Epigenetic Regulations in Diabetic Nephropathy

Cope with copper: From molecular mechanisms of cuproptosis to copper-related kidney diseases

Cuproptosis has recently been identified as a novel regulatory mechanism of cell death. It is characterized by the accumulation of copper in mitochondria and its binding to acylated proteins. These characteristics lead to the downregulation of iron-sulfur cluster proteins and protein toxicity stress, ultimately resulting in cell death. Cuproptosis is distinct from other types of cell death, including necrosis, apoptosis, ferroptosis, and pyroptosis. Cu induces oxidative stress damage, protein acylation, and the oligomerization of acylated TCA cycle proteins. These processes lead to the downregulation of iron-sulfur cluster proteins and protein toxicity stress, disrupting cellular Cu homeostasis, and causing cell death. Cuproptosis plays a significant role in the development and progression of various kidney diseases such as acute kidney injury, chronic kidney disease, diabetic nephropathy, kidney transplantation, and kidney stones. On the one hand, inducers of cuproptosis, such as disulfiram (DSF), chloroquinolone, and elesclomol facilitate cuproptosis by promoting cell oxidative stress. In contrast, inhibitors of Cu chelators, such as tetraethylenepentamine and tetrathiomolybdate, relieve these diseases by inhibiting apoptosis. To summarize, cuproptosis plays a significant role in the pathogenesis of kidney disease. This review comprehensively discusses the molecular mechanisms underlying cuproptosis and its significance in kidney diseases.

CircLARP1B promotes pyroptosis of high glucose-induced renal mesangial cells by regulating the miR-578/TLR4 axis

BACKGROUND

Diabetic nephropathy (DN) is a main cause of end-stage renal disease with high mortality. Circular RNAs (circRNAs) are associated with the pathogenesis of DN. This study aimed to explore the role of circLARP1B in DN.

METHODS

The levels of circLARP1B, miR-578, TLR4 in DN and high glucose (HG)-treated cells using quantitative real-time PCR. Their relationship was analyzed using dual-luciferase reporter assay. The biological behaviors were assessed by MTT assay, EDU assay, flow cytometry, ELISA, and western blot.

RESULTS

The results indicated that circLARP1B and TLR4 were highly expressed, and miR-578 was low expressed in patients with DN and HG-induced cells. Knockdown of circLARP1B promoted the proliferation and cell cycle, and inhibited pyroptosis and inflammation of HG-induced cells. CircLARP1B is a sponge of miR-578, which targets TLR4. Rescue experiments showed that inhibition of miR-578 reversed the effects of circLARP1B knockdown, while TLR4 reversed the effects of miR-578.

CONCLUSION

CircLARP1B/miR-578/TLR4 axis suppressed the proliferation, blocked cell cycle at the G0-G1 phase, promoted pyroptosis, and inflammatory factor release of renal mesangial cells induced by HG. The findings suggested that circLARP1B may be a target for the treatment of DN.

Applicability of mesenchymal stem cell-derived exosomes as a cell-free miRNA therapy and epigenetic modifiers for diabetes

Given that exosome nanovesicles constitute various growth factors, miRNAs and lncRNAs, they have implications for epigenetic modifications. Few studies have shown that exosomes from mesenchymal stem cells (MSCs) exhibit therapeutic effects on diabetic complications by substituting miRNAs and regulating histone modifications. Therefore, reversing epigenetic aberrations in diabetes may provide new insight into its treatment. This review discusses the impact of DNA and histone methylations on the development of diabetes and its complications. Further, we talk about miRNAs dysregulated in diabetic conditions and the possibility of utilizing mesenchymal stem cell (MSC) exosomes for the development of miRNA cell-free therapy and epigenetic modifiers in reversing diabetic-induced epigenetic alterations.

MiR-29b modulates DNA methylation in promoter region of miR-130b in mouse model of Diabetic nephropathy

Epigenetic modifications play a role in Diabetic Nephropathy (DN). Downregulation of miR-29b leads to modulation of DNA methylation via DNA methyl transferases (DNMTs) and hence exaggerated renal fibrosis in DN. Therefore, the main aim of the study was to evaluate effect of miR-29b expression in vivo on DNMTs, renal fibrosis, glomerular and tubular damage as well as renal morphology in DN. In order to explore the role of miR-29b in DNA methylation of other miRNAs, methylation profiling study was performed. It revealed that miR-29b was involved in methylation on of miR-130b on the cytosine guanine dinucleotides rich DNA (CpG) island 1 located on promoter region. In conclusion, miR-29b expression was found to modulate DNA methylation via DNMTs and regulate methylation of miR-130b. The result of this study provides a future direction to unveil role of miRNA expression in DNA methylation and its consequent effect on other miRNAs in DN.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01208-2.

LncRNA CASC15 inhibition relieves renal fibrosis in diabetic nephropathy through down-regulating SP-A by sponging to miR-424

Study has demonstrated the abnormal expression and role of lncRNA CASC15 in diabetes patients with chronic renal failure. However, its role in diabetes nephropathy (DN) is still unclear. This study aimed to investigate the potential mechanism and role of lncRNA CASC15 in DN. The relationship between miR-424 and CASC15/SP-A was predicted by Starbase software and verified by luciferase reporter assay. HK-2 cells were treated with 25 mM glucose (HG) for 24 h to establish DN cell model. MTT and flow cytometry analysis were carried out to test cell proliferation and apoptosis. Epithelial-to-mesenchymal transition (EMT) markers were analyzed by RT-qPCR and western blot assay. We proved that CASC15 could interact with miR-424, and SP-A was a target of miR-424. HG-treatment significantly enhanced lncRNA CASC15 level and decreased miR-424 level in HK-2 cells. LncRNA CASC15-siRNA significantly improved cell viability, repressed apoptosis, promoted E-cadherin expression, and inhibited N-cadherin expression in HG-treated HK-2 cells, and these effects were reversed by miR-424 inhibitor. SP-A was highly expressed in HG-treated HK-2 cells. The biological effects of miR-424 mimic on HG-treated HK-2 cells were reversed by SP-A-plasmid. In conclusion, lncRNA CASC15 inhibition relieved HG-induced HK-2 cell injury and EMT through miR-424/SP-A axis.

Epigenetic modification in diabetic kidney disease

Diabetic kidney disease (DKD) is a common microangiopathy in diabetic patients and the main cause of death in diabetic patients. The main manifestations of DKD are proteinuria and decreased renal filtration capacity. The glomerular filtration rate and urinary albumin level are two of the most important hallmarks of the progression of DKD. The classical treatment of DKD is controlling blood glucose and blood pressure. However, the commonly used clinical therapeutic strategies and the existing biomarkers only partially slow the progression of DKD and roughly predict disease progression. Therefore, novel therapeutic methods, targets and biomarkers are urgently needed to meet clinical requirements. In recent years, increasing attention has been given to the role of epigenetic modification in the pathogenesis of DKD. Epigenetic variation mainly includes DNA methylation, histone modification and changes in the noncoding RNA expression profile, which are deeply involved in DKD-related inflammation, oxidative stress, hemodynamics, and the activation of abnormal signaling pathways. Since DKD is reversible at certain disease stages, it is valuable to identify abnormal epigenetic modifications as early diagnosis and treatment targets to prevent the progression of end-stage renal disease (ESRD). Because the current understanding of the epigenetic mechanism of DKD is not comprehensive, the purpose of this review is to summarize the role of epigenetic modification in the occurrence and development of DKD and evaluate the value of epigenetic therapies in DKD.

LncRNA MEG3 inhibits renal fibrinoid necrosis of diabetic nephropathy via the MEG3/miR-21/ORAI1 axis

INTRODUCTION

Diabetic nephropathy (DN) is one of the most common and lethal diabetic complications worldwide and is associated with a high risk of mortality. However, the exact mechanism behind its development is unknown. The mesangial cells (MCs) and non-coding RNAs are critical for DN, but it is unknown whether a MEG3/miR-21/ORAI1 regulatory axis exists in MCs. Hence, in this study, we aimed to understand whether the MEG3/miR-21/ORAI1 regulatory axis has a role in the pathophysiology of DN.

RESULTS

We demonstrated that high-glucose stimuli downregulated MEG3 and ORAI1 expression while enhancing miR-21 expression. Exogenous miR-21 mimics inhibited ORAI1 expression, which was partially salvaged or reversed by MEG3 overexpression. Furthermore, RIP assay demonstrated that the beads labeled with AGO2 antibody could enrich more miR-21 and MEG3 than those labeled with control IgG antibody; both of them formed the RNA-induced silencing complex. Further, the biochemical indicators of db/db mice significantly improved, and renal fibrinoid necrosis was ameliorated using a miR-21 inhibitor.

CONCLUSION

The MEG3/miR-21/ORAI1 axis regulates the manifestation of DN in diabetic mice and MCs, and the miR-21 inhibitor can be a potential therapeutic strategy to alleviate DN, once the presence of such an axis is found in humans.

Kidney diseases and long non-coding RNAs in the limelight

The most extensively and well-investigated sequences in the human genome are protein-coding genes, while large numbers of non-coding sequences exist in the human body and are even more diverse with more potential roles than coding sequences. With the unveiling of non-coding RNA research, long-stranded non-coding RNAs (lncRNAs), a class of transcripts >200 nucleotides in length primarily expressed in the nucleus and rarely in the cytoplasm, have drawn our attention. LncRNAs are involved in various levels of gene regulatory processes, including but not limited to promoter activity, epigenetics, translation and transcription efficiency, and intracellular transport. They are also dysregulated in various pathophysiological processes, especially in diseases and cancers involving genomic imprinting. In recent years, numerous studies have linked lncRNAs to the pathophysiology of various kidney diseases. This review summarizes the molecular mechanisms involved in lncRNAs, their impact on kidney diseases, and associated complications, as well as the value of lncRNAs as emerging biomarkers for the prevention and prognosis of kidney diseases, suggesting their potential as new therapeutic tools.

Histone modification in podocyte injury of diabetic nephropathy

Diabetic nephropathy (DN), an important complication of diabetic microvascular disease, is one of the leading causes of end-stage renal disease (ESRD), which brings heavy burdens to the whole society. Podocytes are terminally differentiated glomerular cells, which act as a pivotal component of glomerular filtration barrier. When podocytes are injured, glomerular filtration barrier is damaged, and proteinuria would occur. Dysfunction of podocytes contributes to DN. And degrees of podocyte injury influence prognosis of DN. Growing evidences have shown that epigenetics does a lot in the evolvement of podocyte injury. Epigenetics includes DNA methylation, histone modification, and non-coding RNA. Among them, histone modification plays an indelible role. Histone modification includes histone methylation, histone acetylation, and other modifications such as histone phosphorylation, histone ubiquitination, histone ADP-ribosylation, histone crotonylation, and histone β-hydroxybutyrylation. It can affect chromatin structure and regulate gene transcription to exert its function. This review is to summarize documents about pathogenesis of podocyte injury, most importantly, histone modification of podocyte injury in DN recently to provide new ideas for further molecular research, diagnosis, and treatment.

Sodium Butyrate Attenuates Diabetic Kidney Disease Partially via Histone Butyrylation Modification

Inflammation and fibrosis are the important pathophysiologic processes in diabetic kidney disease (DKD), which is induced by epigenetics, especially histone posttranslational modification (HPTMs). Recent reports highlighted that butyrate, one of the short-chain fatty acids (SCFAs) primarily originated from the fermentation of dietary fiber in the gut, attenuates inflammation and fibrosis in the prevention and treatment of DKD; however, the molecular mechanisms are still unclear. Histone lysine butyrylation (Kbu), a novel histone modification marker induced by butyrate, has been found to be involved in the regulation of pathophysiological processes. To reveal the mechanisms of butyrate-induced histone (Kbu), in the prevention and treatment of DKD, both DKD models in vivo and in vitro were treated with sodium butyrate (NaB). Our results confirmed that exogenous NaB improved the disorder of glucose and lipid metabolism, prevented proteinuria and renal failure, and inhibited renal inflammation and fibrosis. Meanwhile, NaB also induced histone Kbu and H3K9 butyrylation (H3K9bu) in vivo and in vitro; however, inhibition of histone Kbu with the histone modification enzyme p300 inhibitor A485 reversed the anti-inflammatory and anti-fibrosis effects of NaB. In conclusion, our data reveal that NaB antagonizes renal inflammatory and fibrosis injury and attenuates DKD possibly via histone Kbu, suggesting that butyrate-induced histone Kbu or H3K9bu may be an important molecular mechanism in the pathogenesis and treatment of DKD.

WTAP-mediated N6-methyladenosine modification of NLRP3 mRNA in kidney injury of diabetic nephropathy

Background

Diabetic nephropathy (DN) is prevalent in patients with diabetes. N⁶-methyladenosine (m⁶A) methylation has been found to cause modification of nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing (NLRP) 3, which is involved in cell pyroptosis and inflammation. WTAP is a key gene in modulating NLRP3 m⁶A.

Methods

In this study, WTAP was silenced or overexpressed in high glucose (HG)-treated HK-2 cells to determine its influence on pyroptosis, NLRP3 inflammasome-related proteins, and the release of pro-inflammatory cytokines. NLRP3 expression and m⁶A levels were assessed in the presence of WTAP shRNA (shWTAP). WTAP expression in HK-2 cells was examined with the introduction of C646, a histone acetyltransferase p300 inhibitor.

Results

We found that WTAP expression was enhanced in patients with DN and in HG-treated HK-2 cells. Knockdown of WTAP attenuated HG-induced cell pyroptosis and NLRP3-related pro-inflammatory cytokines in both HK-2 cells and db/db mice, whereas WTAP overexpression promoted these cellular processes in HK-2 cells. WTAP mediated the m⁶A of NLRP3 mRNA that was stabilized by insulin-like growth factor 2 mRNA binding protein 1. Histone acetyltransferase p300 regulated WTAP expression. WTAP mRNA levels were positively correlated with NLRP3 inflammasome components and pro-inflammatory cytokines.

Conclusion

Taken together, WTAP promotes the m⁶A methylation of NLRP3 mRNA to upregulate NLRP3 inflammasome activation, which further induces cell pyroptosis and inflammation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00350-8.

Long‐segment restrictive tear of radial artery under ultrasound guide for arteriovenous fistula by PTA: A case report

Considerable calcification and stenosis frequently occur in the radial artery (RA) in diabetic nephropathy. PTA was performed successfully using a balloon to expand and restrictively tear the longitudinal axis of the RA. This approach seems to be a useful measure of promoting the maturation of AVF in diabetic nephropathy.

MicroRNA-494-3p Exacerbates Renal Epithelial Cell Dysfunction by Targeting SOCS6 under High Glucose Treatment

BACKGROUND

Diabetic nephropathy is a common complication of the kidneys induced by diabetes and is the main cause of end-stage renal disease. MicroRNA-494-3p was reported to be upregulated in renal tissues collected from db/db mice, but its specific role in diabetic nephropathy was still unclear. This study aimed to explore the effect of miR-494-3p on renal fibrosis using an in vitro cell model of diabetic nephropathy.

METHODS

After human renal tubular epithelial cells (HK-2) were treated with high glucose (HG), the viability and apoptosis of cells were examined by CCK-8 assays and flow cytometry analyses. Additionally, protein levels of fibronectin, collagen I, collagen III, collagen IV, and epithelial-mesenchymal transition (EMT) markers in HG-induced HK-2 cells were quantified by Western blotting. miR-494-3p expression in HK-2 cells was detected by reverse-transcription quantitative polymerase chain reaction. The binding relation between miR-494-3p and the messenger RNA suppressor of cytokine signaling 6 (SOCS6) was detected by luciferase reporter assays.

RESULTS

HG reduced cell viability and enhanced cell apoptosis in a time- or concentration-dependent manner. Additionally, HG induced collagen accumulation and triggered the EMT process. miR-494-3p was upregulated in HG-treated HK-2 cells. miR-494-3p inhibition alleviated HG-induced cell dysfunction. Mechanistically, miR-494-3p bound with SOCS6 and negatively regulated SOCS6 expression. Moreover, silencing SOCS6 rescued the suppressive effect of miR-499-5p inhibition on HG-induced cell dysfunction.

CONCLUSION

miR-494-3p aggravates renal fibrosis, EMT process, and cell apoptosis by targeting SOCS6, suggesting that the miR-494-3p/SOCS6 axis may become a potential strategy for the treatment of diabetic nephropathy.

MicroRNA-122-5p ameliorates tubular injury in diabetic nephropathy via FIH-1/HIF-1α pathway

Diabetes kidney disease (DKD) affects approximately one-third of diabetes patients, however, the specific molecular mechanism of DKD remains unclear, and there is still a lack of effective therapies. Here, we demonstrated a significant increase of microRNA-122-5p (miR-122-5p) in renal tubular cells in STZ induced diabetic nephropathy (DN) mice. Moreover, inhibition of miR-122-5p led to increased cell death and serve tubular injury and promoted DN progression following STZ treatment in mice, whereas supplementation of miR-122-5p mimic had kidney protective effects in this model. In addition, miR-122-5p suppressed the expression of factor inhibiting hypoxia-inducible factor-1 (FIH-1) in vitro models of DN. microRNA target reporter assay further verified FIH-1 as a direct target of miR-122-5p. Generally, FIH-1 inhibits the activity of HIF-1α. Our in vitro study further indicated that overexpression of HIF-1α by transfection of HIF-1α plasmid reduced tubular cell death, suggesting a protective role of HIF-1α in DN. Collectively, these findings may unveil a novel miR-122-5p/FIH-1/HIF-1α pathway which can attenuate the DN progression.

Circ-FBXW12 aggravates the development of diabetic nephropathy by binding to miR-31-5p to induce LIN28B

BACKGROUND

The involvement of circular RNAs (circRNAs) in diabetic nephropathy (DN) has been gradually identified. In this study, we aimed to explore the functions of circRNA F-box/WD repeat-containing protein 12 (circ-FBXW12) in DN development.

METHODS

Reverse transcription quantitative polymerase chain reaction (RT-qPCR) assay was performed for the levels of circ-FBXW12, FBXW12 mRNA, microRNA-31-5p (miR-31-5p) and Lin-28 homolog B (LIN28B) mRNA. RNase R assay was used to analyze the stability of circ-FBXW12. Cell Counting Kit-8 (CCK-8) assay, flow cytometry analysis and 5-ethynyl-2'- deoxyuridine (EdU) assay were employed to evaluate cell viability, cell cycle and proliferation, respectively. Enzyme linked immunosorbent assay (ELISA) was done to measure the concentrations of inflammatory cytokines. Western blot assay was conducted for protein levels. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) level were examined with commercial kits. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the relationships among circ-FBXW12, miR-31-5p and LIN28B.

RESULTS

Circ-FBXW12 level was increased in DN patients' serums and high glucose (HG)-induced human mesangial cells (HMCs). Circ-FBXW12 knockdown suppressed cell proliferation, arrested cell cycle, reduced extracellular matrix (ECM) production and oxidative stress in HG-induced HMCs. Circ-FBXW12 was identified as the sponge for miR-31-5p, which then directly targeted LIN28B. MiR-31-5p inhibition reversed circ-FBXW12 knockdown-mediated effects on cell proliferation, cell cycle process, ECM production and oxidative in HG-triggered HMCs. Moreover, miR-31-5p overexpression showed similar results with circ-FBXW12 knockdown in HG-stimulated HMC progression, while LIN28B elevation reversed the effects.

CONCLUSION

Circ-FBXW12 knockdown suppressed HG-induced HMC growth, inflammation, ECM accumulation and oxidative stress by regulating miR-31-5p/LIN28B axis.

TIMP3 involvement and potentiality in the diagnosis, prognosis and treatment of diabetic nephropathy

Diabetic kidney disease, one of the most severe complications associated with diabetes, is characterized by albuminuria, glomerulosclerosis and progressive loss of renal function. Loss of TIMP3, an Extracellular matrix-bound protein, is a hallmark of diabetic nephropathy in human and mouse models, suggesting its pivotal role in renal diseases associated to diabetes. There is currently no specific therapy for diabetic nephropathy, and the ability to restore high TIMP3 activity specifically in the kidney may represent a potential therapeutic strategy for the amelioration of renal injury under conditions in which its reduction is directly related to the disease. Increasing evidence shows that diabetic nephropathy is also regulated by epigenetic mechanisms, including noncoding RNA. This review recapitulates the pathological, diagnostic and therapeutic potential roles of TIMP3 and the noncoding RNA (microRNA, long noncoding RNA) related to its expression, in the progression of diabetic nephropathy.

Knockdown of transient receptor potential melastatin 2 reduces renal fibrosis and inflammation by blocking transforming growth factor-β1-activated JNK1 activation in diabetic mice

BACKGROUND

Diabetic nephropathy is a major complication of diabetes. We explore the protective effect of TRPM2 knockdown on the progression of diabetic nephropathy.

METHODS

A type 2 diabetes animal model was established in C57BL/6N mice by long-term high-fat diet (HFD) feeding combined with a single injection of 100 mg/kg streptozotocin (STZ). Genetic knockdown of TRPM2 in mouse kidneys was accomplished by the intravenous injection via the tail vein of adeno-associated virus type 2 carrying TRPM2 shRNA.

RESULTS

Mice with HFD/STZ-induced diabetes exhibited kidney dysfunction, as demonstrated by increased blood creatinine and urea nitrogen levels, accompanied by glomerulus derangement, tubule damage and extracellular matrix deposition in the interstitium. The protein expression of TRPM2, transforming growth factor-β1 (TGF-β1), connective tissue growth factor, α-smooth muscles actin, fibronectin, collagen I and collagen III, and the mRNA expression and contents of inflammatory factors, including interleukin-1β, interleukin-6, interferon-α, tumour necrosis factor -α and monocyte chemotactic protein -1, were significantly elevated in the renal tissues of the HFD/STZ-induced diabetes group compared to those of the two control groups. Furthermore, fluorescent staining of TRPM2 was markedly increased in the renal tubular epithelial cells from diabetic mice. Knockdown of TRPM2 significantly attenuated HFD/STZ-induced renal inflammatory responses and fibrosis, which was accompanied by activation of TGF-β1-activated c-Jun N-terminal protein kinase-1 (JNK1) signalling. JNK1 inactivation reversed hyperglycaemia-induced fibrosis and inflammation in HK-2 cells.

CONCLUSION

TRPM2 silencing significantly attenuated fibrosis and inflammation in the kidneys of mice with HFD/STZ-induced diabetes, which was largely achieved via the inhibition of TGF-β1-activated JNK1 activation.

MicroRNA‑499a (rs3746444A/G) gene variant and susceptibility to type 2 diabetes‑associated end‑stage renal disease

Diabetic nephropathy (DN) is a major risk factor for end-stage renal disease (ESRD). MicroRNAs (miRNAs/miRs) and their variants may be implicated in health and disease, including DN. The present study aimed to investigate the association of the miRNA-499a gene (MIR499A) A/G seed region variant (rs3746444) with DN-associated ESRD susceptibility in patients with diabetes mellitus, and to determine whether there was an association between the different genotypes and the patients' laboratory and clinical data. A case-control pilot study was conducted on 180 adult patients with type 2 diabetes mellitus. A total of 90 patients with ESRD on regular hemodialysis were considered as the cases, and 90 age-, sex- and ethnicity-matched diabetic patients with normo-albuminuria were considered as the controls. MIR499A genotyping was performed using a TaqMan Real-Time allele discrimination assay. Results demonstrated that the MIR499A rs3746444*G variant conferred susceptibility to the development of ESRD under co-dominant [(odds ratio (95% confidence interval): 2.49 (1.41-3.89) and 2.41 (1.61-6.68) for heterozygous and homozygous comparison, respectively], dominant [2.30 (1.18-3.90)] and allelic [1.82 (1.17-2.83)] models. Different genotypes of the specified variant did not exhibit significant associations with the clinic-laboratory data of the studied patients or the circulating miR-499a plasma levels. In conclusion, results of the present study suggested that MIR499A rs3746444 may be a susceptibility variant for DN-associated ESRD in the study population. However, larger sample size studies with different ethnicities are warranted to verify these findings.

CircSMAD4 alleviates high glucose-induced inflammation, extracellular matrix deposition and apoptosis in mouse glomerulus mesangial cells by relieving miR-377-3p-mediated BMP7 inhibition

BACKGROUND

Diabetic nephropathy (DN) is a common complication of diabetes mellitus. Accumulating studies suggest that the deregulation of circular RNA (circRNA) is involved in DN pathogenesis. This study aimed to investigate the role of circSMAD4 in DN models.

METHODS

Mice were treated with streptozotocin to establish DN models in vivo. Mouse glomerulus mesangial cells (SV40-MES13) were treated with high glucose to establish DN models in vitro. The expression of circSMAD4, miR-377-3p and bone morphogenetic protein 7 (BMP7) mRNA was measured by quantitative real-time PCR (qPCR). The releases of inflammatory factors were examined by ELISA. The protein levels of fibrosis-related markers, apoptosis-related markers and BMP7 were checked by western blot. Cell apoptosis was monitored by flow cytometry assay. The predicted relationship between miR-377-3p and circSMAD4 or BMP7 was validated by dual-luciferase reporter assay or pull-down assay.

RESULTS

CircSMAD4 was poorly expressed in DN mice and HG-treated SV40-MES13 cells. HG induced SV40-MES13 cell inflammation, extracellular matrix (ECM) deposition and apoptosis. CircSMAD4 overexpression alleviated, while circSMAD4 knockdown aggravated HG-induced SV40-MES13 cell injuries. MiR-377-3p was targeted by circSMAD4, and miR-377-3p enrichment partly reversed the effects of circSMAD4 overexpression. BMP7 was a target of miR-377-3p, and circSMAD4 regulated BMP7 expression by targeting miR-377-3p. MiR-377-3p overexpression aggravated HG-induced injuries by suppressing BMP7.

CONCLUSION

CircSMAD4 alleviates HG-induced SV40-MES13 cell inflammation, ECM deposition and apoptosis by relieving miR-377-3p-mediated inhibition on BMP7 in DN progression.

Immunomodulatory Effects of Heme Oxygenase-1 in Kidney Disease

Kidney disease is a general term for heterogeneous damage that affects the function and the structure of the kidneys. The rising incidence of kidney diseases represents a considerable burden on the healthcare system, so the development of new drugs and the identification of novel therapeutic targets are urgently needed. The pathophysiology of kidney diseases is complex and involves multiple processes, including inflammation, autophagy, cell-cycle progression, and oxidative stress. Heme oxygenase-1 (HO-1), an enzyme involved in the process of heme degradation, has attracted widespread attention in recent years due to its cytoprotective properties. As an enzyme with known anti-oxidative functions, HO-1 plays an indispensable role in the regulation of oxidative stress and is involved in the pathogenesis of several kidney diseases. Moreover, current studies have revealed that HO-1 can affect cell proliferation, cell maturation, and other metabolic processes, thereby altering the function of immune cells. Many strategies, such as the administration of HO-1-overexpressing macrophages, use of phytochemicals, and carbon monoxide-based therapies, have been developed to target HO-1 in a variety of nephropathological animal models, indicating that HO-1 is a promising protein for the treatment of kidney diseases. Here, we briefly review the effects of HO-1 induction on specific immune cell populations with the aim of exploring the potential therapeutic roles of HO-1 and designing HO-1-based therapeutic strategies for the treatment of kidney diseases.

Long non-coding RNA CASC2 restrains high glucose-induced proliferation, inflammation and fibrosis in human glomerular mesangial cells through mediating miR-135a-5p/TIMP3 axis and JNK signaling

BACKGROUND

Diabetic nephropathy (DN) is a common complication of diabetes. Long non-coding RNA (lncRNA) cancer susceptibility candidate 2 (CASC2) is reported to exert a protective role in DN by a previous study. The working mechanism underlying the protective role of CASC2 in DN progression was further explored in this study.

METHODS

The expression of CASC2 and microRNA-135a-5p (miR-135a-5p) was determined by real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation ability was assessed by Cell Counting Kit-8 (CCK8) assay and 5-ethynyl-29-deoxyuridine (EDU) assay. Enzyme-linked immunosorbent assay (ELISA) was conducted to analyze the production of inflammatory cytokines in the supernatant. Western blot assay was performed to analyze protein expression. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the target relationship between miR-135a-5p and CASC2 or tissue inhibitors of metalloproteinase 3 (TIMP3).

RESULTS

High glucose (HG) treatment reduced the expression of CASC2 in human glomerular mesangial cells (HMCs) in a time-dependent manner. CASC2 overexpression suppressed HG-induced proliferation, inflammation and fibrosis in HMCs. miR-135a-5p was validated as a target of CASC2, and CASC2 restrained HG-induced influences in HMCs partly by down-regulating miR-135a-5p. miR-135a-5p bound to the 3' untranslated region (3'UTR) of TIMP3, and CASC2 positively regulated TIMP3 expression by sponging miR-135a-5p in HMCs. miR-135a-5p silencing inhibited HG-induced effects in HMCs partly by up-regulating its target TIMP3. CASC2 overexpression suppressed HG-induced activation of Jun N-terminal Kinase (JNK) signaling partly through mediating miR-135a-5p/TIMP3 signaling.

CONCLUSIONS

In conclusion, CASC2 alleviated proliferation, inflammation and fibrosis in DN cell model by sponging miR-135a-5p to induce TIMP3 expression.

Advanced Glycation End Products: New Clinical and Molecular Perspectives

Diabetes mellitus (DM) is considered one of the most massive epidemics of the twenty-first century due to its high mortality rates caused mainly due to its complications; therefore, the early identification of such complications becomes a race against time to establish a prompt diagnosis. The research of complications of DM over the years has allowed the development of numerous alternatives for diagnosis. Among these emerge the quantification of advanced glycation end products (AGEs) given their increased levels due to chronic hyperglycemia, while also being related to the induction of different stress-associated cellular responses and proinflammatory mechanisms involved in the progression of chronic complications of DM. Additionally, the investigation for more valuable and safe techniques has led to developing a newer, noninvasive, and effective tool, termed skin fluorescence (SAF). Hence, this study aimed to establish an update about the molecular mechanisms induced by AGEs during the evolution of chronic complications of DM and describe the newer measurement techniques available, highlighting SAF as a possible tool to measure the risk of developing DM chronic complications.

LncRNA TUG1/miR-29c-3p/SIRT1 axis regulates endoplasmic reticulum stress-mediated renal epithelial cells injury in diabetic nephropathy model in vitro

Long non-coding RNAs (lncRNAs) are important regulators in diabetic nephropathy. In this study, we investigated the potential role of lncRNA TUG1 in regulating endoplasmic reticulum stress (ERS)-mediated apoptosis in high glucose induced renal tubular epithelial cells. Human renal tubular epithelial cell line HK-2 was challenged with high glucose following transfection with lncRNA TUG1, miR-29c-3p mimics or inhibitor expression plasmid, either alone or in combination, for different experimental purposes. Potential binding effects between TUG1 and miR-29c-3p, as well as between miR-29c-3p and SIRT1 were verified. High glucose induced apoptosis and ERS in HK-2 cells, and significantly decreased TUG1 expression. Overexpressed TUG1 could prevent high glucose-induced apoptosis and alleviated ERS via negatively regulating miR-29c-3p. In contrast, miR-29c-3p increased HK-2 cells apoptosis and ERS upon high glucose-challenge. SIRT1 was a direct target gene of miR-29c-3p in HK-2 cells, which participated in the effects of miR-29c-3p on HK-2 cells. Mechanistically, TUG1 suppressed the expression of miR-29c-3p, thus counteracting its function in downregulating the level of SIRT1. TUG1 regulates miR-29c-3p/SIRT1 and subsequent ERS to relieve high glucose induced renal epithelial cells injury, and suggests a potential role for TUG1 as a promising diagnostic marker of diabetic nephropathy.

circRNA_010383 Acts as a Sponge for miR-135a, and Its Downregulated Expression Contributes to Renal Fibrosis in Diabetic Nephropathy

Diabetic nephropathy (DN), a vascular complication of diabetes, is the leading cause of death in patients with diabetes. The contribution of aberrantly expressed circular RNAs (circRNAs) to DN in vivo is poorly understood. Integrated comparative circRNA microarray profiling was used to examine the expression of circRNAs in diabetic kidney of db/db mice. We found that circRNA_010383 expression was markedly downregulated in diabetic kidneys, mesangial cells, and tubular epithelial cells cultured in high-glucose conditions. circRNA_010383 colocalized with miRNA-135a (miR-135a) and inhibited miR-135a function by directly binding to miR-135a. In vitro, the knockdown of circRNA_010383 promoted the accumulation of extracellular matrix (ECM) proteins and downregulated the expression of transient receptor potential cation channel, subfamily C, member 1 (TRPC1), which is a target protein of miR-135a. Furthermore, circRNA_010383 overexpression effectively inhibited the high-glucose-induced accumulation of ECM and increased TRPC1 levels in vitro. More importantly, the kidney target of circRNA_010383 overexpression inhibited proteinuria and renal fibrosis in db/db mice. Mechanistically, we identified that a loss of circRNA_010383 promoted proteinuria and renal fibrosis in DN by acting as a sponge for miR-135a. This study reveals that circRNA_010383 may be a novel therapeutic target for DN in the future.

Diminution of microRNA-98 alleviates renal fibrosis in diabetic nephropathy by elevating Nedd4L and inactivating TGF-β/Smad2/3 pathway

MicroRNAs (miRNAs) have already been documented to function in diabetic nephropathy (DN), yet little research has focused on the role of miR-98 in this disease. Here, we discuss the mechanism of miR-98 on the renal fibrosis in DN. Recombinant adeno-associated virus carrying miR-98 inhibitor or Nedd4L overexpression plasmid was injected into DN modeled rats to explore their roles in DN. Renal tubular epithelial cell injury models (NRK-52E cells) were induced by high glucose (HG). HG-treated NRK-52E cells were transfected with miR-98 inhibitor or Nedd4L overexpression plasmid for further verification. MiR-98 was upregulated, Nedd4L was downregulated and TGF-β/Smad2/3 signaling was activated in kidney tissues of DN rats and HG-treated NRK-52E cells. miR-98 targeted Nedd4L mRNA 3'UTR. MiR-98 depletion and Nedd4L overexpression inactivated TGF-β/Smad2/3 signaling pathway, alleviated pathological damage and fibrosis, ameliorated inflammation, and depressed cell apoptosis of kidney tissues of DN rats. MiR-98 depletion and Nedd4L overexpression inactivated TGF-β/Smad2/3 signaling pathway, strengthened viability, and limited apoptosis of HG-treated renal tubular epithelial cells. Nedd4L overexpression reversed the effect of up-regulating miR-98 on DN rats and HG-treated renal tubular epithelial cells. Altogether, we find that miR-98 is upregulated in kidney tissues of DN rats, and miR-98 diminution and Nedd4L elevation attenuate renal fibrosis through inactivation of the TGF-β/Smad2/3 pathway, which provides a novel therapy for DN.

LncRNA CASC2 Alleviates the Progression of Diabetic Nephropathy by Regulating the miR-144/SOCS2 Signalling Axis

BACKGROUND

Diabetic nephropathy constitutes a large proportion of end-stage kidney failure in diabetic patients. However, the underlying molecular mechanisms remain unclear.

METHODS

Db/db diabetic mouse models and high glucose (HG)-induced human renal mesangial cells (HRMCs) were used as research models in vivo and in vitro. The expression of cancer susceptibility candidate 2 (CASC2) was quantified by qRT-PCR. The regulatory role of CASC2 in cell apoptosis, inflammatory factor release, and fibrosis was verified by flow cytometry, qRT-PCR, and Western blot assay, respectively. The bioinformatics prediction software DIANA and starBase v2.0 were used to predict the putative binding sites. The interactions among CASC2, miR-144, and SOCS2 were explored by the luciferase assay and Western bolt assay.

RESULTS

The expression of CASC2 in diabetic mouse models and HG-induced HRMCs was lower than that in the control (p < 0.05). Overexpression of CASC2 resulted in a decrease in the apoptosis rate, inflammatory factor release (TNF-α, IL-6, and IL-1β), expression of cleaved caspase-3, and fibrotic proteins (fibronectin, Col-IV, and TGF-β1) and an increase in Bcl-2 expression. Inhibition of CASC2 caused increased expression of miR-144. Furthermore, mechanistic investigations confirmed that activation of the miR-144/SOCS2 regulatory loop by overexpression of miR-144 reversed the in vitro effects of CASC2 on inhibiting cell apoptosis, inflammatory factor release, and fibrosis. In addition, simultaneous overexpression of miR-144 and SOCS2 further increased the inhibition of cell apoptosis, inflammatory factor release, and fibrosis by CASC2.

CONCLUSION

CASC2 could alleviate the degree and process of apoptosis, inflammation, and fibrosis in diabetic nephropathic models by regulating the miR-144/SOCS2 axis.

Extracellular Vesicles From High Glucose-Treated Podocytes Induce Apoptosis of Proximal Tubular Epithelial Cells

Diabetic kidney disease (DKD) is a serious and common complication of diabetes. Extracellular vesicles (EVs) have emerged as crucial vectors in cell-to-cell communication during the development of DKD. EVs may mediate intercellular communication between podocytes and proximal tubules. In this study, EVs were isolated from podocyte culture supernatants under high glucose (HG), normal glucose (NG), and iso-osmolality conditions, and then co-cultured with proximal tubular epithelial cells (PTECs). MicroRNAs (miRNA) sequencing was conducted to identify differentially expressed miRNAs of podocyte EVs and bioinformatics analysis was performed to explore their potential functions. The results showed that EVs secreted from HG-treated podocytes induced apoptosis of PTECs. Moreover, five differentially expressed miRNAs in response to HG condition were identified. Functional enrichment analysis revealed that these five miRNAs are likely involved in biological processes and pathways related to the pathogenesis of DKD. Overall, these findings demonstrate the pro-apoptotic effects of EVs from HG-treated podocytes on PTECs and provide new insights into the pathologic mechanisms underlying DKD.

MicroRNAs in diabetic nephropathy: From molecular mechanisms to new therapeutic targets of treatment

Despite considerable investigation in diabetic nephropathy (DN) pathogenesis and possible treatments, current therapies still do not provide competent prevention from disease progression to end-stage renal disease (ESRD) in most patients. Therefore, investigating exact molecular mechanisms and important mediators underlying DN may help design better therapeutic approaches for proper treatment. MicroRNAs (MiRNAs) are a class of small non-coding RNAs that play a crucial role in post-transcriptional regulation of many gene expression within the cells and present an excellent opportunity for new therapeutic approaches because their profile is often changed during many diseases, including DN. This review discusses the most important signaling pathways involved in DN and changes in miRNAs profile in each signaling pathway. We also suggest possible approaches for miRNA derived interventions for designing better treatment of DN.

Circ_WBSCR17 aggravates inflammatory responses and fibrosis by targeting miR-185-5p/SOX6 regulatory axis in high glucose-induced human kidney tubular cells

BACKGROUND

Diabetic nephropathy (DN), a severe microvascular complication of diabetes, has complex pathogenesis. Circular RNAs (circRNAs) exert broad biological functions on human diseases. This study intended to explore the role and mechanism of circ_WBSCR17 in DN.

METHODS

DN mice models were constructed using streptozotocin injection, and DN cell models were assembled using high glucose (HG) treatment in human kidney 2 cells (HK-2). The expression of circ_WBSCR17, miR-185-5p and SRY-Box Transcription Factor 6 (SOX6) was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The protein levels of SOX6 and fibrosis markers were examined by western blot. The release of inflammatory cytokines, cell proliferation and apoptosis, were assessed by enzyme-linked immunosorbent assay (ELISA), cell counting kit-8 (CCK-8) assay and flow cytometry assay, respectively. The predicted interaction between miR-185-5p and circ_WBSCR17 or SOX6 was verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay.

RESULT

Circ_WBSCR17 was highly expressed in DN mice models and HG-induced HK-2 cells. Circ_WBSCR17 knockdown or SOX6 knockdown promoted cell proliferation and blocked cell apoptosis, inflammatory responses and fibrosis, while circ_WBSCR17 overexpression or SOX6 overexpression conveyed the opposite effects. MiR-185-5p was a target of circ_WBSCR17 and directly bound to SOX6. MiR-185-5p could reverse the role of circ_WBSCR17 or SOX6. Moreover, the expression of SOX6 was modulated by circ_WBSCR17 through intermediating miR-185-5p.

CONCLUSION

Circ_WBSCR17 triggered the dysfunction of HG-induced HK-2 cells, including inflammatory responses and fibrosis, which was accomplished via the miR-185-5p/SOX6 regulatory axis.

Glomerular Endothelial Cells as Instigators of Glomerular Sclerotic Diseases

Glomerular endothelial cell (GEnC) dysfunction is important in the pathogenesis of glomerular sclerotic diseases, including Focal Segmental Glomerulosclerosis (FSGS) and overt diabetic nephropathy (DN). GEnCs form the first cellular barrier in direct contact with cells and factors circulating in the blood. Disturbances in these circulating factors can induce GEnC dysfunction. GEnC dysfunction occurs in early stages of FSGS and DN, and is characterized by a compromised endothelial glycocalyx, an inflammatory phenotype, mitochondrial damage and oxidative stress, aberrant cell signaling, and endothelial-to-mesenchymal transition (EndMT). GEnCs are in an interdependent relationship with podocytes and mesangial cells, which involves bidirectional cross-talk via intercellular signaling. Given that GEnC behavior directly influences podocyte function, it is conceivable that GEnC dysfunction may culminate in podocyte damage, proteinuria, subsequent mesangial activation, and ultimately glomerulosclerosis. Indeed, GEnC dysfunction is sufficient to cause podocyte injury, proteinuria and activation of mesangial cells. Aberrant gene expression patterns largely contribute to GEnC dysfunction and epigenetic changes seem to be involved in causing aberrant transcription. This review summarizes literature that uncovers the importance of cross-talk between GEnCs and podocytes, and GEnCs and mesangial cells in the context of the development of FSGS and DN, and the potential use of GEnCs as efficacious cellular target to pharmacologically halt development and progression of DN and FSGS.

Loss of lncRNA MIAT ameliorates proliferation and fibrosis of diabetic nephropathy through reducing E2F3 expression

Diabetic nephropathy (DN) is a serious kidney disease resulted from diabetes. Dys‐regulated proliferation and extracellular matrix (ECM) accumulation in mesangial cells contribute to DN progression. In this study, we tested expression level of MIAT in DN patients and mesangial cells treated by high glucose (HG). Up‐regulation of MIAT was observed in DN. Then, functional assays displayed that silence of MIAT by siRNA significantly repressed the proliferation and cycle progression in mesangial cells induced by HG. Meanwhile, we found that collagen IV, fibronectin and TGF‐β1 protein expression was obviously triggered by HG, which could be rescued by loss of MIAT. Then, further assessment indicated that MIAT served as sponge harbouring miR‐147a. Moreover, miR‐147a was decreased in DN, which exhibited an antagonistic effect of MIAT on modulating mesangial cell proliferation and fibrosis. Moreover, bioinformatics analysis displayed that E2F transcription factor 3 (E2F3) could act as direct target of miR‐147a. We demonstrated that E2F3 was greatly increased in DN and the direct binding association between miR‐147a and E2F3 was evidenced using luciferase reporter assay. In summary, our data explored the underlying mechanism of DN pathogenesis validated that MIAT induced mesangial cell proliferation and fibrosis via sponging miR‐147a and regulating E2F3.

HDAC6-mediated α-tubulin deacetylation suppresses autophagy and enhances motility of podocytes in diabetic nephropathy

Histone deacetylase 6 (HDAC6) is the specific subtype of HDACs which preferentially located in the cytoplasm, and is crucial in insulin signalling. However, the role of HDAC6 in type 2 diabetic nephropathy (DN) remains undefined. In current study, we observed that HDAC6 was markedly activated in the kidneys of type 2 diabetic patients and db/db mice with albuminuria, along with the advanced glycation end products (AGE)‐treated podocytes. Selective inhibition of HDAC6 activity protected kidneys from hyperglycaemia in db/db mice. Notably, overexpressing HDAC6 inhibited autophagy and promoted motility aside from the apoptosis of podocytes exposed to AGE. We further determined that HDAC6 regulated the autophagy partially by decreasing the acetylation of α‐tubulin at the residue of lysine 40. In contrast, we confirmed that there was no interaction of HDAC6 with α‐tubulin at the sites of lysine 112 and lysine 352. Consistently, inhibiting HDAC6 by siRNA or the selective inhibitor, tubacin, restored the autophagy level and motility of podocytes and rescued podocytes from AGE stimulation. We provide strong evidence of an unexpected role of HDAC6 in the cascade that modulates podocytes autophagy and motility, enlightening that HDAC6 may be a promising therapeutic target for DN treatment.

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

Diabetes is characterized by changed homeostasis of blood glucose levels, which is associated with various complications, including cardiomyopathy, atherosclerosis, endothelial dysfunction, nephropathy, retinopathy and neuropathy. In recent years, accumulative evidence has demonstrated that circular RNAs are identified as a novel type of noncoding RNAs (ncRNAs) involving in the regulation of various physiological processes and pathologic conditions. Specifically, the emergence of complications response to diabetes is finely controlled by a complex gene regulatory network in which circular RNAs play a critical role. Recently, circular RNAs are emerging as messengers that could influence cellular functions under diabetic conditions. Dysregulation of circular RNAs has been closely linked to the pathophysiology of diabetes-related complications. In this review, we aimed to summarize the current progression and underlying mechanisms of circular RNA in the development of diabetes-related complications. We will also provide an overview of circular RNA-regulated cell communications in different types of cells that have been linked to diabetic complications. We anticipated that the completion of this review will provide potential clues for developing novel circular RNAs-based biomarkers or therapeutic targets for diabetes and its associated complications.

Circ-AKT3 inhibits the accumulation of extracellular matrix of mesangial cells in diabetic nephropathy via modulating miR-296-3p/E-cadherin signals

Diabetic nephropathy is a leading cause of end-stage renal disease globally. The vital role of circular RNAs (circRNAs) has been reported in diabetic nephropathy progression, but the molecular mechanism linking diabetic nephropathy to circRNAs remains elusive. In this study, we investigated the significant function of circ-AKT3/miR-296-3p/E-cadherin regulatory network on the extracellular matrix accumulation in mesangial cells in diabetic nephropathy. The expression of circ-AKT3 and fibrosis-associated proteins, including fibronectin, collagen type I and collagen type IV, was assessed via RT-PCR and Western blot analysis in diabetic nephropathy animal model and mouse mesangial SV40-MES13 cells. Luciferase reporter assays were used to investigate interactions among E-cadherin, circ-AKT3 and miR-296-3p in mouse mesangial SV40-MES13 cells. Cell apoptosis was evaluated via flow cytometry. The level of circ-AKT3 was significantly lower in diabetic nephropathy mice model group and mouse mesangial SV40-MES13 cells treated with high-concentration (25 mmol/L) glucose. In addition, circ-AKT3 overexpression inhibited the level of fibrosis-associated protein, such as fibronectin, collagen type I and collagen type IV. Circ-AKT3 overexpression also inhibited the apoptosis of mouse mesangial SV40-MES13 cells treated with high glucose. Luciferase reporter assay and bioinformatics tools identified that circ-AKT3 could act as a sponge of miR-296-3p and E-cadherin was the miR-296-3p direct target. Moreover, circ-AKT3/miR-296-3p/E-cadherin modulated the extracellular matrix of mouse mesangial cells in high-concentration (25 mmol/L) glucose, inhibiting the synthesis of related extracellular matrix protein. In conclusion, circ-AKT3 inhibited the extracellular matrix accumulation in diabetic nephropathy mesangial cells through modulating miR-296-3p/E-cadherin signals, which might offer novel potential opportunities for clinical diagnosis targets and therapeutic biomarkers for diabetic nephropathy.

Inhibition of miRNA‑135a‑5p ameliorates TGF‑β1‑induced human renal fibrosis by targeting SIRT1 in diabetic nephropathy

miRNA-135a-5p upregulation has been identified in renal fibrosis in diabetic nephropathy (DN) with an incompletely known mechanism. Previous data showed that Sirtuin 1 (SIRT1) serves as a novel therapeutic target for DN and interact with the transforming growth factor-β/mothers against decapentaplegic homolog (TGF-β/Smad) signaling pathway. The aim of this study was to investigate the regulatory relationship between miR-135a-5p and SIRT1. The expression of miR-135a-5p and SIRT1 was detected using reverse transcription-quantitative PCR and western blotting. The renal fibrosis and Smad3 signaling pathway were assessed by western blotting, by analyzing protein expression of collegen1A1, α-smooth muscle actin (α-SMA), fibronectin (FN), epithelial-cadherin, Smad3 and phosphorylated Smad3 (p-Smad3). The target binding between miR-135a-5p and SIRT1 was predicted on TargetScan Human software, and confirmed by dual-luciferase reporter assay and RNA immu-noprecipitation. The results demonstrated miR-135a-5p is upregulated and SIRT1 was downregulated in the serum and renal tissue of DN patients, and TGFβ1-induced DN cell models in human HK-2 and HMCs. Knockdown of miR-135a-5p and overexpression of SIRT1 could inhibit TGFβ1-induced renal fibrosis in vitro. Moreover, SIRT1 was a downstream target for miR-135a-5p. Silencing of SIRT1 could abolish the suppressive role of miR-135a-5p knockdown in TGFβ1-induced HK-2 and HMCs. The TGFβ1 induced p-Smad3 expression in HK-2 and HMCs, which could be attenuated by miR-135a-5p knockdown via SIRT1. In conclusion, knockdown of miR-135a-5p inhibits TGFβ1-induced renal fibrosis by targeting SIRT1 and inactivating Smad3 signaling, providing a novel insight into miR-135a-5p as a potential therapeutic approach for DN.

Long non-coding RNA MALAT1 and microRNA-499a expression profiles in diabetic ESRD patients undergoing dialysis: a preliminary cross-sectional analysis

Background: Circulating non-coding RNAs (ncRNAs) have been implicated in health and disease. This study aimed to evaluate the serum expression profile of microRNA-499a (miR-499a) and its selected bioinformatically predicted partner long-ncRNA MALAT1 (metastasis-associated lung adenocarcinoma transcript 1) in diabetes-related end-stage renal disease (ESRD) patients and to correlate the expressions with the patients' clinicolaboratory data.Subjects and methods: Real-time quantitative polymerase chain reaction was applied in diabetics with and without ESRD (n = 90 for each).Results: Serum MALAT1 expression levels were increased in the ESRD group relative to diabetics without ESRD with median (quartile) values of 10.5 (1.41-126.7) (p < .001). However, miR-499a levels were decreased in more than half of ESRD patients with a median of 0.96 (0.13-3.14). Both MALAT1 and miR-499a expression levels were inversely correlated in the ESRD patient-group.Conclusions: MALAT1 up-regulation and miR-499 down-regulation might be involved in diabetic nephropathy-related ESRD pathogenesis. Functional validation studies are warranted to confirm the MALAT1/miR-499a partnership.

Perspectives on the role of PTEN in diabetic nephropathy: an update

Phosphatase and tensin homolog (PTEN) is a potent tumor suppressor gene that antagonizes the proto-oncogenic phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) signaling pathway and governs basic cellular metabolic processes. Recently, its role in cell growth, metabolism, architecture, and motility as an intramolecular and regulatory mediator has gained widespread research interest as it applies to non-tumorous diseases, such as insulin resistance (IR) and diabetic nephropathy (DN). DN is characterized by renal tubulointerstitial fibrosis (TIF) and epithelial-mesenchymal transition (EMT), and PTEN plays a significant role in the regulation of both. Epigenetics and microRNAs (miRNAs) are novel players in post-transcriptional regulation and research evidence demonstrates that they reduce the expression of PTEN by acting as key regulators of autophagy and TIF through activation of the Akt/mammalian target of rapamycin (mTOR) signaling pathway. These regulatory processes might play an important role in solving the complexities of DN pathogenesis and IR, as well as the therapeutic management of DN with the help of PTEN K27-linked polyubiquitination. Currently, there are no comprehensive reviews citing the role PTEN plays in the development of DN and its regulation via miRNA and epigenetic modifications. The present review explores these facets of PTEN in the pathogenesis of IR and DN.

LncRNA KCNQ1OT1 affects cell proliferation, apoptosis and fibrosis through regulating miR-18b-5p/SORBS2 axis and NF-ĸB pathway in diabetic nephropathy

BACKGROUND

It has been reported that long non-coding RNAs (lncRNAs) play vital roles in diabetic nephropathy (DN). Our study aims to research the function of lncRNA KCNQ1OT1 in DN cells and the molecular mechanism.

METHODS

Human glomerular mesangial cells (HGMCs) and human renal glomerular endothelial cells (HRGECs) were cultured in high glucose (30 mM) condition as models of DN cells. KCNQ1 opposite strand/antisense transcript 1 (KCNQ1OT1) and miR-18b-5p levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The mRNA and protein levels of Sorbin and SH3 domain-containing protein 2 (SORBS2), Type IV collagen (Col-4), fibronectin (FN), transcriptional regulatory factor-beta 1 (TGF-β1), Twist, NF-κB and STAT3 were measured by qRT-PCR and western blot. Cell viability was detected by cell counting kit-8 (CCK-8) assay for selecting the proper concentration of glucose treatment. Additionally, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and flow cytometry assay were employed to determine cell proliferation and apoptosis, respectively. The targets of KCNQ1OT1 was predicted by online software and confirmed by dual-luciferase reporter assay.

RESULTS

KCNQ1OT1 and SORBS2 were elevated in DN. Both knockdown of KCNQ1OT1 and silencing of SORBS2 restrained proliferation and fibrosis and induced apoptosis in DN cells. Besides, Overexpression of SORBS2 restored the KCNQ1OT1 knockdown-mediate effects on proliferation, apoptosis and fibrosis in DN cells. In addition, miR-18b-5p served as a target of KCNQ1OT1 as well as targeted SORBS2. KCNQ1OT1 knockdown repressed NF-ĸB pathway.

CONCLUSION

KCNQ1OT1 regulated DN cells proliferation, apoptosis and fibrosis via KCNQ1OT1/miR-18b-5p/SORBS2 axis and NF-ĸB pathway.

Epigenome and transcriptome study of moringa isothiocyanate in mouse kidney mesangial cells induced by high glucose, a potential model for diabetic-induced nephropathy

Moringa isothiocyanate (MIC-1) is a bioactive constituent found abundantly in Moringa oleifera which possesses antioxidant and anti-inflammation properties. However, epigenome and transcriptome effects of MIC-1 in kidney mesangial cells challenged with high glucose (HG), a pre-condition for diabetic nephropathy (DN) remain unknown. Herein, we examined the transcriptome gene expression and epigenome DNA methylation in mouse kidney mesangial cells (MES13) using next-generation sequencing (NGS) technology. After HG treatment, epigenome and transcriptome were significantly altered. More importantly, MIC-1 exposure reversed some of the changes caused by HG. Integrative analysis of RNA-Seq data identified 20 canonical pathways showing inverse correlations between HG and MIC-1. These pathways included GNRH signaling, P2Y purigenic receptor signaling pathway, calcium signaling, LPS/IL-1-mediated inhibition of RXR function, and oxidative ethanol degradation III. In terms of alteration of DNA methylation patterns, 173 differentially methylation regions (DMRs) between the HG group and low glucose (LG) group and 149 DMRs between the MIC-1 group and the HG group were found. Several HG related DMRs could be reversed by MIC-1 treatment. Integrative analysis of RNA-Seq and Methyl-Seq data yielded a subset of genes associated with HG and MIC-1, and the gene expression changes may be driven by promoter CpG status. These genes include Col4a2, Tceal3, Ret, and Agt. In summary, our study provides novel insights related to transcriptomic and epigenomic/CpG methylomic alterations in MES13 upon challenged by HG but importantly, MIC-1 treatment reverses some of the transcriptome and epigenome/CpG methylome. These results may provide potential molecular targets and therapeutic strategies for DN.

Silence of lncRNA GAS5 alleviates high glucose toxicity to human renal tubular epithelial HK-2 cells through regulation of miR-27a

Renal tubular damage caused by persistent high glucose environment has been found to contribute to diabetic nephropathy. This study explored the effects of lncRNA growth arrest-specific 5 (GAS5) on high glucose-stimulated human renal tubular epithelial HK-2 damage, as well as the possible internal molecular mechanism. Viability and apoptosis of HK-2 cells were assessed with the help of CCK-8 assay and Annexin V-FITC/PI staining, respectively. Cell transfection was used to change the expression of GAS5, miR-27a and BNIP3. We found that high glucose stimulation suppressed HK-2 cell viability but induced cell apoptosis. The expression of GAS5 was increased in HK-2 cells under high glucose environment. Silence of GAS5 mitigated the high glucose-caused HK-2 cell viability reduction and apoptosis. Overexpression of miR-27a reversed the effects of GAS5 on high glucose-stimulated HK-2 cells. Overexpression of BNIP3 aggravated the high glucose-caused HK-2 cell viability reduction, apoptosis and activation of JNK pathway. Knockdown of BNIP3 had opposite effects. In conclusion, this research further confirmed the pro-apoptotic roles of GAS5 in renal tubular epithelial cells under high glucose environment. Silence of GAS5 alleviated high glucose toxicity to human renal tubular epithelial HK-2 cells might be via down-regulating miR-27a and BNIP3, and then inactivating JNK pathway. Highlights HG suppresses HK-2 cell viability, but promotes cell apoptosis; HG enhances the expression of GAS5 in HK-2 cells; Silence of GAS5 alleviates the HG-caused HK-2 cell toxicity; miR-27a participates in the effects of GAS5 silencing on HG-stimulated HK-2 cells; BNIP3 is regulated by miR-27a and related to the HG toxicity to HK-2 cells.

Urinary NGAL and RBP Are Biomarkers of Normoalbuminuric Renal Insufficiency in Type 2 Diabetes Mellitus

Objectives

As a screening index of diabetic kidney disease (DKD), urinary albumin/creatine ratio (UACR) is commonly used. However, approximately 23.3%-56.6% of DKD patients with estimated glomerular filtration rate (eGFR) < 60 ml/min per 1.73 m² are normoalbuminuric. Thus, urinary biomarkers of nonalbuminuric renal insufficiency in type 2 diabetes mellitus (T2DM) patients are urgently needed.

Methods

This cross-sectional study enrolled 209 T2DM patients with normoalbuminuria whose diabetes duration was more than 5 years. The patients were classified into two groups, NO-CKD (eGFR ≥ 60 ml/min per 1.73 m², n = 165) and NA-DKD (eGFR < 60 ml/min per 1.73 m², n = 44). Levels of urinary neutrophil gelatinase-associated lipocalin (NGAL), retinol-binding protein (RBP), plasminogen activator inhibitor-1 (PAI-1), vascular cell adhesion molecule-1 (VCAM-1), and E-cadherin were detected, and their correlations with eGFR, plasma TNF-α, IL-6, endothelin-1 (ET-1), and 8-hydroxydeoxyguanosine (8-OHdG) were assessed.

Results

Among patients with renal insufficiency, 26.0% was normoalbuminuric. Compared to the NO-CKD group, the NA-DKD group was older with lower hemoglobin (HB) levels and higher systolic blood pressure (SBP), plasma TNF-α, IL-6, and 8-OHdG levels. Logistic regression analysis suggested that age, TNF-α, and 8-OHdG were independent risk factors for nonalbuminuric renal insufficiency. Compared to the NO-CKD group, the NA-DKD group exhibited significant increases in urinary NGAL and RBP levels but not PAI-1, VCAM-1, and E-cadherin. Urinary NGAL and RBP both correlated negatively with eGFR and positively with plasma IL-6 and 8-OHdG. Multiple linear regression indicated NGAL (β = -0.287, p = 0.008) and RBP (β = -44.545, p < 0.001) were independently correlated with eGFR.

Conclusion

Age, plasma TNF-α, and 8-OHdG are independent risk factors for renal insufficiency in T2DM patients with normoalbuminuria. Urinary NGAL and RBP can serve as noninvasive biomarkers of normoalbuminuric renal insufficiency in T2DM.

Diabetic Nephropathy versus Diabetic Retinopathy in a Chinese Population: A Retrospective Study

BACKGROUND It has been reported that diabetic nephropathy and diabetic retinopathy are associated with each other through a shared pathophysiological mechanism. However, it is quite difficult to differentiate diabetic nephropathy from other glomerular diseases if diabetic retinopathy is absent in patients, and the only way to do this is to perform renal biopsies. The objective of this study was to test the hypothesis that diabetic nephropathy patients with and without diabetic retinopathy have different clinical and laboratory profiles. MATERIAL AND METHODS Medical records of type 2 diabetes mellitus patients with confirmed diabetic nephropathy were reviewed and analyzed with appropriate statistical modalities. Presence of arteriolar sclerosis of the carotid artery, abdominal aorta, upper extremities, and first-order aortic branches was regarded as a peripheral vascular disease. RESULTS Out of 217 type 2 diabetes mellitus patients with confirmed diabetic nephropathy, retinopathy was present in 106 (48.8%), while 111 (51.2%) had no evidence of retinopathy. About 45% of patients had pure diabetic nephropathy without any diagnosis of non-diabetic renal diseases, of which membranous nephropathy was most common. Diabetic nephropathy patients with retinopathy and those without retinopathy differed in duration of hypertension (p=0.041), serum creatinine (p=0.031), albumin (p=0.001), and erythrocyte sedimentation rate (p=0.001). Moreover, male preponderance (p<0.001), older age (p=0.033), and increased levels of albumin (p=0.033) were significantly associated with pure diabetic nephropathy without retinopathy. CONCLUSIONS Diabetic nephropathy patients with and without diabetic retinopathy have different clinical and laboratory profiles.

LncRNA TUG1 ameliorates diabetic nephropathy by inhibiting miR-21 to promote TIMP3-expression

Diabetic nephropathy (DN) is one of the most important microvascular diseases in diabetic patients and has been the first cause of end stage renal disease (ESRD). In this study, we are aims to investigate the genetic mechanisms of lncRNA in the regulation of DN renal fibrosis. First, we have found that the expression of lncRNA TUG1 in db/db DN mice kidney tissue and high glucose-stimulated NRK-52E cells were down-regulated and the overexpression of lncRNA TUG1 could inhibit cell fibrosis of high glucose-stimulated of NRK-52E. Second, online software program Starbase predicts that miR-21 is a target gene of lncRNA TUG1 and TIMP3 is the target gene of miR-21, which have been verified by luciferase reporter assay and RNA Binding Protein Immunoprecipitation (RIP). Last, the renal fibrosis in DN mice and cell fibrosis in high glucose-stimulated NRK-52E cells were also evaluated. We have proven that overexpression of lncRNA TUG1 can promote the expression of TIMP3 through targeting the miR-21, thereby inhibiting cell fibrosis in high glucose-stimulated NRK-52E cells and renal fibrosis in DN mice. Our results indicated that lncRNA TUG1 could indirectly regulated the expression of TIMP3 by targeting miR-21. LncRNA TUG1 inhibited high glucose-stimulated NRK-52E cell fibrosis and renal fibrosis in DN mice, which provides a theoretical basis for the treatment of DN fibrosis.

Microvascular complications in diabetes: A growing concern for cardiologists

Randomized, cross-sectional, and prospective studies have demonstrated that microvascular complications in patients with diabetes are not only the cause of blindness, renal failure and non-traumatic amputations, but also powerful predictors of cardiovascular complications. Beside the metabolic theory, the pathophysiology of diabetic microvascular complications is determined by the interaction among several factors, including epigenetic modifications and the reduced release of progenitor cells by the bone marrow, that contribute simultaneously to damage and impaired vascular protection against hyperglycemia. Identifying and preventing microvascular complications has the significant potential to reduce major adverse cardiovascular events. For these reasons, there may no longer be a rational to consider microangiopathy and macroangiopathy as entirely separate entities, but they should most likely be viewed as a continuum of the widespread vascular damage determined by diabetes mellitus.

Carbohydrate response element binding protein (ChREBP) modulates the inflammatory response of mesangial cells in response to glucose

Diabetic nephropathy (DN) is one of the most devastating complications of diabetes mellitus. Carbohydrate response element binding protein (ChREBP) is a basic helix–loop–helix leucine zipper transcription factor that primarily mediates glucose homeostasis in the body. The present study investigated the role of ChREBP in the pathogenesis of DN. The expression of ChREBP was detected in patients with type 2 diabetes mellitus (T2DM), diabetic mice, and mesangial cells. ELISA was used to measure cytokine production in mesangial cells. Flow cytometry analysis was performed to detect the apoptosis of mesangial cells in the presence of high glucose. The expression levels of ChREBP and several cytokines (TNF-α, IL-1β, and IL-6) were up-regulated in T2DM patients. The mRNA and protein levels of ChREBP were also significantly elevated in the kidneys of diabetic mice. Moreover, glucose treatment promoted mRNA levels of TNF-α, IL-1β, and IL-6 in mesangial cells. Glucose stimulation induced significant apoptosis of SV40 MES 13 cells. In addition, transfection with ChREBP siRNA significantly inhibited ChREBP expression. Consequently, the inflammatory responses and apoptosis were inhibited in SV40 MES 13 cells. These results demonstrated that ChREBP could mediate the inflammatory response and apoptosis of mesangial cells, suggesting that ChREBP may be involved in the pathogenesis of DN.

miR29b regulates aberrant methylation in In-Vitro diabetic nephropathy model of renal proximal tubular cells

The role of DNA methylation has not been enough explored in pathophysiology of diabetic nephropathy (DN). However, according to recent reports it has been inferred that hypermethylation could be one of the principle cause associated with the enhancement of DN. An interrelationship between miR29b and DNA methylation has been studied via in-silico analysis. We have validated that miR29b prominently targets DNA methyl transferase (DNMT), specifically DNMT1, DNMT3A and DNMT3B. We have developed in vitro DN model using renal proximal tubule epithelial cells (RPTECs), contributed to a significant alleviation in RNA and protein expression levels of DNMT3A, DNMT3B and DNMT1. The developed model has also demonstrated downregulation in expression of miR29b. Our studies have also suggested that miR29b targets DNMT1 via targeting its transcription factor SP1. In addition to this, downregulation of a specific biomarker for kidney injury, tubular kidney injury molecule-1 (KIM-1) and fibrosis causing glycoprotein i.e. fibronectin, was also demonstrated. Hence, the developed model revealed that hypermethylation is a key factor incorporated in DN, and miR29b could effectively ameliorate defensive actions in DN pathogenesis.

IL-6 receptor blockade ameliorates diabetic nephropathy via inhibiting inflammasome in mice

BACKGROUND AND OBJECTIVE

Interleukin 6 (IL-6) has been identified as a key mediator in inflammation, immune responses and glucose metabolism. In this study, we assessed the effects of an IL-6 receptor antibody on diabetic nephropathy in a mouse model of type 2 diabetes mellitus.

METHODS

Twelve week old male db/db mice were treated with Tocilizumab (an IL-6 receptor antibody), normal IgG1 control antibody, insulin or normal saline for 12 weeks. Renal injury, inflammation and insulin resistance were assessed.

RESULTS

Db/db mice treated with Tocilizumab exhibited reduced proteinuria and glomerular mesangial matrix accumulation compared to db/db + IgG controls. Additionally, Tocilizumab suppressed inflammatory response, oxidative stress and the IL-6 signaling pathway in the diabetic kidneys. It is noteworthy that blockade of IL-6 receptor blunted the activation of NLRP3 inflammasome partly through inhibition of IL-17A. Furthermore, insulin resistance assessed by glucose tolerance test, was ameliorated by Tocilizumab treatment.

CONCLUSIONS

The protective effects of an IL-6 receptor blockade against diabetic renal injury may be due to decreased insulin resistance and inhibition of the inflammasome.

Association of single nucleotide polymorphisms in CACNA 1A/CACNA 1C/CACNA 1H calcium channel genes with diabetic peripheral neuropathy in Chinese population

The present study was conducted to explore the correlations between single nucleotide polymorphisms (SNPs) in the calcium channel CACNA 1A, CACNA 1C, and CACNA 1H genes and diabetic peripheral neuropathy (DPN) amongst the Chinese population. In total, 281 patients diagnosed with type 2 diabetes participated in the present study. These patients were divided into the case group, which was subdivided into the DPN (143 cases) and the non-DPN groups (138 cases). Subsequently, 180 healthy individuals that had undergone routine health examinations were also recruited and assigned to the control group. PCR-restriction fragment length polymorphism (PCR-RFLP) was used to detect the genotype and allele frequencies of CACNA 1A, CACNA 1C, and CACNA 1H genes; logistic regression analysis to investigate the association of gene polymorphisms with DNP. Gene–gene interactions were then detected by generalized multifactor dimensionality reduction (GMDR). The results revealed that CACNA 1A rs2248069 and rsl6030, CACNA 1C rs216008 and rs2239050, and CACNA 1H rs3794619, and rs7191246 SNPs were all associated with DPN, while rs2248069, rsl6030, rs2239050, and rs7191246 polymorphisms were attributed to the susceptibility to DPN. It was also observed that the optimal models were three-, four- and five-dimensional models with a prediction accuracy of 61.05% and the greatest consistency of cross-validation was 10/10. In summary, these findings demonstrated that the SNPs in the CACNA 1A, CACNA 1C, and CACNA 1H genes were involved in the pathophysiology of DPN. In addition, polymorphisms in the CACNA 1A, CACNA 1C, and CACNA 1H genes and their interactions also had effects on DPN.

ANRIL regulates production of extracellular matrix proteins and vasoactive factors in diabetic complications

noncoding RNAs (lncRNAs) have gained widespread interest due to their prevailing presence in various diseases. lncRNA ANRIL (a. k. a. CDKN2B-AS1) is located on human chromosome 9 (p21.3) and transcribed in opposite direction to the INK4b-ARF-INK4a gene cluster. It has been identified as a highly susceptible region for diseases such as coronary artery diseases and type 2 diabetes. Here, we explored its regulatory role in diabetic nephropathy (DN) and diabetic cardiomyopathy (DCM) in association with epigenetic modifiers p300 and polycomb repressive complex 2 (PRC2) complex. We used an ANRIL-knockout (ANRILKO) mouse model for this study. The wild-type and ANRILKO animals with or without streptozotocin-induced diabetes were monitored for 2 min. At the end of the time point, urine and tissues were collected. The tissues were measured for fibronectin (FN), type IV collagen (Col1α4), and VEGF mRNA and protein expressions. Renal function was determined by the measurement of 24-h urine volume and albumin/creatinine ratio at euthanasia. Renal and cardiac structures were investigated using periodic acid-Schiff stain and/or immunohistochemical analysis. Elevated expressions of extracellular matrix (ECM) proteins were prevented in ANRILKO diabetic animals. Furthermore, ANRILKO had a protective effect on diabetic mouse kidneys, as evidenced by lowering of urine volume and urine albumin levels in comparison with the wild-type diabetic animals. These alterations regulated by ANRIL may be mediated by p300 and enhancer of zeste 2 (EZH2) of the PRC2 complex. Our study concludes that ANRIL regulates functional and structural alterations in the kidneys and hearts in diabetes through controlling the expressions of ECM proteins and VEGF.