Plasma DPP-4 Research Articles

Screening of a natural compound library identifies emodin, a natural compound from Rheum palmatum Linn that inhibits DPP4.

Historically, Chinese herbal medicines have been widely used in the treatment of hyperglycemia, but the mechanisms underlying their effectiveness remain largely unknown. Here, we screened a compound library primarily comprised of natural compounds extracted from herbs and marine organisms. The results showed that emodin, a natural compound from Rheum palmatum Linn, inhibited DPP4 activity with an in vitro IC50 of 5.76 µM without inhibiting either DPP8 or DPP9. A docking model revealed that emodin binds to DPP4 protein through Glu205 and Glu206, although with low affinity. Moreover, emodin treatment (3, 10 and 30 mg/kg, P.O.) in mice decreased plasma DPP4 activity in a dose-dependent manner. Our study suggests that emodin inhibits DPP4 activity and may represent a novel therapeutic for the treatment of type 2 diabetes.

Association of DPP-4 activity with BMD, body composition, and incident hip fracture: the Cardiovascular Health Study.

Dipeptidyl peptidase IV (DPP-4) inactivates several key hormones including those that stimulate postprandial insulin secretion, and DPP-4 inhibitors (gliptins) are approved to treat diabetes. While DPP-4 is known to modulate osteogenesis, the relationship between DPP-4 activity and skeletal health is uncertain. The purpose of the present study was to examine possible associations between DPP-4 activity in elderly subjects enrolled in the Cardiovascular Health Study (CHS) and BMD, body composition measurements, and incident hip fractures. All 1536 male and female CHS participants who had evaluable DXA scans and plasma for DPP-4 activity were included in the analyses. The association between (1) BMD of the total hip, femoral neck, lumbar spine, and total body; (2) body composition measurements (% lean, % fat, and total body mass); and (3) incident hip fractures and plasma levels of DPP-4 activity were determined. Mean plasma levels of DPP-4 activity were significantly higher in blacks (227±78) compared with whites (216±89) (p=0.04). However, there was no significant association of DPP-4 activity with age or gender (p≥0.14 for both). In multivariable adjusted models, there was no association of plasma DPP-4 activity with BMD overall (p≥0.55 for all) or in gender stratified analyses (p≥0.23). There was also no association of DPP-4 levels and incident hip fractures overall (p≥0.24) or in gender stratified analyses (p≥0.39). Plasma DPP-4 activity, within the endogenous physiological range, was significantly associated with race, but not with BMD, body composition, or incident hip fractures in elderly community-dwelling subjects.

Circulating fibroblast activation protein and dipeptidyl peptidase 4 in rheumatoid arthritis and systemic sclerosis.

To quantify circulating fibroblast activation protein (cFAP) and dipeptidyl peptidase 4 (cDPP4) protease activities in patients with rheumatoid arthritis (RA), systemic sclerosis (SSc), and a control group with mechanical back pain and to correlate plasma levels with disease characteristics. Plasma was collected from patients with RA (n = 73), SSc (n = 37) and control subjects (n = 26). DPP4 and FAP were quantified using specific enzyme activity assays. Median cDPP4 was significantly lower in the RA group (P = 0.02), and SSc group (P = 0.002) compared with controls. There were no significant differences in median cFAP between the three groups. DPP4 and FAP demonstrated a negative correlation with inflammatory markers and duration of disease. There were no associations with disease subtypes in RA, including seropositive and erosive disease. Decreased cDPP4 was found in SSc patients with myositis. Plasma FAP was lower in RA patients receiving prednisone (P = 0.001) or leflunomide (P = 0.04), but higher with biologic agents (P = 0.01). RA patients receiving leflunomide also had decreased cDPP4 (P = 0.014). SSc patients receiving prednisone (P = 0.02) had lower cDPP4 but there was no association with cFAP. No association was found between cFAP and RA or SSc. Plasma DPP4 was decreased in RA and SSc when compared with controls. cDPP4 and cFAP correlated negatively with inflammatory markers and there were no significant correlations with disease characteristics in this RA cohort.

A potential contribution of dipeptidyl peptidase-4 by the mediation of monocyte differentiation in the development and progression of abdominal aortic aneurysms

ObjectiveAbdominal aortic aneurysms (AAAs) are characterized by the destruction of elastin and collagen in the media and adventitia. Dipeptidyl peptidase-4 (DPP-4, an adipokine known as CD26) influences cell signaling, cell-matrix interactions, and the regulation of the functional activity of incretins in metabolic and inflammatory disorders. Although the role of DPP-4 in AAA evolution has been demonstrated, the underlying mechanisms of DPP-4-regulated AAA development remains unknown. MethodsPatients with AAA (n = 93) and healthy controls (CTL, n = 20) were recruited. Based on computed tomography image analyses, 93 patients were divided into two groups: those with a small AAA (SAA, aortic diameter <5 cm, n = 16) and those with a large AAA (LAA, aortic diameter ≥5 cm, n = 77). Plasma DPP-4, glucagon-like peptide-1 levels, and expression of CD26 on mononuclear cells were analyzed. In addition, phorbol 12-myristate 13-acetate (PMA)-induced THP-1 cells and angiotensin II-infused apolipoprotein EtmlUnc mice were used to explore the underlying mechanisms. ResultsThe levels of DPP-4 (μU/μg) increased while active glucagon-like peptide-1 (pM) decreased in patients with AAA in a diameter-dependent manner [CTL: 2.3 ± 1.5 and 3.7 ± 2.4, respectively; SAA: 10.0 ± 10.9 and 2.1 ± 0.9, respectively; LAA: 32.2 ± 15.0 and 1.8 ± 1.1, respectively]. A significant decline in monocyte CD26 expression in patients with AAAs was observed relative to the CTL group. In vitro studies demonstrated that the inhibition of DPP-4 promoted PMA-induced monocytic cells differentiation, with increased CD68 and p21 expression, regulated by extracellular signal-regulated protein kinase 1/2 activation. Furthermore, inhibition of DPP-4 significantly increased the phosphorylation of PYK2 and paxillin in PMA-induced THP-1 cell differentiation. Finally, the animal study was used to confirm the in vitro results that LAA mice showed marked macrophage infiltration in the adventitia with a decreased expression of DPP-4 as compared with SAA mice. ConclusionsIncreased plasma DPP-4 activity may correlate with aneurysmal development. CD26 on monocytes plays a critical role in cell differentiation, possibly mediated by extracellular signal-regulated protein kinase 1/2-p21 axis signaling pathways and cytoskeletal proteins reassembly. Exploring the role of DPP-4 further may yield potential therapeutic insights.

Clinical Pharmacokinetics and Pharmacodynamics of Saxagliptin, a Dipeptidyl Peptidase-4 Inhibitor.

Saxagliptin is an orally active, highly potent, selective and competitive dipeptidyl peptidase (DPP)-4 inhibitor used in the treatment of type2 diabetes mellitus at doses of 2.5 or 5mg once daily. DPP-4 is responsible for degrading the intestinally derived hormones glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP). Inhibition of DPP-4 increases intact plasma GLP-1 and GIP concentrations, augmenting glucose-dependent insulin secretion. Both saxagliptin and its major active metabolite, 5-hydroxy saxagliptin, demonstrate high degrees of selectivity for DPP-4 compared with other DPP enzymes. Saxagliptin is orally absorbed and can be administered with or without food. The half-life of plasma DPP-4 inhibition with saxagliptin 5mg is ~27 h, which supports a once-daily dosing regimen. Saxagliptin is metabolized by cytochrome P450 (CYP) 3A4/5 and is eliminated by a combination of renal and hepatic clearance. No clinically meaningful differences in saxagliptin or 5-hydroxy saxagliptin pharmacokinetics have been detected in patients with hepatic impairment. No clinically meaningful differences in saxagliptin or 5-hydroxy saxagliptin pharmacokinetics have been detected in patients with mild renal impairment, whereas dose reduction is recommended in patients with moderate or severe renal impairment because of greater systemic exposure [the area under the plasma concentration-time curve (AUC)] to saxagliptin total active moieties. Clinically relevant drug-drug interactions have not been detected; however, limiting the dose to 2.5mg once daily is recommended in the USA when saxagliptin is coadministered with strong CYP inhibitors, because of increased saxagliptin exposure. In summary, saxagliptin has a predictable pharmacokinetic and pharmacodynamic profile.

The effect of combined treatment with canagliflozin and teneligliptin on glucose intolerance in Zucker diabetic fatty rats

To assess the impact of concomitant inhibition of sodium-glucose cotransporter (SGLT) 2 and dipeptidyl peptidase IV (DPP4) for the treatment of type 2 diabetes mellitus (T2DM), the effect of combined treatment with canagliflozin, a novel SGLT2 inhibitor, and teneligliptin, a DPP4 inhibitor, on glucose intolerance was investigated in Zucker diabetic fatty (ZDF) rats. Canagliflozin potently inhibited human and rat SGLT2 and moderately inhibited human and rat SGLT1 activities but did not affect DPP4 activity. In contrast, teneligliptin inhibited human and rat DPP4 activities but not SGLT activities. A single oral treatment of canagliflozin and teneligliptin suppressed plasma glucose elevation in an oral glucose tolerance test in 13 week-old ZDF rats. This combination of agents elevated plasma active GLP-1 levels in a synergistic manner, probably mediated by intestinal SGLT1 inhibition, and further improved glucose intolerance. In the combination-treated animals, there was no pharmacokinetic interaction of the drugs and no further inhibition of plasma DPP4 activity compared with that in the teneligliptin-treated animals. These results suggest that the inhibition of SGLT2 and DPP4 improves glucose intolerance and that combined treatment with canagliflozin and teneligliptin is a novel therapeutic option for glycemic control in T2DM.

Increased plasma DPP4 activities predict new-onset hyperglycemia in Chinese over a four-year period: Possible associations with inflammation

ObjectiveDPP4, a novel proinflammatory cytokine, is involved in the inflammatory process through its interaction with the IGF-II/M6P receptor. Our objective was to determine whether DPP4 acts as a link between low-grade chronic inflammation and hyperglycemia. Design and methodsA prospective cohort study was conducted with 486 adults (177 men and 309 women) aged 18 to 70years without hyperglycemia examined in 2007 (baseline) and 2011 (follow-up). Circulating DPP4 activity, IGF-II/M6P receptor, and inflammatory markers were measured at baseline and four years later. ResultsAfter a four-year follow-up period, 111 individuals developed hyperglycemia (71 prediabetes and 40 type 2 diabetes). According to the multiple linear regression analysis, the baseline DPP4 activity was an independent predictor of an increase in the IGF-II/M6P receptor, inflammatory markers, and insulin resistance over the four-year period (all P <0.05).In the multivariable-adjusted models, the odds ratio (OR) for incident hyperglycemia comparing the highest and lowest quartiles of DPP4 activity was 2.90 (95% CI 1.47–5.73) after adjustment for confounding risk factors (P=0.002). The incidence of hyperglycemia because of DPP4 activity increased by 9.47%. Furthermore, the plasma DPP4 activity significantly improved the area under the ROC curve for predicting new-onset hyperglycemia based on the information from the baseline levels of the risk factors (P=0.036). ConclusionsDPP4 activity is an important predictor of the onset of insulin resistance and hyperglycemia in apparently healthy Chinese. This finding may have important implications for understanding the proinflammatory role of DPP-4 in the development and pathogenesis of hyperglycemia.

Mechanism of increase in plasma intact GLP-1 by metformin in type 2 diabetes: Stimulation of GLP-1 secretion or reduction in plasma DPP-4 activity?

Metformin was reported to increase plasma intact glucagon-like peptide-1 (GLP-1) concentrations in type 2 diabetes. This is, at least partly, attributable to stimulation of GLP-1 secretion. A reduction in soluble dipeptidyl peptidase-4 activity may also make a modest contribution.

Dipeptidyl Peptidase IV Inhibitor Protects Against Tacrolimus-Induced Pancreatic and Renal Injury.

Background: Dipeptidyl peptidase IV (DPP IV) inhibitors had a protective effect in various disease models. This study was performed to evaluate whether sitagliptin, a DPP IV inhibitor, is effective against tacrolimus-induced pancreatic and renal injury. Method: Tacrolimus (TAC, 1.5mg/kg/day, s.c.) with or without sitagliptin (10, 20 mg/kg/day, gavage) were administered to rats for 4 weeks. We evaluated the effect of sitagliptin on DPP IV activity and GLP-1 level in tacrolimus-treated rats, and assessed the protective effect of sitagliptin in an experimental model of chronic tacrolimus-induced nephropathy and pancreatic injury. Oxidative stress and oxidative resistance were evaluated by measuring 8-hydroxy-2'-deoxyguanosine (8-OHdG) and heme oxygenase-1 (HO-1). The protective mechanism of sitagliptin was also tested based on the glucagon like peptide-1 (GLP-1)/ (forkhead box O) FoxO pathway. Results: Tacrolimus treatment for 4 weeks caused a 2-fold increase in plasma DPP4 activity and a 5-fold decrease in serum active GLP-1 levels; however, concomitant treatment with sitagliptin reversed these effects. Sitagliptin treatment attenuated tacrolimus-induced pancreatic islet and renal dysfunction, with improvement of islet size and renal tubulointerstitial fibrosis. Tacrolimus treatment increased oxidative stress marker, 8-OHdG and decreased oxidative resistance gene (reduced HO-1), and its underlying pathways (FoxO1 activation and FoxO3 deactivation), whereas sitagliptin treatment reversed these changes. Treatment of primary rat islet and HK-2 cells with GLP-1 also decreased the oxidative injury caused by tacrolimus. Consequently, sitagliptin upregulated antioxidant enzymes e.g. manganese superoxide dismutase, and downregulated proapoptotic proteins e.g. B-cell lymphoma 2-interacting mediator of cell death and apoptotic cell death assessed by the number of TDT-mediated dUTP-biotin nick end labeling-positive cells. Conclusion:DPP IV inhibition by sitagliptin attenuated TAC-induced pancreatic islet and renal dysfunction and enhanced the GLP-1 signaling pathway, which may be associated with a decrease in oxidative injury and apoptotic cell death. These beneficial effects of the DPP IV inhibitor may be helpful in delaying the onset of TAC-induced diabetes and nephropathy in renal transplant patients.

Profile of saxagliptin in the treatment of type 2 diabetes: focus on Japanese patients

Saxagliptin is a selective and potent dipeptidyl peptidase (DPP)-4 inhibitor, approved as an adjunct to diet and exercise to improve glycemic control in type 2 diabetes mellitus (T2DM) in the USA on July 2009, and had been launched globally in over 86 countries by September 2013. In patients with T2DM, once-daily administration of saxagliptin before breakfast achieves sustained inhibition of plasma DPP-4 activity and reduction of postprandial hyperglycemia, including after dinner, associated with an increase in plasma glucagon-like peptide-1 levels. This paper reviews the safety and efficacy of saxagliptin in Japanese patients with T2DM. The clinical development study in Japan supported its usefulness for the disease. Saxagliptin 1, 2.5, and 5 mg led to significant improvements in glycated hemoglobin (HbA1c), and was generally well tolerated. Treatment with saxagliptin 5 mg induced a sustained reduction in HbA1c over 52 weeks. Long-term combination therapy with saxagliptin and other oral hypoglycemic agents also provided sustained glycemic control and was well tolerated for up to 52 weeks. Saxagliptin as add-on to sulfonylureas or glinides has a tendency to increase hypoglycemia, but not with other oral antidiabetic agents, such as α-glucosidase inhibitors, metformin, or thiazolidinediones. The results of clinical trials have confirmed the long-term efficacy and safety of saxagliptin monotherapy as well as its use as add-on combination therapy, and support its usefulness as a therapeutic agent for T2DM. Saxagliptin has less concern for hypoglycemia and weight gain, which often becomes problematic in routine care of T2DM. Meta-analysis of clinical trials in the USA showed no evidence of increased risk of cardiovascular events associated with saxagliptin, suggesting the superior of saxagliptin in terms of safety. Recently, investigators in the SAVOR-TIMI (Saxagliptin Assessment of Vascular Outcomes Recorded in Patients with Diabetes Mellitus-Thrombolysis in Myocardial Infarction) 53 study suggested that DPP-4 inhibition with saxagliptin did not increase or decrease the rate of ischemic events, although the rate of hospitalization for heart failure was increased. Although saxagliptin improves glycemic control, other approaches are necessary to reduce cardiovascular risk in patients with diabetes. Saxagliptin is applicable for various pathological conditions, and is considered to be clinically significant as a new therapeutic option for Japanese patients with T2DM.

Discovery of highly potent DPP-4 inhibitors by hybrid compound design based on linagliptin and alogliptin

Highly potent DPP-4 inhibitors have been identified by hybrid compound design based on linagliptin and alogliptin. The most promising compound 2h (IC50 = 0.31 nM) exhibited 8.5-fold and 2.5-fold more potent activity than that of alogliptin (IC50 = 2.63 nM) and linagliptin (IC50 = 0.77 nM), respectively. Compound 2h had a good inhibition selectivity for DPP-4 over DPP-8/9 and thus was selected for further biological evaluation, including oral glucose tolerance, plasma DPP-4 inhibitory activity, pharmacokinetic profile, acute toxicity and hERG inhibition. The assay results showed that 2h displayed significant in vivo glucose-lowering effect and low risk of toxicity. Further studies are expected to confirm 2h as a potential drug candidate for the treatment of type 2 diabetes.

Increased plasma DPP4 activities predict new-onset atherosclerosis in association with its proinflammatory effects in Chinese over a four year period: A prospective study

ObjectiveDPP4, a novel proinflammatory cytokine, is involved in the inflammatory process through its interaction with IGF-II/M6P receptor. We aimed to investigate whether it could predict new-onset atherosclerosis in Chinese. MethodsA prospective study was conducted of 590 adults (213 men and 377 women) aged 18–70 years without atherosclerosis examined in 2007(baseline) and 2011(follow-up). Circulating DPP4 activity, inflammatory markers, IGF-II/M6P receptor and common carotid artery Intima-Media Thickness (C-IMT) were measured at baseline and four years later. ResultsAt baseline, individuals in the highest quartile of DPP4 activity had higher age, WHR, BMI, SBP, fasting insulin, 2h-PG, TG, LDL-C, IL-6, hs-CRP, IGF-II/M6P-R, C-IMT and lower HDL-C compared with individuals in the lowest quartile. After a 4-year follow-up, 71 individuals developed atherosclerosis. In multiple linear regression analysis, baseline DPP4 activity was an independent predictor of an increase in inflammatory markers, IGF-II/M6P receptor, and C-IMT over a 4-year period (all P < 0.01). In multivariable-adjusted models, the odds ratio (OR) for incident atherosclerosis comparing the highest with the lowest quartiles of DPP4 activity was 3.17 (95%CI 1.33–7.58) after adjustment for confounding risk factors (P = 0.009). The incidence of atherosclerosis owing to DPP4 activity increased by 12.41%. ConclusionsDPP4 activity is an important predictor of the onset of inflammation and atherosclerosis in apparently healthy Chinese. This finding may have important implications for understanding the proinflammatory role of DPP-4 in the pathogenesis of atherosclerosis.

GLP-1 released to the mesenteric lymph duct in mice: Effects of glucose and fat

Using a newly developed in vivo model measuring glucagon-like peptide-1 (GLP-1) in gut lymphatics in mice, we quantified GLP-1 secretion in vivo after glucose versus fat ingestion with and without concomitant DPP-4 inhibition. The mesenteric lymphatic duct was cannulated in anesthetized C57BL6/J mice and lymph was collected in 30min intervals. Glucose or fat emulsion (IntralipidR) (0.03, 0.1 or 0.3kcal) with or without DPP-4-inhibition (NVP DPP728; 10μmol/kg) was administered by gastric gavage. Basal intact GLP-1 levels were 0.37±0.04pmol/l (n=61) in lymph compared to 0.07±0.03 in plasma (n=6; P=0.04) and basal DPP-4 activity was 4.7±0.3pmol/min/μl in lymph (n=23) compared to 22.3±0.9pmol/min/μl in plasma (n=8; P<0.001). Lymph flow increased from 1.2±0.1μl/min to 2.3±02μl/min at 30min after glucose and fat administration, with no difference between type of challenge or dose (n=81). Lymph GLP-1 levels increased calorie-dependently after both glucose and fat but with different time courses in that glucose induced a transient increase which had returned to baseline after 90min whereas the lipid induced a sustained increase which was still elevated above baseline after 210min. Lymph GLP-1 appearance during 210min was two to three-fold higher after glucose (7.4±2.3fmol at 0.3kcal) than after isocaloric fat (2.9±0.8fmol at 0.3kcal; P<0.001). The slope between caloric load and lymph GLP-1 appearance was, however, identical after glucose and fat. We conclude that lymph GLP-1 is higher than plasma GLP-1 whereas lymph DPP-4 activity is lower than plasma DPP-4 activity and that both glucose and fat clearly stimulate GLP-1 secretion calorie-dependently in vivo but with different time courses.

Population Pharmacokinetic/Pharmacodynamic Analysis of the DPP-4 Inhibitor Linagliptin in Japanese Patients with Type 2 Diabetes Mellitus

Linagliptin is a novel, highly selective and long acting DPP-4 inhibitor for the treatment of type 2 diabetes mellitus (T2DM). Linagliptin exhibits non-linear pharmacokinetics (PK) due to saturable binding to plasma and tissue DPP-4. The aim of this study was to characterize the PK and PK/DPP-4 inhibition relationship of linagliptin in Japanese patients with T2DM using a population PK/DPP-4 model and to support the rationale for the therapeutic dose in Japanese patients by simulation. Linagliptin plasma concentration and DPP-4 inhibition measurements from a placebo-controlled, parallel group multiple (28 days) dose trial that included 36 T2DM patients (18 patients each in 2.5 mg and 10 mg dose group) were used for analysis. Modeling was performed using FOCE INTERACTION estimation method implemented in NONMEM V. The linagliptin plasma concentration- and DPP-4 inhibition- time profiles were simulated for Japanese patients receiving 5 mg linagliptin once daily by the model established. Nonlinear PK of linagliptin in T2DM patients were well described by a 2-compartment model assuming concentration-dependent binding to DPP-4 in the central and peripheral compartment. Plasma DPP-4 inhibition was integrated in the model by relating the model-predicted DPP-4 occupancy with linagliptin linearly to DPP-4 inhibition. The simulation predicted that for the 5 mg dose group the trough DPP-4 inhibition at steady-state was 84.2%, which is higher than the target inhibition (≥80%) for an effective dose of DPP-4 inhibitor. In 2.5 mg dose group, steady-state DPP-4 inhibition of >80% was not maintained over 24 hours (observed and simulated). The nonlinear PK of linagliptin and its plasma DPP-4 inhibition in patients were well characterized by a target-mediated drug disposition model relating DPP-4 occupancy with linagliptin to DPP-4 inhibition. Simulations of plasma DPP-4 inhibition suggest that 5 mg linagliptin once daily is an appropriate therapeutic dose for Japanese patients with T2DM.

Dipeptidyl peptidase-4 inhibitor anagliptin ameliorates diabetes in mice with haploinsufficiency of glucokinase on a high-fat diet

ObjectiveType 2 diabetes is a chronic metabolic disorder characterized by hyperglycemia with insulin resistance and impaired insulin secretion. DPP-4 inhibitors have attracted attention as a new class of anti-diabetic agents for the treatment of type 2 diabetes. We investigated the effects of anagliptin, a highly selective DPP-4 inhibitor, on insulin secretion and insulin resistance in high-fat diet-fed mice with haploinsufficiency of glucokinase (GckKO) as animal models of type 2 diabetes. Materials/MethodsWild-type and GckKO mice were administered two doses of anagliptin by dietary admixture (0.05% and 0.3%) for 10weeks. ResultsBoth doses of anagliptin significantly inhibited the plasma DPP-4 activity and increased the plasma active GLP-1 levels in both the wild-type and GckKO mice to a similar degree. After 10weeks of treatment with 0.3% anagliptin, body weight gain and food intake were significantly suppressed in both wild-type and GckKO mice. In addition, 0.3% anagliptin ameliorated insulin resistance and glucose intolerance in both genotypes of mice. On the other hand, treatment with 0.05% anagliptin was not associated with any significant change of the body weight, food intake or insulin sensitivity in either genotype of mice, but it did improve the glucose tolerance by enhancing insulin secretion and increasing the β-cell mass in both genotypes of mice. ConclusionsHigh-dose anagliptin treatment improved glucose tolerance by suppression of body weight gain and amelioration of insulin resistance, whereas low-dose anagliptin treatment improved glucose tolerance by enhancing insulin secretion.

Polymorphisms in dipeptidyl peptidase IV gene are associated with the risk of myocardial infarction in patients with atherosclerosis

BackgroundDipeptidyl peptidase IV (DPP-IV) is not only important in pancreatic β-cell regulation but also has proinflammatory actions that can contribute to atherosclerosis progression. Previously, we showed that DPP-IV is co-localized with CD31 (an endothelial cell marker) in the neovessels within the human atherosclerotic plaques.These characteristics of DPP-IV may predispose patients with coronary artery disease (CAD) to plaque rupture and thus to myocardial infarction. The goal of this investigation was to determine whether genetic alterations in DPP-IV predispose to plaque vulnerability and myocardial infarction (MI). MethodsBetween Aug 2004, and March 2007, blood samples of patients (age <60) with angiographically documented CAD were collected. Demographic, clinical, risk factor, and angiographic data were recorded. Eight hundred and seventy five patients of European ancestry with angiographic CAD were divided into those with MI (n=421) and those without (n=454).A genome-wide association study was performed using the Affymetrix 6.0 chip to identify loci that predispose to MI. In the current study we only focused on DPP4 gene to assess the association of single nucleotide polymorphisms (SNPs) in the DPP-IV gene and risk of MI in patients with CAD. For genotyped SNPs, association was tested by logistic regression with significance level of 0.05. Plasma DPP-IV level was measured using a commercial ELISA kit. ResultsAverage patients’ age at diagnosis of CAD was 46.8years for MI group and 50.8 in the non MI group. There was no difference in distribution of traditional risk factors between the two groups. We identified one SNP (rs3788979) that was significantly related to angiographic CAD with MI, vs. without MI (OR: 1.36, p=0.03). The association of the identified SNP to MI risk was not attenuated after adjustment for traditional risk factors. The SNP was associated with lower levels of plasma DPP-IV (p=0.005). Moreover, CAD patients with the major alleles (GG) and no MI had highest plasma DPP-IV levels. (481.6, p=0.002). ConclusionsA polymorphism in the DPP-IV gene in patients with known CAD may increase the risk of MI. This SNP is associated with decreased plasma DPP4 level in patients with MI.

Linagliptin Increases Incretin Levels, Lowers Glucagon, and Improves Glycemic Control in Type 2 Diabetes Mellitus

IntroductionLinagliptin is a xanthine-based dipeptidyl peptidase (DPP)-4 inhibitor that is now available in numerous countries worldwide for the treatment of type 2 diabetes mellitus (T2DM). The aim of this study was to evaluate further the mechanisms underlying the improvements in glycemic control observed with linagliptin. The effects of linagliptin on DPP-4, pharmacodynamic parameters, and glycemic control versus placebo were assessed in patients with inadequately controlled T2DM.MethodsPatients in this phase 2a, multicenter, randomized, double-blind, placebo-controlled study received placebo (n = 40) or linagliptin 5 mg (n = 40). Sitagliptin 100 mg (n = 41) once daily for 4 weeks was included for exploratory purposes. Primary endpoints for linagliptin versus placebo: change from baseline to day 28 in 24-h weighted mean glucose (WMG) and intact glucagon-like peptide (GLP)-1 area under the time–effect curve between 0 and 2 h (AUEC0–2h) following meal tolerance test on day 28.ResultsLinagliptin increased intact GLP-1 AUEC0–2h (+18.1 pmol/h/L) and lowered 24-h WMG (−1.1 mmol/L) versus placebo (both P < 0.0001) after 28 days. Intact glucose-dependent insulinotropic polypeptide increased in line with GLP-1 (+91.4 pmol/h/L increase vs. placebo; P < 0.0001). Glycated hemoglobin (−0.22%; P = 0.0021), fasting plasma glucose (−0.6 mmol/L; P = 0.0283), and glucose (AUEC0–3h) (−5.9 mmol/h/L; P < 0.0001) improved significantly with linagliptin versus placebo. Most adverse events were mild; hypoglycemia or serious adverse events were not reported. Sustained DPP-4 inhibition (≥80%) throughout the treatment period was accompanied by significant reductions in glucagon starting at day 1 of linagliptin administration.ConclusionLinagliptin was well tolerated and effectively inhibited plasma DPP-4 activity in patients with T2DM, producing immediate improvements in incretin levels, glucagon suppression, and glycemic control that were maintained throughout the study period.

Clinical Pharmacokinetics and Pharmacodynamics of Linagliptin

Linagliptin is an orally active small-molecule inhibitor of dipeptidyl peptidase (DPP)-4, which was first licensed in the US, Europe, Japan and other territories in 2011 to improve glycaemic control in adults with type 2 diabetes mellitus. Linagliptin is the first and thus far the only DPP-4 inhibitor, and oral antihyperglycaemic drug in general, to be approved as a single-strength once-daily dose (5 mg). Compared with other available DPP-4 inhibitors, linagliptin has a unique pharmacokinetic/pharmacodynamic profile that is characterized by target-mediated nonlinear pharmacokinetics, concentration-dependent protein binding, minimal renal clearance and no requirements for dose adjustment for any intrinsic or extrinsic factor. After single or multiple oral doses of 1-10 mg, linagliptin displays less than dose-proportional increases in maximum plasma concentration (C(max)) and area under the plasma concentration-time curve (AUC). Linagliptin is rapidly absorbed after oral administration, with C(max) occurring after approximately 90 minutes, and reaches steady-state concentrations within 4 days. With the therapeutic dose, steady-state C(max) (11-12 nmol/L) and AUC (∼150 nmol · h/L) are approximately 1.3-fold greater than after a single dose, indicating little drug accumulation with repeat dosing. Linagliptin exhibits concentration-dependent protein binding in human plasma in vitro (99% at 1 nmol/L to 75-89% at >30 nmol/L) and has a large apparent volume of distribution, demonstrating extensive distribution into tissues. The nonlinear pharmacokinetics of linagliptin are best described by a two-compartmental model that incorporates target-mediated drug disposition resulting from high-affinity, saturable binding to DPP-4. The oral bioavailability of linagliptin estimated with this model is approximately 30%. Linagliptin has a long terminal half-life (>100 hours); however, its accumulation half-life is much shorter (approximately 10 hours), accounting for the rapid attainment of steady state. The majority of linagliptin is eliminated as parent compound, demonstrating that metabolism plays a minor role in the overall pharmacokinetics in humans. The main, pharmacologically inactive S-3-hydroxypiperidinyl metabolite accounted for approximately 17% of the total drug-related compounds in plasma. Linagliptin is eliminated primarily in faeces, with only around 5% of the oral therapeutic dose excreted in the urine at steady state. Linagliptin potently inhibits DPP-4 (inhibition constant 1 nmol/L), and trough drug concentrations achieved with therapeutic dosing inhibit >80% of plasma DPP-4 activity, the threshold associated with maximal antihyperglycaemic effects in animal models. There are no clinically relevant alterations in linagliptin pharmacokinetics resulting from renal impairment, hepatic impairment, coadministration with food, race, body weight, sex or age. In vitro, linagliptin is a weak substrate and weak inhibitor of cytochrome P450 (CYP) 3A4 and permeability glycoprotein (P-gp) but not of other CYP isozymes or ATP-binding cassette transporters. Clinical studies have revealed no relevant drug interactions when coadministered with other drugs commonly prescribed to patients with type 2 diabetes, including the narrow therapeutic index drugs warfarin and digoxin. Linagliptin plasma exposure is reduced by potent inducers of CYP3A4 or P-gp. Linagliptin has demonstrated a large safety window (>100-fold the recommended daily dose) and clinically relevant antihyperglycaemic effects in patients with type 2 diabetes.

Effect of Heart Failure on Dipeptidyl Peptidase IV Activity in Plasma of Dogs

In congestive heart failure (HF), plasma B-type natriuretic peptide (BNP) seems devoid of biological effectiveness. BNP(1-32) could be truncated into BNP(3-32) by dipeptidyl peptidase IV (DPP4), and BNP(3-32) has reduced biological activities. Increased DPP4 activity is associated with pathophysiology of HF. One hundred twenty-eight client-owned dogs and 9 experimental Beagles from the Clinical Veterinary Unit of the University of Liège. We prospectively measured plasma DPP4 activity in 5 groups of dogs: normal growing dogs (n = 21), normal adult dogs (n = 60), healthy Beagle (n = 9), dogs with myxomatous mitral valve disease (n = 35), and dogs with dilated cardiomyopathy (n = 12). The final diagnosis and the severity of HF were determined by Doppler echocardiography. Plasma DPP4 activity was measured kinetically by a fluorimetric method. In growing dogs, DPP4 activity was higher than in adults (P < .001) and inversely correlated with age (r = -0.57, P < .01). In adults, DPP4 activity increased linearly with body weight (r = 0.39, P < .01), but there was no influence of age or sex. No effect of the circadian rhythm was noted. DPP4 activity was significantly higher in HF ISACHC I (16.3 ± 1.14 U/L) compared with healthy adults (12.4 ± 0.65 U/L, P < .05) and HF ISACHC III (11.0 ± 1.50 U/L, P < .05). Mean DPP4 activity in ISACHC II was 15.1 ± 1.4 U/L. We did not find evidence that plasma DPP4 activity is responsible for the "BNP resistance" in overt congestive HF, but it may be implicated in early stages.

Potency, selectivity and prolonged binding of saxagliptin to DPP4: maintenance of DPP4 inhibition by saxagliptin in vitro and ex vivo when compared to a rapidly-dissociating DPP4 inhibitor

BackgroundDipeptidylpeptidase 4 (DPP4) inhibitors have clinical benefit in patients with type 2 diabetes mellitus by increasing levels of glucose-lowering incretin hormones, such as glucagon-like peptide -1 (GLP-1), a peptide with a short half life that is secreted for approximately 1 hour following a meal. Since drugs with prolonged binding to their target have been shown to maximize pharmacodynamic effects while minimizing drug levels, we developed a time-dependent inhibitor that has a half-life for dissociation from DPP4 close to the duration of the first phase of GLP-1 release.ResultsSaxagliptin and its active metabolite (5-hydroxysaxagliptin) are potent inhibitors of human DPP4 with prolonged dissociation from its active site (Ki = 1.3 nM and 2.6 nM, t1/2 = 50 and 23 minutes respectively at 37°C). In comparison, both vildagliptin (3.5 minutes) and sitagliptin ( < 2 minutes) rapidly dissociated from DPP4 at 37°C. Saxagliptin and 5-hydroxysaxagliptin are selective for inhibition of DPP4 versus other DPP family members and a large panel of other proteases, and have similar potency and efficacy across multiple species.Inhibition of plasma DPP activity is used as a biomarker in animal models and clinical trials. However, most DPP4 inhibitors are competitive with substrate and rapidly dissociate from DPP4; therefore, the type of substrate, volume of addition and final concentration of substrate in these assays can change measured inhibition. We show that unlike a rapidly dissociating DPP4 inhibitor, inhibition of plasma DPP activity by saxagliptin and 5-hydroxysaxagliptin in an ex vivo assay was not dependent on substrate concentration when substrate was added rapidly because saxagliptin and 5-hydroxysaxagliptin dissociate slowly from DPP4, once bound. We also show that substrate concentration was important for rapidly dissociating DPP4 inhibitors.ConclusionsSaxagliptin and its active metabolite are potent, selective inhibitors of DPP4, with prolonged dissociation from its active site. They also demonstrate prolonged inhibition of plasma DPP4 ex vivo in animal models, which implies that saxagliptin and 5-hydroxysaxagliptin would continue to inhibit DPP4 during rapid increases in substrates in vivo.