Daniela Gnani

Gut microbiota profiling of pediatric nonalcoholic fatty liver disease and obese patients unveiled by an integrated meta-omics-based approach

There is evidence that nonalcoholic fatty liver disease (NAFLD) is affected by gut microbiota. Therefore, we investigated its modifications in pediatric NAFLD patients using targeted metagenomics and metabolomics. Stools were collected from 61 consecutive patients diagnosed with nonalcoholic fatty liver (NAFL), nonalcoholic steatohepatitis (NASH), or obesity and 54 healthy controls (CTRLs), matched in a case‐control fashion. Operational taxonomic units were pyrosequenced targeting 16S ribosomal RNA and volatile organic compounds determined by solid‐phase microextraction gas chromatography‐mass spectrometry. The α‐diversity was highest in CTRLs, followed by obese, NASH, and NAFL patients; and β‐diversity distinguished between patients and CTRLs but not NAFL and NASH. Compared to CTRLs, in NAFLD patients Actinobacteria were significantly increased and Bacteroidetes reduced. There were no significant differences among the NAFL, NASH, and obese groups. Overall NAFLD patients had increased levels of Bradyrhizobium, Anaerococcus, Peptoniphilus, Propionibacterium acnes, Dorea, and Ruminococcus and reduced proportions of Oscillospira and Rikenellaceae compared to CTRLs. After reducing metagenomics and metabolomics data dimensionality, multivariate analyses indicated a decrease of Oscillospira in NAFL and NASH groups and increases of Ruminococcus, Blautia, and Dorea in NASH patients compared to CTRLs. Of the 292 volatile organic compounds, 26 were up‐regulated and 2 down‐regulated in NAFLD patients. Multivariate analyses found that combination of Oscillospira, Rickenellaceae, Parabacteroides, Bacteroides fragilis, Sutterella, Lachnospiraceae, 4‐methyl‐2‐pentanone, 1‐butanol, and 2‐butanone could discriminate NAFLD patients from CTRLs. Univariate analyses found significantly lower levels of Oscillospira and higher levels of 1‐pentanol and 2‐butanone in NAFL patients compared to CTRLs. In NASH, lower levels of Oscillospira were associated with higher abundance of Dorea and Ruminococcus and higher levels of 2‐butanone and 4‐methyl‐2‐pentanone compared to CTRLs. Conclusion: An Oscillospira decrease coupled to a 2‐butanone up‐regulation and increases in Ruminococcus and Dorea were identified as gut microbiota signatures of NAFL onset and NAFL‐NASH progression, respectively. (Hepatology 2017;65:451‐464)

Dual Role of MicroRNAs in NAFLD

MicroRNAs are important post-transcriptional regulators in different pathophysiological processes. They typically affect the mRNA stability or translation finally leading to the repression of target gene expression. Notably, it is thought that microRNAs are crucial for regulating gene expression during metabolic-related disorders, such as nonalcoholic fatty liver disease (NAFLD). Several studies identify specific microRNA expression profiles associated to different histological features of NAFLD, both in animal models and in patients. Therefore, specific assortments of certain microRNAs could have enormous diagnostic potentiality. In addition, microRNAs have also emerged as possible therapeutic targets for the treatment of NAFLD-related liver damage. In this review, we discuss the experimental evidence about microRNAs both as potential non-invasive early diagnostic markers and as novel therapeutic targets in NAFLD and its more severe liver complications.

EZH2 Down-Regulation Exacerbates Lipid Accumulation and Inflammation in in Vitro and in Vivo NAFLD

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent, chronic liver diseases, worldwide. It is a multifactorial disease caused by complex interactions between genetic, epigenetic and environmental factors. Recently, several microRNAs, some of which epigenetically regulated, have been found to be up- and/or down-regulated during NAFLD development. However, in NAFLD, the essential role of the Polycomb Group protein Enhancer of Zeste Homolog 2 (EZH2), which controls the epigenetic silencing of specific genes and/or microRNAs by trimethylating Lys27 on histone H3, still remains unknown. In this study, we demonstrate that the nuclear expression/activity of the EZH2 protein is down-regulated both in livers from NAFLD rats and in the free fatty acid-treated HepG2. The drop in EZH2 is inversely correlated with: (i) lipid accumulation; (ii) the expression of pro-inflammatory markers including TNF-α and TGF-β; and (iii) the expression of miR-200b and miR-155. Consistently, the pharmacological inhibition of EZH2 by 3-Deazaneplanocin A (DZNep) significantly reduces EZH2 expression/activity, while it increases lipid accumulation, inflammatory molecules and microRNAs. In conclusion, the results of this study suggest that the defective activity of EZH2 can enhance the NAFLD development by favouring steatosis and the de-repression of the inflammatory genes and that of specific microRNAs.

LPS-induced TNF-α factor mediates pro-inflammatory and pro-fibrogenic pattern in non-alcoholic fatty liver disease

Lipopolysaccharide (LPS) is currently considered one of the major players in non-alcoholic fatty liver disease (NAFLD) pathogenesis and progression. Here, we aim to investigate the possible role of LPS-induced TNF-α factor (LITAF) in inducing a pro-inflammatory and pro-fibrogenic phenotype of non-alcoholic steatohepatitis (NASH). We found that children with NAFLD displayed, in different liver-resident cells, an increased expression of LITAF which correlated with histological traits of hepatic inflammation and fibrosis. Total and nuclear LITAF expression increased in mouse and human hepatic stellate cells (HSCs). Moreover, LPS induced LITAF-dependent transcription of IL-1β, IL-6 and TNF-α in the clonal myofibroblastic HSC LX-2 cell line, and this effect was hampered by LITAF silencing. We showed, for the first time in HSCs, that LITAF recruitment to these cytokine promoters is LPS dependent. However, preventing LITAF nuclear translocation by p38MAPK inhibitor, the expression of IL-6 and TNF-α was significantly reduced with the aid of p65NF-ĸB, while IL-1β transcription exclusively required LITAF expression/activity. Finally, IL-1β levels in plasma mirrored those in the liver and correlated with LPS levels and LITAF-positive HSCs in children with NASH. In conclusion, a more severe histological profile in paediatric NAFLD is associated with LITAF over-expression in HSCs, which in turn correlates with hepatic and circulating IL-1β levels outlining a panel of potential biomarkers of NASH-related liver damage. The in vitro study highlights the role of LITAF as a key regulator of the LPS-induced pro-inflammatory pattern in HSCs and suggests p38MAPK inhibitors as a possible therapeutic approach against hepatic inflammation in NASH.

MicroRNAs as controlled systems and controllers in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a multi-faceted condition including simple steatosis alone or associated with inflammation and ballooning (non-alcoholic steatohepatitis) and eventually fibrosis. The NAFLD incidence has increased over the last twenty years becoming the most frequent chronic liver disease in industrialized countries. Obesity, visceral adiposity, insulin resistance, and many other disorders that characterize metabolic syndrome are the major predisposing risk factors for NAFLD. Furthermore, different factors, including genetic background, epigenetic mechanisms and environmental factors, such as diet and physical exercise, contribute to NAFLD development and progression. Several lines of evidence demonstrate that specific microRNAs expression profiles are strongly associated with several pathological conditions including NAFLD. In NAFLD, microRNA deregulation in response to intrinsic genetic or epigenetic factors or environmental factors contributes to metabolic dysfunction. In this review we focused on microRNAs role both as controlled and controllers molecules in NAFLD development and/or their eventual value as non-invasive biomarkers of disease.

Emodin Prevents Intrahepatic Fat Accumulation, Inflammation and Redox Status Imbalance During Diet-Induced Hepatosteatosis in Rats

High-fat and/or high-carbohydrate diets may predispose to several metabolic disturbances including liver fatty infiltration (hepatosteatosis) or be associated with necro-inflammation and fibrosis (steatohepatitis). Several studies have emphasized the hepatoprotective effect of some natural agents. In this study, we investigated the potential therapeutic effects of the treatment with emodin, an anthraquinone derivative with anti-oxidant and anti-cancer abilities, in rats developing diet-induced hepatosteatosis and steatohepatitis. Sprague-Dawley rats were fed a standard diet (SD) for 15 weeks, or a high-fat/high-fructose diet (HFD/HF). After 5 weeks, emodin was added to the drinking water of some of the SD and HFD/HF rats. The experiment ended after an additional 10 weeks. Emodin-treated HFD/HF rats were protected from hepatosteatosis and metabolic derangements usually observed in HFD/HF animals. Furthermore, emodin exerted anti-inflammatory activity by inhibiting the HFD/HF-induced increase of tumor necrosis factor (TNF)-α. Emodin also affected the hepatocytes glutathione homeostasis and levels of the HFD/HF-induced increase of glutathionylated/phosphorylated phosphatase and tensin homolog (PTEN). In conclusion, we demonstrated that a natural agent such as emodin can prevent hepatosteatosis, preserving liver from pro-inflammatory and pro-oxidant damage caused by HFD/HF diet. These findings are promising, proposing emodin as a possible hindrance to progression of hepatosteatosis into steatohepatitis.

Urinary 1 H-NMR-based metabolic profiling of children with NAFLD undergoing VSL#3 treatment

Background:Nowadays, non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases in children. Our recent clinical trial demonstrated that dietary and VSL#3-based interventions may improve fatty liver by ultrasound and body mass index (BMI) after 4 months.Objectives:As in this short-term trial, as in others, it is impracticable to monitor response to therapy or treatment by liver biopsy, we aimed to identify a panel of potential non-invasive metabolic biomarkers by a urinary metabolic profiling.Methods:Urine samples from a group of 31 pediatric NAFLD patients, enrolled in a VSL#3 clinical trial, were analyzed by high-resolution proton nuclear magnetic resonance spectroscopy in combination with analysis of variance-Simultaneous Component Analysis model and multivariate data analyses. Urinary metabolic profiles were interpreted in terms of clinical patient feature, treatment and chronology pattern correlations.Results:VSL#3 treatment induced changes in NAFLD urinary metabolic phenotype mainly at level of host amino-acid metabolism (that is, valine, tyrosine, 3-amino-isobutyrate or β-aminoisobutyric acid (BAIBA)), nucleic acid degradation (pseudouridine), creatinine metabolism (methylguanidine) and secondarily at the level of gut microbial amino-acid metabolism (that is, 2-hydroxyisobutyrate from valine degradation). Furthermore, some of these metabolites correlated with clinical primary and secondary trial end points after VSL#3 treatment: tyrosine and the organic acid U4 positively with alanine aminotransferase (R=0.399, P=0.026) and BMI (R=0.36, P=0.045); BAIBA and tyrosine negatively with active glucagon-like-peptide 1 (R=−0.51, P=0.003; R=-0.41, P=0.021, respectively).Conclusions:VSL#3 treatment-dependent urinary metabotypes of NAFLD children may be considered as non-invasive effective biomarkers to evaluate the response to treatment.

Meta-Omic Platforms to Assist in the Understanding of NAFLD Gut Microbiota Alterations: Tools and Applications

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide as a result of the increasing prevalence of obesity, starting from early life stages. It is characterized by a spectrum of liver diseases ranging from simple fatty liver (NAFL) to steatohepatitis (NASH), with a possible progression to fibrosis, thus increasing liver-related morbidity and mortality. NAFLD development is driven by the co-action of several risk factors, including obesity and metabolic syndrome, which may be both genetically induced and diet-related. Recently, particular attention has been paid to the gut-liver axis, which may play a physio-pathological role in the onset and progression of the disease. The gut microbiota is intended to act as a bioreactor that can guarantee autonomous metabolic and immunological functions and that can drive functional strategies within the environment of the body in response to external stimuli. The complexity of the gut microbiota suggests that it behaves as an organ. Therefore, the concept of the gut-liver axis must be complemented with the gut-microbiota-liver network due to the high intricacy of the microbiota components and metabolic activities; these activities form the active diet-driven power plant of the host. Such complexity can only be revealed using systems biology, which can integrate clinical phenomics and gut microbiota data.

Focal adhesion kinase depletion reduces human hepatocellular carcinoma growth by repressing enhancer of zeste homolog 2

Hepatocellular carcinoma (HCC) is the most common type of liver cancer in humans. The focal adhesion tyrosine kinase (FAK) is often over-expressed in human HCC and FAK inhibition may reduce HCC cell invasiveness. However, the anti-oncogenic effect of FAK knockdown in HCC cells remains to be clarified. We found that FAK depletion in HCC cells reduced in vitro and in vivo tumorigenicity, by inducing G2/M arrest and apoptosis, decreasing anchorage-independent growth, and modulating the expression of several cancer-related genes. Among these genes, we showed that FAK silencing decreased transcription and nuclear localization of enhancer of zeste homolog 2 (EZH2) and its tri-methylation activity on lysine 27 of histone H3 (H3K27me3). Accordingly, FAK, EZH2 and H3K27me3 were concomitantly upregulated in human HCCs compared to non-tumor livers. In vitro experiments demonstrated that FAK affected EZH2 expression and function by modulating, at least in part, p53 and E2F2/3 transcriptional activity. Moreover, FAK silencing downregulated both EZH2 binding and histone H3K27me3 levels at the promoter of its target gene NOTCH2. Finally, we found that pharmacological inhibition of FAK activity resembled these effects although milder. In summary, we demonstrate that FAK depletion reduces HCC cell growth by affecting cancer-promoting genes including the pro-oncogene EZH2. Furthermore, we unveil a novel unprecedented FAK/EZH2 crosstalk in HCC cells, thus identifying a targetable network paving the way for new anticancer therapies.

Focal Adhesion Kinase: Insight into Molecular Roles and Functions in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Due to the high incidence of post-operative recurrence after current treatments, the identification of new and more effective drugs is required. In previous years, new targetable genes/pathways involved in HCC pathogenesis have been discovered through the help of high-throughput sequencing technologies. Mutations in TP53 and β-catenin genes are the most frequent aberrations in HCC. However, approaches able to reverse the effect of these mutations might be unpredictable. In fact, if the reactivation of proteins, such as p53 in tumours, holds great promise as anticancer therapy, there are studies arguing that chronic activation of these types of molecules may be deleterious. Thus, recently the efforts on potential targets have focused on actionable mutations, such as those occurring in the gene encoding for focal adhesion kinase (FAK). This tyrosine kinase, localized to cellular focal contacts, is over-expressed in a variety of human tumours, including HCC. Moreover, several lines of evidence demonstrated that FAK depletion or inhibition impair in vitro and in vivo HCC growth and metastasis. Here, we provide an overview of FAK expression and activity in the context of tumour biology, discussing the current evidence of its connection with HCC development and progression.