Down-regulation of lncRNA-NEAT1 alleviated the non-alcoholic fatty liver disease via mTOR/S6K1 signaling pathway

LncRNA NEAT1 in the pathogenesis of liver-related diseases

Nuclear paraspeckle assembly transcript 1 (NEAT1) is a long noncoding RNA (lncRNA) that is widely expressed in a variety of mammalian cell types. Altered expression levels of the lncRNA NEAT1 have been reported in liver-related disorders including cancer, fatty liver disease, liver fibrosis, viral hepatitis, and hepatic ischemia. lncRNA NEAT1 mostly acts as a competing endogenous RNA (ceRNA) to sponge various miRNAs (miRs) to regulate different functions. In regard to hepatic cancers, the elevated expression of NEAT1 has been reported to have a relation with the proliferation, migration, angiogenesis, apoptosis, as well as epithelial-mesenchymal transition (EMT) of cancer cells. Furthermore, NEAT1 upregulation has contributed to the pathogenesis of other liver diseases such as fibrosis. In this review, we summarize and discuss the molecular mechanisms by which NEAT1 contributes to liver-related disorders including acute liver failure, nonalcoholic fatty liver disease (NAFLD), liver fibrosis, and liver carcinoma, providing novel insights and introducing NEAT1 as a potential therapeutic target in these diseases.

Molecular Insights of Nonalcoholic Fatty Liver Disease Pathogenesis

Nonalcoholic fatty liver disease (NAFLD) is now the most prevalent chronic liver disease. Many hepatic abnormalities are associated with NAFLD such as nonalcoholic steatohepatitis, progressive fibrosis, cirrhosis, and liver failure. Moreover, the pathogenesis of NAFLD has numerous etiologies and can be explained due to the existence of several of stimulus that act simultaneously on genetically susceptible patients. These stimuli include obesity, diabetes, and insulin resistance. In addition, identifying the role of gut microbiota on NAFLD progression has been illustrated. In this review, we clarified the several factors that lead to the development of NAFLD and identify those who are most at risk of developing liver end-stage disease. Highlighting the noninvasive diagnostic NAFLD markers could be helpful in the disease prevention and treatment approaches.

Two sides of the same coin: Non-alcoholic fatty liver disease and atherosclerosis

The prevalence of non-alcoholic fatty liver disease (NAFLD) and atherosclerosis remain high, which is primarily due to widespread adoption of a western diet and sedentary lifestyle. NAFLD, together with advanced forms of this disease such as non-alcoholic steatohepatitis (NASH) and cirrhosis, are closely associated with atherosclerotic-cardiovascular disease (ASCVD). In this review, we discussed the association between NAFLD and atherosclerosis and expounded on the common molecular biomarkers underpinning the pathogenesis of both NAFLD and atherosclerosis. Furthermore, we have summarized the mode of function and potential clinical utility of existing drugs in the context of these diseases.

NEAT1 in inflammatory infectious diseases: An integrated perspective on molecular modulation

The long non-coding RNA (lncRNA), NEAT1, has emerged as a central figure in the intricate network of molecular regulators in inflammatory infectious diseases (IIDs). The review initiates a comprehensive exploration of NEAT1's multifaceted roles and molecular interactions in the context of these complex diseases. The study begins by acknowledging the global health burden of IIDs, underscoring the urgency for innovative insights into their pathogenesis and therapeutic avenues. NEAT1 is introduced as a pivotal lncRNA with growing relevance in immune responses and inflammatory processes. The core of this review unravels the NEAT1 landscape, elucidating its involvement in the modulation of immune signalling pathways, regulation of inflammatory cytokines, and interactions with various immune cells during infection. It explores NEAT1's role in orchestrating immune responses and balancing host defence mechanisms with the risk of immunopathology. Furthermore, the review underscores the clinical significance of NEAT1 in infectious diseases, discussing its associations with disease severity, prognosis, and potential as a diagnostic and therapeutic target. It provides insights into ongoing research endeavours aimed at harnessing NEAT1 for innovative disease management strategies, including developing RNA-based therapeutics. Concluding on a forward-looking note, the review highlights the broader implications of NEAT1 in the context of emerging infectious diseases and the possibility for precision medicine approaches that leverage NEAT1's regulatory capacities. In summary, this review illuminates the pivotal role of NEAT1 in IIDs by navigating its complex landscape, offering profound insights into its implications for disease pathogenesis and the development of targeted therapies.

Investigating the Role of Non-Coding RNA in Non-Alcoholic Fatty Liver Disease

Non-coding RNAs (ncRNAs) are RNA molecules that do not code for protein but play key roles in regulating cellular processes. NcRNAs globally affect gene expression in diverse physiological and pathological contexts. Functionally important ncRNAs act in chromatin modifications, in mRNA stabilization and translation, and in regulation of various signaling pathways. Non-alcoholic fatty liver disease (NAFLD) is a set of conditions caused by the accumulation of triacylglycerol in the liver. Studies of ncRNA in NAFLD are limited but have demonstrated that ncRNAs play a critical role in the pathogenesis of NAFLD. In this review, we summarize NAFLD's pathogenesis and clinical features, discuss current treatment options, and review the involvement of ncRNAs as regulatory molecules in NAFLD and its progression to non-alcoholic steatohepatitis (NASH). In addition, we highlight signaling pathways dysregulated in NAFLD and review their crosstalk with ncRNAs. Having a thorough understanding of the disease process's molecular mechanisms will facilitate development of highly effective diagnostic and therapeutic treatments. Such insights can also inform preventive strategies to minimize the disease's future development.

ZNF143 inhibits hepatocyte mitophagy and promotes non-alcoholic fatty liver disease by targeting increased lncRNA NEAT1 expression to activate ROCK2 pathway

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the most common hepatic disorders worldwide. The mitophagy is suggested to be repressed in NAFLD, but the mechanism remains to be elucidated.

METHODS

NAFLD cell and mouse models were established by treating with free fatty acid (FFA) and feeding a high fat diet (HFD), respectively. QRT-PCR, Western blotting, or IHC measured the expression of ZNF143, lncRNA NEAT1, ROCK2, and lipid formation/mitophagy-related proteins. Cell viability and mitophagy were evaluated by MTT and immunofluorescence. The chloroform-methanol extraction method measured triglyceride and total cholesterol levels. ELISA detected ALT and AST levels. The interactions among ZNF143, lncRNA NEAT1 and SND1 were analysed by ChIP, dual-luciferase reporter, pull-down, and RIP. The lipid droplets were determined by Oil-red O and HE staining.

RESULTS

ZNF143 and lncRNA NEAT1 were upregulated in hepatic cells treated with FFA (p < 0.01 and p < 0.001). Knockdown of ZNF143 or lncRNA NEAT1 inhibited lipid droplets formation, while promoting mitophagy (p < 0.01 and p < 0.001). ZNF143 promoted lncRNA NEAT1 transcriptional expression through binding to its promoter. LncRNA NEAT1 increased ROCK2 mRNA stability by targeting SND1. LncRNA NEAT1 or ROCK2 overexpression reversed the effect of ZNF143 or lncRNA NEAT1 knockdown on hepatic steatosis and mitophagy (p < 0.01 and p < 0.001). ZNF143 or lncRNA NEAT1 knockdown inhibited HFD-induced steatosis and promoted mitophagy in vivo (p < 0.01 and p < 0.001).

CONCLUSION

The upregulation of lncRNA NEAT1 caused by ZNF143 promoted NAFLD through inhibiting mitophagy via activating ROCK2 pathway by targeting SND1, providing potential targets for NAFLD therapy.

A crosstalk between epigenetic modulations and non-alcoholic fatty liver disease progression

Non-alcoholic fatty liver disease (NAFLD) has recently emerged as a major public health concern worldwide due to its rapidly rising prevalence and its potential to progress into end-stage liver disease. While the precise pathophysiology underlying NAFLD remains incompletely understood, it is strongly associated with various environmental triggers and other metabolic disorders. Epigenetics examines changes in gene expression that are not caused by alterations in the DNA sequence itself. There is accumulating evidence that epigenetics plays a key role in linking environmental cues to the onset and progression of NAFLD. Our understanding of how epigenetic mechanisms contribute to NAFLD pathophysiology has expanded considerably in recent years as research on the epigenetics of NAFLD has developed. This review summarizes recent insights into major epigenetic processes that have been implicated in NAFLD pathogenesis including DNA methylation, histone acetylation, and microRNAs that have emerged as promising targets for further investigation. Elucidating epigenetic mechanisms in NAFLD may uncover novel diagnostic biomarkers and therapeutic targets for this disease. However, many questions have remained unanswered regarding how epigenetics promotes NAFLD onset and progression. Additional studies are needed to further characterize the epigenetic landscape of NAFLD and validate the potential of epigenetic markers as clinical tools. Nevertheless, an enhanced understanding of the epigenetic underpinnings of NAFLD promises to provide key insights into disease mechanisms and pave the way for novel prognostic and therapeutic approaches.

Role of Non-Coding RNAs in Hepatocellular Carcinoma Progression: From Classic to Novel Clinicopathogenetic Implications

Hepatocellular carcinoma (HCC) is a predominant malignancy with increasing incidences and mortalities worldwide. In Western countries, the progressive affirmation of Non-alcoholic Fatty Liver Disease (NAFLD) as the main chronic liver disorder in which HCC occurrence is appreciable even in non-cirrhotic stages, constitutes a real health emergency. In light of this, a further comprehension of molecular pathways supporting HCC onset and progression represents a current research challenge to achieve more tailored prognostic models and appropriate therapeutic approaches. RNA non-coding transcripts (ncRNAs) are involved in the regulation of several cancer-related processes, including HCC. When dysregulated, these molecules, conventionally classified as "small ncRNAs" (sncRNAs) and "long ncRNAs" (lncRNAs) have been reported to markedly influence HCC-related progression mechanisms. In this review, we describe the main dysregulated ncRNAs and the relative molecular pathways involved in HCC progression, analyzing their implications in certain etiologically related contexts, and their applicability in clinical practice as novel diagnostic, prognostic, and therapeutic tools. Finally, given the growing evidence supporting the immune system response, the oxidative stress-regulated mechanisms, and the gut microbiota composition as relevant emerging elements mutually influencing liver-cancerogenesis processes, we investigate the relationship of ncRNAs with this triad, shedding light on novel pathogenetic frontiers of HCC progression.

The function of long non-coding RNA in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease is a disease that is currently prevalent in the world, increasingly becoming the mainstay of liver diseases. And its prevalence is rapidly increasing, but its pathogenesis is not entirely understood. Long non-coding RNAs have increasingly gained attention as science has progressed in recent years. Studies have shown that long non-coding RNAs are involved in a variety of biological processes in vivo, such as proliferation, differentiation, and apoptosis, and can affect disease by regulating gene expression. This review explores the biological processes involving long non-coding RNAs, including lipid metabolism, glucose metabolism, liver fibrosis, and apoptosis. In addition, we summarize how the different long non-coding RNAs involved in each process function. Finally, the shortcomings of long non-coding RNAs as potential therapeutic targets are briefly described. In conclusion, this article provides a clear visualization of the link that exists between long non-coding RNAs and non-alcoholic fatty liver disease.

The role of long non-coding RNAs in carbohydrate and fat metabolism in the liver

The metabolism of carbohydrates and lipids (fat) in the liver is closely interconnected both in physiological conditions and in pathology. This relationship in the body is possible due to the regulation by many factors, including epigenetic ones. Histone modifications, DNA methylation, and non-coding RNAs are considered to be the main epigenetic factors. Non-coding RNAs (ncRNAs) refers to ribonucleic acid (RNA) molecules that do not code for a protein. They cover a huge number of RNA classes and perform a wide range of biological functions such as regulating gene expression, protecting the genome from exogenous DNA, and directing DNA synthesis. One such class of ncRNAs that has been extensively studied are long non-coding RNAs (lncRNAs). The important role of lncRNAs in the formation and maintenance of normal homeostasis of biological systems, as well as participation in many pathological processes, has been proven. The results of recent studies indicate the importance of lncRNAs in lipid and carbohydrate metabolism. Modifications of lncRNAs expression can lead to disruption of biological processes in tissues, including fat and protein, such as adipocyte proliferation and differentiation, inflammation, and insulin resistance. Further study of lncRNAs made it possible to partly determine the regulatory mechanisms underlying the formation of an imbalance in carbohydrate and fat metabolism individually and in their relationship, and the degree of interaction between different types of cells involved in this process. This review will focus on the function of lncRNAs and its relation to hepatic carbohydrate and fat metabolism and related diseases in order to elucidate the underlying mechanisms and prospects for studies with lncRNAs.

Could Long Non-Coding RNA MEG3 and PTENP1 Interact with miR-21 in the Pathogenesis of Non-Alcoholic Fatty Liver Disease?

NAFLD is the most common cause of chronic liver disease worldwide. The miRNAs and lncRNAs are important endogenous ncRNAs families that can regulate molecular mechanisms. The aim of this study was to analyze the miRNA and lncRNA expression profiles in serum samples of NAFLD patients with different types of hepatosteatosis compared to healthy controls by the qPCR method. A total of180 NAFLD patients and 60 healthy controls were included. miRCURY LNA miRNA miRNome PCR human panel I + II kit and LncProfiler qPCR Array Kit were used to detect miRNA and lncRNA expression, respectively. DIANA miRPath and DIANA-lncBase web servers were used for interaction analysis. As a result, 75 miRNA and 24 lncRNA expression changes were determined. For miRNAs and lncRNAs, 30 and 5 were downregulated and 45 and 19 were upregulated, respectively. hsa-miR-21 was upregulated 2-fold whereas miR-197 was downregulated 0.25-fold. Among lncRNAs, NEAT1 was upregulated 2.9-fold while lncRNA MEG3 was downregulated 0.41-fold. A weak correlation was found between hsa-miR-122 and lncRNA MALAT1. As a conclusion, it is clear that lncRNA-miRNA interaction is involved in the molecular mechanisms of the emergence of NAFLD. The lncRNAs MEG3 and PTENP1 interacted with hsa-miR-21. It was thought that this interaction should be investigated as a biomarker for the development of NAFLD.

An Updated Review of Contribution of Long Noncoding RNA-NEAT1 to the Progression of Human Cancers

Long non-coding RNAs (lncRNAs) present pivotal roles in cancer tumorigenesis and progression. Recently, nuclear paraspeckle assembly transcript 1 (NEAT1) as a lncRNA has been shown to mediate cell proliferation, migration, and EMT in tumor cells. NEAT1 by targeting several miRNAs/mRNA axes could regulate cancer cell behavior. Therefore, NEAT1 may function as a potent biomarker for the prediction and treatment of some human cancers. In this review, we summarized various NEAT1-related signaling pathways that are critical in cancer initiation and progression.

The essential effect of mTORC1-dependent lipophagy in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a chronic progressive liver disease with increasing prevalence. Lipophagy is a type of programmed cell death that plays an essential role in maintaining the body's balance of fatty acid metabolism. However, the livers of NAFLD patients are abnormally dysregulated in lipophagy. mTORC1 is a critical negative regulator of lipophagy, which has been confirmed to participate in the process of lipophagy through various complex mechanisms. Therefore, targeting mTORC1 to restore failed autophagy may be an effective therapeutic strategy for NAFLD. This article reviews the main pathways through which mTORC1 participates in the formation of lipophagy and the intervention effect of mTORC1-regulated lipophagy in NAFLD, providing new therapeutic strategies for the prevention and treatment of NAFLD in the future.

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.

The Implications of Noncoding RNAs in the Evolution and Progression of Nonalcoholic Fatty Liver Disease (NAFLD)-Related HCC

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver pathology worldwide. Meanwhile, liver cancer represents the sixth most common malignancy, with hepatocellular carcinoma (HCC) as the primary, most prevalent subtype. Due to the rising incidence of metabolic disorders, NAFLD has become one of the main contributing factors to HCC development. However, although NAFLD might account for about a fourth of HCC cases, there is currently a significant gap in HCC surveillance protocols regarding noncirrhotic NAFLD patients, so the majority of NAFLD-related HCC cases were diagnosed in late stages when survival chances are minimal. However, in the past decade, the focus in cancer genomics has shifted towards the noncoding part of the genome, especially on the microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), which have proved to be involved in the regulation of several malignant processes. This review aims to summarize the current knowledge regarding some of the main dysregulated, noncoding RNAs (ncRNAs) and their implications for NAFLD and HCC development. A central focus of the review is on miRNA and lncRNAs that can influence the progression of NAFLD towards HCC and how they can be used as potential screening tools and future therapeutic targets.

Noncoding RNAs as additional mediators of epigenetic regulation in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common cause of chronic liver disorder worldwide. It represents a spectrum that includes a continuum of different clinical entities ranging from simple steatosis to nonalcoholic steatohepatitis, which can evolve to cirrhosis and in some cases to hepatocellular carcinoma, ultimately leading to liver failure. The pathogenesis of NAFLD and the mechanisms underlying its progression to more pathological stages are not completely understood. Besides genetic factors, evidence indicates that epigenetic mechanisms occurring in response to environmental stimuli also contribute to the disease risk. Noncoding RNAs (ncRNAs), including microRNAs, long noncoding RNAs, and circular RNAs, are one of the epigenetic factors that play key regulatory roles in the development of NAFLD. As the field of ncRNAs is rapidly evolving, the present review aims to explore the current state of knowledge on the roles of these RNA species in the pathogenesis of NAFLD, highlight relevant mechanisms by which some ncRNAs can modulate regulatory networks implicated in NAFLD, and discuss key challenges and future directions facing current research in the hopes of developing ncRNAs as next-generation non-invasive diagnostics and therapies in NAFLD and subsequent progression to hepatocellular carcinoma.

Noncoding RNAs Associated with PPARs in Etiology of MAFLD as a Novel Approach for Therapeutics Targets

Background. Metabolic associated fatty liver disease (MAFLD) is a complex disease that results from the accumulation of fat in the liver. MAFLD is directly associated with obesity, insulin resistance, diabetes, and metabolic syndrome. PPARγ ligands, including pioglitazone, are also used in the management of this disease. Noncoding RNAs play a critical role in various diseases such as diabetes, obesity, and liver diseases including MAFLD. However, there is no adequate knowledge about the translation of using these ncRNAs to the clinics, particularly in MAFLD conditions. The aim of this study was to identify ncRNAs in the etiology of MAFLD as a novel approach to the therapeutic targets. Methods. We collected human and mouse MAFLD gene expression datasets available in GEO. We performed pathway enrichment analysis of total mRNAs based on KEGG repository data to screen the most potential pathways in the liver of MAFLD human subjects and mice model, and analyzed pathway interconnections via ClueGO. Finally, we screened disease causality of the MAFLD ncRNAs, which were associated with PPARs, and then discussed the role of revealed ncRNAs in PPAR signaling and MAFLD. Results. We found 127 ncRNAs in MAFLD which 25 out of them were strongly validated before for regulation of PPARs. With a polypharmacology approach, we screened 51 ncRNAs which were causal to a subset of diseases related to MAFLD. Conclusion. This study revealed a subset of ncRNAs that could help in more clear and guided designation of preclinical and clinical studies to verify the therapeutic application of the revealed ncRNAs by manipulating the PPARs molecular mechanism in MAFLD.

Modulation of endoplasmic reticulum stress via sulforaphane-mediated AMPK upregulation against nonalcoholic fatty liver disease in rats

Nonalcoholic fatty liver disease (NAFLD) is a major health concern. Endoplasmic reticulum (ER) stress, inflammation, and metabolic dysfunctions may be targeted to prevent the progress of nonalcoholic fatty liver disease. Sulforaphane (SFN), a sulfur-containing compound that is abundant in broccoli florets, seeds, and sprouts, has been reported to have beneficial effects on attenuating metabolic diseases. In light of this, the present study was designed to elucidate the mechanisms by which SFN ameliorated ER stress, inflammation, lipid metabolism, and insulin resistance - induced by a high-fat diet and ionizing radiation (IR) in rats. In our study, the rats were randomly divided into five groups: control, HFD, HFD + SFN, HFD + IR, and HFD + IR + SFN groups. After the last administration of SFN, liver and blood samples were taken. As a result, the lipid profile, liver enzymes, glucose, insulin, IL-1β, adipokines (leptin and resistin), and PI3K/AKT protein levels, as well as the mRNA gene expression of ER stress markers (IRE-1, sXBP-1, PERK, ATF4, and CHOP), fatty acid synthase (FAS), peroxisome proliferator-activated receptor-α (PPAR-α). Interestingly, SFN treatment modulated the levels of proinflammatory cytokine including IL-1β, metabolic indices (lipid profile, glucose, insulin, and adipokines), and ER stress markers in HFD and HFD + IR groups. SFN also increases the expression of PPAR-α and AMPK genes in the livers of HFD and HFD + IR groups. Meanwhile, the gene expression of FAS and CHOP was significantly attenuated in the SFN-treated groups. Our results clearly show that SFN inhibits liver toxicity induced by HFD and IR by ameliorating the ER stress events in the liver tissue through the upregulation of AMPK and PPAR-α accompanied by downregulation of FAS and CHOP gene expression.

NEAT1: A novel long non-coding RNA involved in mediating type 2 diabetes and its various complications

Background:

Nuclear‐enriched abundant transcript 1 (abbreviated as NEAT1) refers to a long-chain non-coding RNA involved within various physiological and pathological processes. This study aimed at clarifying the effect and molecule system of neat1 within nonalcoholic fatty liver disease (NAFLD) as well as type 2 diabetes (T2DM).

Method:

In this review, we summarize and analyze current studies concerning mechanisms of NEAT1 in the development of type 2 diabetes and its complications. Also, we search the papers of NEAT1 in applying to NAFLD. The related studies were obtained through a systematic search of Pubmed.

Results:

Neat1 displays a close correlation with how T2DM occurs and develops, and it was confirmed to be significantly up-regulated in T2DM and its various complications (e.g., diabetics nephropathy, diabetics cardiomyopathy, diabetics retinopathy as well as diabetic neuropathy). Besides, neat1 is capable of impacting the occurrence, development and prognosis of NAFLD and T2DM.

Conclusion:

LncRNA neat1 is likely to act as a novel therapeutic target for and T2DM and its complications. Moreover, nonalcoholic fatty liver disease is also correlated with NEAT1.

Silencing lncRNA NEAT1 reduces nonalcoholic fatty liver fat deposition by regulating the miR-139-5p/c-Jun/SREBP-1c pathway

INTRODUCTION AND OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) starts with the abnormal accumulation of lipids in the liver. Long noncoding RNA (lncRNA) nuclear enriched abundant transcript 1 (NEAT1) was reported to modulate hepatic metabolic homeostasis in NAFLD. However, little is known about the molecular mechanisms of NAFLD.

MATERIALS AND METHODS

To establish a NAFLD cellular model, HepG2 cells and LO2 cells were treated with 1 mM free fatty acids (FFAs) for 24 h. NEAT1, miRNA (miR)-139-5p, c-Jun and sterol-regulatory element binding protein-1c (SREBP-1c) were evaluated using qPCR. The protein levels of c-Jun, SREBP1c, acetyl-CoA carboxylase (ACC) and fatty acid synthetase (FAS) were determined using western blotting. Moreover, Oil Red O staining was employed to assess lipid accumulation. In addition, a kit assay was performed to evaluate TG levels. Finally, the interactions among NEAT1, miR-139-5p, c-Jun and SREBP1c were identified by dual luciferase reporter gene assay.

RESULTS

NEAT1, c-Jun and SREBP1c expression was markedly elevated, while miR-139-5p expression was reduced in the NAFLD cellular model. NEAT1 knockdown restrained lipid accumulation in the NAFLD cellular model by directly targeting miR-139-5p. Moreover, miR-139-5p overexpression suppressed lipid accumulation by directly suppressing c-Jun expression. In addition, c-Jun silencing suppressed lipid accumulation by directly targeting SREBP1c. Finally, miR-139-5p inhibition mitigated the inhibitory effect of sh-NEAT1 on lipid accumulation.

CONCLUSION

NEAT1 aggravated FFA-induced lipid accumulation in hepatocytes by regulating the c-Jun/SREBP1c axis by sponging miR-139-5p, indicating the potential of NEAT1 as a promising therapeutic target for NAFLD.

Long non-coding RNA GAS5 contributes to the progression of nonalcoholic fatty liver disease by targeting the microRNA-29a-3p/NOTCH2 axis

Long non-coding RNAs (lncRNAs) have been widely recognized as critical players in the development of nonalcoholic fatty liver disease (NAFLD), one of the most prevalent liver diseases globally. In this study, we established a HFD-induced NAFLD mouse model and explored the role of lncRNA GAS5 in NAFLD progression and its possible underlying mechanisms. We showed that NAFLD activity score was elevated in the HFD mice. GAS5 knockdown attenuated HFD-induced hepatic steatosis and lipid accumulation and reduced NAFLD activity score in HFD mice. In addition, GAS5 knockdown reduced serum triglyceride cholesterol levels and inhibited alanine aminotransferase and aspartate aminotransferase activities in HFD mice. Moreover, GAS5 overexpression enhanced NOTCH2 levels in liver cells and promoted NAFLD progression by sponging miR-29a-3p in vivo. Furthermore, miR-29a-3p inhibited NAFLD progression by targeting NOTCH2 in vivo. Overall, our results indicated that GAS5 acts as a sponge of miR-29a-3p to increase NOTCH2 expression and facilitate NAFLD progression by targeting the miR-29a-3p/NOTCH2 axis and demonstrated a new GAS5-mediated mechanism underlying NAFLD development, suggesting that GAS5 could be a potential therapeutic target of NAFLD.

Abbreviations: Alanine aminotransferase: ALT; Aspartate aminotransferase: AST; Enzyme linked immunosorbent assay: ELISA; Hepatocellular carcinoma: HCC; High-fat diet: HFD; Long non-coding RNA: Lnc RNA; Long non-coding RNA GAS5: GAS5; MicroRNAs: MiRNAs; Nonalcoholic fatty liver disease: NAFLD; Quantitative reverse transcription PCRs: RT-qPCRs; siRNA negative control: si-NC; Total cholesterol: TC; Triglyceride: TG

The various regulatory functions of long noncoding RNAs in apoptosis, cell cycle, and cellular senescence

Long noncoding RNAs (lncRNAs) are a group of noncoding cellular RNAs involved in significant biological phenomena such as differentiation, cell development, genomic imprinting, adjusting the enzymatic activity, regulating chromosome conformation, apoptosis, cell cycle, and cellular senescence. The misregulation of lncRNAs interrupting normal biological processes has been implicated in tumor formation and metastasis, resulting in cancer. Apoptosis and cell cycle, two main biological phenomena, are highly conserved and intimately coupled mechanisms. Hence, some cell cycle regulators can influence both programmed cell death and cell division. Apoptosis eliminates defective and unwanted cells, and the cell cycle enables cells to replicate themselves. The improper regulation of apoptosis and cell cycle contributes to numerous disorders such as neurodegenerative and autoimmune diseases, viral infection, anemia, and mainly cancer. Cellular senescence is a tumor-suppressing response initiated by environmental and internal stress factors. This phenomenon has recently attained more attention due to its therapeutic implications in the field of senotherapy. In this review, the regulatory roles of lncRNAs on apoptosis, cell cycle, and senescence will be discussed. First, the role of lncRNAs in mitochondrial dynamics and apoptosis is addressed. Next, the interaction between lncRNAs and caspases, pro/antiapoptotic proteins, and also EGFR/PI3K/PTEN/AKT/mTORC1 signaling pathway will be investigated. Furthermore, the effect of lncRNAs in the cell cycle is surveyed through interaction with cyclins, cdks, p21, and wnt/β-catenin/c-myc pathway. Finally, the function of essential lncRNAs in cellular senescence is mentioned.

The role and possible mechanism of the long noncoding RNA LINC01260 in nonalcoholic fatty liver disease

Objective

To investigate the differential expression profile of lncRNAs in the nonalcoholic fatty liver disease (NAFLD) model induced by oleic acid (OA) and to further explore the role of LINC01260 (ENST00000255183) in NAFLD, providing theoretical support for the clinical value of lncRNAs in NAFLD.

Methods

OA (50 μg/mL) was used to induce steatosis in normal human LO2 hepatocytes for 48 h and was verified by Oil red O staining. Differential expression profiles of lncRNAs were obtained by eukaryotic circular sequencing (RNA/lncRNA/circRNA-seq) techniques. A gain-of-function (GOF) strategy for LINC01260 was adopted, Oil red O staining and semiquantitative analysis were combined to explore whether the GOF of LINC01260 affects LO2 cell steatosis. CeRNA-based bioinformatics analysis of lncRNAs was performed, and the enriched mRNAs were further verified. RXRB siRNAs were applied and verify its role in LINC01260 regulated OA-induced hepatocytes steatosis.

Results

Lipid droplets of different sizes were observed in the cells of the OA group. Absorbance in the OA group was significantly increased after isopropanol decolorization (P < 0.05). Compared with those in the control group, there were 648 lncRNAs with differential expression greater than 1 time in the OA group, of which 351 were upregulated and 297 were downregulated. Fluorescence quantitative PCR showed that the expression of LINC01260 in the OA group was downregulated by 0.35 ± 0.07-fold (P < 0.05). The formation of lipid droplets in LO2 cells of the LINC01260 GOF group decreased significantly (P < 0.05). CeRNA analysis indicated that the mRNA levels of RXRB, RNPEPL1, CD82, MADD and KLC2 were changed to different degrees. Overexpression of LINC01260 significantly induced RXRB transcription (P < 0.05) and translation, and RXRB silence attenuated the lipids decrease induced by LINC01260 overexpression.

Conclusion

The OA-induced NAFLD cell model has a wide range of lncRNA differential expression profiles. LINC01260 participates in the regulation of the lipid droplet formation process of NAFLD, and its overexpression can significantly inhibit the steatosis process of LO2 cells. Mechanistically, LINC01260 may act as a ceRNA to regulate the expression of RXRB, thereby affecting the adipocytokine signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00634-4.

The Role of Long Non-coding RNA, Nuclear Enriched Abundant Transcript 1 (NEAT1) in Cancer and Other Pathologies

Nuclear enriched abundant transcript 1 (NEAT1), consisting of two kinds of lncRNAs of 3.7 kB NEAT1-1 and 23 kB NEAT1-2, can be highly expressed in organs and tissues such as the ovary, prostate, colon, and pancreas, and is involved in paraspeckle formation and mRNA editing and gene expression. Therefore, NEAT1 is a potential biomarker for the treatment of a variety of diseases, which may be caused by two factors (isoforms of NEAT1 and NEAT1 sponging miRNA as ceRNA). However, there is still much confusion about the mechanism and downstream effector between the abnormal expression of NEAT1 and various diseases. This review summarizes recent research progress on NEAT1 in cancer and other pathologies and provides a more reliable theoretical basis for the treatment of related diseases.

Acetylation of H3K27 activated lncRNA NEAT1 and promoted hepatic lipid accumulation in non-alcoholic fatty liver disease via regulating miR-212-5p/GRIA3

Non-alcoholic fatty liver disease (NAFLD) was a world-wide health burden. H3K27 acetylation, long non-coding RNA (lncRNA), and miRNA were all implicated in NAFLD regulation, yet the detailed regulatory mechanism was not well understood. LncRNA NEAT1, miR-212-5p, and GRIA3 expression were detected both in high fatty acid-treated hepatocytes cells and NAFLD patients. Lipid droplets were stained and analyzed by oil red O staining. Expression of fatty acid synthase (FASN), acetyl-CoA carboxylase (ACC), and GRIA3 was detected by qRT-PCR and western blot. RNA level of lncRNA NEAT1 and miR-212-5p was analyzed by qRT-PCR. The binding sequences of lncRNA NEAT1/miR-212-5p and miR-212-5p/GRIA3 were predicted bioinformatically and validated through luciferase assay. ChIP was performed to analyze H3K27 acetylation on the promoter of lncRNA NEAT1. LncRNA NEAT1 and GRIA3 was upregulated, while miR-212-5p was downregulated in NAFLD patients. FFA promoted lncRNA NEAT1 and GRIA3 expression while suppressing miR-212-5p and promoted lipid accumulation as indicated by increased oil red O staining and FAS and ACC expression. ChIP indicated enrichment of H3K27 on NEAT1 promoter. Inhibition of H3K27 acetylation suppressed lncRNA NEAT1 level. Luciferase results indicated direct interaction of NEAT1/miR-212-5p (which was confirmed by RIP) and miR-212-5p/GRIA3. LncRNA NEAT1 knockdown upregulated miR-212-5p level and inhibited FFA-induced lipid accumulation while suppressing GRIA3 expression. Such function was antagonized by miR-212-5p inhibition and GRIA3 knockdown counteracted with miR-212-5p inhibition. H3K27 acetylation was enriched within the promoter of lncRNA NEAT1 and promoted lncRNA NEAT1 transcription. LncRNA NEAT1 could then interact with miR-212-5p and suppress its cellular concentration.

Long non-coding RNAs in metabolic disorders: pathogenetic relevance and potential biomarkers and therapeutic targets

BACKGROUND

It has been suggested that dysregulation of long non-coding RNAs (lncRNAs) could be associated with the incidence and development of metabolic disorders.

AIM

Accordingly, this narrative review described the molecular mechanisms of lncRNAs in the development of metabolic diseases including insulin resistance, diabetes, obesity, non-alcoholic fatty liver disease (NAFLD), cirrhosis, and coronary artery diseases (CAD). Furthermore, we investigated the up-to-date findings on the association of deregulated lncRNAs in the metabolic disorders, and potential use of lncRNAs as biomarkers and therapeutic targets.

CONCLUSION

LncRNAs/miRNA/regulatory proteins axis plays a crucial role in progression of metabolic disorders and may be used in development of therapeutic and diagnostic approaches.

Non-alcoholic Steatohepatitis Pathogenesis, Diagnosis, and Treatment

There has been a rise in the prevalence of non-alcohol fatty liver disease (NAFLD) due to the popularity of western diets and sedentary lifestyles. One quarter of NAFLD patients is diagnosed with non-alcoholic steatohepatitis (NASH), with histological evidence not only of fat accumulation in hepatocytes but also of liver cell injury and death due to long-term inflammation. Severe NASH patients have increased risks of cirrhosis and liver cancer. In this review, we discuss the pathogenesis and current methods of diagnosis for NASH, and current status of drug development for this life-threatening liver disease.

Clinical Significance of HSPD1/MMP14/ITGB1/miR-6881-5P/Lnc-SPARCL1-1:2 RNA Panel in NAFLD/NASH Diagnosis: Egyptian Pilot Study

Background: Non-alcoholic steatohepatitis ((NASH) is the progressive form of (non-alcoholic fatty liver disease) (NAFLD), which can progress to liver cirrhosis and hepatocellular carcinoma. There is no available reliable non-invasive diagnostic tool to diagnose NASH, and still the liver biopsy is the gold standard in diagnosis. In this pilot study, we aimed to evaluate the Nod-like receptor (NLR) signaling pathway related RNA panel in the diagnosis of NASH. Methods: Bioinformatics analysis was done, with retrieval of the HSPD1/MMP14/ITGB1/miR-6881-5P/Lnc-SPARCL1-1:2 RNA panel based on the relation to the NLR-signaling pathway. Hepatitis serum markers, lipid profile, NAFLD score and fibrosis score were assessed in the patients’ sera. Reverse transcriptase real time polymerase chain reaction (RT-PCR) was done to assess the relative expression of the RNA panel among patients who had NAFLD without steatosis, NAFLD with simple steatosis, NASH and healthy controls. Results: We observed up-regulation of Lnc-SPARCL1-1:2 lncRNA that led to upregulation of miR-6881-5P with a subsequent increase in levels of HSPD1, MMP14, and ITGB1 mRNAs. In addition, ROC curve analysis was done, with discriminative cutoff values that aided discrimination between NASH cases and control, and also between NAFLD, simple steatosis and NASH. Conclusion: This pilot study concluded that HSPD1/MMP14/ITGB1/miR-6881-5P/Lnc-SPARCL1-1:2 panel expression has potential in the diagnosis of NASH, and also differentiation between NAFLD, simple steatosis and NASH cases.

NEAT1 as a competing endogenous RNA in tumorigenesis of various cancers: Role, mechanism and therapeutic potential

The nuclear paraspeckle assembly transcript 1 (NEAT1) is a long non-coding RNA (lncRNA) that is upregulated in a variety of human cancer types. Increasing evidence has shown that the elevation of NEAT1 in cancer cells promotes cell growth, migration, and invasion and inhibits cell apoptosis. It is also known that lncRNAs act as a competing endogenous RNA (ceRNA) by sponging microRNAs (miRNAs) to alter the expression levels of their target genes in the development of cancers. Therefore, it is important to understand the molecular mechanisms underlying this observation. In this review, specific emphasis was placed on NEAT1's role in tumor development. We also summarize and discuss the feedback roles of NEAT1/miRNA/target network in the progression of various cancers. As our understanding of the role of NEAT1 during tumorigenesis improves, its therapeutic potential as a biomarker and/or target for cancer also becomes clearer.

Long Noncoding RNAs and Human Liver Disease

Long noncoding RNAs (lncRNAs) are pervasively transcribed in the genome, exhibit a diverse range of biological functions, and exert effects through a variety of mechanisms. The sheer number of lncRNAs in the human genome has raised important questions about their potential biological significance and roles in human health and disease. Technological and computational advances have enabled functional annotation of a large number of lncRNAs. Though the number of publications related to lncRNAs has escalated in recent years, relatively few have focused on those involved in hepatic physiology and pathology. We provide an overview of evolving lncRNA classification systems and characteristics and highlight important advances in our understanding of the contribution of lncRNAs to liver disease, with a focus on nonalcoholic steatohepatitis, hepatocellular carcinoma, and cholestatic liver disease. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Long Noncoding RNAs: Novel Important Players in Adipocyte Lipid Metabolism and Derivative Diseases

Obesity, a global public health issue, is characterized by excessive adiposity and is strongly related to some chronic diseases including cardiovascular diseases and diabetes. Extra energy intake-induced adipogenesis involves various transcription factors and long noncoding RNAs (lncRNAs) that control lipogenic mRNA expression. Currently, lncRNAs draw much attention for their contribution to adipogenesis and adipose tissue function. Increasing evidence also manifests the pivotal role of lncRNAs in modulating white, brown, and beige adipose tissue development and affecting the progression of the diseases induced by adipose dysfunction. The aim of this review is to summarize the roles of lncRNAs in adipose tissue development and obesity-caused diseases to provide novel drug targets for the treatment of obesity and metabolic diseases.

Comprehensive analysis of LncRNAs expression profiles in an in vitro model of steatosis treated with Exendin-4

Background and aims

The hallmark of non-alcoholic fatty liver disease (NAFLD) is the excessive hepatic lipid accumulation. Currently, no pharmacotherapy exists for NAFLD. However, the glucagon-like peptide-1 receptor agonists have recently emerged as potential therapeutics. Here, we sought to identify the long non-coding RNAs (LncRNAs) associated with the steatosis improvement induced by the GLP-1R agonist Exendin-4 (Ex-4) in vitro.

Methods

Steatosis was induced in HepG2 cells with oleic acid. The transcriptomic profiling was performed using total RNA extracted from untreated, steatotic, and Ex-4-treated steatotic cells. We validated a subset of differentially expressed LncRNAs with qRT-PCR and identified the most significantly enriched cellular functions associated with the relevant LncRNAs.

Results

We confirm that Ex-4 improves steatosis in HepG2 cells. We found 379 and 180 differentially expressed LncRNAs between untreated and steatotic cells and between steatotic and Ex-4-treated steatotic cells, respectively. Interestingly, 22 upregulated LncRNAs in steatotic cells became downregulated with Ex-4 exposure, while 50 downregulated LncRNAs in steatotic cells became upregulated in the presence of Ex-4. Although some LncRNAs, such as MALAT1, H19, and NEAT1, were previously associated with NAFLD, the association of others with steatosis and the positive effect of Ex-4 is being reported for the first time. Functional enrichment analysis identified many critical pathways, including fatty acid and pyruvate metabolism, and insulin, PPAR, Wnt, TGF-β, mTOR, VEGF, NOD-like, and Toll-like receptors signaling pathways.

Conclusion

Our results suggest that LncRNAs may play essential roles in the mechanisms underlying steatosis improvement in response to GLP-1R agonists and warrant further functional studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02885-4.

NEAT1/hsa-miR-372-3p axis participates in rapamycin-induced lipid metabolic disorder

Rapamycin is a crucial immunosuppressive regimen for patients that have undergone liver transplantation (LT). However, one of the major side effects of rapamycin include metabolic disorders such as dyslipidemia, and the mechanism remains unknown. This study aims to explore the biomolecules that are responsible for rapamycin-induced dyslipidemia and the control strategies that can reverse the lipid metabolism disorder. In this study, data collected from LT patients, cell and mouse models treated with rapamycin were analyzed. Results showed an increase of triglycerides (TGs) induced by rapamycin. MicroRNAs (miRNAs) play important roles in many vital biological processes including TG metabolism. hsa-miR-372-3p was filtered using RNA sequencing and identified as a key regulator in rapamycin-induced TGs accumulation. Using bioinformatics and experimental analyses, target genes of hsa-miR-372-3p were predicted. These genes were alkylglycerone phosphate synthase (AGPS) and apolipoprotein C4 (APOC4), which are reported to be involved in TG metabolism. LncRNA nuclear paraspeckle assembly transcript 1 (NEAT1) was also identified as an upstream regulatory factor of hsa-miR-372-3p. From the results of this study, NEAT1/hsa-miR-372-3p/AGPS/APOC4 axis plays a vital role in rapamycin-disruption of lipid homeostasis. Therefore, targeting this axis is a potential therapeutic target combating rapamycin-induced dyslipidemia after LT.

Genome-wide screening of circadian and non-circadian impact of Neat1 genetic deletion

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Neat1 deletion affects numerous circadian and non-circadian genes.

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Neat1 deletion causes loss, modification or acquisition of gene circadian pattern.

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Paraspeckles contribute significantly to the circadian transcriptome.

The functions of the long non-coding RNA, Nuclear enriched abundant transcript 1 (Neat1), are poorly understood. Neat1 is required for the formation of paraspeckles, but its respective paraspeckle-dependent or independent functions are unknown. Several studies including ours reported that Neat1 is involved in the regulation of circadian rhythms. We characterized the impact of Neat1 genetic deletion in a rat pituitary cell line. The mRNAs whose circadian expression pattern or expression level is regulated by Neat1 were identified after high-throughput RNA sequencing of the circadian transcriptome of wild-type cells compared to cells in which Neat1 was deleted by CRISPR/Cas9. The numerous RNAs affected by Neat1 deletion were found to be circadian or non-circadian, targets or non-targets of paraspeckles, and to be associated with many key biological processes showing that Neat1, in interaction with the circadian system or independently, could play crucial roles in key physiological functions through diverse mechanisms.

The nuclear functions of long noncoding RNAs come into focus

Long noncoding RNAs (lncRNAs), defined as untranslated and tightly-regulated transcripts with a length exceeding 200 nt, are common outputs of the eukaryotic genome. It is becoming increasingly apparent that many lncRNAs likely serve as important regulators in a variety of biological processes. In particular, some of them accumulate in the nucleus and function in diverse nuclear events, including chromatin remodeling, transcriptional regulation, RNA processing, DNA damage repair, etc. Here, we unite recent progresses on the functions of nuclear lncRNAs and provide insights into the future research directions of this field.

Exploring dysregulated miRNAs in cryptorchidism: a systematic review

Objective

To identify dysregulated miRNAs in testicular tissues from animal models and patients with cryptorchidism.

Methods

Databases were systematically searched for studies published before 10 May 2020 that had investigated miRNAs in cryptorchidism. Predicted targets of the identified miRNA biomarkers were obtained by searching TargetScan and Starbase. Gene ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment analyses were subsequently conducted.

Results

Five publications met the eligibility criteria for the review. 21 differentially expressed miRNAs were the most abundantly reported in 185 animal and human tissue samples. Three miRNAs (miR-210, miR-449a and miR-34c) were dysregulated in both animal and human testicular tissues. The top five relevant lncRNAs associated with the miRNAs were NEAT1, KCNQ1OT1, XIST, AC005154.1, and TUG1.

Conclusions

Further research is warranted to explore the potential of these dysregulated miRNAs as biomarkers or therapeutic targets for male infertility associated with cryptorchidism.

A comprehensive review of long non-coding RNAs in the pathogenesis and development of non-alcoholic fatty liver disease

One of the most prevalent diseases worldwide without a fully-known mechanism is non-alcoholic fatty liver disease (NAFLD). Recently, long non-coding RNAs (lncRNAs) have emerged as significant regulatory molecules. These RNAs have been claimed by bioinformatic research that is involved in biologic processes, including cell cycle, transcription factor regulation, fatty acids metabolism, and-so-forth. There is a body of evidence that lncRNAs have a pivotal role in triglyceride, cholesterol, and lipoprotein metabolism. Moreover, lncRNAs by up- or down-regulation of the downstream molecules in fatty acid metabolism may determine the fatty acid deposition in the liver. Therefore, lncRNAs have attracted considerable interest in NAFLD pathology and research. In this review, we provide all of the lncRNAs and their possible mechanisms which have been introduced up to now. It is hoped that this study would provide deep insight into the role of lncRNAs in NAFLD to recognize the better molecular targets for therapy.

Downregulated microRNA-129-5p by Long Non-coding RNA NEAT1 Upregulates PEG3 Expression to Aggravate Non-alcoholic Steatohepatitis

Long non-coding RNAs (lncRNAs) have recently emerged as inflammation-associated biological molecules with a specific role in the progression of liver fibrosis conditions including non-alcoholic steatohepatitis (NASH). The aim of this study was to elucidate the effects of lncRNA nuclear enriched abundant transcript 1 (NEAT1), microRNA-129-5p (miR-129-5p), and paternally expressed gene 3 (PEG3) on the biological activities of hepatic stellate cells (HSCs) subjected to NASH. First, microarray-based analysis revealed upregulated PEG3 in NASH. Liver tissues from mice fed a methionine–choline-deficient (MCD) diet exhibited increased expression of NEAT1 and PEG3 along with lower miR-129-5p expression. A series of in vitro and in vivo assays were then performed on HSCs after transfection with shPEG3, miR-129-5p mimic, or treatment with pyrrolidine dithiocarbamate (PDTC), an inhibitor of the nuclear factor-kappa B (NF-κB) signaling pathway. Results confirmed the alleviated fibrosis by restoring miR-129-5p, while depleting PEG3 or NEAT1, as evidenced by the inactivation of HSCs. To sum up, NEAT1 can bind specifically to miR-129-5p and consequently regulate miR-129-5p and PEG3 expression in relation to the HSC activation occurring in NASH. Thus, NEAT1-targeted inhibition against miR-129-5p presents a promising therapeutic strategy for the treatment of NASH.

Non-alcoholic fatty liver disease: molecular and cellular interplays of the lipid metabolism in a steatotic liver

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) affects ~25% of world population and cases have increased in recent decades. These anomalies have several etiologies; however, obesity and metabolic dysfunctions are the most relevant causes. Despite being considered a public health problem, no effective therapeutic approach to treat NAFLD is available. For that, a deep understanding of metabolic routes that support hepatic diseases is needed.

AREAS COVERED

This review covers aspects of the onset of NAFLD. Thereby, biochemistry routes as well as cellular and metabolic effects of the gut microbiota in body's homeostasis and epigenetics are contextualized.

EXPERT OPINION

Recently, the development of biological sciences has generated innovative knowledge, bringing new insights and perspectives to clarify the systems biology of liver diseases. A detailed comprehension of epigenetics mechanisms will offer possibilities to develop new therapeutic and diagnostic strategies for NAFLD. Different epigenetic processes have been reported that are modulated by the environment such as gut microbiota, suggesting strong interplays between cellular behavior and pathology. Thus, a more complete description of such mechanisms in hepatic diseases will help to clarify how to control the establishment of fatty liver, and precisely describe molecular interplays that potentially control NAFLD.

LncRNA NEAT1: Shedding light on mechanisms and opportunities in liver diseases

With advances in genome and transcriptome research technology, the function and mechanism of lncRNAs in physiological and pathological states have been gradually revealed. Nuclear Enriched Abundant Transcript 1 (NEAT1, a long non-coding RNA), a vital component of paraspeckles, plays an indispensable role in the formation and integrity of paraspeckles. Throughout the research history, NEAT1 is mostly aberrantly upregulated in various cancers, and high expression of NEAT1 often contributes to poor prognosis of patients. Notably, the role and mechanism of NEAT1 in liver diseases have been increasingly reported. NEAT1 accelerates the progression of non-alcoholic fatty liver disease (NAFLD), liver fibrosis and hepatocellular carcinoma, while exerting a protective role in the pathogenesis of acute-on-chronic liver failure by inhibiting the inflammatory response. In this review, we will elaborate on relevant studies on the different casting of NEAT1 in liver diseases, especially focusing on its regulatory mechanisms and new opportunities for alcoholic liver disease.

Evolutionary conservation of long non-coding RNAs in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of conditions ranging from hepatic steatosis to steatohepatitis (NASH) to fibrosis in the absence of alcohol consumption. Its pathogenesis involves both genetic and environmental factors with a multitude of underlying molecular mechanisms and mediators at each stage. Recent transcriptomic-based studies have led to the identification and association of long non-coding RNAs (lncRNAs) with disease pathology in NAFLD patients and in vivo rodent models. However, the knowledge of function of most of the lncRNAs in NAFLD pathology remains obscure. In the current review, we give a comprehensive catalogue of well reported lncRNAs in NAFLD and classify them using sequence and synteny-based evolutionary conservation across rodents, nonhuman primate and human species. The conserved lncRNAs across all the three species may be dissected in larger clinical studies of NAFLD and can be explored as biomarkers and therapeutic targets. In addition, we also review and analyse single nucleotide polymorphisms (SNPs) in these lncRNAs. It adds another facet to the regulatory role of NAFLD-associated lncRNAs and underscores the significance of a novel genetic landscape of non-coding genome in determining the genetic susceptibility of NAFLD.

Long non-coding RNAs in liver diseases: Focusing on nonalcoholic fatty liver disease, alcohol-related liver disease, and cholestatic liver disease

Long non-coding RNAs (lncRNAs), a class of transcribed RNA molecules with the lengths exceeding 200 nucleotides, are not translated into protein. They can modulate protein-coding genes by controlling transcriptional and posttranscriptional processes. The dysregulation of lncRNAs has been related to various pathological disorders. In this review, we summarized the current knowledge of lncRNAs and their implications in the pathogenesis of three common liver diseases: nonalcoholic fatty liver disease, alcohol-related liver disease, and cholestatic liver disease. Future studies to further define the role of lncRNAs and their mechanisms in various types of liver diseases should be explored. An improved understanding from these studies will provide us a useful perspective leading to mechanism-based intervention by targeting specific lncRNAs for the treatment of liver diseases.

Noncoding RNAs in Nonalcoholic Fatty Liver Disease: Potential Diagnosis and Prognosis Biomarkers

Nonalcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease worldwide in part due to the concomitant obesity pandemic and insulin resistance (IR). It is increasingly becoming evident that NAFLD is a disease affecting numerous extrahepatic vital organs and regulatory pathways. The molecular mechanisms underlying the nonalcoholic steatosis formation are poorly understood, and little information is available on the pathways that are responsible for the progressive hepatocellular damage that follows lipid accumulation. Recently, much research has focused on the identification of the epigenetic modifications that contribute to NAFLD pathogenesis. Noncoding RNAs (ncRNAs) are one of such epigenetic factors that could be implicated in the NAFLD development and progression. In this review, we summarize the current knowledge of the genetic and epigenetic factors potentially underlying the disease. Particular emphasis will be put on the contribution of microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs) to the pathophysiology of NAFLD as well as their potential use as therapeutic targets or as markers for the prediction and the progression of the disease.

LncRNA FTX represses the progression of non-alcoholic fatty liver disease to hepatocellular carcinoma via regulating the M1/M2 polarization of Kupffer cells

Background

The effect of lncRNA FTX on non-alcoholic fatty liver disease (NAFLD) conversion to hepatocellular carcinoma (HCC) is unclear.

Methods

In our study, C57BL/6 mice was fed with high fat diet for obtaining NAFLD mouse model, and diethylnitrosamine induced the formation of HCC tumor. The expression of iNOS and CD206 in tissues were examined using immunohistochemistry. In addition, qRT-PCR was implemented to detect the expression of FTX and mRNAs. The percentage of M1 and M2 Kupffer cells (KCs) were determined using flow cytometry. The pathological change in liver tissues was displayed by H&E staining. Besides, immunofluorescence assay was performed to ensure the primary KCs through labeling F4/80.

Results

Here, we found that the expression of FTX and the ratio of M1/M2 KCs in liver tissues from NAFLD-transformed HCC (NAFLD-HCC) patients lower than in liver tissues from NAFLD patients. Subsequently, we revealed that the expression of FTX and M1/M2 KCs ratio were downregulated during NAFLD conversion to HCC. Importantly, increasing of FTX inhibited HCC tumor growth, improved liver damage and promoted M1 polarization of KCs during NAFLD conversion to HCC, while these effects of FTX were reversed by inactivating of KCs. Finally, in vitro experiments, our data indicated that FTX facilitated the M1 polarization of KCs.

Conclusion

In conclusion, our results demonstrated that upregulation of FTX suppressed NAFLD conversion to HCC though promoting M1 polarization of KCs. Our findings presented a new regulatory mechanism for NAFLD conversion to HCC, and provided a new biomarker for inhibiting this conversion.

Nimodipine Improves Cognitive Impairment After Subarachnoid Hemorrhage in Rats Through IncRNA NEAT1/miR-27a/MAPT Axis

Background

Subarachnoid hemorrhage (SAH) is a cerebral hemorrhage disease that severely damages the brain and causes cognitive impairment (CI). Therefore, accurate and appropriate treatment strategies are urgently needed. The application of nimodipine can not only improve blood circulation in patients with SAH but also repair ischemic neuron injury.

Purpose

To investigate the effects of nimodipine and lncRNA nuclear paraspeckle assembly transcript 1 (NEAT1)/miR-27a/microtubule-associated protein tau (MAPT) axis on CI after SAH.

Methods

One hundred and twenty healthy male rats were selected and equally divided into control group, sham operation group, model group, PBS group, nimodipine group (drug group), NC siRNA group, NC mimics group, NEAT1 siRNA, miR-27a mimics, MAPT siRNA, drug + NEAT1-ad, and drug + NC-ad groups by random number table. Rats in the model group were constructed by double-hemorrhage model, and expression vectors were injected into the tail to regulate the expression of lncRNA NEAT1, miR-27a and MAPT. In addition, Western blot was employed to detect brain tissue protein, flow cytometry was applied to measure brain tissue apoptosis, and MTT was utilized to determine cell activity, so as to evaluate brain damage and cognitive function in each group.

Results

Nimodipine, down-regulated lncRNA NEAT1, up-regulated miR-27a and down-regulated MAPT all improved brain damage and CI, inhibited brain tissue cell apoptosis, and enhanced brain cell activity. The common binding sites of lncRNA NEAT1 and MAPT were found on the miR-27a sequence fragment, and miR-27a could be paired with the former two. Nimodipine was found to cause the down-regulation of lncRNA NEAT1 and MAPT, as well as the up-regulation of miR-27a.

Conclusion

Nimodipine can improve CI after SAH in rats through the lncRNA NEAT1/miR-27a/MAPT axis.

Long noncoding RNAs in nonalcoholic fatty liver disease and liver fibrosis: state-of-the-art and perspectives in diagnosis and treatment

Nonalcoholic fatty liver disease (NAFLD) significantly impacts global health. Despite considerable research, its pathophysiology remains partially unclear. In addition, selective serum biomarkers of disease diagnosis and progression are missing. Long noncoding RNAs (lncRNAs) are a heterogeneous group of ncRNAs with crucial roles in biological processes underlying the pathophysiology of different human diseases. Recent studies have shown that lncRNA could be associated with the genesis and progression of NAFLD towards the most severe forms. Although the field is still in its infancy, it is tempting to speculate that these transcripts could be used as both diagnostic and therapeutic targets. In this review, we summarize recent findings on lncRNAs in the complex research field of NAFLD.

Long noncoding RNA NEAT1 suppresses hepatocyte proliferation in fulminant hepatic failure through increased recruitment of EZH2 to the LATS2 promoter region and promotion of H3K27me3 methylation

Fulminant hepatic failure (FHF) refers to the rapid development of severe acute liver injury with impaired synthetic function and encephalopathy in people with normal liver or well-compensated liver disease. This study aimed to investigate the function of long noncoding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) on the proliferation and apoptosis of hepatocytes in FHF. Our results revealed that lncRNA NEAT1 was upregulated in cell and animal models of FHF induced by D-galactosamine (D-GalN)/lipopolysaccharide (LPS). Overexpression of lncRNA NEAT1 resulted in elevated hepatocyte apoptosis and impaired large tumor-suppressor kinase 2 (LATS2) expression and proliferation. Functional analysis revealed that knockdown of lncRNA NEAT1 inhibited hepatocyte apoptosis and induced proliferation both in vitro and in vivo. RNA immunoprecipitation and chromatin immunoprecipitation assays demonstrated that lncRNA NEAT1 recruited enhancer of zeste homolog 2 (EZH2) to the LATS2 promoter and repressed LATS2 expression. Furthermore, ectopic expression of LATS2 increased proliferation and inhibited hepatocyte apoptosis by regulating the Hippo/Yes-associated protein (YAP) signaling pathway. Taken together, our findings indicate that lncRNA NEAT1 might serve as a novel target for FHF therapy due to its regulation of H3K27me3 methylation-dependent promotion of LATS2.

A long noncoding RNA molecule, one that does not encode the synthesis of protein, is implicated in acute liver failure (AHF) and might offer a new target for drugs to treat the condition. AHF can be induced by various factors, including viruses, drugs, alcohol abuse, and inherited traits. Ke Cheng, Yujun Zhao and colleagues at Central South University in Changsha, China investigated the role of this RNA, called NEAT1, in cell and animal models of AHF. They identified increased production of NEAT1, which suppressed liver cell proliferation and promoted liver cell death. They also uncovered molecular details of the mechanisms underlying these effects, in which the RNA altered the production and regulatory modification of certain proteins. Further research should investigate the therapeutic possibilities of interfering with NEAT1 activity.