Linagliptin-mediated DPP-4 inhibition ameliorates kidney fibrosis in streptozotocin-induced diabetic mice by inhibiting endothelial-to-mesenchymal transition in a therapeutic regimen

miR-29 inhibits endothelial-to-mesenchymal transition in pulmonary hypertension of the newborn by regulating LRP6

Pulmonary hypertension of the newborn (PHN) is a common pulmonary vascular disease in newborns, affecting the prognosis of affected infants and even leading to death. Currently, there is still no specific targeted prevention and treatment program available. In recent years, research on the regulatory mechanism of endothelial-to-mesenchymal transition (EndMT) has become a hot topic, with the interplay between miRNAs and the Wnt signaling pathway playing an important role. MiR-29 is highly expressed in distal pulmonary arteriolar smooth muscle cells and endothelial cells. In miR-29 gene knockout mice, pathological changes in lung tissue can be observed, indicating an obstruction in the maturation of smooth muscle cells in the distal pulmonary arterioles. LRP6 is an important Wnt co-receptor in the Wnt signaling pathway, and the Targetscan website predicts a binding site between miR-29 and LRP6. Therefore, our studies establish a role for decreased miR29a in the endothelial mesenchymal transition through activation of the LRP6-Wnt signaling pathway in neonatal hypoxia-mediated PAH. By generating hypoxic newborn rat models of pulmonary artery hypertension and hypoxic injury models of pulmonary vascular endothelial cells, we observed the presence of EndMT in the model group, as well as the activation of the LRP6 and Wnt/β-catenin signaling pathways and the differential expression of the miR-29 family, particularly miR-29a. Subsequently, We used cell transfection technology to overexpress/knock down miR-29a and LRP6, respectively, to observe changes in EndMT-related indicators and successfully found that miR-29a and LRP6 can negatively and positively regulate the occurrence of EndMT, respectively. Finally, the dual-luciferase reporter gene assay confirmed that LRP6 can directly bind to miR-29a-3p. These findings provide experimental evidence of the potential of miR-29 as a novel target for the prevention and treatment of PHN.

AMPK is dispensable for physiological podocyte and glomerular functions but prevents glomerular fibrosis in experimental diabetes

AMP-activated protein kinase (AMPK) has been postulated to be crucial in regulating various renal physiology and pathophysiology processes, including energy metabolism, ion and water transport, inflammation, and hypertrophy. However, the specific roles of AMPK in the podocyte, a cell critical for maintaining glomerular filtration, have not been fully explored using genetic model animals. In this study, we generated mice lacking both AMPK α1 and α2 catalytic subunits in glomerular podocytes (pmut). Our findings revealed that, surprisingly, AMPK is dispensable for normal podocyte function. These knockout mice could live as long as their wild-type littermates without showing any pathological alterations in their glomeruli or glomerular function at two years of age. However, under type 1 diabetic conditions, the diabetic pmut mice exhibited increased lipid and collagen accumulation and an elevated expression of mesenchymal proteins in their glomeruli. They also showed more significant albuminuria compared to control diabetic mice. Under high glucose culture conditions, glomeruli isolated from pmut mice demonstrated a reduced expression of mitochondrial genes (e.g., Ndufv2) and increased leakage of mitochondrial components. Additionally, there was heightened expression of genes associated with nucleotide sensing and pro-inflammatory pathways (including mb21d2, IL-1 beta, and NF-kB). These observations suggest that while AMPK is not necessary for podocyte function in healthy kidneys, it is crucial for preventing glomerular fibrosis resulting from lipotoxicity and inflammation under diabetic conditions.

The molecular determinants regulating redox signaling in diabetic endothelial cells

Oxidation and reduction are vital for keeping life through several prime mechanisms, including respiration, metabolism, and other energy supplies. Mitochondria are considered the cell's powerhouse and use nutrients to produce redox potential and generate ATP and H2O through the process of oxidative phosphorylation by operating electron transfer and proton pumping. Simultaneously, mitochondria also produce oxygen free radicals, called superoxide (O2 -), non-enzymatically, which interacts with other moieties and generate reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), peroxynitrite (ONOO-), and hydroxyl radical (OH-). These reactive oxygen species modify nucleic acids, proteins, and carbohydrates and ultimately cause damage to organs. The nutrient-sensing kinases, such as AMPK and mTOR, function as a key regulator of cellular ROS levels, as loss of AMPK or aberrant activation of mTOR signaling causes ROS production and compromises the cell's oxidant status, resulting in various cellular injuries. The increased ROS not only directly damages DNA, proteins, and lipids but also alters cellular signaling pathways, such as the activation of MAPK or PI3K, the accumulation of HIF-1α in the nucleus, and NFkB-mediated transcription of pro-inflammatory cytokines. These factors cause mesenchymal activation in renal endothelial cells. Here, we discuss the biology of redox signaling that underlies the pathophysiology of diabetic renal endothelial cells.

MiR-203 improved renal cell injury in diabetic nephropathy by targeting SOCS6/SOCS7 and inhibiting JAK/STAT pathway activation

This study investigates the role of miR-203 in regulating renal cell injury in diabetic nephropathy by targeting the suppressor of cytokine signaling (SOCS) proteins SOCS6 and SOCS7. Using NRK cells, we assessed apoptosis through flow cytometry and TUNEL assays, while real-time quantitative PCR (RT-PCR) quantified miRNA and mRNA expressions. Cell viability was measured using the CCK-8 assay, and cytokine levels were determined through ELISA. We also evaluated reactive oxygen species (ROS) and malondialdehyde (MDA) levels with specific assay kits. The dual luciferase assay confirmed the interaction of miR-203 with SOCS6 and SOCS7. Western blotting analyzed the protein levels of key signaling molecules including JAK1, p-JAK1, JAK2, p-JAK2, STAT3, and p-STAT3.Our findings revealed that high glucose (HG) treatment reduced miR-203 levels, leading to decreased NRK cell proliferation, increased cytokine concentrations (TNF-α, IL-1β, IL-4, IL-6), heightened ROS and MDA levels, and increased cell apoptosis. Notably, miR-203 mimics counteracted HG's detrimental effects, while miR-203 inhibitors exacerbated them. Mechanistically, miR-203 directly decreased SOCS6 and SOCS7 expression, thereby inhibiting JAK/STAT3 signaling. Thus, miR-203 provides protective effects against renal cell injury by modulating SOCS and their associated pathways.

Epithelium-derived exosomal dipeptidyl peptidase-4 involved in arecoline-induced oral submucous fibrosis

INTRODUCTION

Dipeptidyl peptidase-4 is known to be involved in the progression of several fibrogenic diseases, but its association with oral submucous fibrosis remains unclear. This study aims to ascertain whether dipeptidyl peptidase-4 plays a role in the pathogenesis of arecoline-induced oral submucous fibrosis.

METHODS

We assessed the expression of dipeptidyl peptidase-4 in arecoline-treated epithelial cells and the exosomes derived from cells. We cocultured the fibroblast and exosomes derived from epithelium cells and assessed fibrogenic activity by measuring collagen secretion, α-SMA expression, and gel contraction capability. An animal study was conducted to confirm the fibrogenic activity of exosomes derived from arecoline-treated epithelial cells. Additionally, we employed a dipeptidyl peptidase-4 inhibitor to assess its efficacy in mitigating fibrogenesis.

RESULTS

Following arecoline treatment, an increase dipeptidyl peptidase-4 expression was observed in exosomes from the treated epithelium cells. When these exosomes cocultured with fibroblast, fibrogenic gene α-SMA was upregulated, increased collagen secretion, and enhanced gel contraction capability. In a mouse model, the administration of arecoline-treated epithelium-derived exosomes induced oral submucous fibrosis phenotype, characterized by a reduction in incisal distance and epithelial atrophy.

CONCLUSIONS

These findings offer valuable insights into clinical strategies for combating oral fibrotic disease and contribute to the foundation of future research in this field.

FGF21 ameliorates diabetic nephropathy through CDK1-dependently regulating the cell cycle

Background

Diabetic nephropathy (DN) is a prevalent global renal illness and one of the main causes of end-stage renal disease (ESRD). FGF21 has been shown to ameliorate diabetic nephropathy, and in addition FGF-21-treated mice impeded mitogenicity, whereas it is unclear whether FGF21 can influence DN progression by regulating the cell cycle in diabetic nephropathy.

Methods

In order to create a diabetic model, STZ injections were given to C57BL/6J mice for this investigation. Then, FGF21 was administered, and renal tissue examination and pathological observation were combined with an assessment of glomerular injury, inflammation, oxidative stress, and the fibrinogen system in mice following the administration of the intervention. Furthermore, we used db/db mice and FGF21 direct therapy for 8 weeks to investigate changes in fasting glucose and creatinine expression as well as pathological changes in glomeruli glycogen deposition, fibrosis, and nephrin expression. To investigate the mechanism of action of FGF21 in the treatment of glycolytic kidney, transcriptome sequencing of renal tissues and KEGG pathway enrichment analysis of differential genes were performed.

Results

The study's findings demonstrated that FGF21 intervention increased clotting time, decreased oxidative stress and inflammation, and avoided thrombosis in addition to considerably improving glomerular filtration damage. After 8 weeks of FGF21 treatment, glomerular glycogen deposition, fibrosis, and renin expression decreased in db/db mice. Moreover, there was a notable reduction of creatinine and fasting blood glucose levels. Additionally, the CDK1 gene, a key player in controlling the cell cycle, was discovered through examination of the transcriptome sequencing data. It was also shown that FGF21 dramatically reduces the expression of CDK1, which may help diabetic nephropathy by averting mitotic catastrophe and changing the renal cell cycle.

Conclusion

In short, FGF21 improved the development of diabetic nephropathy in diabetic nephropathy-affected animals by reducing glomerular filtration damage, inflammation, and oxidative stress, inhibiting the formation of thrombus, and controlling the cell cycle through CDK1.

Renal Angptl4 is a key fibrogenic molecule in progressive diabetic kidney disease

Angiopoietin-like 4 (ANGPTL4), a key protein involved in lipoprotein metabolism, has diverse effects. There is an association between Angptl4 and diabetic kidney disease; however, this association has not been well investigated. We show that both podocyte- and tubule-specific ANGPTL4 are crucial fibrogenic molecules in diabetes. Diabetes accelerates the fibrogenic phenotype in control mice but not in ANGPTL4 mutant mice. The protective effect observed in ANGPTL4 mutant mice is correlated with a reduction in stimulator of interferon genes pathway activation, expression of pro-inflammatory cytokines, reduced epithelial-to-mesenchymal transition and endothelial-to-mesenchymal transition, lessened mitochondrial damage, and increased fatty acid oxidation. Mechanistically, we demonstrate that podocyte- or tubule-secreted Angptl4 interacts with Integrin β1 and influences the association between dipeptidyl-4 with Integrin β1. We demonstrate the utility of a targeted pharmacologic therapy that specifically inhibits Angptl4 gene expression in the kidneys and protects diabetic kidneys from proteinuria and fibrosis. Together, these data demonstrate that podocyte- and tubule-derived Angptl4 is fibrogenic in diabetic kidneys.

Comparison of sGC activator and sGC stimulator in 5/6 nephrectomized rats on high-salt-diet

Introduction

Soluble guanylate cyclase (sGC) stimulators and activators are known to enhance kidney function in various models of chronic kidney disease (CKD) by increasing cyclic guanosine monophosphate (cGMP). Their differential effects on CKD progression, particularly under conditions of oxidative stress, remain unexplored by direct comparative studies.

Methods

We conducted a side-by-side comparison using 5/6 nephrectomized rats on a high salt diet (5/6Nx+HSD) to evaluate the efficacy of the sGC stimulator BAY 41-8543 and the sGC activator BAY 60-2770 in CKD progression. BAY 41-8543 (1 mg/kg; twice daily) and BAY 60-2770 (1 mg/kg; once daily) were administered by gavage for 11 weeks.

Results

The 5/6Nx+HSD model led to increased plasma creatinine, proteinuria, and blood pressure. Both BAY 41-8543 and BAY 60-2770 significantly reduced systolic and diastolic blood pressure to a similar extent but did not improve renal function parameters. Notably, BAY 60-2770 reduced renal fibrosis, including interstitial fibrosis and glomerulosclerosis, whereas BAY 41-8543 did not. These antifibrotic effects of BAY 60-2770 were independent of blood pressure reduction. Proteomic analysis revealed that BAY 60-2770 corrected the upregulation of 9 proteins associated with apoptosis and fibrosis, including Caspase-3, MKK6 (Mitogen-Activated Protein Kinase Kinase 6), Prdx5 (Peroxiredoxin-5), in the 5/6Nx+HSD group.

Discussion

In contrast, BAY 41-8543 had no significant impact on these proteins. sGC activators were more effective than sGC stimulators in reducing renal fibrosis in 5/6 nephrectomized rats on a high salt diet, and this effect was due to modulation of apoptosis-associated proteins beyond the control of blood pressure.

New Insights into the Pleiotropic Actions of Dipeptidyl Peptidase-4 Inhibitors Beyond Glycaemic Control

Dipeptidyl peptidase-4 (DPP-4) is a multifunctional serine ectopeptidase that cleaves and modifies a plethora of substrates, including regulatory peptides, cytokines and chemokines. DPP-4 is implicated in the regulation of immune response, viral entry, cellular adhesion, metastasis and chemotaxis. Regarding its numerous substrates and extensive expression inside the body, multitasking DPP-4 has been assumed to participate in different pathophysiological mechanisms. DPP-4 inhibitors or gliptins are increasingly used for the treatment of type 2 diabetes mellitus. Several reports from experimental and clinical studies have clarified that DPP-4 inhibitors exert many beneficial pleiotropic effects beyond glycaemic control, which are mediated by anti-inflammatory, anti-oxidant, anti-fibrotic and anti-apoptotic actions. The present review will highlight the most recent findings in the literature about these pleiotropic effects and the potential mechanisms underlying these benefits, with a specific focus on the potential effectiveness of DPP-4 inhibitors in coronavirus disease-19 and diabetic kidney disease.

Molecular Therapeutics for Diabetic Kidney Disease: An Update

Diabetic kidney disease (DKD) is a common microvascular complication of diabetes mellitus (DM). With the increasing prevalence of DM worldwide, the incidence of DKD remains high. If DKD is not well controlled, it can develop into chronic kidney disease or end-stage renal disease (ESRD), which places considerable economic pressure on society. Traditional therapies, including glycemic control, blood pressure control, blood lipid control, the use of renin-angiotensin system blockers and novel drugs, such as sodium-glucose cotransporter 2 inhibitors, mineralocorticoid receptor inhibitors and glucagon-like peptide-1 receptor agonists, have been used in DKD patients. Although the above treatment strategies can delay the progression of DKD, most DKD patients still ultimately progress to ESRD. Therefore, new and multimodal treatment methods need to be explored. In recent years, researchers have continuously developed new treatment methods and targets to delay the progression of DKD, including miRNA therapy, stem cell therapy, gene therapy, gut microbiota-targeted therapy and lifestyle intervention. These new molecular therapy methods constitute opportunities to better understand and treat DKD. In this review, we summarize the progress of molecular therapeutics for DKD, leading to new treatment strategies.

Activation of AMPK/SIRT1/FOXO3a signaling by BMS-477118 (saxagliptin) mitigates chronic colitis in rats: uncovering new anti-inflammatory and antifibrotic roles

Ulcerative colitis (UC) is a debilitating chronic disease marked by persistent inflammation and intestinal fibrosis. Despite the availability of various treatments, many patients fail to achieve long-term remission, underscoring a significant unmet therapeutic need. BMS-477118, a reversible inhibitor of dipeptidyl peptidase 4 (DPP4), has demonstrated anti-inflammatory properties in preclinical and clinical studies with minimal adverse effects compared to other antidiabetic agents. However, the potential benefits of BMS-477118 in chronic UC have not yet been explored. In this study, we aimed to investigate the effects of BMS-477118 in rats subjected to chronic dextran sodium sulfate (DSS) administration. Our findings indicate that BMS-477118 activates the interconnected positive feedback loop involving AMPK, SIRT1, and FOXO3a, improving histological appearance in injured rat colons. BMS-477118 also reduced fibrotic changes associated with the chronic nature of the animal model, alleviated macroscopic damage and disease severity, and improved the colon weight-to-length ratio. Additionally, BMS-477118 prevented DSS-induced weight loss and enhanced tight junction proteins. These effects, in conjunction with reduced oxidative stress and its potential anti-inflammatory, antiapoptotic, and autophagy-inducing properties, fostered prolonged survival in rats with chronic UC. To conclude, BMS-477118 has the potential to activate the AMPK/SIRT1/FOXO3a signaling pathway in inflamed colons. These results suggest that the AMPK/SIRT1/FOXO3a pathway could be a new therapeutic target for UC. Further research is mandatory to explore the therapeutic possibilities of this pathway. Additionally, continued studies on the therapeutic potential of BMS-477118 and other DPP4 inhibitors are promising for creating new treatments for various conditions, including UC in diabetic patients.

Dipeptidyl Peptidase (DPP)-4 Inhibitors and Pituitary Adenylate Cyclase-Activating Polypeptide, a DPP-4 Substrate, Extend Neurite Outgrowth of Mouse Dorsal Root Ganglia Neurons: A Promising Approach in Diabetic Polyneuropathy Treatment

Individuals suffering from diabetic polyneuropathy (DPN) experience debilitating symptoms such as pain, paranesthesia, and sensory disturbances, prompting a quest for effective treatments. Dipeptidyl-peptidase (DPP)-4 inhibitors, recognized for their potential in ameliorating DPN, have sparked interest, yet the precise mechanism underlying their neurotrophic impact on the peripheral nerve system (PNS) remains elusive. Our study delves into the neurotrophic effects of DPP-4 inhibitors, including Diprotin A, linagliptin, and sitagliptin, alongside pituitary adenylate cyclase-activating polypeptide (PACAP), Neuropeptide Y (NPY), and Stromal cell-derived factor (SDF)-1a-known DPP-4 substrates with neurotrophic properties. Utilizing primary culture dorsal root ganglia (DRG) neurons, we meticulously evaluated neurite outgrowth in response to these agents. Remarkably, all DPP-4 inhibitors and PACAP demonstrated a significant elongation of neurite length in DRG neurons (PACAP 0.1 μM: 2221 ± 466 μm, control: 1379 ± 420, p < 0.0001), underscoring their potential in nerve regeneration. Conversely, NPY and SDF-1a failed to induce neurite elongation, accentuating the unique neurotrophic properties of DPP-4 inhibition and PACAP. Our findings suggest that the upregulation of PACAP, facilitated by DPP-4 inhibition, plays a pivotal role in promoting neurite elongation within the PNS, presenting a promising avenue for the development of novel DPN therapies with enhanced neurodegenerative capabilities.

Extracellular Vesicles Derived from Type 2 Diabetic Mesenchymal Stem Cells Induce Endothelial Mesenchymal Transition under High Glucose Conditions Through the TGFβ/Smad3 Signaling Pathway

Type 2 diabetes mellitus (T2DM) is associated with endothelial dysfunction, which results in delayed wound healing. Mesenchymal stem cells (MSCs) play a vital role in supporting endothelial cells (ECs) and promoting wound healing by paracrine effects through their secretome-containing extracellular vesicles. We previously reported the impaired wound healing ability of adipose tissue-derived MSC from T2DM donors; however, whether extracellular vesicles isolated from T2DM adipose tissue-derived MSCs (dEVs) exhibit altered functions in comparison to those derived from healthy donors (nEVs) is still unclear. In this study, we found that nEVs induced EC survival and angiogenesis, whereas dEVs lost these abilities. In addition, under high glucose conditions, nEV protected ECs from endothelial-mesenchymal transition (EndMT), whereas dEV significantly induced EndMT by activating the transforming growth factor-β/Smad3 signaling pathway, which impaired the tube formation and in vivo wound healing abilities of ECs. Interestingly, the treatment of dEV-internalized ECs with nEVs rescued the induced EndMT effects. Of note, the internalization of nEV into T2DM adipose tissue-derived MSC resulted in the production of an altered n-dEV, which inhibited EndMT and supported the survival of T2DM db/db mice from severe wounds. Taken together, our findings suggest the role of dEV in endothelial dysfunction and delayed wound healing in T2DM by the promotion of EndMT. Moreover, nEV treatment can be considered a promising candidate for cell-free therapy to protect ECs in T2DM.

A cross talk study on sitagliptin mediated reclamation on TGF β signalling, DPP 4, miR-29a and miR-24 expression in PCOS rats fed with high fat-high fructose diet

Polycystic Ovary Syndrome (PCOS) is a multifactorial reproductive, endocrine and metabolic disturbance which is very commonly observed in females of reproductive age group. The disease is still incurable however the use of synthetic drugs in combination with lifestyle is recommended. Accordingly, the present study was conducted to investigate the possible beneficial effects of sitagliptin on PCOS induced rats on control diet (CD)/high fat- high fructose diet (HFFD). PCOS was induced by giving testosterone propionate (TP) for 28 days to both the CD/HFFD rats and treated with STG i.p. for last 15 days. At the end of the experiment lipid profile, inflammatory markers, expression of NF-κB-p65, miR-24 and miR-29a, fibrotic and apoptotic proteins from ovary tissue were examined. Moreover, lipid accumulation and fibrosis of ovary tissue was further confirmed using Sudan III and Masson's trichrome stain. STG treated rats exerted a significant decrease in levels of cholesterol, TG, LDL-C, VLDL-C, IL-6 and TNF-α and increased HDL-C level, miR-24 and miR-29a expression. STG treated groups expressed significantly decreased expression of NF-κB-p65, TGF-β1, p-Smad 2 and p-Smad 3 followed by no significant changes in the expression of BAX, caspase-9, caspase-3 and Bcl-2 in all the PCOS induced groups. Among all the CD/ HFFD fed groups, rats on HFFD showed more devastating effect which suggests that diet plays a major role in genesis of PCOS. In conclusion, current results reflect the potential impact of STG against dyslipidaemia, inflammation and fibrosis in PCOS rats via regulating dyslipidaemia and fibrosis via DPP 4 mediated miR-29a expression.

Effect of DPP-4i inhibitors on renal function in patients with type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials

AIMS

About 20-40% patients with type 2 diabetes mellitus (T2DM) had an increased risk of developing diabetic nephropathy (DN). Dipeptidyl peptidase-4 inhibitors (DPP-4i) were recommended for treatment of T2DM, while the impact of DPP-4i on renal function remained unclear. This study aimed to explore the effect of DPP-4i on renal parameter of estimated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) in T2DM.

METHODS

A systematic search was performed across PubMed, Embase and Cochrane Library. A fixed or random-effects model was used for quantitative synthesis according to the heterogeneity, which was assessed with I2 index. Sensitivity analysis and publication bias were performed with standard methods, respectively.

RESULTS

A total of 17 randomized controlled trials were identified. Administration of DPP-4i produced no significant effect on eGFR (WMD, -0.92 mL/min/1.73m2, 95% CI, -2.04 to 0.19) in diabetic condition. DPP-4i produced a favorable effect on attenuating ACR (WMD, -2.76 mg/g, 95% CI, -5.23 to -0.29) in patients with T2DM. The pooled estimate was stable based on the sensitivity test. No publication bias was observed according to Begg's and Egger's tests.

CONCLUSIONS

Treatment with DPP-4i preserved the renal parameter of eGFR in diabetic condition. Available evidences suggested that administration of DPP-4i produced a favorable effect on attenuating ACR in patients with T2DM. INTERNATIONAL PROSPECTIVE REGISTER FOR SYSTEMATIC REVIEW (PROSPERO) NUMBER: CRD.42020144642.

Renal and cardiac effects of the PDE9 inhibitor BAY 73-6691 in 5/6 nephrectomized rats

It has been suggested that the novel selective phosphodiesterase 9 (PDE9) inhibitor may improve cardiac and renal function by blocking 3',5'-cyclic guanosine monophosphate (cGMP) degradation. 5/6 nephrectomized (5/6Nx) rats were used to investigate the effects of the PDE9 inhibitor (BAY 73-6691) on the heart and kidney. Two doses of BAY 73-6691 (1 mg/kg/day and 5 mg/kg/day) were given for 95 days. The 5/6Nx rats developed albuminuria, a decrease in serum creatinine clearance (Ccr), and elevated serum troponin T levels. Echocardiographic data showed that 5/6 nephrectomy resulted in increased fractional shortening (FS), stroke volume (SV), and left ventricular ejection fraction (EF). However, 95 days of PDE9 inhibitor treatment did not improve any cardiac and renal functional parameter. Histopathologically, 5/6 nephrectomy resulted in severe kidney and heart damage, such as renal interstitial fibrosis, glomerulosclerosis, and enlarged cardiomyocytes. Telmisartan attenuated renal interstitial fibrosis and glomerulosclerosis as well as improved cardiomyocyte size. However, except for cardiomyocyte size and renal perivascular fibrosis, BAY 73-6691 had no effect on other cardiac and renal histologic parameters. Pathway enrichment analysis using RNA sequencing data of kidney and heart tissue identified chronic kidney disease pathways, such as phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt) signaling pathway, complement and coagulation cascades, and nuclear factor kappa B (NF-κB) signaling pathway. PDE9i did not affect any of these disease-related pathways. Two dosages of the PDE9 inhibitor BAY 73-6691 known to be effective in other rat models have only limited cardio-renal protective effects in 5/6 nephrectomized rats.

Sirt7/HIC1 complex participates in hyperglycaemia-mediated EndMT via modulation of SDC1 expression in diabetic kidney disease and metabolic memory

Diabetic kidney disease (DKD), a primary microvascular complication arising from diabetes, may result in end-stage renal disease. Epigenetic regulation of endothelial mesenchymal transition (EndMT) has been recently reported to exert function in metabolic memory and DKD. Here, we investigated the mechanism which Sirt7 modulated EndMT in human glomerular endothelial cells (HGECs) in the occurrence of metabolic memory in DKD. Lower levels of SDC1 and Sirt7 were noted in the glomeruli of both DKD patients and diabetes-induced renal injury rats, as well as in human glomerular endothelial cells (HGECs) with high blood sugar. Endothelial-to-mesenchymal transition (EndMT) was sustained despite the normalization of glycaemic control. We also found that Sirt7 overexpression associated with glucose normalization promoted the SDC1 expression and reversed EndMT in HGECs. Furthermore, the sh-Sirt7-mediated EndMT could be reversed by SDC1 overexpression. The ChIP assay revealed enrichment of Sirt7 and H3K18ac in the SDC1 promoter region. Furthermore, hypermethylated in cancer 1 (HIC1) was found to be associated with Sirt7. Overexpression of HIC1 with normoglycaemia reversed high glucose-mediated EndMT in HGECs. The knockdown of HIC1-mediated EndMT was reversed by SDC1 upregulation. In addition, the enrichment of HIC1 and Sirt7 was observed in the same promoter region of SDC1. The overexpressed Sirt7 reversed EndMT and improved renal function in insulin-treated diabetic models. This study demonstrated that the hyperglycaemia-mediated interaction between Sirt7 and HIC1 exerts a role in the metabolic memory in DKD by inactivating SDC1 transcription and mediating EndMT despite glucose normalization in HGECs.

SirT7-mediated transcription of fascin in hyperglycemic glomerular endothelial cells contributes to EndMT in diabetic nephropathy

Diabetic nephropathy (DN) is the main cause of end-stage renal disease worldwide. It is reported that the endothelial-to-mesenchymal transition (EndMT) in glomerular endothelial cells plays an important role in DN. As a specific form of epithelial-to-mesenchymal transition, EndMT may involve common regulators of epithelial-to-mesenchymal transition. Fascin has been shown to mediate epithelial-to-mesenchymal transition. In addition, SirT7 has been confir med to contribute to inflammation in hyperglycemic endothelial cells via the modulation of gene transcription. In this study, we speculate that SirT7 modulates fascin transcription and is thus involved in EndMT in hyperglycemic glomerular endothelial cells. Our data indicate that α-smooth muscle actin (α-SMA) and fascin levels are increased, while CD31 levels are decreased in the kidneys of DN rats. Consistently, our cellular experiments reveal that high glucose treatment elevates fascin levels and induces EndMT in human glomerular endothelial cells (HGECs). Moreover, silencing of fascin inhibits EndMT in hyperglycaemic HGECs. In addition, SirT7 is found to be decreased in hyperglycemic cells and in the kidneys of DN mice. Moreover, the inhibition of SirT7 increases fascin level and mediates EndMT. An increase in SirtT7 expression decreases fascin expression, inhibits EndMT, and improves renal function in hyperglycemic cells and DN mice. SirT7 is found to bind to the promoter region of fascin. In summary, the present study indicates that SirT7 transcribes fascin to contribute to hyperglycemia-induced EndMT in DN patients.

Endothelial dysfunction in vascular complications of diabetes: a comprehensive review of mechanisms and implications

Diabetic vascular complications are prevalent and severe among diabetic patients, profoundly affecting both their quality of life and long-term prospects. These complications can be classified into macrovascular and microvascular complications. Under the impact of risk factors such as elevated blood glucose, blood pressure, and cholesterol lipids, the vascular endothelium undergoes endothelial dysfunction, characterized by increased inflammation and oxidative stress, decreased NO biosynthesis, endothelial-mesenchymal transition, senescence, and even cell death. These processes will ultimately lead to macrovascular and microvascular diseases, with macrovascular diseases mainly characterized by atherosclerosis (AS) and microvascular diseases mainly characterized by thickening of the basement membrane. It further indicates a primary contributor to the elevated morbidity and mortality observed in individuals with diabetes. In this review, we will delve into the intricate mechanisms that drive endothelial dysfunction during diabetes progression and its associated vascular complications. Furthermore, we will outline various pharmacotherapies targeting diabetic endothelial dysfunction in the hope of accelerating effective therapeutic drug discovery for early control of diabetes and its vascular complications.

Bidirectional relation between dipeptidyl peptidase 4 and angiotensin II type I receptor signaling

Cardiometabolic diseases are often associated with heightened levels of angiotensin II (Ang II), which accounts for the observed oxidative stress, inflammation, and fibrosis. Accumulating evidence indicates a parallel upregulation of dipeptidyl dipeptidase 4 (DPP4) activity in cardiometabolic diseases, with its inhibition shown to mitigate oxidative stress, inflammation, and fibrosis. These findings highlight an overlap between the pathophysiological mechanisms used by Ang II and DPP4. Recent evidence demonstrates that targeted inhibition of DPP4 prevents the rise in Ang II and its associated molecules in experimental models of cardiometabolic diseases. Similarly, inhibitors of the angiotensin I-converting enzyme (ACE) or Ang II type 1 receptor (AT1R) blockers downregulate DPP4 activity, establishing a bidirectional relationship between DPP4 and Ang II. Here, we discuss the current evidence supporting the cross talk between Ang II and DPP4, along with the potential mechanisms promoting this cross regulation. A comprehensive analysis of this bidirectional relationship across tissues will advance our understanding of how DPP4 and Ang II collectively promote the development and progression of cardiometabolic diseases.

Modelling and targeting mechanical forces in organ fibrosis

Few efficacious therapies exist for the treatment of fibrotic diseases, such as skin scarring, liver cirrhosis and pulmonary fibrosis, which is related to our limited understanding of the fundamental causes and mechanisms of fibrosis. Mechanical forces from cell-matrix interactions, cell-cell contact, fluid flow and other physical stimuli may play a central role in the initiation and propagation of fibrosis. In this Review, we highlight the mechanotransduction mechanisms by which various sources of physical force drive fibrotic disease processes, with an emphasis on central pathways that may be therapeutically targeted to prevent and reverse fibrosis. We then discuss engineered models of mechanotransduction in fibrosis, as well as molecular and biomaterials-based therapeutic approaches for limiting fibrosis and promoting regenerative healing phenotypes in various organs. Finally, we discuss challenges within fibrosis research that remain to be addressed and that may greatly benefit from next-generation bioengineered model systems.

Long non-coding RNAs as emerging regulators of miRNAs and epigenetics in diabetes-related chronic kidney disease

Diabetes is one of the major cause of chronic kidney disease (CKD), including "diabetic nephropathy," and is an increasingly prevalent accelerator of the progression of non-diabetic forms of CKD. The long non-coding RNAs (lncRNAs) have come into the limelight in the past few years as one of the emerging weapons against CKD in diabetes. Available data over the past few years demonstrate the interaction of lncRNAs with miRNAs and epigenetic machinery. Interestingly, the evolving data suggest that lncRNAs play a vital role in diabetes-associated CKD by regulation of epigenetic enzymes such as DNA methyltransferase, histone deacetylases, and histone methyltransferases. LncRNAs are also engaged in the regulation of several miRNAs in diabetic nephropathy. Hence this review will elaborate on the association between lncRNAs and their interaction with epigenetic regulators involved in different aspects and thus the progression of CKD in diabetes.

Urinary miR-185-5p is a biomarker of renal tubulointerstitial fibrosis in IgA nephropathy

Background

For IgA nephropathy (IgAN), tubular atrophy/interstitial fibrosis is the most important prognostic pathological indicator in the mesangial and endocapillary hypercellularity, segmental sclerosis, interstitial fibrosis/tubular atrophy, and presence of crescents (MEST-C) score. The identification of non-invasive biomarkers for tubular atrophy/interstitial fibrosis would aid clinical monitoring of IgAN progression and improve patient prognosis.

Methods

The study included 188 patients with primary IgAN in separate confirmation and validation cohorts. The associations of miR-92a-3p, miR-425-5p, and miR-185-5p with renal histopathological lesions and prognosis were explored using Spearman correlation analysis and Kaplan-Meier survival curves. Bioinformatics analysis and dual luciferase experiments were used to identify hub genes for miR-185-5p. The fibrotic phenotypes of tubular epithelial cells were evaluated in vivo and in HK-2 cells.

Results

miRNA sequencing and cohort validation revealed that the expression levels of miR-92a-3p, miR-425-5p, and miR-185-5p in urine were significantly increased among patients with IgAN; these levels could predict the extent of tubular atrophy/interstitial fibrosis in such patients. The combination of the three biomarkers resulted in an area under the receiver operating characteristic curve of 0.742. The renal prognosis was significantly worse in the miR-185-5p high expression group than in the low expression group (P=0.003). Renal tissue in situ hybridization, bioinformatics analysis, and dual luciferase experiments confirmed that miR-185-5p affects prognosis in patients with IgAN mainly by influencing expression of the target gene tight junction protein 1 (TJP1) in renal tubular epithelial cells. In vitro experiment revealed that an miR-185-5p mimic could reduce TJP1 expression in HK-2 cells, while increasing the levels of α-smooth muscle actin, fibronectin, collagen I, and collagen III; these changes promoted the transformation of renal tubular epithelial cells to a fibrotic phenotype. An miR-185-5p inhibitor can reverse the fibrotic phenotype in renal tubular epithelial cells. In a unilateral ureteral obstruction model, the inhibition of miR-185-5p expression alleviated tubular atrophy/interstitial fibrosis.

Conclusion

Urinary miR-185-5p, a non-invasive biomarker of tubular atrophy/interstitial fibrosis in IgAN, may promote the transformation of renal tubular epithelial cells to a fibrotic phenotype via TJP1.

Emerging role of antidiabetic drugs in cardiorenal protection

The global prevalence of diabetes mellitus (DM) has led to widespread multi-system damage, especially in cardiovascular and renal functions, heightening morbidity and mortality. Emerging antidiabetic drugs sodium-glucose cotransporter 2 inhibitors (SGLT2i), glucagon-like peptide-1 receptor agonists (GLP-1RAs), and dipeptidyl peptidase-4 inhibitors (DPP-4i) have demonstrated efficacy in preserving cardiac and renal function, both in type 2 diabetic and non-diabetic individuals. To understand the exact impact of these drugs on cardiorenal protection and underlying mechanisms, we conducted a comprehensive review of recent large-scale clinical trials and basic research focusing on SGLT2i, GLP-1RAs, and DPP-4i. Accumulating evidence highlights the diverse mechanisms including glucose-dependent and independent pathways, and revealing their potential cardiorenal protection in diabetic and non-diabetic cardiorenal disease. This review provides critical insights into the cardiorenal protective effects of SGLT2i, GLP-1RAs, and DPP-4i and underscores the importance of these medications in mitigating the progression of cardiovascular and renal complications, and their broader clinical implications beyond glycemic management.

Pylorus ligation-induced hyperacidity: synergistic prophylactic effects of linagliptin and L-arginine via up-regulation of EP4 receptor subtype and improvement of vascular endothelial damage

Gastric hyperacidity and ulceration are chronic diseases characterized by repeated healing followed by re-exacerbation. The study aims to protect against gastric hyperacidity without interfering with gastric acid secretion. Pylorus ligation-induced hyperacidity is commonly utilized in the induction of gastric ulcers.Forty-two rats were distributed into seven groups (n = 6). Group I comprised sham-operated group. Group II served as pylorus-ligation group. Groups III-VII were given oral Linagliptin (LN; 3 and 6 mg/kg), L-arginine (LA; 150 and 300 mg/kg) and their combination (LN 3 + LA 150 mg/kg), respectively for 7 days. On the 8th day, groups II-VII were subjected to pylorus-ligation.Treatment of pylorus-ligated rats with LN, LA and their combination improved the gastric hyperacidity as exhibited by a marked reduction in the gastric juice volume, total and free acidities and pepsin contents with a noticeable increase in pH. Pre-treatment with LN, LA and their combination showed a marked alleviation in the gastric inflammatory indicators evidenced by reduction in the gastric levels of MCP-1and Il-1β as well as elevation of eNOS levels versus the sham-operated group. A marked up-regulation in the gastric gene expression of PGE, EP4 and VEGF accompanied by an improvement of the histopathologic pictures/scores, and TNF-α and caspase-3 immuno-staining were also recorded.By estimating the combination-index, it can be concluded that combining LN with LA exhibited prophylactic synergistic effects in ameliorating pylorus ligated-induced hyperacidity, mainly via up-regulation of EP4 receptor and improvement of vascular endothelial damage through VEGF expression in gastric mucosa.

(Pro)renin receptor mediates tubular epithelial cell pyroptosis in diabetic kidney disease via DPP4-JNK pathway

BACKGROUND

(Pro)renin receptor (PRR) is highly expressed in renal tubules, which is involved in physiological and pathological processes. However, the role of PRR, expressed in renal tubular epithelial cells, in diabetic kidney disease (DKD) remain largely unknown.

METHODS

In this study, kidney biopsies, urine samples, and public RNA-seq data from DKD patients were used to assess PRR expression and cell pyroptosis in tubular epithelial cells. The regulation of tubular epithelial cell pyroptosis by PRR was investigated by in situ renal injection of adeno-associated virus9 (AAV9)-shRNA into db/db mice, and knockdown or overexpression of PRR in HK-2 cells. To reveal the underlined mechanism, the interaction of PRR with potential binding proteins was explored by using BioGrid database. Furthermore, the direct binding of PRR to dipeptidyl peptidase 4 (DPP4), a pleiotropic serine peptidase which increases blood glucose by degrading incretins under diabetic conditions, was confirmed by co-immunoprecipitation assay and immunostaining.

RESULTS

Higher expression of PRR was found in renal tubules and positively correlated with kidney injuries of DKD patients, in parallel with tubular epithelial cells pyroptosis. Knockdown of PRR in kidneys significantly blunted db/db mice to kidney injury by alleviating renal tubular epithelial cells pyroptosis and the resultant interstitial inflammation. Moreover, silencing of PRR blocked high glucose-induced HK-2 pyroptosis, whereas overexpression of PRR enhanced pyroptotic cell death of HK-2 cells. Mechanistically, PRR selectively bound to cysteine-enrich region of C-terminal of DPP4 and augmented the protein abundance of DPP4, leading to the downstream activation of JNK signaling and suppression of SIRT3 signaling and FGFR1 signaling, and then subsequently mediated pyroptotic cell death.

CONCLUSIONS

This study identified the significant role of PRR in the pathogenesis of DKD; specifically, PRR promoted tubular epithelial cell pyroptosis via DPP4 mediated signaling, highlighting that PRR could be a promising therapeutic target in DKD.

The SOX4/EZH2/SLC7A11 signaling axis mediates ferroptosis in calcium oxalate crystal deposition-induced kidney injury

Epigenetic regulation is reported to play a significant role in the pathogenesis of various kidney diseases, including renal cell carcinoma, acute kidney injury, renal fibrosis, diabetic nephropathy, and lupus nephritis. However, the role of epigenetic regulation in calcium oxalate (CaOx) crystal deposition-induced kidney injury remains unclear. Our study demonstrated that the upregulation of enhancer of zeste homolog 2 (EZH2)-mediated ferroptosis facilitates CaOx-induced kidney injury. CaOx crystal deposition promoted ferroptosis in vivo and in vitro. Usage of liproxstatin-1 (Lip-1), a ferroptosis inhibitor, mitigated CaOx-induced kidney damage. Single-nucleus RNA-sequencing, RNA-sequencing, immunohistochemical and western blotting analyses revealed that EZH2 was upregulated in kidney stone patients, kidney stone mice, and oxalate-stimulated HK-2 cells. Experiments involving in vivo EZH2 knockout, in vitro EZH2 knockdown, and in vivo GSK-126 (an EZH2 inhibitor) treatment confirmed the protective effects of EZH2 inhibition on kidney injury and ferroptosis. Mechanistically, the results of RNA-sequencing and chromatin immunoprecipitation assays demonstrated that EZH2 regulates ferroptosis by suppressing solute carrier family 7, member 11 (SLC7A11) expression through trimethylation of histone H3 lysine 27 (H3K27me3) modification. Additionally, SOX4 regulated ferroptosis by directly modulating EZH2 expression. Thus, this study demonstrated that SOX4 facilitates ferroptosis in CaOx-induced kidney injury through EZH2/H3K27me3-mediated suppression of SLC7A11.

Targeting cluster of differentiation 26 / dipeptidyl peptidase 4 (CD26/DPP4) in organ fibrosis

Cluster of differentiation 26 (CD26)/dipeptidyl peptidase 4 (DPP4) is an exopeptidase that is expressed as a transmembrane protein in many organs but also present in a circulating soluble form. Beyond its enzymatic and costimulatory activity, CD26/DPP4 is involved in the pathogenesis of chronic fibrotic diseases across many organ types, such as liver cirrhosis, kidney fibrosis and lung fibrosis. Organ fibrosis is associated with a high morbidity and mortality, and there are no causative therapies that can effectively attenuate the progress of the disease. Growing evidence suggests that inhibiting CD26/DPP4 can modulate the profibrotic tissue microenvironment and thus reduce fibrotic changes within affected organs. This review summarizes the role of CD26/DPP4 in fibroproliferative disorders and highlights new opportunities for an antifibrotic treatment by CD26/DPP4 inhibition. As a major advantage, CD26/DPP4 inhibitors have been in safe and routine clinical use in type 2 diabetes for many years and thus qualify for repurposing to repurpose as a promising therapeutic against fibrosis. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

Endothelial cell plasticity in kidney fibrosis and disease

Renal endothelial cells demonstrate an impressive remodeling potential during angiogenic sprouting, vessel repair or while transitioning into mesenchymal cells. These different processes may play important roles in both renal disease progression or regeneration while underlying signaling pathways of different endothelial cell plasticity routes partly overlap. Angiogenesis contributes to wound healing after kidney injury and pharmaceutical modulation of angiogenesis may home a great therapeutic potential. Yet, it is not clear whether any differentiated endothelial cell can proliferate or whether regenerative processes are largely controlled by resident or circulating endothelial progenitor cells. In the glomerular compartment for example, a distinct endothelial progenitor cell population may remodel the glomerular endothelium after injury. Endothelial-to-mesenchymal transition (EndoMT) in the kidney is vastly documented and often associated with endothelial dysfunction, fibrosis, and kidney disease progression. Especially the role of EndoMT in renal fibrosis is controversial. Studies on EndoMT in vivo determined possible conclusions on the pathophysiological role of EndoMT in the kidney, but whether endothelial cells really contribute to kidney fibrosis and if not what other cellular and functional outcomes derive from EndoMT in kidney disease is unclear. Sequencing data, however, suggest no participation of endothelial cells in extracellular matrix deposition. Thus, more in-depth classification of cellular markers and the fate of EndoMT cells in the kidney is needed. In this review, we describe different signaling pathways of endothelial plasticity, outline methodological approaches and evidence for functional and structural implications of angiogenesis and EndoMT in the kidney, and eventually discuss controversial aspects in the literature.

Endothelial to mesenchymal cell transition in diabetic retinopathy: targets and therapeutics

Diabetic retinopathy (DR) is a result of neurovacular insults from hyperglycemia in diabetes mellitus (DM), and it is one of the top causes of vision loss throughout the modern world. This review article explores the role endothelial to mesenchymal transition (EndMT) has on the pathogenesis of DR. EndMT contributes to the disruption of the blood-retinal barrier, vascular leakage, neovascularization, and fibrosis observed in DR. Risk factors and biomarkers associated with DR severity are discussed, highlighting the importance of early detection and targeted therapies. Current treatments primarily focus on anti-vascular endothelial growth factor (anti-VEGF) agents, corticosteroids, and laser photocoagulation. However, emerging therapeutic strategies aimed at inhibiting EndMT and its downstream effects show promise in preventing the development and progression of DR. Understanding the molecular and cellular mechanisms underlying EndMT in DR provides valuable insights into the disease process and offers potential options for the development of potential treatments.

Current findings on the efficacy of incretin-based drugs for diabetic kidney disease: A narrative review

Diabetic kidney disease (DKD) is the most common cause of chronic kidney disease (CKD), leading end-stage renal disease. Thus, DKD is one of the most important diabetic complications. Incretin-based therapeutic agents, such as glucagon-like peptide-1 (GLP-1) receptor agonizts and dipeptidyl peptidase-4 (DPP-4) inhibitors have been reported to elicit vasotropic actions, suggesting a potential for effecting reduction in DKD. Glucose-dependent insulinotropic polypeptide (GIP) is also classified as an incretin. However, the insulin action after GIP secretion is known to be drastically reduced in patients with type 2 diabetes. Therefore, GIP has been formally considered unsuitable as a treatment for type 2 diabetes in the past. This concept is changing as it has been reported that resistance to GIP can be reversed and its effect restored with improved glycemic control. The development of novel dual- or triple- receptor agonizts that can bind to the receptors, not only for GLP-1 but also to GIP and glucagon receptors, is intended to simultaneously address several metabolic pathways including protein, lipid, and carbohydrate metabolism. These led to the development of GIP receptor agonist-based drugs for type 2 diabetes. The possibility of combined GIP/GLP-1 receptor agonist was also explored. The novel dual GIP and GLP-1 receptor agonist tirzepatide has recently been launched (Mounjaro®, Lilly). We have revealed precise mechanisms of the renoprotective effect of GLP-1 receptor agonizts or DPP-4 inhibitors, while the long-term effect of tirzepatide will need to be determined and its potential effects on kidneys should be properly tested.

Ginsenoside Rg3 attenuates pulmonary fibrosis by inhibiting endothelial to mesenchymal transition

Pulmonary fibrosis (PF) is a progressive and chronic lung disease characterized by excessive extracellular matrix (ECM) deposition and fibroblast proliferation. Endothelial-to-mesenchymal transition (EndMT) serves as a source of fibroblasts and contributes to PF progression. Ginsenoside Rg3 (Rg3), a steroidal saponin extracted from ginseng, is known to have pharmacological effects on vascular diseases. We have previously demonstrated that Rg3 inhibits EndMT and prevents endothelial dysfunction. Thus, we hypothesized that Rg3 may be a potential therapeutic agent for PF-targeting EndMT. EndMT occurs in the lung tissue of a bleomycin-induced PF mouse model, which was confirmed by co-staining of endothelial and mesenchymal markers in the pulmonary vasculature and changes in the expression of these markers. Rg3 administration decreased EndMT and suppressed PF development. We also examined the effect of Rg3 in an in vitro EndMT model induced by co-treatment with TGF-β2 and IL-1β. Rg3 treatment alleviated the characteristics of EndMT such as spindle-shaped morphological changes, EndMT marker expression changes, Dil-Ac-LDL uptake and migratory properties. In addition, we demonstrated the mechanism by which Rg3 inhibits EndMT by regulating the Smad2/3 signaling pathway. Collectively, Rg3 can be a potential therapeutic agent for PF using the EndMT inhibition strategy, furthermore, it can be considered Rg3 as a therapeutic candidate for various EndMT-associated vascular diseases.

[Molecular and Cellular Aspects of the Endothelial-Mesenchymal Transition in Cardiovascular Diseases]

Endothelial cells (ECs), which form the inner surface of the blood vessels, contact the blood, withstand mechanical pressure, and demonstrate heterogeneous reactions to exogenous and endogenous stimuli. ECs have unique properties in accordance with their niches and play an important role in regulating vascular homeostasis. Endothelial cells may undergo a dynamic phenotypic switch in terms of its heterogeneity, which may lead to endothelial dysfunction and a number of associated pathologies. Endothelial-mesenchymal transition (EndMT) is one of the possible molecular and cellular mechanisms of this kind. EndMT is characterized by phenotypic changes in ECs through which endothelial cells acquire new properties, i.e., start producing mesenchymal markers such as alpha-SMA and vimentin, change morphology, and become able to migrate. EndMT is a complex biological process that can be induced by inflammation, hypoxia, or oxidative stress and be involved in pathogenesis of cardiovascular disease. This review describes the key markers, inhibitors, and inducers of endothelial-mesenchymal transition and overall state-of-the-art of EndMT in cardiovascular diseases.

Predictive significance of glomerular insulin receptor substrate-1 in patients with diabetic kidney disease

Background

In rodents, glomerular expression of insulin receptor substrate 1 (IRS1) is decreased in diabetic kidney disease (DKD) and reduced associated functioning is involved in the development and progression of DKD. This study aimed to evaluate the significance of glomerular IRS1 expression in DKD patients, and investigated whether glomerular IRS1 expression can reflect renal pathology and predict renal outcomes.

Methods

This study included 10 patients who underwent renal biopsy and were diagnosed with DKD or minor glomerular abnormality (MGA). IRS1-positive cells were determined based on renal biopsy and immunostaining, and the associations of the number of these cells with baseline and prognostic parameters were analyzed.

Results

IRS1-positive cells were significantly decreased in DKD than in MGA. IRS1 positivity tended to be negatively correlated with global glomerulosclerosis and tubulointerstitial fibrosis. The rate of change in estimated glomerular filtration rate before and 12 months after renal biopsy was positively correlated to the number of IRS1-positive cells. Furthermore, a tendency towards negative correlation was observed between the number of glomerular IRS1-positive cells and the proteinuria.

Conclusions

This study shows the glomerular IRS1-positive cell count was significantly decreased in DKD, and that the degree IRS1 positivity was partially correlated with renal pathology and function.

Translation Animal Models of Diabetic Kidney Disease: Biochemical and Histological Phenotypes, Advantages and Limitations

Animal models play a crucial role in studying the pathogenesis of diseases, developing new drugs, identifying disease risk markers, and improving means of prevention and treatment. However, modeling diabetic kidney disease (DKD) has posed a challenge for scientists. Although numerous models have been successfully developed, none of them can encompass all the key characteristics of human DKD. It is essential to choose the appropriate model according to the research needs, as different models develop different phenotypes and have their limitations. This paper provides a comprehensive overview of biochemical and histological phenotypes, modeling mechanisms, advantages and limitations of DKD animal models, in order to update relevant model information and provide insights and references for generating or selecting the appropriate animal models to fit different experimental needs.

Effects of incretin-based therapeutic agents including tirzepatide on renal outcomes in patients with type 2 diabetes: A systemic review and meta-analysis

Background

This meta-analysis was conducted to investigate the effects of incretin-based therapeutic agents, including the latest agent tirzepatide, on renal outcomes in patients with type 2 diabetes.

Methods

MEDLINE (via PubMed) and Cochrane databases were searched for studies involving incretin-based therapeutic agents up to July 2022. Randomized and controlled trials comparing incretin-based therapeutic agents with placebo or other antidiabetic agents, and reporting renal outcomes were selected. The inclusion criteria were items related to the effects on albuminuria and the kidney-specific composite outcomes. A network meta-analysis was conducted to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs).

Results

Twelve trials consisting of 75,346 participants were included in this meta-analysis. Glucagon-like peptide-1 (GLP-1) receptor agonists reduced the risk of the kidney-specific composite outcome by 21% (HR 0.79, 95% CI 0.75-0.85), and worsening albuminuria by 24% (HR 0.76, 95% CI 0.71-0.82). In particular, the dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonist tirzepatide remarkably reduced the risk of the kidney-specific composite outcome by 45% (HR 0.55, 95% CI 0.40-0.77), and worsening albuminuria by 62% (HR 0.38, 95% CI 0.24-0.61).

Conclusions

Among incretin-based therapeutic agents, tirzepatide was associated with a significantly reduced risk of diabetic kidney disease.

Clinical trials with reno-vascular end points in patients with diabetes: Changing the scenario over the past 20 years

Major clinical advances over the last 20 years in the area of diabetic kidney disease (DKD) have been confirmed in large seminal clinical trials. These findings add to the previously identified benefits resulting from intensive glucose and blood pressure control therapies. Furthermore, newer glucose lowering treatments such as SGLT2 inhibitors and GLP-1 agonists appear very promising and are likely to transform the management and outlook of DKD over the next decade. In addition, novel mineralocorticoid receptor antagonists and a recently reported trial with an endothelin receptor blocker also have the potential to change clinical practice.

Pediatric Diabetic Nephropathy: Novel Insights from microRNAs

Diabetic nephropathy (DN) represents the most common microvascular complication in patients with diabetes. This progressive kidney disease has been recognized as the major cause of end-stage renal disease with higher morbidity and mortality. However, its tangled pathophysiology is still not fully known. Due to the serious health burden of DN, novel potential biomarkers have been proposed to improve early identification of the disease. In this complex landscape, several lines of evidence supported a critical role of microRNAs (miRNAs) in regulating posttranscriptional levels of protein-coding genes involved in DN pathophysiology. Indeed, intriguing data showed that deregulation of certain miRNAs (e.g., miRNAs 21, -25, -92, -210, -126, -216, and -377) were pathogenically linked to the onset and the progression of DN, suggesting not only a role as early biomarkers but also as potential therapeutic targets. To date, these regulatory biomolecules represent the most promising diagnostic and therapeutic options for DN in adult patients, while similar pediatric evidence is still limited. More, findings from these elegant studies, although promising, need to be deeper investigated in larger validation studies. In an attempt to provide a comprehensive pediatric overview in the field, we aimed to summarize the most recent evidence on the emerging role of miRNAs in pediatric DN pathophysiology.

Endothelial-to-mesenchymal transition: An underappreciated mediator of diabetic complications

Diabetes and its complications represent a great burden on the global healthcare system. Diabetic complications are fundamentally diseases of the vasculature, with endothelial cells being the centerpiece of early hyperglycemia-induced changes. Endothelial-to-mesenchymal transition is a tightly regulated process that results in endothelial cells losing endothelial characteristics and developing mesenchymal traits. Although endothelial-to-mesenchymal transition has been found to occur within most of the major complications of diabetes, it has not been a major focus of study or a common target in the treatment or prevention of diabetic complications. In this review we summarize the importance of endothelial-to-mesenchymal transition in each major diabetic complication, examine specific mechanisms at play, and highlight potential mechanisms to prevent endothelial-to-mesenchymal transition in each of the major chronic complications of diabetes.

Renal fibrosis as a hallmark of diabetic kidney disease: Potential role of targeting transforming growth factor-beta (TGF-β) and related molecules

INTRODUCTION

Diabetic kidney disease (DKD) is the most common cause of end-stage renal disease (ESRD) worldwide. Currently, there is no effective treatment to completely prevent DKD progression to ESRD. Renal fibrosis and inflammation are the major pathological features of DKD, being pursued as potential therapeutic targets for DKD.

AREAS COVERED

Inflammation and renal fibrosis are involved in the pathogenesis of DKD. Anti-inflammatory drugs have been developed to combat DKD but without efficacy demonstrated. Thus, we have focused on the mechanisms of TGF-β-induced renal fibrosis in DKD, as well as discussing the important molecules influencing the TGF-β signaling pathway and their potential development into new pharmacotherapies, rather than targeting the ligand TGF-β and/or its receptors, such options include Smads, microRNAs, histone deacetylases, connective tissue growth factor, bone morphogenetic protein 7, hepatocyte growth factor, and cell division autoantigen 1.

EXPERT OPINION

TGF-β is a critical driver of renal fibrosis in DKD. Molecules that modulate TGF-β signaling rather than TGF-β itself are potentially superior targets to safely combat DKD. A comprehensive elucidation of the pathogenesis of DKD is important, which requires a better model system and access to clinical samples via collaboration between basic and clinical researchers.

Unraveling the interplay between dipeptidyl peptidase 4 and the renin-angiotensin system in heart failure

AIMS

Emerging evidence suggests the existence of a crosstalk between dipeptidyl peptidase 4 (DPP4) and the renin-angiotensin system (RAS). Therefore, combined inhibition of DPP4 and RAS may produce similar pharmacological effects rather than being additive. This study tested the hypothesis that combining an inhibitor of DPP4 with an angiotensin II (Ang II) receptor blocker does not provide additional cardioprotection compared to monotherapy in heart failure (HF) rats.

MAIN METHODS

Male Wistar rats were subjected to left ventricle (LV) radiofrequency ablation or sham operation. Six weeks after surgery, radiofrequency-ablated rats who developed HF were assigned into four groups and received vehicle (water), vildagliptin, valsartan, or both drugs, for four weeks by oral gavage.

KEY FINDINGS

Vildagliptin and valsartan in monotherapy reduced LV hypertrophy, alleviated cardiac interstitial fibrosis, and improved systolic and diastolic function in HF rats, with no additional effect of combination treatment. HF rats displayed higher cardiac and serum DPP4 activity and abundance than sham. Surprisingly, not only vildagliptin but also valsartan in monotherapy downregulated the catalytic function and expression levels of systemic and cardiac DPP4. Moreover, vildagliptin and valsartan alone or in combination comparably upregulate the components of the cardiac ACE2/Ang-(1-7)/MasR while downregulating the ACE/Ang II/AT1R axis.

SIGNIFICANCE

Vildagliptin or valsartan alone is as effective as combined to treat cardiac dysfunction and remodeling in experimental HF. DPP4 inhibition downregulates classic RAS components, and pharmacological RAS blockade downregulates DPP4 in the heart and serum of HF rats. This interplay between DPP4 and RAS may affect HF progression and pharmacotherapy.

Dipeptidyl peptidase 4 expression is not associated with an activated fibroblast phenotype in idiopathic pulmonary fibrosis

Dipeptidyl peptidase 4 (DPP4) has been proposed as a marker for activated fibroblasts in fibrotic disease. We aimed to investigate whether a profibrotic DPP4 phenotype is present in lung tissue from patients with idiopathic pulmonary fibrosis (IPF). The presence of DPP4⁺ fibroblasts in normal and IPF lung tissue was investigated using flow cytometry and immunohistology. In addition, the involvement of DPP4 in fibroblast activation was examined in vitro, using CRISPR/Cas9 mediated genetic inactivation to generate primary DPP4 knockout lung fibroblasts. We observed a reduced frequency of primary DPP4⁺ fibroblasts in IPF tissue using flow cytometry, and an absence of DPP4⁺ fibroblasts in pathohistological features of IPF. The in vivo observations were supported by results in vitro showing a decreased expression of DPP4 on normal and IPF fibroblasts after profibrotic stimuli (transforming growth factor β) and no effect on the expression of activation markers (α-smooth muscle actin, collagen I and connective tissue growth factor) upon knockout of DPP4 in lung fibroblasts with or without activation with profibrotic stimuli.

Importance of Fibrosis in the Pathogenesis of Uterine Leiomyoma and the Promising Anti-fibrotic Effects of Dipeptidyl Peptidase-4 and Fibroblast Activation Protein Inhibitors in the Treatment of Uterine Leiomyoma

Uterine fibroid or leiomyoma is the most common benign uterus tumor. The tumor is primarily composed of smooth muscle (fibroid) cells, myofibroblast, and a significant amount of extracellular matrix components. It mainly affects women of reproductive age. They are uncommon before menarche and usually disappear after menopause. The fibroids have excessive extracellular matrix components secreted by activated fibroblast cells (myofibroblast). Myofibroblast has the characteristics of fibroblast and smooth muscle cells. These cells possess contractile capability due to the expression of contractile proteins which are normally found only in muscle tissues. The rigid nature of the tumor is responsible for many side effects associated with uterine fibroids. The current drug treatment strategies are primarily hormone-driven and not anti-fibrotic. This paper emphasizes the fibrotic background of uterine fibroids and the mechanisms behind the deposition of excessive extracellular matrix components. The transforming growth factor-β, hippo, and focal adhesion kinase-mediated signaling pathways activate the fibroblast cells and deposit excessive extracellular matrix materials. We also exemplify how dipeptidyl peptidase-4 and fibroblast activation protein inhibitors could be beneficial in reducing the fibrotic process in leiomyoma. Dipeptidyl peptidase-4 and fibroblast activation protein inhibitors prevent the fibrotic process in organs such as the kidneys, lungs, liver, and heart. These inhibitors are proven to inhibit the signaling pathways mentioned above at various stages of their activation. Based on literature evidence, we constructed a narrative review on the mechanisms that support the beneficial effects of dipeptidyl peptidase-4 and fibroblast activation protein inhibitors for treating uterine fibroids.

Association of acute increases in serum creatinine with subsequent outcomes in patients with type 2 diabetes mellitus treated with sodium-glucose cotransporter 2 inhibitor or dipeptidyl peptidase-4 inhibitor

AIMS

The frequency of an acute increase in serum creatinine (sCr) of >30%, following treatment of sodium-glucose cotransporter-2 inhibitors (SGLT2i) and its clinical implications in patients with type 2 diabetes remains unclear.

METHODS AND RESULTS

We used medical data from a multicenter health care provider in Taiwan and recruited 11,657 and 8,117 diabetic patients with baseline/follow-up sCr data available within 12 weeks of SGLT2i and dipeptidyl peptidase-4 inhibitor (DPP4i) treatment from June 1, 2016, to December 31, 2018. Participants receiving SGLT2i or DPP4i were categorized by initial sCr change into three groups:>30% sCr increase, 0-30% increase, or no-sCr increase. Participants receiving SGLT2i was associated with a higher proportion of sCr increase of 0-30% (52.7% vs. 42.6%) but a lower proportion of sCr increase of >30% (5.9% vs. 9.6%) when compared with DPP4i. In contrast to DPP4i, the mean estimated glomerular filtration rate over time became stable after 24 weeks in three categories of sCr increase following SGLT2i initiation. Compared with no sCr increase, an initial sCr increase of >30% was associated with a higher risk of major adverse cardiovascular events (adjusted hazard ratio [aHR]:2.91, [95% confidence interval [CI]:1.37-6.17]), heart failure hospitalization (HHF) (aHR:1.91,[95%CI:1.08-3.40]), and composite renal outcome (aHR:1.53,[95%CI:1.05-2.25]) in SGLT2i group; an initial sCr increase of >30% associated with a higher risk of HHF and composite renal outcome in DPP4i group after multivariate adjustment. Overall, participants receiving SGLT2i was associated with a lower risk of HHF (aHR:0.64,[95%CI:0.48-0.85]) and composite renal outcomes (aHR:0.40,[95%CI:0.34-0.48]) compared with DPP4i after multivariate adjustment, and the treatment benefit was persistent across three categories of sCr increase (P interaction>.05).

CONCLUSIONS

A modest increase in serum creatinine (<30%) was common following SGLT2i initiation, and was not associated with worse clinical outcomes, therefore should not stop therapy prematurely, but a larger increase in creatinine following drug therapy was not typical and should raise concern and review of the patient.

A Narrative Review of Diabetic Kidney Disease: Previous and Current Evidence-Based Therapeutic Approaches

Diabetic kidney disease (DKD) is one of the most important diabetic complications. DKD is also the most common cause of chronic kidney disease (CKD) and end-stage renal disease. This review focused on potential therapeutic drugs for which there is established evidence of treatment for DKD. The earliest evidence for DKD treatment was established with renin-angiotensin system (RAS) inhibitors; however, their efficacy was partial. Recently, the sodium-glucose co-transporter 2 (SGLT2) inhibitors, including empagliflozin (EMPA-REG Outcome), canagliflozin (CREDENCE trial), and dapagliflozin (DAPA-CKD), demonstrated a significant and clinically relevant reduction in the risks of albuminuria and progression of nephropathy, doubling of serum creatinine levels, and initiation of renal replacement therapy. Additionally, incretin-based therapeutic agents, such as glucagon-like peptide 1, liraglutide (LEADER), and dipeptidyl peptidase 4 inhibitors, linagliptin (CARMERINA) have elicited vasotropic actions, suggesting a potential for reducing the risk of DKD. Until recently, mineralocorticoid receptor antagonists (MRAs) have not been suitable for DKD treatment because of their adverse effect of hyperkalemia. In contrast, finerenone, a non-steroidal MRA, significantly reduced renal composite endpoint without severe hyperkalemia that would force its discontinuation (FIDELIO-DKD). Thus, the mainstay treatments of DKD are RAS inhibitors, SGLT2 inhibitors, incretin-based therapeutic agents, and non-steroidal MRA, or in other words, the DKD "fantastic four".

Comparison of effects of Empagliflozin and Linagliptin on renal function and glycaemic control: a double-blind, randomized clinical trial

Background

This study aimed to compare the effects of Linagliptin and Empagliflozin on renal function and glycaemic control in patients with type 2 diabetes mellitus (DM).

Method

We conducted a randomized, double-blind, parallel trial on patients aged 30 to 80 years with type 2 DM and HbA1c ≤ 9%, regardless of background medical therapy, to compare the effects of Empagliflozin and Linagliptin on albuminuria, FBS, HbA1c, and eGFR. Participants were given the mentioned drugs for 12 weeks. Statistical analysis was performed using appropriate tests in IBM™SPSS® statistics software for windows version 24.

Results

In total, 60 patients participated in the study, thirty patients in each group. The mean age of participants was 56.8 (SD = 8.15) in the Empagliflozin group and 60.9 (SD = 7.22) in the Linagliptin group. Before the intervention, FBS, HbA1C, and albuminuria values were significantly higher in the Empagliflozin group than those in the Linagliptin group (P < 0.05), but there was no significant difference between groups regarding eGFR (P = 0.271). Changes in the FBS, HbA1C, and eGFR were not significantly different between groups (P > 0.05), but there was more decrease in albuminuria in the Empagliflozin group compared to the Linagliptin group (P = 0.001, Cohen’s d = 0.98).

Conclusions

Regardless of baseline albuminuria, eGFR, or HbA1c, Empagliflozin 10 mg daily significantly reduced albuminuria at 12 weeks compared to Linagliptin 5 mg daily in patients with type 2 diabetes.

Trial registration

Iranian Registry of Clinical Trials, IRCT20200722048176N1. Registered 3 August 2020.

Therapeutic Implications of Ferroptosis in Renal Fibrosis

Renal fibrosis is a common feature of chronic kidney disease (CKD), and can lead to the destruction of normal renal structure and loss of kidney function. Little progress has been made in reversing fibrosis in recent years. Ferroptosis is more immunogenic than apoptosis due to the release and activation of damage-related molecular patterns (DAMPs) signals. In this paper, the relationship between renal fibrosis and ferroptosis was reviewed from the perspective of iron metabolism and lipid peroxidation, and some pharmaceuticals or chemicals associated with both ferroptosis and renal fibrosis were summarized. Other programmed cell death and ferroptosis in renal fibrosis were also firstly reviewed for comparison and further investigation.