The Placement of DPP-4 Inhibitors in Clinical Practice Recommendations for the Treatment of Types 2 Diabetes

ObjectiveTo review the most recent clinical data on the safety and efficacy of dipeptidyl peptidase-4 (DPP-4) inhibitors and to evaluate their position in current treatment guidelines and algorithms.MethodsPubMed searches were performed to identify published data regarding both the safety and efficacy of DPP-4 inhibitors approved for use in the United States and clinical guidelines describing recommendations for their use.ResultsIn the past 2 years, more than 100 publications have added clinical trial data on DPP-4 inhibitors to the medical literature. Since becoming available in 2006, these agents have demonstrated an excellent safety/tolerability profile, and as add-on to metformin, DPP-4 inhibitors may have comparable glycemic efficacy as other oral agents. As a result, DPP-4 inhibitors have assumed roles in clinical practice guidelines and treatment algorithms that are comparable to the sulfonylurea class. Advantages of DPP-4 inhibitors include an oral route of administration, a mechanism of action based on glucose-stimulated insulin secretion, and a low risk of hypoglycemia. The main disadvantage associated with this class is a relatively high cost. There is also less clinical experience with DPP-4 agents than classes of agents that have been in use for decades; however, long-term data on the safety and efficacy of DPP-4 agents will be available in the near future to refine their place in therapy. From 2 large clinical trials recently reported, EXAMINE and SAVOR, this class of agents does not increase overall adverse cardiovascular outcomes nor the risk of pancreatitis or pancreatic cancer.ConclusionBased on comparisons of nonglycemic effects such as risk of hypoglycemia, weight gain, and durability, DPP-4 inhibitors may be considered as an alternative to sulfonylureas. However, direct cost may be a determining factor in the choice of therapy. (Endocr Pract. 2013;19:1050-1061)     

Medicinal chemistry approaches to the inhibition of dipeptidyl peptidase-4 for the treatment of type 2 diabetes

Emerging as an epidemic of the 21st century type 2 diabetes has become a major health problem throughout the globe. The number of deaths attributable to diabetes reflects the insufficient glycemic control achieved with the treatments used in recent past. DPP-4 inhibitors have been investigated as a new therapy with novel mechanisms of action and improved tolerability. DPP-4, a protease that specifically cleaves dipeptides from proteins and oligopeptides after a penultimate N-terminal proline or alanine, is involved in the degradation of a number of neuropeptides, peptide hormones and cytokines, including the incretins GLP-1 and GIP. As soon as released from the gut in response to food intake, GLP-1 and GIP exert a potent glucose-dependent insulinotropic action, thereby playing a key role in the maintenance of post-meal glycemic control. Consequently, inhibiting DPP-4 prolongs the action of GLP-1 and GIP, which in turn improves glucose homeostasis with a low risk of hypoglycemia and potential for disease modification. Indeed, clinical trials involving diabetic patients have shown improved glucose control by administering DPP-4 inhibitors, thus demonstrating the benefit of this promising new class of antidiabetics. Intense research activities in this area have resulted in the launch of sitagliptin and vildagliptin (in Europe only) and the advancement of a few others into preregistration/phase 3, for example, saxagliptin, alogliptin and ABT-279. Achieving desired selectivity for DPP-4 over other related peptidases such as DPP-8 and DPP-9 (inhibition of which was linked to toxicity in animal studies) and long-acting potential for maximal efficacy (particularly in more severe diabetic patients) were the major challenges. Whether these goals are achieved with the present series of inhibitors in the advanced stages of clinical development is yet to be confirmed. Nevertheless, treatment of this metabolic disorder especially in the early stages of the disease via DPP-4 inhibition has been recognized as a validated principle and a large number of inhibitors are presently in various stage of pre-clinical/clinical development. Sitagliptin is a new weapon in the arsenal of oral antihyperglycemic agents. This review will focus on the journey of drug discovery of DPP-4 inhibitors for oral delivery covering a brief scientific background and medicinal chemistry approaches along with the status of advanced clinical candidates.     

Discovery of potent, selective, and orally bioavailable quinoline-based dipeptidyl peptidase IV inhibitors targeting Lys554

Dipeptidyl peptidase IV (DPP-4) inhibition is a validated therapeutic option for type 2 diabetes, exhibiting multiple antidiabetic effects with little or no risk of hypoglycemia. In our studies involving non-covalent DPP-4 inhibitors, a novel series of quinoline-based inhibitors were designed based on the co-crystal structure of isoquinolone 2 in complex with DPP-4 to target the side chain of Lys554. Synthesis and evaluation of designed compounds revealed 1-[3-(aminomethyl)-4-(4-methylphenyl)-2-(2-methylpropyl)quinolin-6-yl]piperazine-2,5-dione (1) as a potent, selective, and orally active DPP-4 inhibitor (IC??=1.3 nM) with long-lasting ex vivo activity in dogs and excellent antihyperglycemic effects in rats. A docking study of compound 1 revealed a hydrogen-bonding interaction with the side chain of Lys554, suggesting this residue as a potential target site useful for enhancing DPP-4 inhibition.     

Reshaping Diabetes Care: The Fundamental Role of Dipeptidyl Peptidase-4 Inhibitors and Glucagon-Like Peptide-1 Receptor Agonists in Clinical Practice

ObjectiveTo update clinicians on the most recent safety and efficacy data on current incretin-based strategies for the treatment of type 2 diabetes (T2D).MethodsTitle searches were conducted in the Pubmed database to identify literature pertaining to the safety and efficacy of glucagon-like peptide-1 receptor agonists (GLP-1RAs) and dipeptidyl peptidase-4 (DPP-4) inhibitors. Product-specific title searches included the terms exenatide, liraglutide, linagliptin, saxagliptin, sita-gliptin, and vildagliptin.ResultsThe recent literature has introduced us to newer DPP-4 inhibitors and longer-acting GLP-1RAs, updated meta-analyses assessing the safety and efficacy of incretin-based therapies, and studies exploring the use of incretin-based treatments in broader clinical settings such as combination therapy with insulin. Meta-analyses have demonstrated placebo-adjusted glycated hemoglobin (HbA1c) reductions of ~1% with GLP-1RAs and 0.6 to 0.8% with DPP-4 inhibitors and have suggested cardioprotective effects such as reduction of cardiovascular events and improvement of lipid profile. As a class, these agents have consistently demonstrated low risks of hypoglycemia relative to other agents.ConclusionIncretin-based therapies are characterized by an overall favorable safety profile and weight effect, a low risk of hypoglycemia, and clinically meaningful improvements in HbA1c. Based on an expanding and favorable literature describing their use in various patient populations, the guidelines of the American Association of Clinical Endocrinologists and the recently updated guidelines from the American Diabetes Association assign these agents a central role in the treatment of T2D. (Endocr Pract. 2013;19:718-728)     

Discovery of 3H-imidazo[4,5-c]quinolin-4(5H)-ones as potent and selective dipeptidyl peptidase IV (DPP-4) inhibitors

In recent years, dipeptidyl peptidase IV inhibitors have been noted as valuable agents for treatment of type 2 diabetes. Herein, we report the discovery of a novel potent DPP-4 inhibitor with 3H-imidazo[4,5-c]quinolin-4(5H)-one as skeleton. After efficient optimization of the lead compound 2a at the 7- and 8-positions using a docking study, we found 28 as a novel DPP-4 inhibitor with excellent selectivity against various DPP-4 homologues. Compound 28 showed strong DPP-4 inhibitory activity compared to marketed DPP-4 inhibitors. We also found that a carboxyl group at the 7-position could interact with the residue of Lys554 to form a salt bridge. Additionally, introduction of a carboxyl group to 7-position led to both activity enhancement and reduced risk for hERG channel inhibition and induced phospholipidosis. In our synthesis of compounds with 7-carboxyl group, we achieved efficient regioselective synthesis using bulky ester in the intramolecular palladium coupling reaction.     

Macrocarpal C isolated from Eucalyptus globulus inhibits dipeptidyl peptidase 4 in an aggregated form

Dipeptidyl peptidase 4 (DPP-4) inhibitors are used for the treatment of type-2 diabetes mellitus. Various synthetic inhibitors have been developed to date, and plants containing natural DPP-4 inhibitors have also been identified. Here, 13 plant samples were tested for their DPP-4 inhibitory activity. Macrocarpals A–C were isolated from Eucalyptus globulus through activity-guided fractionation and shown to be DPP-4 inhibitors. Of these, macrocarpal C showed the highest inhibitory activity, demonstrating an inhibition curve characterised by a pronounced increase in activity within a narrow concentration range. Evaluation of macrocarpal C solution by turbidity, nuclear magnetic resonance spectroscopy and mass spectrometry indicated its aggregation, which may explain the characteristics of the inhibition curve. These findings will be valuable for further study of potential small molecule DPP-4 inhibitors.     

Safety And Efficacy Of Dpp-4 Inhibitors For The Management Of Hospitalized General Medicine And Surgery Patients with Type 2 Diabetes

Objective: DPP-4 inhibitors (DPP-4i) have been shown to be effective for the management of inpatient diabetes. We report pooled data from 3 prospective studies using DPP-4i in general medicine and surgery patients with type 2 diabetes (T2D).Methods: We combined data from 3 randomized studies comparing DPP-4i alone or in combination with basal insulin or a basal-bolus insulin regimen. Medicine (n = 266) and surgery (n = 319) patients admitted with a blood glucose (BG) between 140 and 400 mg/dL, treated with diet, oral agents, or low-dose insulin therapy were included. Patients received DPP-4i alone (n = 144), DPP-4i plus basal insulin (n = 158) or basal-bolus regimen (n = 283). All groups received correctional doses with rapid-acting insulin for BG >140 mg/dL. The primary endpoint was differences in mean daily BG between groups. Secondary endpoints included differences in hypoglycemia and hospital complications.Results: There were no differences in mean hospital daily BG among patients treated with DPP-4i alone (170 ± 37 mg/dL), DPP-4i plus basal (172 ± 42 mg/dL), or basalbolus (172 ± 43 mg/dL), P = .94; or in the percentage of BG readings within target of 70 to 180 mg/dL (63 ± 32%, 60 ± 31%, and 64 ± 28%, respectively; P = .42). There were no differences in length of stay or complications, but hypoglycemia was less common with DPP-4i alone (2%) compared to DPP-4i plus basal (9%) and basal-bolus (10%); P = .004.Conclusion: Treatment with DPP-4i alone or in combination with basal insulin is effective and results in a lower incidence of hypoglycemia compared to a basal-bolus insulin regimen in general medicine and surgery patients with T2D.Abbreviations: BG = blood glucose; BMI = body mass index; CI = confidence interval; DPP-4i = dipeptidyl peptidase-4 inhibitors; HbA1c = hemoglobin A1c; OR = odds ratio; T2D = type 2 diabetes     

Use Of Incretin-Based Therapy in Hospitalized Patients with Hyperglycemia

ObjectiveHyperglycemia is common in hospitalized patients with and without prior history of diabetes and is an independent marker of morbidity and mortality in critically and noncritically ill patients. Tight glycemic control using insulin has been shown to reduce cardiac morbidity and mortality in hospitalized patients, but it also results in hypoglycemic episodes, which have been linked to poor outcomes. Thus, alternative treatment options that can normalize blood glucose levels without undue hypoglycemia are being sought. Incretin-based therapies, such as glucagon-like peptide (GLP)-1 receptor agonists (RAs) and dipeptidyl peptidase (DPP)-4 inhibitors, may have this potential.MethodsA PubMed database was searched to find literature describing the use of incretins in hospital settings. Title searches included the terms “diabetes” (care, management, treatment), “hospital,” “inpatient,” “hypoglycemia,” “hyperglycemia,” “glycemic,” “incretin,” “dipeptidyl peptidase-4 inhibitor,” “glucagon-like peptide-1,” and “glucagon-like peptide-1 receptor agonist.”ResultsThe preliminary research experience with native GLP-1 therapy has shown promise, achieving improved glycemic control with a low risk of hypoglycemia, counteracting the hyperglycemic effects of stress hormones, and improving cardiac function in patients with heart failure and acute ischemia. Large, randomized controlled clinical trials are necessary to determine whether these favorable results will extend to the use of GLP-1 RAs and DPP-4 inhibitors.ConclusionsThis review offers hospitalist physicians and healthcare providers involved in inpatient diabetes care a pathophysiologic-based approach for the use of incretin agents in patients with hyperglycemia and diabetes, as well as a summary of benefits and concerns of insulin and incretin-based therapy in the hospital setting. (Endocr Pract. 2014;20:933-944)     

Effects of novel chalcone derivatives on α-glucosidase, dipeptidyl peptidase-4, and adipocyte differentiation in vitro

Chana series are new chalcone derivatives. To evaluate the possibility of Chana series as therapeutic agents of type 2 diabetes, the inhibitory effects of Chana series on the activities of α-glucosidase and DPP-4 were investigated using in vitro enzyme assays, and their effects on adipocyte differentiation were investigated in C3H10T1/2 cells. Chana 1 and Chana 7 among the Chana series showed significant inhibition of α-glucosidase activity. In DPP-4 enzyme assay, Chana 1 exhibited the highest inhibitory activity while Chana 7 did not. In MTT assay, Chana 1 did not show significant cytotoxicity up to a concentration of 250 μM, whereas cytotoxicity was observed with Chana 7 at a concentration of 300 μM. In addition, Chana 1 induced adipocyte differentiation. Therefore, Chana 1 showed inhibitory effects on α-glucosidase and DPP-4 as well as a stimulatory effect on adipocyte differentiation, suggesting that Chana 1 may be a potential beneficial agent for the treatment of type 2 diabetes.     

A DPP-4 Inhibitor Suppresses Fibrosis and Inflammation on Experimental Autoimmune Myocarditis in Mice

Myocarditis is a critical inflammatory disorder which causes life-threatening conditions. No specific or effective treatment has been established. DPP-4 inhibitors have salutary effects not only on type 2 diabetes but also on certain cardiovascular diseases. However, the role of a DPP-4 inhibitor on myocarditis has not been investigated. To clarify the effects of a DPP-4 inhibitor on myocarditis, we used an experimental autoimmune myocarditis (EAM) model in Balb/c mice. EAM mice were assigned to the following groups: EAM mice group treated with a DPP-4 inhibitor (linagliptin) (n = 19) and those untreated (n = 22). Pathological analysis revealed that the myocardial fibrosis area ratio in the treated group was significantly lower than in the untreated group. RT-PCR analysis demonstrated that the levels of mRNA expression of IL-2, TNF-α, IL-1β and IL-6 were significantly lower in the treated group than in the untreated group. Lymphocyte proliferation assay showed that treatment with the DPP-4 inhibitor had no effect on antigen-induced spleen cell proliferation. Administration of the DPP-4 inhibitor remarkably suppressed cardiac fibrosis and reduced inflammatory cytokine gene expression in EAM mice. Thus, the agents present in DPP-4 inhibitors may be useful to treat and/or prevent clinical myocarditis.     

Palmitate and insulin synergistically induce IL-6 expression in human monocytes

Objectives

To summarize data supporting the effects of antidiabetes agents on glucose control and cardiovascular risk factors in patients with type 2 diabetes.

Methods

Studies reporting on the effects of antidiabetes agents on glycemic control, body weight, lipid levels, and blood pressure parameters are reviewed and summarized for the purpose of selecting optimal therapeutic regimens for patients with type 2 diabetes.

Results

National guidelines recommend the aggressive management of cardiovascular risk factors in patients with type 2 diabetes, including weight loss and achieving lipid and blood pressure treatment goals. All antidiabetes pharmacotherapies lower glucose; however, effects on cardiovascular risk factors vary greatly among agents. While thiazolidinediones, sulfonylureas, and insulin are associated with weight gain, dipeptidyl peptidase-4 inhibitors are considered weight neutral and metformin can be weight neutral or associated with a small weight loss. Glucagon-like peptide-1 receptor agonists and amylinomimetics (e.g. pramlintide) result in weight loss. Additionally, metformin, thiazolidinediones, insulin, and glucagon-like peptide-1 receptor agonists have demonstrated beneficial effects on lipid and blood pressure parameters.

Conclusion

Management of the cardiovascular risk factors experienced by patients with type 2 diabetes requires a multidisciplinary approach with implementation of treatment strategies to achieve not only glycemic goals but to improve and/or correct the underlying cardiovascular risk factors.     

Discovery and preclinical profile of teneligliptin (3-[(2S,4S)-4-[4-(3-methyl-1-phenyl-1H-pyrazol-5-yl)piperazin-1-yl]pyrrolidin-2-ylcarbonyl]thiazolidine): A highly potent,selective, long-lasting and orally active dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes

Dipeptidyl peptidase IV (DPP-4) inhibition is suitable mechanism for once daily oral dosing regimen because of its low risk of hypoglycemia. We explored linked bicyclic heteroarylpiperazines substituted at the γ-position of the proline structure in the course of the investigation of l-prolylthiazolidines. The efforts led to the discovery of a highly potent, selective, long-lasting and orally active DPP-4 inhibitor, 3-[(2S,4S)-4-[4-(3-methyl-1-phenyl-1H-pyrazol-5-yl)piperazin-1-yl]pyrrolidin-2-ylcarbonyl]thiazolidine (8g), which has a unique structure characterized by five consecutive rings. An X-ray co-crystal structure of 8g in DPP-4 demonstrated that the key interaction between the phenyl ring on the pyrazole and the S₂ extensive subsite of DPP-4 not only boosted potency, but also increased selectivity. Compound 8g, at 0.03 mg/kg or higher doses, significantly inhibited the increase of plasma glucose levels after an oral glucose load in Zucker fatty rats. Compound 8g (teneligliptin) has been approved for the treatment of type 2 diabetes in Japan.     

Design,synthesis and anti-diabetic activity of triazolotriazine derivatives as dipeptidyl peptidase-4 (DPP-4) inhibitors

Type 2 diabetes mellitus (T2DM) is one of the major global metabolic disorders characterized by insulin resistance and chronic hyperglycemia. Inhibition of the enzyme, dipeptidyl peptidase-4 (DPP-4) has been proved as successful and safe therapy for the treatment of T2DM since last decade. In order to design novel DPP-4 inhibitors, various in silico studies such as 3D-QSAR, pharmacophore modeling and virtual screening were performed and on the basis of the combined results of them, total 50 triazolo[5,1-c][1,2,4]triazine derivatives were designed and mapped on the best pharmacophore model. From this, best 25 derivatives were docked onto the active site of DPP-4 enzyme and in silico ADMET properties were also predicted. Finally, top 17 derivatives were synthesized and characterized using FT-IR, Mass, ¹H NMR and ¹³C NMR spectroscopy. Purity of compounds was checked using HPLC. These derivatives were then evaluated for in vitro DPP-4 inhibition. The most promising compound 15q showed 28.05 μM DPP-4 IC₅₀ with 8–10-fold selectivity over DPP-8 and DPP-9 so selected for further in vivo anti-diabetic evaluation. During OGTT in normal C57BL/6J mice, compound 15q reduced blood glucose excursion in a dose-dependent manner. Chronic treatment for 28 days with compound 15q improved the serum glucose levels in type 2 diabetic Sprague Dawley rats wherein diabetes was induced by high fat diet and low dose streptozotocin. This suggested that compound 15q is a moderately potent and selective hit molecule which can be further optimized structurally to increase the efficacy and overall pharmacological profile as DPP-4 inhibitor.     

Discovery of triazole-based uracil derivatives bearing amide moieties as novel dipeptidyl peptidase-IV inhibitors

Dipeptidyl peptidase-IV (DPP-4) is a validated target for T2DM treatment. We previously reported a novel series of triazole-based uracil derivatives bearing aliphatic carboxylic acids with potent DPP-4 inhibitory activities in vitro, but these compounds showed poor hypoglycemic effects in vivo. Herein we further optimized the triazole moiety by amidation of the carboxylic acid to improve in vivo activities. Two series of compounds 3a-f and 4a-g were designed and synthesized. By screening in DPP-4, compound 4c was identified as a potent DPP-4 inhibitor with the IC₅₀ value of 28.62 nM. Docking study revealed compound 4c has a favorable binding mode and interpreted the SAR of these analogs. DPP-8 and DPP-9 tests indicated compound 4c had excellent selectivity over DPP-8 and DPP-9. Further in vivo evaluations revealed that compound 4c showed more potent hypoglycemic activity than its corresponding carboxylic acid in ICR mice and dose-dependently reduced glucose levels in type 2 diabetic C57BL/6 mice. The overall results have shown that compound 4c could be a promising lead for further development of novel DPP-4 agents treating T2DM.     

The Emerging Role Of Adjunctive Noninsulin Antihyperglycemic Therapy In The Management Of Type 1 Diabetes

Objective: Review available data on adjunctive therapies for type 1 diabetes (T1D), with a special focus on newer antihyperglycemic agents.Methods: Published data on hypoglycemia, obesity, mortality, and goal attainment in T1D were reviewed to determine unmet therapeutic needs. PubMed databases and abstracts from recent diabetes meetings were searched using the term “type 1 diabetes” and the available and investigational sodium-glucose cotransporter (SGLT) inhibitors, glucagon-like peptide 1 (GLP-1) receptor agonists, dipeptidyl peptidase 4 inhibitors, and metformin.Results: The majority of patients with T1D do not meet glycated hemoglobin (A1C) goals established by major diabetes organizations. Hypoglycemia risks and a rising incidence of obesity and metabolic syndrome featured in the T1D population limit optimal use of intensive insulin therapy. Noninsulin antihyperglycemic agents may enable T1D patients to achieve target A1C levels using lower insulin doses, which may reduce the risk of hypoglycemia. In pilot studies, the SGLT2 inhibitor dapagliflozin and the GLP-1 receptor agonist liraglutide reduced blood glucose, weight, and insulin dose in patients with T1D. Phase 2 studies with the SGLT2 inhibitor empagliflozin and the dual SGLT1 and SGLT2 inhibitor sotagliflozin, which acts in the gut and the kidney, have demonstrated reductions in A1C, weight, and glucose variability without an increased incidence of hypoglycemia.Conclusion: Newer antihyperglycemic agents, particularly GLP-1 agonists, SGLT2 inhibitors, and dual SGLT1 and SGLT2 inhibitors, show promise as adjunctive treatment for T1D that may help patients achieve better glucose control without weight gain or increased hypoglycemia.Abbreviations:A1C = glycated hemoglobinBMI = body mass indexCI = confidence intervalDKA = diabetic ketoacidosisDPP-4 = dipeptidyl peptidase 4GLP-1 = glucagonlike peptide 1PYY = polypeptide tyrosine tyrosineSGLT = sodium-glucose cotransporterSGLT1 = sodium-glucose cotransporter 1SGLT2 = sodium-glucose cotransporter 2T1D = type 1 diabetesT2D = type 2 diabetesTDD = total daily dosage     

Efficacy and Safety of Dipeptidyl Peptidase-4 Inhibitors in Type 2 Diabetes Mellitus Patients with Moderate to Severe Renal Impairment: A Systematic Review and Meta-Analysis

Objective

To perform a systematic review and meta-analysis regarding the efficacy and safety of dipeptidyl peptidase-4 (DDP-4) inhibitors (“gliptins”) for the treatment of type 2 diabetes mellitus (T2DM) patients with moderate to severe renal impairment.

Methods

All available randomized-controlled trials (RCTs) that assessed the efficacy and safety of DDP-4 inhibitors compared with placebo, no treatment, or active drugs were identified using PubMed, EMBASE, Cochrane CENTRAL, conference abstracts, clinical trials.gov, pharmaceutical company websites, the FDA, and the EMA (up to June 2014). Two independent reviewers extracted the data, and a random-effects model was applied to estimate summary effects.

Results

Thirteen reports of ten studies with a total of 1,915 participants were included in the final analysis. Compared with placebo or no treatment, DPP-4 inhibitors reduced HbA1c significantly (−0.52%, 95%CI −0.64 to −0.39) and had no increased risk of hypoglycemia (RR 1.10, 95%CI 0.92 to 1.32) or weight gain. In contrast to glipizide monotherapy, DPP-4 inhibitors showed no difference in HbA1c lowering effect (−0.08%, 95% CI −0.40 to 0.25) but had a lower incidence of hypoglycemia (RR 0.40, 95%CI 0.23 to 0.69). Furthermore, DPP-4 inhibitors were well-tolerated, without any additional mortality and adverse events. However, the quality of evidence was mostly as low, as assessed using the GRADE system for each outcome.

Conclusions

DPP-4 inhibitors are effective at lowering HbA1c in T2DM patients with moderate to severe renal impairment. DPP-4 inhibitors also have a potential advantage in lowering the risk of adverse events. Regarding the low quality of the evidence according to GRADE, additional well-designed randomized trials that focus on the safety and efficacy of DPP-4 inhibitors in various CKD stages are needed urgently.     

Di-peptidyl peptidase-4 inhibitor sitagliptin protects vascular function in metabolic syndrome: possible role of epigenetic regulation

Metabolic syndrome (MetS) is a complex medical disorder characterized by insulin resistance, hypertension, and high risk of coronary disease and stroke. Microvascular rarefaction and endothelial dysfunction have also been linked with MetS, and recent evidence from clinical studies supports the efficacy of incretin-based antidiabetic therapies for vascular protection in diabetes. Previous studies pointed out the importance of dipeptidyl peptidase-4 (DPP-4) inhibition in endothelial cells due to getting protection against metabolic pathologies. We therefore aimed to investigate the acute effects of a DPP-4 inhibitor, sitagliptin, on vascular function in rats with high-sucrose diet-induced MetS. In order to elucidate the mechanisms implicated in the effects of DPP-4 inhibition, we tested the involvement of NO pathway and epigenetic regulation in the MetS. Acute use of sitagliptin protects the vascular function in the rats with MetS in part due to NO pathway via restoring the depressed aortic relaxation responses mediated by receptors. Application of sitagliptin enhanced the depressed phosphorylation levels of both the endothelial NO synthase and the apoptotic status of protein kinase B, known as Akt, in endothelium-intact thoracic aorta from rats with MetS. One-hour application of sitagliptin on aortic rings from rats with MetS also induced remarkable histon posttranslational modifications such as increased expression of H3K27Me3, but not of H3K27Me2, resulting in an accumulation of the H3K27Me3. Our findings suggest that, in addition to its well-known hypoglycemic action, sitagliptin may also have beneficial effects on hyperglycemia-induced vascular changes in an endotheium-dependent manner. These present results with sitagliptin aside from the glycaemic control, may demonstrate its important role in the treatment of patients with MetS.     

Understanding the Molecular Dynamics of Type-2 Diabetes Drug Target DPP-4 and its Interaction with Sitagliptin and Inhibitor Diprotin-A

The occurrence of type 2 diabetes (T2D) accounts for 90–95 % of all diabetes. Intestine hormone glucagon-like peptide-1 (GLP-1) has an antidiabetic role that enhances insulin secretion and pancreatic β-cell proliferation. GLP-1 is degraded by the enzyme dipeptidyl peptidase-4 (DPP-4) rapidly. Hence, the DPP-4 inhibition has been preferred not only for the treatment but also as a major drug target. Sitagliptin and Diprotin-A are antihyperglycemic agents for the treatment of T2D. However, little is known on the molecular dynamics of DPP-4 and the interaction properties with its ligands, namely Sitagliptin and Diprotin-A. This study has used the latest bioinformatic tools to understand the molecular dynamics and its interaction properties of DPP-4. This study has explored the number of α helices, β strands, β hairpins, Ψ loop, β bulges, β turns, and ? turns and they were 19, 46, 25, 1, 14, 70, and 4, respectively. The highest number of H-bonds was recorded in α helix of domain-1, and the lowest number H-bonds were noted in α helix of domain-2. During interaction between residues, in A- and B-chain, 47 and 48 residues are involved for interaction, and interaction interface area was more in A-Chain (2176 Å²). From DPP-4 and Sitagliptin interaction, three residues in active sites such as Try226, Glu205, and Glu206 were involved in three H-bond formation, while 10 other amino acids (Try547, Try667, Asn710, Val711, His740, Ser630, Ser209, Arg358, Phe357, and Val207) were involved in hydrophobic interactions. In this review, we have shown the importance of bioinformatics as an excellent tool for a rapid method to assess the molecular dynamics and its interaction properties of DPP-4. Our predictions highlighted in this review will help researchers to understand the interaction properties and recognition of interactive sites to design more DPP-4 inhibitors for the treatment of T2D and drug discovery.