Lysophosphatidylcholine enhances the suppressive function of human naturally occurring regulatory T cells through TGF-β production

Immunomodulation of Proton-activated G Protein-coupled Receptors in Inflammation

Proton-activated G protein-coupled receptors (GPCRs), initially discovered by Ludwig in 2003, are widely distributed in various tissues. These receptors have been found to modulate the immune system in several inflammatory diseases, including inflammatory bowel disease, atopic dermatitis, and asthma. Proton-activated GPCRs belong to the G protein-coupled receptor family and can detect alternations in extracellular pH. This detection triggers downstream signaling pathways within the cells, ultimately influencing the function of immune cells. In this review, we specifically focused on investigating the immune response of proton-activated GPCRs under inflammatory conditions.

Identification of Plasma Biomarkers in Drug-Naïve Schizophrenia Using Targeted Metabolomics

OBJECTIVE

Schizophrenia (SCZ) is a severe psychiatric disorder with unknown etiology and lacking specific biomarkers. Herein, we aimed to explore plasma biomarkers relevant to SCZ using targeted metabolomics.

METHODS

Sixty drug-naïve SCZ patients and 36 healthy controls were recruited. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale. We analyzed the levels of 271 metabolites in plasma samples from all subjects using targeted metabolomics, and identified metabolites that differed significantly between the two groups. Then we evaluated the diagnostic power of the metabolites based on receiver operating characteristic curves, and explored metabolites associated with the psychotic symptoms in SCZ patients.

RESULTS

Twenty-six metabolites showed significant differences between SCZ patients and healthy controls. Among them, 12 metabolites were phosphatidylcholines and cortisol, ceramide (d18:1/22:0), acetylcarnitine, and γ-aminobutyric acid, which could significantly distinguish SCZ from healthy controls with the area under the curve (AUC) above 0.7. Further, a panel consisting of the above 4 metabolites had an excellent performance with an AUC of 0.867. In SCZ patients, phosphatidylcholines were positively related with positive symptoms, and cholic acid was positively associated with negative symptoms.

CONCLUSION

Our study provides insights into the metabolite alterations associated with SCZ and potential biomarkers for its diagnosis and symptom severity assessment.

Exploring the anti-metastatic effects of Astragalus mongholicus Bunge-Curcuma aromatica Salisb. on colorectal cancer: A network-based metabolomics and pharmacology approach

BACKGROUND

Colorectal cancer (CRC) is a common malignancy that can significantly diminish patients' quality of life. Astragalus mongholicus Bunge-Curcuma aromatica Salisb. (AC) is an ancient Chinese medicinal combination used for the treatment of CRC. However, the core ingredients and targets involved in regulating lipid and amino acid metabolism in CRC remain unknown. We aimed to explore the key components and pharmacological mechanisms of AC in the treatment of CRC through a comprehensive analysis of network metabolomics, network pharmacology, molecular docking, and biological methods.

METHODS

Ultra-performance liquid chromatography/mass spectrometry (MS) was used for quality control. Gas chromatography/MS and liquid chromatography/MS were used to detect metabolites in the feces and serum of CRC mice. A network pharmacology approach and molecular docking were used to explore the potential genes involved in the CRC-target-component network. The effect of AC on tumor immunity was investigated using flow cytometry and polymerase chain reaction.

RESULTS

AC, high-dose AC, and 5-fluorouracil treatment reduced liver metastasis and tumor mass. Compared with the CRC group, 2 amino acid metabolites and 14 lipid metabolites (LPC, PC, PE) were upregulated and 15 amino acid metabolites and 9 lipid metabolites (TG, PE, PG, 12-HETE) were downregulated. Subsequently, through network analysis, four components and six hub genes were identified for molecular docking. AC can bind to ALDH1B1, ALDH2, CAT, GOT2, NOS3, and ASS1 through beta-Elemene, canavanine, betaine, and chrysanthemaxanthin. AC promoted the responses of M1 macrophages and down-regulated the responses of M2 macrophages, Treg cells, and the gene expression of related factors.

CONCLUSION

Our research showed that AC effectively inhibited the growth and metastasis of tumors and regulated metabolism and immunity in a CRC mouse model. Thus, AC may be an effective alternative treatment option for CRC.

Marine Fish-Derived Lysophosphatidylcholine: Properties, Extraction, Quantification, and Brain Health Application

Long-chain omega-3 fatty acids esterified in lysophosphatidylcholine (LPC-omega-3) are the most bioavailable omega-3 fatty acid form and are considered important for brain health. Lysophosphatidylcholine is a hydrolyzed phospholipid that is generated from the action of either phospholipase PLA1 or PLA2. There are two types of LPC; 1-LPC (where the omega-3 fatty acid at the sn-2 position is acylated) and 2-LPC (where the omega-3 fatty acid at the sn-1 position is acylated). The 2-LPC type is more highly bioavailable to the brain than the 1-LPC type. Given the biological and health aspects of LPC types, it is important to understand the structure, properties, extraction, quantification, functional role, and effect of the processing of LPC. This review examines various aspects involved in the extraction, characterization, and quantification of LPC. Further, the effects of processing methods on LPC and the potential biological roles of LPC in health and wellbeing are discussed. DHA-rich-LysoPLs, including LPC, can be enzymatically produced using lipases and phospholipases from wide microbial strains, and the highest yields were obtained by Lipozyme RM-IM®, Lipozyme TL-IM®, and Novozym 435®. Terrestrial-based phospholipids generally contain lower levels of long-chain omega-3 PUFAs, and therefore, they are considered less effective in providing the same health benefits as marine-based LPC. Processing (e.g., thermal, fermentation, and freezing) reduces the PL in fish. LPC containing omega-3 PUFA, mainly DHA (C22:6 omega-3) and eicosapentaenoic acid EPA (C20:5 omega-3) play important role in brain development and neuronal cell growth. Additionally, they have been implicated in supporting treatment programs for depression and Alzheimer’s. These activities appear to be facilitated by the acute function of a major facilitator superfamily domain-containing protein 2 (Mfsd2a), expressed in BBB endothelium, as a chief transporter for LPC-DHA uptake to the brain. LPC-based delivery systems also provide the opportunity to improve the properties of some bioactive compounds during storage and absorption. Overall, LPCs have great potential for improving brain health, but their safety and potentially negative effects should also be taken into consideration.

Lysophosphatidylcholine induces adenosine release from macrophages via TRPM7-mediated mitochondrial activation

Even though macrophages have the potential to harm tissues through excessive release of inflammatory mediators, they play protective roles to maintain tissue integrity. In this study, we hypothesized that lysophosphatidylcholine (LPC), via G2A and A2B receptors, puts brakes on macrophages by the induction of adenosine release which could contribute to termination of inflammation. Mechanistically, LPC-induced PGE2 production followed by the activation of cAMP/protein kinase A (PKA) pathway which results in the activation of LKB1/AMPK signaling pathway leading to increasing Mg2+ influx concomitantly with an increase in mitochondrial membrane potential (MMP, Δψm) and ATP production. Then, ATP is converted to adenosine intracellularly followed by efflux via ENT1. In a parallel pathway, LPC-induced elevation of cytosolic calcium was essential for adenosine release, and Ca2+/calmodulin signaling cooperated with PKA to regulate ENT1 permeation to adenosine. Pharmacological blockade of TRPM7 and antisense treatment suppressed LPC-induced adenosine release and magnesium influx in bone marrow-derived macrophages (BMDMs). Moreover, LPC suppressed LPS-induced phosphorylation of connexin-43, which may counteract TLR4-mediated inflammatory response. Intriguingly, we found LPC increased netrin-1 production from BMDMs. Netrin-1 induces anti-inflammatory signaling via A2B receptor. In the presence of adenosine deaminase which removes adenosine in the medium, the chemotaxis of macrophages toward LPC was significantly increased. Hypoxia and metabolic acidosis are usually developed in a variety of inflammatory situations such as sepsis. We found LPC augmented hypoxia- or acidosis-induced adenosine release from BMDMs. These results provide evidence of LPC-induced brake-like action on macrophages by adenosine release via cellular magnesium signaling.

Toward Personalized Interventions for Psoriasis Vulgaris: Molecular Subtyping of Patients by Using a Metabolomics Approach

Aim: Psoriasis vulgaris (PV) is a complicated autoimmune disease characterized by erythema of the skin and a lack of available cures. PV is associated with an increased risk of metabolic syndrome and cardiovascular disease, which are both mediated by the interaction between systemic inflammation and aberrant metabolism. However, whether there are differences in the lipid metabolism between different levels of severity of PV remains elusive. Hence, we explored the molecular evidence for the subtyping of PV according to alterations in lipid metabolism using serum metabolomics, with the idea that such subtyping may contribute to the development of personalized treatment.

Methods: Patients with PV were recruited at a dermatology clinic and classified based on the presence of metabolic comorbidities and their Psoriasis Area and Severity Index (PASI) from January 2019 to November 2019. Age- and sex-matched healthy controls were recruited from the preventive health department of the same institution for comparison. We performed targeted metabolomic analyses of serum samples and determined the correlation between metabolite composition and PASI scores.

Results: A total of 123 participants, 88 patients with PV and 35 healthy subjects, were enrolled in this study. The patients with PV were assigned to a “PVM group” (PV with metabolic comorbidities) or a “PV group” (PV without metabolic comorbidities) and further subdivided into a “mild PV” (MP, PASI <10) and a “severe PV” (SP, PASI ≥10) groups. Compared with the matched healthy controls, levels of 27 metabolites in the MP subgroup and 28 metabolites in the SP subgroup were found to be altered. Among these, SM (d16:0/17:1) and SM (d19:1/20:0) were positively correlated with the PASI in the MP subgroup, while Cer (d18:1/18:0), PC (18:0/22:4), and PC (20:0/22:4) were positively correlated with the PASI in the SP subgroup. In the PVM group, levels of 17 metabolites were increased, especially ceramides and phosphatidylcholine, compared with matched patients from the PV group. In addition, the correlation analysis indicated that Cer (d18:1/18:0) and SM (d16:1/16:1) were not only correlated with PASI but also has strongly positive correlations with biochemical indicators.

Conclusion: The results of this study indicate that patients with PV at different severity levels have distinct metabolic profiles, and that metabolic disorders complicate the disease development. These findings will help us understand the pathological progression and establish strategies for the precision treatment of PV.

Persistent hyperammonia and altered concentrations of urea cycle metabolites in a 5-day swine experiment of sepsis

We measured plasma and cerebrospinal fluid (CSF) metabolite concentrations in a 5-day porcine sepsis model of fecal peritonitis. The objectives were: (i) to verify whether the expected pathways that had emerged in previous studies pertain only to the early inflammatory response or persist for the subsequent days; (ii) to identify metabolic derangements that arise later; (iii) to verify whether CSF metabolite concentrations were altered and if these alterations were similar to those in the blood or delayed. We observed an early response to inflammation and cytokine storms with alterations in lipid and glucose metabolism. The arginine/asymmetric dimethylarginine (ADMA) and phenylalanine/tyrosine balances changed 24 h after resuscitation in plasma, and later in CSF. There was a rise in ammonia concentration, with altered concentrations of metabolites in the urea cycle. Whether persistent derangement of these pathways have a role not only on short-term outcomes but also on longer-term comorbidities, such as septic encephalopathy, should be addressed in further studies.

Lysophosphatidylcholine induces oxidative stress in human endothelial cells via NOX5 activation - implications in atherosclerosis

OBJECTIVE

The mechanisms involved in NOX5 activation in atherosclerotic processes are not completely understood.  This study tested the hypothesis that lysophosphatidylcholine (LPC), a proatherogenic component of oxLDL, induces endothelial calcium influx, which drives NOX5-dependent reactive oxygen species (ROS) production, oxidative stress, and endothelial cell dysfunction.  Approach: Human aortic endothelial cells (HAEC) were stimulated with LPC (10-5 M, for different time points).  Pharmacological inhibition of NOX5 (Melittin, 10-7 M) and NOX5 gene silencing (siRNA) were used to determine the role of NOX5-dependent ROS production in endothelial oxidative stress induced by LPC.  ROS production was determined by lucigenin assay and electron paramagnetic spectroscopy (EPR), calcium transients by Fluo4 fluorimetry, and NOX5 activity and protein expression by pharmacological assays and immunoblotting, respectively.

RESULTS

LPC increased ROS generation in endothelial cells at short (15 min) and long (4 h) stimulation times.  LPC-induced ROS was abolished by a selective NOX5 inhibitor and by NOX5 siRNA. NOX1/4 dual inhibition and selective NOX1 inhibition only decreased ROS generation at 4 h.  LPC increased HAEC intracellular calcium, important for NOX5 activation, and this was blocked by nifedipine and thapsigargin.  Bapta-AM, selective Ca2+ chelator, prevented LPC-induced ROS production.  NOX5 knockdown decreased LPC-induced ICAM-1 mRNA expression and monocyte adhesion to endothelial cells.

CONCLUSION

These results suggest that NOX5, by mechanisms linked to increased intracellular calcium, is key to early LPC-induced endothelial oxidative stress and pro-inflammatory processes.  Since these are essential events in the formation and progression of atherosclerotic lesions, this study highlights an important role for NOX5 in atherosclerosis.

Radiation-induced lipoprotein-associated phospholipase A2 increases lysophosphatidylcholine and induces endothelial cell damage

The cardiotoxicity of various anticancer therapies, including radiotherapy, can lead to cardiovascular complications. These complications can range from damaging cardiac tissues within the irradiation field to increasing the long-term risks of developing heart failure, coronary artery disease, and myocardial infarction. We analyzed radiation-induced metabolites capable of mediating critical biological processes, such as inflammation, senescence, and apoptosis. Previously, by applying QTOF-MASS analysis to irradiated human fibroblasts, we identified that metabolite sets of lysophosphatidylcholine (LPC) were increased in these cells. In this study, radiation-induced LPC accumulation in human aortic endothelial cells (HAECs) increased reactive oxygen species (ROS) production and senescence-associated-beta-galactosidase staining, in addition to decreasing their tube-forming ability. Knockdown of lipoprotein-associated phospholipase A2 (Lp-PLA2) with small interfering RNA (siRNA) inhibited the increased LPC production induced by radiation, and reduced the radiation-induced cell damage produced by ROS and oxidized low-density lipoprotein (LDL). Lp-PLA2 depletion abolished the induction of proinflammatory factors, such as interleukin 1β, tumor necrosis factor-alpha, matrix metalloproteinase 2, and matrix metalloproteinase 9, as well as adhesion molecules, such as intercellular adhesion molecule 1 (ICAM-1) and E-selection. Likewise, we showed that Lp-PLA2 expression was upregulated in the vasculature of irradiated rat, resulting in increased LPC production and LDL oxidation. Our data demonstrate that radiation-induced LPC production is a potential risk factor for cardiotoxicity that is mediated by Lp-PLA2 activity, suggesting that LPC and Lp-PLA2 offer potential diagnostic and therapeutic approaches to cardiovascular damage during radiotherapy.

Plasma Lipidomic Profiles and Risk of Diabetes: 2 Prospective Cohorts of HIV-Infected and HIV-Uninfected Individuals

OBJECTIVES

Antiretroviral therapy (ART) use is associated with disrupted lipid and glucose metabolism in people with HIV infection. We aimed to identify plasma lipid species associated with risk of diabetes in the context of HIV infection.

RESEARCH DESIGN AND METHODS

We profiled 211 plasma lipid species in 491 HIV-infected and 203 HIV-uninfected participants aged 35 to 55 years from the Women's Interagency HIV Study and the Multicenter AIDS Cohort Study. Cox proportional hazards model was used to examine associations between baseline lipid species and incident diabetes (166 diabetes cases were identified during a median follow-up of 12.6 years).

RESULTS

We identified 11 lipid species, representing independent signals for 8 lipid classes/subclasses, associated with risk of diabetes (P < 0.05 after FDR correction). After adjustment for multiple covariates, cholesteryl ester (CE) (22:4), lysophosphatidylcholine (LPC) (18:2), phosphatidylcholine (PC) (36:4), phosphatidylcholine plasmalogen (34:3), and phosphatidylethanolamine (PE) (38:2) were associated with decreased risk of diabetes (HRs = 0.70 to 0.82 per SD increment), while diacylglycerol (32:0), LPC (14:0), PC (38:3), PE (36:1), and triacylglycerol (50:1) were associated with increased risk of diabetes (HRs = 1.26 to 1.56 per SD increment). HIV serostatus did not modify any lipid-diabetes associations; however, most of these lipid species were positively associated with HIV and/or ART use, including 3 diabetes-decreased ( CE [22:4], LPC [18:2], PE [38:2]) and all 5 diabetes-increased lipid species.

CONCLUSIONS

This study identified multiple plasma lipid species associated with incident diabetes. Regardless of the directions of their associations with diabetes, most diabetes-associated lipid species were elevated in ART-treated people with HIV infection. This suggests a complex role of lipids in the link between ART and diabetes in HIV infection.

Characterising phospholipids and free fatty acids in patients with schizophrenia: A case-control study

OBJECTIVES

Previous studies have indicated that schizophrenia (SCZ) is linked to abnormal phospholipid and fatty acid metabolism. However, comprehensive analysis of phospholipids and free fatty acids (FFAs) for SCZ is very limited. Herein, we sought to compare serum levels of phospholipids and FFAs between patients with SCZ and healthy controls (HCs).

METHODS

One hundred and nineteen SCZ patients and 109 HCs were enrolled in the study. The levels of 177 phospholipids and FFAs were measured in serum samples using a targeted liquid chromatography-mass spectrometry (LC-MS)-based platform.

RESULTS

One hundred and ten metabolites, including 16 FFAs, 25 phosphatidylcholines, 23 lysophosphatidylcholines, 11 phosphatidylcholine plasmalogens, 7 phosphatidylethanolamines, 9 lysophosphatidylethanolamines, 6 phosphatidylethanolamine plasmalogens, and 13 sphingomyelins, were observed to be significantly altered in SCZ patients compared to HCs. These disturbances may represent underlying pathophysiology, including but not limited to altered activity of phospholipases and acyltransferases, increased oxidative stress, dysfunctional oligodendrocyte glycosynapses, and elevated lipid mobilisation and β-oxidation.

CONCLUSIONS

Our findings suggest that complex lipid profile abnormalities are associated with SCZ. This study may contribute to investigating the role of phospholipid and FFA alterations in the pathoetiology of SCZ.

Uterine Metabolomics Reveals Protection of Taohong Siwu Decoction Against Abnormal Uterine Bleeding

Incomplete abortion, a procedure for terminating pregnancy, will lead to abnormal uterine bleeding (AUB), infections, and even death. Taohong Siwu decoction (TSD) is a traditional Chinese medicine (TCM) formula, which has been developed to treat AUB for hundreds of years. However, the mechanism of the protective effect of TSD against AUB is not clear. We performed mass spectrometry (MS) of uterine samples to observe metabolic profile resulting from the treatment with TSD. An integrated gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry based untargeted metabolomics approach combined with multivariate statistical analyses were used to investigate the metabolic profile of TSD against AUB. There was clear separation between pregnant and incomplete aborting rats as well as incomplete aborting and TSD administered rats. Based on random forest algorithm and receiver operator characteristic analysis, 12 biomarkers were optimized related to TSD administered. The effect of TSD on AUB are related to several pathways, such as AA metabolism, glyoxylate and dicarboxylate metabolism, alanine, aspartate, and glutamate metabolism. To our knowledge, this is the first uterine metabolomics study focusing on TSD on AUB and provide a new perspective for explaining the mechanism of TSD on AUB.

An Updated Review of Pro- and Anti-Inflammatory Properties of Plasma Lysophosphatidylcholines in the Vascular System

Lysophosphatidylcholines are a group of bioactive lipids heavily investigated in the context of inflammation and atherosclerosis development. While present in plasma during physiological conditions, their concentration can drastically increase in certain inflammatory states. Lysophosphatidylcholines are widely regarded as potent pro-inflammatory and deleterious mediators, but an increasing number of more recent studies show multiple beneficial properties under various pathological conditions. Many of the discrepancies in the published studies are due to the investigation of different species or mixtures of lysophatidylcholines and the use of supra-physiological concentrations in the absence of serum or other carrier proteins. Furthermore, interpretation of the results is complicated by the rapid metabolism of lysophosphatidylcholine (LPC) in cells and tissues to pro-inflammatory lysophosphatidic acid. Interestingly, most of the recent studies, in contrast to older studies, found lower LPC plasma levels associated with unfavorable disease outcomes. Being the most abundant lysophospholipid in plasma, it is of utmost importance to understand its physiological functions and shed light on the discordant literature connected to its research. LPCs should be recognized as important homeostatic mediators involved in all stages of vascular inflammation. In this review, we want to point out potential pro- and anti-inflammatory activities of lysophospholipids in the vascular system and highlight recent discoveries about the effect of lysophosphatidylcholines on immune cells at the endothelial vascular interface. We will also look at their potential clinical application as biomarkers.

Targeting lipid droplet lysophosphatidylcholine for cisplatin chemotherapy

This study aims to explore lipidic mechanism towards low‐density lipoprotein receptor (LDLR)‐mediated platinum chemotherapy resistance. By using the lipid profiling technology, LDLR knockdown was found to increase lysosomal lipids and decrease membranous lipid levels in EOC cells. LDLR knockdown also down‐regulated ether‐linked phosphatidylethanolamine (PE‐O, lysosomes or peroxisomes) and up‐regulated lysophosphatidylcholine [LPC, lipid droplet (LD)]. This implies that the manner of using Lands cycle (conversion of lysophospholipids) for LDs might affect cisplatin sensitivity. The bioinformatics analyses illustrated that LDLR‐related lipid entry into LD, rather than an endogenous lipid resource (eg Kennedy pathway), controls the EOC prognosis of platinum chemotherapy patients. Moreover, LDLR knockdown increased the number of platinum‐DNA adducts and reduced the LD platinum amount. By using a manufactured LPC‐liposome‐cisplatin (LLC) drug, the number of platinum‐DNA adducts increased significantly in LLC‐treated insensitive cells. Moreover, the cisplatin content in LDs increased upon LLC treatment. Furthermore, lipid profiles of 22 carcinoma cells with differential cisplatin sensitivity (9 sensitive vs 13 insensitive) were acquired. These profiles revealed low storage lipid levels in insensitive cells. This result recommends that LD lipidome might be a common pathway in multiple cancers for platinum sensitivity in EOC. Finally, LLC suppressed both cisplatin‐insensitive human carcinoma cell training and testing sets. Thus, LDLR‐platinum insensitivity can be due to a defective Lands cycle that hinders LPC production in LDs. Using lipidome assessment with the newly formulated LLC can be a promising cancer chemotherapy method.

Mechanisms of TREG cell adaptation to inflammation

Inflammation is an important defense mechanism. In this complex and dynamic process, drastic changes in the tissue micro-environment play key roles in dictating the nature of the evolving immune response. However, uncontrolled inflammation is detrimental, leading to unwanted cellular damage, loss of physiological functions, and even death. As such, the immune system possesses tools to limit inflammation while ensuring rapid and effective clearance of the inflammatory trigger. Foxp3⁺ regulatory T (T_REG ) cells, a potently immunosuppressive CD4⁺ T cell subset, play a crucial role in immune tolerance by controlling the extent of the response to self and non-self Ags, all-the-while promoting a quick return to immune homeostasis. T_REG cells adapt to changes in the local micro-environment enabling them to migrate, proliferate, survive, differentiate, and tailor their suppressive ability at inflamed sites. Several inflammation-associated factors can impact T_REG cell functional adaptation in situ including locally released alarmins, oxygen availability, tissue acidity and osmolarity and nutrient availability. Here, we review some of these key signals and pathways that control the adaptation of T_REG cell function in inflammatory settings.

Proton-sensing G protein-coupled receptors: detectors of tumor acidosis and candidate drug targets

Cells in tumor microenvironments (TMEs) use several mechanisms to sense their low pH (<7.0), including via proton-sensing G protein-coupled receptors (psGPCRs): GPR4, GPR65/TDAG8, GPR68/OGR1 and GPR132/G2A. Numerous cancers have increased expression of psGPCRs. The psGPCRs may contribute to features of the malignant phenotype via actions on specific cell-types in the TME and thereby promote tumor survival and growth. Here, we review data regarding psGPCR expression in tumors and cancer cells, impact of psGPCRs on survival in solid tumors and a bioinformatics approach to infer psGPCR expression in cell types in the TME. New tools are needed to help define contributions of psGPCRs in tumor biology and to identify potentially novel therapeutic agents for a variety of cancers.

Acyl chain that matters: introducing sn-2 acyl chain preference to a phospholipase D by protein engineering

Phospholipase D (PLD) is an enzyme widely used for enzymatic synthesis of structured phospholipids (PLs) with modified head groups. These PLs are mainly used as food supplements and liposome ingredients. Still, there is a need for an enzyme that discriminates between PLs and lysoPLs, for specific detection of lysoPLs in various specimens and enzymatic synthesis of certain PLs from a mixed substrate. To meet this demand, we aimed at altering sn-2 acyl chain recognition of a PLD, leading to a variant enzyme preferably reacting on lysoPLs, by protein engineering. Based on the crystal structure of Streptomyces antibioticus PLD, W166 was targeted for saturation mutagenesis due to its strong interaction with the sn-2 acyl chain of the PL. Screening result pointed at W166R and W166K PLDs to selectively react on lysophosphatidylcholine (lysoPC), while not on PC. These variants showed a negative correlation between activity and sn-2 chain length of PL substrates. This behavior was not observed in the wild-type (WT)-PLD. Kinetic analysis revealed that the W166R and W166K variants have 7–10 times higher preference to lysoPC compared to the WT-PLD. Additionally, W166R PLD showed detectable activity toward glycero-3-phosphocholine, unlike the WT-PLD. Applicability of the lysoPC-preferring PLD was demonstrated by detection of lysoPC in the mixed PC/lysoPC sample and by the synthesis of cyclic phosphatidic acid. Structure model analyses supported the experimental findings and provided a basis for the structure model-based hypothesis on the observed behavior of the enzymes.

An Updated Review of Lysophosphatidylcholine Metabolism in Human Diseases

Lysophosphatidylcholine (LPC) is increasingly recognized as a key marker/factor positively associated with cardiovascular and neurodegenerative diseases. However, findings from recent clinical lipidomic studies of LPC have been controversial. A key issue is the complexity of the enzymatic cascade involved in LPC metabolism. Here, we address the coordination of these enzymes and the derangement that may disrupt LPC homeostasis, leading to metabolic disorders. LPC is mainly derived from the turnover of phosphatidylcholine (PC) in the circulation by phospholipase A₂ (PLA₂). In the presence of Acyl-CoA, lysophosphatidylcholine acyltransferase (LPCAT) converts LPC to PC, which rapidly gets recycled by the Lands cycle. However, overexpression or enhanced activity of PLA₂ increases the LPC content in modified low-density lipoprotein (LDL) and oxidized LDL, which play significant roles in the development of atherosclerotic plaques and endothelial dysfunction. The intracellular enzyme LPCAT cannot directly remove LPC from circulation. Hydrolysis of LPC by autotaxin, an enzyme with lysophospholipase D activity, generates lysophosphatidic acid, which is highly associated with cancers. Although enzymes with lysophospholipase A₁ activity could theoretically degrade LPC into harmless metabolites, they have not been found in the circulation. In conclusion, understanding enzyme kinetics and LPC metabolism may help identify novel therapeutic targets in LPC-associated diseases.

Metabolic profiling identifies phospholipids as potential serum biomarkers for schizophrenia

Schizophrenia (SCZ) is a multifactorial psychiatric disorder. However, the molecular pathogenesis of SCZ remains largely unknown, and no reliable diagnostic test is currently available. Phospholipid metabolism is known to be disturbed during disease processes of SCZ. In this study, we used an untargeted liquid chromatography-mass spectrometry (LC-MS)-based metabolic profiling approach to measure lipid metabolites in serum samples from 119 SCZ patients and 109 healthy controls, to identify potential lipid biomarkers for the discrimination between SCZ patients and healthy controls. 51 lipid metabolites were identified to be significant for discriminating SCZ patients from healthy controls, including phosphatidylcholines (PCs), lysophosphatidylcholines (LPCs), phosphatidylethanolamines (PEs), lysophosphatidylethanolamines (LPEs) and sphingomyelins (SMs). Compared to healthy controls, most PCs and LPCs, as well as all PEs in patients were decreased, while most LPEs and all SMs were increased. A panel of six lipid metabolites could effectively discriminate SCZ patients from healthy controls with an area under the receiver-operating characteristic curve of 0.991 in the training samples and 0.980 in the test samples. These findings suggest that extensive disturbances of phospholipids may be involved in the development of SCZ. This LC-MS-based metabolic profiling approach shows potential for the identification of putative serum biomarkers for the diagnosis of SCZ.

The Systemic Alterations of Lipids, Alanine-Glucose Cycle and Inter-Organ Amino Acid Metabolism in Swine Model Confirms the Role of Liver in Early Phase of Septic Shock

Septic shock is a medical emergency and is one of the main causes of mortality in critically ill patients. Given the pathophysiological complexity of sepsis spectrum and progression in clinical settings, animal models become essential tools to improve patient care, and to understand key mechanisms that may remain masked from the heterogeneity of clinical practice. Our aim was to verify whether the metabolic constellations we previously reported for septic shock patients appear also in our septic shock swine model as systemic markers of early disturbances in energy metabolism and hepatic homeostasis. Septic shock was induced in anesthetized, instrumented, and ventilated adult swines by polymicrobial peritonitis. Hemodynamic and serial measurements of arterial and mixed venous blood gasses were made. Laboratory measurements and mass spectrometry-based targeted quantitative plasma metabolomics were performed in blood samples collected at baseline, at shock and at fully resuscitation after fluids and vasopressors administration. Data elaboration was performed by multilevel and multivariate analysis. Changes in hemodynamic, blood chemistry, and inflammatory markers were in line with a septic shock phenotype. Time course alteration of systemic metabolites were characterized by marked decreased in phosphatidylcholines and lysophosphatidylcholines species, altered alanine-glucose cycle and inter-organ amino acid metabolism, pointing toward an early hepatic impairment similarly to what we previously reported for septic shock. This is the first study in which an experimental swine model of septic shock recapitulates the main metabolic derangements reported in a clinical setting of shock. These events occur within hours from infections and may act as early metabolic features to assist in evaluating subclinical hepatic alterations and pave the way to improve the management of septic shock.

Effect of TGF-β1 on blood CD4+CD25high regulatory T cell proliferation and Foxp3 expression during non-small cell lung cancer blood metastasis

Metastatic circulating tumor cells in non-small cell lung cancer (NSCLC) metastasis have been reported to be associated with an immune response. The present study aimed to provide a theoretical basis for the immunomodulatory processes during NSCLC blood metastasis. NSCLC blood and normal peripheral blood mononuclear cells (PBMCs) were collected. The quantity of cluster of differentiation (CD)4⁺CD25^high regulatory T (Treg) cells and the intracellular forkhead box protein 3 (Foxp3) expression in CD4⁺CD25^high Treg cells were determined by flow cytometry. Furthermore, the effect of transforming growth factor β1 (TGF-β1) on NSCLC blood CD4⁺CD25⁺ Treg cell proliferation was explored by activating blood mononuclear cells with an anti-CD3 monoclonal antibody, interleukin-2 and different doses of TGF-β1. Reverse transcription-quantitative polymerase chain reaction assays were used to detect the mRNA expression of Foxp3. Carboxyfluorescein succinimidyl ester staining was used to analyze the proliferation dynamics of lymphocyte subsets. Results indicate that the proportion of CD4⁺ T cells in the blood of patients with NSCLC was significantly higher compared with normal peripheral blood (P<0.01). Foxp3 expression in NSCLC blood Treg cells was significantly decreased compared with normal peripheral blood (P<0.01). NSCLC blood mononuclear cells treated with TGF-β1 at 1, 5 and 25 ng/ml significantly induced Foxp3 expression in CD4⁺CD25⁺ Treg cells compared with the control group (P<0.05). The proportion of CD4⁺CD25⁺ Treg and CD8⁺ T cells were elevated in generation 6, 7, 8 after 6 days of TGF-β1 treatment compared with untreated cells. The proportion of CD4⁺CD25⁺ Treg and CD8⁺ T cells were elevated in generation 8, 9 and with TGF-β1 treatment after 8 days compared with untreated cells. These results indicate that CD4⁺CD25⁺ Treg cells proliferate at a greater rate compared with CD8⁺ T cells after 4, 6 or 8 days of treatment. The proportion of CD4⁺CD25^high Treg cells in NSCLC blood was significantly higher (P<0.05) compared with normal peripheral blood. The number of Foxp3⁺ T cells was significantly lower (P<0.05) compared with normal peripheral blood. The data presented in this study suggest that NSCLC blood CD4⁺CD25^high Treg cells are functionally immature and that TGF-β1 may promote maturation.

Lysophosphatidylcholine induces cytotoxicity/apoptosis and IL-8 production of human endothelial cells: Related mechanisms

Increased levels of oxidized low-density lipoprotein oxLDL) are shown to elevate the risk of cardiovascular diseases such as atherosclerosis, thrombosis, stroke, and myocardial infarction. This is possibly due to the toxic effects of oxLDLs on vascular cells. Various oxLDLs including lysophosphatidylcholine (LPC) and 7-ketocholesterol injure vascular endothelial cells and stimulate inflammatory reaction. However the toxicity of LPC on endothelial cells is not clear. In this study, human endothelial cells were exposed to LPC. Cytotoxicity was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. Propidium iodide (PI) staining or PI/Annexin V dual staining flow cytometry were used to determine cell cycle progression and apoptosis. Reactive oxygen species (ROS) level was analyzed by DCFH-DA labeling flow cytometry. RNA and protein expression of endothelial cells was studied by reverse transcriptase-polymerase chain reaction and western blotting. IL-8 secretion was measured by enzyme-linked immunosorbant assay. LPC showed cytotoxicity to endothelial cells (>50 µg/ml). LPC induced cell cycle arrest and apoptosis with concomitant inhibition of cdc2 and cyclin B1 expression. LPC stimulated intracellular ROS production and ATM/Chk2, ATR/Chk1 and Akt activation. IL-8 expression and secretion in endothelial cells were induced by LPC. LPC-induced apoptosis, and IL-8 expression/secretion was attenuated by LY294002, a PI3K/Akt inhibitor. These results reveal that LPC is involved in the pathogenesis of atherosclerosis and vascular diseases by stimulation of inflammation and injury to endothelial cells. These events are related to ROS, ATM/Chk2, ATR/Chk2 and PI3K/Akt signaling. Understanding the toxic mechanisms of LPC is useful for future prevention and treatment atherosclerosis.

UHPLC/Q-TOFMS-based metabolomics for the characterization of cold and hot properties of Chinese materia medica

ETHNOPHARMACOLOGICAL RELEVANCE

The cold/hot property of Chinese materia medica (CMM) and the application of its corresponding knowledge in the diagnosis, differentiation and treatment of diseases have been considered to be the extremely important part of traditional Chinese medicine (TCM). As highly abstracted TCM theory, the cold/hot property of CMMs is still not fully understood and remains to be elucidated by systems biology approach. The cold and hot properties of CMM are mainly defined by the response of the body to a given CMM. Metabolomics is a promising systems biology method to profile entire endogenous metabolites and monitor their fluctuations related to an exogenous stimulus. Thus, a metabolomics approach was applied to characterize the cold and hot properties of CMMs.

MATERIAL AND METHODS

Mice were intragastrically administered three selected cold property CMMs (i.e., Rheum palmatum L., radix et rhizoma; Coptis chinensis Franch, rhizome and Scutellaria baicalensis Georgi, radix) and three hot property CMMs (i.e., Cinnamomum cassia (L.) J. Presl, cortex; Zingiber officinale Roscoe, rhizoma and Evodia rutaecarpa (Juss.) Benth., fructus) once daily for one week. The comprehensive metabolome changes in the plasma of mice after treatment with cold or hot property CMMs were characterized by ultra-high performance liquid chromatography/time of flight mass spectrometry (UHPLC/Q-TOF-MS), and the potential biomarkers related to cold and hot properties of CMM were explored.

RESULTS

Metabolites perturbation in plasma occurs after treatment with cold CMMs and hot CMMs in mice, and 15 and 16 differential biomarkers were identified to be associated with the cold and hot properties of CMMs, respectively. Among them, LPC (18:0), LPC (18:1), LPC (20:4) and LPC (20:5) showed decreased trends in the cold property CMM treated groups, but increased in the hot property CMM treated groups.

CONCLUSIONS

There is a strong connection between the cold/hot property of CMMs and lysophosphatidylcholines metabolism. This study offers new insight into CMM properties and their clinical application.

Characteristic Distribution Pattern of Lysophosphatidylcholine in Fibromuscular Dysplasia-Associated Visceral Artery Aneurysms Compared with Atherosclerotic Visceral Artery Aneurysms

AIM

Asymptomatic visceral artery aneurysms (VAAs) have increasingly been found, with most being either atherosclerotic VAAs or fibromuscular dysplasia (FMD)-associated VAAs. However, little is known about the pathogenesis of both diseases. We aimed to identify the differences in the distribution pattern of lipid molecules between atherosclerotic VAAs and FMD-associated VAAs.

METHODS

We conducted a histological study of VAAs using imaging mass spectrometry (IMS) to assess the accumulation of lipid molecules in both the aneurysmal sac and the adjacent arteries without aneurysmal changes in 17 VAA samples, which were resected during the surgery.

RESULTS

IMS revealed characteristic distributions of cholesterol ester in intima and media in the atherosclerotic VAAs, which was hardly detected in FMD-associated VAAs. However, lysophosphatidylcholine (lysoPC), a proinflammatory and proapoptotic lipid mediator, was accumulated in the medial ridge of the adventitia of FMD-associated in the aneurysmal sac, and it was also diffusely accumulated in the adjacent arteries. In contrast, lysoPC was accumulated in the area of intimal hyperplasia in atherosclerotic VAAs and the adjacent arteries.

CONCLUSION

The distribution patterns of lipid molecules were different between the FMD-associated and atherosclerotic VAAs. The diffuse accumulation of lysoPCs in the visceral arteries may be a predisposition for the formation of FMD-associated VAAs.

Functional metagenomic discovery of bacterial effectors in the human microbiome and isolation of commendamide, a GPCR G2A/132 agonist

The trillions of bacteria that make up the human microbiome are believed to encode functions that are important to human health; however, little is known about the specific effectors that commensal bacteria use to interact with the human host. Functional metagenomics provides a systematic means of surveying commensal DNA for genes that encode effector functions. Here, we examine 3,000 Mb of metagenomic DNA cloned from three phenotypically distinct patients for effectors that activate NF-κB, a transcription factor known to play a central role in mediating responses to environmental stimuli. This screen led to the identification of 26 unique commensal bacteria effector genes (Cbegs) that are predicted to encode proteins with diverse catabolic, anabolic, and ligand-binding functions and most frequently interact with either glycans or lipids. Detailed analysis of one effector gene family (Cbeg12) recovered from all three patient libraries found that it encodes for the production of N-acyl-3-hydroxypalmitoyl-glycine (commendamide). This metabolite was also found in culture broth from the commensal bacterium Bacteroides vulgatus, which harbors a gene highly similar to Cbeg12. Commendamide resembles long-chain N-acyl-amides that function as mammalian signaling molecules through activation of G-protein-coupled receptors (GPCRs), which led us to the observation that commendamide activates the GPCR G2A/GPR132. G2A has been implicated in disease models of autoimmunity and atherosclerosis. This study shows the utility of functional metagenomics for identifying potential mechanisms used by commensal bacteria for host interactions and outlines a functional metagenomics-based pipeline for the systematic identification of diverse commensal bacteria effectors that impact host cellular functions.

Comparative metabolomics analysis on hematopoietic functions of herb pair Gui-Xiong by ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry and pattern recognition approach

The compatibility of Angelicae Sinensis Radix (Danggui, DG) and Chuanxiong Rhizoma (Chuanxiong, CX), a famous herb pair Gui-Xiong (GX), can produce synergistic and complementary hematopoiesis. In present study, global metabolic profiling with ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) combined with pattern recognition method was performed to discover the underlying hematopoietic regulation mechanisms of DG, CX and GX on hemolytic and aplastic anemia rats (HAA) induced by acetyl phenylhydrazine (APH) and cyclophosphamide (CP). Thirteen endogenous metabolites contributing to the separation of model group and control group were tentatively identified. The levels of LPCs including lysoPC (18:0), lysoPC (20:4), lysoPC (16:0) and lysoPC (18:2), sphinganine, nicotinic acid, thiamine pyrophosphate, phytosphingosine, and glycerophosphocholine increased significantly (p<0.05) in HAA, while the levels of oleic acid, 8,11,14-eicosatrienoic acid, ceramides (d18:1/14:0), and 17a-hydroxypregnenolone decreased significantly (p<0.05) in comparison with control rats. Those endogenous metabolites were chiefly involved in thiamine metabolism and sphingolipid metabolism. The metabolic deviations could be regulated closer to normal level after DG, CX and GX intervention. In term of hematopoietic function, GX was the most effective as shown by the relative distance in PLS-DA score plots and relative intensity of metabolomic strategy, reflecting the synergic action between DG and CX. The relative distance calculation was firstly used in metabolomics for semi-quantization.

Tipping the inflammatory balance: inflammasome activation distinguishes metabolically unhealthy from healthy obesity

Expansion of adipose tissue mass, predominantly in the visceral depot, strongly associates with the development of metabolic complications that are often observed in obesity. In addition, in obesity, an increased prevalence of nonalcoholic fatty liver disease and reduced cardiorespiratory fitness are observed. However, not all obese individuals develop metabolic abnormalities. To better understand the molecular mechanisms that predispose obese humans to the development of metabolic diseases, comparing the metabolically healthy obese (MHO) vs an unhealthy obese phenotype (MUO) may be of great value. A new study by Esser et al (DOI: 10.1007/s00125-013-3023-9 ) now provides important evidence that the MHO phenotype is associated with a lower activation of the NOD-like receptor family pyrin domain containing-3 (NLPR3) inflammasome in macrophages of visceral adipose tissue and a more favourable inflammatory profile as compared with the MUO phenotype. This finding could promote novel studies in humans to decipher stimuli and mechanisms leading to increased inflammasome activity, not only in adipose tissue, but also in other organs that are involved in the regulation of metabolism.

Circulating lysophosphatidylcholines are markers of a metabolically benign nonalcoholic fatty liver

OBJECTIVE

Nonalcoholic fatty liver (NAFL) is thought to contribute to insulin resistance and its metabolic complications. However, some individuals with NAFL remain insulin sensitive. Mechanisms involved in the susceptibility to develop insulin resistance in humans with NAFL are largely unknown. We investigated circulating markers and mechanisms of a metabolically benign and malignant NAFL by applying a metabolomic approach.

RESEARCH DESIGN AND METHODS

A total of 265 metabolites were analyzed before and after a 9-month lifestyle intervention in plasma from 20 insulin-sensitive and 20 insulin-resistant subjects with NAFL. The relevant plasma metabolites were then tested for relationships with insulin sensitivity in 17 subjects without NAFL and in plasma from 29 subjects with liver tissue samples.

RESULTS

The best separation of the insulin-sensitive from the insulin-resistant NAFL group was achieved by a metabolite pattern including the branched-chain amino acids leucine and isoleucine, ornithine, the acylcarnitines C3:0-, C16:0-, and C18:0-carnitine, and lysophosphatidylcholine (lyso-PC) C16:0 (area under the ROC curve, 0.77 [P = 0.00023] at baseline and 0.80 [P = 0.000019] at follow-up). Among the individual metabolites, predominantly higher levels of lyso-PC C16:0, both at baseline (P = 0.0039) and at follow-up (P = 0.001), were found in the insulin-sensitive compared with the insulin-resistant subjects. In the non-NAFL groups, no differences in lyso-PC C16:0 levels were found between the insulin-sensitive and insulin-resistant subjects, and these relationships were replicated in plasma from subjects with liver tissue samples.

CONCLUSIONS

From a plasma metabolomic pattern, particularly lyso-PCs are able to separate metabolically benign from malignant NAFL in humans and may highlight important pathways in the pathogenesis of fatty liver-induced insulin resistance.

Lysophosphatidylcholine enhances NGF-induced MAPK and Akt signals through the extracellular domain of TrkA in PC12 cells

Lysophosphatidylcholine (LPC) is one of the major lysophospholipids mainly generated by phospholipase A₂ (PLA₂)-mediated hydrolysis of phosphatidylcholine (PC). We previously found that LPC displays neurotrophin-like activity in the rat pheochromocytoma PC12 cells and in cerebellar granule neurons, but the molecular mechanism remains unclear. We report here that LPC specifically enhances nerve growth factor (NGF)-induced signals in PC12 cells. When PC12 cells were treated with NGF, MAPK was phosphorylated, but this phosphorylation was significantly elevated when LPC was added together. In accordance, NGF-induced expression of immediate early genes, c-fos and NGF-IA, was upregulated by LPC. Phosphorylation of the upstream components, MEK and NGF receptor TrkA, was also promoted by LPC, which was in line with increased phosphorylation of Akt. In contrast, LPC did not enhance epidermal growth factor (EGF)-, basic fibroblast growth factor-, or insulin-like growth factor-1-induced signals. Studies using TrkA/EGF receptor chimeras demonstrated that the extracellular domain, but not the transmembrane or intracellular domains, of TrkA is responsible for the effect of LPC. Exogenously-added secretory PLA₂ (sPLA₂) enhanced NGF-induced MAPK phosphorylation at a comparable level to LPC, suggesting that LPC generated in situ by sPLA₂-mediated hydrolysis of membrane PC stimulated NGF-TrkA signal. Taken together, these results indicate a specific role and function of LPC on NGF-TrkA signaling pathway.

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LPC potentiates NGF-induced MAPK and Akt phosphorylation in PC12 cells.

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LPC enhances NGF-induced MEK and TrkA phosphorylation.

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LPC does not affect the signals of EGF, FGF, and IGF-1.

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The effect of LPC requires the extracellular domain of TrkA.

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sPLA2 also potentiates NGF-induced MAPK phosphorylation.

Novel bioactive glycerol-based lysophospholipids: new data -- new insight into their function

Based on the results of research conducted over last two decades, lysophospholipids (LPLs) were observed to be not only structural components of cellular membranes but also biologically active molecules influencing a broad variety of processes such as carcinogenesis, neurogenesis, immunity, vascular development or regulation of metabolic diseases. With a growing interest in the involvement of extracellular lysophospholipids in both normal physiology and pathology, it has become evident that those small molecules may have therapeutic potential. While lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) have been studied in detail, other LPLs such as lysophosphatidylglycerol (LPG), lysophosphatidylserine (LPS), lysophosphatidylinositol (LPI), lysophosphatidylethanolamine (LPE) or even lysophosphatidylcholine (LPC) have not been elucidated to such a high degree. Although information concerning the latter LPLs is sparse as compared to LPA and S1P, within the last couple of years much progress has been made. Recently published data suggest that these compounds may regulate fundamental cellular activities by modulating multiple molecular targets, e.g. by binding to specific receptors and/or altering the structure and fluidity of lipid rafts. Therefore, the present review is devoted to novel bioactive glycerol-based lysophospholipids and recent findings concerning their functions and possible signaling pathways regulating physiological and pathological processes.

Return of the metabolic trajectory to the original area after human bone marrow mesenchymal stem cell transplantation for the treatment of fulminant hepatic failure

Our recent study first demonstrated that human bone marrow mesenchymal stem cell (hBMSC) transplantation could prevent death from fulminant hepatic failure (FHF) in pigs. To further clarify the metabolic mechanism of hBMSC transplantation in FHF, the plasma collected from FHF pigs that received transplantation of hBMSCs was examined using metabolic analysis to identify the key molecular markers that regulate recovery. The results showed that obvious metabolic disturbance occurred during FHF, whereas the hBMSC transplantation group showed less severe liver injury. The metabolic trajectory returns to its original state at week 3 following the hBMSC transplantation. In total, the concentration of 26 metabolites, including conjugated bile acids, phosphatidylcholines, lysophosphatidylcholines, fatty acids, amino acid and sphingomyelin, are significantly different between the FHF group and the hBMSC transplantation group. Moreover, the time course of changes in the metabolites corresponded with that of the biochemical and histological analyses. Real-time PCR further confirmed that the gene expression of phospholipase A1, lecithin-cholesterol acyltransferase and lysophosphatidylcholine acyltransferase 1 decreased significantly, whereas that of phospholipase A2 remained stable, which explains the decrease of the phosphatidylcholines and lysophosphatidylcholines. These novel results have revealed a metabolic mechanism for the hBMSC transplantation in FHF, which could lead to the future development of treatment strategies for stem cell therapies.