Function and Mechanism of Long Noncoding RNAs in Adipocyte Biology

Mapping adipocyte interactome networks by HaloTag-enrichment-mass spectrometry

Mapping protein interaction complexes in their natural state in vivo is arguably the Holy Grail of protein network analysis. Detection of protein interaction stoichiometry has been an important technical challenge, as few studies have focused on this. This may, however, be solved by artificial intelligence (AI) and proteomics. Here, we describe the development of HaloTag-based affinity purification mass spectrometry (HaloMS), a high-throughput HaloMS assay for protein interaction discovery. The approach enables the rapid capture of newly expressed proteins, eliminating tedious conventional one-by-one assays. As a proof-of-principle, we used HaloMS to evaluate the protein complex interactions of 17 regulatory proteins in human adipocytes. The adipocyte interactome network was validated using an in vitro pull-down assay and AI-based prediction tools. Applying HaloMS to probe adipocyte differentiation facilitated the identification of previously unknown transcription factor (TF)-protein complexes, revealing proteome-wide human adipocyte TF networks and shedding light on how different pathways are integrated.

Pulling the trigger: Noncoding RNAs in white adipose tissue browning

White adipose tissue (WAT) serves as the primary site for energy storage and endocrine regulation in mammals, while brown adipose tissue (BAT) is specialized for thermogenesis and energy expenditure. The conversion of white adipocytes to brown-like fat cells, known as browning, has emerged as a promising therapeutic strategy for reversing obesity and its associated co-morbidities. Noncoding RNAs (ncRNAs) are a class of transcripts that do not encode proteins but exert regulatory functions on gene expression at various levels. Recent studies have shed light on the involvement of ncRNAs in adipose tissue development, differentiation, and function. In this review, we aim to summarize the current understanding of ncRNAs in adipose biology, with a focus on their role and intricate mechanisms in WAT browning. Also, we discuss the potential applications and challenges of ncRNA-based therapies for overweight and its metabolic disorders, so as to combat the obesity epidemic in the future.

Cold-inducible lncRNA266 promotes browning and the thermogenic program in white adipose tissue

Cold-induced nonshivering thermogenesis has contributed to the improvement of several metabolic syndromes caused by obesity. Several long noncoding RNAs (lncRNAs) have been shown to play a role in brown fat biogenesis and thermogenesis. Here we show that the lncRNA lnc266 is induced by cold exposure in inguinal white adipose tissue (iWAT). In vitro functional studies reveal that lnc266 promotes brown adipocyte differentiation and thermogenic gene expression. At room temperature, lnc266 has no effects on white fat browning and systemic energy consumption. However, in a cold environment, lnc266 promotes white fat browning and thermogenic gene expression in obese mice. Moreover, lnc266 increases core body temperature and reduces body weight gain. Mechanistically, lnc266 does not directly regulate Ucp1 expression. Instead, lnc266 sponges miR-16-1-3p and thus abolishes the repression of miR-16-1-3p on Ucp1 expression. As a result, lnc266 promotes preadipocyte differentiation toward brown-like adipocytes and stimulates thermogenic gene expression. Overall, lnc266 is a cold-inducible lncRNA in iWAT, with a key role in white fat browning and the thermogenic program.

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.

A Novel LncRNA MSTRG.310246.1 Promotes Differentiation and Thermogenesis in Goat Brown Adipocytes

Brown adipose tissue (BAT) plays a critical role in maintaining the body temperature in newborn lamb due to its unique non-shivering thermogenesis. Previous studies have found that BAT thermogenesis is regulated by several long non-coding RNAs (lncRNAs). Here, we identified a novel lncRNA, MSTRG.310246.1, which was enriched in BAT. MSTRG.310246.1 was localized in both the nuclear and cytoplasmic compartments. In addition, MSTRG.310246.1 expression was upregulated during brown adipocyte differentiation. Overexpression of MSTRG.310246.1 increased the differentiation and thermogenesis of goat brown adipocytes. On the contrary, the knockdown of MSTRG.310246.1 inhibited the differentiation and thermogenesis of goat brown adipocytes. However, MSTRG.310246.1 had no effect on goat white adipocyte differentiation and thermogenesis. Our results show that MSTRG.310246.1 is a BAT-enriched LncRNA that improves the differentiation and thermogenesis of goat brown adipocytes.

Identification and characterization of the long non-coding RNA NFIA-AS2 as a novel locus for body mass index in American Indians

BACKGROUND

Genome-wide association studies have shown that body mass index (BMI), an estimate of obesity, is highly polygenic. Individual variants typically have small effect sizes, making it challenging to identify unique loci in under-represented ethnic groups which lack statistical power due to their small sample size. Yet obesity is a major health disparity and is particularly prevalent in southwestern American Indians. Here, we identify and characterize a new locus for BMI that was detected by analyzing moderate associations with BMI obtained in a population-based sample of southwestern American Indians together with the well-powered GIANT dataset.

METHODS

Genotypes for 10.5 million variants were tested for association with BMI in 5870 American Indians and 2600 variants that showed an association P < 10^-3 in the American Indian sample were combined in a meta-analysis with the BMI data reported in GIANT (N = 240,608). The newly identified gene, NFIA-AS2 was functionally characterized, and the impact of its lead associated variant rs1777538 was studied both in-silico and in-vitro.

RESULTS

Rs1777538 (T/C; C allele frequency = 0.16 in American Indians and 0.04 in GIANT, meta-analysis P = 5.0 × 10^-7) exhibited a large effect in American Indians (1 kg/m² decrease in BMI per copy of C allele). NFIA-AS2 was found to be a nuclear localized long non-coding RNA expressed in tissues pertinent to human obesity. Analysis of this variant in human brown preadipocytes showed that NFIA-AS2 transcripts carrying the C allele had increased RNA degradation compared to the T allele transcripts (half-lives = 9 h, 13 h respectively). During brown adipogenesis, NFIA-AS2 featured a stage-specific regulation of nearby gene expression where rs1777538 demonstrated an allelic difference in regulation in the mature adipocytes (the strongest difference was observed for L1TD1, P = 0.007).

CONCLUSION

Our findings support a role for NFIA-AS2 in regulating pathways that impact BMI.

Plant non-coding RNAs function in pollen development and male sterility

Male sterility is classified as either cytoplasmic male sterility (CMS) or genic male sterility (GMS). Generally, CMS involves mitochondrial genomes interacting with the nuclear genome, while GMS is caused by nuclear genes alone. Male sterility is regulated by multilevel mechanisms in which non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and phased small interfering RNAs (phasiRNAs), which have been proven to be critical elements. The development of high-throughput sequencing technology offers new opportunities to evaluate the genetic mechanism of ncRNAs in plant male sterility. In this review, we summarize the critical ncRNAs that regulate gene expression in ways dependent on or independent of hormones, which involve the differentiation of the stamen primordia, degradation of the tapetum, formation of microspores, and the release of pollen. In addition, the key mechanisms of the miRNA-lncRNA-mRNA interaction networks mediating male sterility in plants are elaborated. We present a different perspective on exploring the ncRNA-mediated regulatory pathways that control CMS in plants and create male-sterile lines through hormones or genome editing. A refined understanding of the ncRNA regulatory mechanisms in plant male sterility for the development of new sterile lines would be conducive to improve hybridization breeding.

Role of lncRNAs and circRNAs in Orofacial Clefts

Different modes of gene regulation, such as histone modification, transcription factor binding, DNA methylation, and microRNA (miRNA) expression, are critical for the spatiotemporal expression of genes in developing orofacial tissues. Aberrant regulation in any of these modes may contribute to orofacial defects. Noncoding RNAs (ncRNAs), such as long ncRNAs (lncRNAs) and circular RNAs (circRNAs), have been shown to alter miRNA expression, and are thus emerging as novel contributors to gene regulation. Some of these appear to function as 'miRNA sponges', thereby diminishing the availability of these miRNAs to inhibit the expression of target genes. Such ncRNAs are also termed competitive endogenous RNAs (ceRNAs). Here, we examine emerging data that shed light on how lncRNAs and circRNAs may alter miRNA regulation, thus affecting orofacial development and potentially contributing to orofacial clefting.

miR-379 mediates insulin resistance and obesity through impaired angiogenesis and adipogenesis regulated by ER stress

We investigated the role of microRNA (miR-379) in the pathogenesis of obesity, adipose tissue dysfunction, and insulin resistance (IR). We used miR-379 knockout (miR-379KO) mice to test whether loss of miR-379 affects high-fat diet (HFD)-induced obesity and IR via dysregulation of key miR-379 targets in adipose tissue. Increases in body weight, hyperinsulinemia, and IR in wild-type (WT)-HFD mice were significantly attenuated in miR-379KO-HFD mice with some sex differences. Relative to control chow-fed mice, in WT-HFD mice, expression of miR-379 and C/EBP homologous protein (Chop) (pro-endoplasmic reticulum [ER] stress) and inflammation in perigonadal white adipose tissue (gWAT) were increased, whereas adipogenic genes and miR-379 target genes (Vegfb and Edem3) were decreased. These changes, as well as key parameters of brown adipose tissue dysfunction (including mitochondrial defects), were significantly attenuated in miR-379KO-HFD mice. WAT from obese human subjects with and without type 2 diabetes showed increased miR-379 and decreased miR-379 target genes. In cultured 3T3L1 pre-adipocytes, miR-379 inhibitors increased miR-379 targets and adipogenic genes. These data suggest that miR-379 plays an important role in HFD-induced obesity through increased adipose inflammation, mitochondrial dysfunction, and ER stress as well as impaired adipogenesis and angiogenesis. miR-379 inhibitors may be developed as novel therapies for obesity and associated complications.

HOTAIR interacts with PRC2 complex regulating the regional preadipocyte transcriptome and human fat distribution

Mechanisms governing regional human adipose tissue (AT) development remain undefined. Here, we show that the long non-coding RNA HOTAIR (HOX transcript antisense RNA) is exclusively expressed in gluteofemoral AT, where it is essential for adipocyte development. We find that HOTAIR interacts with polycomb repressive complex 2 (PRC2) and we identify core HOTAIR-PRC2 target genes involved in adipocyte lineage determination. Repression of target genes coincides with PRC2 promoter occupancy and H3K27 trimethylation. HOTAIR is also involved in modifying the gluteal adipocyte transcriptome through alternative splicing. Gluteal-specific expression of HOTAIR is maintained by defined regions of open chromatin across the HOTAIR promoter. HOTAIR expression levels can be modified by hormonal (estrogen, glucocorticoids) and genetic variation (rs1443512 is a HOTAIR eQTL associated with reduced gynoid fat mass). These data identify HOTAIR as a dynamic regulator of the gluteal adipocyte transcriptome and epigenome with functional importance for human regional AT development.

LPI-CSFFR: Combining serial fusion with feature reuse for predicting LncRNA-protein interactions

Long non-coding RNAs (LncRNAs) play important roles in a series of life activities, and they function primarily with proteins. The wet experimental-based methods in lncRNA-protein interactions (lncRPIs) study are time-consuming and expensive. In this study, we propose for the first time a novel feature fusion method, the LPI-CSFFR, to train and predict LncRPIs based on a Convolutional Neural Network (CNN) with feature reuse and serial fusion in sequences, secondary structures, and physicochemical properties of proteins and lncRNAs. The experimental results indicate that LPI-CSFFR achieves excellent performance on the datasets RPI1460 and RPI1807 with an accuracy of 83.7 % and 98.1 %, respectively. We further compare LPI-CSFFR with the state-of-the-art existing methods on the same benchmark datasets to evaluate the performance. In addition, to test the generalization performance of the model, we independently test sample pairs of five model organisms, where Mus musculus are the highest prediction accuracy of 99.5 %, and we find multiple hotspot proteins after constructing an interaction network. Finally, we test the predictive power of the LPI-CSFFR for sample pairs with unknown interactions. The results indicate that LPI-CSFFR is promising for predicting potential LncRPIs. The relevant source code and the data used in this study are available at https://github.com/JianjunTan-Beijing/LPI-CSFFR.

Comprehensive Transcriptional Profiling and Mouse Phenotyping Reveals Dispensable Role for Adipose Tissue Selective Long Noncoding RNA Gm15551

Cold and nutrient-activated brown adipose tissue (BAT) is capable of increasing systemic energy expenditure via the uncoupled respiration and secretion of endocrine factors, thereby protecting mice against diet-induced obesity and improving insulin response and glucose tolerance in men. Long non-coding RNAs (lncRNAs) have recently been identified as fine-tuning regulators of cellular function. While certain lncRNAs have been functionally characterised in adipose tissue, their overall contribution in the activation of BAT remains elusive. We identified lncRNAs correlating to interscapular brown adipose tissue (iBAT) function in a high fat diet (HFD) and cold stressed mice. We focused on Gm15551, which has an adipose tissue specific expression profile, is highly upregulated during adipogenesis, and downregulated by β-adrenergic activation in mature adipocytes. Although we performed comprehensive transcriptional and adipocyte physiology profiling in vitro and in vivo, we could not detect an effect of gain or loss of function of Gm15551.

Long Non-Coding RNAs in the Pathogenesis of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is one of the major microvascular complications of diabetes mellitus, with relatively high morbidity and mortality globally but still in short therapeutic options. Over the decades, a large body of data has demonstrated that oxidative stress, inflammatory responses, and hemodynamic disorders might exert critical influence in the initiation and development of DKD, whereas the delicate pathogenesis of DKD remains profoundly elusive. Recently, long non-coding RNAs (lncRNAs), extensively studied in the field of cancer, are attracting increasing attentions on the development of diabetes mellitus and its complications including DKD, diabetic retinopathy, and diabetic cardiomyopathy. In this review, we chiefly focused on abnormal expression and function of lncRNAs in major resident cells (mesangial cell, endothelial cell, podocyte, and tubular epithelial cell) in the kidney, summarized the critical roles of lncRNAs in the pathogenesis of DKD, and elaborated their potential therapeutic significance, in order to advance our knowledge in this field, which might help in future research and clinical treatment for the disease.

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.

Identification of a Long Noncoding RNA (lncPRDM16) Inhibiting Preadipocyte Proliferation in the Chicken

Long noncoding RNAs are vital to a variety of biological and physiological processes through multiple modes of functional interaction with DNA, RNA, and proteins. In chickens, numerous lncRNAs were discovered to be important to growth or disease progression. However, the detailed molecular function and role of lncRNAs remain less explored. Here, we performed lncRNA sequencing on abdominal adipose tissues from broiler lines divergently selected for abdominal fat content, and significantly differentially expressed lncRNAs were found, including lncPRDM16, a divergently transcribed and conserved lncRNA near PRDM16. Full lengths of two transcripts of lncPRDM16 were obtained, and their genomic structures were compared. Expression dynamics of lncPRDM16 in different tissues and during preadipocyte proliferation and differentiation were profiled. Moreover, a 250-nucleotide sequence at 5'-end was found to be inevitable to the function of lncPRDM16 in inhibiting preadipocyte proliferation and regulating the promoter activities of both lncPRDM16 and PRDM16. Taken together, we identified the 5'-end functional elements of lncPRDM16 and their potential importance in inhibiting preadipocyte proliferation. Our findings provide the foundation for further exploration of lncPRDM16 function and potential improvement of chicken muscle quality.

Characterization of transcript enrichment and detection bias in single-nucleus RNA-seq for mapping of distinct human adipocyte lineages

Single-cell RNA sequencing (scRNA-seq) enables molecular characterization of complex biological tissues at high resolution. The requirement of single-cell extraction, however, makes it challenging for profiling tissues such as adipose tissue, for which collection of intact single adipocytes is complicated by their fragile nature. For such tissues, single-nucleus extraction is often much more efficient and therefore single-nucleus RNA sequencing (snRNA-seq) presents an alternative to scRNA-seq. However, nuclear transcripts represent only a fraction of the transcriptome in a single cell, with snRNA-seq marked with inherent transcript enrichment and detection biases. Therefore, snRNA-seq may be inadequate for mapping important transcriptional signatures in adipose tissue. In this study, we compare the transcriptomic landscape of single nuclei isolated from preadipocytes and mature adipocytes across human white and brown adipocyte lineages, with whole-cell transcriptome. We show that snRNA-seq is capable of identifying the broad cell types present in scRNA-seq at all states of adipogenesis. However, we also explore how and why the nuclear transcriptome is biased and limited, as well as how it can be advantageous. We robustly characterize the enrichment of nuclear-localized transcripts and adipogenic regulatory lncRNAs in snRNA-seq, while also providing a detailed understanding for the preferential detection of long genes upon using this technique. To remove such technical detection biases, we propose a normalization strategy for a more accurate comparison of nuclear and cellular data. Finally, we show successful integration of scRNA-seq and snRNA-seq data sets with existing bioinformatic tools. Overall, our results illustrate the applicability of snRNA-seq for the characterization of cellular diversity in the adipose tissue.

An adipose lncRAP2-Igf2bp2 complex enhances adipogenesis and energy expenditure by stabilizing target mRNAs

lncRAP2 is a conserved cytoplasmic lncRNA enriched in adipose tissue and required for adipogenesis. Using purification and in vivo interactome analyses, we show that lncRAP2 forms complexes with proteins that stabilize mRNAs and modulate translation, among them Igf2bp2. Surveying transcriptome-wide Igf2bp2 client mRNAs in white adipocytes reveals selective binding to mRNAs encoding adipogenic regulators and energy expenditure effectors, including adiponectin. These same target proteins are downregulated when either Igf2bp2 or lncRAP2 is downregulated, hindering adipocyte lipolysis. Proteomics and ribosome profiling show this occurs predominantly through mRNA accumulation, as lncRAP2-Igf2bp2 complex binding does not impact translation efficiency. Phenome-wide association studies reveal specific associations of genetic variants within both lncRAP2 and Igf2bp2 with body mass and type 2 diabetes, and both lncRAP2 and Igf2bp2 are suppressed in adipose depots of obese and diabetic individuals. Thus, the lncRAP2-Igf2bp2 complex potentiates adipose development and energy expenditure and is associated with susceptibility to obesity-linked diabetes.

The Role of LncRNA TUG1 in Obesity-Related Diseases

With the continuous improvement of living standards, obesity has become an inevitable hotspot in our daily life. It remains a chronic and recurrent disease with serious adverse consequences. Over the past few years, several articles suggested that long non-coding RNA taurine increased gene 1（lncRNA TUG1）, a useful RNA, was suggested to show a relationship to obesity-related disease occurrence and development. Exosome is an emerging research field, which contains substances that are actively involved in regulating the molecular mechanisms of disease. This review summarizes the current relevant TUG1 in different molecular pathways of diseases related to obesity, relationship between exosomes and TUG1 or diseases related to obesity. The aim is to explore TUG1 as a novel target for obesity, which can deepen the knowledge regarding epigenetic regulation pathway. Besides, it is likely to be a potential future targeting diseases related to obesity site treatment and diagnosis.

Epigenetic modifications in diabetes

Diabetes is now considered as a 'silent epidemic' that claims over four million lives every year, and the disease knows no socioeconomic boundaries. Despite extensive efforts by the National and International organizations, and cutting-edge research, about 11% world's population is expected to suffer from diabetes (and its complications) by year 2045. This life-long disease damages both the microvasculature and the macrovasculature of the body, and affects many metabolic and molecular pathways, altering the expression of many genes. Recent research has shown that external factors, such as environmental factors, lifestyle and pollutants can also regulate gene expression, and contribute in the disease development and progression. Many epigenetic modifications are implicated in the development of micro- and macro- vascular complications including DNA methylation and histone modifications of several genes implicated in their development. Furthermore, several noncoding RNAs, such as micro RNAs and long noncoding RNAs, are also altered, affecting many biochemical pathways. Epigenetic modifications, however, have the advantage that they could be passed to the next generation, or can be erased. They are now being explored as therapeutical target(s) in the cancer field, which opens up the possibility to use them for treating diabetes and preventing/slowing down its complications.

Senolytic effects of quercetin in an in vitro model of pre-adipocytes and adipocytes induced senescence

The dysfunction of adipose tissue with aging and the accumulation of senescent cells has been implicated in the pathophysiology of chronic diseases. Recently interventions capable of reducing the burden of senescent cells and in particular the identification of a new class of drugs termed senolytics have been object of extensive investigation. We used an in vitro model of induced senescence by treating both pre-adipocytes as well as mature adipocytes with hydrogen peroxide (H₂O₂) at a sub-lethal concentration for 3 h for three consecutive days, and hereafter with 20 uM quercetin at a dose that in preliminary experiments resulted to be senolytic without cytotoxicity. H₂O₂ treated pre-adipocytes and adipocytes showed typical senescence-associated features including increased beta-galactosidase activity (SA-ß-gal) and p21, activation of ROS and increased expression of pro-inflammatory cytokines. The treatment with quercetin in senescent pre-adipocytes and adipocytes was associated to a significant decrease in the number of the SA-β-gal positive cells along with the suppression of ROS and of inflammatory cytokines. Besides, quercetin treatment decreased miR-155-5p expression in both models, with down-regulation of p65 and a trend toward an up-regulation of SIRT-1 in complete cell extracts. The senolytic compound quercetin could affect AT ageing by reducing senescence, induced in our in vitro model by oxidative stress. The downregulation of miRNA-155-5p, possibly through the modulation of NF-κB and SIRT-1, could have a key role in the effects of quercetin on both pre-adipocytes and adipocytes.

The impact of obesity on adipocyte-derived extracellular vesicles

Recently, the emerging roles of adipocyte-derived extracellular vesicles (EVs) linking obesity and its comorbidities have been recognized. In obese subjects, adipocytes are having hypertrophic growth and are under stressed. The dysfunction adipocytes dysregulate the assembly of the biological components in the EVs including exosomes. This article critically reviews the current findings on the impact of obesity on the exosomal cargo contents that induce the pathophysiological changes. Besides, this review also summarizes the understanding on how obesity affects the biogenesis of adipocyte-derived exosomes and the exosome secretion. Furthermore, the differences of the exosomal contents in different adipose depots, and the impact of obesity on the exosomes that are derived from the stromal vascular fraction such as the adipose tissue macrophages and adipocyte-derived stem cells will also be discussed. The current development and potential application of exosome-based therapy will be summarized. This review provides crucial information for the design of novel exosome-based therapy for the treatment of obesity and its comorbidities.

Nuclear Genome-Encoded Long Noncoding RNAs and Mitochondrial Damage in Diabetic Retinopathy

Retinal mitochondria are damaged in diabetes-accelerating apoptosis of capillary cells, and ultimately, leading to degenerative capillaries. Diabetes also upregulates many long noncoding RNAs (LncRNAs), including LncMALAT1 and LncNEAT1. These RNAs have more than 200 nucleotides and no open reading frame for translation. LncMALAT1 and LncNEAT1 are encoded by nuclear genome, but nuclear-encoded LncRNAs can also translocate in the mitochondria. Our aim was to investigate the role of LncMALAT1 and LncNEAT1 in mitochondrial homeostasis. Using human retinal endothelial cells, the effect of high glucose on LncMALAT1 and LncNEAT1 mitochondrial localization was examined by RNA fluorescence in situ hybridization. The role of these LncRNAs in mitochondrial membrane potential (by JC-I staining), mtDNA integrity (by extended length PCR) and in protective mtDNA nucleoids (by SYBR green staining) was examined in MALAT1- or NEAT1-siRNA transfected cells. High glucose increased LncMALAT1 and LncNEAT1 mitochondrial expression, and MALAT1-siRNA or NEAT1-siRNA ameliorated glucose-induced damage to mitochondrial membrane potential and mtDNA, and prevented decrease in mtDNA nucleoids. Thus, increased mitochondrial translocation of LncMALAT1 or LncNEAT1 in a hyperglycemic milieu plays a major role in damaging the mitochondrial structural and genomic integrity. Regulation of these LncRNAs can protect mitochondrial homeostasis, and ameliorate formation of degenerative capillaries in diabetic retinopathy.

Role of mammalian long non-coding RNAs in normal and neuro oncological disorders

Long non-coding RNAs (lncRNAs) are expressed at lower levels than protein-coding genes but have a crucial role in gene regulation. LncRNA is distinct, they are being transcribed using RNA polymerase II, and their functionality depends on subcellular localization. Depending on their niche, they specifically interact with DNA, RNA, and proteins and modify chromatin function, regulate transcription at various stages, forms nuclear condensation bodies and nucleolar organization. lncRNAs may also change the stability and translation of cytoplasmic mRNAs and hamper signaling pathways. Thus, lncRNAs affect the physio-pathological states and lead to the development of various disorders, immune responses, and cancer. To date, ~40% of lncRNAs have been reported in the nervous system (NS) and are involved in the early development/differentiation of the NS to synaptogenesis. LncRNA expression patterns in the most common adult and pediatric tumor suggest them as potential biomarkers and provide a rationale for targeting them pharmaceutically. Here, we discuss the mechanisms of lncRNA synthesis, localization, and functions in transcriptional, post-transcriptional, and other forms of gene regulation, methods of lncRNA identification, and their potential therapeutic applications in neuro oncological disorders as explained by molecular mechanisms in other malignant disorders.

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

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

TET1 promotes RXRα expression and adipogenesis through DNA demethylation

Adipose tissue is important for systemic metabolic homeostasis in response to environmental changes, and adipogenesis involves dynamic transcriptional regulation. Ten-eleven translocation (TET) enzymes (TET1, 2 and 3) oxidize the 5-methylcytosine (5mC) in DNA to 5-hydroxylmethylcytosine (5hmC), which associates with transcriptional activation. Step by step, 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) are further generated by TETs and the cytosine can be restored through base-excision repair. It is still unclear how DNA demethylation is involved in adipogenesis. Through a phenotypic screen, we found TET inhibition decreased adipocyte differentiation from mesenchymal stem cells (MSCs). Comparing with the undifferentiated MSCs, the differentiated adipocytes exhibited much higher levels of 5hmC and slightly increased 5fC and 5caC. Higher 5hmC was associated with better differentiation at single-cell level by image analysis. TET1 is upregulated in differentiation and depletion of it significantly impaired the gain of 5hmC. Furthermore, Tet1 depletion significantly hampered the adipocyte differentiation. Using RNA-seq, 5mC and 5hmC-DNA immunoprecipitation, we found that Tet1 knockout led to lower expression of genes associated with lipid metabolism and fat cell differentiation. Genes with loss of 5mC or gain of 5hmC in adipocytes include Lipe, Bmp4 and Rxra, etc. RXRα agonist partially rescued the inhibitory effect of Tet1 knockout for adipogenesis. So, Rxra is one of the critical TET1 modulated genes. Together, TET1-mediated active DNA demethylation plays an important role in adipogenesis.

Suppression of circulating AP001429.1 long non-coding RNA in obese patients with breast cancer

Long non-coding RNAs (lncRNAs), a type of cellular RNA, play a critical regulatory role in several physiological developments and pathological processes, such as tumorigenesis and tumor progression. Obesity is a risk factor for a number of serious health conditions, including breast cancer (BC). However, the underlying mechanisms behind the association between obesity and increased BC incidence and mortality remain unclear. Several studies have reported changes in lncRNA expression due to obesity and BC, independently encouraging further investigation of the relationship between the two in connection with lncRNAs. The present study was designed to first screen for the expression of 29 selected lncRNAs that showed a link to cancer or obesity in the blood of a selected cohort of 6 obese and 6 non-obese patients with BC. The expression levels of significantly expressed lncRNAs, AP001429.1, PCAT6, P5549, P19461 and P3134, were further investigated in a larger cohort of 69 patients with BC (36 obese and 33 non-obese), using reverse transcription-quantitative polymerase chain reaction. Results showed not only that AP001429.1 remained significantly downregulated in the larger cohort (P=0.002), but also that it was associated with several clinicopathological characteristics, such as negative HER2 status, negative E-cadherin expression, negative vascular invasion, negative margin invasion and LCIS. These findings suggest that obesity may have a role in inhibiting AP001429.1 expression, which may serve as a novel potential biomarker and therapeutic target for BC.

Long Non-coding RNA: A Key Regulator in the Pathogenesis of Diabetic Cardiomyopathy

In recent years, diabetes mellitus has become a global issue with increasing incidence rate worldwide. Diabetic cardiomyopathy (DCM), one of the important complications of diabetes, refers to patients with type 1 and type 2 diabetes who have ventricular hypertrophy, fibrosis and even diastolic dysfunction. The pathogenesis of DCM is related to oxidative stress, inflammatory response, apoptosis, autophagy, myocardial fibrosis and, diabetic microangiopathy. Long non-coding RNAs (lncRNA) is a non-coding RNA with a length longer than 200 nucleotides which lack the ability of protein coding. With the development of molecular technology, massive evidence demonstrates that lncRNA play a critical role in the molecular mechanism of DCM. Moreover, it can also be used as potential diagnostic markers for DCM. In this review, we intend to summarize the pathological roles and molecular mechanism of lncRNA in the progression of diabetic cardiomyopathy, which may provide promising diagnosis and treatment strategies for DCM.

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.

An update on brown adipose tissue biology: a discussion of recent findings

Brown adipose tissue (BAT) has been encouraged as a potential treatment for obesity and comorbidities due to its thermogenic activity capacity and contribution to energy expenditure. Some interventions such as cold and β-adrenergic drugs are able to activate BAT thermogenesis as well as promote differentiation of white adipocytes into brown-like cells (browning), enhancing the thermogenic activity of these cells. In this mini-review, we discuss new mechanisms related to BAT and energy expenditure. In this regard, we will also discuss recent studies that have revealed the existence of important secretory molecules from BAT "batokines" that act in autocrine, paracrine, and endocrine mechanisms, which in turn may explain some of the beneficial roles of BAT on whole body glucose and fat metabolism. Finally, we will discuss new insights related to BAT thermogenesis with an additional focus on the distinct features of BAT metabolism between rodents and humans.

Dietary diversity modifies the association between FTO polymorphisms and obesity phenotypes

The current study aimed to evaluate the interaction of the dietary diversity score (DDS) and FTO polymorphisms concerning obesity phenotypes. The 4480 subjects of this cohort study were selected. The polymorphisms rs1121980, rs14211085 and rs8050136 were selected and genotyped. The weighted method was used to calculate the genetic risk score (GRS). Obesity marker changes were calculated. Those with minor allele carriers of rs1121980 had lower body mass index changes (Q1: 1.58 ± 0.60 vs. Q4: 0.13 ± 0.59) and visceral adiposity index (VAI) (Q1: -0.00 ± 0.02 vs. Q4: -0.04 ± 0.02) when they had higher DDS (P interaction = 0.05). Carriers of the minor allele of rs8050136 had significant VAI change across DDS quartiles (Q1: -0.01 ± 0.02 vs. Q4: -0.02 ± 0.02, P interaction = 0.05). No significant interaction was found between the GRS and DDS on general obesity. The pattern of dietary diversity may have a mediatory role in improving obesity markers in subjects with a more genetic predisposition to adiposity.

Long Noncoding RNA MALAT1 and Regulation of the Antioxidant Defense System in Diabetic Retinopathy

The retina experiences increased oxidative stress in diabetes, and the transcriptional activity of Nrf2, which is critical in regulating many antioxidant genes, is decreased. The nuclear movement/transcriptional activity of Nrf2 is mediated by its intracellular inhibitor Keap1, and retinal Keap1 levels are increased in diabetes. Gene expression is also regulated by long noncoding RNAs (LncRNAs). Our aim was to investigate the role of LncRNA MALAT1 in the regulation of Keap1-Nrf2-antioxidant defense in diabetic retinopathy. LncRNA MALAT1 expression (quantitative real-time PCR, immunofluorescence, and RNA sequencing), its interactions with Keap1 (FACS), Keap1-Nrf2 interactions, and transcription of the antioxidant response genes (immunofluorescence and nuclear RNA sequencing) were investigated in retinal endothelial cells exposed to high glucose. Glucose increased LncRNA MALAT1 levels by increasing Sp1 transcription factor binding at its promoter. Downregulation of LncRNA MALAT1 by its siRNA prevented glucose-induced increase in Keap1 and facilitated Nrf2 nuclear translocation and antioxidant gene transcription. Retinal microvessels from streptozotocin-induced diabetic mice and human donors with diabetic retinopathy also presented similar increases in LncRNA MALAT1 and its interactions with Keap1 and decreases in Nrf2-mediated antioxidant defense genes. Thus, LncRNA MALAT1, via Keap1-Nrf2, regulates antioxidant defense in diabetic retinopathy. Inhibition of LncRNA MALAT1 has potential to protect the retina from oxidative damage and to prevent or slow down diabetic retinopathy.

Gene regulation by long non-coding RNAs and its biological functions

Evidence accumulated over the past decade shows that long non-coding RNAs (lncRNAs) are widely expressed and have key roles in gene regulation. Recent studies have begun to unravel how the biogenesis of lncRNAs is distinct from that of mRNAs and is linked with their specific subcellular localizations and functions. Depending on their localization and their specific interactions with DNA, RNA and proteins, lncRNAs can modulate chromatin function, regulate the assembly and function of membraneless nuclear bodies, alter the stability and translation of cytoplasmic mRNAs and interfere with signalling pathways. Many of these functions ultimately affect gene expression in diverse biological and physiopathological contexts, such as in neuronal disorders, immune responses and cancer. Tissue-specific and condition-specific expression patterns suggest that lncRNAs are potential biomarkers and provide a rationale to target them clinically. In this Review, we discuss the mechanisms of lncRNA biogenesis, localization and functions in transcriptional, post-transcriptional and other modes of gene regulation, and their potential therapeutic applications.

Regulation of bone marrow mesenchymal stem cell fate by long non-coding RNA

Bone mesenchymal stem cells (BMSCs) are progenitor cells isolated from bone marrow, which keep potential to differentiate into several kinds of cells including osteoblasts and adipocytes. A dynamic mutual regulation exists between osteogenesis and adipogenesis processes. Long non-coding RNA (lncRNA) performs diverse functions in biological activities including regulation of BMSCs commitment. Evidence has shown that lncRNA regulates key signaling pathways including TGFβ/BMP, Wnt and Notch pathways, and several transcription factors in BMSCs differention. Dysregulation of lncRNA in BMSCs leads to disruption of osteo-adipogenesis difffrentiation and results in impairment of bone homeostasis. In this review, we focus on the role of lncRNA in several critical signaling pathways that involved in regulation of osteo-adipogenesis of BMSC and prospects the potential clinical application of lncRNA.

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.

Microarray Analysis of lncRNA and mRNA Reveals Enhanced Lipolysis Along With Metabolic Remodeling in Mice Infected With Larval Echinococcus granulosus

Parasitic infection improves metabolic homeostasis in “western diet”-induced obesity through the regulation of adipogenesis. However, the underlying mechanism is not yet fully understood. Using microarray analysis, this study investigated the long non-coding RNA (lncRNA) and messenger RNA (mRNA) profiles of subcutaneous adipose tissues from mice infected with Echinococcus granulosus protoscoleces. A total of 1052 mRNA (541 upregulated, 511 downregulated) and 220 lncRNA (126 upregulated, 94 downregulated) transcripts were differentially expressed (fold change ≥2, P < 0.05) in the infected subcutaneous adipose tissues. When compared with the control group, the infected mice showed a decrease in adipose tissue mass and a reduction in adipocyte size. Indirect calorimetry revealed the change in the energy metabolism after infection, characterized by a lower CO₂ production and O₂ consumption, a sharp decline in carbohydrate oxidation, and a slight increase in fat oxidation. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses showed that the parasitic infection reprogrammed a complex metabolic network. Notably, “lipoxygenase” and “arginine and proline metabolism” pathways were significantly upregulated while “glycolysis,” “tricarboxylic acid cycle,” “de novo lipogenesis,” and “lipid droplet” pathways were dramatically downregulated. In addition, several key lncRNAs were associated with insulin resistance and adipocyte differentiation. Overall, the present study suggested that E. granulosus infection could enhance lipolysis. Thus, our findings provide novel insights into parasite-mediated metabolic homeostasis, and into the mechanism of hypertrophic adipocytes in obesity.

Long non-coding RNAs in regulation of adipogenesis and adipose tissue function

Complex interaction between genetics, epigenetics, environment, and nutrition affect the physiological activities of adipose tissues and their dysfunctions, which lead to several metabolic diseases including obesity or type 2 diabetes. Here, adipogenesis appears to be a process characterized by an intricate network that involves many transcription factors and long noncoding RNAs (lncRNAs) that regulate gene expression. LncRNAs are being investigated to determine their contribution to adipose tissue development and function. LncRNAs possess multiple cellular functions, and they regulate chromatin remodeling, along with transcriptional and post-transcriptional events; in this way, they affect gene expression. New investigations have demonstrated the pivotal role of these molecules in modulating white and brown/beige adipogenic tissue development and activity. This review aims to provide an update on the role of lncRNAs in adipogenesis and adipose tissue function to promote identification of new drug targets for treating obesity and related metabolic diseases.

Integrated Transcriptome Analysis of Human Visceral Adipocytes Unravels Dysregulated microRNA-Long Non-coding RNA-mRNA Networks in Obesity and Colorectal Cancer

Obesity, and the obesity-associated inflammation, represents a major risk factor for the development of chronic diseases, including colorectal cancer (CRC). Dysfunctional visceral adipose tissue (AT) is now recognized as key player in obesity-associated morbidities, although the biological processes underpinning the increased CRC risk in obese subjects are still a matter of debate. Recent findings have pointed to specific alterations in the expression pattern of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), and long non-coding RNAs (lncRNAs), as mechanisms underlying dysfunctional adipocyte phenotype in obesity. Nevertheless, the regulatory networks and interrelated processes relevant for adipocyte functions, that may contribute to a tumor-promoting microenvironment, are poorly known yet. To this end, based on RNA sequencing data, we identified lncRNAs and miRNAs, which are aberrantly expressed in visceral adipocytes from obese and CRC subjects, as compared to healthy lean control, and validated a panel of modulated ncRNAs by real-time qPCR. Furthermore, by combining the differentially expressed lncRNA and miRNA profiles with the transcriptome analysis dataset of adipocytes from lean and obese subjects affected or not by CRC, lncRNA-miRNA-mRNA adipocyte networks were defined for obese and CRC subjects. This analysis highlighted several ncRNAs modulation that are common to both obesity and CRC or unique of each disorder. Functional enrichment analysis of network-related mRNA targets, revealed dysregulated pathways associated with metabolic processes, lipid and energy metabolism, inflammation, and cancer. Moreover, adipocytes from obese subjects affected by CRC exhibited a higher complexity, in terms of number of genes, lncRNAs, miRNAs, and biological processes found to be dysregulated, providing evidence that the transcriptional and post-transcriptional program of adipocytes from CRC patients is deeply affected by obesity. Overall, this study adds further evidence for a central role of visceral adipocyte dysfunctions in the obesity-cancer relationship.

A Newly Identified LncRNA LncIMF4 Controls Adipogenesis of Porcine Intramuscular Preadipocyte through Attenuating Autophagy to Inhibit Lipolysis

Simple Summary

Compared with lean-type pigs, the intramuscular fat content of fat-type Bamei pigs was greater. LncRNA, as a vital regular, plays an important role in numerous biological processes. However, there were a few studies on the role of lncRNAs during IMF development in pigs. Based on these, lncRNA sequencing in intramuscular adipocytes was performed to explore the effects of lncRNA on intramuscular fat deposition. RNA sequencing analysis of intramuscular adipocyte from Bamei pig (fat-type) and Yorkshire pig (lean-type) indicated that, a novel lncRNA, lncIMF4, was associated with intramuscular adipogenesis. In addition, further researches showed that knockdown lncIMF4 promoted proliferation and adipogenic differentiation of porcine intramuscular adipocytes, whereas inhibited autophagy. Moreover, knockdown lncIMF4 facilitated intramuscular adipogenesis through attenuating autophagy to repress the lipolysis. Our findings will contribute to better understand the mechanism of lncRNA controlling adipogenesis in pig. Furthermore, it also provides a new perspective to study the role of lncRNA in regulating porcine intramuscular adipogenesis for promoting pork quality.

Abstract

Intramuscular fat (IMF) is implicated in juiciness, tenderness, and flavor of pork. Meat quality of Chinese fat-type pig is much better than that of lean-type pig because of its higher IMF content. LncRNA is a vital regulator that contributes to adipogenesis. However, it is unknown about the regulation of lncRNA on IMF content. Here, by RNA sequence analysis of intramuscular adipocyte from Bamei pig (fat-type) and Yorkshire pig (lean-type), we found that a novel lncRNA, lncIMF4, was associated with adipogenesis. LncIMF4, abundant in adipose, differently expressed along with intramuscular preadipocyte proliferation and differentiation. Meanwhile, it is located both in cytoplasm and nucleus. Besides, lncIMF4 knockdown promoted proliferation and differentiation of porcine intramuscular preadipocytes, whereas inhibited autophagy. Moreover, lncIMF4 knockdown facilitated intramuscular adipogenesis through attenuating autophagy to repress the lipolysis. Our findings will contribute to understand better the mechanism of lncRNA controlling intramuscular adipogenesis for promoting pork quality.

Circular RNA SAMD4A controls adipogenesis in obesity through the miR-138-5p/EZH2 axis

A growing body of evidence has suggested that circular RNAs (circRNAs) are crucial for the regulation of gene expression and their dysregulation is implicated in several diseases. However, the function of circRNAs in obesity remains largely unexplored.

Methods: Global changes in the circRNA expression patterns were detected in adipose tissues derived from obese and lean individuals. In particular, circSAMD4A was identified as significantly differentially upregulated and was functionally analyzed, both in vitro and in vivo, using various approaches.

Results: CircSAMD4A overexpression was correlated with a poor prognosis in obese patients. By contrast, circSAMD4A knockdown inhibited differentiation in isolated preadipocytes. In high-fat diet (HFD) -induced obese mice, circSAMD4A knockdown reversed the associated weight gain, reduced food intake, lower body fat, and increased energy expenditure. These mice also exhibited increased insulin sensitivity and glucose tolerance. Furthermore, in vitro experiments indicated that circSAMD4A affected differentiation by binding to miR-138-5p and regulating EZH2 expression.

Conclusions: CircSAMD4A regulated preadipocyte differentiation by acting as a miR-138-5p sponge, and thus increasing EZH2 expression. These results suggested that circSAMD4A can serve as a potential target for obesity treatments and/or as a potential prognostic marker for obese patients following bariatric surgery.

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."

Long non-coding RNA 2310069B03Rik functions as a suppressor of Ucp1 expression under prolonged cold exposure in murine beige adipocytes

Specific conditions, such as exposure to cold, can induce the production of brown-like adipocytes in white adipose tissue. These adipocytes express high levels of uncoupling protein 1 (UCP1) and energy expended by generating heat. Thus, these are a potential target for the prevention or treatment of obesity. The present study involved a comprehensive analysis of the adipose tissue to understand the relationship between long non-coding RNA (lncRNA) 2310069B03Rik and UCP1. Cold exposure increased both lncRNA 2310069B03Rik and Ucp1 expression in inguinal white adipose tissue (iWAT). However, overexpression of lncRNA 2310069B03Rik suppressed the Ucp1 mRNA expression and the promoter activity of UCP1 in the iWAT primary adipocytes. In addition, compared to the early induction of Ucp1 expression by cold stimulation, the induction of lncRNA 2310069B03Rik expression was later. These results suggest that lncRNA 2310069B03Rik functions as a suppression factor of Ucp1 expression.