DPP-4 inhibition with alogliptin on top of angiotensin II type 1 receptor blockade ameliorates albuminuria via up-regulation of SDF-1α in type 2 diabetic patients with incipient nephropathy

Nutritional control of thyroid morphogenesis through gastrointestinal hormones

Developing animals absorb nutrients either through the placenta or from ingested food; however, the mechanisms by which embryos use external nutrients for individual organ morphogenesis remain to be elucidated. In this study, we assessed nutrient-dependent thyroid follicle morphogenesis in Xenopus laevis and investigated the role of secreted gastrointestinal (GI) hormones post-feeding. We found that feeding triggers thyroid follicle formation, and the thyroid cells showed transient inactivation of cell proliferation after feeding. In addition, the thyroid cells with multi-lumina were frequently observed in the fed tadpoles. The expression of the particular GI hormone incretin, glucose-dependent insulinotropic polypeptide (GIP), responded to feeding in the intestines of Xenopus tadpoles. Inhibition of dipeptidyl peptidase 4 (Dpp4), a degradative enzyme of incretin, increased the size of the thyroid follicles by facilitating follicular lumina connection, whereas inhibition of the sodium-glucose cotransporter (SGLT) reversed the effects of Dpp4 inhibition. Furthermore, injection of GIP peptide in unfed tadpoles initiated thyroid follicle formation-without requiring feeding-and injection of an incretin receptor antagonist suppressed follicle enlargement in the fed tadpoles. Lastly, GIP receptor knockout in neonatal mice showed smaller follicles in the thyroid, suggesting that the GI hormone-dependent thyroid morphogenesis is conserved in mammals. In conclusion, our study links external nutrients to thyroid morphogenesis and provides new insights into the function of GI hormone as a regulator of organ morphology in developing animals.

Recent therapeutic targets in diabetic nephropathy

BACKGROUND

The prevalence of diabetes mellitus has been increased dramatically which in turn leads to complications including cardiovascular diseases, diabetic kidney disease, and substantially end-stage renal disease.

METHODS

We reviewed articles discussing the pathophysiology of diabetic nephropathy with new agents that may be useful in the management of the disease. We used PubMed, Scopus, Google Scholar and the Open-access searching engines.

RESULTS

The recent recommendations primarily depend on glycaemic and blood pressure control and the use of standard renin-angiotensin system blockade. Currently, the use of agents with nephroprotective effects beyond the hyperglycaemic lowering effect has been evidenced clinically.

CONCLUSIONS

In his review, the pathophysiology, clinical manifestations, and lines of treatment of diabetic nephropathy are discussed. In addition, a focus on the clinical role and nephroprotective effects of the emerging therapeutic class, dipeptidyl peptidase IV (DPP-4) inhibitors, is addressed in detail.

The Role of CXCL12 in Kidney Diseases: A Friend or Foe?

Background

Chemokines are a family of proteins mainly mediating the homing and migration of various cells. The CXC chemokine CXCL12 is a member of low-weight-molecular chemokines. In the kidney, CXCL12 is pivotal for renal development and exerts a modulatory effect in kidney diseases under different etiologic settings by binding with CXC chemokine receptor 4 (CXCR4) or CXC chemokine receptor 7 (CXCR7). Besides, CXCL12 also exerts homeostasis influence in diverse physical conditions and various pathological situations. Thus, we conclude the complicated relationship between CXCL12 and kidney diseases in this review.

Summary

In renal development, CXCL12 contributes a lot to nephrogenesis and the formation of renal vasculature via correlating with CXCR4. CXCL12 also plays an essential role in renal recovery from acute kidney injury. However, the CXCL12/CXCR4 axis plays a dual regulatory role in the initiation and development of diabetic kidney disease as well as chronic allogeneic nephropathy after kidney transplantation through dialectical consideration. Additionally, the CXCL12/CXCR4 link is considered as a new risk factor for lupus nephritis and renal cell carcinoma.

Key Messages

Plenty of studies have presented the influence of CXCL12 and the relation with corresponding receptors in diverse biological and pathological statuses. Simultaneously, some drugs and antagonists targeting CXCL12/CXCR4 axis effectively treat various kidney diseases. However, more researches are needed to explore thorough influence and mechanisms, providing more cues for clinical treatments.

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.

Dipeptidyl-Peptidase 4 Inhibitors did not Improve Renal Endpoints in Advanced Diabetic Kidney Disease

OBJECTIVE

The efficacy of dipeptidyl-peptidase 4 inhibitors (DPP4is) in advanced diabetic kidney disease (DKD) is unknown. We investigated whether DPP4is confer renal protective benefits in DKD patients.

METHODS

We conducted a retrospective cohort study between 2012 and 2018 in Taiwan. We only included type 2 diabetes patients with estimated glomerular filtration rate (eGFR) between 30 and 90 mL/min/1.73 m² and urine albumin to creatinine ratio between 300 and 5,000 mg/g. Patients with DPP4i prescriptions were selected as cases, while non-DPP4i users served as controls. We followed these patients until the presence of composite primary renal endpoints, which was defined by the earliest occur-rence of clinical renal outcomes.

RESULTS

A total of 522 patients were included in the analysis, comprising 273 patients with a DPP4i prescription who were selected as cases and 249 patients without DPP4i prescription who were assigned as controls. Median follow-up duration for DPP4i users and nonusers was 2.2 years and 3.4 years, respectively. At baseline, the mean glycated hemoglobin levels for DPP4i users and nonusers were 8.1% and 8.3%, respectively. Among patients with DPP4i prescriptions, there was no reduction in composite primary renal outcome, with a crude hazard ratio (HR) of 1.50 (95% confidence interval [CI], 0.95 to 2.36). Similar results were observed for the risk of persistent eGFR <15 mL/min/1.73 m², with a HR of 1.68 (95% CI, 0.90 to 3.13), doubling of serum creatinine level, with a HR of 1.05 (95% CI, 0.15 to 7.45), and end-stage renal disease, with a HR of 0.87 (95% CI, 0.14 to 5.19).

CONCLUSION

DPP4i prescription did not reduce the risk of composite renal endpoints in DKD patients.

ABBREVIATIONS

BMI = body mass index; CI = confidence interval; CVOT = cardiovascular outcomes trial; DPP4i = dipeptidyl-peptidase 4 inhibitor; DKD = diabetic kidney disease; eGFR = estimated glomerular filtration rate; ESRD = end-stage renal disease; HbA1c = glycated hemoglobin; HR = hazard ratio; SGLT2i = sodium-glucose cotransporter 2 inhibitor; T2D = type 2 diabetes; UACR = urine albumin to creatinine ratio.

Drug discovery approaches targeting the incretin pathway

Incretin pathway plays an important role in the development of diabetes medications. Interventions in DPP-4 and GLP-1 receptor have shown remarkable efficacy in experimental and clinical studies and imperatively become one of the most promising therapeutic approaches in the T2DM drug discovery pipeline. Herein, we analyzed the actionmechanismsof DPP-4 and GLP-1 receptor targeting the incretin pathway in T2DM treatment. We gave an insight into the structural requirements for the potent DPP-4 inhibitors and revealed a classification of DPP-4 inhibitors by stressing on the binding modes of these ligands to the enzyme. We then reviewed the drug discovery strategies for the development of peptide and non-peptide GLP-1 receptor agonists (GLP-1 RAs). Furthermore, the drug design strategies for DPP-4 inhibitors and GLP-1R agonists were detailed accurately. This review might provide an efficient evidence for the highly potent and selective DPP-4 inhibitors and the GLP-1 RAs, as novel medicines for patients suffering from T2DM.

Renal outcomes with the newer antidiabetes drugs: the era before and after CREDENCE

In 2008, the US Food and Drug Administration provided guidance for the evaluation of the cardiovascular safety of antidiabetes drugs. The newer antidiabetes drugs, approved after 2008, were therefore evaluated in long-term cardiovascular outcome trials, designed and powered for the assessment of cardiovascular safety. Accordingly, the primary endpoint of these trials was a cardiac composite endpoint. Since 2008, the data from various cardiovascular outcome trials have been reported, including SAVOR-TIMI 53 (saxagliptin), EXAMINE (alogliptin), TECOS (sitagliptin), CARMELINA (linagliptin), CAROLINA (linagliptin), ELIXA (lixisenatide), LEADER (liraglutide), EXSCEL (exenatide once-weekly), SUSTAIN-6 (injectable semaglutide), HARMONY Outcomes (albiglutide), REWIND (dulaglutide), PIONEER-6 (oral semaglutide), EMPA-REG OUTCOME (empagliflozin), the CANVAS Program (canagliflozin) and DECLARE-TIMI 53 (dapagliflozin). Some of these trials subsequently also published data on renal outcomes, although these were secondary or exploratory analyses. Dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists had beneficial effects on albuminuria, while sodium-glucose co-transporter-2 inhibitors additionally showed a positive effect on 'hard' renal outcomes. In contrast to the cardiovascular outcome trials, the renal outcome trial of canagliflozin, CREDENCE, assessed a hard renal endpoint as its primary endpoint and showed positive effects on these hard renal outcomes. In this review, we aim to highlight the renal outcome data from the cardiovascular outcome trials and the CREDENCE trial and understand the differences between their results. The post CREDENCE era would appear to reinforce the position of sodium-glucose co-transporter-2 inhibitors as drugs providing cardiorenal protection, in addition to their anti-glycaemic effects.

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.

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.

Effect of switching to teneligliptin from other dipeptidyl peptidase-4 inhibitors on glucose control and renoprotection in type 2 diabetes patients with diabetic kidney disease

AIMS/INTRODUCTION

The objective of the present study was to elucidate the effect of switching to teneligliptin from other dipeptidyl peptidase-4 (DPP-4) inhibitors on glucose control and renoprotection in type 2 diabetes mellitus patients with diabetic kidney disease.

MATERIALS AND METHODS

The present study was a single-arm, open-label, observational study. A total of 23 patients, who had urinary albumin/creatinine ratios (UACR) ≥30 mg/gCr in their first urine in the early morning, and received other DPP-4 inhibitors and renin-angiotensin system inhibitors, switched to teneligliptin 20 mg/day. After switching to teneligliptin for 24 weeks, we evaluated changes in glycated hemoglobin (HbA1c), fasting plasma glucose levels, plasma DPP-4 activity and UACR.

RESULTS

HbA1c, fasting plasma glucose and UACR values showed no significant change after 24 weeks compared with baseline. However, plasma DPP-4 activity was significantly reduced after 24 weeks (0.57 ± 0.26 nmol/min/mL, P = 0.012, vs baseline), compared with baseline (1.49 ± 1.73 nmol/min/mL), and there was a positive relationship between the change rate of plasma DPP-4 activity (Δ%DPP-4) for 24 weeks and the levels of plasma DPP-4 activity (r = -0.5997, P = 0.0025) and fasting plasma glucose (r = -0.4235, P = 0.0440) at baseline. Additionally, the Δ%DPP-4 for 24 weeks was significantly correlated to the change rate of UACR (r = 0.556, P = 0.0059). However, there was no relationship between Δ%DPP-4 and ΔHbA1c (amount of HbA1c change).

CONCLUSIONS

Switching to teneligliptin from other DPP-4 inhibitors for 24 weeks reduces plasma DPP-4 activity, which is associated with a reduction in albuminuria, independent of the change in glucose levels, in type 2 diabetes mellitus patients with diabetic kidney disease.

Nonglycemic Outcomes of Antidiabetic Medications

IN BRIEF The number of medications used to treat diabetes has increased dramatically in the past 15 years. With so many options that have shown significant A1C improvement, it is important to consider side effects, precautions, and additional benefits these agents may offer. This article is a review of some of the most compelling literature available on the nonglycemic benefits of sulfonylureas, thiazolidinediones, biguanides, glucagon-like peptide 1 receptor agonists, dipeptidyl peptidase 4 inhibitors, and sodium-glucose cotransporter 2 inhibitors. Other classes of antihyperglycemic agents, such as dopamine agonists, meglitinides, and amylin agonists, are not discussed in this article.

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.

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.

The Effects of Novel Antidiabetic Drugs on Albuminuria in Type 2 Diabetes Mellitus: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND AND OBJECTIVE

The effects of novel antidiabetic drugs, including sodium-glucose cotransporter 2 (SGLT-2) inhibitors, glucagon-like peptide 1 (GLP-1) receptor agonists, and dipeptidyl peptidase 4 (DPP-4) inhibitors, on albuminuria in patients with type 2 diabetes mellitus (T2DM) are still controversial. Therefore, we performed a meta-analysis to evaluate the effects of novel antidiabetic drugs on albuminuria in patients with T2DM.

METHODS

We conducted a random-effects meta-analysis of randomized controlled trials (RCTs) by searching the MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials databases up to 16 August 2018. The effects of novel antidiabetic drugs on albuminuria were evaluated as percent changes from baseline to follow-up urinary albumin excretion/urinary albumin to creatinine ratio (UAE/UACR) levels in both the intervention and control groups. Data regarding percent changes were used to generate weighted mean differences (WMDs) and 95% confidence intervals (CIs).

RESULTS

In this meta-analysis, 26 RCTs involving 14,929 patients were included. Pooled analysis suggested that SGLT-2 inhibitors (WMD - 26.23%, 95% CI - 35.90 to - 16.56; p < 0.00001) and GLP-1 receptor agonists (WMD - 13.85%, 95% CI - 15.96 to - 11.74; p < 0.00001) were associated with a significant reduction in albuminuria compared with other conventional therapies or placebo. DPP-4 inhibitors (WMD - 6.19%, 95% CI - 14.03 to 1.66; p = 0.12) were not significantly associated with lower albuminuria than other conventional therapies or placebo.

CONCLUSION

This meta-analysis indicates that SGLT-2 inhibitors and GLP-1 receptor agonists were associated with a reduction in albuminuria compared with other conventional therapies or placebo, while DPP-4 inhibitors were not associated with albuminuria-reducing effects compared with other conventional therapies or placebo.

Improvement in Mortality and End-Stage Renal Disease in Patients With Type 2 Diabetes After Acute Kidney Injury Who Are Prescribed Dipeptidyl Peptidase-4 Inhibitors

OBJECTIVE

To focus on the potential beneficial effects of the pleiotropic effects of dipeptidyl peptidase-4 inhibitors (DPP4is) on attenuating progression of diabetic kidney disease in reducing the long-term effect of the acute kidney injury (AKI) to chronic kidney disease (CKD) transition.

PATIENTS AND METHODS

Data from the National Health Insurance Research Database from January 1, 1999, to July 31, 2011, were analyzed, and patients with diabetes weaning from dialysis-requiring AKI were identified. Cox proportional hazards models and inverse-weighted estimates of the probability of treatment were used to adjust for treatment selection bias. The outcomes were incident end-stage renal disease (ESRD) and mortality, major adverse cardiovascular events, and hospitalized heart failure.

RESULTS

Of a total of 6165 patients with diabetes weaning from dialysis-requiring AKI identified, 5635 (91.4%) patients were DPP4i nonusers and 530 (8.6%) patients were DPP4i users. Compared with DPP4i nonusers, DPP4i users had a lower risk of ESRD (hazard ratio, 0.81; 95% CI, 0.70-0.94; P=.04) and all-cause mortality (hazard ratio, 0.28; 95% CI, 0.23-0.34; P<.001) after adjustments for CKD, advanced CKD, and angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker use. In contrast, the risk of major adverse cardiovascular events and hospitalized heart failure did not differ significantly between groups.

CONCLUSION

Dipeptidyl peptidase-4 inhibitor users had a lower risk of ESRD and mortality than did nonusers among patients with diabetes after weaning from dialysis-requiring AKI. Therefore, a prospective study of AKI to CKD transitions after episodes of AKI is needed to optimally target DPP4i interventions.

Meta-analysis of the benefit of sitagliptin treatment in patients with type 2 diabetes complicated with incipient nephropathy

The purpose of this meta-analysis was to evaluate the evidence of the clinical efficacy and safety of sitagliptin in diabetic patients with incipient nephropathy. PubMed, Ovid, Cochrane library, Chinese National Knowledge Infrastructure, and Wanfang databases were searched in September 2017 to identify randomized controlled trials (RCTs) of sitagliptin in diabetic patients with incipient nephropathy. Study selection, data extraction and study quality assessment were performed independently by two investigators, while disagreements were resolved by a third reviewer. The treatment effect was estimated by calculating the mean difference (MD) or standard mean difference (SMD). Heterogeneity was assessed with the χ² and I² tests. Additionally, risk of bias graphs and summaries were used to assess the quality of the included trials. Thirteen RCTs were included in this review; their results suggested that sitagliptin has obvious advantages in lowering the 24-hour urinary albumin excretion [MD, -25.71; 95% confidence interval (CI), -30.75 to -20.66; P<0.00001], serum cystatin C (MD, -0.59; 95% CI, -0.64 to -0.54; P<0.00001), inflammation (MD, -0.81; 95% CI, -1.20 to -0.42; P<0.0001), and total cholesterol (MD, -0.13; 95% CI, -0.22 to -0.03; P=0.009). However, sitagliptin did not appear to influence serum creatinine, fasting blood glucose, postprandial blood glucose, glycosylated hemoglobin A1c, or triglyceride levels, although these results may have been influenced by biases in the included trials. The most common adverse effects of sitagliptin were gastrointestinal tract reaction and hypoglycemia, although these symptoms resolved quickly. Sitagliptin appears to be effective in reducing proteinuria, ameliorating renal function, and producing an anti-inflammatory effect in patients with early-stage diabetic nephropathy. The present analysis provides important guidance for the clinical application of sitagliptin.

Renal Outcomes of Antidiabetic Treatment Options for Type 2 Diabetes-A Proposed MARE Definition

One of the most critical long-term complications of type 2 diabetes is nephropathy, currently termed diabetic kidney disease. Although the prevalence is increasing, renal outcomes are heterogeneously defined. Intensive glucose control is effective for the prevention of microvascular complications, including kidney disease. However, the impact of specific drugs on renal outcome measures such as the incidence of kidney disease, albuminuria, progression to end-stage kidney disease, or death of renal cause remains unclear. Comparison of agents or drug classes is impossible, as renal outcomes are inconsistently defined in trials. Recent publications include more stringent criteria, but use only composite endpoints, which can reveal significant results driven by a single surrogate marker but not clinical events of true relevance to patients. This review discusses renal outcomes related to antidiabetic agents for type 2 diabetes, in an attempt to determine the influence of specific drugs on the incidence of diabetic kidney disease and various renal outcomes. There are marked differences among the various agents, but direct comparisons are difficult due to heterogeneous measures. Statements from Kidney Disease Improving Global Outcomes (KDIGO) or European Renal Best Practice (ERBP) highlight that “standardized outcome reporting is key to achieving evidence-based guidance and improving clinical care for patients.” Renal outcome studies including a well-defined, standardized core set of patient-relevant outcomes are needed. Here, we propose to define and establish major adverse renal events (MARE) as the outcome measure for future studies.

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.

Renoprotective Effect of Dipeptidyl Peptidase-4 Inhibitors in Patients with Type 2 Diabetes Mellitus

Diabetic nephropathy is one of three major complications of diabetes mellitus, often leading to chronic renal failure requiring dialysis. Recently developed dipeptidyl peptidase-4 (DPP-4) inhibitors may exhibit renoprotective effects in addition to antihyperglycemic effects. In this study, we retrospectively investigated temporal changes in the renal function index of patients with type 2 diabetes mellitus (DM) and examined the influence of DPP-4 inhibitors on renal function. Patients with type 2 DM (>18 years old) prescribed hypoglycemic agents at Gifu Municipal Hospital for ≥3 months between March 2010 and April 2014 were included in the study. Renal function was evaluated as estimated the decline in 12-month glomerular filtration rate from the baseline in patients receiving and not receiving DPP-4 inhibitors. Patient data from the DPP-4 inhibitor-treated (501 patients, 58.6%) and untreated (354, 41.4%) groups were analyzed using multiple logistic regression analysis, as well as Cox proportional-hazards regression analysis (616, 55.6% and 491, 44.4%, for DPP-4 inhibitors-treated and untreated groups). Multiple logistic regression analysis indicated that DPP-4 inhibitors significantly lowered the estimated glomerular filtration rate (eGFR) decline [20% over 12 months; odds ratio (OR), 0.626; 95% confidence interval [CI], 0.409–0.958; P = 0.031]. Similar results were obtained using Cox proportional-hazards regression analysis (hazard ratio [HR], 0.707; 95% CI, 0.572–0.874; P = 0.001). These findings suggest that DPP-4 inhibitors suppress the decrease of estimated glomerular filtration rate in patients with type 2 DM and show a renoprotective effect.

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.

Saxagliptin Attenuates Albuminuria by Inhibiting Podocyte Epithelial- to-Mesenchymal Transition via SDF-1α in Diabetic Nephropathy

The dipeptidyl peptidase-4 (DPP-4) inhibitor saxagliptin has been found to reduce progressive albuminuria, but the exact mechanism of inhibition is unclear. Podocyte epithelial-to-mesenchymal transition (EMT) has emerged as a potential pathway leading to proteinuria in diabetic nephropathy (DN). Stromal cell–derived factor-1α (SDF-1α), one of the substrates of DPP-4, can activate the protein kinase A pathway and subsequently inhibit its downstream effector, transforming growth factor-β1 (TGF-β1), which induces podocyte EMT. Thus, this study was designed to test the hypothesis that saxagliptin reduces progressive albuminuria by preventing podocyte EMT through inhibition of SDF-1α cleavage in DN. The results of a series of assays, including ELISA, western blotting, and immunochemistry/immunofluorescence, showed that saxagliptin treatment obviously ameliorated urinary microalbumin excretion and renal histological changes in high-fat diet/streptozotocin-induced diabetic rats. Furthermore, saxagliptin-treated diabetic rats presented with suppression of DPP-4 activity/protein expression accompanied by restoration of SDF-1α levels, which subsequently hindered NOX2 expression and podocyte EMT. In vitro, we consistently observed that saxagliptin significantly inhibited increased DPP-4 activity/expression, oxidative stress and podocyte EMT. Application of an SDF-1α receptor inhibitor (AMD3100) to cultured podocytes further confirmed the essential role of SDF-1α in podocyte EMT inhibition. In sum, we demonstrated for the first time that saxagliptin treatment plays an essential role in ameliorating progressive DN by preventing podocyte EMT through a SDF-1α-related pathway, suggesting that saxagliptin could offer renoprotection and that SDF-1α might be a potential therapeutic target for DN.

GLP-1 and the kidney: from physiology to pharmacology and outcomes in diabetes

The gastrointestinal tract - the largest endocrine network in human physiology - orchestrates signals from the external environment to maintain neural and hormonal control of homeostasis. Advances in understanding entero-endocrine cell biology in health and disease have important translational relevance. The gut-derived incretin hormone glucagon-like peptide 1 (GLP-1) is secreted upon meal ingestion and controls glucose metabolism by modulating pancreatic islet cell function, food intake and gastrointestinal motility, amongst other effects. The observation that the insulinotropic actions of GLP-1 are reduced in type 2 diabetes mellitus (T2DM) led to the development of incretin-based therapies - GLP-1 receptor agonists and dipeptidyl peptidase 4 (DPP-4) inhibitors - for the treatment of hyperglycaemia in these patients. Considerable interest exists in identifying effects of these drugs beyond glucose-lowering, possibly resulting in improved macrovascular and microvascular outcomes, including in diabetic kidney disease. As GLP-1 has been implicated as a mediator in the putative gut-renal axis (a rapid-acting feed-forward loop that regulates postprandial fluid and electrolyte homeostasis), direct actions on the kidney have been proposed. Here, we review the role of GLP-1 and the actions of associated therapies on glucose metabolism, the gut-renal axis, classical renal risk factors, and renal end points in randomized controlled trials of GLP-1 receptor agonists and DPP-4 inhibitors in patients with T2DM.

Effects of Incretin-Based Therapies on Diabetic Microvascular Complications

The morbidity and mortality associated with diabetic complications impose a huge socioeconomic burden worldwide. Therefore, the ultimate goal of managing diabetes mellitus (DM) is to lower the risk of macrovascular complications and highly morbid microvascular complications such as diabetic nephropathy (DN) and diabetic retinopathy (DR). Potential benefits of incretin-based therapies such as glucagon-like peptide 1 receptor agonists (GLP-1 RAs) and dipeptidyl peptidase-4 (DPP-4) inhibitors on the diabetic macrovascular complications have been recently suggested, owing to their pleiotropic effects on multiple organ systems. However, studies primarily investigating the role of these therapies in diabetic microvascular complications are rare. Nevertheless, preclinical and limited clinical data suggest the potential protective effect of incretin-based agents against DN and DR via their anti-inflammatory, antioxidative, and antiapoptotic properties. Evidence also suggests that these incretin-dependent and independent beneficial effects are not necessarily associated with the glucose-lowering properties of GLP-1 RAs and DPP-4 inhibitors. Hence, in this review, we revisit the preclinical and clinical evidence of incretin-based therapy for DR and DN, the two most common, morbid complications in individuals with DM. In addition, the review discusses a few recent studies raising concerns of aggravating DR with the use of incretin-based therapies.

Dipeptidyl peptidase 4 inhibitor use is associated with a lower risk of incident acute kidney injury in patients with diabetes

OBJECTIVES

Dipeptidyl peptidase 4 inhibitor (DPP4i) use potentially slows the progression of diabetic kidney disease, but its effects on the risk of acute kidney injury (AKI) are unclear. We aimed to assess the association between DPP4i use and incident AKI episodes from a nationally representative cohort in Taiwan.

MATERIALS AND METHODS

All patients newly diagnosed with diabetes mellitus (DM) between 2008, when DPP4i use was first approved in Taiwan, and mid-2013 were enrolled. Propensity score-matched diabetic DPP4i users, who received DPP4i for at least 90 days, and nonusers were selected. The primary and secondary outcomes were incident AKI and dialysis-requiring AKI during follow-up. Cox proportional hazard analyses were performed to examine the effect of DPP4i on the risk of AKI.

RESULTS

We enrolled 923,936 diabetic patients; of these, 83,638 DPP4i users (75.7% sitagliptin, 14.6% vildagliptin, and 9.7% saxagliptin) were propensity score-matched to 83,638 non-users. After an average 3.6-year follow-up, 1.56% and 0.35% of DPP4i users and 2.53% and 0.56% of non-users developed incident AKI and dialysis-requiring AKI, respectively. DPP4i use was significantly associated with lower risk of incident AKI (hazard ratio [HR] 0.57, 95% confidence interval [CI] 0.53-0.61) and risk of dialysis-requiring AKI (HR 0.57, 95% CI 0.49-0.66). The risk reduction was consistent regardless of DPP4i type, the presence of chronic kidney disease, the previous acute kidney injury, and age.

CONCLUSIONS

DPP4i use is associated with reduced risk of mild and severe forms of AKI among patients with incident DM. DPP4i may be an important class of anti-glycaemic agent with reno-protective effects.

Role of soluble and membrane-bound dipeptidyl peptidase-4 in diabetic nephropathy

Diabetic nephropathy is one of the most frequent, devastating and costly complications of diabetes. The available therapeutic approaches are limited. Dipeptidyl peptidase type 4 (DPP-4) inhibitors represent a new class of glucose-lowering drugs that might also have reno-protective properties. DPP-4 exists in two forms: a plasma membrane-bound form and a soluble form, and can exert many biological actions mainly through its peptidase activity and interaction with extracellular matrix components. The kidneys have the highest DPP-4 expression level in mammalians. DPP-4 expression and urinary activity are up-regulated in diabetic nephropathy, highlighting its role as a potential target to manage diabetic nephropathy. Preclinical animal studies and some clinical data suggest that DPP-4 inhibitors decrease the progression of diabetic nephropathy in a blood pressure- and glucose-independent manner. Many studies reported that these reno-protective effects could be due to increased half-life of DPP-4 substrates such as glucagon-like peptide-1 (GLP-1) and stromal derived factor-1 alpha (SDF-1a). However, the underlying mechanisms are far from being completely understood and clearly need further investigations.

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.

Metabolite profiling in identifying metabolic biomarkers in older people with late-onset type 2 diabetes mellitus

Regulation of blood glucose requires precise coordination between different endocrine systems and multiple organs. Type 2 diabetes mellitus (T2D) arises from a dysregulated response to elevated glucose levels in the circulation. Globally, the prevalence of T2D has increased dramatically in all age groups. T2D in older adults is associated with higher mortality and reduced functional status, leading to higher rate of institutionalization. Despite the potential healthcare challenges associated with the presence of T2D in the elderly, the pathogenesis and phenotype of late-onset T2D is not well studied. Here we applied untargeted metabolite profiling of urine samples from people with and without late-onset T2D using ultra-performance liquid-chromatography mass-spectrometry (UPLC-MS) to identify urinary biomarkers for late-onset T2D in the elderly. Statistical modeling of measurements and thorough validation of structural assignment using liquid chromatography tandem mass-spectrometry (LC-MS/MS) have led to the identification of metabolite biomarkers associated with late-onset T2D. Lower levels of phenylalanine, acetylhistidine, and cyclic adenosine monophosphate (cAMP) were found in urine samples of T2D subjects validated with commercial standards. Elevated levels of 5′-methylthioadenosine (MTA), which previously has only been implicated in animal model of diabetes, was found in urine of older people with T2D.

Diabetic nephropathy: Time to withhold development and progression - A review

The recent discoveries in the fields of pathogenesis and management of diabetic nephropathy have revolutionized the knowledge about this disease. Little was added to the management of diabetic nephropathy after the introduction of renin angiotensin system blockers. The ineffective role of the renin- angiotensin system blockers in primary prevention of diabetic nephropathy in type 1 diabetes mellitus necessitated the search for other early therapeutic interventions that target alternative pathogenic mechanisms. Among the different classes of oral hypoglycemic agents, recent studies highlighted the distinguished mechanisms of sodium glucose transporter 2 blockers and dipeptidyl peptidase-4 inhibitors that settle their renoprotective actions beyond the hypoglycemic effects. The introduction of antioxidant and anti-inflammatory agents to this field had also added wealth of knowledge. However, many of these agents are still waiting well-designed clinical studies in order to prove their beneficial therapeutic role. The aim of this review of literature is to highlight the recent advances in understanding the pathogenesis, diagnosis, the established and the potential renoprotective therapeutic agents that would prevent the development or the progression of diabetic nephropathy.

Influence of Dipeptidyl Peptidase-IV Inhibitor Sitagliptin on Extracellular Signal-Regulated Kinases 1/2 Signaling in Rats with Diabetic Nephropathy

The protective effects of sitagliptin on the kidneys of rats with diabetic nephropathy (DN) and its influence on extracellular signal-regulated kinases 1/2 (ERK1/2) signaling were investigated. Male Wistar rats (n = 40) were randomly assigned to normal control, DN, low-dose sitagliptin intervention (ST1), or high-dose sitagliptin intervention (ST2) groups. Animals were euthanized after a 16-week treatment, and blood glucose (BG), glycosylated hemoglobin (HbA1c), urinary albumin excretion rate (AER), serum creatinine (Scr), creatinine clearance rate (Ccr), active glucagon-like peptide-1 (GLP-1) levels, kidney hypertrophy index, and renal pathohistology were determined. Immunohistochemical methods and real-time polymerase chain reaction (PCR) were used to detect protein and mRNA expression of podocalyxin, ERK1/2, GLP-1 receptor (GLP-1R) and transforming growth factor-β (TGF-β). After 16 weeks, BG, AER, Scr, HbA1c and the kidney hypertrophy index were all significantly decreased (p < 0.05) in ST1 and ST2 groups, while Ccr and active GLP-1 levels were increased (p < 0.05), with changes more pronounced in ST2 (p < 0.05). Glomerular pathological lesions were also improved following sitagliptin treatment, especially in ST2. Immunohistochemical and real-time PCR revealed that protein and mRNA expression levels of podocalyxin and GLP-1R were increased significantly in ST1 and ST2, while expression of ERK1/2 and TGF-β was decreased (p < 0.05). Sitagliptin therefore delayed DN progression, possibly via the inhibition of ERK1/2 signaling and promotion of the interaction between GLP-1 and the GLP-1R.

Anagliptin ameliorates albuminuria and urinary liver-type fatty acid-binding protein excretion in patients with type 2 diabetes with nephropathy in a glucose-lowering-independent manner

OBJECTIVE

The objective of this study is to elucidate the effect of anagliptin on glucose/lipid metabolism and renoprotection in patients with type 2 diabetic nephropathy.

METHODS

Twenty-five patients with type 2 diabetic nephropathy received anagliptin 200 mg/day for 24 weeks, and 20 patients who were switched to anagliptin from other dipeptidyl peptidase-4 (DPP-4) inhibitors were analyzed regarding primary and secondary endpoints. The primary endpoint was change in hemoglobin A1c (HbA1c) during treatment with anagliptin. Additionally, we evaluated changes in lipid data (low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol and triglyceride), blood pressure (BP), urinary albumin to creatinine ratio (UACR), liver-type fatty acid-binding protein to creatinine ratio (ULFABP) and renal function (estimated glomerular filtration rate and serum cystatin C) as secondary endpoints.

RESULTS

After switching to anagliptin from other DPP-4 inhibitors, the levels of HbA1c in the 20 participants showed no significant change, 7.5%±1.2% at 24 weeks compared with 7.3%±0.9% at baseline. The levels of the log10-transformed UACR were significantly reduced from 1.95±0.51 mg/g creatinine (Cr) at baseline to 1.76±0.53 mg/g Cr at 24 weeks after anagliptin treatment (p<0.01). The percentage change in the UACR (Δ%UACR) from baseline to 24 weeks was also significantly lower by -10.6% (p<0.001). Lipid data, systolic BP and renal function were not changed during anagliptin treatment. Additionally, ULFABP in eight participants, who had ≥5 µg/g Cr at baseline, was significantly decreased from baseline (8.5±2.8 µg/g Cr) to 24 weeks (3.1±1.7 µg/g Cr, p<0.01) after anagliptin treatment, and the percentage change in the ULFABP during anagliptin treatment was -58.1% (p<0.001).

CONCLUSIONS

Anagliptin induced no significant change in HbA1c, lipid data, systolic BP and renal function. However, anagliptin reduced the UACR and ULFABP, although without a corresponding change in HbA1c, indicating direct action of anagliptin on renoprotection in patients with type 2 diabetic nephropathy.

Vildagliptin reduces plasma stromal cell-derived factor-1α in patients with type 2 diabetes compared with glimepiride

AIMS/INTRODUCTION

Dipeptidyl peptidase-4 inhibitors might have pleiotropic protective effects on cardiovascular disease (CVD), in contrast to sulfonylureas. Therefore, we compared various CVD risk factors between vildagliptin and glimepiride.

MATERIALS AND METHODS

We carried out a randomized, prospective and crossover trial. A total of 16 patients with type 2 diabetes whose glycated hemoglobin was >7% were randomized to add vildagliptin or glimepiride. After 12-week treatment, each drug was replaced with the other for another 12 weeks. Before and after each treatment, glucose homeostasis and CVD risk factors were assessed, and the continuous glucose monitoring system was applied to calculate glycemic variability.

RESULTS

The mean age of the participants was 60 years, 31% were men, body mass index 25.5 kg/m² and HbA1c 8.41%. Both vildagliptin and glimepiride significantly decreased glycated hemoglobin and glycemic variability indices. Despite the improved glucose homeostasis, favorable change of CVD markers was not prominent in both the arms, along with significant weight gain. Only plasma stromal cell-derived factor (SDF)-1α decreased by 30% in the vildagliptin arm. According to regression analyses, the reduction of SDF-1α was independently associated with vildagliptin usage and serum interleukin-6 changes, but white blood cells were not related with the SDF-1α changes.

CONCLUSION

Compared with glimepiride, vildagliptin arrestingly decreased plasma SDF-1α, and its clinical implications should be further investigated.

Incretin-Based Therapies for Diabetic Complications: Basic Mechanisms and Clinical Evidence

An increase in the rates of morbidity and mortality associated with diabetic complications is a global concern. Glycemic control is important to prevent the development and progression of diabetic complications. Various classes of anti-diabetic agents are currently available, and their pleiotropic effects on diabetic complications have been investigated. Incretin-based therapies such as dipeptidyl peptidase (DPP)-4 inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1RA) are now widely used in the treatment of patients with type 2 diabetes. A series of experimental studies showed that incretin-based therapies have beneficial effects on diabetic complications, independent of their glucose-lowering abilities, which are mediated by anti-inflammatory and anti-oxidative stress properties. Based on these findings, clinical studies to assess the effects of DPP-4 inhibitors and GLP-1RA on diabetic microvascular and macrovascular complications have been performed. Several but not all studies have provided evidence to support the beneficial effects of incretin-based therapies on diabetic complications in patients with type 2 diabetes. We herein discuss the experimental and clinical evidence of incretin-based therapy for diabetic complications.

An updated systematic review and meta-analysis on the efficacy and tolerability of dipeptidyl peptidase-4 inhibitors in patients with type 2 diabetes with moderate to severe chronic kidney disease

OBJECTIVE

This updated meta-analysis determines the effect of dipeptidyl peptidase-4 inhibitors on glycemic and tolerability outcomes in patients with type 2 diabetes mellitus and chronic kidney disease with glomerular filtration rate of ⩽60 mL/min or on dialysis.

METHODS

In all, 14 citations were identified from multiple databases. Qualitative assessments and quantitative analyses were performed.

RESULTS

There were 2261 participants, 49-79 years of age, 49% men and 44% Caucasians. In seven placebo-comparator studies, reduction in hemoglobin A1c at weeks 12-24 was 0.55% (95% confidence interval: -0.68 to -0.43), P < 0.00001). In three sulfonylurea-comparator studies, dipeptidyl peptidase-4 inhibitors did not significantly reduce hemoglobin A1c at weeks 52-54 (-0.15% (95% confidence interval: -0.32 to 0.02)). In one sitagliptin versus albiglutide study, albiglutide significantly reduced hemoglobin A1c in patients with moderate renal impairment (-0.51%). A similar reduction in hemoglobin A1c was seen with sitagliptin versus vildagliptin (-0.56% vs -0.54%). Compared with placebo or sulfonylurea, dipeptidyl peptidase-4 inhibitors did not significantly reduce hemoglobin A1c after 12 and 54 weeks in patients on dialysis. Hypoglycemia was reported by ~30% of patients in both dipeptidyl peptidase-4 inhibitors and placebo groups over 24-52 weeks. While hypoglycemia was more common with a sulfonylurea at 52-54 weeks (risk ratio: 0.46 (95% confidence interval: 0.18 to 1.18)), there was significant heterogeneity (I (2) = 87%). Limitations included high drop-out rate from most studies and small number of active-comparator studies.

CONCLUSIONS

Dipeptidyl peptidase-4 inhibitors in patients with chronic kidney disease caused a modest reduction in hemoglobin A1c versus placebo, but not when compared with sulfonylureas or albiglutide, or when used in patients on dialysis. Additional active-comparator studies are needed to further elucidate the role of dipeptidyl peptidase-4 inhibitors in patients with chronic kidney disease stages 3-5 or on dialysis.

Dipeptidyl Peptidase-4 Inhibitor Increases Vascular Leakage in Retina through VE-cadherin Phosphorylation

The inhibitors of CD26 (dipeptidyl peptidase-4; DPP4) have been widely prescribed to control glucose level in diabetic patients. DPP4-inhibitors, however, accumulate stromal cell-derived factor-1α (SDF-1α), a well-known inducer of vascular leakage and angiogenesis both of which are fundamental pathophysiology of diabetic retinopathy. The aim of this study was to investigate the effects of DPP4-inhibitors on vascular permeability and diabetic retinopathy. DPP4-inhibitor (diprotin A or sitagliptin) increased the phosphorylation of Src and vascular endothelial-cadherin (VE-cadherin) in human endothelial cells and disrupted endothelial cell-to-cell junctions, which were attenuated by CXCR4 (receptor of SDF-1α)-blocker or Src-inhibitor. Disruption of endothelial cell-to-cell junctions in the immuno-fluorescence images correlated with the actual leakage of the endothelial monolayer in the transwell endothelial permeability assay. In the Miles assay, vascular leakage was observed in the ears into which SDF-1α was injected, and this effect was aggravated by DPP4-inhibitor. In the model of retinopathy of prematurity, DPP4-inhibitor increased not only retinal vascularity but also leakage. Additionally, in the murine diabetic retinopathy model, DPP4-inhibitor increased the phosphorylation of Src and VE-cadherin and aggravated vascular leakage in the retinas. Collectively, DPP4-inhibitor induced vascular leakage by augmenting the SDF-1α/CXCR4/Src/VE-cadherin signaling pathway. These data highlight safety issues associated with the use of DPP4-inhibitors.

Renoprotective Effect of Gemigliptin, a Dipeptidyl Peptidase-4 Inhibitor, in Streptozotocin-Induced Type 1 Diabetic Mice

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) inhibitors are widely used in the treatment of patients with type 2 diabetes and have proven protective effects on diabetic kidney disease (DKD). Whether DPP-4 inhibitors have renoprotective effects on insulin-deficient type 1 diabetes has not been comprehensively examined. The aim of this study was to determine whether gemigliptin, a new DPP-4 inhibitor, has renoprotective effects in streptozotocin (STZ)-induced type 1 diabetic mice.

METHODS

Diabetes was induced by intraperitoneal administration of a single dose of STZ. Mice with diabetes were treated without or with gemigliptin (300 mg/kg) for 8 weeks. Morphological changes of the glomerular basement membrane (GBM) were observed by electron microscopy and periodic-acid Schiff staining. In addition, we measured blood glucose and urinary albumin excretion and evaluated fibrotic markers using immunohistochemical staining, quantitative reverse transcription polymerase chain reaction analysis, and Western blot analysis.

RESULTS

Gemigliptin did not reduce the blood glucose levels of STZ-treated mice. In gemigliptin-treated mice with STZ, a significant reduction in urinary albumin excretion and GBM thickness was observed. Immunohistological examination revealed that gemigliptin attenuated renal fibrosis induced by STZ and decreased extracellular matrix protein levels, including those of type I collagen and fibronectin, and Smad3 phosphorylation. In cultured rat renal cells, gemigliptin inhibited transforming growth factor β-stimulated type I collagen and fibronectin mRNA and protein levels via down-regulation of Smad3 phosphorylation.

CONCLUSION

Our data demonstrate that gemigliptin has renoprotective effects on DKD, regardless of its glucose-lowering effect, suggesting that it could be used to prevent DKD, including in patients with type 1 diabetes.

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

AIMS

Type 2 diabetes mellitus (T2DM) is associated with a high risk of chronic kidney disease (CKD). About 20% of patients with T2DM have CKD of stage ≥ 3; up to 40% have some degree of CKD. Beyond targeting all renal risk factors together, renin-angiotensin-aldosterone system blockers are to date the only effective mainstay for the treatment of diabetic kidney disease (DKD). Indeed, several potentially nephroprotective agents have been in use, which have been unsuccessful. Some glucose-lowering agents, including dipeptidyl peptidase-4 inhibitors (DPP-4i), have shown promising results. Here, we discuss the evidence that glucose lowering with DPP-4i may be an option for protecting against diabetes-related renal injury.

DATA SYNTHESIS

A comprehensive search was performed of the literature using the terms "alogliptin," "linagliptin," "saxagliptin," "sitagliptin," and "vildagliptin" for original articles and reviews addressing this topic. DPP-4i are an effective, well-tolerated treatment option for T2DM with any degree of renal impairment. Preclinical observations and clinical studies suggest that DPP-4i might also be a promising strategy for the treatment of DKD. The available data are in favor of saxagliptin and linagliptin, but the consistency of results points to the possible nephroprotective effect of DPP-4i. This property appears to be independent of glucose lowering and can potentially complement other therapies that preserve renal function. Larger prospective clinical trials are ongoing, which might strengthen these hypothesis-generating findings.

CONCLUSIONS

The improvement in albuminuria associated with DPP-4i suggests that these agents may provide renal benefits beyond their glucose-lowering effects, thus offering direct protection from DKD. These promising results must be interpreted with caution and need to be confirmed in forthcoming studies.

Cardiovascular efficacy of sitagliptin in patients with diabetes at high risk of cardiovascular disease: a 12-month follow-up

BACKGROUND

Gliptins should have beneficial effects beyond glycemic control, potentially on the pathophysiology of cardiovascular (CV) diseases, with some basic studies demonstrating this possibility. However, we are yet to answer whether there are any direct CV effects in the clinical setting. We aimed to examine the beneficial effects of sitagliptin in Japanese patients with diabetes and high CV risk for 12 months.

METHODS

This was a prospective, multicenter, observational study of 205 patients with type 2 diabetes. All participants had more than one major CV risk factor and were treated with sitagliptin for 12 months. At 3 or 12 months, we examined the effects of treatment on glycemic control, CV function (by electrocardiography, echocardiography, and reactive hyperemia-peripheral arterial tonometry), and CV biomarkers.

RESULTS

Patients were predominantly elderly (68.8 ± 9.9 years) and male (71.5 %) and typically had more than three CV risk factors (79.2 %). Treatment with sitagliptin significantly reduced the hemoglobin A1c (HbA1c) level from 7.09 % ± 0.81 % at baseline to 6.67 % ± 0.69 % at 3 months and 6.68 % ± 0.73 % at 12 months (both P < 0.001). The reduction in HbA1c was also in tandem with the decrease in the level of high-sensitive C-reactive protein throughout the study. Independent of the change in HbA1c, sitagliptin reduced systolic (-7.0 ± 18.9 mmHg) and diastolic blood pressure (-5.1 ± 11.7 mmHg) at 12 months, and this was associated with a decrease in urinary albumin. In contrast, there were no beneficial effects on cardiac and endothelial function or on the levels of serum B-type natriuretic peptide, high-sensitive troponin T, and urinary 8-hydroxy-2'-deoxyguanosine.

CONCLUSIONS

In Japanese patients with diabetes and multiple CV risk factors, sitagliptin showed a decrease in blood pressure associated with an improvement in albuminuria in addition to glycemic control.

TRIAL REGISTRATION

UMIN000005663.

Endothelial cell dysfunction and cardiac hypertrophy in the STOX1 model of preeclampsia

Preeclampsia is a disease of pregnancy involving systemic endothelial dysfunction. However, cardiovascular consequences of preeclampsia are difficult to analyze in humans. The objective of the present study is to evaluate the cardiovascular dysfunction induced by preeclampsia by examining the endothelium of mice suffering of severe preeclampsia induced by STOX1 overexpression. Using Next Generation Sequencing on endothelial cells of mice carrying either transgenic or control embryos, we discovered significant alterations of gene networks involved in inflammation, cell cycle, and cardiac hypertrophy. In addition, the heart of the preeclamptic mice revealed cardiac hypertrophy associated with histological anomalies. Bioinformatics comparison of the networks of modified genes in the endothelial cells of the preeclamptic mice and HUVECs exposed to plasma from preeclamptic women identified striking similarities. The cardiovascular alterations in the pregnant mice are comparable to those endured by the cardiovascular system of preeclamptic women. The STOX1 mice could help to better understand the endothelial dysfunction in the context of preeclampsia, and guide the search for efficient therapies able to protect the maternal endothelium during the disease and its aftermath.

Incretin-Based Therapy for Prevention of Diabetic Vascular Complications

Diabetic vascular complications are the most common cause of mortality and morbidity worldwide, with numbers of affected individuals steadily increasing. Diabetic vascular complications can be divided into two categories: macrovascular andmicrovascular complications. Macrovascular complications include coronary artery diseaseand cerebrovascular disease, while microvascular complications include retinopathy and chronic kidney disease. These complications result from metabolic abnormalities, including hyperglycemia, elevated levels of free fatty acids, and insulin resistance. Multiple mechanisms have been proposed to mediate the adverse effects of these metabolic disorders on vascular tissues, including stimulation of protein kinase C signaling and activation of the polyol pathway by oxidative stress and inflammation. Additionally, the loss of tissue-specific insulin signaling induced by hyperglycemia and toxic metabolites can induce cellular dysfunction and both macro- and microvascular complications characteristic of diabetes. Despite these insights, few therapeutic methods are available for the management of diabetic complications. Recently, incretin-based therapeutic agents, such as glucagon-like peptide-1 and dipeptidyl peptidase-4 inhibitors, have been reported to elicit vasotropic actions, suggesting a potential for effecting an actual reduction in diabetic vascular complications. The present review will summarize the relationship between multiple adverse biological mechanisms in diabetes and putative incretin-based therapeutic interventions intended to prevent diabetic vascular complications.