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

A microRNA signature for valproate-induced steatosis in human hepatocytes and its application to predict fatty liver in paediatric epileptic patients on valproate therapy

Valproate (VPA) has been the first-line, most frequently prescribed antiepileptic drug in children over the past 50 years. VPA causes, idiosyncratic hepatotoxicity in some patients, who often presents with hepatic steatosis. Experimental studies also support that VPA has high potential to induce steatosis. However, there is an apparent lack of significant hepatic problems in neuropediatric units, likely because iatrogenic liver steatosis lacks specific biomarkers. Thus, it is possible that a relevant number of children under VPA have asymptomatic fatty liver. AIMS: 1) to demonstrate VPA-induced triglyceride (TG) accumulation in cultured human upcyte hepatocytes, 2) to identify miRNAs that are deregulated by VPA and associated with TG levels in these cells, and 3) to test these miRNAs, as potential non-invasive biomarkers, in plasma of paediatric epileptic patients on VPA, to identify those with a potential risk of liver steatosis. Human upcyte hepatocytes were exposed to subcytotoxic VPA concentrations. Hepatocytes increased intracellular TGs by 27 % and 45 % after 2 and 4 mM VPA for 24 h. The profiling of cellular miRNAs by microarray analysis after 4 mM VPA identified 43 deregulated human miRNAs (fold-change > 1.5 or < -1.5; FDR p<0.05). Some of them (n=11), which were validated by RTqPCR and showed correlation (Pearson r≥ 0.6) with intracellular TG levels, were selected as potential VPA-induced steatosis biomarkers. Next, we investigated the expression of these miRNAs in human plasma and found that 9 of them could be reliably quantified by RTqPCR: miR-485-3p, miR-127-3p, miR-30a-3p, miR-92b-3p, miR-212-3p, miR-182-5p, miR-183-5p, miR-500a-5p and miR-675-5p. Screening of this 9-miRNA signature in 80 paediatric epileptic patients on VPA identified 18 patients (23 %) that clustered separately because of important alterations in the selected plasma miRNAs. These patients were younger and had higher VPA blood concentrations and serum liver enzyme levels. In conclusion, VPA induced both TG accumulation and deregulation of a set of miRNAs in cultured human hepatocytes. Nine of these miRNAs have demonstrated potential as circulating biomarkers to identify VPA-induced steatosis in epileptic patients, which should require closer clinical follow-up.

Hepatic miR-363 promotes nonalcoholic fatty liver disease by suppressing INSIG1

Nonalcoholic fatty liver disease (NAFLD) constitutes one of major worldwide health problem which typically progressively results in nonalcoholic steatohepatitis (NASH) and eventually cirrhosis and liver cancer. Liver-specific deletion of INSIG1 promotes SREBP1 nuclear translocation to activate downstream lipogenic genes expression, leading to lipid accumulation. However, the underlying pathogenesis of NAFLD, and particularly involved in miRNA participation are still to be thoroughly explored. Here, we found that miR-363-3p was significantly overexpressed in high-fat, high-cholesterol (HFHC) diet mice liver tissue and fatty acid-induced steatosis cells. miR-363-3p directly targets INSIG1 to inhibit its expression, thereby facilitating the cleavage of SREBP and nuclear translocation to activate subsequent transcription of lipogenic genes in vitro and in vivo. In addition, we identified apigenin, a natural flavonoid compound, inhibited miR-363-3p expression to up-regulate INSIG1 and suppress nuclear translocation of SREBP1, thereby down-regulated lipogenic genes expression in steatosis cells and HFHC diet mice liver tissues. Taken together, our results demonstrated that miR-363-3p as a key regulator of hepatic lipid homeostasis targeted INSIG1, and apigenin alleviated NAFLD through the miR-363-3p/INSIG1/SREBP1 pathway. This indicates that reduction of miR-363-3p levels as a possible treatment of hepatic steatosis and provides a potential new therapeutic strategy for targeting miRNA to ameliorate NAFLD.

The roles of the gut microbiota, metabolites, and epigenetics in the effects of maternal exercise on offspring metabolism

Metabolic diseases, including obesity, dyslipidemia, and type 2 diabetes, have become severe challenges worldwide. The Developmental Origins of Health and Disease (DOHaD) hypothesis suggests that an adverse intrauterine environment can increase the risk of metabolic disorders in offspring. Studies have demonstrated that maternal exercise is an effective intervention for improving the offspring metabolic health. However, the pathways through which exercise works are unclear. It has been reported that the gut microbiota mediates the effect of maternal exercise on offspring metabolism, and epigenetic modifications have also been proposed to be important molecular mechanisms. Microbial metabolites can influence epigenetics by providing substrates for DNA or histone modifications, binding to G-protein-coupled receptors to affect downstream pathways, or regulating the activity of epigenetic modifying enzymes. This review aims to summarize the intergenerational effect of maternal exercise and proposes that gut microbiota-metabolites-epigenetic regulation is an important mechanism by which maternal exercise improves offspring metabolism, which may yield novel targets for the early prevention and intervention of metabolic diseases.

Does the liver facilitate aging-related cognitive impairment: Conversation between liver and brain during exercise?

Liver, an important regulator of metabolic homeostasis, is critical for healthy brain function. In particular, age-related neurodegenerative diseases seriously reduce the quality of life for the elderly. As population aging progresses rapidly, unraveling the mechanisms that effectively delay aging has become critical. Appropriate exercise is reported to improve aging-related cognitive impairment. Whereas current studies focused on exploring the effect of exercise on the aging brain itself, ignoring the persistent effects of peripheral organs on the brain through the blood circulation. The aim of this paper is to summarize the communication and aging processes of the liver and brain and to emphasize the metabolic mechanisms of the liver-brain axis about exercise ameliorating aging-related neurodegenerative diseases. A comprehensive understanding of the potential mechanisms about exercise ameliorating aging is critical for improving adaptation to age-related brain changes and formulating effective interventions against age-related cognitive decline.

Human MicroRNAs Modulated by Diet: A Scoping Review

Because of their role in regulating and fine-tuning gene expression in the posttranscriptional period, microRNA (miRNA) may represent a mediating factor that connects diet and metabolic regulation. Given the vast number of miRNAs and that modulations in miRNA happen in response to a variety of stimuli, a comprehensive registry of miRNAs impacted by diet and the food items that modulate them, would have utility in the identification of miRNA complements for analysis of diet interventions and in helping to establish linkages between the specific impacts of diet components. A scoping literature search of online databases (PubMed, SCOPUS, EMBASE, and Web of Science) was performed. Only studies in human populations, those that used a diet intervention or meal challenge, and those that measured miRNA profiles in the same subject at multiple time points were included. Of the 6167 studies screened, only 25 met the study criteria and were included in the review. Seven studies examined miRNA following a meal challenge, whereas 18 investigated miRNA following a sustained diet intervention. The results demonstrated that miRNA are modulated following a variety of diet interventions and that intensity of miRNA response is greater in metabolically healthy subjects. Heterogeneity in the intensity and length of the diet intervention, the study populations being observed, and the methodology through which target miRNA are identified contribute to a lack of comparability across studies. The findings of this review highlight the need for more study of miRNA responsiveness to intake and provide recommendations for future research.

Vitamin D/vitamin D receptor pathway in non-alcoholic fatty liver disease

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide, but underlying mechanisms are not fully understood. In recent years, a growing body of evidence has emphasized the therapeutic role of vitamin D in NAFLD, but the specific mechanism remains to be investigated.

AREAS COVERED

This review summarized the roles of vitamin D/VDR (vitamin D receptor) pathway in different types of liver cells (such as hepatocytes, hepatic stellate cells, liver macrophages, T lymphocytes, and other hepatic immune cells) in case of NAFLD. Meanwhile, the effects of pathways in the gut-liver axis, adipose tissue-liver axis, and skeletal muscle-liver axis on the development of NAFLD were further reviewed. Relevant literature was searched on PubMed for the writing of this review.

EXPERT OPINION

The precise regulation of regional vitamin D/VDR signaling pathway based on cell-specific or tissue-specific function will help clarify the potential mechanism of vitamin D in NAFLD, which may provide new therapeutic targets to improve the safety and efficacy of vitamin D based drugs.

Therapeutic Effects of microRNAs on Nonalcoholic Fatty Liver Disease (NAFLD) and Nonalcoholic Steatohepatitis (NASH): A Systematic Review and Meta-Analysis

Nonalcoholic fatty liver disease (NAFLD) has emerged as a global health problem that affects people even at young ages due to unhealthy lifestyles. Without intervention, NAFLD will develop into nonalcoholic steatohepatitis (NASH) and eventually liver cirrhosis and hepatocellular carcinoma. Although lifestyle interventions are therapeutic, effective implementation remains challenging. In the efforts to establish effective treatment for NAFLD/NASH, microRNA (miRNA)-based therapies began to evolve in the last decade. Therefore, this systematic review aims to summarize current knowledge on the promising miRNA-based approaches in NAFLD/NASH therapies. A current systematic evaluation and a meta-analysis were conducted according to the PRISMA statement. In addition, a comprehensive exploration of PubMed, Cochrane, and Scopus databases was conducted to perform article searches. A total of 56 different miRNAs were reported as potential therapeutic agents in these studies. miRNA-34a antagonist/inhibitor was found to be the most studied variant (n = 7), and it significantly improved the hepatic total cholesterol, total triglyceride, Aspartate Aminotransferase (AST), and Alanine Transaminase (ALT) levels based on a meta-analysis. The biological processes mediated by these miRNAs involved hepatic fat accumulation, inflammation, and fibrosis. miRNAs have shown enormous therapeutic potential in the management of NAFLD/NASH, wherein miRNA-34a antagonist has been found to be an exceptional potential agent for the treatment of NAFLD/NASH.

Fibroblast Growth Factor-21 as a Potential Therapeutic Target of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent disease without any approved treatment to-date despite intensive research efforts by researchers and pharmaceutical industry. Fibroblast growth factor (FGF)-21 has been gaining increasing attention as a possible contributing factor and thus therapeutic target for obesity-related metabolic disorders, including NAFLD, mainly due to its effects on lipid and carbohydrate metabolism. Most animal and human observational studies have shown higher FGF-21 concentrations in NAFLD than non-NAFLD, implying that FGF-21 may be increased to counteract hepatic steatosis and inflammation. However, although Mendelian Randomization studies have revealed that variations of FGF-21 levels within the physiological range may have effects in hyperlipidemia and possibly nonalcoholic steatohepatitis, they also indicate that FGF-21, in physiological concentrations, may fail to reverse NAFLD and may not be able to control obesity and other diseases, indicating a state of FGF-21 resistance or insensitivity that could not respond to administration of FGF-21 in supraphysiological concentrations. Interventional studies with FGF-21 analogs (eg, pegbelfermin, efruxifermin, BOS-580) in humans have provided some favorable results in Phase 1 and Phase 2 studies. However, the definite effect of FGF-21 on NAFLD may be clarified after the completion of the ongoing clinical trials with paired liver biopsies and histological endpoints. The aim of this review is to critically summarize experimental and clinical data of FGF-21 in NAFLD, in an attempt to highlight existing knowledge and areas of uncertainty, and subsequently, to focus on the potential therapeutic effects of FGF-21 and its analogs in NAFLD.

Gene therapy targeting miR‑212‑3p exerts therapeutic effects on MAFLD similar to those of exercise

Exercise is the main treatment for patients with metabolic‑associated fatty liver disease (MAFLD); however, it may be difficult for some patients to adhere to or tolerate an exercise regime. Thus, finding a treatment alternative to exercise is of particular importance. The authors have previously demonstrated that the high expression of microRNA (miRNA/miR)‑212 promotes lipogenesis in vitro. The present study aimed to explore the therapeutic potential, as well as the mechanisms of action of miR‑212 in MAFLD. The expression of miR‑212‑3p, but not that of miR‑212‑5p, was found to be significantly elevated in MAFLD and to be decreased by exercise. Compared with exercise treatment, the inhibition of miR‑212‑3p expression in a mouse model fed a high‑fat diet exerted beneficial effects on MAFLD similar to those of exercise. Conversely, the overexpression of miR‑212‑3p abolished the ameliorative effects of exercise on MAFLD. Fibroblast growth factor 21 (FGF21) and chromodomain helicase DNA binding protein 1 (CHD1) were identified as target genes of miR‑212‑3p in lipid metabolism using bioinformatics analysis. Mechanistically, the inhibition of miR‑212‑3p mimicked the effects of exercise on lipid metabolism by regulating FGF21, but not CHD1. The exercise‑related transcription factor, early growth response 1 (EGR1), was identified upstream of miR‑212‑3p through promoter motif analysis. EGR1 overexpression inhibited miR‑212‑3p expression. The overexpression of miR‑212‑3p abolished the effects of exercise on lipid metabolism by exogenously attenuating the transcriptional repression of EGR1. Moreover, the overexpression of miR‑212‑3p abolished the regulatory effects of EGR1 on FGF21. On the whole, the present study demonstrates that miR‑212‑3p plays a key role in the effects of exercise on MAFLD. The findings presented herein suggest a potential therapeutic effect of targeting miR‑212‑3p in MAFLD.

Exercise-Induced ADAR2 Protects against Nonalcoholic Fatty Liver Disease through miR-34a

Nonalcoholic fatty liver disease (NAFLD) is a growing health problem that is closely associated with insulin resistance and hereditary susceptibility. Exercise is a beneficial approach to NAFLD. However, the relief mechanism of exercise training is still unknown. In this study, mice on a normal diet or a high-fat diet (HFD), combined with Nω-nitro-L-arginine methyl ester, hydrochloride (L-NAME) mice, were either kept sedentary or were subjected to a 12-week exercise running scheme. We found that exercise reduced liver steatosis in mice with diet-induced NAFLD. The hepatic adenosine deaminases acting on RNA 2 (ADAR2) were downregulated in NAFLD and were upregulated in the liver after 12-week exercise. Next, overexpression of ADAR2 inhibited and suppression promoted lipogenesis in HepG2 cells treated with oleic acid (OA), respectively. We found that ADAR2 could down-regulate mature miR-34a in hepatocytes. Functional reverse experiments further proved that miR-34a mimicry eliminated the suppression of ADAR2 overexpression in lipogenesis in vitro. Moreover, miR-34a inhibition and mimicry could also affect lipogenesis in hepatocytes. In conclusion, exercise-induced ADAR2 protects against lipogenesis during NAFLD by editing miR-34a. RNA editing mediated by ADAR2 may be a promising therapeutic candidate for NAFLD.

The comprehensive detection of miRNA and circRNA in the regulation of intramuscular and subcutaneous adipose tissue of Laiwu pig

circRNAs, as miRNA sponges, participate in many important biological processes. However, it remains unclear whether circRNAs can regulate lipid metabolism. This study aimed to explore the competing endogenouse RNA (ceRNA) regulatory network that affects the difference between intramuscular fat (IMF) and subcutaneous fat (SCF) deposition, and to screen key circRNAs and their regulatory genes. In this experiment, we identified 265 differentially expressed circRNAs, of which 187 up-regulated circRNA and 78 down-regulated circRNA in IMF. Subsequently, we annotated the function of DEcircRNA's host genes, and found that DEcircRNA's host genes were mainly involved in GO terms (including cellular response to fatty acids, lysophosphatidic acid acyltransferase activity, R-SMAD binding, etc.) and signaling pathways (fatty acid biosynthesis, Citrate cycle, TGF- β Signal pathway) related to adipogenesis, differentiation and lipid metabolism. By constructing a circRNA-miRNA network, we screened out DEcircRNA that can competitively bind to more miRNAs as key circRNAs (circRNA_06424 and circRNA_08840). Through the functional annotation of indirect target genes and protein network analysis, we found that circRNA_06424 affects the expression of PPARD, MMP9, UBA7 and other indirect target genes by competitively binding to miRNAs such as ssc-miR-339-5p, ssc-miR-744 and ssc-miR-328, and participates in PPAR signaling pathway, Wnt signaling pathway, unsaturated fatty acid and other signaling pathways, resulting in the difference of fat deposition between IMF and SCF. This study provide a theoretical basis for further research investigating the differences of lipid metabolism in different adipose tissues, providing potential therapeutic targets for ectopic fat deposition and lipid metabolism diseases.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

M2 macrophage-derived exosomal microRNA-411-5p impedes the activation of hepatic stellate cells by targeting CAMSAP1 in NASH model

Liver fibrosis is a severe stage of nonalcoholic fatty liver disease (NAFLD), which is closely associated with the activation of hepatic stellate cells (HSCs) and their interaction with macrophages. Exosomes can mediate crosstalk between macrophages and HSCs in NAFLD-associated fibrosis. We found that M2 macrophage-derived exosomes significantly inhibit HSCs activation. RNA-seq studies revealed that miRNA-411-5p was decreased in serum exosomes of nonalcoholic steatohepatitis (NASH) patients as compared with that in healthy controls. Besides, miR-411-5p and M2 macrophage markers are decreased in the liver of the NASH model. We further proved that exosomal miR-411-5p from M2 macrophages inhibit HSCs activation and miR-411-5p directly downregulated the expression of Calmodulin-Regulated Spectrin-Associated Protein 1 (CAMSAP1) to inactivate stellate cells. Importantly, knockdown of CAMSAP1 also inhibited HSCs activation. This study contributes to understanding the underlying mechanism of HSCs activation and indicates CAMSAP1 may serve as a potential therapeutic target for NASH.

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M2 macrophage markers are decreased in the HFHCD-induced rat model of NASH

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M2 macrophage-derived exosomes inhibit HSCs activation via miR-411-5p

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CAMSAP1 is a direct target of miR-411-5p

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Knockdown of CAMSAP1 inhibits HSCs activation

The Role of MicroRNAs in Hyperlipidemia: From Pathogenesis to Therapeutical Application

Hyperlipidemia is a common metabolic disorder with high morbidity and mortality, which brings heavy burden on social. Understanding its pathogenesis and finding its potential therapeutic targets are the focus of current research in this field. In recent years, an increasing number of studies have proved that miRNAs play vital roles in regulating lipid metabolism and were considered as promising therapeutic targets for hyperlipidemia and related diseases. It is demonstrated that miR-191, miR-222, miR-224, miR-27a, miR-378a-3p, miR-140-5p, miR-483, and miR-520d-5p were closely associated with the pathogenesis of hyperlipidemia. In this review, we provide brief overviews about advances in miRNAs in hyperlipidemia and its potential clinical application value.

Physical exercise and the functions of microRNAs

MicroRNAs (miRNAs) control RNA translation and are a class of small, tissue-specific, non-protein-coding RNAs that maintain cellular homeostasis through negative gene regulation. Maintenance of the physiological environment depends on the proper control of miRNA expression, as these molecules influence almost all genetic pathways, from the cell cycle checkpoint to cell proliferation and apoptosis, with a wide range of target genes. Dysregulation of the expression of miRNAs is correlated with several types of diseases, acting as regulators of cardiovascular functions, myogenesis, adipogenesis, osteogenesis, hepatic lipogenesis, and important brain functions. miRNAs can be modulated by environmental factors or external stimuli, such as physical exercise, and can eventually induce specific and adjusted changes in the transcriptional response. Physical exercise is used as a preventive and non-pharmacological treatment for many diseases. It is well established that physical exercise promotes various benefits in the human body such as muscle hypertrophy, mental health improvement, cellular apoptosis, weight loss, and inhibition of cell proliferation. This review highlights the current knowledge on the main miRNAs altered by exercise in the skeletal muscle, cardiac muscle, bone, adipose tissue, liver, brain, and body fluids. In addition, knowing the modifications induced by miRNAs and relating them to the results of prescribed physical exercise with different protocols and intensities can serve as markers of physical adaptation to training and responses to the effects of physical exercise for some types of chronic diseases. This narrative review consists of randomized exercise training experiments with humans and/or animals, combined with analyses of miRNA modulation.

Adipocytes-derived exosomal microRNA-1224 inhibits M2 macrophage polarization in obesity-induced adipose tissue inflammation via MSI2-mediated Wnt/β-catenin axis

SCOPE

Phenotypic switch of macrophage polarization in adipose tissue has been associated with obesity-induced adipose tissue inflammation (OATI). Therefore, we aimed to explore the possible mechanism of adipocytes-derived exosomes (ADEs) carrying microRNA-1224 (miR-1224) in M2 macrophage polarization of OATI.

METHODS AND RESULTS

We developed miR-1224-knockout (miR-1224-KO) mice for this study, and isolated primary adipocytes from high-fat diet (HFD) or normal diet (SD)-fed mice. ADEs were extracted and cocultured with bone marrow-derived macrophages (BMDMs). The macrophagic crown-like structures (CLS) and M1 and M2 phenotype macrophages in epididymal white adipose tissue (epiWAT) were observed by immunohistochemistry and flow cytometry. The obtained data indicated that miR-1224 was highly expressed in adipose tissues and adipocytes of obese mice. miR-1224 knockout decreased CLS number and increased M2 macrophages polarization in epiWAT. In addition, miR-1224 could be transferred to BMDMs via ADEs, which targeted musashi RNA binding protein 2 (MSI2) expression and inactivated Wnt/β-catenin pathway, inhibiting macrophage M2 polarization and promoting inflammatory factor release.

CONCLUSION

Exosomal miR-1224 derived by adipocytes targets MSI2 and blocks the Wnt/β-catenin pathway, which inhibits macrophage M2 polarization and promotes inflammatory factor release, ultimately promoting OATI. This article is protected by copyright. All rights reserved.

Impact of Physical Activity and Exercise on the Epigenome in Skeletal Muscle and Effects on Systemic Metabolism

Exercise and physical activity induces physiological responses in organisms, and adaptations in skeletal muscle, which is beneficial for maintaining health and preventing and/or treating most chronic diseases. These adaptations are mainly instigated by transcriptional responses that ensue in reaction to each individual exercise, either resistance or endurance. Consequently, changes in key metabolic, regulatory, and myogenic genes in skeletal muscle occur as both an early and late response to exercise, and these epigenetic modifications, which are influenced by environmental and genetic factors, trigger those alterations in the transcriptional responses. DNA methylation and histone modifications are the most significant epigenetic changes described in gene transcription, linked to the skeletal muscle transcriptional response to exercise, and mediating the exercise adaptations. Nevertheless, other alterations in the epigenetics markers, such as epitranscriptomics, modifications mediated by miRNAs, and lactylation as a novel epigenetic modification, are emerging as key events for gene transcription. Here, we provide an overview and update of the impact of exercise on epigenetic modifications, including the well-described DNA methylations and histone modifications, and the emerging modifications in the skeletal muscle. In addition, we describe the effects of exercise on epigenetic markers in other metabolic tissues; also, we provide information about how systemic metabolism or its metabolites influence epigenetic modifications in the skeletal muscle.

Newly discovered endocrine functions of the liver

The liver, the largest solid visceral organ of the body, has numerous endocrine functions, such as direct hormone and hepatokine production, hormone metabolism, synthesis of binding proteins, and processing and redistribution of metabolic fuels. In the last 10 years, many new endocrine functions of the liver have been discovered. Advances in the classical endocrine functions include delineation of mechanisms of liver production of endocrine hormones [including 25-hydroxyvitamin D, insulin-like growth factor 1 (IGF-1), and angiotensinogen], hepatic metabolism of hormones (including thyroid hormones, glucagon-like peptide-1, and steroid hormones), and actions of specific binding proteins to glucocorticoids, sex steroids, and thyroid hormones. These studies have furthered insight into cirrhosis-associated endocrinopathies, such as hypogonadism, osteoporosis, IGF-1 deficiency, vitamin D deficiency, alterations in glucose and lipid homeostasis, and controversially relative adrenal insufficiency. Several novel endocrine functions of the liver have also been unraveled, elucidating the liver’s key negative feedback regulatory role in the pancreatic α cell-liver axis, which regulates pancreatic α cell mass, glucagon secretion, and circulating amino acid levels. Betatrophin and other hepatokines, such as fetuin-A and fibroblast growth factor 21, have also been discovered to play important endocrine roles in modulating insulin sensitivity, lipid metabolism, and body weight. It is expected that more endocrine functions of the liver will be revealed in the near future.

Interaction between PSMD10 and GRP78 accelerates endoplasmic reticulum stress-mediated hepatic apoptosis induced by homocysteine

Background

The liver plays an important role in production and metabolism of homocysteine (Hcy), which has been reported to be involved in liver injury. In our previous work, we confirm that Hcy can induce liver injury by activating endoplasmic reticulum (ER) stress. However, the underlying mechanisms remain largely unknown.

Results

In present study, we established the Hcy-induced liver injury model by feeding cbs^+/− mice with high methionine diet, and found that a considerable mass of disordered arrangement of hepatocytes and enlarged space between hepatocytes were frequently occurred in the liver of cbs^+/− mice, accompanied with elevated expression levels of apoptosis-related proteins. In addition, Hcy could activate ER stress both in cbs^+/− mice and hepatocytes. Mechanistically, Hcy promoted the expression levels of proteasome 26S subunit non-ATPase 10 (PSMD10) in hepatocytes; and the expression of ER stress indicators and apoptosis-associated proteins were significantly suppressed when PSMD10 was silenced in hepatocytes under Hcy treatment. Moreover, bioinformatics analysis and luciferase reporter assay demonstrated that PSMD10 was a target gene of miR-212-5p. Consistently, miR-212-5p overexpression could inhibit ER stress-mediated apoptosis of hepatocytes under Hcy treatment. With the help of co-immunoprecipitation assay, we identified that the interaction between PSMD10 and GRP78 accelerated ER stress-mediated hepatic apoptosis induced by Hcy.

Conclusions

Our findings indicate that miR-212-5p directly targets PSMD10 and subsequently activates ER stress to promote Hcy-induced apoptosis of hepatocytes. We propose that endogenous PSMD10 physically interacts with GRP78 to regulate ER stress. Our study may provide the therapeutic target for the liver injury induced by Hcy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00455-z.

Modulation of Fibroblast Growth Factor-21 and βklotho Proteins Expression in Type 2 Diabetic Women with Non-alcoholic Fatty Liver Disease Following Endurance and Strength Training

Background: There is limited research on the effects of physical activity with moderate intensity on βklotho (BKL) and fibroblast growth factor-21 (FGF-21) proteins expression in diabetic patients with non-alcoholic fatty liver disease (NAFLD). Objectives: This study was aimed to determine the effects of eight weeks of endurance and resistance training on BKL and FGF-21 proteins expression in diabetic women with NAFLD. Methods: Forty-five diabetic women (age: 51 ± 8 years, height: 158 ± 2 cm, weight: 75 ± 8 kg) with NAFLD participated. The subjects were randomly divided into three groups, including control (n = 15), endurance training (n = 15), and resistance training (n = 15). The enzyme-linked immunosorbent assay (ELISA) was used to measure BKL and FGF-21 proteins. Two-way ANOVA with repeated measures was applied to determine differences at a significant level of P < 0.05. Results: Eight weeks of endurance and resistance training reduced AST, ALT, and FGF-21 (25, 26, 19% and 13, 16, 13%, respectively) and increased BKL (16% and 18, respectively). However, in the variables of HDL, insulin, AST, ALT, FGF-21, and BKL, a significant difference was observed in the control group (P < 0.05). Also, there was a significant difference between the control and training groups in BKL and FGF21 proteins expression (P < 0.05), but no significant difference was observed between the two training groups (P > 0.05). Conclusions: The results suggest that both moderate-intensity endurance and resistance training can modulate the destructive effects of type 2 diabetes and NAFLD on BKL and FGF-21 proteins expression, and there is no difference between the two training methods.

Improvement of hyperlipidemia by aerobic exercise in mice through a regulatory effect of miR-21a-5p on its target genes

Hyperlipidemia is a risk factor for cardiovascular disease, and miR-21a-5p plays an important role in the occurrence and progression of hyperlipidemia. Here, we aimed to investigate the mechanism of aerobic exercise improved hyperlipidemia through enhancing miR-21a-5p expression. In this study, high-fat/high-cholesterol diet mice received 8 weeks of aerobic exercise intervention, then we collected plasma and liver samples, we found that there had a notable improvement in weight gain, blood lipid level, and liver steatosis in hyperlipidemia mice after 8 weeks of aerobic exercise intervention. Besides, aerobic exercise significantly up-regulated the expression of miR-21a-5p and provoked favorable changes in the expression of target genes. Knockdown of miR-21a-5p resulted in dysregulation of lipid metabolism and increased expression of FABP7, HMGCR, ACAT1, and OLR1. While aerobic exercise could alleviate miR-21a-5p knock-down induced lipid metabolism disorder. Taken together, these results demonstrated that aerobic exercise improved hyperlipidemia through miR-21a-5p-induced inhibition of target genes FABP7, HMGCR, ACAT1, and OLR1.

Differential microRNAs expression profiles in liver from three different lifestyle modification mice models

Background

MicroRNAs play an important role in many fundamental biological and pathological processes. Defining the microRNAs profile underlying the processes by beneficial and detrimental lifestyles, including caloric restriction (CR), exercise and high-fat diet (HF), is necessary for understanding both normal physiology and the pathogenesis of metabolic disease. We used the microarray to detect microRNAs expression in livers from CR, EX and HF mice models. After predicted potential target genes of differentially expressed microRNAs with four algorithms, we applied GO and KEGG to analyze the function of predicted microRNA targets.

Results

We describe the overall microRNAs expression pattern, and identified 84 differentially expressed microRNAs changed by one or two or even all the three lifestyle modifications. The common and different enriched categories of gene function and main biochemical and signal transduction pathways were presented.

Conclusions

We provided for the first time a comprehensive and thorough comparison of microRNAs expression profiles in liver among these lifestyle modifications. With this knowledge, our findings provide us with an overall vision of microRNAs in the molecular impact of lifestyle on health as well as useful clues for future and thorough research of the role of microRNAs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07507-3.

Advances in Biological Functions and Clinical Studies of FGF21

Fibroblast growth factor 21 (FGF21) regulates many crucial biological processes in human and mammals, particularly metabolic modulation and protective effect after injury. Therefore, determining complex regulatory mechanisms and elucidating the signaling pathway may greatly promote the prevention, diagnosis, and treatment of related injury and metabolic diseases. This review focused on the metabolic modulation and protective effect of FGF21 and summarized the molecular mechanisms and clinical research developments.

Physiopathology of Lifestyle Interventions in Non-Alcoholic Fatty Liver Disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a major health problem, and its prevalence has increased in recent years. Diet and exercise interventions are the first-line treatment options, with weight loss via a hypocaloric diet being the most important therapeutic target in NAFLD. However, most NAFLD patients are not able to achieve such weight loss. Therefore, the requisite is the investigation of other effective therapeutic approaches. This review summarizes research on understanding complex pathophysiology underlying dietary approaches and exercise interventions with the potential to prevent and treat 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.

Relationship between FGF21 and drug or nondrug therapy of type 2 diabetes mellitus

Sedentary and high-calorie diets are associated with increased risk of obesity and type 2 diabetes mellitus, while exercise and diet control are also important nondrug treatments for diabetes. Fibroblast growth factor 21 (FGF21) is an important cytokine, which is mainly expressed in liver, fat and muscle tissue responding to nutrition and exercise, and plays an important role in the improvement of glucose and lipid metabolism. Due to the increasing serum FGF21 level in obesity and diabetes, FGF21 can be used as a predictor or biomarker of diabetes. A variety of clinical antidiabetic drugs can reduce the content of FGF21, possibly for the improvement of FGF21 sensitivity. In this paper, we reviewed the interactions between FGF21 and nondrug therapy (diet and exercise) for diabetes and explored the potential value of the combined application of clinical antidiabetic drugs and FGF21.

Uric acid induced hepatocytes lipid accumulation through regulation of miR-149-5p/FGF21 axis

BACKGROUND

Hyperuricemia is a major risk for non-alcoholic fatty liver disease. However, the mechanisms for this phenomenon are not fully understood. This study aimed to investigate whether microRNAs mediated the pathogenic effects of uric acid on non-alcoholic fatty liver disease.

METHODS

Microarray was used to determine the hepatic miRNA expression profiles of male C57BL/6 mice fed on standard chow diet, high fat diet (HFD), and HFD combined with uric acid-lowering therapy by allopurinol. We validated the expression of the most significant differentially expressed microRNAs and explored its role and downstream target in uric acid-induced hepatocytes lipid accumulation.

RESULTS

Microarray analysis and subsequent validation showed that miR-149-5p was significantly up-regulated in the livers of HFD-fed mice, while the expression was down-regulated by allopurinol therapy. MiR-149-5p expression was also significantly up-regulated in uric acid-stimulated hepatocytes. Over-expression of miR-149-5p significantly aggregated uric acid-induced triglyceride accumulation in hepatocytes, while inhibiting miR-149-5p ameliorated the triglyceride accumulation. Luciferase report assay confirmed that FGF21 is a target gene of miR-149-5p. Silencing FGF21 abolished the ameliorative effects of miR-149-5p inhibitor on uric acid-induced hepatocytes lipid accumulation, while overexpression of FGF21 prevented the lipid accumulation induced by miR-149-5p mimics.

CONCLUSIONS

Uric acid significantly up-regulated the expression of miR-149-5p in hepatocytes and induced hepatocytes lipid accumulation via regulation of miR-149-5p/FGF21 axis.

Physical exercise and liver "fitness": Role of mitochondrial function and epigenetics-related mechanisms in non-alcoholic fatty liver disease

BACKGROUND

Modern lifestyles, especially high-caloric intake and physical inactivity, contribute to the increased prevalence of non-alcoholic fatty liver disease (NAFLD), which becomes a significant health problem worldwide. Lifestyle changes, however, affect not only parental generation, but also their offspring, reinforcing the need for efficient preventive approaches to deal with this disease. This transgenerational influence of phenotypes dependent on parents (particularly maternal) behaviours may open additional research avenues. Despite persistent attempts to design an effective pharmacological therapy against NAFLD, physical activity, as a non-pharmacological approach, emerges as an exciting strategy.

SCOPE OF REVIEW

Here we briefly review the effect of physical exercise on liver mitochondria adaptations in NAFLD, highlighting the importance of mitochondrial metabolism and transgenerational and epigenetic mechanisms in liver diseases.

MAJOR CONCLUSIONS

A deeper look into cellular mechanisms sheds a light on possible effects of physical activity in the prevention and treatment of NAFLD through modulation of function and structure of particular organelles, namely mitochondria. Additionally, despite of increasing evidence regarding the contribution of epigenetic mechanisms in the pathogenesis of different diseases, the role of microRNAs, DNA methylation, and histone modification in NAFLD pathogenesis still needs to be elucidated.

miR-212-5p attenuates ferroptotic neuronal death after traumatic brain injury by targeting Ptgs2

Ferroptosis, a newly discovered form of iron-dependent regulated cell death, has been implicated in traumatic brain injury (TBI). MiR-212-5p has previously been reported to be downregulated in extracellular vesicles following TBI. To investigate whether miR-212-5p is involved in the ferroptotic neuronal death in TBI mice, we first examined the accumulation of malondialdehyde (MDA) and ferrous ion, and the expression of ferroptosis-related molecules at 6 h, 12 h, 24 h, 48 h and 72 h following controlled cortical impact (CCI) in mice. There was a significant upregulation in the expression of Gpx4 and Acsl4 at 6 h, Slc7a11 from 12 h to 72 h, and Nox2 and Sat1 from 6 h to 72 h post injury. Similarly, an upregulation in the expression of Gpx4 at 6 h, Nox2 from 6 h to 72 h, xCT from 12 h to 72 h, and Sat1 at 72 h after CCI was observed at the protein level. Interestingly, MDA and ferrous ion were increased whereas miR-212-5p was decreased in the CCI group compared to the sham group. Furthermore, we found that overexpression of miR-212-5p attenuated ferroptosis while downregulation of miR-212-5p promoted ferroptotic cell death partially by targeting prostaglandin-endoperoxide synthase-2 (Ptgs2) in HT-22 and Neuro-2a cell lines. In addition, administration of miR-212-5p in CCI mice significantly improved learning and spatial memory. Collectively, these findings indicate that miR-212-5p may protect against ferroptotic neuronal death in CCI mice partially by targeting Ptgs2.

The cross-talk between adipokines and miRNAs in health and obesity-mediated diseases

BACKGROUND

Multiple studies have revealed a direct correlation between obesity and the development of multiple comorbidities, including metabolic diseases, cardiovascular disorders, chronic inflammatory disease, and cancers. However, the molecular mechanism underlying the link between obesity and the progression of these diseases is not completely understood. Adipokines are factors that are secreted by adipocytes and play a key role in whole body homeostasis. Collaboratively, miRNAs are suggested to have key functions in the development of obesity and obesity-related disorders. Based on recently emerging evidence, obesity leads to the dysregulation of both adipokines and obesity-related miRNAs. In the present study, we described the correlations between obesity and its related diseases that are mediated by the mutual regulatory effects of adipokines and miRNAs.

METHODS

We reviewed current knowledge of the modulatory effects of adipokines on miRNAs activity and their relevant functions in pathological conditions and vice versa.

RESULTS

Our research reveals the ability of adipokines and miRNAs to control the expression and activity of the other class of molecules, and their effects on obesity-related diseases.

CONCLUSIONS

This study may help researchers develop a roadmap for future investigations and provide opportunities to develop new therapeutic and diagnostic methods for treating obesity-related diseases.

Role of Noncoding RNA in Development of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is increasing in prevalence globally, but little is known about its specific molecular mechanisms. During the past decade, noncoding RNAs (ncRNAs) have been linked to NAFLD initiation and progression. They are a class of RNAs that play an important role in regulating gene expression despite not encoding proteins. This review summarizes recent research on the relationship between ncRNAs and NAFLD. We discussed the potential applicability of ncRNAs as a biomarker for early NAFLD diagnosis and assessment of disease severity. With further study, ncRNAs should prove to be valuable new targets for NAFLD treatment and benefit the development of noninvasive diagnostic methods.

MicroRNAs as a Novel Tool in the Diagnosis of Liver Lipid Dysregulation and Fatty Liver Disease

In recent years, metabolic disorder, especially fatty liver disease, has been considered a major challenge to global health. The attention of researchers focused on expanding knowledge of the regulation mechanism behind these diseases and towards the new diagnostics tools and treatments. The pathophysiology of the fatty liver disease is undoubtedly complex. Abnormal hepatic lipid accumulation is a major symptom of most metabolic diseases. Therefore, the identification of novel regulation factors of lipid metabolism is important and meaningful. As a new diagnostic tool, the function of microRNAs during fatty liver disease has recently come into notice in biological research. Accumulating evidence supports the influence of miRNAs in lipid metabolism. In this review, we discuss the potential role of miRNAs in liver lipid metabolism and the pathogenesis of fatty liver disease.

MicroRNA-212 promotes the recovery function and vascular regeneration of endothelial progenitor cells in mice with ischemic stroke through inactivation of the notch signaling pathway via downregulating MMP9 expression

Ischemic stroke is a refractory disease caused by cerebral ischemic injury, which results in brain dysfunction. This study intends to investigate the effects of microRNA-212 (miR-212) on the recovery function and vascular regeneration of endothelial progenitor cells (EPCs) by inactivation of the Notch signaling pathway by binding to matrix metallopeptidase 9 (MMP9) in mice with ischemic stroke. According to the results of database retrieval systems and data analysis, MMP9 was predicted as a gene related to ischemic stroke and miR-212 is a potential regulating mRNA of MMP9. All 72 healthy adult C57BL6 mice were selected for middle cerebral artery occlusion (MCAO) establishment. Cerebral infarction was observed under triphenyltetrazolium chloride staining. A series of inhibitors, activators, and siRNAs were introduced to the verified regulatory functions for miR-212 governing MMP9 in ischemic stroke. Cell proliferation was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and tube-forming ability by tubule formation test. Reverse transcription quantitative polymerase chain reaction and Western blot analysis were used to detect the expressions of miR-212, MMP9, Hes-1, and Notch-1. The corresponding results demonstrated that the area of cerebral infarction and the number of neuronal necrosis increased in the MCAO group in contrast to the sham group. Meanwhile, upregulation of miR-212 or downregulation of MMP9 decreases the expressions of MMP9, Hes-1 Notch-1, increases cell proliferation and tube-forming ability and improves the pathological conditions of EPCs. Our study suggests that miR-212 promotes recovery function and vascular regeneration of EPCs through negative regulation of the Notch signaling pathway via downregulating expression of MMP9, thus provides a clinical theoretical basis for ischemic stroke therapy.

Role of microRNAs in alcohol-induced liver disorders and non-alcoholic fatty liver disease

MicroRNAs (miRNAs) are small non-coding RNAs that regulate multiple physiological and pathological functions through the modulation of gene expression at the post-transcriptional level. Accumulating evidence has established a role for miRNAs in the development and pathogenesis of liver disease. Specifically, a large number of studies have assessed the role of miRNAs in alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD), two diseases that share common underlying mechanisms and pathological characteristics. The purpose of the current review is to summarize and update the body of literature investigating the role of miRNAs in liver disease. In addition, the potential use of miRNAs as biomarkers and/or therapeutic targets is discussed. Among all miRNAs analyzed, miR-34a, miR-122 and miR-155 are most involved in the pathogenesis of NAFLD. Of note, these three miRNAs have also been implicated in ALD, reinforcing a common disease mechanism between these two entities and the pleiotropic effects of specific miRNAs. Currently, no single miRNA or panel of miRNAs has been identified for the detection of, or staging of ALD or NAFLD. While promising results have been shown in murine models, no therapeutic based-miRNA agents have been developed for use in humans with liver disease.

Critical Roles of microRNAs in the Pathogenesis of Fatty Liver: New Advances, Challenges, and Potential Directions

In this review, we summarize the current understanding of microRNA (miRNA)-mediated modulation of the gene expression in the fatty liver as well as related signaling pathways. Because of the breadth and diversity of miRNAs, miRNAs may have a very wide variety of biological functions, and much evidence has confirmed that miRNAs are involved in the pathogenesis of fatty liver. In the pathophysiological mechanism of fatty liver, miRNAs may be regulated by upstream regulators, and have their own regulatory targets. miRNAs display important roles in the pathological mechanisms of alcoholic liver disease and non-alcoholic fatty liver disease. At present, most of the miRNA studies are focused on cell and tissue levels, and in vivo studies will help us elucidate the regulation of miRNAs and help us evaluate the potential of miRNAs as diagnostic markers and therapeutic targets. Furthermore, there is evidence that miRNAs are involved in the mechanism of natural medicine treatment in fatty liver. Given the important roles of miRNAs in the pathogenesis of fatty liver, we predict that studies of miRNAs in the pathogenesis of fatty liver will contribute to the elucidation of fatty liver pathology and the treatment of fatty liver patients.

miR-1224-5p Enhances Hepatic Lipogenesis by Targeting Adenosine Monophosphate-Activated Protein Kinase α1 in Male Mice

MicroRNAs are potential therapeutic targets for metabolic diseases. Here, miR-1224-5p was highly expressed in the livers of mice fed a high-fat diet (HFD) and in obese (ob/ob) mice. To examine the potential role of miR-1224-5p, we constructed liver-specific adenoviral vectors expressing either an miR-1224-5p inhibitor sequence or miR-1224-5p mimic sequences. After tail-vein vector injection, HFD-fed mice were examined for expression of lipogenic genes. We found that miR-1224-5p inhibitors significantly attenuated hepatic lipogenesis and steatosis in HFD-fed mice, whereas miR-1224-5p mimicked promoted lipid accumulation in the liver of chow-fed C57BL/6 mice. Additional in vitro studies demonstrated that downregulation of miR-1224-5p in HepG2 and primary hepatocytes led to a reduction of cellular triglycerides after treatment with an oleic acid and palmitic acid mixture. Importantly, this study also identified adenosine monophosphate-activated protein kinase (AMPK)-α1 as a direct target of miR-1224-5p. miR-1224-5p binding to the 3' untranslated region of AMPKα1 suppressed expression of the AMPKα1 protein and its downstream molecules. Metformin, an activator of AMPK, also inhibited hepatic expression of miR-1224-5p. Together, these findings indicate that miR-1224-5p promotes hepatic lipogenesis by suppressing AMPKα1 expression and suggest that miR-1224-5p inhibitors warrant further investigation as potential therapeutic tools in the treatment of nonalcoholic fatty liver disease.

Pyridostigmine protects against cardiomyopathy associated with adipose tissue browning and improvement of vagal activity in high-fat diet rats

Obesity, a major contributor to the development of cardiovascular diseases, is associated with an autonomic imbalance characterized by sympathetic hyperactivity and diminished vagal activity. Vagal activation plays important roles in weight loss and improvement of cardiac function. Pyridostigmine is a reversible acetylcholinesterase inhibitor, but whether it ameliorates cardiac lipid accumulation and cardiac remodeling in rats fed a high-fat diet has not been determined. This study investigated the effects of pyridostigmine on high-fat diet-induced cardiac dysfunction and explored the potential mechanisms. Rats were fed a normal or high-fat diet and treated with pyridostigmine. Vagal discharge was evaluated using the BL-420S system, and cardiac function by echocardiograms. Lipid deposition and cardiac remodeling were determined histologically. Lipid utility was assessed by qPCR. A high-fat diet led to a significant reduction in vagal discharge and lipid utility and a marked increase in lipid accumulation, cardiac remodeling, and cardiac dysfunction. Pyridostigmine improved vagal activity and lipid metabolism disorder and cardiac remodeling, accompanied by an improvement of cardiac function in high-fat diet-fed rats. An increase in the browning of white adipose tissue in pyridostigmine-treated rats was also observed and linked to the expression of UCP-1 and CIDEA. Additionally, pyridostigmine facilitated activation of brown adipose tissue via activation of the SIRT-1/AMPK/PGC-1α pathway. In conclusion, a high-fat diet resulted in cardiac lipid accumulation, cardiac remodeling, and a significant decrease in vagal discharge. Pyridostigmine ameliorated cardiomyopathy, an effect related to reduced cardiac lipid accumulation, and facilitated the browning of white adipose tissue while activating brown adipose tissue.

Therapeutic Approaches to Nonalcoholic Fatty Liver Disease: Exercise Intervention and Related Mechanisms

Exercise training ameliorates nonalcoholic fatty liver disease (NAFLD) as well as obesity and metabolic syndrome. Although it is difficult to eliminate the effects of body weight reduction and increased energy expenditure-some pleiotropic effects of exercise training-a number of studies involving either aerobic exercise training or resistance training programs showed ameliorations in NAFLD that are independent of the improvements in obesity and insulin resistance. In vivo studies have identified effects of exercise training on the liver, which may help to explain the "direct" or "independent" effect of exercise training on NAFLD. Exercise training increases peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) expression, improves mitochondrial function and leads to reduced hepatic steatosis, inflammation, fibrosis, and tumor genesis. Crosstalk between the liver and adipose tissue, skeletal muscle and the microbiome is also a possible mechanism for the effect of exercise training on NAFLD. Although numerous studies have reported benefits of exercise training on NAFLD, the optimal duration and intensity of exercise for the prevention or treatment of NAFLD have not been established. Maintaining adherence of patients with NAFLD to exercise training regimes is another issue to be resolved. The use of comprehensive analytical approaches to identify biomarkers such as hepatokines that specifically reflect the effect of exercise training on liver functions might help to monitor the effect of exercise on NAFLD, and thereby improve adherence of these patients to exercise training. Exercise training is a robust approach for alleviating the pathogenesis of NAFLD, although further clinical and experimental studies are required.

microRNA-212 promotes lipid accumulation and attenuates cholesterol efflux in THP-1 human macrophages by targeting SIRT1

Macrophage foam cell formation is a key initiating event in the pathogenesis of atherosclerosis. This work was conducted to determine the role of microRNA (miR)-212 in the transformation of foam cells from macrophages. We examined the expression of miR-212 in atherosclerotic lesions in an apoE-deficient (apoE^-/-) mouse model. The effects of miR-212 overexpression and knockdown on lipid accumulation and cholesterol homeostasis in THP-1 macrophages after exposure to oxidized low-density lipoprotein (oxLDL). The mechanism underlying the activity of miR-212 was explored. It was found that miR-212 was downregulated in atherosclerotic lesions and macrophages from apoE^-/- mice fed high-fat diet, compared to the equivalents from apoE^-/- mice fed standard diet. Overexpression of miR-212 promoted lipid accumulation in oxLDL-treated THP-1 macrophages, whereas miR-212 depletion exerted an opposite effect. Macrophage cholesterol efflux to apolipoprotein A-I was significantly reduced by miR-212, which was accompanied by reduced ABCA1 expression. Mechanistically, miR-212 targeted sirtuin 1 (SIRT1) to repress the expression of ABCA1 in THP-1 macrophages. Rescue experiments confirmed that co-expression of SIRT1 attenuated lipid accumulation and restored cholesterol efflux in miR-212-overexpressing THP-1 macrophages. Collectively, miR-212 facilitates macrophage foam cell formation and suppresses ABCA1-dependent cholesterol efflux through downregulation of SIRT1. Targeting miR-212 may provide a potential therapeutic strategy for atherosclerosis.

Friends Turned Foes: Angiogenic Growth Factors beyond Angiogenesis

Angiogenesis, the formation of new blood vessels from pre-existing ones is a biological process that ensures an adequate blood flow is maintained to provide the cells with a sufficient supply of nutrients and oxygen within the body. Numerous soluble growth factors and inhibitors, cytokines, proteases as well as extracellular matrix proteins and adhesion molecules stringently regulate the multi-factorial process of angiogenesis. The properties and interactions of key angiogenic molecules such as vascular endothelial growth factors (VEGFs), fibroblast growth factors (FGFs) and angiopoietins have been investigated in great detail with respect to their molecular impact on angiogenesis. Since the discovery of angiogenic growth factors, much research has been focused on their biological actions and their potential use as therapeutic targets for angiogenic or anti-angiogenic strategies in a context-dependent manner depending on the pathologies. It is generally accepted that these factors play an indispensable role in angiogenesis. However, it is becoming increasingly evident that this is not their only role and it is likely that the angiogenic factors have important functions in a wider range of biological and pathological processes. The additional roles played by these molecules in numerous pathologies and biological processes beyond angiogenesis are discussed in this review.

MiR-149 Compromises the Reactions of Liver Cells to Fatty Acid via its Polymorphism and Increases Non-Alcoholic Fatty Liver Disease (NAFLD) Risk by Targeting Methylene Tetrahydrofolate Reductase (MTHFR)

BACKGROUND Non-alcoholic fatty liver disease (NAFLD) is a worldwide health problem, and microRNA (miRNA) has been reported to be involved in NAFLD. The objective of our study was to explore the effect of polymorphism in miR-149 on the pathogenesis of NAFLD. MATERIAL AND METHODS Real-time PCR was performed to explore the effect of long-chain fatty acid (FFA) on the level of miR-149 and methylene tetrahydrofolate reductase (MTHFR). Then in-silicon analysis and luciferase assay were investigated to verify MTHFR was the target gene of miR-149. Finally, Western-blot analysis and real-time PCR were performed to confirm the control of MTHFR by miR-149. RESULTS In this study, we found that miR-149 was apparently upregulated in hepatocytes genotyped as TT treated with FFA; and MTHFR in hepatocytes genotyped as TT treated with FFA was evidently downregulated compared to control. Whereas, FFA had no obvious effect on MTHFR level in hepatocytes genotyped as CC. We searched an online miRNA database and found that miR-149 was a regulator of MTHFR expression, which was confirmed by luciferase assay. In hepatocytes genotyped as TT and treated with or without FFA, miR-149 mimic dose-dependently decreased the level of MTHFR, and miR-149 inhibitor dose-dependently increased the level of MTHFR. And in hepatocytes genotyped as CC treated with or without FFA exhibited a similar inhibition effect of miR-149 on expression of MTHFR. CONCLUSIONS The data suggested that the polymorphism in miR-149 played an important role in the development of NAFLD via altering the expression of miR-149 as well as its target, MTHFR.

The Effect of Sitagliptin on Lipid Metabolism of Fatty Liver Mice and Related Mechanisms

Background

In clinics, patients with type 2 diabetes complicated with non-alcoholic fatty liver disease (NAFLD) have been shown to receive significant improvements in blood glucose levels, lipid levels, and liver function after sitagliptin treatment, although the mechanism of drug action remains poorly understood. This study investigated the possible mechanism of sitagliptin on lipid metabolism of NAFLD mice.

Material/Methods

Male C57/BL6 mice were induced for NAFLD via 16 weeks of a high-fat diet, and were treated with 15 mg/kg/day sitagliptin for 16 consecutive weeks. Blood lipid levels were measured and samples were stained with hematoxylin and eosin (H&E) and oil red staining for liver pathology and lipid deposition. Serum levels of fibroblast growth factor (FGF)-9 and FGF-21 were quantified by enzyme-linked immunosorbent assay (ELISA). Peroxisome proliferator-activated receptor (PPAR)-α, and cAMP reactive element binding homolog (CREBH) were measured by Western blotting, while fatty acid synthase and carnitine palmitoyltransferase 1 (CPT1) mRNA levels were assayed by RT-PCR.

Results

Compared to the control group, the NAFLD model mice had liver fatty disease, lower serum FGF-21 and FGF-19 levels, elevated serum lipid levels, depressed PPAR-α, CREBH, and CPT1 expression, and enhanced FAS expression (p<0.05). Sitagliptin treatment depressed blood lipid levels, increased serum FGF-21 and FGF-19 levels, PPAR-α, CREBH, and CPT1 expression, and suppressed FAS expression (p<0.05).

Conclusions

Sitagliptin can protect liver tissue and modulate lipid metabolism in NAFLD mice via elevating FGF-21 and FGF-19, upregulating liver PPAR-α and CREBH levels, and mediating expression levels of key enzymes for lipid metabolism.

Aberrant expression of microRNA induced by high-fructose diet: implications in the pathogenesis of hyperlipidemia and hepatic insulin resistance

Fructose is a highly lipogenic sugar that can alter energy metabolism and trigger metabolic disorders. In the current study, microRNAs (miRNAs) altered by a high-fructose diet were comprehensively explored to elucidate their significance in the pathogenesis of chronic metabolic disorders. miRNA expression profiling using small noncoding RNA sequencing revealed that 19 miRNAs were significantly upregulated and 26 were downregulated in the livers of high-fructose-fed mice compared to chow-fed mice. Computational prediction and functional analysis identified 10 miRNAs, miR-19b-3p, miR-101a-3p, miR-30a-5p, miR-223-3p, miR-378a-3p, miR-33-5p, miR-145a-3p, miR-128-3p, miR-125b-5p and miR-582-3p, assembled as a regulatory network to potentially target key genes in lipid and lipoprotein metabolism and insulin signaling at multiple levels. qRT-PCR analysis of their potential target genes [IRS-1, FOXO1, SREBP-1c/2, ChREBP, insulin-induced gene-2 (Insig-2), microsomal triglyceride transfer protein (MTTP) and apolipoprotein B (apoB)] demonstrated that fructose-induced alterations of miRNAs were also reflected in mRNA expression profiles of their target genes. Moreover, the miRNA profile induced by high-fructose diet differed from that induced by high-fat diet, indicating that miRNAs mediate distinct pathogenic mechanisms in dietary-induced metabolic disorders. This study presents a comprehensive analysis of a new set of hepatic miRNAs, which were altered by high-fructose diet and provides novel insights into the interaction between miRNAs and their target genes in the development of metabolic syndrome.

Changes in the MicroRNA Profile Observed in the Subcutaneous Adipose Tissue of Obese Patients after Laparoscopic Adjustable Gastric Banding

Background. Laparoscopic adjustable gastric banding (LAGB) results in significant lasting weight loss and improved metabolism in obese patients. To evaluate whether epigenetic factors could concur to these benefits, we investigated the subcutaneous adipose tissue (SAT) microRNA (miRNA) profile before (T0) and three years (T1) after LAGB in three morbidly obese women. Case Reports. SAT miRNA profiling, evaluated by TaqMan Array, showed four downexpressed (miR-519d, miR-299-5p, miR-212, and miR-671-3p) and two upexpressed (miR-370 and miR-487a) miRNAs at T1 versus T0. Bioinformatics predicted that these miRNAs regulate genes belonging to pathways associated with the cytoskeleton, inflammation, and metabolism. Western blot analysis showed that PPAR-alpha, which is the target gene of miR-519d, increased after LAGB, thereby suggesting an improvement in SAT lipid metabolism. Accordingly, the number and diameter of adipocytes were significantly higher and lower, respectively, at T1 versus T0. Bioinformatics predicted that the decreased levels of miR-212, miR-299-5p, and miR-671-3p at T1 concur in reducing SAT inflammation. Conclusion. We show that the miRNA profile changes after LAGB. This finding, although obtained in only three cases, suggests that this epigenetic mechanism, by regulating the expression of genes involved in inflammation and lipid metabolism, could concur to improve SAT functionality in postoperative obese patients.

miRNAs in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver cirrhosis and hepatocellular carcinoma and is a considerable threat to public health. miRNAs are important post-transcriptional regulators of gene expression, and the dysregulation of miRNAs is involved in various biological processes in the liver, including lipid homeostasis, inflammation, apoptosis, and cell proliferation. Recently, a number of studies have described the association between miRNAs and NAFLD progression and have shown that circulating miRNAs reflect histological changes in the liver. Therefore, circulating miRNAs have potential use for the evaluation of NAFLD severity. In this review, we discuss the involvement of miRNAs in NAFLD pathogenesis and the key role of miRNAs in the screening, diagnosis, and staging of NAFLD.

The regulation of FGF21 gene expression by metabolic factors and nutrients

Fibroblast growth factor 21 (FGF21) gene expression is altered by a wide array of physiological, metabolic, and environmental factors. Among dietary factors, high dextrose, low protein, methionine restriction, short-chain fatty acids (butyric acid and lipoic acid), and all-trans-retinoic acid were repeatedly shown to induce FGF21 expression and circulating levels. These effects are usually more pronounced in liver or isolated hepatocytes than in adipose tissue or isolated fat cells. Although peroxisome proliferator-activated receptor α (PPARα) is a key mediator of hepatic FGF21 expression and function, including the regulation of gluconeogenesis, ketogenesis, torpor, and growth inhibition, there is increasing evidence of PPARα-independent transactivation of the FGF21 gene by dietary molecules. FGF21 expression is believed to follow the circadian rhythm and be placed under the control of first order clock-controlled transcription factors, retinoic acid receptor-related orphan receptors (RORs) and nuclear receptors subfamily 1 group D (REV-ERBs), with FGF21 rhythm being anti-phase to REV-ERBs. Key metabolic hormones such as glucagon, insulin, and thyroid hormone have presumed or clearly demonstrated roles in regulating FGF21 transcription and secretion. The control of the FGF21 gene by glucagon and insulin appears more complex than first anticipated. Some discrepancies are noted and will need continued studies. The complexity in assessing the significance of FGF21 gene expression resides in the difficulty to ascertain (i) when transcription results in local or systemic increase of FGF21 protein; (ii) if FGF21 is among the first or second order genes upregulated by physiological, metabolic, and environmental stimuli, or merely an epiphenomenon; and (iii) whether FGF21 may have some adverse effects alongside beneficial outcomes.

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.

miR-19b controls cardiac fibroblast proliferation and migration

Cardiac fibrosis is a fundamental constituent of a variety of cardiac dysfunction, making it a leading cause of death worldwide. However, no effective treatment for cardiac fibrosis is available. Therefore, novel therapeutics for cardiac fibrosis are highly needed. Recently, miR‐19b has been found to be able to protect hydrogen peroxide (H₂O₂)‐induced apoptosis and improve cell survival in H9C2 cardiomyocytes, while down‐regulation of miR‐19b had opposite effects, indicating that increasing miR‐19b may be a new therapeutic strategy for attenuating cellular apoptosis during myocardial ischaemia–reperfusion injury. However, considering the fact that microRNAs might exert a cell‐specific role, it is highly interesting to determine the role of miR‐19b in cardiac fibroblasts. Here, we found that miR‐19b was able to promote cardiac fibroblast proliferation and migration. However, miR‐19b mimics and inhibitors did not modulate the expression level of collagen I. Pten was identified as a target gene of miR‐19b, which was responsible for the effect of miR‐19b in controlling cardiac fibroblast proliferation and migration. Our data suggest that the role of miR‐19b is cell specific, and systemic miR‐19b targeting in cardiac remodelling might be problematic. Therefore, it is highly needed and also urgent to investigate the role of miR‐19b in cardiac remodelling in vivo.

Decoding Telocytes

Telocytes (TCs) are a novel type of interstitial cells, with extremely long and thin cellular prolongations termed telopodes (Tps). TCs were first identified by Popescu et al. and described their finding as "cells with telopodes." The presence of TCs has been reported in the majority of tissues and organs (for details please visit www.telocytes.com ). TCs have been ignored or overlooked for a long time due to our inability to observe these cells via a light microscopy. TCs represent a distinct cell population, different from other types of interstitial cells, based on their distinct (ultra)structure, immunophenotype, microRNA profile, gene feature, proteome signature, and secretome features. As TCs have been suggested as new cellular targets for forthcoming therapies, developing specific methods to modulate TC numbers represents an important objective.