Dual Role of MicroRNAs in NAFLD. Int J Mol Sci. 2013;14:8437-8455. [PMID: 23594995 PMCID: PMC3645753 DOI: 10.3390/ijms14048437]

Diagnostic potential and pathogenic performance of circulating miR-146b, miR-194, and miR-214 in liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins. Due to the lack of an accurate test for an early diagnosis of liver fibrosis and the invasiveness of the liver biopsy procedure, there is an urgent need for effective non-invasive biomarkers for screening the patients. we aimed to evaluate the diagnostic performance of circulating miRNAs (miR-146b, -194, -214) and their related mechanisms in the pathogenesis of liver fibrosis. The expression levels of miR-146b, -194, and -214 were quantified in whole blood samples from NAFLD patients using real-time PCR. The competing endogenous RNA (ceRNA) network was constructed and a gene set enrichment analysis (GSEA) was performed for HSC activation-related genes. Also, the transcription factor (TF)-miR co-regulatory network and the survival plot for three miRNAs and core genes were illustrated. The qPCR results showed that the relative expression of miR-146b and miR-214 significantly increased in NAFLD patients, while miR-194 showed significant down-regulation. The ceRNA network analysis implicated NEAT1 and XIST as sponge candidates for these miRNAs. The GSEA results identified 15 core genes involved in HSC activation, primarily enriched in NF-κB activation and autophagy pathways. STAT3, TCF3, RELA, and RUNX1 were considered potential transcription factors connected to miRNAs in the TF-miR network. Our study elucidated three candidate circulating miRNAs differentially expressed in NAFLD that could serve as a promising non-invasive diagnostic tool for early detection strategies. Also, NF-κB activation, autophagy, and negative regulation of the apoptotic process are the main potential underlying mechanisms regulated by these miRNAs in liver fibrosis pathogenesis.

Maternal Weight Management to Prevent the Developmental Programming of MAFLD in Offspring of Obese Mothers

The global surge of obesity amongst women of reproductive age has raised concerns surrounding the health consequences for their offspring as there is a formidable link between an obesogenic maternal environment and the developmental programming of metabolic dysfunction in the offspring. Specifically, the offspring of mothers with obesity have a three-fold higher risk of developing metabolic-associated fatty liver disease (MAFLD) compared to the offspring of healthy-weight mothers. Given the burgeoning burden of obesity and its comorbidities, it is essential to focus research efforts on methods to alleviate the intergenerational onset of obesity and MAFLD. This review summarizes the current research surrounding the developmental programming of MAFLD in the offspring of mothers with obesity and examines the potential for weight interventions to prevent such metabolic dysfunction in the offspring. It focuses on the benefits of pre-pregnancy interventional strategies, including dietary and exercise intervention, to ameliorate adverse liver health outcomes in the offspring. The utility and translation of these interventions for humans may be difficult for prospective mothers with obesity, thus the use of pre-pregnancy therapeutic weight loss aids, such as glucagon-like peptide-1 receptor agonists, is also discussed.

The Emerging Role of Circular RNA Homeodomain Interacting Protein Kinase 3 and Circular RNA 0046367 through Wnt/Beta-Catenin Pathway on the Pathogenesis of Nonalcoholic Steatohepatitis in Egyptian Patients

Background

Non-alcoholic fatty liver disease is a major problem worldwide that needs non-invasive biomarkers for early diagnosis and treatment response assessment. We aimed to assess the correlation between circRNA-HIPK3 and miRNA-29a expression and its role as miRNA-29a sponge, as well as the correlation between circRNA-0046367 and miRNA-34a expression and its role as miRNA-34a sponge and their effect on regulation of the Wnt/β catenin pathway, which may provide a new target for treatment of non-alcoholic steatohepatitis.

Methods

the research was performed on 110 participants: group (I): fifty-five healthy donors served as controls and group (II): fifty-five patients with fatty liver pattern on abdominal ultrasound. Lipid profile and liver functions were assessed. RT-PCR was performed to assess the RNAs: circRNA-HIPK3, circRNA-0046367, miRNA-29a, miRNA-34a and Wnt mRNA gene expression. ELISA was performed to determine β-catenin protein levels.

Results

miRNA-34a and circRNA-HIPK3 expression were significantly greater, while miRNA-29a and circRNA-0046367 expression were significantly less, in patients than in controls. Wnt/β-catenin regulated by miRNA-29a and miRNA-34a showed a significant decrease that leads to its abnormal effect on lipid metabolism.

Conclusions

our results imply that miRNA-29a can be investigated as a target for circRNA-HIPK3, while miRNA-34a can be investigated as a target for circRNA-0046367, and that circRNA-HIPK3 and circRNA-0046367 may have emerging roles that can affect the pathogenesis of nonalcoholic steatohepatitis through the Wnt/β-catenin pathway and thus be used as therapeutic targets for the disease.

Short-term fructose feeding alters tissue metabolic pathways by modulating microRNAs expression both in young and adult rats

Dietary high fructose (HFrD) is known as a metabolic disruptor contributing to the development of obesity, diabetes, and dyslipidemia. Children are more sensitive to sugar than adults due to the distinct metabolic profile, therefore it is especially relevant to study the metabolic alterations induced by HFrD and the mechanisms underlying such changes in animal models of different ages. Emerging research suggests the fundamental role of epigenetic factors such as microRNAs (miRNAs) in metabolic tissue injury. In this perspective, the aim of the present study was to investigate the involvement of miR-122-5p, miR-34a-5p, and miR-125b-5p examining the effects induced by fructose overconsumption and to evaluate whether a differential miRNA regulation exists between young and adult animals. We used young rats (30 days) and adult rats (90 days) fed on HFrD for a short period (2 weeks) as animal models. The results indicate that both young and adult rats fed on HFrD exhibit an increase in systemic oxidative stress, the establishment of an inflammatory state, and metabolic perturbations involving the relevant miRNAs and their axes. In the skeletal muscle of adult rats, HFrD impair insulin sensitivity and triglyceride accumulation affecting the miR-122-5p/PTP1B/P-IRS-1(Tyr612) axis. In liver and skeletal muscle, HFrD acts on miR-34a-5p/SIRT-1: AMPK pathway resulting in a decrease of fat oxidation and an increase in fat synthesis. In addition, liver and skeletal muscle of young and adult rats exhibit an imbalance in antioxidant enzyme. Finally, HFrD modulates miR-125b-5p expression levels in liver and white adipose tissue determining modifications in de novo lipogenesis. Therefore, miRNA modulation displays a specific tissue trend indicative of a regulatory network that contributes in targeting genes of various pathways, subsequently yielding extensive effects on cell metabolism.

Exploring the Regulatory Role of ncRNA in NAFLD: A Particular Focus on PPARs

Liver diseases are responsible for global mortality and morbidity and are a significant cause of death worldwide. Consequently, the advancement of new liver disease targets is of great interest. Non-coding RNA (ncRNA), such as microRNA (miRNA) and long ncRNA (lncRNA), has been proven to play a significant role in the pathogenesis of virtually all acute and chronic liver disorders. Recent studies demonstrated the medical applications of miRNA in various phases of hepatic pathology. PPARs play a major role in regulating many signaling pathways involved in various metabolic disorders. Non-alcoholic fatty liver disease (NAFLD) is the most prevalent form of chronic liver disease in the world, encompassing a spectrum spanning from mild steatosis to severe non-alcoholic steatohepatitis (NASH). PPARs were found to be one of the major regulators in the progression of NAFLD. There is no recognized treatment for NAFLD, even though numerous clinical trials are now underway. NAFLD is a major risk factor for developing hepatocellular carcinoma (HCC), and its frequency increases as obesity and diabetes become more prevalent. Reprogramming anti-diabetic and anti-obesity drugs is an effective therapy option for NAFLD and NASH. Several studies have also focused on the role of ncRNAs in the pathophysiology of NAFLD. The regulatory effects of these ncRNAs make them a primary target for treatments and as early biomarkers. In this study, the main focus will be to understand the regulation of PPARs through ncRNAs and their role in NAFLD.

Mechanistic insights into the pleiotropic effects of butyrate as a potential therapeutic agent on NAFLD management: A systematic review

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic diseases worldwide. As a multifaceted disease, NAFLD's pathogenesis is not entirely understood, but recent evidence reveals that gut microbiota plays a significant role in its progression. Butyrate, a gut microbiota metabolite, has been reported to have hepato-protective effects in NAFLD animal models. The purpose of this systematic review is to determine how butyrate affects the risk factors for NAFLD. Searches were conducted using relevant keywords in electronic databases up to March 2022. According to the evidence presented in this study, butyrate contributes to a wide variety of biological processes in the gut-liver axis. Its beneficial properties include improving intestinal homeostasis and liver health as well as anti-inflammatory, metabolism regulatory and anti-oxidative effects. These effects may be attributed to butyrate's ability to regulate gene expression as an epigenetic modulator and trigger cellular responses as a signalling molecule. However, the exact underlying mechanisms remain unclear. Human trials have not been performed on the effect of butyrate on NAFLD, so there are concerns about whether the results of animal studies can be translated to humans. This review summarises the current knowledge about the properties of butyrate, particularly its potential effects and mechanisms on liver health and NAFLD management.

microRNA-103a-3p promotes inflammation and fibrosis in nonalcoholic fatty liver disease by targeting HBP1

BACKGROUND

As a metabolic-associated disease, nonalcoholic fatty liver disease (NAFLD) development is tightly linked to lipid accumulation, inflammatory response, and fibrosis. Our study was intended to expound the role of microRNA (miR)-103a-3p in the pathogenesis of NAFLD.

METHODS

First, potentially relevant genes in NAFLD were screened using microarray analysis. The expression of lipid metabolism-related, inflammatory, and liver fibrosis indicators in the serum of patients with NAFLD was analyzed. We established a NAFLD mouse model and analyzed the serum level of lipid metabolism- and inflammation-related factors and fibrosis in the liver tissues of NAFLD mice. The targeting relationship between miR-103a-3p and HBP1 was examined by dual-luciferase reporter gene assay, RT-qPCR, and Western blot. Finally, the simultaneous effects of miR-103a-3p and HBP1 knockdown on lipid metabolism, inflammatory response, and liver fibrosis in NAFLD mice were analyzed by rescue experiments.

RESULTS

MiR-103a-3p was upregulated in the serum of NAFLD patients and liver tissues of NAFLD mice, with increased lipid accumulation, inflammation, and liver fibrosis. HBP1 was reduced in liver tissues of NAFLD mice, and miR-103a-3p bound to and negatively regulated HBP1. Inhibition of miR-103a-3p or promotion of HBP1 improved liver function, decreased lipid accumulation, suppressed inflammatory response, and reduced liver fibrosis in NAFLD mice. Moreover, sh-HBP1 partially reversed the effect of miR-103a-3p inhibitor on NAFLD mice, leading to increased lipid accumulation, elevated inflammation, and fibrosis in the liver of mice.

CONCLUSIONS

miR-103a-3p inhibits the expression of HBP1, thus suppressing lipid metabolism, stimulating inflammatory responses, and promoting liver fibrosis in NAFLD.

miR-139 Protects Liver Tissue Damage and Oxidative Stress in Diabetic Mice by Up-Regulating (Silent Mating Type Information Regulation 2 Homolog-1) SIRT1

Diabetes affects human health. This study aimed to investigate the molecular regulation mechanism of miR-139 on liver injury and oxidative stress in diabetic mice. The diabetic mice were divided into miR-139 inhibitor group, si-SIRT group, miR-139 mimic group, and the mRNA expression and protein level of miR-139 and SIRT1 were analyzed, respectively. Bioinformatics revealed the relationship between miR-139 and SIRT1. In addition, histological analysis and oxidation reaction indicators were performed on mouse livers induced by high glucose. After induction, a mouse diabetes model was established with highly expressed ALT. Bioinformatics found that miR-139 negatively regulated SIRT1. Furthermore, markers of hepatic oxidative stress were increased and blood glucose levels decreased in mice overexpressing miR-139. Up-regulation of miR-139 can protect the liver tissue of diabetic mice from oxidative stress injury by inhibiting the expression of SIRT1, and si-SIRT treatment reversed the increased blood glucose level and oxidative stress injury caused by the reduction of miR-139.

NAFLD: Mechanisms, Treatments, and Biomarkers

Nonalcoholic fatty liver disease (NAFLD), recently renamed metabolic-associated fatty liver disease (MAFLD), is one of the most common causes of liver diseases worldwide. NAFLD is growing in parallel with the obesity epidemic. No pharmacological treatment is available to treat NAFLD, specifically. The reason might be that NAFLD is a multi-factorial disease with an incomplete understanding of the mechanisms involved, an absence of accurate and inexpensive imaging tools, and lack of adequate non-invasive biomarkers. NAFLD consists of the accumulation of excess lipids in the liver, causing lipotoxicity that might progress to metabolic-associated steatohepatitis (NASH), liver fibrosis, and hepatocellular carcinoma. The mechanisms for the pathogenesis of NAFLD, current interventions in the management of the disease, and the role of sirtuins as potential targets for treatment are discussed here. In addition, the current diagnostic tools, and the role of non-coding RNAs as emerging diagnostic biomarkers are summarized. The availability of non-invasive biomarkers, and accurate and inexpensive non-invasive diagnosis tools are crucial in the detection of the early signs in the progression of NAFLD. This will expedite clinical trials and the validation of the emerging therapeutic treatments.

Maternal Western diet exposure increases periportal fibrosis beginning in utero in nonhuman primate offspring

Maternal obesity affects nearly one-third of pregnancies and is a major risk factor for nonalcoholic fatty liver disease (NAFLD) in adolescent offspring, yet the mechanisms behind NAFLD remain poorly understood. Here, we demonstrate that nonhuman primate fetuses exposed to maternal Western-style diet (WSD) displayed increased fibrillar collagen deposition in the liver periportal region, with increased ACTA2 and TIMP1 staining, indicating localized hepatic stellate cell (HSC) and myofibroblast activation. This collagen deposition pattern persisted in 1-year-old offspring, despite weaning to a control diet (CD). Maternal WSD exposure increased the frequency of DCs and reduced memory CD4+ T cells in fetal liver without affecting systemic or hepatic inflammatory cytokines. Switching obese dams from WSD to CD before conception or supplementation of the WSD with resveratrol decreased fetal hepatic collagen deposition and reduced markers of portal triad fibrosis, oxidative stress, and fetal hypoxemia. These results demonstrate that HSCs and myofibroblasts are sensitive to maternal WSD-associated oxidative stress in the fetal liver, which is accompanied by increased periportal collagen deposition, indicative of early fibrogenesis beginning in utero. Alleviating maternal WSD-driven oxidative stress in the fetal liver holds promise for halting steatosis and fibrosis and preventing developmental programming of NAFLD.

Circulatory Endothelin 1-Regulating RNAs Panel: Promising Biomarkers for Non-Invasive NAFLD/NASH Diagnosis and Stratification: Clinical and Molecular Pilot Study

Nonalcoholic fatty liver disease (NAFLD) is one of the major seeds of liver cirrhosis and hepatocellular carcinoma. There is no convenient reliable non-invasive early diagnostic tool available for NAFLD/NASH diagnosis and stratification. Recently, the role of cytosolic sensor, stimulator of interferon genes (STING) signaling pathway in pathogenesis of nonalcoholic steatohepatitis (NASH) has been evidenced in research. We have selected EDN1/TNF/MAPK3/EP300/hsa-miR-6888-5p/lncRNA RABGAP1L-DT-206 RNA panel from bioinformatics microarrays databases related to STING pathway and NAFLD/NASH pathogenesis. We have used reverse-transcriptase real-time polymerase chain reaction to assess the expression of the serum RNAs panel in NAFLD/NASH without suspicion of advanced fibrosis, NAFLD/with NASH patients with suspicion of advanced fibrosis and controls. Additionally, we have assessed the diagnostic performance of the Ribonucleic acid (RNA) panel. We have detected upregulation of the EDN1 regulating RNAs panel expression in NAFLD/NASH cases compared to healthy controls. We concluded that this circulatory RNA panel could enable us to discriminate NAFLD/NASH cases from controls, and also NAFLD/NASH cases (F1, F2) from advanced fibrosis stages (F3, F4).

MicroRNA-506-3p targets SIRT1 and suppresses AMPK pathway activation to promote hepatic steatosis

Nonalcoholic fatty liver disease (NAFLD) is a complex type of liver disease that represents an important global health threat. The mechanistic basis of this disease remains incompletely understood. The present study sought to explore whether microRNA (miR)-506-3p served a functional role in the onset and/or progression of NAFLD. To that end, high levels of glucose were used to treat liver cancer cell lines (HepG2 and Huh7) to model hepatic steatosis, and the expression levels of miR-506-3p and its downstream target genes were assessed. The cells of this hepatic steatosis model were transfected with miR-506-3p mimic molecules to explore the effect of miR-506-3p overexpression on cell viability, target gene expression and AMP-activated protein kinase (AMPK) phosphorylation. Via bioinformatics approaches, sirtuin 1 (SIRT1) was identified as a potential miR-506-3p target gene with relevance in NAFLD, and this interaction was confirmed via luciferase reporter assay. In the hepatic steatosis model of the present study, miR-506-3p expression level was significantly increased, whereas SIRT1 mRNA/protein levels and AMPK phosphorylation levels were markedly decreased. Transfection of the cells with miR-506-3p mimics led to significant SIRT1 downregulation, while miR-506-3p inhibitor molecules exhibited the opposite effect, with similar trends observed in the phosphorylation status of AMPK. These results suggested that miR-506-3p can inhibit SIRT1 expression and associated AMPK phosphorylation in HepG2 and Huh7 cells in an in vitro hepatic steatosis model system. These data indicated that the miR-506-3p/SIRT1/AMPK axis may be valuable as a therapeutic target in patients affected by NAFLD.

The relationship between polyphenols and miRNAs: A novel therapeutic strategy for metabolic associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) is a public health problem that is increasingly recognized, currently affecting up to a quarter of the world's adult population. Although a biopsy is the current gold standard to diagnose MAFLD, there are potentially serious complications, making it inadequate. Thus far, noninvasive methods have not been able to determine the stage and the subtype of MAFLD. The development and prognosis of MAFLD are modulated by epigenetic factors, including microRNAs (miRNAs), which may be potential biomarkers for MAFLD. Polyphenols, found in many fruits and vegetables, may be useful, as they alter gene expression with epigenetic factors, such as miRNAs. This review presents an overview of the relationship between polyphenols and miRNAs in MAFLD. The literature suggests that miRNAs could be used as a diagnostic method for MAFLD, especially miRNA-122 and miRNA-34a. However, though it has been demonstrated that polyphenols may contribute to improving MAFLD, to our knowledge, no study to date has shown the relationship between polyphenols and miRNAs in MAFLD. The exact mechanisms of polyphenols on miRNAs in MAFLD remain unclear. Future studies may provide hope for diet therapy for MAFLD patients as well as the development of polyphenol-related foods or drugs that target miRNAs to treat MAFLD.

MicroRNA Let-7 targets AMPK and impairs hepatic lipid metabolism in offspring of maternal obese pregnancies

Nutritional status during gestation may lead to a phenomenon known as metabolic programming, which can be triggered by epigenetic mechanisms. The Let-7 family of microRNAs were one of the first to be discovered, and are closely related to metabolic processes. Bioinformatic analysis revealed that Prkaa2, the gene that encodes AMPK α2, is a predicted target of Let-7. Here we aimed to investigate whether Let-7 has a role in AMPKα2 levels in the NAFLD development in the offspring programmed by maternal obesity. Let-7 levels were upregulated in the liver of newborn mice from obese dams, while the levels of Prkaa2 were downregulated. Let-7 levels strongly correlated with serum glucose, insulin and NEFA, and in vitro treatment of AML12 with glucose and NEFA lead to higher Let-7 expression. Transfection of Let-7a mimic lead to downregulation of AMPKα2 levels, while the transfection with Let-7a inhibitor impaired both NEFA-mediated reduction of Prkaa2 levels and the fat accumulation driven by NEFA. The transfection of Let-7a inhibitor in ex-vivo liver slices from the offspring of obese dams restored phospho-AMPKα2 levels. In summary, Let-7a appears to regulate hepatic AMPKα2 protein levels and lead to the early hepatic metabolic disturbances in the offspring of obese dams.

Aging Liver: Can Exercise be a Better Way to Delay the Process than Nutritional and Pharmacological Intervention? Focus on Lipid Metabolism

BACKGROUND & AIMS

Nowadays, the world is facing a common problem that the population aging process is accelerating. How to delay metabolic disorders in middle-aged and elderly people, has become a hot scientific and social issue worthy of attention. The liver plays an important role in lipid metabolism, and abnormal lipid metabolism may lead to liver diseases. Exercise is an easily controlled and implemented intervention, which has attracted extensive attention in improving the health of liver lipid metabolism in the elderly. This article reviewed the body aging process, changes of lipid metabolism in the aging liver, and the mechanism and effects of different interventions on lipid metabolism in the aging liver, especially focusing on exercise intervention.

METHODS

A literature search was performed using PubMed-NCBI, EBSCO Host and Web of Science, and also a report from WHO. In total, 143 studies were included from 1986 to 15 February 2020.

CONCLUSION

Nutritional and pharmacological interventions can improve liver disorders, and nutritional interventions are less risky relatively. Exercise intervention can prevent and improve age-related liver disease, especially the best high-intensity interval training intensity and duration is expected to be one of the research directions in the future.

Epigenetics in NAFLD/NASH: Targets and therapy

Recently non-alcoholic fatty liver disease (NAFLD) has grabbed considerable scientific attention, owing to its rapid increase in prevalence worldwide and growing burden on end-stage liver diseases. Metabolic syndrome including obesity, diabetes, and hypertension poses a grave risk to NAFLD etiology and progression. With no drugs available, the mainstay of NAFLD management remains lifestyle changes with exercise and dietary modifications. Nonselective drugs such as metformin, thiazolidinediones (TZDs), ursodeoxycholic acid (UDCA), silymarin, etc., are also being used to target the interrelated pathways for treating NAFLD. Considering the enormous disease burden and the unmet need for drugs, fresh insights into pathogenesis and drug discovery are required. The emergence of the field of epigenetics offers a convincing explanation for the basis of lifestyle, environmental, and other risk factors to influence NAFLD pathogenesis. Therefore, understanding these epigenetic modifications to target the primary cause of the disease might prove a rational strategy to prevent the disease and develop novel therapeutic interventions. Apart from describing the role of epigenetics in the pathogenesis of NAFLD as in other reviews, this review additionally provides an elaborate discussion on exploiting the high plasticity of epigenetic modifications in response to environmental cues, for developing novel therapeutics for NAFLD. Besides, this extensive review provides evidence for epigenetic mechanisms utilized by several potential drugs for NAFLD.

High-intensity interval training (HIIT) alleviated NAFLD feature via miR-122 induction in liver of high-fat high-fructose diet induced diabetic rats

Background: Exercise intervention is strongly recommended to manage metabolic diseases. In this study, we investigate, whether HIIT and CET can induce hepatic miR-122 expression, NAFLD rats with diabetes.Methods: 40 Wistar rats divided into 2 groups, non-diabetic (NDC) and diabetic .Type 2 diabetes was induced by high-fat high-fructose diet (HFHFD). Then diabetic rats were subdivided into three groups: diabetic control (HFHFD + DC), CET (HFHFD + CET), and HIIT (HFHFD + HIIT). After eight weeks of exercise on a rodent treadmill, we measured miR-122 and its target genes expression in the liver of rats.Results: HIIT decreased the expression of FAS, ACC, SREBP-1c compared with HFHFD + DC (p = .004, p = .032, p = .043, respectively), and could partially increase miR-122 expression as compared with HFHFD + DC (26.8%, p = .68).Conclusions: Exercise training could be a non-pharmacological intervention for improvement of NAFLD of diabetic rats by induction of miR-122. HIIT had a greater effect on NAFLD amelioration than CET.

MiR-149 attenuates endoplasmic reticulum stress-induced inflammation and apoptosis in nonalcoholic fatty liver disease by negatively targeting ATF6 pathway

This study aimed to research the effect of miR-149 on endoplasmic reticulum stress (ERS)-induced inflammation and apoptosis in non-alcoholic fatty liver disease (NAFLD). The mouse model with NAFLD was established by feeding with a high-fat diet, and the model establishment was subsequently confirmed by H&E staining and oil red O staining. MiR-149 agomir was injected into NAFLD mice to observe changes in liver tissues. After cell transfection, qRT-PCR and Western blot were performed to measure the expressions of lipid metabolism-related proteins (SCD-1, PPARα, and ABCA1), miR-149 and ATF6. Luciferase reporter gene assay was applied to verify the relationship between miR-149 and ATF6. Inflammatory factors (TNF-α, IL-1β, IL-6 and NF-κB) and apoptotic-related factors (caspase-12 and CHOP) were measured by ELISA and flow cytometry. qRT-PCR and Western blot were applied to detect expressions of ATF6 signaling pathway-related proteins (GRP94 and Akt). NAFLD progression was attenuated in mice injected with miR-149 agomir. The expression of miR-149 was reduced in liver tissues of NAFLD mice, while the expression of ATF6 was increased. Transfection of miR-149 can result in a decrease of ATF6 expression. ATF6 was a target gene of miR-149. MiR-149 could down-regulate the expressions of inflammatory factors and apoptotic-related factors. MiR-149 could down-regulate expressions of ATF6 signaling pathway-related proteins. MiR-149 alleviates ERS-induced inflammation and apoptosis by down-regulating the ATF6 signaling pathway, thus inhibiting the progression of NAFLD.

microRNA-141 is associated with hepatic steatosis by downregulating the sirtuin1/AMP-activated protein kinase pathway in hepatocytes

Sirtuin1 (SIRT1) is a crucial regulator of metabolism and it is implicated in the metabolic pathophysiology of several disorders inclusive of Type 2 diabetes and fatty liver disease (NAFLD). The aim of this study was to investigate the role of miR-141 in hepatic steatosis via regulation of SIRT1/AMP-activated protein kinase (AMPK) pathway in hepatocytes. Liver hepatocellular cells (HepG2) were treated with high concentration of glucose to be subsequently used for the assessment of miR-141 and SIRT1 levels in a model of hepatic steatosis. On the other hand, cells were transfected with miR-141 to investigate its effect on hepatocyte steatosis and viability as well as SIRT1 expression and activity along with AMPK phosphorylation. Targeting of SIRT1 by miR-141 was evaluated by bioinformatics tools and confirmed by luciferase reporter assay. Following the intracellular accumulation of lipids in HepG2 cells, the level of miR-141 was increased while SIRT1 mRNA and protein levels, as well as AMPK phosphorylation, was decreased. Transfection with miR-141 mimic significantly downregulated SIRT1 expression and activity while miR-141 inhibitor had the opposite effects. Additionally, modulation of miR-141 levels significantly influenced AMPK phosphorylation status. The results of luciferase reporter assay verified SIRT1 to be directly targeted by miR-141. miR-141 could effectively suppress SIRT1 and lead to decreased AMPK phosphorylation in HepG2 cells. Thus, miR-141/SIRT1/AMPK signaling pathway may be considered a potential target for the therapeutic management of NAFLD.

miR-122 promotes hepatic lipogenesis via inhibiting the LKB1/AMPK pathway by targeting Sirt1 in non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a common hepatic disease with an increasing prevalence but an unclear aetiology. This study aimed to investigate the functional implications of microRNA-122 (miR-122) in the pathogenesis of NAFLD and the possible molecular mechanisms.

METHODS

Both in vitro and in vivo models of NAFLD were generated by treating HepG2 and Huh-7 cells with free fatty acids (FFA) and by feeding mice a high-fat diet (HFD), respectively. HE and Oil Red O staining were used to examine liver tissue morphology and lipid deposition, respectively. Immunohistochemical (IHC) staining was used to examine Sirt1 expression in liver tissues. qRT-PCR and Western blotting were employed to measure the expression of miR-122, Sirt1, and proteins involved in lipogenesis and the AMPK pathway. Enzyme-linked immunosorbent assay (ELISA) was used to quantify triglyceride (TG) levels in HepG2 and Huh-7 cells and in liver tissues. The interaction between miR-122 and the Sirt1 gene was further examined by a dual luciferase reporter assay and RNA-immunoprecipitation (RIP).

RESULTS

NAFLD hepatic tissues and FFA-treated HepG2 and Huh-7 cells presented excess lipid production and TG secretion, accompanied by miR-122 upregulation, Sirt1 downregulation, and potentiated lipogenesis-related genes. miR-122 suppressed Sirt1 expression via binding to its 3'-untranslated region (UTR). Knockdown of miR-122 effectively mitigated excessive lipid production and suppressed the expression of lipogenic genes in FFA-treated HepG2 and Huh-7 cells via upregulating Sirt1. Furthermore, miR-122 knockdown activated the LKB1/AMPK signalling pathway.

CONCLUSION

The inhibition of miR-122 protects hepatocytes from lipid metabolic disorders such as NAFLD and suppresses lipogenesis via elevating Sirt1 and activating the AMPK pathway. These data support miR-122 as a promising biomarker and drug target for NAFLD.

Primate fetal hepatic responses to maternal obesity: epigenetic signalling pathways and lipid accumulation

KEY POINTS

Maternal obesity (MO) and exposure to a high-fat, high-simple-carbohydrate diet during pregnancy predisposes offspring to obesity, metabolic and cardiovascular disorders in later life. Underlying molecular pathways and potential epigenetic factors that are dysregulated in MO were identified using unbiased transcriptomic methods. There was increased lipid accumulation and severe steatosis in the MO baboon fetal liver suggesting that these offspring are on an early trajectory of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis.

ABSTRACT

Maternal obesity (MO) increases offspring cardiometabolic disease risk. Altered fetal liver development in response to the challenge of MO has metabolic consequences underlying adverse offspring life-course health outcomes. Little is known about the molecular pathways and potential epigenetic changes regulating primate fetal liver responses to MO. We hypothesized that MO would induce fetal baboon liver epigenetic changes resulting in dysregulation of key metabolic pathways that impact lipid metabolism. MO was induced prior to pregnancy by a high-fat, high-fructose diet. Unbiased gene and microRNA (small RNA Seq) abundance analyses were performed on fetal baboon livers at 0.9 gestation and subjected to pathway analyses to identify fetal liver molecular responses to MO. Fetal baboon liver lipid and glycogen content were quantified by the Computer Assisted Stereology Toolbox. In response to MO, fetal livers revealed dysregulation of TCA cycle, proteasome, oxidative phosphorylation, glycolysis and Wnt/β-catenin signalling pathways together with marked lipid accumulation supporting our hypothesis that multiple pathway dysregulation detrimentally impacts lipid management. This is the first study of MO programming of the non-human primate fetal liver using unbiased transcriptome analysis to detect changes in hepatic gene expression levels and identify potential microRNA epigenetic regulators of metabolic disruption.

Role of EZH2 in liver disease

Overexpression of enhancer of zeste homolog 2 (EZH2) protein has been found in several malignant tumor tissues and is closely related to the degree of tumor differentiation, clinical stage, tumor size, and prognosis. The latest research shows that overexpression of EZH2 is related not only with immunoregulation but also with the replication of hepatitis B virus, the occurrence of non-alcoholic fatty liver disease, and the progress of liver fibrosis, which may become an important subject in the field of liver disease research. This paper reviews the role of EZH2 in some liver diseases and its potential application in treatment of these diseases in recent ten years.

Transgenic expression of the RNA binding protein IMP2 stabilizes miRNA targets in murine microsteatosis

Adult expression of IMP2 is often associated with several types of disease and cancer. The RNA binding protein IMP2 binds and stabilizes the IGF2 mRNA as well as hundreds of other transcripts during development. To gain insight into the molecular action of IMP2 and its contribution to disease in context of adult cellular metabolism, we analyze transgenic overexpression of IMP2 in mouse livers, which has been shown to induce a steatosis-like phenotype and enhanced risk to develop hepatocellular carcinoma (HCC). Our data show up-regulation of several HCC marker genes and miRNAs (miR438-3p and miR151-5p). To characterize the impact of miRNAs to their targets, integrative analysis of transcriptome-and miRNAome-dynamics in combination with IMP2 target prediction was carried out. Our analyses show that targets of expressed miRNAs become accumulated in the case that these transcripts have positive IMP2 binding prediction. Therefore, our data indicates that overexpression of IMP2 alters the regulatory capacity of many miRNAs and we conclude that IMP2 competes with miRNAs for binding sites on thousands of transcripts. As a result, our data implicates that overexpression of IMP2 has distinct effects to the regulatory capacity of miRNAs with yet unknown consequences for translational efficiency.

MicroRNA-190b regulates lipid metabolism and insulin sensitivity by targeting IGF-1 and ADAMTS9 in non-alcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is characterized by ectopic lipid accumulation and insulin resistance, yet the underlying molecular mechanisms are poorly understood. MiR-190b is thought to play a role in hepatocellular carcinoma by modulating insulin resistance; however, its role in NAFLD remains unknown. Here, we found that miR-190b expression was significantly increased in the liver tissues of patients with NAFLD, compared to normal tissues. Moreover, miR-190b was upregulated in a high-fat diet NAFLD mouse model and a free fatty acid-induced NAFLD cellular model. Knockdown of miR-190b decreased aspartate transaminase (AST), alanine transaminase (ALT), triglyceride (TG), and total cholesterol (TC). It also reduced expression of the lipogenic genes fatty acid synthase (FAS) and 3-hydroxy-3-methylglutarylCoA reductase (HMGCR), alleviated hepatic steatosis, improved glucose tolerance, elevated insulin sensitivity, and activated insulin receptor substrate (IRS)2/Akt signaling in vivo and/or in vitro. Furthermore, we confirmed that miR-190b directly targeted IGF-1 and ADAMTS9. MiR-190b overexpression suppressed expression of IGF-1 and ADAMTS9, which were increased by miR-190b inhibition. Expression of IGF-1 and ADAMTS9 was inversely correlated with miR-190b in liver tissues of patients with NAFLD, respectively. We also found that IGF-1 or ADAMTS9 inhibition partially reversed the effects of miR-190b on lipid metabolism and insulin signaling in vitro. Taken together, the data reveal that miR-190b inhibition suppressed lipid accumulation and improved insulin sensitivity by targeting IGF-1 and ADAMTS9, suggesting that miR-190b inhibition may be a therapeutic strategy against NAFLD.

Identification of differentially expressed miRNAs in the fatty liver of Landes goose (Anser anser)

Unlike mammals, in palmipedes de novo lipogenesis from diet takes place mostly in the liver. The French Landes Goose is famous for its high capacity and susceptibility to fatty liver production. While miRNAs play a critical role in the posttranscriptional regulation of gene expression, miRNAs that are involved in the regulation of goose hepatic steatosis have yet to be elucidated. Using high-throughput sequencing, we analyzed miRNAs expression profile of Landes goose liver after overfeeding for 21 days. Aan-miR-122-5p was the most frequently sequenced known miRNA, but it was unchanged after overfeeding. Compared with normal liver, we identified that 16 conserved miRNAs were up-regulated while the other 9 conserved miRNAs were down-regulated in fatty livers. Many of their predicted target genes played key roles in metabolic pathways leading to the development of hepatic steatosis in the goose by KEGG pathways analysis. ACSL1 and ELOVL6 were critical genes in hepatic lipid metabolism and had opposite expression patterns with aan-miR-203a and aan-miR-125b-5p, respectively. And we validated that aan-miR-203a and aan-miR-125b-5p might involve in the regulation of hepatic lipid metabolism by targeting ACSL1 and ELOVL6, respectively. These results add to our current understanding of the regulation network in goose lipid metabolism.

Fish Oil Feeding Modulates the Expression of Hepatic MicroRNAs in a Western-Style Diet-Induced Nonalcoholic Fatty Liver Disease Rat Model

Nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases worldwide. Recent studies have indicated that fish oil supplementation has benefits against NAFLD. Our previous transcriptomic study has validated the effect of fish oil supplementation on altering hepatic gene expression in a NAFLD rat model. In the current study, we examined the effects of fish oil on the expression of hepatic microRNAs. Male Sprague–Dawley rats were fed with a lab chow (CON), high-fat high-cholesterol diet (WD), or WD supplemented with fish oil (FOH), respectively. Small RNAs were extracted from livers for RNA-sequencing. A total of 79 miRNAs were identified as differentially expressed miRNAs (DEMs) between FOH and WD groups, exemplified by rno-miR-29c-3p, rno-miR-30d-5p, rno-miR-33-5p, rno-miR-34a, and rno-miR-328a-3p. Functional annotation of DEMs predicted target genes suggested that the altered hepatic miRNAs contributed to fish oil modification of hepatic lipid metabolism and signaling transduction. Integrative analysis of DEMs and differentially expressed genes suggested that the expression difference of Pcsk9, Insig2, Per3, and Socs1/3 between FOH and WD groups may be due to miRNA modification. Our study reveals that fish oil supplementation alters hepatic expression of miRNAs, which may contribute to fish oil amelioration of NAFLD in rats.

Serum microRNA-34a is potential biomarker for inflammation in nonalcoholic fatty liver disease

Background

MicroRNA-34a (miR-34a) contributes to liver injury through an apoptosis pathway.

Objective

To determine the correlation between serum miR-34a and liver inflammation as assessed by nonalcoholic fatty liver disease (NAFLD) activity score (NAS).

Method

We included a cross-selectional study of 50 patients with NAFLD in this observational study and confirmed diagnosis by liver biopsy, with NAS grading. A control group comprised 23 healthy individuals without chronic liver disease. Serum miR-34a was assayed using a real-time quantitative PCR (Applied Biosystems).

Result

The mean age of NAFLD patients was 46.0 ± 13.7 years, and 52% were female. Metabolic syndrome was found in 76%. Liver histopathology showed that 54% of patients had NAS ≥4 and significant fibrosis (≥2) was found in 22%. Serum levels of miR-34a were significantly correlated with NAS (r = 0.39, P = 0.005), and the degree of steatosis (r = 0.28, P = 0.049), ballooning (r = 0.30, P = 0.034), and fibrosis (r = 0.39, P = 0.005). Serum miR-34a in patients with NAS ≥4 was significantly higher than in those with NAS <4 (P = 0.011) and controls (P < 0.001). There was no significant correlation between serum miR-34a and other variables. The area under receiver operating characteristic curve for serum miR-34a comparing patients with NAS ≥4 and with NAS <4 was 0.67 (95% CI 0.52, 0.82).

Conclusion

Serum level of miR-34a has a significant fair to good correlation with NAS and may serve as a biomarker of liver inflammation and fibrosis in patients with NAFLD.

Salvia-Nelumbinis Naturalis Formula Improved Inflammation in LPS Stressed Macrophages via Upregulating MicroRNA-152

Salvia-Nelumbinis naturalis (SNN) formula is an effective agent in treating nonalcoholic steatohepatitis (NASH); however, the precise mechanisms are still undefined. Activation of Kupffer cells by gut-derived lipopolysaccharide (LPS) plays a central role in the pathogenesis of NASH. In the present study, we aimed to explore the epigenetic regulation of microRNAs under the beneficial effects of SNN-containing serum in LPS stressed macrophages. Kupffer cells were isolated from C57BL/6 mice and treated with LPS or LPS and SNN-containing serum; the mRNA expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) was assessed. By using microarray chips, we investigated differentially expressed microRNA profiles to decipher the underlining mechanisms of SNN-containing serum. It was revealed that SNN-containing serum decreased TNF-α and IL-6 expression, and microRNA-152 was identified as the potential epigenetic regulator. We further verified the pharmacological effects in Raw264.7 cells; while transfection with miRNA-152 mimics could reduce TNF-α and IL-6, transfection with miRNA-152 inhibitor blocked the anti-inflammatory effect of SNN-containing serum. These results suggested that SNN-containing serum could improve inflammation in LPS stressed Kupffer cells and macrophages via upregulating microRNA-152.

MicroRNA-124 promotes hepatic triglyceride accumulation through targeting tribbles homolog 3

An increase in hepatic triglyceride (TG) contents usually results in non-alcoholic fatty liver disease (NAFLD) and related metabolic diseases. However, the mechanisms underlying perturbations of hepatic TG homeostasis remain largely unknown. Here, we showed that MicroRNA-124 was up-regulated in the livers of C57BL/6 mice fed a short-term high-fat-diet (HFD). Adenoviral overexpression of miR-124 in C57BL/6 mice led to accumulation of excessive triglycerides and up-regulation of lipogenic genes in the liver. We further identified tribbles homolog 3 (TRB3) as a direct target of miR-124. AKT signaling, which is negatively regulated by TRB3, was enhanced by miR-124 overexpression. Moreover, restoration of TRB3 expression markedly abolished the effect of miR-124 on hepatic TG metabolism. Therefore, our findings revealed that miR-124 played a role in mediating high-fat-diet induced TG accumulation in the liver.

Stress-activated miR-21/miR-21* in hepatocytes promotes lipid and glucose metabolic disorders associated with high-fat diet consumption

OBJECTIVE

miR-21 is an oncomir highly upregulated in hepatocellular carcinoma and in early stages of liver diseases characterised by the presence of steatosis. Whether upregulation of miR-21 contributes to hepatic metabolic disorders and their progression towards cancer is unknown. This study aims at investigating the role of miR-21/miR-21* in early stages of metabolic liver disorders associated with diet-induced obesity (DIO).

DESIGN

Constitutive miR-21/miR-21* knockout (miR21KO) and liver-specific miR-21/miR-21* knockout (LImiR21KO) mice were generated. Mice were then fed with high-fat diet (HFD) and alterations of the lipid and glucose metabolism were investigated. Serum and ex vivo explanted liver tissue were analysed.

RESULTS

Under normal breeding conditions and standard diet, miR-21/miR-21* deletion in mice was not associated with any detectable phenotypic alterations. However, when mice were challenged with an obesogenic diet, glucose intolerance, steatosis and adiposity were improved in mice lacking miR-21/miR-21*. Deletion of miR-21/miR-21* specifically in hepatocytes led to similar improvements in mice fed an HFD, indicating a crucial role for hepatic miR-21/miR-21* in metabolic disorders associated with DIO. Further molecular analyses demonstrated that miR-21/miR-21* deletion in hepatocytes increases insulin sensitivity and modulates the expression of multiple key metabolic transcription factors involved in fatty acid uptake, de novo lipogenesis, gluconeogenesis and glucose output.

CONCLUSIONS

Hepatic miR-21/miR-21* deficiency prevents glucose intolerance and steatosis in mice fed an obesogenic diet by altering the expression of several master metabolic regulators. This study points out miR-21/miR-21* as a potential therapeutic target for non-alcoholic fatty liver disease and the metabolic syndrome.

Deregulated hepatic microRNAs underlie the association between non-alcoholic fatty liver disease and coronary artery disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) appears to be a new risk factor for the development of coronary artery disease (CAD). Members of a class of non-coding RNAs, termed microRNAs (miRNAs), have been identified as post-transcriptional regulators of cholesterol homoeostasis and can contribute to the development of NAFLD. The aims of this study were to (i) to assess the relationship between NAFLD and sudden cardiac death (SCD) from severe CAD in forensic autopsies and (ii) to quantify several hepatic miRNAs previously associated with lipid metabolism and NAFLD to correlate their expression with the presence of NAFLD, CAD, obesity parameters and postmortem lipid profile.

METHODS

A total of 133 cases of autopsies with SCD and established CAD (patient group, CAD-SCD) and 106 cases of non-CAD sudden death (control group, non-CAD-SD) were included. miRNAs were quantified in frozen liver tissues.

RESULTS

Males predominated in both groups. Patients more frequently exhibited NAFLD and necroinflammatory steatohepatitis (NASH) than controls (62% vs 26%, P = 0.001 and 42% vs 26%, P = 0.001 respectively). In both groups, the presence of NAFLD correlated with body mass index and abdominal circumference (P < 0.05). An increase in miR-34a-5p and a decrease in miR-122-5p and -29c-3p in patients with NASH vs controls without NAFLD were observed (P < 0.05). Finally, significant correlations between miR-122-5p and unfavourable lipid profile and also hs-CRP and miR-34a-5p were noted.

CONCLUSIONS

CAD is associated with NAFLD and NASH. The hepatic miRNAs studied appear to be associated with NAFLD severity and may promote CAD through lipid metabolism alteration and/or promotion of the systemic inflammation.

Fatty Acid Binding Protein-1 (FABP1) and the Human FABP1 T94A Variant: Roles in the Endocannabinoid System and Dyslipidemias

The first discovered member of the mammalian FABP family, liver fatty acid binding protein (FABP1, L-FABP), occurs at high cytosolic concentration in liver, intestine, and in the case of humans also in kidney. While the rat FABP1 is well studied, the extent these findings translate to human FABP1 is not clear-especially in view of recent studies showing that endocannabinoids and cannabinoids represent novel rat FABP1 ligands and FABP1 gene ablation impacts the hepatic endocannabinoid system, known to be involved in non-alcoholic fatty liver (NAFLD) development. Although not detectable in brain, FABP1 ablation nevertheless also impacts brain endocannabinoids. Despite overall tertiary structure similarity, human FABP1 differs significantly from rat FABP1 in secondary structure, much larger ligand binding cavity, and affinities/specificities for some ligands. Moreover, while both mouse and human FABP1 mediate ligand induction of peroxisome proliferator activated receptor-α (PPARα), they differ markedly in pattern of genes induced. This is critically important because a highly prevalent human single nucleotide polymorphism (SNP) (26-38 % minor allele frequency and 8.3 ± 1.9 % homozygous) results in a FABP1 T94A substitution that further accentuates these species differences. The human FABP1 T94A variant is associated with altered body mass index (BMI), clinical dyslipidemias (elevated plasma triglycerides and LDL cholesterol), atherothrombotic cerebral infarction, and non-alcoholic fatty liver disease (NAFLD). Resolving human FABP1 and the T94A variant's impact on the endocannabinoid and cannabinoid system is an exciting challenge due to the importance of this system in hepatic lipid accumulation as well as behavior, pain, inflammation, and satiety.

miR-149 controls non-alcoholic fatty liver by targeting FGF-21

Non‐alcoholic fatty liver disease (NAFLD), a lipid metabolism disorder characterized by the accumulation of intrahepatic fat, has emerged as a global public health problem. However, its underlying molecular mechanism remains unclear. We previously have found that miR‐149 was elevated in NAFLD induced by high‐fat diet mice model, whereas decreased by a 16‐week running programme. Here, we reported that miR‐149 was increased in HepG2 cells treated with long‐chain fatty acid (FFA). In addition, miR‐149 was able to promote lipogenesis in HepG2 cells in the absence of FFA treatment. Moreover, inhibition of miR‐149 was capable of inhibiting lipogenesis in HepG2 cells in the presence of FFA treatment. Meanwhile, fibroblast growth factor‐21 (FGF‐21) was identified as a target gene of miR‐149, which was demonstrated by the fact that miR‐149 could negatively regulate the protein expression level of FGF‐21, and FGF‐21 was also responsible for the effect of miR‐149 inhibitor in decreasing lipogenesis in HepG2 cells in the presence of FFA treatment. These data implicate that miR‐149 might be a novel therapeutic target for NAFLD.

Lipid deposition in liver cells: The influence of short form augmenter of liver regeneration

BACKGROUND AND OBJECTIVE

The short form augmenter of liver regeneration (sfALR) is a novel human hepatotrophic growth factor. The aim of this study was to investigate the potential role of sfALR in NAFLD.

METHODS

The free fatty acids (FFA) induced lipid accumulation in mouse liver parenchymal cells was examined by Oil Red O staining and triglyceride level determination. The cell cycle was determined by flow cytometry and the proliferation was assessed by CCK8. The expression levels of gfer, miR-122, srebp-1c, fas, dgat2, acc1 and Lrp1B were assessed by quantitative real-time PCR. Furthermore, the MAPK pathway was detected by western blot.

RESULTS

The results showed that sfALR could alleviate the lipid accumulation in mice both in vivo and in vitro. sfALR relieved the proliferation inhibition and G2 arrest of mouse liver parenchymal cells induced by FFAs. Free fatty acids affected gfer expression in a time-and dose-dependent way. And sfALR suppressed JNK activation, increased miR-122 level and reduced fatty acid synthesis-related gene expression.

CONCLUSION

These findings suggested that sfALR could alleviate the severity of fatty liver in mice.

miR-212 downregulation contributes to the protective effect of exercise against non-alcoholic fatty liver via targeting FGF-21

Non-alcoholic fatty liver disease (NAFLD) is associated with obesity and lifestyle, while exercise is beneficial for NAFLD. Dysregulated microRNAs (miRs) control the pathogenesis of NAFLD. However, whether exercise could prevent NAFLD via targeting microRNA is unknown. In this study, normal or high-fat diet (HF) mice were either subjected to a 16-week running program or kept sedentary. Exercise attenuated liver steatosis in HF mice. MicroRNA array and qRT-PCR demonstrated that miR-212 was overexpressed in HF liver, while reduced by exercise. Next, we investigated the role of miR-212 in lipogenesis using HepG2 cells with/without long-chain fatty acid treatment (± FFA). FFA increased miR-212 in HepG2 cells. Moreover, miR-212 promoted lipogenesis in HepG2 cells (± FFA). Fibroblast growth factor (FGF)-21, a key regulator for lipid metabolism, was negatively regulated by miR-212 at protein level in HepG2 cells. Meanwhile, FFA downregulated FGF-21 both at mRNA and protein levels in HepG2 cells. Also, FGF-21 protein level was reduced in HF liver, while reversed by exercise in vivo. Furthermore, siRNA-FGF-21 abolished the lipogenesis-reducing effect of miR-212 inhibitor in HepG2 cells (± FFA), validating FGF-21 as a target gene of miR-212. These data link the benefit of exercise and miR-212 downregulation in preventing NAFLD via targeting FGF-21.

Effect of miR-34a in regulating steatosis by targeting PPARα expression in nonalcoholic fatty liver disease

MicroRNA-34a (miR-34a) is thought to be involved in nonalcoholic fatty liver disease (NAFLD). However, the association between altered expression of miR-34a and the pathophysiological features of NAFLD remains unclear. Here, we investigated the mechanisms by which miR-34a influences NAFLD through the PPARα-related pathway. Real-time quantitative PCR, western blotting and other assays kit were used to investigate the expression and function of miR-34a in an NAFLD model. Cultured cells transfected with miR-34a inhibitor and C57BL/6 mice injected with the miR-34a inhibitor through vein tail were conducted for the effects of miR-34a on its target. MiR-34a levels were significantly upregulated in steatosis-induced hepatocytes and in liver tissues of high-fat diet-fed mice. The upregulation of miR-34a resulted in the downregulation of hepatic PPARα and SIRT1 that are the direct targets of miR-34a. Silencing miR-34a led to an initially increased expression of PPARα, SIRT1 and PPARα’s downstream genes. Activation of the central metabolic sensor AMPK was also increased. The miR-34a inhibitor suppressed lipid accumulation and improved the degree of steatosis. Taken together, our data indicated that decreased expression of miR-34a potentially contributes to altered lipid metabolism in NAFLD. Downregulation of miR-34a may be a therapeutic strategy against NAFLD by regulating its target PPARα and SIRT1.

Regulation of MicroRNA 183 by Cyclooxygenase 2 in Liver Is DEAD-Box Helicase p68 (DDX5) Dependent: Role in Insulin Signaling

Cyclooxygenase (COX) catalyzes the first step in prostanoid biosynthesis and exists as two isoforms. COX-1 is a constitutive enzyme involved in physiological processes, whereas COX-2 is induced by a variety of stimuli. MicroRNAs (miRNAs) are noncoding RNAs that function as key posttranscriptional regulators of gene expression. Although it is known that COX-2 expression is regulated by miRNAs, there are no data regarding COX-2 involvement in miRNA regulation. Considering our previous results showing that COX-2 expression in hepatocytes protects against insulin resistance, we evaluated the role of COX-2 in the regulation of a specific set of miRNAs implicated in insulin signaling in liver cells. Our results provide evidence of the molecular basis for a novel function of COX-2 in miRNA processing. COX-2 represses miRNA 23b (miR-23b), miR-146b, and miR-183 expression in liver cells by increasing the level of DEAD-box helicase p68 (DDX5) through phosphatidylinositol 3-kinase (PI3K)/p300 signaling and by modulating the enzymatic function of the Drosha (RNase type III) complex through its physical association with DDX5. The decrease of miR-183 expression promotes protection against insulin resistance by increasing insulin receptor substrate 1 (IRS1) levels. These results indicate that the modulation of miRNA processing by COX-2 is a key event in insulin signaling in liver and has potential clinical implications for the management of various hepatic dysfunctions.

Downregulation of microRNA-451 in non-alcoholic steatohepatitis inhibits fatty acid-induced proinflammatory cytokine production through the AMPK/AKT pathway

Mechanisms associated with the progression of non-alcoholic fatty liver disease (NAFLD) remain unclear. We attempted to identify the pattern of altered gene expression at different time points in a high fat diet (HFD)-induced NAFLD mouse model. The early up-regulated genes are mainly involved in the innate immune responses, while the late up-regulated genes represent the inflammation processes. Although recent studies have shown that microRNAs play important roles in hepatic metabolic functions, the pivotal role of microRNAs in the progression of NAFLD is not fully understood. We investigated the functions of miR-451, which was identified as a target gene in the inflammatory process in NAFLD. miR-451 expression was significantly decreased in the palmitate (PA)-exposed HepG2 cells and in liver tissues of HFD-induced non-alcoholic steatohepatitis (NASH) mice. Its decreased expressions were also observed in liver specimens of NASH patients. In vitro analysis of the effect of miR-451 on proinflammatory cytokine provided evidence for negative regulation of PA-induced interleukin (IL)-8 and tumor necrosis factor-alpha (TNF-α) production. Furthermore, miR-451 over-expression inhibited translocation of the PA-induced NF-κB p65 subunit into the nucleus. Our result showed that Cab39 is a direct target of miRNA-451 in steatotic cells. Further study showed that AMPK activated through Cab39 inhibits NF-κB transactivation induced in steatotic HepG2 cells. miR-451 over-expression in steatotic cells significantly suppressed PA-induced inflammatory cytokine. These results provide new insights into the negative regulation of miR-451 in fatty acid-induced inflammation via the AMPK/AKT pathway and demonstrate potential therapeutic applications for miR-451 in preventing the progression from simple steatosis to severely advanced liver disease.

Upregulation of miR21 and repression of Grhl3 by leptin mediates sinusoidal endothelial injury in experimental nonalcoholic steatohepatitis

Sinusoidal endothelial dysfunction (SED) has been found to be an early event in nonalcoholic steatohepatitis (NASH) progression but the molecular mechanisms underlying its causation remains elusive. We hypothesized that adipokine leptin worsens sinusoidal injury by decreasing functionally active nitric oxide synthase 3 (NOS)3 via miR21. Using rodent models of NASH, and transgenic mice lacking leptin and leptin receptor, results showed that hyperleptinemia caused a 4-5 fold upregulation of hepatic miR21 as assessed by qRTPCR. The upregulation of miR21 led to a time-dependent repression of its target protein Grhl3 levels as shown by western blot analyses. NOS3-p/NOS3 ratio which is controlled by Grhl3 was significantly decreased in NASH models. SED markers ICAM-1, VEGFR-2, and E-selectin as assessed by immunofluorescence microscopy were significantly up regulated in the progressive phases of NASH. Lack of leptin or its receptor in vivo, reversed the upregulation of miR21 and restored the levels of Grhl3 and NOS3-p/NOS3 ratio coupled with decreased SED dysfunction markers. Interestingly, leptin supplementation in mice lacking leptin, significantly enhanced miR21 levels, decreased Grhl3 repression and NOS3 phosphorylation. Leptin supplementation in isolated primary endothelial cells, Kupffer cells and stellate cells showed increased mir21 expression in stellate cells while sinusoidal injury was significantly higher in all cell types. Finally miR21 KO mice showed increased NOS3-p/NOS3 ratio and reversed SED markers in the rodent models of NASH. The experimental results described here show a close association of leptin-induced miR21 in aiding sinusoidal injury in NASH.

Aberrant miR199a-5p/caveolin1/PPARα axis in hepatic steatosis

The prevalence of non-alcoholic fatty liver disease (NAFLD), a condition characterized by an excessive accumulation of triglycerides (TGs) in hepatocytes, has dramatically increased globally during recent decades. MicroRNAs (miRs) have been suggested to play crucial roles in many complex diseases and lipid metabolism. Our results indicated that miR199a-5p was remarkably upregulated in free fatty acid (FA)-treated hepatocytes. To investigate the role of miR199a-5p in the pathogenesis of fatty liver and the potential mechanism by which miR199a-5p regulates NAFLD, we first transfected two hepatocyte cell lines, HepG2 and AML12 cells, with agomiR199a-5p or antagomiR199a-5p. Our results indicated that miR199a-5p overexpression exacerbated deposition of FA and inhibited ATP levels and mitochondrial DNA (mtDNA) contents. Consistently, suppression of miR199a-5p partially alleviated deposition of FA and increased ATP levels and mtDNA contents. Moreover, miR199a-5p suppressed the expression of mitochondrial FA β-oxidation-related genes through inhibition of caveolin1 (CAV1) and the related peroxisome proliferator-activated receptor alpha (PPARα) pathway. Furthermore, suppression of CAV1 gene expression by CAV1 siRNA inhibited the PPARα signalling pathway. Finally, we examined the expression of miR199a-5p in liver samples derived from mice fed a high-fat diet, db/db mice, ob/ob mice and NAFLD patients, and found that miR199a-5p was upregulated while CAV1 and PPARA were downregulated in these systems, which was strongly indicative of the essential role of miR199a-5p in NAFLD. In summary, miR199a-5p plays a vital role in lipid metabolism, mitochondrial activity and mitochondrial β-oxidation in liver. Upregulated miR199a-5p in hepatocytes may contribute to impaired FA β-oxidation in mitochondria and aberrant lipid deposits, probably via CAV1 and the PPARα pathway.

Toll-like receptor-mediated signaling cascade as a regulator of the inflammation network during alcoholic liver disease

Chronic abuse of alcohol leads to various histological abnormalities in the liver. These are conditions collectively known as alcoholic liver disease (ALD). Currently, ALD is considered to be one of the major causes of death worldwide. An impaired intestinal barrier with related endotoxemia is among the various pathogenetic factors. This is mainly characterized by circulating levels of lipopolysaccharide (LPS), considered critical for the onset of intra-hepatic inflammation. This in turn promotes hepatocellular damage and fibrosis in ALD. Elevated levels of LPS exert their effects by binding to Toll-like receptors (TLRs) which are expressed by all liver-resident cells. The activation of TLR signaling triggers an overproduction and release of some cytokines, which promote an autocatalytic cascade of other pro-inflammatory signals. In this review, we provide an overview of the mechanisms that sustain LPS-mediated activation of TLR signaling, reporting current experimental and clinical evidence of its role during inflammation in ALD.

The effect of miRNA-122 in regulating fat deposition in a cell line model

Accumulating evidence supports the role of miR-122 in fatty liver disease. We investigated miR-122 expression in a steatotic hepatocyte model, the effect of miR-122 over-expression and inhibition in the pathogenesis. Human hepatic cell line L02 was induced with oleic acid to establish the steatotic hepatocyte model. Intracellular lipid content was observed with laser scanning confocal microscope (LSCM), and triglyceride content was determined with kits. Total RNA was extracted and reversely transcribed into cDNA. miR-122 expression was measured using qRT-PCR. Subsequently, miR-122 mimic and miR-122 inhibitor were transfected into steatotic hepatocytes to observe their effect on intracellular lipid content. The lipid fluorescence intensity and triglyceride content within the steatotic hepatocytes were significantly higher than those in normal control (860.01 ± 26.52 vs. 257.77 ± 29.69 and 3.47 ± 0.12 vs. 1.85 ± 0.02 at 24 h) (P < 0.01). miR-122 expression in steatotic hepatocytes was down-regulated compared with that in control (2-ΔCt value: 0.0286 ± 0.0078 vs. 0.0075 ± 0.0012) (P ≪ 0.01). After transfection, miR-122 expression (2-ΔCt value) in the miR-122 mimic group increased 2.96-fold compared with that in control, and its lipid fluorescence intensity was significantly lower than that in control (790.92 ± 46.72 vs. 1,022.16 ± 49.66) (P < 0.01). Nevertheless, miR-122 expression decreased 3.45-fold in the miR-122 inhibitor group compared with that in control, and its fluorescence intensity was significantly higher than that in control (1,386.49 ± 40.34 vs 1,022.16 ± 49.66)(P ≪ 0.01). We concluded that miR-122 was down-regulated in steatotic hepatocytes model. The pathogenesis of hepatocyte steatosis was enhanced by miR-122 mimic and reduced with miR-122 inhibitor.

Progress in the search for circulating biomarkers of nonalcoholic fatty liver disease

CONTEXT

The definitive standard for the diagnosis of nonalcoholic fatty liver disease (NAFLD) is clinico-pathological correlation, but frequently the only laboratory abnormality is an elevation of serum aminotransferases.

OBJECTIVE

This has resulted in the search for more specific laboratory biomarkers.

METHODS

The literature was searched for novel plasma/serum markers of NAFLD.

RESULTS

Studies reviewed here included histologically-confirmed patients presenting some stage of NAFLD and monitored one or more novel serum/plasma biomarkers.

CONCLUSION

The most promising application of some of these novel biomarkers for the detection and quantification of NAFLD and particularly NASH appears to be in the combination of several into diagnostic panels.

Regulation of microRNAs and their role in liver development, regeneration and disease

Since their discovery more than a decade ago microRNAs have been demonstrated to have profound effects on almost every aspect of biology. Numerous studies in recent years have shown that microRNAs have important roles in development and in the etiology and progression of disease. This review is focused on microRNAs and the roles they play in liver development, regeneration and liver disease; particularly chronic liver diseases such as alcoholic liver disease, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, viral hepatitis and primary liver cancer. The key microRNAs identified in liver development and chronic liver disease will be discussed together with, where possible, the target messenger RNAs that these microRNAs regulate to profoundly alter these processes. This article is part of a Directed Issue entitled: The Non-coding RNA Revolution.