DPP4 inhibition attenuates filtration barrier injury and oxidant stress in the zucker obese rat

The Dipeptidyl Peptidase-4 Inhibitor Linagliptin Preserves Endothelial Function in Mesenteric Arteries from Type 1 Diabetic Rats without Decreasing Plasma Glucose

The aim of the study was to investigate the effect of the DPP-4 inhibitor linagliptin on the mechanism(s) of endothelium-dependent relaxation in mesenteric arteries from STZ-induced diabetic rats. Both normal and diabetic animals received linagliptin (2 mg/kg) daily by oral gavage for a period of 4 weeks. To measure superoxide generation in mesenteric arteries, lucigenin-enhanced chemiluminescence was used. ACh-induced relaxation of mesenteric arteries was assessed using organ bath techniques and Western blotting was used to investigate protein expression. Pharmacological tools (1μM TRAM-34, 1μM apamin, 100 nM Ibtx, 100 μM L-NNA, 10 μM ODQ) were used to distinguish between NO and EDH-mediated relaxation. Linagliptin did not affect plasma glucose, but did decrease vascular superoxide levels. Diabetes reduced responses to ACh but did not affect endothelium-independent responses to SNP. Linagliptin improved endothelial function indicated by a significant increase in responses to ACh. Diabetes impaired the contribution of both nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH) to endothelium-dependent relaxation and linagliptin treatment significantly enhanced the contribution of both relaxing factors. Western blotting demonstrated that diabetes also increased expression of Nox2 and decreased expression and dimerization of endothelial NO synthase, effects that were reversed by linagliptin. These findings demonstrate treatment of type 1 diabetic rats with linagliptin significantly reduced vascular superoxide levels and preserved both NO and EDH-mediated relaxation indicating that linagliptin can improve endothelial function in diabetes independently of any glucose lowering activity.

Dipeptidyl peptidase-4 inhibition with linagliptin and effects on hyperglycaemia and albuminuria in patients with type 2 diabetes and renal dysfunction: Rationale and design of the MARLINA-T2D™ trial

Efficacy, Safety & Modification of Albuminuria in Type 2 Diabetes Subjects with Renal Disease with LINAgliptin (MARLINA-T2D™), a multicentre, multinational, randomized, double-blind, placebo-controlled, parallel-group, phase 3b clinical trial, aims to further define the potential renal effects of dipeptidyl peptidase-4 inhibition beyond glycaemic control. A total of 350 eligible individuals with inadequately controlled type 2 diabetes and evidence of renal disease are planned to be randomized in a 1:1 ratio to receive either linagliptin 5 mg or placebo in addition to their stable glucose-lowering background therapy for 24 weeks. Two predefined main endpoints will be tested in a hierarchical manner: (1) change from baseline in glycated haemoglobin and (2) time-weighted average of percentage change from baseline in urinary albumin-to-creatinine ratio. Both endpoints are sufficiently powered to test for superiority versus placebo after 24 weeks with α = 0.05. MARLINA-T2D™ is the first of its class to prospectively explore both the glucose- and albuminuria-lowering potential of a dipeptidyl peptidase-4 inhibitor in patients with type 2 diabetes and evidence of renal disease.

The Role of Dipeptidyl Peptidase - 4 Inhibitors in Diabetic Kidney Disease

Despite major advances in the understanding of the molecular mechanisms that underpin the development of diabetic kidney disease, current best practice still leaves a significant proportion of patients with end-stage kidney disease requiring renal replacement therapy. This is on a background of an increasing diabetes epidemic worldwide. Although kidney failure is a major cause of morbidity the main cause of death remains cardiovascular in nature. Hence, diabetic therapies which are both “cardio-renal” protective seem the logical way forward. In this review, we discuss the dipeptidyl peptidase 4 (DPP4) inhibitors (DPP4inh), which are glucose-lowering agents used clinically and their role in diabetic kidney disease with specific focus on renoprotection and surrogate markers of cardiovascular disease. We highlight the novel pleiotropic effects of DPP4 that make it an attractive additional target to combat the fibrotic and inflammatory pathways in diabetic kidney disease and also discuss the current literature on the cardiovascular safety profile of DPP4inh. Clearly, these observed renoprotective effects will need to be confirmed by clinical trials to determine whether they translate into beneficial effects to patients with diabetes.

DPP-4 inhibition with linagliptin ameliorates cognitive impairment and brain atrophy induced by transient cerebral ischemia in type 2 diabetic mice

Background

It is unclear whether dipeptidylpeptidase-4 (DPP-4) inhibition can counteract the impairment of cognitive function and brain injury caused by transient cerebral ischemia in type 2 diabetes. The present study was undertaken to test our hypothesis that linagliptin, a DPP-4 inhibitor, administration following transient cerebral ischemia can ameliorate cognitive impairment and brain injury in diabetic mice.

Methods

db/db mice, a model of obese type 2 diabetes, were subjected to transient cerebral ischemia by 17 min of bilateral common carotid artery occlusion (BCCAO), and were administered (1) vehicle or (2) linagliptin for 8 weeks or 1 week. For the long-term experiment on 8 weeks of linagliptin treatment, cognitive function, and volume and neuronal cell number of hippocampus and cortex were estimated in each group of mice. For the short-term experiment on 1 week of linagliptin treatment, cerebral IgG extravasation, Iba-1 positive cell number (reactive microglia), oxidative stress, and claudin-5 and gp91phox protein levels were measured in each group of mice.

Results

Linagliptin administration almost completely suppressed the circulating DPP-4 activity in db/db mice, but did not significantly reduce blood glucose or ameliorate glucose intolerance in db/db mice. Linagliptin administration following transient cerebral ischemia significantly counteracted cognitive impairment in diabetic mice, as estimated by water maze test and passive avoidance test. Linagliptin administration ameliorated the decrease in cerebral volume and neuronal cell number in hippocampus and cortex of diabetic mice. Linagliptin administration significantly reduced the increase in cerebral IgG extravasation and the increase in reactive microglia caused by transient cerebral ischemia in diabetic mice. Furthermore, linagliptin significantly suppressed the increase in cerebral oxidative stress in transient cerebral ischemia-subjected diabetic mice. Furthermore, linagliptin significantly increased cerebral claudin-5 and significantly decreased gp91phox in diabetic mice subjected to transient cerebral ischemia.

Conclusions

DPP-4 inhibition with linagliptin counteracted cognitive impairment and brain atrophy induced by transient cerebral ischemia in diabetic mice, independently of blood glucose lowering effect. This cerebroprotective effect of linagliptin was associated with the suppression of blood-brain barrier disruption and the attenuation of cerebral oxidative stress. Thus, our present work highlights DPP-4 inhibition as a promising therapeutic strategy for cognitive impairment and cerebral vascular complications in type 2 diabetes.

The Place of Dipeptidyl Peptidase-4 Inhibitors in Type 2 Diabetes Therapeutics: A "Me Too" or "the Special One" Antidiabetic Class?

Incretin-based therapies, the most recent therapeutic options for type 2 diabetes mellitus (T2DM) management, can modify various elements of the disease, including hypersecretion of glucagon, abnormal gastric emptying, postprandial hyperglycaemia, and, possibly, pancreatic β cell dysfunction. Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) increase glucagon-like peptide-1 (GLP-1) availability and correct the "incretin defect" seen in T2DM patients. Clinical studies have shown good glycaemic control with minimal risk of hypoglycaemia or any other adverse effects, despite the reports of pancreatitis, whose association remains to be proved. Recent studies have been focusing on the putative ability of DPP-4 inhibitors to preserve pancreas function, in particular due to the inhibition of apoptotic pathways and stimulation of β cell proliferation. In addition, other cytoprotective effects on other organs/tissues that are involved in serious T2DM complications, including the heart, kidney, and retina, have been increasingly reported. This review outlines the therapeutic potential of DPP-4 inhibitors for the treatment of T2DM, focusing on their main features, clinical applications, and risks, and discusses the major challenges for the future, in particular the possibility of becoming the preferred therapy for T2DM due to their ability to modify the natural history of the disease and ameliorate nephropathy, retinopathy, and cardiovascular complications.

DPP4 in cardiometabolic disease: recent insights from the laboratory and clinical trials of DPP4 inhibition

The discovery of incretin-based medications represents a major therapeutic advance in the pharmacological management of type 2 diabetes mellitus (T2DM), as these agents avoid hypoglycemia, weight gain, and simplify the management of T2DM. Dipeptidyl peptidase-4 (CD26, DPP4) inhibitors are the most widely used incretin-based therapy for the treatment of T2DM globally. DPP4 inhibitors are modestly effective in reducing HbA1c (glycated hemoglobin) (≈0.5%) and while these agents were synthesized with the understanding of the role that DPP4 plays in prolonging the half-life of incretins such as glucagon-like peptide-1 and gastric inhibitory peptide, it is now recognized that incretins are only one of many targets of DPP4. The widespread expression of DPP4 on blood vessels, myocardium, and myeloid cells and the nonenzymatic function of CD26 as a signaling and binding protein, across a wide range of species, suggest a teleological role in cardiovascular regulation and inflammation. Indeed, DPP4 is upregulated in proinflammatory states including obesity, T2DM, and atherosclerosis. Consistent with this maladaptive role, the effects of DPP4 inhibition seem to exert a protective role in cardiovascular disease at least in preclinical animal models. Although 2 large clinical trials suggest a neutral effect on cardiovascular end points, current limitations of performing trials in T2DM over a limited time horizon on top of maximal medical therapy must be acknowledged before rendering judgment on the cardiovascular efficacy of these agents. This review will critically review the science of DPP4 and the effects of DPP4 inhibitors on the cardiovascular system.

DPP-4 inhibitor sitagliptin prevents inflammation and oxidative stress of heart and kidney in two kidney and one clip (2K1C) rats

BACKGROUND

Hyperglycemia and insulin resistance often develop cardiovascular and nephrological dysfunction in diabetic patients. Sitagliptin is used to treat diabetes and showed potential benefit in lowering increased blood glucose level in diabetes. This investigation reports the effect of sitagliptin treatment on oxidative stress in kidney and heart of 2K1C rats.

METHODS

Male Long Evans rats underwent unilateral surgical stenosis of the renal artery [2-kidney-1-clip (2K1C) method]. These animals entered a 4-weeks dosing period with sitagliptin. Blood and urine sampling and organ harvesting were finally performed. Blood plasma, heart, kidney tissues and urine were tested for the assessment of inflammation and oxidative stress in kidney and heart of 2K1C rats after 4 weeks of surgery.

RESULTS

2K1C rats showed cardiac hypertrophy, increased left ventricular wet weight compared to sham which was not significantly altered by sitagliptin treatment. Uric acid and creatinin concentrations were also increased in 2K1C rats. Sitagliptin significantly prevented the elevation of uric acid and creatinin concentration in plasma and urine in this rat model. Oxidative stress markers in plasma such as malondialdehyde (MDA), nitric oxide (NO), and advanced protein oxidation product (APOP) concentrations were increased in the 2K1C rats as compared to sham-operated animals. Increased concentrations of these oxidative stress markers were also normalized by sitagliptin treatment. 2K1C rats also showed increased level of uric acid and creatinine both in plasma and urine; which are also reduced to normal level in sitagliptin treated rats. Moreover, 2K1C surgery initiated inflammatory cell infiltration, increased MPO activity and fibrosis in both heart and kidneys which were further ameliorated by sitagliptin treatment.

CONCLUSION

Our study suggests that sitagliptin treatment in 2K1C rats prevented inflammation and fibrosis of heart and kidney by ameliorating elevated oxidative stress in heart and kidney tissues.

DPP-4 inhibitor linagliptin ameliorates cardiovascular injury in salt-sensitive hypertensive rats independently of blood glucose and blood pressure

Background

It remains to be elucidated whether dipeptidylpeptidase-4 (DPP-4) inhibitor can ameliorate cardiovascular injury in salt-sensitive hypertension. The present study was undertaken to test our hypothesis that linagliptin, a DPP-4 inhibitor, administration initiated after onset of hypertension and cardiac hypertrophy can ameliorate cardiovascular injury in Dahl salt-sensitive hypertensive rats (DS rats).

Methods

High-salt loaded DS rats with established hypertension and cardiac hypertrophy were divided into two groups, and were orally given (1) vehicle or (2) linagliptin (3 mg/kg/day) once a day for 4 weeks, and cardiovascular protective effects of linagliptin in DS rats were evaluated.

Results

Linagliptin did not significantly affect blood pressure and blood glucose levels in DS rats. Linagliptin significantly lessened cardiac hypertrophy in DS rats, as estimated by cardiac weight and echocardiographic parameters. Linagliptin significantly ameliorated cardiac fibrosis, cardiac macrophage infiltration, and coronary arterial remodeling in DS rats. Furthermore, linagliptin significantly mitigated the impairment of vascular function in DS rats, as shown by the improvement of acetylcholine-induced or sodium nitroprusside-induced vascular relaxation by linagliptin. These cardiovascular protective effects of linagliptin were associated with the attenuation of oxidative stress, NADPH oxidase subunits, p67^phox and p22 ^phox, and angiotensin-converting enzyme (ACE).

Conclusions

Our results provided the experimental evidence that linagliptin treatment initiated after the appearance of hypertension and cardiac hypertrophy protected against cardiovascular injury induced by salt-sensitive hypertension, independently of blood pressure and blood glucose. These beneficial effects of linagliptin seem to be attributed to the reduction of oxidative stress and ACE.