Pathology Of Non-alcoholic Fatty Liver Disease Research Articles

PMFs-rich Citrus extract prevents the development of non-alcoholic fatty liver disease in C57BL/6J mice induced by a high-fat diet

Oxidative stress and excessive lipid accumulation in liver tissues are considered as important factors in development of non-alcoholic fatty liver disease (NAFLD), which is the most common chronic liver disease worldwide and strongly associated with insulin resistance, obesity and dyslipidemia. In this study, the effect of PMFs-enriched extract of Daoxianyeju (Citrus daoxianensis S.W. He) (EDX) on NAFLD were examined using high fat diet-induced obesity (DIO) C57BL/6 mice. Daily supplementation of 0.2% and 0.5% EDX with high fat diet (w/w) over ten weeks markedly improved glucose tolerance and insulin resistance as well as lipid profiles, alleviated hepatic steatosis, inflammatory and oxidative stress. The benefit of EDX on improving pathology of NAFLD induced by high fat diet may associate with the activation of nuclear factor erythroid-2 related factor 2 (Nrf2) pathways in liver tissues. Our study showed that citrus PMFs may use as a dietary therapy for NAFLD and related metabolic disorders.

Non-alcoholic fatty liver disease: Insights from sphingolipidomics

Non-alcoholic fatty liver disease (NAFLD) is a major clinical concern and its treatment consumes abundant resources. While accumulation of lipids in hepatocytes initiates the disease, this in itself is not necessarily harmful; rather, initiation of inflammation and subsequent fibrosis and cirrhosis are critical steps in NAFLD pathology. Mechanisms linking lipid overload to downstream disease progression are not fully understood; however, bioactive lipid metabolism may underlie instigation of proinflammatory signaling. With the advent of high-throughput, sensitive, and quantitative mass spectrometry-based methods for assessing lipid profiles in NAFLD, several trends have emerged, including that increases in specific sphingolipids correlate with the transition from the relatively benign condition of simple fatty liver to the much more concerning inflamed state. Continued studies that implement sphingolipid profiling will enable the extrapolations of candidate enzymes and pathways involved in NAFLD, either in biopsies or plasma from human samples, and also in animal models, from which data are much more abundant. While most data thus far are derived from targeted lipidomics approaches, unbiased, semi-quantitative approaches hold additional promise for furthering our understanding of sphingolipids as markers of and players in NAFLD.

Investigation of nonalcoholic fatty liver disease-induced drug metabolism by comparative global toxicoproteomics

Non-alcoholic fatty liver disease (NAFLD) includes conditions such as steatosis, non-alcoholic steatohepatitis, and ultimately hepatocellular carcinoma. Although the pathology of NAFLD is well-established, NAFLD-induced drug metabolism mediated by cytochrome P450 (CYP) in the liver has remained largely unexplored. Therefore, we investigated NAFLD-induced drug metabolism mediated by CYP by quantitative toxicoproteomics analysis. After administration of a methionine-choline deficient (MCD) diet to induce development of NAFLD, tandem mass tags-based liquid chromatography-tandem mass spectrometry analysis was conducted to investigate the dynamics of hepatic proteins. A total of 1295 proteins were identified, of which 934 were quantified by proteomic analysis. Among these proteins, 21 proteins were up-regulated and 51 proteins were down-regulated by the MCD diet. Notably, domain annotation enrichment using InterPro indicated that proteins related to CYPs were significantly decreased. When we investigated CYP activity using in vivo and in vitro CYP cocktail assays, most CYPs were significantly decreased, whereas CYP2D was not changed after administration of the MCD diet. In conclusion, we identified significantly altered levels of CYPs and their activities induced by the MCD diet and confirmed the NAFLD-induced drug metabolism by pharmacokinetic analysis.

Bile acid regulation: A novel therapeutic strategy in non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive fat deposition in the liver in the absence of significant alcohol consumption. Dysregulated bile acid (BA) metabolism is an important indicator in the pathology of NAFLD, which could progress into more severe forms of liver injury. Lipid metabolism, immune environment and intestinal bacteria are all affected by dysregulated BA metabolism directly, but the mechanisms remain unclear. Several drug candidates that target BA metabolism, either used alone or in combination with other agents, are currently under development for treatment of NAFLD. Here, we summarize the relationship of dysregulated BA metabolism and NAFLD, discuss the effects and mechanisms of dysregulated BAs-induced lipid metabolism disorder. Challenges in developing novel treatments are also discussed.

The genetic backgrounds in nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide. Nonalcoholic steatohepatitis (NASH), a severe form of NAFLD, can lead to hepatocellular carcinoma (HCC) and hepatic failure. The development and progression of NAFLD are determined by environmental and genetic factors. The effect of genetic factors has been demonstrated by familial studies, twin studies and several cross-sectional studies. In the past 10years, genome-wide association studies have revealed several single nucleotide polymorphisms (SNPs) associated with the pathology of NAFLD. Among them, the Patatin-like phospholipase domain-containing 3 (PNPLA3) gene variant I148M showed a strong relationship with the development and progression of NAFLD, NASH, and NAFLD-related HCC. The transmembrane 6 superfamily member 2 (TM6SF2) gene variant E167K was also associated with NAFLD, and it has a relationship with cardiovascular disease. Furthermore, several genes have been proposed as candidate genes to be associated with NAFLD based on case-control studies. We conducted a comprehensive literature search and review on the genetic background of NAFLD.

Dietary Iron Supplementation Alters Hepatic Inflammation in a Rat Model of Nonalcoholic Steatohepatitis.

Nonalcoholic fatty liver disease (NAFLD) is now the most common liver disease in the world. NAFLD can progress to nonalcoholic steatohepatitis (NASH), cirrhosis and eventually hepatocellular carcinoma. Acquired hepatic iron overload is seen in a number of patients with NAFLD; however, its significance in the pathology of NAFLD is still debated. Here, we investigated the role of dietary iron supplementation in experimental steatohepatitis in rats. Rats were fed a control, high-fat (HF), high-fat high-iron (HFHI) and high-iron (HI) diet for 30 weeks. Blood biochemical, histopathological and gut microbiota analyses were performed. Rats in HF and HFHI groups showed an ALT-dominant elevation of serum transaminases, hepatic steatosis, hepatic inflammation, and upregulation of proinflammatory cytokines. The number of large inflammatory foci, corresponding to lobular inflammation in NASH patients, was significantly higher in HFHI than in HF group; within the lesion, macrophages with intense iron staining were observed. Hepatic expression of TNFα was higher in HFHI than that in HF group. There was no significant change in hepatic oxidative stress, gut microbiota or serum endotoxin levels between HF and HFHI groups. These results suggested that dietary iron supplementation enhances experimental steatohepatitis induced by long-term high-fat diet feeding in rats. Iron-laden macrophages can play an important role in the enhancement of hepatic inflammation.

Animal Models of Non-alcoholic Fatty Liver Diseases and Its Associated Liver Cancer.

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of diseases, which include simple liver steatosis, non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma (HCC). It is a burgeoning health problem worldwide in line with the trend towards unhealthy diet and increased prevalence of obesity and type 2 diabetes mellitus (T2DM). Many animal models that illustrate both the histology and pathology of human NAFLD have been established. It is important to choose an animal model that best conforms to the aim of the study. This chapter presents a critical analysis of the histopathology and pathogenesis of NAFLD and the most commonly used and recently developed animal models of hepatic steatosis, NASH and NAFLD-induced hepatocellular carcinoma (NAFLD-HCC). The main mechanisms involved in the experimental pathogenesis of NAFLD in various animal models were also discussed. This chapter also includes a brief summary of recent therapeutic targets found using animal models. Although current animal models provide important guidance in understanding the pathogenesis and development of NAFLD, future study is essential to develop more precise models that better mimic the disease spectrum for both improved mechanistic understanding and identification of novel therapeutic options.

Micronutrients in Nonalcoholic Fatty Liver Disease Pathogenesis.

Micronutrients include electrolytes, minerals, vitamins, and carotenoids, and are required in microgram or milligram quantities for cellular metabolism. The liver plays an important role in micronutrient metabolism and this metabolism often is altered in chronic liver diseases. Here, we review how the liver contributes to micronutrient metabolism; how impaired micronutrient metabolism may be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD), a systemic disorder of energy, glucose, and lipid homeostasis; and how insights gained from micronutrient biology have informed NAFLD therapeutics. Finally, we highlight some of the challenges and opportunities that remain with investigating the contribution of micronutrients to NAFLD pathology and suggest strategies to incorporate our understanding into the care of NAFLD patients.

70 - Microcystin exposure Exacerbates Non-alcoholic Fatty Liver Disease (NAFLD) via NOX2 Dependent Activation of miR21-induced Inflammatory Pathways

Non-alcoholic fatty liver disease is an emerging global pandemic with 15% of the cases progressing to steatohepatitis or cirrhosis and eventually to hepatocellular carcinoma. Though significant progress has been made in unravelling the pathophysiology of the disease, the effect of environmental and genetic factors in an underlying NAFLD pathophysiology remains unclear. The present report tests the hypothesis that microcystin (MC), a principal component of harmful algal blooms activates Kupffer cells and hepatic stellate cells, crucial mediators in hepatic fibrogenesis via NOX2 dependent pathway in an underlying condition of NAFLD. Mice that had mild steatosis and showed signs of NAFLD were exposed to microcystin via an intraperitoneal route. Results showed that MC exposure led to exacerbation of NAFLD pathology with increased CD68 immunoreactivity, release of proinflammatory cytokines and stellate cell activation, a process that was attenuated in miR21 knockout mice and mice that lacked the p47 phox gene. Mechanistically, immortalized Kupffer cells treated with apocynin or nitrone spin trap DMPO had significantly decreased CD68, decreased miR21 and α-SMA levels signifying the role of NOX2-dedendent reactive oxygen species in miR21-induced Kupffer cell activation and stellate cell pathology. Further, NOX2 dependent peroxynitrite generation was primarily responsible for cellular events observed following MC exposure since incubation with phenyl boronic acid attenuated miR21 levels, Kuppfer cell activation and inflammatory cytokine release. Taken together, we show that MC exposure exacerbates NAFLD pathology via NOX2 dependent peroxynitrite generation by increasing miR21 levels.

HMGB1-RAGE pathway drives peroxynitrite signaling-induced IBD-like inflammation in murine nonalcoholic fatty liver disease

Recent clinical studies found a strong association of colonic inflammation and Inflammatory bowel disease (IBD)-like phenotype with NonAlcoholic Fatty liver Disease (NAFLD) yet the mechanisms remain unknown. The present study identifies high mobility group box 1 (HMGB1) as a key mediator of intestinal inflammation in NAFLD and outlines a detailed redox signaling mechanism for such a pathway. NAFLD mice showed liver damage and release of elevated HMGB1 in systemic circulation and increased intestinal tyrosine nitration that was dependent on NADPH oxidase. Intestines from NAFLD mice showed higher Toll like receptor 4 (TLR4) activation and proinflammatory cytokine release, an outcome strongly dependent on the existence of NAFLD pathology and NADPH oxidase. Mechanistically intestinal epithelial cells showed the HMGB1 activation of TLR-4 was both NADPH oxidase and peroxynitrite dependent with the latter being formed by the activation of NADPH oxidase. Proinflammatory cytokine production was significantly blocked by the specific peroxynitrite scavenger phenyl boronic acid (FBA), AKT inhibition and NADPH oxidase inhibitor Apocynin suggesting NADPH oxidase-dependent peroxynitrite is a key mediator in TLR-4 activation and cytokine release via an AKT dependent pathway. Studies to ascertain the mechanism of HMGB1-mediated NADPH oxidase activation showed a distinct role of Receptor for advanced glycation end products (RAGE) as the use of inhibitors targeted against RAGE or use of deformed HMGB1 protein prevented NADPH oxidase activation, peroxynitrite formation, TLR4 activation and finally cytokine release. Thus, in conclusion the present study identifies a novel role of HMGB1 mediated inflammatory pathway that is RAGE and redox signaling dependent and helps promote ectopic intestinal inflammation in NAFLD.

NLRP3 inflammasome blockade reduces liver inflammation and fibrosis in experimental NASH in mice

NOD-like receptor protein 3 (NLRP3) inflammasome activation occurs in Non-alcoholic fatty liver disease (NAFLD). We used the first small molecule NLRP3 inhibitor, MCC950, to test whether inflammasome blockade alters inflammatory recruitment and liver fibrosis in two murine models of steatohepatitis. We fed foz/foz and wild-type mice an atherogenic diet for 16weeks, gavaged MCC950 or vehicle until 24weeks, then determined NAFLD phenotype. In mice fed an methionine/choline deficient (MCD) diet, we gavaged MCC950 or vehicle for 6weeks and determined the effects on liver fibrosis. In vehicle-treated foz/foz mice, hepatic expression of NLRP3, pro-IL-1β, active caspase-1 and IL-1β increased at 24weeks, in association with cholesterol crystal formation and NASH pathology; plasma IL-1β, IL-6, MCP-1, ALT/AST all increased. MCC950 treatment normalized hepatic caspase 1 and IL-1β expression, plasma IL-1β, MCP-1 and IL-6, lowered ALT/AST, and reduced the severity of liver inflammation including designation as NASH pathology, and liver fibrosis. In vitro, cholesterol crystals activated Kupffer cells and macrophages to release IL-1β; MCC950 abolished this, and the associated neutrophil migration. MCD diet-fed mice developed fibrotic steatohepatitis; MCC950 suppressed the increase in hepatic caspase 1 and IL-1β, lowered numbers of macrophages and neutrophils in the liver, and improved liver fibrosis. MCC950, an NLRP3 selective inhibitor, improved NAFLD pathology and fibrosis in obese diabetic mice. This is potentially attributable to the blockade of cholesterol crystal-mediated NLRP3 activation in myeloid cells. MCC950 reduced liver fibrosis in MCD-fed mice. Targeting NLRP3 is a logical direction in pharmacotherapy of NASH. Fatty liver disease caused by being overweight with diabetes and a high risk of heart attack, termed non-alcoholic steatohepatitis (NASH), is the most common serious liver disease with no current treatment. There could be several causes of inflammation in NASH, but activation of a protein scaffold within cells termed the inflammasome (NLRP3) has been suggested to play a role. Here we show that cholesterol crystals could be one pathway to activate the inflammasome in NASH. We used a drug called MCC950, which has already been shown to block NLRP3 activation, in an attempt to reduce liver injury in NASH. This drug partly reversed liver inflammation, particularly in obese diabetic mice that most closely resembles the human context of NASH. In addition, such dampening of liver inflammation in NASH achieved with MCC950 partly reversed liver scarring, the process that links NASH to the development of cirrhosis.

Is There Consensus among Sonographers and Radiologists in Grading Fatty Liver Disease and Detecting Liver Pathological Features in B-Mode Images?

Hepatic steatosis is the leading cause of chronic liver disease. Reliable detection and staging of liver disease using ultrasound is important to facilitate diagnosis and treatment. The aim of this study was to evaluate the interobserver agreement between trainee sonographers, qualified sonographers and radiologists in grading non-alcoholic fatty liver disease (NAFLD) and detecting common liver pathological features on B-mode images. 150 B-mode liver ultrasound images from 50 adult patients referred for abdominal ultrasound were obtained retrospectively from a PACS system. The images were independently graded for the severity of hepatic steatosis (normal, mild, moderate or severe) and the detection of incidental findings, focal fatty sparing, liver surface irregularity and rounded liver edge (present or absent) by 17 qualified, six trainee sonographers and six radiologists. Fleiss’ kappa statistic was used to calculate interobserver agreement. The interobserver agreement rates among trainee sonographers for the detection of incidental findings, focal fatty sparing, liver surface irregularity and rounded liver edge were: κ = 0.243, 0.486, 0.155 and 0.079 respectively. Among qualified sonographers, the agreement rates were: κ = 0.323, 0.428, 0.167 and 0.152 respectively. Among radiologists, the agreement rates were: κ = 0.156, 0.266, 0.015 and 0.154 respectively. Visual assessment of NAFLD and common liver pathology in B-mode imaging has low interobserver agreement among sonographers and radiologists. The low agreement levels are likely caused by a lack of standardised assessment criteria. The development of standardised criteria for staging common liver pathological features are recommended.

From the Cover: Coagulation-Driven Hepatic Fibrosis Requires Protease Activated Receptor-1 (PAR-1) in a Mouse Model of TCDD-Elicited Steatohepatitis.

Emerging evidence supports a role for environmental chemical exposure in the pathology of non-alcoholic fatty liver disease (NAFLD), a disease process tightly linked to increased activity of the blood coagulation cascade. Exposure of C57BL/6 mice to the persistent environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) recapitulates features of the NAFLD spectrum, including steatosis, hepatic injury, inflammation, and fibrosis. We assessed coagulation cascade activation, and determined the role of the thrombin receptor protease activated receptor-1 (PAR-1) in experimental TCDD-elicited NAFLD. Chronic exposure to TCDD (30 µg/kg every 4 days for 28 days) was associated with intrahepatic coagulation, indicated by increased plasma thrombin-antithrombin levels and hepatic fibrin(ogen) deposition. PAR-1 deficiency diminished TCDD-elicited body weight loss and relative liver weight was reduced in TCDD-exposed PAR-1-/- mice compared with TCDD-exposed wild-type mice. PAR-1 deficiency did not affect TCDD-induced hepatic steatosis or hepatocellular injury, as indicated by serum alanine aminotransferase activity. Despite a lack of effect on these 2 features of NAFLD pathology, PAR-1 deficiency was associated with a reduction in hepatic inflammation evident in liver histopathology, and reflected by a reduction in serum levels of the proinflammatory cytokine interleukin-6. Moreover, TCDD-driven hepatic collagen deposition was markedly reduced in PAR-1-deficient mice. These results indicate that experimental TCDD-elicited steatohepatitis is associated with coagulation cascade activation and PAR-1-driven hepatic inflammation and fibrosis.

Fatty Liver Disease: A Crosstalk Between Lipid Species

The role of different lipid species such as free fatty acids and sphingolipids in non-alcoholic fatty liver disease (NAFLD) has been extensively studied during the last decade. In addition, free cholesterol accumulation in hepatocytes plays a crucial role in the transition from steatosis to steatohepatitis. However, the contribution of these lipids to NAFLD pathology is often evaluated individually. This review attempts to enclose the main metabolic and signalling connections between lipotoxic lipid species, and how their homeostasis is disrupted in NAFLD.

Weight loss as a treatment for nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease that can progress to cirrhosis and hepatocellular carcinoma. NAFLD has been associated with obesity and other features of the metabolic syndrome, including insulin resistance, impaired glucose tolerance, and dyslipidemia. As a result, and with a lack of other effective treatments, weight loss achieved through lifestyle modifications (diet and exercise) has been promoted as the standard treatment. However, there is very little empiric evidence to support the effectiveness of weight loss for NAFLD. This article reviews the current literature on the effects of weight loss achieved through lifestyle modification or medications on NAFLD. To date, there have been no randomized controlled trials of weight loss interventions on hepatic pathology. Only three published trials (N = 89 subjects), which include a comparison group, have been published. These studies suggest improvement in liver enzymes and/or hepatic pathology; however, direct between group comparisons are lacking. Four small, nonrandomized studies (N = 59 subjects) have evaluated the effect of weight loss achieved with medications (4 of orlistat, 1 of sibutramine) on NAFLD. These suggest some improvement in liver enzymes and histopathology. Finally, a brief review of observational studies on the association between NAFLD pathology or liver enzymes and diet composition suggests a possible role for the manipulation of macronutrients and/or micronutrients in NAFLD treatment. In summary, there is little empiric evidence to support the role of weight loss achieved through lifestyle modification or medication in the treatment of NAFLD. Rigorously conducted, randomized controlled trials are needed in this area.

Association of maternal diabetes/glycosuria and pre-pregnancy body mass index with offspring indicators of non-alcoholic fatty liver disease.

BackgroundLittle is known about early life determinants of non-alcoholic fatty liver disease (NAFLD). We examined associations of maternal pregnancy diabetes/glycosuria and pre-pregnancy body mass index (BMI) with offspring markers of NAFLD and liver pathology and examined mediation by birthweight and concurrent offspring adiposity.MethodsWe used data from a UK prospective pregnancy cohort. Offspring underwent abdominal ultrasonography (USS) at mean age 17.8 years. Outcomes included USS-assessed fatty liver, estimated liver volume and shear velocity, a variant of elastography (a marker of liver fibrosis) (N = 1 215) and blood-based markers of liver pathology [alanine amino transferase, aspartate amino transferase, gamma- glutamyltransferase and haptoglobin] (N = 2 359).Results2.1 % (N = 25) of participants had USS-assessed fatty liver [maternal diabetes/glycosuria (N = 7) and no diabetes/glycosuria (N = 18)]. Maternal diabetes/glycosuria was associated with greater odds of offspring USS fatty liver in confounder adjusted models [adjusted odds ratio (aOR) 6.74 (95 % confidence interval (CI) 2.47, 18.40)] and higher shear velocity [adjusted ratio of geometric mean (aRGM):1.10 (95 % CI 1.05, 1.15)]. These associations were not mediated by offspring birthweight or concurrent adiposity. Maternal diabetes/glycosuria was not associated with liver volume or blood-based outcomes. Greater maternal pre-pregnancy BMI was associated with greater odds of offspring USS fatty liver [aOR 2.72 (95 % CI: 1.20, 6.15)], higher liver volume [aRGM 1.03 (95 % CI 1.00, 1.07)] and shear velocity [aRGM1.03 (95 % CI: 1.01, 1.06)] in confounder adjusted models. These associations were largely mediated by offspring adiposity. Maternal pre-pregnancy BMI was not consistently associated with blood-based outcomes.ConclusionsResults suggest that maternal pregnancy diabetes/glycosuria is associated with offspring NAFLD through mechanisms other than offspring’s own adiposity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12887-016-0585-y) contains supplementary material, which is available to authorized users.

Fructose consumption induces hypomethylation of hepatic mitochondrial DNA in rats

AimsFructose may play a crucial role in the pathogenesis of metabolic syndrome (MetS). However, the pathogenic mechanism of the fructose-induced MetS has not yet been investigated fully. Recently, several reports have investigated the association between mitochondrial DNA (mtDNA) and MetS. We examined the effect of fructose-rich diets on mtDNA content, transcription, and epigenetic changes. Main methodsFour-week-old male Sprague-Dawley rats were offered a 20% fructose solution for 14weeks. We quantified mRNAs for hepatic mitochondrial genes and analyzed the mtDNA methylation (5-mC and 5-hmC) levels using ELISA kits. Key findingsHistological analysis revealed non-alcoholic fatty liver disease (NAFLD) in fructose-fed rats. Hepatic mtDNA content and transcription were higher in fructose-fed rats than in the control group. Global hypomethylation of mtDNA was also observed in fructose-fed rats. SignificanceWe showed that fructose consumption stimulates hepatic mtDNA-encoded gene expression. This phenomenon might be due to epigenetic changes in mtDNA. Fructose-induced mitochondrial epigenetic changes appear to be a novel mechanism underlying the pathology of MetS and NAFLD.

Systematic transcriptome analysis reveals elevated expression of alcohol‐metabolizing genes in NAFLD livers

Obese animals and non-alcoholic fatty liver disease (NAFLD) patients exhibit elevated blood alcohol, suggesting potential contributions of alcohol metabolism to the development of NAFLD. Liver gene expression in patients with biopsy-proven mild (N = 40) and severe (N = 32) NAFLD were compared to that in healthy liver donors (N = 7) and alcoholic hepatitis (AH; N = 15) using microarrays. Principal components analyses (PCA) revealed similar gene expression patterns between mild and severe NAFLD which clustered with those of AH but were distinct from those of healthy livers. Differential gene expression between NAFLD and healthy livers was consistent with established NAFLD-associated genes and NAFLD pathophysiology. Alcohol-metabolizing enzymes including ADH, ALDH, CYP2E1, and CAT were up-regulated in NAFLD livers. The expression level of alcohol-metabolizing genes in severe NAFLD was similar to that in AH. The NAFLD gene expression profiles provide new directions for future investigations to identify disease markers and targets for prevention and treatment, as well as to foster our understanding of NAFLD pathogenesis and pathophysiology. Particularly, increased expression of alcohol-metabolizing genes in NAFLD livers supports a role for endogenous alcohol metabolism in NAFLD pathology and provides further support for gut microbiome therapy in NAFLD management. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley © Sons, Ltd.

Molecular Mechanisms of NAFLD in Metabolic Syndrome

Metabolic syndrome (MetSyn) and nonalcoholic fatty liver disease (NAFLD) are increasing worldwide, as often mentioned in this special issue. Lifestyles (with diet being one of the relevant factors) play an important role as preventive determinants of MetSyn and NAFLD, conversely being potential inducers of MetSyn and NAFLD. Liver steatosis has been considered not only the hepatic MetSyn manifestation but also one of the earliest MetSyn signs. Liver steatosis represents the initial step of the whole spectrum of NAFLD. Review and experimental articles including both basic and clinical data, pursuing the cross-talk between obesity/insulin resistance/MetSyn features and diet, lipid metabolism, redox state, oxidative and endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory processes and mediators, glucocorticoid excess, developmental programming, and gut microbiota in NAFLD, are included in this special issue. Possible strategies for intervention against NAFLD are also presented and discussed. There is growing evidence that the transcription factor nuclear factor erythroid-2 related factor 2 (Nrf2), a key regulator of cellular antioxidant responses, is also implicated in the regulation of hepatic lipid metabolism. The topic is addressed in the article of S. S. Chambel et al. N. Duarte et al. comprehensively reviewed the role of Kupffer cells on inflammation under conditions of hepatic fat deposition. E. Lau et al. analyzed in detail the recent research on the contribution of gut microbiota to NAFLD. A broad and extensive review on the growing evidences regarding the developmental programming of NAFLD by both maternal obesity and undernutrition is presented (M. Li et al.). E. Maslak et al. showed that rats fed with a MetSyn-inducing diet supplemented with conjugated linoleic acid isomers (c9t11 and t10c12) had (globally) beneficial effects on the hepatic lipid content and glycogen accumulation as well as on the circulating lipid profile; the isomers also modulated the fatty acid composition and decreased lipogenic enzymes mRNA expression in the liver. A. Cordeiro et al. found that, in class III obesity, triglycerides, HDL-cholesterol and insulin levels (as well as insulin resistance index and waist circumference values), independently considered MetSyn features, linked to NAFLD, diagnosed by liver biopsy. The analyzed topics included in the present special issue allow a better mechanistic understanding of NAFLD pathology in the context of the MetSyn and further contribute to the possible implementation of important countermeasures, either preventive or therapeutic, against the disease. Therefore, we hope that this special issue will be of interest to a wide audience in basic and applied biomedical areas, especially those that embrace with excitement the search for new hypothesis and approaching challenges regarding NAFLD pathophysiology in the context of the MetSyn. Maria Joao Martins Antonio Ascensao Jose Magalhaes Maria Carmen Collado Piero Portincasa

Reduced hepatic lipid content in Pten-haplodeficient mice because of enhanced AKT2/PKBβ activation in skeletal muscle.

Non-alcoholic fatty liver disease (NAFLD) is a major health problem and occurs frequently in the context of metabolic syndrome and type 2 diabetes mellitus. Hepatocyte-specific Pten-deficiency in mice was shown previously to result in hepatic steatosis due to hyperactivated AKT2. However, the role of peripheral insulin-sensitive tissues on PTEN- and AKT2-dependent accumulation of hepatic lipids has not been addressed. Effects of systemically perturbed PTEN/AKT2 signalling on hepatic lipid content were studied in Pten-haplodeficient (Pten(+/-) /Akt2(+/+) ) mice and Pten-haplodeficient mice lacking Akt2 (Pten(+/-) /Akt2(-/-) ). The liver and skeletal muscle were characterized by histology and/or analysis of insulin signalling. To assess the effects of AKT2 activity in skeletal muscle on hepatic lipid content, AKT2 mutants were expressed in skeletal muscle of Pten(+/+) /Akt2(+/+) and Pten(+/-) /Akt2(+/+) mice using adeno-associated virus 8. Pten(+/-) /Akt2(+/+) mice were found to have a more than 2-fold reduction in hepatic lipid content, at a level similar to that observed in Pten(+/-) /Akt2(-/-) mice. Insulin signalling in the livers of Pten(+/-) /Akt2(+/+) mice was enhanced, indicating that extrahepatic factors prevent lipid accumulation. The skeletal muscle of Pten(+/-) /Akt2(+/+) mice also showed enhanced insulin signalling. Skeletal muscle-specific expression of constitutively active AKT2 reduced hepatic lipid content in Pten(+/+) /Akt2(+/+) mice, and dominant negative AKT2 led to an increase in accumulation of hepatic lipids in both Pten(+/+) /Akt2(+/+) and Pten(+/-) /Akt2(+/+) mice. Our results demonstrate that AKT2 activity in skeletal muscle critically affects lipid accumulation in the livers of Pten(+/+) /Akt2(+/+) and Pten(+/-) /Akt2(+/+) mice, and emphasize the role of skeletal muscle in the pathology of NAFLD.