Lipidomics studies reveal dynamic changes in polar lipids of developing endosperm of oat and wheat varieties with differing oil contents

Polar lipids have biosynthetic pathways which intersect and overlap with triacylglycerol biosynthesis; however, polar lipids have not been well characterized in the developing endosperms of oat with high oil accumulation. The polar lipids in endosperms of oat and wheat varieties having different oil contents were analyzed and compared at different developmental stages. Our study shows that the relative contents of polar lipid by mass were decreased more slowly in wheat than in oat. Phosphatidylcholine and phosphatidylethanolamine were the major phospholipids, which showed similar abundance and gradual decreases during endosperm development in oat and wheat, while lysophospholipids were noticeably higher in oat. Monogalactosyldiacylglycerol showed a gradual increase in wheat and a decrease in oat during endosperm development. The relative contents of some polar lipid species and their unsaturation index were significantly different in their endosperms. These characteristics of polar lipids might indicate an adaption of oat to accommodate oil accumulation.

Membrane phospholipids activate the inflammatory response in macrophages by various mechanisms

Exosomes, which are small membrane-encapsulated particles derived from all cell types, are emerging as important mechanisms for intercellular communication. In addition, exosomes are currently envisioned as potential carriers for the delivery of drugs to target tissues. The natural population of exosomes is very variable due to the limited amount of cargo components present in these small vesicles. Consequently, common components of exosomes may play a role in their function. We have proposed that membrane phospholipids could be a common denominator in the effect of exosomes on cellular functions. In this regard, we have previously shown that liposomes made of phosphatidylcholine (PC) or phosphatidylserine (PS) induced a robust alteration of macrophage (Mϕ) gene expression. We herewith report that these two phospholipids modulate gene expression in Mϕs by different mechanisms. PS alters cellular responses by the interaction with surface receptors, particularly CD36. In contrast, PC is captured by a receptor-independent process and likely triggers an activity within endocytic vesicles. Despite this difference in the capture mechanisms, both lipids mounted similar gene expression responses. This investigation suggests that multiple mechanisms mediated by membrane phospholipids could be participating in the alteration of cellular functions by exosomes.

Synthesis of phospholipids in human placenta

INTRODUCTION

Placental phospholipid synthesis is critical for the expansion of the placental exchange surface area and for production of signaling molecules. Despite their importance, it is not yet established which enzymes involved in the de novo synthesis and remodeling of placental phospholipids are expressed and active in the human placenta.

METHODS

We identified phospholipid synthesis enzymes by immunoblotting in placental homogenates and immunofluorescence in placenta tissue sections. Primary human trophoblast (PHT) cells from term healthy placentas (n = 10) were cultured and exposed to 13C labeled fatty acids (16:0, 18:1 and 18:2 n-6, 22:6 n-3) for 2 and 24 h. Three phospholipid classes; phosphatidic acid, phosphatidylcholine, and lysophosphatidylcholine containing 13C fatty acids were quantified by Liquid Chromatography with tandem mass spectrometry (LC/MS-MS).

RESULTS

Acyl transferase and phospholipase enzymes were detected in human placenta homogenate and primarily expressed in the syncytiotrophoblast. Three representative 13C fatty acids (16:0, 18:1 and 18:2 n-6) were incorporated rapidly into phosphatidic acid in trophoblasts, but 13C labeled docosahexaenoic acid (DHA; 22:6 n-3) incorporation was not detected. 13C DHA was incorporated into phosphatidylcholine. Lysophosphatidylcholine containing all four 13C labeled fatty acids were found in high abundance.

CONCLUSIONS

Phospholipid synthesis and remodeling enzymes are present in the syncytiotrophoblast. 13C labeled fatty acids were rapidly incorporated into cellular phospholipids. 13C DHA was incorporated into phospholipids through the remodeling pathway rather than by de novo synthesis. These understudied pathways are highly active and critical for structure and function of the placenta.

Association between pre-diagnostic circulating lipid metabolites and colorectal cancer risk: a nested case-control study in the European Prospective Investigation into Cancer and Nutrition (EPIC)

BACKGROUND

Altered lipid metabolism is a hallmark of cancer development. However, the role of specific lipid metabolites in colorectal cancer development is uncertain.

METHODS

In a case-control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC), we examined associations between pre-diagnostic circulating concentrations of 97 lipid metabolites (acylcarnitines, glycerophospholipids and sphingolipids) and colorectal cancer risk. Circulating lipids were measured using targeted mass spectrometry in 1591 incident colorectal cancer cases (55% women) and 1591 matched controls. Multivariable conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for associations between concentrations of individual lipid metabolites and metabolite patterns with colorectal cancer risk.

FINDINGS

Of the 97 assayed lipids, 24 were inversely associated (nominally p < 0.05) with colorectal cancer risk. Hydroxysphingomyelin (SM (OH)) C22:2 (ORper doubling 0.60, 95% CI 0.47-0.77) and acylakyl-phosphatidylcholine (PC ae) C34:3 (ORper doubling 0.71, 95% CI 0.59-0.87) remained associated after multiple comparisons correction. These associations were unaltered after excluding the first 5 years of follow-up after blood collection and were consistent according to sex, age at diagnosis, BMI, and colorectal subsite. Two lipid patterns, one including 26 phosphatidylcholines and all sphingolipids, and another 30 phosphatidylcholines, were weakly inversely associated with colorectal cancer.

INTERPRETATION

Elevated pre-diagnostic circulating levels of SM (OH) C22:2 and PC ae C34:3 and lipid patterns including phosphatidylcholines and sphingolipids were associated with lower colorectal cancer risk. This study may provide insight into potential links between specific lipids and colorectal cancer development. Additional prospective studies are needed to validate the observed associations.

FUNDING

World Cancer Research Fund (reference: 2013/1002); European Commission (FP7: BBMRI-LPC; reference: 313010).

Spatial MS multiomics on clinical prostate cancer tissues

Mass spectrometry (MS) and MS imaging (MSI) are used extensively for both the spatial and bulk characterization of samples in lipidomics and proteomics workflows. These datasets are typically generated independently due to different requirements for sample preparation. However, modern omics technologies now provide higher sample throughput and deeper molecular coverage, which, in combination with more sophisticated bioinformatic and statistical pipelines, make generating multiomics data from a single sample a reality. In this workflow, we use spatial lipidomics data generated by matrix-assisted laser desorption/ionization MSI (MALDI-MSI) on prostate cancer (PCa) radical prostatectomy cores to guide the definition of tumor and benign tissue regions for laser capture microdissection (LCM) and bottom-up proteomics all on the same sample and using the same mass spectrometer. Accurate region of interest (ROI) mapping was facilitated by the SCiLS region mapper software and dissected regions were analyzed using a dia-PASEF workflow. A total of 5525 unique protein groups were identified from all dissected regions. Lysophosphatidylcholine acyltransferase 1 (LPCAT1), a lipid remodelling enzyme, was significantly enriched in the dissected regions of cancerous epithelium (CE) compared to benign epithelium (BE). The increased abundance of this protein was reflected in the lipidomics data with an increased ion intensity ratio for pairs of phosphatidylcholines (PC) and lysophosphatidylcholines (LPC) in CE compared to BE.

Overexpression of the Phosphatidylcholine:DiacylglycerolCholinephosphotransferase (PDCT) gene increases carbon flux toward triacylglycerol (TAG) synthesis in Camelinasativa seeds

Camelinasativa has considerable promise as a dedicated industrial oilseed crop. Its oil-based blends have been tested and approved as liquid transportation fuels. Previously, we utilized metabolomic and transcriptomic profiling approaches and identified metabolic bottlenecks that control oil production and accumulation in seeds. Accordingly, we selected candidate genes for the metabolic engineering of Camelina. Here we targeted the overexpression of Camelina PDCT gene, which encodes the phosphatidylcholine: diacylglycerol cholinephosphotransferase enzyme. PDCT is proposed as a gatekeeper responsible for the interconversions of diacylglycerol (DAG) and phosphatidylcholine (PC) pools and has the potential to increase the levels of TAG in seeds. To confirm whether increased CsPDCT activity in developing Camelina seeds would enhance carbon flux toward increased levels of TAG and alter oil composition, we overexpressed the CsPDCT gene under the control of the seed-specific phaseolin promoter. Camelina transgenics exhibited significant increases in seed yield (19-56%), seed oil content (9-13%), oil yields per plant (32-76%), and altered polyunsaturated fatty acid (PUFA) content compared to their parental wild-type (WT) plants. Results from [14C] acetate labeling of Camelina developing embryos expressing CsPDCT in culture indicated increased rates of radiolabeled fatty acid incorporation into glycerolipids (up to 64%, 59%, and 43% higher in TAG, DAG, and PC, respectively), relative to WT embryos. We conclude that overexpression of PDCT appears to be a positive strategy to achieve a synergistic effect on the flux through the TAG synthesis pathway, thereby further increasing oil yields in Camelina.

Decreased sarcoplasmic reticulum phospholipids in human skeletal muscle are associated with metabolic syndrome

Metabolic syndrome affects more than one in three adults and is associated with increased risk of diabetes, cardiovascular disease, and all-cause mortality. Muscle insulin resistance is a major contributor to the development of the metabolic syndrome. Studies in mice have linked skeletal muscle sarcoplasmic reticulum (SR) phospholipid composition to sarcoplasmic/endoplasmic reticulum Ca2+-ATPase activity and insulin sensitivity. To determine if the presence of metabolic syndrome alters specific phosphatidylcholine (PC) and phosphatidylethanolamine (PE) species in human SR, we compared SR phospholipid composition in skeletal muscle from sedentary subjects with metabolic syndrome and sedentary control subjects without metabolic syndrome. Both total PC and total PE were significantly decreased in skeletal muscle SR of sedentary metabolic syndrome patients compared with sedentary controls, particularly in female participants, but there was no difference in the PC:PE ratio between groups. Total SR PC levels, but not total SR PE levels or PC:PE ratio, were significantly negatively correlated with BMI, waist circumference, total fat, visceral adipose tissue, triglycerides, fasting insulin, and homeostatic model assessment for insulin resistance. These findings are consistent with the existence of a relationship between skeletal muscle SR PC content and insulin resistance in humans.

Regulation of β-cell death by ADP-ribosylhydrolase ARH3 via lipid signaling in insulitis

BACKGROUND

Lipids are regulators of insulitis and β-cell death in type 1 diabetes development, but the underlying mechanisms are poorly understood. Here, we investigated how the islet lipid composition and downstream signaling regulate β-cell death.

METHODS

We performed lipidomics using three models of insulitis: human islets and EndoC-βH1 β cells treated with the pro-inflammatory cytokines interlukine-1β and interferon-γ, and islets from pre-diabetic non-obese mice. We also performed mass spectrometry and fluorescence imaging to determine the localization of lipids and enzyme in islets. RNAi, apoptotic assay, and qPCR were performed to determine the role of a specific factor in lipid-mediated cytokine signaling.

RESULTS

Across all three models, lipidomic analyses showed a consistent increase of lysophosphatidylcholine species and phosphatidylcholines with polyunsaturated fatty acids and a reduction of triacylglycerol species. Imaging assays showed that phosphatidylcholines with polyunsaturated fatty acids and their hydrolyzing enzyme phospholipase PLA2G6 are enriched in islets. In downstream signaling, omega-3 fatty acids reduce cytokine-induced β-cell death by improving the expression of ADP-ribosylhydrolase ARH3. The mechanism involves omega-3 fatty acid-mediated reduction of the histone methylation polycomb complex PRC2 component Suz12, upregulating the expression of Arh3, which in turn decreases cell apoptosis.

CONCLUSIONS

Our data provide insights into the change of lipidomics landscape in β cells during insulitis and identify a protective mechanism by omega-3 fatty acids. Video Abstract.

Molecular cloning, tissue expression pattern, responses to different fatty acids and potential functions of lysophosphatidylcholine acyltransferase 1 (LPCAT1) in large yellow croaker (Larimichthys crocea)

In farmed fish, diets rich in palm oil have been observed to promote abnormal lipid build-up in the liver, subsequently leading to physiological harm and disease onset. Emerging research suggests that integrating phospholipids into the feed could serve as a potent countermeasure against hepatic impairments induced by vegetable oil consumption. Phosphatidylcholine is the most abundant type among phospholipids. In the metabolic processes of mammal, lysophosphatidylcholine acyltransferase 1 (LPCAT1), crucial for phosphatidylcholine remodeling, demonstrates a marked affinity towards palmitic acid (PA). Nonetheless, aspects concerning the cloning, tissue-specific distribution, and affinity of the LPCAT1 gene to diverse oil sources have yet to be elucidated in the large yellow croaker (Larimichthys crocea). Within the scope of this study, we successfully isolated and cloned the cDNA of the LPCAT1 gene from the large yellow croaker. Subsequent analysis revealed distinct gene expression patterns of LPCAT1 across ten different tissues of the species. The fully sequenced coding DNA sequence (CDS) of LPCAT1 spans 1503 bp and encodes a sequence of 500 amino acids. Comparative sequence alignment indicates that LPCAT1 shares a 69.75 % amino acid similarity with its counterparts in other species. Although LPCAT1 manifests across various tissues of the large yellow croaker, its predominance is markedly evident in the liver and gills. Furthermore, post exposure of the large yellow croaker's hepatocytes to varied fatty acids, PA has a strong response to LPCAT1. Upon the addition of appropriate lysolecithin to palm oil feed, the mRNA expression of LPCAT1 in the liver cells of the large yellow croaker showed significant variations compared to other subtypes. Concurrently, the mRNA expression of pro-inflammatory genes il-1β, il-6, il-8, tnf-α and ifn-γ in the liver tissue of the large yellow croaker decreased. Interestingly, they exhibit the same trend of change. In conclusion, we have cloned the LPCAT1 gene on fish successfully and find the augmented gene response of LPCAT1 in hepatocytes under PA treatment first. The results of this study suggest that LPCAT1 may be associated with liver inflammation in fish and offer new insights into mitigating liver diseases in fish caused by palm oil feed.

In Vivo Cellular Phosphatidylcholine Kinetics of CD15+ Leucocytes and CD3+ T-Lymphocytes in Adults with Acute Respiratory Distress Syndrome

Mammalian cell membranes composed of a mixture of glycerophospholipids, the relative composition of individual phospholipids and the dynamic flux vary between cells. In addition to their structural role, membrane phospholipids are involved in cellular signalling and immunomodulatory functions. In this study, we investigate the molecular membrane composition and dynamic flux of phosphatidylcholines in CD15+ leucocytes and CD3+ lymphocytes extracted from patients with acute respiratory distress syndrome (ARDS). We identified compositional variations between these cell types, where CD15+ cells had relatively higher quantities of alkyl-acyl PC species and CD3+ cells contained more arachidonoyl-PC species. There was a significant loss of arachidonoyl-PC in CD3+ cells in ARDS patients. Moreover, there were significant changes in PC composition and the methyl-D9 enrichment of individual molecular species in CD15+ cells from ARDS patients. This is the first study to perform an in vivo assessment of membrane composition and dynamic changes in immunological cells from ARDS patients.

Inhibition of choline metabolism in an angioimmunoblastic T-cell lymphoma preclinical model reveals a new metabolic vulnerability as possible target for treatment

BACKGROUND

Angioimmunoblastic T-cell lymphoma (AITL) is a malignancy with very poor survival outcome, in urgent need of more specific therapeutic strategies. The drivers of malignancy in this disease are CD4+ follicular helper T cells (Tfh). The metabolism of these malignant Tfh cells was not yet elucidated. Therefore, we decided to identify their metabolic requirements with the objective to propose a novel therapeutic option.

METHODS

To reveal the prominent metabolic pathways used by the AITL lymphoma cells, we relied on metabolomic and proteomic analysis of murine AITL (mAITL) T cells isolated from our established mAITL model. We confirmed these results using AITL patient and healthy T cell expression data.

RESULTS

Strikingly, the mAITL Tfh cells were highly dependent on the second branch of the Kennedy pathway, the choline lipid pathway, responsible for the production of the major membrane constituent phosphatidylcholine. Moreover, gene expression data from Tfh cells isolated from AITL patient tumors, confirmed the upregulation of the choline lipid pathway. Several enzymes involved in this pathway such as choline kinase, catalyzing the first step in the phosphatidylcholine pathway, are upregulated in multiple tumors other than AITL. Here we showed that treatment of our mAITL preclinical mouse model with a fatty acid oxydation inhibitor, significantly increased their survival and even reverted the exhausted CD8 T cells in the tumor into potent cytotoxic anti-tumor cells. Specific inhibition of Chokα confirmed the importance of the phosphatidylcholine production pathway in neoplastic CD4 + T cells, nearly eradicating mAITL Tfh cells from the tumors. Finally, the same inhibitor induced in human AITL lymphoma biopsies cell death of the majority of the hAITL PD-1high neoplastic cells.

CONCLUSION

Our results suggest that interfering with choline metabolism in AITL reveals a specific metabolic vulnerability and might represent a new therapeutic strategy for these patients.

p53 suppresses lipid droplet-fueled tumorigenesis through phosphatidylcholine

Choline deficiency causes disorders including hepatic abnormalities and is associated with an increased risk of multiple types of cancer. Here, by choline-free diet-associated RNA-Seq analyses, we found that the tumor suppressor p53 drives the Kennedy pathway via PCYT1B to control the growth of lipid droplets (LDs) and their fueling role in tumorigenesis. Mechanistically, through upregulation of PCYT1B, p53 channeled depleted choline stores to phosphatidylcholine (PC) biosynthesis during choline starvation, thus preventing LD coalescence. Cells lacking p53 failed to complete this response to choline depletion, leading to hepatic steatosis and tumorigenesis, and these effects could be reversed by enforcement of PCYT1B expression or restoration of PC abundance. Furthermore, loss of p53 or defects in the Kennedy pathway increased surface localization of hormone-sensitive lipase on LDs to release specific fatty acids that fueled tumor cells in vivo and in vitro. Thus, p53 loss leads to dysregulation of choline metabolism and LD growth and couples perturbed LD homeostasis to tumorigenesis.

The glycerophosphocholine acyltransferase Gpc1 contributes to phosphatidylcholine biosynthesis, long-term viability, and embedded hyphal growth in Candida albicans

Candida albicans is a commensal fungus, opportunistic pathogen, and the most common cause of fungal infection in humans. The biosynthesis of phosphatidylcholine (PC), a major eukaryotic glycerophospholipid, occurs through two primary pathways. In Saccharomyces cerevisiae and some plants, a third PC synthesis pathway, the PC deacylation/reacylation pathway (PC-DRP), has been characterized. PC-DRP begins with the acylation of the lipid turnover product, glycerophosphocholine (GPC), by the GPC acyltransferase, Gpc1, to form Lyso-PC. Lyso-PC is then acylated by lysolipid acyltransferase, Lpt1, to produce PC. Importantly, GPC, the substrate for Gpc1, is a ubiquitous metabolite available within the host. GPC is imported by C. albicans, and deletion of the major GPC transporter, Git3, leads to decreased virulence in a murine model. Here we report that GPC can be directly acylated in C. albicans by the protein product of orf19.988, a homolog of ScGpc1. Through lipidomic studies, we show loss of Gpc1 leads to a decrease in PC levels. This decrease occurs in the absence of exogenous GPC, indicating that the impact on PC levels may be greater in the human host where GPC is available. A gpc1Δ/Δ strain exhibits several sensitivities to antifungals that target lipid metabolism. Furthermore, loss of Gpc1 results in both a hyphal growth defect in embedded conditions and a decrease in long-term cell viability. These results demonstrate for the first time the importance of Gpc1 and this alternative PC biosynthesis route (PC-DRP) to the physiology of a pathogenic fungus.

Designing and fabrication of colloidal nano-phytosomes with gamma-oryzanol and phosphatidylcholine for encapsulation and delivery of polyphenol-rich extract from pomegranate peel

Nano-carriers are well-known delivery systems to encapsulate different bioactive compounds and extracts. Such nano-systems are used in various food and drug areas to protect active ingredients, increase bioavailability, control the release, and deliver bioactive substances. This study aimed to design and fabricate a stable colloidal nano-delivery system to better preserve the antioxidant properties of pomegranate peel extract (PPE) and protect its sustained release in a gastrointestinal model. To achieve this goal, a nano-phytosomal system was fabricated with plant-based, cost-effective, and food-grade compounds, i.e., phosphatidylcholine (PC) and gamma-oryzanol (GO) for encapsulation of PPE. To fabricate the nano-phytosomes, thin film hydration/sonication method was used. The parameters of particle size, zeta potential, polydispersity index (PDI), loading capacity (LC), and encapsulation efficiency (EE) were investigated to evaluate the efficiency of the produced nano-system. In summary, the size, zeta potential, PDI, LC, and EE of homogenous spherical PC-GO-PPE nano-phytosomes (NPs) in the ratio of 8:2:2 % w/w were achieved as 60.61 ± 0.81 nm, -32.24 ± 0.84 mV, 0.19 ± 0.01, 19.13 ± 0.30 %, and 95.66 ± 1.52 %, respectively. Also, the structure of NPs was approved by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). The optimized NPs were stable during one month of storage at 4 °C, and changes in the size of particles and PPE retention rate were insignificant (p > 0.05). The nano-encapsulation of PPE significantly decreased the loss of its antioxidant activity during one month of storage at 4 °C. The optimized NPs exhibited prolonged and sustained release of PPE in a gastrointestinal model, so that after 2 h in simulated gastric fluid (SGF) and 4 h in simulated intestinal fluid (SIF), 22.66 ± 2.51 % and 69.33 ± 4.50 % of initially loaded PPE was released, respectively. Optimized NPs had considerable cytotoxicity against the Michigan Cancer Foundation-7 cell line (MCF7) (IC50 = 103 μg/ml), but not against Human Foreskin Fibroblast cell line (HFF-2) (IC50 = 453 μg/ml). In conclusion, spherical PC-GO-PPE NPs were identified as a promising delivery system to efficiently encapsulate PPE, as well as protect and preserve its bioactivity, including antioxidant and cytotoxicity against cancer cell line.

Deciphering Lipid Arrangement in Phosphatidylserine/Phosphatidylcholine Mixed Membranes: Simulations and Experiments

Phosphatidylserine (PS) exposure on the plasma membrane is crucial for many cellular processes including apoptotic cell recognition, blood clotting regulation, cellular signaling, and intercellular interactions. In this study, we investigated the arrangement of PS headgroups in mixed PS/phosphatidylcholine (PC) bilayers, serving as a simplified model of the outer leaflets of mammalian cell plasma membranes. Combining atomistic-scale molecular dynamics (MD) simulations with Langmuir monolayer experiments, we unraveled the mutual miscibility of POPC and POPS lipids and the intricate intermolecular interactions inherent to these membranes as well as the disparities in position and orientation of PC and PS headgroups. Our experiments revealed micrometer-scale miscibility at all mole fractions of POPC and POPS, marked by modest deviations from ideal mixing with no apparent microscale phase separation. The MD simulations, meanwhile, demonstrated that these deviations were due to strong electrostatic interactions between like-lipid pairs (POPC-POPC and POPS-POPS), culminating in lateral segregation and nanoscale clustering. Notably, PS headgroups profoundly affect the ordering of the lipid acyl chains, leading to lipid elongation and subtle PS protrusion above the zwitterionic membrane. In addition, PC headgroups are more tilted with respect to the membrane normal, while PS headgroups align at a smaller angle, making them more exposed to the surface of the mixed PC/PS membranes. These findings provide a detailed molecular-level account of the organization of mixed PC/PS membranes, corroborated by experimental data. The insights gained here extend our comprehension of the physiological role of PSs.

Oxidized Phosphatidylcholines Trigger TRPA1 and Ryanodine Receptor-dependent Airway Smooth Muscle Contraction

Asthma pathobiology includes oxidative stress that modifies cell membranes and extracellular phospholipids. Oxidized phosphatidylcholines (OxPCs) in lung lavage from allergen-challenged human participants correlate with airway hyperresponsiveness and induce bronchial narrowing in murine thin-cut lung slices. OxPCs activate many signaling pathways, but mechanisms for these responses are unclear. We hypothesize that OxPCs stimulate intracellular free Ca2+ flux to trigger airway smooth muscle contraction. Intracellular Ca2+ flux was assessed in Fura-2-loaded, cultured human airway smooth muscle cells. Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) induced an approximately threefold increase in 20 kD myosin light chain phosphorylation. This correlated with a rapid peak in intracellular cytoplasmic Ca2+ concentration ([Ca2+]i) (143 nM) and a sustained plateau that included slow oscillations in [Ca2+]i. Sustained [Ca2+]i elevation was ablated in Ca2+-free buffer and by TRPA1 inhibition. Conversely, OxPAPC-induced peak [Ca2+]i was unaffected in Ca2+-free buffer, by TRPA1 inhibition, or by inositol 1,4,5-triphosphate receptor inhibition. Peak [Ca2+]i was ablated by pharmacologic inhibition of ryanodine receptor (RyR) Ca2+ release from the sarcoplasmic reticulum. Inhibiting the upstream RyR activator cyclic adenosine diphosphate ribose with 8-bromo-cyclic adenosine diphosphate ribose was sufficient to abolish OxPAPC-induced cytoplasmic Ca2+ flux. OxPAPC induced ∼15% bronchial narrowing in thin-cut lung slices that could be prevented by pharmacologic inhibition of either TRPA1 or RyR, which similarly inhibited OxPC-induced myosin light chain phosphorylation in cultured human airway smooth muscle cells. In summary, OxPC mediates airway narrowing by triggering TRPA1 and RyR-mediated mobilization of intracellular and extracellular Ca2+ in airway smooth muscle. These data suggest that OxPC in the airways of allergen-challenged subjects and subjects with asthma may contribute to airway hyperresponsiveness.

Intestinal Atp8b1 dysfunction causes hepatic choline deficiency and steatohepatitis

Choline is an essential nutrient, and its deficiency causes steatohepatitis. Dietary phosphatidylcholine (PC) is digested into lysoPC (LPC), glycerophosphocholine, and choline in the intestinal lumen and is the primary source of systemic choline. However, the major PC metabolites absorbed in the intestinal tract remain unidentified. ATP8B1 is a P4-ATPase phospholipid flippase expressed in the apical membrane of the epithelium. Here, we use intestinal epithelial cell (IEC)-specific Atp8b1-knockout (Atp8b1IEC-KO) mice. These mice progress to steatohepatitis by 4 weeks. Metabolomic analysis and cell-based assays show that loss of Atp8b1 in IEC causes LPC malabsorption and thereby hepatic choline deficiency. Feeding choline-supplemented diets to lactating mice achieves complete recovery from steatohepatitis in Atp8b1IEC-KO mice. Analysis of samples from pediatric patients with ATP8B1 deficiency suggests its translational potential. This study indicates that Atp8b1 regulates hepatic choline levels through intestinal LPC absorption, encouraging the evaluation of choline supplementation therapy for steatohepatitis caused by ATP8B1 dysfunction.

Inhibiting Phosphatidylcholine Remodeling in Adipose Tissue Increases Insulin Sensitivity

Cell membrane phosphatidylcholine (PC) composition is regulated by lysophosphatidylcholine acyltransferase (LPCAT); changes in membrane PC saturation are implicated in metabolic disorders. Here, we identified LPCAT3 as the major isoform of LPCAT in adipose tissue and created adipocyte-specific Lpcat3-knockout mice to study adipose tissue lipid metabolism. Transcriptome sequencing and plasma adipokine profiling were used to investigate how LPCAT3 regulates adipose tissue insulin signaling. LPCAT3 deficiency reduced polyunsaturated PCs in adipocyte plasma membranes, increasing insulin sensitivity. LPCAT3 deficiency influenced membrane lipid rafts, which activated insulin receptors and AKT in adipose tissue, and attenuated diet-induced insulin resistance. Conversely, higher LPCAT3 activity in adipose tissue from ob/ob, db/db, and high-fat diet-fed mice reduced insulin signaling. Adding polyunsaturated PCs to mature human or mouse adipocytes in vitro worsened insulin signaling. We suggest that targeting LPCAT3 in adipose tissue to manipulate membrane phospholipid saturation is a new strategy to treat insulin resistance.

ARTICLE HIGHLIGHTS

Distribution of malaria parasite-derived phosphatidylcholine in the infected erythrocyte

Malaria parasites modify their host erythrocyte in multiple ways, leading to changes in the deformability, adhesiveness, and permeability of the host erythrocyte. Most of these changes are mediated by proteins exported from the parasite to the host erythrocyte, where these proteins interact with the host cell cytoskeleton or form complexes in the plasma membrane of the infected erythrocyte. In addition, malaria parasites induce the formation of membranous compartments-the parasitophorous vacuole, the tubovesicular network (TVN), the Maurer's clefts and small vesicles-within the infected erythrocyte, a cell that is normally devoid of internal membranes. After infection, changes also occur in the composition and asymmetry of the erythrocyte plasma membrane. Although many aspects of the mechanism of export of parasite proteins have become clear, the mechanism by which these membranous compartments are formed and expanded is almost entirely unknown. To determine whether parasite-derived phospholipids play a part in these processes, we applied a metabolic labeling technique that allows phosphatidylcholine to be labeled with a fluorophore. As the host erythrocyte cannot synthesize phospholipids, within infected erythrocytes, only parasite-derived phosphatidylcholine will be labeled with this technique. The results revealed that phosphatidylcholine produced by the parasite is distributed throughout the infected erythrocyte, including the TVN and the erythrocyte plasma membrane, but not Maurer's clefts. Interestingly, labeled phospholipids were also detected in the erythrocyte plasma membrane very soon after invasion of the parasites, indicating that the parasite may add phospholipids to the host erythrocyte during invasion. IMPORTANCE Here, we describe a previously unappreciated way in which the malaria parasite interacts with the host erythrocyte, namely, by the transfer of parasite phospholipids to the erythrocyte plasma membrane. This likely has important consequences for the survival of the parasite in the host cell and the host organism. We show that parasite-derived phospholipids are transferred from the parasite to the host erythrocyte plasma membrane and that other internal membranes that are produced after the parasite has invaded the cell are produced, at least in part, using parasite-derived phospholipids. The one exception to this is the Maurer's cleft, a membranous organelle that is involved in the transport of parasite proteins to the surface of the erythrocyte. This reveals that the Maurer's cleft is produced in a different manner than the other parasite-induced membranes. Overall, these findings provide a platform for the study of a new aspect of the host-parasite interaction.

Metabolomic analysis of lipid changes in Bombyx mori infected with Nosema bombycis

The silkworm (Bombyx mori) is a model species of lepidopteran insect. Microsporidium spp. are obligate intracellular eukaryotic parasites. Infection by the microsporidian Nosema bombycis (Nb) results in an outbreak of Pébrine disease in silkworms and causes substantial losses to the sericulture industry. It has been suggested that Nb depends on nutrients from host cells for spore growth. However, little is known about changes in lipid levels after Nb infection. In this study, ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was performed to analyze the effect of Nb infection on lipid metabolism in the midgut of silkworms. A total of 1601 individual lipid molecules were detected in the midgut of silkworms, of which 15 were significantly decreased after Nb challenge. Classification, chain length, and chain saturation analysis revealed that these 15 differential lipids can be classified into different lipid subclasses, of which 13 belong to glycerol phospholipid lipids and two belong to glyceride esters. The results indicated that Nb uses the host lipids to complete its own replication, and the acquisition of host lipid subclasses is selective; not all lipid subclasses are required for microsporidium growth or proliferation. Based on lipid metabolism data, phosphatidylcholine (PC) was found to be an important nutrient for Nb replication. Diet supplementation with lecithin substantially promoted the replication of Nb. Knockdown and overexpression of the key enzyme phosphatidate phosphatase (PAP) and phosphatidylcholine (Bbc) for PC synthesis also confirmed that PC is necessary for Nb replication. Our results showed that most lipids in the host midgut decreased when silkworms were infected with Nb. Reduction of or supplementation with PC may be a strategy to suppress or promote microsporidial replication.

Fetal sex differences in placental LCPUFA ether and plasmalogen phosphatidylethanolamine and phosphatidylcholine contents in pregnancies complicated by obesity

BACKGROUND

We have previously reported that maternal obesity reduces placental transport capacity for lysophosphatidylcholine-docosahexaenoic acid (LPC-DHA), a preferred form for transfer of DHA (omega 3) to the fetal brain, but only in male fetuses. Phosphatidylethanolamine (PE) and phosphatidylcholine (PC), have either sn-1 ester, ether or vinyl ether (plasmalogen) linkages to primarily unsaturated and monounsaturated fatty acids and DHA or arachidonic acid (ARA, omega 6) in the sn-2 position. Whether ether and plasmalogen PC and PE metabolism in placenta impacts transfer to the fetus is unexplored. We hypothesized that ether and plasmalogen PC and PE containing DHA and ARA are reduced in maternal-fetal unit in pregnancies complicated by obesity and these differences are dependent on fetal sex.

METHODS

In maternal, umbilical cord plasma and placentas from obese women (11 female/5 male infants) and normal weight women (9 female/7 male infants), all PC and PE species containing DHA and ARA were analyzed by LC-MS/MS. Placental protein expression of enzymes involved in phospholipid synthesis, were determined by immunoblotting. All variables were compared between control vs obese groups and separated by fetal sex, in each sample using the Benjamini-Hochberg false discovery rate adjustment to account for multiple testing.

RESULTS

Levels of ester PC containing DHA and ARA were profoundly reduced by 60-92% in male placentas of obese mothers, while levels of ether and plasmalogen PE containing DHA and ARA were decreased by 51-84% in female placentas. PLA2G4C abundance was lower in male placentas and LPCAT4 abundance was lower solely in females in obesity. In umbilical cord, levels of ester, ether and plasmalogen PC and PE with DHA were reduced by 43-61% in male, but not female, fetuses of obese mothers.

CONCLUSIONS

We found a fetal sex effect in placental PE and PC ester, ether and plasmalogen PE and PC containing DHA in response to maternal obesity which appears to reflect an ability of female placentas to adapt to maintain optimal fetal DHA transfer in maternal obesity.

Blood-derived lysophospholipid sustains hepatic phospholipids and fat storage necessary for hepatoprotection in overnutrition

The liver has a high demand for phosphatidylcholine (PC), particularly in overnutrition, where reduced phospholipid levels have been implicated in the development of nonalcoholic fatty liver disease (NAFLD). Whether other pathways exist in addition to de novo PC synthesis that contribute to hepatic PC pools remains unknown. Here, we identified the lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain containing 2A (Mfsd2a) as critical for maintaining hepatic phospholipid pools. Hepatic Mfsd2a expression was induced in patients having NAFLD and in mice in response to dietary fat via glucocorticoid receptor action. Mfsd2a liver-specific deficiency in mice (L2aKO) led to a robust nonalcoholic steatohepatitis-like (NASH-like) phenotype within just 2 weeks of dietary fat challenge associated with reduced hepatic phospholipids containing linoleic acid. Reducing dietary choline intake in L2aKO mice exacerbated liver pathology and deficiency of liver phospholipids containing polyunsaturated fatty acids (PUFAs). Treating hepatocytes with LPCs containing oleate and linoleate, two abundant blood-derived LPCs, specifically induced lipid droplet biogenesis and contributed to phospholipid pools, while LPC containing the omega-3 fatty acid docosahexaenoic acid (DHA) promoted lipid droplet formation and suppressed lipogenesis. This study revealed that PUFA-containing LPCs drive hepatic lipid droplet formation, suppress lipogenesis, and sustain hepatic phospholipid pools - processes that are critical for protecting the liver from excess dietary fat.

The plasma membrane of focal adhesions has a high content of cholesterol and phosphatidylcholine with saturated acyl chains

Cellular functions, such as differentiation and migration, are regulated by the extracellular microenvironment, including the extracellular matrix (ECM). Cells adhere to ECM through focal adhesions (FAs) and sense the surrounding microenvironments. Although FA proteins have been actively investigated, little is known about the lipids in the plasma membrane at FAs. In this study, we examine the lipid composition at FAs with imaging and biochemical approaches. Using the cholesterol-specific probe D4 with total internal reflection fluorescence microscopy and super-resolution microscopy, we show an enrichment of cholesterol at FAs simultaneously with FA assembly. Furthermore, we establish a method to isolate the lipid from FA-rich fractions, and biochemical quantification of the lipids reveals that there is a higher content of cholesterol and phosphatidylcholine with saturated fatty acid chains in the lipids of the FA-rich fraction than in either the plasma membrane fraction or the whole-cell membrane. These results demonstrate that plasma membrane at FAs has a locally distinct lipid composition compared to the bulk plasma membrane.

Lipidome Profiling in Childhood Obesity Compared to Adults: A Pilot Study

The objective is to assess the circulating lipidome of children with obesity before and after lifestyle intervention and to compare the data to the circulating lipidome of adults with obesity before and after bariatric surgery. Ten pediatric (PE) and thirty adult (AD) patients with obesity were prospectively recruited at a referral single center. The PE cohort received lifestyle recommendations. The AD cohort underwent bariatric surgery. Clinical parameters and lipidome were analyzed in serum before and after six months of metabolic intervention. The abundance of phosphatidylinositols in the PE cohort and phosphatidylcholines in the AD significantly increased, while O-phosphatidylserines in the PE cohort and diacyl/triacylglycerols in the AD decreased. Fifteen lipid species were coincident in both groups after lifestyle intervention and bariatric surgery. Five species of phosphatidylinositols, sphingomyelins, and cholesteryl esters were upregulated. Eight species of diacylglycerols, glycerophosphoglycerols, glycerophosphoethanolamines, and phosphatidylcholines were downregulated. Most matching species were regulated in the same direction except for two phosphatidylinositols: PI(O-36:2) and PI(O-34:0). A specific set of lipid species regulated after bariatric surgery in adult individuals was also modulated in children undergoing lifestyle intervention, suggesting they may constitute a core circulating lipid profile signature indicative of early development of obesity and improvement after clinical interventions regardless of individual age.

Phosphatidylcholine-Specific Phospholipase C as a Promising Drug Target

Phosphatidylcholine-specific phospholipase C (PC-PLC) is an enzyme that catalyzes the formation of the important secondary messengers phosphocholine and diacylglycerol (DAG) from phosphatidylcholine. Although PC-PLC has been linked to the progression of many pathological conditions, including cancer, atherosclerosis, inflammation and neuronal cell death, studies of PC-PLC on the protein level have been somewhat neglected with relatively scarce data. To date, the human gene expressing PC-PLC has not yet been found, and the only protein structure of PC-PLC that has been solved was from Bacillus cereus (PC-PLCBc). Nonetheless, there is evidence for PC-PLC activity as a human functional equivalent of its prokaryotic counterpart. Additionally, inhibitors of PC-PLCBc have been developed as potential therapeutic agents. The most notable classes include 2-aminohydroxamic acids, xanthates, N,N'-hydroxyureas, phospholipid analogues, 1,4-oxazepines, pyrido[3,4-b]indoles, morpholinobenzoic acids and univalent ions. However, many medicinal chemistry studies lack evidence for their cellular and in vivo effects, which hampers the progression of the inhibitors towards the clinic. This review outlines the pathological implications of PC-PLC and highlights current progress and future challenges in the development of PC-PLC inhibitors from the literature.

The acyltransferase Gpc1 is both a target and an effector of the unfolded protein response in Saccharomyces cerevisiae

The unfolded protein response (UPR) is sensitive to proteotoxic and membrane bilayer stress, both of which are sensed by the ER protein Ire1. When activated, Ire1 splices HAC1 mRNA, producing a transcription factor that targets genes involved in proteostasis and lipid metabolism, among others. The major membrane lipid phosphatidylcholine (PC) is subject to phospholipase-mediated deacylation, producing glycerophosphocholine (GPC), followed by reacylation of GPC through the PC deacylation/reacylation pathway (PC-DRP). The reacylation events occur via a two-step process catalyzed first by the GPC acyltransferase Gpc1, followed by acylation of the lyso-PC molecule by Ale1. However, whether Gpc1 is critical for ER bilayer homeostasis is unclear. Using an improved method for C14-choline-GPC radiolabeling, we first show that loss of Gpc1 results in abrogation of PC synthesis through PC-DRP and that Gpc1 colocalizes with the ER. We then probe the role of Gpc1 as both a target and an effector of the UPR. Exposure to the UPR-inducing compounds tunicamycin, DTT, and canavanine results in a Hac1-dependent increase in GPC1 message. Further, cells lacking Gpc1 exhibit increased sensitivity to those proteotoxic stressors. Inositol limitation, known to induce the UPR via bilayer stress, also induces GPC1 expression. Finally, we show that loss of GPC1 induces the UPR. A gpc1Δ mutant displays upregulation of the UPR in strains expressing a mutant form of Ire1 that is unresponsive to unfolded proteins, indicating that bilayer stress is responsible for the observed upregulation. Collectively, our data indicate an important role for Gpc1 in yeast ER bilayer homeostasis.

Ethanolaminephosphate cytidylyltransferase is essential for survival, lipid homeostasis and stress tolerance in Leishmania major

Glycerophospholipids including phosphatidylethanolamine (PE) and phosphatidylcholine (PC) are vital components of biological membranes. Trypanosomatid parasites of the genus Leishmania can acquire PE and PC via de novo synthesis and the uptake/remodeling of host lipids. In this study, we investigated the ethanolaminephosphate cytidylyltransferase (EPCT) in Leishmania major, which is the causative agent for cutaneous leishmaniasis. EPCT is a key enzyme in the ethanolamine branch of the Kennedy pathway which is responsible for the de novo synthesis of PE. Our results demonstrate that L. major EPCT is a cytosolic protein capable of catalyzing the formation of CDP-ethanolamine from ethanolamine-phosphate and cytidine triphosphate. Genetic manipulation experiments indicate that EPCT is essential in both the promastigote and amastigote stages of L. major as the chromosomal null mutants cannot survive without the episomal expression of EPCT. This differs from our previous findings on the choline branch of the Kennedy pathway (responsible for PC synthesis) which is required only in promastigotes but not amastigotes. While episomal EPCT expression does not affect promastigote proliferation under normal conditions, it leads to reduced production of ethanolamine plasmalogen or plasmenylethanolamine, the dominant PE subtype in Leishmania. In addition, parasites with episomal EPCT exhibit heightened sensitivity to acidic pH and starvation stress, and significant reduction in virulence. In summary, our investigation demonstrates that proper regulation of EPCT expression is crucial for PE synthesis, stress response, and survival of Leishmania parasites throughout their life cycle.

Structure of a eukaryotic cholinephosphotransferase-1 reveals mechanisms of substrate recognition and catalysis

Phosphatidylcholine (PC) is the most abundant phospholipid in eukaryotic cell membranes. In eukaryotes, two highly homologous enzymes, cholinephosphotransferase-1 (CHPT1) and choline/ethanolamine phosphotransferase-1 (CEPT1) catalyze the final step of de novo PC synthesis. CHPT1/CEPT1 joins two substrates, cytidine diphosphate-choline (CDP-choline) and diacylglycerol (DAG), to produce PC, and Mg2+ is required for the reaction. However, mechanisms of substrate recognition and catalysis remain unresolved. Here we report structures of a CHPT1 from Xenopus laevis (xlCHPT1) determined by cryo-electron microscopy to an overall resolution of ~3.2 Å. xlCHPT1 forms a homodimer, and each protomer has 10 transmembrane helices (TMs). The first 6 TMs carve out a cone-shaped enclosure in the membrane in which the catalysis occurs. The enclosure opens to the cytosolic side, where a CDP-choline and two Mg2+ are coordinated. The structures identify a catalytic site unique to eukaryotic CHPT1/CEPT1 and suggest an entryway for DAG. The structures also reveal an internal pseudo two-fold symmetry between TM3-6 and TM7-10, and suggest that CHPT1/CEPT1 may have evolved from their distant prokaryotic ancestors through gene duplication.

Maturation of the malarial phosphatidylserine decarboxylase is mediated by high affinity binding to anionic phospholipids

Decarboxylation of phosphatidylserine (PS) to form phosphatidylethanolamine by PS decarboxylases (PSDs) is an essential process in most eukaryotes. Processing of a malarial PSD proenzyme into its active alpha and beta subunits is by an autoendoproteolytic mechanism regulated by anionic phospholipids, with PS serving as an activator and phosphatidylglycerol (PG), phosphatidylinositol, and phosphatidic acid acting as inhibitors. The biophysical mechanism underlying this regulation remains unknown. We used solid phase lipid binding, liposome-binding assays, and surface plasmon resonance to examine the binding specificity of a processing-deficient Plasmodium PSD (PkPSDS308A) mutant enzyme and demonstrated that the PSD proenzyme binds strongly to PS and PG but not to phosphatidylethanolamine and phosphatidylcholine. The equilibrium dissociation constants (Kd) of PkPSD with PS and PG were 80.4 nM and 66.4 nM, respectively. The interaction of PSD with PS is inhibited by calcium, suggesting that the binding mechanism involves ionic interactions. In vitro processing of WT PkPSD proenzyme was also inhibited by calcium, consistent with the conclusion that PS binding to PkPSD through ionic interactions is required for the proenzyme processing. Peptide mapping identified polybasic amino acid motifs in the proenzyme responsible for binding to PS. Altogether, the data demonstrate that malarial PSD maturation is regulated through a strong physical association between PkPSD proenzyme and anionic lipids. Inhibition of the specific interaction between the proenzyme and the lipids can provide a novel mechanism to disrupt PSD enzyme activity, which has been suggested as a target for antimicrobials, and anticancer therapies.

An SPNS1-dependent lysosomal lipid transport pathway that enables cell survival under choline limitation

Lysosomes degrade macromolecules and recycle their nutrient content to support cell function and survival. However, the machineries involved in lysosomal recycling of many nutrients remain to be discovered, with a notable example being choline, an essential metabolite liberated via lipid degradation. Here, we engineered metabolic dependency on lysosome-derived choline in pancreatic cancer cells to perform an endolysosome-focused CRISPR-Cas9 screen for genes mediating lysosomal choline recycling. We identified the orphan lysosomal transmembrane protein SPNS1 as critical for cell survival under choline limitation. SPNS1 loss leads to intralysosomal accumulation of lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE). Mechanistically, we reveal that SPNS1 is a proton gradient-dependent transporter of LPC species from the lysosome for their re-esterification into phosphatidylcholine in the cytosol. Last, we establish that LPC efflux by SPNS1 is required for cell survival under choline limitation. Collectively, our work defines a lysosomal phospholipid salvage pathway that is essential under nutrient limitation and, more broadly, provides a robust platform to deorphan lysosomal gene function.

Hepatic phosphatidylcholine catabolism driven by PNPLA7 and PNPLA8 supplies endogenous choline to replenish the methionine cycle with methyl groups

Choline supplies methyl groups for regeneration of methionine and the methyl donor S-adenosylmethionine in the liver. Here, we report that the catabolism of membrane phosphatidylcholine (PC) into water-soluble glycerophosphocholine (GPC) by the phospholipase/lysophospholipase PNPLA8-PNPLA7 axis enables endogenous choline stored in hepatic PC to be utilized in methyl metabolism. PNPLA7-deficient mice show marked decreases in hepatic GPC, choline, and several metabolites related to the methionine cycle, accompanied by various signs of methionine insufficiency, including growth retardation, hypoglycemia, hypolipidemia, increased energy consumption, reduced adiposity, increased fibroblast growth factor 21 (FGF21), and an altered histone/DNA methylation landscape. Moreover, PNPLA8-deficient mice recapitulate most of these phenotypes. In contrast to wild-type mice fed a methionine/choline-deficient diet, both knockout strains display decreased hepatic triglyceride, likely via reductions of lipogenesis and GPC-derived glycerol flux. Collectively, our findings highlight the biological importance of phospholipid catabolism driven by PNPLA8/PNPLA7 in methyl group flux and triglyceride synthesis in the liver.

Accelerated Breakdown of Phosphatidylcholine and Phosphatidylethanolamine Is a Predominant Brain Metabolic Defect in Alzheimer's Disease

Numerous studies have demonstrated defects in multiple metabolic pathways in Alzheimer's disease (AD), detected in autopsy brains and in the cerebrospinal fluid in vivo. However, until the advent of techniques capable of measuring thousands of metabolites in a single sample, it has not been possible to rank the relative magnitude of these abnormalities. A recent study provides evidence that the abnormal turnover of the brain's most abundant phospholipids: phosphatidylcholine and phosphatidylethanolamine, constitutes a major metabolic pathology in AD. We place this observation in a historical context and discuss the implications of a central role for phospholipid metabolism in AD pathogenesis.

Targeted Lipidomics Analysis of Adipose and Skeletal Muscle Tissues by Multiple Reaction Monitoring Profiling

Lipid homeostasis is critical for maintaining normal cellular functions including membrane structural integrity, cell metabolism, and signal transduction. Adipose tissue and skeletal muscle are two major tissues involved in lipid metabolism. Adipose tissue can store excessive lipids in the form of triacylglyceride (TG), which can be hydrolyzed to release free fatty acids (FFAs) under insufficient nutrition states. In the highly energy-demanding skeletal muscle, lipids serve as oxidative substrates for energy production but can cause muscle dysfunction when overloaded. Lipids undergo fascinating cycles of biogenesis and degradation depending on physiological demands, while dysregulation of lipid metabolism has been increasingly recognized as a hallmark of diseases such as obesity and insulin resistance. Thus, it is important to understand the diversity and dynamics of lipid composition in adipose tissue and skeletal muscle. Here, we describe the use of multiple reaction monitoring profiling, based on lipid class and fatty acyl chain specific fragmentation, to explore various classes of lipids in skeletal muscle and adipose tissues. We provide a detailed method for exploratory analysis of acylcarnitine (AC), ceramide (Cer), cholesteryl ester (CE), diacylglyceride (DG), FFA, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylserine (PS), sphingomyelin (SM), and TG. Characterization of lipid composition within adipose tissue and skeletal muscle under different physiological situations will provide biomarkers and therapeutic targets for obesity-related diseases.

The characterization and expression analysis under stress conditions of PCST1 in Arabidopsis

Analysis of PCST1 expression characteristics and the role of PCST1 in response to osmotic stress in Arabidopsis thaliana. The structure of PCST1 was analyzed using Bioinformatics method. Real-time PCR, GUS tissue localization and subcellular localization were adopted to analyze the expression pattern of PCST1 in Arabidopsis. To validate the transgenic positive strain of PCST1 using Real-time PCR, overexpression experiments were performed in wild type. Full-length cDNA was cloned and connected into a binary vector with 35S promoter, and the construction was transformed into wild type. With NaCl and mannitol treatments, the germination rate, green leaves rate, physiological indexes were carried out and counted in Arabidopsis with overexpression of PCST1 and T-DNA insertion mutants. The molecular mechanism of PCST1 in response to osmotic stress in Arabidopsis was analyzed. Based on the bioinformatic analysis, PCST1 is a hydrophobin with 403 amino acids, and the molecular weight is 45.3236 KDa. It contains only the START (the lipid/sterol - binding StAR - related lipid transfer protein domains) conservative domain. PCST1 possesses phosphatidylcholine binding sites and transmembrane region. Expression pattern analysis showed that expression of PCST1 increased with time. The PCST1 widely expressed in Arabidopsis, including roots, axils of stem leaves, flowers (sepal, conductive tissue of the petal, thrum, anther and stigmas), and the top and basal parts of the siliquas. It mainly localized in cell membrane. The overexpression of PCST1 enhanced the sensitivity to osmotic stress in Arabidopsis based on the germination rate. While expression of PCST1 decreased, and the sensitivity to osmotic stress had no obvious change in Arabidopsis. Its molecular mechanism study showed, that PCST1 response to osmotic stress resistance by regulating the proline, betaine synthesis, as well as the expression of key genes SOS, NCED, CIPK. PCST1 is composed of 403 amino acids. The START conservative domain, a transmembrane structure, the phosphatidyl choline binding sites are contained in PCST1. It is localized in cytoplasmic membrane. The PCST1 widely expressed in the root, leaf, flower and siliquas. NaCl and mannitol suppressed the expression of PCST1 and PCST1 can negatively control action of Arabidopsis in the osmotic stress. PCST1 regulates the synthetic pathway of proline, betaine and the expression of SOS, NCED and CIPK in response to the osmotic stress resistance.

Lipidome analysis and characterization of Buglossoides arvensis acyltransferases that incorporate polyunsaturated fatty acids into triacylglycerols

Buglossoides arvensis is a burgeoning oilseed crop that contains an unique combination of ω-3 and ω-6 polyunsaturated fatty acids (PUFA), constituting ~80-85% of seed triacylglycerols (TAGs). To uncover the critical TAG biosynthetic pathways contributing for high PUFA accumulation, we performed lipidome of developing seeds and characterized acyltransferases involved in the final step of TAG biosynthesis. During seed development, distribution of lipid molecular species in individual lipid classes showed distinct patterns from an early-stage (6 days after flowering (DAF)) to the middle-stage (12 and 18 DAF) of oil biosynthesis. PUFA-containing TAG species drastically increased from 6 to 12 DAF. The expression profiles of key triacylglycerol biosynthesis genes and patterns of phosphatidylcholine, diacylglycerol and triacylglycerol molecular species during seed development were used to predict the contribution of diacylglycerol acyltransferases (DGAT1 and DGAT2) and phospholipid: diacylglycerol acyltransferases (PDAT1 and PDAT2) to PUFA-rich TAG biosynthesis. Our analysis suggests that DGATs play a crucial role in enriching TAGs with PUFA compared to PDATs. This was further confirmed by fatty acid feeding studies in yeast expressing acyltransferases. BaDGAT2 preferentially incorporated high amounts of PUFAs into TAG, compared to BaDGAT1. Our results provide insight into the molecular mechanisms of TAG accumulation in this plant and identify target genes for transgenic production of SDA in traditional oilseed crops.

Exploring the binding kinetics and behaviors of self-aggregated beta-amyloid oligomers to phase-separated lipid rafts with or without ganglioside-clusters

Lipid binding kinetics and energetics of self-aggregated and disordered beta-amyloid oligomers of various sizes, from solution to lipid raft surfaces, were investigated using MD simulations. Our systems include small (monomers to tetramers) and larger (octamers and dodecamers) oligomers. Our lipid rafts contain saturated and unsaturated phosphatidylcholine (PC), cholesterol, and with or without asymmetrically distributed monosialotetrahexosylganglioside (GM1). All rafts exhibited dynamic and structurally diversified domains including liquid-ordered (Lo), liquid-disordered (Ld), and interfacial Lod domains. For rafts without GM1, all oligomers bound to the Lod domain. For GM1-containing rafts, all small oligomers and most larger oligomers bound specifically to the GM1-clusters embedded in the Lo domain. Lipid-protein binding energies followed an order of GM1 >> unsaturated PC > saturated PC > cholesterol for all rafts. In addition, protein-induced membrane structural disruption increased progressively with the size of the oligomer for the annular lipids surrounding the membrane-bound protein in non-GM1-containing rafts. We propose that the tight binding of beta-amyloid oligomers to the GM1-clusters and the structural perturbation of lipids surrounding the membrane-bound proteins at the Lod domain are early molecular events of the beta-amyloid aggregation process on neuronal membrane surfaces that trigger the onset of Alzheimer's.

The Anticancer Drug Bleomycin Shows Potent Antifungal Activity by Altering Phospholipid Biosynthesis

Invasive fungal infections are difficult to treat with limited drug options, mainly because fungi are eukaryotes and share many cellular mechanisms with the human host. Most current antifungal drugs are either fungistatic or highly toxic. Therefore, there is a critical need to identify important fungal specific drug targets for novel antifungal development. Numerous studies have shown the fungal phosphatidylserine (PS) biosynthetic pathway to be a potential target. It is synthesized from CDP-diacylglycerol and serine, and the fungal PS synthesis route is different from that in mammalian cells, in which preexisting phospholipids are utilized to produce PS in a base-exchange reaction. In this study, we utilized a Saccharomyces cerevisiae heterologous expression system to screen for inhibitors of Cryptococcus PS synthase Cho1, a fungi-specific enzyme essential for cell viability. We identified an anticancer compound, bleomycin, as a positive candidate that showed a phospholipid-dependent antifungal effect. Its inhibition on fungal growth can be restored by ethanolamine supplementation. Further exploration of the mechanism of action showed that bleomycin treatment damaged the mitochondrial membrane in yeast cells, leading to increased generation of reactive oxygen species (ROS), whereas supplementation with ethanolamine helped to rescue bleomycin-induced damage. Our results indicate that bleomycin does not specifically inhibit the PS synthase enzyme; however, it may affect phospholipid biosynthesis through disruption of mitochondrial function, namely, the synthesis of phosphatidylethanolamine (PE) and phosphatidylcholine (PC), which helps cells maintain membrane composition and functionality. IMPORTANCE Invasive fungal pathogens cause significant morbidity and mortality, with over 1.5 million deaths annually. Because fungi are eukaryotes that share much of their cellular machinery with the host, our armamentarium of antifungal drugs is highly limited, with only three classes of antifungal drugs available. Drug toxicity and emerging resistance have limited their use. Hence, targeting fungi-specific enzymes that are important for fungal survival, growth, or virulence poses a strategy for novel antifungal development. In this study, we developed a heterologous expression system to screen for chemical compounds with activity against Cryptococcus phosphatidylserine synthase, Cho1, a fungi-specific enzyme that is essential for viability in C. neoformans. We confirmed the feasibility of this screen method and identified a previously unexplored role of the anticancer compound bleomycin in disrupting mitochondrial function and inhibiting phospholipid synthesis.

Protective Effects of Phosphatidylcholine against Hepatic and Renal Cell Injury from Advanced Glycation End Products

Background and Objectives: Receptors of the advanced glycation products (RAGE) are activated to promote cell death and contributes to chronic diseases such as diabetes and inflammation. Advanced glycation end products (AGEs), which interact with RAGE are complex compounds synthesized during diabetes development and are presumed to play a significant role in pathogenesis of diabetes. Phosphatidylcholine (PC), a polyunsaturated fatty acid found in egg yolk, mustard, and soybean, is thought to exert anti-inflammatory activity. We investigated the effects of PC on AGEs-induced hepatic and renal cell injury. Materials and Methods: In this study, we evaluated cytokine and NF-κB/MAPK signal pathway activity in AGEs induced human liver (HepG2) cells and human kidney (HK2) cells with and without PC treatment. Results: PC reduced RAGE expression and attenuated levels of inflammatory cytokines and NF-kB/MAPK signaling. Moreover, cells treated with PC exhibited a significant reduction in cytotoxicity, oxidative stress, and inflammatory factor levels. Conclusions: These findings suggest that PC could be an effective functional material for hepatic and renal injury involving with oxidative stress caused by AGEs during diabetic conditions.

Human placental lipid content and lipid metabolic enzyme abundance in obesity and across gestation

Changes in placental lipid metabolism influence the delivery of lipids critical for fetal development and fetal requirements for lipids change across gestation. We hypothesized that placental lipid content and metabolic enzyme protein levels increase across gestation and are elevated in obesity. Placentas (4-40 weeks' gestation) were collected from control (body mass index, BMI = 18.5-24.9, n=37) and obese (BMI > 30, n=19) pregnant women. Trophoblast villous tissue was homogenized and subjected to liquid chromatography tandem mass spectrometry (LC-MS/MS) for phospholipid and triacylglycerol (TAG) analysis and western blot for protein quantification. The placental content of TAG species and nine of 35 identified phosphatidylcholines (PC) were significantly higher (P<0.05) in first trimester (28-79%, 10-47%, respectively). Furthermore, two TAG and three PC differed by maternal BMI and were significantly increased (P<0.05) in the obese group in first trimester (72-87%, 88-119%, respectively). Placental protein abundance of glycerol-2-phosphate (GPAT3) and 1-acyl-sn-glycerol-3-phosphate acyltransferase 2 (AGPAT2), involved in de novo synthesis of PC and TAG, were higher (P<0.05) in the first trimester (66 and 74%, respectively). The protein abundance of the PC-remodeling enzyme PLA2G4c was also higher (63%) in first trimester (P<0.05). In conclusion, the placental content of many phospholipid and TAG species and the protein level of associated synthesis enzymes are higher in first-trimester human placenta. The high PC content may be related to the rapid membrane expansion in early pregnancy and the low placental oxygen tension may promote the accumulation of tissue TAGs in first trimester. Maternal obesity had only limited impact on placental lipid content and metabolic enzyme protein abundance.

Metabolic Regulation and Lipidomic Remodeling in Relation to Spermidine-Induced Stress Tolerance to High Temperature in Plants

Beneficial effects of spermidine (Spd) on alleviating abiotic stress damage have been explored in plants for hundreds of years, but limited information is available about its roles in regulating lipids signaling and metabolism during heat stress. White clover (Trifolium repens) plants were pretreated with 70 μM Spd and then subjected to high temperature (38/33 °C) stress for 20 days. To further investigate the effect of Spd on heat tolerance, transgenic Arabidopsisthaliana overexpressing a TrSAMS encoding a key enzyme involved in Spd biosynthesis was exposed to high temperature (38/33 °C) stress for 10 days. A significant increase in endogenous Spd content in white clover by exogenous application of Spd or the TrSAMS overexpression in Arabidopsisthaliana could effectively mitigate heat-induced growth retardation, oxidative damage to lipids, and declines in photochemical efficiency and cell membrane stability. Based on the analysis of metabolomics, the amino acids and vitamins metabolism, biosynthesis of secondary metabolites, and lipids metabolism were main metabolic pathways regulated by the Spd in cool-season white clover under heat stress. Further analysis of lipidomics found the TrSAMS-transgenic plants maintained relatively higher accumulations of total lipids, eight phospholipids (PC, phosphatidylcholine; PG, phosphatidylglycerol; PS, phosphatidylserine; CL, cardiolipin; LPA, lysophosphatidic acid; LPC, lyso phosphatidylcholine; LPG, lyso phosphatidylglycerol; and LPI, lyso phosphatidylinositol), one glycoglycerolipid (DGDG, digalactosyl diacylglycerol), and four sphingolipids (Cer, ceramide; CerG2GNAc1, dihexosyl N-acetylhexosyl ceramide; Hex1Cer, hexosyl ceramide; and ST, sulfatide), higher ratio of DGDG: monogalactosyl diacylglycerol (MGDG), and lower unsaturation level than wild-type Arabidopsisthaliana in response to heat stress. Spd-induced lipids accumulation and remodeling could contribute to better maintenance of membrane stability, integrity, and functionality when plants underwent a long period of heat stress. In addition, the Spd significantly up-regulated PIP2 and PA signaling pathways, which was beneficial to signal perception and transduction for stress defense. Current findings provide a novel insight into the function of Spd against heat stress through regulating lipids signaling and reprograming in plants.

Alterations of Lipid Profile in Livers with Impaired Lipophagy

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation in the liver. Various mechanisms such as an increased uptake in fatty acids or de novo synthesis contribute to the development of steatosis and progression to more severe stages. Furthermore, it has been shown that impaired lipophagy, the degradation of lipids by autophagic processes, contributes to NAFLD. Through an unbiased lipidome analysis of mouse livers in a genetic model of impaired lipophagy, we aimed to determine the resulting alterations in the lipidome. Observed changes overlap with those of the human disease. Overall, the entire lipid content and in particular the triacylglycerol concentration increased under conditions of impaired lipophagy. In addition, we detected a reduction in long-chain polyunsaturated fatty acids (PUFAs) and an increased ratio of n-6 PUFAs to n-3 PUFAs, which was due to the depletion of n-3 PUFAs. Although the abundance of major phospholipid classes was reduced, the ratio of phosphatidylcholines to phosphatidylethanolamines was not affected. In conclusion, this study demonstrates that impaired lipophagy contributes to the pathology of NAFLD and is associated with an altered lipid profile. However, the lipid pattern does not appear to be specific for lipophagic alterations, as it resembles mainly that described in relation to fatty liver disease.

Intestinal metabolomics of juvenile lenok (Brachymystax lenok) in response to heat stress

Changes in the metabolic profile within the intestine of lenok (Brachymystax lenok) when challenged to acute and lethal heat stress (HS) are studied using no-target HPLC-MS/MS metabonomic analysis. A total of 51 differentially expressed metabolites (VIP > 1, P < 0.05) were identified in response to HS, and 34 occurred in the positive ion mode and 17 in negative ion mode, respectively. After heat stress, changes in metabolites related to glycolysis (i.e., alpha-D-glucose, stachyose, and L-lactate) were identified. The metabolites (acetyl carnitine, palmitoylcarnitine, carnitine, and erucic acid) related to fatty acid β-oxidation accumulated significantly, and many amino acids (L-tryptophan, D-proline, L-leucine, L-phenylalanine, L-aspartate, L-tyrosine, L-methionine, L-histidine, and L-glutamine) were significantly decreased in HS-treated lenok. The mitochondrial β-oxidation pathway might be inhibited, while severe heat stress might activate the anaerobic glycolysis and catabolism of amino acid for energy expenditure. Oxidative damage in HS-treated lenok was indicated by the decreased glycerophospholipid metabolites (i.e., glycerophosphocholine, 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine, 1-palmitoyl-sn-glycero-3-phosphocholine, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 1, 2-dioleoyl-sn-glycero-3-phosphatidylcholine) and the increased oxylipin production (12-HETE and 9R, 10S-EpOME). The minor oxidative pathways (omega-oxidation and peroxisomal beta-oxidation) were likely to be induced in HS-treated lenok.

Dietary choline prevents high fat-induced disorder of hepatic cholesterol metabolism through SREBP-2/HNF-4α/CYP7A1 pathway in a freshwater teleost yellow catfish Pelteobagrus fulvidraco

Lipid overload-induced hepatic cholesterol accumulation is a major public health problem worldwide, and choline has been reported to ameliorate cholesterol accumulation, but its mechanism remains unclear. Our study found that choline prevented high-fat diet (HFD)-induced cholesterol metabolism disorder and enhanced choline uptake and phosphatidylcholine synthesis in the liver tissues; choline incubation prevented fatty acid (FA)-induced cholesterol accumulation and FA-induced inhibition of bile acid synthesis. Moreover, compared to single FA incubation, choline incubation or FA + choline co-incubation increased the mRNA abundances and protein levels of HNF4α and up-regulated the degradation of cholesterol into bile acids. Mechanistically, choline prevented the FA-induced accumulation of SREBP2 protein and the interaction between SREBP2 and HNF4α, thereby enhancing the DNA binding capacity of the HNF4α to the CYP7A1 promoter, and promoting the degradation of cholesterol into bile acids. Our study elucidated the novel regulatory mechanisms of choline preventing HFD-induced cholesterol accumulation and increasing bile acid synthesis by SREBP-2/HNF-4α/CYP7A1 pathway.

Relative Abundance of Lipid Metabolites in Spermatozoa across Three Compartments

Male fertility, as manifest by the quantity and progressive motility of spermatozoa, is negatively impacted by obesity, dyslipidaemia and metabolic disease. However, the relative distribution of lipids in spermatozoa and the two compartments which supply lipids for spermatogenesis (seminal fluid and blood serum) has not been studied. We hypothesised that altered availability of lipids in blood serum and seminal fluid may affect the lipid composition and progressive motility of sperm. 60 men of age 35 years (median (range 20-45) and BMI 30.4 kg/m² (24-36.5) under preliminary investigation for subfertility were recruited at an NHS clinic. Men provided samples of serum and semen, subject to strict acceptance criteria, for analysis of spermatozoa count and motility. Blood serum (n = 60), spermatozoa (n = 26) and seminal fluid (n = 60) were frozen for batch lipidomics analysis. Spermatozoa and seminal fluid had comparable lipid composition but showed marked differences with the serum lipidome. Spermatozoa demonstrated high abundance of ceramides, very-long-chain fatty acids (C20-22), and certain phospholipids (sphingomyelins, plasmalogens, phosphatidylethanolamines) with low abundance of phosphatidylcholines, cholesterol and triglycerides. Men with spermatozoa of low progressive motility had evidence of fewer concentration gradients for many lipid species between blood serum and spermatozoa compartments. Spermatozoa are abundant in multiple lipid species which are likely to contribute to key cellular functions. Lipid metabolism shows reduced regulation between compartments in men with spermatozoa with reduced progressive motility.

Elevating Phospholipids Production Yarrowia lipolytica from Crude Glycerol

Phospholipids (PLs) are a class of lipids with many proven biological functions. They are commonly used in lipid replacement therapy to enrich cell membranes damaged in chronic neurodegenerative diseases, cancer, or aging processes. Due to their amphipathic nature, PLs have been widely used in food, cosmetic, and pharmaceutical products as natural emulsifiers and components of liposomes. In Yarrowia lipolytica, PLs are synthesized through a similar pathway like in higher eukaryotes. However, PL biosynthesis in this yeast is still poorly understood. The key intermediate in this pathway is phosphatidic acid, which in Y. lipolytica is mostly directed to the production of triacylglycerols and, in a lower amount, to PL. This study aimed to deliver a strain with improved PL production, with a particular emphasis on increased biosynthesis of phosphatidylcholine (PC). Several genetic modifications were performed: overexpression of genes from PL biosynthesis pathways as well as the deletion of genes responsible for PL degradation. The best performing strain (overexpressing CDP-diacylglycerol synthase (CDS) and phospholipid methyltransferase (OPI3)) reached 360% of PL improvement compared to the wild-type strain in glucose-based medium. With the substitution of glucose by glycerol, a preferred carbon source by Y. lipolytica, an almost 280% improvement of PL was obtained by transformant overexpressing CDS, OPI3, diacylglycerol kinase (DGK1), and glycerol kinase (GUT1) in comparison to the wild-type strain. To further increase the amount of PL, the optimization of culture conditions, followed by the upscaling to a 2 L bioreactor, were performed. Crude glycerol, being a cheap and renewable substrate, was used to reduce the costs of PL production. In this process 653.7 mg/L of PL, including 352.6 mg/L of PC, was obtained. This study proved that Y. lipolytica is an excellent potential producer of phospholipids, especially from waste substrates.

Lipid metabolism disorders contribute to hepatotoxicity of ICR mice induced by nitrosamines exposure

Health risks caused by crucial environmental carcinogens N-nitrosamines triggered ubiquitous attention. As the liver exerted vital function through metabolic process, lipid metabolism disorders have been confirmed as potential drivers for toxicological effects, and the mechanisms of lipid regulation related to hepatotoxicity induced by N-nitrosamines remained largely unclear. In this study, we comprehensively explored the disturbance of hepatic lipid homeostasis in mice induced by nitrosamines. The results implied that nitrosamines exposure induced hepatotoxicity accompanied by liver injury, inflammatory infiltration, and hepatic edema. Lipidomics profiling analysis indicated the decreased levels of phosphatidic acids (PA), phosphatidylcholines (PC), phosphatidylethanolamines (PE), lyso-phosphatidylcholines (LPC), lyso-phosphatidylethanolamines (LPE), diacylglycerols (DAG) and triacylglycerols (TAG), the elevation of ceramides (Cer) and decomposition of free fatty acids (FFA) in high-dose nitrosamines exposure group. Importantly, nitrosamines exposure promoted fatty acid oxidation (FAO) by facilitating fatty acid uptake and decomposition, together with the upregulation of genes associated with FAO accompanied by the activation of inflammatory cytokines TNF-α, IL-1β and NLRP3. Furthermore, fatty acid translocase CD36-mediated fatty acid oxidation was correlated with the enhancement of oxidative stress in the liver caused by nitrosamines exposure. Overall, our results contributed to the new strategies to interpret the early toxic effects of nitrosamines exposure.

Plasma lipidomics in subjects with combat posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is complex neuropsychiatric disorder triggered by a traumatic event and characterized by the symptoms that represent large burden to patients, as well as to society. Lipidomic approach can be applied as a useful tool for discovery of novel diagnostic, prognostic and therapeutic lipid biomarkers of various disorders, whose etiology is complex and still unknown, including PTSD. Since changes in the levels of lipid metabolites might indicate impairments in various metabolic pathways and cellular processes, the aim of this lipidomic study was to determine altered levels of lipid compounds in PTSD. The study enrolled 235 male patients with combat PTSD and 241 healthy male control subjects. Targeted lipidomic analysis of plasma samples was conducted using reverse-phase liquid chromatography coupled with mass spectrometry. Lipids that have been analyzed belong to the group of ceramides, cholesterol esters, diacylglycerols, lysophosphatidylcholines, lysophosphatidylethanolamines, phosphatidylcholines, phosphatidylethanolamines, sphingomyelins and triglycerides. The levels of fifteen lipid compounds were found to be significantly different between PTSD patients and healthy control subjects, including four phosphatidylcholines, two phosphatidylethanolamines, five sphingomyelins, two cholesterol esters and two ceramides. The lipid metabolites whose levels significantly differed between patients with PTSD and control subjects are associated with various biological processes, including impairments of membrane integrity and function, mitochondrial dysfunction, inflammation and oxidative stress. As these processes might be associated with development and progression of PTSD, altered lipid compounds represent potential biomarkers that could facilitate the diagnosis of PTSD, prediction of the disease, as well as identification of novel treatment approaches in PTSD.

Hepatic PEMT Expression Decreases with Increasing NAFLD Severity

Choline deficiency causes hepatic fat accumulation, and is associated with a higher risk of nonalcoholic fatty liver disease (NAFLD) and more advanced NAFLD-related hepatic fibrosis. Reduced expression of hepatic phosphatidylethanolamine N-methyltransferase (PEMT), which catalyzes the production of phosphatidylcholine, causes steatosis, inflammation, and fibrosis in mice. In humans, common PEMT variants impair phosphatidylcholine synthesis, and are associated with NAFLD risk. We investigated hepatic PEMT expression in a large cohort of patients representing the spectrum of NAFLD, and examined the relationship between PEMT genetic variants and gene expression. Hepatic PEMT expression was reduced in NAFLD patients with inflammation and fibrosis (i.e., nonalcoholic steatohepatitis or NASH) compared to participants with normal liver histology (β = −1.497; p = 0.005). PEMT levels also declined with increasing severity of fibrosis with cirrhosis < incomplete cirrhosis < bridging fibrosis (β = −1.185; p = 0.011). Hepatic PEMT expression was reduced in postmenopausal women with NASH compared to those with normal liver histology (β = −3.698; p = 0.030). We detected a suggestive association between rs7946 and hepatic fibrosis (p = 0.083). Although none of the tested variants were associated with hepatic PEMT expression, computational fine mapping analysis indicated that rs4646385 may impact PEMT levels in the liver. Hepatic PEMT expression decreases with increasing severity of NAFLD in obese individuals and postmenopausal women, and may contribute to disease pathogenesis in a subset of NASH patients.

Dimethyl Fumarate-Loaded Transethosomes: A Formulative Study and Preliminary Ex Vivo and In Vivo Evaluation

In this study, transethosomes were investigated as potential delivery systems for dimethyl fumarate. A formulative study was performed investigating the effect of the composition of transethosomes on the morphology and size of vesicles, as well as drug entrapment capacity, using cryogenic transmission electron microscopy, photon correlation spectroscopy, and HPLC. The stability of vesicles was evaluated, both for size increase and capability to control the drug degradation. Drug release kinetics and permeability profiles were evaluated in vitro using Franz cells, associated with different synthetic membranes. The in vitro viability, as well as the capacity to improve wound healing, were evaluated in human keratinocytes. Transmission electron microscopy enabled the evaluation of transethosome uptake and intracellular fate. Based on the obtained results, a transethosome gel was further formulated for the cutaneous application of dimethyl fumarate, the safety of which was evaluated in vivo with a patch test. It was found that the phosphatidylcholine concentration affected vesicle size and lamellarity, influencing the capacity to control dimethyl fumarate’s chemical stability and release kinetics. Indeed, phosphatidylcholine 2.7% w/w led to multivesicular vesicles with 344 nm mean size, controlling the drug’s chemical stability for at least 90 days. Conversely, phosphatidylcholine 0.9% w/w resulted in 130 nm sized unilamellar vesicles, which maintained 55% of the drug over 3 months. These latest kinds of transethosomes were able to improve wound healing in vitro and were easily internalised by keratinocytes. The selected transethosome gel, loading 25 mg/mL dimethyl fumarate, was not irritant after cutaneous application under occlusion, suggesting its possible suitability in the treatment of wounds caused by diabetes mellitus or peripheral vascular diseases.

Expression of Physaria longchain acyl-CoA synthetases and hydroxy fatty acid accumulation in transgenic Arabidopsis

Hydroxy fatty acids (HFA) are industrially useful chemical feedstocks that accumulate in seed-storage triacylglycerols (TAG) of several plant species, including castor (Ricinus communis) and Physaria (Physaria fendleri). For researchers, HFA also offer a unique opportunity to trace fatty acid metabolism and modification. Past work producing HFA in Arabidopsis (Arabidopsis thaliana) has demonstrated the importance of isozymes of TAG synthesis from plants that evolved to store HFA and as a result have a high degree of specificity towards HFA substrates. Castor phospholipase A2α (RcPLA2) has specificity for HFA-containing phosphatidylcholine. However, expression of RcPLA2 in HFA-accumulating Arabidopsis line CL37-PLA2 reduced HFA content of TAG. This loss was interpreted as being due to poor ability of Arabidopsis longchain acyl-CoA synthetases (LACSs) to utilize HFAs substrates. LACS enzymes are essential to activate HFA to HFA-CoA for TAG synthesis. Physaria is a close relative of Arabidopsis in the Brassicaceae family. To test the hypothesis that this close relatedness would allow Physaria LACSs to interface successfully with Arabidopsis enzymes of seed lipid metabolism and thereby restore HFA accumulation, we transformed PfLACS4 and PfLACS8 constructs into the CL37-PLA2 line. However, HFA content was not recovered, and biochemical characterization of recombinant PfLACS4 and PfLACS8 indicated that these isozymes have substrate specificities and selectivities that are similar to their Arabidopsis orthologues. These and other results pose an important question about how HFA synthesized on phosphatidylcholine can be transferred into the acyl-CoA pool for TAG synthesis.