Metabolic Circuit Involving Free Fatty Acids, microRNA 122, and Triglyceride Synthesis in Liver and Muscle Tissues

Extracellular Vesicles miRNome Profiling Reveals miRNAs Engagement in Dysfunctional Lipid Metabolism, Chronic Inflammation and Liver Damage in Subjects With Metabolic Dysfunction-Associated Steatotic Liver Disease

BACKGROUND AND AIMS

MicroRNAs (miRNAs) are short non-coding oligonucleotides involved in the post-transcriptional regulation of gene expression. We investigated the association between the miRNome profile of circulating extracellular vesicles (EVs) and metabolic derangements, circulating and hepatic pro-inflammatory cytokines, and liver damage across the histological spectrum of metabolic dysfunction-associated steatotic liver disease (MASLD).

METHODS

EV miRNAs expression was determined by NGS (NextSeq550, Illumina Inc) in 228 biopsy-proven MASLD patients. In vivo metabolic studies were performed in a subgroup of 54 patients by tracer infusion ([6,6-2H2]glucose and [2H5]glycerol) to assess glucose and lipid fluxes and insulin resistance (IR) in the adipose tissue.

RESULTS

Seven miRNAs (miR-27b-3p, miR-30a-5p, miR-122-5p, miR-375-3p, miR-103a-3p, let-7d-5p, and let-7f-5p) were differentially expressed according to the diagnosis of steatohepatitis and the presence of significant fibrosis (F ≥ 2), thus marking subjects with 'at-risk MASH'. In the metabolic studies, the above-reported miRNAs had the strongest associations with lipid metabolism: miR-122-5p and miR-375-3p levels directly correlated with circulating free fatty acids (FFAs) and adipose tissue (AT)-IR, while let-7d-5p and let-7f-5p inversely correlated with lipolysis, FFAs, and progressively decreased according to AT-IR severity. In addition, let-7d-5p and let-7f-5p inversely correlated with the circulating and hepatic expression of pro-inflammatory cytokines, which increased by increasing degrees of AT-IR.

CONCLUSIONS

Our results suggest an intertwined connection between miR-122-5p, miR-375-3p, and the let-7 family in modulating lipid derangements and inflammatory pathways in patients with 'at-risk MASH', paving the basis for further studies aiming at investigating their potential therapeutic value.

The miRNomics of antiretroviral therapy-induced obesity

Human immunodeficiency virus (HIV) is a retrovirus that incorporates its genetic material into the host's chromosome. The resulting diseases and related conditions constitute a global health problem as there are no treatments to eliminate HIV from an infected individual. However, the potent, complex, and active antiretroviral therapy (ART) strategies have been able to successfully inhibit HIV replication in patients. Unfortunately, obesity following ART is frequent among HIV-infected patients. The mechanism underlying ART-induced obesity is characterized based on expression of traditional markers such as genes and proteins. However, little is known about, yet another key component of molecular biology known as microRNAs (miRNAs). Micro-RNAs are ~ 22 base-long non-coding nucleotides capable of regulating more than 60% of all human protein-coding genes. The interest in miRNA molecules is increasing and their roles in HIV and obesity are beginning to be apparent. In this review, we provide an overview of HIV and its associated diseases, ART-induced obesity, and discuss the roles and plausible benefits of miRNAs in regulating obesity genes in HIV-infected patients. Understanding the roles of miRNAs in ART-induced obesity will aid in tracking the disease progression and designing beneficial therapeutic approaches.

Expression Analysis of Circulating miR-21, miR-34a and miR-122 and Redox Status Markers in Metabolic Dysfunction-Associated Steatotic Liver Disease Patients with and Without Type 2 Diabetes

Metabolic dysfunction-associated steatotic liver disease (MASLD), a hepatic form of metabolic syndrome, often co-occurs with type 2 diabetes (T2D) and now affects approximately 30% of the global population. MASLD encompasses conditions from simple steatosis to metabolic dysfunction-associated steatohepatitis, with oxidative stress (OS) driving progression through inflammation. This study analyzes the expression levels of circulating miRNAs and redox status markers in MASLD patients with and without T2D, exploring their potential as disease biomarkers. The expressions of miR-21, miR-34a, and miR-122 were analyzed in the platelet-poor plasma of 147 participants, divided into three groups: MASLD + T2D (48), MASLD (50), and a control group (49). Total oxidant status (TOS), total antioxidant status (TAS), ischemia-modified albumin (IMA), and superoxide anion radical (O2•-) were measured in serum and plasma. Logistic regression showed that miR-21, miR-34a, TOS, TAS, O2•-, and IMA were positive predictors of MASLD, while miR-21 and TAS were negative predictors of T2D in MASLD. Although miR-122 did not show a significant association with either condition, in combination with miR-34a and other markers such as lipid status and liver enzymes, a new significant predictor of MASLD was identified. Circulating miRNAs in combination with redox status markers, lipid status and liver enzymes show potential as MASLD biomarkers.

From fatty liver to fibrosis: the impact of miRNAs on NAFLD and NASH

Non-alcoholic fatty liver disease (NAFLD) is a disease with various levels varying from fatty liver steatosis to acute steatosis which is non-alcoholic steatohepatitis (NASH), which can develop into hepatic failure, as well as in some conditions it can develop into hepatocellular carcinoma (HCC). In the NAFLD and NASH context, aberrant microRNA (miRNA) expression has a thorough contribution to the incidence and development of these liver disorders by influencing key biological actions, involving lipid metabolism, inflammation, and fibrosis. Dysregulated miRNAs can disrupt the balance between lipid accumulation and clearance, exacerbate inflammatory responses, and promote fibrogenesis, thus advancing the severeness of the disorder from simple steatosis to more complex NASH. In the current review, the latest development concerned with the activity of complex regulatory networks of miRNA in the incidence as well as the evolution of NAFLD is to be discussed, also conferring about the miRNAs' role in the onset, pathogenesis as well as diagnosis of NAFLD and NASH discussing miRNAs' role as diagnostic biomarkers and their therapeutic effects on NAFLD/NASH.

Isolation and purification of flavonoids from quinoa whole grain and its inhibitory effect on lipid accumulation in nonalcoholic fatty liver disease by inhibiting the expression of CD36 and FASN

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD), a chronic metabolic disorder marked by excessive lipid deposition, represents a considerable health burden with no established efficacious treatment strategy. Quinoa (Chenopodium quinoa Willd.), valued for its health benefits, is replete with flavonoid bioactives. The aims of this work are to isolate and purify flavonoids from quinoa whole grain that can intervene in NAFLD and to elucidate some of the underlying mechanisms.

RESULTS

Chenopodium quinoa Willd. flavonoids (CQWF) were obtained successfully through an optimized ultrasonic extraction methodology, followed by isolation and purification utilizing macroporous resin D101. The study then explored the therapeutic potential of CQWF and its eluted fractions in models emulating NAFLD conditions: an in vitro fatty liver cell model induced by oleic acid (OA) and palmitic acid (PA) in the HepG2 and BEL-7402 cell lines, and an in vivo high-fat diet (HFD)-induced NAFLD model in C57BL/6N mice. The findings revealed a comprehensive mitigating effect of CQWF30 on NAFLD, manifesting in reduced intracellular lipid accumulation in steatotic hepatocytes and a concerted downregulation of key lipid metabolism genes, CD36 and FASN. Administration of CQWF30 reduced triglyceride (TG) levels in both the cellular model and the livers of HFD-fed mice. It also reduced serum concentrations of TG, total cholesterol (T-CHO), low-density lipoprotein cholesterol (LDL-C), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), while increasing high-density lipoprotein cholesterol (HDL-C) in the mice.

CONCLUSION

These results highlighted the promising therapeutic capacity of CQWF, particularly CQWF30. This research advances the exploration and utilization of flavonoids derived from quinoa whole grain, providing innovative dietary intervention strategies for NAFLD. © 2024 Society of Chemical Industry.

Immunology and treatments of fatty liver disease

Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are two major chronic liver diseases worldwide. The triggers for fatty liver can be derived from external sources such as adipose tissue, the gut, personal diet, and genetics, or internal sources, including immune cell responses, lipotoxicity, hepatocyte death, mitochondrial dysfunction, and extracellular vesicles. However, their pathogenesis varies to some extent. This review summarizes various immune mechanisms and therapeutic targets associated with these two types of fatty liver disease. It describes the gut-liver axis and adipose tissue-liver crosstalk, as well as the roles of different immune cells (both innate and adaptive immune cells) in fatty liver disease. Additionally, mitochondrial dysfunction, extracellular vesicles, microRNAs (miRNAs), and gastrointestinal hormones are also related to the pathogenesis of fatty liver. Understanding the pathogenesis of fatty liver and corresponding therapeutic strategies provides a new perspective for developing novel treatments for fatty liver disease.

Extracellular Vesicles and Micro-RNAs in Liver Disease

Progression of liver disease is dependent on intercellular signaling, including those mediated by extracellular vesicles (EVs). Within these EVs, microRNAs (miRNAs) are packaged to selectively silence gene expression in recipient cells for upregulating or downregulating a specific pathway. Injured hepatocytes secrete EV-associated miRNAs which can be taken up by liver sinusoidal endothelial cells, immune cells, hepatic stellate cells, and other cell types. In addition, these recipient cells will secrete their own EV-associated miRNAs to propagate a response throughout the tissue and the circulation. In this review, we comment on the implications of EV-miRNAs in the progression of alcohol-associated liver disease, metabolic dysfunction-associated steatohepatitis, viral and parasitic infections, liver fibrosis, and liver malignancies. We summarize how circulating miRNAs can be used as biomarkers and the potential of utilizing EVs and miRNAs as therapeutic methods to treat liver disease.

β-Carotene Impacts the Liver MicroRNA Profile in a Sex-Specific Manner in Mouse Offspring of Western Diet-Fed Mothers: Results from Microarray Analysis by Direct Hybridization

Maternal unbalanced diets cause adverse metabolic programming and affect the offspring's liver microRNA (miRNA) profile. The liver is a site of β-carotene (BC) metabolism and a target of BC action. We studied the interaction of maternal Western diet (WD) and early-life BC supplementation on the epigenetic remodeling of offspring's liver microRNAs. Mouse offspring of WD-fed mothers were given a daily placebo (controls) or BC during suckling. Biometric parameters and liver miRNAome by microarray hybridization were analyzed in newly weaned animals. BC sex-dependently impacted the liver triacylglycerol content. The liver miRNAome was also differently affected in male and female offspring, with no overlap in differentially expressed (DE) miRNAs between sexes and more impact in females. Bioinformatic analysis of DE miRNA predicted target genes revealed enrichment in biological processes/pathways related to metabolic processes, regulation of developmental growth and circadian rhythm, liver homeostasis and metabolism, insulin resistance, and neurodegeneration, among others, with differences between sexes. Fifty-five percent of the overlapping target genes in both sexes identified were targeted by DE miRNAs changed in opposite directions in males and females. The results identify sex-dependent responses of the liver miRNA expression profile to BC supplementation during suckling and may sustain further investigations regarding the long-term impact of early postnatal life BC supplementation on top of an unbalanced maternal diet.

Recent Advances in miRNA-Based Therapy for MASLD/MASH and MASH-Associated HCC

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), is a growing health concern worldwide, affecting more than 1 billion adults. It may progress to metabolic dysfunction-associated steatohepatitis (MASH), cirrhosis, and ultimately hepatocellular carcinoma (HCC). Emerging evidence has demonstrated the role in this transition of microRNAs (miRNAs), which regulate the expression of genes associated with lipid metabolism, inflammation, fibrosis, and cell proliferation. Specific miRNAs have been identified to exacerbate or mitigate fibrotic and carcinogenic processes in hepatic cells. The modulation of these miRNAs through synthetic mimics or inhibitors represents a promising therapeutic strategy. Preclinical models have demonstrated that miRNA-based therapies can attenuate liver inflammation, reduce fibrosis, and inhibit tumorigenesis, thus delaying or preventing the onset of HCC. However, challenges such as delivery mechanisms, off-target effects, and long-term safety remain to be addressed. This review, focusing on recently published preclinical and clinical studies, explores the pharmacological potential of miRNA-based interventions to prevent MASLD/MASH and progression toward HCC.

The Development of a Non-Invasive Screening Method Based on Serum microRNAs to Quantify the Percentage of Liver Steatosis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is often asymptomatic and underdiagnosed; consequently, there is a demand for simple, non-invasive diagnostic tools. In this study, we developed a method to quantify liver steatosis based on miRNAs, present in liver and serum, that correlate with liver fat. The miRNAs were analyzed by miRNAseq in liver samples from two cohorts of patients with a precise quantification of liver steatosis. Common miRNAs showing correlation with liver steatosis were validated by RT-qPCR in paired liver and serum samples. Multivariate models were built using partial least squares (PLS) regression to predict the percentage of liver steatosis from serum miRNA levels. Leave-one-out cross validation and external validation were used for model selection and to estimate predictive performance. The miRNAseq results disclosed (a) 144 miRNAs correlating with triglycerides in a set of liver biobank samples (n = 20); and (b) 124 and 102 miRNAs correlating with steatosis by biopsy digital image and MRI analyses, respectively, in liver samples from morbidly obese patients (n = 24). However, only 35 miRNAs were common in both sets of samples. RT-qPCR allowed to validate the correlation of 10 miRNAs in paired liver and serum samples. The development of PLS models to quantitatively predict steatosis demonstrated that the combination of serum miR-145-3p, 122-5p, 143-3p, 500a-5p, and 182-5p provided the lowest root mean square error of cross validation (RMSECV = 1.1, p-value = 0.005). External validation of this model with a cohort of mixed MASLD patients (n = 25) showed a root mean squared error of prediction (RMSEP) of 5.3. In conclusion, it is possible to predict the percentage of hepatic steatosis with a low error rate by quantifying the serum level of five miRNAs using a cost-effective and easy-to-implement RT-qPCR method.

Heterogeneity of extracellular vesicles in porcine myoblasts regulates adipocyte differentiation

The interactions between myogenic cells and adipocytes play an important role in improving carcass traits and the efficiency of energy utilization. However, there are few reports about the interaction between them mediated by small extracellular vesicles (sEV). In this study, sEV derived from porcine primary skeletal muscle stem cells (MuSCs) was found to be involved in the inhibition of porcine primary adipocyte viability, triglyceride content, Oil Red O enrichment and the expression of adipogenic genes. When the MuSCs were treated with insulin (INS) and oleic acid (OA), the effects of their secreted sEVs on adipose precursor cells were reversed, suggesting that the signaling effects of sEV are related to their own heterogeneity. Further by component heterogeneity analysis, miR-146a-5p was found to be enriched in sEVs of MuSCs and to regulate and suppress adipogenesis through its heterogeneity. This study provides an important mechanism and molecular target for small extracellular vesicles to regulate the interaction between muscle and adipose tissue and improve carcass traits at the intercellular level.

Transcriptomic Analysis Reveals the Effects of miR-122 Overexpression in the Liver of Qingyuan Partridge Chickens

The liver of chickens is essential for maintaining physiological activities and homeostasis. This study aims to investigate the specific function and molecular regulatory mechanism of microRNA-122 (miR-122), which is highly expressed in chicken liver. A lentivirus-mediated overexpression vector of miR-122 was constructed and used to infect 12-day-old female Qingyuan Partridge chickens. Transcriptome sequencing analysis was performed to identify differentially expressed genes in the liver. Overexpression of miR-122 resulted in 776 differentially expressed genes (DEGs). Enrichment analyses, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) revealed associations with lipid metabolism, cellular senescence, cell adhesion molecules, and the MAPK signaling pathway. Eight potential target genes of miR-122 (ARHGAP32, CTSD, LBH, PLEKHB2, SEC14L1, SLC2A1, SLC6A14, and SP8) were identified through miRNA target prediction platforms and literature integration. This study provides novel insights into the molecular regulatory mechanisms of miR-122 in chicken liver, highlighting its role in key biological processes and signaling pathways. These discoveries enhance our understanding of miR-122's impact on chicken liver function and offer valuable information for improving chicken production performance and health.

The significance of lipid metabolism reprogramming of tumor-associated macrophages in hepatocellular carcinoma

In the intricate landscape of the tumor microenvironment, tumor-associated macrophages (TAMs) emerge as a ubiquitous cellular component that profoundly affects the oncogenic process. The microenvironment of hepatocellular carcinoma (HCC) is characterized by a pronounced infiltration of TAMs, underscoring their pivotal role in modulating the trajectory of the disease. Amidst the evolving therapeutic paradigms for HCC, the strategic reprogramming of metabolic pathways presents a promising avenue for intervention, garnering escalating interest within the scientific community. Previous investigations have predominantly focused on elucidating the mechanisms of metabolic reprogramming in cancer cells without paying sufficient attention to understanding how TAM metabolic reprogramming, particularly lipid metabolism, affects the progression of HCC. In this review article, we intend to elucidate how TAMs exert their regulatory effects via diverse pathways such as E2F1-E2F2-CPT2, LKB1-AMPK, and mTORC1-SREBP, and discuss correlations of TAMs with these processes and the characteristics of relevant pathways in HCC progression by consolidating various studies on TAM lipid uptake, storage, synthesis, and catabolism. It is our hope that our summary could delineate the impact of specific mechanisms underlying TAM lipid metabolic reprogramming on HCC progression and provide useful information for future research on HCC and the development of new treatment strategies.

Ketone bodies promote epididymal white adipose expansion to alleviate liver steatosis in response to a ketogenic diet

Liver can sense the nutrient status and send signals to other organs to regulate overall metabolic homoeostasis. Herein, we demonstrate that ketone bodies act as signals released from the liver that specifically determine the distribution of excess lipid in epididymal white adipose tissue (eWAT) when exposed to a ketogenic diet (KD). An acute KD can immediately result in excess lipid deposition in the liver. Subsequently, the liver sends the ketone body β-hydroxybutyrate (BHB) to regulate white adipose expansion, including adipogenesis and lipogenesis, to alleviate hepatic lipid accumulation. When ketone bodies are depleted by deleting 3-hydroxy-3-methylglutaryl-CoA synthase 2 gene in the liver, the enhanced lipid deposition in eWAT but not in inguinal white adipose tissue is preferentially blocked, while lipid accumulation in liver is not alleviated. Mechanistically, ketone body BHB can significantly decrease lysine acetylation of peroxisome proliferator-activated receptor gamma in eWAT, causing enhanced activity of peroxisome proliferator-activated receptor gamma, the key adipogenic transcription factor. These observations suggest that the liver senses metabolic stress first and sends a corresponding signal, that is, ketone body BHB, to specifically promote eWAT expansion to adapt to metabolic challenges.

Myosteatosis: Diagnosis, pathophysiology and consequences in metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is associated with an increased risk of multisystemic complications, including muscle changes such as sarcopenia and myosteatosis that can reciprocally affect liver function. We conducted a systematic review to highlight innovative assessment tools, pathophysiological mechanisms and metabolic consequences related to myosteatosis in MASLD, based on original articles screened from PUBMED, EMBASE and COCHRANE databases. Forty-six original manuscripts (14 pre-clinical and 32 clinical studies) were included. Microscopy (8/14) and tissue lipid extraction (8/14) are the two main assessment techniques used to measure muscle lipid content in pre-clinical studies. In clinical studies, imaging is the most used assessment tool and included CT (14/32), MRI (12/32) and ultrasound (4/32). Assessed muscles varied across studies but mainly included paravertebral (4/14 in pre-clinical; 13/32 in clinical studies) and lower limb muscles (10/14 in preclinical; 13/32 in clinical studies). Myosteatosis is already highly prevalent in non-cirrhotic stages of MASLD and correlates with disease activity when using muscle density assessed by CT. Numerous pathophysiological mechanisms were found and included: high-fat and high-fructose diet, dysregulation in fatty acid transport and ketogenesis, endocrine disorders and impaired microRNA122 pathway signalling. In this review we also uncover several potential consequences of myosteatosis in MASLD, such as insulin resistance, MASLD progression from steatosis to metabolic steatohepatitis and loss of muscle strength. In conclusion, data on myosteatosis in MASLD are already available. Screening for myosteatosis could be highly relevant in the context of MASLD, considering its correlation with MASLD activity as well as its related consequences.

Circulating microRNA expression and nonalcoholic fatty liver disease in adolescents with severe obesity

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases in children and adolescents. NAFLD ranges in severity from isolated hepatic steatosis to nonalcoholic steatohepatitis (NASH), wherein hepatocellular inflammation and/or fibrosis coexist with steatosis. Circulating microRNA (miRNA) levels have been suggested to be altered in NAFLD, but the extent to which miRNA are related to NAFLD features remains unknown. This analysis tested the hypothesis that plasma miRNAs are significantly associated with histological features of NAFLD in adolescents.

AIM

To investigate the relationship between plasma miRNA expression and NAFLD features among adolescents with NAFLD.

METHODS

This study included 81 adolescents diagnosed with NAFLD and 54 adolescents without NAFLD from the Teen-Longitudinal Assessment of Bariatric Surgery study. Intra-operative core liver biopsies were collected from participants and used to characterize histological features of NAFLD. Plasma samples were collected during surgery for miRNA profiling. A total of 843 plasma miRNAs were profiled using the HTG EdgeSeq platform. We examined associations of plasma miRNAs and NAFLD features using logistic regression after adjusting for age, sex, race, and other key covariates. Ingenuity Pathways Analysis was used to identify biological functions of miRNAs that were associated with multiple histological features of NAFLD.

RESULTS

We identified 16 upregulated plasma miRNAs, including miR-193a-5p and miR-193b-5p, and 22 downregulated plasma miRNAs, including miR-1282 and miR-6734-5p, in adolescents with NAFLD. Moreover, 52, 16, 15, and 9 plasma miRNAs were associated with NASH, fibrosis, ballooning degeneration, and lobular inflammation, respectively. Collectively, 16 miRNAs were associated with two or more histological features of NAFLD. Among those miRNAs, miR-411-5p was downregulated in NASH, ballooning, and fibrosis, while miR-122-5p, miR-1343-5p, miR-193a-5p, miR-193b-5p, and miR-7845-5p were consistently and positively associated with all histological features of NAFLD. Pathway analysis revealed that most common pathways of miRNAs associated with multiple NAFLD features have been associated with tumor progression, while we also identified linkages between miR-122-5p and hepatitis C virus and between miR-199b-5p and chronic hepatitis B.

CONCLUSION

Plasma miRNAs were associated with NAFLD features in adolescent with severe obesity. Larger studies with more heterogeneous NAFLD phenotypes are needed to evaluate miRNAs as potential biomarkers of NAFLD.

Mechanistic illustration on lipid-metabolism disorders induced by triclosan exposure from the viewpoint of m6A-RNA epigenetic modification

As a typically anthropogenic contaminant, the toxicity effects of triclosan (TCS) were investigated in-depth from the viewpoint of m6A-pre-miRNAs modification. Based on miRNAs high-throughput sequencing, we unravelled the underlying molecular mechanisms regarding TCS-induced lipid-metabolism functional disorders. TCS exposure caused severe lipid accumulation in 120 hpf zebrafish liver and reduced their locomotor activity. Both bioinformatics analysis and experimental validation verified that TCS targeted miR-27b up-regulation to further trigger lipid-metabolism disorders and developmental malformations, including shortened body length, yolk cysts, curved spine and delayed yolk absorption. TCS exposure and miR-27b upregulation both caused the enhanced levels of triglyceride and total cholesterol. Knockdown and overexpression of miR-27b regulated the expression changes of several functional genes related to downstream lipid metabolism of miR-27b, and most downstream target genes of miR-27b were suppressed and enriched in the AMPK signaling pathway. The experiments of pathway inhibitors and agonists further evidenced that TCS caused lipid-metabolism disorders by suppressing the AMPK signaling pathway. In upstream of miR-27b, TCS decreased total m6A-RNA level by targeting upregulation of demethylase and downregulation of methylase reader ythdf1. Molecular docking and ythdf1 siRNA interference further confirmed that TCS targeted the expression change of ythdf1. Under ythdf1 knockdown in upstream of miR-27b, both abnormal lipid metabolism and miR-27b upregulation highlighted that TCS-induced lipid-metabolism disorders were attributable to the decreasing m6A-RNA methylation levels in vivo. These perspectives provide an innovative idea for prevention and treatment of the lipid metabolism-related diseases and these findings open a novel avene for TCS's risk assessment and early intervention of the contaminant.

Role of MicroRNAs in Dietary Interventions for Obesity and Obesity-Related Diseases

Obesity and related metabolic syndromes pose a serious threat to human health and quality of life. A proper diet is a safe and effective strategy to prevent and control obesity, thus maintaining overall health. However, no consensus exists on the connotations of proper diet, and it is attributed to various factors, including "nutritional dark matter" and the "matrix effect" of food. Accumulating evidence confirms that obesity is associated with the in vivo levels of miRNAs, which serve as potential markers and regulatory targets for obesity onset and progression; food-derived miRNAs can regulate host obesity by targeting the related genes or gut microbiota across the animal kingdom. Host miRNAs mediate food nutrient-gut microbiota-obesity interactions. Thus, miRNAs are important correlates of diet and obesity onset. This review outlines the recent findings on miRNA-mediated food interventions for obesity, thereby elucidating their potential applications. Overall, we provide new perspectives and views on the evaluation of dietary nutrition, which may bear important implications for dietary control and obesity prevention.

Exosomal noncoding RNA-mediated spatiotemporal regulation of lipid metabolism: Implications in immune evasion and chronic inflammation

The hallmark of chronic inflammatory diseases is immune evasion. Successful immune evasion involves numerous mechanisms to suppress both adaptive and innate immune responses. Either direct contact between cells or paracrine signaling triggers these responses. Exosomes are critical drivers of these interactions and exhibit both immunogenic and immune evasion properties during the development and progression of various chronic inflammatory diseases. Exosomes carry diverse molecular cargo, including lipids, proteins, and RNAs that are crucial for immunomodulation. Moreover, recent studies have revealed that exosomes and their cargo-loaded molecules are extensively involved in lipid remodeling and metabolism during immune surveillance and disease. Many studies have also shown the involvement of lipids in controlling immune cell activities and their crucial upstream functions in regulating inflammasome activation, suggesting that any perturbation in lipid metabolism results in abnormal immune responses. Strikingly, the expanded immunometabolic reprogramming capacities of exosomes and their contents provided insights into the novel mechanisms behind the prophylaxis of inflammatory diseases. By summarizing the tremendous therapeutic potential of exosomes, this review emphasizes the role of exosome-derived noncoding RNAs in regulating immune responses through the modulation of lipid metabolism and their promising therapeutic applications.

The challenging role of micro-RNAs in non-alcoholic fatty liver disease in children with obesity: is it time for a new era?

INTRODUCTION

As the pediatric obesity epidemic, nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in childhood. Pediatric NAFLD pathophysiology is tangled and still unclear, but insulin resistance (IR), genetics, epigenetics, oxidative stress, and inflammation act as key players. Due to the increased cardiometabolic risk of these patients, several biomarkers have been proposed for early NAFLD identification, but their clinical utility is poor. Recently, hepatic dysregulation of microRNAs (miRNAs) has been linked to metabolic dysfunction, which in turn implied in NAFLD development. Evidence on the intriguing role of miRNAs in NAFLD pathogenesis has emerging especially in at-risk children such as those with obesity. However, pediatric evidence supporting their potential use as early noninvasive NAFLD tools is still limited but promising.

AREAS COVERED

We provided an overview on the emerging role of miRNAs in pediatric NAFLD by addressing some issues regarding their pathophysiological link with the metabolic milieu and their role as reliable NAFLD markers in children with obesity.

EXPERT OPINION

Strong evidence supports a potential role of miRNAs as early biomarkers of NAFLD in children with obesity. They might represent a valid diagnostic and targeted therapeutic tool due to its close pathogenic link with the metabolic milieu.

miR-27b targets MAIP1 to mediate lipid accumulation in cultured human and mouse hepatic cells

Non-alcoholic liver disease (NAFLD) is a condition caused by excessive fat accumulation in the liver and developed via multiple pathways. miR-27b has been suggested to play crucial roles in the development of NAFLD, assuming via targeting genes involved in lipid catabolism and anabolism. However, other pathways regulated by miR-27b are largely unknown. Here we show that lipid accumulation was induced in miR-27b-transfected human and mouse hepatic cells and that knockdowns of three miR-27b-target genes, β-1,4-galactosyltransferase 3 (B4GALT3), matrix AAA peptidase interacting protein 1 (MAIP1) and PH domain and leucine rich repeat protein phosphatase 2 (PHLPP2), induced lipid accumulation. We also show that B4GALT3 and MAIP1 were direct targets of miR-27b and overexpression of MAIP1 ameliorated miR-27b-induced lipid accumulation. In addition, we show that hepatic Maip1 expression declined in mice fed a high-fat diet, suggesting the involvement of decreased Maip1 expression in the condition of fatty liver. Overall, we identified MAIP1/miR-27b axis as a mediator of hepatic lipid accumulation, a potential therapeutic target for NAFLD.

Insight into the Inter-Organ Crosstalk and Prognostic Role of Liver-Derived MicroRNAs in Metabolic Disease Progression

Dysfunctional hepatic metabolism has been linked to numerous diseases, including non-alcoholic fatty liver disease, the most common chronic liver disorder worldwide, which can progress to hepatic fibrosis, and is closely associated with insulin resistance and cardiovascular diseases. In addition, the liver secretes a wide array of metabolites, biomolecules, and microRNAs (miRNAs) and many of these secreted factors exert significant effects on metabolic processes both in the liver and in peripheral tissues. In this review, we summarize the involvement of liver-derived miRNAs in biological processes with an emphasis on delineating the communication between the liver and other tissues associated with metabolic disease progression. Furthermore, the review identifies the primary molecular targets by which miRNAs act. These consolidated findings from numerous studies provide insight into the underlying mechanism of various metabolic disease progression and suggest the possibility of using circulatory miRNAs as prognostic predictors and therapeutic targets for improving clinical intervention strategies.

An Insight into the Arising Role of MicroRNAs in Hepatocellular Carcinoma: Future Diagnostic and Therapeutic Approaches

Hepatocellular carcinoma (HCC) constitutes a frequent highly malignant form of primary liver cancer and is the third cause of death attributable to malignancy. Despite the improvement in the therapeutic strategies with the exploration of novel pharmacological agents, the survival rate for HCC is still low. Shedding light on the multiplex genetic and epigenetic background of HCC, such as on the emerging role of microRNAs, is considered quite promising for the diagnosis and the prediction of this malignancy, as well as for combatting drug resistance. MicroRNAs (miRNAs) constitute small noncoding RNA sequences, which play a key role in the regulation of several signaling and metabolic pathways, as well as of pivotal cellular functions such as autophagy, apoptosis, and cell proliferation. It is also demonstrated that miRNAs are significantly implicated in carcinogenesis, either acting as tumor suppressors or oncomiRs, while aberrations in their expression levels are closely associated with tumor growth and progression, as well as with local invasion and metastatic dissemination. The arising role of miRNAs in HCC is in the spotlight of the current scientific research, aiming at the development of novel therapeutic perspectives. In this review, we will shed light on the emerging role of miRNAs in HCC.

The protective effect of lncRNA NEAT1/miR-122-5p/Wnt1 axis on hippocampal damage in hepatic ischemic reperfusion young mice

Hepatic ischemic reperfusion (HIR) is a common pathophysiological process in many surgical procedures such as liver transplantation (LT) and hepatectomy. And it is also an important factor leading to perioperative distant organ damage. Children undergoing major liver surgery are more susceptible to various pathophysiological processes, including HIR, since their brains are still developing and the physiological functions are still incomplete, which can lead to brain damage and postoperative cognitive impairment, thus seriously affecting the long-term prognosis of the children. However, the present treatments of mitigating HIR-induced hippocampal damage are not proven to be effective. The important role of microRNAs (miRNAs) in the pathophysiological processes of many diseases and in the normal development of the body has been confirmed in several studies. The current study explored the role of miR-122-5p in HIR-induced hippocampal damage progression. HIR-induced hippocampal damage mouse model was induced by clamping the left and middle lobe vessels of the liver of young mice for 1 h, removing the vessel clamps and re-perfusing them for 6 h. The changes in the level of miR-122-5p in the hippocampal tissues were measured, and its influences on the activity as well as apoptotic rate of neuronal cells were investigated. Short interfering RNA modified with 2'-O-methoxy substitution targeting long-stranded non-coding RNA (lncRNA) nuclear enriched transcript 1 (NEAT1) as well as miR-122-5p antagomir were used to further clarify the role played by the corresponding molecules in hippocampal injury in young mice with HIR. The result obtained in our study was that the expression of miR-122-5p in the hippocampal tissue of young mice receiving HIR is reduced. Upregulated expression of miR-122-5p reduces the viability of neuronal cells and promotes the development of apoptosis, thereby aggravating the damage of hippocampal tissue in HIR young mice. Additionally, in the hippocampal tissue of young mice receiving HIR, lncRNA NEAT1 exerts some anti-apoptotic effects by binding to miR-122-5p, promoting the expression of Wnt1 pathway. An essential observation of this study was the binding of lncRNA NEAT1 to miR-122-5p, which upregulates Wnt1 and inhibits HIR-induced hippocampal damage in young mice.

The role of hepatokines in NAFLD

Non-alcoholic fatty liver disease (NAFLD) is not only a consequence of insulin resistance, but it is also an important cause of insulin resistance and major non-communicable diseases (NCDs). The close relationship of NAFLD with visceral obesity obscures the role of fatty liver from visceral adiposity as the main pathomechanism of insulin resistance and NCDs. To overcome this limitation, in analogy to the concept of adipokines, in 2008 we introduced the term hepatokines to describe the role of fetuin-A in metabolism. Since then, several other hepatokines were tested for their effects on metabolism. Here we address the dysregulation of hepatokines in people with NAFLD. Then, we discuss pathophysiological mechanisms of cardiometabolic diseases specifically related to NAFLD by focusing on hepatokine-related organ crosstalk. Finally, we propose how the determination of major hepatokines and adipokines can be used for pathomechanism-based clustering of insulin resistance in NAFLD and visceral obesity to better implement precision medicine in clinical practice.

CircRNA-PI4KB Induces Hepatic Lipid Deposition in Non-Alcoholic Fatty Liver Disease by Transporting miRNA-122 to Extra-Hepatocytes

Ectopic fat deposition in the liver, known as non-alcoholic fatty liver disease (NAFLD), affects up to 30% of the worldwide population. miRNA-122, the most abundant liver-specific miRNA, protects hepatic steatosis and inhibits cholesterol and fatty acid synthesis in NAFLD. Previously, we have shown that compared with its expression in healthy controls, miRNA-122 decreased in the liver tissue but gradually increased in the serum of patients with non-alcoholic fatty liver disease and non-alcoholic steatohepatitis, suggesting that miRNA-122 could have been transported to the serum. Here, we aimed to confirm and unravel the mechanism of transportation of miRNA-122 to extra-hepatocytes. Our findings showed a decrease in the intra-hepatocyte miRNA-122 and an increase in the extra-hepatocyte (medium level) miRNA-122, suggesting the miRNA-122 "escaped" from the intra-hepatocyte due to an increased extra-hepatocyte excretion. Using bioinformatics tools, we showed that miRNA-122 binds to circPI4KB, which was further validated by an RNA pull-down and luciferase reporter assay. The levels of circPI4KB in intra- and extra-hepatocytes corresponded to that of miRNA-122, and the overexpression of circPI4KB increased the miRNA-122 in extra-hepatocytes, consequently accomplishing a decreased protective role of miRNA-122 in inhibiting the lipid deposition. The present study provides a new explanation for the pathogenesis of the hepatic lipid deposition in NAFLD.

A novel regulatory facet for hypertriglyceridemia: The role of microRNAs in the regulation of triglyceride-rich lipoprotein biosynthesis

Atherosclerotic cardiovascular disease (ASCVD) is one of the major leading global causes of death. Genetic and epidemiological studies strongly support the causal association between triacylglycerol-rich lipoproteins (TAGRL) and atherogenesis, even in statin-treated patients. Recent genetic evidence has clarified that variants in several key genes implicated in TAGRL metabolism are strongly linked to the increased ASCVD risk. There are several triacylglycerol-lowering agents; however, new therapeutic options are in development, among which are miRNA-based therapeutic approaches. MicroRNAs (miRNAs) are small non-coding RNAs (18-25 nucleotides) that negatively modulate gene expression through translational repression or degradation of target mRNAs, thereby reducing the levels of functional genes. MiRNAs play a crucial role in the development of hypertriglyceridemia as several miRNAs are dysregulated in both synthesis and clearance of TAGRL particles. MiRNA-based therapies in ASCVD have not yet been applied in human trials but are attractive. This review provides a concise overview of current interventions for hypertriglyceridemia and the development of novel miRNA and siRNA-based drugs. We summarize the miRNAs involved in the regulation of key genes in the TAGRLs synthesis pathway, which has gained attention as a novel target for therapeutic applications in CVD.

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

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

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

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

Dihydroquercetin Supplementation Improved Hepatic Lipid Dysmetabolism Mediated by Gut Microbiota in High-Fat Diet (HFD)-Fed Mice

Dihydroquercetin (DHQ) is a natural flavonoid with multiple bioactivities, including hepatoprotective effects. This study aimed to investigate whether DHQ improved lipid dysmetabolism in the body, especially in the liver, and whether there is a relationship between hepatic metabolism and altered gut flora in high-fat diet (HFD)-induced mice. HFD-induced mice were given 50 mg/kg body weight DHQ intragastrically for 10 weeks. The data showed that DHQ reduced body weight, the weight of the liver and white adipose tissue as well as serum leptin, LPS, triglyceride and cholesterol levels. RNA-seq results indicated that DHQ down-regulated lipogenesis-related genes and up-regulated fatty acid oxidation-related genes, including MOGAT1 and CPT1A. Furthermore, DHQ had a tendency to decrease hepatic cholesterol contents by reducing the mRNA levels of cholesterol synthesis genes such as FDPS and HMGCS1. 16S rRNA sequencing analysis indicated that DHQ significantly decreased the richness of Lactococcus, Lachnoclostridium, and Eubacterium_xylanophilum_group. Correlation analysis further demonstrated that these bacteria, Lactococcus and Eubacterium_xylanophilum_group in particular, had significantly positive correlation with lipid and cholesterol synthesis genes, and negative correlation with fatty acid oxidation genes. In conclusion, DHQ could improve hepatic lipid dysmetabolism potentially by improved gut microbial community, which may be used as an intervention strategy in hepatic metabolism diseases.

Role of Adipose Tissue microRNAs in the Onset of Metabolic Diseases and Implications in the Context of the DOHaD

The worldwide epidemic of obesity is associated with numerous comorbid conditions, including metabolic diseases such as insulin resistance and diabetes, in particular. The situation is likely to worsen, as the increase in obesity rates among children will probably lead to an earlier onset and more severe course for metabolic diseases. The origin of this earlier development of obesity may lie in both behavior (changes in nutrition, physical activity, etc.) and in children's history, as it appears to be at least partly programmed by the fetal/neonatal environment. The concept of the developmental origin of health and diseases (DOHaD), involving both organogenesis and epigenetic mechanisms, encompasses such programming. Epigenetic mechanisms include the action of microRNAs, which seem to play an important role in adipocyte functions. Interestingly, microRNAs seem to play a particular role in propagating local insulin resistance to other key organs, thereby inducing global insulin resistance and type 2 diabetes. This propagation involves the active secretion of exosomes containing microRNAs by adipocytes and adipose tissue-resident macrophages, as well as long-distance communication targeting the muscles and liver, for example. Circulating microRNAs may also be useful as biomarkers for the identification of populations at risk of subsequently developing obesity and metabolic diseases.

Non-coding RNAs: The link between maternal malnutrition and offspring metabolism

Early life nutrition is associated with the development and metabolism in later life, which is known as the Developmental Origin of Health and Diseases (DOHaD). Epigenetics have been proposed as an important explanation for this link between early life malnutrition and long-term diseases. Non-coding RNAs (ncRNAs) may play a role in this epigenetic programming. The expression of ncRNAs (such as long non-coding RNA H19, microRNA-122, and circular RNA-SETD2) was significantly altered in specific tissues of offspring exposed to maternal malnutrition. Changes in these downstream targets of ncRNAs lead to abnormal development and metabolism. This review aims to summarize the existing knowledge on ncRNAs linking the maternal nutrition condition and offspring metabolic diseases, such as obesity, type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD).

Non-coding RNAs in hepatocellular carcinoma: Insights into regulatory mechanisms, clinical significance, and therapeutic potential

Hepatocellular carcinoma (HCC) is a complex and heterogeneous malignancy with high incidence and poor prognosis. In addition, owing to the lack of diagnostic and prognostic markers, current multimodal treatment options fail to achieve satisfactory outcomes. Tumor immune microenvironment (TIME), angiogenesis, epithelial-mesenchymal transition (EMT), invasion, metastasis, metabolism, and drug resistance are important factors influencing tumor development and therapy. The intercellular communication of these important processes is mediated by a variety of bioactive molecules to regulate pathophysiological processes in recipient cells. Among these bioactive molecules, non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), account for a large part of the human transcriptome, and their dysregulation affects the progression of HCC. The purpose of this review is to evaluate the potential regulatory mechanisms of ncRNAs in HCC, summarize novel biomarkers from somatic fluids (plasma/serum/urine), and explore the potential of some small-molecule modulators as drugs. Thus, through this review, we aim to contribute to a deeper understanding of the regulatory mechanisms, early diagnosis, prognosis, and precise treatment of HCC.

MicroRNAs in non-alcoholic fatty liver disease: Progress and perspectives

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of disease ranging from simple hepatic steatosis (NAFL) to non-alcoholic steatohepatitis (NASH) which may progress to cirrhosis and liver cancer. NAFLD is rapidly becoming a global health challenge, and there is a need for improved diagnostic- and prognostic tools and for effective pharmacotherapies to treat NASH. The molecular mechanisms of NAFLD development and progression remain incompletely understood, though ample evidence supports a role of microRNAs (miRNAs) - small non-coding RNAs regulating gene expression - in the progression of metabolic liver disease.

SCOPE OF REVIEW

In this review, we summarise the currently available liver miRNA profiling studies in people with various stages of NAFLD. We further describe the mechanistic role of three of the most extensively studied miRNA species, miR-34a, miR-122 and miR-21, and highlight selected findings on novel NAFLD-linked miRNAs. We also examine the literature on exosomal microRNAs (exomiRs) as inter-hepatocellular or -organ messengers in NAFLD. Furthermore, we address the status for utilizing circulating NAFLD-associated miRNAs as minimally invasive tools for disease diagnosis, staging and prognosis as well as their potential use as NASH pharmacotherapeutic targets. Finally, we reflect on future directions for research in the miRNA field.

MAJOR CONCLUSIONS

NAFLD is associated with changes in hepatic miRNA expression patterns at early, intermediate and late stages, and specific miRNA species appear to be involved in steatosis development and NAFL progression to NASH and cirrhosis. These miRNAs act either within or between hepatocytes and other liver cell types such as hepatic stellate cells and Kupffer cells or as circulating inter-organ messengers carrying signals between the liver and extra-hepatic metabolic tissues, including the adipose tissues and the cardiovascular system. Among circulating miRNAs linked to NAFLD, miR-34a, miR-122 and miR-192 are the best candidates as biomarkers for NAFLD diagnosis and staging. To date, no miRNA-targeting pharmacotherapy has been approved for the treatment of NASH, and no such therapy is currently under clinical development. Further research should be conducted to translate the contribution of miRNAs in NAFLD into innovative therapeutic strategies.

MicroRNA-379-5p regulates free cholesterol accumulation and relieves diet induced-liver damage in db/db mice via STAT1/HMGCS1 axis

Lipotoxicity induced by the overload of lipid in the liver, especially excess free cholesterol (FC), has been recognized as one of driving factors in the transition from non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH). MicroRNA (miR)-379-5p has been reported to play regulatory roles in hepatic triglyceride homeostasis, but the relationship of miR-379-5p and hepatic cholesterol homeostasis has never been touched. In the current study, we found that hepatic miR-379-5p levels were decreased obviously in NAFLD patients and model mice compared with their controls. Moreover, miR-379-5p was discovered to be able to inhibit intracellular FC accumulation and alleviate mitochondrial damage induced by palmitic acid (PA) in vitro. Furthermore, overexpression of miR-379-5p in HFHC-fed db/db mice could reduce the level of hepatic total cholesterol (TC) and FC, and ameliorate hepatic injury reflected by the lower serum alanine aminotransferase (ALT) and aspartate transaminase (AST). Subsequently, by combining spectrometry (MS) and luciferase assay, we identified miR-379-5p suppressed STAT1 through transcriptional and translational regulation. Finally, we confirmed that STAT1 was a transcriptional factor of HMGCS1. In conclusion, miR-379-5p inhibits STAT1 expression and regulates cholesterol metabolism through the STAT1/HMGCS1 axis, suggesting miR-379-5p might be applied to improve lipotoxicity in the future.

Liver Steatosis: A Marker of Metabolic Risk in Children

Obesity is one of the greatest health challenges affecting children of all ages and ethnicities. Almost 19% of children and adolescents worldwide are overweight or obese, with an upward trend in the last decades. These reports imply an increased risk of fat accumulation in hepatic cells leading to a series of histological hepatic damages gathered under the acronym NAFLD (Non-Alcoholic Fatty Liver Disease). Due to the complex dynamics underlying this condition, it has been recently renamed as 'Metabolic Dysfunction Associated Fatty Liver Disease (MAFLD)', supporting the hypothesis that hepatic steatosis is a key component of the large group of clinical and laboratory abnormalities of Metabolic Syndrome (MetS). This review aims to share the latest scientific knowledge on MAFLD in children in an attempt to offer novel insights into the complex dynamics underlying this condition, focusing on the novel molecular aspects. Although there is still no treatment with a proven efficacy for this condition, starting from the molecular basis of the disease, MAFLD's therapeutic landscape is rapidly expanding, and different medications seem to act as modifiers of liver steatosis, inflammation, and fibrosis.

Helicoverpa armigera miR-2055 regulates lipid metabolism via fatty acid synthase expression

Insect hormones and microRNAs regulate lipid metabolism, but the mechanisms are not fully elucidated. Here, we found that cotton bollworm larvae feeding on Arabidopsis thaliana (AT) leaves had a lower triacylglycerol (TAG) level and more delayed development than individuals feeding on artificial diet (AD). Association analysis of small RNA and mRNA revealed that the level of miR-2055, a microRNA related to lipid metabolism, was significantly higher in larvae feeding on AT. Dual-luciferase reporter assays demonstrated miR-2055 binding to 3' UTR of fatty acid synthase (FAS) mRNA to suppress its expression. Elevating the level of miR-2055 in larvae by agomir injection decreased FAS mRNA and protein levels, which resulted in reduction of free fatty acid (FFA) and TAG in fat body. Interestingly, in vitro assays illustrated that juvenile hormone (JH) increased miR-2055 accumulation in a dosage-dependent manner, whereas knockdown of Methoprene tolerant (Met) or Kruppel homologue 1 (Kr-h1) decreased the miR-2055 level. This implied that JH induces the expression of miR-2055 via a Met-Kr-h1 signal. These findings demonstrate that JH and miRNA cooperate to modulate lipid synthesis, which provides new insights into the regulatory mechanisms of metabolism in insects.

Gestational hypercholesterolemia programs hepatic steatosis in a sex-specific manner in ApoE-deficient mice

Maternal hypercholesterolemia (MHC), a pathological condition characterized by an exaggerated rise in maternal serum cholesterol during pregnancy, may influence offspring hepatic lipid metabolism and increase the risk of nonalcoholic fatty liver disease (NAFLD). As NAFLD is characterized by a sexual dimorphic response, we assessed whether early-life exposure to excessive cholesterol influences the development of NAFLD in offspring and whether this occurs in a sex-specific manner. Female apoE-/- mice were randomly assigned to a control (CON) or a high cholesterol (CH; 0.15%) diet prior to breeding. At parturition, a cross-fostering approach was used to establish three groups: (1) normal cholesterol exposure throughout gestation and lactation (CON-CON); (2) excessive cholesterol exposure throughout gestation and lactation (CH-CH); and (3) excessive cholesterol exposure in the gestation period only (CH-CON). Adult male offspring (PND 84) exposed to excessive cholesterol during gestation only (CH-CON) demonstrated hepatic triglyceride (TG) accumulation and reduced lipogenic gene expression. However, male mice with a prolonged cholesterol exposure throughout gestation and lactation (CH-CH) had a similar, but not exacerbated hepatic response. Further, with the exception of higher serum TG in adult CH-CH females, evidence for a programming effect in female offspring was largely absent in comparison with males. These results indicate a sexual dimorphic response with respect to the effect of MHC on later life hepatic steatosis and highlight the gestation period as the most influential malprogramming window for hepatic lipid dysfunction in males.

NAFLD and Vitamin D: Evidence for Intersection of MicroRNA Regulated Pathways

Non-alcoholic fatty liver disease (NAFLD) is now the most common cause of chronic liver disease, worldwide. The molecular pathogenesis of NAFLD is complex, involving numerous signalling molecules including microRNAs (miRNAs). Dysregulation of miRNA expression is associated with hepatic inflammation, fibrosis and hepatocellular carcinoma. Although miRNAs are also critical to the cellular response to vitamin D, mediating regulation of the vitamin D receptor (VDR) and vitamin D’s anticancer effects, a role for vitamin D regulated miRNAs in NAFLD pathogenesis has been relatively unexplored. Therefore, this review aimed to critically assess the evidence for a potential subset of miRNAs that are both dysregulated in NAFLD and modulated by vitamin D. Comprehensive review of 89 human studies identified 25 miRNAs found dysregulated in more than one NAFLD study. In contrast, only 17 studies, including a protocol for a trial in NAFLD, had examined miRNAs in relation to vitamin D status, response to supplementation, or vitamin D in the context of the liver. This paper summarises these data and reviews the biological roles of six miRNAs (miR-21, miR-30, miR-34, miR-122, miR-146, miR-200) found dysregulated in multiple independent NAFLD studies. While modulation of miRNAs by vitamin D has been understudied, integrating the data suggests seven vitamin D modulated miRNAs (miR-27, miR-125, miR-155, miR-192, miR-223, miR-375, miR-378) potentially relevant to NAFLD pathogenesis. Our summary tables provide a significant resource to underpin future hypothesis-driven research, and we conclude that the measurement of serum and hepatic miRNAs in response to vitamin D supplementation in larger trials is warranted.

Non-alcoholic fatty liver disease and microRNAs expression, how it affects the development and progression of the disease

The obesity pandemic that affects the global population generates one of the most unfavorable microenvironmental conditions in the hepatocyte, which triggers the metabolic hepatopathy known as non-alcoholic fatty liver; its annual rates increase in its prevalence and does not seem to improve in the future. The international consortia, LITMUS by the European Union and NIMBLE by the United States of America, have started a race for the development of hepatic steatosis and steatohepatitis reliable biomarkers to have an adequate diagnosis. MicroRNAs have been proposed as diagnostic and prognostic biomarkers involved in adaptation to changes in the liver microenvironment, which could improve clinical intervention strategies in patients with hepatic steatosis.

Cadmium induces triglyceride levels via microsomal triglyceride transfer protein (MTTP) accumulation caused by lysosomal deacidification regulated by endoplasmic reticulum (ER) Ca2+ homeostasis

Cadmium (Cd) exposure induced lipid metabolic disorder with changes in lipid composition, as well as triglyceride (TG) levels. Liver is the main organ maintaining body TG level and previous studies suggested that Cd exposure might increase TG synthesis but reduce TG uptake in liver. However, the effects of Cd exposure on TG secretion from liver and underlying mechanism are still unclear. In the present study, the data revealed that Cd exposure increased TG levels in the HepG2 cells and the cultured medium by increasing the expression of microsomal triglyceride transfer protein (MTTP), which was abrogated by siRNA knockdown of MTTP. MTTP was synergistically accumulated after Cd exposure or treated with proteasome inhibitor MG132 and lysosome inhibitor chloroquine (CQ), which suggested the Cd increased MTTP protein stability by inhibiting both the proteasome and the lysosomal protein degradation pathways. In addition, our results demonstrated that Cd exposure inhibited the lysosomal acidic degradation pathway through disrupting endoplastic reticulum (ER) Ca2+ homeostasis. Cd-induced MTTP protein and TG levels were significantly reduced by pretreatments of BAPTA/AM chelation of intracellular Ca2+, 2-APB inhibition of ER Ca2+ release channel inositol 1,4,5-trisphosphate receptor (IP3R) and CDN1163 activation of ER Ca2+ reuptake pump sarcoplasmic reticulum Ca2+-ATPase (SERCA). These results suggest that Cd-induced ER Ca2+ release impaired the lysosomal acidity, which associated with MTTP protein accumulation and contributed to increased TG levels.

miR-23b Ameliorates nonalcoholic steatohepatitis by targeting Acyl-CoA thioesterases 4

Non-alcoholic fatty liver disease (NAFLD) and its more advanced stages, Non-alcoholic steatohepatitis and Cirrhosis, are the most common liver diseases in the worldwide, especially in developing countries. NAFLD is distinguished by the accumulation of triglycerides within hepatocytes. An increasing body of evidence suggests that hepatic MicroRNAs play an important role in NAFLD by controlling lipid metabolism, inflammation, and fibrosis. However, the precise causative functions of miRNA in NAFLD remain unknown. Here, we discovered that mice lacking MicroRNA-23b developed NAFLD-like phenotypes such as increased serum triglyceride and lipid droplet accumulation. In db/db mice fed a high fat diet, MicroRNA-23b overexpression reduced liver weight and alleviated liver inflammation, apoptosis, and fibrosis. MicroRNA-23b regulates the acyl-CoA metabolic process via Acyl-CoA thioesterase 4 (Acot4), which interacts with Acetyl CoA Carboxylase (ACC), according to the RNA-seq analysis.

Non-Coding RNAs: Novel Players in Insulin Resistance and Related Diseases

The rising prevalence of metabolic diseases related to insulin resistance (IR) have stressed the urgent need of accurate and applicable tools for early diagnosis and treatment. In the last decade, non-coding RNAs (ncRNAs) have gained growing interest because of their potential role in IR modulation. NcRNAs are variable-length transcripts which are not translated into proteins but are involved in gene expression regulation. Thanks to their stability and easy detection in biological fluids, ncRNAs have been investigated as promising diagnostic and therapeutic markers in metabolic diseases, such as type 2 diabetes mellitus (T2D), obesity and non-alcoholic fatty liver disease (NAFLD). Here we review the emerging role of ncRNAs in the development of IR and related diseases such as obesity, T2D and NAFLD, and summarize current evidence concerning their potential clinical application.

Circulating microRNA signatures that predict liver fibrosis progression in patients with HIV-1/hepatitis C virus coinfections

OBJECTIVE

The lack of available biomarkers for diagnosing and predicting different stages of liver disease with a noninvasive strategy is currently one of the main challenges that clinicians are facing. Recent evidence indicates that the plasma levels of specific microRNAs (miRNAs) may be significantly altered in patients with liver injury, including those with HIV type 1 (HIV-1) infections.

DESIGN/METHODS

Large-scale deep sequencing analysis of small RNA expression was performed on plasma samples from 46 patients with HIV-1/hepatitis C virus (HCV) coinfections that did not exhibit liver fibrosis at the time of sampling.

RESULTS

A total of 1065 different miRNAs were identified. After a mean of 10.3 years, 26 out of the 46 patients developed liver fibrosis (stage F2-4) and 20 remained without signs of liver fibrosis (stage F0-1). We identified a signature of seven miRNAs: 100-5p, 192-5p, 99a-5p, 122-5p, 125b-2-3p, 1246 and 194-5p, which were highly correlated with progression to liver fibrosis. These seven miRNAs detected liver fibrosis progression with an area under the curve (AUC) of 0.910-0.806. Two miRNAs, 100-5p and 192-5p, which displayed the best AUC values, yielded a sensitivity of 88% and a specificity of 85% for detecting liver fibrosis progression.

CONCLUSION

Our results demonstrated that circulating miRNA levels had potential in predicting liver fibrosis progression before the clinical detection of liver fibrosis or significant clinical signs, such as elevated liver transaminases or platelets. Thus, our results might facilitate predictions of liver injury progression in patients with HIV-1-infections.

Methodological considerations for measuring biofluid-based microRNA biomarkers

MicroRNAs (miRNAs) are small non-coding RNA that regulate the expression of messenger RNA and are implicated in almost all cellular processes. Importantly, miRNAs can be released extracellularly and are stable in these matrices where they may serve as indicators of organ or cell-specific toxicity, disease, and biological status. There has thus been great enthusiasm for developing miRNAs as biomarkers of adverse outcomes for scientific, regulatory, and clinical purposes. Despite advances in measurement capabilities for miRNAs, miRNAs are still not routinely employed as noninvasive biomarkers. This is in part due to the lack of standard approaches for sample preparation and miRNA measurement and uncertainty in their biological interpretation. Members of the microRNA Biomarkers Workgroup within the Health and Environmental Sciences Institute's (HESI) Committee on Emerging Systems Toxicology for the Assessment of Risk (eSTAR) are a consortium of private- and public-sector scientists dedicated to developing miRNAs as applied biomarkers. Here, we explore major impediments to routine acceptance and use of miRNA biomarkers and case examples of successes and deficiencies in development. Finally, we provide insight on miRNA measurement, collection, and analysis tools to provide solid footing for addressing knowledge gaps toward routine biomarker use.

MicroRNAs as Modulators of Tumor Metabolism, Microenvironment, and Immune Response in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related mortality. Molecular heterogeneity and absence of biomarkers helping patient allocation to the best therapeutic option contribute to poor prognosis in advanced stages. MicroRNAs’ (miRNAs) deregulated expression contributes to tumor development and progression and influences drug resistance in HCC. Accordingly, miRNAs have been extensively investigated as both biomarkers and therapeutic targets. The diagnostic and prognostic roles of circulating miRNAs have been ascertained, though with some inconsistencies across studies. From a therapeutic perspective, miRNA-based approaches demonstrated safety profiles and antitumor efficacy in HCC animal models. Nevertheless, caution should be used when transferring preclinical findings to the clinic, due to possible molecular inconsistency between animal models and the heterogeneous patterns of human diseases. A wealth of information is offered by preclinical studies exploring the mechanisms driving miRNAs’ aberrant expression, the molecular cascades triggered by miRNAs and the corresponding phenotypic changes. Ex-vivo analyses confirmed these results, further shedding light on the intricacy of the human disease often overcoming pre-clinical models. This complexity seems to be ascribed to the intrinsic heterogeneity of HCC, to different risk factors driving its development, as well as to changes across stages and previous treatments. Preliminary findings suggest that miRNAs associated with specific risk factors might be more informative in defined patients’ subgroups. The first issue to be considered when trying to envisage a possible translational perspective is the molecular context that often drives different miRNA functions, as clearly evidenced by “dual” miRNAs. Concerning the possible roles of miRNAs as biomarkers and therapeutic targets, we will focus on miRNAs’ involvement in metabolic pathways and in the modulation of tumor microenvironment, to support their exploitation in defined contexts.

Small-RNA Sequencing Reveals Altered Skeletal Muscle microRNAs and snoRNAs Signatures in Weanling Male Offspring from Mouse Dams Fed a Low Protein Diet during Lactation

Maternal diet during gestation and lactation affects the development of skeletal muscles in offspring and determines muscle health in later life. In this paper, we describe the association between maternal low protein diet-induced changes in offspring skeletal muscle and the differential expression (DE) of small non-coding RNAs (sncRNAs). We used a mouse model of maternal protein restriction, where dams were fed either a normal (N, 20%) or a low protein (L, 8%) diet during gestation and newborns were cross-fostered to N or L lactating dams, resulting in the generation of NN, NL and LN offspring groups. Total body and tibialis anterior (TA) weights were decreased in weanling NL male offspring but were not different in the LN group, as compared to NN. However, histological evaluation of TA muscle revealed reduced muscle fibre size in both groups at weaning. Small RNA-sequencing demonstrated DE of multiple miRs, snoRNAs and snRNAs. Bioinformatic analyses of miRs-15a, -34a, -122 and -199a, in combination with known myomiRs, confirmed their implication in key muscle-specific biological processes. This is the first comprehensive report for the DE of sncRNAs in nutrition-associated programming of skeletal muscle development, highlighting the need for further research to unravel the detailed molecular mechanisms.

MicroRNAs in the Pathogenesis of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), or, more accurately, metabolic associated fatty liver disease, accounts for a large proportion of chronic liver disorders worldwide and is closely associated with other conditions such as cardiovascular disease, obesity, and type 2 diabetes mellitus. NAFLD ranges from simple steatosis to nonalcoholic steatohepatitis (NASH) and can progress to cirrhosis and, eventually, also hepatocellular carcinoma. The morbidity and mortality associated with NAFLD are increasing rapidly year on year. Consequently, there is an urgent need to understand the etiology and pathogenesis of NAFLD and identify effective therapeutic targets. MicroRNAs (miRNAs), important epigenetic factors, have recently been proposed to participate in NAFLD pathogenesis. Here, we review the roles of miRNAs in lipid metabolism, inflammation, apoptosis, fibrosis, hepatic stellate cell activation, insulin resistance, and oxidative stress, key factors that contribute to the occurrence and progression of NAFLD. Additionally, we summarize the role of miRNA-enriched extracellular vesicles in NAFLD. These miRNAs may comprise suitable therapeutic targets for the treatment of this condition.

MicroRNAs as regulators, biomarkers and therapeutic targets in liver diseases

MicroRNAs (miRNAs) are small, non-coding RNAs that post-transcriptionally regulate gene expression by binding to specific mRNA targets and promoting their degradation and/or translational inhibition. miRNAs regulate both physiological and pathological liver functions. Altered expression of miRNAs is associated with liver metabolism dysregulation, liver injury, liver fibrosis and tumour development, making miRNAs attractive therapeutic strategies for the diagnosis and treatment of liver diseases. Here, we review recent advances regarding the regulation and function of miRNAs in liver diseases with a major focus on miRNAs that are specifically expressed or enriched in hepatocytes (miR-122, miR-194/192), neutrophils (miR-223), hepatic stellate cells (miR-29), immune cells (miR-155) and in circulation (miR-21). The functions and target genes of these miRNAs are emphasised in alcohol-associated liver disease, non-alcoholic fatty liver disease, drug-induced liver injury, viral hepatitis and hepatocellular carcinoma, as well liver fibrosis and liver failure. We touch on the roles of miRNAs in intercellular communication between hepatocytes and other types of cells via extracellular vesicles in the pathogenesis of liver diseases. We provide perspective on the application of miRNAs as biomarkers for early diagnosis, prognosis and assessment of liver diseases and discuss the challenges in miRNA-based therapy for liver diseases. Further investigation of miRNAs in the liver will help us better understand the pathogeneses of liver diseases and may identify biomarkers and therapeutic targets for liver diseases in the future.