Autotaxin is a valuable biomarker for the prediction of liver fibrosis in patients with non-alcoholic fatty liver disease

Serum autotaxin is a prognostic indicator of liver-related events in patients with non-alcoholic fatty liver disease

BACKGROUND

Circulating autotaxin (ATX) levels have been reported to correlate with liver inflammation activity and liver fibrosis severity in patients with non-alcoholic fatty liver disease (NAFLD). The objective of this study is to investigate whether serum ATX could predict liver-related events (LRE) in NAFLD patients.

METHODS

This retrospective investigation includes 309 biopsy-proven NAFLD patients registered at Shinshu University Hospital. All patients are followed for at least 1 year, during which time the prevalence of LRE, including newly developing hepatocellular carcinoma, hepatic encephalopathy, ascites, and esophagogastric varices, is investigated in relation to ATX levels at the time of liver biopsy.

RESULTS

During the median follow-up period of 7.0 years, LRE are observed in 20 patients (6.5%). The area under the receiver operating characteristic curve and cut-off value of serum ATX for predicting LRE are 0.81 and 1.227 mg/l, respectively. Multivariate Cox proportional hazards models for LRE determine ATX and advanced fibrosis as independently associated factors. Furthermore, in a competing risk analysis that considered non-liver-related death as a competing event, ATX (HR 2.29, 95% CI 1.22-4.30, p = 0.010) is identified as an independent factor associated with LRE, along with advanced fibrosis (HR 8.01, 95% CI 2.10-30.60, p = 0.002). The predictive utility of ATX for LRE is validated in an independent cohort.

CONCLUSIONS

Serum ATX may serve as a predictive marker for LRE in patients with NAFLD.

Bioactive signalling lipids as drivers of chronic liver diseases

Lipids are important in multiple cellular functions, with most having structural or energy storage roles. However, a small fraction of lipids exert bioactive roles through binding to G protein-coupled receptors and induce a plethora of processes including cell proliferation, differentiation, growth, migration, apoptosis, senescence and survival. Bioactive signalling lipids are potent modulators of metabolism and energy homeostasis, inflammation, tissue repair and malignant transformation. All these events are involved in the initiation and progression of chronic liver diseases. In this review, we focus specifically on the roles of bioactive lipids derived from phospholipids (lyso-phospholipids) and poly-unsaturated fatty acids (eicosanoids, pro-resolving lipid mediators and endocannabinoids) in prevalent chronic liver diseases (alcohol-associated liver disease, non-alcoholic fatty liver disease, viral hepatitis and hepatocellular carcinoma). We discuss the balance between pathogenic and beneficial bioactive lipids as well as potential therapeutic targets related to the agonism or antagonism of their receptors.

Association of lysophosphatidic acid molecules with liver fibrosis: different roles indicated

Lysophosphatidic acid is composed of lysophosphatidic acid (LPA) molecules with varied chemical forms. The present cross-sectional study was conducted to investigate the associations of various LPA molecules with liver fibrosis. Forty-six patients affected by various types of liver disease who underwent an ultrasound-guided liver biopsy were recruited for this study. Liver fibrosis was evaluated using histological grading, as well as shear wave velocity (Vs) and serum level of type IV collagen 7S (T4c7s). Serum levels of LPA molecules were determined using liquid-chromatography tandem mass-spectrometry (LC-MSMS). Total LPA showed a significant positive association with fibrosis severity evaluated based on histological grading, Vs, and T4c7s used as parameters, following adjustment for other confounding factors, including disease type, age, gender, body mass index, and high-sensitivity C-reactive protein. This association was replicated when 16:0-LPA was substituted for total LPA. In contrast, when 20:4-LPA was substituted for total LPA, no significant association with liver fibrosis was observed. In conclusion, the degree of association varied among the different LPA molecule chemical forms, suggesting different pathophysiological roles of individual LPA molecules, although total LPA concentration was shown to be associated with liver fibrosis.

The Surreptitious Burden of Nonalcoholic Fatty Liver Disease in the Elderly in the Asia-Pacific Region: An Insight from the Global Burden of Disease Study 2019

Nonalcoholic fatty liver disease (NAFLD) represents a significant health threat worldwide. The aging population and a rise in metabolic syndrome in Asia might influence the epidemiology of NAFLD among the elderly. However, there is a lack of understanding of the burden and recommendations for NAFLD in this group. Our study sought to investigate the trends in the NAFLD burden among the elderly in the Asia-Pacific region. We employed data from the Global Burden of Disease 2019 study for an in-depth analysis of the prevalence and disability-adjusted life years (DALYs) along with age-standardized rate (ASR) associated with NAFLD in elderly populations (age 65-89 years) across the Asia-Pacific region, including the Southeast Asia (SEA) and Western Pacific (WP) regions, from 2010 to 2019. This study also examined the trends and disparities in NAFLD burden across different nations and sexes. In 2019, there were over 120 million cases of NAFLD in the elderly in the Asia-Pacific region. The ASR of prevalence was higher in SEA compared to WP (36,995.37 vs. 32,821.78 per 100,000). ASR of prevalence increased with annual percentage change (APC) +0.95% in the WP while it increased by +0.87% in SEA. During the study period, the ASR of DALYs decreased in SEA (APC -0.41%) but remained stable in the WP region. The burden of NAFLD in the elderly population in Asia-Pacific has increased, underscoring the timely intervention to tackle this high and rising burden.

PLAAT1 deficiency alleviates high-fat diet-induced hepatic lipid accumulation in mice

The phospholipase A and acyltransferase (PLAAT) family is composed of three isoforms in mice (PLAAT1, 3, and 5), all of which function as phospholipid-metabolizing enzymes exhibiting phospholipase A1 /A2 and acyltransferase activities. Plaat3-deficient (Plaat3-/- ) mice were previously reported to show lean phenotype and remarkable hepatic fat accumulation under high-fat diet (HFD) feeding, while Plaat1-/- mice have not been analyzed. In the present study, we generated Plaat1-/- mice and investigated the effects of PLAAT1 deficiency on HFD-induced obesity, hepatic lipid accumulation, and insulin resistance. After HFD treatment, PLAAT1 deficiency caused a lower body weight gain compared to wild-type mice. Plaat1-/- mice also showed reduced liver weight with negligible hepatic lipid accumulation. In accordance with these findings, PLAAT1 deficiency improved HFD-induced hepatic dysfunction and lipid metabolism disorders. Lipidomics analysis in the liver revealed that in Plaat1-/- mice, the levels of various glycerophospholipids tended to increase, while all classes of lysophospholipids examined tended to decrease, suggesting that PLAAT1 functions as phospholipase A1 /A2 in the liver. Interestingly, the HFD treatment of wild-type mice significantly increased the mRNA level of PLAAT1 in the liver. Furthermore, the deficiency did not appear to elevate the risk of insulin resistance in contrast to PLAAT3 deficiency. These results suggested that the suppression of PLAAT1 improves HFD-induced overweight and concomitant hepatic lipid accumulation.

Meta-analysis of the diagnostic accuracy of serum type IV collagen 7S concentration for the staging of liver fibrosis in nonalcoholic fatty liver disease

AIM

We aimed to evaluate the diagnostic accuracy of the measurement of serum type IV collagen 7S (T4C7S) concentration for the staging of liver fibrosis in patients with nonalcoholic fatty liver disease (NAFLD).

METHODS

A systematic search or published works was carried out using the PubMed, Cochrane Library, and Web of Science Core Collection databases for studies of the accuracy of serum T4C7S concentration for the staging of fibrosis using Fibrosis stage (F)0-4 in patients with NAFLD diagnosed by liver biopsy.

RESULTS

Nine articles describing 1475 participants with NAFLD were included. For fibrosis ≥F1, with n = 849, summary estimates of sensitivity of 0.79, specificity of 0.69, and area under the curve (AUC) of 0.80 were obtained using a median T7C4S cut-off value of 4.6 ng/ml. For fibrosis ≥F2, with n = 1,090, summary estimates of sensitivity of 0.78, specificity of 0.78, and AUC of 0.84 were obtained using a median cut-off value of 4.9 ng/ml. For fibrosis ≥F3, with n = 1311 participants and a median cut-off value of 5.4 ng/ml, a pooled sensitivity of 0.82, specificity of 0.81, and AUC of 0.83 were obtained. For fibrosis ≥F4, with n = 753 and a median cut-off value of 6.6 ng/ml, a pooled sensitivity of 0.85, specificity of 0.81, and AUC of 0.85 were obtained.

CONCLUSIONS

Serum T4C7S concentration was found to be an accurate method of staging liver fibrosis in patients with NAFLD.

SWOT analysis of noninvasive tests for diagnosing NAFLD with severe fibrosis: an expert review by the JANIT Forum

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. Nonalcoholic steatohepatitis (NASH) is an advanced form of NAFLD can progress to liver cirrhosis and hepatocellular carcinoma (HCC). Recently, the prognosis of NAFLD/NASH has been reported to be dependent on liver fibrosis degree. Liver biopsy remains the gold standard, but it has several issues that must be addressed, including its invasiveness, cost, and inter-observer diagnosis variability. To solve these issues, a variety of noninvasive tests (NITs) have been in development for the assessment of NAFLD progression, including blood biomarkers and imaging methods, although the use of NITs varies around the world. The aim of the Japan NASH NIT (JANIT) Forum organized in 2020 is to advance the development of various NITs to assess disease severity and/or response to treatment in NAFLD patients from a scientific perspective through multi-stakeholder dialogue with open innovation, including clinicians with expertise in NAFLD/NASH, companies that develop medical devices and biomarkers, and professionals in the pharmaceutical industry. In addition to conventional NITs, artificial intelligence will soon be deployed in many areas of the NAFLD landscape. To discuss the characteristics of each NIT, we conducted a SWOT (strengths, weaknesses, opportunities, and threats) analysis in this study with the 36 JANIT Forum members (16 physicians and 20 company representatives). Based on this SWOT analysis, the JANIT Forum identified currently available NITs able to accurately select NAFLD patients at high risk of NASH for HCC surveillance/therapeutic intervention and evaluate the effectiveness of therapeutic interventions.

A 3-step approach to predict advanced fibrosis in nonalcoholic fatty liver disease: impact on diagnosis, patient burden, and medical costs

A 2-step approach, Fibrosis-4 index (FIB-4) followed by vibration-controlled transient elastography (VCTE), has been proposed to predict advanced fibrosis in patients with nonalcoholic fatty liver disease (NAFLD). We aimed to develop a novel 3-step approach for predicting advanced fibrosis. We enrolled 284 biopsy-confirmed NAFLD patients from two tertiary care centers and developed subgroups (n = 190), including 3.7% of patients with advanced fibrosis, assuming a primary care setting. In the 3-step approach, patients with intermediate-to-high FIB-4 in the first step underwent an enhanced liver fibrosis test or measurement of type IV collagen 7S domain as the second step, and VCTE was performed if the second step value was higher than the cutoff. In 284 cases, a tertiary care cohort with 36.3% advanced fibrosis, the 3-step approach showed significantly higher specificity and positive predictive value than the 2-step approach. In the subgroup with 3.7% advanced fibrosis, the 3-step approach significantly reduced the referral rate to specialists, the number of high-risk patients (i.e., liver biopsy candidates), and healthcare costs by 12.5% to 15.8%. The 3-step approach may improve the diagnostic performance to predict advanced fibrosis in NAFLD, which could lower rates of referrals to specialists, liver biopsies, and medical costs.

Glucagon-like Peptide-1 Secretion Is Inhibited by Lysophosphatidic Acid

Glucagon-like peptide-1 (GLP-1) potentiates glucose-stimulated insulin secretion (GSIS). While dozens of compounds stimulate GLP-1 secretion, few inhibit. Reduced GLP-1 secretion and impaired GSIS occur in chronic inflammation. Lysophosphatidic acids (LPAs) are bioactive phospholipids elevated in inflammation. The aim of this study was to test whether LPA inhibits GLP-1 secretion in vitro and in vivo. GLUTag L-cells were treated with various LPA species, with or without LPA receptor (LPAR) antagonists, and media GLP-1 levels, cellular cyclic AMP and calcium ion concentrations, and DPP4 activity levels were analyzed. Mice were injected with LPA, with or without LPAR antagonists, and serum GLP-1 and DPP4 activity were measured. GLUTag GLP-1 secretion was decreased ~70–90% by various LPAs. GLUTag expression of Lpar1, 2, and 3 was orders of magnitude higher than Lpar4, 5, and 6, implicating the former group in this effect. In agreement, inhibition of GLP-1 secretion was reversed by the LPAR1/3 antagonist Ki16425, the LPAR1 antagonists AM095 and AM966, or the LPAR2 antagonist LPA2-antagonist 1. We hypothesized involvement of Gαi-mediated LPAR activity, and found that intracellular cyclic AMP and calcium ion concentrations were decreased by LPA, but restored by Ki16425. Mouse LPA injection caused an ~50% fall in circulating GLP-1, although only LPAR1 or LPAR1/3 antagonists, but not LPAR2 antagonism, prevented this. GLUTag L-cell and mouse serum DPP4 activity was unchanged by LPA or LPAR antagonists. LPA therefore impairs GLP-1 secretion in vitro and in vivo through Gαi-coupled LPAR1/3 signaling, providing a new mechanism linking inflammation with impaired GSIS.

Plasma Concentrations of Lysophosphatidic Acid and Autotaxin in Abstinent Patients with Alcohol Use Disorder and Comorbid Liver Disease

Lysophosphatidic acid (LPA) is an endogenous lysophospholipid and a bioactive lipid that is synthesized by the enzyme autotaxin (ATX). The ATX-LPA axis has been associated with cognitive dysfunction and inflammatory diseases, mainly in a range of nonalcoholic liver diseases. Recently, preclinical and clinical evidence has suggested a role of LPA signaling in alcohol use disorder (AUD) and AUD-related cognitive function. However, the ATX-LPA axis has not been sufficiently investigated in alcoholic liver diseases. An exploratory study was conducted in 136 participants, 66 abstinent patients with AUD seeking treatment for alcohol (alcohol group), and 70 healthy control subjects (control group). The alcohol group was divided according to the presence of comorbid liver diseases (i.e., fatty liver/steatosis, alcoholic steatohepatitis, or cirrhosis). All participants were clinically evaluated, and plasma concentrations of total LPA and ATX were measured using enzyme-linked immunosorbent assays. Data were primarily analyzed using analysis of covariance (ANCOVA) while controlling for age, body mass index, and sex. Logistic regression models were created to assess the association of the ATX-LPA axis and AUD or liver disease. LPA and ATX were log₁₀-transformed to fit the assumptions of parametric testing.The main results were as follows: total LPA and ATX concentrations were dysregulated in the alcohol group, and patients with AUD had significantly lower LPA (F_(1,131) = 10.677, p = 0.001) and higher ATX (F_(1,131) = 8.327, p = 0.005) concentrations than control subjects; patients with AUD and liver disease had significantly higher ATX concentrations (post hoc test, p < 0.05) than patients with AUD but not liver disease; significant correlations between AUD-related variables and concentrations of LPA and ATX were only found in the non-liver disease subgroup (the duration of alcohol abstinence with LPA and ATX (r = +0.33, p < 0.05); and the severity of AUD with ATX (rho = -0.33, p < 0.05)); and a logistic regression model with LPA, ATX, and AUD-related variables showed an excellent discriminative power (area under the curve (AUC) = 0.915, p < 0.001) for distinguishing patients with AUD and comorbid liver disease. In conclusion, our data show that the ATX-LPA axis is dysregulated in AUD and suggest this lipid signaling, in combination with relevant AUD-related variables, as a reliable biomarker of alcoholic liver diseases.

Dysregulation of the Lysophosphatidylcholine/Autotaxin/Lysophosphatidic Acid Axis in Acute-on-Chronic Liver Failure Is Associated With Mortality and Systemic Inflammation by Lysophosphatidic Acid-Dependent Monocyte Activation

BACKGROUND & AIMS

Acute-on-chronic liver failure (ACLF) is characterized by systemic inflammation, monocyte dysfunction, and susceptibility to infection. Lysophosphatidylcholines (LPCs) are immune-active lipids whose metabolic regulation and effect on monocyte function in ACLF is open for study.

APPROACHES & RESULTS

Three hundred forty-two subjects were recruited and characterized for blood lipid, cytokines, phospholipase (PLA), and autotaxin (ATX) concentration. Peripheral blood mononuclear cells and CD14⁺ monocytes were cultured with LPC, or its autotaxin (ATX)-derived product, lysophosphatidic acid (LPA), with or without lipopolysaccharide stimulation and assessed for surface marker phenotype, cytokines production, ATX and LPA-receptor expression, and phagocytosis. Hepatic ATX expression was determined by immunohistochemistry. Healthy volunteers and patients with sepsis or acute liver failure served as controls. ACLF serum was depleted in LPCs with up-regulated LPA levels. Patients who died had lower LPC levels than survivors (area under the receiver operating characteristic curve, 0.94; P < 0.001). Patients with high-grade ACLF had the lowest LPC concentrations and these rose over the first 3 days of admission. ATX concentrations were higher in patients with AD and ACLF and correlated with Model for End-Stage Liver Disease, Consortium on Chronic Liver Failure-Sequential Organ Failure Assessment, and LPC/LPA concentrations. Reduction in LPC correlated with higher monocyte Mer-tyrosine-kinase (MerTK) and CD163 expression. Plasma ATX concentrations rose dynamically during ACLF evolution, correlating with IL-6 and TNF-α, and were associated with increased hepatocyte ATX expression. ACLF patients had lower human leukocyte antigen-DR isotype and higher CD163/MerTK monocyte expression than controls; both CD163/MerTK expression levels were reduced in ACLF ex vivo following LPA, but not LPC, treatment. LPA induced up-regulation of proinflammatory cytokines by CD14⁺ cells without increasing phagocytic capacity.

CONCLUSIONS

ATX up-regulation in ACLF promotes LPA production from LPC. LPA suppresses MerTK/CD163 expression and increases monocyte proinflammatory cytokine production. This metabolic pathway could be investigated to therapeutically reprogram monocytes in ACLF.

FIB-4 First in the Diagnostic Algorithm of Metabolic-Dysfunction-Associated Fatty Liver Disease in the Era of the Global Metabodemic

The prevalence of obesity or metabolic syndrome is increasing worldwide (globally metabodemic). Approximately 25% of the adult general population is suffering from nonalcoholic fatty liver disease (NAFLD), which has become a serious health problem. In 2020, global experts suggested that the nomenclature of NAFLD should be updated to metabolic-dysfunction-associated fatty liver disease (MAFLD). Hepatic fibrosis is the most significant determinant of all cause- and liver -related mortality in MAFLD. The non-invasive test (NIT) is urgently required to evaluate hepatic fibrosis in MAFLD. The fibrosis-4 (FIB-4) index is the first triaging tool for excluding advanced fibrosis because of its accuracy, simplicity, and cheapness, especially for general physicians or endocrinologists, although the FIB-4 index has several drawbacks. Accumulating evidence has suggested that vibration-controlled transient elastography (VCTE) and the enhanced liver fibrosis (ELF) test may become useful as the second step after triaging by the FIB-4 index. The leading cause of mortality in MAFLD is cardiovascular disease (CVD), extrahepatic malignancy, and liver-related diseases. MAFLD often complicates chronic kidney disease (CKD), resulting in increased simultaneous liver kidney transplantation. The FIB-4 index could be a predictor of not only liver-related mortality and incident hepatocellular carcinoma, but also prevalent and incident CKD, CVD, and extrahepatic malignancy. Although NITs as milestones for evaluating treatment efficacy have never been established, the FIB-4 index is expected to reflect histological hepatic fibrosis after treatment in several longitudinal studies. We here review the role of the FIB-4 index in the management of MAFLD.

Liver Fibrosis in Non-alcoholic Fatty Liver Disease: From Liver Biopsy to Non-invasive Biomarkers in Diagnosis and Treatment

An increasing percentage of people have or are at risk to develop non-alcoholic fatty liver disease (NAFLD) worldwide. NAFLD comprises different stadia going from isolated steatosis to non-alcoholic steatohepatitis (NASH). NASH is a chronic state of liver inflammation that leads to the transformation of hepatic stellate cells to myofibroblasts. These cells produce extra-cellular matrix that results in liver fibrosis. In a normal situation, fibrogenesis is a wound healing process that preserves tissue integrity. However, sustained and progressive fibrosis can become pathogenic. This process takes many years and is often asymptomatic. Therefore, patients usually present themselves with end-stage liver disease e.g., liver cirrhosis, decompensated liver disease or even hepatocellular carcinoma. Fibrosis has also been identified as the most important predictor of prognosis in patients with NAFLD. Currently, only a minority of patients with liver fibrosis are identified to be at risk and hence referred for treatment. This is not only because the disease is largely asymptomatic, but also due to the fact that currently liver biopsy is still the golden standard for accurate detection of liver fibrosis. However, performing a liver biopsy harbors some risks and requires resources and expertise, hence is not applicable in every clinical setting and is unsuitable for screening. Consequently, different non-invasive diagnostic tools, mainly based on analysis of blood or other specimens or based on imaging have been developed or are in development. In this review, we will first give an overview of the pathogenic mechanisms of the evolution from isolated steatosis to fibrosis. This serves as the basis for the subsequent discussion of the current and future diagnostic biomarkers and anti-fibrotic drugs.

Wisteria floribunda Agglutinin-Positive Mac-2 Binding Protein as a Screening Tool for Significant Liver Fibrosis in Health Checkup

Chronic liver disease is generally widespread, and a test for screening fibrotic subjects in a large population is needed. The ability of Wisteria floribunda agglutinin-positive mac-2 binding protein (WFA⁺-M2BP) to detect significant fibrosis was investigated in health checkup subjects in this research. Of 2021 health checkup subjects enrolled in this prospective cross-sectional study, those with WFA⁺-M2BP ≥ 1.0 were defined as high risk. Liver fibrosis was evaluated using magnetic resonance elastography (MRE) in subjects with high risk. The primary outcome was the positive predictive value (PPV) of WFA⁺-M2BP for significant fibrosis (liver stiffness ≥ 2.97 kPa by MRE). This trial was registered with the UMIN clinical trial registry, UMIN000036175. WFA⁺-M2BP ≥ 1.0 was observed in 5.3% of the 2021 subjects. The PPV for significant fibrosis with the threshold of WFA⁺-M2BP at ≥1.0, ≥1.1, ≥1.2, ≥1.3, ≥1.4, and ≥1.5 was 29.2%, 36.4%, 43.5%, 42.9%, 62.5%, and 71.4%, respectively. A WFA⁺-M2BP of 1.2 was selected as the optimal threshold for significant fibrosis among high-risk subjects, and the PPV, negative predictive value, sensitivity, and specificity for significant fibrosis were 43.5%, 84.0%, 71.4%, and 61.8%, respectively. WFA⁺-M2BP ≥ 1.2 was significantly associated with significant fibrosis, with an odds ratio (OR) of 4.04 (95% confidence interval (CI): 1.1–16, p = 0.04), but not FIB-4 ≥ 2.67 (OR: 2.40, 95%CI: 0.7–8.6, p-value = 0.2). In conclusion, WFA⁺-M2BP is associated with significant fibrosis and could narrow down potential subjects with liver fibrosis. The strategy of narrowing down fibrosis subjects using WFA⁺-M2BP may be used to screen for fibrotic subjects in a large population.

Autotaxin: An Early Warning Biomarker for Acute-on-chronic Liver Failure

Background and Aims: Recent accumulating evidence indicates the biological actions of autotaxin (ATX) in liver disease. However, the relationship between ATX and liver failure has not been reported. The present study aimed to examine alterations of serum ATX in acute-on-chronic liver failure (ACLF) and evaluate whether serum ATX could be useful as an early warning biomarker of ACLF. Methods: Serum ATX was measured in 50 patients with hepatitis B-related ACLF, 14 patients with alcohol-related ACLF, 11 patients with hepatitis B-related pre-ACLF, 11 patients with alcohol-related Child-Pugh A cirrhosis, 39 patients with hepatitis B-related Child-Pugh A cirrhosis, 26 patients with chronic hepatitis B, and 38 healthy volunteers by enzyme-linked immunosorbent assay. Results: Serum ATX level was significantly higher in the pre-ACLF group than in the Child-Pugh A cirrhosis and chronic hepatitis B groups but lower than in the ACLF group; furthermore, patients with pre-ACLF deteriorated to ACLF had significantly higher serum ATX levels than pre-ACLF patients that did not progress to ACLF. Serum ATX levels were significantly higher among male ACLF patients with preclinical infection, spontaneous bacterial peritonitis or pneumonia, as compared to patients with ACLF but no spontaneous bacterial peritonitis or pneumonia. Serum ATX levels were well correlated with serum biochemical parameters of liver function and model for end-stage liver disease score. Serum ATX ≥ 584.1 ng/mL was a poor prognostic factor for ACLF (hazard ratio of 4.750, 95% confidence interval of 1.106-20.392, p=0.036). Conclusions: Serum ATX level may be a useful early warning biomarker for ACLF.

Metabolomic/lipidomic-based analysis of plasma to diagnose hepatocellular ballooning in patients with non-alcoholic fatty liver disease: A multicenter study

AIM

Liver biopsy is still required for the diagnosis of hepatocellular ballooning and inflammation, which are important histological features of non-alcoholic steatohepatitis. We undertook this multicenter, cross-sectional study to identify novel blood markers for the diagnosis of hepatocellular ballooning.

METHODS

We enrolled 176 patients, of whom 132 were proven by liver biopsy as having non-alcoholic fatty liver disease (NAFLD) and classified as non-ballooning (ballooning grade 0) (n = 83) or ballooning (ballooning grade 1 and 2) (n = 49) by a central pathology review. We carried out gas chromatography-mass spectrometry, hydrophilic interaction liquid chromatography tandem mass spectrometry, and lipidomics with plasma.

RESULTS

As correlates of hepatocellular ballooning, among the clinical parameters, serum type IV collagen 7S correlated most significantly with the ballooning grade (correlation coefficient [CC] = 0.463; P < 0.001). Among the metabolic/lipidomic markers, phosphatidylcholine (PC) (aa-44:8) correlated most significantly with the ballooning grade (CC = 0.394; P < 0.001). The area under the receiver operating characteristic curve of type IV collagen 7S, choline, and lysophosphatidylethanolamine (LPE) (e-18:2), was 0.846 (95% confidence interval, 0.772-0.919).

CONCLUSIONS

Plasma levels of PC were positively correlated, and those of lysophosphatidylcholine and LPE were negatively correlated with hepatocellular ballooning in NAFLD patients. These non-invasive metabolic/lipidomic-based plasma tests might be useful to distinguish between cases of NAFLD with and without hepatocellular ballooning.

The Role of Insulin Resistance and Diabetes in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) consists of the entire spectrum of fatty liver disease in patients without significant alcohol consumption, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) to cirrhosis, with NASH recently shown as an important cause of hepatocellular carcinoma (HCC). There is a close relationship between insulin resistance (IR) and NAFLD, with a five-fold higher prevalence of NAFLD in patients with type 2 diabetes (T2DM) compared to that in patients without T2DM. IR is involved in the progression of disease conditions such as steatosis and NASH, as well as hepatic fibrosis progression. The mechanisms underlying these processes involve genetic factors, hepatic fat accumulation, alterations in energy metabolism, and inflammatory signals derived from various cell types including immune cells. In NASH-associated fibrosis, the principal cell type responsible for extracellular matrix production is the hepatic stellate cell (HSC). HSC activation by IR involves “direct” and “indirect” pathways. This review will describe the molecular mechanisms of inflammation and hepatic fibrosis in IR, the relationship between T2DM and hepatic fibrosis, and the relationship between T2DM and HCC in patients with NAFLD.

Identification of Potent In Vivo Autotaxin Inhibitors that Bind to Both Hydrophobic Pockets and Channels in the Catalytic Domain

Autotaxin (ATX, also known as ENPP2) is a predominant lysophosphatidic acid (LPA)-producing enzyme in the body, and LPA regulates various physiological functions, such as angiogenesis and wound healing, as well as pathological functions, including proliferation, metastasis, and fibrosis, via specific LPA receptors. Therefore, the ATX-LPA axis is a promising therapeutic target for dozens of diseases, including cancers, pulmonary and liver fibroses, and neuropathic pain. Previous structural studies revealed that the catalytic domain of ATX has a hydrophobic pocket and a hydrophobic channel; these serve to recognize the substrate, lysophosphatidylcholine (LPC), and deliver generated LPA to LPA receptors on the plasma membrane. Most reported ATX inhibitors bind to either the hydrophobic pocket or the hydrophobic channel. Herein, we present a unique ATX inhibitor that binds mainly to the hydrophobic pocket and also partly to the hydrophobic channel, inhibiting ATX activity with high potency and selectivity in vitro and in vivo. Notably, our inhibitor can rescue the cardia bifida (two hearts) phenotype in ATX-overexpressing zebrafish embryos.

Elevated Autotaxin and LPA Levels During Chronic Viral Hepatitis and Hepatocellular Carcinoma Associate with Systemic Immune Activation

Circulating autotaxin (ATX) is elevated in persons with liver disease, particularly in the setting of chronic hepatitis C virus (HCV) and HCV/HIV infection. It is thought that plasma ATX levels are, in part, attributable to impaired liver clearance that is secondary to fibrotic liver disease. In a discovery data set, we identified plasma ATX to be associated with parameters of systemic immune activation during chronic HCV and HCV/HIV infection. We and others have observed a partial normalization of ATX levels within months of starting interferon-free direct-acting antiviral (DAA) HCV therapy, consistent with a non-fibrotic liver disease contribution to elevated ATX levels, or HCV-mediated hepatocyte activation. Relationships between ATX, lysophosphatidic acid (LPA) and parameters of systemic immune activation will be discussed in the context of HCV infection, age, immune health, liver health, and hepatocellular carcinoma (HCC).

Deregulated Lysophosphatidic Acid Metabolism and Signaling in Liver Cancer

Liver cancer is one of the leading causes of death worldwide due to late diagnosis and scarcity of treatment options. The major risk factor for liver cancer is cirrhosis with the underlying causes of cirrhosis being viral infection (hepatitis B or C), metabolic deregulation (Non-alcoholic fatty liver disease (NAFLD) in the presence of obesity and diabetes), alcohol or cholestatic disorders. Lysophosphatidic acid (LPA) is a bioactive phospholipid with numerous effects, most of them compatible with the hallmarks of cancer (proliferation, migration, invasion, survival, evasion of apoptosis, deregulated metabolism, neoangiogenesis, etc.). Autotaxin (ATX) is the enzyme responsible for the bulk of extracellular LPA production, and together with LPA signaling is involved in chronic inflammatory diseases, fibrosis and cancer. This review discusses the most important findings and the mechanisms related to ATX/LPA/LPAR involvement on metabolic, viral and cholestatic liver disorders and their progression to liver cancer in the context of human patients and mouse models. It focuses on the role of ATX/LPA in NAFLD development and its progression to liver cancer as NAFLD has an increasing incidence which is associated with the increasing incidence of liver cancer. Bearing in mind that adipose tissue accounts for the largest amount of LPA production, many studies have implicated LPA in adipose tissue metabolism and inflammation, liver steatosis, insulin resistance, glucose intolerance and lipogenesis. At the same time, LPA and ATX play crucial roles in fibrotic diseases. Given that hepatocellular carcinoma (HCC) is usually developed on the background of liver fibrosis, therapies that both delay the progression of fibrosis and prevent its development to malignancy would be very promising. Therefore, ATX/LPA signaling appears as an attractive therapeutic target as evidenced by the fact that it is involved in both liver fibrosis progression and liver cancer development.