Genetic variants in STAT3 are associated with nonalcoholic fatty liver disease

Opportunities and challenges: interleukin-22 comprehensively regulates polycystic ovary syndrome from metabolic and immune aspects

Polycystic ovary syndrome (PCOS) is known as a prevalent but complicated gynecologic disease throughout the reproductive period. Typically, it is characterized by phenotypic manifestations of hyperandrogenism, polycystic ovary morphology, and persistent anovulation. For now, the therapeutic modality of PCOS is still a formidable challenge. Metabolic aberrations and immune challenge of chronic low-grade inflammatory state are significant in PCOS individuals. Recently, interleukin-22 (IL-22) has been shown to be therapeutically effective in immunological dysfunction and metabolic diseases, which suggests a role in the treatment of PCOS. In this review, we outline the potential mechanisms and limitations of IL-22 therapy in PCOS-related metabolic disorders including its regulation of insulin resistance, gut barrier, systemic inflammation, and hepatic steatosis to generate insights into developing novel strategies in clinical practice.

Exploring the Therapeutic Effects of Black Ginseng on Non-alcoholic Fatty Liver Disease by Using Network Pharmacology and Molecular Docking

This study aimed to investigate the therapeutic effect of BG on non-alcoholic fatty liver disease (NAFLD) using network pharmacology combined with the molecular docking strategy. The saponin composition of BG was analyzed by liquid chromatography-mass spectrometry (LC-MS) instrument. Then the network pharmacology was applied to explore the potential targets and related mechanisms of BG in the treatment of NAFLD. After screening out key targets, molecular docking was used to predict the binding modes between ginsenoside and target. Finally, a methionine and choline deficiency (MCD) diet-induced NAFLD mice model was established to further confirm the therapeutic effect of BG on NAFLD. Twenty-four ginsenosides were annotated based on the MS and tandem MS information. Ten proteins were screened out as key targets closely related to BG treatment of NAFLD. The molecular docking showed that most of the ginsenosides had good binding affinities with ALT1. The validation experiment revealed that BG administration could reduce serum ALT, and AST levels and improve the MCD diet-induced histological changes in liver tissue. Moreover, BG could upregulate the phosphorylation level of AKT in the liver of NAFLD mice, thereby exerting the therapeutic effect on NAFLD. Further studies on the active ginsenosides as well as their synergistic action on NAFLD will be required to reveal the underlying mechanisms in-depth. This study demonstrates that network pharmacological prediction in conjunction with molecular docking is a viable technique for screening the active chemicals and related targets of BG that can be applied to other herbal medicines.

Network Pharmacology-Based Analysis on the Potential Biological Mechanisms of Sinisan Against Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease in China. Sinisan (SNS) is a traditional Chinese medicine formula that has been widely used in treating chronic liver diseases, including NAFLD. However, its underlying biological mechanisms are still unclear. In this study, we employed a network pharmacology approach consisting of overlapped terms- (genes or pathway terms-) based analysis, protein-protein interaction (PPI) network-based analysis, and PPI clusters identification. Unlike the previous network pharmacology study, we used the shortest path length-based network proximity algorithm to evaluate the efficacy of SNS against NAFLD. And we also used random walk with restart (RWR) algorithm and Community Cluster (Glay) algorithm to identify important targets and clusters. The screening results showed that the mean shortest path length between genes of SNS and NAFLD was significantly smaller than degree-matched random ones. Six PPI clusters were identified and ten hub targets were obtained, including STAT3, CTNNB1, MAPK1, MAPK3, AGT, NQO1, TOP2A, FDFT1, ALDH4A1, and KCNH2. The experimental study indicated that SNS reduced hyperlipidemia, liver steatosis, and inflammation. Most importantly, JAK2/STAT3 signal was inhibited by SNS treatment and was recognized as the most important signal considering the network pharmacology part. This study provides a systems perspective to study the relationship between Chinese medicines and diseases and helps to discover potential mechanisms by which SNS ameliorates NAFLD.

Lipid nanoparticle formulations for targeting leukocytes with therapeutic RNA in liver fibrosis

Obesity and low-grade inflammation are promoters of a multitude of diseases including liver fibrosis. Activation of the mobile leukocytes has a major impact on the outcome of inflammatory disease and can hence foster or mitigate liver fibrosis. This renders immunological targets valuable for directed interventions using nanomedicines. Particularly, RNA-based drugs formulated as lipid nanoparticles (LNP) can open new avenues for the personalized treatment of liver fibrosis both through specific interference and via the induction of the expression of functional and therapeutic proteins. Using microfluidics technology, all components, including lipid-anchored targeting ligands, are assembled in a single-step mixing process. A highlight is set to immunologically relevant liver cell types that are most vulnerable for being reached by LNP. A selection of LNP from other therapeutic fields applicable for reaching these cells in liver fbrosis is summarized. Furthermore, recent proceedings and major obstacles in the field of these targeted LNP are presented.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

The Effectiveness of Mediterranean Diet in Nonalcoholic Fatty Liver Disease Clinical Course: An Intervention Study

Diet is a modifiable key factor targeted in prevention and management of nonalcoholic fatty liver disease (NAFLD). The aim was to study the effect of Mediterranean Diet (MedDiet) on clinical, biochemical, and inflammatory profile in NAFLD patients with simple steatosis. Potential associations of signal transducer and activator of transcription 3 (STAT3) rs2293152 genotype to diet composition and patients' profile were investigated. In this nonrandomized, open-label, 24-week prospective intervention study, 44 untreated NAFLD patients with nonsignificant fibrosis received nutritional counsel to increase adherence to MedDiet. Adherence to MedDiet was estimated with MedDietScore. Furthermore, we genotyped STAT3 rs2293152 single nucleotide polymorphism and performed clinical and inflammatory measurements. In all patients, MedDietScore increased and anthropometric indices improved, whereas liver imaging, liver fibrosis score, blood pressure, fasting glucose, glycated hemoglobin (HbA1c), C-reactive protein (CRP), visfatin, and oxidized low-density lipoprotein levels were also significantly ameliorated compared with baseline (P < .05). No association of STAT3 polymorphism with diet composition was found. Comparisons of mean differences between G- and C-carriers at the end point of the trial showed that only visfatin was significantly associated with the STAT3 genotype (-0.0 ± 4.6 vs. -4.2 ± 3.9, P = .04, respectively). Carrying the G-allele was associated with an increase of the visfatin levels (3.4 ± 1.5 ng/mL, P = .028). Our results show amelioration of clinical, biochemical, and inflammatory biomarkers in NAFLD patients in response to MedDiet. STAT3 rs2293152 G-carriers experienced more beneficial changes at the end of the intervention compared with baseline. An association between visfatin levels and STAT3 genotype has been shown for the first time.

Stanniocalcin 2 Ameliorates Hepatosteatosis Through Activation of STAT3 Signaling

Stanniocalcin 2 (STC2), a secreted glycoprotein hormone, regulates many biological processes, including cell proliferation, apoptosis, tumorigenesis, and atherosclerosis. However, its role in hepatic triglyceride metabolism remains unknown. In the present study, we found that expression levels of STC2 were significantly reduced in the livers of leptin-deficient and high fat diet-induced obese mice. Systemic administration of STC2 recombinant protein or adenovirus-mediated overexpression of STC2 markedly attenuated hepatosteatosis and hypertriglyceridemia in obese mice. At the molecular level, we found that STC2 activated the STAT3 signaling pathway to inhibit lipogenic gene expression. Consistently, in vitro studies further showed that inhibition of STAT3 signaling abolished the anti-steatotic effects of STC2. Together, our results revealed an important role of STC2 in the regulation of hepatic triglyceride metabolism, which might provide a potential therapeutic target for the treatment of fatty liver and related metabolic disorders.

The Interleukin-20 Cytokine Family in Liver Disease

The three main causes of inflammation and chronic injury in the liver are viral hepatitis, alcohol consumption, and non-alcoholic steatohepatitis, all of which can lead to liver fibrosis, cirrhosis, and hepatocellular carcinoma, which in turn may prompt the need for liver transplant. The interleukin (IL)-20 is a subfamily part of the IL-10 family of cytokines that helps the liver respond to damage and disease, they participate in the control of tissue homeostasis, and in the immunological responses developed in this organ. The best-studied member of the family in inflammatory balance of the liver is the IL-22 cytokine, which on the one hand may have a protective role in fibrosis progression but on the other may induce liver tissue susceptibility in hepatocellular carcinoma development. Other members of the family might also carry out this dual function, as some of them share IL receptor subunits and signal through common intracellular pathways. Investigators are starting to consider the potential for targeting IL-20 subfamily members in liver disease. The recently explored role of miRNA in the transcriptional regulation of IL-22 and IL-24 opens the door to promising new approaches for controlling the local immune response and limiting organ injury. The IL-20RA cytokine receptor has also been classified as being under miRNA control in non-alcoholic steatohepatitis. Moreover, researchers have proposed combining anti-inflammatory drugs with IL-22 as a hepatoprotective IL for alcoholic liver disease (ALD) treatment, and clinical trials of ILs for managing severe alcoholic-derived liver degeneration are ongoing. In this review, we focus on exploring the role of the IL-20 subfamily of cytokines in viral hepatitis, ALD, non-alcoholic steatohepatitis, and hepatocellular carcinoma, as well as delineating the main strategies explored so far in terms of therapeutic possibilities of the IL-20 subfamily of cytokines in liver disease.

Metastasis-associated lung adenocarcinoma transcript 1 as a common molecular driver in the pathogenesis of nonalcoholic steatohepatitis and chronic immune-mediated liver damage

Long noncoding RNAs (lncRNAs) are functional molecules that orchestrate gene expression. To identify lncRNAs involved in nonalcoholic fatty liver disease (NAFLD) severity, we performed a multiscale study that included: (a) systems biology modeling that indicated metastasis‐associated lung adenocarcinoma transcript 1 (MALAT1) as a candidate lncRNA for exploring disease‐related associations, (b) translational exploration in the clinical setting, and (c) mechanistic modeling. MALAT1 liver profiling was performed in three consecutive phases, including an exploratory stage (liver samples from patients with NAFLD who were morbidly obese [n = 47] and from 13 individuals with normal liver histology); a replication stage (patients with NAFLD and metabolic syndrome [n =49]); and a hypothesis‐driven stage (patients with chronic hepatitis C and autoimmune liver diseases, [n = 65]). Liver abundance of MALAT1 was associated with NAFLD severity (P = 1 × 10^–6); MALAT1 expression levels were up‐regulated 1.75‐fold (P = 0.029) and 3.6‐fold (P = 0.012) in patients with nonalcoholic steatohepatitis compared to those diagnosed with simple steatosis (discovery and replication set, respectively; analysis of covariance adjusted by age, homeostasis model assessment, and body mass index). Quantification of liver vascular endothelial growth factor A messenger RNA, a target of MALAT1, revealed a significant correlation between the two RNAs (R, 0.58; P = 5 × 10^–8). Increased levels of MALAT1 were also associated with autoimmune liver diseases. Interactome assessment uncovered significant biological pathways, including Janus kinase‐signal transducers and activators of transcription and response to interferon‐γ. Conclusion: Deregulated expression of MALAT1 stratifies patients into the histologic phenotypes associated with NAFLD severity. MALAT1 up‐regulation seems to be a common molecular mechanism in immune‐mediated chronic inflammatory liver damage. This suggests that convergent pathophenotypes (inflammation and fibrosis) share similar molecular mediators. (Hepatology Communications 2018;2:654‐665)

Identification of key genes in non‑alcoholic fatty liver disease progression based on bioinformatics analysis

Due to economic development and lifestyle changes, the incidence of non-alcoholic fatty liver disease (NAFLD) has gradually increased in recent years. However, the pathogenesis of NAFLD is not yet fully understood. To identify candidate genes that contribute to the development and progression of NAFLD, two microarray datasets were downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified and functional enrichment analyses were performed. A protein-protein interaction network was constructed and modules were extracted using the Search Tool for the Retrieval of Interacting Genes and Cytoscape. The enriched functions and pathways of the DEGs included ‘cellular macromolecule biosynthetic process’, ‘cellular response to chemical stimulus’, ‘extracellular matrix organization’, ‘metabolic pathways’, ‘insulin resistance’ and ‘forkhead box protein O1 signaling pathway’. The DEGs, including type-1 angiotensin II receptor, formin-binding protein 1-like, RNA-binding protein with serine-rich domain 1, Ras-related C3 botulinum toxin substrate 1 and polyubiquitin-C, were identified using multiple bioinformatics methods and validated in vitro with reverse transcription-quantitative polymerase chain reaction analysis. In conclusion, five hub genes were identified in the present study, and they may aid in understanding of the molecular mechanisms underlying the development and progression of NAFLD.

Genetic variation in long noncoding RNAs and the risk of nonalcoholic fatty liver disease

The human transcriptome comprises a myriad of non protein-coding RNA species, including long noncoding RNAs (lncRNAs), which have a remarkable role in transcriptional and epigenetic regulation. We hypothesized that variants in lncRNAs influence the susceptibility to nonalcoholic fatty liver disease (NAFLD). Using next generation sequencing, we performed a survey of genetic variation associated with randomly selected lncRNA-genomic regions located within both experimentally validated and computationally predicted regulatory elements. We used a two-stage (exploratory, n = 96 and replication, n = 390) case-control approach that included well-characterized patients with NAFLD diagnosed by liver biopsy. We sequenced > 263 megabase pairs at quality score > Q17, in a total of 2,027,565 reads, including 170 lncRNA-genomic regions. In the sequencing analysis and the validated dataset, we found that the rs2829145 A/G located in a lncRNA (lnc-JAM2-6) was associated with NAFLD and the disease severity. Prediction of regulatory elements in lnc-JAM2-6 showed potential sequence-specific binding motifs of oncogenes MAFK and JUND, and the transcription factor CEBPB that is involved in inflammatory response. The A-allele was significantly associated with NAFLD as disease trait (p = 0.0081) and the disease severity (NASH-nonalcoholic steatohepatitis vs controls: OR 2.36 [95% CI: 1.54-3.62], p = 0.000078). The A-allele carriers also have significantly higher body mass index and glucose-related traits compared with homozygous GG. Hence, our results suggest that variation in lncRNAs contributes to NAFLD severity, while pointing toward the complexity of the genetic component of NAFLD, which involves still unexplored regulatory regions of the genome.

Polychlorinated biphenyls disrupt hepatic epidermal growth factor receptor signaling

1. Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that disrupt hepatic xenobiotic and intermediary metabolism, leading to metabolic syndrome and nonalcoholic steatohepatitis (NASH). 2. Since phenobarbital indirectly activates Constitutive Androstane Receptor (CAR) by antagonizing growth factor binding to the epidermal growth factor receptor (EGFR), we hypothesized that PCBs may also diminish EGFR signaling. 3. The effects of the PCB mixture Aroclor 1260 on the protein phosphorylation cascade triggered by EGFR activation were determined in murine (in vitro and in vivo) and human models (in vitro). EGFR tyrosine residue phosphorylation was decreased by PCBs in all models tested. 4. The IC₅₀ values for Aroclor 1260 concentrations that decreased Y1173 phosphorylation of EGFR were similar in murine AML-12 and human HepG2 cells (∼2-4 μg/mL). Both dioxin and non-dioxin-like PCB congeners decreased EGFR phosphorylation in cell culture. 5. PCB treatment reduced phosphorylation of downstream EGFR effectors including Akt and mTOR, as well as other phosphoprotein targets including STAT3 and c-RAF in vivo. 6. PCBs diminish EGFR signaling in human and murine hepatocyte models and may dysregulate critical phosphoprotein regulators of energy metabolism and nutrition, providing a new mechanism of action in environmental diseases.

Genetic predisposition in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease whose prevalence has reached global epidemic proportions. Although the disease is relatively benign in the early stages, when severe clinical forms, including nonalcoholic steatohepatitis (NASH), cirrhosis and even hepatocellular carcinoma, occur, they result in worsening the long-term prognosis. A growing body of evidence indicates that NAFLD develops from a complex process in which many factors, including genetic susceptibility and environmental insults, are involved. In this review, we focused on the genetic component of NAFLD, with special emphasis on the role of genetics in the disease pathogenesis and natural history. Insights into the topic of the genetic susceptibility in lean individuals with NAFLD and the potential use of genetic tests in identifying individuals at risk are also discussed.

Association between PNPLA3 (rs738409), LYPLAL1 (rs12137855), PPP1R3B (rs4240624), GCKR (rs780094), and elevated transaminase levels in overweight/obese Mexican adults

There is scarce information about the link between specific single-nucleotide polymorphisms (SNPs) and risk of liver disease among Latinos, despite the disproportionate burden of disease among this population. Our aim was to investigate nine SNPs in or near the following genes: PNPLA3, LYPLAL1, PPP1R3B, GCKR, NCAN, IRS1, PPARG, and ADIPOR2 and examine their association with persistently elevated alanine aminotransferase (ALT) or aspartate aminotransferase (AST) levels in Mexican adults. Data and samples were collected from 741 participants in the Mexican Health Worker Cohort Study, in Cuernavaca, Mexico. We identified 207 cases who had persistently elevated levels of ALT or AST (≥40 U/L) and 534 controls with at least two consecutive normal ALT or AST results in a 6 month period, during 2004-2006 and 2011-2013. TaqMan assays were used to genotype the SNPs. The risk allele of PNPLA3 rs738409 was found to be associated with persistently elevated levels of ALT or AST, adjusting for age, sex, BMI, type 2 diabetes, and ancestry: (OR 2.28, 95 % CI 1.13, 4.58). A significant association was found between the LYPLAL1, PPP1R3B, and GCKR risk alleles and elevated ALT or AST levels among overweight/obese adults. These results suggest that among Mexicans, the PNPLA3 (rs738409), LYPLAL1 (rs12137855), PPP1R3B (rs4240624), and GCKR (rs780094) polymorphisms may be associated with a greater risk of chronic liver disease among overweight adults. This study is the first to examine these nine SNPs in a sample of adults in Mexico.

APOC3 rs2070666 Is Associated with the Hepatic Steatosis Independently of PNPLA3 rs738409 in Chinese Han Patients with Nonalcoholic Fatty Liver Diseases

BACKGROUND AND AIM

The association between nonalcoholic fatty liver disease (NAFLD) and apolipoprotein C3 gene (APOC3) promoter region single-nucleotide polymorphisms (SNPs) rs2854117 and rs2854116 is controversial. The aim of this study was to investigate the relationship between other polymorphisms of APOC3 and NAFLD in Chinese.

METHODS

Fifty-nine liver biopsy-proven NAFLD patients and 72 healthy control subjects were recruited to a cohort representing Chinese Han population. The polymorphisms in the exons and flanking regions of APOC3 and patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 polymorphisms were genotyped.

RESULTS

Among the five SNPs (rs4225, rs4520, rs5128, rs2070666, and rs2070667) in APOC3, only rs2070666 (c.179 + 62 T/A) was significantly different in genotype and allele frequency (both p < 0.01) between groups of NAFLD and control. After adjusting for sex, age, serum triglycerides, total cholesterol, body mass index, and the PNPLA3 rs738409 polymorphism, the APOC3 rs2070666 A allele was an independent risk factor for NAFLD with an odds ratio (OR) of 3.683 and 95 % confidence interval (CI) of 1.037-13.084. The APOC3 rs2070666 A allele was linked to the fourth quartile of the controlled attenuation parameter values (OR 2.769, 95 % CI 1.002-7.651) in 131 subjects, and also linked to the significant histological steatosis (OR 4.986, 95 % CI 1.020-24.371), but neither to liver stiffness measurement values nor to hepatic histological activity and fibrosis in NAFLD patients.

CONCLUSIONS

The APOC3 rs2070666 A allele is a risk factor for NAFLD independent of obesity, dyslipidemia, and PNPLA3 rs738409, and it might contribute to increased liver fat content in Chinese Han population.

I148M variant in PNPLA3 reduces central adiposity and metabolic disease risks while increasing nonalcoholic fatty liver disease

BACKGROUND & AIMS

The I148M variant because of the substitution of C to G in PNPLA3 (rs738409) is associated with the increased risk of nonalcoholic fatty liver disease (NAFLD). In liver, I148M variant reduces hydrolytic function of PNPLA3, which results in hepatic steatosis; however, its association with the other clinical phenotype such as adiposity and metabolic diseases is not well established.

METHODS

To identify the impact of I148M variant on clinical risk factors of NAFLD, we recruited 1363 generally healthy Korean males after excluding alcoholic and secondary causes of hepatic steatosis. Central adiposity was assessed by computed tomography, and hepatic steatosis was evaluated by abdominal ultrasonography.

RESULTS

The participants were predominantly middle-aged (49.0 ± 7.1 years; range 30-60 years), and the frequency of NAFLD was 44.2%. The rs738409-G allele carriers had a 1.19-fold increased risk for NAFLD (minor allele frequency 0.43; allelic odds ratio 1.38; P = 4.3 × 10(-5) ). Interestingly, the rs738409 GG carriers showed significantly lower levels of visceral and subcutaneous adiposity (P < 0.001 and = 0.015, respectively), BMI (P < 0.001), triglycerides (P < 0.001) and insulin resistance (P = 0.002) compared to CC carriers. These negative associations between clinical risk factors and rs738409-G dosage were more prominent in non-NAFLD group compared to those in NAFLD group.

CONCLUSIONS

The I148M variant, although increasing the risk of NAFLD, was associated with reduced levels of central adiposity, BMI, serum triglycerides and insulin resistance, suggesting differential roles in fat storage and distribution according to cell types and metabolic status.

Genetic, metabolic and environmental factors involved in the development of liver cirrhosis in Mexico

Liver cirrhosis (LC) is a chronic illness caused by inflammatory responses and progressive fibrosis. Globally, the most common causes of chronic liver disease include persistent alcohol abuse, followed by viral hepatitis infections and nonalcoholic fatty liver disease. However, regardless of the etiological factors, the susceptibility and degree of liver damage may be influenced by genetic polymorphisms that are associated with distinct ethnic and cultural backgrounds. Consequently, metabolic genes are influenced by variable environmental lifestyle factors, such as diet, physical inactivity, and emotional stress, which are associated with regional differences among populations. This Topic Highlight will focus on the genetic and environmental factors that may influence the metabolism of alcohol and nutrients in the setting of distinct etiologies of liver disease. The interaction between genes and environment in the current-day admixed population, Mestizo and Native Mexican, will be described. Additionally, genes involved in immune regulation, insulin sensitivity, oxidative stress and extracellular matrix deposition may modulate the degree of severity. In conclusion, LC is a complex disease. The onset, progression, and clinical outcome of LC among the Mexican population are influenced by specific genetic and environmental factors. Among these are an admixed genome with a heterogenic distribution of European, Amerindian and African ancestry; a high score of alcohol consumption; viral infections; a hepatopathogenic diet; and a high prevalence of obesity. The variance in risk factors among populations suggests that intervention strategies directed towards the prevention and management of LC should be tailored according to such population-based features.

Berry intake changes hepatic gene expression and DNA methylation patterns associated with high-fat diet

The liver is a critical organ for regulation of energy homeostasis and fatty liver disease is closely associated with obesity and insulin resistance. We have previously found that lingonberries, blackcurrants and bilberries prevent, whereas açai berries exacerbate, the development of hepatic steatosis and obesity in the high-fat (HF)-fed C57BL/6J mouse model. In this follow-up study, we investigated the mechanisms behind these effects. Genome-wide hepatic gene expression profiling indicates that the protective effects of lingonberries and bilberries are accounted for by several-fold downregulation of genes involved in acute-phase and inflammatory pathways (e.g. Saa1, Cxcl1, Lcn2). In contrast, açai-fed mice exhibit marked upregulation of genes associated with steatosis (e.g. Cfd, Cidea, Crat) and lipid and cholesterol biosynthesis, which is in line with the exacerbation of HF-induced hepatic steatosis in these mice. In silico transcription factor analysis together with immunoblot analysis identified NF-κB, STAT3 and mTOR as upstream regulators involved in mediating the observed transcriptional effects. To gain further insight into mechanisms involved in the gene expression changes, the HELP-tagging assay was used to identify differentially methylated CpG sites. Compared to the HF control group, lingonberries induced genome-wide hypermethylation and specific hypermethylation of Ncor2, encoding the corepressor NCoR/SMRT implicated in the regulation of pathways of metabolic homeostasis and inflammation. We conclude that the beneficial metabolic effects of lingonberries and bilberries are associated with downregulation of inflammatory pathways, whereas for blackcurrants, exerting similar metabolic effects, different mechanisms of action appear to dominate. NF-κB, STAT3 and mTOR are potential targets of the health-promoting effects of berries.

Genetic analysis of nonalcoholic fatty liver disease within a Caribbean-Hispanic population

We explored potential genetic risk factors implicated in nonalcoholic fatty liver disease (NAFLD) within a Caribbean–Hispanic population in New York City. A total of 316 individuals including 40 subjects with biopsy‐proven NAFLD, 24 ethnically matched non‐NAFLD controls, and a 252 ethnically mixed random sampling of Bronx County, New York were analyzed. Genotype analysis was performed to determine allelic frequencies of 74 known single‐nucleotide polymorphisms (SNPs) associated with NAFLD risk based on previous genome‐wide association study (GWAS) and candidate gene studies. Additionally, the entire coding region of PNPLA3, a gene showing the strongest association to NAFLD was subjected to Sanger sequencing. Results suggest that both rare and common DNA variations in PNPLA3 and SAMM50 may be correlated with NAFLD in this small population study, while common DNA variations in CHUK and ERLIN1, may have a protective interaction. Common SNPs in ENPP1 and ABCC2 have suggestive association with fatty liver, but with less compelling significance. In conclusion, Hispanic patients of Caribbean ancestry may have different interactions with NAFLD genetic modifiers; therefore, further investigation with a larger sample size, into this Caribbean–Hispanic population is warranted.

Adipocytokine expression associated with miRNA regulation and diagnosis of NASH in obese patients with NAFLD

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with visceral adiposity. The secretion of adipocytokines from white adipose tissue (WAT) promoting necroinflammation, and/or fibrosis may play important roles in the pathogenesis of non-alcoholic steatohepatits (NASH). In a previous study, reduced expression of a number of miRNA species in WAT concomitant with histological diagnosis of NASH was successfully demonstrated. In this study, we measure the expression of several predicted miRNA regulatory targets relevant to NAFLD and NASH including mTOR, FAS, IL20, SEMA4C, ADAMTS6 and IL13RA. We then examine hepatic receptor expression by immunohistochemical staining and qPCR.

METHODS

White adipose tissue was collected from 24 obese patients undergoing bariatric surgery with biopsy-proven NAFLD. Extracted total RNAs from the adipose tissue were reverse transcribed and profiled for gene expression by qPCR for specific individual mRNA targets defined after identification by any two of three of the major prediction services: miRanda, TarBase or PicTar. All liver biopsies were read by a singly hepatopathologist. The same liver tissue was used to stain for hepatic receptor expression for FASLG and IL20. Additionally, the same tissue was used for qPCR for FASLG and IL20.

RESULTS

Increases in the expression of IL13RA, mTOR, IL20, SEMA4C and FAS were detected and negatively correlated with putative regulatory miRNA. Hepatic receptor expression for FAS and IL20 was noted to correlate with markers of inflammation and severity of NAFLD.

CONCLUSION

These data are consistent with the hypothesis that specific adipocytokines secreted by WAT will impact hepatic tissue and participate in the pathogenesis of NASH.

Systematic review of genetic association studies involving histologically confirmed non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease has an increasing prevalence in Western countries, affecting up to 20% of the population.

A network biology workflow to study transcriptomics data of the diabetic liver

BACKGROUND

Nowadays a broad collection of transcriptomics data is publicly available in online repositories. Methods for analyzing these data often aim at deciphering the influence of gene expression at the process level. Biological pathway diagrams depict known processes and capture the interactions of gene products and metabolites, information that is essential for the computational analysis and interpretation of transcriptomics data.The present study describes a comprehensive network biology workflow that integrates differential gene expression in the human diabetic liver with pathway information by building a network of interconnected pathways. Worldwide, the incidence of type 2 diabetes mellitus is increasing dramatically, and to better understand this multifactorial disease, more insight into the concerted action of the disease-related processes is needed. The liver is a key player in metabolic diseases and diabetic patients often develop non-alcoholic fatty liver disease.

RESULTS

A publicly available dataset comparing the liver transcriptome from lean and healthy vs. obese and insulin-resistant subjects was selected after a thorough analysis. Pathway analysis revealed seven significantly altered pathways in the WikiPathways human pathway collection. These pathways were then merged into one combined network with 408 gene products, 38 metabolites and 5 pathway nodes. Further analysis highlighted 17 nodes present in multiple pathways, and revealed the connections between different pathways in the network. The integration of transcription factor-gene interactions from the ENCODE project identified new links between the pathways on a regulatory level. The extension of the network with known drug-target interactions from DrugBank allows for a more complete study of drug actions and helps with the identification of other drugs that target proteins up- or downstream which might interfere with the action or efficiency of a drug.

CONCLUSIONS

The described network biology workflow uses state-of-the-art pathway and network analysis methods to study the rewiring of the diabetic liver. The integration of experimental data and knowledge on disease-affected biological pathways, including regulatory elements like transcription factors or drugs, leads to improved insights and a clearer illustration of the overall process. It also provides a resource for building new hypotheses for further follow-up studies. The approach is highly generic and can be applied in different research fields.

Personalizing care for nonalcoholic fatty liver disease patients: what are the research priorities?

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease whose prevalence has reached global epidemic proportions, not only in adults but also in children. From a clinical point of view, NAFLD stems a myriad of challenges to physicians, researchers and patients. In this study, we revise the current knowledge and recent insights on NAFLD pathogenesis and diagnosis in the context of a personalized perspective with special focus on the following issues: noninvasive biomarkers for the evaluation of disease severity and progression, lifestyle-related patients' recommendations, risk prediction of disease by genetic testing, management of NAFLD-associated comorbidities and patient-oriented therapeutic intervention strategies.

Non-alcoholic fatty liver disease: the role of nuclear receptors and circadian rhythmicity

Non-alcoholic fatty liver disease (NAFLD) is the accumulation of triglycerides in the hepatocytes in the absence of excess alcohol intake, and is caused by an imbalance between hepatic synthesis and breakdown of fats, as well as fatty acid storage and disposal. Liver metabolic pathways are driven by circadian biological clocks, and hepatic health is maintained by proper timing of circadian patterns of metabolic gene expression with the alternation of anabolic processes corresponding to feeding/activity during wake times, and catabolic processes characterizing fasting/resting during sleep. A number of nuclear receptors in the liver are expressed rhythmically, bind hormones and metabolites, sense energy flux and expenditure, and connect the metabolic pathways to the molecular clockwork throughout the 24-h day. In this review, we describe the role played by the nuclear receptors in the genesis of NAFLD in relationship with the circadian clock circuitry.

MTTP polymorphisms and susceptibility to non-alcoholic fatty liver disease in a Han Chinese population

BACKGROUND

The microsomal triglyceride transfer protein (MTP) is required for the assembly and secretion of apolipoprotein B (ApoB)-containing lipoproteins from the liver and intestine. Previous studies showed that functional polymorphisms in the MTTP gene correspond to lower LDL levels and protect against other traits of the metabolic syndrome.

AIMS

Here, we aimed to investigate whether MTTP single nucleotide polymorphisms (SNPs) and their predicted haplotypes of linkage disequilibrium blocks contribute to non-alcoholic fatty liver disease (NAFLD) susceptibility in a Han Chinese population.

METHODS

Seven tag SNPs in the MTTP gene were selected and genotyped in a frequency-matched case-control study in a population from Fuzhou City, China. We enrolled 580 patients with NAFLD and 580 healthy controls.

RESULTS

In the multivariate logistic regression analysis, the rs1800804 (-164 T/C) was associated with an increased risk of NAFLD, while the rs1057613 A/G and rs3805335 C/T SNPs were associated with a decreased risk of NAFLD. The cumulative effect of the rs1800804 (-164 T/C), rs1057613 and rs3805335 was estimated, and a significant increased trend in the risk of NAFLD with increasing genetic risk score was observed (adjusted P(trend) = 0.014). Furthermore, the results of haplotype analysis suggested that the haplotype GC in block 1 containing the -164 C allele was associated with an increased risk of NAFLD, while haplotype TGTTC in block 2 was associated with a decreased risk of NAFLD.

CONCLUSIONS

Our data show that MTTP genetic polymorphisms influence the susceptibility to developing NAFLD independently or jointly in the Han Chinese population.

Association of genetic variation in adaptor protein APPL1/APPL2 loci with non-alcoholic fatty liver disease

The importance of genetics and epigenetic changes in the pathogenesis of non alcoholic fatty liver disease (NAFLD) has been increasingly recognized. Adiponectin has a central role in regulating glucose and lipid metabolism and controlling inflammation in insulin-sensitive tissues and low adiponectin levels have been linked to NAFLD. APPL1 and APPL2 are adaptor proteins that interact with the intracellular region of adiponectin receptors and mediate adiponectin signaling and its effects on metabolism. The aim of our study was the evaluation of a potential association between variants at APPL1 and APPL2 loci and NAFLD occurrence. The impact on liver damage and hepatic steatosis severity has been also evaluated. To this aim allele frequency and genotype distribution of APPL1- rs3806622 and -rs4640525 and APPL2-rs 11112412 variants were evaluated in 223 subjects with clinical diagnosis of NAFLD and compared with 231 healthy subjects. The impact of APPL1 and APPL2 SNPs on liver damage and hepatic steatosis severity has been also evaluated. The minor-allele combination APPL1-C/APPL2-A was associated with an increased risk of NAFLD (OR = 2.50 95% CI 1.45–4.32; p<0.001) even after adjustment for age, sex, body mass index, insulin resistance (HOMA-IR), triglycerides and adiponectin levels. This allele combination carrier had higher plasma alanine aminotransferase levels (Diff = 15.08 [7.60–22.57] p = 0.001) and an increased frequency of severe steatosis compared to the reference allele combination (OR = 3.88; 95% CI 1.582–9.531; p<0.001). In conclusion, C-APPL1/A-APPL2 allele combination is associated with NAFLD occurrence, with a more severe hepatic steatosis grade and with a reduced adiponectin cytoprotective effect on liver.

Fetal metabolic programming and epigenetic modifications: a systems biology approach

A growing body of evidence supports the notion that epigenetic changes such as DNA methylation and histone modifications, both involving chromatin remodeling, contribute to fetal metabolic programming. We use a combination of gene-protein enrichment analysis resources along with functional annotations and protein interaction networks for an integrative approach to understanding the mechanisms underlying fetal metabolic programming. Systems biology approaches suggested that fetal adaptation to an impaired nutritional environment presumes profound changes in gene expression that involve regulation of tissue-specific patterns of methylated cytosine residues, modulation of the histone acetylation-deacetylation switch, cell differentiation, and stem cell pluripotency. The hypothalamus and the liver seem to be differently involved. In addition, new putative explanations have emerged about the question of whether in utero overnutrition modulates fetal metabolic programming in the same fashion as that of a maternal environment of undernutrition, suggesting that the mechanisms behind these two fetal nutritional imbalances are different. In conclusion, intrauterine growth restriction is most likely to be associated with the induction of persistent changes in tissue structure and functionality. Conversely, a maternal obesogenic environment is most probably associated with metabolic reprogramming of glucose and lipid metabolism, as well as future risk of metabolic syndrome (MS), fatty liver, and insulin (INS) resistance.

Genetic signatures in choline and 1-carbon metabolism are associated with the severity of hepatic steatosis

Choline metabolism is important for very low-density lipoprotein secretion, making this nutritional pathway an important contributor to hepatic lipid balance. The purpose of this study was to assess whether the cumulative effects of multiple single nucleotide polymorphisms (SNPs) across genes of choline/1-carbon metabolism and functionally related pathways increase susceptibility to developing hepatic steatosis. In biopsy-characterized cases of nonalcoholic fatty liver disease and controls, we assessed 260 SNPs across 21 genes in choline/1-carbon metabolism. When SNPs were examined individually, using logistic regression, we only identified a single SNP (PNPLA3 rs738409) that was significantly associated with severity of hepatic steatosis after adjusting for confounders and multiple comparisons (P=0.02). However, when groupings of SNPs in similar metabolic pathways were defined using unsupervised hierarchical clustering, we identified groups of subjects with shared SNP signatures that were significantly correlated with steatosis burden (P=0.0002). The lowest and highest steatosis clusters could also be differentiated by ethnicity. However, unique SNP patterns defined steatosis burden irrespective of ethnicity. Our results suggest that analysis of SNP patterns in genes of choline/1-carbon metabolism may be useful for prediction of severity of steatosis in specific subsets of people, and the metabolic inefficiencies caused by these SNPs should be examined further.

Genetic variants in PNPLA3 and risk of non-alcoholic fatty liver disease in a Han Chinese population

We investigated the possible association between genetic variants in the Patatin like phospholipase-3 (PNPLA3) gene and nonalcoholic fatty liver disease (NAFLD) in a Han Chinese population. We evaluated twelve tagging single-nucleotide polymorphisms (tSNPs) of the PNPLA3 gene in a frequency matched case–control study from Fuzhou city of China (553 cases, 553 controls). In the multivariate logistic regression analysis, the rs738409 GG or GC, and rs139051 TT genotypes were found to be associated with increased risk of NAFLD, and a significant trend of increased risk with increasing numbers of risk genotype was observed in the cumulative effect analysis of these single nucleotide polymorphisms. Furthermore, haplotype association analysis showed that, compared with the most common haplotype, the CAAGAATGCGTG and CGAAGGTGTCCG haplotypes conferred a statistically significant increased risk for NAFLD, while the CGGGAACCCGCG haplotype decreased the risk of NAFLD. Moreover, rs738409 C>G appeared to have a multiplicative joint effect with tea drinking (P<0.005) and an additive joint effect with obesity (Interaction contrast ratio (ICR) = 2.31, 95% CI: 0.7–8.86), hypertriglyceridemia (ICR = 3.07, 95% CI: 0.98–5.09) or hypertension (ICR = 1.74, 95% CI: 0.52–3.12). Our data suggests that PNPLA3 genetic polymorphisms might influence the susceptibility to NAFLD development independently or jointly in Han Chinese.

The genetic epidemiology of nonalcoholic fatty liver disease: toward a personalized medicine

The understanding of the genetic bases of complex diseases such as nonalcoholic fatty liver disease opens new opportunities and challenges. This article explores new tools designed toward moving genomic data into clinical medicine, providing putative answers to more practical questions.

Genetic factors associated with the presence and progression of nonalcoholic fatty liver disease: a narrative review

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world. Whereas insulin resistance and obesity are considered major risk factors for the development and progression of NAFLD, the genetic underpinnings are unclear. Before 2008, candidate gene studies based on prior knowledge of pathophysiology of fatty liver yielded conflicting results. In 2008, Romeo et al. published the first genome wide association study and reported the strongest genetic signal for the presence of fatty liver (PNPLA3, patatin-like phospholipase domain containing 3; rs738409). Since then, two additional genome wide scans were published and identified 9 additional genetic variants. Whereas these results shed light into the understanding of the genetics of NAFLD, most of associations have not been replicated in independent samples and, therefore, remain undetermined the significance of these findings. This review aims to summarize the understanding of genetic epidemiology of NAFLD and highlights the gaps in knowledge.

Association between polymorphisms in the signal transducer and activator of transcription and dilated cardiomyopathy in the Chinese Han population

The signal transduction pathways mediating the progress of heart failure have been intensively studied. Altered signaling of the signal transducers and activators of transcription (STATs), which play important roles in regulating cell proliferation, differentiation, and apoptosis, has been observed in the heart. We conducted a pilot study to test whether single nucleotide polymorphisms (SNPs) in STATs were associated with dilated cardiomyopathy (DCM). Genotypes of two SNPs of STATs (rs6503691 C/T in exon 1 of STAT5B and rs4796793 C/G in the 5' region of STAT3) in 251 DCM patients and 484 control subjects were determined with the use of PCR-restriction fragment length polymorphism assay and TaqMan assay, respectively. Significantly increased DCM risk was found to be associated with T allele of rs6503691 (P = 0.012, OR = 1.37, 95% CI = 1.07-1.74). We found that increased DCM risk statistically significantly associated with rs6503691 in a dominant model (P = 0.009, OR = 1.50, 95% CI = 1.11-2.04). No association between DCM risk and rs4796793 was observed (P = 0.706, OR = 1.05, 95% CI = 0.83-1.32). The present pilot study provides evidence that both rs6503691 T allele and CT/TT genotypes, but not rs4796793 C/G in the 5' region of STAT3, are associated with a significantly increased risk of DCM, indicating that common genetic polymorphism in STATs is associated with DCM.

Mitochondrial DNA copy number is modulated by genetic variation in the signal transducer and activator of transcription 3 (STAT3)

The regulation of mitochondrial DNA (mtDNA) copy number not only is critical for the maintenance of the normal mitochondrial function but has a strong clinical significance. A recent report revealed that the signal transducer and activator of transcription 3 (STAT3) is involved in the regulation of the mitochondrial function and is required for the optimal function of the electron transport chain. In this study, we explored whether gene variants in the STAT3 influence the leukocyte mtDNA copy number. Clinical data and blood samples were collected from 179 subjects (aged 52.8 ± 0.9 years). Mitochondrial DNA quantification using nuclear DNA (nDNA) as a reference was carried out by a real-time quantitative polymerase chain reaction method; results are presented as the mtDNA/nDNA ratio. We selected 3 tag single nucleotide polymorphisms showing a minor allele frequency greater than 10% (rs2293152 C/G, rs6503695 C/T, and rs9891119 A/C), representing 24 polymorphic sites of the STAT3 (r(2) > 0.8). We observed a significant association between mtDNA/nDNA ratio and both rs6503695 and rs9891119, adjusted by age and homeostasis model assessment index. The proportion of the total variance of the mtDNA/nDNA ratio accounted for by the rs6503695 and rs9891119 genotypes was 4.7% and 6.53%, respectively. Common variation in the STAT3 may influence mtDNA copy number.

Sensitized phenotypic screening identifies gene dosage sensitive region on chromosome 11 that predisposes to disease in mice

The identification of susceptibility genes for human disease is a major goal of current biomedical research. Both sequence and structural variation have emerged as major genetic sources of phenotypic variability and growing evidence points to copy number variation as a particularly important source of susceptibility for disease. Here we propose and validate a strategy to identify genes in which changes in dosage alter susceptibility to disease-relevant phenotypes in the mouse. Our approach relies on sensitized phenotypic screening of megabase-sized chromosomal deletion and deficiency lines carrying altered copy numbers of ∼30 linked genes. This approach offers several advantages as a method to systematically identify genes involved in disease susceptibility. To examine the feasibility of such a screen, we performed sensitized phenotyping in five therapeutic areas (metabolic syndrome, immune dysfunction, atherosclerosis, cancer and behaviour) of a 0.8 Mb reciprocal chromosomal duplication and deficiency on chromosome 11 containing 27 genes. Gene dosage in the region significantly affected risk for high-fat diet-induced metabolic syndrome, antigen-induced immune hypersensitivity, ApoE-induced atherosclerosis, and home cage activity. Follow up studies on individual gene knockouts for two candidates in the region showed that copy number variation in Stat5 was responsible for the phenotypic variation in antigen-induced immune hypersensitivity and metabolic syndrome. These data demonstrate the power of sensitized phenotypic screening of segmental aneuploidy lines to identify disease susceptibility genes.

Genetic determinants of hepatic steatosis in man

Hepatic steatosis is one of the most common liver disorders in the general population. The main cause of hepatic steatosis is nonalcoholic fatty liver disease (NAFLD), representing the hepatic component of the metabolic syndrome, which is characterized by type 2 diabetes, obesity, and dyslipidemia. Insulin resistance and excess adiposity are considered to play key roles in the pathogenesis of NAFLD. Although the risk factors for NAFLD are well established, the genetic basis of hepatic steatosis is largely unknown. Here we review recent progress on genomic variants and their association with hepatic steatosis and discuss the potential impact of these genetic studies on clinical practice. Identifying the genetic determinants of hepatic steatosis will lead to a better understanding of the pathogenesis and progression of NAFLD.

A nonsynonymous gene variant in the adiponutrin gene is associated with nonalcoholic fatty liver disease severity

We explored the role of the adiponutrin (PNPLA3) nonsynonymous-rs738409 single nucleotide polymorphism (SNP) in genetic susceptibility to nonalcoholic fatty liver disease (NAFLD) and whether this SNP contributes to the severity of histological disease. Two hundred sixty-six individuals were evaluated in a case-control association study, which included 172 patients with features of NAFLD and 94 control subjects. The rs738409 G allele was significantly associated with NAFLD (P < 0.001; OR 2.8 95%, CI 1.5-5.2), independent of age, sex, body mass index (BMI), and Homeostasis Model Assessment (HOMA) index. When we tested the hypothesis of a relation between the SNP and the histological spectrum of NAFLD, a significant association was observed [chi2 19.9, degree of freedom (df): 2, P < 5 x 10(-5), adjusted for HOMA and BMI]. The degree of liver steatosis, as evaluated by liver biopsy, was significantly associated with the rs738409 G allele. Patients with CC genotype showed a lower steatosis score (14.9% +/- 3.9) in comparison with the CG genotype (26.3% +/- 3.5) and GG genotype (33.3% +/- 4.0) (P < 0.005). The proportion of the total variation attributed to rs738409 genotypes was 5.3% (beta 0.23 +/- 0.07; P < 0.002). Our data suggest that the rs738409 G allele is associated not only with fat accumulation in the liver but also with liver injury, possibly triggered by lipotoxicity.

A nonsynonymous gene variant in the adiponutrin gene is associated with nonalcoholic fatty liver disease severity

We explored the role of the adiponutrin (PNPLA3) nonsynonymous-rs738409 single nucleotide polymorphism (SNP) in genetic susceptibility to nonalcoholic fatty liver disease (NAFLD) and whether this SNP contributes to the severity of histological disease. Two hundred sixty-six individuals were evaluated in a case-control association study, which included 172 patients with features of NAFLD and 94 control subjects. The rs738409 G allele was significantly associated with NAFLD (P < 0.001; OR 2.8 95%, CI 1.5-5.2), independent of age, sex, body mass index (BMI), and Homeostasis Model Assessment (HOMA) index. When we tested the hypothesis of a relation between the SNP and the histological spectrum of NAFLD, a significant association was observed [chi2 19.9, degree of freedom (df): 2, P < 5 x 10(-5), adjusted for HOMA and BMI]. The degree of liver steatosis, as evaluated by liver biopsy, was significantly associated with the rs738409 G allele. Patients with CC genotype showed a lower steatosis score (14.9% +/- 3.9) in comparison with the CG genotype (26.3% +/- 3.5) and GG genotype (33.3% +/- 4.0) (P < 0.005). The proportion of the total variation attributed to rs738409 genotypes was 5.3% (beta 0.23 +/- 0.07; P < 0.002). Our data suggest that the rs738409 G allele is associated not only with fat accumulation in the liver but also with liver injury, possibly triggered by lipotoxicity.

Amelioration of high fat diet induced liver lipogenesis and hepatic steatosis by interleukin-22

BACKGROUND & AIMS

Interleukin-22 (IL-22) is a Th17-related cytokine within the IL-10 family and plays an important role in host defense and inflammatory responses in orchestration with other Th17 cytokines. IL-22 exerts its functions in non-immune cells as its functional receptor IL-22R1 is restricted in peripheral tissues but not in immune cells. It was recently found that IL-22 serves as a protective molecule to counteract the destructive nature of the T cell-mediated immune response to liver damage. However, it is currently unknown whether IL-22 has an effect on lipid metabolism in the liver.

METHODS

In this study, we demonstrate that IL-22 alleviates hepatic steatosis induced by high fat diet (HFD).

RESULTS

Administration of recombinant murine IL-22 (rmIL-22) was able to stimulate STAT3 phosphorylation in HepG2 cells and mouse liver. The activation of STAT3 by rmIL-22 was reduced by the over-expression of a dominant negative IL-22R1. Within hours after rmIL-22 treatment, the expression of lipogenesis-related genes including critical transcription factors and enzymes for lipid synthesis in the liver was significantly down-regulated. The levels of triglyceride and cholesterol in the liver were significantly reduced by long-term treatment of rmIL-22 in C57BL/6 and ob/ob mice fed with HFD. The HFD-induced increases of ALT and AST in ob/ob mice were ameliorated by rmIL-22 treatment. In addition, the expression of fatty acid synthase and TNF-alpha in the liver was decreased by long-term rmIL-22 administration.

CONCLUSIONS

Collectively, these data indicate that IL-22, in addition to its known functions in host defense and inflammation, has a protective role in HFD-induced hepatic steatosis via its regulation on lipid metabolism in the liver.

Update on nonalcoholic fatty liver disease: genes involved in nonalcoholic fatty liver disease and associated inflammation

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent liver diseases worldwide. Advanced age, extensive overweight and a number of features of the metabolic syndrome are associated with NAFLD severity. The cause of NAFLD is considered multifactorial with a substantial genetic component.

RECENT FINDINGS

Family members of children with NAFLD demonstrate a higher risk for NAFLD. Whereas such an association only suggests that familial factors are major determinants of whether or not an individual will develop NAFLD, recent genome-wide association studies were able to identify first candidate genes. An allele in patatin-like phospholipase 3, encoding a protein of unknown function with homology to lipid acyl hydrolases, is strongly associated with increased hepatic fat and inflammation. Apolipoprotein C3 gene variants are also associated with NAFLD and insulin resistance. Several other genetic variants have been identified, although with less convincing evidence. These genetic variants involve molecules regulating insulin signaling, lipid metabolism, oxidative stress or fibrogenesis. Furthermore, genetic variants of several cytokines and adipocytokines have been associated with NAFLD.

SUMMARY

Several genetic factors such as patatin-like phospholipase 3 or apolipoprotein C3 have been recently characterized in NAFLD. Further studies to identify their interaction with environmental factors are eagerly warranted.

STAT3 polymorphisms linked with idiopathic recurrent miscarriages

PROBLEM

We investigated the association of signal transducers and activators of transcription (STAT)3 gene variants with idiopathic recurrent miscarriage (RM).

METHOD OF STUDY

A case-control study involving 189 RM patients and 244 control women was carried out. STAT3 (rs1053004 and rs1023023) genotyping was performed by allelic discrimination/real-time PCR method.

RESULTS

STAT3 rs1053004 C allele [OR (95% CI) = 1.60 (1.22-2.10)] and C/C genotype [OR (95% CI) = 3.42 (1.70-6.92)] were positively associated with RM. Two-locus (rs1053004/rs1053023) haplotype analysis revealed increased frequency of CG and CA haplotypes in RM patients, of which only CA haplotype (Pc = 0.020) remained positively associated with RM after applying the Bonferroni correction. This was confirmed by multivariate regression analysis (OR = 1.70; 95% CI = 1.17-2.46) after adjusting for a number of covariates.

CONCLUSION

STAT3 rs1053004 variant is significantly associated with idiopathic RM. Replication studies on other racial groups and other STAT3 gene variants are warranted.

The nuclear receptor PXR gene variants are associated with liver injury in nonalcoholic fatty liver disease

OBJECTIVE

To explore the contribution of gene variants and derived haplotypes of the pregnane X receptor (NR1I2) to the severity of nonalcoholic fatty liver disease (NAFLD).

METHODS

A total of 290 individuals were evaluated in a case-control association study, including 188 NAFLD patients with different stages of disease severity and 102 healthy individuals. Four tag single nucleotide polymorphisms (SNPs; rs12488820 C/T, rs2472671 C/T, rs2461823 A/G, and rs1054191 A/G) encompassing 36 kb in chromosome 3 and representing 33 polymorphic sites (r2>0.8) were genotyped. Four additional SNPs (rs3814055, rs3814057, rs6785049, and rs7643645) were also included because they showed earlier evidence of functionality.

RESULTS

Genotypic tests for single SNPs showed that rs7643645 and rs2461823 were significantly associated with disease severity by ordinal multinomial analysis (P<0.0015 and 0.039, respectively). A significant association was also observed under the additive model for both variants (P<0.00038 and 0.012, respectively). Consistent with the analysis of individual markers, we observed that the multimarker composed of rs2461823/A-rs7643645/G was significantly associated with disease severity (P<6.9 x 10(-5), beta: 0.45). In addition, the rs7643645/G variant was significantly associated with ALT level (P<0.026), a surrogate marker of severe liver injury. Finally, in univariate analysis rs7643645/G was significantly associated with fatty liver disease (P<0.04), with an odds ratio of 1.457 (95% confidence interval: 1.018-2.086).

CONCLUSION

Our study suggests that pregnane X receptor polymorphisms and related haplotypes may contribute to disease severity in NAFLD by influencing the individual susceptibility to progress to more severe stages of the disease.