The long noncoding RNA Tug1 connects metabolic changes with kidney disease in podocytes

Role of LncRNA in Pathogenesis, Diagnosis and Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) is a clinical syndrome of metabolic disorder caused by progressive kidney impairment for more than 3 months. CKD has become a global public health problem due to its high morbidity and mortality, which is difficult to be cured for most patients. The pathogenesis of CKD is still unclear, which is closely related to glomerulosclerosis, kidney tubular injury and kidney fibrosis. LncRNA is a non-coding RNA with a length of more than 200 nucleotides. It not only participates in intracellular transcriptional regulation, post-transcriptional regulation and epigenetic activities, but also forms a regulatory network together with miRNA and mRNA, to further conduct the reticular regulation in cells. Recently, it has been found that lncRNA participates in pathophysiological mechanism of CKD by regulating glomerulosclerosis, kidney tubular injury and kidney fibrosis. This has also become a new direction of lncRNA in early diagnosis and targeted therapy of CKD.

LncRNA Tug1 Regulates Post-Stroke Microglial Pyroptosis via PINK1/Parkin-Mediated Mitophagy

Microglia, the central nervous system's primary immune cells, play a key role in the progression of cerebral ischemic stroke, particularly through their involvement in pyroptosis. The long non-coding RNA taurine up-regulated gene 1 (Tug1) is elevated during ischemic stroke and is critical in driving post-stroke neuroinflammation. However, the underlying molecular mechanisms remain unclear. This study explores the biological role of Tug1 and its potential mechanisms in regulating pyroptosis in microglia. We utilized an in vivo photothrombosis (PT) mice model and an in vitro oxygen-glucose deprivation and reperfusion (OGD/R) BV2 cell model to explore the mechanisms underlying ischemic stroke. Initially, we assessed the expression levels of Tug1 in the OGD/R model in vitro and the PT model in vivo. Subsequently, we investigated the impact of Tug1 on microglial pyroptosis by knocking down Tug1, silencing the PTEN-induced putative kinase 1 (Pink1) expression, and employing the mitophagy inhibitor mdivi-1. Tug1 exacerbated microglial pyroptosis by inhibiting mitophagy in both in vivo and in vitro models. The increase in mitophagy observed following Tug1 knockdown was reversed by either silencing Pink1 expression or using the mitophagy inhibitor mdivi-1. This reversal resulted in exacerbated pyroptosis and worsened neurological damage. Further mechanistic studies revealed that Tug1 knockdown significantly reduced microglial pyroptosis and alleviated neuronal damage by enhancing PINK1/Parkin-mediated mitophagy. For the first time, this study reveals that Tug1 promotes hypoxia-induced microglial pyroptosis by inhibiting PINK1/Parkin-mediated mitophagy, potentially providing a promising therapeutic target for ischemic inflammatory injury.

M6A RNA Methylation-Mediated TUG1 Stability Maintains Mitochondrial Homeostasis during Kidney Aging by Epigenetically Regulating PGC1-α Expression

Background: Aging is a significant risk factor for the increased incidence of acute kidney injury and chronic kidney disease, posing significant challenges to global public health. The role of N6-methyladenosine (m6A) in the development of chronic kidney disease has been reported, but the regulatory mechanism of m6A in kidney aging remains unclear. Results: In this study, we identified a long noncoding RNA (lncRNA), called taurine up-regulated 1 (TUG1), which exhibited a significantly decreased level of m6A modification in human aged kidney through the m6A-lncRNA epitranscriptome microarray. Bioinformatics analysis and machine learning predicted that TUG1 had potentially strong interaction with PGC1-α. RNA immunoprecipitation and chromatin immunoprecipitation analysis showed that TUG1 promoted proliferator-activated receptor γ coactivator-1α (PGC1-α) expression by directly interacting with its TUG-1 binding element region, thereby impacting mitochondrial quality control (MQC), cellular senescence, and renal fibrosis. Silencing the RNA m6A methylase methyltransferase 14 (METTL14) or the reader protein insulin-like growth factor 2 mRNA-binding proteins (IGF2BP2) resulted in the weakened stability of lncRNA TUG1, contributing to an imbalance in MQC. Conclusion: Our study demonstrated that the m6A modification and stability of TUG1 were mediated by METTL14 in an IGF2BP2-dependent manner, and modulate the mitochondrial homeostasis in kidney aging by direct targeting PGC-1α. These findings provide a new perspective on potential therapeutic targets for kidney aging. Antioxid. Redox Signal. 41, 993-1013.

METTL3-Mediated N 6 -Methyladenosine mRNA Modification and cGAS-STING Pathway Activity in Kidney Fibrosis

Background

Chemical modifications on RNA profoundly affect RNA function and regulation. m6A, the most abundant RNA modification in eukaryotes, plays a pivotal role in diverse cellular processes and disease mechanisms. However, its importance is understudied in human CKD samples regarding its influence on pathological mechanisms.

Methods

Liquid chromatography–tandem mass spectrometry and methylated RNA immunoprecipitation sequencing were used to examine alterations in m6A levels and patterns in CKD samples. Overexpression of the m6A writer METTL3 in cultured kidney tubular cells was performed to confirm the effect of m6A in tubular cells and explore the biological functions of m6A modification on target genes. In addition, tubule-specific deletion of Mettl3 (Ksp-Cre Mettl3f/f) mice and antisense oligonucleotides inhibiting Mettl3 expression were used to reduce m6A modification in an animal kidney disease model.

Results

By examining 127 human CKD samples, we observed a significant increase in m6A modification and METTL3 expression in diseased kidneys. Epitranscriptomic analysis unveiled an enrichment of m6A modifications in transcripts associated with the activation of inflammatory signaling pathways, particularly the cyclic guanosine monophosphate–AMP synthase (cGAS)-stimulator of IFN genes (STING) pathway. m6A hypermethylation increased mRNA stability in cGAS and STING1 as well as elevated the expression of key proteins within the cGAS-STING pathway. Both the tubule-specific deletion of Mettl3 and the use of antisense oligonucleotides to inhibit Mettl3 expression protected mice from inflammation, reduced cytokine expression, decreased immune cell recruitment, and attenuated kidney fibrosis.

Conclusions

Our research revealed heightened METTL3-mediated m6A modification in fibrotic kidneys, particularly enriching the cGAS-STING pathway. This hypermethylation increased mRNA stability for cGAS and STING1, leading to sterile inflammation and fibrosis.

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

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

An increase in SNHG5 expression is associated with poor cancer prognosis, according to a meta-analysis

BACKGROUND

He long noncoding RNA small nucleolar host RNA 5 (SNHG5) is highly expressed in many cancers, and there is a notable correlation between the elevated expression of SNHG5 and survival outcome in cancer patients. The objective of this study was to conduct a meta-analysis to evaluate the correlation between SNHG5 expression and the clinical outcome of cancer patients.

METHODS

Six relevant electronic databases were exhaustively searched, and, depending on the inclusion and exclusion criteria, appropriate literature was obtained. The Newcastle-Ottawa Scale (NOS) score was utilized to evaluate the quality of the research for every article included, and pertinent data from each study were carefully extracted. Hazard ratios (HRs), odds ratios (ORs) and 95% confidence intervals (CIs) were combined to explore the association of SNHG5 expression levels with cancer prognosis, and sensitivity analyses and assessments of publication bias were also conducted to investigate any possibility in the publication of the studies.

RESULTS

Eleven studies encompassing 721 patients were ultimately collected. When combined, the hazard ratios (HRs) revealed a substantial direct correlation between elevated SNHG5 expression and an unfavourable prognosis for cancer patients (HR = 1.90, 95% CI 0.87-4.15); however, the correlation did not reach statistical significance. Furthermore, high SNHG5 expression was predictive of advanced TNM stage (OR: 1.988, 95% CI 1.205-3.278) and larger tumour size (OR: 1.571, 95% CI 1.090-2.264); moreover, there were nonsignificant relationships between SNHG5 expression and DM (OR: 0.449, 95% CI 0.077-2.630), lymph node metastasis (OR: 1.443, 95% CI 0.709-2.939), histological grade (OR: 2.098, 95% CI 0.910-4.838), depth of invasion (OR: 1.106, 95% CI 0.376-3.248), age (OR: 0.946, 95% CI 0.718-1.247) and sex (OR: 0.762, 95% CI 0.521-1.115).

CONCLUSION

SNHG5 expression is typically increased in the majority of tumour tissues. Elevated SNHG5 expression may indicate poor prognosis in cancer patients. Therefore, SNHG5 is a promising potential therapeutic target for tumours and a reliable prognostic biomarker.

Chk2 Modulates Bmi1-Deficiency-Induced Renal Aging and Fibrosis via Oxidative Stress, DNA Damage, and p53/TGFβ1-Induced Epithelial-Mesenchymal Transition

Renal aging may lead to fibrosis and dysfunction, yet underlying mechanisms remain unclear. We explored whether deficiency of the Polycomb protein Bmi1 causes renal aging via DNA damage response (DDR) activation, inducing renal tubular epithelial cell (RTEC) senescence and epithelial-mesenchymal transition (EMT). Bmi1 knockout mice exhibited oxidative stress, DDR activation, RTEC senescence, senescence-associated secretory phenotype (SASP), and age-related fibrosis in kidneys. Bmi1 deficiency impaired renal structure and function, increasing serum creatinine/urea, reducing creatinine clearance, and decreasing cortical thickness and glomerular number. However, knockout of the serine-threonine kinase Chk2 alleviated these aging phenotypes. Transcriptomics identified transforming growth factor beta 1 (TGFβ1) upregulation in Bmi1-deficient RTECs, but TGFβ1 was downregulated upon Chk2 knockout. The tumor suppressor protein p53 transcriptionally activated TGFβ1, promoting EMT in RTECs. Bmi1 knockout or oxidative stress (induced with H2O2) increased TGFβ1 expression, and EMT in RTECs and was partly reversed by p53 inhibition. Together, Bmi1 deficiency causes oxidative stress and DDR-mediated RTEC senescence/SASP, thus activating p53 and TGFβ1 to induce EMT and age-related fibrosis. However, blocking DDR (via Chk2 knockout) or p53 ameliorates these changes. Our study reveals mechanisms whereby Bmi1 preserves renal structure and function during aging by suppressing DDR and p53/TGFβ1-mediated EMT. These pathways represent potential targets for detecting and attenuating age-related renal decline.

Klotho-derived peptide 1 inhibits cellular senescence in the fibrotic kidney by restoring Klotho expression via posttranscriptional regulation

Background: Klotho deficiency is a common feature of premature aging and chronic kidney disease (CKD). As such, restoring Klotho expression could be a logic strategy for protecting against various nephropathies. In this study, we demonstrate that KP1, a Klotho-derived peptide, inhibits cellular senescence by restoring endogenous Klotho expression. Methods: The effects of KP1 on cellular senescence and Klotho expression were assessed in mouse models of CKD. RNA-sequencing was employed to identify the microRNA involved in regulating Klotho by KP1. Gain- or loss-of-function approaches were used to assess the role of miR-223-3p and IncRNA-TUG1 in regulating Klotho and cellular senescence. Results: KP1 inhibited senescence markers p21, p16 and γ-H2AX in tubular epithelial cells of diseased kidneys, which was associated with its restoration of Klotho expression at the posttranscriptional level. Profiling of kidney microRNAs by RNA sequencing identified miR-223-3p that bound to Klotho mRNA and inhibited its protein expression. Overexpression of miR-223-3p inhibited Klotho and induced p21, p16 and γ-H2AX, which were negated by KP1. Conversely, inhibition of miR-223-3p restored Klotho expression, inhibited cellular senescence. Furthermore, miR-223-3p interacted with lncRNA-TUG1 and inhibited its expression. Knockdown of lncRNA-TUG1 increased miR-223-3p, aggravated Klotho loss and worsened cellular senescence, whereas KP1 mitigated all these changes. Conclusion: These studies demonstrate that KP1 inhibits cellular senescence and induces Klotho expression via posttranscriptional regulation mediated by miR-223-3p and lncRNA-TUG1. By restoring endogenous Klotho, KP1 elicits a broad spectrum of protective actions and could serve as a promising therapeutic agent for fibrotic kidney disorders.

Long noncoding RNA: An emerging diagnostic and therapeutic target in kidney diseases

Long noncoding RNAs (lncRNAs) have critical roles in the development of many diseases including kidney disease. An increasing number of studies have shown that lncRNAs are involved in kidney development and that their dysregulation can result in distinct disease processes, including acute kidney injury, chronic kidney disease, and renal cell carcinoma. Understanding the roles of lncRNAs in kidney disease may provide new diagnostic and therapeutic opportunities in the clinic. This review provides an overview of lncRNA characteristics, and biological function and discusses specific studies that provide insight into the function and potential application of lncRNAs in kidney disease treatment.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

The Mission of Long Non-Coding RNAs in Human Adult Renal Stem/Progenitor Cells and Renal Diseases

Long non-coding RNAs (lncRNAs) are a large, heterogeneous class of transcripts and key regulators of gene expression at both the transcriptional and post-transcriptional levels in different cellular contexts and biological processes. Understanding the potential mechanisms of action of lncRNAs and their role in disease onset and development may open up new possibilities for therapeutic approaches in the future. LncRNAs also play an important role in renal pathogenesis. However, little is known about lncRNAs that are expressed in the healthy kidney and that are involved in renal cell homeostasis and development, and even less is known about lncRNAs involved in human adult renal stem/progenitor cells (ARPC) homeostasis. Here we give a thorough overview of the biogenesis, degradation, and functions of lncRNAs and highlight our current understanding of their functional roles in kidney diseases. We also discuss how lncRNAs regulate stem cell biology, focusing finally on their role in human adult renal stem/progenitor cells, in which the lncRNA HOTAIR prevents them from becoming senescent and supports these cells to secrete high quantities of α-Klotho, an anti-aging protein capable of influencing the surrounding tissues and therefore modulating the renal aging.

Molecular pathways that drive diabetic kidney disease

Kidney disease is a major driver of mortality among patients with diabetes and diabetic kidney disease (DKD) is responsible for close to half of all chronic kidney disease cases. DKD usually develops in a genetically susceptible individual as a result of poor metabolic (glycemic) control. Molecular and genetic studies indicate the key role of podocytes and endothelial cells in driving albuminuria and early kidney disease in diabetes. Proximal tubule changes show a strong association with the glomerular filtration rate. Hyperglycemia represents a key cellular stress in the kidney by altering cellular metabolism in endothelial cells and podocytes and by imposing an excess workload requiring energy and oxygen for proximal tubule cells. Changes in metabolism induce early adaptive cellular hypertrophy and reorganization of the actin cytoskeleton. Later, mitochondrial defects contribute to increased oxidative stress and activation of inflammatory pathways, causing progressive kidney function decline and fibrosis. Blockade of the renin-angiotensin system or the sodium-glucose cotransporter is associated with cellular protection and slowing kidney function decline. Newly identified molecular pathways could provide the basis for the development of much-needed novel therapeutics.

Therapeutic mechanism and clinical application of Chinese herbal medicine against diabetic kidney disease

Diabetic kidney disease (DKD) is the major complications of type 1 and 2 diabetes, and is the predominant cause of chronic kidney disease and end-stage renal disease. The treatment of DKD normally consists of controlling blood glucose and improving kidney function. The blockade of renin-angiotensin-aldosterone system and the inhibition of sodium glucose cotransporter 2 (SGLT2) have become the first-line therapy of DKD, but such treatments have been difficult to effectively block continuous kidney function decline, eventually resulting in kidney failure and cardiovascular comorbidities. The complex mechanism of DKD highlights the importance of multiple therapeutic targets in treatment. Chinese herbal medicine (active compound, extract and formula) synergistically improves metabolism regulation, suppresses oxidative stress and inflammation, inhibits mitochondrial dysfunction, and regulates gut microbiota and related metabolism via modulating GLP-receptor, SGLT2, Sirt1/AMPK, AGE/RAGE, NF-κB, Nrf2, NLRP3, PGC-1α, and PINK1/Parkin pathways. Clinical trials prove the reliable evidences for Chinese herbal medicine against DKD, but more efforts are still needed to ensure the efficacy and safety of Chinese herbal medicine. Additionally, the ideal combined therapy of Chinese herbal medicine and conventional medicine normally yields more favorable benefits on DKD treatment, laying the foundation for novel strategies to treat DKD.

The role of lncRNAs in regulation of DKD and diabetes-related cancer

Diabetes mellitus often results in several complications, such as diabetic kidney disease (DKD) and end-stage renal diseases (ESRDs). Cancer patients often have the dysregulated glucose metabolism. Abnormal glucose metabolism can enhance the tumor malignant progression. Recently, lncRNAs have been reported to regulate the key proteins and signaling pathways in DKD development and progression and in cancer patients with diabetes. In this review article, we elaborate the evidence to support the function of lncRNAs in development of DKD and diabetes-associated cancer. Moreover, we envisage that lncRNAs could be diagnosis and prognosis biomarkers for DKD and cancer patients with diabetes. Furthermore, we delineated that targeting lncRNAs might be an alternative approach for treating DKD and cancer with dysregulated glucose metabolism.

PGC1 plays a pivotal role in renal fibrosis via regulation of fatty acid metabolism in renal tissue

Renal fibrosis is a common and irreversible pathological feature of end-stage renal disease caused by multiple etiologies. The role of inflammation in renal fibrosis tissue has been generally accepted. The latest view is that fatty acid metabolism disorder contributes to renal fibrosis. peroxisome proliferator activated receptor-gamma coactivator 1α (PGC1α) plays a key role in fatty acid metabolism, regulating fatty acid uptake and oxidized protein synthesis, preventing the accumulation of lipid in the cytoplasm, and maintaining a dynamic balanced state of intracellular lipid. In multiple animal models of renal fibrosis caused by acute or chronic kidney disease, or even age-related kidney disease, almost all of the kidney specimens show the down-regulation of PGC1α. Upregulation of PGC1α can reduce the degree of renal fibrosis in animal models, and PGC1α knockout animals exhibit severe renal fibrosis. Studies have demonstrated that AMP-activated protein kinase (AMPK), MAPK, Notch, tumor necrosis factor-like weak inducer of apoptosis (TWEAK), epidermal growth factor receptor (EGFR), non-coding RNA (ncRNAs), liver kinase B1 (LKB1), hairy and enhancer of split 1 (Hes1), and other pathways regulate the expression of PGC1α and affect fatty acid metabolism. But some of these pathways interact with each other, and the effect of the integrated pathway on renal fibrosis is not clear.

Down-regulation of Risa improves podocyte injury by enhancing autophagy in diabetic nephropathy

BACKGROUND

LncRNA AK044604 (regulator of insulin sensitivity and autophagy, Risa) and autophagy-related factors Sirt1 and GSK3β play important roles in diabetic nephropathy (DN). In this study, we sought to explore the effect of Risa on Sirt1/GSK3β-induced podocyte injury.

METHODS

Diabetic db/db mice received Risa-inhibition adeno-associated virus (AAV) via tail vein injection, and intraperitoneal injection of lithium chloride (LiCl). Blood, urine, and kidney tissue samples were collected and analyzed at different time points. Immortalized mouse podocyte cells (MPCs) were cultured and treated with Risa-inhibition lentivirus (LV), EX-527, and LiCl. MPCs were collected under different stimulations as noted. The effects of Risa on podocyte autophagy were examined by qRT-PCR, Western blotting analysis, transmission electron microscopy, Periodic Acid-Schiff staining, and immunofluorescence staining.

RESULTS

Risa and activated GSK3β were overexpressed, but Sirt1 was downregulated in DN mice and high glucose-treated MPCs (P < 0.001, db/m vs. db/db, NG or HM vs. HG), which was correlated with poor prognosis. Risa overexpression attenuated Sirt1-mediated downstream autophagy levels and aggravated podocyte injury by inhibiting the expression of Sirt1 (P < 0.001, db/m vs. db/db, NG or HM vs. HG). In contrast, Risa suppression enhanced Sirt1-induced autophagy and attenuated podocyte injury, which could be abrogated by EX-527 (P < 0.001, db/db + Risa-AAV vs. db/db, HG + Risa-LV vs. HG). Furthermore, LiCl treatment could restore GSK3β-mediated autophagy of podocytes (P < 0.001, db/db + LiCl vs. db/db, HG + LiCl vs. HG), suggesting that Risa overexpression aggravated podocyte injury by decreasing autophagy.

CONCLUSION

Risa could inhibit autophagy by regulating the Sirt1/GSK3β axis, thereby aggravating podocyte injury in DN. Risa may serve as a therapeutic target for the treatment of DN.

Long non-coding RNA TUG1 sponges microRNA-9 to protect podocytes from high glucose-induced apoptosis and mitochondrial dysfunction via SIRT1 upregulation

Podocyte apoptosis and mitochondrial dysfunction serve a major role in diabetic nephropathy progression. The present study revealed a molecular mechanism regulating podocyte apoptosis and mitochondrial dysfunction. In vitro models were established using conditionally immortalized mouse podocyte clonal cells treated with high glucose (HG). Reverse quantitative-transcription PCR were used to detect gene expression, western blotting and immunofluorescence were used to detect protein expression, Cell Counting Kit-8 was used to detect cell viability and flow cytometry was used to detect cell apoptosis. HG treatment in the mouse podocyte clonal cells downregulated taurine-upregulated gene 1 (TUG1) expression and decreased viability in a dose-dependent manner. In addition, TUG1 knockdown (KD) increased HG-induced apoptosis, while TUG1 overexpression (OE) reduced HG-induced apoptosis in podocytes. HG-induced mitochondrial dysfunction was identified in podocytes, with increased reactive oxygen species levels, decreased complex I/III activity and decreased basal/maximal oxygen consumption rate. TUG1 KD worsened HG-induced mitochondrial dysfunction, and TUG1 OE reversed these effects. At the molecular level, TUG1 was revealed to promote sirtuin 1 (SIRT1) expression by sponging microRNA (miR)-9, and SIRT1 OE reversed the HG-induced apoptosis and mitochondrial dysfunction increased by TUG1 KD. The present data indicated that downregulation of TUG1 induced by HG was associated with HG-induced apoptosis and mitochondrial dysfunction in podocytes, and that TUG1 protected HG-induced podocytes by promoting SIRT1 expression via miR-9 inhibition.

Epigenetics in the pathogenesis of diabetic nephropathy

Diabetic nephropathy (DN), which is a common microvascular complication with a high incidence in diabetic patients, greatly increases the mortality of patients. With further study on DN, it is found that epigenetics plays a crucial role in the pathophysiological process of DN. Epigenetics has an important impact on the development of DN through a variety of mechanisms, and promotes the generation and maintenance of metabolic memory, thus ultimately leading to a poor prognosis. In this review we discuss the methylation of DNA, modification of histone, and regulation of non-coding RNA involved in the progress of cell dysfunction, inflammation and fibrosis in the kidney, which ultimately lead to the deterioration of DN.

LncRNA TUG1 attenuates ischaemia-reperfusion-induced apoptosis of renal tubular epithelial cells by sponging miR-144-3p via targeting Nrf2

Renal ischaemia/reperfusion (I/R) injury may induce kidney damage and dysfunction, in which oxidative stress and apoptosis play important roles. Long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) are reported to be closely related to renal I/R, but the specific molecular mechanism is still unclear. The purpose of this research was to explore the regulatory effect of lncRNA TUG1 on oxidative stress and apoptosis in renal I/R injury. This research revealed that in renal I/R injury and hypoxia/reperfusion (H/R) injury in vitro, the expression level of lncRNA TUG1 was upregulated, and oxidative stress levels and apoptosis levels were negatively correlated with the expression level of lncRNA TUG1. Using bioinformatics databases such as TargetScan and microRNA.org, microRNA-144-3p (miR-144-3p) was predicted to be involved in the association between lncRNA TUG1 and Nrf2. This study confirmed that the level of miR-144-3p was significantly reduced following renal I/R injury and H/R injury in vitro, and miR-144-3p was determined to target Nrf2 and inhibit its expression. In addition, lncRNA TUG1 can reduce the inhibitory effect of miR-144-3p on Nrf2 by sponging miR-144-3p. In summary, our research shows that lncRNA TUG1 regulates oxidative stress and apoptosis during renal I/R injury through the miR-144-3p/Nrf2 axis, which may be a new treatment target for renal I/R injury.

PGC1α is required for the renoprotective effect of lncRNA Tug1 in vivo and links Tug1 with urea cycle metabolites

lncRNA taurine-upregulated gene 1 (Tug1) is a promising therapeutic target in the progression of diabetic nephropathy (DN), but the molecular basis of its protection remains poorly understood. Here, we generate a triple-mutant diabetic mouse model coupled with metabolomic profiling data to interrogate whether Tug1 interaction with peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α) is required for mitochondrial remodeling and progression of DN in vivo. We find that, compared with diabetic conditional deletion of Pgc1α in podocytes alone (db/db; Pgc1αPod-f/f), diabetic Pgc1α knockout combined with podocyte-specific Tug1 overexpression (db/db; TugPodTg; Pgc1αPod-f/f) reverses the protective phenotype of Tug1 overexpression, suggesting that PGC1α is required for the renoprotective effect of Tug1. Using unbiased metabolomic profiling, we find that altered urea cycle metabolites and mitochondrial arginase 2 play an important role in Tug1/PGC1α-induced mitochondrial remodeling. Our work identifies a functional role of the Tug1/PGC1α axis on mitochondrial metabolic homeostasis and urea cycle metabolites in experimental models of diabetes.

Association of the Expression Levels of Long-Chain Noncoding RNA TUG1 and Its Gene Polymorphisms with Knee Osteoarthritis

Objective: To study the association of the expression levels of long noncoding RNA Taurine-upregulated gene 1 (lncRNA TUG1) and TUG1 polymorphisms with knee osteoarthritis (KOA). Materials and Methods: A total of 255 KOA patients and 255 controls from May 2017 to December 2019 were selected for the study. Sanger sequencing was conducted to detect the genotypes of the TUG1 rs5749201, rs7284767, and rs886471 loci in all study subjects. Unconditional logistic regression analysis was used to calculate odds ratios and 95% confidence intervals, and the associations between the TUG1 rs574901, rs7284767 and rs886471 loci and KOA risk were analyzed. Multifactor dimensionality reduction was used to analyze the interactions among alleles at the three TUG1 loci examined. Quantitative real-time polymerase chain reaction was used to evaluate the expression levels of TUG1 lncRNA in plasma. Results: A total of 255 KOA patients and 255 control subjects completed the study. After adjusting for the factors of gender, age, body mass index, smoking history, drinking history, and family history, we found that the carriers of the A allele of the TUG1 rs5749201 locus were 1.36 times more likely to develop KOA than the carriers of the T allele (95% confidence interval [CI] = 1.05-1.75, p = 0.02); the G allele of the rs7284767 locus was a protective factor for KOA (odds ratio [OR] = 0.71, 95% CI = 0.54-0.92, p = 0.01); and the allelic variation at rs886471 G > T led to an increased risk of KOA by 2.34 times (95% CI = 1.53-3.57, p < 0.01). We also found that the GAG haplotype for the three loci was significantly associated with the increased risk of KOA (OR = 2.77, 95% CI = 1.67-4.57, p < 0.01). There was no correlation found between the TUG1 rs886471, rs5749201, and rs7284767 single nucleotide polymorphisms loci and the severity of KOA. The allelic variation at TUG1 rs5749201 T > A, rs886471 T > G were associated with decreased levels of TUG1 lncRNA in the plasma of the subjects, while the allelic variation at rs7284767 A > G was associated with increased levels of TUG1 lncRNA in plasma (p = 0.01, p < 0.01, p < 0.01). Conclusion: Plasma TUG1 lncRNA levels and loci at the TUG1 rs5749201, rs7284767, and rs886471 loci are associated with KOA risk.

Role of long non-coding RNAs in adipogenesis: State of the art and implications in obesity and obesity-associated diseases

Obesity is an evolutionary, chronic, and relapsing disease that consists of a pathological accumulation of adipose tissue able to increase morbidity for high blood pressure, type 2 diabetes, metabolic syndrome, and obstructive sleep apnea in adults, children, and adolescents. Despite intense research over the last 20 years, obesity remains today a disease with a complex and multifactorial etiology. Recently, long non-coding RNAs (lncRNAs) are emerging as interesting new regulators as different lncRNAs have been found to play a role in early and late phases of adipogenesis and to be implicated in obesity-associated complications onset. In this review, we discuss the most recent advances on the role of lncRNAs in adipocyte biology and in obesity-associated complications. Indeed, more and more researchers are focusing on investigating the underlying roles that these molecular modulators could play. Even if a significant number of evidence is correlation-based, with lncRNAs being differentially expressed in a specific disease, recent works are now focused on deeply analyzing how lncRNAs can effectively modulate the disease pathogenesis onset and progression. LncRNAs possibly represent new molecular markers useful in the future for both the early diagnosis and a prompt clinical management of patients with obesity.

LncRNA HCP5 knockdown inhibits high glucose-induced excessive proliferation, fibrosis and inflammation of human glomerular mesangial cells by regulating the miR-93-5p/HMGA2 axis

BACKGROUND

Long non-coding RNAs (lncRNAs) are widely reported to be involved in the development of human diseases. HLA complex P5 (HCP5) deregulation is associated with various diseases. However, the function of HCP5 in diabetic nephropathy (DN) is unclear.

METHODS

Human glomerular mesangial cells (HGMCs) were treated with high glucose (HG) to establish DN cell models. The expression of HCP5, miR-93-5p and high mobility group AT-hook 2 (HMGA2) mRNA was detected using quantitative polymerase chain reaction (QPCR). Cell proliferation and cell apoptosis were assessed using cell counting kit-8 (CCK-8) assay and flow cytometry assay, respectively. The expression of apoptosis- and fibrosis-related proteins and HMGA2 protein was quantified by western blot. The release of pro-inflammatory factor was checked using enzyme-linked immunosorbent assay (ELISA). The predicted relationship between miR-93-5p and HCP5 or HMGA2 was verified using dual-luciferase reporter assay, pull-down assay or RNA immunoprecipitation (RIP) assay.

RESULTS

The expression of HCP5 and HMGA2 was enhanced, while the expression of miR-93-5p was declined in DN serum samples and HG-treated HGMCs. HCP5 knockdown or miR-93-5p restoration ameliorated HG-induced HGMC proliferation, fibrosis and inflammation. MiR-93-5p was a target of HCP5, and miR-93-5p inhibition reversed the effects caused by HCP5 knockdown. Moreover, HMGA2 was a target of miR-93-5p, and HMGA2 overexpression abolished the effects of miR-93-5p restoration. HCP5 knockdown inhibited the AKT/mTOR signaling pathway.

CONCLUSION

HCP5 was implicated in DN progression by modulating the miR-93-5p/HMGA2 axis, which provided new insights into the understanding of DN pathogenesis.

Non-Coding RNAs in Kidney Diseases: The Long and Short of Them

Recent progress in genomic research has highlighted the genome to be much more transcribed than expected. The formerly so-called junk DNA encodes a miscellaneous group of largely unknown RNA transcripts, which contain the long non-coding RNAs (lncRNAs) family. lncRNAs are instrumental in gene regulation. Moreover, understanding their biological roles in the physiopathology of many diseases, including renal, is a new challenge. lncRNAs regulate the effects of microRNAs (miRNA) on mRNA expression. Understanding the complex crosstalk between lncRNA–miRNA–mRNA is one of the main challenges of modern molecular biology. This review aims to summarize the role of lncRNA on kidney diseases, the molecular mechanisms involved, and their function as emerging prognostic biomarkers for both acute and chronic kidney diseases. Finally, we will also outline new therapeutic opportunities to diminish renal injury by targeting lncRNA with antisense oligonucleotides.

LncRNA TUG1 ameliorates diabetic nephropathy via inhibition of PU.1/RTN1 signaling pathway

Diabetic nephropathy (DN) is a leading cause of end-stage renal failure. The study aimed to investigate whether long noncoding RNA taurine-upregulated gene 1 (TUG1) can ameliorate the endoplasmic reticulum stress (ERS) and apoptosis of renal tubular epithelial cells in DN, and the underlying mechanism. The DN mouse model was established by streptozocin injection, and the human renal tubular epithelial cell line HK-2 was treated with high glucose (HG) to mimic DN in vitro. The molecular mechanism was explored through dual-luciferase activity assay, RNA pull-down assay, RNA immunoprecipitation (RIP), and chromatin immunoprecipitation (CHIP) assay. The expression of TUG1 was significantly decreased in the renal tubules of DN model mice. Overexpression of TUG1 reduced the levels of ERS markers and apoptosis markers by inhibiting reticulon-1 (RTN1) expression in HG-induced HK-2 cells. Furthermore, TUG1 down-regulated RTN1 expression by inhibiting the binding of transcription factor PU.1 to the RTN1 promoter, thereby reducing the levels of ERS markers and apoptosis markers. Meanwhile, TUG1-overexpression adenovirus plasmids injection significantly alleviated tubular lesions, and reduced RTN1 expression, ERS markers and apoptosis markers, whereas these results were reversed by injection of PU.1-overexpression adenovirus plasmids. TUG1 restrains the ERS and apoptosis of renal tubular epithelial cells and ameliorates DN through inhibition of transcription factor PU.1.

Total Glucosides of Paeony Inhibited Autophagy and Improved Acute Kidney Injury Induced by Ischemia-Reperfusion via the lncRNA TUG1/miR-29a/PTEN Axis

Objective

Total glucosides of paeony (TGP) has been proven to affect anti-inflammatory, immunomodulatory and hypoxia tolerance. This study investigates the effect of TGP on autophagy in acute kidney injury (AKI) induced by ischemia-reperfusion (I/R).

Methods

Rat model of AKI induced by I/R was established. Rats were administered with TGP at different doses by oral gavage. The contents of BUN, creatinine, NGAL, Kim-1 and IL-18 were detected. The levels of inflammatory factors (TNF-α, IL-1β and IL-6) and autophagy were measured. The expressions of lncRNA TUG1, miR-29a and PTEN were detected and their binding relationships were verified. I/R rat model with overexpressed TUG1 was established to explore the effect of TGP on kidney injury and autophagy. The hypoxia/reoxygenation (HR) model of HK-2 cells and the HR model of HK-2 cells overexpressing TUG1 and low-expressing PTEN were established.

Results

TGP decreased the contents of BUN, creatinine, NGAL, Kim-1 and IL-18, and reduced the levels of inflammatory factors. LncRNA TUG1 and PTEN were downregulated, and miR-29a was upregulated in kidney tissues. The binding relationships between lncRNA TUG1 and miR-29a, and miR-29a and PTEN were confirmed. TGP suppressed PTEN expression via the lncRNA TUG1/miR-29a axis. Overexpressing lncRNA TUG1 attenuated the protective effect of TGP on AKI and autophagy in HK-2 cells. TGP improved cell viability and inhibited the autophagy in HR model of HK-2 cells via lncRNA TUG1/miR-29a/PTEN axis.

Conclusion

TGP inhibited autophagy and improved AKI induced by I/R via the lncRNA TUG1/miR-29a/PTEN axis.

Long Noncoding RNAs and Their Therapeutic Promise in Diabetic Nephropathy

Recent advances in large-scale RNA sequencing and genome-wide profiling projects have unraveled a heterogeneous group of RNAs, collectively known as long noncoding RNAs (lncRNAs), which play central roles in many diverse biological processes. Importantly, an association between aberrant expression of lncRNAs and diverse human pathologies has been reported, including in a variety of kidney diseases. These observations have raised the possibility that lncRNAs may represent unexploited potential therapeutic targets for kidney diseases. Several important questions regarding the functionality of lncRNAs and their impact in kidney diseases, however, remain to be carefully addressed. Here, we provide an overview of the main functions and mechanisms of actions of lncRNAs, and their promise as therapeutic targets in kidney diseases, emphasizing on the role of some of the best-characterized lncRNAs implicated in the pathogenesis and progression of diabetic nephropathy.

New insight into the role of isorhamnetin as a regulator of insulin signaling pathway in type 2 diabetes mellitus rat model: Molecular and computational approach

We intended to examine the molecular mechanism of action of isorhamnetin (IHN) to regulate the pathway of insulin signaling. Molecular analysis, immunofluorescence, and histopathological examination were used to assess the anti-hyperglycemic and insulin resistance lowering effects of IHN in streptozotocin /high fat diet-induced type 2 diabetes using Wistar rats. At the microscopic level, treatment with IHN resulted in the restoration of myofibrils uniform arrangement and adipose tissue normal architecture. At the molecular level, treatment with IHN at three different doses showed a significant decrease in m-TOR, IGF1-R & LncRNA-RP11-773H22.4. expression and it up-regulated the expression of AKT2 mRNA, miR-1, and miR-3163 in both skeletal muscle and adipose tissue. At the protein level, IHN treated group showed a discrete spread with a moderate faint expression of m-TOR in skeletal muscles as well as adipose tissues. We concluded that IHN could be used in the in ameliorating insulin resistance associated with type 2 diabetes mellitus.

Non-Coding RNAs as Biomarkers and Therapeutic Targets for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the most common diabetic complication and is a leading cause of end-stage kidney disease. Increasing evidence shows that DKD is regulated not only by many classical signaling pathways but also by epigenetic mechanisms involving chromatin histone modifications, DNA methylation, and non-coding RNA (ncRNAs). In this review, we focus on our current understanding of the role and mechanisms of ncRNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) in the pathogenesis of DKD. Of them, the regulatory role of TGF-β/Smad3-dependent miRNAs and lncRNAs in DKD is highlighted. Importantly, miRNAs and lncRNAs as biomarkers and therapeutic targets for DKD are also described, and the perspective of ncRNAs as a novel therapeutic approach for combating diabetic nephropathy is also discussed.

LncRNA XIST protects podocyte from high glucose-induced cell injury in diabetic nephropathy by sponging miR-30 and regulating AVEN expression

Diabetic nephropathy (DN) is one of the most important complications of diabetes mellitus. Thus, it is urgent to develop a novel diagnosis or therapeutic strategy that could suspend DN progression. Moreover, there is increasing evidence demonstrating that long non-coding RNA (lncRNA) acts as critical players in regulating autophagy and are involved in DN. We demonstrated that lncRNA X-inactive specific transcript (XIST) was downregulated in high glucose (HG) treated podocytes, accompanied by increased apoptosis of podocytes. Overexpression of XIST significantly reduced the apoptosis and promoted the number of viable cells of podocyte under HG treatment. Prediction by Targets can and dual-luciferase reporter assay revealed the interaction between miR-30 and XIST and AVEN. Further WB (Western Blot), MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), and flow cytometry confirmed that XIST could reverse the expression of AVEN and ameliorate HG-induced apoptosis. In conclusion, our research revealed that XIST plays a protective effect on podocyte injury induced by HG through miR-30/AVEN axis.

The complicated role of mitochondria in the podocyte

Mitochondria play a complex role in maintaining cellular function including ATP generation, generation of biosynthetic precursors for macromolecules, maintenance of redox homeostasis, and metabolic waste management. Although the contribution of mitochondrial function in various kidney diseases has been studied, there are still avenues that need to be explored under healthy and diseased conditions. Mitochondrial damage and dysfunction have been implicated in experimental models of podocytopathy as well as in humans with glomerular diseases resulting from podocyte dysfunction. Specifically, in the podocyte, metabolism is largely driven by oxidative phosphorylation or glycolysis depending on the metabolic needs. These metabolic needs may change drastically in the presence of podocyte injury in glomerular diseases such as diabetic kidney disease or focal segmental glomerulosclerosis. Here, we review the role of mitochondria in the podocyte and the factors regulating its function at baseline and in a variety of podocytopathies to identify potential targets for therapy.

Urinary expression of long non-coding RNA TUG1 in non-diabetic patients with glomerulonephritides

Metabolic alterations serve a significant role in the pathogenesis of kidney disease. Long non-coding RNA (lncRNA) taurine upregulated gene 1 (TUG1) is a known regulator of podocyte health and mitochondrial biogenesis. Although TUG1 protects against podocyte loss in models of diabetic nephropathy, it is unknown if urinary TUG1 expression is associated with clinical and histopathological findings in non-diabetic patients diagnosed with glomerulonephritides. In the present study, the expression of TUG1, podocyte-specific markers (nephrin and podocin) and mitochondrial biogenesis-associated mRNAs (transcription factor A mitochondrial, cytochrome C oxidase subunit 5A and peroxisome proliferator-activated receptor γ coactivator 1α) were examined in urinary sediment of non-diabetic patients with biopsy-confirmed glomerulonephritides and healthy controls. Urinary expression of TUG1 was significantly lower in patients with glomerulonephritides, particularly those diagnosed with Focal Segmental Glomerulosclerosis (FSGS). Furthermore, TUG1 levels were associated with urinary expression of podocyte-specific markers and mRNAs associated with mitochondrial biogenesis. Loss of TUG1 expression in urinary sediment was strongly associated with FSGS, highlighting the potential of this lncRNA and its mitochondrial biogenesis-associated targets as non-invasive biomarkers of assessing podocytopathy.

Role of taurine, its haloamines and its lncRNA TUG1 in both inflammation and cancer progression. On the road to therapeutics? (Review)

For one century, taurine is considered as an end product of sulfur metabolism. In this review, we discuss the beneficial effect of taurine, its haloamines and taurine upregulated gene 1 (TUG1) long non‑coding RNA (lncRNA) in both cancer and inflammation. We outline how taurine or its haloamines (N‑Bromotaurine or N‑Chlorotaurine) can induce robust and efficient responses against inflammatory diseases, providing insight into their molecular mechanisms. We also provide information about the use of taurine as a therapeutic approach to cancer. Taurine can be combined with other chemotherapeutic drugs, not only mediating durable responses in various malignancies, but also circumventing the limitations met from chemotherapeutic drugs, thus improving the therapeutic outcome. Interestingly, the lncRNA TUG1 is regarded as a promising therapeutic approach, which can overcome acquired resistance of cancer cells to selected strategies. In this regard, we can translate basic knowledge about taurine and its TUG1 lncRNA into potential therapeutic options directed against specific oncogenic signaling targets, thereby bridging the gap between bench and bedside.

Emerging role of lncRNAs in renal fibrosis

Fibrosis is the final common pathological feature of a wide variety of chronic kidney disease (CKD). However, an understanding of the mechanisms underlying the development of renal fibrosis remains challenging and controversial. As the current focus of molecular research, noncoding RNAs (ncRNAs), mainly microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular noncoding RNAs (circRNAs), have powerful and abundant biological functions, which essentially makes them mediators of the physiological and pathological processes of various system diseases. The role of ncRNAs in renal fibrosis has also received great attention in recent years, but most research has mainly focused on miRNAs. In fact, although a large number of studies of lncRNAs have emerged recently, the role these molecules play in renal fibrosis haven't been fully understood till now. Thus, this review discusses the discovery of lncRNAs and their biological functions in different types of renal fibrosis, as well as the imminent applications of these findings in clinical use. Undoubtedly, in the future, further understanding of the function of all types of lncRNAs will reveal large breakthroughs in the treatment of renal fibrosis.

Renal tubular Bim mediates the tubule-podocyte crosstalk via NFAT2 to induce podocyte cytoskeletal dysfunction

Diabetic nephropathy (DN) is mainly regarded as diabetic glomerulopathy, and its progression is tightly correlated with tubular epithelial lesions. However, the underlying molecular mechanisms linking tubular damage and glomerulopathy are poorly understood.

Methods: We previously reported that the upregulation of Bim mediated proximal tubular epithelial cell (PTEC) apoptosis and was crucial in the early stages of DN. Herein we modulated Bim expression in PTECs and subsequently determined podocyte (PC) cytoskeletal arrangement by building a Transwell co-culture system in high glucose (HG).

Results: Compared to normal glucose, exposure to 40 mM of HG for 48 h induced significant expression of Bim in PTECs and disorganization in the PC cytoskeleton. When cocultured with PTECs in HG, exacerbated filamentous actin (F-actin) rearrangement and reduced synaptopodin levels were detected in PCs. In contrast, gene knockdown of Bim in PTECs was correlated with the absence of PC cytoskeletal disorganization. NFAT2 level and its nuclear translocation in PTECs were decreased by suppressing Bim expression. Upregulating NFAT2 disrupted the beneficial effects on F-actin organization in PCs obtained by inhibiting Bim. LncRNA microarray analysis identified NONHSAT179542.1, which was implicated in Bim-mediated PC cytoskeletal disorder.

Conclusion: Our study clarified the functional role of Bim, a pro-apoptotic factor, which is involved in the crosstalk between PTECs and PCs. Bim promotes NFAT2 activation in PTECs, inducing the downregulation of lncRNA NONHSAT179542.1 in PCs, contributing to the cytoskeletal damage. Identification of the role of the Bim/NFAT2 pathway may represent a promising research direction for a better understanding of DN development.

Potential Roles of Long Noncoding RNAs as Therapeutic Targets in Renal Fibrosis

Many studies have made clear that most of the genome is transcribed into noncoding RNAs, including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), both of which can affect different cell features. LncRNAs are long heterogeneous RNAs that regulate gene expression and a variety of signaling pathways involved in cellular homeostasis and development. Several studies have demonstrated that lncRNA is an important class of regulatory molecule that can be targeted to change cellular physiology and function. The expression or dysfunction of lncRNAs is closely related to various hereditary, autoimmune, and metabolic diseases, and tumors. Specifically, recent work has shown that lncRNAs have an important role in kidney pathogenesis. The effective roles of lncRNAs have been recognized in renal ischemia, injury, inflammation, fibrosis, glomerular diseases, renal transplantation, and renal-cell carcinoma. The present review focuses on the emerging role and function of lncRNAs in the pathogenesis of kidney inflammation and fibrosis as novel essential regulators. Although lncRNAs are important players in the initiation and progression of many pathological processes, their role in renal fibrosis remains unclear. This review summarizes the current understanding of lncRNAs in the pathogenesis of kidney fibrosis and elucidates the potential role of these novel regulatory molecules as therapeutic targets for the clinical treatment of kidney inflammation and fibrosis.

m6A-induced lncRNA MALAT1 aggravates renal fibrogenesis in obstructive nephropathy through the miR-145/FAK pathway

Renal fibrosis is a key factor in chronic kidney disease (CKD). Long non-coding RNAs (lncRNAs) play important roles in the physiological and pathological progression of human diseases. However, the roles and underlying mechanisms of lncRNAs in renal fibrosis still need to be discovered. In this study, we first displayed the increased lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) expression in renal fibrosis in patients with obstructive nephropathy (ON). Then we found that transforming growth factor beta 1 (TGF-β1) induced epithelial-mesenchymal transition (EMT) and extracellular matrix (ECM) protein deposition, which promoted the viability, proliferation and migration of human renal proximal tubular epithelial (HK2) cells. Next, MALAT1/miR-145/focal adhesion kinase (FAK) pathway was confirmed to play an importment role in TGF-β1-induced renal fibrosis. In addition, the MALAT1/miR-145/FAK pathway was involved in the effect of dihydroartemisinin (DHA) on TGF-β1-induced renal fibrosis in vitro and in vivo. Furthermore, m⁶A methyltransferase methyltransferase-like 3 (METTL3) was shown to be the main methyltransferase of m⁶A modification on MALAT1.

Adipose tissue gene expression of long non-coding RNAs; MALAT1, TUG1 in obesity: is it associated with metabolic profile and lipid homeostasis-related genes expression?

BACKGROUND

Recent studies point toward the possible regulatory roles of two lncRNAs; metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and taurine upregulated gene 1 (TUG1) in the pathogenesis of obesity-related disorders and regulation of lipogenesis and adipogenesis. In an attempt to understand the molecules involved in human obesity pathogenesis, we aimed to evaluate the expression of MALAT1 and TUG1 in visceral adipose tissues (VAT) and subcutaneous adipose tissues (SAT) of obese women, as compared to normal-weight women. The mRNA expression of possible target genes including peroxisome proliferator-activated receptor gamma (PPARγ), PPARγ coactivator-1 alpha (PGC1α), sterol regulatory element-binding protein-1c (SREBP-1c), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) which are involved in adipogenesis and lipogenesis were also examined.

METHODS

This study was conducted on 20 obese [body mass index (BMI) ≥ 30 kg/m 2] female participants and 19 normal-weight (BMI < 25 kg/m 2) female participants. Real-time PCR was performed to investigate the mRNA expression of the above-mentioned genes in VAT and SAT from all participants.

RESULTS

The results showed lower mRNA levels of TUG1 in both the VAT and SAT of obese women, compared to normal-weight women. Furthermore, TUG1 expression in SAT positively correlated with BMI, waist circumference (WC), hip circumference, HOMA-IR, and insulin levels, eGFR value, creatinine levels, and hs-CRP in all participants independent of age and HOMA-IR. However, VAT mRNA expression of TUG1 had a positive correlation with obesity indices and HOMA-IR and insulin levels in the whole population. Moreover, SAT mRNA level of TUG1 was positively correlated with SAT gene expression of PGC1α, SREBP-1c, FAS, and ACC independent of age and HOMA-IR. Although mRNA expression of MALAT1 did not differ between two groups for any tissue, it was positively correlated with SAT mRNA levels of SREBP-1c, PPARγ, and their targets; FAS and ACC, as well as with VAT mRNA levels of PGC1α.

CONCLUSIONS

It seems likely that TUG1 with distinct expression pattern in VAT and SAT are involved in the regulation of lipogenic and adipogenic genes and obesity-related parameters. However, more studies are necessary to establish this concept.

Long noncoding RNA FAM3D-AS1 inhibits development of colorectal cancer through NF-κB signaling pathway

Although numerous differential long noncoding RNAs (IncRNAs) have been identified, the relationship between lncRNA and colorectal cancer (CRC) still remains largely unclear. In the present study, we investigated the function and provided a possible mechanism of lncRNA FAM3D-AS1 in CRC. CCK8, transwell, and trypan blue staining were used to evaluate the proliferation, invasion, and cell death rates. Real-time PCR was used to elucidate the expression level of FAM3D-AS1. We found that lncRNA FAM3D-AS1 located in cytoplasm. Overexpression of FAM3D-AS1 significantly inhibited the cell proliferation, cell survival rates, and invaded cells. We also provided evidence that FAM3D-AS1 reversed the EMT process. Moreover, we proved that FAM3D-AS1 inhibits CRC development through NF-κB signaling pathway. Taken together, we performed functional analysis of FAM3D-AS1 and provided a possible mechanism in the development of CRC. Our study provided new targets for clinical treatment.

Long noncoding RNA: an emerging player in diabetes and diabetic kidney disease

Diabetic kidney disease (DKD) is among the most common complications of diabetes mellitus (DM), and remains the leading cause of end-stage renal diseases (ESRDs) in developed countries, with no definitive therapy yet available. It is imperative to decipher the exact mechanisms underlying DKD and identify novel therapeutic targets. Burgeoning evidence indicates that long non-coding RNAs (lncRNAs) are essential for diverse biological processes. However, their roles and the mechanisms of action remain to be defined in disease conditions like diabetes and DKD. The pathogenesis of DKD is twofold, so is the principle of treatments. As the underlying disease, diabetes per se is the root cause of DKD and thus a primary focus of therapy. Meanwhile, aberrant molecular signaling in kidney parenchymal cells and inflammatory cells may directly contribute to DKD. Evidence suggests that a number of lncRNAs are centrally involved in development and progression of DKD either via direct pathogenic roles or as indirect mediators of some nephropathic pathways, like TGF-β1, NF-κB, STAT3 and GSK-3β signaling. Some lncRNAs are thus likely to serve as biomarkers for early diagnosis or prognosis of DKD or as therapeutic targets for slowing progression or even inducing regression of established DKD. Here, we elaborated the latest evidence in support of lncRNAs as a key player in DKD. In an attempt to strengthen our understanding of the pathogenesis of DKD, and to envisage novel therapeutic strategies based on targeting lncRNAs, we also delineated the potential mechanisms of action as well as the efficacy of targeting lncRNA in preclinical models of DKD.

Long Noncoding RNA: Genomics and Relevance to Physiology

The mammalian cell expresses thousands of long noncoding RNAs (lncRNAs) that are longer than 200 nucleotides but do not encode any protein. lncRNAs can change the expression of protein-coding genes through both cis and trans mechanisms, including imprinting and other types of transcriptional regulation, and posttranscriptional regulation including serving as molecular sponges. Deep sequencing, coupled with analysis of sequence characteristics, is the primary method used to identify lncRNAs. Physiological roles of specific lncRNAs can be examined using genetic targeting or knockdown with modified oligonucleotides. Identification of nucleic acids or proteins with which an lncRNA interacts is essential for understanding the molecular mechanism underlying its physiological role. lncRNAs have been reported to contribute to the regulation of physiological functions and disease development in several organ systems, including the cardiovascular, renal, muscular, endocrine, digestive, nervous, respiratory, and reproductive systems. The physiological role of the majority of lncRNAs, many of which are species and tissue specific, remains to be determined. © 2019 American Physiological Society. Compr Physiol 9:933-946, 2019.

The protective effect of the TUG1/miR‑197/MAPK1 axis on lipopolysaccharide‑induced podocyte injury

The podocyte, a type of glomerular epithelial cell, is the key constituent of the filtration barrier layer in the kidney. Previous studies have shown that long non‑coding RNA (lncRNA)‑taurine‑upregulated gene 1 (TUG1) served a protective role in diabetes‑induced podocyte damage. The aim of the present study was to investigate the potential role of TUG1 in the progress of podocyte injury induced by lipopolysaccharide (LPS), and explore the underlying mechanisms. The results showed that TUG1 expression was suppressed in LPS‑induced podocytes. Enhanced TUG1 expression by exogenous recombinant vector regulated the expression of podocyte associated proteins [Nephrin, Podocin and CCAAT/enhancer‑binding protein (CHOP)]. A marked decrease was observed in the level the albumin influx in cells transfected with TUG1. Further study indicated that microRNA (miR)‑197 is a potential target of TUG1. The enhanced level of miR‑197 induced by LPS was inhibited in cells transfected with TUG1. The decreased Nephrin and Podocin expression, upregulated CHOP expression and the increased albumin influx were slightly enhanced by miR‑197 mimic transfection, while markedly suppressed by miR‑197 inhibitor transfection in LPS‑induced podocytes. Mitogen‑activated protein kinase (MAPK) protein was predicted as a potential target of miR‑197. The downregulated expression of phosphorylated‑MAPK/MAPK induced by LPS was significantly suppressed by TUG1 transfection in podocytes. In addition to this, autophagy was promoted by TUG1 transfection via the elevation of the Beclin1 and light chain (LC)3 II/LC3 I levels, and suppressing p62 expression. However, the p38 MAPK inhibitor SB203580 reversed the changes that TUG1 induced in the levels of Beclin1, LC3 II/LC3 I and p62. Taken together, these results demonstrated that LPS‑induced podocyte injury could be alleviated by the TUG1/miR‑197/MAPK1 axis.

Expression analysis of long non-coding RNAs in a renal ischemia-reperfusion injury model

PURPOSE

To investigate the long non-coding RNAs (lncRNAs) profile on renal ischemia reperfusion in a mouse model.

METHODS

Microarray analysis was used to study the expression of misregulated lncRNA in a mouse model of renal ischemia reperfusion(I/R) with long ischemia time. Quantitative real-time PCR (qPCR) was used to verify the expression of selected lncRNAs and mRNAs.The potential functions of the lncRNA was analyzed by bioinformatics tools and databases.

RESULTS

Kidney function was impaired in I/R group compared to the normal group. Analysis showed that a total of 2267 lncRNAs and 2341 messenger RNAs (mRNAs) were significantly expressed in I/R group (≥2.0-fold, p < 0.05).The qPCR result showed that lncRNAs and mRNAs expression were consistent with the microarray analysis. The co-expression network profile analysis based on five validated lncRNAs and 203 interacted mRNAs showed it existed a total of 208 nodes and 333 connections. The GO and KEEG pathway analysis results showed that multiple lncRNAs are involved the mechanism of I/R.

CONCLUSION

Multiple lncRNAs are involved in the mechanism of I/R.These analysis results will help us to further understand the mechanism of I/R and promote the new methods targeted at lncRNA to improve I/R injury.

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.

The Role of Peroxisome Proliferator-Activated Receptor γ Coactivator 1α (PGC-1α) in Kidney Disease

Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is a key transcriptional regulator of mitochondrial biogenesis and function. Several recent studies have evaluated the role of PGC-1α in various renal cell types in healthy and disease conditions. Renal tubule cells mostly depend on mitochondrial fatty acid oxidation for energy generation. A decrease in PGC-1α expression and fatty acid oxidation is commonly observed in patient samples and mouse models with acute and chronic kidney disease. Conversely, increasing PGC-1α expression in renal tubule cells restores energy deficit and has been shown to protect from acute and chronic kidney disease. Other kidney cells, such as podocytes and endothelial cells, are less metabolically active and have a narrow PGC-1α tolerance. Increasing PGC-1α levels in podocytes induces podocyte proliferation and collapsing glomerulopathy development, while increasing PGC1-α in endothelial cells alters endothelial function and causes microangiopathy, thus highlighting the cell-type-specific role of PGC-1α in different kidney cells.

Roles of Identified Long Noncoding RNA in Diabetic Nephropathy

Diabetes mellitus is the leading chronic disease in the world, and diabetic nephropathy (DN) as one of its complications could increase the mortality. The development of DN is associated to abnormal hemodynamic factors like cytokine networks and the intervention of metabolic risk factors like blood pressure, blood glucose, and blood lipid. However, the pathogenesis of DN is still poorly understood. Although glucose-lowering drugs and insulins have significant effects on blood glucose, the fluctuation of blood glucose or other risk factors could continuously damage the kidney. Recent studies reported that the progression of DN is closely related to the expression of long noncoding RNA (lncRNA), which is important for the early diagnosis and targeted intervention of DN. In this review, we briefly summarize the published studies on the functions and potential mechanism of reported lncRNA in the regulation of DN.

Differential expression of long non-coding RNA and mRNA in children with Henoch-Schönlein purpura nephritis

Long non-coding RNAs (lncRNAs) serve an essential role in regulating immunological functions. However, their impact on Henoch-Schönlein purpura nephritis (HSPN), has remained elusive. The present study determined the expression of lncRNAs and mRNAs in the peripheral blood of 6 children with HSPN and recruited 4 healthy children for comparative study. High-throughput sequencing revealed outstanding differences in lncRNA and mRNA expression, which were verified through reverse transcription-quantitative polymerase chain reaction. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were used to investigate the associated biological functions and possible mechanisms of lncRNAs and mRNAs in HSPN. A total of 820 differentially expressed lncRNAs between the two groups were identified, of which 34 were upregulated and 786 were downregulated. Simultaneously, a total of 3,557 mRNAs were also identified to be differentially expressed, of which 1,232 were upregulated and 2,325 were downregulated. The results revealed that the expression of lncRNAs including ENST00000378432, ENST00000571370, uc001kfc.1 and uc010qna.2 was decreased in HSPN patients compared with that in healthy controls. These lncRNAs were associated with the p53 signaling pathway and apoptosis-associated genes (AKT2, tumor protein 53, phosphatase and tensin homolog and FAS). Further studies of those lncRNAs will be performed to elucidate their functions in apoptosis. Complete raw data files were deposited in the Gene Expression Omnibus (GEO) at National Center for Biotechnology information under the GEO accession no. GSE102114 (www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE102114).