Roles of circular RNAs in diabetic complications: From molecular mechanisms to therapeutic potential

Bacteroides uniformis Ameliorates Carbohydrate and Lipid Metabolism Disorders in Diabetic Mice by Regulating Bile Acid Metabolism via the Gut-Liver Axis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a metabolic syndrome characterized by chronic inflammation, insulin resistance, and islet cell damage. The prevention of T2DM and its associated complications is an urgent public health issue that affects hundreds of millions of people globally. Numerous studies suggest that disturbances in gut metabolites are important driving forces for the pathogenesis of diabetes. However, the functions and mechanisms of action of most commensal bacteria in T2DM remain largely unknown.

METHODS

The quantification of bile acids (BAs) in fecal samples was performed using ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS). The anti-diabetic effects of Bacteroides uniformis (B. uniformis) and its metabolites cholic acid (CA) and chenodeoxycholic acid (CDCA) were assessed in T2DM mice induced by streptozocin (STZ) plus high-fat diet (HFD).

RESULTS

We found that the abundance of B. uniformis in the feces and the contents of CA and CDCA were significantly downregulated in T2DM mice. B. uniformis was diminished in diabetic individuals and this bacterium was sufficient to promote the production of BAs. Colonization of B. uniformis and intragastric gavage of CA and CDCA effectively improved the disorder of glucose and lipid metabolism in T2DM mice by inhibiting gluconeogenesis and lipolysis in the liver. CA and CDCA improved hepatic glucose and lipid metabolism by acting on the Takeda G protein-coupled receptor 5 (TGR5)/adenosine monophosphate-activated protein kinase (AMPK) signaling pathway since knockdown of TGR5 minimized the benefit of CA and CDCA. Furthermore, we screened a natural product-vaccarin (VAC)-that exhibited anti-diabetic effects by promoting the growth of B. uniformis in vitro and in vivo. Gut microbiota pre-depletion abolished the favorable effects of VAC in diabetic mice.

CONCLUSIONS

These data suggest that supplementation of B. uniformis may be a promising avenue to ameliorate T2DM by linking the gut and liver.

The m6A-ncRNAs axis in diabetes complications: novel mechanism and therapeutic potential

Diabetes, a multifaceted metabolic disorder, poses a significant global health burden with its increasing prevalence and associated complications, such as diabetic nephropathy, diabetic retinopathy, diabetic cardiomyopathy, and diabetic angiopathy. Recent studies have highlighted the intricate interplay between N6-methyladenosine (m6A) and non-coding RNAs (ncRNAs) in key pathways implicated in these diabetes complications, like cell apoptosis, oxidative stress, and inflammation. Thus, understanding the mechanistic insights into how m6A dysregulation impacts the expression and function of ncRNAs opens new avenues for therapeutic interventions targeting the m6A-ncRNAs axis in diabetes complications. This review explores the regulatory roles of m6A modifications and ncRNAs, and stresses the role of the m6A-ncRNA axis in diabetes complications, providing a therapeutic potential for these diseases.

Deficiency of neutral cholesterol ester hydrolase 1 (NCEH1) impairs endothelial function in diet-induced diabetic mice

BACKGROUND

Neutral cholesterol ester hydrolase 1 (NCEH1) plays a critical role in the regulation of cholesterol ester metabolism. Deficiency of NCHE1 accelerated atherosclerotic lesion formation in mice. Nonetheless, the role of NCEH1 in endothelial dysfunction associated with diabetes has not been explored. The present study sought to investigate whether NCEH1 improved endothelial function in diabetes, and the underlying mechanisms were explored.

METHODS

The expression and activity of NCEH1 were determined in obese mice with high-fat diet (HFD) feeding, high glucose (HG)-induced mouse aortae or primary endothelial cells (ECs). Endothelium-dependent relaxation (EDR) in aortae response to acetylcholine (Ach) was measured.

RESULTS

Results showed that the expression and activity of NCEH1 were lower in HFD-induced mouse aortae, HG-exposed mouse aortae ex vivo, and HG-incubated primary ECs. HG exposure reduced EDR in mouse aortae, which was exaggerated by endothelial-specific deficiency of NCEH1, whereas NCEH1 overexpression restored the impaired EDR. Similar results were observed in HFD mice. Mechanically, NCEH1 ameliorated the disrupted EDR by dissociating endothelial nitric oxide synthase (eNOS) from caveolin-1 (Cav-1), leading to eNOS activation and nitric oxide (NO) release. Moreover, interaction of NCEH1 with the E3 ubiquitin-protein ligase ZNRF1 led to the degradation of Cav-1 through the ubiquitination pathway. Silencing Cav-1 and upregulating ZNRF1 were sufficient to improve EDR of diabetic aortas, while overexpression of Cav-1 and downregulation of ZNRF1 abolished the effects of NCEH1 on endothelial function in diabetes. Thus, NCEH1 preserves endothelial function through increasing NO bioavailability secondary to the disruption of the Cav-1/eNOS complex in the endothelium of diabetic mice, depending on ZNRF1-induced ubiquitination of Cav-1.

CONCLUSIONS

NCEH1 may be a promising candidate for the prevention and treatment of vascular complications of diabetes.

Circular RNAs: An emerging precise weapon for diabetic nephropathy diagnosis and therapy

Diabetic nephropathy (DN) is a prevalent chronic microvascular complication associated with diabetes mellitus and represents a major cause of chronic kidney disease and renal failure. Current treatment strategies for DN primarily focus on symptom alleviation, lacking effective approaches to halt or reverse DN progression. Circular RNA (circRNA), characterized by a closed-loop structure, has emerged as a novel non-coding RNA regulator of gene expression, attributed to its conservation, stability, specificity, and multifunctionality. Dysregulation of circRNA expression is closely associated with DN progression, whereby circRNA impacts kidney cell injury by modulating cell cycle, differentiation, cell death, as well as influencing the release of inflammatory factors and stromal fibronectin expression. Consequently, circRNA is considered a predictive biomarker and a potential therapeutic target for DN. This review provides an overview of the latest research progress in the classification, functions, monitoring methods, and databases related to circRNA. The paper focuses on elucidating the impact and underlying mechanisms of circRNA on kidney cells under diabetic conditions, aiming to offer novel insights into the prevention, diagnosis, and treatment of DN.

Optogenetic engineered umbilical cord MSC-derived exosomes for remodeling of the immune microenvironment in diabetic wounds and the promotion of tissue repair

BACKGROUND

Angiogenesis and tissue repair in chronic non-healing diabetic wounds remain critical clinical problems. Engineered MSC-derived exosomes have significant potential for the promotion of wound healing. Here, we discuss the effects and mechanisms of eNOS-rich umbilical cord MSC exosomes (UCMSC-exo/eNOS) modified by genetic engineering and optogenetic techniques on diabetic chronic wound repair.

METHODS

Umbilical cord mesenchymal stem cells were engineered to express two recombinant proteins. Large amounts of eNOS were loaded into UCMSC-exo using the EXPLOR system under blue light irradiation. The effects of UCMSC-exo/eNOS on the biological functions of fibroblasts and vascular endothelial cells in vitro were evaluated. Full-thickness skin wounds were constructed on the backs of diabetic mice to assess the role of UCMSC-exo/eNOS in vascular neogenesis and the immune microenvironment, and to explore the related molecular mechanisms.

RESULTS

eNOS was substantially enriched in UCMSCs-exo by endogenous cellular activities under blue light irradiation. UCMSC-exo/eNOS significantly improved the biological functions of cells after high-glucose treatment and reduced the expression of inflammatory factors and apoptosis induced by oxidative stress. In vivo, UCMSC-exo/eNOS significantly improved the rate of wound closure and enhanced vascular neogenesis and matrix remodeling in diabetic mice. UCMSC-exo/eNOS also improved the inflammatory profile at the wound site and modulated the associated immune microenvironment, thus significantly promoting tissue repair.

CONCLUSION

This study provides a novel therapeutic strategy based on engineered stem cell-derived exosomes for the promotion of angiogenesis and tissue repair in chronic diabetic wounds.

CDA-SKAG: Predicting circRNA-disease associations using similarity kernel fusion and an attention-enhancing graph autoencoder

Circular RNAs (circRNAs) constitute a category of circular non-coding RNA molecules whose abnormal expression is closely associated with the development of diseases. As biological data become abundant, a lot of computational prediction models have been used for circRNA-disease association prediction. However, existing prediction models ignore the non-linear information of circRNAs and diseases when fusing multi-source similarities. In addition, these models fail to take full advantage of the vital feature information of high-similarity neighbor nodes when extracting features of circRNAs or diseases. In this paper, we propose a deep learning model, CDA-SKAG, which introduces a similarity kernel fusion algorithm to integrate multi-source similarity matrices to capture the non-linear information of circRNAs or diseases, and construct a circRNA information space and a disease information space. The model embeds an attention-enhancing layer in the graph autoencoder to enhance the associations between nodes with higher similarity. A cost-sensitive neural network is introduced to address the problem of positive and negative sample imbalance, consequently improving our model's generalization capability. The experimental results show that the prediction performance of our model CDA-SKAG outperformed existing circRNA-disease association prediction models. The results of the case studies on lung and cervical cancer suggest that CDA-SKAG can be utilized as an effective tool to assist in predicting circRNA-disease associations.

Silencing circ_0080425 alleviates high-glucose-induced endothelial cell dysfunction in diabetic nephropathy by targeting miR-140-3p/FN1 axis

BACKGROUND

Hsa_circ_0080425 (circ_0080425) is newly identified to correlate with the progression of diabetic nephropathy (DN). However, its role and mechanism in DN process is not very clear.

METHODS

Cell counting kit-8 assay, flow cytometry, scratch wound assay, and western blotting were performed to measure endothelial cell dysfunction. Expression of circ_0080425, microRNA (miR)-140-3p and fibronectin 1 (FN1) were determined by quantitative real-time PCR and western blotting. The direct interaction was confirmed by dual-luciferase reporter assay.

RESULTS

High-glucose (HG) treatment could induce inhibition of cell proliferation, cell cycle entrance and wound healing rate in human umbilical vein endothelial cells (HRGEC), and enhancement of apoptosis rate. Circ_0080425 expression was upregulated by HG, and exhausting circ_0080425 could attenuate HG-induced above effects in HRGEC. MiR-140-3p was sponged by circ_0080425, and its inhibitor reversed the regulation of circ_0080425 knockdown on HG-induced HRGEC injury. FN1 was targeted by miR-140-3p, and its overexpression also restored the inhibitory effect of miR-140-3p on HC-induced HRGEC injury.

CONCLUSION

Circ_0080425 expression might contribute to HG-induced endothelial cell injury, and circ_0080425/miR-140-3p/FN1 axis was a potential therapeutic approach to interfere DN process.

Hydrogen Sulfide in Diabetic Complications Revisited: The State of the Art, Challenges, and Future Directions

Significance: Diabetes and its related complications are becoming an increasing public health problem that affects hundreds of millions of people globally. Increased disability and mortality rate of diabetic individuals are closely associated with various life-threatening complications, such as atherosclerosis, nephropathy, retinopathy, and cardiomyopathy. Recent Advances: Conventional treatments for diabetes are still limited because of undesirable side effects, including obesity, hypoglycemia, and hepatic and renal toxicity. Studies have shown that hydrogen sulfide (H₂S) plays a critical role in the modulation of glycolipid metabolism, pancreatic β cell functions, and diabetic complications. Critical Issues: Preservation of endogenous H₂S systems and supplementation of H₂S donors are effective in attenuating diabetes-induced complications, thus representing a new avenue to treat diabetes and its associated complications. Future Directions: This review systematically recapitulates and discusses the most recent updates regarding the therapeutic effects of H₂S on diabetes and its various complications, with an emphasis on the molecular mechanisms that underlie H₂S-mediated protection against diabetic complications. Furthermore, current clinical trials of H₂S in diabetic populations are highlighted, and the challenges and solutions to the clinical transformation of H₂S-derived therapies in diabetes are proposed. Finally, future research directions of the pharmacological actions of H₂S in diabetes and its related complications are summarized. Antioxid. Redox Signal. 38, 18-44.

Circ_0060077 Knockdown Alleviates High-Glucose-Induced Cell Apoptosis, Oxidative Stress, Inflammation and Fibrosis in HK-2 Cells via miR-145-5p/VASN Pathway

The involvement of circular RNAs (circRNAs) in the progression of diabetic nephropathy (DN) has been reported. However, the functions of circ_0060077 in DN remain unclear. HK-2 cells were treated with high glucose (HG) to establish DN cell model. Quantitative real-time polymerase chain reaction (qRT-PCR) was proceeded to determine the levels of circ_0060077, microRNA-145-5p (miR-145-5p) and vasorin (VASN). Cell counting kit-8 (CCK-8) assay, 5-ethynyl-2'-deoxyuridine (EdU) assay and colony formation assay were conducted to assess cell proliferation ability. Flow cytometry analysis was employed for cell apoptosis. The oxidative stress level was evaluated by commercial kits. Enzyme-linked immunosorbent assay (ELISA) was adopted to examine the concentrations of inflammatory factors. Western blot assay was utilized for protein levels. Dual-luciferase reporter assay and RNA pull-down assay were manipulated to analyze the relationships among circ_0060077, miR-145-5p and VASN. Circ_0060077 level was increased in DN patients and HG-stimulated HK-2 cells. Circ_0060077 knockdown ameliorated the inhibitory effect of HG on HK-2 cell proliferation and the promotional effects on cell apoptosis, oxidative stress, inflammation and fibrosis. MiR-145-5p was identified as the target for circ_0060077 and miR-145-5p inhibition ameliorated the effect of circ_0060077 silencing on HG-induced HK-2 cell injury. Moreover, miR-145-5p directly bound to VASN. Overexpression of miR-145-5p facilitated cell proliferation and repressed apoptosis, oxidative injury, inflammation and fibrosis in HG-induced HK-2 cells by targeting VASN. Circ_0060077 silencing protected HK-2 cells from HG-induced damage by regulating miR-145-5p/VASN axis.

Circ_0123996 promotes the proliferation, inflammation, and fibrosis of mesangial cells by sponging miR-203a-3p to upregulate SOX6 in diabetic nephropathy

Circular RNA has been reported to participate in human diseases including diabetic nephropathy (DN). However, the role and mechanism of circ_0123996 in DN need to be further explored. Relative expression levels of circ_0123996, microRNA (miR)-203a-3p, SRY-box 6 (SOX6), and inflammatory cytokines were determined using quantitative real-time PCR. Western blot analysis was used to detect the protein expression of SOX6 and fibrosis-related markers. Cell proliferation was measured using the Cell Counting Kit 8 assay. The interaction between miR-203a-3p and circ_0123996 or SOX6 was verified using the dual-luciferase reporter assay. The circ_0123996 and SOX6 expression were increased and the miR-203a-3p expression was decreased in high glucose-induced mesangial cells. Silenced circ_0123996 could hinder the proliferation, inflammation, and fibrosis of mesangial cells. In terms of mechanism, circ_0123996 could sponge miR-203a-3p to positively regulate SOX6 expression. Function experiments revealed that miR-203a-3p inhibitor could abolish the regulation of circ_0123996 silencing on mesangial cell proliferation, inflammation, and fibrosis. In addition, the knockdown of SOX6 could inhibit mesangial cell proliferation, inflammation, and fibrosis. Also, SOX6 overexpression could reverse the regulation of circ_0123996 silencing on mesangial cell progression. In summary, our data revealed that circ_0123996 promoted the proliferation, inflammation, and fibrosis of mesangial cells via modulating the miR-203a-3p/SOX6 axis, suggesting that circ_0123996 might be a target for alleviating DN progression.

circ_0041795 Induces YAP1 Upregulation to Accelerate the Progression of Diabetic Retinopathy through Binding to miR-589-5p

Background

Circular RNAs (circRNAs) are involved in the pathogenesis of many diseases, and circ_0041795 was shown to promote the progression of diabetic retinopathy (DR). The aim of this study was to explore the molecular mechanism of circ_0041795 in DR.

Methods

Human retinal pigment epithelial cells ARPE-19 were treated with high glucose (HG). circ_0041795, miR-589-5p, and Yes-associated protein 1 (YAP1) levels were measured by reverse transcription-quantitative polymerase chain reaction assay. Biological behaviors were examined by Cell Counting Kit-8 assay for cell viability, EdU assay for cell proliferation, flow cytometry for cell apoptosis, and enzyme-linked immunosorbent assay for cell inflammation. Oxidative stress was assessed via the commercial kits. Western blot was performed for analysis of protein expression. The molecular binding was assessed via dual-luciferase reporter assay and pull-down assay.

Results

HG-induced inhibiting effects on cell viability and proliferation but promoting effects on cell apoptosis, inflammation, and oxidative stress were ameliorated by silence of circ_0041795. circ_0041795 was identified to act as a miR-589-5p sponge. The regulation of circ_0041795 in HG-induced cell injury was achieved by inhibiting miR-589-5p. miR-589-5p targeted YAP1 and relieved HG-induced cell dysfunction via downregulating YAP1. circ_0041795 sponged miR-589-5p to regulate YAP1 level and activated the NF-κB pathway through the miR-589-5p/YAP1 axis.

Conclusion

All these results elucidated that circ_0041795 facilitated the development of DR by inducing miR-589-5p-mediated YAP1 upregulation.

Circular ribonucleic acid nucleoporin 98 knockdown alleviates high glucose-induced proliferation, fibrosis, inflammation and oxidative stress in human glomerular mesangial cells by regulating the microribonucleic acid-151-3p-high mobility group AT-hook 2 axis

AIMS/INTRODUCTION

This study aimed to investigate the role and mechanism of circular ribonucleic acid nucleoporin 98 (circNUP98) in diabetic nephropathy (DN).

MATERIALS AND METHODS

Human glomerular mesangial cells (HMCs) were stimulated with high glucose (HG) to imitate the growth environment of cells under the DN condition. Levels of genes and proteins were tested by quantitative reverse transcription polymerase chain reaction and western blot. Cell proliferation, apoptosis and inflammatory response were analyzed by using cell counting kit-8, flow cytometry and enzyme-linked immunosorbent assay analysis, respectively. Oxidative stress and fibrosis were evaluated by detecting the activity of reactive oxygen species, malondialdehyde, superoxide dismutase, fibronectin and collagen IV. The binding interaction between microribonucleic acid (miR)-151-3p and high mobility group AT-hook 2 (HMGA2) or circNUP98 was confirmed using dual-luciferase reporter, pull-down and ribonucleic acid immunoprecipitation assays. Exosomes were isolated by ultracentrifugation, and qualified by transmission electron microscopy, nanoparticle tracking analysis and western blot.

RESULTS

CircNUP98 expression was higher in the serum of DN patients and HG-stimulated HMCs. Functionally, circNUP98 knockdown alleviated HG-induced proliferation, fibrosis, inflammatory response and oxidative stress in HMCs. Mechanistically, circNUP98 directly sponged miR-151-3p, which targeted HMGA2. Rescue experiments showed that miR-151-3p reversed the inhibitory effects of circNUP98 knockdown on HG-induced HMC dysfunction. Furthermore, miR-151-3p re-expression also led to an inhibition of the aforementioned biological behaviors, which was attenuated by HMGA2 upregulation. Besides that, CircNUP98 was found to be packaged into exosomes of DN, and exosomal circNUP98 possessed diagnostic value for DN patients.

CONCLUSION

CircNUP98 knockdown alleviates HG-induced proliferation, fibrosis inflammation and oxidative stress in HMCs by regulating the miR-151-3p-HMGA2 axis, which might provide a potential approach for DN therapeutics.

CircPVT1 promotes the tumorigenesis and metastasis of osteosarcoma via mediation of miR-26b-5p/CCNB1 axis

INTRODUCTION

Osteosarcoma (OS) is the most aggressive malignancy among the bone tumors in the world. Circular RNAs (circRNAs) have been reported to be participated in multiple cancers, including OS. Meanwhile, circPVT1 has been proved to be upregulated in OS. However, the mechanism by which circPVT1 mediates the tumorigenesis of OS remains to be further explored.

MATERIALS AND METHODS

Protein and gene expressions in OS cells were measured by western blot and RT-qPCR, respectively. Cell growth was assessed by flow cytometry and colony formation, respectively. In addition, cell migration was assessed by wound healing, and invasion was evaluated by Transwell assay. Meanwhile, the correlation among circPVT1, miR-26b-5p and CCNB1 was explored by RNA pull-down and dual luciferase assay. Finally, in vivo model was established to explore the role of circPVT1 in OS in vivo.

RESULTS

CircPVT1 and CCNB1 were significantly upregulated in OS cells, while miR-26b-5p was downregulated. Knockdown of circPVT1 notably inhibited proliferation and induced apoptosis of OS cells. CircPVT1 shRNA significantly suppressed the OS cell invasion and migration. Meanwhile, circPVT1 sponged miR-26b-5p and CCNB1 was found to be the direct target of miR-26b-5p. Furthermore, silencing of circPVT1 inhibited the growth and metastasis of OS in vivo.

CONCLUSION

Silencing of circPVT1 notably suppressed the tumorigenesis and metastasis of OS via miR-26b-5p/CCNB1 axis. Therefore, circPVT1 might be used as a target for OS treatment.

CircZNF532 knockdown protects retinal pigment epithelial cells against high glucose-induced apoptosis and pyroptosis by regulating the miR-20b-5p/STAT3 axis

INTRODUCTION

The loss of retinal pigment epithelial (RPE) cells is associated with the etiology of diabetic retinopathy (DR). This study investigated the effects of circular RNA ZNF532 (circZNF532) on apoptosis and pyroptosis of RPE cells.

MATERIALS AND METHODS

Blood samples were collected from patients with DR and healthy volunteers. A human RPE cell line ARPE-19 was induced by high glucose (HG) and assayed for cell viability, apoptosis, and pyroptosis. The binding of miR-20b-5p with circZNF532 and STAT3 was confirmed by a luciferase activity assay. A mouse model of diabetic retinopathy was established.

RESULTS

CircZNF532 and STAT3 were upregulated but miR-20b-5p was downregulated in the serum samples of patients with DR and HG-induced ARPE-19 cells. Elevated miR-20b-5p or CircZNF532 knockdown enhanced proliferation but reduced apoptosis and pyroptosis of ARPE-19 cells. CircZNF532 sponged miR-20b-5p and inhibited its expression. STAT3 was verified as a target of miR-20b-5p. MiR-20b-5p modulated ARPE-19 cell viability, apoptosis, and pyroptosis by targeting STAT3. Mice with STZ-induced diabetes showed elevated expressions of circZNF532 and STAT3 but decreased the level of miR-20b-5p compared with the controls. Knockdown of circZNF532 inhibited apoptosis and pyroptosis in mouse retinal tissues.

CONCLUSION

CircZNF532 knockdown rescued human RPE cells from HG-induced apoptosis and pyroptosis by regulating STAT3 via miR-20b-5p.

Exosomal circTAOK1 contributes to diabetic kidney disease progression through regulating SMAD3 expression by sponging miR-520h

BACKGROUND

Diabetic nephropathy (DN) is a frequent diabetes complication with complex pathogenesis. Circular RNA (circRNA) circTAOK1 (also named circ_0003928) has been reported to be upregulated in high glucose (HG)-treated human umbilical vein endothelial cells. Also, exosomal circRNAs can exert significant roles in the pathology of various diseases. This study is designed to explore the role and mechanism of exosomal circTAOK1 on the glomerular mesangial cell (GMC) injury in DN.

METHODS

Exosomes were detected by a transmission electron microscope. The protein levels of CD9, CD63, proliferating cell nuclear antigen (PCNA), cyclinD1, α-SMA, fibronectin, E-cadherin, N-cadherin, and SMAD family member 3 (SMAD3) were examined by western blot assay. circTAOK1, microRNA-520h (miR-520h), and SMAD3 levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation and cell cycle progression were detected by cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and flow cytometry assays. The binding relationship between miR-520h and circTAOK1 or SMAD3 was predicted by Starbase and then verified by a dual-luciferase reporter and RNA immunoprecipitation (RIP), RNA pull-down assays.

RESULTS

CircTAOK1 expression was upregulated in the exosomes isolated from HG-treated glomerular epithelial cells (GEC). Moreover, GEC-circTAOK1-Exo could promote proliferation, fibrosis, and epithelial-mesenchymal transition (EMT) of glomerular mesangial cells (GMCs). Mechanically, circTAOK1 could regulate SMAD3 expression by sponging miR-520h, GEO-si-circTAOK1 Exo-induced miR-520h and repressed SMAD3 expression in GMC.

CONCLUSION

GEC-circTAOK1-Exo could boost proliferation, fibrosis, and EMT of GMC through targeting the miR-520h/SMAD3 axis, providing new insights into the pathogenesis of DN.

Human Umbilical Cord Mesenchymal Stem Cell-Derived Exosomes Accelerate Diabetic Wound Healing via Ameliorating Oxidative Stress and Promoting Angiogenesis

Diabetic wounds remain a great challenge for clinicians due to the multiple bacterial infections and oxidative damage. Exosomes, as an appealing nanodrug delivery system, have been widely applied in the treatment of diabetic wounds. Endovascular cells are important component cells of the vascular wall. Herein, we investigated the effects of HUCMSCs and HUC-Exos (exosomes secreted by HUCMSCs) on diabetic wound healing. In this study, HUVECs were coincubated with HUCMSCs, and HUC-Exos were utilized for in vitro and in vivo experiments to verify their roles in the regulation of diabetic wound healing. Our results demonstrated that HUCMSCs have the ability to regulate oxidative stress injuries of endothelial cells through exosomes and accelerate diabetic cutaneous wound healing in vitro. The present study suggests that HUC-Exos accelerate diabetic cutaneous wound healing, providing a promising therapeutic strategy for chronic diabetic wound repair.

An Updated Insight Into Molecular Mechanism of Hydrogen Sulfide in Cardiomyopathy and Myocardial Ischemia/Reperfusion Injury Under Diabetes

Cardiovascular diseases are the most common complications of diabetes, and diabetic cardiomyopathy is a major cause of people death in diabetes. Molecular, transcriptional, animal, and clinical studies have discovered numerous therapeutic targets or drugs for diabetic cardiomyopathy. Within this, hydrogen sulfide (H₂S), an endogenous gasotransmitter alongside with nitric oxide (NO) and carbon monoxide (CO), is found to play a critical role in diabetic cardiomyopathy. Recently, the protective roles of H₂S in diabetic cardiomyopathy have attracted enormous attention. In addition, H₂S donors confer favorable effects in myocardial infarction, ischaemia-reperfusion injury, and heart failure under diabetic conditions. Further studies have disclosed that multiplex molecular mechanisms are responsible for the protective effects of H₂S against diabetes-elicited cardiac injury, such as anti-oxidative, anti-apoptotic, anti-inflammatory, and anti-necrotic properties. In this review, we will summarize the current findings on H₂S biology and pharmacology, especially focusing on the novel mechanisms of H₂S-based protection against diabetic cardiomyopathy. Also, the potential roles of H₂S in diabetes-aggravated ischaemia-reperfusion injury are discussed.

Circular RNA_0037128 aggravates high glucose-induced damage in HK-2 cells via regulation of microRNA-497-5p/nuclear factor of activated T cells 5 axis

Circular RNAs (CircRNAs) were reported to play vital roles in the progression of DN. Herein, the action of circular RNA_0037128 (circ_0037128) was investigated in DN. The level of circ_0037128, microRNA-497-5p (miR-497-5p) and nuclear factor of activated T cells 5 (NFAT5) was determined using quantitative real-time polymerase chain reaction (qRT-PCR). The feature of circ_0037128 was tested by RNase R and Actinomycin D treatment assays. Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2ʹ-deoxyuridine (EdU) staining assays were conducted to evaluate the proliferation ability. The relative protein expression was determined via Western blot analysis. Levels of the inflammatory cytokines, like tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6), were assessed by enzyme-linked immunosorbent assay (ELISA). Reactive oxygen species (ROS) production, lactate dehydrogenase (LDH) and superoxide dismutase (SOD) activity were determined by the matched kits. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were conducted for evaluating the correlation between miR-497-5p and circ_0037128 or NFAT5. Circ_0037128 and NFAT5 were enhanced, while miR-497-5p was weakened in kidney tissues of DN patients and high glucose (HG)-cultured HK-2 cells. Circ_0037128 inhibition bated HG-caused inhibition effect on cell proliferation and promotion effects on oxidative stress, inflammation and fibrosis in HK-2 cells. Moreover, circ_0037128 knockdown alleviated HG-caused cell damage via regulating miR-497-5p. In addition, NFAT5 overexpression could reverse the influence of miR-497-5p on HG-induced injury in HK-2 cells. Mechanically, circ_0037128 sponged miR-497-5p to modulate NFAT5. Circ_0037128 downregulation could mitigate HG-stimulated cell damage via regulating the miR-497-5p/NFAT5 axis in HK-2 cells in vitro, providing a possible therapy target for DN.

Circular RNA circ_0000712 regulates high glucose-induced apoptosis, inflammation, oxidative stress, and fibrosis in (DN) by targeting the miR-879-5p/SOX6 axis

Diabetic nephropathy (DN), a frequent diabetes complication, has complex pathogenesis. Circular RNAs (circRNAs) circ_0000712 has been reported to be upregulated in kidney tissues and high glucose (HG)-inducted Mesangial cells (MCs). This study is designed to explore the role and mechanism of circ_0000712 in the HG-inducted MCs injury in DN. Circ_0000712, microRNA-879-5p (miR-879-5p), and SRY-Box Transcription Factor 6 (SOX6) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell apoptosis was examined by flow cytometry assay. Protein levels of B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), fibronectin (FN), collagen type I (Col. I), collagen type IV (Col. IV), and SOX6 were assessed by western blot assay. Levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA). Reactive oxygen species (ROS) generation, Lactate Dehydrogenase (LDH) activity, and Superoxide Dismutase (SOD) activity were detected by the corresponding kits. The binding relationship between miR-879-5p and circ_0000712 or SOX6 was predicted by starBase and Targetscan, and then verified by a dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays. Circ_0000712 and SOX6 were highly expressed, and miR-879-5p was decreased in db/db DN mice and HG-inducted SV40-MES13 cells. Furthermore, circ_0000712 deficiency repressed HG-caused apoptosis, inflammation, oxidative stress, and fibrosis in SV40-MES13 cells. Mechanically, circ_0000712 could regulate SOX6 expression by sponging miR-879-5p. Circ_0000712 knockdown could hinder HG-inducted SV40-MES13 cell injury through targeting the miR-879-5p/SOX6 axis, implying a possible circRNA-targeted therapy for DN.

MicroRNA-195-5p Downregulation Inhibits Endothelial Mesenchymal Transition and Myocardial Fibrosis in Diabetic Cardiomyopathy by Targeting Smad7 and Inhibiting Transforming Growth Factor Beta 1-Smads-Snail Pathway

Diabetic cardiomyopathy (DCM) is a complication of diabetes mellitus, which is associated with fibrosis and microRNAs (miRs). This study estimated the mechanism of miR-195-5p in endothelial mesenchymal transition (EndMT) and myocardial fibrosis in DCM. After the establishment of DCM rat models, miR-195-5p was silenced by miR-195-5p antagomir. The cardiac function-related indexes diastolic left ventricular anterior wall (LVAW, d), systolic LVAW (d), diastolic left ventricular posterior wall (LVPW, d), systolic LVPW (d), left ventricular ejection fraction (LVEF), and fractional shortening (FS) were measured and miR-195-5p expression in myocardial tissue was detected. Myocardial fibrosis, collagen deposition, and levels of fibrosis markers were detected. Human umbilical vein endothelial cells (HUVECs) were exposed to high glucose (HG) and miR-195-5p was silenced. The levels of fibrosis proteins, endothelial markers, fibrosis markers, EndMT markers, and transforming growth factor beta 1 (TGF-β1)/Smads pathway-related proteins were measured in HUVECs. The interaction between miR-195-5p and Smad7 was verified. In vivo, miR-195-5p was highly expressed in the myocardium of DCM rats. Diastolic and systolic LVAW, diastolic and systolic LVPW were increased and LVEF and FS were decreased. Inhibition of miR-195-5p reduced cardiac dysfunction, myocardial fibrosis, collagen deposition, and EndMT, promoted CD31 and VE-cadehrin expressions, and inhibited α-SMA and vimentin expressions. In vitro, HG-induced high expression of miR-195-5p and the expression changes of endothelial markers CD31, VE-cadehrin and fibrosis markers α-SMA and vimentin were consistent with those in vivo after silencing miR-195-5p. In mechanism, miR-195-5p downregulation blocked EndMT by inhibiting TGF-β1-smads pathway. Smad7 was the direct target of miR-195-5p and silencing miR-195-5p inhibited EndMT by promoting Smad7 expression. Collectively, silencing miR-195-5p inhibits TGF-β1-smads-snail pathway by targeting Smad7, thus inhibiting EndMT and alleviating myocardial fibrosis in DCM.

Circular RNAs; powerful microRNA sponges to overcome diabetic nephropathy

Diabetic nephropathy (DN), also known as diabetic kidney disease (DKD), is a drastic renal complication of type 1 and type 2 diabetes mellitus (DM). Poorly controlled DM over the years, may disrupt kidneys' blood vessels, leading to the hypertension (HTN) and DN onset. During DN, kidneys' waste filtering ability becomes disturbed. Being on a healthy lifestyle and controlling both DM and HTN are now the best proceedings to prevent or at least delay DN occurrence. Unfortunately, about one-fourth of diabetic individuals eventually experience the corresponding renal failure, and thus it is critical to discover effective diagnostic biomarkers and therapeutic strategies to combat DN. In the past few years, circular RNAs (circRNAs), as covalently closed endogenous non-coding RNAs (ncRNAs), are believed to affect DN pathogenesis in a positive manner. CircRNAs are able to impact different cellular processes and signaling pathways by targeting biological molecules or various molecular mechanisms. Still, as a key regulatory axis, circRNAs can select miRNAs as their molecular targets, in which they are considered as miRNA sponges. In this way, circRNA-induced suppression of particular miRNAs may prevent from DN progression or promotes the DN elimination. Since the expression of circRNAs has also been reported to be increased in DN-associated cells and tissues, they can be employed as either diagnostic biomarkers or therapeutic targets.

Recent research progress on circular RNAs: Biogenesis, properties, functions, and therapeutic potential

Circular RNAs (circRNAs), an emerging family member of RNAs, have gained importance in research due to their new functional roles in cellular physiology and disease progression. circRNAs are usually available in a wide range of cells and have shown tissue-specific expression as well as developmental specific expression. circRNAs are characterized by structural stability, conservation, and high abundance in the cell. In this review, we discuss the different models of biogenesis. The properties of circRNAs such as localization, structure and conserved pattern, stability, and expression specificity are also been illustrated. Furthermore, we discuss the biological functions of circRNAs such as microRNA (miRNA) sponging, cell cycle regulation, cell-to-cell communication, transcription regulation, translational regulation, disease diagnosis, and therapeutic potential. Finally, we discuss the recent research progress and future perspective of circRNAs. This review provides an understanding of potential diagnostic markers and the therapeutic potential of circRNAs, which are emerging daily.

Overexpression of mm9_circ_013935 alleviates renal inflammation and fibrosis in diabetic nephropathy via the miR-153-3p/NFIC axis

BACKGROUND

Circ-RBM4 (mm9_circ_013935) has been revealed to be low-expressed in the renal tissues of diabetic nephropathy (DN) mice while its underlying regulatory mechanism remains unexplored.

METHODS

The high glucose (HG)-treated mouse podocytes were used to establish the DN cell models. A CCK-8 assay was used to examine the viability of mouse podocytes. The expression of proteins related to fibrosis (Collagen I, Collagen III, fibronectin) was detected using western blot. The concentration of inflammation cytokines (TNF-α, IL-1β, IL-8) in mouse podocytes was assessed by ELISA. The interaction between genes was explored by luciferase reporter assays.

RESULTS

HG treatement decreased the viability and elevated the expression of fibrosis and inflammation factors in mouse podocytes. Circ-RBM4 expression was downregulated in HG-treated mouse podocytes. Circ-RBM4 overexpression reversed HG-induced increase in levels of proteins related to fibrosis and the concentration of inflammation factors. MiR-153-3p was revealed to bind with circ-RBM4 and directly targeted nuclear factor I/C (NFIC) in mouse podocytes. Rescue assays indicated that circ-RBM4 attenuated HG-induced fibrosis and inflammation response in mouse podocytes by inhibiting miR-153-3p expression or upregulating NFIC expression.

CONCLUSION

Circ-RBM4 alleviated the renal inflamation and renal fibrosis in DN by targeting the miR-153-3p/NFIC axis.

Molecular prospect of type-2 diabetes: Nanotechnology based diagnostics and therapeutic intervention

About ninety percent of all diabetic conditions account for T2D caused due to abnormal insulin secretion/ action or increased hepatic glucose production. Factors that contribute towards the aetiology of T2D could be well explained through biochemical, molecular, and cellular aspects. In this review, we attempt to explain the recent evolving molecular and cellular advancement associated with T2D pathophysiology. Current progress fabricated in T2D research concerning intracellular signaling cascade, inflammasome, autophagy, genetic and epigenetics changes is discretely explained in simple terms. Present available anti-diabetic therapeutic strategies commercialized and their limitations which are needed to be acknowledged are addressed in the current review. In particular, the pre-eminence of nanotechnology-based approaches to nullify the inadequacy of conventional anti-diabetic therapeutics and heterogeneous nanoparticulated systems exploited in diabetic researches are also discretely mentioned and are also listed in a tabular format in the review. Additionally, as a future prospect of nanotechnology, the review presents several strategic hypotheses to ameliorate the austerity of T2D by an engineered smart targeted nano-delivery system. In detail, an effort has been made to hypothesize novel nanotechnological based therapeutic strategies, which exploits previously described inflammasome, autophagic target points. Utilizing graphical description it is explained how a smart targeted nano-delivery system could promote β-cell growth and development by inducing the Wnt signaling pathway (inhibiting Gsk3β), inhibiting inflammasome (inhibiting NLRP3), and activating autophagic target points (protecting Atg3/Atg7 complex from oxidative stress) thereby might ameliorate the severity of T2D. Additionally, several targeting molecules associated with autophagic and epigenetic factors are also highlighted, which can be exploited in future diabetic research.

Exosomes derived from pioglitazone-pretreated MSCs accelerate diabetic wound healing through enhancing angiogenesis

BACKGROUND

Enhanced angiogenesis can promote diabetic wound healing. Mesenchymal stem cells (MSCs)-derived exosomes, which are cell-free therapeutics, are promising candidates for the treatment of diabetic wound healing. The present study aimed to investigate the effect of exosomes derived from MSCs pretreated with pioglitazone (PGZ-Exos) on diabetic wound healing.

RESULTS

We isolated PGZ-Exos from the supernatants of pioglitazone-treated BMSCs and found that PGZ-Exos significantly promote the cell viability and proliferation of Human Umbilical Vein Vascular Endothelial Cells (HUVECs) injured by high glucose (HG). PGZ-Exos enhanced the biological functions of HUVECs, including migration, tube formation, wound repair and VEGF expression in vitro. In addition, PGZ-Exos promoted the protein expression of p-AKT, p-PI3K and p-eNOS and suppressed that of PTEN. LY294002 inhibited the biological function of HUVECs through inhibition of the PI3K/AKT/eNOS pathway. In vivo modeling in diabetic rat wounds showed that pioglitazone pretreatment enhanced the therapeutic efficacy of MSCs-derived exosomes and accelerated diabetic wound healing via enhanced angiogenesis. In addition, PGZ-Exos promoted collagen deposition, ECM remodeling and VEGF and CD31 expression, indicating adequate angiogenesis in diabetic wound healing.

CONCLUSIONS

PGZ-Exos accelerated diabetic wound healing by promoting the angiogenic function of HUVECs through activation of the PI3K/AKT/eNOS pathway. This offers a promising novel cell-free therapy for treating diabetic wound healing.

miRNA, lncRNA and circRNA: Targeted Molecules Full of Therapeutic Prospects in the Development of Diabetic Retinopathy

Diabetic retinopathy (DR) is a common diabetic complication and the main cause of blindness worldwide, which seriously affects the quality of life of patients. Studies have shown that noncoding RNA (ncRNA) has distinct differentiated expression in DR and plays an important role in the occurrence and development of DR. ncRNAs represented by microRNAs (miRNAs), lncRNAs (lncRNAs), and circRNAs (circRNAs) have been shown to be widely involved in the regulation of gene expression and affect multiple biological processes of retinopathy. This article will review three RNAs related to the occurrence and development of DR on the basis of previous studies (especially their effects on retinal microangiopathy, retinal pigment epithelial cells, and retinal nerve cells) and discuss their underlying mechanisms and connections. Overall, this review will help us better understand the role of ncRNAs in the occurrence and development of DR and provide ideas for exploring potential therapeutic directions and targets.

Acrolein: A Potential Mediator of Oxidative Damage in Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of vision loss among working-age adults. Extensive evidences have documented that oxidative stress mediates a critical role in the pathogenesis of DR. Acrolein, a product of polyamines oxidation and lipid peroxidation, has been demonstrated to be involved in the pathogenesis of various human diseases. Acrolein’s harmful effects are mediated through multiple mechanisms, including DNA damage, inflammation, ROS formation, protein adduction, membrane disruption, endoplasmic reticulum stress, and mitochondrial dysfunction. Recent investigations have reported the involvement of acrolein in the pathogenesis of DR. These studies have shown a detrimental effect of acrolein on the retinal neurovascular unit under diabetic conditions. The current review summarizes the existing literature on the sources of acrolein, the impact of acrolein in the generation of oxidative damage in the diabetic retina, and the mechanisms of acrolein action in the pathogenesis of DR. The possible therapeutic interventions such as the use of polyamine oxidase inhibitors, agents with antioxidant properties, and acrolein scavengers to reduce acrolein toxicity are also discussed.

Chronic Microvascular Complications in Prediabetic States-An Overview

A prediabetic state is a major risk factor for the development of diabetes, and, because of an identical pathophysiological background of both conditions, their prevalence increases parallelly and equally fast. Long-term hyperglycemia is the main cause inducing chronic complications of diabetes, yet the range of glucose levels at which they start has not been yet unequivocally determined. The current data show that chronic microvascular complications of diabetes can be observed in patients with abnormal glucose metabolism in whom glycaemia is higher than optimal but below diagnostic criteria for diabetes. Prediabetes is a heterogenous nosological unit in which particular types are differently characterized and show different correlations with particular kinds of complications. Analysis of the latest research results shows the need to continue studies in a larger population and can imply the need to verify the currently employed criteria of diagnosing diabetes and chronic complications of diabetes in people with prediabetes.