Dipeptidyl peptidase-4 inhibition in chronic kidney disease and potential for protection against diabetes-related renal injury

Sitagliptin alleviates renal steatosis and endoplasmic reticulum stress in high fat diet-induced obese rats by targeting SREBP-1/CD36 signaling pathway

High fat diet (HFD) consumption can cause dysregulation of glucose and lipid metabolism, coupled with increased ectopic lipid deposition in renal tissue leading to steatosis and dysfunction. Sitagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor clinically used for type II diabetes therapy; however its effect on renal steatosis in obese state is still uncertain. Herein, obesity was induced by feeding male Wistar rats HFD for 18 weeks, thereafter received either drug vehicle, or sitagliptin (10 mg/kg, PO) along with HFD for further 6 weeks and compared with age-matched rats receiving normal chow diet (NCD). After 24 weeks, serum and kidneys were collected for histological and biochemical assessments. Compared to NCD-fed group, HFD-fed rats displayed marked weight gain, increased fat mass, insulin resistance, dyslipidemia, impaired kidney functions and renal histological alterations. Sitagliptin effectively ameliorated obesity and related metabolic perturbations and improved kidney architecture and function. There were increased levels of triglycerides and cluster of differentiation 36 (CD36) in kidneys of obese rats, that were lowered by sitagliptin therapy. Sitagliptin significantly repressed the expression of lipogenesis genes, while up-regulated genes involved in mitochondrial biogenesis and fatty acid oxidation in kidneys of HFD-fed rats. Sitagliptin was found to induce down-regulation of endoplasmic reticulum (ER) stress and apoptotic markers in kidneys of obese rats. These findings together may emphasize a novel concept that sitagliptin can be an effective therapeutic approach for halting obesity-related renal steatosis and CKD.

The role of basal insulins in the treatment of people with type 2 diabetes and chronic kidney disease: A narrative review

The majority of cases of chronic kidney disease (CKD) worldwide are driven by the presence of type 2 diabetes (T2D), resulting in an increase in CKD rates over the past few decades. The existence of CKD alongside diabetes is associated with increased burden of cardiovascular disease and increased risk of death. Optimal glycaemic control is essential to prevent progression of CKD, but achieving glycaemic targets in people with CKD and diabetes can be challenging because of increased risk of hypoglycaemia and limitations on glucose-lowering therapeutic options. This review considers the challenges in management of T2D in people with impaired kidney function and assesses evidence for use of basal insulin analogues in people with CKD.

Cyclosporine-induced kidney damage was halted by sitagliptin and hesperidin via increasing Nrf2 and suppressing TNF-α, NF-κB, and Bax

Cyclosporine A (CsA) is employed for organ transplantation and autoimmune disorders. Nephrotoxicity is a serious side effect that hampers the therapeutic use of CsA. Hesperidin and sitagliptin were investigated for their antioxidant, anti-inflammatory, and tissue-protective properties. We aimed to investigate and compare the possible nephroprotective effects of hesperidin and sitagliptin. Male Wistar rats were utilized for induction of CsA nephrotoxicity (20 mg/kg/day, intraperitoneally for 7 days). Animals were treated with sitagliptin (10 mg/kg/day, orally for 14 days) or hesperidin (200 mg/kg/day, orally for 14 days). Blood urea, serum creatinine, albumin, cystatin-C (CYS-C), myeloperoxidase (MPO), and glucose were measured. The renal malondialdehyde (MDA), glutathione (GSH), catalase, and SOD were estimated. Renal TNF-α protein expression was evaluated. Histopathological examination and immunostaining study of Bax, Nrf-2, and NF-κB were performed. Sitagliptin or hesperidin attenuated CsA-mediated elevations of blood urea, serum creatinine, CYS-C, glucose, renal MDA, and MPO, and preserved the serum albumin, renal catalase, SOD, and GSH. They reduced the expressions of TNF-α, Bax, NF-κB, and pathological kidney damage. Nrf2 expression in the kidney was raised. Hesperidin or sitagliptin could protect the kidney against CsA through the mitigation of oxidative stress, apoptosis, and inflammation. Sitagliptin proved to be more beneficial than hesperidin.

Linagliptin Mitigates TGF-β1 Mediated Epithelial-Mesenchymal Transition in Tacrolimus-Induced Renal Interstitial Fibrosis via Smad/ERK/P38 and HIF-1α/LOXL2 Signaling Pathways

The dipeptidyl peptidase-4 (DPP-4) inhibitors, a novel anti-diabetic medication family, are renoprotective in diabetes, but a comparable benefit in chronic non-diabetic kidney diseases is still under investigation. This study aimed to elucidate the molecular mechanisms of linagliptin's (Lina) protective role in a rat model of chronic kidney injury caused by tacrolimus (TAC) independent of blood glucose levels. Thirty-two adult male Sprague Dawley rats were equally randomized into four groups and treated daily for 28 d as follows: The control group; received olive oil (1 mL/kg/d, subcutaneously), group 2; received Lina (5 mg/kg/d, orally), group 3; received TAC (1.5 mg/kg/d, subcutaneously), group 4; received TAC plus Lina concomitantly in doses as the same previous groups. Blood and urine samples were collected to investigate renal function indices and tubular injury markers. Additionally, signaling molecules, epithelial-mesenchymal transition (EMT), and fibrotic-related proteins in kidney tissue were assessed by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis, immunohistochemical and histological examinations. Tacrolimus markedly induced renal injury and fibrosis as indicated by renal dysfunction, histological damage, and deposition of extracellular matrix (ECM) proteins. It also increased transforming growth factor β1 (TGF-β1), Smad4, p-extracellular signal-regulated kinase (ERK)1/2/ERK1/2, and p-P38/P38 mitogen-activated protein kinase (MAPK) protein levels. These alterations were markedly attenuated by the Lina administration. Moreover, Lina significantly inhibited EMT, evidenced by inhibiting Vimentin and α-smooth muscle actin (α-SMA) and elevating E-cadherin. Furthermore, Lina diminished hypoxia-related protein levels with a subsequent reduction in Snail and Twist expressions. We concluded that Lina may protect against TAC-induced interstitial fibrosis by modulating TGF-β1 mediated EMT via Smad-dependent and independent signaling pathways.

Pharmacotherapy of type 2 diabetes: An update and future directions

Type 2 diabetes (T2D) is a widely prevalent disease with substantial economic and social impact for which multiple conventional and novel pharmacotherapies are currently available; however, the landscape of T2D treatment is constantly changing as new therapies emerge and the understanding of currently available agents deepens. This review aims to provide an updated summary of the pharmacotherapeutic approach to T2D. Each class of agents is presented by mechanism of action, details of administration, side effect profile, cost, and use in certain populations including heart failure, non-alcoholic fatty liver disease, obesity, chronic kidney disease, and older individuals. We also review targets of novel therapeutic T2D agent development. Finally, we outline an up-to-date treatment approach that starts with identification of an individualized goal for glycemic control then selection, initiation, and further intensification of a personalized therapeutic plan for T2D.

Renal outcomes with sodium-glucose cotransporters 2 inhibitors

Diabetic nephropathy (DN) is one of the most serious complications of diabetes. Therefore, delaying and preventing the progression of DN becomes an important goal in the clinical treatment of type 2 diabetes mellitus. Recent studies confirm that sodium-glucose cotransporters 2 inhibitors (SGLT2is) have been regarded as effective glucose-lowering drugs with renal protective effect. In this review, we summarize in detail the present knowledge of the effects of SGLT2is on renal outcomes by analyzing the experimental data in preclinical study, the effects of SGLT2is on estimated glomerular flitration rates (eGFRs) and urinary albumin-creatinine ratios (UACRs) from clinical trials and observational studies, and renal events (such as renal death or renal failure requiring renal replacement therapy) in some large prospective cardiovaslucar outcomes trials. The underlying mechanisms for renoprotective activity of SGLT2is have been demondtrated in multiple diabetic and nondiabetic animal models including kidney-specific effects and secondary kidney effects related to amelioration in blood glucose and blood pressure. In conclusion, these promising results show that SGLT2is act beneficially in terms of the kidney for diabetic patients.

Clinical efficacy of linagliptin combined with irbesartan in patients with diabetic nephropathy

Objective

To determine the clinical efficacy of linagliptin combined with irbesartan in patients with diabetic nephropathy (DN).

Methods

Seventy-two patients who were admitted to our department of endocrinology in our hospital during January 2018 and June 2019 were randomly divided into a control group (administered with irbesartan only, n=36) and a treatment group (treated with irbesartan and linagliptin, n=36). The course of treatment lasted for three months. FBG (fasting blood glucose), 2hPBG (2h postprandial blood sugar), HbA1C (hemoglobin A1c), Cys-C (cystatin C), SCr (serum creatinine), BUN (blood urea nitrogen), UACR (urine albumin-to-creatinine ratio), CRP (C-reactive protein), IL-6 (interleukin-6), and SOD (superoxide dismutase) were tested pre- and post-treatment to evaluate the clinical efficacy and adverse effects of the two treatment plans after three months of treatment.

Results

Compared with the pre-treatment levels, FBG, 2hPBG, HbA1c, Cys-C, SCr, BUN, UACR, CRP, IL-6, and SOD in both groups were significantly improved following the three-month treatment (P<0.05, respectively). Post-treatment levels of FBG, 2hPBG, HbA1c, Cys-C, SCr, BUN, UACR, CRP, and IL-6 in the treatment group were significantly lower than in the control group (P<0.05, respectively), while the treatment group exhibited a higher level of SOD compared with the control group (P<0.05). No serious adverse reaction occurred in either group (P>0.05).

Conclusion

Combined-modality treatment with linagliptin and irbesartan shows favorable clinical efficacy in treating diabetic nephropathy as it effectively protects the kidneys and improves kidney function by inhibiting inflammatory and oxidative stress responses.

Structure-Activity Relationship Analysis of Cocrystallized Gliptin-like Pyrrolidine, Trifluorophenyl, and Pyrimidine-2,4-Dione Dipeptidyl Peptidase-4 Inhibitors

Approved and potent reported dipeptidyl peptidase-4 (DPP-4) inhibitors with gliptin-like structures are classified here according to their structures and mechanisms of the inhibition in three groups: (i) those with pyrrolidine or analogs as P1 fragment with α-aminoacyl linker, (ii) structures with trifluorophenyl moiety or analogs as P1 fragment with β-aminobutanoyl linker, and (iii) DPP-4 inhibitors with pyrimidine-2,4-dione or analogs as P1' fragment. The structure-activity relationship analysis was performed for those whose cocrystallized structures with the enzyme were published. While inhibitors with pyrrolidine and trifluorophenyl moiety or analogs as P1 fragment bind in a similar way in S1, S2 and S2 extensive domains of the enzyme, the binding mode of pyrimidine-2,4-dione derivatives/analogs differs with additional interactions in S1' and S2' pockets. Three general schemes of fragmented gliptins and gliptin-like structures with the enzyme and protein-ligand interaction fingerprints were made, which might be useful in the creation of DPP-4 inhibitor's design strategies.

Towards Better Drug Repositioning: Targeted Immunoinflammatory Therapy for Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common and important microvascular complications of diabetes mellitus (DM). The main clinical features of DN are proteinuria and a progressive decline in renal function, which are associated with structural and functional changes in the kidney. The pathogenesis of DN is multifactorial, including genetic, metabolic, and haemodynamic factors, which can trigger a sequence of events. Controlling metabolic risks such as hyperglycaemia, hypertension, and dyslipidaemia is not enough to slow the progression of DN. Recent studies emphasized immunoinflammation as a critical pathogenic factor in the progression of DN. Therefore, targeting inflammation is considered a potential and novel treatment strategy for DN. In this review, we will briefly introduce the inflammatory process of DN and discuss the anti-inflammatory effects of antidiabetic drugs when treating DN.

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.

Diabetic Nephropathy: Novel Molecular Mechanisms and Therapeutic Targets

Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes mellitus and the leading cause of end-stage kidney disease. The standard treatments for diabetic patients are glucose and blood pressure control, lipid lowering, and renin-angiotensin system blockade; however, these therapeutic approaches can provide only partial renoprotection if started late in the course of the disease. One major limitation in developing efficient therapies for DN is the complex pathobiology of the diabetic kidney, which undergoes a set of profound structural, metabolic and functional changes. Despite these difficulties, experimental models of diabetes have revealed promising therapeutic targets by identifying pathways that modulate key functions of podocytes and glomerular endothelial cells. In this review we will describe recent advances in the field, analyze key molecular pathways that contribute to the pathogenesis of the disease, and discuss how they could be modulated to prevent or reverse DN.

Use of incretin-based medications: what do current international recommendations suggest with respect to GLP-1 receptor agonists and DPP-4 inhibitors?

In recent years guidelines for the treatment of type 2 diabetes (T2DM) have evolved substantially. Initially limited to a few glucose lowering agents, early guidelines predicated strict glycemic control as a main goal in the attempt to reduce the risk of long-term diabetic complications. Nowadays, guidelines are not limited to such a goal but include cardiovascular (and renal) protection. This rapid evolution was made possible by the introduction of new glucose lowering agents, which have been extensively tested in randomized clinical studies including large cardiovascular outcome trials (CVOTs). In this review we will specifically consider the use of incretin-based medications in T2DM as recommended in the recent ADA/EASD consensus, and other international guidelines, with special consideration of their glucose-lowering efficacy, their cardiovascular (and renal) benefit, their effect on body weight and risk of hypoglycemia, as well as the economic implications for their use.

Safety of Liraglutide in Type 2 Diabetes and Chronic Kidney Disease

BACKGROUND AND OBJECTIVES

The glucagon-like peptide-1 receptor agonist liraglutide demonstrated cardiovascular and kidney benefits in the LEADER trial, particularly in participants with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This post hoc analysis evaluated the safety of liraglutide treatment in patients with CKD in LEADER. Overall, 9340 patients were randomized to liraglutide or placebo, both in addition to standard of care. Of those, 2158 patients had CKD versus 7182 without CKD (defined as eGFR <60 versus ≥60 ml/min per 1.73 m2, respectively); 966 patients had macroalbuminuria and 2456 had microalbuminuria (urine albumin-creatinine ratio >300 mg/g and ≥30 to ≤300 mg/g, respectively). At baseline, the mean eGFR in patients with CKD was 46±11 ml/min per 1.73 m2 versus 91±22 ml/min per 1.73 m2 in those without CKD. Time to first event within event groups was analyzed using Cox regression with treatment group, baseline eGFR group, or baseline albuminuria group as fixed factors.

RESULTS

Overall, serious adverse events were more frequently recorded in patients with CKD compared with those without CKD (59% versus 50%; interaction P=0.11); however, they occurred to the same extent in those on liraglutide versus placebo. Similarly, no interaction of adverse events with randomized therapy was observed in patients with micro- or macro- versus normoalbuminuria (interaction P=0.11). Risk of severe hypoglycemia was significantly reduced with liraglutide versus placebo in patients with CKD or with micro- or macroalbuminuria (hazard ratio, 0.63 [95% CI, 0.43 to 0.91] and 0.57 [95% CI, 0.40 to 0.82], respectively).

CONCLUSIONS

In LEADER, the use of liraglutide in those with CKD was safe, with no difference between patients with and without CKD.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

ClinicalTrials.gov; NCT01179048 (https://clinicaltrials.gov/ct2/show/NCT01179048).

Chitosan-Coated Alginate Nanoparticles Enhanced Absorption Profile of Insulin Via Oral Administration

BACKGROUND

In this study, four nanoparticle formulations (F1 to F4) comprising varying ratios of alginate, Pluronic F-68 and calcium chloride with a constant amount of insulin and chitosan as a coating material were prepared using polyelectrolyte complexation and ionotropic gelation methods to protect insulin against enzymatic degradation.

METHODS

This study describes the formulation design, optimisation, characterisation and evaluation of insulin concentration via oral delivery in rats. A reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated to quantify insulin concentration in rat plasma. The proposed method produced a linear response over the concentration range of 0.39 to 50 µg/ml.

RESULTS

In vitro release study showed that dissolution of insulin in simulated gastric juice of pH 1.2 was prevented by alginate core and chitosan coating but rapidly released in simulated intestinal fluid (pH 6.8). Additionally, Formulation 3 (F3) has a particle size of 340.40 ± 2.39 nm with narrow uniformity exhibiting encapsulation efficiency (EE) of 72.78 ± 1.25 % produced highest absorption profile of insulin with a bioavailability of 40.23 ±1.29% and reduced blood glucose after its oral administration in rats.

CONCLUSION

In conclusion, insulin oral delivery system containing alginate and chitosan as a coating material has the ability to protect the insulin from enzymatic degradation thus enhance its absorption in the intestine. However, more work should be done for instance to involve human study to materialise this delivery system for human use.

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.

Comparing the Effect of Dipeptidyl-Peptidase 4 Inhibitors and Sulfonylureas on Albuminuria in Patients with Newly Diagnosed Type 2 Diabetes Mellitus: A Prospective Open-Label Study

Diabetic kidney disease (DKD) leads to substantial morbidity in patients with type 2 diabetes mellitus (T2DM). Evidence suggests that antidiabetic drug dipeptidyl-peptidase 4 (DPP-4) inhibitors may be able to attenuate albuminuria, whereas the influence of sulfonylureas on albuminuria remains unclear. This prospective open-label study investigated the effect of DPP-4 inhibitors and sulfonylureas on urinary albumin excretion, which is a marker of renal microvascular abnormality. A total of 101 participants with newly diagnosed T2DM were enrolled. In addition to metformin therapy, 45 patients were assigned to receive DPP-4 inhibitors and 56 to receive sulfonylureas. Urinary albumin-to-creatinine ratio (ACR) was significantly reduced in recipients of DPP-4 inhibitors after 24 weeks (29.2 µg/mg creatinine vs. 14.9 µg/mg creatinine, P < 0.001), whereas urinary ACR was not significantly changed by sulfonylureas (39.9 µg/mg creatinine vs. 43.2 µg/mg creatinine, P = 0.641). The effect on albuminuria occurred even though both treatment groups had a similar change in serum glycated hemoglobin A_1c (-1.87 % vs.-2.40 %, P = 0.250). Therefore, in diabetic patients the addition of DPP-4 inhibitors lowered urinary albumin excretion compared to sulfonylureas, and attenuation of albuminuria may be a consideration when choosing between antidiabetic medications.

Artificial intelligence predicts the progression of diabetic kidney disease using big data machine learning

Artificial intelligence (AI) is expected to support clinical judgement in medicine. We constructed a new predictive model for diabetic kidney diseases (DKD) using AI, processing natural language and longitudinal data with big data machine learning, based on the electronic medical records (EMR) of 64,059 diabetes patients. AI extracted raw features from the previous 6 months as the reference period and selected 24 factors to find time series patterns relating to 6-month DKD aggravation, using a convolutional autoencoder. AI constructed the predictive model with 3,073 features, including time series data using logistic regression analysis. AI could predict DKD aggravation with 71% accuracy. Furthermore, the group with DKD aggravation had a significantly higher incidence of hemodialysis than the non-aggravation group, over 10 years (N = 2,900). The new predictive model by AI could detect progression of DKD and may contribute to more effective and accurate intervention to reduce hemodialysis.

DPP-4 Inhibition Leads to Decreased Pancreatic Inflammatory Profile and Increased Frequency of Regulatory T Cells in Experimental Type 1 Diabetes

Sitagliptin is a dipeptidyl peptidase-4 inhibitor (iDPP-4), which has been used for type 2 diabetes treatment. Recently, iDPP-4 has been described as a promising treatment of type 1 diabetes (T1D) but is still necessary to evaluate immune effects of sitagliptin. C57BL/6 mice were induced by multiple low doses of streptozotocin. Diabetes incidence, insulin, glucagon, glucagon-like peptide-1 (GLP-1) serum levels, and inflammatory cytokine levels were quantified in pancreas homogenate after 30 and 90 days of treatment. In addition, frequencies of inflammatory and regulatory T cell subsets were determined in the spleen and in the pancreatic lymph nodes. iDPP-4 decreased blood glucose level while increased GLP-1 and insulin levels. After long-term treatment, treated diabetic mice presented decreased frequency of CD4⁺CD26⁺ T cells and increased percentage of CD4⁺CD25^hiFoxp3⁺ T cells in the spleen. Besides, pancreatic lymph nodes from diabetic mice treated with iDPP-4 presented lower percentage of CD11b⁺ cells and decreased levels of inflammatory cytokines in the pancreas. Treatment of type 1 diabetic mice with iDPP-4 improved metabolic control, decreased inflammatory profile in the pancreatic microenvironment, and increased systemic regulatory T cell frequency. Therefore, we suggest the long-term use of sitagliptin as a feasible and effective therapy for T1D.

Dipeptidyl peptidase-4 inhibitor compared with sulfonylurea in combination with metformin: cardiovascular and renal outcomes in a propensity-matched cohort study

Background

To determine the impact of dipeptidyl peptidase-4 inhibitor (DPP4i) on the risk of major cardiocerebrovascular and renal outcomes compared with sulfonylurea (SU) combined with metformin in patients with type 2 diabetes from a population-based cohort.

Methods

From a nationwide cohort in Korea (2008–2013), 23,674 patients with type 2 diabetes treated with DPP4i plus metformin or SU plus metformin were selected and matched by propensity score. Composite cardiocerebrovascular events including incident ischemic heart disease (IHD), ischemic stroke (IS), hospitalization for heart failure (HHF), and cardiocerebrovascular death, as well as renal events including incident end-stage renal disease or initiation of renal-replacement therapy were assessed by Cox proportional-hazards models.

Results

During a median follow-up of 19.6 months (interquartile range 7.2–36.4), 762 composite cardiocerebrovascular events and 17 end-stage renal events occurred. There was no significant difference in the risk of IHD (hazard ratio [HR], 1.00; 95% CI 0.81–1.23), IS (HR, 0.95; 95% CI 0.74–1.23), or cardiocerebrovascular death (HR, 0.74; 95% CI 0.46–1.18) in the DPP4i group compared to that in the SU group. Likewise, DPP4i therapy was not associated with the risk of end-stage renal outcomes (HR, 1.23; 95% CI 0.41–3.62). However, the risk of HHF was significantly higher in the DPP4i group than in the SU group (HR, 1.47; 95% CI 1.07–2.04).

Conclusions

This real-world database analysis showed that DPP4i therapy did not increase the overall risk of major cardiovascular and renal outcomes compared to SU therapy. However, the DPP4i-associated risk of HHF remained significant.

Electronic supplementary material

The online version of this article (10.1186/s12933-019-0835-z) contains supplementary material, which is available to authorized users.

Dipeptidyl Peptidase 4 Inhibition Ameliorates Chronic Kidney Disease in a Model of Salt-Dependent Hypertension

Cardiovascular diseases frequently coexist with chronic kidney disease that constitutes a major determinant of outcome in patients with heart failure. Dysfunction of both organs is related to chronic inflammation, endothelial dysfunction, oxidative stress, and fibrosis. Widespread expression of serine protease DPP4 that degrades varieties of substrates suggests its involvement in numerous physiological processes. In this study, we tested the effects of selective DPP4 inhibition on the progression of renal disease in a nondiabetic model of hypertensive heart disease using Dahl salt-sensitive rats. Chronic DPP4 inhibition positively affected renal function with a significant reduction in albuminuria and serum creatinine. DPP4 inhibition attenuated the inflammatory component by reducing the expression of NF-κB, TNFα, IL-1β, IL-6, and MCP-1. Kidney macrophages expressed GLP-1R, and DPP4 inhibition promoted macrophage polarization toward the anti-inflammatory M2 phenotype. Finally, high degrees of NADPH oxidase 4 expression and oxidation of nucleic acids, lipids, and proteins were reduced upon DPP4 inhibition. Our study provides evidence of renoprotection by DPP4 inhibition in a nondiabetic hypertension-induced model of chronic cardiorenal syndrome, indicating that DPP4 pathway remains a valid object to study in the context of chronic multiorgan diseases.

Diabetic nephropathy: An update on pathogenesis and drug development

Diabetic nephropathy (DN) is a major cause of end-stage renal disease and affects a large number of individuals with diabetes. However, the development of specific treatments for DN has not yet been identified. Hence, this review is concisely designed to understand the molecular pathways leading to DN in order to develop suitable therapeutic strategies. Extensive literature search have been carried in regard with the pathogenesis and pathophysiology of DN, drug targets and updates on clinical trials, the consequences associated with DN and the potential biomarkers for diagnosis and prediction of DN are discussed in this review. DN is characterised by microalbuminuria and macroalbuminuria, and morphological changes such as glomerular thickening, interstitial fibrosis, formation of nodular glomerulosclerosis and decreased endothelial cell fenestration. Besides, the involvement of renin-angiotensin-aldosterone system, inflammation and genetic factors are the key pathways in the progression of DN. In regard with drug development drugs targeted to epidermal growth factor, inflammatory cytokines, ACTH receptor and TGFβ1 receptors are in pipeline for clinical trials whereas, several drugs have also failed in phase III and phase IV of clinical trials due to lack of efficacy and severe adverse effect. The research on DN is limited with respect to its pathogenesis and drug development. Thus, a more detailed understanding of the pathogenesis of DN is very essential to progress in the drug development process.

Astragaloside IV ameliorates high glucose‑induced renal tubular epithelial‑mesenchymal transition by blocking mTORC1/p70S6K signaling in HK‑2 cells

Astragaloside IV (AST) is the major active saponin in Astragalus membranaceus and, reportedly, has a variety of pharmacological activities. However, the potential of AST to ameliorate high glucose‑mediated renal tubular epithelial‑mesenchymal transition (EMT) remains undetermined. The aim of the present research was to explore the effect and mechanism of AST in EMT of renal tubular epithelial cells, as an underlying mechanism of renal fibrosis and a vital feature involved in diabetic nephropathy. The effect of AST on the EMT of renal tubular epithelial cells (HK‑2) stimulated by high glucose was investigated and it was attempted to elucidate the potential underlying mechanism. The expression of E‑cadherin and α‑smooth muscle actin were determined by western blotting and immunofluorescence assays. The expression of the mammalian target of rapamycin complex 1 (mTORC1)/ ribosomal protein S6 kinase β‑1 (p70S6K) signaling pathway and protein levels of four transcriptional factors (snail, slug, twist and zinc finger E‑box‑binding homeobox 1) were also determined by western blotting. Additionally, extracellular matrix components, including fibronectin (FN) and collagen type IV (Col IV) were detected by ELISA. The results suggested that the EMT of HK‑2 cells and the mTORC1/p70S6K pathway were activated by high glucose. The expression of snail and twist in HK‑2 cells was elevated by high glucose. Furthermore, extracellular matrix components, FN and Col IV, were increased in HK‑2 cells cultured with high glucose. In turn, treatment with AST reduced EMT features in HK‑2 cells, inhibited mTORC1/p70S6K pathway activation, downregulated expression of snail and twist, and reduced secretion of FN and Col IV. In summary, the findings suggested that AST ameliorates high glucose‑mediated renal tubular EMT by blocking the mTORC1/p70S6K signaling pathway in HK‑2 cells.

Effects of glucose-lowering agents on surrogate endpoints and hard clinical renal outcomes in patients with type 2 diabetes

Diabetic kidney disease (DKD) represents an enormous burden in patients with type 2 diabetes mellitus (T2DM). Preclinical studies using most glucose-lowering agents have suggested renal-protective effects, but the proposed mechanisms of renoprotection have yet to be defined, and the promising results from experimental studies remain to be translated into human clinical findings to improve the prognosis of patients at risk of DKD. Also, it is important to distinguish effects on surrogate endpoints, such as decreases in albuminuria and estimated glomerular filtration rate (eGFR), and hard clinical endpoints, such as progression to end-stage renal disease (ESRD) and death from renal causes. Data regarding insulin therapy are surprisingly scarce, and it is nearly impossible to separate the effects of better glucose control from those of insulin per se, whereas favourable preclinical data with metformin, thiazolidinediones and dipeptidyl peptidase (DPP)-4 inhibitors are plentiful, and positive effects have been observed in clinical studies, at least for surrogate endpoints. The most favourable renal results have been reported with glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter type-2 inhibitors (SGLT2is). Significant reductions in both albuminuria and eGFR decline have been reported with these classes of glucose-lowering medications compared with placebo and other glucose-lowering agents. Moreover, in large prospective cardiovascular outcome trials using composite renal outcomes as secondary endpoints, both GLP-1RAs and SGLT2is added to standard care reduced renal outcomes combining persistent macro-albuminuria, doubling of serum creatinine, progression to ESRD and kidney-related death; however, to date, only SGLT2is have been clearly shown to reduce such hard clinical outcomes. Yet, as the renoprotective effects of SGLT2is and GLP-1RAs appear to be independent of glucose-lowering activity, the underlying mechanisms are still a matter of debate. For this reason, further studies with renal outcomes as primary endpoints are now awaited in T2DM patients at high risk of DKD, including trials evaluating the potential add-on benefits of combined GLP-1RA-SGLT2i therapies.

Inhibition of Akt/mTOR/p70S6K Signaling Activity With Huangkui Capsule Alleviates the Early Glomerular Pathological Changes in Diabetic Nephropathy

Huangkui capsule (HKC), a Chinese modern patent medicine extracted from Abelmoschus manihot (L.) medic, has been widely applied to clinical therapy in the early diabetic nephropathy (DN) patients. However, it remains elusive whether HKC can ameliorate the inchoate glomerular injuries in hyperglycemia. Recently the activation of phosphatidylinositol-3-kinase (PI3K)/serine-threonine kinase (Akt)/mammalian target of rapamycin (mTOR) signaling and its downstream regulator, 70-kDa ribosomal protein S6 kinase (p70S6K), play important roles in the early glomerular pathological changes of DN including glomerular hypertrophy, glomerular basement membrane (GBM) thickening and mild mesangial expansion. This study thereby aimed to clarify therapeutic effects of HKC during the initial phase of DN and its underlying mechanisms. Fifteen rats were randomly divided into 3 groups: the normal group, the model group and the HKC group. The early DN model rats were induced by unilateral nephrectomy combined with intraperitoneal injection of streptozotocin, and administered with either HKC suspension or vehicle after modeling and for a period of 4 weeks. Changes in the incipient glomerular lesions-related parameters in urine and blood were analyzed. Kidneys were isolated for histomorphometry, immunohistochemistry, immunofluorescence and Western blotting (WB) at sacrifice. In vitro, murine mesangial cells (MCs) were used to investigate inhibitory actions of hyperoside (HYP), a bioactive component of HKC, on cellular hypertrophy-associated signaling pathway by WB, compared with rapamycin (RAP). For the early DN model rats, HKC ameliorated micro-urinary albumin, body weight and serum albumin, but had no significant effects on renal function and liver enzymes; HKC improved renal shape, kidney weight and kidney hypertrophy index; HKC attenuated glomerular hypertrophy, GBM thickening and mild mesangial expansion; HKC inhibited the phosphorylation of Akt, mTOR and p70S6K, and the protein over-expression of transforming growth factor-β1 in kidneys. In vitro, the phosphorylation of PI3K, Akt, mTOR and p70S6K in MCs induced by high-glucose was abrogated by treatment of HYP or RAP. On the whole, this study further demonstrated HKC safely and efficiently alleviates the early glomerular pathological changes of DN, likely by inhibiting Akt/mTOR/p70S6K signaling activity in vivo and in vitro, and provided the first evidence that HKC directly contributes to the prevention of the early DN.

Delayed allogeneic skin graft rejection in CD26-deficient mice

Organ transplantation is an effective therapeutic tool for treating many terminal diseases. However, one of the biggest challenges of transplantation is determining how to achieve the long-term survival of the allogeneic or xenogeneic transplant by, for example, preventing transplant rejection. In the current study, CD26 gene-knockout mice were used to investigate the potential role of CD26/dipeptidyl peptidase-4 (DPPIV) in allogeneic skin graft rejection by tail-skin transplantation. Compared with wild-type (CD26^+/+) counterparts, CD26^-/- mice showed reduced necrosis of grafts and delayed graft rejection after skin transplantation. Concentrations of serum IgG, including its subclasses IgG1 and IgG2a, were significantly reduced in CD26^-/- mice during graft rejection. Moreover, after allogeneic skin transplantation, the secretion levels of the cytokines IFN-γ, IL-2, IL-6, IL-4, and IL-13 were significantly reduced, whereas the level of the cytokine IL-10 was increased in the serum of CD26^-/- mice compared with that in the serum of CD26^+/+ mice. Additionally, the concentration of IL-17 in serum and the percentage of cells secreting IL-17 in mouse peripheral blood lymphocytes (MPBLs) were both significantly lower, while the percentage of regulatory T cells (Tregs) was significantly higher in MPBLs of CD26^-/- mice than in those of CD26^+/+ mice. Furthermore, a lower percentage of CD8⁺ T cells in MPBLs and fewer infiltrated macrophages and T cells in graft tissues of CD26^-/- mice were detected during graft rejection. These results indicate that CD26 is involved in allogeneic skin graft rejection and provides another hint that CD26 deficiency leads to less rejection due to lower activation and proliferation of host immune cells.

The kidney and cardiovascular outcome trials

Chronic kidney disease (CKD) affects a substantial minority of people with type 2 diabetes (T2D). Analysis of US National Health and Nutrition Examination Survey (NHANES) datasets from 2007 through 2012 showed Stage 3 or worse disease (estimated glomerular filtration rate [eGFR] <60 mL/min per 1.73 m² ) in nearly one in five patients, with increasing age, blood pressure, obesity, and levels of glycemia all associated with higher likelihood of Stage 3 or worse CKD, comparable to findings from surveys from many other areas, which also show micro- or macroalbuminuria to be present in one-sixth to one-third of diabetic people. Improvement in albuminuria has been shown in clinical trials of glycemic interventions, including the Action to Control Cardiovascular Disease in Diabetes (ACCORD) trial, the Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation (ADVANCE) trial, in which the nephroprotective effect of blood pressure lowering was also demonstrated, and the UK Prospective Diabetes Study (UKPDS). However, over the past decade a host of cardiovascular outcome trials (CVOTs) have been performed with newer T2D therapeutic agents, and many of these have included intriguing information pertaining to renal disease and renal outcomes not necessarily related to changes in glycemia. It is of interest to review some of these findings. Glucagon-like peptide-1 (GLP-1) has been reported to increase glomerular filtration rate (GFR), renal blood flow, and the fractional excretion both of sodium and potassium, with renal GLP-1 receptors present in afferent arteriolar vascular smooth muscle cells, glomerular endothelial cells and macrophages, juxtaglomerular cells, and the proximal tubule, perhaps mediating the greater natriuresis seen after oral than intravenous sodium. In the Liraglutide Effect and Action in Diabetes: Evaluation of Cardiovascular Outcome Results (LEADER) trial, the significant 13% reduction in the primary composite outcome of cardiovascular death, myocardial infarction, and stroke was found on subgroup analysis to particularly occur among participants with Stage 3 CKD, having eGFR 30-59 mL/min per 1.73 m² . No significant effect on eGFR was found with liraglutide, although both those receiving and not receiving the drug showed a decline in eGFR from approximately 75 to 65 mL/min per 1.73 m² over the 48-month period of observation. Liraglutide administration was associated with a significant reduction in albuminuria, with nearly a 25% lower likelihood of development of macroalbuminuria, and with the albumin:  creatinine ratio (ACR) approximately 20% lower among treated people, regardless of the baseline level of eGFR. Similarly, in the Evaluation of Lixisenatide in Acute Coronary Syndrome (ELIXA) trial, a 34% increase in the urine ACR was reported among people receiving placebo, but the increase was 24% among those receiving lixisenatide, and in the Trial to Evaluate Cardiovascular and Other Long-term Outcomes with Semaglutide in Subjects with Type 2 Diabetes (SUSTAIN-6), persistent macroalbuminuria developed among 2.7% of those receiving semaglutide, but among 4.9% of those receiving placebo. The enzyme dipeptidyl peptidase (DPP)-4 is, like the GLP-1 receptor, present in multiple renal membrane-bound locations, including afferent arteriolar vascular smooth muscle cells, mesangial cells, podocytes, and proximal tubular cells, and DPP-4 inhibitors appear to have salutary effects on albuminuria similar to those of the GLP-1 agents. In the Saxagliptin Assessment of Vascular Outcomes Recorded in Patients with Diabetes Mellitus (SAVOR)-Thrombolysis in Myocardial Infarction (TIMI) 53 trial, saxagliptin was associated with significantly less worsening and more improvement in microalbumin levels at 1 year, at 2 years, and by end-of-treatment. The reduction in microalbumin levels was similar in patients with and without renal impairment. Interestingly, there was no relationship between improvement in albuminuria and improvement in HbA1c. The other DPP4i CVOTs have not reported effects of these agents on renal function or albuminuria, but studies of sitagliptin and linagliptin suggest that these agents may also reduce albuminuria. Sodium-glucose cotransporter (SGLT) 2 inhibitors affect multiple sites, with the potential to affect renal function. The Canagliflozin Cardiovascular Assessment Study (CANVAS) showed a 27% reduction in progression of albuminuria, with a 40% reduction in eGFR, need for renal-replacement therapy, or death from renal causes associated with the use of canagliflozin. After a fall in mean eGFR with canagliflozin from 76 to 73 mL/min per 1.73 m² at 3 months, eGFR remained stable through 6 years while gradually declining during the period of observation with placebo. Evidence of dual effects of SGLT2 inhibition on both albuminuria and GFR was even more strongly shown in the Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients (EMPA-REG OUTCOME); in that CVOT, although there was an initial decline in eGFR with empagliflozin, from 94 mL/min per 1.73 m² through 192 weeks, eGFR was consistently higher with empagliflozin, although this was less clear in trial participants with baseline eGFR <60 mL/min per 1.73 m² . Empagliflozin also reduced the development of acute renal failure. Further analysis showed empagliflozin to be associated with a reduction in albuminuria, regardless of the baseline urine albumin level. The CVOTs have offered the possibility that diabetes treatment may move beyond surrogate endpoints to actual cardiovascular outcome benefits. It appears that these drugs will also lead to a reduction in adverse renal outcomes. We should look with optimism at this potential approach to a major complication of diabetes.

The Role of Vildagliptin in the Therapy of Type 2 Diabetic Patients with Renal Dysfunction

Diabetes is the leading cause of chronic kidney disease, and even in the absence of albuminuria, decreased renal function in type 2 diabetes mellitus (T2DM) patients increases the risk for major adverse cardiovascular events and death. The evidence derived from recent studies suggests that intensive glucose control not only reduces the risk for microalbuminuria and macroalbuminuria but may also decrease the rate of decline of glomerular filtration rate (GFR). Although insulin therapy is widely used in patients with T2DM and renal disease, metabolic control is particularly difficult to achieve and manage because of the limited therapeutic options and the frequent comorbidities seen in this population. Recent evidence suggests that dipeptidyl peptidase-4 (DPP-4) inhibitors may offer a better choice for improving glycemic control in T2DM patients with low GFR. This review will focus on vildagliptin, a DPP-4 inhibitor with a large body of evidence in patients with moderate to severe renal failure and a good clinical profile in terms of efficacy and safety. In particular, vildagliptin, with appropriate dose adjustment, provides clinically important reductions in glycated hemoglobin, without increasing weight and the risk of hypoglycemia even in patients with severe chronic kidney disease.

Effects of Intensive Control of Glycemia on Clinical Kidney Outcomes in Type 2 Diabetes Patients Compared with Standard Control: A Meta-Analysis

Background: Association between poor control of glycemia and the onset of microvascular complications in type 2 diabetes mellitus (T2DM) patients is a hard issue. However, it seems that the impact of pharmacological treatment is important only in early stages of diabetic nephropathy. We sought to examine whether intensive glycemic control is associated with improvement of clinical Chronic Kidney Disease (CKD) outcomes compared to standard glycemic control. Methods: Meta-analysis of published and unpublished randomized controlled trials (RCT) and post-hoc analysis of RCTs comparing anti-diabetic drugs and/or insulin (intensive control) vs. dietary measures (standard control) for relevant outcomes related to progression of CKD clinically manifest was undertaken. Summary estimates obtained by random effects model and funnel plots for assessing reporting bias are presented. Results: Our analysis was based on four RCTs representing 27,391 adult T2DM patients with CKD from around the world. The pooled OR for the outcomes of doubling of serum creatinine and need of dialysis were, respectively, of 0.98 with 95% confidence interval (95% CI) 0.81-1.19, and 0.84 with 95% CI 0.69-1.02. The pooled OR for the outcome of death from kidney failure was 0.62 with 95% CI 0.39-0.98. Clinical differences between studies were not translated in statistical heterogeneity. Reporting bias may be present. Conclusions: Intensive glycemic control has an effect on death from kidney failure compared to standard glycemic control. Better comprehension of glycemic control effects on both T2DM patients with and without CKD is important for individualization of these two treatment modalities.

Renal outcomes with dipeptidyl peptidase-4 inhibitors

Dipeptidyl peptidase-4 inhibitors (DPP-4is) are increasingly being used in the management of type 2 diabetes (T2D). The present review summarizes the current knowledge of the effects of DPP-4is on renal outcomes by analyzing the experimental preclinical data, the effects of DPP-4is on urinary albumin-creatinine ratios (UACRs) and estimated glomerular filtration rates (eGFRs) from observational studies and clinical trials, and renal events (including kidney failure requiring renal replacement therapy) in recent large prospective cardiovascular outcome trials. Renal protection has been demonstrated in various animal models that have implicated different underlying mechanisms independent of glucose control, whereas prevention of new onset microalbuminuria and/or progression of albuminuria has been reported in some clinical studies, but with no significant effects on eGFR in most of them. The long-term clinical effects of DPP-4is on renal outcomes and the development of end-stage renal disease remain largely unknown and, thus, demand further investigations in prospective trials and long-term observational studies. In conclusion, despite promising results in animal models, data on surrogate biological markers of renal function and clinical renal outcomes remain rather scanty in patients with T2D, and mostly demonstrate the safety rather than true efficacy of DPP-4is.

Treatment of diabetic kidney disease: current and future targets

Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease in Korea and worldwide, and is a risk factor for the development of cardiovascular complications. The conventional treatments for DKD are control of blood glucose and blood pressure levels by inhibiting the renin-angiotensin system. However, the prevalence of DKD continues to increase and additional therapies are required to prevent or ameliorate the condition. Many drugs have been, or are being, developed to target the molecular mechanisms in play in DKD. This review focuses on DVD treatment, considering current and emerging therapeutic targets and the clinical trial-based evidence.