Adipocyte Long-Noncoding RNA Transcriptome Analysis of Obese Mice Identified Lnc-Leptin, Which Regulates Leptin

Metabolic memory: mechanisms and diseases

Metabolic diseases and their complications impose health and economic burdens worldwide. Evidence from past experimental studies and clinical trials suggests our body may have the ability to remember the past metabolic environment, such as hyperglycemia or hyperlipidemia, thus leading to chronic inflammatory disorders and other diseases even after the elimination of these metabolic environments. The long-term effects of that aberrant metabolism on the body have been summarized as metabolic memory and are found to assume a crucial role in states of health and disease. Multiple molecular mechanisms collectively participate in metabolic memory management, resulting in different cellular alterations as well as tissue and organ dysfunctions, culminating in disease progression and even affecting offspring. The elucidation and expansion of the concept of metabolic memory provides more comprehensive insight into pathogenic mechanisms underlying metabolic diseases and complications and promises to be a new target in disease detection and management. Here, we retrace the history of relevant research on metabolic memory and summarize its salient characteristics. We provide a detailed discussion of the mechanisms by which metabolic memory may be involved in disease development at molecular, cellular, and organ levels, with emphasis on the impact of epigenetic modulations. Finally, we present some of the pivotal findings arguing in favor of targeting metabolic memory to develop therapeutic strategies for metabolic diseases and provide the latest reflections on the consequences of metabolic memory as well as their implications for human health and diseases.

The interaction between MALAT1 and TUG1 with dietary fatty acid quality indices on visceral adiposity index and body adiposity index

We aimed to investigate the interaction between the transcript levels of taurine-upregulated gene 1 (TUG1) and metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and the Cholesterol-Saturated Fat Index (CSI) in relation to the visceral adiposity index (VAI) and body adiposity index (BAI). This cross-sectional study involved 346 women classified as obese and overweight, aged between 18 and 48 years. Dietary intake and the quality of dietary fat were assessed using a validated and reliable 147-item semi-quantitative food frequency questionnaire, with the Cholesterol-Saturated Fat Index (CSI) used as an indicator. Transcription levels of MALAT1 and TUG1 were evaluated through real-time polymerase chain reaction following the criteria outlined in the Minimum Information for Publication of Quantitative standards. Serum profiles were measured using standard protocols. We observed a positive association between transcription level of MALAT1 and VAI in both crude (β = 3.646, 95% CI 1.950-5.341, p < 0.001) and adjusted (β = 8.338, 95% CI 6.110-10.566, p < 0.001) models. Furthermore, after adjusting for confounders, a significant positive interaction was noted between MALAT1 expression and CSI on BAI (β: 0.130, 95% CI 0.019, 0.240, p = 0.022), with a marginal positive interaction observed on VAI (β: 0.718, 95% CI - 0.028, 1.463, p = 0.059). It seems that there may be a positive interaction between MALAT1 transcription level and CSI on VAI and BAI among overweight and obese women. However, no associations were seen between TUG1 mRNA level and the above-mentioned outcomes. Further functional studies are still required to elucidate this concept.

Clinical relevance of circulating non-coding RNAs in metabolic diseases: Emphasis on obesity, diabetes, cardiovascular diseases and metabolic syndrome

Non-coding RNAs (ncRNAs) participate in the regulation of several cellular processes including transcription, RNA processing and genome rearrangement. The aberrant expression of ncRNAs is associated with several pathological conditions. In this review, we focused on recent information to elucidate the role of various regulatory ncRNAs i.e., micro RNAs (miRNAs), circular RNAs (circRNAs) and long-chain non-coding RNAs (lncRNAs), in metabolic diseases, e.g., obesity, diabetes mellitus (DM), cardiovascular diseases (CVD) and metabolic syndrome (MetS). The mechanisms by which ncRNAs participated in disease pathophysiology were also highlighted. miRNAs regulate the expression of genes at transcriptional and translational levels. circRNAs modulate the regulation of gene expression via miRNA sponging activity, interacting with RNA binding protein and polymerase II transcription regulation. lncRNAs regulate the expression of genes by acting as a protein decoy, miRNA sponging, miRNA host gene, binding to miRNA response elements (MRE) and the recruitment of transcriptional element or chromatin modifiers. We examined the role of ncRNAs in the disease pathogenesis and their potential role as molecular markers for diagnosis, prognosis and therapeutic targets. We showed the involvement of ncRNAs in the onset of obesity and its progression to MetS and CVD. miRNA-192, miRNA-122, and miRNA-221 were dysregulated in all these metabolic diseases. Other ncRNAs, implicated in at least three diseases include miRNA-15a, miRNA-26, miRNA-27a, miRNA-320, and miRNA-375. Dysregulation of ncRNAs increased the risk of development of DM and MetS and its progression to CVD in obese individuals. Hence, these molecules are potential targets to arrest or delay the progression of metabolic diseases.

The obesity-linked human lncRNA AATBC stimulates mitochondrial function in adipocytes

Adipocytes are critical regulators of metabolism and energy balance. While white adipocyte dysfunction is a hallmark of obesity-associated disorders, thermogenic adipocytes are linked to cardiometabolic health. As adipocytes dynamically adapt to environmental cues by functionally switching between white and thermogenic phenotypes, a molecular understanding of this plasticity could help improving metabolism. Here, we show that the lncRNA Apoptosis associated transcript in bladder cancer (AATBC) is a human-specific regulator of adipocyte plasticity. Comparing transcriptional profiles of human adipose tissues and cultured adipocytes we discovered that AATBC was enriched in thermogenic conditions. Using primary and immortalized human adipocytes we found that AATBC enhanced the thermogenic phenotype, which was linked to increased respiration and a more fragmented mitochondrial network. Expression of AATBC in adipose tissue of mice led to lower plasma leptin levels. Interestingly, this association was also present in human subjects, as AATBC in adipose tissue was inversely correlated with plasma leptin levels, BMI, and other measures of metabolic health. In conclusion, AATBC is a novel obesity-linked regulator of adipocyte plasticity and mitochondrial function in humans.

Inversely Regulated Inflammation-Related Processes Mediate Anxiety-Obesity Links in Zebrafish Larvae and Adults

Anxiety and metabolic impairments are often inter-related, but the underlying mechanisms are unknown. To seek RNAs involved in the anxiety disorder-metabolic disorder link, we subjected zebrafish larvae to caffeine-induced anxiety or high-fat diet (HFD)-induced obesity followed by RNA sequencing and analyses. Notably, differentially expressed (DE) transcripts in these larval models and an adult zebrafish caffeine-induced anxiety model, as well as the transcript profiles of inherently anxious versus less anxious zebrafish strains and high-fat diet-fed versus standard diet-fed adult zebrafish, revealed inversely regulated DE transcripts. In both larval anxiety and obesity models, these included long noncoding RNAs and transfer RNA fragments, with the overrepresented immune system and inflammation pathways, e.g., the "interleukin signaling pathway" and "inflammation mediated by chemokine and cytokine signaling pathway". In adulthood, overrepresented immune system processes included "T cell activation", "leukocyte cell-cell adhesion", and "antigen processing and presentation". Furthermore, unlike adult zebrafish, obesity in larvae was not accompanied by anxiety-like behavior. Together, these results may reflect an antagonistic pleiotropic phenomenon involving a re-adjusted modulation of the anxiety-metabolic links with an occurrence of the acquired immune system. Furthermore, the HFD potential to normalize anxiety-upregulated immune-related genes may reflect the high-fat diet protection of anxiety and neurodegeneration reported by others.

Association between Inflammatory Factors, Vitamin D, Long Non-Coding RNAs, MALAT1, and Adiponectin Antisense in Individuals with Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MetS) is a common clustering of cardiovascular risk factors associated with increased inflammation. Long non-coding RNA (LncRNA) are involved in many of the body's metabolic activities, including inflammation. Vitamin D may play a vital role in preventing metabolic syndrome risk factors. This study aimed to evaluate the status of inflammation and expression of LncRNA and their relationship with serum vitamin D levels in patients with metabolic syndrome.

METHOD

This cross-sectional study included staff and Mashhad University of Medical Sciences students between 30 and 50 years old who met the International Diabetes Federation criteria for Mets. Total RNA was extracted from both frozen clinical samples using the Trizol reagent.

RESULTS

A total of eighty people were recruited into the two groups, with and without MetS. Inflammatory markers were higher in the individuals in the MetS group, and linear regression showed an inverse association between serum vitamin D and LncRNAs. There was a positive association between inflammatory biomarkers, lipid profiles and Adiponectin Antisense (APQ AS) expression.

CONCLUSION

APQ AS and MALAT1 levels are positively associated with inflammatory biomarkers and inverse relation between MALAT1 and serum 25 (OH) D concentration.

Long noncoding RNA ACART knockdown decreases 3T3-L1 preadipocyte proliferation and differentiation

Obesity is a main risk factor for diabetes and cardiovascular disorders and is closely linked to preadipocyte differentiation or adipogenesis. Peroxisome proliferator-activated receptor γ (PPARγ) is an indispensable transcription factor in adipogenesis. A newly identified long noncoding RNA, Acart, exerts a protective effect against cardiomyocyte injury by transactivating PPARγ signaling. However, the function of Acart in preadipocyte differentiation is unclear. To investigate the function of Acart in adipogenesis, a well-established preadipocyte, the 3T3-L1 cell line, was induced to differentiate, and Acart level was assessed during differentiation using quantitative real-time PCR. The biological role of Acart in adipogenesis was analyzed by assessing lipid droplet accumulation, PPARγ and CCAAT/enhancer-binding protein α (C/EBPα) expression, and 3T3-L1 cell proliferation and apoptosis after Acart silencing. We found that Acart level was promptly increased during preadipocyte differentiation in vitro. Acart was also significantly upregulated in obese mouse-derived subcutaneous, perirenal, and epididymal fat tissues compared with nonobese mouse-derived adipose tissues. Functionally, Acart depletion inhibited preadipocyte differentiation, as evidenced by a significant decrease in lipid accumulation and PPARγ and C/EBPα expression levels. Acart silencing also inhibited 3T3-L1 cell proliferation, whereas Acart overexpression accelerated 3T3-L1 cell proliferation and decreased cell apoptosis. Taken together, the current results reveal a novel function of Acart in regulating preadipocyte proliferation and differentiation.

Potential Involvement of LncRNAs in Cardiometabolic Diseases

Characterized by cardiovascular disease and diabetes, cardiometabolic diseases are a major cause of mortality around the world. As such, there is an urgent need to understand the pathogenesis of cardiometabolic diseases. Increasing evidence suggests that most of the mammalian genome are transcribed as RNA, but only a few percent of them encode for proteins. All of the RNAs that do not encode for proteins are collectively called non-protein-coding RNAs (ncRNAs). Among these ncRNAs, long ncRNAs (lncRNAs) are considered as missing keys to understand the pathogeneses of various diseases, including cardiometabolic diseases. Given the increased interest in lncRNAs, in this study, we will summarize the latest trend in the lncRNA research from the perspective of cardiometabolism and disease by focusing on the major risk factors of cardiometabolic diseases: obesity, cholesterol, diabetes, and hypertension. Because genetic inheritance is unavoidable in cardiometabolic diseases, we paid special attention to the genetic factors of lncRNAs that may influence cardiometabolic diseases.

Bioinformatics analysis of candidate genes and potential therapeutic drugs targeting adipose tissue in obesity

Obesity is a complex medical condition that affects multiple organs in the body. However, the underlying mechanisms of obesity, as well as its treatment, are largely unexplored. The focus of this research was to use bioinformatics to discover possible treatment targets for obesity. To begin, the GSE133099 database was used to identify 364 differentially expressed genes (DEGs). Then, DEGs were subjected to tissue-specific analyses and enrichment analyses, followed by the creation of a protein-protein interaction (PPI) network and generation of a drug-gene interaction database to screen key genes and potential future drugs targeting obesity. Findings have illustrated that the tissue-specific expression of neurologic markers varied significantly (34.7%, 52/150). Among these genes, Lep, ApoE, Fyn, and FN1 were the key genes observed in the adipocyte samples from obese patients relative to the controls. Furthermore, nine potential therapeutic drugs (dasatinib, ocriplasmin, risperidone, gemfibrozil, ritonavir, fluvastatin, pravastatin, warfarin, atorvastatin) that target the key genes were also screened and selected. To conclude the key genes discovered (Lep, ApoE, Fyn, and FN1), as well as 9 candidate drugs, could be used as therapeutic targets in treating obesity.

Enhancer RNA (eRNA) in Human Diseases

Enhancer RNAs (eRNAs), a class of non-coding RNAs (ncRNAs) transcribed from enhancer regions, serve as a type of critical regulatory element in gene expression. There is increasing evidence demonstrating that the aberrant expression of eRNAs can be broadly detected in various human diseases. Some studies also revealed the potential clinical utility of eRNAs in these diseases. In this review, we summarized the recent studies regarding the pathological mechanisms of eRNAs as well as their potential utility across human diseases, including cancers, neurodegenerative disorders, cardiovascular diseases and metabolic diseases. It could help us to understand how eRNAs are engaged in the processes of diseases and to obtain better insight of eRNAs in diagnosis, prognosis or therapy. The studies we reviewed here indicate the enormous therapeutic potency of eRNAs across human diseases.

Long Noncoding RNAs That Function in Nutrition: Lnc-ing Nutritional Cues to Metabolic Pathways

Long noncoding RNAs (lncRNAs) are sensitive to changing environments and play key roles in health and disease. Emerging evidence indicates that lncRNAs regulate gene expression to shape metabolic processes in response to changing nutritional cues. Here we review various lncRNAs sensitive to fasting, feeding, and high-fat diet in key metabolic tissues (liver, adipose, and muscle), highlighting regulatory mechanisms that trigger expression changes of lncRNAs themselves, and how these lncRNAs regulate gene expression of key metabolic genes in specific cell types or across tissues. Determining how lncRNAs respond to changes in nutrition is critical for our understanding of the complex downstream cascades following dietary changes and can shape how we treat metabolic disease. Furthermore, investigating sex biases that might influence lncRNA-regulated responses will likely reveal contributions toward the observed disparities between the sexes in metabolic diseases.

LncRNA-Mediated Adipogenesis in Different Adipocytes

Long-chain noncoding RNAs (lncRNAs) are RNAs that do not code for proteins, widely present in eukaryotes. They regulate gene expression at multiple levels through different mechanisms at epigenetic, transcription, translation, and the maturation of mRNA transcripts or regulation of the chromatin structure, and compete with microRNAs for binding to endogenous RNA. Adipose tissue is a large and endocrine-rich functional tissue in mammals. Excessive accumulation of white adipose tissue in mammals can cause metabolic diseases. However, unlike white fat, brown and beige fats release energy as heat. In recent years, many lncRNAs associated with adipogenesis have been reported. The molecular mechanisms of how lncRNAs regulate adipogenesis are continually investigated. In this review, we discuss the classification of lncRNAs according to their transcriptional location. lncRNAs that participate in the adipogenesis of white or brown fats are also discussed. The function of lncRNAs as decoy molecules and RNA double-stranded complexes, among other functions, is also discussed.

Long non-Coding RNAs and Obesity: New Potential Pathogenic Biomarkers

Background:

A portion of the human genome is characterized by long non-coding RNAs (lncRNAs), a class of non-coding RNA longer than 200 nucleotides. Recently, the development of new biomolecular methods, made it possible to delineate the involvement of lncRNAs in the regulation of different biological processes, both physiological and pathological, by acting within the cell with different regulatory mechanisms based on their specific target. To date, obesity is one of the most important health problems spread all over the world, including the child population: the search for new potential early biomarkers could open the doors to novel therapeutic strategies useful to fight the disease early in life and to reduce the risk of obesity-related co-morbidities.

Objective:

This review highlights the lncRNAs involved in obesity, in adipogenesis, and lipid metabolism, particularly in lipogenesis.

Conclusion:

LncRNAs involved in adipogenesis and lipogenesis, being at the cross-road of obesity, should be deeply analysed in this contest, allowing to understand possible causative actions in starting obesity and whether they might be helpful to treat obesity.

Role of lncRNAs into Mesenchymal Stromal Cell Differentiation

Currently, findings support that 75% of the human genome is actively transcribed, but only 2% is translated into a protein, according to databases such as ENCODE (Encyclopedia of DNA Elements) [1]. The development of high-throughput sequencing technologies, computational methods for genome assembly and biological models have led to the realization of the importance of the previously unconsidered non-coding fraction of the genome. Along with this, noncoding RNAs have been shown to be epigenetic, transcriptional and post-transcriptional regulators in a large number of cellular processes [2]. Within the group of non-coding RNAs, lncRNAs represent a fascinating field of study, given the functional versatility in their mode of action on their molecular targets. In recent years, there has been an interest in learning about lncRNAs in MSC differentiation. The aim of this review is to address the signaling mechanisms where lncRNAs are involved, emphasizing their role in either stimulating or inhibiting the transition to differentiated cell. Specifically, the main types of MSC differentiation are discussed: myogenesis, osteogenesis, adipogenesis and chondrogenesis. The description of increasingly new lncRNAs reinforces their role as players in the well-studied field of MSC differentiation, allowing a step towards a better understanding of their biology and their potential application in the clinic.

Lnc-hipk1 inhibits mouse adipocyte apoptosis as a sponge of miR-497

Noncoding RNAs (ncRNAs) such as microRNAs (miRNAs), long noncoding RNAs (lncRNA), and circular RNAs are closely related to the biological processes related to obesity. As a miRNA that widely present in different cell types, miR497 is proved to be involved in cell development. However, research on the role of miR-497 as a key factor in regulating the development of adipocytes is still in gap. The role of miR-497 in the apoptosis and proliferation of mouse-derived adipocytes was detected by RNA-seq analysis, RT-qPCR, Western blot, immunofluorescence, and dual-luciferase reporter assay. Using miR-497 mimics to treat 3T3-L1 cells, we found that miR-497 targeted Bcl-2 to promote adipocyte apoptosis through the mitochondrial pathway, and this effect was consistent in the apoptosis model composed of palmitic acid (PA) and hydrogen peroxide (H₂ O₂ ). LncRNA homeodomain-interacting protein kinase 1 (lnc-hipk1) sponged miR-148b to weaken its silencing of Bcl-2, forming the competitive endogenous RNAs (CeRNAs) regulatory network. Furthermore, overexpression of lnc-hipk1 inhibited the apoptosis of adipocytes by targeting miR-497/Bcl-2. Co-treatment of miR-497 and lnc-hipk1 showed that lnc-hipk1 reversed the apoptosis of adipocytes caused by miR-497 overexpression. And in vivo experiments further confirmed that this effect was also achieved by the CeRNA system of lnc-hipk1/miR-497/Bcl-2. In summary, lnc-hipk1 targets miR-497/Bcl-2 to regulate adipocyte apoptosis through the mitochondrial pathway. This research enriches the research content of ncRNAs and CeRNA in adipocyte development, and provides new targets for the treatment of obesity and other metabolic syndromes.

Epigenetic regulation of energy metabolism in obesity

Obesity has reached epidemic proportions globally. Although modern adoption of a sedentary lifestyle coupled with energy-dense nutrition is considered to be the main cause of obesity epidemic, genetic preposition contributes significantly to the imbalanced energy metabolism in obesity. However, the variants of genetic loci identified from large-scale genetic studies do not appear to fully explain the rapid increase in obesity epidemic in the last four to five decades. Recent advancements of next-generation sequencing technologies and studies of tissue-specific effects of epigenetic factors in metabolic organs have significantly advanced our understanding of epigenetic regulation of energy metabolism in obesity. The epigenome, including DNA methylation, histone modifications, and RNA-mediated processes, is characterized as mitotically or meiotically heritable changes in gene function without alteration of DNA sequence. Importantly, epigenetic modifications are reversible. Therefore, comprehensively understanding the landscape of epigenetic regulation of energy metabolism could unravel novel molecular targets for obesity treatment. In this review, we summarize the current knowledge on the roles of DNA methylation, histone modifications such as methylation and acetylation, and RNA-mediated processes in regulating energy metabolism. We also discuss the effects of lifestyle modifications and therapeutic agents on epigenetic regulation of energy metabolism in obesity.

Identification of human long noncoding RNAs associated with nonalcoholic fatty liver disease and metabolic homeostasis

A growing number of long noncoding RNAs (lncRNAs) have emerged as vital metabolic regulators. However, most human lncRNAs are nonconserved and highly tissue specific, vastly limiting our ability to identify human lncRNA metabolic regulators (hLMRs). In this study, we established a pipeline to identify putative hLMRs that are metabolically sensitive, disease relevant, and population applicable. We first progressively processed multilevel human transcriptome data to select liver lncRNAs that exhibit highly dynamic expression in the general population, show differential expression in a nonalcoholic fatty liver disease (NAFLD) population, and respond to dietary intervention in a small NAFLD cohort. We then experimentally demonstrated the responsiveness of selected hepatic lncRNAs to defined metabolic milieus in a liver-specific humanized mouse model. Furthermore, by extracting a concise list of protein-coding genes that are persistently correlated with lncRNAs in general and NAFLD populations, we predicted the specific function for each hLMR. Using gain- and loss-of-function approaches in humanized mice as well as ectopic expression in conventional mice, we validated the regulatory role of one nonconserved hLMR in cholesterol metabolism by coordinating with an RNA-binding protein, PTBP1, to modulate the transcription of cholesterol synthesis genes. Our work overcame the heterogeneity intrinsic to human data to enable the efficient identification and functional definition of disease-relevant human lncRNAs in metabolic homeostasis.

Role of long non-coding RNAs in adipogenesis: State of the art and implications in obesity and obesity-associated diseases

Obesity is an evolutionary, chronic, and relapsing disease that consists of a pathological accumulation of adipose tissue able to increase morbidity for high blood pressure, type 2 diabetes, metabolic syndrome, and obstructive sleep apnea in adults, children, and adolescents. Despite intense research over the last 20 years, obesity remains today a disease with a complex and multifactorial etiology. Recently, long non-coding RNAs (lncRNAs) are emerging as interesting new regulators as different lncRNAs have been found to play a role in early and late phases of adipogenesis and to be implicated in obesity-associated complications onset. In this review, we discuss the most recent advances on the role of lncRNAs in adipocyte biology and in obesity-associated complications. Indeed, more and more researchers are focusing on investigating the underlying roles that these molecular modulators could play. Even if a significant number of evidence is correlation-based, with lncRNAs being differentially expressed in a specific disease, recent works are now focused on deeply analyzing how lncRNAs can effectively modulate the disease pathogenesis onset and progression. LncRNAs possibly represent new molecular markers useful in the future for both the early diagnosis and a prompt clinical management of patients with obesity.

Impaired Leptin Signalling in Obesity: Is Leptin a New Thermolipokine?

Leptin is a principal adipose-derived hormone mostly implicated in the regulation of energy balance through the activation of anorexigenic neuronal pathways. Comprehensive studies have established that the maintenance of certain concentrations of circulating leptin is essential to avoid an imbalance in nutrient intake. Indeed, genetic modifications of the leptin/leptin receptor axis and the obesogenic environment may induce changes in leptin levels or action in a manner that accelerates metabolic dysfunctions, resulting in a hyperphagic status and adipose tissue expansion. As a result, a vicious cycle begins wherein hyperleptinaemia and leptin resistance occur, in turn leading to increased food intake and fat enlargement, which is followed by leptin overproduction. In addition, in the context of obesity, a defective thermoregulatory response is associated with impaired leptin signalling overall within the ventromedial nucleus of the hypothalamus. These recent findings highlight the role of leptin in the regulation of adaptive thermogenesis, thus suggesting leptin to be potentially considered as a new thermolipokine. This review provides new insight into the link between obesity, hyperleptinaemia, leptin resistance and leptin deficiency, focusing on the ability to restore leptin sensitiveness by way of enhanced thermogenic responses and highlighting novel anti-obesity therapeutic strategies.

Long Non-coding RNA 332443 Inhibits Preadipocyte Differentiation by Targeting Runx1 and p38-MAPK and ERK1/2-MAPK Signaling Pathways

Long non-coding RNAs (lncRNAs) have emerged as integral regulators of pathophysiological processes, but their specific roles and mechanisms in adipose tissue development remain largely unknown. Here, through microarray analysis, co-expression, and tissue specific analysis of adipocyte tissues after fasting for 72 h, we found that Lnc-FR332443 expression was dramatically decreased, as well as the expression of Runx1. The UCSC database and Ensembl database indicated that Lnc-FR332443 is the antisense lncRNA of Runx1. Lnc-FR332443 and Runx1 are highly enriched in adipose tissue and downregulated during adipogenic differentiation. Adipose tissue-specific knockdown of Lnc-FR332443 increased fat mass in vivo, and specific knockdown of Lnc-FR332443 in 3T3-L1 preadipocytes promoted adipogenic differentiation. In this process, Runx1 expression was decreased when Lnc-FR332443 was downregulated in adipocytes or 3T3-L1 preadipocytes, and vice versa, when Lnc-FR332443 was upregulated, the expression of Runx1 was increased. However, overexpression of Runx1 decreased the expression of the adipocyte cell marker genes PPARγ, C/EBPα and FABP4 significantly, while not affected the expression of Lnc-FR332443. Mechanistically, Lnc-FR332443 positively regulates Runx1 expression in mouse adipocytes and suppresses adipocyte differentiation by attenuating the phosphorylation of MAPK-p38 and MAPK-ERK1/2 expression. Thus, this study indicated that Lnc-FR332443 inhibits adipogenesis and which might be a drug target for the prevention and treatment of obesity.

LncRNA Ctcflos orchestrates transcription and alternative splicing in thermogenic adipogenesis

The recruitment of thermogenic brite adipocytes within white adipose tissue attenuates obesity and metabolic comorbidities, arousing interest in understanding the underlying regulatory mechanisms. The molecular network of brite adipogenesis, however, remains largely unresolved. In this light, long noncoding RNAs (lncRNAs) emerged as a versatile class of modulators that control many steps within the differentiation machinery. Leveraging the naturally varying propensities of different inbred mouse strains for white adipose tissue browning, we identify the nuclear lncRNA Ctcflos as a pivotal orchestrator of thermogenic gene expression during brite adipocyte differentiation. Mechanistically, Ctcflos acts as a pleiotropic regulator, being essential for the transcriptional recruitment of the early core thermogenic regulatory program and the modulation of alternative splicing to drive brite adipogenesis. This is showcased by Ctcflos‐regulated gene transcription and splicing of the key browning factor Prdm16 toward the isoform that is specific for the thermogenic gene program. Conclusively, our findings emphasize the mechanistic versatility of lncRNAs acting at several independent levels of gene expression for effective regulation of key differentiation factors to direct cell fate and function.

AGO HITS-CLIP reveals distinct miRNA regulation of white and brown adipose tissue identity

MicroRNAs (miRNAs) are short, noncoding RNAs that associate with Argonaute (AGO) to influence mRNA stability and translation, thereby regulating cellular determination and phenotype. While several individual miRNAs have been shown to control adipocyte function, including energy storage in white fat and energy dissipation in brown fat, a comprehensive analysis of miRNA activity in these tissues has not been performed. We used high-throughput sequencing of RNA isolated by cross-linking immunoprecipitation (HITS-CLIP) to comprehensively characterize the network of high-confidence, in vivo mRNA:miRNA interactions across white and brown fat, revealing >20,000 unique AGO binding sites. When coupled with miRNA and mRNA sequencing, we found an inverse correlation between depot-enriched miRNAs and their targets. To illustrate the functionality of our HITS-CLIP data set in identifying specific miRNA:mRNA interactions, we show that miR-29 is a novel regulator of leptin, an adipocyte-derived hormone that coordinates food intake and energy homeostasis. Two independent miR-29 binding sites in the leptin 3' UTR were validated using luciferase assays, and miR-29 gain and loss of function modulated leptin mRNA and protein secretion in primary adipocytes. This work represents the only experimentally generated miRNA targetome in adipose tissue and identifies multiple regulatory pathways that may specify the unique identities of white and brown fat.

The Potential Role of Exosomes in Child and Adolescent Obesity

Child and adolescent obesity constitute one of the greatest contemporary public health menaces. The enduring disproportion between calorie intake and energy consumption, determined by a complex interaction of genetic, epigenetic, and environmental factors, finally leads to the development of overweight and obesity. Child and adolescent overweight/obesity promotes smoldering systemic inflammation (“para-inflammation”) and increases the likelihood of later metabolic and cardiovascular complications, including metabolic syndrome and its components, which progressively deteriorate during adulthood. Exosomes are endosome-derived extracellular vesicles that are secreted by a variety of cells, are naturally taken-up by target cells, and may be involved in many physiological and pathological processes. Over the last decade, intensive research has been conducted regarding the special role of exosomes and the non-coding (nc) RNAs they contain (primarily micro (mi) RNAs, long (l) non-coding RNAs, messenger (m) RNAs and other molecules) in inter-cellular communications. Through their action as communication mediators, exosomes may contribute to the pathogenesis of obesity and associated disorders. There is increasing evidence that exosomal miRNAs and lncRNAs are involved in pivotal processes of adipocyte biology and that, possibly, play important roles in gene regulation linked to human obesity. This review aims to improve our understanding of the roles of exosomes and their cargo in the development of obesity and related metabolic and inflammatory disorders. We examined their potential roles in adipose tissue physiology and reviewed the scarce data regarding the altered patterns of circulating miRNAs and lncRNAs observed in obese children and adolescents, compared them to the equivalent, more abundant existing findings of adult studies, and speculated on their proposed mechanisms of action. Exosomal miRNAs and lncRNAs could be applied as cardiometabolic risk biomarkers, useful in the early diagnosis and prevention of obesity. Furthermore, the targeting of crucial circulating exosomal cargo to tissues involved in the pathogenesis and maintenance of obesity could provide a novel therapeutic approach to this devastating and management-resistant pandemic.

Transcriptome Analysis of Subcutaneous Adipose Tissue from Severely Obese Patients Highlights Deregulation Profiles in Coding and Non-Coding Oncogenes

Obesity is a major risk factor for a large number of secondary diseases, including cancer. Specific insights into the role of gender differences and secondary comorbidities, such as type 2 diabetes (T2D) and cancer risk, are yet to be fully identified. The aim of this study is thus to find a correlation between the transcriptional deregulation present in the subcutaneous adipose tissue of obese patients and the oncogenic signature present in multiple cancers, in the presence of T2D, and considering gender differences. The subcutaneous adipose tissue (SAT) of five healthy, normal-weight women, five obese women, five obese women with T2D and five obese men were subjected to RNA-sequencing, leading to the identification of deregulated coding and non-coding RNAs, classified for their oncogenic score. A panel of DE RNAs was validated via Real-Time PCR and oncogene expression levels correlated the oncogenes with anthropometrical parameters, highlighting significant trends. For each analyzed condition, we identified the deregulated pathways associated with cancer, the prediction of possible prognosis for different cancer types and the lncRNAs involved in oncogenic networks and tissues. Our results provided a comprehensive characterization of oncogenesis correlation in SAT, providing specific insights into the possible molecular targets implicated in this process. Indeed, the identification of deregulated oncogenes also in SAT highlights hypothetical targets implicated in the increased oncogenic risk in highly obese subjects. These results could shed light on new molecular targets to be specifically modulated in obesity and highlight which cancers should receive the most attention in terms of better prevention in obesity-affected patients.

The role of long noncoding RNA in lipid, cholesterol, and glucose metabolism and treatment of obesity syndrome

Obesity syndromes, characterized by abnormal lipid, cholesterol, and glucose metabolism, are detrimental to human health and cause many diseases, including obesity and type II diabetes. Increasing evidence has shown that long noncoding RNA (lncRNA), transcripts longer than 200 nucleotides that are not translated into proteins, play an important role in regulating abnormal metabolism in obesity syndromes. For the first time, we systematically summarize how lncRNA is involved in complex obesity metabolic syndromes, including the regulation of lipid, cholesterol, and glucose metabolism. Moreover, we discuss lncRNA involvement in food intake that mediates obesity syndromes. Furthermore, this review might shed new light on a lncRNA-based strategy for the prevention and treatment of obesity syndromes. Recent investigations support that lncRNA is a novel molecular target of obesity syndromes and should be emphasized. Namely, lncRNA plays a crucial role in the development of obesity syndrome process. Various lncRNAs are involved in the process of lipid, cholesterol, and glucose metabolism by regulating gene transcription, signaling pathway, and epigenetic modification of metabolism-related genes, proteins, and enzymes. Food intake could also induce abnormal expression of lncRNA associated with obesity syndrome, especially high-fat diet. Notably, some nanomolecules and natural extracts may target lncRNAs, associated with obesity syndrome, as a potential treatment for obesity syndromes.

Identification of differentially expressed mRNA and the Hub mRNAs modulated by lncRNA Meg3 as a competing endogenous RNA in brown adipose tissue of mice on a high-fat diet

Obesity is associated with insulin resistance, diabetes, and obesity-related metabolic disorders. Brown adipocytes have emerged as potential targets for the treatment of obesity and obesity-related diseases. However, changes that occur in brown adipose tissue during various stages of high fat diet (HFD)-induced obesity remain poorly understood. The present study aimed to determine the changes occurring in brown adipose tissue during various stages of an HFD by analyzing two microarray expression profiles. A total of 1,337 differentially expressed RNAs (DE RNAs) were identified between the HFD and ND groups, using the limma package in R. The DE RNAs included 1,249 mRNAs, 74 long non coding RNAs (lncRNAs), and 14 pseudogenes. Functional annotation of the DE mRNAs, including GO terms and KEGG pathways were identified using the Database for Annotation, Visualization, and Integrated Discovery. A protein-protein interaction network was constructed using STRING and clusters were obtained through the Molecular Complex Detection plug-in. In the present study, the lncRNA,maternally expressed gene 3 (Meg3), was identified as the DE lncRNA with a significant fold change. The network of Meg3 as a ceRNA was constructed, which demonstrated that Meg3 modulated five hub DE mRNAs via competitive binding to microRNAs.

RNA-sequencing analysis reveals the potential contribution of lncRNAs in palmitic acid-induced insulin resistance of skeletal muscle cells

Insulin resistance (IR) has been considered as the common pathological basis and developmental driving force for most metabolic diseases. Long noncoding RNAs (lncRNAs) have emerged as pivotal regulators in modulation of glucose and lipid metabolism. However, the comprehensive profile of lncRNAs in skeletal muscle cells under the insulin resistant status and the possible biological effects of them were not fully studied. In this research, using C2C12 myotubes as cell models in vitro, deep RNA-sequencing was performed to profile lncRNAs and mRNAs between palmitic acid-induced IR C2C12 myotubes and control ones. The results revealed that a total of 144 lncRNAs including 70 up-regulated and 74 down-regulated (|fold change| > 2, q < 0.05) were significantly differentially expressed in palmitic acid-induced insulin resistant cells. In addition, functional annotation analysis based on the Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) databases revealed that the target genes of the differentially expressed lncRNAs were significantly enriched in fatty acid oxidation, lipid oxidation, PPAR signaling pathway, and insulin signaling pathway. Moreover, Via qPCR, most of selected lncRNAs in myotubes and db/db mice skeletal muscle showed the consistent expression trends with RNA-sequencing. Co-expression analysis also explicated the key lncRNA–mRNA interactions and pointed out a potential regulatory network of candidate lncRNA ENSMUST00000160839. In conclusion, the present study extended the skeletal muscle lncRNA database and provided novel potential regulators for future genetic and molecular studies on insulin resistance, which is helpful for prevention and treatment of the related metabolic diseases.

Leptin production capacity determines food intake and susceptibility to obesity-induced diabetes in Oikawa-Nagao Diabetes-Prone and Diabetes-Resistant mice

AIMS/HYPOTHESIS

Obesity caused by overeating plays a pivotal role in the development of type 2 diabetes. However, it remains poorly understood how individual meal size differences are determined before the development of obesity. Here, we investigated the underlying mechanisms in determining spontaneous food intake in newly established Oikawa-Nagao Diabetes-Prone (ON-DP) and Diabetes-Resistant (ON-DR) mice.

METHODS

Food intake and metabolic phenotypes of ON-DP and ON-DR mice under high-fat-diet feeding were compared from 5 weeks to 10 weeks of age. Differences in leptin status at 5 weeks of age were assessed between the two mouse lines. Adipose tissue explant culture was also performed to evaluate leptin production capacity in vitro.

RESULTS

ON-DP mice showed spontaneous overfeeding compared with ON-DR mice. Excessive body weight gain and fat accumulation in ON-DP mice were completely suppressed to the levels seen in ON-DR mice by pair-feeding with ON-DR mice. Deterioration of glucose tolerance in ON-DP mice was also ameliorated under the pair-feeding conditions. While no differences were seen in body weight and adipose tissue mass when comparing the two mouse lines at 5 weeks of age, the ON-DP mice had lower plasma leptin concentrations and adipose tissue leptin gene expression levels. In accordance with peripheral leptin status, ON-DP mice displayed lower anorexigenic leptin signalling in the hypothalamic arcuate nucleus when compared with ON-DR mice without apparent leptin resistance. Explant culture studies revealed that ON-DP mice had lower leptin production capacity in adipose tissue. ON-DP mice also displayed higher DNA methylation levels in the leptin gene promoter region of adipocytes when compared with ON-DR mice.

CONCLUSIONS/INTERPRETATION

The results suggest that heritable lower leptin production capacity plays a critical role in overfeeding-induced obesity and subsequent deterioration of glucose tolerance in ON-DP mice. Leptin production capacity in adipocytes, especially before the development of obesity, may have diagnostic potential for predicting individual risk of obesity caused by overeating and future onset of type 2 diabetes. Graphical abstract.

Identification of novel alternative splicing of bovine lncRNA lncFAM200B and its effects on preadipocyte proliferation

Adipogenesis is closely related to human health, livestock growth, and meat quality. A previous study identified that bovine lncFAM200B promoter has high activity in 3T3-L1 mice preadipocytes. Thus, lncFAM200B was a candidate gene for regulating adipogenesis. This study aimed to uncover the role of lncFAM200B in bovine adipogenesis and identify novel genetic variations within the bovine lncFAM200B gene. An expression analysis found that lncFAM200B was expressed higher in fat than that in muscle, but the difference was not related to the total methylation level of the promoter active region. Moreover, the expression of lncFAM200B exhibited a significant positive correlation with the expression of C/EBPa during bovine adipocyte differentiation. To uncover the function of lncFAM200B, the full-length lncFAM200B was cloned, and four kinds of transcript variants were found. Protein-coding potential prediction and prokaryotic expression system analysis showed that these four transcript variants were noncoding RNAs. The quantitative reverse-transcription polymerase chain reaction and 5-ethynyl-2'-deoxyuridine assay showed that the transcript variants decreased the messenger RNA expression of Cyclin D1 and inhibited the proliferation of bovine preadipocytes. Considering the important role of lncFAM200B in adipogenesis, we identified genetic variations in lncFAM200B. Three single-nucleotide polymorphisms (SNPs) were revealed, and two of them (SNP1 and SNP3) were associated with Nanyang cattle body measurement traits. In conclusion, this study found that bovine lncFAM200B inhibited preadipocyte proliferation, and two genetic variations of lncFAM200B could be used in cattle breeding.

Relative leptin deficiency in children with severe early-onset obesity (SEOO) - results of the Early-onset Obesity and Leptin - German-Polish Study (EOL-GPS)

Background Severe early-onset obesity (SEOO) in children is a common feature of monogenic obesity. Gene defects of the leptin-melanocortin pathway can be analysed biochemically and genetically. The aim of this study was to search for children with leptin deficiency or biologically inactive leptin in a cohort of children with SEOO and to study associations between leptin parameters and anthropometric data. Methods The cohort included n = 50 children with SEOO (22 boys) who were recruited at one of four study centres (Germany: Ulm; Poland: Katowice, Szczecin, Rzeszow) between October 2015 and October 2017. Weight (kg) and height (m) were measured, Tanner stage was obtained and a fasting serum blood sample was taken. Serum levels of total leptin (LEP, ng/mL), biologically active leptin (bioLEP, ng/mL) and soluble leptin receptor (sLEPR, ng/mL) were measured. The body mass index (BMI [kg/m2]), BMI z-score (World Health Organization [WHO]), quotient of bioLEP/LEP and leptin-standard deviation score (LEP-SDS) (Tanner stage, BMI and sex-adjusted) were calculated. Results We did not find any child with leptin deficiency or biologically inactive leptin in our cohort. The serum LEP and bioLEP levels were strongly correlated with age (r = 0.50, p < 0.05) and BMI (r = 0.70; p < 0.0001). Girls had higher LEP and bioLEP levels (49.7 ± 35.9 vs. 37.1 ± 25.5 ng/mL, p > 0.05) as well as lower LEP-SDS than boys (-1.77 ± 2.61 vs. -1.40 ± 2.60, p > 0.05). sLEPR levels were negatively correlated with BMI values (r = -0.44; p < 0.05), LEP (r = -0.39; p < 0.05) and bioLEP levels (r = -0.37; p < 0.05). Interestingly, there was a strong inverse relationship between LEP-SDS and BMI (r = -0.72, p < 0.001). Conclusions In this cohort with SEOO, we identified no new cases of children with leptin deficiency or bioinactive leptin. A strong negative correlation between the LEP-SDS and BMI values could be interpreted as relative leptin deficiency in children with SEOO. In case this hypothesis can be confirmed, these children would benefit from a substitution therapy with methionyl human leptin (metreleptin™).

Knockdown of long noncoding RNA dreh facilitates cell surface GLUT4 expression and glucose uptake through the involvement of vimentin in 3T3-L1 adipocytes

Glucose uptake in adipocytes is crucial for regulating systemic metabolism. Long noncoding RNAs (lncRNAs), defined as being transcripts with lengths exceeding 200 nucleotides that are not translated, are recently identified regulators of cellular functions. Previously, we have shown that an lncRNA, "down-regulated expression by hepatitis B virus X" (dreh), is involved in glucose transport in skeletal muscle cells. Here, we aimed to examine the involvement of dreh in glucose transport in 3T3-L1 adipocytes. Expression analysis showed that dreh was expressed in 3T3-L1 fibroblasts and adipocytes. Knockdown of dreh expression using its specific siRNAs lowered the glucose concentration of the medium and facilitated [³H]-2-deoxyglucose transport in adipocytes. Additionally, dreh silencing enhanced the protein expression of glucose transporter (GLUT4) in the plasma membrane of adipocytes. Treatment with siRNA against vimentin attenuated the glucose-lowering effect of dreh depletion. These results suggest that the repression of dreh facilitates glucose transport via increased GLUT4 expression in the plasma membrane through the involvement of vimentin in 3T3-L1 adipocytes. In conclusion, dreh is the first observed lncRNA that regulates glucose transport in adipocytes and could serve as a novel therapeutic target for diabetes by modulating adipocyte function. Considering the new function of dreh, we propose that dreh be renamed "down-regulated expression-related hexose/glucose transport enhancer."

Comprehensive Analysis of the Characteristics and Differences in Adult and Newborn Brown Adipose Tissue (BAT): Newborn BAT Is a More Active/Dynamic BAT

Brown adipose tissue (BAT) plays an essential role in maintaining body temperature and in treating obesity and diabetes. The adult BAT (aBAT) and neonatal BAT (neBAT) vary greatly in capacity, but the characteristics and differences between them on the molecular level, as well as the related features of BAT as it develops post-delivery, have not yet been fully determined. In this study, we examined the morphological features of aBAT and neBAT of mice by using hematoxylin-eosin (H&E) staining, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). We found that neBAT contains a smaller number and size of lipid droplets, as well as more abundant mitochondria, compared with aBAT. The dynamic morphological changes revealed that the number and size of lipid droplets increase, but the number of mitochondria gradually decrease during the post-delivery development, which consisted of some differences in RNA or protein expression levels, such as gradually decreased uncoupling protein 1 (UCP1) expression levels and mitochondrial genes, such as mitochondrial transcription factor A (Tfam). The adipocyte differentiation-related genes, such as transcription factor CCAAT enhancer-binding protein β (CEBPβ), were also continuously upregulated. Additionally, the different features of aBAT and neBAT were analyzed from the global transcription (RNA-Seq) level, which included messenger RNA (mRNA), microRNA, long non-coding RNA (lncRNA), circRNA, and DNA methylation, as well as proteins (proteomics). Differentially methylated region (DMR) analysis identified 383 hyper- and 503 hypo-methylated genes, as well as 1221 new circRNA in ne-BAT and 1991 new circRNA in a-BAT, with significantly higher expression of circRNA in aBAT compared with neBAT. Gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that mitochondrial activity, protein synthesis, and cell life activity levels were higher in neBAT, and pathways related to ribosomes, spliceosomes, and metabolism were significantly activated in neBAT compared to aBAT. Collectively, this study describes the dynamic changes occurring throughout post-delivery development from the morphological, molecular and omics perspectives. Our study provides information that may be utilized in improving BAT functional activity through gene regulation and/or epigenetic regulation.

Adipose tissue gene expression of long non-coding RNAs; MALAT1, TUG1 in obesity: is it associated with metabolic profile and lipid homeostasis-related genes expression?

BACKGROUND

Recent studies point toward the possible regulatory roles of two lncRNAs; metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and taurine upregulated gene 1 (TUG1) in the pathogenesis of obesity-related disorders and regulation of lipogenesis and adipogenesis. In an attempt to understand the molecules involved in human obesity pathogenesis, we aimed to evaluate the expression of MALAT1 and TUG1 in visceral adipose tissues (VAT) and subcutaneous adipose tissues (SAT) of obese women, as compared to normal-weight women. The mRNA expression of possible target genes including peroxisome proliferator-activated receptor gamma (PPARγ), PPARγ coactivator-1 alpha (PGC1α), sterol regulatory element-binding protein-1c (SREBP-1c), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) which are involved in adipogenesis and lipogenesis were also examined.

METHODS

This study was conducted on 20 obese [body mass index (BMI) ≥ 30 kg/m 2] female participants and 19 normal-weight (BMI < 25 kg/m 2) female participants. Real-time PCR was performed to investigate the mRNA expression of the above-mentioned genes in VAT and SAT from all participants.

RESULTS

The results showed lower mRNA levels of TUG1 in both the VAT and SAT of obese women, compared to normal-weight women. Furthermore, TUG1 expression in SAT positively correlated with BMI, waist circumference (WC), hip circumference, HOMA-IR, and insulin levels, eGFR value, creatinine levels, and hs-CRP in all participants independent of age and HOMA-IR. However, VAT mRNA expression of TUG1 had a positive correlation with obesity indices and HOMA-IR and insulin levels in the whole population. Moreover, SAT mRNA level of TUG1 was positively correlated with SAT gene expression of PGC1α, SREBP-1c, FAS, and ACC independent of age and HOMA-IR. Although mRNA expression of MALAT1 did not differ between two groups for any tissue, it was positively correlated with SAT mRNA levels of SREBP-1c, PPARγ, and their targets; FAS and ACC, as well as with VAT mRNA levels of PGC1α.

CONCLUSIONS

It seems likely that TUG1 with distinct expression pattern in VAT and SAT are involved in the regulation of lipogenic and adipogenic genes and obesity-related parameters. However, more studies are necessary to establish this concept.

Long noncoding RNAs in lipid metabolism: literature review and conservation analysis across species

BACKGROUND

Lipids are important for the cell and organism life since they are major components of membranes, energy reserves and are also signal molecules. The main organs for the energy synthesis and storage are the liver and adipose tissue, both in humans and in more distant species such as chicken. Long noncoding RNAs (lncRNAs) are known to be involved in many biological processes including lipid metabolism.

RESULTS

In this context, this paper provides the most exhaustive list of lncRNAs involved in lipid metabolism with 60 genes identified after an in-depth analysis of the bibliography, while all "review" type articles list a total of 27 genes. These 60 lncRNAs are mainly described in human or mice and only a few of them have a precise described mode-of-action. Because these genes are still named in a non-standard way making such a study tedious, we propose a standard name for this list according to the rules dictated by the HUGO consortium. Moreover, we identified about 10% of lncRNAs which are conserved between mammals and chicken and 2% between mammals and fishes. Finally, we demonstrated that two lncRNA were wrongly considered as lncRNAs in the literature since they are 3' extensions of the closest coding gene.

CONCLUSIONS

Such a lncRNAs catalogue can participate to the understanding of the lipid metabolism regulators; it can be useful to better understand the genetic regulation of some human diseases (obesity, hepatic steatosis) or traits of economic interest in livestock species (meat quality, carcass composition). We have no doubt that this first set will be rapidly enriched in coming years.

Genome-wide identification and characterization of long non-coding RNAs during differentiation of visceral preadipocytes in rabbit

Emerging evidence suggests that long non-coding RNAs (lncRNAs) are critical regulators of diverse biological processes, including adipogenesis. Despite being considered an ideal animal model for studying adipogenesis, little is known about the roles of lncRNAs in the regulation of rabbit preadipocyte differentiation. In the present study, visceral preadipocytes isolated from newborn rabbits were cultured in vitro and induced for differentiation, and global lncRNA expression profiles of adipocytes collected at days 0, 3, and 9 of differentiation were analyzed by RNA-seq. A total of 2066 lncRNAs were identified from nine RNA-seq libraries. Compared to protein-coding transcripts, lncRNA transcripts exhibited characteristics of a longer length and lower expression level. Furthermore, 486 and 357 differentially expressed (DE) lncRNAs were identified when comparing day 3 vs. day 0 and day 9 vs. day 3, respectively. Target genes of DE lncRNAs were predicted by the cis-regulating approach. Prediction of functions revealed that DE lncRNAs when comparing day 3 vs. day 0 were involved in gene ontology (GO) terms of developmental growth, growth, developmental cell growth, and stem cell proliferation, and involved in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of PI3K-Akt signaling pathway, fatty acid biosynthesis, and the insulin signaling pathway. The DE lncRNAs when comparing day 9 vs. day 3 were involved in GO terms that associated with epigenetic modification and were involved in the KEGG pathway of cAMP signaling pathway. This study provides further insight into the regulatory function of lncRNAs in rabbit visceral adipose and facilitates a better understanding of different stages of preadipocyte differentiation.

Adipose circular RNAs exhibit dynamic regulation in obesity and functional role in adipogenesis

Non-coding RNAs are emerging as novel regulators in adipocyte differentiation and function. Circular RNAs (circRNAs) are a new class of non-coding transcripts generated across all eukaryotic tissues, but their function in adipose biology remains unknown. Here we perform deep sequencing of visceral and subcutaneous fat to discover thousands of adipose circRNAs, many of which are species conserved, tissue specific and dynamically regulated during adipogenesis and obesity. We identify circTshz2-1 and circArhgap5-2 as indispensable regulators of adipogenesis in vitro. To characterize the function of circRNAs in vivo, we deliver adenoviral shRNA targeting circArhgap5-2 into mouse inguinal tissue and show that the expression of this circRNA is essential in maintaining the global adipocyte transcriptional programme involved in lipid biosynthesis and metabolism. We also demonstrate that the pro-adipogenic function of circArhgap5-2 is conserved in human adipocytes. Our results provide important evidence that circRNAs serve as important regulators in adipocyte differentiation and metabolism.

GROWTH AND DEVELOPMENT SYMPOSIUM: STEM AND PROGENITOR CELLS IN ANIMAL GROWTH: Long noncoding RNAs in adipogenesis and adipose development of meat animals12

Sequencing technology, especially next-generation RNA sequencing, has greatly facilitated the identification and annotation of long noncoding RNAs (lncRNAs). In mammals, a large number of lncRNAs have been identified, which regulate various biological processes. An increasing number of lncRNAs have been identified which could function as key regulators of adipogenesis (adipocyte formation), a key step of the development of adipose tissue. Because proper adipose tissue development is a key factor affecting animal growth efficiency, lean/fat ratio, and meat quality, summarizing the roles and recent advances of lncRNAs in adipogenesis is needed in order to develop strategies to effectively manage fat deposition. In this review, we updated lncRNAs contributed to the regulation of adipogenesis, focusing on their roles in fat development of farm animals.

A Novel lnc-RNA, Named lnc-ORA, Is Identified by RNA-Seq Analysis, and Its Knockdown Inhibits Adipogenesis by Regulating the PI3K/AKT/mTOR Signaling Pathway

Obesity is closely associated with numerous adipogenic regulatory factors, including coding and non-coding genes. Long noncoding RNAs (lncRNAs) play a major role in adipogenesis. However, differential expression profiles of lncRNAs in inguinal white adipose tissue (iWAT) between wild-type (WT) and ob/ob mice, as well as their roles in adipogenesis, are not well understood. Here, a total of 2809 lncRNAs were detected in the iWAT of WT and ob/ob mice by RNA-Sequencing (RNA-Seq), including 248 novel lncRNAs. Of them, 46 lncRNAs were expressed differentially in WT and ob/ob mice and were enriched in adipogenesis signaling pathways as determined by KEGG enrichment analysis, including the PI3K/AKT/mTOR and cytokine-cytokine receptor interaction signaling pathways. Furthermore, we focused on one novel lncRNA, which we named lnc-ORA (obesity-related lncRNA), which had a seven-fold higher expression in ob/ob mice than in WT mice. Knockdown of lnc-ORA inhibited preadipocyte proliferation by decreasing the mRNA and protein expression levels of cell cycle markers. Interestingly, lnc-ORA knockdown inhibited adipocyte differentiation by regulating the PI3K/AKT/mTOR signaling pathway. In summary, these findings contribute to a better understanding of adipogenesis in relation to lncRNAs and provide novel potential therapeutic targets for obesity-related metabolic diseases.

Function and Mechanism of Long Noncoding RNAs in Adipocyte Biology

The last two decades have witnessed an explosion of interest in adipocyte biology, coinciding with the upsurge of obesity and metabolic syndrome. Now we have new perspectives on the distinct developmental origins of white, brown, and beige adipocytes and their role in metabolic physiology and disease. Beyond fuel metabolism, adipocytes communicate with the immune system and other tissues by releasing diverse paracrine and endocrine factors to orchestrate adipose tissue remodeling and maintain systemic homeostasis. Significant progress has been made in delineating the regulatory networks that govern different aspects of adipocyte biology. Here we provide an overview on the emerging role of long noncoding RNAs (lncRNAs) in the regulation of adipocyte development and metabolism and discuss the implications of the RNA-protein regulatory interface in metabolic control.

Long Noncoding RNA: Function and Mechanism on Differentiation of Mesenchymal Stem Cells and Embryonic Stem Cells

Background:

Long suspected as transcriptional noise, recently recognized, long non-coding RNAs (lncRNAs) are emerging as an indicator, biomarker and therapy target in the physiologic and pathologic process. Mesenchymal stem cells and embryonic stem cells are important source for normal and therapeutic tissue repair. However, the mechanism of stem cell differentiation is not completely understood. Research on lncRNAs may provide novel insights into the mechanism of differentiation process of the stem cell which is important for the application of stem cell therapy. The lncRNAs field is still very young, new insights into lncRNAs function are emerging to a greater understanding of biological processes.

Objective:

In this review, we summarize the recent researches studying lncRNAs and illustrate how they act in the differentiation of the mesenchymal stem cells and embryonic stem cells, and discuss some future directions in this field.

Results:

Numerous lncRNAs were differentially expressed during differentiation of mesenchymal stem cells and embryonic stem cells. LncRNAs were able to regulate the differentiation processes through epigenetic regulation, transcription regulation and post-transcription regulation.

Conclusion:

LncRNAs are involved in the differentiation process of mesenchymal stem cells and embryonic stem cells, and they could become promising indicator, biomarker and therapeutic targets in the physiologic and pathologic process. However, the mechanisms of the role of lncRNAs still require further investigation.

Knockdown of slincRAD leads to defective adipose development in vivo

The development of adipose tissue is a precisely coordinated cellular process, in which both protein-coding and non-coding genes are involved. To characterize the in vivo function of a novel long non-coding RNA (lncRNAs), loss-of-function assays were performed with slincRAD knockdown mice. Down-regulation of slincRAD expression was found to impair the development of adipose tissue, leading to a slim phenotype for both of the male and female mice. Compared to normal adipocytes, slincRAD knockdown cells had defective differentiation features, such as smaller sizes and decreased lipid production. For elder mice, slincRAD knockdown led to abnormal glucose and lipid metabolism. Therefore, a physiologically important lncRNA was characterized in the development of adipose tissue.

Silencing an insulin-induced lncRNA, LncASIR, impairs the transcriptional response to insulin signalling in adipocytes

Long noncoding RNA(lncRNA)s are new regulators governing the metabolism in adipose tissue. In this study, we aimed to understand how lncRNAs respond to insulin signalling and explore whether lncRNAs have a functional role in insulin signalling pathway. We treated primary adipocyte cultures with insulin and collected RNA for RNA-sequencing to profile the non-coding transcriptome changes, through which we identified a top Adipose Specific Insulin Responsive LncRNA (LncASIR). To determine its biological function, we knocked down LncASIR using dcas9-KRAB, followed by RNA-seq to examine the effect on insulin-induced gene expression program. We identified a set of lncRNAs regulated by insulin signalling pathway. LncASIR is transcribed from a super enhancer region and responds robustly to insulin treatment. Silencing LncASIR resulted in an impaired global insulin-responsive gene program. LncASIR is a novel and integral component in the insulin signalling pathway in adipocytes.

Role of long non-coding RNAs in metabolic control

Long non-coding RNAs (lncRNAs) have emerged as pivotal regulators of gene expression by influencing various biological processes including proliferation, apoptosis, differentiation, and senescence. Accumulating evidence implicates lncRNAs in the maintenance of metabolic homeostasis; dysregulation of certain lncRNAs promotes the progression of metabolic disorders such as diabetes, obesity, and cardiovascular diseases. In this review, we discuss our understanding of lncRNAs implicated in metabolic control, focusing on in particular diseases arising from chronic inflammation, insulin resistance, and lipid homeostasis. We have analyzed lncRNAs and their molecular targets involved in the pathogenesis of chronic liver disease, diabetes, and obesity, and have discussed the rising interest in lncRNAs as diagnostic and therapeutic targets improving metabolic homeostasis. This article is part of a Special Issue entitled: ncRNA in control of gene expression edited by Kotb Abdelmohsen.

Long non-coding RNAs regulation in adipogenesis and lipid metabolism: Emerging insights in obesity

Obesity is a widespread health problem that brings about various adipose tissue dysfunctions. The balance of energy storage and energy expenditure is critical for normal fat accumulation and lipid metabolism. Therefore, understanding the molecular basis of adipogenesis and thermogenesis is essential to maintain adipose development and lipid homeostasis. Increasing evidence demonstrated that lncRNAs (long non-coding RNAs), a class of non-protein coding RNAs of >200 nucleotides in length, are identified as key regulators in obesity-related biological processes through diverse regulatory mechanisms. In this review, we concentrate on recent and relevant studies on the roles of lncRNAs in regulation of white adipogenesis, brown adipocyte differentiation and lipid metabolism. In addition, the diagnostic and therapeutic potential of lncRNAs is highlighted, and that will make recommendations for the future application of lncRNAs in the treatment of obesity.