METTL14 promotes glomerular endothelial cell injury and diabetic nephropathy via m6A modification of α-klotho

Systematic molecular profiling of non-native N6-substitution effects on m6A binding to the YTH domains of human RNA m6A readers in diabetes

The RNA N6-adenosine methylation, resulting in N6-methyl adenosine (m6A), is one of the most important post-transcriptional modification events in the eukaryotic transcriptome, which is dynamically regulated by methyltransferases (writers), recognition proteins (readers) and demethylases (erasers). Human has five m6A readers namely YTHDC1, YTHDC2, YTHDF1, YTHDF2 and YTHDF3 that specifically recognize and bind to the methylated m6A residue of RNA through their YT521-B homology (YTH) domains, which have been involved in the pathogenesis of diabetes mellitus and its diverse complications such as diabetic nephropathy. Instead of the native N6-methylation, we herein attempted to explore the molecular effect of various non-native N6-substitutions on adenosine (A) binding behavior to YTH domains. A systematic interaction profile of 40 reported N6-substituted adenosine (x6A) mononucleotides with 5 human reader YTH domains was created computationally. Heuristic clustering of the profile divided these YTH domains and these x6A mononucleotides into two subfamilies and three classes, respectively; they represent distinct intrinsic interaction modes between the domains and mononucleotides. Statistical survey unraveled that the volume (Vg) and hydrophobicity (Hg) of N6-substituted chemical groups exhibit linear and nonlinear correlations with the binding energy (ΔGttl) of x6A mononucleotides to YTH domains, respectively; N6-substitutions with moderate size and weak polarity are favorable for the x6A binding. From the profile the N6-bromomethyl adenosine (brm6A) was identified as a potent binder of YTHDF2 YTH domain; its affinity was improved significantly by 77.2-fold from A and considerably by 19.5-fold from m6A. Structural modeling observed that the N6-bromomethyl group of brm6A is tightly packed against an aromatic cage defined by the Trp432-Trp486-Trp491 triad of YTHDF2 YTH domain. Electron-correlation analysis revealed that the bromine atom can form geometrically and energetically satisfactory halogen-π interactions with the aromatic cage, thus conferring considerable affinity and specificity to the domain-brm6A interaction.

The role and mechanism of m6A methylation in diabetic nephropathy

Diabetic nephropathy (DN) is one of the most common microvascular complications of diabetes mellitus, characterized by progressive deterioration of renal structure and function, which may eventually lead to end-stage kidney disease (ESKD). The N6-methyladenosine (m6A) methylation, an important modality of RNA modification, involves three classes of key regulators, writers (e.g., METTL3), erasers (e.g., FTO, ALKBH5) and readers (e.g., YTHDF2), which play important roles in DN. Writers are responsible for introducing m6A modifications on RNAs, erasers remove m6A modifications and readers recognize and bind m6A-modified RNAs to regulate RNAs functions, such as mRNA stability, translation and localization. In DN, abnormal m6A modification may promote kidney injury and proteinuria by regulating key pathways involved in multiple processes, including lipid metabolism and inflammatory response, in kidney cells such as podocytes. Therefore, an in-depth study of the role and mechanism of m6A methylation that are regulated by "writers", "erasers" and "readers" in DN is expected to provide new targets and strategies for the prevention and treatment of DN.

The Emerging Role of m6A and Programmed Cell Death in Cardiovascular Diseases

N6-methyladenosine (m6A) is the most prevalent internal chemical modification in eukaryotic messenger RNA (mRNA), significantly impacting its lifecycle through dynamic and reversible processes involving methyltransferase, demethylase, and binding proteins. These processes regulate mRNA stability, splicing, nuclear export, translation, and degradation. Programmed cell death (PCD), a tightly controlled process encompassing apoptosis, pyroptosis, ferroptosis, autophagy, and necroptosis, plays a crucial role in maintaining cellular homeostasis, tissue development, and function. Recently, m6A modification has emerged as a significant research area due to its role in regulating PCD and its implications in cardiovascular diseases (CVDs). In this review, we delve into the intricate relationship between various PCD types and m6A modification, emphasizing their pivotal roles in the initiation and progression of CVDs such as myocardial ischemia-reperfusion (I/R), atherosclerosis (AS), pulmonary hypertension (PH), cardiomyopathy, doxorubicin (Dox)-induced cardiotoxicity (DIC), heart failure (HF), and myocardial infarction (MI). Our findings underscore the potential of elucidating the roles of m6A and PCD in CVD to pave new pathways for prevention and treatment strategies.

N6-methyladenosine in inflammatory diseases: Important actors and regulatory targets

N6-methyladenosine (m6A) is one of the most prevalent epigenetic modifications in eukaryotic cells. It regulates RNA function and stability by modifying RNA methylation through writers, erasers, and readers. As a result, m6A plays a critical role in a wide range of biological processes. Inflammation is a common and fundamental pathological process. Numerous studies have investigated the role of m6A modifications in inflammatory diseases. This review highlights the mechanisms by which m6A contributes to inflammation, focusing on pathogen-induced infectious diseases, autoimmune disorders, allergic conditions, and metabolic disorder-related inflammatory diseases.

METTL10 attenuates adriamycin-induced podocyte injury by targeting cell dedifferentiation

Chronic kidney disease (CKD) is a worldwide public health problem. Podocyte damage is a hallmark of glomerular diseases including focal segmental glomerulosclerosis (FSGS) and one of the leading causes of CKD. Lysine methylation is a crucial post-translational modification. Beyond epidemic regulation, various lysine methyltransferases have been recently reported to participate in disease progression, including cancers and kidney diseases. Among them, Methyltransferase-like 10 (METTL10), is recognized as a gene associated with estimated glomerular filtration rate (eGFR) and CKD risk. However, its role in podocyte damage remains unclear. We identified the differentially expressed genes(DEGs)in podocyte injury by bioinformatics analysis. Patients diagnosed as idiopathic FSGS by renal biopsy were enrolled. Mouse model was established by Adriamycin(ADR) and urinary albumin/ creatinine ratio(UACR) was detected. Murine podocyte cell line was stimulated with ADR. We determined METTL10 was one of the significantly downregulated genes in damaged podocytes, confirmed the decreased glomerular expression of METTL10 in patients with idiopathic FSGS and in mice with ADR-induced nephrosis, respectively. Moreover, we found a negative correlation between glomerular METTL10 levels and UACR in mice. METTL10 was reduced in ADR-treated podocytes, accompanied by podocyte dedifferentiation (loss of synaptopodin, podocin, nephrin, WT-1) and acquisition of mesenchymal cell markers (snail, desmin, pax2). Knockdown of METTL10 promoted their dedifferentiation. METTL10 regulates podocyte dedifferentiation under damaging stimuli and protects podocytes.

METTL14 downregulates GLUT9 through m6A methylation and attenuates hyperuricemia-induced fibrosis in mouse renal tubular epithelial cells

Hyperuricemia is a known risk factor for chronic kidney disease (CKD) and subsequent renal fibrosis. N6-methyladenosine (m6A) is the most prevalent chemical modification in eukaryotic mRNAs and has been implicated in various diseases. However, its role in hyperuricemic nephropathy (HN) remains unclear. This study investigated the involvement of the methylase METTL14 in HN pathogenesis. Our in vitro and in vivo function experiments demonstrated that METTL14 plays a crucial role in HN. In mouse models of uric acid (UA)-induced renal injury, we detected impaired kidney function, increased renal interstitial fibrosis, and significantly decreased m6A methylation levels in renal tissues. Treatment with benzbromarone, a UA-lowering drug, alleviated renal injury, restored m6A methylation levels, and upregulated METTL14 expression. Cellular experiments showed that METTL14 overexpression attenuated high UA-induced fibrosis in renal tubular epithelial cells. This overexpression significantly decreases the expression of GLUT9, a key protein involved in UA transport, leading to reduced UA reabsorption. Additionally, MeRIP-qPCR and dual-luciferase reporter gene experiments further demonstrated that METTL14 overexpression enhanced Glut9 mRNA m6A methylation modification, accelerating its degradation and decreasing expression levels. Thus, METTL14-mediated RNA m6A modification plays a role in the renal tubular epithelial cell damage induced by high UA, by regulating Glut9 mRNA post-transcriptionally. These findings provide valuable insights for the diagnosis and development of therapeutic drugs for HN.

WTAP and METTL14 regulate the m6A modification of DKK3 in renal tubular epithelial cells of diabetic nephropathy

Diabetic nephropathy (DN) is an important cause of death in diabetes patients, which is mainly due to its complex pathogenesis. Here, we explored the role of N6-methyladenosine (m6A) RNA methylation in DN development. Renal tubular epithelial cells from DN patients and experimental DN mice treated with streptozotocin (STZ) exhibited a considerable increase in METTL14 and WTAP expression as well as overall m6A methylation. Knocking down the expression of METTL14 and WTAP inhibited the migration and proliferation of tubular epithelial cells. MeRIP-seq analysis of the renal tissues of DN patients revealed that the genes with elevated m6A methylation were concentrated in the Wnt/β-Catenin signaling pathway. Dickkopf homolog 3 (DKK3) was screened out as the gene with the most significant increase in m6A methylation. In addition, the expression change pattern of DKK3 under DN circumstances is in line with those of METTL14 and WTAP. DKK3's m6A methylation sites were confirmed to be located in the 3'UTR region, which is how METTL14 and WTAP improved DKK3's mRNA stability. Finally, YTHDF1, a m6A reader, was demonstrated to recognize m6A-methylated DKK3 and promote DKK3 expression.

β-Arrestin-2 enhances endoplasmic reticulum stress-induced glomerular endothelial cell injury by activating transcription factor 6 in diabetic nephropathy

BACKGROUND

Glomerular endothelial cell (GENC) injury is a characteristic of early-stage diabetic nephropathy (DN), and the investigation of potential therapeutic targets for preventing GENC injury is of clinical importance.

AIM

To investigate the role of β-arrestin-2 in GENCs under DN conditions.

METHODS

Eight-week-old C57BL/6J mice were intraperitoneally injected with streptozotocin to induce DN. GENCs were transfected with plasmids containing siRNA-β-arrestin-2, shRNA-activating transcription factor 6 (ATF6), pCDNA-β-arrestin-2, or pCDNA-ATF6. Additionally, adeno-associated virus (AAV) containing shRNA-β-arrestin-2 was administered via a tail vein injection in DN mice.

RESULTS

The upregulation of β-arrestin-2 was observed in patients with DN as well as in GENCs from DN mice. Knockdown of β-arrestin-2 reduced apoptosis in high glucose-treated GENCs, which was reversed by the overexpression of ATF6. Moreover, overexpression of β-arrestin-2 Led to the activation of endoplasmic reticulum (ER) stress and the apoptosis of GENCs which could be mitigated by silencing of ATF6. Furthermore, knockdown of β-arrestin-2 by the administration of AAV-shRNA-β-arrestin-2 alleviated renal injury in DN mice.

CONCLUSION

Knockdown of β-arrestin-2 prevents GENC apoptosis by inhibiting ATF6-mediated ER stress in vivo and in vitro. Consequently, β-arrestin-2 may represent a promising therapeutic target for the clinical management of patients with DN.

Activation of MST1 protects filtration barrier integrity of diabetic kidney disease in mice through restoring the tight junctions of glomerular endothelial cells

As a pathological feature of diabetic kidney disease (DKD), dysregulated glomerular filtration barrier function could lead to the increased levels of proteinuria. The integrity of tight junctions (TJs) of glomerular endothelial cells (GECs) is a guarantee of physiological function of glomerular filtration barrier. Mammalian sterile 20-like kinase (MST1) is a key regulatory protein in the blood-brain barrier (BBB), and it regulates the expression of TJs-related proteins in cerebral vascular endothelial cells. Our previous study showed that MST1 was involved in renal tubulointerstitial fibrosis of DKD. In the present study we investigated the role of MST1 in barrier function of GECs of DKD, and explored its regulatory mechanisms. In kidney tissue section of DKD patients and db/db mice, and high glucose (HG)-cultured mouse glomerular endothelial cells (mGECs), we showed that MST1 was inactivated in the GECs of DKD accompanied by disrupted glomerular endothelial barrier. In db/db mice and HG-cultured mGECs, knockdown of MST1 increased proteinuria levels, and disrupted glomerular endothelial barrier through decreasing TJs-related proteins, whereas MST1 overexpression restored glomerular endothelial barrier through regaining TJs-related proteins. In db/db mice and HG-cultured mGECs, we demonstrated that MST1 inhibition induced TJs's disruption of GECs via activating YAP1/TEAD signaling. Verteporfin (an inhibitor of YAP1-TEAD interaction) and PY-60 (a YAP1 agonist) were used to verify the role of YAP1/TEAD signaling in the regulation effect of MST1 on barrier function of mGECs. In conclusion, MST1 activation recovers glomerular endothelial barrier of DKD by regaining TJs-related proteins via inhibiting YAP1/TEAD signaling. This study highlights the multiple regulation of MST1 activation on kidney injury.

METTL14 is Involved in TNF-α-Induced Inflammation in Colorectal Epithelial Cells via Autophagy Modulation

Ulcerative colitis (UC) is a chronic and relapsing inflammatory bowel disease (IBD) characterized by colorectal inflammation. The N6-methyladenosine (m6A) modification of RNA regulates gene expression through the modulation of RNA metabolism, thus influencing various physiological and pathological processes. The aim of this study was to investigate the biological function of m6A methyltransferase METTL14 in colorectal epithelial cell inflammation. Bioinformatics analysis indicated that METTL14 expression was decreased in UC and was associated with disease severity and immune infiltration. We also noted a downregulation of METTL14 expression and a decrease in the total m6A RNA levels in TNF-α-stimulated Caco-2 cells. Moreover, METTL14 knockdown promoted inflammation and inhibited autophagy in TNF-α-stimulated Caco-2 cells, as indicated by the upregulation of NF-κB signaling and pro-inflammatory cytokine expression as well as LC3B protein downregulation. Treatment with the autophagy activator Torin-1 ameliorated the pro-inflammatory effects of METTL14 silencing. Furthermore, METTL14 knockdown significantly reduced the expression of ATG5. ATG5 overexpression could nullify the pro-inflammatory effect of METTL14 knockdown in TNF-α-stimulated Caco-2 cells. Mechanistically, METTL14 knockdown promoted ATG5 mRNA degradation, and luciferase analysis identified ATG5 as a target of m6A modification by METTL14. Taken together, silencing METTL14 promoted inflammation in Caco-2 cells via the downregulation of ATG5. Our findings revealed the importance of the m6A modification in colonic inflammation and autophagy, indicating that targeting METTL14 might be a potential therapeutic strategy for anti-inflammatory treatment in UC.

METTL14 derived from exosomes of M1 macrophages promotes high glucose-induced apoptosis, inflammation and oxidative stress in glomerular endothelial cells by mediating PAQR3 m6A modification

BACKGROUND

Methyltransferase 14 (METTL14) mediated N6-methyladenine (m6A) RNA methylation and progestin and AdipoQ receptor family member 3 (PAQR3) are reported to be involved in diabetic nephropathy (DN) progression. Here, we explored whether the effects of PAQR3 on DN was associated with METTL14-induced m6A and their relationship with macrophage-related exosomes in DN progression.

METHODS

Human glomerular endothelial cells (GECs) were incubated in high glucose (HG) condition to mimic DN condition in vitro. Exosomes were isolated from M1 macrophages and co-cultured with GECs. qRT-PCR and western blotting detected the levels of genes and proteins. Cell functions were determined using cell counting kit-8 assay and flow cytometry. ELISA analysis detected inflammatory factors, and oxidative stress was evaluated by measuring reactive oxygen species and malondialdehyde. The m6A modification profile was determined by methylated RNA immunoprecipitation assay and the interaction was verified by dual-luciferase reporter assay.

RESULTS

HG elevated PAQR3 expression levels in GECs. PAQR3 silencing reversed HG-induced viability arrest, apoptosis, inflammatory response, and oxidative stress. M1 macrophage co-culture could suppress HG-induced GEC injury. PAQR3 was packaged into M1 macrophage-derived exosomes, and M1 macrophages regulated HG-induced GEC injury by secreting PAQR3 into cells via exosomes. Mechanistically, METTL14 induced PAQR3 m6A modification. METTL14 was enriched in M1 macrophage-derived exosomes. METTL14 knockdown in M1 macrophage-derived exosomes protected GEC from HG-induced viability arrest, apoptosis, inflammation and oxidative stress by regulating PAQR3.

CONCLUSION

Exosomal METTL14 derived from M1 macrophages promoted HG-induced apoptosis, inflammation and oxidative stress in GECs by mediating PAQR3 m6A modification.

Systemic immune-inflammation mediates the association between Klotho protein and metabolic syndrome: findings from a large-scale population-based study

BACKGROUND

This study utilized large-scale population data from the National Health and Nutrition Examination Survey (NHANES) to elucidate the relationship between the Klotho protein and metabolic syndrome along with its components. We further investigated the possible mediating effect of inflammation on these relationships. Our objective was to identify biomarkers for risk stratification and potential therapeutic targets for metabolic syndrome.

METHODS

This study enrolled 13,119 participants aged 40-79 years, spanning five NHANES cycles from 2007 to 2016, with complete information on metabolic syndrome and the Klotho protein. The definition of metabolic syndrome followed the criteria of the National Cholesterol Education Program-Adult Treatment Panel III. Survey-weighted logistic regression and subgroup analysis were used to explore the associations between serum Klotho protein levels and metabolic syndrome, along with its components. Mediation analysis was performed to investigate the mediating effects of inflammation-related markers, including white blood cells, neutrophils, lymphocytes, monocytes, the neutrophil-to-lymphocyte ratio (NLR), the platelet-to-lymphocyte ratio (PLR), the systemic immune-inflammation index (SII) and the monocyte-to-HDL ratio (MHR), with the aim of elucidating how the Klotho protein influences the onset and progression of metabolic syndrome.

RESULTS

The study participants had an average age of 56.06 years (95% CI: 55.76-56.37), with a Klotho protein concentration of 798.10 pg/ml (95% CI: 656.50-980.50) and a 43.77% prevalence of metabolic syndrome (n = 5742). In the crude model, Klotho was negatively correlated with metabolic syndrome and its components, including central obesity, hypertension, and hypertriglyceridemia. After adjusting for all confounding factors, Klotho was demonstrated to be negatively associated only with metabolic syndrome (OR: 0.82, 95% CI: 0.70-0.97), hypertension (OR: 0.83, 95% CI: 0.70-0.98), and hypertriglyceridemia (OR: 0.78, 95% CI: 0.67-0.91). Subgroup and interaction analyses revealed significant interactions between age, sex, race/ethnicity, body mass index, and Klotho. Additionally, mediation analysis demonstrated that leukocytes, neutrophils and monocytes accounted for 34.78%, 31.91% and 7.13%, respectively, of the associations between Klotho and metabolic syndrome.

CONCLUSION

The serum concentration of Klotho protein was negatively associated with metabolic syndrome, with the relationship being partly mediated by systemic immune inflammation. The findings of this research revealed that the Klotho protein may be a valuable biomarker for risk stratification and a potential therapeutic target for metabolic syndrome.

METTL3 aggravates renal fibrogenesis in obstructive nephropathy via the miR-199a-3p/PAR4 axis

Renal fibrosis is among the major factors contributing to the development of chronic kidney disease. In this regard, although N6-methyladenosine (m6A) modification and micro-RNAs (miRNAs) have been established to play key roles in diverse physiological processes and disease/disorder development, further research is required to identify the probable mechanisms and processes associated with their involvement in renal fibrosis. In this study, we show that transforming growth factor β1 (TGF-β1)-induced human proximal tubule epithelial cells (HK2) are characterized by dose-dependently higher methyltransferase-like 3 (METTL3) expression. Furthermore, METTL3 was found to enhance pri-miR-199a-3p maturation and miR-199a-3p expression in an m6A-dependent manner, whereas miR-199a-3p sponges prostate apoptotic response 4 (Par4), thereby regulating its expression. Collectively, our findings in this study indicate that the METTL3/miR-199a-3p/Par4 axis plays a key role in the development of obstructive nephrogenic fibrosis.

A semantic segmentation method to analyze retinal vascular parameters of diabetic nephropathy

Introduction

By using spectral domain optical coherence tomography (SD-OCT) to measure retinal blood vessels. The correlation between the changes of retinal vascular structure and the degree of diabetic nephropathy is analyzed with a full-pixel Semantic segmentation method.

Methods

A total of 120 patients with diabetic nephropathy who were treated in the nephrology department of Quzhou People's Hospital from March 2023 to March 2024 were selected and divided into three groups according to the urinary albumin creatinine ratio (UACR). The groups included simple diabetes group (UACR < 30 mg/g), microalbuminuria group (30 mg/g ≤ UACR <300 mg/g) and macroalbuminuria group (UACR ≥300 mg/g). SD-OCT was used to scan the arteries and veins in the superior temporal area B of the retina. The semantic segmentation method built into the SD-eye software was used to automatically identify the morphology and structure of the vessels and calculate the parameters of arteriovenous vessels. The parameters of arteriovenous vessels are as follows: outer diameter of the retinal artery (RAOD); inner diameter of the retinal artery (RALD); arterial wall thickness (AWT); arterial wall to lumen ratio (AWLR); cross sectional area of arterial wall (AWCSA); retinal vein outer diameter (RVOD); retinal vein inner diameter (RVLD); vein wall thickness (VWT); vein wall to lumen ratio (VWLR); cross sectional area of vein wall (VWCSA). Statistical analysis software was used to compare and analyze the parameters of retinal arteriovenous vessels of the three groups.

Results

The study revealed statistically significant differences in RAOD and RALD among the three groups (p < 0.05) with the RAOD and RALD of the macroalbuminuria group and microalbuminuria group being lower than those of the simple diabetes group. Conversely, there were no significant differences in AWT, AWLR and AWCSA among the three groups (p > 0.05). Additionally, the differences in RVOD and RVLD among the three groups were found to be statistically significant (p < 0.05) with the RVOD and RVLD of the simple diabetes group being lower than those of the microalbuminuria group and macroalbuminuria group. No significant differences were observed in VWT and VWL among the groups. Additionally, RVOD and RVLD were weakly associated with UACR (R = 0.247, p = 0.007; R = 0.210, p = 0.021). Full-pixel semantic segmentation method combined with OCT images is a new retinal vascular scanning technology, which can be used as a new method for early diagnosis of diabetic nephropathy. The structural changes of retinal vessels can be used to predict the severity of diabetic nephropathy during the development of diabetic nephropathy.

FTO mediates the diabetic kidney disease progression through regulating the m6A modification of NLRP3

BACKGROUND

The objective of our research was to investigate the specific mechanism of FTO in diabetic kidney disease (DKD) progression.

METHODS

The DKD model was established with renal tubular epithelial HK-2 cells and mice in vitro and in vivo. The N6-methyladenosine (m6A) content in cells was detected using dot plot assay and the m6A levels of NLRP3 was detected with the MeRIP assay. The mRNA and protein levels were tested with real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) and western blot. The IL-1β and IL-18 levels were assessed with enzyme-linked immunosorbent assay (ELISA). The cell viability was measured by cell counting kit (CCK)-8 assay and cell pyroptosis was determined with Annexin V and propidium iodide (PI) double staining followed by flow cytometry analysis. RNA-binding protein immunoprecipitation (RIP) and dual luciferase reporter assays were conducted to detect the interaction between FTO and NLRP3. m6A levels were detected by Me-RIP assay. The renal injury was measured by observing the renal morphology and urine and blood levels of relevant indicators.

RESULTS

The results indicated that high glucose treatment induced HK-2 cell pyroptosis. m6A levels were prominently elevated in high glucose treated HK-2 cells while FTO expression were significantly down-regulated. FTO over-expression promoted cell viability but inhibited pyroptosis of HK-2 cells under high glucose (HG) treatment. Moreover, FTO could inhibit NLRP3 expression. RIP and Me-RIP assays indicated that FTO could bind with NLRP3 and regulate its m6A modification level. Further luciferase assay confirmed that FTO binds with the 233-237 bp region of NLRP3. NLRP3 neutralized the function of FTO in the HG stimulated HK-2 cells. In vivo, the H&E staining showed that FTO over-expression alleviated the kidney injury and suppressed the pyroptosis induced by DKD.

CONCLUSION

We found that FTO could inhibit the DKD progression in vivo and in vitro by regulated the m6A modification of NLRP3.

N6-methyladenine RNA methylation epigenetic modification and diabetic microvascular complications

N6-methyladensine (m6A) has been identified as the best-characterized and the most abundant mRNA modification in eukaryotes. It can be dynamically regulated, removed, and recognized by its specific cellular components (respectively called "writers," "erasers," "readers") and have become a hot research field in a variety of biological processes and diseases. Currently, the underlying molecular mechanisms of m6A epigenetic modification in diabetes mellitus (DM) and diabetic microvascular complications have not been extensively clarified. In this review, we focus on the effects and possible mechanisms of m6A as possible potential biomarkers and therapeutic targets in the treatment of DM and diabetic microvascular complications.

Research progress on miR-124-3p in the field of kidney disease

MicroRNAs (miRNAs) are 18-25 nucleotides long, single-stranded, non-coding RNA molecules that regulate gene expression. They play a crucial role in maintaining normal cellular functions and homeostasis in organisms. Studies have shown that miR-124-3p is highly expressed in brain tissue and plays a significant role in nervous system development. It is also described as a tumor suppressor, regulating biological processes like cancer cell proliferation, apoptosis, migration, and invasion by controlling multiple downstream target genes. miR-124-3p has been found to be involved in the progression of various kidney diseases, including diabetic kidney disease, calcium oxalate kidney stones, acute kidney injury, lupus nephritis, and renal interstitial fibrosis. It mediates these processes through mechanisms like oxidative stress, inflammation, autophagy, and ferroptosis. To lay the foundation for future therapeutic strategies, this research group reviewed recent studies on the functional roles of miR-124-3p in renal diseases and the regulation of its downstream target genes. Additionally, the feasibility, limitations, and potential application of miR-124-3p as a diagnostic biomarker and therapeutic target were thoroughly investigated.

The role of RNA methylation in tumor immunity and its potential in immunotherapy

RNA methylation, a prevalent post-transcriptional modification, has garnered considerable attention in research circles. It exerts regulatory control over diverse biological functions by modulating RNA splicing, translation, transport, and stability. Notably, studies have illuminated the substantial impact of RNA methylation on tumor immunity. The primary types of RNA methylation encompass N6-methyladenosine (m6A), 5-methylcytosine (m5C), N1-methyladenosine (m1A), and N7-methylguanosine (m7G), and 3-methylcytidine (m3C). Compelling evidence underscores the involvement of RNA methylation in regulating the tumor microenvironment (TME). By affecting RNA translation and stability through the "writers", "erasers" and "readers", RNA methylation exerts influence over the dysregulation of immune cells and immune factors. Consequently, RNA methylation plays a pivotal role in modulating tumor immunity and mediating various biological behaviors, encompassing proliferation, invasion, metastasis, etc. In this review, we discussed the mechanisms and functions of several RNA methylations, providing a comprehensive overview of their biological roles and underlying mechanisms within the tumor microenvironment and among immunocytes. By exploring how these RNA modifications mediate tumor immune evasion, we also examine their potential applications in immunotherapy. This review aims to provide novel insights and strategies for identifying novel targets in RNA methylation and advancing cancer immunotherapy efficacy.

Diabetes and diabetic associative diseases: An overview of epigenetic regulations of TUG1

The epigenetic regulation of lncRNA TUG1 has garnered significant attention in the context of diabetes and its associated disorders. TUG1's multifaceted roles in gene expression modulation, and cellular differentiation, and it plays a major role in the growth of diabetes and the issues that are related to it due to pathological processes. In diabetes, aberrant epigenetic modifications can lead to dysregulation of TUG1 expression, contributing to disrupted insulin signaling, impaired glucose metabolism, and beta-cell dysfunction. Moreover, it has been reported that TUG1 contributes to the development of problems linked to diabetes, such as nephropathy, retinopathy, and cardiovascular complications, through epigenetically mediated mechanisms. Understanding the epigenetic regulations of TUG1 offers novel insights into the primary molecular mechanisms of diabetes and provides a possible path for healing interventions. Targeting epigenetic modifications associated with TUG1 holds promise for restoring proper gene expression patterns, ameliorating insulin sensitivity, and mitigating the inception and development of diabetic associative diseases. This review highlights the intricate epigenetic landscape that governs TUG1 expression in diabetes, encompassing DNA methylation and alterations in histone structure, as well as microRNA interactions.

Klotho-mediated activation of the anti-oxidant Nrf2/ARE signal pathway affects cell apoptosis, senescence and mobility in hypoxic human trophoblasts: involvement of Klotho in the pathogenesis of preeclampsia

The anti-aging gene Klotho is implicated in the pathogenesis of preeclampsia (PE), which is a pregnancy disease characterized by hypertension and proteinuria. Oxidative stress is closely associated with the worse outcomes in PE, and Klotho can eliminate Reactive Oxygen Species (ROS), but it is still unclear whether Klotho regulates PE pathogenesis through modulating oxidative damages. Here, by analyzing the clinical data, we found that Klotho was aberrantly downregulated in PE umbilical cord serum and placental tissues, compared to their normal counterparts. In in vitro experiments, the human trophoblasts were subjected to hypoxic pressure to establish the PE models, and we confirmed that hypoxia also decreased the expression levels of Klotho in those trophoblasts. In addition, through performing functional experiments, we confirmed that hypoxia promoted oxidative damages, cell apoptosis and senescence, whereas suppressed cell invasion in human trophoblasts, which were all reversed overexpressing Klotho. The following mechanical experiments verified that Klotho increased the levels of nuclear Nrf2, total Nrf2, SOD2 and NQO1 to activate the anti-oxidant Nrf2/ARE signal pathway, and silencing of Nrf2 abrogated the protective effects of Klotho overexpression on hypoxic human trophoblasts. Consistently, in in vivo experiments, Klotho overexpression restrained oxidative damages and facilitated cell mitosis in PE rats' placental tissues. In conclusion, this study validated that Klotho activated the Nrf2/ARE signal pathway to eliminate hypoxia-induced oxidative damages, cell apoptosis and senescence to recover normal cellular functions in human trophoblasts, and our data supported that Klotho could be used as novel biomarker for PE diagnosis and treatment.

Nucleic acid and protein methylation modification in renal diseases

Although great efforts have been made to elucidate the pathological mechanisms of renal diseases and potential prevention and treatment targets that would allow us to retard kidney disease progression, we still lack specific and effective management methods. Epigenetic mechanisms are able to alter gene expression without requiring DNA mutations. Accumulating evidence suggests the critical roles of epigenetic events and processes in a variety of renal diseases, involving functionally relevant alterations in DNA methylation, histone methylation, RNA methylation, and expression of various non-coding RNAs. In this review, we highlight recent advances in the impact of methylation events (especially RNA m6A methylation, DNA methylation, and histone methylation) on renal disease progression, and their impact on treatments of renal diseases. We believe that a better understanding of methylation modification changes in kidneys may contribute to the development of novel strategies for the prevention and management of renal diseases.

METTL3/YTHDF2 m6A axis mediates the progression of diabetic nephropathy through epigenetically suppressing PINK1 and mitophagy

AIMS

This research aimed to investigate the specific mechanism of methyltransferase like 3 (METTL3) in the progression of diabetic kidney disease (DKD).

MATERIALS AND METHODS

The model of diabetic kidney disease was established with HK-2 cells and mice in vitro and in vivo. The N6 methyladenosine (m6A) contents in the cells and tissues were detected with a commercial kit and the m6A levels of PTEN induced putative kinase 1 (PINK2) were detected with a MeRIP kit. The mRNA and protein levels were determined with RT-qPCR and western blot. The ROS, TNF-α, and IL-6 levels were assessed with ELISA. The cell proliferative ability was measured by a CCK-8 assay and cell apoptosis was determined with TUNEL staining. The HE and Masson staining was performed to observe the renal morphology. The RIP assay was conducted to detect the interaction between METTL3/YTHDF2 and PINK1.

RESULTS

The m6A content and METTL3 levels were prominently elevated in diabetic kidney disease. METTL3 silencing promoted the cell growth and the expression of LC3 II, PINK1, and Parkin, while inhibiting the cell apoptosis and the expression of LC3 I and p62 in the high glucose (HG) stimulated HK-2 cells. METTL3 silencing also decreased the ROS, TNF-α, and IL-6 levels in diabetic kidney disease. PINK1 silencing neutralized the function of sh-METTL3 in the HG stimulated HK-2 cells. The HE and Masson staining showed that METTL3 silencing alleviated the kidney injury induced by DKD. METTL3 silencing decreased the m6A levels of PINK1, while increased the mRNA levels of PINK1 which depended on YTHDF2.

CONCLUSIONS

METTL3 silencing could inhibit the progression of diabetic nephropathy in vivo and in vitro by regulating the m6A modification of PINK1, which depends on YTHDF2. Our research lays the theoretical foundation for the precise treatment of diabetic kidney disease and the development of targeted drugs in the future.

N6-methyladenosine modification in ischemic stroke: Functions, regulation, and therapeutic potential

N6-methyladenosine (m6A) modification is the most frequently occurring internal modification in eukaryotic RNAs. By modulating various aspects of the RNA life cycle, it has been implicated in a wide range of pathological and physiological processes associated with human diseases. Ischemic stroke is a major cause of death and disability worldwide with few treatment options and a narrow therapeutic window, and accumulating evidence has indicated the involvement of m6A modifications in the development and progression of this type of stroke. In this review, which provides insights for the prevention and clinical treatment of stroke, we present an overview of the roles played by m6A modification in ischemic stroke from three main perspectives: (1) the association of m6A modification with established risk factors for stroke, including hypertension, diabetes mellitus, hyperlipidemia, obesity, and heart disease; (2) the roles of m6A modification regulators and their functional regulation in the pathophysiological injury mechanisms of stroke, namely oxidative stress, mitochondrial dysfunction, endothelial dysfunction, neuroinflammation, and cell death processes; and (3) the diagnostic and therapeutic potential of m6A regulators in the treatment of stroke.

Endothelial downregulation of nuclear m6A reader YTHDC1 promotes pulmonary vascular remodeling in sugen hypoxia model of pulmonary hypertension

Background

Pulmonary hypertension (PH) is characterized with vascular remodeling, which is intiated by vascular endothelial dysfunction. N6-methyladenosine (m6A) modification mediates gene expression in many ways including mediating RNA degradation, splicing, nuclear export et al. m6A modification have been found to be associated with the development of PH. However, the role of m6A regulators in pulmonary artery endothelial cells (PAECs) dysfunction of PH is still under research.

Methods

The expression levels of m6A regulators in PAECs were analyzed with the single-cell sequencing Data(scRNA). Next, the target differentially expressed genes (DEGs) of m6A regulators in PAECs were functionally annotated. The analysis of cellular interactions included the examination of receptor-ligand pairs regulated by m6A regulators. Pseudo-time trajectory analyses and a ceRNA network involving lncRNAs, miRNAs, and mRNAs were conducted in PAECs. Furthermore, microarray data (GSE180169) for Sugen Hypoxia PH (SuHx PH) mouse models was screened for DEGs and m6A regulators in PAECs. Moreover, the expression of YTHDC1 in the lung samples of SuHx PH models was determined using immunofluorescence. In vitro, the mRNA expression of YTHDC1 in HPAECs under hypoxia conditions was detected. The effect of YTHDC1 recombinant protein on HPAEC proliferation was detected by Cell Counting Kit-8 (CCK8).

Results

Dysregulation of m6A regulators was observed in mouse PAECs. The m6A reader of YTHDC1 was decreased in PAECs in scRNA data and RNAseq data of isolated PAECs of SuHx PH models. Downregulation of YTHDC1 was caused by hypoxia in PAECs in vitro and similar results was observed in PAECs of SuHx PH mouse models. Next, YTHDC1 recombinant protein was found to inhibit HPAECs proliferation. The DEGs targeted by YTHDC1 were enriched in angiogenesis, endothelial cell migration, fluid shear stress, and stem cell maintenance. Analysis indicates that interactions among endothelial cells, smooth muscle cells, fibroblasts, and immune cells, mediated by specific YTHDC1 target genes (e.g., PTPRC-MRC1, ITBG2-ICAM1, COL4A1-CD44), contribute to PH development. Also, the YTHDC1 expression were consistent with Thioredoxin interacting protein (TXNIP). What's more, the predicted transcription factors showed that NFKB1, Foxd3 may be involved in the regulation of YTHDC1. Lastly, our data suggest that YTHDC1 may be involved in regulating PAECs dysfunction through lncRNA/miRNA/mRNA network.

Conclusion

For the first time, we analyzed changes in the expression and biological functions of m6A regulators in SuHx PH mouse models. We causatively linked YTHDC1 to PAECs dysfunction, providing novel insight into and opportunities to diagnose and treat PH.

Exosomes as nanostructures deliver miR-204 in alleviation of mitochondrial dysfunction in diabetic nephropathy through suppressing methyltransferase-like 7A-mediated CIDEC N6-methyladenosine methylation

OBJECTIVE

The exosomal cargo mainly comprises proteins, lipids, and microRNAs (miRNAs). Among these, miRNAs undertake multiple biological effects of exosomes (Exos). Some stem cell-derived exosomal miRNAs have shown the potential to treat diabetic nephropathy (DN). However, there is little research into the therapeutic effects of adipose-derived stem cell (ADSC)-derived exosomal miRNAs on DN. We aimed to explore the potential of miR-204-modified ADSC-derived Exos to mitigate DN.

METHODS

Exos were extracted and identified from ADSCs. Histopathological injury, oxidative stress (OS), mitochondrial function, cell viability, and apoptosis were assessed to explore the effects of ADSC-derived Exos on DN. For mechanism exploration, quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to measure miR-204, methyltransferase (METTL3, METTL14, and METTL7A), and CIDEC. Also, CIDEC m6A methylation and miR-204-METTL7A, and METTL7A-CIDEC interactions were determined.

RESULTS

Initially, OS-induced mitochondrial dysfunction was observed in DN rats. ADSC-derived Exos inhibited histopathological injury, cell apoptosis, OS, and mitochondrial dysfunction in DN rats. The similar therapeutic effects of ADSC-derived Exos were detected in the in vitro model. Intriguingly, miR-204 was released by ADSC-derived Exos and its upregulation enhanced the anti-DN effects of Exos. Mechanically, miR-204 reduced METTL7A expression to CIDEC m6A methylation, thus suppressing OS and mitochondrial dysfunction.

CONCLUSIONS

ADSC-derived exosomal miR-204 rescued OS-induced mitochondrial dysfunction by inhibiting METTL7A-mediated CIDEC m6A methylation. This study first revealed the significant role of ADSC-derived exosomal miR-204 in DN, paving the way for the development of novel therapeutic strategies to improve the clinical outcomes of DN patients.

N6-methyladenosine RNA methylation in diabetic kidney disease

Diabetic kidney disease (DKD) is a major microvascular complication of diabetes, and hyperglycemic memory associated with diabetes carries the risk of disease occurrence, even after the termination of blood glucose injury. The existence of hyperglycemic memory supports the concept of an epigenetic mechanism involving n6-methyladenosine (m6A) modification. Several studies have shown that m6A plays a key role in the pathogenesis of DKD. This review addresses the role and mechanism of m6A RNA modification in the progression of DKD, including the regulatory role of m6A modification in pathological processes, such as inflammation, oxidative stress, fibrosis, and non-coding (nc) RNA. This reveals the importance of m6A in the occurrence and development of DKD, suggesting that m6A may play a role in hyperglycemic memory phenomenon. This review also discusses how some gray areas, such as m6A modified multiple enzymes, interact to affect the development of DKD and provides countermeasures. In conclusion, this review enhances our understanding of DKD from the perspective of m6A modifications and provides new targets for future therapeutic strategies. In addition, the insights discussed here support the existence of hyperglycemic memory effects in DKD, which may have far-reaching implications for the development of novel treatments. We hypothesize that m6A RNA modification, as a key factor regulating the development of DKD, provides a new perspective for the in-depth exploration of DKD and provides a novel option for the clinical management of patients with DKD.

FTO-mediated m6A modification of serum amyloid A2 mRNA promotes podocyte injury and inflammation by activating the NF-κB signaling pathway

Diabetic kidney disease (DKD) is one of the severe complications of diabetes mellitus, yet there is no effective treatment. Exploring the development of DKD is essential to treatment. Podocyte injury and inflammation are closely related to the development of DKD. However, the mechanism of podocyte injury and progression in DKD remains largely unclear. Here, we observed that FTO expression was significantly upregulated in high glucose-induced podocytes and that overexpression of FTO promoted podocyte injury and inflammation. By performing RNA-seq and MeRIP-seq with control podocytes and high glucose-induced podocytes with or without FTO knockdown, we revealed that serum amyloid A2 (SAA2) is a target of FTO-mediated m6A modification. Knockdown of FTO markedly increased SAA2 mRNA m6A modification and decreased SAA2 mRNA expression. Mechanistically, we demonstrated that SAA2 might participate in podocyte injury and inflammation through activation of the NF-κB signaling pathway. Furthermore, by generating podocyte-specific adeno-associated virus 9 (AAV9) to knockdown SAA2 in mice, we discovered that the depletion of SAA2 significantly restored podocyte injury and inflammation. Together, our results suggested that upregulation of SAA2 promoted podocyte injury through m6A-dependent regulation, thus suggesting that SAA2 may be a therapeutic target for diabetic kidney disease.

Silencing of METTL3 prevents the proliferation, migration, epithelial-mesenchymal transition, and renal fibrosis of high glucose-induced HK2 cells by mediating WISP1 in m6A-dependent manner

Diabetic nephropathy (DN) is one of the most serious complications in diabetic patients. And m6A modifications mediated by METTL3 are involved multiple biological processes. However, the specific function and mechanism of METTL3 in DN remains unclear. DN model mice were first established with streptozotocin, and WISP1 expression was confirmed by qRT-PCR. Then the influences of WISP1 or/and METTL3 on the proliferation, migration, and epithelial-mesenchymal transition (EMT) and fibrosis-related proteins of high glucose (HG)-induced HK2 cells or HK2 cells were tested through CCK-8, wound healing, and western blot. We first revealed that WISP1 was highly expressed in renal tissues of DN model mice and HG-induced HK2 cells. Functionally, WISP1 or METTL3 silencing could weaken the proliferation, migration, EMT, and fibrosis of HG-treated HK2 cells, and WISP1 or METTL3 overexpression could induce the proliferation, migration, EMT, and fibrosis of HK2 cells. Additionally, METTL3 silencing could decrease WISP1 m6A modification, and silencing of METTL3 also could notably suppress the biological functions of HG-induced HK2 cells by downregulating WISP1. Silencing of METTL3 prevents DN development process by decreasing WISP1 with m6A modification pattern. Therefore, we suggest that METTL3/WISP1 axis might be a novel therapeutic target for DN.

Comprehensive analysis of m6A modification in lipopolysaccharide-induced acute lung injury in mice

BACKGROUND

N6-Methyladenosine (m6A) methylation is the most prevalent post-transcriptional modification in mRNA, and plays significant roles in various diseases. Nevertheless, the precise functions of m6A modification in the formation of ALI remain unclear. In this study we explore the transcriptome distribution of m6A methylation and its probable roles of in ALI.

METHODS

Lipopolysaccharide (LPS) was utilized to establish an ALI mouse model. Real-time qPCR, Western blotting and m6A dot blot were utilized to assess m6A methylation level and the expression of m6A methylation enzymes. MeRIP-Seq and RNA-seq were utilized to explore differential m6A modifications and differentially expressed genes in ALI mice. The hub genes and enriched pathways were assessed by Real-time qPCR and Western blotting.

RESULTS

Our findings showed that overall m6A methylation level was increased in ALI mice lung tissues, accompanied by lower levels of METTL3 and FTO. Notably, the protein expression of these methylases were different in various cells. There were 772 differently expressed m6A peaks in ALI as compared to the control group, with 316 being hypermethylated and 456 being hypomethylated. GO and KEGG analyses demonstrated these differentially methylated genes were associated with the calcium signaling pathway and cAMP signaling pathway. Furthermore, we identified 50 genes with distinct m6A peaks and mRNA expressions by combined analysis of MeRIP-Seq and RNA-Seq. KEGG analysis also demonstrated that these overlapped genes were closely associated with the calcium signaling pathway, cGMP-PKG signaling pathway, etc. Besides, Western blotting results demonstrated that the protein expression of Fibronectin leucine-rich transmembrane protein 3 (Flrt3) as well as the calcium signaling pathway and cGMP-PKG signaling pathway, increased significantly after ALI.

CONCLUSIONS

m6A modification was paramount in the pathogenesis of ALI, and provided a foundation for the further investigation in the prevention and treatment of ALI.

The current and emerging Klotho-enhancement strategies

Klotho is well known as a gene with antiaging properties. It has membrane and soluble forms, providing a unique system that controls various metabolic processes essential to health and disease. Klotho deficiency has been revealed to be associated with various aging-related disorders. Based on its various known and unknown protective properties, upregulating the Klotho gene may be a possible therapeutic and/or preventive approach in aging-related complications. Some agents, such as hormonal compounds, renin-angiotensin system inhibitors, antioxidants, peroxisome proliferator-activated receptor gamma (PPAR-γ) agonists, statins, vitamin D receptor agonists, antioxidants, anti-inflammatory agents, mammalian target of rapamycin (mTOR) signaling inhibitors, and receptor-interacting serine/threonine-protein kinase 1 (RIPK1) inhibitors, can possibly lead to the upregulation and elevation of Klotho levels. Demethylation and deacetylation of the Klotho gene can also be considered other possible Klotho-enhancement methods. Some emerging techniques, such as RNA modifications, gene therapy, gene editing, and exosome therapy, probably have the potential to be applied for increasing Klotho. In the present study, these current and emerging Klotho-enhancement strategies and their underlying mechanisms were comprehensively reviewed, which could highlight some potential avenues for future research.

Emerging role of N6-methyladenosine in the homeostasis of glucose metabolism

N6-methyladenosine (m6A) is the most prevalent post-transcriptional internal RNA modification, which is involved in the regulation of diverse physiological processes. Dynamic and reversible m6A modification has been shown to regulate glucose metabolism, and dysregulation of m6A modification contributes to glucose metabolic disorders in multiple organs and tissues including the pancreas, liver, adipose tissue, skeletal muscle, kidney, blood vessels, and so forth. In this review, the role and molecular mechanism of m6A modification in the regulation of glucose metabolism were summarized, the potential therapeutic strategies that improve glucose metabolism by targeting m6A modifiers were outlined, and feasible directions of future research in this field were discussed as well, providing clues for translational research on combating metabolic diseases based on m6A modification in the future.

The role of N-methyladenosine modification in acute and chronic kidney diseases

N6-methyladenosine (m6A) modification is a kind of RNA modification in which methylation occurs at the sixth N position in adenosine in RNA, which can occur in various RNAs such as mRNAs, lncRNAs and miRNAs. This is one of the most prominent and frequent posttranscriptional modifications within organisms and has been shown to function dynamically and reversibly in a variety of ways, including splicing, export, attenuation and translation initiation efficiency to regulate RNA expression. There are three main enzymes associated with m6A modification: writers, readers and erasers. Increasing evidence has shown that m6A modification is associated with the onset and development of kidney disease. In this article, we address the important physiological and pathological roles of m6A modification in kidney diseases (uremia, ischemia-reperfusion kidney injury, drug-induced kidney injury, and diabetic nephropathy) and its molecular mechanisms to provide reference for the diagnosis and clinical management of kidney diseases.

N6-methyladenosine (m6A) methylation in kidney diseases: Mechanisms and therapeutic potential

The N6-methyladenosine (m6A) modification is regulated by methylases, commonly referred to as "writers," and demethylases, known as "erasers," leading to a dynamic and reversible process. Changes in m6A levels have been implicated in a wide range of cellular processes, including nuclear RNA export, mRNA metabolism, protein translation, and RNA splicing, establishing a strong correlation with various diseases. Both physiologically and pathologically, m6A methylation plays a critical role in the initiation and progression of kidney disease. The methylation of m6A may also facilitate the early diagnosis and treatment of kidney diseases, according to accumulating research. This review aims to provide a comprehensive overview of the potential role and mechanism of m6A methylation in kidney diseases, as well as its potential application in the treatment of such diseases. There will be a thorough examination of m6A methylation mechanisms, paying particular attention to the interplay between m6A writers, m6A erasers, and m6A readers. Furthermore, this paper will elucidate the interplay between various kidney diseases and m6A methylation, summarize the expression patterns of m6A in pathological kidney tissues, and discuss the potential therapeutic benefits of targeting m6A in the context of kidney diseases.

METTL14 promotes the development of diabetic kidney disease by regulating m6A modification of TUG1

BACKGROUND

Diabetic kidney disease (DKD) is one of the most common diabetic complications. Endoplasmic reticulum stress (ERS) is an important step for renal tubular epithelial cell apoptosis during DKD progression. Herein, the role and regulatory mechanism of METTL14 in ERS during DKD progression were investigated.

METHODS

DKD animal and cell models were established by streptozotocin (STZ) and high glucose (HG), respectively. HE and Masson staining were performed to analyze renal lesions in DKD mouse. Cell viability and proliferation were determined by MTT and EdU staining, respectively. HK2 cell apoptosis was analyzed by flow cytometry. TUG1 m6A level was determined by Me-RIP. The interaction between TUG1, LIN28B and MAPK1 was analyzed by RIP and RNA pull-down assays.

RESULTS

HG stimulation promoted apoptosis and increased ERS marker proteins (GRP78, CHOP and caspase12) expression in HK2 cells, while these changes were reversed by METTL14 knockdown. METTL14 inhibited TUG1 stability and expression level in an m6A-dependent manner. As expected, TUG1 knockdown abrogated METTL14 knockdown's inhibition on HG-induced HK2 cell apoptosis and ERS. In addition, TUG1 inactivated MAPK1/ERK signaling by binding with LIN28B. And TUG1 overexpression's repression on HG-induced HK2 cell apoptosis and ERS was abrogated by MAPK1 signaling activation. Meanwhile, METTL14 knockdown or TUG1 overexpression protected against STZ-induced renal lesions and renal fibrosis in DKD mouse.

CONCLUSION

METTL14 promoted renal tubular epithelial cell apoptosis and ERS by activating MAPK/ERK pathway through m6A modification of TUG1, thereby accelerating DKD progression.

N6-methyladenosine methylation regulator RBM15 promotes the progression of diabetic nephropathy by regulating cell proliferation, inflammation, oxidative stress, and pyroptosis through activating the AGE-RAGE pathway

BACKGROUND

Diabetic nephropathy (DN) is a major cause of end-stage renal disease throughout the world, and m6A modification plays a critical role in the progression of DN. We aimed to find m6A-related genes and their regulatory mechanisms in DN.

METHODS

The expression levels of four important m6A-related genes (METTL16, RBM15, IGF2BP1, and ALKBH5) were detected by quantitative real-time PCR (RT-qPCR). RBM15 was chosen and its function was explored. The downstream pathway of RBM15 was screened by transcriptome sequencing. The levels of AGE, inflammation, and oxidative stress were determined with enzyme-linked immunosorbent assay, and the expression of AGE-RAGE pathway-related proteins were detected by Western blot (WB). Cell proliferation was assessed by Cell counting Kit-8 (CCK-8). The levels of pyroptosis-related proteins were evaluated by RT-qPCR or WB.

RESULTS

METTL16 and RBM15 were up regulated in the mouse model of DN, in which RBM15 was more significant. Silencing RBM15 recovered cell proliferation, reduced the levels of inflammation factors, and inhibited cell pyroptosis in high glucose-induced HK-2 cells. Transcriptome sequencing suggested that the AGE-RAGE pathway might be downstream of RBM15. RBM15 knockdown reduced AGE level and the expression of AGE-RAGE pathway-related proteins. After silencing RBM15, we found that activating the AGE-RAGE pathway inhibited cell proliferation, increased the levels of inflammation factors, promoted oxidative stress, and induced cell pyroptosis in HK-2 cell model of DN.

CONCLUSION

The m6A-related gene RBM15 inhibited cell proliferation, promoted inflammation, oxidative stress, and cell pyroptosis, thereby facilitating the progression of DN through the activation of the AGE-RAGE pathway.

Role of m6A modification in regulating the PI3K/AKT signaling pathway in cancer

The phosphoinositide 3-kinase (PI3K)/AKT signaling pathway plays a crucial role in the pathogenesis of cancer. The dysregulation of this pathway has been linked to the development and initiation of various types of cancer. Recently, epigenetic modifications, particularly N6-methyladenosine (m6A), have been recognized as essential contributors to mRNA-related biological processes and translation. The abnormal expression of m6A modification enzymes has been associated with oncogenesis, tumor progression, and drug resistance. Here, we review the role of m6A modification in regulating the PI3K/AKT pathway in cancer and its implications in the development of novel strategies for cancer treatment.

m6A epitranscriptomic modification in diabetic microvascular complications

N6-methyladenosine (m6A) modifications are modulated by m6A methyltransferases, m6A demethylases, and m6A-binding proteins. The dynamic and reversible patterns of m6A modification control cell fate programming by regulating RNA splicing, translation, and decay. Emerging evidence demonstrates that m6A modification of coding and noncoding RNAs exerts crucial effects that influence the pathogenesis of diabetic microvascular complications that include diabetic cardiomyopathy, diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, and diabetic dermatosis. In this review, we summarize the roles of m6A modification and m6A modification-related enzymes in diabetic microvascular complications and discuss potential m6A modification-related enzyme-targeting therapeutic strategies.

N6-methyladenosine methylation in kidney injury

Multiple mechanisms are involved in kidney damage, among which the role of epigenetic modifications in the occurrence and development of kidney diseases is constantly being revealed. However, N6-methyladenosine (M6A), a well-known post-transcriptional modification, has been regarded as the most prevalent epigenetic modifications in higher eukaryotic, which is involved in various biological processes of cells such as maintaining the stability of mRNA. The role of M6A modification in the mechanism of kidney damage has attracted widespread attention. In this review, we mainly summarize the role of M6A modification in the progression of kidney diseases from the following aspects: the regulatory pattern of N6-methyladenosine, the critical roles of N6-methyladenosine in chronic kidney disease, acute kidney injury and renal cell carcinoma, and then reveal its potential significance in the diagnosis and treatment of various kidney diseases. A better understanding of this field will be helpful for future research and clinical treatment of kidney diseases.

The role of N6-methyladenosine (m6A) in kidney diseases

Chemical modifications are a specific and efficient way to regulate the function of biological macromolecules. Among them, RNA molecules exhibit a variety of modifications that play important regulatory roles in various biological processes. More than 170 modifications have been identified in RNA molecules, among which the most common internal modifications include N6-methyladenine (m6A), n1-methyladenosine (m1A), 5-methylcytosine (m5C), and 7-methylguanine nucleotide (m7G). The most widely affected RNA modification is m6A, whose writers, readers, and erasers all have regulatory effects on RNA localization, splicing, translation, and degradation. These functions, in turn, affect RNA functionality and disease development. RNA modifications, especially m6A, play a unique role in renal cell carcinoma disease. In this manuscript, we will focus on the biological roles of m6A in renal diseases such as acute kidney injury, chronic kidney disease, lupus nephritis, diabetic kidney disease, and renal cancer.

Preliminary Feasibility Study on Diffusion Kurtosis Imaging to Monitor the Early Functional Alterations of Kidneys in Streptozocin-Induced Diabetic Rats

RATIONALE AND OBJECTIVES

The aim of this study was to investigate the potential of diffusion kurtosis imaging (DKI) to assess the early renal functional undulation of diabetic mellitus (DM).

MATERIALS AND METHODS

Fifty-seven Sprague-Dawley (SD) rats were randomly divided into two groups and eventually 48 rats were included in this study: the normal control (CON) group and diabetic mellitus (DM) group. Weeks 0, 4, 8, and 12 after the diabetes model was successfully established, all the rats were scanned on the 3.0T MRI. The DKI derived parameters of renal parenchyma, including fractional anisotropy (FAco, FAme), mean diffusivity (MDco, MDme), and mean kurtosis (MKco, MKme) were measured. Their alteration over time was analyzed and then correlated with urine volume (UV), blood urea nitrogen (BUN), and serum creatinine (Scr) using Pearson correlation analysis. Finally, hematoxylin and eosin (H&E) staining was performed on the kidneys of the two groups.

RESULT

There was a decreasing trend in FA, MK, and MD values over time in diabetic rats. Also, the gradually worsening histological damage of kidneys was noted over time in diabetic rats. The cortical FA and MK values and medullary FA, MK and MD values of diabetic rats were significantly lower than those of controls at most time points after DM induction. In addition, negative correlations were revealed between the BUN and FAco (r = -0.43, p = 0.03) or FAme value (r = -0.49, p = 0.01). The cortical MK value was moderately correlated with UV (r = -0.46, p = 0.03) and BUN (r = -0.55, p = 0.01).

CONCLUSION

The preliminary findings suggest that DKI might be an effective and sensitive tool to assess the early changes of renal function impairment in diabetic rats. The FA values of the cortex and medulla and the MK value of the cortex are sensitive markers in detecting renal injury in diabetic rats.

Role of TNF-α-induced m6A RNA methylation in diseases: a comprehensive review

Tumor Necrosis Factor-alpha (TNF-α) is ubiquitous in the human body and plays a significant role in various physiological and pathological processes. However, TNF-α-induced diseases remain poorly understood with limited efficacy due to the intricate nature of their mechanisms. N6-methyladenosine (m6A) methylation, a prevalent type of epigenetic modification of mRNA, primarily occurs at the post-transcriptional level and is involved in intranuclear and extranuclear mRNA metabolism. Evidence suggests that m6A methylation participates in TNF-α-induced diseases and signaling pathways associated with TNF-α. This review summarizes the involvement of TNF-α and m6A methylation regulators in various diseases, investigates the impact of m6A methylation on TNF-α-induced diseases, and puts forth potential therapeutic targets for treating TNF-α-induced diseases.

The role of m6A and m6Am RNA modifications in the pathogenesis of diabetes mellitus

The rapidly developing research field of epitranscriptomics has recently emerged into the spotlight of researchers due to its vast regulatory effects on gene expression and thereby cellular physiology and pathophysiology. N⁶-methyladenosine (m⁶A) and N⁶,2'-O-dimethyladenosine (m⁶Am) are among the most prevalent and well-characterized modified nucleosides in eukaryotic RNA. Both of these modifications are dynamically regulated by a complex set of epitranscriptomic regulators called writers, readers, and erasers. Altered levels of m⁶A and also several regulatory proteins were already associated with diabetic tissues. This review summarizes the current knowledge and gaps about m⁶A and m⁶Am modifications and their respective regulators in the pathophysiology of diabetes mellitus. It focuses mainly on the more prevalent type 2 diabetes mellitus (T2DM) and its treatment by metformin, the first-line antidiabetic agent. A better understanding of epitranscriptomic modifications in this highly prevalent disease deserves further investigation and might reveal clinically relevant discoveries in the future.

Sema3G activates YAP and promotes VSMCs proliferation and migration via Nrp2/PlexinA1

BACKGROUND

Diabetes exacerbates neointima formation after vascular procedures, manifested by accelerated proliferation and migration of vascular smooth muscle cells (VSMCs). Semaphorin 3G (Sema3G), secreted mainly from endothelial cells (ECs), regulates various cellular functions and vascular pathologies. However, the function and potential mechanism of ECs-derived Sema3G in VSMCs under diabetic condition remain unclear.

OBJECTIVE

To investigate the role and the mechanism of ECs-derived Sema3G in the regulation of VSMCs proliferation and migration.

RESULTS

ECs-derived Sema3G promoted human aortic SMCs (HASMCs) cell cycle progression and proliferation. Sema3G upregulated the expression of MMP2 and MMP9, which might explain the increased HASMCs migration by Sema3G. Inhibition of Nrp2/PlexinA1 mitigated the effect of Sema3G on promoting HASMCs proliferation and migration. Mechanistically, Sema3G inhibited LATS1 and activated YAP via Nrp2/PlexinA1. Verteporfin, an FDA-approved YAP pathway inhibitor, counteracted Sema3G-induced cyclin E and cyclin D1 expression. Besides, Sema3G expression was upregulated in ECs of diabetic mouse aortas. Serum Sema3G level was increased in type 2 diabetic patients and mice. Moreover, compared to chow diet-fed mice, high-fat diet (HFD)-fed obese mice showed thicker neointima and higher Sema3G expression in vasculature after femoral injury.

CONCLUSIONS

Our results indicated that ECs-derived Sema3G under diabetic condition activated YAP and promoted HASMCs proliferation and migration via Nrp2/PlexinA1. Thus, inhibition of Sema3G may hold therapeutic potential against diabetes-associated intimal hyperplasia.

Nrf2 signaling in diabetic nephropathy, cardiomyopathy and neuropathy: Therapeutic targeting, challenges and future prospective

Western lifestyle contributes to an overt increase in the prevalence of metabolic anomalies including diabetes mellitus (DM) and obesity. Prevalence of DM is rapidly growing worldwide, affecting many individuals in both developing and developed countries. DM is correlated with the onset and development of complications with diabetic nephropathy (DN), diabetic cardiomyopathy (DC) and diabetic neuropathy being the most devastating pathological events. On the other hand, Nrf2 is a regulator for redox balance in cells and accounts for activation of antioxidant enzymes. Dysregulation of Nrf2 signaling has been shown in various human diseases such as DM. This review focuses on the role Nrf2 signaling in major diabetic complications and targeting Nrf2 for treatment of this disease. These three complications share similarities including the presence of oxidative stress, inflammation and fibrosis. Onset and development of fibrosis impairs organ function, while oxidative stress and inflammation can evoke damage to cells. Activation of Nrf2 signaling significantly dampens inflammation and oxidative damage, and is beneficial in retarding interstitial fibrosis in diabetic complications. SIRT1 and AMPK are among the predominant pathways to upregulate Nrf2 expression in the amelioration of DN, DC and diabetic neuropathy. Moreover, certain therapeutic agents such as resveratrol and curcumin, among others, have been employed in promoting Nrf2 expression to upregulate HO-1 and other antioxidant enzymes in the combat of oxidative stress in the face of DM.

N6-methyladenosine (m6A) writer METTL3 accelerates the apoptosis of vascular endothelial cells in high glucose

Recent studies have shown that N⁶-methyladenosine (m⁶A) methylation, one of the most prevalent epigenetic modifications, is involved in diabetes mellitus. However, whether m⁶A regulates diabetic vascular endothelium injury is still elusive. Present research aimed to investigate the regulation and mechanism of m⁶A on vascular endothelium injury. Upregulation of METTL3 was observed in the high glucose (HG)-induced human umbilical vein endothelial cells (HUVECs), following with the upregulation of m⁶A methylation level. Functionally, METTL3 silencing repressed the apoptosis and recovered the proliferation of HUVECs disposed by HG. Moreover, HG exposure upregulated the expression of suppressor of cytokine signaling3 (SOCS3). Mechanistically, METTL3 targeted the m⁶A site on SOCS3 mRNA, which positively regulated the mRNA stability of SOCS3. In conclusion, METTL3 silencing attenuated the HG-induced vascular endothelium cells injury via promoting SOCS3 stability. In conclusion, this research expands the understanding of m⁶A on vasculopathy in diabetes mellitus and provides a potential strategy for the protection of vascular endothelial injury.

RNA N6 -methyladenosine modifications and potential targeted therapeutic strategies in kidney disease

Epigenetic modifications have received increasing attention and have been shown to be extensively involved in kidney development and disease progression. Among them, the most common RNA modification, N⁶ -methyladenosine (m⁶ A), has been shown to dynamically and reversibly exert its functions in multiple ways, including splicing, export, decay and translation initiation efficiency to regulate mRNA fate. Moreover, m⁶ A has also been reported to exert biological effects by destabilizing base pairing to modulate various functions of RNAs. Most importantly, an increasing number of kidney diseases, such as renal cell carcinoma, acute kidney injury and chronic kidney disease, have been found to be associated with aberrant m⁶ A patterns. In this review, we comprehensively review the critical roles of m⁶ A in kidney diseases and discuss the possibilities and relevance of m⁶ A-targeted epigenetic therapy, with an integrated comprehensive description of the detailed alterations in specific loci that contribute to cellular processes that are associated with kidney diseases.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

The impact of oxidative stress-induced mitochondrial dysfunction on diabetic microvascular complications

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycaemia, with absolute insulin deficiency or insulin resistance as the main cause, and causes damage to various target organs including the heart, kidney and neurovascular. In terms of the pathological and physiological mechanisms of DM, oxidative stress is one of the main mechanisms leading to DM and is an important link between DM and its complications. Oxidative stress is a pathological phenomenon resulting from an imbalance between the production of free radicals and the scavenging of antioxidant systems. The main site of reactive oxygen species (ROS) production is the mitochondria, which are also the main organelles damaged. In a chronic high glucose environment, impaired electron transport chain within the mitochondria leads to the production of ROS, prompts increased proton leakage and altered mitochondrial membrane potential (MMP), which in turn releases cytochrome c (cyt-c), leading to apoptosis. This subsequently leads to a vicious cycle of impaired clearance by the body's antioxidant system, impaired transcription and protein synthesis of mitochondrial DNA (mtDNA), which is responsible for encoding mitochondrial proteins, and impaired DNA repair systems, contributing to mitochondrial dysfunction. This paper reviews the dysfunction of mitochondria in the environment of high glucose induced oxidative stress in the DM model, and looks forward to providing a new treatment plan for oxidative stress based on mitochondrial dysfunction.

The Role of N6-Methyladenosine in Inflammatory Diseases

N⁶-Methyladenosine (m⁶A) is the most abundant epigenetic RNA modification in eukaryotes, regulating RNA metabolism (export, stability, translation, and decay) in cells through changes in the activity of writers, erasers, and readers and ultimately affecting human life or disease processes. Inflammation is a response to infection and injury in various diseases and has therefore attracted significant attention. Currently, extensive evidence indicates that m⁶A plays an essential role in inflammation. In this review, we focus on the mechanisms of m⁶A in inflammatory autoimmune diseases, metabolic disorder, cardio-cerebrovascular diseases, cancer, and pathogen-induced inflammation, as well as its possible role as targets for clinical diagnosis and treatment.

The Effect of Allograft Inflammatory Factor-1 on Inflammation, Oxidative Stress, and Autophagy via miR-34a/ATG4B Pathway in Diabetic Kidney Disease

Increasing evidence suggests that disorders of inflammation, oxidative stress, and autophagy contribute to the pathogenesis of diabetic kidney disease (DKD). This study attempted to clarify the effect of allograft inflammatory factor-1 (AIF-1), miR-34a, and ATG4B on inflammation, oxidative stress, and autophagy in DKD both in vitro and in vivo experiments. In vivo, it was found that the levels of AIF-1, miR-34a, oxidative stress, and inflammatory factors were significantly increased in blood and urine samples of DKD patients and mouse models and correlated with the level of urinary protein. In vitro, it was also found that the expressions of AIF-1, miR-34a, ROS, and inflammatory factors were increased, while ATG4B and other autophagy related proteins were decreased in human renal glomerular endothelial cells (HRGECs) cultured with high concentration glucose medium (30 mmol/L). When AIF-1 gene was overexpressed, the levels of miR-34a, ROS, and inflammatory factors were significantly upregulated, and autophagy-related proteins such as ATG4B were downregulated, while downregulation of AIF-1 gene had the opposite effect. In addition, miR-34a inhibited the expression of ATG4B and autophagy-related proteins and increased the levels of ROS and inflammation. Furthermore, the result of luciferase reporter assay suggested that ATG4B was the target gene of miR-34a. When ATG4B gene was overexpressed, the level of autophagy was upregulated, and inflammatory factors were downregulated. Conversely, when ATG4B gene was inhibited, the level of autophagy was downregulated, and inflammatory factors were upregulated. Then, autophagy inducers inhibited the levels of inflammation and ROS, whereas autophagy inhibitors had the opposite function in HRGECs induced by glucose (30 mmol/L). In conclusion, the above data suggested that AIF-1 regulated the levels of inflammation, oxidative stress, and autophagy in HRGECs via miR-34a/ATG4B pathway to contribute to the pathogenesis of diabetic kidney disease.