Loss of FTO in adipose tissue decreases Angptl4 translation and alters triglyceride metabolism

TGF-β1 facilitates gallbladder carcinoma metastasis by regulating FOXA1 translation efficiency through m6A modification

TGF-β1 plays a pivotal role in the metastatic cascade of malignant neoplasms. N6-methyladenosine (m6A) stands as one of the most abundant modifications on the mRNA transcriptome. However, in the metastasis of gallbladder carcinoma (GBC), the effect of TGF-β1 with mRNA m6A modification, especially the effect of mRNA translation efficiency associated with m6A modification, remains poorly elucidated. Here we demonstrated a negative correlation between FOXA1 and TGF-β1 expression in GBC. Overexpression of FOXA1 inhibited TGF-β1-induced migration and epithelial-mesenchymal transition (EMT) in GBC cells. Mechanistically, we confirmed that TGF-β1 suppressed the translation efficiency of FOXA1 mRNA through polysome profiling analysis. Importantly, both in vivo and in vitro experiments showed that TGF-β1 promoted m6A modification on the coding sequence (CDS) region of FOXA1 mRNA, which was responsible for the inhibition of FOXA1 mRNA translation by TGF-β1. We demonstrated through MeRIP and RIP assays, dual-luciferase reporter assays and site-directed mutagenesis that ALKBH5 promoted FOXA1 protein expression by inhibiting m6A modification on the CDS region of FOXA1 mRNA. Moreover, TGF-β1 inhibited the binding capacity of ALKBH5 to the FOXA1 CDS region. Lastly, our study confirmed that overexpression of FOXA1 suppressed lung metastasis and EMT in a nude mice lung metastasis model. In summary, our research findings underscore the role of TGF-β1 in regulating TGF-β1/FOXA1-induced GBC EMT and metastasis by inhibiting FOXA1 translation efficiency through m6A modification.

The rs1421085 variant within FTO promotes brown fat thermogenesis

One lead genetic risk signal of obesity-the rs1421085 T>C variant within the FTO gene-is reported to be functional in vitro but lacks evidence at an organism level. Here we recapitulate the homologous human variant in mice with global and brown adipocyte-specific variant knock-in and reveal that mice carrying the C-allele show increased brown fat thermogenic capacity and resistance to high-fat diet-induced adiposity, whereas the obesity-related phenotypic changes are blunted at thermoneutrality. Both in vivo and in vitro data reveal that the C-allele in brown adipocytes enhances the transcription of the Fto gene, which is associated with stronger chromatin looping linking the enhancer region and Fto promoter. Moreover, FTO knockdown or inhibition effectively eliminates the increased thermogenic ability of brown adipocytes carrying the C-allele. Taken together, these findings identify rs1421085 T>C as a functional variant promoting brown fat thermogenesis.

Technologies, strategies, and cautions when deconvoluting genome-wide association signals: FTO in focus

Genome-wide association studies have revealed a plethora of genetic variants that correlate with polygenic conditions. However, causal molecular mechanisms have proven challenging to fully define. Without such information, the associations are not physiologically useful or clinically actionable. By reviewing studies of the FTO locus in the genetic etiology of obesity, we wish to highlight advances in the field fueled by the evolution of technical and analytic strategies in assessing the molecular bases for genetic associations. Particular attention is drawn to extrapolating experimental findings from animal models and cell types to humans, as well as technical aspects used to identify long-range DNA interactions and their biological relevance with regard to the associated trait. A unifying model is proposed by which independent obesogenic pathways regulated by multiple FTO variants and genes are integrated at the primary cilium, a cellular antenna where signaling molecules that control energy balance convene.

Novel insights into the N6-methyladenosine RNA modification and phytochemical intervention in lipid metabolism

Epitranscriptome (RNA modification) plays a vital role in a variety of biological events. N6-methyladenosine (m6A) modification is the most prevalent mRNA modification in eukaryotic cells. Dynamic and reversible m6A modification affects the plasticity of epitranscriptome, which plays an essential role in lipid metabolism. In this review, we comprehensively delineated the role and mechanism of m6A modification in the regulation of lipid metabolism in adipose tissue and liver, and summarized phytochemicals that improve lipid metabolism disturbance by targeting m6A regulator, providing potential lead candidates for drug therapeutics. Moreover, we discussed the main challenges and possible future directions in this field.

PGE2 -EP3 axis promotes brown adipose tissue formation through stabilization of WTAP RNA methyltransferase

Brown adipose tissue (BAT) functions as a thermogenic organ and is negatively associated with cardiometabolic diseases. N⁶ -methyladenosine (m⁶ A) modulation regulates the fate of stem cells. Here, we show that the prostaglandin E₂ (PGE₂ )-E-prostanoid receptor 3 (EP3) axis was activated during mouse interscapular BAT development. Disruption of EP3 impaired the browning process during adipocyte differentiation from pre-adipocytes. Brown adipocyte-specific depletion of EP3 compromised interscapular BAT formation and aggravated high-fat diet-induced obesity and insulin resistance in vivo. Mechanistically, activation of EP3 stabilized the Zfp410 mRNA via WTAP-mediated m⁶ A modification, while knockdown of Zfp410 abolished the EP3-induced enhancement of brown adipogenesis. EP3 prevented ubiquitin-mediated degradation of WTAP by eliminating PKA-mediated ERK1/2 inhibition during brown adipocyte differentiation. Ablation of WTAP in brown adipocytes abrogated the protective effect of EP3 overexpression in high-fat diet-fed mice. Inhibition of EP3 also retarded human embryonic stem cell differentiation into mature brown adipocytes by reducing the WTAP levels. Thus, a conserved PGE₂ -EP3 axis promotes BAT development by stabilizing WTAP/Zfp410 signaling in a PKA/ERK1/2-dependent manner.

The Potential Role of m6A RNA Methylation in the Aging Process and Aging-Associated Diseases

N6-methyladenosine (m⁶A) is the most common and conserved internal eukaryotic mRNA modification. m⁶A modification is a dynamic and reversible post-transcriptional regulatory modification, initiated by methylase and removed by RNA demethylase. m⁶A-binding proteins recognise the m⁶A modification to regulate gene expression. Recent studies have shown that altered m⁶A levels and abnormal regulator expression are crucial in the ageing process and the occurrence of age-related diseases. In this review, we summarise some key findings in the field of m⁶A modification in the ageing process and age-related diseases, including cell senescence, autophagy, inflammation, oxidative stress, DNA damage, tumours, neurodegenerative diseases, diabetes, and cardiovascular diseases (CVDs). We focused on the biological function and potential molecular mechanisms of m⁶A RNA methylation in ageing and age-related disease progression. We believe that m⁶A modification may provide a new target for anti-ageing therapies.

Brown adipose TRX2 deficiency activates mtDNA-NLRP3 to impair thermogenesis and protect against diet-induced insulin resistance

Brown adipose tissue (BAT), a crucial heat-generating organ, regulates whole-body energy metabolism by mediating thermogenesis. BAT inflammation is implicated in the pathogenesis of mitochondrial dysfunction and impaired thermogenesis. However, the link between BAT inflammation and systematic metabolism remains unclear. Herein, we use mice with BAT deficiency of thioredoxin-2 (TRX2), a protein that scavenges mitochondrial reactive oxygen species (ROS), to evaluate the impact of BAT inflammation on metabolism and thermogenesis and its underlying mechanism. Our results show that BAT-specific TRX2 ablation improves systematic metabolic performance via enhancing lipid uptake, which protects mice from diet-induced obesity, hypertriglyceridemia, and insulin resistance. TRX2 deficiency impairs adaptive thermogenesis by suppressing fatty acid oxidation. Mechanistically, loss of TRX2 induces excessive mitochondrial ROS, mitochondrial integrity disruption, and cytosolic release of mitochondrial DNA, which in turn activate aberrant innate immune responses in BAT, including the cGAS/STING and the NLRP3 inflammasome pathways. We identify NLRP3 as a key converging point, as its inhibition reverses both the thermogenesis defect and the metabolic benefits seen under nutrient overload in BAT-specific Trx2-deficient mice. In conclusion, we identify TRX2 as a critical hub integrating oxidative stress, inflammation, and lipid metabolism in BAT, uncovering an adaptive mechanism underlying the link between BAT inflammation and systematic metabolism.

Critical roles of FTO-mediated mRNA m6A demethylation in regulating adipogenesis and lipid metabolism: Implications in lipid metabolic disorders

The goal this review is to clarify the effects of the fat mass and obesity-associated protein (FTO) in lipid metabolism regulation and related underlying mechanisms through the FTO-mediated demethylation of m⁶A modification. FTO catalyzes the demethylation of m⁶A to alter the processing, maturation and translation of the mRNAs of lipid-related genes. FTO overexpression in the liver promotes lipogenesis and lipid droplet (LD) enlargement and suppresses CPT-1–mediated fatty acid oxidation via the SREBP1c pathway, promoting excessive lipid storage and nonalcoholic fatty liver diseases (NAFLD). FTO enhances preadipocyte differentiation through the C/EBPβ pathway, and facilitates adipogenesis and fat deposition by altering the alternative splicing of RUNX1T1, the expression of PPARγ and ANGPTL4, and the phosphorylation of PLIN1, whereas it inhibits lipolysis by inhibiting IRX3 expression and the leptin pathway, causing the occurrence and development of obesity. Suppression of the PPARβ/δ and AMPK pathways by FTO-mediated m⁶A demethylation damages lipid utilization in skeletal muscles, leading to the occurrence of diabetic hyperlipidemia. m⁶A demethylation by FTO inhibits macrophage lipid influx by downregulating PPARγ protein expression and accelerates cholesterol efflux by phosphorylating AMPK, thereby impeding foam cell formation and atherosclerosis development. In summary, FTO-mediated m⁶A demethylation modulates the expression of lipid-related genes to regulate lipid metabolism and lipid disorder diseases.

The role of RNA m6A methylation in lipid metabolism

The m6A methylation is the most numerous modification of mRNA in mammals, coordinated by RNA m6A methyltransferases, RNA m6A demethylases, and RNA m6A binding proteins. They change the RNA m6A methylation level in their specific manner. RNA m6A modification has a significant impact on lipid metabolic regulation. The "writer" METTL3/METTL14 and the "eraser" FTO can promote the accumulation of lipids in various cells by affecting the decomposition and synthesis of lipids. The "reader" YTHDF recognizes m6A methylation sites of RNA and regulates the target genes' translation. Due to this function that regulates lipid metabolism, RNA m6A methylation plays a pivotal role in metabolic diseases and makes it a great potential target for therapy.

LuHui Derivative, A Novel Compound That Inhibits the Fat Mass and Obesity-Associated (FTO), Alleviates the Inflammatory Response and Injury in Hyperlipidemia-Induced Cardiomyopathy

Hyperlipidemia is a major risk factor for metabolic disorders and cardiovascular injury. The excessive deposition of saturated fatty acids in the heart leads to chronic cardiac inflammation, which in turn causes myocardial damage and systolic dysfunction. However, the effective suppression of cardiac inflammation has emerged as a new strategy to reduce the impact of hyperlipidemia on cardiovascular disease. In this study, we identified a novel monomer, known as LuHui Derivative (LHD), which reduced the serum levels of total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and reduced lipid deposition in cardiomyocytes. In addition, LHD treatment improved cardiac function, reduced hyperlipidemia-induced inflammatory infiltration in cardiomyocytes and suppressed the release of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). From a mechanistic perspective, cluster of differentiation 36 (CD36), an important cell surface receptor, was identified as a downstream target following the LHD treatment of palmitic acid-induced inflammation in cardiomyocytes. LHD specifically binds the pocket containing the regulatory sites of RNA methylation in the fat mass and obesity-associated (FTO) protein that is responsible for elevated intracellular m⁶A levels. Moreover, the overexpression of the N6-methyladenosine (m⁶A) demethylase FTO markedly increased CD36 expression and suppressed the anti-inflammatory effects of LHD. Conversely, loss-of-function of FTO inhibited palmitic acid-induced cardiac inflammation and altered CD36 expression by diminishing the stability of CD36 mRNA. Overall, our results provide evidence for the crucial role of LHD in fatty acid-induced cardiomyocyte inflammation and present a new strategy for the treatment of hyperlipidemia and its complications.

Regulatory role and mechanism of m6A RNA modification in human metabolic diseases

Metabolic diseases caused by disorders in amino acids, glucose, lipid metabolism, and other metabolic risk factors show high incidences in young people, and current treatments are ineffective. N⁶-methyladenosine (m⁶A) RNA modification is a post-transcriptional regulation of gene expression with several effects on physiological processes and biological functions. Recent studies report that m⁶A RNA modification is involved in various metabolic pathways and development of common metabolic diseases, making it a potential disease-specific therapeutic target. This review explores components, mechanisms, and research methods of m⁶A RNA modification. In addition, we summarize the progress of research on m⁶A RNA modification in metabolism-related human diseases, including diabetes, obesity, non-alcoholic fatty liver disease, osteoporosis, and cancer. Furthermore, opportunities and the challenges facing basic research and clinical application of m⁶A RNA modification in metabolism-related human diseases are discussed. This review is meant to enhance our understanding of the molecular mechanisms, research methods, and clinical significance of m⁶A RNA modification in metabolism-related human diseases.

FTO inhibits UPRmt-induced apoptosis by activating JAK2/STAT3 pathway and reducing m6A level in adipocytes

As a nucleic acid demethylase, Fat and obesity associated gene (FTO) plays a vital role in modulating adipose metabolism. However, it is still unknown how FTO affects apoptosis in adipocytes. In this study, we found that overexpression of FTO inhibited the expression of pro-apoptosis factors Caspase-3, Caspase-9 and Bax and mitochondrial unfolded protein response (UPR^mt) markers HSP60 and ClpP in vivo and in vitro. Particularly, overexpression of FTO inhibited mitochondria-dependent apoptosis in adipocytes. Further studies revealed that FTO suppressed UPR^mt by reducing HSP60 mRNA N6-methyladenosine (m6A) modification. Moreover, FTO inhibited the activation of Caspase-3 via JAK2/STAT3 signaling pathway in adipocytes. Further experiments showed that pro-apoptosis gene Bax was upregulated by UPR^mt-activated PKR/eIF2α/ATF5 axis in adipocytes. In summary, this study confirms that FTO reduces adipocytes apoptosis by activiting JAK2/STAT3 signaling pathway and inhibiting UPR^mt, revealing a novel mechanism of FTO on adipocytes apoptosis, which provides some new potential therapy for treating obesity and related metabolic syndromes.

Epigenetic role of N6-methyladenosine (m6A) RNA methylation in the cardiovascular system

As the most prevalent and abundant transcriptional modification in the eukaryotic genome, the continuous and dynamic regulation of N6-methyladenosine (m6A) has been shown to play a vital role in physiological and pathological processes of cardiovascular diseases (CVDs), such as ischemic heart failure (HF), myocardial hypertrophy, myocardial infarction (MI), and cardiomyogenesis. Regulation is achieved by modulating the expression of m6A enzymes and their downstream cardiac genes. In addition, this process has a major impact on different aspects of internal biological metabolism and several other external environmental effects associated with the development of CVDs. However, the exact molecular mechanism of m6A epigenetic regulation has not been fully elucidated. In this review, we outline recent advances and discuss potential therapeutic strategies for managing m6A in relation to several common CVD-related metabolic disorders and external environmental factors. Note that an appropriate understanding of the biological function of m6A in the cardiovascular system will pave the way towards exploring the mechanisms responsible for the development of other CVDs and their associated symptoms. Finally, it can provide new insights for the development of novel therapeutic agents for use in clinical practice.

Epigenetic regulation of adipose tissue expansion and adipogenesis by N6 -methyladenosine

Obesity, defined as excessive fat accumulation, is strongly associated with metabolic diseases and cancer, and its prevalence is rising worldwide. Thus, understanding the molecular mechanism of adipogenesis is of fundamental significance. Epigenetic modifications play important roles in regulating adipogenesis. N⁶ -methyladenosine (m⁶ A), the most prevalent and abundant mRNA modification in eukaryotic cells, modulates multiple aspects of RNA metabolism, including mRNA stability, translation, splicing and export. Recent studies indicate that m⁶ A methylation plays important roles in modulating gene expression and signal pathways in various physiologic processes and diseases. Notably, the significant function and regulatory mechanisms of m⁶ A in adipogenesis are now emerging. In this review, we summarize recent studies that elucidate the vital roles of m⁶ A modifications in regulating adipogenesis and adipose tissue expansion. Furthermore, we highlight the nutritional regulation of m⁶ A methylation and adipogenesis, which may prove a novel therapeutic strategy to fight against obesity.

m6A RNA Methylation: Ramifications for Gene Expression and Human Health

Cellular transcriptomes are frequently adorned by a variety of chemical modification marks, which in turn have a profound influence on its functioning. Of these modifications, the one which has invited a lot of attention in the recent years is m6A RNA methylation, leading to the development of RNA epigenetics or epitranscriptomics as a frontier research area. m6A RNA methylation is one of the most abundant reversible internal modification seen in cellular RNAs. Studies in the last few years have not only shed light on the molecular machinery involved in m6A RNA methylation but also on the impact of this modification in regulating gene expression and hence biological processes. In this review, we will emphasize the biological impact of this modification in normal organismal development and diseases.

FTO variants are associated with ANGPTL4 abundances and correlated with body weight reduction after bariatric surgery

BACKGROUND

The FTO (fat mass- and obesity-associated) gene variant is an established obesity-susceptibility locus. FTO protein is a nucleic acid demethylase and FTO genetic variants form long-range functional connections with IRX3, which regulates fat mass and metabolism in humans. From our previous results, we found FTO regulates the metabolism of triglyceride in adipocytes through demethylating Angptl4 (angiopoietin-like protein 4) mRNA in mice. We hypothesized that the FTO genetic variants regulate ANGPTL4 abundances in human adipose tissues and affect the outcome after bariatric surgery.

METHODS AND RESULTS

We recruited 188 obesity subjects with body mass indices (BMI)>35kg/m² and 102 non-obese subjects with BMI<30kg/m² from the OCEAN registry between 2011 and 2014. The distribution of FTO variants rs9939609 among participates was 73.79% TT, 23.79% AT, and 2.41% AA. The subjects with FTO variants AA or AT were correlated with higher BMI than those with FTO variants TT. The serum ANGPTL4 levels were significantly higher in obese subjects and positively correlated with the presence of FTO AA or AT haplotype. Of these participates, 84 obese subjects underwent bariatric surgery and adipose Angptl4 expressions were analyzed. The adipose Angptl4 mRNA levels and protein abundances were correlated with FTO AA or AT haplotype. The magnitude of excess body weight reduction 2 years after bariatric surgery was correlated with the adipose ANGPTL4 protein levels.

CONCLUSION

Adipose ANGPTL4 abundances were affected by the presence of FTO obesity risk haplotype and correlated with excess weight loss percentage after bariatric surgery. These data signify the critical role of FTO variants and adipose ANGPTL4 in fatty acid metabolism and bariatric outcomes in humans.

Regulation of autophagy in leukocytes through RNA N6-adenosine methylation in chronic kidney disease patients

Patients with chronic kidney diseases have multiple cellular dysfunctions leading to increased atherosclerosis, impaired immunity, and disturbed metabolism. However, it is unclear what is the fundamental signaling served as a marker or as a mediator for the dysregulated function in their leukocytes or tissues. Here we hypothesized that the N⁶-Methyladenosine (m⁶A) modification of the RNA in the leukocytes is responsible for the cellular dysfunction in chronic kidney diseases. Patients with chronic kidney diseases had significantly less m⁶A abundances in leukocytes and elevated RNA demethylase FTO proteins. The uremic toxin, indoxyl sulfate, activated the autophagy flux through modulation of FTO and m⁶A modifications in RNA. Notably, knockdown of FTO or inhibit the m⁶A by 3-deazaadenosine blocks the effects of indoxyl sulfate on autophagy activation in cells. These findings provide new insights into the mechanisms underlying chronic kidney disease-associated cellular dysfunction. Targeting RNA m⁶A modification may be a novel strategy for the treatment of chronic kidney diseases and autophagy.

Molecular pathway analysis associates alterations in obesity-related genes and antipsychotic-induced weight gain

OBJECTIVE

Antipsychotics often induce excessive weight gain. We hypothesised that individuals with genetic variations related to known obesity-risk genes have an increased risk of excessive antipsychotic-induced weight gain (AIWG). This hypothesis was tested in a subset of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) trial data set.

METHODS

The CATIE trial compared effects and side effects of five different antipsychotics through an 18-month period. Based on the maximum weight gain recorded, excessive weight gain was defined as >7% weight gain. Cytoscape and GeneMANIA were instrumental in composing a molecular pathway from eight selected genes linked to obesity. Genetic information on a total of 495.172 single-nucleotide polymorphisms (SNPs) were available from 765 (556 males) individuals. Enrichment test was conducted through ReactomePA and Bioconductor. A permutation test was performed, testing the generated pathway against 105 permutated pathways (p ≤ 0.05). In addition, a standard genome-wide association study (GWAS) analysis was performed.

RESULT

GWAS analysis did not detect significant differences related to excessive weight gain. The pathway generated contained 28 genes. A total of 2067 SNPs were significantly expressed (p < 0.01) within this pathway when comparing excessive weight gainers to the rest of the sample. Affected genes including PPARG and PCSK1 were not previously related to treatment-induced weight gain.

CONCLUSIONS

The molecular pathway composed from high-risk obesity genes was shown to overlap with genetics of patients who gained >7% weight gain during the CATIE trial. This suggests that genes related to obesity compose a pathway of increased risk of excessive AIWG. Further independent analyses are warranted that may confirm or clarify the possible reasoning behind.

The RNA demethylase FTO is required for maintenance of bone mass and functions to protect osteoblasts from genotoxic damage

The fat mass and obesity-associated gene (FTO) encodes an m6A RNA demethylase that controls mRNA processing and has been linked to both obesity and bone mineral density in humans by genome-wide association studies. To examine the role of FTO in bone, we characterized the phenotype of mice lacking Fto globally (FtoKO ) or selectively in osteoblasts (FtoOcKO ). Both mouse models developed age-related reductions in bone volume in both the trabecular and cortical compartments. RNA profiling in osteoblasts following acute disruption of Fto revealed changes in transcripts of Hspa1a and other genes in the DNA repair pathway containing consensus m6A motifs required for demethylation by FtoFto KO osteoblasts were more susceptible to genotoxic agents (UV and H2O2) and exhibited increased rates of apoptosis. Importantly, forced expression of Hspa1a or inhibition of NF-κB signaling normalized the DNA damage and apoptotic rates in Fto KO osteoblasts. Furthermore, increased metabolic stress induced in mice by feeding a high-fat diet induced greater DNA damage in osteoblast of FtoOc KO mice compared to controls. These data suggest that FTO functions intrinsically in osteoblasts through Hspa1a-NF-κB signaling to enhance the stability of mRNA of proteins that function to protect cells from genotoxic damage.

Epitranscriptomic RNA Methylation in Plant Development and Abiotic Stress Responses

Recent advances in methylated RNA immunoprecipitation followed by sequencing and mass spectrometry have revealed widespread chemical modifications on mRNAs. Methylation of RNA bases such as N ⁶-methyladenosine (m⁶A) and 5-methylcytidine (m⁵C) is the most prevalent mRNA modifications found in eukaryotes. In recent years, cellular factors introducing, interpreting, and deleting specific methylation marks on mRNAs, designated as "writers (methyltransferase)," "readers (RNA-binding protein)," and "erasers (demethylase)," respectively, have been identified in plants and animals. An emerging body of evidence shows that methylation on mRNAs affects diverse aspects of RNA metabolism, including stability, splicing, nucleus-to-cytoplasm export, alternative polyadenylation, and translation. Although our understanding for roles of writers, readers, and erasers in plants is far behind that for their animal counterparts, accumulating reports clearly demonstrate that these factors are essential for plant growth and abiotic stress responses. This review emphasizes the crucial roles of epitranscriptomic modifications of RNAs in new layer of gene expression regulation during the growth and response of plants to abiotic stresses.

MiR-122 marks the differences between subcutaneous and visceral adipose tissues and associates with the outcome of bariatric surgery

The physiological roles and clinical impacts of the differences between visceral fat (VF) and subcutaneous fat (SF) are unclear. The present study aimed to compare the miRNA signatures between visceral fat (VF) and subcutaneous fat (SF) and study their influences on outcomes of bariatric surgery. To study the microRNA signatures of the VF and SF in obesity, we performed paired microRNA arrays of the adipose tissues from 20 bariatric surgery patients. The microRNA analysis identified miR-122 as the most significant signature between VF and SF. The tissue distribution, functions, and influences on adipogensis of miR-122 were analysed by Northern blotting, microRNA mimics and inhibitors, and whole-genome microarray analysis. The outcomes of body weight changes after bariatric surgery were analysed and correlated with the miR-122 abundances. Northern blotting confirmed that miR-122 was highly expressed in VF and SF. Bioinformatics analysis of the microarray revealed that proliferator activator receptor-γ (PPAR-γ) signalling was critically affected by miR-122. The modulation of PPAR-γ by miR-122 was confirmed in murine adipocytes and human adipose tissues. Furthermore, the differentiation of preadipocytes was significantly influenced by miR-122. In obese patients receiving bariatric surgery, the ratio of VF and SF miR-122 abundance correlated with 6-month and 1-year % excess body weight loss. Our findings indicate that miR-122 is highly expressed in adipose tissue. The abundance of miR-122 affects PPAR-γ signalling and adipocytes differentiation in vitro and human adipose tissues. Higher miR-122 in VF may be associated with greater body weight loss after bariatric surgery.

FTO mediates cell-autonomous effects on adipogenesis and adipocyte lipid content by regulating gene expression via 6mA DNA modifications

SNPs in the first intron of α-ketoglutarate-dependent dioxygenase (FTO) convey effects on adiposity by mechanisms that remain unclear, but appear to include modulation of expression of FTO itself, as well as other genes in cisFTO expression is lower in fibroblasts and iPSC-derived neurons of individuals segregating for FTO obesity risk alleles. We employed in vitro adipogenesis models to investigate the molecular mechanisms by which Fto affects adipocyte development and function. Fto expression was upregulated during adipogenesis, and was required for the maintenance of CEBPB and Cebpd/CEBPD expression in murine and human adipocytes in vitro. Fto knockdown decreased the number of 3T3-L1 cells that differentiated into adipocytes as well as the amount of lipid per mature adipocyte. This effect on adipocyte programming was conveyed, in part, by modulation of CCAAT enhancer binding protein (C/ebp)β-regulated transcription. We found that Fto also affected Cebpd transcription by demethylating DNA N6-methyldeoxyadenosine in the Cebpd promoter. Fto is permissive for adipogenesis and promotes maintenance of lipid content in mature adipocytes by enabling C/ebpβ-driven transcription and expression of Cebpd These findings are consistent with the loss of fat mass in mice segregating for a dominant-negative Fto allele.

Regulatory Role of N6 -methyladenosine (m6 A) Methylation in RNA Processing and Human Diseases

N⁶ -methyladenosine (m⁶ A) modification is an abundant and conservative RNA modification in bacterial and eukaryotic cells. m⁶ A modification mainly occurs in the 3' untranslated regions (UTRs) and near the stop codons of mRNA. Diverse strategies have been developed for identifying m⁶ A sites in single nucleotide resolution. Dynamic regulation of m⁶ A is found in metabolism, embryogenesis, and developmental processes, indicating a possible epigenetic regulation role along RNA processing and exerting biological functions. It has been known that m⁶ A editing involves in nuclear RNA export, mRNA degradation, protein translation, and RNA splicing. Deficiency of m⁶ A modification will lead to kinds of diseases, such as obesity, cancer, type 2 diabetes mellitus (T2DM), infertility, and developmental arrest. Some specific inhibitors against methyltransferase and demethylase have been developed to selectively regulate m⁶ A modification, which may be advantageous for treatment of m⁶ A related diseases. J. Cell. Biochem. 118: 2534-2543, 2017. © 2017 Wiley Periodicals, Inc.

MicroRNA-4739 regulates osteogenic and adipocytic differentiation of immortalized human bone marrow stromal cells via targeting LRP3

Understanding the regulatory networks underlying lineage differentiation and fate determination of human bone marrow stromal cells (hBMSC) is a prerequisite for their therapeutic use. The goal of the current study was to unravel the novel role of the low-density lipoprotein receptor-related protein 3 (LRP3) in regulating the osteogenic and adipogenic differentiation of immortalized hBMSCs. Gene expression profiling revealed significantly higher LRP3 levels in the highly osteogenic hBMSC clone imCL1 than in the less osteogenic clone imCL2, as well as a significant upregulation of LRP3 during the osteogenic induction of the imCL1 clone. Data from functional and gene expression assays demonstrated the role of LRP3 as a molecular switch promoting hBMSC lineage differentiation into osteoblasts and inhibiting differentiation into adipocytes. Interestingly, microRNA (miRNA) expression profiling identified miR-4739 as the most under-represented miRNA (-36.11 fold) in imCL1 compared to imCL2. The TargetScan prediction algorithm, combined with functional and biochemical assays, identified LRP3 mRNA as a novel target of miR-4739, with a single potential binding site for miR-4739 located in the LRP3 3' UTR. Regulation of LRP3 expression by miR-4739 was subsequently confirmed by qRT-PCR, western blotting, and luciferase assays. Over-expression of miR-4739 mimicked the effects of LRP3 knockdown on promoting adipogenic and suppressing osteogenic differentiation of hBMSCs. Hence, we report for the first time a novel biological role for the LRP3/hsa-miR-4739 axis in balancing osteogenic and adipocytic differentiation of hBMSCs. Our data support the potential utilization of miRNA-based therapies in regenerative medicine.

A Method for Measuring RNA N 6-methyladenosine Modifications in Cells and Tissues

N⁶-Methyladenosine (m⁶A) modifications of RNA are diverse and ubiquitous amongst eukaryotes. They occur in mRNA, rRNA, tRNA, and microRNA. Recent studies have revealed that these reversible RNA modifications affect RNA splicing, translation, degradation, and localization. Multiple physiological processes, like circadian rhythms, stem cell pluripotency, fibrosis, triglyceride metabolism, and obesity are also controlled by m⁶A modifications. Immunoprecipitation/sequencing, mass spectrometry, and modified northern blotting are some of the methods commonly employed to measure m⁶A modifications. Herein, we present a northeastern blotting technique for measuring m⁶A modifications. The current protocol provides good size separation of RNA, better accommodation and standardization for various experimental designs, and clear delineation of m⁶A modifications in various sources of RNA. While m⁶A modifications are known to have a crucial impact on human physiology relating to circadian rhythms and obesity, their roles in other (patho)physiological states are unclear. Therefore, investigations on m⁶A modifications have immense possibility to provide key insights into molecular physiology.

Hepatic expression of FTO and fatty acid metabolic genes changes in response to lipopolysaccharide with alterations in m6A modification of relevant mRNAs in the chicken

The fat mass and obesity associated (FTO) gene, which encodes a demethylase of m⁶A, has been reported to respond to lipopolysaccharide (LPS) and to serve as a link between inflammation and metabolic responses. The objective of this study was to determine whether LPS-induced changes in the expression of FTO and metabolic genes are associated with alterations of m⁶A in relevant mRNAs. LPS challenge significantly decreased hepatic mRNA expression of carnitine palmitoyl transferase 1 (CPT1) and CPT2, which coincided with a tendency of higher triglyceride accumulation in the liver. LPS significantly down-regulated the full length cFTO1, yet up-regulated the truncated cFTO4 protein in the liver nuclear extracts. Nuclear protein content of cFTO4 in the liver was negatively correlated with the mRNA abundances of CPT1 (r = 0.629) and CPT2 (r = 0.622). Methylated RNA immunoprecipitation analysis revealed that the m⁶A level around the translation start site of CPT1 was markably decreased in the liver of LPS-treated chickens. These results indicate that LPS-induced changes in FTO protein expression are associated with alteration of mRNA m⁶A modification in chicken liver.