Decrease in circulating autotaxin by oral administration of prednisolone

Serum autotaxin level: a promising diagnostic biomarker in differentiating Graves' disease and thyroiditis

BACKGROUND

Recent studies have suggested that serum autotaxin (ATX) may be a promising diagnostic biomarker in differentiating between Graves' disease (GD) and thyroiditis, as well as serving as a monitoring biomarker for GD. This study will evaluate the use of serum ATX as a diagnostic biomarker in these conditions.

METHODS

In this prospective interventional study, blood samples were collected from the patients who met both inclusion and exclusion criteria, and serum ATX levels were measured by using the MyBioSource human Autotaxin ELISA kit.

RESULTS

A total of 32 patients were enrolled, of which 18.8% were newly diagnosed with GD, 21.9% were thyroiditis, and 59.3% were on treatment for GD. Serum autotaxin antigen was significantly higher in GD patients than in thyroiditis (603.3217 ± 444.24 v/s 214.74 ± 55.91, P = <.005). Serum ATX measurement successfully discriminated GD patients from thyroiditis (AUC = 0.952, 95%CI: 0.00-1.00) with an optimal cutoff value of ≥257.20 ng/L (sensitivity = 100 and specificity = 81.71). Monitoring the efficacy of serum ATX was analyzed and showed a significant difference.

CONCLUSION

The serum ATX was higher in subjects with GD as compared to thyroiditis, and ATX levels were found to be decreased during the treatment period. In conclusion, serum ATX can be used as a diagnostic and monitoring biomarker in GD.

Autotaxin is a potential predictive marker for the development of veno-occlusive disease/sinusoidal obstruction syndrome after allogeneic hematopoietic cell transplantation

Veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is a life-threatening complication after allogeneic hematopoietic cell transplantation (allo-HCT), and stratification of the high-risk group before transplantation is significant. Serum autotaxin (ATX) levels have been reported to increase in patients with liver fibrosis caused by metabolic inhibition from liver sinusoidal endothelial cells. Considering that the pathophysiology of VOD/SOS begins with liver sinusoidal endothelial cell injury, an increase in serum ATX levels may precede the onset of VOD/SOS. A retrospective study with 252 patients, including 12 patients with VOD/SOS, who had received allo-HCT was performed. The cumulative incidence of VOD/SOS was higher in the group with serum ATX levels before conditioning (baseline ATX) above the upper reference limit (high ATX group, p < 0.001), and 1-year cumulative incidences were 22.7% (95% confidence interval [95%CI], 3.1-42.4%) and 3.5% (95%CI, 1.1-5.8%), respectively. In the multivariate analysis, elevated baseline ATX was identified as an independent risk factor for VOD/SOS development and showed an additive effect on the predictive ability of known risk factors. Furthermore, the incidence of VOD/SOS-related mortality was greater in the high ATX group (16.7% vs. 1.3%; p = 0.005). Serum ATX is a potential predictive marker for the development of VOD/SOS.

Role of autotaxin in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disease characterized by the production of various autoantibodies and deposition of immune complexes. SLE is a heterogenous disease, and the pattern of organ involvement and response to treatment differs significantly among patients. Novel biological markers are necessary to assess the extent of organ involvement and predict treatment response in SLE. Lysophosphatidic acid is a lysophospholipid involved in various biological processes, and autotaxin (ATX), which catalyzes the production of lysophosphatidic acid in the extracellular space, has gained attention in various diseases as a potential biomarker. The concentration of ATX is increased in the serum and urine of patients with SLE and lupus nephritis. Recent evidence suggests that ATX produced by plasmacytoid dendritic cells may play an important role in the immune system and pathogenesis of SLE. Furthermore, the production of ATX is associated with type I interferons, a key cytokine in SLE pathogenesis, and ATX may be a potential biomarker and key molecule in SLE.

Decrease in serum levels of autotaxin in COVID-19 patients

INTRODUCTION

In order to identify therapeutic targets in Coronavirus disease 2019 (COVID-19), it is important to identify molecules involved in the biological responses that are modulated in COVID-19. Lysophosphatidic acids (LPAs) are involved in the pulmonary inflammation and fibrosis are one of the candidate molecules. The aim of this study was to evaluate the association between the serum levels of autotaxin (ATX), which are enzymes involved in the synthesis of lysophosphatidic acids.

MATERIAL AND METHODS

We enrolled 134 subjects with COVID-19 and 58 normal healthy subjects for the study. We measured serum ATX levels longitudinally in COVID-19 patients and investigated the time course and the association with severity and clinical parameters.

RESULTS

The serum ATX levels were reduced in all patients with COVID-19, irrespective of the disease severity, and were negatively associated with the serum CRP, D-dimer, and anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody levels.

DISCUSSION

Considering the biological properties of LPAs in the pulmonary inflammation and fibrosis, modulation of ATX might be compensatory biological responses to suppress immunological overreaction especially in the lung, which is an important underlying mechanism for the mortality of the disease.

CONCLUSIONS

COVID-19 patients showed a decrease in the serum levels of ATX, irrespective of the disease severity. Key MessagesAutotaxin (ATX) is an enzyme involved in the synthesis of lysophosphatidic acid (LPA), which has been reported to be involved in pulmonary inflammation and fibrosis. Patients with COVID-19 show decrease in the serum levels of ATX. Modulation of ATX might be compensatory biological responses to suppress immunological overreaction.

Serum autotaxin levels in chronic disease and acute exacerbation of fibrosing interstitial lung disease

Background

Autotaxin (ATX) is an ecto-enzyme that catalyses the hydrolysis of lysophospholipids to the lipid mediator lysophosphatidic acid (LPA). LPA/ATX signalling has emerged as a new therapeutic target for pulmonary fibrosis; however, the serum levels and dynamics of ATX during the clinical course of fibrosing interstitial lung disease (ILD) remain unknown. This study sought to examine the serum ATX levels in fibrosing ILD in the chronic phase and in acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF). We aimed to elucidate the association between serum ATX level and clinical characteristics including disease progression and prognosis.

Methods

In total, 119 patients with fibrosing ILD and 38 healthy volunteers as controls were enrolled in the study and their serum ATX activity was analysed. We also included six male patients with AE-IPF in order to analyse the changes in serum ATX at the onset of AE-IPF.

Results

Patients with fibrosing ILD showed significantly higher serum ATX levels compared with healthy controls in both sexes. Per cent change in forced vital capacity after 1 year correlated with serum ATX levels in female patients. High serum ATX levels (>0.721 mg· L⁻¹) were associated with worse outcome in survival curve and multivariate analysis of male patients. Serum ATX activity decreased after the onset of AE-IPF.

Conclusion

Serum ATX levels were significantly higher in patients with fibrosing ILD compared with healthy controls, and this was associated with disease progression and outcome. This suggests the potential of serum ATX as a promising biomarker for the treatment of fibrosing ILD.

Serum ATX levels are higher in fibrosing ILD than in healthy controls; this is associated with disease progression and outcome. Serum ATX levels decrease at the onset of AE-IPF.https://bit.ly/3hLR9jN

Urine autotaxin levels reflect the disease activity of sarcoidosis

Since the clinical outcome of patients with sarcoidosis is still unpredictable, a good prognostic biomarker is necessary. Autotaxin (ATX) and phosphatidylserine-specific phospholipase A1 (PS-PLA1) function as main enzymes to produce lysophospholipids (LPLs), and these enzymes are attracting attention as useful biomarkers for several chronic inflammatory diseases. Here, we investigated the relationships between LPLs-producing enzymes and the disease activity of sarcoidosis. In total, 157 patients with sarcoidosis (active state, 51%) were consecutively enrolled. Using plasma or urine specimens, we measured the values of LPLs-producing enzymes. Urine ATX (U-ATX) levels were significantly lower in the active state compared to those in the inactive state, while the plasma ATX (P-ATX) and PS-PLA1 levels showed no significant difference between these two states. Concerning the comparison with existing clinical biomarkers for sarcoidosis, U-ATX showed a weak negative correlation to ACE, P-ATX a weak positive correlation to both ACE and sIL-2R, and PS-PLA1 a weak positive one to sIL-2R. Notably, only the U-ATX levels inversely fluctuated depending on the status of disease activity whether OCS had been used or not. These findings suggest that U-ATX is likely to be a novel and useful molecule for assessing the disease activity of sarcoidosis.

Serum autotaxin as a novel prognostic marker in patients with non-ischaemic dilated cardiomyopathy

Aims

Autotaxin (ATX) promotes myocardial inflammation, fibrosis, and the subsequent cardiac remodelling through lysophosphatidic acid production. However, the prognostic impact of serum ATX in non‐ischaemic dilated cardiomyopathy (NIDCM) has not been clarified. We investigated the prognostic impact of serum ATX in patients with NIDCM.

Methods and results

We enrolled 104 patients with NIDCM (49.8 ± 13.4 years, 76 men). We divided the patients into two groups using different cutoffs of median serum ATX levels for men and women: high‐ATX group and low‐ATX group. Cardiac events were defined as a composite of cardiac death and heart failure resulting in hospitalization. Median ATX level was 203.5 ng/mL for men and 257.0 ng/mL for women. Brain natriuretic peptide levels [224.0 (59.6–689.5) pg/mL vs. 96.5 (40.8–191.5) pg/mL, P = 0.010] were higher in the high‐ATX group than low‐ATX group, whereas high‐sensitivity C‐reactive protein and collagen volume fraction levels in endomyocardial biopsy samples were not significantly different between the two groups. Kaplan–Meier survival analysis revealed that the event‐free survival rate was significantly lower in the high‐ATX group than low‐ATX group (log‐rank; P = 0.007). Cox proportional hazard analysis revealed that high‐ATX was an independent determinant of composite cardiac events. In both sexes, serum ATX levels did not correlate with high‐sensitivity C‐reactive protein levels and collagen volume fraction but had a weak correlation with brain natriuretic peptide levels (men; spearman's rank: 0.274, P = 0.017, women; spearman's rank: 0.378, P = 0.048).

Conclusion

High serum ATX levels can be associated with increasing adverse clinical outcomes in patients with NIDCM. These results indicate serum ATX may be a novel biomarker or therapeutic target in NIDCM.

Altered plasma levels of lysophospholipids in response to adrenalectomy of rats

The aim of this study was to investigate effects of reduced stress hormone by adrenalectomy on rat plasma levels of lysophosphatidic acid (LPA) and other lysophospholipids. We measured activities of lysophospholipase D (lysoPLD) in plasma and lipid phosphate phosphatase (LPP) in blood by determining choline and inorganic phosphate, respectively. LPA, lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), lysophosphatidylinositol (LPI), lysophosphatidylserine (LPS) and lysophosphatodylglycerol were quantified by LC-MS/MS. In adrenalectomized rats, plasma levels of LPA, LPE, LPS and LPI, but not LPC, were increased. The increased level of LPA were due to decreased LPC level, increases plasma activity of lysoPLD toward LPC and decreased LPP activity toward LPA. Daily injections of deoxycoricosterone into rats selectively reversed increased level of LPS. Our results suggest enzymatic mechanism for increased plasma level of LPA, and indicate that the circulating levels of lysophospholipids including LPA in rats are differently affected by artificial suppression of release of adrenergic hormones.

Cholestasis-Associated Pruritus and Its Pruritogens

Pruritus is a debilitating symptom of various cholestatic disorders, including primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) and inherited progressive familial intrahepatic cholestasis (PFIC). The molecular mechanisms leading to cholestasis-associated pruritus are still unresolved and the involved pruritogens are indecisive. As a consequence of pruritus, patients suffer from sleep deprivation, loss of daytime concentration, auto-mutilation and sometimes even suicidal ideations. Current guideline-approved therapy of cholestasis-associated pruritus includes stepwise administration of several medications, which may alleviate complaints in some, but not all affected patients. Therefore, also experimental therapeutic approaches are required to improve patients' quality of life. This article reviews the current state of research on pruritogens and their receptors, and shortly discusses the most recent experimental therapies.

Effect of postoperative corticosteroids on surgical outcome and aqueous autotaxin following combined cataract and microhook ab interno trabeculotomy

To evaluate the effect of postoperative corticosteroids on surgical outcome and autotaxin (ATX) levels after microhook ab interno trabeculotomy combined with cataract surgery (μLOT-CS), prospective, consecutive non-randomized case series comparing outcomes of 30 eyes with primary open angle glaucoma was performed. The aqueous ATX, intraocular pressure (IOP) and glaucoma medications were monitored for 3 months postoperatively. An in-vivo mouse μLOT model was generated. In vitro, ATX and fibrotic changes induced by dexamethasone (Dex) treatment following scratch (S) in cultured human trabecular meshwork (hTM) cells were assessed by immunofluorescence, immunoenzymatic assay, and RT-qPCR. Postoperative ATX at 1 week and the number of antiglaucoma medications at 3 months were significantly lower in non-steroid group, and steroid use was the only variable significantly associated with postoperative medications at 3 months in multiregression analyses. In vitro, ATX activity was significantly upregulated in the Dex + S group, and αSMA was significantly upregulated in the Dex and Dex + S groups. Fibronectin and COL1A1 were significantly upregulated in the S group. μLOT-CS decreased IOP and medications in the overall cohort, and non-use of postoperative steroids resulted in a smaller number of postoperative medications. Limiting postoperative steroids in μLOT may minimize IOP elevation and postoperative fibrosis.

Higher serum levels of autotaxin and phosphatidylserine-specific phospholipase A1 in patients with lupus nephritis

BACKGROUND

Recent studies revealed that lysophospholipids (LPLs) and related molecules, such as autotaxin (ATX) and phosphatidylserine-specific phospholipase A₁ (PS-PLA₁ ), are candidates for novel biomarkers in melanoma, glaucoma and diabetic nephropathy. However, it is not clear whether serum levels of ATX/ PS-PLA₁ would be associated with pathological and clinical findings of lupus nephritis (LN).

METHODS

In this retrospective cohort study, serum samples were collected from 39 patients with LN and 37 patients with other glomerular diseases. The serum levels of ATX and PS-PLA₁ were evaluated for an association with renal pathology and clinical phenotypes of LN.

RESULTS

The serum levels of ATX and PS-PLA₁ were higher in the patients with LN as compared to those with other glomerular diseases. Among the classes of LN, the patients with class IV showed the trend of lower serum levels of ATX. Moreover, the patients with lower levels of ATX exhibited higher scores of activity index (AI) and chronicity index (CI). The level of ATX tended to be negatively correlated with AI and CI. These results might be explained by the effect of treatment, because the serum levels of ATX and PS-PLA₁ were inversely correlated with the daily amount of oral prednisolone. Moreover, they did not reflect the level of proteinuria or kidney survival in LN patients.

CONCLUSION

Although the serum levels of ATX and PS-PLA₁ were affected by the treatment, these levels were higher in the patients with LN. The potential clinical benefits of these markers need to be clarified in further studies.

Reduced Serum and Cerebrospinal Fluid Levels of Autotaxin in Major Depressive Disorder

BACKGROUND

The autotaxin/lysophosphatidic acid axis is involved in diverse biological processes including neurodevelopment, inflammation, and immunological functioning. The lysophosphatidic acid 1 receptor has been implicated in the pathophysiology of major depressive disorder and in the mechanism of action of antidepressants. However, it is unclear whether central or peripheral autotaxin levels are altered in patients with major depressive disorder.

METHODS

Serum autotaxin levels were measured by an enzyme-linked immunosorbent assay in 37 patients with major depressive disorder diagnosed using DSM-IV-TR who underwent electroconvulsive therapy and were compared with those of 47 nondepressed controls matched for age and sex between January 2011 and December 2015. Patient serum levels of autotaxin before and after electroconvulsive therapy were also compared. In a separate sample set, cerebrospinal fluid autotaxin levels were compared between 26 patients with major depressive disorder and 27 nondepressed controls between December 2010 and December 2015. A potential association was examined between autotaxin levels and clinical symptoms assessed with the Hamilton Depression Rating Scale.

RESULTS

Before electroconvulsive therapy, both serum and cerebrospinal fluidautotaxin levels were significantly lower in major depressive disorder patients than in controls (serum: P = .001, cerebrospinal fluid: P = .038). A significantly negative correlation between serum, but not cerebrospinal fluid, autotaxin levels and depressive symptoms was observed (P = .032). After electroconvulsive therapy, a parallel increase in serum autotaxin levels and depressive symptoms improvement was observed (P = .005).

CONCLUSION

The current results suggest that serum autotaxin levels are reduced in a state-dependent manner. The reduction of cerebrospinal fluidautotaxin levels suggests a dysfunction in the autotaxin/lysophosphatidic acid axis in the brains of patients with major depressive disorder.

Machine-learning based lipid mediator serum concentration patterns allow identification of multiple sclerosis patients with high accuracy

Based on increasing evidence suggesting that MS pathology involves alterations in bioactive lipid metabolism, the present analysis was aimed at generating a complex serum lipid-biomarker. Using unsupervised machine-learning, implemented as emergent self-organizing maps of neuronal networks, swarm intelligence and Minimum Curvilinear Embedding, a cluster structure was found in the input data space comprising serum concentrations of d = 43 different lipid-markers of various classes. The structure coincided largely with the clinical diagnosis, indicating that the data provide a basis for the creation of a biomarker (classifier). This was subsequently assessed using supervised machine-learning, implemented as random forests and computed ABC analysis-based feature selection. Bayesian statistics-based biomarker creation was used to map the diagnostic classes of either MS patients (n = 102) or healthy subjects (n = 301). Eight lipid-markers passed the feature selection and comprised GluCerC16, LPA20:4, HETE15S, LacCerC24:1, C16Sphinganine, biopterin and the endocannabinoids PEA and OEA. A complex classifier or biomarker was developed that predicted MS at a sensitivity, specificity and accuracy of approximately 95% in training and test data sets, respectively. The present successful application of serum lipid marker concentrations to MS data is encouraging for further efforts to establish an MS biomarker based on serum lipidomics.

Dexamethasone decreases the autotaxin-lysophosphatidate-inflammatory axis in adipose tissue: implications for the metabolic syndrome and breast cancer

Lysophosphatidate (LPA) signaling through 6 receptors is regulated by the balance of LPA production by autotaxin (ATX) vs. LPA degradation by lipid phosphate phosphatases (LPPs). LPA promotes an inflammatory cycle by increasing the synthesis of cyclooxygenase-2 and multiple inflammatory cytokines that stimulate further ATX production. We aimed to determine whether the anti-inflammatory glucocorticoid (GC) dexamethasone (Dex) functions partly by decreasing the ATX-LPA inflammatory cycle in adipose tissue, a major site of ATX secretion. Treatment of human adipose tissue with 10-1000 nM Dex decreased ATX secretion, increased LPP1 expression, and decreased mRNA expressions of IL-6, TNF-α, peroxisome proliferator-activated receptor (PPAR)-γ, and adiponectin. Cotreatment with rosiglitazone (an insulin sensitizer), insulin, or both abolished Dex-induced decreases in ATX and adiponectin secretion, but did not reverse Dex-induced decreases in secretions of 20 inflammatory cytokines and chemokines. Dex-treated mice exhibited lower ATX activity in plasma, brain, and adipose tissue; decreased mRNA levels for LPA and sphingosine 1-phosphate (S1P) receptors in brain; and decreased plasma concentrations of LPA and S1P. Our results establish a novel mechanism for the anti-inflammatory effects of Dex through decreased signaling by the ATX-LPA-inflammatory axis. The GC action in adipose tissue has implications for the pathogenesis of insulin resistance and obesity in metabolic syndrome and breast cancer treatment.-Meng, G., Tang, X., Yang, Z., Zhao, Y., Curtis, J. M., McMullen, T. P. W., Brindley, D. N. Dexamethasone decreases the autotaxin-lysophosphatidate-inflammatory axis in adipose tissue: implications for the metabolic syndrome and breast cancer.

Serum Autotaxin Concentrations Reflect Changes in Liver Stiffness and Fibrosis After Antiviral Therapy in Patients with Chronic Hepatitis C

The purpose of this study was to determine whether serum autotaxin concentrations reflect liver stiffness in patients with chronic hepatitis C virus (HCV) treated with direct‐acting antiviral agents. Adult patients with chronic HCV were enrolled from January 2016 to August 2017. Autotaxin concentrations in these patients were compared with those of a control group consisting of healthy individuals. Liver stiffness was determined by transient elastography. The relationship between fibrosis markers and fibrosis scores was evaluated before and after treatment. Data from 155 HCV patients and 56 control subjects were analyzed. Autotaxin concentrations were significantly higher in HCV patients with liver stiffness scores less than or equal to 7.4 kPa versus controls. Autotaxin concentrations at the end of treatment and beyond were significantly lower than those prior to treatment. Pretreatment and posttreatment autotaxin concentrations in male and female patients with liver stiffness scores greater than 14.9 kPa changed significantly (P < 0.01 and P < 0.01, respectively). From the start of treatment to 6 months following treatment, the fibrosis marker/liver stiffness score ratios changed as follows: autotaxin: 0.189 (95% confidence interval [CI]: 0.169‐0.209) to 0.191 (95% CI: 0.166‐0.216; P= 0.88); Wisteria floribundaagglutinin‐positive Mac‐2‐binding protein: 0.294 (95% CI: 0.256‐0.332) to 0.223 (95% CI: 0.191‐0.255; P< 0.001); hyaluronic acid: 19.05 (95% CI: 14.29‐23.81) to 13.92 (95% CI: 11.16‐16.70; P = 0.044); and type IV collagen 7S: 0.560 (95% CI: 0.515‐0.604) to 0.546 (95% CI: 0.497‐0.895; P = 0.052). Conclusion: Autotaxin concentrations reflect liver stiffness before and after antiviral treatment in patients with chronic HCV infection.

Lysophospholipids in laboratory medicine

Lysophospholipids (LPLs), such as lysophosphatidic acid (LPA), sphingosine 1-phosphate (S1P), and lysophosphatidylserine (LysoPS), are attracting attention as second-generation lipid mediators. In our laboratory, the functional roles of these lipid mediators and the mechanisms by which the levels of these mediators are regulated in vivo have been studied. Based on these studies, the clinical introduction of assays for LPLs and related proteins has been pursued and will be described in this review. Although assays of these lipids themselves are possible, autotaxin (ATX), apolipoprotein M (ApoM), and phosphatidylserine-specific phospholipase A₁ (PS-PLA₁) are more promising as alternate biomarkers for LPA, S1P, and LysoPS, respectively. Presently, ATX, which produces LPA through its lysophospholipase D activity, has been shown to be a useful laboratory test for the diagnosis and staging of liver fibrosis, whereas PS-PLA₁ and ApoM are considered to be promising clinical markers reflecting the in vivo actions induced by LysoPS and S1P.

Dysregulation of lysophosphatidic acids in multiple sclerosis and autoimmune encephalomyelitis

Abstract

Bioactive lipids contribute to the pathophysiology of multiple sclerosis. Here, we show that lysophosphatidic acids (LPAs) are dysregulated in multiple sclerosis (MS) and are functionally relevant in this disease. LPAs and autotaxin, the major enzyme producing extracellular LPAs, were analyzed in serum and cerebrospinal fluid in a cross-sectional population of MS patients and were compared with respective data from mice in the experimental autoimmune encephalomyelitis (EAE) model, spontaneous EAE in TCR¹⁶⁴⁰ mice, and EAE in Lpar2^-/- mice. Serum LPAs were reduced in MS and EAE whereas spinal cord LPAs in TCR¹⁶⁴⁰ mice increased during the ‘symptom-free’ intervals, i.e. on resolution of inflammation during recovery hence possibly pointing to positive effects of brain LPAs during remyelination as suggested in previous studies. Peripheral LPAs mildly re-raised during relapses but further dropped in refractory relapses. The peripheral loss led to a redistribution of immune cells from the spleen to the spinal cord, suggesting defects of lymphocyte homing. In support, LPAR2 positive T-cells were reduced in EAE and the disease was intensified in Lpar2 deficient mice. Further, treatment with an LPAR2 agonist reduced clinical signs of relapsing-remitting EAE suggesting that the LPAR2 agonist partially compensated the endogenous loss of LPAs and implicating LPA signaling as a novel treatment approach.

Graphical abstract

Graphical summary of lysophosphatidic signaling in multiple sclerosis

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-017-0446-4) contains supplementary material, which is available to authorized users.

Autotaxin, Pruritus and Primary Biliary Cholangitis (PBC)

Autotaxin (ATX) is a 125-kD type II ectonucleotide pyrophosphatase/phosphodiesterase (ENPP2 or NPP2) originally discovered as an unknown "autocrine motility factor" in human melanoma cells. In addition to its pyrophosphatase/phosphodiesterase activities ATX has lysophospholipase D (lysoPLD) activity, catalyzing the conversion of lysophosphatidylcholine (LPC) into lysophosphatidic acid (LPA). ATX is the only ENPP family member with lysoPLD activity and it produces most of the LPA in circulation. In support of this, ATX heterozygous mice have 50% of normal LPA plasma levels. The ATX-LPA signaling axis plays an important role in both normal physiology and disease pathogenesis and recently has been linked to pruritus in chronic cholestatic liver diseases, including primary biliary cholangitis (PBC). Several lines of evidence have suggested that a circulating puritogen is responsible, but the identification of the molecule has yet to be definitively identified. In contrast, plasma ATX activity is strongly associated with pruritus in PBC, suggesting a targetable molecule for treatment. We review herein the biochemistry of ATX and the rationale for its role in pruritus.

Serum Autotaxin Levels Are Associated with Proteinuria and Kidney Lesions in Japanese Type 2 Diabetic Patients with Biopsy-proven Diabetic Nephropathy

Objective We evaluated the relationships between the serum autotaxin (ATX) levels and the clinical and pathological parameters, as well as the long-term renal outcome, in type 2 diabetic patients with biopsy-proven diabetic nephropathy. Methods In this retrospective single-center cohort study, serum samples were collected from 38 Japanese type 2 diabetic patients with biopsy-proven diabetic nephropathy at the time of renal biopsy. The serum ATX levels were measured using a specific sandwich enzyme immunoassay. Results A multivariate linear regression analysis revealed the urinary protein excretion to be independently associated with the serum ATX levels. In addition, patients with serum ATX levels above the median showed more advanced diffuse lesions, nodular lesions and arteriolar hyalinosis compared to those with serum ATX levels below the median. However, high serum ATX levels were not associated with any increase in the number of renal composite events [a need for dialysis or a 50% decline in the estimated glomerular filtration rate (eGFR) from baseline]. Conclusion The serum ATX levels in type 2 diabetic patients with diabetic nephropathy were associated with proteinuria and diabetic kidney lesions, although the serum ATX levels were not identified to be a predictive indicator for the renal outcome.

Autotaxin in the crosshairs: taking aim at cancer and other inflammatory conditions

Autotaxin is a secreted enzyme that produces most of the extracellular lysophosphatidate from lysophosphatidylcholine, the most abundant phospholipid in blood plasma. Lysophosphatidate mediates many physiological and pathological processes by signaling through at least six G-protein coupled receptors to promote cell survival, proliferation and migration. The autotaxin/lysophosphatidate signaling axis is involved in wound healing and tissue remodeling, and it drives many chronic inflammatory conditions from fibrosis to colitis, asthma and cancer. In cancer, lysophosphatidate signaling promotes resistance to chemotherapy and radiotherapy, and increases both angiogenesis and metastasis. Research into autotaxin inhibitors is accelerating, both as primary and adjuvant therapy. Historically, autotaxin inhibitors had poor bioavailability profiles and thus had limited efficacy in vivo. This situation is now changing, especially since the recent crystal structure of autotaxin is now enabling rational inhibitor design. In this review, we will summarize current knowledge on autotaxin-mediated disease processes including cancer, and discuss recent advancements in the development of autotaxin-targeting strategies. We will also provide new insights into autotaxin as an inflammatory mediator in the tumor microenvironment that promotes cancer progression and therapy resistance.

Involvement of autotaxin/lysophosphatidic acid signaling in obesity and impaired glucose homeostasis

Autotaxin (ATX) is a secreted lysophospholipase D involved in synthesis of lysophosphatidic acid (LPA), a phospholipid growth factor acting via specific receptors (LPA1R to LPA6R) and involved in several pathologies including obesity. ATX is secreted by adipocytes and contributes to circulating LPA. ATX expression is up-regulated in obese patients and mice in relationship with insulin resistance and impaired glucose tolerance. LPA1R is the most abundant subtype in adipose tissue. Its expression is higher in non-adipocyte cells than in adipocytes and is not altered in obesity. ATX increases and LPA1R decreases while preadipocytes differentiate into adipocytes (adipogenesis). LPA inhibits adipogenesis through down-regulation of the pro-adipogenic transcription factor PPARγ2. Adipocyte-specific knockout (FATX-KO) mice or mice treated with the LPAR antagonist Ki16425 gain more weight and accumulate more adipose tissue than wild type or control mice fed a high fat diet (HFD). These observations suggest that LPA (via LPA1R) exerts a tonic inhibitory effect on adipose tissue expansion that could, at least in part, result from the anti-adipogenic activity of LPA. A possible negative impact of LPA on insulin-sensitivity might also be considered. Despite being more sensitive to nutritional obesity, FATX-KO and Ki16425-treated mice fed a HFD show improved glucose tolerance when compared to wild type mice. Moreover, exogenously injected LPA acutely impairs glucose tolerance and insulin secretion. These observations show that LPA exerts a tonic deleterious impact on glucose homeostasis. In conclusion, ATX and LPA1R represent potential interesting pharmacological targets for the treatment of obesity-associated metabolic diseases.