Phosphatidylserine and Tyro3-Axl-Mertk Receptor Tyrosine Kinase level detection in plasma and on plasma-derived extracellular vesicle surface in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is a chronic lymphoproliferative disorder characterized by monoclonal B cell proliferation. Studies carried out in recent years suggest that extracellular vesicles (EVs) may be a potential biomarker in cancer. Tyro3-Axl-Mertk (TAM) Receptor Tyrosine Kinases (RTKs) and Phosphatidylserine (PS) have crucial roles in macrophage-mediated immune response under normal conditions. In the tumor microenvironment, these molecules contribute to immunosuppressive signals and prevent the formation of local and systemic antitumor immune responses. Based on this, we aimed to evaluate the amount of PS and TAM RTK in plasma and on the surface of EVs in CLL patients and healthy volunteers in this study. In this study, 25 CLL (11 F/14 M) patients in the Rai (O-I) stage, newly diagnosed or followed up without treatment, and 15 healthy volunteers (11 F/4 M) as a control group were included. For all samples, PS and TAM RTK levels were examined first in the plasma and then in the EVs obtained from the plasma. We detected a significant decrease in plasma PS, and TAM RTK levels in CLL patients compared to the control. Besides, we determined a significant increase in TAM RTK levels on the EV surface in CLL, except for PS. In conclusion, these receptor levels measured by ELISA in plasma may not be effective for the preliminary detection of CLL. However, especially TAM RTKs on the surface of EVs may be good biomarkers and potential targets for CLL therapies.

Disruption of Transmembrane Phosphatidylserine Asymmetry by HIV-1 Incorporated SERINC5 Is Not Responsible for Virus Restriction.

Host restriction factor SERINC5 (SER5) incorporates into the HIV-1 membrane and inhibits infectivity by a poorly understood mechanism. Recently, SER5 was found to exhibit scramblase-like activity leading to the externalization of phosphatidylserine (PS) on the viral surface, which has been proposed to be responsible for SER5's antiviral activity. This and other reports that document modulation of HIV-1 infectivity by viral lipid composition prompted us to investigate the role of PS in regulating SER5-mediated HIV-1 restriction. First, we show that the level of SER5 incorporation into virions correlates with an increase in PS levels in the outer leaflet of the viral membrane. We developed an assay to estimate the PS distribution across the viral membrane and found that SER5, but not SER2, which lacks antiviral activity, abrogates PS asymmetry by externalizing this lipid. Second, SER5 incorporation diminished the infectivity of pseudoviruses produced from cells lacking a flippase subunit CDC50a and, therefore, exhibited a higher baseline level of surface-accessible PS. Finally, exogenous manipulation of the viral PS levels utilizing methyl-alpha-cyclodextrin revealed a lack of correlation between external PS and virion infectivity. Taken together, our study implies that the increased PS exposure to SER5-containing virions itself is not directly linked to HIV-1 restriction.

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.

The small molecule CBR-5884 inhibits the Candida albicans phosphatidylserine synthase.

Systemic infections by Candida spp. are associated with high mortality rates, partly due to limitations in current antifungals, highlighting the need for novel drugs and drug targets. The fungal phosphatidylserine synthase, Cho1, from Candida albicans is a logical antifungal drug target due to its importance in virulence, absence in the host, and conservation among fungal pathogens. Inhibitors of Cho1 could serve as lead compounds for drug development, so we developed a target-based screen for inhibitors of purified Cho1. This enzyme condenses serine and cytidyldiphosphate-diacylglycerol (CDP-DAG) into phosphatidylserine (PS) and releases cytidylmonophosphate (CMP). Accordingly, we developed an in vitro nucleotidase-coupled malachite-green-based high throughput assay for purified C. albicans Cho1 that monitors CMP production as a proxy for PS synthesis. Over 7,300 molecules curated from repurposing chemical libraries were interrogated in primary and dose-responsivity assays using this platform. The screen had a promising average Z' score of ~0.8, and seven compounds were identified that inhibit Cho1. Three of these, ebselen, LOC14, and CBR-5884, exhibited antifungal effects against C. albicans cells, with fungicidal inhibition by ebselen and fungistatic inhibition by LOC14 and CBR-5884. Only CBR-5884 showed evidence of disrupting in vivo Cho1 function by inducing phenotypes consistent with the cho1∆∆ mutant, including a reduction of cellular PS levels. Kinetics curves and computational docking indicate that CBR-5884 competes with serine for binding to Cho1 with a Ki of 1,550 ± 245.6 nM. Thus, this compound has the potential for development into an antifungal compound. IMPORTANCE: Fungal phosphatidylserine synthase (Cho1) is a logical antifungal target due to its crucial role in the virulence and viability of various fungal pathogens, and since it is absent in humans, drugs targeted at Cho1 are less likely to cause toxicity in patients. Using fungal Cho1 as a model, there have been two unsuccessful attempts to discover inhibitors for Cho1 homologs in whole-cell screens prior to this study. The compounds identified in these attempts do not act directly on the protein, resulting in the absence of known Cho1 inhibitors. The significance of our research is that we developed a high-throughput target-based assay and identified the first Cho1 inhibitor, CBR-5884, which acts both on the purified protein and its function in the cell. This molecule acts as a competitive inhibitor with a Ki value of 1,550 ± 245.6 nM and, thus, has the potential for development into a new class of antifungals targeting PS synthase.

Macrophages and Natural Killers Degrade α-Synuclein Aggregates.

Amyloid oligomers and fibrils are protein aggregates that exert a high cell toxicity. Efficient degradation of these protein aggregates can minimize the spread and progression of neurodegeneration. In this study, we investigate the properties of natural killer (NK) cells and macrophages in the degradation of α-synuclein (α-Syn) aggregates grown in a lipid-free environment and in the presence of phosphatidylserine and cholesterol (PS/Cho), which are lipids that are directly associated with the onset and progression of Parkinson's disease. We found that both types of α-Syn aggregates were endocytosed by neurons, which caused strong damage to cell endosomes. Our results also indicated that PS/Cho vesicles drastically increased the toxicity of α-Syn fibrils formed in their presence compared to the toxicity of α-Syn aggregates grown in a lipid-free environment. Both NK cells and macrophages were able to degrade α-Syn and α-Syn/Cho monomers, oligomers, and fibrils. Quantitative analysis of protein degradation showed that macrophages demonstrated substantially more efficient internalization and degradation of amyloid aggregates in comparison to NK cells. We also found that amyloid aggregates induced the proliferation of macrophages and NK cells and significantly changed the expression of their cytokines and chemokines.

Whole-Cell Display of Phospholipase D in Escherichia coli for High-Efficiency Extracellular Phosphatidylserine Production.

Phospholipids are widely utilized in various industries, including food, medicine, and cosmetics, due to their unique chemical properties and healthcare benefits. Phospholipase D (PLD) plays a crucial role in the biotransformation of phospholipids. Here, we have constructed a super-folder green fluorescent protein (sfGFP)-based phospholipase D (PLD) expression and surface-display system in Escherichia coli, enabling the surface display of sfGFP-PLDr34 on the bacteria. The displayed sfGFP-PLDr34 showed maximum enzymatic activity at pH 5.0 and 45 °C. The optimum Ca2+ concentrations for the transphosphatidylation activity and hydrolysis activity are 100 mM and 10 mM, respectively. The use of displayed sfGFP-PLDr34 for the conversion of phosphatidylcholine (PC) and L-serine to phosphatidylserine (PS) showed that nearly all the PC was converted into PS at the optimum conditions. The displayed enzyme can be reused for up to three rounds while still producing detectable levels of PS. Thus, Escherichia coli/sfGFP-PLD shows potential for the feasible industrial-scale production of PS. Moreover, this system is particularly valuable for quickly screening higher-activity PLDs. The fluorescence of sfGFP can indicate the expression level of the fused PLD and changes that occur during reuse.

Modulating Lipid-Polymer Nanoparticles' Physicochemical Properties to Alter Macrophage Uptake.

Macrophage uptake of nanoparticles is highly dependent on the physicochemical characteristics of those nanoparticles. Here, we have created a collection of lipid-polymer nanoparticles (LPNPs) varying in size, stiffness, and lipid makeup to determine the effects of these factors on uptake in murine bone marrow-derived macrophages. The LPNPs varied in diameter from 232 to 812 nm, in storage modulus from 21.2 to 287 kPa, and in phosphatidylserine content from 0 to 20%. Stiff, large nanoparticles with a coating containing phosphatidylserine were taken up by macrophages to a much higher degree than any other formulation (between 9.3× and 166× higher than other LPNPs). LPNPs with phosphatidylserine were taken up most by M2-polarized macrophages, while those without were taken up most by M1-polarized macrophages. Differences in total LPNP uptake were not dependent on endocytosis pathway(s) other than phagocytosis. This work acts as a basis for understanding how the interactions between nanoparticle physicochemical characteristics may act synergistically to facilitate particle uptake.

Bending of a lipid membrane edge by annexin A5 trimers.

Plasma membrane damage occurs in healthy cells and more frequently in cancer cells where high growth rates and metastasis result in frequent membrane damage. The annexin family of proteins plays a key role in membrane repair. Annexins are recruited at the membrane injury site by Ca+2 and repair the damaged membrane in concert with several other proteins. Annexin A4 (ANXA4) and ANXA5 form trimers at the bilayer surface, and previous simulations show that the trimers induce high local negative membrane curvature on a flat bilayer. The membrane-curvature-inducing property of ANXA5 is presumed to be vital to the membrane repair mechanism. A previously proposed descriptive model hypothesizes that ANXA5-mediated curvature force is utilized at the free edge of the membrane at a wound site to pull the wound edges together, resulting in the formation of a "neck"-shaped structure, which, when combined with a constriction force exerted by ANXA6, leads to membrane repair. The molecular details and mechanisms of repair remain unknown, in part because the membrane edge is a transient structure that is difficult to investigate both experimentally and computationally. For the first time, we investigate the impact of ANXA5 near a membrane edge, which is modeled by a bicelle under periodic boundary conditions. ANXA5 trimers induce local curvature on the membrane leading to global bending of the bicelle. The global curvature depends on the density of annexins on the bicelle, and the curvature increases with the ANXA5 concentration until it reaches a plateau. The simulations suggest that not only do annexins induce local membrane curvature, but they can change the overall shape of a free-standing membrane. We also demonstrate that ANXA5 trimers reduce the rate of phosphatidylserine lipid diffusion from the cytoplasmic to the exoplasmic leaflet along the edge of the bicelle. In this way, membrane-bound annexins can potentially delay the apoptotic signal triggered by the presence of phosphatidylserine lipids in the outer leaflet, thus biding time for repair of the membrane hole. Our findings provide new insights into the role of ANXA5 at the edges of the membrane (the injury site) and support the curvature-constriction model of membrane repair.

Coordinated regulation of phosphatidylinositol 4-phosphate and phosphatidylserine levels by Osh4p and Osh5p is an essential regulatory mechanism in autophagy.

Macroautophagy (hereafter autophagy) is an intracellular degradative pathway in budding yeast cells. Certain lipid types play essential roles in autophagy; yet the precise mechanisms regulating lipid composition during autophagy remain unknown. Here, we explored the role of the Osh family proteins in the modulating lipid composition during autophagy in budding yeast. Our results showed that osh1-osh7∆ deletions lead to autophagic dysfunction, with impaired GFP-Atg8 processing and the absence of autophagosomes and autophagic bodies in the cytosol and vacuole, respectively. Freeze-fracture electron microscopy (EM) revealed elevated phosphatidylinositol 4-phosphate (PtdIns(4)P) levels in cytoplasmic and luminal leaflets of autophagic bodies and vacuolar membranes in all deletion mutants. Phosphatidylserine (PtdSer) levels were significantly decreased in the autophagic bodies and vacuolar membranes in osh4∆ and osh5∆ mutants, whereas no significant changes were observed in other osh deletion mutants. Furthermore, we identified defects in autophagic processes in the osh4∆ and osh5∆ mutants, including rare autophagosome formation in the osh5∆ mutant and accumulation of autophagic bodies in the vacuole in the osh4∆ mutant, even in the absence of the proteinase inhibitor PMSF. These findings suggest that Osh4p and Osh5p play crucial roles in the transport of PtdSer to autophagic bodies and autophagosome membranes, respectively. The precise control of lipid composition in the membranes of autophagosomes and autophagic bodies by Osh4p and Osh5p represents an important regulatory mechanism in autophagy.

Blockade of CD300A enhances the ability of human NK cells to lyse hematologic malignancies.

OBJECTIVE: The human cluster of differentiation (CD)300A, a type-I transmembrane protein with immunoreceptor tyrosine-based inhibitory motifs, was investigated as a potential immune checkpoint for human natural killer (NK) cells targeting hematologic malignancies (HMs). METHODS: We implemented a stimulation system involving the CD300A ligand, phosphatidylserine (PS), exposed to the outer surface of malignant cells. Additionally, we utilized CD300A overexpression, a CD300A blocking system, and a xenotransplantation model to evaluate the impact of CD300A on NK cell efficacy against HMs in in vitro and in vivo settings. Furthermore, we explored the association between CD300A and HM progression in patients. RESULTS: Our findings indicated that PS hampers the function of NK cells. Increased CD300A expression inhibited HM lysis by NK cells. CD300A overexpression shortened the survival of HM-xenografted mice by impairing transplanted NK cells. Blocking PS-CD300A signals with antibodies significantly amplified the expression of lysis function-related proteins and effector cytokines in NK cells, thereby augmenting the ability to lyse HMs. Clinically, heightened CD300A expression correlated with shorter survival and an "exhausted" phenotype of intratumoral NK cells in patients with HMs or solid tumors. CONCLUSIONS: These results propose CD300A as a potential target for invigorating NK cell-based treatments against HMs.

Targeting macrophages with phosphatidylserine-rich liposomes as a potential antigen-specific immunotherapy for type 1 diabetes.

Type 1 diabetes (T1D) results from a breakdown in immunological tolerance, with pivotal involvement of antigen-presenting cells. In this context, antigen-specific immunotherapies have been developed to arrest autoimmunity, such as phosphatidylserine (PS)-liposomes. However, the role of certain antigen-presenting cells in immunotherapy, particularly human macrophages (Mφ) in T1D remains elusive. The aim of this study was to determine the role of Mφ in antigen-specific immune tolerance and T1D. To that end, we evaluated Mφ ability to capture apoptotic-body mimicking PS-liposomes in mice and conducted a phenotypic and functional characterisation of four human monocyte-derived Mφ (MoMφ) subpopulations (M0, M1, M2a and M2c) after PS-liposomes uptake. Our findings in mice identified Mφ as the most phagocytic cell subset in the spleen and liver. In humans, while phagocytosis rates were comparable between T1D and control individuals, PS-liposome capture dynamics differed among Mφ subtypes, favouring inflammatory (M1) and deactivated (M2c) Mφ. Notably, high nanoparticle concentrations did not affect macrophage viability. PS-liposome uptake by Mφ induced alterations in membrane molecule expression related to immunoregulation, reduced secretion of IL-6 and IL-12, and diminished autologous T-cell proliferation in the context of autoantigen stimulation. These results underscore the tolerogenic effects of PS-liposomes and emphasize their potential to target human Mφ, providing valuable insights into the mechanism of action of this preclinical immunotherapy.

OxLDL enhances procoagulant activity of endothelial cells by TMEM16F-mediated phosphatidylserine exposure.

Oxidized low-density lipoprotein (oxLDL), a key component in atherosclerosis and hyperlipidemia, is a risk factor for atherothrombosis in dyslipidemia, yet its mechanism is poorly understood. In this study, we used oxLDL-induced human aortic endothelial cells (HAECs) and high-fat diet (HFD)-fed mice as a hyperlipidemia model. Phosphatidylserine (PS) exposure, cytosolic Ca2+, reactive oxygen species (ROS), and lipid peroxidation were measured by flow cytometer. TMEM16F expression was detected by immunofluorescence, western blot, and reverse transcription polymerase chain reaction. Procoagulant activity (PCA) was measured by coagulation time, intrinsic/extrinsic factor Xase, and thrombin generation. We found that oxLDL-induced PS exposure and the corresponding PCA of HAECs were increased significantly compared with control, which could be inhibited over 90% by lactadherin. Importantly, TMEM16F expression in oxLDL-induced HAECs was upregulated by enhanced intracellular Ca2+ concentration, ROS, and lipid peroxidation, which led to PS exposure. Meanwhile, the knockdown of TMEM16F by short hairpin RNA significantly inhibited PS exposure in oxLDL-induced HAECs. Moreover, we observed that HFD-fed mice dramatically increased the progress of thrombus formation and accompanied upregulated TMEM16F expression by thromboelastography analysis, FeCl3-induced carotid artery thrombosis model, and western blot. Collectively, these results demonstrate that TMEM16F-mediated PS exposure may contribute to prothrombotic status under hyperlipidemic conditions, which may serve as a novel therapeutic target for the prevention of thrombosis in hyperlipidemia.

The Relevance, Predictability, and Utility of Annexin A5 for Human Physiopathology.

As an important functional protein molecule in the human body, human annexin A5 (hAnxA5) is widely found in human cells and body fluids. hAnxA5, the smallest type of annexin, performs a variety of biological functions by reversibly and specifically binding phosphatidylserine (PS) in a calcium-dependent manner and plays an important role in many human physiological and pathological processes. The free state hAnxA5 exists in the form of monomers and usually forms a polymer in a specific self-assembly manner when exerting biological activity. This review systematically discusses the current knowledge and understanding of hAnxA5 from three perspectives: physiopathological relevance, diagnostic value, and therapeutic utility. hAnxA5 affects the occurrence and development of many physiopathological processes. Moreover, hAnxA5 can be used independently or in combination as a biomarker of physiopathological phenomena for the diagnosis of certain diseases. Importantly, based on the properties of hAnxA5, many novel drug candidates have been designed and prepared for application in actual medical practice. However, there are also some gaps and shortcomings in hAnxA5 research. This in-depth study will not only expand the understanding of structural and functional relationships but also promote the application of hAnxA5 in the field of biomedicine.

Redistribution of the glycocalyx exposes phagocytic determinants on apoptotic cells.

Phagocytes remove dead and dying cells by engaging "eat-me" ligands such as phosphatidylserine (PtdSer) on the surface of apoptotic targets. However, PtdSer is obscured by the bulky exofacial glycocalyx, which also exposes ligands that activate "don't-eat-me" receptors such as Siglecs. Clearly, unshielding the juxtamembrane "eat-me" ligands is required for the successful engulfment of apoptotic cells, but the mechanisms underlying this process have not been described. Using human and murine cells, we find that apoptosis-induced retraction and weakening of the cytoskeleton that anchors transmembrane proteins cause an inhomogeneous redistribution of the glycocalyx: actin-depleted blebs emerge, lacking the glycocalyx, while the rest of the apoptotic cell body retains sufficient actin to tether the glycocalyx in place. Thus, apoptotic blebs can be engaged by phagocytes and are targeted for engulfment. Therefore, in cells with an elaborate glycocalyx, such as mucinous cancer cells, this "don't-come-close-to-me" barrier must be removed to enable clearance by phagocytosis.

Reconstitution of ORP-mediated lipid exchange coupled to PI4P metabolism.

Oxysterol-binding protein-related proteins (ORPs) play key roles in the distribution of lipids in eukaryotic cells by exchanging sterol or phosphatidylserine for PI4P between the endoplasmic reticulum (ER) and other cell regions. However, it is unclear how their exchange capacity is coupled to PI4P metabolism. To address this question quantitatively, we analyze the activity of a representative ORP, Osh4p, in an ER/Golgi interface reconstituted with ER- and Golgi-mimetic membranes functionalized with PI4P phosphatase Sac1p and phosphatidylinositol (PI) 4-kinase, respectively. Using real-time assays, we demonstrate that upon adenosine triphosphate (ATP) addition, Osh4p creates a sterol gradient between these membranes, relying on the spatially distant synthesis and hydrolysis of PI4P, and quantify how much PI4P is needed for this process. Then, we develop a quantitatively accurate kinetic model, validated by our data, and extrapolate this to estimate to what extent PI4P metabolism can drive ORP-mediated sterol transfer in cells. Finally, we show that Sec14p can support PI4P metabolism and Osh4p activity by transferring PI between membranes. This study establishes that PI4P synthesis drives ORP-mediated lipid exchange and that ATP energy is needed to generate intermembrane lipid gradients. Furthermore, it defines to what extent ORPs can distribute lipids in the cell and reassesses the role of PI-transfer proteins in PI4P metabolism.

Smoking is associated with increased eryptosis, suicidal erythrocyte death, in a large population-based cohort.

Smoking has multiple detrimental effects on health, and is a major preventable cause of premature death and chronic disease. Despite the well-described effect of inhaled substances from tobacco smoke on cell toxicity, the association between smoking and suicidal erythrocyte death, termed eryptosis, is virtually unknown. Therefore, the blood samples of 2023 participants of the German National Cohort Study (NAKO) were analyzed using flow cytometry analysis to determine eryptosis from fluorescent annexin V-FITC-binding to phosphatidylserine-exposing erythrocytes. Blood analyses were complemented by the measurement of hematologic parameters including red blood cell count, hematocrit, hemoglobin, mean corpuscular cell volume (MCV) and mean corpuscular hemoglobin (MCH). Eryptosis was higher in smokers than in non- and ex-smokers, and positively associated with the number of cigarettes smoked daily (r = 0.08, 95% CI [0.03, 0.12]). Interestingly, despite increased eryptosis, smokers had higher red blood cell indices than non-smokers. To conclude, smokers were characterized by higher eryptosis than non-smokers, without showing any obvious detrimental effect on classic hematological parameters.

Bufalin reprograms erythrocyte lifespan through p38 MAPK and Rac1 GTPase.

Ample evidence indicates that bufalin (BFN), a cardiotonic steroid in Bufo toad toxin, possesses a potent anticancer activity mainly by stimulating apoptosis in cancer cells. Human red blood cells (RBCs) undergo eryptosis which contributes to a plethora of pathological conditions. No reports, however, have examined the potential toxicity of BFN to RBCs. This study aims to characterize the biochemical mechanisms governing the influence of BFN on the physiology and lifespan of RBCs. Isolated RBCs from healthy volunteers were exposed to anticancer concentrations of commercially available BFN from the skin of Bufo gargarizans (10-200 µM) for 24 h at 37 °C. Photometric assays were used to estimate hemolysis and hemolytic markers, and flow cytometry was used to detect eryptotic markers. Phosphatidylserine externalization was captured by fluorescein isothiocyante-labeled annexin V, cellular dimensions by light scatter patterns, and intracellular Ca2+ and reactive oxygen species (ROS) by fluorogenic dyes Fluo4/AM and 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA), respectively. BFN caused Ca2+-independent hemolysis and release of LDH, AST, CK, and K+, and increased annexin V-bound cells, cytosolic Ca2+, cell shrinkage, and ROS levels. BFN also disrupted Na+ and Mg2+ trafficking, and was sensitive to PEG 8000, sucrose, SB203580, and NSC 23766. In whole blood, BFN depleted hemoglobin stores, increased fragmented RBCs, and was selectively toxic to reticulocytes, lymphocytes, and platelets. In conclusion, BFN elicits premature RBC death, subject to regulation by p38 MAPK and Rac1 GTPase, and is detrimental to other peripheral blood cells. Altogether, these novel findings prompt cautious consideration of the toxin in anticancer therapy.

Responses of the Serum Lipid Profile to Exercise and Diet Interventions in Nonalcoholic Fatty Liver Disease.

BACKGROUND: This study aimed to assess the response patterns of circulating lipids to exercise and diet interventions in nonalcoholic fatty liver disease (NAFLD). METHODS: The 8.6-month four-arm randomized controlled study comprised 115 NAFLD patients with prediabetes who were assigned to aerobic exercise (AEx; n = 29), low-carbohydrate diet (Diet; n = 28), AEx plus low-carbohydrate diet (AED; n = 29), and nonintervention (NI, n = 29) groups. Hepatic fat content (HFC) was quantified by proton magnetic resonance spectroscopy. Serum lipidomic analytes were measured using liquid chromatography-mass spectrometry. RESULTS: After intervention, the total level of phosphatidylcholine (PC) increased significantly in the AEx group ( P = 0.043), whereas phosphatidylethanolamine (PE) and triacylglycerol decreased significantly in the AED group ( P = 0.046 and P = 0.036, respectively), and phosphatidylserine decreased in the NI group ( P = 0.002). Changes of 21 lipid metabolites were significantly associated with changes of HFC, among which half belonged to PC. Most of the molecules related to insulin sensitivity belonged to sphingomyelin (40 of 79). Controlling for the change of visceral fat, the significant associations between lipid metabolites and HFC remained. In addition, baseline serum lipids could predict the response of HFC to exercise and/or diet interventions (PE15:0/18:0 for AED, area under the curve (AUC) = 0.97; PE22:6(4Z,7Z,10Z,13Z,16Z,19Z)/0:0 for AEx, AUC = 0.90; and PC14:1(9Z)/19:1(9Z) for Diet, AUC = 0.92). CONCLUSIONS: Changes of lipidome after exercise and/or diet interventions were associated with HFC reductions, which are independent of visceral fat reduction, particularly in metabolites belonging to PC. Importantly, baseline PE could predict the HFC response to exercise, and PC predicted the response to diet. These results indicate that a circulating metabolomics panel can be used to facilitate clinical implementation of lifestyle interventions for NAFLD management.

Phosphatidylserine turns the gears of phospholipids in B cell lymphoma.

Phosphatidylserine levels and distribution are tightly controlled by dedicated enzymes at the ER and plasma membrane. Nakatsu and Kawasaki discuss new work by Aoki and colleagues (https://doi.org/10.1083/jcb.202212074), which reveals an acute reliance on phosphatidylserine synthesis in B cell lymphomas needed to prevent aberrant B cell receptor activation and ensuing apoptosis.

Differential interactions of essential and toxic metal ions with biologically relevant phosphatidic acid and phosphatidylserine membranes.

Metal pollutants are a growing concern due to increased use in mining and other industrial processes. Moreover, the use of metals in daily life is becoming increasingly prevalent. Metals such as manganese (Mn), cobalt (Co), and nickel (Ni) are toxic in high amounts whereas lead (Pb) and cadmium (Cd) are acutely toxic at low µM concentrations. These metals are associated with system dysfunction in humans including cancer, neurodegenerative diseases, Alzheimer's disease, Parkinson's disease, and other cellular process'. One known but lesser studied target of these metals are lipids that are key membrane building blocks or serve signalling functions. It was shown that Mn, Co, Ni, Pb, and Cd cause rigidification of liposomes and increase the phase transition in membranes composed of both saturated or partly unsaturated phosphatidic acid (PA) and phosphatidylserine (PS). The selected metals showed differential effects that were more pronounced on saturated lipids. In addition, more rigidity was induced in the biologically relevant liquid-crystalline phase. Moreover, metal affinity, induced rigidification and liposome size increases also varied with the headgroup architecture, whereby the carboxyl group of PS appeared to play an important role. Thus, it can be inferred that Mn, Co, Ni, Cd, and Pb may have preferred binding coordination with the lipid headgroup, degree of acyl chain unsaturation, and membrane phase.