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 P465L pparγ mutation confers partial resistance to the hypolipidemic action of fibrates P465L pparγ mutation confers partial resistance to the hypolipidemic action of fibrates

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Date added: 06/30/2019
Date modified: 06/30/2019
Filesize: 1.63 MB
Downloads: 116

Aims
Familial partial lipodystrophic syndrome 3 (FPLD3) is associated with mutations in the transcription factor PPARγ. One of these mutations, the P467L, confers a dominant negative effect. We and others have previously investigated the pathophysiology associated with this mutation using a humanized mouse model that recapitulates most of the clinical symptoms observed in patients who have been phenotyped under different experimental conditions. One of the key clinical manifestations observed, both in humans and mouse models, is the ectopic accumulation of fat in the liver. With this study we aim to dissect the molecular mechanisms that contribute to the excessive accumulation of lipids in the liver and characterize the negative effect of this PPARγ mutation on the activity of PPARα in vivo when activated by fibrates.

Material and Methods
P465L‐PPAR mutant and wild‐type mice were divided into 8 experimental groups, 4 different conditions per genotype. Briefly, mice were fed a chow diet or a high‐fat diet (HFD 45% Kcal from fat) for a period of 28 days and treated with WY14643 or vehicle for five days before culling. At the end of the experiment, tissues and plasma were collected. We performed extensive gene expression, fatty acid composition and histological analysis in the livers. The serum collected was used to measure several metabolites and to perform basic lipoprotein profile.

Results
P465L mice showed increased levels of insulin and free fatty acids (FFA) as well as increased liver steatosis. They also exhibit decreased levels of very low density lipoproteins (VLDL) when fed an HFD. We also provide evidence of impaired expression of a number of well‐established PPARα target genes in the P465L mutant livers.

Conclusion
Our data demonstrate that P465L confers partial resistance to the hypolipidemic action of fibrates. These results show that the fatty liver phenotype observed in P465L mutant mice is not only the consequence of dysfunctional adipose tissue, but also involves defective liver metabolism. All in all, the deleterious effects of P465L‐PPARγ mutation may be magnified by their collateral negative effect on PPARα function.

Fibrosis and alcohol-related liver disease Fibrosis and alcohol-related liver disease

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Date added: 08/10/2019
Date modified: 08/10/2019
Filesize: 256 Bytes
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Histological fibrosis stage is one of the most important prognostic factors in compensated and decompensated alcohol-related liver disease (ALD). Morphological assessment of fibrosis is useful for patient stratification, enabling individualised management, and for evaluation of treatment effects in clinical studies. In contrast to most chronic liver diseases where fibrosis is portal-based, fatty liver disease (FLD) of alcoholic or non-alcoholic aetiology (NAFLD) is associated with a centrilobular pattern of injury which leads to perivenular fibrosis and/or pericellular fibrosis. Progression of FLD drives expansive pericellular fibrosis, linking vascular structures and paving the way for the development of cirrhosis. At the cirrhotic stage, ongoing tissue damage leads to increasing fibrosis severity due to parenchymal loss and proliferation of fibrous scars. Histologic fibrosis staging systems have been devised, based on topography and the extent of fibrosis, for most chronic liver diseases. The utility of histological staging is reflected in different risks associated with individual fibrosis stages which cannot be reliably distinguished by non-invasive fibrosis assessment. In contrast to NAFLD, ALD-specific staging systems that enable the standardised prognostication required for clinical management and trials are lacking. Although morphological similarities between NAFLD and ALD exist, differences in clinical and histological features may substantially limit the utility of established NAFLD-specific staging systems for prognostication in ALD. This review summarises morphological features of fibrosis in ALD and compares them to other chronic liver diseases, particularly NAFLD. ALD-related fibrosis is examined in the context of pathogenetic mechanisms of fibrosis progression, regression and clinical settings that need to be considered in future prognostically relevant ALD staging approaches.

Phosphatidylglycerols are induced by gut dysbiosis and inflammation, and favorably modulate... Phosphatidylglycerols are induced by gut dysbiosis and inflammation, and favorably modulate...

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Date added: 08/10/2019
Date modified: 08/10/2019
Filesize: 256 Bytes
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"Phosphatidylglycerols are induced by gut dysbiosis and inflammation, and favorably modulate adipose tissue remodeling in obesity"

Lipidomic techniques can improve our understanding of complex lipid interactions that regulate metabolic diseases. Here, a serum phospholipidomics analysis identified associations between phosphatidylglycerols (PGs) and gut microbiota dysbiosis. Compared with the other phospholipids, serum PGs were the most elevated in patients with low microbiota gene richness, which were normalized after a dietary intervention that restored gut microbial diversity. Serum PG levels were positively correlated with metagenomic functional capacities for bacterial LPS synthesis and host markers of low-grade inflammation; transcriptome databases identified PG synthase, the first committed enzyme in PG synthesis, as a potential mediator. Experiments in mice and cultured human-derived macrophages demonstrated that LPS induces PG release. Acute PG treatment in mice altered adipose tissue gene expression toward remodeling and inhibited ex vivo lipolysis in adipose tissue, suggesting that PGs favor lipid storage. Indeed, several PG species were associated with the severity of obesity in mice and humans. Finally, despite enrichment in PGs in bacterial membranes, experiments employing gnotobiotic mice colonized with recombinant PG overproducing Lactococcus lactis showed limited direct contribution of microbial PGs to the host. In summary, PGs are inflammation-responsive lipids indirectly regulated by the gut microbiota via endotoxins and regulate adipose tissue homeostasis in obesity.

A spotlight on pathogenesis, interactions and novel therapeutic options in NAFLD A spotlight on pathogenesis, interactions and novel therapeutic options in NAFLD

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Date added: 07/29/2019
Date modified: 07/29/2019
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In 2018, there have been substantial advances in our understanding of the risk factors for advanced liver disease in nonalcoholic fatty liver disease, including genetic variants and the gut microbiota. Promising results have also arisen from drugs targeting metabolic pathways involved in the progression of liver damage.

Assessment of Liver Fibrosis Progression and Regression by a Serological Collagen Turnover Profile Assessment of Liver Fibrosis Progression and Regression by a Serological Collagen Turnover Profile

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Date added: 07/29/2019
Date modified: 07/29/2019
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There is a need for noninvasive biomarkers that can identify patients with progressive liver fibrosis and monitor response to antifibrotic therapy. An equally important need is identification of patients with spontaneous fibrosis regression, since they may not need treatment nor be included in clinical studies with fibrosis as end point. Circulating biomarkers, originating from defined fragments of the scar tissue itself, may serve as valuable tools for this aspect of precision medicine. We investigated a panel of serological collagen formation and degradation markers to identify patients likely to regress or progress in absence of a therapeutic intervention. Plasma samples from patients with moderate-stage hepatitis C receiving placebo treatment in a phase II trial of the peroxisome proliferator-activated receptor agonist farglitazar were included. The patients had matched liver biopsies at baseline and 52 wk of follow-up. Serological biomarkers of collagen formation (PRO-C3, PRO-C4, PRO-C5) and collagen degradation (C3M, C4M, and C6M) were analyzed. Logistic regression analysis including PRO-C3 and C6M identified subjects with progressive liver fibrosis with an AUROC of 0.91 (P < 0.0001) and positive and negative predictive values (PPV/NPV) of 75.0%/88.6%. Low levels of PRO-C5 predicted a spontaneous regression phenotype, with an odds ratio of 33.8 times higher compared with patients with high levels (P < 0.0025) with an AUROC of 0.78 (P < 0.0001) and PPV/NPV of 60.0%/95.7%. Two collagen fragments (PRO-C3 and C6M) identified liver fibrosis progressors, and one collagen fragment (PRO-C5) identified liver fibrosis regressors. These biomarkers may improve patient stratification and monitor treatment efficacy in studies with fibrosis as clinical end point.

In this study we report two biomarkers of collagen fragments (PRO-C3 and C6M) that are able to identify liver fibrosis progressors while one biomarker (PRO-C5) identified liver fibrosis regressors. In particular, we present three noninvasive biomarkers that can be used to identify patients with progressive liver fibrosis, monitor response to antifibrotic therapy, and also identify the spontaneous liver fibrosis regression phenotype.

Saturated Fat Is More Metabolically Harmful for the Human Liver Than Unsaturated Fat or Simple Sugar Saturated Fat Is More Metabolically Harmful for the Human Liver Than Unsaturated Fat or Simple Sugar

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Date added: 04/11/2019
Date modified: 04/11/2019
Filesize: 256 Bytes
Downloads: 263

OBJECTIVE:
Nonalcoholic fatty liver disease (i.e., increased intrahepatic triglyceride [IHTG] content), predisposes to type 2 diabetes and cardiovascular disease. Adipose tissue lipolysis and hepatic de novo lipogenesis (DNL) are the main pathways contributing to IHTG. We hypothesized that dietary macronutrient composition influences the pathways, mediators, and magnitude of weight gain-induced changes in IHTG.

RESEARCH DESIGN AND METHODS:
We overfed 38 overweight subjects (age 48 ± 2 years, BMI 31 ± 1 kg/m2, liver fat 4.7 ± 0.9%) 1,000 extra kcal/day of saturated (SAT) or unsaturated (UNSAT) fat or simple sugars (CARB) for 3 weeks. We measured IHTG (1H-MRS), pathways contributing to IHTG (lipolysis ([2H5]glycerol) and DNL (2H2O) basally and during euglycemic hyperinsulinemia), insulin resistance, endotoxemia, plasma ceramides, and adipose tissue gene expression at 0 and 3 weeks.

RESULTS:
Overfeeding SAT increased IHTG more (+55%) than UNSAT (+15%, P < 0.05). CARB increased IHTG (+33%) by stimulating DNL (+98%). SAT significantly increased while UNSAT decreased lipolysis. SAT induced insulin resistance and endotoxemia and significantly increased multiple plasma ceramides. The diets had distinct effects on adipose tissue gene expression.

CONCLUSIONS:
Macronutrient composition of excess energy influences pathways of IHTG: CARB increases DNL, while SAT increases and UNSAT decreases lipolysis. SAT induced the greatest increase in IHTG, insulin resistance, and harmful ceramides. Decreased intakes of SAT could be beneficial in reducing IHTG and the associated risk of diabetes.

Hypoxia-inducible factor 2α drives nonalcoholic fatty liver progression by triggering hepatocyte... Hypoxia-inducible factor 2α drives nonalcoholic fatty liver progression by triggering hepatocyte...

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Date added: 02/13/2019
Date modified: 02/13/2019
Filesize: 256 Bytes
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"Hypoxia-inducible factor 2α drives nonalcoholic fatty liver progression by triggering hepatocyte release of histidine rich glycoprotein"

Mechanisms underlying progression of nonalcoholic fatty liver disease (NAFLD) are still incompletely characterized. Hypoxia and hypoxia‐inducible factors (HIFs) have been implicated in the pathogenesis of chronic liver diseases, but the actual role of HIF‐2α in the evolution of NAFLD has never been investigated in detail. In this study, we show that HIF‐2α is selectively overexpressed in the cytosol and the nuclei of hepatocytes in a very high percentage (>90%) of liver biopsies from a cohort of NAFLD patients at different stages of the disease evolution. Similar features were also observed in mice with steatohepatitis induced by feeding a methionine/choline‐deficient diet. Experiments performed in mice carrying hepatocyte‐specific deletion of HIF‐2α and related control littermates fed either a choline‐deficient L‐amino acid–defined or a methionine/choline‐deficient diet showed that HIF‐2α deletion ameliorated the evolution of NAFLD by decreasing parenchymal injury, fatty liver, lobular inflammation, and the development of liver fibrosis. The improvement in NAFLD progression in HIF‐2α‐deficient mice was related to a selective down‐regulation in the hepatocyte production of histidine‐rich glycoprotein (HRGP), recently proposed to sustain macrophage M1 polarization. In vitro experiments confirmed that the up‐regulation of hepatocyte HRGP expression was hypoxia‐dependent and HIF‐2α‐dependent. Finally, analyses performed on specimens from NAFLD patients indicated that HRGP was overexpressed in all patients showing hepatocyte nuclear staining for HIF‐2α and revealed a significant positive correlation between HIF‐2α and HRGP liver transcript levels in these patients. Conclusions: These results indicate that hepatocyte HIF‐2α activation is a key feature in both human and experimental NAFLD and significantly contributes to the disease progression through the up‐regulation of HRGP production.

MBOAT7 rs641738 variant and hepatocellular carcinoma in non-cirrhotic individuals MBOAT7 rs641738 variant and hepatocellular carcinoma in non-cirrhotic individuals

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Date added: 06/02/2018
Date modified: 06/02/2018
Filesize: 1.44 MB
Downloads: 380

Nonalcoholic fatty liver disease (NAFLD) represents an emerging cause of hepatocellular carcinoma (HCC), especially in non-cirrhotic individuals. The rs641738 C > T MBOAT7/TMC4 variant predisposes to progressive NAFLD, but the impact on hepatic carcinogenesis is unknown. In Italian NAFLD patients, the rs641738 T allele was associated with NAFLD-HCC (OR 1.65, 1.08–2.55; n = 765), particularly in those without advanced fibrosis (p < 0.001). The risk T allele was linked to 3’-UTR variation in MBOAT7 and to reduced MBOAT7 expression in patients without severe fibrosis. The number of PNPLA3, TM6SF2, and MBOAT7 risk variants was associated with NAFLD-HCC independently of clinical factors (p < 0.001), but did not significantly improve their predictive accuracy. When combining data from an independent UK NAFLD cohort, in the overall cohort of non-cirrhotic patients (n = 913, 41 with HCC) the T allele remained associated with HCC (OR 2.10, 1.33–3.31). Finally, in a combined cohort of non-cirrhotic patients with chronic hepatitis C or alcoholic liver disease (n = 1121), the T allele was independently associated with HCC risk (OR 1.93, 1.07–3.58). In conclusion, the MBOAT7 rs641738 T allele is associated with reduced MBOAT7 expression and may predispose to HCC in patients without cirrhosis, suggesting it should be evaluated in future prospective studies aimed at stratifying NAFLD-HCC risk.

Liver fibrosis: Direct antifibrotic agents and targeted therapies Liver fibrosis: Direct antifibrotic agents and targeted therapies

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Date added: 12/31/2018
Date modified: 12/31/2018
Filesize: 256 Bytes
Downloads: 387

Liver fibrosis and in particular cirrhosis are the major causes of morbidity and mortality of patients with chronic liver disease. Their prevention or reversal have become major endpoints in clinical trials with novel liver specific drugs. Remarkable progress has been made with therapies that efficiently address the cause of the underlying liver disease, as in chronic hepatitis B and C. Highly effective antiviral therapy can prevent progression or even induce reversal in the majority of patients, but such treatment remains elusive for the majority of liver patients with advanced alcoholic or nonalcoholic steatohepatitis, genetic or autoimmune liver diseases. Moreover, drugs that would speed up fibrosis reversal are needed for patients with cirrhosis, since even with effective causal therapy reversal is slow or the disease may further progress. Therefore, highly efficient and specific antifibrotic agents are needed that can address advanced fibrosis, i.e., the detrimental downstream result of all chronic liver diseases. This review discusses targeted antifibrotic therapies that address molecules and mechanisms that are central to fibrogenesis or fibrolysis, including strategies that allow targeting of activated hepatic stellate cells and myofibroblasts and other fibrogenic effector cells. Focus is on collagen synthesis, integrins and cells and mechanisms specific including specific downregulation of TGFbeta signaling, major extracellular matrix (ECM) components, ECM-crosslinking, and ECM-receptors such as integrins and discoidin domain receptors, ECM-crosslinking and methods for targeted delivery of small interfering RNA, antisense oligonucleotides and small molecules to increase potency and reduce side effects. With an increased understanding of the biology of the ECM and liver fibrosis and an improved preclinical validation, the translation of these approaches to the clinic is currently ongoing. Application to patients with liver fibrosis and a personalized treatment is tightly linked to the development of non-invasive biomarkers of fibrosis, fibrogenesis and fibrolysis.

Altered amino acid concentrations in NAFLD: Impact of obesity and insulin resistance Altered amino acid concentrations in NAFLD: Impact of obesity and insulin resistance

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Date added: 11/01/2018
Date modified: 11/01/2018
Filesize: 256 Bytes
Downloads: 408

Plasma concentrations of amino acids (AAs), in particular, branched chain AAs (BCAAs), are often found increased in nonalcoholic fatty liver disease (NAFLD); however, if this is due to increased muscular protein catabolism, obesity, and/or increased insulin resistance (IR) or impaired tissue metabolism is unknown. Thus, we evaluated a) if subjects with NAFLD without obesity (NAFLD-NO) compared to those with obesity (NAFLD-Ob) display altered plasma AAs compared to controls (CTs); and b) if AA concentrations are associated with IR and liver histology. Glutamic acid, serine, and glycine concentrations are known to be altered in NAFLD. Because these AAs are involved in glutathione synthesis, we hypothesized they might be related to the severity of NAFLD. We therefore measured the AA profile of 44 subjects with NAFLD without diabetes and who had a liver biopsy (29 NAFLD-NO and 15 NAFLD-Ob) and 20 CTs without obesity, by gas chromatography–mass
spectrometry, homeostasis model assessment of insulin resistance, hepatic IR (Hep-IR; Hep-IR 5 endogenous glucose production 3 insulin), and the new glutamate–serine–glycine (GSG) index (glutamate/[serine 1 glycine]) and tested for an association with liver histology. Most AAs were increased only in NAFLD-Ob subjects. Only alanine, glutamate, isoleucine, and valine, but not leucine, were increased in NAFLD-NO subjects compared to CTs. Glutamate, tyrosine, and the GSG-index were correlated with Hep-IR. The GSG-index correlated with liver enzymes, in particular, gamma-glutamyltransferase (R 5 0.70), independent of body mass index. Ballooning and/or inflammation at liver biopsy were associated with increased plasma BCAAs and aromatic AAs and were mildly associated with the GSG-index, while only the new GSG-index was able to discriminate fibrosis F3-4 from F0-2 in this cohort.

Conclusion: Increased plasma AA concentrations were observed mainly in subjects with obesity and NAFLD, likely as a consequence of increased IR and protein catabolism. The GSG-index is a possible marker of severity of liver disease independent of body mass index.