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Lipid Zonation and Phospholipid Remodeling in Nonalcoholic Fatty Liver Disease Lipid Zonation and Phospholipid Remodeling in Nonalcoholic Fatty Liver Disease

Date added: 08/22/2017
Date modified: 08/22/2017
Filesize: 1.49 MB
Downloads: 26

Nonalcoholic fatty liver disease (NAFLD) can progress from simple steatosis (i.e., nonalcoholic fatty liver [NAFL]) to nonalcoholic steatohepatitis (NASH), cirrhosis, and cancer. Currently, the driver for this progression is not fully understood; in particular, it is not known how NAFLD and its early progression affects the distribution of lipids in the liver, producing lipotoxicity and inflammation. In this study, we used dietary and genetic mouse models of NAFL and NASH and translated the results to humans by correlating the spatial distribution of lipids in liver tissue with disease progression using advanced mass spectrometry imaging technology. We identified several lipids with distinct zonal distributions in control and NAFL samples and observed partial to complete loss of lipid zonation in NASH. In addition, we found increased hepatic expression of genes associated with remodeling the phospholipid membrane, release of arachidonic acid (AA) from the membrane, and production of eicosanoid species that promote inflammation and cell injury. The results of our immunohistochemistry analyses suggest that the zonal location of remodeling enzyme LPCAT2 plays a role in the change in spatial distribution for AA-containing lipids. This results in a cycle of AA-enrichment in pericentral hepatocytes, membrane release of AA, and generation of proinflammatory eicosanoids and may account for increased oxidative damage in pericentral regions in NASH. Conclusion: NAFLD is associated not only with lipid enrichment, but also with zonal changes of specific lipids and their associated metabolic pathways. This may play a role in the heterogeneous development of NAFLD.

Age as a Confounding Factor for the Accurate Non-Invasive Diagnosis of Advanced NAFLD Fibrosis Age as a Confounding Factor for the Accurate Non-Invasive Diagnosis of Advanced NAFLD Fibrosis

Date added: 08/22/2017
Date modified: 08/22/2017
Filesize: 338.38 kB
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OBJECTIVES: Non-invasive fibrosis scores are widely used to identify/exclude advanced fibrosis in patients with non-alcoholic fatty liver disease (NAFLD). However, these scores were principally developed and validated in patients aged between 35 and 65 years of age. The objective of this study was to assess the effect of age on the performance of non-invasive fibrosis tests in NAFLD.

METHODS: Patients were recruited from European specialist hepatology clinics. The cohort was divided into five age-based groups: ≤35 (n=74), 36–45 (n=96), 46–55 (n=197), 56–64 (n=191), and ≥65 years (n=76), and the performance of the aspartate aminotransferase (AST)/alanine transaminase (ALT) ratio, fibrosis 4 (FIB-4), and NAFLD fibrosis score (NFS) for advanced fibrosis (stage F3–F4) for each group was assessed using liver biopsy as the standard.

RESULTS: Six hundred and thirty-four patients were included. The diagnostic accuracy of the AST/ALT ratio was lower than NFS and FIB-4 in all the age groups. The AST/ALT ratio, NFS, and FIB-4 score performed poorly for a diagnosis of advanced fibrosis in those aged ≤35 years (area under the receiver operating characteristic curves (AUROCs 0.52, 0.52, and 0.60, respectively). For all groups >35 years, AUROCs for advanced fibrosis were similar for the NFS and FIB-4 score (range 0.77–0.84). However, the specificity for advanced fibrosis using the FIB-4 and NFS declined with age, becoming unacceptably low in those aged ≥65 years (35% for FIB-4 and 20% for NFS). New cutoffs were derived (and validated) for those aged ≥65 years, which improved specificity to 70% without adversely affecting sensitivity (FIB-4 2.0, sensitivity 77%; NFS 0.12, sensitivity 80%).

CONCLUSIONS: The NFS and FIB-4 scores have similar accuracy for advanced fibrosis in patients aged >35 years. However, the specificity for advanced fibrosis is unacceptably low in patients aged ≥65 years, resulting in a high false positive rate. New thresholds for use in patients aged ≥65 years are proposed to address this issue.

Obesity/insulin resistance rather than liver fat increases coagulation factor activities and express Obesity/insulin resistance rather than liver fat increases coagulation factor activities and express

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Date added: 03/08/2017
Date modified: 03/08/2017
Filesize: 256 Bytes
Downloads: 408

Increased liver fat may be caused by insulin resistance and adipose tissue inflammation or by the common I148M variant in PNPLA3 at rs738409, which lacks both of these features. We hypothesised that obesity/insulin resistance rather than liver fat increases circulating coagulation factor activities. We measured plasma prothrombin time (PT, Owren method), activated partial thromboplastin time (APTT), activities of several coagulation factors, VWF:RCo and fibrinogen, and D-dimer concentration in 92 subjects divided into groups based on insulin sensitivity and PNPLA3 genotype.

We conclude that obesity/insulin resistance rather than an increase in liver fat is associated with a procoagulant plasma profile. This reflects adipose tissue inflammation and increased hepatic production of coagulation factors and their susceptibility for activation.

The MBOAT7 variant rs641738 alters hepatic phosphatidylinositols and increases severity of NAFLD The MBOAT7 variant rs641738 alters hepatic phosphatidylinositols and increases severity of NAFLD

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Date added: 03/08/2017
Date modified: 03/08/2017
Filesize: 256 Bytes
Downloads: 392

We have recently shown in 125 subjects that insulin resistance and the PNPLA3 I148M gene variant, two common risk factors of NAFLD, are characterized with markedly different content and composition of lipids in the human liver. In 2015, a variant in membrane bound O-acyltransferase domain containing 7 (MBOAT7) at rs641738 was discovered to increase the risk of alcohol-related cirrhosis. This variant was also shown to increase the risk of steatosis and histologic liver damage in NAFLD, independent of obesity.

Lipotoxicity, obesity and metabolic diseases Lipotoxicity, obesity and metabolic diseases

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Date added: 03/07/2017
Date modified: 03/07/2017
Filesize: 256 Bytes
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Article published in the Newsletter of the Spanish Society of Biochemistry and Molecular Biology (SEBBM)

Serum endotrophin identifies optimal responders to PPARγ agonists in type 2 diabetes Serum endotrophin identifies optimal responders to PPARγ agonists in type 2 diabetes

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Date added: 03/05/2017
Date modified: 03/05/2017
Filesize: 491.44 kB
Downloads: 224

Aims/hypothesis

The treatment of type 2 diabetes with full peroxisome proliferator-activated receptor gamma (PPARγ) agonists improves insulin sensitivity, but is associated with weight gain, heart failure, peripheral oedema and bone loss. Endotrophin, the C-terminal fragment of the α3 chain of procollagen type VI (also called Pro-C6), is involved in both adipose tissue matrix remodelling and metabolic control. We established a serum assay for endotrophin to assess if this novel adipokine could identify type 2 diabetic patients who respond optimally to PPARγ agonists, improving the risk-to-benefit ratio.

Methods

The BALLET trial (NCT00515632) compared the glucose-lowering effects and safety of the partial PPARγ agonist balaglitazone with those of pioglitazone in individuals with type 2 diabetes on stable insulin therapy. The per protocol population (n = 297) was stratified into tertiles based on baseline endotrophin levels. Participants were followed-up after 26 weeks, after which correlational analysis was carried out between endotrophin levels and measures of glucose control. This is a secondary post hoc analysis.

Results

Endotrophin was significantly associated with therapeutic response to balaglitazone and pioglitazone. At week 26, only individuals in the upper two tertiles showed significant reductions in HbA1c and fasting serum glucose compared with baseline. The OR for a 1% and a 0.5% reduction in HbA1c for individuals in the upper two tertiles were 3.83 (95% CI 1.62, 9.04) p < 0.01, and 3.85 (95% CI 1.94, 7.61) p < 0.001, respectively. Endotrophin levels correlated with adipose tissue mass, insulin resistance and fatty liver index. Notably, PPARγ-associated adverse effects, such as moderate-to-severe lower extremity oedema, only occurred in the lower tertile.

Conclusions/interpretation

Elevated endotrophin serum levels predict response to two insulin sensitisers and reduce the risk of associated adverse effects, thereby, identifying patients with type 2 diabetes who may profit from PPARγ agonist treatment.

Emerging anti-fibrotic therapies in the treatment of non-alcoholic steatohepatitis Emerging anti-fibrotic therapies in the treatment of non-alcoholic steatohepatitis

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Date added: 03/05/2017
Date modified: 03/05/2017
Filesize: 256 Bytes
Downloads: 435

Background

Non-alcoholic fatty liver disease (NAFLD) can lead to non-alcoholic steatohepatitis (NASH) and cirrhosis. Fibrosis predicts worse outcomes and mortality. New treatments targeting fibrosis are being investigated to reverse disease progression.

Aim

To review the new pipeline therapeutic agents targeting fibrosis in NASH patients, with particular focus on clinical trials in which reversing fibrosis and portal hypertension are the primary outcomes.

Methods

The literature was searched in PubMed between January 2000 and January 2016 using search terms non-alcoholic fatty liver disease and NASH, with filters of ‘English language’. We focused on fibrosis improvement as the key outcome. We also searched the ClinicalTrials.gov for promising agents that target fibrosis in NASH patients.

Results

Significant advances have been made on approaches targeting fibrosis in NASH patients. Many therapeutic agents are already in development, some of which have shown promising results in preclinical and phase I studies. Novel therapies have entered phase II and III studies targeting fibrosis reversal and/or improvement in portal hypertension. Innovative studies have also started looking into combining these agents, aiming at different mechanisms to maximise therapeutic outcomes. We found five clinical trials in phase II and one in phase III focusing on fibrosis in NASH patients as key outcomes. One of the phase II trials is using combination therapy to target fibrosis.

Conclusions

Ongoing research studies are already investigating new pathways aimed at reversing fibrosis in NASH patients. Novel therapeutic agents are in development and are expected to offer unique options to NASH patients with advanced fibrosis.

Genetic Factors that Affect Risk of Alcoholic and Non-Alcoholic Fatty Liver Disease Genetic Factors that Affect Risk of Alcoholic and Non-Alcoholic Fatty Liver Disease

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Date added: 03/05/2017
Date modified: 03/05/2017
Filesize: 256 Bytes
Downloads: 390

Genome-wide association studies and candidate gene studies have informed our understanding of factors contributing to the well-recognized interindividual variation in the progression and outcomes of alcoholic liver disease and nonalcoholic fatty liver disease. We discuss the mounting evidence for shared modifiers and common pathophysiological processes that contribute to development of both diseases. We discuss the functions of proteins encoded by risk variants of genes including patatin-like phospholipase domain-containing 3 and transmembrane 6 superfamily member 2, as well as epigenetic factors that contribute to the pathogenesis of alcoholic liver disease and nonalcoholic fatty liver disease. We also discuss important areas of future genetic research and their potential to affect clinical management of patients.

Definitions of Normal Liver Fat and the Association of Insulin Sensitivity with Acquired and Genetic Definitions of Normal Liver Fat and the Association of Insulin Sensitivity with Acquired and Genetic

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Date added: 01/10/2017
Date modified: 01/10/2017
Filesize: 661.91 kB
Downloads: 383

Non-alcoholic fatty liver disease (NAFLD) covers a spectrum of disease ranging from simple steatosis (NAFL) to non-alcoholic steatohepatitis (NASH) and fibrosis. “Obese/Metabolic NAFLD” is closely associated with obesity and insulin resistance and therefore predisposes to type 2 diabetes and cardiovascular disease. NAFLD can also be caused by common genetic variants, the patatin-like phospholipase domain-containing 3 (PNPLA3) or the transmembrane 6 superfamily member 2 (TM6SF2). Since NAFL, irrespective of its cause, can progress to NASH and liver fibrosis, its definition is of interest. We reviewed the literature to identify data on definition of normal liver fat using liver histology and different imaging tools, and analyzed whether NAFLD caused by the gene variants is associated with insulin resistance. Histologically, normal liver fat content in liver biopsies is most commonly defined as macroscopic steatosis in less than 5% of hepatocytes. In the population-based Dallas Heart Study, the upper 95th percentile of liver fat measured by proton magnetic spectroscopy (1H-MRS) in healthy subjects was 5.6%, which corresponds to approximately 15% histological liver fat. When measured by magnetic resonance imaging (MRI)-based techniques such as the proton density fat fraction (PDFF), 5% macroscopic steatosis corresponds to a PDFF of 6% to 6.4%. In contrast to “Obese/metabolic NAFLD”, NAFLD caused by genetic variants is not associated with insulin resistance. This implies that NAFLD is heterogeneous and that “Obese/Metabolic NAFLD” but not NAFLD due to the PNPLA3 or TM6SF2 genetic variants predisposes to type 2 diabetes and cardiovascular disease.

Phosphorylated IGFBP-1 as a non-invasive predictor of liver fat in NAFLD Phosphorylated IGFBP-1 as a non-invasive predictor of liver fat in NAFLD

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Date added: 01/10/2017
Date modified: 01/10/2017
Filesize: 505.25 kB
Downloads: 338

Insulin-like growth factor binding protein 1 (IGFBP-1) is a potentially interesting marker for liver fat in NAFLD as it is exclusively produced by the liver, and insulin is its main regulator. We determined whether measurement of fasting serum phosphorylated IGFBP-1 (fS-pIGFBP-1) helps to predict liver fat compared to routinely available clinical parameters and PNPLA3 genotype at rs738409. Liver fat content (proton magnetic resonance spectroscopy) was measured in 378 subjects (62% women, age 43 [30–54] years, BMI 32.7 [28.1–39.7] kg/m2, 46% with NAFLD). Subjects were randomized to discovery and validation groups, which were matched for clinical and biochemical parameters and PNPLA3 genotype. Multiple linear regression and Random Forest modeling were used to identify predictors of liver fat. The final model, % Liver Fat Equation’, included age, fS-pIGFBP-1, S-ALT, waist-to-hip ratio, fP-Glucose and fS-Insulin (adjusted R2 = 0.44 in the discovery group, 0.49 in the validation group, 0.47 in all subjects). The model was significantly better than a model without fS-pIGFBP-1 or S-ALT or S-AST alone. Random Forest modeling identified fS-p-IGFBP-1 as one of the top five predictors of liver fat (adjusted R2 = 0.39). Therefore, measurement of fS-pIGFBP-1 may help in non-invasive prediction of liver fat content.