FTO variant is associated with changes in BMI, ghrelin, and brain function following bariatric surgery

BACKGROUNDA polymorphism in the fat mass and obesity-associated gene (FTO) is linked to enhanced neural sensitivity to food cues and attenuated ghrelin suppression. Risk allele carriers regain more weight than noncarriers after bariatric surgery. It remains unclear how FTO variation affects brain function and ghrelin following surgery.METHODSResting-state functional magnetic resonance imaging and cue-reactivity functional magnetic resonance imaging with high-/low-caloric food cues were performed before surgery and at 1, 6, and 12 months after surgery to examine brain function in 16 carriers with 1 copy of the rs9939609 A allele (AT) and 26 noncarriers (TT). Behavioral assessments up to 5 years after surgery were also conducted.RESULTSThe AT group relative to the TT group had smaller BMI loss at 12-60 months after surgery and lower resting-state activity in posterior cingulate cortex following laparoscopic sleeve gastrectomy (group-by-time interaction effects). Meanwhile, the AT group relative to the TT group showed greater food cue responses in dorsolateral prefrontal cortex (DLPFC), dorsomedial prefrontal cortex (DMPFC), and insula (group effects). There were negative associations of weight loss with ghrelin and greater activation in DLPFC, DMPFC and insula in the AT but not the TT group.CONCLUSIONThese findings indicate that FTO variation is associated with the evolution of ghrelin signaling and brain function after bariatric surgery, which might hinder weight loss.TRIAL REGISTRATIONChinese Clinical Trial Registry Center, ChiCTR-OOB-15006346.FUNDINGThis work was supported by the National Natural Science Foundation of China (grant nos. 82172023, 82202252, 82302292); National Key R&D Program of China (no. 2022YFC3500603); Natural Science Basic Research Program of Shaanxi (grant nos. 2022JC-44, 2022JQ-622, 2023-JC-QN-0922, 2023-ZDLSF-07); Fundamental Research Funds for the Central Universities (grant nos. ZYTS23188, XJSJ23190, XJS221201, QTZX23093); and the Intramural Research Program of the National Institute on Alcoholism and Alcohol Abuse (grant no. Y1AA3009).

Identification of key genes involved in collagen hydrogel-induced chondrogenic differentiation of mesenchymal stem cells through transcriptome analysis: the role of m6A modification

Collagen hydrogel has been shown promise as an inducer for chondrogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), contributing to the repair of cartilage defects. However, the precise molecular mechanism underlying this phenomenon remains poorly elucidated. Here, we induced chondrogenic differentiation of BMSCs using collagen hydrogel and identified 4451 differentially expressed genes (DEGs) through transcriptomic sequencing. Our analysis revealed that DEGs were enriched in the focal adhesion pathway, with a notable decrease in expression levels in the collagen hydrogel group compared to the control group. Protein-protein interaction network analysis suggested that actinin alpha 1 (ACTN1) and actinin alpha 4 (ACTN4), two proteins also involved in cytoskeletal recombination, may be crucial in collagen hydrogel-induced chondrogenic differentiation of BMSCs. Additionally, we found that N6-methyladenosine RNA methylation (m6A) modification was involved in collagen hydrogel-mediated chondrogenic differentiation, with fat mass and obesity-associated protein (FTO) implicated in regulating the expression of ACTN1 and ACTN4. These findings suggest that collagen hydrogel might regulate focal adhesion and actin cytoskeletal signaling pathways through down-regulation of ACTN1 and ACTN4 mRNA via FTO-mediated m6A modification, ultimately driving chondrogenic differentiation of BMSCs. In conclusion, our study provides valuable insights into the molecular mechanisms of collagen hydrogel-induced chondrogenic differentiation of BMSCs, which may aid in developing more effective strategies for cartilage regeneration.

Risk of Fat Mass- and Obesity-Associated Gene-Dependent Obesogenic Programming by Formula Feeding Compared to Breastfeeding

It is the purpose of this review to compare differences in postnatal epigenetic programming at the level of DNA and RNA methylation and later obesity risk between infants receiving artificial formula feeding (FF) in contrast to natural breastfeeding (BF). FF bears the risk of aberrant epigenetic programming at the level of DNA methylation and enhances the expression of the RNA demethylase fat mass- and obesity-associated gene (FTO), pointing to further deviations in the RNA methylome. Based on a literature search through Web of Science, Google Scholar, and PubMed databases concerning the dietary and epigenetic factors influencing FTO gene and FTO protein expression and FTO activity, FTO's impact on postnatal adipogenic programming was investigated. Accumulated translational evidence underscores that total protein intake as well as tryptophan, kynurenine, branched-chain amino acids, milk exosomal miRNAs, NADP, and NADPH are crucial regulators modifying FTO gene expression and FTO activity. Increased FTO-mTORC1-S6K1 signaling may epigenetically suppress the WNT/β-catenin pathway, enhancing adipocyte precursor cell proliferation and adipogenesis. Formula-induced FTO-dependent alterations of the N6-methyladenosine (m6A) RNA methylome may represent novel unfavorable molecular events in the postnatal development of adipogenesis and obesity, necessitating further investigations. BF provides physiological epigenetic DNA and RNA regulation, a compelling reason to rely on BF.

Highly sensitive and selective demethylase FTO detection using a DNAzyme-mediated CRISPR/Cas12a signal cascade amplification electrochemiluminescence biosensor with C-CN/PCNV heterojunction as emitter

Fat mass and obesity-associated protein (FTO) has gained attention as the first RNA N6-methyladenosine (m6A) modification eraser due to its overexpression being associated with various cancers. In this study, an electrochemiluminescence (ECL) biosensor for the detection of demethylase FTO was developed based on DNAzyme-mediated CRISPR/Cas12a signal cascade amplification system and carboxylated carbon nitride nanosheets/phosphorus-doped nitrogen-vacancy modified carbon nitride nanosheets (C-CN/PCNV) heterojunction as the emitter. The biosensor was constructed by modifying the C-CN/PCNV heterojunction and a ferrocene-tagged probe (ssDNA-Fc) on a glassy carbon electrode. The presence of FTO removes the m6A modification on the catalytic core of DNAzyme, restoring its cleavage activity and generating activator DNA. This activator DNA further activates the trans-cleavage ability of Cas12a, leading to the cleavage of the ssDNA-Fc and the recovery of the ECL signal. The C-CN/PCNV heterojunction prevents electrode passivation and improves the electron-hole recombination, resulting in significantly enhanced ECL signal. The biosensor demonstrates high sensitivity with a low detection limit of 0.63 pM in the range from 1.0 pM to 100 nM. Furthermore, the biosensor was successfully applied to detect FTO in cancer cell lysate and screen FTO inhibitors, showing great potential in early clinical diagnosis and drug discovery.

SUMOylation modification of FTO facilitates oxidative damage response of arsenic by IGF2BP3 in an m6A-dependent manner

N6-methyladenosine (m6A) is the most common form of internal post-transcriptional methylation observed in eukaryotic mRNAs. The abnormally increased level of m6A within the cells can be catalyzed by specific demethylase fat mass and obesity-associated protein (FTO) and stay in a dynamic and reversible state. However, whether and how FTO regulates oxidative damage via m6A modification remain largely unclear. Herein, by using both in vitro and in vivo models of oxidative damage induced by arsenic, we demonstrated for the first time that exposure to arsenic caused a significant increase in SUMOylation of FTO protein, and FTO SUMOylation at lysine (K)- 216 site promoted the down-regulation of FTO expression in arsenic target organ lung, and therefore, remarkably elevating the oxidative damage via an m6A-dependent pathway by its specific m6A reader insulin-like growth factor-2 mRNA-binding protein-3 (IGF2BP3). Consequently, these findings not only reveal a novel mechanism underlying FTO-mediated oxidative damage from the perspective of m6A, but also imply that regulation of FTO SUMOylation may serve as potential approach for treatment of oxidative damage.

RNA demethylase FTO participates in malignant progression of gastric cancer by regulating SP1-AURKB-ATM pathway

Gastric cancer (GC) is the 5th most prevalent cancer and the 4th primary cancer-associated mortality globally. As the first identified m6A demethylase for removing RNA methylation modification, fat mass and obesity-associated protein (FTO) plays instrumental roles in cancer development. Therefore, we study the biological functions and oncogenic mechanisms of FTO in GC tumorigenesis and progression. In our study, FTO expression is obviously upregulated in GC tissues and cells. The upregulation of FTO is associated with advanced nerve invasion, tumor size, and LNM, as well as the poor prognosis in GC patients, and promoted GC cell viability, colony formation, migration and invasion. Mechanistically, FTO targeted specificity protein 1 and Aurora Kinase B, resulting in the phosphorylation of ataxia telangiectasia mutated and P38 and dephosphorylation of P53. In conclusion, the m6A demethylase FTO promotes GC tumorigenesis and progression by regulating the SP1-AURKB-ATM pathway, which may highlight the potential of FTO as a diagnostic biomarker for GC patients' therapy response and prognosis.

Silencing of FTO inhibits oxidative stress to relieve neuropathic pain by m6A modification of GPR177

BACKGROUND

Neuropathic pain (NP) is a challenging health condition owing to its complex nature and associated multiple etiologies. The occurrence of NP involves the abnormal activity of neurons mediated by oxidative stress (OS). Previous research has demonstrated that m6A methylation plays a role in the regulatory pathway of NP. This study aimed to investigate the specific molecular pathways through which m6A methylation modifiers alleviate NP.

METHODS

For this purpose, an NO rat model was developed via spared nerve injury (SNI), followed by quantifying the animal's pain assessment via paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). The OS in SNI rats was evaluated by measuring reactive oxygen species, superoxide dismutase, and catalase (CAT) in spinal cord tissues. Moreover, quantitative-real-time polymerase chain reaction and western blot analysis were employed for detecting fat mass and obesity-associated (FTO) and GPR177 levels, while m6A levels of GPR117 were analyzed via MeRIP.

RESULTS

The results indicated an enhanced OS with highly expressed FTO in spinal cord tissue samples, where knocking down Fto effectively relieved NP and OS in SNI rats. Mechanistic investigations revealed that Fto-mediated reduction of Grp177 m6A modification was involved in the WNT5a/TRPV1 axis-mediated OS remission of NP. Moreover, in vitro experiment results indicated that YTHDF2 was an important m6A methylated reading protein for this process.

CONCLUSIONS

Fto silencing leads to increased m6A methylation of Grp177 through a YTHDF2-dependent mechanism, resulting in decreased Grp177 stability and ultimately reducing NP in rats by OS suppression.

FTO elicits tumor neovascularization in cancer-associated fibroblasts through eliminating m6A modifications of multiple pro-angiogenic factors

Cancer-associated fibroblasts (CAFs) exhibit notable versatility, plasticity, and robustness, actively participating in cancer progression through intricate interactions within the tumor microenvironment (TME). N6-methyladenosine (m6A) modification is the most prevalent modification in eukaryotic mRNA, playing essential roles in mRNA metabolism and various biological processes. Howbeit, the precise involvement of m6A in CAF activation remains enigmatic. In this study, we revealed that the m6A demethylase FTO supports CAF-mediated angiogenesis through activation of EGR1 and VEGFA in conjunctival melanoma (CoM). First, single-cell transcriptome analysis revealed that FTO was specifically upregulated in the CAF population, thereby contributing to the hypo-m6A status in the TME of CoM. Moreover, CAFs of CoM displayed extensive proangiogenic potential, which was largely compromised by FTO inhibition, both in vitro and in vivo. By employing multi-omics analysis, we showed that FTO effectively eliminates the m6A modifications of VEGFA and EGR1. This process subsequently disrupts the YTHDF2-dependent mRNA decay pathway, resulting in increased mRNA stability and upregulated expression of these molecules. Collectively, our findings initially indicate that the upregulation of FTO plays a pivotal role in tumor development by promoting CAF-mediated angiogenesis. Therapeutically, targeting FTO may show promise as a potential antiangiogenic strategy to optimize cancer treatment.

M6A demethylase FTO-stabilized exosomal circBRCA1 alleviates oxidative stress-induced granulosa cell damage via the miR-642a-5p/FOXO1 axis

BACKGROUND

Premature ovarian insufficiency (POI) is an important cause of female infertility and seriously impacts the physical and psychological health of patients. Human umbilical cord mesenchymal stem cell-derived exosomes (HucMSCs-Exs, H-Exs) have exhibited protective effects on ovarian function with unclear mechanisms.

METHODS

A comprehensive analysis of the Gene Expression Omnibus (GEO) database were used to identify POI-associated circRNAs and miRNAs. The relationship between HucMSC-derived exosomal circBRCA1/miR-642a-5p/FOXO1 axis and POI was examined by RT-qPCR, Western blotting, reactive oxygen species (ROS) staining, senescence-associated β-gal (SA-β-gal) staining, JC-1 staining, TEM, oxygen consumption rate (OCR) measurements and ATP assay in vivo and in vitro. RT-qPCR detected the expression of circBRCA1 in GCs and serum of patients with normal ovarian reserve function (n = 50) and patients with POI (n = 50); then, the correlation of circBRCA1 with ovarian reserve function indexes was analyzed.

RESULTS

Herein, we found that circBRCA1 was decreased in the serum and ovarian granulosa cells (GCs) of patients with POI and was associated with decreased ovarian reserve. H-Exs improved the disorder of the estrous cycles and reproductive hormone levels, reduced the number of atretic follicles, and alleviated the apoptosis and senescence of GCs in rats with POI. Moreover, H-Exs mitigated mitochondrial damage and reversed the reduced circBRCA1 expression induced by oxidative stress in GCs. Mechanistically, FTO served as an eraser to increase the stability and expression of circBRCA1 by mediating the m6A demethylation of circBRCA1, and exosomal circBRCA1 sponged miR-642a-5p to block its interaction with FOXO1. CircBRCA1 insufficiency aggravated mitochondrial dysfunction, mimicking FTO or FOXO1 depletion effects, which was counteracted by miR-642a-5p inhibition.

CONCLUSION

H-Exs secreted circBRCA1 regulated by m6A modification, directly sponged miR-642a-5p to upregulate FOXO1, resisted oxidative stress injuries in GCs and protected ovarian function in rats with POI. Exosomal circBRCA1 supplementation may be a general prospect for the prevention and treatment of POI.

An α-ketoglutarate conformational switch controls iron accessibility, activation, and substrate selection of the human FTO protein

The fat mass and obesity-associated fatso (FTO) protein is a member of the Alkb family of dioxygenases and catalyzes oxidative demethylation of N6-methyladenosine (m6A), N1-methyladenosine (m1A), 3-methylthymine (m3T), and 3-methyluracil (m3U) in single-stranded nucleic acids. It is well established that the catalytic activity of FTO proceeds via two coupled reactions. The first reaction involves decarboxylation of alpha-ketoglutarate (αKG) and formation of an oxyferryl species. In the second reaction, the oxyferryl intermediate oxidizes the methylated nucleic acid to reestablish Fe(II) and the canonical base. However, it remains unclear how binding of the nucleic acid activates the αKG decarboxylation reaction and why FTO demethylates different methyl modifications at different rates. Here, we investigate the interaction of FTO with 5-mer DNA oligos incorporating the m6A, m1A, or m3T modifications using solution NMR, molecular dynamics (MD) simulations, and enzymatic assays. We show that binding of the nucleic acid to FTO activates a two-state conformational equilibrium in the αKG cosubstrate that modulates the O2 accessibility of the Fe(II) catalyst. Notably, the substrates that provide better stabilization to the αKG conformation in which Fe(II) is exposed to O2 are demethylated more efficiently by FTO. These results indicate that i) binding of the methylated nucleic acid is required to expose the catalytic metal to O2 and activate the αKG decarboxylation reaction, and ii) the measured turnover of the demethylation reaction (which is an ensemble average over the entire sample) depends on the ability of the methylated base to favor the Fe(II) state accessible to O2.

FTO deficiency in older livers exacerbates ferroptosis during ischaemia/reperfusion injury by upregulating ACSL4 and TFRC

Older livers are more prone to hepatic ischaemia/reperfusion injury (HIRI), which severely limits their utilization in liver transplantation. The potential mechanism remains unclear. Here, we demonstrate older livers exhibit increased ferroptosis during HIRI. Inhibiting ferroptosis significantly attenuates older HIRI phenotypes. Mass spectrometry reveals that fat mass and obesity-associated gene (FTO) expression is downregulated in older livers, especially during HIRI. Overexpressing FTO improves older HIRI phenotypes by inhibiting ferroptosis. Mechanistically, acyl-CoA synthetase long chain family 4 (ACSL4) and transferrin receptor protein 1 (TFRC), two key positive contributors to ferroptosis, are FTO targets. For ameliorative effect, FTO requires the inhibition of Acsl4 and Tfrc mRNA stability in a m6A-dependent manner. Furthermore, we demonstrate nicotinamide mononucleotide can upregulate FTO demethylase activity, suppressing ferroptosis and decreasing older HIRI. Collectively, these findings reveal an FTO-ACSL4/TFRC regulatory pathway that contributes to the pathogenesis of older HIRI, providing insight into the clinical translation of strategies related to the demethylase activity of FTO to improve graft function after older donor liver transplantation.

FTO-mediated regulation of m6A methylation is closely related to apoptosis induced by repeated UV irradiation

BACKGROUND

Ultraviolet (UV) damage is closely related to skin photoaging and many skin diseases, including dermatic tumors. N6-methyladenosine (m6A) modification is an important epigenetic regulatory mechanism. However, the role of m6A methylation in apoptosis induced by repeated UV irradiation has not been characterized.

OBJECTIVE

To explore m6A methylation changes and regulatory mechanisms in the repeated UV-induced skin damage process, especially apoptosis.

METHODS

HaCaT cells and BALB/c-Nu nude mice were exposed to repeated UVB/UVA+UVB irradiation. Colorimetry and flow cytometry were used to measure cellular viability and apoptosis. m6A-modified genes were detected via colorimetry and methylated RNA immunoprecipitation (MeRIP) sequencing. Methyltransferases and demethylases were detected via RT-PCR, western blotting and immunohistochemistry. Transfection of siRNA and plasmid was performed to knock down or overexpress the selected genes.

RESULTS

After UVB irradiation, 861 m6A peaks were increased and 425 m6A peaks were decreased in HaCaT cells. The differentially modified genes were enriched in apoptosis-related pathways. The m6A demethylase FTO was decreased in both HaCaT cells and mouse skin after UV damage. Overexpressing FTO could improve cell viability, inhibit apoptosis and decrease RNA-m6A methylation, including LPCAT3-m6A, which increase LPCAT3 expression, cell viability promotion and apoptosis inhibition.

CONCLUSION

Our study identified the cell m6A methylation change lists after repeated UVB irradiation, and revealed that FTO and LPCAT3 play key roles in the m6A methylation pathogenesis of UV-induced skin cell apoptosis. FTO-m6A-LPCAT3 might serve as a novel upstream target for preventing and treating photoaging and UV-induced skin diseases.

Fat mass and obesity-associated protein regulates RNA methylation associated with spatial cognitive dysfunction after chronic cerebral hypoperfusion

RNA methylation can epigenetically regulate learning and memory. However, it is unclear whether RNA methylation plays a critical role in the pathophysiology of Vascular dementia (VD). Here, we report that expression of the fat mass and obesity associated gene (FTO), an RNA demethylase, is downregulated in the hippocampus in models of VD. Through prediction and dual-luciferase reporters validation studies, we observed that miRNA-711 was upregulated after VD and could bind to the 3'-untranslated region of FTO mRNA and regulate its expression in vitro. Methylated RNA immunoprecipitation (MeRIP)-qPCR assay and functional study confirmed that Syn1 was an important target gene of FTO. This suggests that FTO is an important regulator of Syn1. FTO upregulation by inhibition of miR-711 in the hippocampus relieves synaptic association protein and synapse deterioration in vivo, whereas FTO downregulation by miR-711 agomir in the hippocampus leads to aggravate the synapse deterioration. FTO upregulation by inhibition of miR-711 relieves cognitive impairment of rats VD model, whereas FTO downregulation by miR-711 deteriorate cognitive impairment. Our findings suggest that FTO is a regulator of a mechanism underlying RNA methylation associated with spatial cognitive dysfunction after chronic cerebral hypoperfusion.

Increased m6A modification of BDNF mRNA via FTO promotes neuronal apoptosis following aluminum-induced oxidative stress

N6-methyladenosine (m6A) RNA modification is a new epigenetic molecular mechanism involved in various biological or pathological processes. Exposure to aluminum (Al) has been considered to promote neuronal apoptosis resulting in cognitive dysfunction, yet whether m6A modification participates in the underlying mechanism remains largely unknown. Here, rats exposed to aluminum-maltolate [Al(mal)3] for 90 days showed impaired learning and memory function and elevated apoptosis, which were related to the increased m6A level and decreased fat mass and obesity-associated protein (FTO, an m6A demethylase) in the hippocampus. Accordingly, similar results presented in PC12 cells following Al(mal)3 treatment and FTO overexpression relieved the increased apoptosis and m6A level in vitro. Next, we identified brain-derived neurotrophic factor (BDNF) as the functional downstream target of FTO in a m6A-dependent manner. Furthermore, it was found that as the onset of aluminum neurotoxicity, oxidative stress may be the upstream regulator of FTO in aluminum-induced apoptosis. Taken together, these results suggest that increased m6A modification of BDNF mRNA via FTO promotes neuronal apoptosis following aluminum-induced oxidative stress.

Palmatine inhibits expression fat mass and obesity associated protein (FTO) and exhibits a curative effect in dextran sulfate sodium (DSS)-induced experimental colitis

BACKGROUND

Ulcerative colitis (UC) is an inflammatory disease whose pathogenesis and mechanisms have not been fully described. The m6A methylation modification is a general mRNA modification in mammalian cells and is closely associated with the onset and progression of inflammatory bowel disease (IBD). Palmatine (PAL) is a biologically active alkaloid with anti-inflammatory and protective effects in animal models of colitis. Accordingly, we examined the role of PAL on colitis by regulating N6-methyladenosine (m6A) methylation.

METHODS

A rat experimental colitis model was established by 5 % dextran sulfate sodium (DSS) in drinking water for seven days, then PAL treatment was administered for seven days. The colonic tissue pathology was assessed using hematoxylin-eosin (HE) and disease activity index (DAI). In in vitro studies, a human, spontaneously immortalized non-cancerous colon mucosal epithelial cell line (NCM460) was exposed to 2 % DSS and treated with PAL and cell viability was assayed using Cell Counting Kit-8 (CCK-8). The levels of tumor necrosis factor α (TNF-α), interleukin (IL)-1β, IL-6, and IL-8 were detected by enzyme-linked immunosorbent assay (ELISA) kits. The level of Zonula occludens-1 (ZO-1) was dectected by immunofluorescence. Transepithelial electrical resistance (TEER) of cells was also assessed. The methyltransferase-like 3 (METTL3), METTL14, AlkB homologate 5 (ALKBH5), and fat mass and obesity-associated protein (FTO) expression levels were assessed by western blotting. The localized expression of m6A was measured by immunofluorescence.

RESULTS

PAL significantly prevented bodyweight loss and shortening of the colon in experimental colitis rats, as well as decreasing the DAI and histological damage scores. Furthermore, PAL inhibited the levels of inflammatory factors (TNF-α, IL-6, IL-8, and IL-1β) in both DSS treated rats and NCM460 cells. In addition, PAL enhanced the expression level of ZO-1, and increased the transepithelial electrical resistance to repaire intestinal barrier dysfunction. Colitis occurred due to decreased m6A levels, and the increased FTO expression led to a colitis phenotype. PAL markedly enhanced the METTL3 and METTL14 expression levels while decreasing ALKBH5 and FTO expression levels.

CONCLUSIONS

The findings demonstrated that PAL improved DSS-induced experimental colitis. This effect was associated with inhibiting FTO expression and regulating m6A methylation.

GnRH-driven FTO-mediated RNA m6A modification promotes gonadotropin synthesis and secretion

BACKGROUND

Gonadotropin precisely controls mammalian reproductive activities. Systematic analysis of the mechanisms by which epigenetic modifications regulate the synthesis and secretion of gonadotropin can be useful for more precise regulation of the animal reproductive process. Previous studies have identified many differential m6A modifications in the GnRH-treated adenohypophysis. However, the molecular mechanism by which m6A modification regulates gonadotropin synthesis and secretion remains unclear.

RESULTS

Herein, it was found that GnRH can promote gonadotropin synthesis and secretion by promoting the expression of FTO. Highly expressed FTO binds to Foxp2 mRNA in the nucleus, exerting a demethylation function and reducing m6A modification. After Foxp2 mRNA exits the nucleus, the lack of m6A modification prevents YTHDF3 from binding to it, resulting in increased stability and upregulation of Foxp2 mRNA expression, which activates the cAMP/PKA signaling pathway to promote gonadotropin synthesis and secretion.

CONCLUSIONS

Overall, the study reveals the molecular mechanism of GnRH regulating the gonadotropin synthesis and secretion through FTO-mediated m6A modification. The results of this study allow systematic interpretation of the regulatory mechanism of gonadotropin synthesis and secretion in the pituitary at the epigenetic level and provide a theoretical basis for the application of reproductive hormones in the regulation of animal artificial reproduction.

FTO Deficiency Alleviates LPS-induced Acute Lung Injury by TXNIP/NLRP3-mediated Alveolar Epithelial Cell Pyroptosis

N6-methyladenosine (m6A) plays a role in various diseases, but it has rarely been reported in acute lung injury (ALI). The FTO (fat mass and obesity-associated) protein can regulate mRNA metabolism by removing m6A residues. The aim of this study was to examine the role and mechanism of the m6A demethylase FTO in LPS-induced ALI. Lung epithelial FTO-knockout mice and FTO-knockdown/overexpression human alveolar epithelial (A549) cell lines were constructed to evaluate the effects of FTO on ALI. Bioinformatics analysis and a series of in vivo and in vitro assays were used to examine the mechanism of FTO regulation. Rescue assays were conducted to examine whether the impact of FTO on ALI depended on the TXNIP/NLRP3 pathway. In LPS-induced ALI, RNA m6A modification amounts were upregulated, and FTO expression was downregulated. In vivo, lung epithelial FTO knockout alleviated alveolar structure disorder, tissue edema, and pulmonary inflammation and improved the survival of ALI mice. In vitro, FTO knockdown reduced A549 cell damage and death induced by LPS, whereas FTO overexpression exacerbated cell damage and death. Mechanistically, bioinformatics analysis revealed that TXNIP was a downstream target of FTO. FTO deficiency mitigated pyroptosis in LPS-induced ALI via the TXNIP/NLRP3 pathway. Rescue assays confirmed that the impact of FTO on the TXNIP/NLRP3 pathway was significantly reversed by the TXNIP inhibitor SRI-37330. Deficiency of FTO alleviates LPS-induced ALI via TXNIP/NLRP3 pathway-mediated alveolar epithelial cell pyroptosis, which might be a novel therapeutic strategy for combating ALI.

Demethylases in tumors and the tumor microenvironment: Key modifiers of N6-methyladenosine methylation

RNA methylation modifications are widespread in eukaryotes and prokaryotes, with N6-methyladenosine (m6A) the most common among them. Demethylases, including Fat mass and obesity associated gene (FTO) and AlkB homolog 5 (ALKBH5), are important in maintaining the balance between RNA methylation and demethylation. Recent studies have clearly shown that demethylases affect the biological functions of tumors by regulating their m6A levels. However, their effects are complicated, and even opposite results have appeared in different articles. Here, we summarize the complex regulatory networks of demethylases, including the most important and common pathways, to clarify the role of demethylases in tumors. In addition, we describe the relationships between demethylases and the tumor microenvironment, and introduce their regulatory mechanisms. Finally, we discuss evaluation of demethylases for tumor diagnosis and prognosis, as well as the clinical application of demethylase inhibitors, providing a strong basis for their large-scale clinical application in the future.

Mechanism of Fat Mass and Obesity-Related Gene-Mediated Heme Oxygenase-1 m6A Modification in the Recovery of Neurological Function in Mice with Spinal Cord Injury

OBJECTIVES

This study examined the mechanism of fat mass and obesity-related gene (FTO)-mediated heme oxygenase-1 (HO-1) m6A modification facilitating neurological recovery in spinal cord injury (SCI) mice. FTO/HO-1 was identified as a key regulator of SCI as well as a potential target for treatment of SCI.

METHODS

An SCI mouse was treated with pcDNA3.1-FTO/pcDNA3.1-NC/Dac51. An oxygen/glucose deprivation (OGD) cell model simulated SCI, with cells treated with pcDNA3.1-FTO/si-HO-1/Dac51. Motor function and neurobehavioral evaluation were assessed using the Basso, Beattie, and Bresnahan (BBB) scale and modified neurological severity score (mNSS). Spinal cord pathology and neuronal apoptosis were assessed. Further, FTO/HO-1 mRNA and protein levels, HO-1 mRNA stability, the interaction of YTHDF2 with HO-1 mRNA, neuronal viability/apoptosis, and HO-1 m6A modification were evaluated.

RESULTS

Spinal cord injury mice exhibited reduced BBB, elevated mNSS scores, disorganized spinal cord cells, scattered nuclei, and severe nucleus pyknosis. pcDNA3.1-FTO elevated FTO mRNA, protein expression, and BBB score; reduced the mNSS score of SCI mice; decreased neuronal apoptosis; improved the cell arrangement; and improved nucleus pyknosis in spinal cord tissues. OGD decreased FTO expression. FTO upregulation ameliorated OGD-induced neuronal apoptosis. pcDNA3.1-FTO reduced HO-1 mRNA and protein and HO-1 m6A modification, while increasing HO-1 mRNA stability and FTO in OGD-treated cells. FTO upregulated HO-1 by modulating m6A modification. HO-1 downregulation attenuated the effect of FTO. pcDNA3.1-FTO/Dac51 increased the HO-1 m6A level in mouse spinal cord tissue homogenate, reduced BBB, boosted mNSS scores of SCI mice, aggravated nucleus pyknosis, and increased neuronal apoptosis in spinal cord tissues, confirming that FTO mediated HO-1 m6A modification facilitated neurological recovery in SCI mice.

CONCLUSION

The fat mass and obesity-related gene modulates HO-1 mRNA stability by regulating m6A modification levels, thereby influencing HO-1 expression and promoting neurological recovery in SCI mice.

RNA m6A modification, signals for degradation or stabilisation?

The RNA modification N6-methyladenosine (m6A) is conserved across eukaryotes, and profoundly influences RNA metabolism, including regulating RNA stability. METTL3 and METTL14, together with several accessory components, form a 'writer' complex catalysing m6A modification. Conversely, FTO and ALKBH5 function as demethylases, rendering m6A dynamic. Key to understanding the functional significance of m6A is its 'reader' proteins, exemplified by YTH-domain-containing proteins (YTHDFs) canonical reader and insulin-like growth factor 2 mRNA-binding proteins (IGF2BPs) non-canonical reader. These proteins play a crucial role in determining RNA stability: YTHDFs mainly promote mRNA degradation through different cytoplasmic pathways, whereas IGF2BPs function to maintain mRNA stability. Additionally, YTHDC1 functions within the nucleus to degrade or protect certain m6A-containing RNAs, and other non-canonical readers also contribute to RNA stability regulation. Notably, m6A regulates retrotransposon LINE1 RNA stability and/or transcription via multiple mechanisms. However, conflicting observations underscore the complexities underlying m6A's regulation of RNA stability depending upon the RNA sequence/structure context, developmental stage, and/or cellular environment. Understanding the interplay between m6A and other RNA regulatory elements is pivotal in deciphering the multifaceted roles m6A plays in RNA stability regulation and broader cellular biology.

FTO promotes gastric cancer progression by modulating MAP4K4 expression via demethylation in an m6A-dependent manner

Gastric cancer (GC) is a serious malignant tumour with a high mortality rate and a poor prognosis. Recently, emerging evidence has suggested that N6-methyladenosine (m6A) modification plays a crucial regulatory role in cancer progression. However, the exact role of m6A regulatory factors FTO in GC is unclear. First, the expression of m6A methylation-related regulatory factors in clinical samples and the clinical data of the corresponding patients were obtained from The Cancer Genome Atlas (TCGA-STAD) dataset, and correlation analysis between FTO expression and patient clinicopathological parameters was subsequently performed. qRT-PCR, immunohistochemistry (IHC) and western blotting (WB) were used to verify FTO expression in GC. CCK-8, EdU, flow cytometry and transwell assays were used to evaluate the effect of FTO on the behaviour of GC cells. Transcriptome sequencing and RNA immunoprecipitation analysis were used to explore the potential regulatory mechanisms mediated by FTO. FTO was highly expressed in GC tissues and cells, and high expression of FTO predicted a worse prognosis than low expression. Functionally, overexpression of FTO promoted the proliferation, migration and invasion of GC cells but inhibited cell apoptosis. Mechanistically, we found that FTO is upregulated in GC and promotes GC progression by modulating the expression of MAP4K4. Taken together, our findings provide new insights into the effects of FTO-mediated m6A demethylation and could lead to the development of new strategies for GC monitoring and aggressive treatment.

FTO-mediated ZNF687 accelerates tumor growth, metastasis, and angiogenesis in colorectal cancer through the Wnt/β-catenin pathway

Colorectal cancer (CRC) is a common and lethal cancer. ZNF687 has been disclosed to take part in diversified cancers' progression by serving as a facilitator. However, the detailed regulatory functions of ZNF687 in the CRC have not been investigated. This work is planned to probe the impacts of ZNF687 on CRC progression. The IHC, RT-qPCR, and western blot assays were used to examine mRNA and protein gene expressions. The cell proliferation measurement was accompanied by a CCK-8 assay. The Transwell assay was performed to evaluate cell invasion and migration. The angiogenesis ability was evaluated by a tube formation experiment. The m6A level was evaluated through MeRIP and m6A dot blot assays. The binding ability between ZNF687 and FTO (fat mass and obesity associated protein) was tested through an RIP assay. The β-catenin nuclear translocation was assessed through an immunofluorescence assay. The tumor growth was evaluated through an in vivo assay. ZNF687 exhibited higher expression in CRC cells and resulted in a poor prognosis. Additionally, ZNF687 inhibition suppressed CRC cell proliferation, invasion, migration, and angiogenesis. Furthermore, the suppression of ZNF687 retarded the Wnt pathway. Through rescue assays, the reduced cell migration, proliferation, invasion, and angiogenesis mediated by ZNF687 knockdown could be reversed after BML-284 (the activator of the Wnt pathway) treatment. Finally, it was explained that ZNF687 knockdown inhibited in vivo tumor growth. This study manifested that FTO-mediated ZNF687 aggravated tumor growth, metastasis, and angiogenesis of CRC through Wnt/β-catenin pathway. This finding may provide a hopeful molecular target for CRC treatment.

Fat mass and obesity-associated protein (FTO) mediated m6A modification of circFAM192A promoted gastric cancer proliferation by suppressing SLC7A5 decay

Gastric cancer (GC) is a common malignant tumor worldwide, especially in East Asia, with high incidence and mortality rate. Epigenetic modifications have been reported to participate in the progression of gastric cancer, among which m6A is the most abundant and important chemical modification in RNAs. Fat mass and obesity-associated protein (FTO) is the first identified RNA demethylase but little is known about its role in gastric cancer. In our study, data from TCGA and clinical samples showed that FTO was highly expressed in gastric cancer tissues. Kaplan-Meier plotter suggested that patients with the high level of FTO had a poor prognosis. In vitro and in vivo experiments confirmed the role of FTO in promoting gastric cancer cell proliferation. Mechanistically, we found that FTO bound to circFAM192A at the specific site and removed the m6A modification in circFAM192A, protecting it from degradation. CircFAM192A subsequently interacted with the leucine transporter solute carrier family 7 member 5 (SLC7A5) and enhancing its stability. As a result, an increased amount of SLC7A5 was on the membrane, which facilitated leucine uptake and activated the mTOR signaling pathway. Therefore, our study demonstrated that FTO promoted gastric cancer proliferation through the circFAM192A/SLC7A5 axis in the m6A-dependent manner. Our study shed new light on the role of FTO in gastric cancer progression.

The role of the m6A/m demethylase FTO in memory is both task and sex-dependent in mice

Formation of long-term memories requires learning-induced changes in both transcription and translation. Epitranscriptomic modifications of RNA recently emerged as critical regulators of RNA dynamics, whereby adenosine methylation (m6A) regulates translation, mRNA stability, mRNA localization, and memory formation. Prior work demonstrated a pro-memory phenotype of m6A, as loss of m6A impairs and loss of the m6A/m demethylase FTO improves memory formation. Critically, these experiments focused exclusively on aversive memory tasks and were only performed in male mice. Here we show that the task type and sex of the animal alter effects of m6A on memory, whereby FTO-depletion impaired object location memory in male mice, in contrast to the previously reported beneficial effects of FTO depletion on aversive memory. Additionally, we show that female mice have no change in performance after FTO depletion, demonstrating that sex of the mouse is a critical variable for understanding how m6A contributes to memory formation. Our study provides the first evidence for FTO regulation of non-aversive spatial memory and sexspecific effects of m6A, suggesting that identification of differentially methylated targets in each sex and task will be critical for understanding how epitranscriptomic modifications regulate memory.

Highly pathogenic PRRSV upregulates IL-13 production through nonstructural protein 9-mediated inhibition of N6-methyladenosine demethylase FTO

Porcine reproductive and respiratory syndrome virus (PRRSV), a highly infectious virus, causes severe losses in the swine industry by regulating the inflammatory response, inducing tissue damage, suppressing the innate immune response, and promoting persistent infection in hosts. Interleukin-13 (IL-13) is a cytokine that plays a critical role in regulating immune responses and inflammation, particularly in immune-related disorders, certain types of cancer, and numerous bacterial and viral infections; however, the underlying mechanisms of IL-13 regulation during PRRSV infection are not well understood. In this study, we demonstrated that PRRSV infection elevates IL-13 levels in porcine alveolar macrophages. PRRSV enhances m6A-methylated RNA levels while reducing the expression of fat mass and obesity associated protein (FTO, an m6A demethylase), thereby augmenting IL-13 production. PRRSV nonstructural protein 9 (nsp9) was a key factor for this modulation. Furthermore, we found that the residues Asp567, Tyr586, Leu593, and Asp595 were essential for nsp9 to induce IL-13 production via attenuation of FTO expression. These insights delineate PRRSV nsp9's role in FTO-mediated IL-13 release, advancing our understanding of PRRSV's impact on host immune and inflammatory responses.