normal aging conditions. Specifically, in the context of this special issue on the biology of cognitive aging we portray the opportunities offered by the identifiable neurons and behaviorally characterized neural circuits of the freshwater snail Lymnaea stagnalis in neuronal aging research and recapitulate recent insights indicating a key role of lipid peroxidation-induced PLA₂ as instruments of aging, oxidative stress and inflammation in age-associated neuronal and memory impairment in this model system. The findings are discussed in view of accumulating evidence suggesting involvement of analogous mechanisms in the etiology of age-associated dysfunction and disease of the human and mammalian brain.

The action of peroxyl radicals, powerful deleterious reagents, explains why neither cholesterol nor saturated fatty acids cause atherogenesis and age-related diseases

Cells respond to alterations in their membrane structure by activating hydrolytic enzymes. Thus, polyunsaturated fatty acids (PUFAs) are liberated. Free PUFAs react with molecular oxygen to give lipid hydroperoxide molecules (LOOHs). In case of severe cell injury, this physiological reaction switches to the generation of lipid peroxide radicals (LOO(·)). These radicals can attack nearly all biomolecules such as lipids, carbohydrates, proteins, nucleic acids and enzymes, impairing their biological functions. Identical cell responses are triggered by manipulation of food, for example, heating/grilling and particularly homogenization, representing cell injury. Cholesterol as well as diets rich in saturated fat have been postulated to accelerate the risk of atherosclerosis while food rich in unsaturated fatty acids has been claimed to lower this risk. However, the fact is that LOO(·) radicals generated from PUFAs can oxidize cholesterol to toxic cholesterol oxides, simulating a reduction in cholesterol level. In this review it is shown how active LOO(·) radicals interact with biomolecules at a speed transcending usual molecule-molecule reactions by several orders of magnitude. Here, it is explained how functional groups are fundamentally transformed by an attack of LOO(·) with an obliteration of essential biomolecules leading to pathological conditions. A serious reconsideration of the health and diet guidelines is required.

Emerging roles of secreted phospholipase A2 enzymes: the 3rd edition

Within the phospholipase A2 (PLA2) superfamily, secreted PLA2 (sPLA2) enzymes comprise the largest family that contains 11 to 12 mammalian isoforms with a conserved His-Asp catalytic dyad. Individual sPLA2s exhibit unique tissue and cellular localizations and specific enzymatic properties, suggesting distinct biological roles. Individual sPLA2s are involved in diverse biological events through lipid mediator-dependent or -independent processes and act redundantly or non-redundantly in a given microenvironment. In the past few years, new biological aspects of sPLA2s have been clarified using their transgenic and knockout mouse lines in combination with mass spectrometric lipidomics to unveil their target substrates and products in vivo. In the 3rd edition of this review series, we highlight the newest understanding of the in vivo functions of sPLA2s in pathophysiological conditions in the context of immunity and metabolism. We will also describe the latest knowledge on PLA2R1, the best known sPLA2 receptor, which may serve either as a clearance or signaling receptor for sPLA2 or may even act independently of sPLA2 function.

Monitoring of lipids, enzymes, and creatine kinase in patients on lipid-lowering drug therapy

A number of plasma lipid parameters have been used to estimate cardiovascular risk and to be targets for treatment to reduce risk. Most risk algorithms are based on total cholesterol (T-C) or low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), and most intervention trials have targeted the LDL-C levels. Emerging measures, which in some cases may be better for risk calculation and as alternative treatment targets, are apolipoprotein B and non-HDL-C. Other lipid measures that may contribute in risk analysis are triglycerides (TG), lipoprotein(a), and lipoprotein-associated phospholipase A2. The primary treatment target in cardiovascular prevention is LDL-C, and potential alternative targets are apoB and non-HDL-C. In selected individuals at high cardiovascular (CV) risk, TG should be targeted, but HDL-C, Lp(a), and ratios such as LDL-C/HDL-C or apoB/apoAI are not recommended as treatment targets. Lipids should be monitored during titration to targets. Thereafter, lipids should be checked at least once a year or more frequently to improve treatment adherence if indicated. Monitoring of muscle and liver enzymes should be done before the start of treatment. In stable conditions during treatment, the focus should be on clinical symptoms that may alert muscle or liver complications. Routine measurement of CK or ALT is not necessary during treatment with statins.

Novel links among peroxiredoxins, endothelial dysfunction, and severity of atherosclerosis in type 2 diabetic patients with peripheral atherosclerotic disease

Peroxiredoxins, a group of antioxidant protein enzymes (PRDX1 to 6), are reported as antiatherogenic factors in animals; however, human studies are lacking. The present work aims to provide baseline data regarding the phenotype of PRDX1, 2, 4, and 6 in diabetic patients with peripheral atherosclerosis disease (PAD) and their relation to endothelial dysfunction (ED) and disease severity. Plasma levels of PRDX1, 2, 4, and 6 and markers of endothelial dysfunction (ICAM-1 and VCAM-1) were measured using ELISA in 55 type 2 diabetic patients having PAD and 25 healthy subjects. Ankle-brachial index (ABI), body mass index (BMI), triglycerides (TG), total cholesterol, HbA1c, and insulin resistance (HOMA IR) were measured. PRDX1, 2, 4, and 6 levels were significantly higher in patients compared to controls (PRDX1 21.9 ± 5.71 vs 16.8 ± 3.9 ng/ml, P < 0.001, PRDX2 36.5 ± 14.83 vs 20.4 ± 8.61 ng/ml, P < 0.001, PRDX4 3,840 ± 1,440 vs 2,696 ± 1,972 pg/ml, P < 0.005, PRDX6 311 ± 110 vs 287.9 ± 114 pg/ml, P < 0.05). PRDX1 and PRDX4 correlated negatively with ABI (r = -0.273, P < 0.05 and r = -0.28, P < 0.05, respectively), while PRDX1 and PRDX2 correlated positively with HOMA/IR and TG (r = 0.276, P < 0.01 and r = 0.295, P < 0.01, respectively). ICAM-1 was associated with PRDX2 and log PRDX6 (r = 0.345, P = 0.0037 and r = 0.344, P = 0.0038). Our results provide strong links among PRDXs, ED, and severity of PAD in diabetic patients which warrants further evaluation to clarify whether high circulating levels of PRDXs are a consequence of chronic atherosclerotic disease or a predisposing factor for later cardiovascular events.

Lipoprotein-associated phospholipase A₂ mass level is increased in elderly subjects with type 2 diabetes mellitus

OBJECTIVE. Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is extensively expressed by advanced atherosclerotic lesions and may play a role in plaque instability. We selected a group of elderly subjects that underwent transcatheter aortic valve implantation (TAVI) or balloon angioplasty (BA) and separated them into two groups, diabetic and nondiabetic, to compare the level of Lp-PLA₂ mass between them. METHODS. 44 patients aged 79.6 ± 5.6 years with symptomatic severe aortic valve stenosis underwent TAVI (n = 35) or BA (n = 9). 21 subjects had confirmed type 2 diabetes mellitus. Lp-PLA₂ mass was measured using an enzyme-linked immunosorbent assay kit (USCN Life Science, China) before and 3 days after the procedure. RESULTS. Lp-PLA₂ mass was significantly elevated in this population (1296 ± 358 ng/mL before TAVI; 1413 ± 268 ng/mL before BA) and further increased after TAVI (1604 ± 437 ng/mL, P < 0.01) or BA (1808 ± 303 ng/mL, P < 0.01). Lp-PLA₂ mass was significantly increased on the diabetic group before these interventions. CONCLUSION. Lp-PLA₂ may be a novel biomarker for the presence of rupture-prone atherosclerotic lesions in elderly patients. Levels of Lp-PLA₂ in diabetic patients may accompany the higher amount of small dense LDL particles seen in these subjects.

Phospholipids in milk fat: composition, biological and technological significance, and analytical strategies

Glycerophospholipids and sphingolipids are quantitatively the most important phospholipids (PLs) in milk. They are located on the milk fat globule membrane (MFGM) and in other membranous material of the skim milk phase. They include principally phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine, while sphingomyelin is the dominant species of sphingolipids There is considerable evidence that PLs have beneficial health effects, such as regulation of the inflammatory reactions, chemopreventive and chemotherapeutic activity on some types of cancer, and inhibition of the cholesterol absorption. PLs show good emulsifying properties and can be used as a delivery system for liposoluble constituents. Due to the amphiphilic characteristics of these molecules, their extraction, separation and detection are critical points in the analytical approach. The extraction by using chloroform and methanol, followed by the determination by high pressure liquid chromatography (HPLC), coupled with evaporative light scattering (ELSD) or mass detector (MS), are the most applied procedures for the PL evaluation. More recently, nuclear magnetic resonance spectrometry (NMR) was also used, but despite it demonstrating high sensitivity, it requires more studies to obtain accurate results. This review is focused on milk fat phospholipids; their composition, biological activity, technological properties, and significance in the structure of milk fat. Different analytical methodologies are also discussed.