Production of extracellular lysophosphatidic acid in the regulation of adipocyte functions and liver fibrosis

The Emerging Role of LPA as an Oncometabolite

Lysophosphatidic acid (LPA) is a phospholipid that displays potent signalling activities that are regulated in both an autocrine and paracrine manner. It can be found both extra- and intracellularly, where it interacts with different receptors to activate signalling pathways that regulate a plethora of cellular processes, including mitosis, proliferation and migration. LPA metabolism is complex, and its biosynthesis and catabolism are under tight control to ensure proper LPA levels in the body. In cancer patient specimens, LPA levels are frequently higher compared to those of healthy individuals and often correlate with poor responses and more aggressive disease. Accordingly, LPA, through promoting cancer cell migration and invasion, enhances the metastasis and dissemination of tumour cells. In this review, we summarise the role of LPA in the regulation of critical aspects of tumour biology and further discuss the available pre-clinical and clinical evidence regarding the feasibility and efficacy of targeting LPA metabolism for effective anticancer therapy.

Fuzhuan brick tea ameliorates hepatic steatosis and steatohepatitis through gut microbiota-derived aryl hydrocarbon receptor ligands in high-fat diet-induced obese mice

High-fat diet (HFD) induced obesity and its associated conditions, such as hepatic steatosis and steatohepatitis, are major health concerns worldwide. Previous studies have reported the excellent efficiency of Fuzhuan brick tea (FBT) in attenuating HFD-induced obesity and metabolic disorders. In this study, we investigated the effects of FBT on hepatic steatosis and simple steatohepatitis in HFD-induced obese mice, as well as the metabolic function of the gut microbiome using metagenomics and metabolomics. The results showed that FBT ameliorated dyslipidemia, hepatic steatosis and steatohepatitis in HFD-induced obese mice by normalizing the gut microbiota structure and tryptophan metabolism. FBT increased the cecal abundance of aryl hydrocarbon receptor (AhR)-ligand producing bacteria such as Lactobacillus_reuteri and Lactobacillus_johnsonii, at the expense of AhR-ligand consuming bacteria, such as Faecalibaculum_rodentium and Escherichia_coli, and elevated the cecal contents of AhR-ligands such as IAA, IPA, and KYNA. Furthermore, FBT regulated the expressions of AhR and its targeted lipometabolic genes such as Pemt, Fasn, and SREBP-1c, as well as other inflammatory genes including TNF-α, IL-6, and IL-1β in the liver of mice. Overall, these findings highlight the beneficial effects of FBT on obesity-related hepatic steatosis and steatohepatitis via microbiota-derived AhR signaling.

Bioactive lipid lysophosphatidic acid species are associated with disease progression in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with significant mortality. Prognostic biomarkers to identify rapid progressors are urgently needed to improve patient management. Since the lysophosphatidic acid (LPA) pathway has been implicated in lung fibrosis in preclinical models and identified as a potential therapeutic target, we aimed to investigate if bioactive lipid LPA species could be prognostic biomarkers that predict IPF disease progression. LPAs and lipidomics were measured in baseline placebo plasma of a randomized IPF-controlled trial. The association of lipids with disease progression indices were assessed using statistical models. Compared to healthy, IPF patients had significantly higher levels of five LPAs (LPA16:0, 16:1, 18:1, 18:2, 20:4) and reduced levels of two triglycerides species (TAG48:4-FA12:0, -FA18:2) (false discovery rate < 0.05, fold change > 2). Patients with higher levels of LPAs had greater declines in diffusion capacity of carbon monoxide over 52 weeks (P < 0.01); additionally, LPA20:4-high (≥median) patients had earlier time to exacerbation compared to LPA20:4-low ( Collapse

Key Words

• DLCO
• Lysophosphatidic acid
• exacerbation
• idiopathic pulmonary fibrosis
• mortality

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MESH Headings

• Humans
• Idiopathic Pulmonary Fibrosis/metabolism
• Disease Progression
• Lysophospholipids
• Biomarkers

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Grants Collapse

Affiliation(s)

Margaret Neighbors OMNI Translational Medicine, Genentech Inc., South San Francisco, USA
Qingling Li Department of Microchemistry, Proteomics & Lipidomics, Genentech Inc., South San Francisco, USA
Sha Joe Zhu PD Data Science, F Hoffmann-La Roche, Shanghai, China
Jia Liu PD Data Science, F Hoffmann-La Roche, Shanghai, China
Weng Ruh Wong Department of Microchemistry, Proteomics & Lipidomics, Genentech Inc., South San Francisco, USA
Guiquan Jia Department of Biomarker Discovery OMNI, Genentech Inc., South San Francisco, USA
Wendy Sandoval Department of Microchemistry, Proteomics & Lipidomics, Genentech Inc., South San Francisco, USA
Gaik W Tew I2O Technology and Translational Research, Genentech Inc., South San Francisco, USA.

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Preventing the Increase in Lysophosphatidic Acids: A New Therapeutic Target in Pulmonary Hypertension?

Cardiovascular diseases (CVD) are the leading cause of premature death and disability in humans that are closely related to lipid metabolism and signaling. This study aimed to assess whether circulating lysophospholipids (LPL), lysophosphatidic acids (LPA) and monoacylglycerols (MAG) may be considered as potential therapeutic targets in CVD. For this objective, plasma levels of 22 compounds (13 LPL, 6 LPA and 3 MAG) were monitored by liquid chromatography coupled with tandem mass spectrometry (HPLC/MS²) in different rat models of CVD, i.e., angiotensin-II-induced hypertension (HTN), ischemic chronic heart failure (CHF) and sugen/hypoxia(SuHx)-induced pulmonary hypertension (PH). On one hand, there were modest changes on the monitored compounds in HTN (LPA 16:0, 18:1 and 20:4, LPC 16:1) and CHF (LPA 16:0, LPC 18:1 and LPE 16:0 and 18:0) models compared to control rats but these changes were no longer significant after multiple testing corrections. On the other hand, PH was associated with important changes in plasma LPA with a significant increase in LPA 16:0, 18:1, 18:2, 20:4 and 22:6 species. A deleterious impact of LPA was confirmed on cultured human pulmonary smooth muscle cells (PA-SMCs) with an increase in their proliferation. Finally, plasma level of LPA(16:0) was positively associated with the increase in pulmonary artery systolic pressure in patients with cardiac dysfunction. This study demonstrates that circulating LPA may contribute to the pathophysiology of PH. Additional experiments are needed to assess whether the modulation of LPA signaling in PH may be of interest.

Reduced Cerebrospinal Fluid Levels of Lysophosphatidic Acid Docosahexaenoic Acid in Patients With Major Depressive Disorder and Schizophrenia

BACKGROUND

Lysophosphatidic acid (LPA) is involved in numerous biological processes, including neurodevelopment, chronic inflammation, and immunologic response in the central nervous system. Autotaxin (ATX) is a secreted enzyme that produces LPA from lysophosphatidylcholine (LPC). Previous studies have demonstrated decreased protein levels of ATX in cerebrospinal fluid (CSF) of patients with major depressive disorder (MDD). Based on those studies, the current study investigated the levels of lysophospholipids species including LPA and related metabolic enzymes, in CSF of patients with MDD and schizophrenia (SCZ).

METHODS

The levels of lysophospholipids species and related metabolic enzymes were measured with either liquid chromatography-tandem mass spectrometry or enzyme-linked immunosorbent assay. Japanese patients were diagnosed with DSM-IV-TR. CSF was obtained from age- and sex-matched healthy controls (n = 27) and patients with MDD (n = 26) and SCZ (n = 27).

RESULTS

Of all lysophospholipids species, the levels of LPA 22:6 (LPA - docosahexaenoic acid) were significantly lower in patients with MDD and SCZ than in healthy controls. These levels were negatively correlated with several clinical symptomatic scores of MDD, but not those of SCZ. In addition, the levels of LPA 22:6 were significantly correlated with the levels of LPC 22:6 among all 3 groups. On the other hand, the levels of LPA 22:6 were not correlated with ATX activity in patients with MDD and SCZ.

CONCLUSION

The lower levels of LPA 22:6 in patients with MDD and SCZ suggest an abnormality of LPA 22:6 metabolism. In addition, several depressive symptoms in patients with MDD were significantly associated with the lower levels of LPA 22:6, suggesting an involvement of LPA 22:6 in the pathophysiology of MDD.

Understanding molecular mechanisms of biologics drug delivery and stability from NMR spectroscopy

Protein therapeutics carry inherent limitations of membrane impermeability and structural instability, despite their predominant role in the modern pharmaceutical market. Effective formulations are needed to overcome physiological and physicochemical barriers, respectively, for improving bioavailability and stability. Knowledge of membrane affinity, cellular internalization, encapsulation, and release of drug-loaded carrier vehicles uncover the structural basis for designing and optimizing biopharmaceuticals with enhanced delivery efficiency and therapeutic efficacy. Understanding stabilizing and destabilizing interactions between protein drugs and formulation excipients provide fundamental mechanisms for ensuring the stability and quality of biological products. This article reviews the molecular studies of biologics using solution and solid-state NMR spectroscopy on structural attributes pivotal to drug delivery and stability. In-depth investigation of the structure-function relationship of drug delivery systems based on cell-penetrating peptides, lipid nanoparticles and polymeric colloidal, and biophysical and biochemical stability of peptide, protein, monoclonal antibody, and vaccine, as the integrative efforts on drug product design, will be elaborated.

The LPA3 Receptor: Regulation and Activation of Signaling Pathways

The lysophosphatidic acid 3 receptor (LPA₃) participates in different physiological actions and in the pathogenesis of many diseases through the activation of different signal pathways. Knowledge of the regulation of the function of the LPA₃ receptor is a crucial element for defining its roles in health and disease. This review describes what is known about the signaling pathways activated in terms of its various actions. Next, we review knowledge on the structure of the LPA₃ receptor, the domains found, and the roles that the latter might play in ligand recognition, signaling, and cellular localization. Currently, there is some information on the action of LPA₃ in different cells and whole organisms, but very little is known about the regulation of its function. Areas in which there is a gap in our knowledge are indicated in order to further stimulate experimental work on this receptor and on other members of the LPA receptor family. We are convinced that knowledge on how this receptor is activated, the signaling pathways employed and how the receptor internalization and desensitization are controlled will help design new therapeutic interventions for treating diseases in which the LPA₃ receptor is implicated.

The lysophosphatidic acid axis in fibrosis: Implications for glaucoma

Glaucoma is a common progressive optic neuropathy that results in visual field defects and can lead to irreversible blindness. The pathophysiology of glaucoma involves dysregulated extracellular matrix remodelling in both the trabecular meshwork in the anterior chamber and in the lamina cribrosa of the optic nerve head. Fibrosis in these regions leads to raised intraocular pressure and retinal ganglion cell degeneration, respectively. Lysophosphatidic acid (LPA) is a bioactive lipid mediator which acts via six G-protein coupled receptors on the cell surface to activate intracellular pathways that promote cell proliferation, transcription and survival. LPA signalling has been implicated in both normal wound healing and pathological fibrosis. LPA enhances fibroblast proliferation, migration and contraction, and induces expression of pro-fibrotic mediators such as connective tissue growth factor. The LPA axis plays a major role in diseases such as idiopathic pulmonary fibrosis, where it has been identified as an important pharmacological target. In glaucoma, LPA is present in high levels in the aqueous humour, and its signalling has been found to increase resistance to aqueous humour outflow through altered trabecular meshwork cellular contraction and extracellular matrix deposition. LPA signalling may, therefore, also represent an attractive target for treatment of glaucoma. In this review we wish to describe the role of LPA and its related proteins in tissue fibrosis and glaucoma.

Lipid composition of the cancer cell membrane

Cancer cell possesses numerous adaptations to resist the immune system response and chemotherapy. One of the most significant properties of the neoplastic cells is the altered lipid metabolism, and consequently, the abnormal cell membrane composition. Like in the case of phosphatidylcholine, these changes result in the modulation of certain enzymes and accumulation of energetic material, which could be used for a higher proliferation rate. The changes are so prominent, that some lipids, such as phosphatidylserines, could even be considered as the cancer biomarkers. Additionally, some changes of biophysical properties of cell membranes lead to the higher resistance to chemotherapy, and finally to the disturbances in signalling pathways. Namely, the increased levels of certain lipids, like for instance phosphatidylserine, lead to the attenuation of the immune system response. Also, changes in lipid saturation prevent the cells from demanding conditions of the microenvironment. Particularly interesting is the significance of cell membrane cholesterol content in the modulation of metastasis. This review paper discusses the roles of each lipid type in cancer physiology. The review combined theoretical data with clinical studies to show novel therapeutic options concerning the modulation of cell membranes in oncology.

Lipid Profiles of Five Essential Phospholipid Preparations for the Treatment of Nonalcoholic Fatty Liver Disease: A Comparative Study

Nonalcoholic fatty liver disease (NAFLD) is associated with an imbalance in fatty acid composition and can progress from simple steatosis to steatohepatitis, liver cirrhosis, and hepatocellular carcinoma. Essential phospholipids (EPL), which contain high levels of 1,2-dilinoleoylphosphatidylcholine, can be used to treat NAFLD. Polyenylphosphatidylcholine (PPC) preparations are external, commercially available EPL products. The lipid composition of five commercially available PPC preparations, including Essentiale Forte, Fortifikat, Hepatoprotect Regenerator, Fortifikat Forte, and Esentin Forte were compared, the outcome of which may impact physician choice in the treatment of NAFLD. Following lipid extraction, a comparative analysis of key lipid content was performed using a QTRAP6500+ triple quadruple ion trap hybrid mass spectrometer (Sciex) in nanoelectrospray ionization mode. The glycerophospholipid composition of each PPC was determined, including levels of phosphatidylcholine (PtdCho), and phosphatidylethanolamine (PtdEtn) species, as well as PtdCho:PtdEtn ratio. Of the five preparations analyzed, Essentiale Forte contained the highest PtdCho levels (61.9 mol%) and lowest PtdEtn levels (4.9 mol%). PtdCho 36:4 levels, a polyunsaturated species of PtdCho, were highest in Esentin Forte (39.3 mol%) and Essentiale Forte (38.3 mol%) compared with other PPCs (28.7-35.8 mol%). Levels of lysophosphatidylcholine, phosphatidylinositol, phosphatidic acid, and phosphatidylglycerol were low in all five preparations. Lipid composition was consistent between the preparations. The high PtdCho:PtdEtn ratio composition of Essentiale Forte compared with the other PPC analyzed, as well as the presence of polyunsaturated fatty acids, suggest it could be the most clinically beneficial commercially available hepatoprotective product in the treatment of NAFLD.

Lysophosphatidic Acid and Hematopoiesis: From Microenvironmental Effects to Intracellular Signaling

Vertebrate hematopoiesis is a complex physiological process that is tightly regulated by intracellular signaling and extracellular microenvironment. In recent decades, breakthroughs in lineage-tracing technologies and lipidomics have revealed the existence of numerous lipid molecules in hematopoietic microenvironment. Lysophosphatidic acid (LPA), a bioactive phospholipid molecule, is one of the identified lipids that participates in hematopoiesis. LPA exhibits various physiological functions through activation of G-protein-coupled receptors. The functions of these LPARs have been widely studied in stem cells, while the roles of LPARs in hematopoietic stem cells have rarely been examined. Nonetheless, mounting evidence supports the importance of the LPA-LPAR axis in hematopoiesis. In this article, we have reviewed regulation of hematopoiesis in general and focused on the microenvironmental and intracellular effects of the LPA in hematopoiesis. Discoveries in these areas may be beneficial to our understanding of blood-related disorders, especially in the context of prevention and therapy for anemia.

The roles of autotaxin/lysophosphatidic acid in immune regulation and asthma

Lysophosphatidic acid (LPA) species are present in almost all organ systems and play diverse roles through its receptors. Asthma is an airway disease characterized by chronic allergic inflammation where various innate and adaptive immune cells participate in establishing Th2 immune response. Here, we will review the contribution of LPA and its receptors to the functions of immune cells that play a key role in establishing allergic airway inflammation and aggravation of allergic asthma.

The dysfunctional lipids in prostate cancer

Prostate cancer (PCa) is well-recognized as a lipid-enriched tumor. Lipids represent a diverse array of molecules essential to the cellular structure, defense, energy, and communication. Lipid metabolism can often become dysregulated during tumor development. The increasing body of knowledge on the biological actions of steroid hormone-androgens in PCa has led to the development of several targeted therapies that still represent the standard of care for cancer patients to this day. Sequencing technologies for functional analyses of androgen receptors (ARs) have revealed that AR is also a master regulator of cellular energy metabolism such as fatty acid ß-oxidation, and de novo lipid synthesis. In addition, bioactive lipids are also used as physiological signaling molecules, which have been shown to be involved in PCa progression. This review discusses the potent player(s) in altered lipid metabolism of PCa and describes how lipids and their interactions with proteins can be used for therapeutic advantage. We also discuss the possibility that the altered bioactive lipid mediators affect intracellular signaling pathway and the related transcriptional regulation be of therapeutic interest.

Adipose-derived autotaxin regulates inflammation and steatosis associated with diet-induced obesity

Autotaxin (ATX) is a secreted enzyme that generates the bioactive lipid lysophosphatidic acid (LPA). We generated mice with global inducible post-natal inactivation or adipose-specific loss of the Enpp2 gene encoding ATX. The animals are phenotypically unremarkable and exhibit differences in adipocyte size and adipose tissue expression of inflammatory genes after high fat feeding without gross differences in fat distribution or body mass. Surprisingly, both models of Enpp2- deficiency exhibited marked protection from high fat diet-induced hepatic steatosis. This phenotype was not associated with differences in dietary fat absorption but may be accounted for by differences in hepatic expression of genes involved in de novo synthesis of triglycerides. These findings suggest that pharmacological inhibition of ATX might be protective against hepatic steatosis.