The dipeptidyl peptidase inhibitor linagliptin and the angiotensin II receptor blocker telmisartan show renal benefit by different pathways in rats with 5/6 nephrectomy

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.

TMEM16A inhibits renal tubulointerstitial fibrosis via Wnt/β-catenin signaling during hypertension nephropathy

BACKGROUND AND OBJECTIVE

Hypertensive nephropathy is the second leading cause of end-stage renal disease, but its underlying pathogenesis remains unclear. Therefore, this study aimed to explore whether transmembrane protein 16 A (TMEM16A), the molecular basis of calcium-activated chloride channels (CaCC), is involved in the development and progression of hypertensive nephropathy.

METHODS

In vivo and in vitro experiments were conducted using a hypertensive murine model and human kidney proximal tubular epithelial cells (HK-2 cells), respectively.

EXPERIMENTAL RESULTS

The expression of TMEM16A was down-regulated in renal samples of hypertensive nephropathy patients and hypertensive model mice, accompanied by excessive deposition of extracellular matrix proteins (ECM) such as Fibronectin, Laminin, Collagen I and Collagen III, the up-regulation of α-smooth muscle actin (α-SMA) expression, and the decrease of E-cadherin. Overexpression of TMEM16A or knockdown of TMEM16A inhibited or promoted the expression of Wnt/β-catenin signaling pathway proteins Wnt3a, LRP5 and active β-catenin in HK-2 cells, preventing the epithelial-to-mesenchymal transition (EMT) of renal tubules, and the synthesis of ECM components.

CONCLUSION

In angiotensin II (Ang II)-induced hypertensive nephropathy, TMEM16A was identified as a key player inhibiting the detrimental changes in renal tubules, suggesting a potential avenue for mitigating renal damage in hypertensive nephropathy.

Integrated analysis reveals crosstalk between pyroptosis and immune regulation in renal fibrosis

Purpose

The pathogenesis of renal fibrosis (RF) involves intricate interactions between profibrotic processes and immune responses. This study aimed to explore the potential involvement of the pyroptosis signaling pathway in immune microenvironment regulation within the context of RF. Through comprehensive bioinformatics analysis and experimental validation, we investigated the influence of pyroptosis on the immune landscape in RF.

Methods

We obtained RNA-seq datasets from Gene Expression Omnibus (GEO) databases and identified Pyroptosis-Associated Regulators (PARs) through literature reviews. Systematic evaluation of alterations in 27 PARs was performed in RF and normal kidney samples, followed by relevant functional analyses. Unsupervised cluster analysis revealed distinct pyroptosis modification patterns. Using single-sample gene set enrichment analysis (ssGSEA), we examined the correlation between pyroptosis and immune infiltration. Hub regulators were identified via weighted gene coexpression network analysis (WGCNA) and further validated in a single-cell RNA-seq dataset. We also established a unilateral ureteral obstruction-induced RF mouse model to verify the expression of key regulators at the mRNA and protein levels.

Results

Our comprehensive analysis revealed altered expression of 19 PARs in RF samples compared to normal samples. Five hub regulators, namely PYCARD, CASP1, AIM2, NOD2, and CASP9, exhibited potential as biomarkers for RF. Based on these regulators, a classifier capable of distinguishing normal samples from RF samples was developed. Furthermore, we identified correlations between immune features and PARs expression, with PYCARD positively associated with regulatory T cells abundance in fibrotic tissues. Unsupervised clustering of RF samples yielded two distinct subtypes (Subtype A and Subtype B), with Subtype B characterized by active immune responses against RF. Subsequent WGCNA analysis identified PYCARD, CASP1, and NOD2 as hub PARs in the pyroptosis modification patterns. Single-cell level validation confirmed PYCARD expression in myofibroblasts, implicating its significance in the stress response of myofibroblasts to injury. In vivo experimental validation further demonstrated elevated PYCARD expression in RF, accompanied by infiltration of Foxp3+ regulatory T cells.

Conclusions

Our findings suggest that pyroptosis plays a pivotal role in orchestrating the immune microenvironment of RF. This study provides valuable insights into the pathogenesis of RF and highlights potential targets for future therapeutic interventions.

Neuroprotective Impact of Linagliptin against Cadmium-Induced Cognitive Impairment and Neuropathological Aberrations: Targeting SIRT1/Nrf2 Axis, Apoptosis, and Autophagy

Cadmium is an environmental contaminant associated with marked neurotoxicity and cognitive impairment. Linagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, has demonstrated promising neuroprotection against cerebral ischemia and diabetic dementia. However, there has been no study of its effect on cadmium-induced cognitive deficits. In the present work, linagliptin's prospective neuroprotective effects against cadmium-evoked cognitive decline were examined in vivo in rats. The molecular pathways related to oxidative stress, apoptosis, and autophagy were investigated. Histology, immunohistochemistry, ELISA, and biochemical assays were performed on brain hippocampi after receiving linagliptin (5 mg/kg/day). The current findings revealed that cadmium-induced learning and memory impairment were improved by linagliptin as seen in the Morris water maze, Y-maze, and novel object recognition test. Moreover, linagliptin lowered hippocampal neurodegeneration as seen in histopathology. At the molecular level, linagliptin curtailed hippocampal DPP-4 and augmented GLP-1 levels, triggering dampening of the hippocampal neurotoxic signals Aβ42 and p-tau in rats. Meanwhile, it enhanced hippocampal acetylcholine and GABA and diminished the glutamate spike. The behavioral recovery was associated with dampening of the hippocampal pro-oxidant response alongside SIRT1/Nrf2/HO-1 axis stimulation. Meanwhile, linagliptin counteracted hippocampal apoptosis markers and inhibited the pro-apoptotic kinase GSK-3β. In tandem, linagliptin activated hippocampal autophagy by lowering SQSTM-1/p62 accumulation, upregulating Beclin 1, and stimulating AMPK/mTOR pathway. In conclusion, linagliptin's antioxidant, antiapoptotic, and pro-autophagic properties advocated its promising neuroprotective impact. Thus, linagliptin may serve as a management approach against cadmium-induced cognitive deficits.

Icariin, the main prenylflavonoid of Epimedii Folium, ameliorated chronic kidney disease by modulating energy metabolism via AMPK activation

ETHNOPHARMACOLOGICAL RELEVANCE

Epimedii Folium is a famous traditional Chinese medicine (TCM) widely used in classic formulas, Chinese patent drugs and health care products for treating kidney diseases. Therefore, we speculated that icariin, its main component, might also have a good therapeutic effect on chronic kidney disease (CKD).

AIM OF STUDY

To investigate the efficacy and potential mechanism of icariin on CKD.

MATERIALS AND METHODS

A CKD model was established by intragastric administration of adenine (200 mg/kg/d) to adult male SD rats for 28 consecutive days. TGF-β1-induced fibrotic HK-2 cells were applied to establish the renal fibrosis model in vitro. Biochemical determination, pathological staining, flow cytometry and ELISA were performed to preliminarily evaluate the renoprotection of icariin. The intervention effect of icariin on renal fibrosis progression was assessed by cell stiffness determination and multiple immunological methods. The potential mechanism of icariin on CKD was revealed by means of ¹H NMR metabolomics, qRT-PCR and Western blotting analysis.

RESULTS

Icariin at the dosage of 100 mg/kg/d and 200 mg/kg/d markedly ameliorated rat renal function in a dose-dependent manner. Based on renal pathological features, the mechanism of icariin intervention in CKD was initially revealed by metabolomics, which was closely related to energy metabolism pathways. Furthermore, the detection results of AMPK and related factors in its mediated signaling pathways indicated that icariin exerted a therapeutic effect on CKD by attenuating inflammation and oxidative stress responses and retarding renal fibrosis progression through regulating AMPK/SIRT1/NF-κB and AMPK/ACC signaling pathways.

CONCLUSION

It was the first time to demonstrate that icariin could treat adenine-induced CKD by modulating energy metabolism via AMPK activation in a dose-dependent manner.

Salvianolic Acid A Improves Rat Kidney Injury by Regulating MAPKs and TGF-β1/Smads Signaling Pathways

Salvianolic acid A (SAA) is one of the major components in Salvia miltiorrhiza Bge., with various pharmacological activities, and is likely to be a promising agent for the treatment of kidney diseases. The purpose of this study was to explore the protective effect and mechanisms of SAA on kidney disease. In this study, the improvement effects of SAA (10, 20, 40 mg/kg, i.g.) on kidney injury rats were investigated by detecting the levels of KIM-1, NGAL in serum and UP in the urine of AKI model rats established with gentamicin, as well as the levels of SCr and UREA in serum and IL-6, IL-12, MDA and T-SOD in the kidneys of CKD model rats established with 5/6 nephrectomy. HE and Masson staining were used to observe the histopathological changes in the kidney. Network pharmacology and Western blotting were used to explore the mechanism of SAA in improving kidney injury. The results showed that SAA improved kidney function in kidney injury rats by reducing the kidney index and pathological injury by HE and Masson staining, reducing the levels of KIM-1, NGAL and UP in AKI rats and UREA, SCr and UP in CKD rats, as well as exerting anti-inflammatory and anti-oxidative stress effects by inhibiting the release of IL-6 and IL-12, reducing MDA and increasing T-SOD. Western blotting results showed that SAA significantly reduced the phosphorylation levels of ERK1/2, p38, JNK and smad2/3, and the expression of TLR-4 and smad7. In conclusion, SAA plays a significant role in improving kidney injury in rats and the mechanism may be achieved by regulating the MAPKs and TGF-β1/smads signaling pathways.

Niaoduqing alleviates podocyte injury in high glucose model via regulating multiple targets and AGE/RAGE pathway: Network pharmacology and experimental validation

Purpose: The aim of present study was to explore the pharmacological mechanisms of Niaoduqing granules on the treatment of podocyte injury in diabetic nephropathy (DN) via network pharmacology and experimental validation. Methods: Active ingredients and related targets of Niaoduqing, as well as related genes of podocyte injury, proteinuria and DN, were obtained from public databases. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein-protein interaction (PPI) network analysis were performed to investigate the potential mechanisms. High glucose (HG) -induced MPC5 cell injury model was treated with the major core active ingredients of Niaoduqing and used to validate the predicted targets and signaling pathways. Results: Totally, 16 potential therapeutic targets were identified by intersecting the targets of Niaoduqing and disease, in which 7 of them were considered as the core targets via PPI network analysis. KEGG enrichment analysis showed that AGE-RAGE signaling pathway was identified as the most crucial signaling pathway. The results of in vitro experiments revealed that the treatment of Niaoduqing active ingredients significantly protected MPC5 cells from HG-induced apoptosis. Moreover, Niaoduqing could significantly attenuate the HG-induced activation of AGE-RAGE signaling pathway, whereas inhibited the over-expression of VEGF-A, ICAM-1, PTGS-2 and ACE in HG-induced MPC5 cells. Conclusion: Niaoduqing might protect against podocyte injury in DN through regulating the activity of AGE/RAGE pathway and expression of multiple genes. Further clinical and animal experimental studies are necessary to confirm present findings.

Nicotinamide riboside kinase 1 protects against diet and age-induced pancreatic β-cell failure

OBJECTIVE

Disturbances in NAD⁺ metabolism have been described as a hallmark for multiple metabolic and age-related diseases, including type 2 diabetes. While alterations in pancreatic β-cell function are critical determinants of whole-body glucose homeostasis, the role of NAD⁺ metabolism in the endocrine pancreas remains poorly explored. Here, we aimed to evaluate the role of nicotinamide riboside (NR) metabolism in maintaining NAD⁺ levels and pancreatic β-cell function in pathophysiological conditions.

METHODS

Whole body and pancreatic β-cell-specific NRK1 knockout (KO) mice were metabolically phenotyped in situations of high-fat feeding and aging. We also analyzed pancreatic β-cell function, β-cell mass and gene expression.

RESULTS

We first demonstrate that NRK1, the essential enzyme for the utilization of NR, is abundantly expressed in pancreatic β-cells. While NR treatment did not alter glucose-stimulated insulin secretion in pancreatic islets from young healthy mice, NRK1 knockout mice displayed glucose intolerance and compromised β-cells response to a glucose challenge upon high-fat feeding or aging. Interestingly, β cell dysfunction stemmed from the functional failure of other organs, such as liver and kidney, and the associated changes in circulating peptides and hormones, as mice lacking NRK1 exclusively in β-cells did not show altered glucose homeostasis.

CONCLUSIONS

This work unveils a new physiological role for NR metabolism in the maintenance of glucose tolerance and pancreatic β-cell function in high-fat feeding or aging conditions.

Recent Advances in the Emerging Therapeutic Strategies for Diabetic Kidney Diseases

Diabetic kidney disease (DKD) is one of the most common causes of end-stage renal disease worldwide. The treatment of DKD is strongly associated with clinical outcomes in patients with diabetes mellitus. Traditional therapeutic strategies focus on the control of major risk factors, such as blood glucose, blood lipids, and blood pressure. Renin–angiotensin–aldosterone system inhibitors have been the main therapeutic measures in the past, but the emergence of sodium–glucose cotransporter 2 inhibitors, incretin mimetics, and endothelin-1 receptor antagonists has provided more options for the management of DKD. Simultaneously, with advances in research on the pathogenesis of DKD, some new therapies targeting renal inflammation, fibrosis, and oxidative stress have gradually entered clinical application. In addition, some recently discovered therapeutic targets and signaling pathways, mainly in preclinical and early clinical trial stages, are expected to provide benefits for patients with DKD in the future. This review summarizes the traditional treatments and emerging management options for DKD, demonstrating recent advances in the therapeutic strategies for DKD.

Repositioning Linagliptin for the Mitigation of Cadmium-Induced Testicular Dysfunction in Rats: Targeting HMGB1/TLR4/NLRP3 Axis and Autophagy

Cadmium, a ubiquitous environmental toxicant, disrupts testicular function and fertility. The dipeptidyl peptidase-4 inhibitor linagliptin has shown pronounced anti-inflammatory and anti-apoptotic features; however, its effects against cadmium-evoked testicular impairment have not been examined. Herein, the present study investigated targeting inflammation, apoptosis, and autophagy by linagliptin for potential modulation of cadmium-induced testicular dysfunction in rats. After 60 days of cadmium chloride administration (5 mg/kg/day, by gavage), testes, epididymis, and blood were collected for analysis. The present findings revealed that linagliptin improved the histopathological lesions, including spermatogenesis impairment and germ cell loss. Moreover, it improved sperm count/motility and serum testosterone. The favorable effects of linagliptin were mediated by curbing testicular inflammation seen by dampening of HMGB1/TLR4 pathway and associated lowering of nuclear NF-κBp65. In tandem, linagliptin suppressed the activation of NLRP3 inflammasome/caspase 1 axis with consequent lowering of the pro-inflammatory IL-1β and IL-18. Jointly, linagliptin attenuated testicular apoptotic responses seen by Bax downregulation, Bcl-2 upregulation, and suppressed caspase 3 activity. With respect to autophagy, linagliptin enhanced the testicular autophagy flux seen by lowered accumulation of p62 SQSTM1 alongside upregulation of Beclin 1. The observed autophagy stimulation was associated with elevated AMPK (Ser487) phosphorylation and lowered mTOR (Ser2448) phosphorylation, indicating AMPK/mTOR pathway activation. In conclusion, inhibition of testicular HMGB1/TLR4/NLRP3 pro-inflammatory axis and apoptosis alongside stimulation of autophagy were implicated in the favorable actions of linagliptin against cadmium-triggered testicular impairment.

Insight into the role of DPP-4 in fibrotic wound healing

Wound healing is a complex and long-term process consisting of hemostasis, inflammation, proliferation, and maturation/remodeling. These four stages overlap and influence each other; they affect wound healing in different ways, and if they do not function perfectly, they may cause scarring, proliferative scarring and keloid formation. A therapeutic target affecting wound healing in multiple ways will help the healing process proceed more effectively. DPP-4/CD26 is a multifunctional dimorphic glycoprotein widely distributed on the surface of a variety of cells, including fibroblasts and keratin-forming cells. It has been found to affect periwound inflammation, re-epithelialization, extracellular matrix secretion and skin fibrosis and is a potential target for promoting wound healing and inhibiting scar formation. After presenting a brief introduction of the wound healing process and DPP-4/CD26, this paper summarizes the effects of DPP-4/CD26 on cells involved in different stages of wound healing and discusses the feasibility of DPP-4/CD26 as a multifunctional target for the treatment of wound healing and inhibition of scar formation.

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.

Regulation of SARS CoV-2 host factors in the kidney and heart in rats with 5/6 nephrectomy-effects of salt, ARB, DPP4 inhibitor and SGLT2 blocker

Background

Host factors such as angiotensin-converting enzyme 2 (ACE2) and the transmembrane protease, serine-subtype-2 (TMPRSS2) are important factors for SARS-CoV-2 infection. Clinical and pre-clinical studies demonstrated that RAAS-blocking agents can be safely used during a SARS-CoV-2 infection but it is unknown if DPP-4 inhibitors or SGLT2-blockers may promote COVID-19 by increasing the host viral entry enzymes ACE2 and TMPRSS2.

Methods

We investigated telmisartan, linagliptin and empagliflozin induced effects on renal and cardiac expression of ACE2, TMPRSS2 and key enzymes involved in RAAS (REN, AGTR2, AGT) under high-salt conditions in a non-diabetic experimental 5/6 nephrectomy (5/6 Nx) model. In the present study, the gene expression of Ace2, Tmprss2, Ren, Agtr2 and Agt was assessed with qRT-PCR and the protein expression of ACE2 and TMPRSS2 with immunohistochemistry in the following experimental groups: Sham + normal diet (ND) + placebo (PBO); 5/6Nx + ND + PBO; 5/6Nx + high salt-diet (HSD) + PBO; 5/6Nx + HSD + telmisartan; 5/6Nx + HSD + linagliptin; 5/6Nx + HSD + empagliflozin.

Results

In the kidney, the expression of Ace2 was not altered on mRNA level under disease and treatment conditions. The renal TMPRSS2 levels (mRNA and protein) were not affected, whereas the cardiac level was significantly increased in 5/6Nx rats. Intriguingly, the elevated TMPRSS2 protein expression in the heart was significantly normalized after treatment with telmisartan, linagliptin and empagliflozin.

Conclusions

Our study indicated that there is no upregulation regarding host factors potentially promoting SARS-CoV-2 virus entry into host cells when the SGLT2-blocker empagliflozin, telmisartan and the DPP4-inhibitor blocker linagliptin are used. The results obtained in a preclinical, experimental non-diabetic kidney failure model need confirmation in ongoing interventional clinical trials.

Effect of linagliptin plus insulin in comparison to insulin alone on metabolic control and prognosis in hospitalized patients with SARS-CoV-2 infection

To evaluate the effect of the combination of linagliptin and insulin on metabolic control and prognosis in hospitalized patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and hyperglycemia. A parallel double-blind randomized clinical trial including hospitalized patients with SARS-CoV-2 infection and hyperglycemia, randomized to receive 5 mg linagliptin + insulin (LI group) or insulin alone (I group) was performed. The main outcomes were the need for assisted mechanical ventilation and glucose levels during hospitalization. Subjects were screened for eligibility at hospital admission if they were not with assisted mechanical ventilation and presented hyperglycemia, and a total of 73 patients with SARS-CoV-2 infection and hyperglycemia were randomized to the LI group (n = 35) or I group (n = 38). The average hospital stay was 12 ± 1 vs 10 ± 1 days for the I and LI groups, respectively (p = 0.343). There were no baseline clinical differences between the study groups, but the percentage of males was higher in the LI group (26 vs 18, p = 0.030). The improvements in fasting and postprandial glucose levels were better in the LI group that the I group (122 ± 7 vs 149 ± 10, p = 0.033; and 137 ± 7 vs 173 ± 12, p = 0.017, respectively), and insulin requirements tended to be lower in the LI group than the I group. Three patients in the LI group and 12 in the I group required assisted mechanical ventilation (HR 0.258, CI 95% 0.092–0.719, p = 0.009); 2 patients in the LI group and 6 in the I group died after a follow-up of 30 days (p = 0.139). No major side effects were observed. The combination of linagliptin and insulin in hospitalized patients with SARS-CoV-2 infection and hyperglycemia reduced the relative risk of assisted mechanical ventilation by 74% and improved better pre and postprandial glucose levels with lower insulin requirements, and no higher risk of hypoglycemia.

This study is registered at clinicaltrials.gov, number NCT04542213 on 09/03/2020.

Antifibrotic effects of low dose SGLT2 Inhibition with empagliflozin in comparison to Ang II receptor blockade with telmisartan in 5/6 nephrectomised rats on high salt diet

To date, the lowest protective SGLT2 inhibitor dose is unknown. We initially performed a dose-response pilot study in normal rats. Based on the results of this pilot study we compared the cardio-renal effects of the SGLT-2 inhibitor empagliflozin, with placebo or telmisartan in rats with 5/6 nephrectomy (5/6 Nx) on a high salt diet (HSD). The experimental set up was as follows: Sham operation (Sham) with normal diet and placebo; 5/6 Nx with 2% HSD and placebo; 5/6 Nx with HSD and empagliflozin (0.6 mg/kg/day, bid); 5/6 Nx with HSD and telmisartan (5 mg/kg/day, qd). Empagliflozin treatment increased urinary glucose excretion, in parallel to empagliflozin plasma levels, in a dose-dependent manner starting at doses of 1 mg/kg in the pilot study. 5/6Nx rats on HSD treated with this low empagliflozin dose showed significantly reduced cardiac (-34.85%; P < 0.05) and renal (-33.68%; P < 0.05) fibrosis in comparison to 5/6Nx rats on HSD treated with placebo. These effects were comparable to the effects observed when implementing the standard dose (5 mg/kg/day) of telmisartan (cardiac fibrosis: -36.37%; P < 0.01; renal fibrosis; -43.96%; P < 0.01). RNA-sequencing followed by confirmatory qRT-PCR revealed that both telmisartan and empagliflozin exert their cardiac effects on genes involved in vascular cell stability and cardiac iron homeostasis, whereas in the kidneys expression of genes involved in endothelial function and oxidative stress were differentially expressed. Urinary adenosine excretion, a surrogate marker of the tubuloglomerular feedback (TGF) mechanism, was not affected. In conclusion, the antifibrotic properties of low dose empagliflozin were comparable to a standard dose of telmisartan. The underlying pathways appear to be TGF independent.

Sitagliptin's renoprotective effect in a diabetic nephropathy model in rats: The potential role of PI3K/AKT pathway

Management of diabetic nephropathy (DN) is far from satisfactory. There is a rising role of the involvement of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway in the pathogenesis of DN. This study aimed at investigating the renoprotective effects of PI3K/AKT pathway via sitagliptin in a rat model of DN. Thirty-two male Wistar rats were divided into four groups (eight rats each): (I) control, (II) sitagliptin, (III) DN, and (IV) DN + sitagliptin. Fasting blood glucose (FBG), kidney index, and kidney function tests in both blood and urine were measured. The levels of superoxide dismutase (SOD), tumor necrosis factor-alpha (TNF-α), and transforming growth factor-beta (TGF-β) and gene expressions of PI3K, pPI3K, AKT, and pAKT in renal tissue were detected. Renal histopathological and immunohistochemical studies were evaluated. DN + sitagliptin group showed significant decrease in FBG and kidney index, improvement in kidney function tests, and a decrease in levels of TNF-α and TGF-β in renal tissues compared with DN group. This was associated with significant increase in SOD and gene expressions of PI3K and AKT and their phosphorylated active forms in renal tissue in DN + sitagliptin group compared with DN group. Moreover, DN + sitagliptin group showed apparent decrease in amount of collagen fibers and expression of alpha-smooth muscle actin (α-SMA) compared with DN group. This work shows that sitagliptin improved renal functions and histopathological changes, impeded inflammation, and oxidative stress and upregulated PI3K/AKT pathway which highlights its renoprotective effects in a rat model of DN.

High-dose vitamin D3 supplementation ameliorates renal fibrosis by vitamin D receptor activation and inhibiting TGF-β1/Smad3 signaling pathway in 5/6 nephrectomized rats

Renal fibrosis is the pathological consequence of progressive chronic kidney disease. Although it has been reported that vitamin D3 exerts antifibrotic effects, the underlying mechanisms remain unclear. This study is aimed at investigating the effects and molecular mechanisms in high-dose vitamin D3 treatment on renal fibrosis. A model of chronic kidney disease was established by 5/6 nephrectomy in rats characterised by high levels of serum creatine, urea nitrogen, and urinary protein. Serum 25-dihydroxyvitamin D3, calcium and parathormone levels were measured to evaluate vitamin D levels. Hematoxylin and eosin, periodic acid Schiff and Mallory's Trichrome staining were used to evaluate histopathological changes in rats. Moreover, the expression of vimentin, collagen I, α-smooth muscle actin and E-cadherin were analyzed at molecular and histopathological levels. Our results showed that exposure to vitamin D3 decreased the levels of serum creatine, urea nitrogen and urine protein and restored the homeostasis of calcium and parathormone. Vitamin D3 also downregulated the expression of vimentin, collagen I and α-smooth muscle actin and attenuated renal fibrosis and epithelial to mesenchymal transition in the kidney. Importantly, vitamin D3 treatment increased the expression of the vitamin D receptor and inhibited Transforming growth factor-β1 (TGF-β1)/Smad3 signaling pathway in rats kidneys with chronic kidney disease. Mechanistically, the upregulation of TGF-β1 and phosphorylation of Smad3 induced by vitamin D3 was reversed by activation of the vitamin D receptor. Our findings indicated that vitamin D3 is a potential antifibrotic drug in chronic kidney disease via the vitmin D receptor and inhibiting TGF-β1/Smad3 signaling pathway.

Urinary dipeptidyl peptidase-4 protein is increased by linagliptin and is a potential predictive marker of urine albumin-to-creatinine ratio reduction in patients with type 2 diabetes

Results of a post hoc analysis of urinary dipeptidyl peptidase-4 (DPP-4) protein as a predictor of urine albumin-to-creatinine ratio (UACR) response to linagliptin treatment based on MARLINA-T2D trial data are described. MARLINA was a 24-week, phase 3b, multinational, placebo-controlled clinical trial, in which patients with type 2 diabetes (T2D), HbA1c 6.5%-10.0% and UACR 30-3000 mg/g (n = 360) were treated with linagliptin or placebo. After 24 weeks of treatment, linagliptin significantly inhibited urinary DPP-4 activity and increased urinary DPP-4 protein. Furthermore, medium urinary DPP-4 protein levels (between 5.5 and 7.5 natural logarithmic [ln] μg/g creatinine) at baseline allowed for prediction of improved UACR in linagliptin-treated individuals. In patients with lower or higher levels of urinary DPP-4 protein at baseline, no association between linagliptin treatment and improved UACR was present. This might suggest a varying degree of importance of DPP-4 as a pathophysiological factor in T2D-associated kidney disease. In summary, urinary DPP-4 might be a useful predictive biomarker for UACR improvement by linagliptin.

Use of Anti-Diabetic Agents in Non-Diabetic Kidney Disease: From Bench to Bedside

New drugs were recently developed to treat hyperglycemia in patients with type 2 diabetes mellitus (T2D). However, metformin remains the first-line anti-diabetic agent because of its cost-effectiveness. It has pleiotropic action that produces cardiovascular benefits, and it can be useful in diabetic nephropathy, although metformin-associated lactic acidosis is a hindrance to its use in patients with kidney failure. New anti-diabetic agents, including glucagon-like peptide-1 receptor (GLP-1R) agonists, dipeptidyl peptidase-4 (DPP-4) inhibitors, and sodium-glucose transporter-2 (SGLT-2) inhibitors, also produce cardiovascular or renal benefits in T2D patients. Their glucose-independent beneficial actions can lead to cardiorenal protection via hemodynamic stabilization and inflammatory modulation. Systemic hypertension is relieved by natriuresis and improved vascular dysfunction. Enhanced tubuloglomerular feedback can be restored by SGLT-2 inhibition, reducing glomerular hypertension. Patients with non-diabetic kidney disease might also benefit from those drugs because hypertension, proteinuria, oxidative stress, and inflammation are common factors in the progression of kidney disease, irrespective of the presence of diabetes. In various animal models of non-diabetic kidney disease, metformin, GLP-1R agonists, DPP-4 inhibitors, and SGLT-2 inhibitors were favorable to kidney morphology and function. They strikingly attenuated biomarkers of oxidative stress and inflammatory responses in diseased kidneys. However, whether those animal results translate to patients with non-diabetic kidney disease has yet to be evaluated. Considering the paucity of new agents to treat kidney disease and the minimal adverse effects of metformin, GLP-1R agonists, DPP-4 inhibitors, and SGLT-2 inhibitors, these anti-diabetic agents could be used in patients with non-diabetic kidney disease. This paper provides a rationale for clinical trials that apply metformin, GLP-1R agonists, DPP-4 inhibitors, and SGLT-2 inhibitors to non-diabetic kidney disease.

A Novel Dipeptidyl Peptidase-4 Inhibitor DA-1229 Ameliorates Tubulointerstitial Fibrosis in Cyclosporine Nephrotoxicity in Mice

Cyclosporine A (CyA) is an immunosuppressive agent that induces nephrotoxicity with long-term treatment. The roles of DPP-4 and its inhibitors in cyclosporine nephrotoxicity are not fully understood. Therefore, we investigated the effects of a novel DPP-4 inhibitor, DA-1229, on the progression of renal disease in an experimental cyclosporine nephrotoxicity model. Chronic cyclosporine nephrotoxicity was induced in six-week-old male ICR mice by subcutaneous injections of CyA at a dose of 30 mg/kg for four weeks. Animals were treated with DA-1229 at a dose of 300 mg/kg per day in food for four weeks. Although DPP-4 activity did not increase in the kidneys of mice with induced cyclosporine nephrotoxicity, DA-1229 treatment significantly suppressed DPP-4 activity in both plasma and renal tissues. DPP-4 inhibition by DA-1229 led to significantly decreased albuminuria and urinary excretion of 8-isoprosatane. DPP-4 inhibition also substantially suppressed pro-inflammatory effects, profibrotic molecules, and macrophage infiltration, and led to the improvement in renal structural changes. Our results suggest that DPP-4 inhibition by DA-1229 provides renoprotective effects in an animal model of cyclosporine nephrotoxicity via antioxidant, anti-inflammatory, and anti-fibrotic mechanisms. DPP-4 inhibition may be a useful new therapeutic approach for the management of progressive renal disease in cyclosporine nephrotoxicity.

Linagliptin mitigates experimental inflammatory bowel disease in rats by targeting inflammatory and redox signaling

AIMS

Dipeptidyl peptidase-4 (DPP-4) has been involved in the pathogenesis of inflammatory bowel diseases (IBD), yet the underlying mechanisms remain inconclusive. The present study aimed to investigate the potential of linagliptin, a potent/selective DPP-4 inhibitor with marked anti-inflammatory actions, to attenuate trinitrobenzene sulfonic acid (TNBS)-evoked colitis in rats; an experimental model of IBD, and the implicated molecular mechanisms. This may add to the clinical utility of linagliptin for the management of patients with coexisting IBD and diabetes mellitus. Notably, no former studies have linked JAK2/STAT3, HMGB1/NF-κB, and Nrf2/HO-1 signaling in TNBS-evoked colitis.

MATERIALS AND METHODS

Western blotting and ELISA were used to determine the levels of target signals.

KEY FINDINGS

Administration of linagliptin (1.5 mg/kg; p.o.) mitigated the colitis severity via diminishing the disease activity index, colon weight/length ratio, and macroscopic scores. Linagliptin also lowered the colonic histologic scores and leukocyte invasion. Notably, linagliptin inhibited the colonic DPP-4 activity and upregulated the expression of intestinotrophic GLP-2 without incurring hypoglycemia in animals. Linagliptin curbed inflammation through the suppression of colonic IL-6, TNF-α, and myeloperoxidase and upregulation of IL-10. It also inhibited the IL-6/JAK2/STAT3 pathway via downregulating p-JAK2/JAK2 and p-STAT3/STAT3 protein expression and HMGB1/RAGE/NF-κB cascade through lowering HMGB1, RAGE, and p-NF-κB p65/NF-κB p65 protein expression. In the context of mucosal oxidative stress, linagliptin diminished lipid peroxides and augmented GSH, GPx, and total antioxidant capacity. It also activated Nrf2/HO-1 pathway via upregulating Nrf2 and HO-1 protein expression.

SIGNIFICANCE

Linagliptin shows a promise for the management of IBD via targeting IL-6/JAK2/STAT3, HMGB1/RAGE/NF-κB, and Nrf2/HO-1 pathways.

Saxagliptin and vildagliptin lowered albuminuria in patients with diabetes and hypertension independent on glycaemic control

BACKGROUND

Preclinical data illustrated that the dipeptidyl peptidase-4(DPP-4) inhibitors did lower urinary albumin excretion in diabetes-induced rats. We evaluated the effects of saxagliptin and vildagliptin on albuminuria in patients with diabetic nephropathy on top of the renin-angiotensin-aldosterone system (RAAS) blockade therapy.

METHODS

This study included 120 patients with type 2 diabetes (T2D), hypertension, and prevalent albuminuria [defined as urine albumin-to-creatinine ratio (UACR) 30-3000mg/g creatinine] on a stable dose of olmesartan as a standard RAAS blocker for diabetic nephropathy. Patients were assigned to receive either of saxagliptin 5mg/day (n = 40), vildagliptin 100mg/day (n = 40), or traditional antidiabetic therapy as control patients (n = 40) for 12 weeks.

RESULTS

Each of saxagliptin and vildagliptin significantly reduced albuminuria after 12 weeks, with mean percentage changes (%) of -57.9% [95% confidence interval (CI) -66.1 to -49.8], and -55.2% (95% CI -64.9 to -45.4); P < .001, respectively, compared with the control group. Significantly, saxagliptin shifted higher proportions of patients towards lower albuminuria categories (P < .001) compared with vildagliptin despite a similar UACR rate of changes. Results of binary logistic models confirmed that the change in UACR because saxagliptin was independent of changes in systolic blood pressure (SBP), glycated hemoglobin (HbA_1c ), estimated glomerular filtration rate (eGFR), or body weight (overall regression: P = .002, R²  = 0.398) vs control. Likewise, vildagliptin reduced UACR independently on other confounders (overall regression: P = .002, R²  = 0.388). Furthermore, no significant correlation was observed between the change in UACR and changes in HbA1c, SBP or eGFR with either saxagliptin or vildagliptin (Pearson coefficients: 0.203, 0.143, -0.190; P > .05, and 0.003, 0.241, 0.019; P > .05, respectively).

CONCLUSIONS

DPP-4 inhibitors, saxagliptin, and vildagliptin, resulted in substantial reductions in albuminuria in patients with T2D and hypertension on top of RAAS blockade after short term therapy independently on glycaemic or hemodynamic changes. Saxagliptin was superior to vildagliptin in albuminuria-categorical shifting.

Renoprotective Effects of DPP-4 Inhibitors

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD) worldwide. Dipeptidyl peptidase (DPP)-4 inhibitors are widely used in the treatment of patients with type 2 diabetes (T2D). DPP-4 inhibitors reduce glucose levels by inhibiting degradation of incretins. DPP-4 is a ubiquitous protein with exopeptidase activity that exists in cell membrane-bound and soluble forms. It has been shown that an increased renal DPP-4 activity is associated with the development of DKD. A series of clinical and experimental studies showed that DPP-4 inhibitors have beneficial effects on DKD, independent of their glucose-lowering abilities, which are mediated by anti-fibrotic, anti-inflammatory, and anti-oxidative stress properties. In this review article, we highlight the current understanding of the clinical efficacy and the mechanisms underlying renoprotection by DPP-4 inhibitors under diabetic conditions.

The dipeptidyl peptidase 4 inhibitor linagliptin ameliorates renal injury and accelerated resolution in a rat model of crescentic nephritis

BACKGROUND AND PURPOSE

Dipeptidyl peptidase 4 (DPP-4) inhibitors are a class of oral glucose-lowering drugs used in the treatment of type 2 diabetes. In a pilot study using human kidney biopsies, we observed high DPP-4 expression in early crescent formation. This glomerular lesion occurs in different kidney diseases and is a hallmark in the pathogenesis of renal dysfunction. Therefore, we investigated the potential involvement of DPP-4 in the pathogenesis of nephritis induced by anti-glomerular basement membrane (GBM) antibody in rats.

EXPERIMENTAL APPROACH

Linagliptin and vehicle were used to treat anti-GBM nephritis in a 2- and 8-week regimen, that is either preventive or therapeutic (treatment started 7 days or 4 weeks after disease induction). Kidney function, morphologic changes, inflammation and fibrosis were monitored.

KEY RESULTS

In the long-term experiment, linagliptin preventive treatment in anti-GBM nephritic rats significantly reduced the number of crescents, glomerulosclerosis, tubular injury and renal fibrosis, compared with those in untreated nephritic rats. Both linagliptin regimes significantly lowered the number of Pax8+ cells on the glomerular tuft in anti-GBM nephritis, indicating accelerated resolution of the cellular crescents. The linagliptin treatment did not change the podocyte stress in both therapeutic groups. Therapeutic intervention with linagliptin resulted in weaker amelioration of renal disease on Week 8 than did preventive intervention.

CONCLUSION AND IMPLICATIONS

DPP-4 inhibition with linagliptin ameliorates renal injury in a rat model of anti-GBM, indicating that linagliptin not only is a secure therapy in diabetes but also can improve resolution of glomerular injury and healing in non-diabetic renal disease.

Protective effects of DPP-4 inhibitor on podocyte injury in glomerular diseases

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) is a serine protease that inhibits the degradation of glucagon-like peptide 1. DPP-4 inhibitors are used worldwide to treat type 2 diabetes mellitus and were recently shown to have pleiotropic effects such as anti-oxidant, anti-inflammatory, and anti-fibrotic actions. DPP-4 inhibitors improve albuminuria and renal injury including glomerular damage independent of its hypoglycemic effect. Although DPP-4 is mainly expressed in the kidney, the physiological function of DPP-4 remains unclear.

METHODS

The localization of renal DPP-4 activity was determined in human renal biopsy specimens with glycyl-1-prolyl-4-methoxy-2-naphthylamide and the effects of a DPP-4 inhibitor were examined in human cultured podocyte.

RESULTS

DPP-4 activity under normal conditions was observed in some Bowman's capsular epithelial cells and proximal tubules, but not in the glomerulus. DPP-4 activity was observed in crescent formation in anti-neutrophil myeloperoxidase cytoplasmic antigen antibody nephritis, nodular lesions in diabetic nephropathy, and some podocytes in focal segmental glomerulosclerosis. Notably, the DPP-4 inhibitor saxagliptin suppressed DPP-4 activity in podocytes and the proximal tubules. To assess the effect of DPP-4 inhibitor on podocytes, human cultured podocytes were injured by Adriamycin, which increased DPP-4 activity; this activity was dose-dependently suppressed by saxagliptin. Treatment with saxagliptin maintained the structure of synaptopodin and RhoA. Saxagliptin also improved the detachment of podocytes.

CONCLUSIONS

DPP-4 activity induces degradation of synaptopodin and reduction of RhoA, resulting in destruction of the podocyte cytoskeleton. Saxagliptin may have pleiotropic effects to prevent podocyte injury.

The effect of linagliptin on renal progression in type-2 diabetes mellitus patients with chronic kidney disease: A prospective randomized controlled study

BACKGROUND

Linagliptin does not require dose adjustment in diabetes mellitus patients with chronic kidney disease (CKD). But, renal effects of linagliptin are not clear. Our aim was to examine the effect of linagliptin on renal disease progression in only insulin dependent type 2 diabetes mellitus (DM) patients with CKD.

METHODS

Stage 3-4 CKD patients were randomized into 2 groups in this prospective randomized controlled study. In the first group, linagliptin 5mg was added in addition to the background insulin therapy. In the second group, patients continued their insulin therapy. Patients were followed up at 3-month intervals for one year.

RESULTS

The study population consisted of 164 patients (90 patients in linagliptin group, 74 patients in other group) with a mean age of 67.5±8.8 years. eGFR significantly increased in linagliptin group (p=0.033), but decreased in other group (p=0.003). No significant change was observed in total insulin dose in linagliptin group (p=0.111), but in other group, total insulin dose significantly increased (p<0.001). Proteinuria levels decreased in both groups, but there was no significant change. In the multiple logistic regression analysis, male gender and proteinuria emerged as variables that showed significant association with increased risk and the use of linagliptin emerged as variable that showed significant association with decreased risk for CKD progression.

CONCLUSION

Linagliptin in DM patients with CKD was able to improve renal progression without significant effect on proteinuria and glucose control. With regard to treating diabetic nephropathy, linagliptin may offer a new therapeutic approach.

Poricoic acid A activates AMPK to attenuate fibroblast activation and abnormal extracellular matrix remodelling in renal fibrosis

BACKGROUND

In chronic kidney disease, although fibrosis prevention is beneficial, few interventions are available that specifically target fibrogenesis. Poricoic acid A (PAA) isolated from Poria cocos exhibits anti-fibrotic effects in the kidney, however the underlying mechanisms remain obscure.

PURPOSE

We isolated PAA and investigated its effects and the underlying mechanisms in renal fibrosis.

STUDY DESIGN

Unilateral ureteral obstruction (UUO) and 5/6 nephrectomy (Nx) animal models and TGF-β1-induced renal fibroblasts (NRK-49F) were used to investigate the anti-fibrotic activity of PAA and its underlying mechanisms.

METHODS

Western blots, qRT-PCR, immunofluorescence staining, co-immunoprecipitation and molecular docking methods were used. Knock-down and knock-in of adenosine monophosphate-activated protein kinase (AMPK) in the UUO model and cultured NRK-49F cells were employed to verify the mechanisms of action of PAA.

RESULTS

PAA improved renal function and alleviated fibrosis by stimulating AMPK and inhibiting Smad3 specifically in Nx and UUO models. Reduced AMPK activity was associated with Smad3 induction, fibroblast activation, and the accumulation and aberrant remodelling of extracellular matrix (ECM) in human renal puncture samples and cultured NRK-49F cells. PAA stimulated AMPK activity and decreased fibrosis in a dose-dependent manner, thus showing that AMPK was essential for PAA to exert its anti-fibrotic effects. AMPK deficiency reduced the anti-fibrotic effects of PAA, while AMPK overexpression enhanced its effect.

CONCLUSION

PAA activated AMPK and further inhibited Smad3 specifically to suppress fibrosis by preventing aberrant ECM accumulation and remodelling and facilitating the deactivation of fibroblasts.

Sitagliptin ameliorates renal tubular injury in diabetic kidney disease via STAT3-dependent mitochondrial homeostasis through SDF-1α/CXCR4 pathway

Mitochondrial abnormalities play critical roles in diabetic tubular injury progression. Dipeptidyl peptidase-4 (DPP4) inhibitors are widely used antihyperglycemic agents that exert renal protective and positive effects against mitochondrial dysfunction in diabetic kidney disease (DKD). However, their underlying mechanism remains unclear. In this study, DPP4 upregulation, mitochondrial fragmentation, and altered mitochondrial dynamics-associated protein expression were observed in the tubules of DBA2/J (D2) diabetic mice with unilateral nephrectomy and in albumin-stimulated tubular cells. The inhibition of DPP4 by sitagliptin (Sita) ameliorated these mitochondrial perturbations both in vivo and in vitro, whereas DPP4 overexpression aggravated mitochondrial fusion-fission disorder and tubular cell injury in albumin-treated HK-2 cells. Downstream of DPP4, the SDF-1α/CXCR4 pathway was significantly suppressed in diabetic tubules. After Sita treatment, this signaling pathway was restored, and the mitochondrial dynamics was improved. Furthermore, a direct interaction between STAT3 and OPA1 was found in the mitochondria of tubular cells, and this effect was weakened by overloading albumin and by CXCR4 siRNA treatment, suggesting a possible link between DPP4-mediated SDF-1α/CXCR4/STAT3 signaling and mitochondrial dysfunction in diabetic tubular cells. The results suggest that a novel mechanism links the DPP4 enzyme to impaired mitochondrial dynamics homeostasis during tubular injury in DKD and highlight that the SDF-1α/CXCR4/STAT3 signaling pathway could become a potential target for managing DKD.

Dipeptidyl peptidase-4 inhibitor teneligliptin accelerates recovery from cisplatin-induced acute kidney injury by attenuating inflammation and promoting tubular regeneration

BACKGROUND

Cisplatin is an effective chemotherapeutic agent. However, acute kidney injury (AKI) and subsequent kidney function decline limits its use. Dipeptidyl peptidase-4 (DPP-4) inhibitor has been reported to attenuate kidney injury in some in vivo models, but the mechanisms-of-action in tubule recovery upon AKI remain speculative. We hypothesized that DPP-4 inhibitor teneligliptin (TG) can facilitate kidney recovery after cisplatin-induced AKI.

METHODS

In in vivo experiment, AKI was induced in rats by injecting 5 mg/kg of cisplatin intravenously. Oral administration of 10 mg/kg of TG, once a day, was started just before injecting cisplatin or from Day 5 after cisplatin injection. In an in vitro experiment, proliferation of isolated murine tubular cells was evaluated with 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, cell cycle analysis and cell counting. Cell viability was analysed by MTT assay or lactate dehydrogenase (LDH) assay.

RESULTS

In in vivo experiments, we found that TG attenuates cisplatin-induced AKI and accelerates kidney recovery after the injury by promoting the proliferation of surviving epithelial cells of the proximal tubule. TG also suppressed intrarenal tumour necrosis factor-α expression, and induced macrophage polarization towards the anti-inflammatory M2 phenotype, both indirectly endorsing tubule recovery upon cisplatin injury. In in vitro experiments, TG directly accelerated the proliferation of primary tubular epithelial cells. Systematic screening of the DPP-4 substrate chemokines in vitro identified CXC chemokine ligand (CXCL)-12 as a promoted mitogenic factor. CXCL12 not only accelerated proliferation but also inhibited cell death of primary tubular epithelial cells after cisplatin exposure. CXC chemokine receptor (CXCR)-4 antagonism abolished the proliferative effect of TG.

CONCLUSIONS

The DPP-4 inhibitor TG can accelerate tubule regeneration and functional recovery from toxic AKI via an anti-inflammatory effect and probably via inhibition of CXCL12 breakdown. Hence, DPP-4 inhibitors may limit cisplatin-induced nephrotoxicity and improve kidney function in cancer patients.

Linagliptin affects IRS1/Akt signaling and prevents high glucose-induced apoptosis in podocytes

Diabetes-induced podocyte apoptosis is considered to play a critical role in the pathogenesis of diabetic kidney disease (DKD). We proposed that hyperglycaemia can induce podocyte apoptosis by inhibiting the action of podocyte survival factors, thus inactivating the cellular effects of insulin signalling. In this study, we aimed to determine the effects of linagliptin on high glucose-induced podocyte apoptosis. Linagliptin reduced the increase in DNA fragmentation as well as the increase in TUNEL-positive cells in podocytes induced by high-glucose condition. Furthermore, linagliptin improved insulin-induced phosphorylation of insulin receptor substrate 1 (IRS1) and Akt, which was inhibited in high-glucose conditions. Adenoviral vector-mediated IRS1 overexpression in podocytes partially normalised DNA fragmentation in high-glucose conditions, while downregulation of IRS1 expression using small interfering RNA increased DNA fragmentation even in low-glucose conditions. Because reactive oxygen species inhibit glomerular insulin signalling in diabetes and Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway is one of the most important intrinsic antioxidative systems, we evaluated whether linagliptin increased Nrf2 in podocytes. High-glucose condition and linagliptin addition increased Nrf2 levels compared to low-glucose conditions. In summary, linagliptin offers protection against DKD by enhancing IRS1/Akt insulin signalling in podocytes and partially via the Keap1/Nrf2 pathway. Our findings suggest that linagliptin may induce protective effects in patients with DKD, and increasing IRS1 levels could be a potential therapeutic target in DKD.

Linagliptin and telmisartan induced effects on renal and urinary exosomal miRNA expression in rats with 5/6 nephrectomy

Dipeptidyl peptidase 4 inhibitors and angiotensin II receptor blockers attenuate chronic kidney disease progression in experimental diabetic and non-diabetic nephropathy in a blood pressure and glucose independent manner, but the exact molecular mechanisms remain unclear. MicroRNAs (miRNAs) are short, non-coding RNA species that are important post-transcriptional regulators of gene expression and play an important role in the pathogenesis of nephropathy. miRNAs are present in urine in a remarkably stable form, packaged in extracellular vesicles. Here, we investigated linagliptin and telmisartan induced effects on renal and urinary exosomal miRNA expression in 5/6 nephrectomized rats. In the present study, renal miRNA profiling was conducted using the Nanostring nCounter technology and mRNA profiling using RNA sequencing from the following groups of rats: sham operated plus placebo; 5/6 nephrectomy plus placebo; 5/6 nephrectomy plus telmisartan; and 5/6 nephrectomy plus linagliptin. TaqMan Array miRNA Cards were used to evaluate which of the deregulated miRNAs in the kidney are present in urinary exosomes. In kidneys from 5/6 nephrectomized rats, the expression of 13 miRNAs was significantly increased (>1.5-fold, P < 0.05), whereas the expression of 7 miRNAs was significantly decreased (>1.5-fold, P < 0.05). Most of the deregulated miRNA species are implicated in endothelial-to-mesenchymal transition and inflammatory processes. Both telmisartan and linagliptin suppressed the induction of pro-fibrotic miRNAs, such as miR-199a-3p, and restored levels of anti-fibrotic miR-29c. In conclusion, the linagliptin and telmisartan-induced restorative effects on miR-29c expression were reflected in urinary exosomes, suggesting that miRNA profiling of urinary exosomes might be used as a biomarker for CKD progression and monitoring of treatment effects.

Effect of dipeptidyl peptidase-4 inhibitors on cisplatin-induced acute nephrotoxicity in cancer patients with diabetes mellitus: A retrospective study

BACKGROUND

Cisplatin is a highly effective chemotherapeutic agent. However, acute kidney injury (AKI) limits its subsequent use, resulting in poor cancer prognosis. Dipeptidyl peptidase-4 (DPP-4) inhibitors have been reported to attenuate cisplatin-induced AKI in animal models, but the effect in human patients remains to be clarified. We hypothesized that DPP-4 inhibitors can prevent cisplatin-induced AKI in diabetic-cancer patients.

METHODS

We retrospectively reviewed all consecutive cancer patients who were treated with a first cycle of cisplatin-containing regimen between January 2011 and October 2019. We analysed data of diabetic-cancer patients treated with high-dose cisplatin (> 50 mg/m2)-containing regimens. The change of estimated glomerular filtration rate (eGFR) within 2 weeks after cisplatin treatment was compared between the patients treated with DPP-4 inhibitors and those treated without DPP-4 inhibitors.

RESULTS

A total of 455 patients were treated with cisplatin during the period. Of these, 34 patients were eligible for the analysis. The change of eGFR was significantly less in the patients treated with DPP-4 inhibitors, compared to those without DPP-4 inhibitors [the percentages of eGFR decline (mean ± SD) was 23.6 ± 20.3% vs 43.1± 20.1%, respectively; P = 0.010]. Furthermore, the incidence of AKI was significantly less in the patients treated with DPP-4 inhibitors (25% vs 64%, respectively; P = 0.026).

CONCLUSIONS

DPP-4 inhibitors may decrease the risk of cisplatin-induced AKI in diabetic patients.

Gemigliptin Attenuates Renal Fibrosis Through Down-Regulation of the NLRP3 Inflammasome

BACKGROUND

The hypoglycemic drugs dipeptidyl peptidase-4 (DPP-4) inhibitors have proven protective effects on diabetic kidney disease, including renal fibrosis. Although NOD-like receptor protein 3 (NLRP3) inflammasome activation is known to play an important role in the progression of renal fibrosis, the impact of DPP-4 inhibition on NLRP3-mediated inflammation while ameliorating renal fibrosis has not been fully elucidated. Here, we report that the renoprotective effect of gemigliptin is associated with a reduction in NLRP3-mediated inflammation in a murine model of renal fibrosis.

METHODS

We examined the effects of gemigliptin on renal tubulointerstitial fibrosis induced in mice by unilateral ureteral obstruction (UUO). Using immunohistochemical and Western blot analysis, we quantitated components of the NLRP3 inflammasome in kidneys with and without gemigliptin treatment, and in vitro in human kidney tubular epithelial human renal proximal tubule cells (HK-2) cells, we further analyzed the effect of gemigliptin on transforming growth factor-β (TGF-β)-stimulated production of profibrotic proteins.

RESULTS

Immunohistological examination revealed that gemigliptin ameliorated UUO-induced tubular atrophy and renal fibrosis. Gemigliptin-treated kidneys showed a reduction in levels of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, and interleukin-1β, which had all been markedly increased by UUO. In line with the in vivo results, TGF-β markedly increased NLRP3 inflammasome markers, which were attenuated by gemigliptin treatment. Furthermore, gemigliptin treatment attenuated phosphorylated nuclear factor-κB levels, which had been increased in the UUO kidney as well as in TGF-β-treated cultured renal cells.

CONCLUSION

The present study shows that activation of the NLRP3 inflammasome contributes to UUO-induced renal fibrosis and the renoprotective effect of gemigliptin is associated with attenuation of NLRP3 inflammasome activation.

Reno-protective effect of linagliptin against gentamycin nephrotoxicity in rats

BACKGROUND

Recent studies demonstrated the reno-protective effects of two dipeptidyl peptidase-4 (DPP-4) inhibitors, saxagliptin and sitagliptin, against gentamycin-induced renal injury. However, none of these studies investigated whether renal DPP-4 contributes to the pathogenesis of this nephrotoxicity or not. This prompted us to test this hypothesis and to assess, for the first time, the potential reno-protective effect of linagliptin and whether this action is related or not to DPP-4 inhibition. Lingliptin was chosen since it is mainly excreted through a non-renal pathway and can therefore be used safely in individuals with renal injury.

METHODS

Male Sprague-Dawley rats were administered gentamycin (100 mg/kg/day, ip for 10 days) alone or combined with linagliptin (3 mg/kg/day, orally for 14 days). Gentamycin was administered once daily during the last ten days of the linagliptin treatment.

RESULTS

Linagliptin administration ameliorated gentamycin-induced renal injury and restored renal functional, oxidative, inflammatory, apoptotic and histopathological changes. Furthermore, the current study highlighted the role of increased plasma and renal DPP-4 in the pathogenesis of gentamycin renal insults and showed that the potential reno-protective effect of linagliptin is partly, mediated via inhibition of DPP-4, in addition to other antioxidant, anti-inflammatory and anti-apoptotic actions.

CONCLUSION

Linagliptin may serve as a beneficial adjutant to reduce gentamycin-induced renal injury.

More than just an enzyme: Dipeptidyl peptidase-4 (DPP-4) and its association with diabetic kidney remodelling

PURPOSE OF THE REVIEW

This review article discusses recent advances in the mechanism of dipeptidyl peptidase-4 (DPP-4) actions in renal diseases, especially diabetic kidney fibrosis, and summarizes anti-fibrotic functions of various DPP-4 inhibitors in diabetic nephropathy (DN).

RECENT FINDINGS

DN is a common complication of diabetes and is a leading cause of the end-stage renal disease (ESRD). DPP-4 is a member of serine proteases, and more than 30 substrates have been identified that act via several biochemical messengers in a variety of tissues including kidney. Intriguingly, DPP-4 actions on the diabetic kidney is a complex mechanism, and a variety of pathways are involved including increasing GLP-1/SDF-1, disrupting AGE-RAGE pathways, and integrin-β- and TGF-β-Smad-mediated signalling pathways that finally lead to endothelial to mesenchymal transition. Interestingly, an array of DPP-4 inhibitors is well recognized as oral drugs to treat type 2 diabetic (T2D) patients, which promote better glycemic control. Furthermore, recent experimental and preclinical data reveal that DPP-4 inhibitors may also exhibit protective effects in renal disease progression including anti-fibrotic effects in the diabetic kidney by attenuating above signalling cascade(s), either singly or as a combinatorial effect. In this review, we discussed the anti-fibrotic effects of DPP-4 inhibitors based on recent reports along with the possible mechanism of actions and future perspectives to underscore the beneficial effects of DPP-4 inhibitors in DN.

SUMMARY

With recent experimental, preclinical, and clinical evidence, we summarized DPP-4 activities and its mechanism of actions in diabetic kidney diseases. A knowledge gap of DPP-4 inhibition in controlling renal fibrosis in DN has also been postulated in this review for future research perspectives.

Cardioprotection Conferred by Sitagliptin Is Associated with Reduced Cardiac Angiotensin II/Angiotensin-(1-7) Balance in Experimental Chronic Kidney Disease

Dipeptidyl peptidase IV (DPPIV) inhibitors are antidiabetic agents that exert renoprotective actions independently of glucose lowering. Cardiac dysfunction is one of the main outcomes of chronic kidney disease (CKD); however, the effects of DPPIV inhibition on cardiac impairment during CKD progression remain elusive. This study investigated whether DPPIV inhibition mitigates cardiac dysfunction and remodeling in rats with a 5/6 renal ablation and evaluated if these effects are associated with changes in the cardiac renin-angiotensin system (RAS). To this end, male Wistar rats underwent a 5/6 nephrectomy (Nx) or sham operation, followed by an 8-week treatment period with the DPPIV inhibitor sitagliptin (IDPPIV) or vehicle. Nx rats had lower glomerular filtration rate, overt albuminuria and higher blood pressure compared to sham rats, whereas CKD progression was attenuated in Nx + IDPPIV rats. Additionally, Nx rats exhibited cardiac hypertrophy and fibrosis, which were associated with higher cardiac DPPIV activity and expression. The sitagliptin treatment prevented cardiac fibrosis and mitigated cardiac hypertrophy. The isovolumic relaxation time (IRVT) was higher in Nx than in sham rats, which was suggestive of CKD-associated-diastolic dysfunction. Sitagliptin significantly attenuated the increase in IRVT. Levels of angiotensin II (Ang II) in the heart tissue from Nx rats were higher while those of angiotensin-(1-7) Ang-(1-7) were lower than that in sham rats. This cardiac hormonal imbalance was completely prevented by sitagliptin. Collectively, these results suggest that DPPIV inhibition may delay the onset of cardiovascular impairment in CKD. Furthermore, these findings strengthen the hypothesis that a crosstalk between DPPIV and the renin-angiotensin system plays a role in the pathophysiology of cardiorenal syndromes.

Mechanisms of GLP-1 receptor-independent renoprotective effects of the dipeptidyl peptidase type 4 inhibitor linagliptin in GLP-1 receptor knockout mice with 5/6 nephrectomy

Dipeptidyl peptidase type 4 (DPP-4) inhibitors were reported to have beneficial effects in experimental models of chronic kidney disease. The underlying mechanisms are not completely understood. However, these effects could be mediated via the glucagon-like peptide-1 (GLP-1)/GLP-1 receptor (GLP1R) pathway. Here we investigated the renal effects of the DPP-4 inhibitor linagliptin in Glp1r-/- knock out and wild-type mice with 5/6 nephrectomy (5/6Nx). Mice were allocated to groups: sham+wild type+placebo; 5/6Nx+ wild type+placebo; 5/6Nx+wild type+linagliptin; sham+knock out+placebo; 5/6Nx+knock out+ placebo; 5/6Nx+knock out+linagliptin. 5/6Nx caused the development of renal interstitial fibrosis, significantly increased plasma cystatin C and creatinine levels and suppressed renal gelatinase/collagenase, matrix metalloproteinase-1 and -13 activities; effects counteracted by linagliptin treatment in wildtype and Glp1r-/- mice. Two hundred ninety-eight proteomics signals were differentially regulated in kidneys among the groups, with 150 signals specific to linagliptin treatment as shown by mass spectrometry. Treatment significantly upregulated three peptides derived from collagen alpha-1(I), thymosin β4 and heterogeneous nuclear ribonucleoprotein A1 (HNRNPA1) and significantly downregulated one peptide derived from Y box binding protein-1 (YB-1). The proteomics results were further confirmed using western blot and immunofluorescence microscopy. Also, 5/6Nx led to significant up-regulation of renal transforming growth factor-β1 and pSMAD3 expression in wild type mice and linagliptin significantly counteracted this up-regulation in wild type and Glp1r-/- mice. Thus, the renoprotective effects of linagliptin cannot solely be attributed to the GLP-1/GLP1R pathway, highlighting the importance of other signaling pathways (collagen I homeostasis, HNRNPA1, YB-1, thymosin β4 and TGF-β1) influenced by DPP-4 inhibition.

Protective effects of Pai-Du-Yang-Shen formula on chronic renal failure in rats

This study aimed to elucidate the therapeutic effects of a traditional Chinese medicine, Pai-Du-Yang-Shen (PDYS) Formula, in 5/6 nephrectomy-induced chronic renal failure (CRF). The CRF model was established via 5/6 nephrectomy (Nx) in rats. Then, PDYS (0.9 and 1.8 g/kg/day), or an equal amount of normal saline, was administrated to the rats in respective groups. Our results showed that PDYS treatment improved degeneration, fibrosis, and histopathological abnormalities of renal tissues in 5/6 Nx rats. Furthermore, the increase in serum creatinine (Scr), blood urea nitrogen (BUN), and total urinary protein (TUP) in 5/6 Nx rats was reduced by PDYS treatment. In addition, the levels of tumor necrosis factor (TNF), fibronectin (FN), and laminin (LN) that were induced in 5/6 Nx rats were also decreased by PDYS treatment. Finally, relative mRNA expression of α-smooth muscle actin (α-SMA), FN, transforming growth factor-β (TGF-β), and TNF as well as protein levels of TGF-β, NF-κB p65, and phosphorylated NF-κB p65 (p-p65) in renal tissues correlated with the concentration of TNF. In conclusion, PDYS shows therapeutic effects against CRF as determined by a reduction in markers for inflammation and fibrosis.

Contribution of bone marrow-derived cells to in situ engineered tissue capsules in a rat model of chronic kidney disease

Tissue engineered blood vessels (TEBVs) hold great promise for clinical use in patients with end stage renal disease (ESRD) requiring vascular access for hemodialysis. A promising way to make TEBVs is to exploit foreign body response (FBR) of polymeric rods used as templates. However, since the FBR predominantly involves bone-marrow (BM) derived cells and ESRD coincides with impaired function of BM, it is important to assess the generation of TEBVs in conditions of renal failure. To this end, we implanted polymer rods in the subcutis of rats after BM-transplantation with GFP-labeled BM cells in a model of chronic kidney disease (CKD). At 3 weeks after implantation, rods were encapsulated by tissue capsule (TC) composed of collagen, myofibroblasts and macrophages. On average, 13% of CD68⁺ macrophages were GFP⁺, indicating BM origin. Macrophage-to-myofibroblasts differentiation appeared to play an important role in TC formation as 26% of SMA⁺/GFP⁺ myofibroblasts co-expressed the macrophage marker CD68. Three weeks after rod implantation, the cellular response changed towards tissue repair, characterized by 40% increase in CD68⁺/CD163⁺ repair associated macrophages and 95% increase in TGFβ and IL10 gene expression as compared to TCs harvested at 1 week. These results show that both BM derived and tissue resident cells, contribute to TC formation, whereas macrophages serve as precursors of myofibroblasts in mature TCs. Finally, the presence of CKD did not significantly alter the process of TC formation, which holds the potential to support our approach for future clinical use in ESRD patients.

Folate treatment of pregnant rat dams abolishes metabolic effects in female offspring induced by a paternal pre-conception unhealthy diet

AIMS/HYPOTHESIS

Paternal high-fat diet prior to mating programmes impaired glucose tolerance in female offspring. We examined whether the metabolic consequences in offspring could be abolished by folate treatment of either the male rats before mating or the corresponding female rats during pregnancy.

METHODS

Male F0 rats were fed either control diet or high-fat, high-sucrose and high-salt diet (HFSSD), with or without folate, before mating. Male rats were mated with control-diet-fed dams. After mating, the F0 dams were fed control diet with or without folate during pregnancy.

RESULTS

Male, but not female offspring of HFSSD-fed founders were heavier than those of control-diet-fed counterparts (p < 0.05 and p = 0.066 in males and females, respectively). Both male and female offspring of HFSSD-fed founders were longer compared with control (p < 0.01 for both sexes). Folate treatment of the pregnant dams abolished the effect of the paternal diet on the offspring's body length (p ˂ 0.05). Female offspring of HFSSD-fed founders developed impaired glucose tolerance, which was restored by folate treatment of the dams during pregnancy. The beta cell density per pancreatic islet was decreased in offspring of HFSSD-fed rats (-20% in male and -15% in female F1 offspring, p ˂ 0.001 vs controls). Folate treatment significantly increased the beta cell density (4.3% and 3.3% after folate supplementation given to dams and founders, respectively, p ˂ 0.05 vs the offspring of HFSSD-fed male rats). Changes in liver connective tissue of female offspring of HFSSD-fed founders were ameliorated by treatment of dams with folate (p ˂ 0.01). Hepatic Ppara gene expression was upregulated in female offspring only (1.51-fold, p ˂ 0.05) and was restored in the female offspring by folate treatment (p ˂ 0.05). We observed an increase in hepatic Lcn2 and Tmcc2 expression in female offspring born to male rats exposed to an unhealthy diet during spermatogenesis before mating (p ˂ 0.05 vs controls). Folate treatment of the corresponding dams during pregnancy abolished this effect (p ˂ 0.05). Analysis of DNA methylation levels of CpG islands in the Ppara, Lcn2 and Tmcc2 promoter regions revealed that the paternal unhealthy diet induced alterations in the methylation pattern. These patterns were also affected by folate treatment. Total liver DNA methylation was increased by 1.52-fold in female offspring born to male rats on an unhealthy diet prior to mating (p ˂ 0.05). This effect was abolished by folate treatment during pregnancy (p ˂ 0.05 vs the offspring of HFSSD-fed male rats).

CONCLUSIONS/INTERPRETATION

Folate treatment of pregnant dams restores effects on female offspring's glucose metabolism induced by pre-conception male founder HFSSD.

Long-Term Effects of Ipragliflozin on Diabetic Nephropathy and Blood Pressure in Patients With Type 2 Diabetes: 104-Week Follow-up of an Open-Label Study

Background

In our previous study, we investigated the efficacy of ipragliflozin, a sodium-glucose cotransporter (SGLT) 2 inhibitor on diabetic nephropathy in patients with type 2 diabetes and demonstrated that ipragliflozin significantly improved diabetic nephropathy in addition to reducing HbA1c and body weight. Herein, we conducted post-trial monitoring to determine whether these lowering effects on blood glucose and body weight or the beneficial effects on diabetic nephropathy were maintained long-term (104 weeks) after starting ipragliflozin treatment.

Methods

Initially, during a 24-week interventional trial period, a 50 mg dose of ipragliflozin was administered to 50 patients with type 2 diabetes without changing other treatments. During the post-trial monitoring period, these patients returned to hospital-based diabetes care according to their clinical needs. We continued monitoring their clinical data for 104 weeks in each hospital and analyzed the results on an intention-to-treat basis.

Results

The improvements in glycemic control and body weight reduction provided by 24-week ipragliflozin administration were maintained for 104 weeks. Despite a transient decrease during the intervention period, the estimated glomerular filtration rate (eGFR) was restored to near the baseline level at 104 weeks. Notably, in patients with diabetic nephropathy, the median urinary albumin-to-creatinine ratio (UACR) was significantly decreased from 119.2 (98.9 - 201.8) at baseline to 36.9 (19.7 - 204.7) mg/gCr at 104 weeks. In addition, eGFR was stable for 104 weeks, showing no decrease. In contrast, a significant positive correlation between UACR and blood pressure observed at 24 weeks disappeared after discontinuation of the intervention therapy.

Conclusions

The well-controlled HbA1c and body weight reductions were maintained for 104 weeks of post-trial follow-up. Moreover, ipragliflozin significantly reduced urinary albumin excretion in patients with diabetic nephropathy without decreasing eGFR.

AMP-activated kinase is a regulator of fibroblast growth factor 23 production

Fibroblast growth factor 23 (FGF23) is a proteohormone regulating renal phosphate transport and vitamin D metabolism as well as inducing left heart hypertrophy. FGF23-deficient mice suffer from severe tissue calcification, accelerated aging and a myriad of aging-associated diseases. Bone cells produce FGF23 upon store-operated calcium ion entry (SOCE) through the calcium selective ion channel Orai1. AMP-activated kinase (AMPK) is a powerful energy sensor helping cells survive states of energy deficiency, and AMPK down-regulates Orai1. Here we investigated the role of AMPK in FGF23 production. Fgf23 gene transcription was analyzed by qRT-PCR and SOCE by fluorescence optics in UMR106 osteoblast-like cells while the serum FGF23 concentration and phosphate metabolism were assessed in AMPKα1-knockout and wild-type mice. The AMPK activator, 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) down-regulated, whereas the AMPK inhibitor, dorsomorphin dihydrochloride (compound C) and AMPK gene silencing induced Fgf23 transcription. AICAR decreased membrane abundance of Orai1 and SOCE. SOCE inhibitors lowered Fgf23 gene expression induced by AMPK inhibition. AMPKα1-knockout mice had a higher serum FGF23 concentration compared to wild-type mice. Thus, AMPK participates in the regulation of FGF23 production in vitro and in vivo. The inhibitory effect of AMPK on FGF23 production is at least in part mediated by Orai1-involving SOCE.

Plant dipeptidyl peptidase-IV inhibitors as antidiabetic agents: a brief review

Diabetes mellitus is an increasing public health problem in the world. Type 2 diabetes is the most common type of diabetes whose complications contribute to its high death rate. It seriously impacts healthcare systems and patients' quality of life. Therefore, effective measures and new treatment strategies are needed to solve this increasingly serious global problem. In recent years, inhibition of dipeptidyl peptidase IV (DPP-IV) has emerged as a new treatment option for Type 2 diabetes. This article reviews various plant DPP-IV inhibitors that showed inhibition toward enzyme as a major target for the management of Type 2 diabetes. These studies can contribute to the future development of DPP-IV inhibitors as drugs.

The MARLINA-T2D trial: putting the results into clinical perspective

Chronic kidney disease (CKD) and type 2 diabetes mellitus (T2D) frequently coexist and are associated with poor clinical outcomes. Dipeptidyl peptidase-4 (DPP-4) inhibitors can be used for patients with T2D and CKD, and preclinical evidence suggests these agents may slow the progression of kidney disease in T2D. Although clinical evidence of the renal effects of DPP-4 inhibitors is limited, the recent publication of the MARLINA-T2D study provided important new data. In MARLINA-T2D, linagliptin was associated with significant improvements in glycemic control with a non-significant reduction in albuminuria and no evidence of renal adverse effects in a high-risk population of patients with T2D and early diabetic kidney disease. Although there was no conclusive evidence of renoprotective effects, previous research suggests that clinically apparent renal benefits might develop with longer term treatment. The results of ongoing trials with primary renal endpoints are awaited with interest.

Dipeptidyl peptidase-4 inhibition and renoprotection: the role of antifibrotic effects

PURPOSE OF REVIEW

This article analyzes the potential beneficial effects of dipeptidyl peptidase (DPP)-4 inhibitors on renal diseases.

RECENT FINDINGS

The pathological significance of DPP-4, either dependent or independent on catalytic activities, on renal diseases has been reported in preclinical studies. With regard to this, we have shown that damaged endothelial cells are converted to a mesenchymal cell phenotype, which is associated with the induction of DPP-4 in endothelial cells. The endothelial mesenchymal transition may contribute to kidney fibrosis; indeed, the antifibrotic effects of DPP-4 inhibitors have been reported elsewhere. However, even though such potential benefits of DPP-4 inhibitors on renal diseases were shown in preclinical studies, clinical trials have not yet revealed significant benefits in renal hard outcomes of DPP-4 inhibitors.

SUMMARY

To completely understand the beneficial effects of DPP-4 inhibitors, both the following studies are required: first, preclinical studies that analyze deeper molecular mechanisms of DPP-4 inhibition, and, second, clinical studies that investigate whether such potential beneficial effects of DPP-4 inhibitors are relevant to the patients in the clinic.

The role of dipeptidylpeptidase-4 inhibitors in management of cardiovascular disease in diabetes; focus on linagliptin

Multiple population based analyses have demonstrated a high incidence of cardiovascular disease (CVD) and cardiovascular (CV) mortality in subjects with T2DM that reduces life expectancy by as much as 15 years. Importantly, the CV system is particularly sensitive to the metabolic and immune derangements present in obese pre-diabetic and diabetic individuals; consequently, CV dysfunction is often the initial CV derangement to occur and promotes the progression to end organ/tissue damage in T2DM. Specifically, diabetic CVD can manifest as microvascular complications, such as nephropathy, retinopathy, and neuropathy, as well as, macrovascular impairments, including ischemic heart disease, peripheral vascular disease, and cerebrovascular disease. Despite some progress in prevention and treatment of CVD, mainly via blood pressure and dyslipidemia control strategies, the impact of metabolic disease on CV outcomes is still a major challenge and persists in proportion to the epidemics of obesity and diabetes. There is abundant pre-clinical and clinical evidence implicating the DPP-4-incretin axis in CVD. In this regard, linagliptin is a unique DPP-4 inhibitor with both CV and renal safety profiles. Moreover, it exerts beneficial CV effects beyond glycemic control and beyond class effects. Linagliptin is protective for both macrovascular and microvascular complications of diabetes in preclinical models, as well as clinical models. Given the role of endothelial-immune cell interactions as one of the key events in the initiation and progression of CVD, linagliptin modulates these cell–cell interactions by affecting two important pathways involving stimulation of NO signaling and potent inhibition of a key immunoregulatory molecule.

Rationale, design, and baseline characteristics of the CArdiovascular safety and Renal Microvascular outcomE study with LINAgliptin (CARMELINA®): a randomized, double-blind, placebo-controlled clinical trial in patients with type 2 diabetes and high cardio-renal risk

Background

Cardiovascular (CV) outcome trials in type 2 diabetes (T2D) have underrepresented patients with chronic kidney disease (CKD), leading to uncertainty regarding their kidney efficacy and safety. The CARMELINA^® trial aims to evaluate the effects of linagliptin, a DPP-4 inhibitor, on both CV and kidney outcomes in a study population enriched for cardio-renal risk.

Methods

CARMELINA^® is a randomized, double-blind, placebo-controlled clinical trial conducted in 27 countries in T2D patients at high risk of CV and/or kidney events. Participants with evidence of CKD with or without CV disease and HbA1c 6.5–10.0% (48–86 mmol/mol) were randomized 1:1 to receive linagliptin once daily or matching placebo, added to standard of care adjusted according to local guidelines. The primary outcome is time to first occurrence of CV death, non-fatal myocardial infarction, or non-fatal stroke. The key secondary outcome is a composite of time to first sustained occurrence of end-stage kidney disease, ≥ 40% decrease in estimated glomerular filtration rate (eGFR) from baseline, or renal death. CV and kidney events are prospectively adjudicated by independent, blinded clinical event committees. CARMELINA^® was designed to continue until at least 611 participants had confirmed primary outcome events. Assuming a hazard ratio of 1.0, this provides 90% power to demonstrate non-inferiority of linagliptin versus placebo within the pre-specified non-inferiority margin of 1.3 at a one-sided α-level of 2.5%. If non-inferiority of linagliptin for the primary outcome is demonstrated, then its superiority for both the primary outcome and the key secondary outcome will be investigated with a sequentially rejective multiple test procedure.

Results

Between July 2013 and August 2016, 6980 patients were randomized and took ≥ 1 dose of study drug (40.6, 33.1, 16.9, and 9.4% from Europe, South America, North America, and Asia, respectively). At baseline, mean ± SD age was 65.8 ± 9.1 years, HbA1c 7.9 ± 1.0%, BMI 31.3 ± 5.3 kg/m², and eGFR 55 ± 25 mL/min/1.73 m². A total of 5148 patients (73.8%) had prevalent kidney disease (defined as eGFR < 60 mL/min/1.73 m² or macroalbuminuria [albumin-to-creatinine ratio > 300 mg/g]) and 3990 patients (57.2%) had established CV disease with increased albuminuria; these characteristics were not mutually exclusive. Microalbuminuria (n = 2896 [41.5%]) and macroalbuminuria (n = 2691 [38.6%]) were common.

Conclusions

CARMELINA^® will add important information regarding the CV and kidney disease clinical profile of linagliptin by including an understudied, vulnerable cohort of patients with T2D at highest cardio-renal risk.

Trial registration ClinicalTrials.gov identifier—NCT01897532; registered July 9, 2013

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0682-3) contains supplementary material, which is available to authorized users.