Dipeptidyl peptidase-4 inhibitors and preservation of pancreatic islet-cell function: a critical appraisal of the evidence

Synthesis and clinical application of representative small-molecule dipeptidyl Peptidase-4 (DPP-4) inhibitors for the treatment of type 2 diabetes mellitus (T2DM)

Diabetes mellitus is a chronic metabolic disorder characterized by high blood glucose levels, which can cause many diseases, including osteoporosis, fractures, arthritis, and foot complications. The inhibitors of dipeptidyl peptidase-4 (DPP-4), an enzyme involved in glucose metabolism regulation, are essential for managing Type 2 Diabetes Mellitus (T2DM). The inhibition of DPP-4 has become a promising treatment approach for T2DM because it can increase levels of active glucagon-like peptide-1 (GLP-1), leading to improved insulin secretion in response to glucose and reduced release of glucagon. The review commences by elucidating the role of DPP-4 in glucose homeostasis and its significance in T2DM pathophysiology. Furthermore, it presents the mechanism of action, preclinical pharmacodynamics, clinical efficacy, and toxicity profiles of small-molecule DPP-4 inhibitors across various clinical stages. This comprehensive review provides valuable insights into the synthesis and clinical application of DPP-4 inhibitors, serving as an invaluable resource for researchers, clinicians, and pharmaceutical professionals interested in diabetes therapeutics and drug development.

Pancreatic beta-cell mass and function and therapeutic implications of using antidiabetic medications in type 2 diabetes

Nowadays, the focus of diabetes treatment has switched from lowering the glucose level to preserving glycemic homeostasis and slowing the disease progression. The main pathophysiology of both type 1 diabetes and long-standing type 2 diabetes is pancreatic β-cell mass loss and dysfunction. According to recent research, human pancreatic β-cells possess the ability to proliferate in response to elevated insulin demands. It has been demonstrated that in insulin-resistant conditions in humans, such as obesity or pregnancy, the β-cell mass increases. This ability could be helpful in developing novel treatment approaches to restore a functional β-cell mass. Treatment strategies aimed at boosting β-cell function and mass may be a useful tool for managing diabetes mellitus and stopping its progression. This review outlines the processes of β-cell failure and detail the many β-cell abnormalities that manifest in people with diabetes mellitus. We also go over standard techniques for determining the mass and function of β-cells. Lastly, we provide the therapeutic implications of utilizing antidiabetic drugs in controlling the mass and function of pancreatic β-cells.

Expert eValuation of Efficacy and Rationality of Vildagliptin "EVER-Vilda": An Indian Perspective

Vildagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor is effective in reducing HbA1c levels in patients with type 2 diabetes (T2DM) when administered as monotherapy, dual or triple combination therapy. In India, Vildagliptin is commonly prescribed in T2DM patients because it reduces mean amplitude of glycemic excursion (MAGE), has lower risk of hypoglycemia and is weight neutral. Early combination therapy with vildagliptin and metformin is effective and well-tolerated in patients with T2DM, regardless of age or ethnicity. In view of already existing data on vildagliptin and the latest emerging clinical evidence, a group of endocrinologists, diabetologists and cardiologists convened for an expert group meeting to discuss the role and various combinations of vildagliptin in T2DM management. This practical document aims to guide Physicians and Specialists regarding the different available strengths and formulations of vildagliptin for the initiation and intensification of T2DM therapy.

Saxagliptin combined with additional oral antihyperglycaemic agents in drug-naive diabetic patients with high glycosylated haemoglobin: A 24-week, multicentre, randomized, open-label, active parallel-controlled group clinical trial in China (SUCCESS)

AIM

To assess the efficacy and safety of a dipeptidyl peptidase-4 (DPP-4) inhibitor combined respectively with three oral antihyperglycaemic agents in Chinese patients with newly diagnosed type 2 diabetes mellitus (T2DM) with high levels of glycated haemoglobin (HbA1c).

MATERIALS AND METHODS

Between 30 December 2014 and 1 November 2017, a 24-week, multicentre, parallel-controlled study was performed on drug-naive T2DM patients. In total, 648 patients with 8.0% ≤ HbA1c ≤ 11.0%, aged 18-80 years and body mass index (BMI) 19-40 kg/m² were randomly assigned 1:1:1 to receive saxagliptin (Saxa) combined with metformin (Met), acarbose (Aca) or gliclazide (Gli) modified release (MR) tablets (Saxa + Met, Saxa + Aca and Saxa + Gli). The primary outcome was the absolute change in HbA1c from baseline; secondary outcome was the percentage of patients achieving HbA1c <7.0% and ≤6.5%.

RESULTS

Each treatment arm contained 216 patients; overall, 583 completed the 24-week trial. At 24 weeks, the mean (95% confidence interval) change in HbA1c from baseline in Saxa + Met, Saxa + Aca and Saxa + Gli were, respectively: -2.9% [-3.1, -2.8]; -2.6% [-2.8, -2.5]; and -2.8% [-2.9, -2.6] (overall p = .04, Saxa + Aca vs. Saxa + Met, p = .010, Saxa + Gli vs. Saxa + Met, p = 0.18). At 24 weeks, 84.9%, 74.7% and 80.3% of participants were at HbA1c <7.0% (overall p = .05); and 72.6%, 59.8% and 63.3% were HbA1c ≤6.5% (overall p = 0.10). The rates of minor or symptomatic hypoglycaemia were very low.

CONCLUSIONS

Initial treatment with a DPP-4 inhibitor combined with Metform, alpha-glycosidase inhibitor or sulphonylurea was safe and effective for patients with newly diagnosed T2DM and high HbA1c. DPP-4 inhibitor combined with Met showed the best efficacy for this population.

Endogenous GLP-1 levels play an important role in determining the efficacy of DPP-IV Inhibitors in both prediabetes and type 2 diabetes

Background

In contrast to Western population, glucagon-like peptide-1 (GLP-1) levels are preserved in some East Asian population with type 2 diabetes (T2D), explaining why dipeptidyl peptidase-IV (DPP-IV) inhibitors are more effective in East Asians. We assessed whether differences in endogenous GLP-1 levels resulted in different treatment responses to DPP-IV inhibitors in prediabetes and T2D.

Methods

A prospective 12-week study using linagliptin 5mg once daily in 50 subjects (28 prediabetes and 22 T2D) who were stratified into high versus low fasting GLP-1 groups. A 75-g oral glucose tolerance test (OGTT) was performed at week 0 and 12. Primary outcomes were changes in HbA1c, fasting and post-OGTT glucose after 12 weeks. Secondary outcomes included changes in insulin resistance and beta cell function indices.

Results

There was a greater HbA1c reduction in subjects with high GLP-1 compared to low GLP-1 levels in both the prediabetes and T2D populations [least-squares mean (LS-mean) change of -0.33% vs. -0.11% and -1.48% vs. -0.90% respectively)]. Linagliptin significantly reduced glucose excursion by 18% in high GLP-1 compared with 8% in low GLP-1 prediabetes groups. The reduction in glucose excursion was greater in high GLP-1 compared to low GLP-1 T2D by 30% and 21% respectively. There were significant LS-mean between-group differences in fasting glucose (-0.95 mmol/L), 2-hour glucose post-OGTT (-2.4 mmol/L) in the high GLP-1 T2D group. Improvement in insulin resistance indices were seen in the high GLP-1 T2D group while high GLP-1 prediabetes group demonstrated improvement in beta cell function indices. No incidence of hypoglycemia was reported.

Conclusions

Linagliptin resulted in a greater HbA1c reduction in the high GLP-1 prediabetes and T2D compared to low GLP-1 groups. Endogenous GLP-1 level play an important role in determining the efficacy of DPP-IV inhibitors irrespective of the abnormal glucose tolerance states.

A novel therapeutic combination of sitagliptin and melatonin regenerates pancreatic β-cells in mouse and human islets

Autoimmune-led challenge resulting in β-cell loss is responsible for the development of type 1 diabetes (T1D). Melatonin, a pineal hormone or sitagliptin, a dipeptidyl peptidase IV (DPP-IV) inhibitor, has increased β-cell mass in various diabetic models and has immunoregulatory property. Both β-cell regenerative capacity and melatonin secretion decrease with ageing. Thus, we aimed to investigate the therapeutic potential of melatonin combined with sitagliptin on β-cell regeneration under glucotoxic stress, in the streptozotocin-induced young and old diabetic mouse models, and euglycemic humanized islet transplant mouse model. Our results suggest that combination therapy of sitagliptin and melatonin show an additive effect in inducing mouse β-cell regeneration under glucotoxic stress, and in the human islet transplant mouse model. Further, in the young diabetic mouse model, the monotherapies induce β-cell transdifferentiation and reduce β-cell apoptosis whereas, in the old diabetic mouse model, melatonin and sitagliptin induce β-cell proliferation and β-cell transdifferentiation, and it also reduces β-cell apoptosis. Further, in both the models, combination therapy reduces fasting blood glucose levels, increases plasma insulin levels and glucose tolerance and promotes β-cell proliferation, β-cell transdifferentiation, and reduces β-cell apoptosis. It can be concluded that combination therapy is superior to monotherapies in ameliorating diabetic manifestations, and it can be used as a future therapy for β-cell regeneration in diabetes patients.

Influence of dipeptidyl peptidase-4 inhibitors on glycemic variability in patients with type 2 diabetes: A meta-analysis of randomized controlled trials

OBJECTIVE

The influence of dipeptidyl peptidase-4 (DPP4) inhibitors on glycemic variability compared to other oral antidiabetic drugs (OADs), measured based on the mean amplitude of glycemic excursions (MAGE), has not been comprehensively analyzed. The aim of the study was to perform a meta-analysis to compare the effects of DPP4 inhibitors on MAGE with other OADs in type 2 diabetes mellitus (T2DM) patients without concurrent insulin treatments.

METHODS

The Medline (PubMed), Embase (Ovid), and CENTER (Cochrane Library) databases were searched for relevant randomized controlled trials (RCTs). Study characteristics and outcome data were independently extracted by two authors. A random-effect model was used to combine the results.

RESULTS

Fourteen studies with 855 patients were included. Compared to other OADs, DPP4 inhibitors significantly reduced MAGE (mean difference [MD]: -0.69 mmol/L, 95% confidence interval [CI]: -0.95 to -0.43, P<0.001) with mild heterogeneity (I^{2 =} 28%). Predefined subgroup analyses suggested that DPP4 inhibitors were more effective in reducing MAGE compared to insulin secretagogues (MD: -0.92 mmol/L, P<0.001) and non-secretagogues (MD: -0.43 mmol/L, P=0.02), as well as compared to sulfonylureas (MD: -0.91 mmol/L, P<0.001) and sodium glucose cotransporter 2 inhibitors (MD: -0.67 mmol/L, P=0.03).

CONCLUSIONS

DPP4 inhibitors may significantly reduce glycemic variability compared to other oral anti-diabetic drugs, as evidenced by MAGE in T2DM patients with no concurrent insulin treatment.

SYSTEMATIC REVIEW REGISTRATION

INPLASY, registration number: INPLASY2021120113.

Favorable Effects of GLP-1 Receptor Agonist against Pancreatic β-Cell Glucose Toxicity and the Development of Arteriosclerosis: "The Earlier, the Better" in Therapy with Incretin-Based Medicine

Fundamental pancreatic β-cell function is to produce and secrete insulin in response to blood glucose levels. However, when β-cells are chronically exposed to hyperglycemia in type 2 diabetes mellitus (T2DM), insulin biosynthesis and secretion are decreased together with reduced expression of insulin transcription factors. Glucagon-like peptide-1 (GLP-1) plays a crucial role in pancreatic β-cells; GLP-1 binds to the GLP-1 receptor (GLP-1R) in the β-cell membrane and thereby enhances insulin secretion, suppresses apoptotic cell death and increase proliferation of β-cells. However, GLP-1R expression in β-cells is reduced under diabetic conditions and thus the GLP-1R activator (GLP-1RA) shows more favorable effects on β-cells at an early stage of T2DM compared to an advanced stage. On the other hand, it has been drawing much attention to the idea that GLP-1 signaling is important in arterial cells; GLP-1 increases nitric oxide, which leads to facilitation of vascular relaxation and suppression of arteriosclerosis. However, GLP-1R expression in arterial cells is also reduced under diabetic conditions and thus GLP-1RA shows more protective effects on arteriosclerosis at an early stage of T2DM. Furthermore, it has been reported recently that administration of GLP-1RA leads to the reduction of cardiovascular events in various large-scale clinical trials. Therefore, we think that it would be better to start GLP-1RA at an early stage of T2DM for the prevention of arteriosclerosis and protection of β-cells against glucose toxicity in routine medical care.

Therapeutic potential of targeting intestinal bitter taste receptors in diabetes associated with dyslipidemia

Intestinal release of incretin hormones after food intake promotes glucose-dependent insulin secretion and regulates glucose homeostasis. The impaired incretin effects observed in the pathophysiologic abnormality of type 2 diabetes have triggered the pharmacological development of incretin-based therapy through the activation of glucagon-like peptide-1 (GLP-1) receptor, including GLP-1 receptor agonists (GLP-1 RAs) and dipeptidyl peptidase 4 (DPP4) inhibitors. In the light of the mechanisms involved in the stimulation of GLP-1 secretion, it is a fundamental question to explore whether glucose and lipid homeostasis can be manipulated by the digestive system in response to nutrient ingestion and taste perception along the gastrointestinal tract. While glucose is a potent stimulant of GLP-1 secretion, emerging evidence highlights the importance of bitter tastants in the enteroendocrine secretion of gut hormones through activation of bitter taste receptors. This review summarizes bitter chemosensation in the intestines for GLP-1 secretion and metabolic regulation based on recent advances in biological research of bitter taste receptors and preclinical and clinical investigation of bitter medicinal plants, including bitter melon, hops strobile, and berberine-containing herbs (e.g. coptis rhizome and barberry root). Multiple mechanisms of action of relevant bitter phytochemicals are discussed with the consideration of pharmacokinetic studies. Current evidence suggests that specific agonists targeting bitter taste receptors, such as human TAS2R1 and TAS2R38, may provide both metabolic benefits and anti-inflammatory effects with the modulation of the enteroendocrine hormone secretion and bile acid turnover in metabolic syndrome individuals or diabetic patients with dyslipidemia-related comorbidities.

High glucose-induced PRDX3 acetylation contributes to glucotoxicity in pancreatic β-cells: Prevention by Teneligliptin

Chronic hyperglycemia has deleterious effects on pancreatic β-cell function and survival in type 2 diabetes (T2D) due to the low expression level of endogenous antioxidants in the β-cells. Peroxiredoxin-3 (PRDX3) is a mitochondria specific H202 scavenger and protects the cell from mitochondrial damage. However, nothing is known about how glucotoxicity influences PRDX3 function in the pancreatic beta cells. Exposure of rat insulinoma INS-1 cells and human beta cells (1.1B4) to high glucose conditions (30mM) stimulated acetylation of PRDX3 which facilitates its hyper-oxidation causing mitochondrial dysfunction by SIRT1 degradation. SIRT1 deficiency induces beta cell apoptosis via NOX-JNK-p66Shc signalosome activation. Herein we investigated the direct effect of Teneligliptin, a newer DPP-4 inhibitor on beta-cell function and survival in response to high glucose conditions. Teneligliptin treatment enhances SIRT1 protein levels and activity by USP22, an ubiquitin specific peptidase. Activated SIRT1 prevents high glucose-induced PRDX3 acetylation by SIRT3 resulted in inhibition of PRDX3 hyper-oxidation thereby strengthening the mitochondrial antioxidant defense. Notably, we identify PRDX3 as a novel SIRT3 target and show their physical interaction. Intriguingly, inhibition of SIRT1 activity by EX-527 or SIRT1 siRNA knockdown exacerbated the SIRT3 mediated PRDX3 deacetylation which leads to peroxiredoxin-3 hyper-oxidation and beta-cell apoptosis by the activation of NOX-JNK-p66Shc signalosome. Collectively, our results unveil a novel and first direct effect of high glucose on PRDX3 acetylation on beta-cell dysfunction by impaired antioxidant defense and SIRT1 mediated SIRT3-PRDX3 activation by Teneligliptin suppresses high glucose-mediated mitochondrial dysfunction.

Comparisons between dipeptidyl peptidase-4 inhibitors and other classes of hypoglycemic drugs using two distinct biomarkers of pancreatic beta-cell function: A meta-analysis

Background and objective

Dipeptidyl peptidase-4 (DPP-4) inhibitors have been suggested to have pancreatic beta-cell preserving effect according to studies using homeostatic model of assessment for beta-cell function (HOMA-β). However, whether HOMA-β is a suitable biomarker for comparisons between hypoglycemic drugs with different mechanisms of action remains unclear. Therefore, we conducted a meta-analysis to compare the effects of DPP-4 inhibitors and other classes of hypoglycemic drugs on HOMA-β and proinsulin-to-insulin ratio (PIR).

Methods

We searched MEDLINE, CENTRAL, and Ichushi-web for the period of 1966 to May 2020. We collected randomized, controlled clinical trials in patients with type 2 diabetes mellitus comparing DPP-4 inhibitors and other classes of hypoglycemic agents [α-glucosidase inhibitors (α-GIs), glucagon-like peptide-1 (GLP-1) analogues, metformin, sodium-glucose cotransporter 2 (SGLT2) inhibitors, sulfonylureas, or thiazolidinediones]. Weighted mean differences and 95% confidence intervals of changes in HOMA-β or PIR during study periods were calculated for pairwise comparisons.

Results

Thirty-seven and 21 relevant trials were retrieved for comparisons of HOMA-β and PIR, respectively. HOMA-β and PIR consistently showed superiority of DPP-4 inhibitors compared with α-GIs. Both biomarkers consistently supported inferiority of DPP-4 inhibitors compared with GLP-1 analogues. However, PIR showed inferiority of DPP-4 inhibitors compared with metformin, and superiority compared with SGLT2 inhibitors, whereas HOMA-β showed no significant differences between DPP-4 inhibitors and the two other agents.

Conclusion

DPP-4 inhibitors appear to be superior to α-GIs but inferior to GLP-1 analogues in preservation of beta-cell function assessed by either HOMA-β or PIR. DPP-4 inhibitors seem to be superior to SGLT2 inhibitors but inferior to metformin on islet function assessed only by PIR. Because HOMA-β and PIR may indicate different aspects of beta-cell function, results of beta-cell function preserving effects of hypoglycemic agents should be interpreted with caution.

Differential Effects of Thiazolidinediones and Dipeptidyl Peptidase-4 Inhibitors on Insulin Resistance and β-Cell Function in Type 2 Diabetes Mellitus: A Propensity Score-Matched Analysis

INTRODUCTION

Comparisons of the glycemic durability between thiazolidinediones (TZDs) and dipeptidyl peptidase-4 (DPP-4) inhibitors remain insufficient. This study aimed to find clues for the differences in glycemic durability between TZDs and DPP-4 inhibitors by comparing the insulin resistance and β-cell function among patients using these agents.

METHODS

A total of 241 patients with type 2 diabetes mellitus (T2DM) treated with either pioglitazone (a TZD) or DPP-4 inhibitors as combination therapy with metformin for at least 1 year were analyzed. A propensity score based on the patients' baseline characteristics and glycated hemoglobin (HbA1c) was used to match them. Indices for insulin resistance and secretory function of β-cells, namely the homeostasis model assessment of insulin resistance (HOMA-IR) or β-cells (HOMA-β), were calculated and compared. Multiple regression analysis was performed to find the independent variables correlated with β-cell function or insulin resistance.

RESULTS

Evaluation of the data from 168 matched patients with T2DM showed that TZD users had significantly better insulin sensitivity compared with DPP-4 inhibitor users (HOMA-IR 2.3 ± 1.9 vs. 3.5 ± 3.2, p = 0.003). Conversely, DPP-4 inhibitor users secreted more insulin than TZD users (HOMA-β 45.7 ± 31.6 vs. 61.4 ± 49.5, p = 0.016). Multiple linear regression analysis showed that these agents were independently associated with both insulin resistance and β-cell function.

CONCLUSION

TZD users showed significantly better insulin sensitivity, whereas DPP-4 inhibitor users secreted more insulin from β-cells under similar glycemic control.

Effect of Linagliptin and Voglibose on metabolic profile in patients with Type 2 Diabetes: a randomized, double-blind, placebo-controlled trial

Background

Dipeptidyl peptidase 4 (DPP4) inhibitors improve glycemic control by promoting GLP1-mediated glucose-dependent insulin secretion and suppression of glucagon. Sitagliptin and vildagliptin have been shown to improve insulin sensitivity in patients with type 2 diabetes mellitus (T2DM). However, these patients had uncontrolled blood glucose at inclusion; therefore, the improvement in insulin sensitivity observed in these studies could be attributed to the drug per se and/or reduction in glucotoxicity. This study examines the effect of linagliptin on insulin sensitivity and β-cell function in patients with well-controlled T2DM.

Methods

Thirty patients with T2DM of duration ≤5 years, and having HbA1c < 7.5% were randomized to receive linagliptin, voglibose or placebo (n = 10 each), and were followed up for 6 months. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp, and insulin secretory response was measured by basal (M₀) and postprandial (M₁) β-cell function, and area under curve (AUC) for C-peptide during mixed meal tolerance test.

Results

The median HbA1c of the study subjects at inclusion was 6.9% and there was no significant difference among the groups in terms of age, duration of diabetes, body mass index (BMI), HbA1c, insulin sensitivity, AUC of C-peptide and M₀ and M₁ at baseline. At the end of the study, there was a modest reduction in HbA1c (− 0.2%) in the linagliptin group, and a significant decrease (− 0.8%) in the voglibose group, as compared to placebo (p = 0.038). However, there were no significant differences in insulin sensitivity, M₀ and M₁ and AUC of C-peptide, within, or among the groups.

Conclusion

Linagliptin modestly improves glycemic profile in patients with well controlled T2DM; however, it may not have an effect on insulin sensitivity in these patients.

Trial registration

Retrospectively Registered in Clinicaltrials.gov (ID number, NCT02097342). Registered: March 27, 2014.

Dipeptidyl peptidase inhibitor therapy in type 2 diabetes: Control of the incretin axis and regulation of postprandial glucose and lipid metabolism

Dipeptidyl peptidase 4 (DPP4) is a widely expressed, serine protease which regulates the bioactivity of many peptides through cleavage and inactivation including the incretin hormones, glucagon like peptide -1 (GLP-1) and glucose dependent insulinotropic polypeptide (GIP). Inhibitors of DPP4 are used therapeutically to treat patients with Type 2 Diabetes Mellitus (T2DM) as they potentiate incretin action to regulate islet hormone secretion and improve glycemia and post-prandial lipid excursions. The widespread clinical use of DPP4 inhibitors has increased interest in the molecular mechanisms by which these drugs mediate their beneficial effects. Traditionally, focus has remained on inhibiting the catalytic activity of DPP4 within the plasma compartment, however evidence is emerging on the importance of inactivation of membrane-bound DPP4 in selective tissue beds to potentiate local hormone gradients. Here we review the recent advances in identifying the cellular sources of both circulating and membrane-bound DPP4 important for cleavage of the incretin hormones and regulation of glucose and lipoprotein metabolism.

Clinical and Physiological Characterization of Elevated Plasma Glucagon-Like Peptide-1 Levels (Hyperglipemia) in a Dipeptidyl Peptidase IV Mutation Carrier

The clinical application of dipeptidyl peptidase IV inhibitors (DPP4i) increasing active glucagon-like peptide-1 (AGLP-1) levels has been linked to pancreatitis, pancreatic tumors, and cardiovascular events. However, DPP4 mutations in humans or the long-term outcomes of high glucagon-like peptide-1 (GLP-1) level exposure have not been reported. A trio family with a proband showing an extremely high AGLP-1 level [defined here as hyperglipemia (hyper-glucagon-like peptide-1-emia)] were conducted whole-exome sequencing for potential pathogenic genetic defects. One novel DPP4 mutation, p.V486M (c.1456 G>A), was identified in the proband and showed damaged enzymatic activity of DPP4. Ex vivo functional study further showed that the serum from the proband markedly enhanced insulin production of primary rat islet cells. Furthermore, V486M variant and another eight DPP4 variants were identified in our in-home database and seven showed decreased enzymatic activities than wild-type DPP4, consistent with their alterations in their protein expression levels. Of note, the levels of glucose, lipids, and tumor markers (especially for CA15-3 and CA125), increased gradually in the proband during a 4-year follow-up period, although no abnormal physical symptoms or imaging results were observed at present. The other two old carriers in the pedigree both had type 2 diabetes, and one of them also had hyperlipidemia and myocarditis. We first identified hyperglipemia in a female subject harboring a loss-of-function DPP4 mutation with decreased DPP4 activity. Other sporadic DPP4 mutations verified the low-frequent occurrence of genetic inhibition of DPP4 activity, at least in the Chinese population studied. These results may provide new evidence for evaluation of the potential long-term effects of DPP4i and GLP-1 analogs.

DPP4 INHIBITOR SITAGLIPTIN AS A POTENTIAL TREATMENT OPTION IN METFORMIN-INTOLERANT OBESE WOMEN WITH POLYCYSTIC OVARY SYNDROME: A PILOT RANDOMIZED STUDY

OBJECTIVE

Metformin has an established role in the management of polycystic ovary syndrome (PCOS). Some patients cannot tolerate it due to associated gastrointestinal adverse events. The present study evaluated the dipeptidyl peptidase 4 inhibitor sitagliptin as a potential treatment option in metformin-intolerant PCOS.

METHODS

We conducted a 12-week, prospective, randomized, open-label study with 30 obese metformin-intolerant women with PCOS (age 35.0 ± 7.2 years; body mass index, 36.9 ± 5.5 kg/m²). After metformin withdrawal, they were randomized to lifestyle intervention and sitagliptin 100 mg daily (SITA) or lifestyle intervention alone as controls (CON). All participants underwent anthropometric and endocrine measurements and oral glucose tolerance testing. Model-derived indexes of insulin resistance and beta-cell function were calculated.

RESULTS

SITA improved beta-cell function as assessed by the homeostasis model assessment for beta-cell function index (HOMA-B) of 45.9 ± 35.8 ( P = .001), modified beta-cell function index (MBCI) of 7.9 ± 7 ( P = .002), and quantitative insulin-sensitivity check index (QUICKI) of -0.03 ± 0.03 ( P = .002). By contrast, beta-cell function decreased in CON. The between-group differences were significant for HOMA-B ( P = 0.001), MBCI ( P = .010), and QUICKI ( P = .025). The conversion rate to impaired glucose homeostasis was prevented in SITA: 3 of 15 subjects had impaired glucose tolerance (IGT) before and after the study. In CON, none had type 2 diabetes (T2D), and 4 had IGT at the beginning. After 12 weeks, IGT was observed in 2 and T2D in 3 subjects.

CONCLUSION

SITA improved beta-cell function and prevented a conversion to IGT and T2D in metformin-intolerant obese PCOS patients.

ABBREVIATIONS

BMI = body mass index; DPP-4 = dipeptidyl peptidase-4; DXA = dual energy X-ray absorptiometry; GIP = glucose-dependent insulinotropic peptide; GLP-1 = glucagon-like peptide-1; HOMA-B = homeostasis model assessment for beta-cell function; HOMA-IR = homeostasis model assessment of insulin resistance; IAI = insulin action index; IGT = impaired glucose tolerance; IR = insulin resistance; MBCI = modified beta-cell function index; OGTT = oral glucose tolerance test; QUICKI = quantitative insulin sensitivity check index; PCOS = polycystic ovary syndrome; SHBG = sex hormone-binding globulin; T2D = type 2 diabetes.

Add on DPP-4 inhibitor alogliptin alone or in combination with pioglitazone improved β-cell function and insulin sensitivity in metformin treated PCOS

PURPOSE

Impaired β-cell function remains unaddressed in PCOS. The aim of the study was to evaluate whether dipeptidyl peptidase-4 (DPP-4) inhibitor alogliptin (ALO) alone or in combination with pioglitazone (PIO) improves β-cell function along with insulin resistance (IR) in metformin (MET) treated obese women with PCOS with persistent IR.

MATERIALS AND METHODS

In 12-week randomized study, ALO 25 mg QD (n=15) or ALO 25 mg QD and PIO 30 mg QD (n=15) was added to MET 1000 mg BID in PCOS women (aged 34.4 ± 6.5 years, BMI 39.0 ± 4.9 kg/m², HOMA-IR 4.82 ± 2.52, mean ± SD). Model derived parameters of glucose homeostasis from the meal tolerance test (MTT) were determined. The ability of the β-cell function was assessed by the adaptation index (AI).

RESULTS

MET-ALO and MET-ALO-PIO resulted in a significant decrease of HOMA-IR (by 1.6±2.3 (p=0.039) and 2.9±3.3 (p=0.001), respectively) and an increase in insulin sensitivity (IS) after meal ingestion (oral glucose IS) by 31.4±97.5 ml·min^-1·m^-2 (p=0.007) vs 39.0±58.1 ml·min^-1·m^-2 (p=0.039), respectively. AI across the entire group was significantly improved from 329.6±200.6 to 442.5±303.9 (p=0.048).

CONCLUSIONS

ALO alone and in combination with PIO improved IR along with dynamic IS and meal related β-cell function when added to MET treated PCOS.

Renoprotective Effects of the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin: A Review in Type 2 Diabetes

Diabetic nephropathy (DN) is now the single commonest cause of end-stage renal disease (ESRD) worldwide and one of the main causes of death in diabetic patients. It is also acknowledged as an independent risk factor for cardiovascular disease (CVD). Since sitagliptin was approved, many studies have been carried out revealing its ability to not only improve metabolic control but also ameliorate dysfunction in various diabetes-targeted organs, especially the kidney, due to putative underlying cytoprotective properties, namely, its antiapoptotic, antioxidant, anti-inflammatory, and antifibrotic properties. Despite overall recommendations, many patients spend a long time well outside the recommended glycaemic range and, therefore, have an increased risk for developing micro- and macrovascular complications. Currently, it is becoming clearer that type 2 diabetes mellitus (T2DM) management must envision not only the improvement in glycaemic control but also, and particularly, the prevention of pancreatic deterioration and the evolution of complications, such as DN. This review aims to provide an overview of the current knowledge in the field of renoprotective actions of sitagliptin, namely, improvement in diabetic dysmetabolism, hemodynamic factors, renal function, diabetic kidney lesions, and cytoprotective properties.

Efficacy and safety of adding evogliptin versus sitagliptin for metformin-treated patients with type 2 diabetes: A 24-week randomized, controlled trial with open label extension

AIMS

This trial consisted of a 24-week multicentre, randomized, double-blind, double-dummy, active-controlled study and a 52-week open label extension study to assess the efficacy and safety of evogliptin, a novel dipeptidyl peptidase-4 inhibitor, compared to sitagliptin in patients with type 2 diabetes who have inadequate glycaemic control with metformin alone.

METHODS

Adult patients with type 2 diabetes mellitus (N = 222) with HbA1c 6.5% to 11% who were receiving stable doses of metformin (≥1000 mg/d) were randomized 1:1 to add-on evogliptin 5 mg (N = 112) or sitagliptin 100 mg (N = 110) once daily for 24 weeks. The primary efficacy analysis consisted of a comparison of the change from baseline HbA1c at week 24. Non-inferiority was concluded if the upper limit of the 2-sided 95% confidence interval for the HbA1c difference between treatments was <0.35%.

RESULTS

Mean changes in HbA1c following addition of evogliptin or sitagliptin were -0.59% and -0.65%, respectively. The between-group difference was 0.06% (2-sided 95% confidence interval, -0.10 to 0.22), demonstrating non-inferiority. After the 52-week treatment, evogliptin caused a persistently decreased level of HbA1c (-0.44% ± 0.65%, P  < .0001). In general, both treatments were well tolerated, with incidences and types of adverse events comparable between the two groups. Hypoglycaemic events, mostly mild, were reported in 0.9% of patients treated with evogliptin and in 2.8% of patients treated with sitagliptin for 24 weeks.

CONCLUSIONS

Evogliptin 5 mg added to metformin therapy effectively improved glycaemic control and was non-inferior to sitagliptin and well tolerated in patients with type 2 diabetes mellitus that was inadequately controlled by metformin alone.

Effects of dipeptidyl peptidase-4 inhibitors on beta-cell function and insulin resistance in type 2 diabetes: meta-analysis of randomized controlled trials

Dipeptidyl peptidase-4 (DPP-4) inhibitors are a novel family of glucose-lowering agents. Accumulating evidence suggests that DPP-4 inhibitors preserve pancreatic beta-cell function, but results in previous studies have been inconsistent. We assessed the effects of DPP-4 inhibitors on the homoeostasis model assessment beta-cell function (HOMA-B) or insulin resistance (HOMA-IR) index in patients with type 2 diabetes through a systematic review and meta-analysis of randomized controlled trials (RCTs). Relevant articles were identified from PubMed, Embase, and Cochrane Library databases up to December 27, 2016. We calculated weighted mean differences (WMDs) and 95% confidence intervals (CIs) in each included trial and pooled the data using a random-effects model. Fifty-two trials were included in the present analysis. Compared with placebo control, DPP-4 inhibitors as monotherapy significantly improved HOMA-B (WMD 9.15; 95% CI 7.48, 10.81). Similarly, DPP-4 inhibitors as add-on therapy in combination with other drugs showed significant improvement in HOMA-B (WMD 9.04; 95% CI 5.72, 12.37). However, we found no significant improvement in HOMA-IR following treatment with DPP-4 inhibitors as mono-therapy or as add-on therapy. In conclusion, DPP-4 inhibitors as monotherapy or as add-on therapy significantly improved beta-cell function but had no significant effect on insulin resistance in type 2 diabetes.

DPP-4 inhibitors in diabetic complications: role of DPP-4 beyond glucose control

Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) are an emerging class of antidiabetic drugs that constitutes approximately fifty percent of the market share of the oral hypoglycemic drugs. Its mechanism of action for lowering blood glucose is essentially via inhibition of the rapid degradation of incretin hormones, such as glucagon-like peptide (GLP)-1 and gastric inhibitory polypeptide (GIP), thus the plasma concentration of GLP-1 increases, which promotes insulin secretion from the pancreatic β cells and suppresses glucagon secretion from the α cells. In addition to the direct actions on the pancreas, GLP-1 exhibits diverse actions on different tissues through its action on GLP-1 receptor, which is expressed ubiquitously. Moreover, DPP-4 has multiple substrates besides GLP-1 and GIP, including cytokines, chemokines, neuropeptides, and growth factors, which are involved in many pathophysiological conditions. Recently, it was suggested that DPP-4 is a new adipokine secreted from the adipose tissue, which plays an important role in the regulation of the endocrine function in obesity-associated type 2 diabetes. Consequently, DPP-4 inhibitors have been reported to exhibit cytoprotective functions against various diabetic complications affecting the liver, heart, kidneys, retina, and neurons. This review outlines the current understanding of the effect of DPP-4 inhibitors on the complications associated with type 2 diabetes, such as liver steatosis and inflammation, dysfunction of the adipose tissue and pancreas, cardiovascular diseases, nephropathy, and neuropathy in preclinical and clinical studies.

In vivo dual-delivery of glucagon like peptide-1 (GLP-1) and dipeptidyl peptidase-4 (DPP4) inhibitor through composites prepared by microfluidics for diabetes therapy

Oral delivery of proteins is still a challenge in the pharmaceutical field. Nanoparticles are among the most promising carrier systems for the oral delivery of proteins by increasing their oral bioavailability. However, most of the existent data regarding nanosystems for oral protein delivery is from in vitro studies, lacking in vivo experiments to evaluate the efficacy of these systems. Herein, a multifunctional composite system, tailored by droplet microfluidics, was used for dual delivery of glucagon like peptide-1 (GLP-1) and dipeptidyl peptidase-4 inhibitor (iDPP4) in vivo. Oral delivery of GLP-1 with nano- or micro-systems has been studied before, but the simultaneous nanodelivery of GLP-1 with iDPP4 is a novel strategy presented here. The type 2 diabetes mellitus (T2DM) rat model, induced through the combined administration of streptozotocin and nicotinamide, a non-obese model of T2DM, was used. The combination of both drugs resulted in an increase in the hypoglycemic effects in a sustained, but prolonged manner, where the iDPP4 improved the therapeutic efficacy of GLP-1. Four hours after the oral administration of the system, blood glucose levels were decreased by 44%, and were constant for another 4 h, representing half of the glucose area under the curve when compared to the control. An enhancement of the plasmatic insulin levels was also observed 6 h after the oral administration of the dual-drug composite system and, although no statistically significant differences existed, the amount of pancreatic insulin was also higher. These are promising results for the oral delivery of GLP-1 to be pursued further in a chronic diabetic model study.

Combination therapy of SGLT2 inhibitors with incretin-based therapies for the treatment of type 2 diabetes mellitus: Effects and mechanisms of action

Type 2 diabetes mellitus (T2DM) is a growing health problem worldwide; its pathogenesis is multifactorial and its progressive nature often necessitates a combination therapy with multiple antihyperglycemic agents. Sodium glucose cotransporter 2 (SGLT2) inhibitors and the incretin-based therapies - dipeptidyl peptidase 4(DPP-4) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists - were introduced for the treatment of T2DM within the last decade. Evidence of the beneficial effects of these antihyperglycemic agents on micro- and macrovascular complications have started to emerge, which will become important in individualizing different combinations of antihyperglycemic agents to different patient populations. We review here the mechanisms of action, glycemic and cardiovascular effects of SGLT2 inhibitors and incretin-based therapies and their combination in the treatment of T2DM.

Oral hypoglycaemic effect of GLP-1 and DPP4 inhibitor based nanocomposites in a diabetic animal model

Glucagon-like peptide-1 (GLP-1), an incretin hormone, is used for type 2 diabetes mellitus (T2DM) treatment because of its ability to stimulate insulin secretion and release in a glucose-dependent manner. Despite of its potent insulinotropic effect, oral GLP-1 delivery is greatly limited by its instability in the gastrointestinal tract, poor absorption efficiency and rapid degradation by dipeptidylpeptidase-4 (DPP4) enzyme leading to a short half-life (~2min). Thus, a multistage dual-drug delivery nanosystem was developed to deliver GLP-1 and DPP4 inhibitor simultaneously. The system comprised of chitosan-modified porous silicon (CSUn) nanoparticles, which were coated by an enteric polymer, hydroxypropylmethylcellulose acetate succinate MF, using aerosol flow reactor technology. A non-obese T2DM rat model induced by co-administration of nicotinamide and streptozotocin was used to evaluate the in vivo efficacy of the nanosystem. The oral administration of H-CSUn nanoparticles resulted in 32% reduction in blood glucose levels and ~6.0-fold enhancement in pancreatic insulin content, as compared to the GLP-1+DPP4 inhibitor solution. Overall, these results present a promising system for oral co-delivery of GLP-1 and DPP4 inhibitor that could be further evaluated in a chronic diabetic study.

Empagliflozin/Linagliptin: Combination therapy in patients with type 2 diabetes

Glyxambi^® (empagliflozin/linagliptin) is a fixed-dose, once-daily tablet combining a sodium glucose co-transporter-2 (SGLT2) inhibitor with a dipeptidyl peptidase-4 (DPP-4) inhibitor. Glyxambi^® is served as an adjuvant to diet and exercise to improve glycemic control in adults with type 2 diabetes when both empagliflozin and linagliptin are appropriate treatments. Glyxambi^® combines 10mg or 25mg empagliflozin with 5mg linagliptin, with different, complementary mechanisms of action to improve glycemic control in patients with type 2 diabetes. Empagliflozin removes glucose through the urine by blocking blood glucose re-absorption in the kidney, and linagliptin exerts glucose-lowering activity by increasing hormones that stimulate the pancreas to produce more insulin and decreasing the levels of glucagon in the circulation. In addition, this combination therapy modestly reduces body weight and blood pressure without significant safety issues.

An Update on the Effect of Incretin-Based Therapies on β-Cell Function and Mass

Type 2 diabetes mellitus (T2DM) is a multifactorial disease with a complex and progressive pathogenesis. The two primary mechanisms of T2DM pathogenesis are pancreatic β-cell dysfunction and insulin resistance. Pancreatic β-cell dysfunction is recognized to be a prerequisite for the development of T2DM. Therapeutic modalities that improve β-cell function are considered critical to T2DM management; however, blood glucose control remains a challenge for many patients due to suboptimal treatment efficacy and the progressive nature of T2DM. Incretin-based therapies are now the most frequently prescribed antidiabetic drugs in Korea. Incretin-based therapies are a favorable class of drugs due to their ability to reduce blood glucose by targeting the incretin hormone system and, most notably, their potential to improve pancreatic β-cell function. This review outlines the current understanding of the incretin hormone system in T2DM and summarizes recent updates on the effect of incretin-based therapies on β-cell function and β-cell mass in animals and humans.

Hepatic role in an early glucose-lowering effect by a novel dipeptidyl peptidase 4 inhibitor, evogliptin, in a rodent model of type 2 diabetes

Although multiple dipeptidyl peptidase 4 (DPP4) inhibitors have shown glucose-lowering effects by preserving pancreatic cells in high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice, the hepatic role in regulation of glucose homeostasis by DPP4 inhibitors in HFD/STZ mice remains elusive. In herein study, parallel comparison of effects on the liver (expression of gluconeogenic genes and the linked signaling molecules) and pancreas (islet morphology and relative area of alpha or beta cells) in combination with glucose-lowering effects were made at the end of 2- and 10-week of evogliptin treatment in HFD/STZ mice. Significant control of hyperglycemia was observed from the second week and persisted during 10-week treatment of 0.3% evogliptin in HFD/STZ mice. This effect was accompanied by increased level of plasma glucagon-like peptide-1 and preserved pancreas islet structure. Furthermore, the hepatic increases in gluconeogenic gene expression in HFD/STZ mice was significantly reduced by evogliptin treatment, which was accompanied by the suppression of cAMP response element-binding protein (CREB) phosphorylation and expression of transducer of regulated CREB protein 2. This hepatic effect of evogliptin treatment was reproduced in 2-week study, however, pancreatic beta-cell area was not altered yet although the expression of pancreatic and duodenal homeobox protein 1 was increased. We conclude that the suppression of hepatic gluconeogenesis by evogliptin is followed by preservation of pancreatic islet, leading to remarkable and persistent glucose-lowering effect in HFD/STZ mice. Our findings provide further insight for the hepatic role in DPP4 inhibitor-mediated glucose control in diabetes.

Combination of DPP-4 inhibitor and PPARγ agonist exerts protective effects on pancreatic β-cells in diabetic db/db mice through the augmentation of IRS-2 expression

We investigated the effects of long- and short-term treatment with pioglitazone (Pio) and/or alogliptin (Alo) on β-cells in diabetic db/db mice. Six-week-old male db/db mice received Pio (25 mg/kg, oral) and/or Alo (30 mg/kg, oral) for 4 weeks and for 2 days. Blood glucose levels were decreased after 4-week intervention, but not after 2-day intervention. Pio increased adiponectin levels, and Alo decreased glucagon levels and increased active GlP-1 levels. Insulin sensitivity was restored by Pio. After 4-week treatment, β-cell mass was increased (over 2-fold increase) and expression levels of various β-cell-related factors were restored. Expression levels of IRS-2 and various downstream factors were up-regulated by Pio and Alo after 2-day and 4-week intervention. In addition, mRNA and protein levels of IRS-2 and various downstream factors were up-regulated in MIN6 cells after 24-h exposure to Pio and exendin-4. These results suggest that Pio and Alo additively up-regulate IRS-2 expression independently of the alteration of glycemic control. Taken together, combination of Pio and Alo exerts protective effects on β-cells in diabetic db/db mice, at least in part, through the augmentation of IRS-2 expression.

Dipeptidyl peptidase-4 inhibitor sitagliptin improves pancreatic β-cell function in hypertensive diabetic patients treated with angiotensin receptor blockers

INTRODUCTION

Dipeptidyl peptidase (DPP)-4 inhibitors, a novel oral anti-diabetic agents, exert a protective effect on pancreatic β-cell function in patients with type 2 diabetic mellitus (T2DM). However, their beneficial effect in hypertensive T2DM patients treated with angiotensin receptor blockers (ARBs) has not been investigated.

METHODS

In this open-label multicenter randomized study, a total of 55 hypertensive T2DM patients treated with ARBs were randomly assigned to receive the DPP-4 inhibitor sitagliptin or sulfonylurea (SU).

RESULTS

After 24 weeks of treatment, a significant reduction in fasting blood glucose was only observed in the sitagliptin group, while HbA1c was significantly reduced in both groups. Homeostasis model assessment of insulin resistance was not significantly improved in either group. Indicators of pancreatic β-cell function, including proinsulin to insulin ratio and homeostasis model assessment of β-cell function, were significantly improved in the sitagliptin group, but not in the SU group. The beneficial effects of sitagliptin were observed in hypoglycemic drug naïve patients, but not in patients who had received SU monotherapy prior to the study.

CONCLUSION

Treatment with the DPP-4 inhibitor sitagliptin might exert beneficial effects on pancreatic β-cell function in ARB-treated T2DM patients and its efficacy might be more pronounced in hypoglycemic drug naïve patients.

Long-term efficacy of sitagliptin as either monotherapy or add-on therapy to metformin: improvement in glycemic control over 2 years in patients with type 2 diabetes

OBJECTIVE

To evaluate the efficacy of once daily sitagliptin 100 mg as monotherapy or as add-on to metformin in patients with type 2 diabetes mellitus (T2DM) over 2 years of treatment.

RESEARCH DESIGN AND METHODS

The monotherapy analysis used pooled 104 week data from 64 patients in two randomized, double-blind trials evaluating the safety and efficacy of sitagliptin monotherapy. Data used were from patients who were randomized to sitagliptin 100 mg/day, were not on an antihyperglycemic agent at the screening visit, had baseline A1C of 7.0%-10.0%, and had Week 104 A1C measurements. The add-on to metformin analysis used pooled data from 347 patients in two randomized double-blind trials evaluating the safety and efficacy of sitagliptin + metformin combination therapy. Data used were from patients who were randomized to sitagliptin 100 mg/day + metformin ≥1500 mg/day, had baseline A1C of 7%-10%, and had Week 104 A1C measurements. Excluded from either analysis were patients who discontinued prior to 2 years (e.g., due to lack of efficacy, a need for rescue medications, or adverse experiences). Analysis endpoints were A1C, fasting plasma glucose (FPG), HOMA-β, proinsulin/insulin (P/I) ratio, and for monotherapy, 2 hour post-meal plasma glucose (PMG).

RESULTS

For the pooled monotherapy cohort, after 2 years of treatment, mean A1C, FPG, and 2 hour PMG decreased from baseline values of 7.9%, 156 mg/dL, and 223 mg/dL to 6.9%, 143 mg/dL, and 191 mg/dL, respectively, while HOMA-β increased from 67% to 85% and P/I ratio improved from 0.57 to 0.28. For the pooled add-on to metformin cohort, after 2 years of treatment, mean A1C and FPG decreased from baseline values of 7.7% and 160 mg/dL to 6.9% and 140 mg/dL, respectively, while HOMA-β increased from 50% to 62% and P/I ratio improved from 0.33 to 0.28. These analyses are limited in that only patients who were able to complete 104 weeks of study were included.

CONCLUSION

In the subset of patients with T2DM who maintained and completed treatment for 2 years with sitagliptin as monotherapy or as add-on to metformin, improvements in glycemic control and measures of β-cell function were observed over the course of treatment.

Design and baseline characteristics of the CARdiovascular Outcome Trial of LINAgliptin Versus Glimepiride in Type 2 Diabetes (CAROLINA®)

CARdiovascular Outcome Trial of LINAgliptin Versus Glimepiride in Type 2 Diabetes (NCT01243424) is an ongoing, randomized trial in subjects with early type 2 diabetes and increased cardiovascular risk or established complications that will determine the long-term cardiovascular impact of linagliptin versus the sulphonylurea glimepiride. Eligible patients were sulphonylurea-naïve with HbA1c 6.5%-8.5% or previously exposed to sulphonylurea (in monotherapy or in a combination regimen <5 years) with HbA1c 6.5%-7.5%. Primary outcome is time to first occurrence of cardiovascular death, non-fatal myocardial infarction, non-fatal stroke or hospitalization for unstable angina. A total of 631 patients with primary outcome events will be required to provide 91% power to demonstrate non-inferiority in cardiovascular safety by comparing the upper limit of the two-sided 95% confidence interval as being below 1.3 for a given hazard ratio. Hierarchical testing for superiority will follow, and the trial has 80% power to demonstrate a 20% relative cardiovascular risk reduction. A total of 6041 patients were treated with median type 2 diabetes duration 6.2 years, 40.0% female, mean HbA1c 7.2%, 66% on 1 and 24% on 2 glucose-lowering agents and 34.5% had previous cardiovascular complications. The results of CARdiovascular Outcome Trial of LINAgliptin Versus Glimepiride in Type 2 Diabetes may influence the decision-making process for selecting a second glucose-lowering agent after metformin in type 2 diabetes.

Combination of linagliptin and metformin for the treatment of patients with type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a progressive condition requiring long-term treatment. Most patients with T2DM are unable to maintain normoglycemia using metformin alone; thus, combination therapy is a pivotal part of disease management. Addition of the dipeptidyl peptidase-4 inhibitor linagliptin, with its proven efficacy, low propensity for hypoglycemia, and weight neutrality, has been shown to improve glycemic control for patients who are not well controlled with metformin. As patients often have other comorbidities requiring pharmacotherapy, an increase in pill number, different prescribing frequencies, and timing of medications may adversely impact patients’ adherence. Studies have shown that treatment nonadherence contributes to increased morbidity, mortality, and healthcare cost. In the United States, the single-pill combination (SPC) of linagliptin/metformin is available in three strengths approved for twice-daily administration: 2.5/500 mg, 2.5/850 mg, and 2.5/1000 mg. The SPC has the potential to reduce pill burden and simplify patients’ treatment regimens, thereby promoting improved adherence and efficacy.

Comparative analysis of therapeutic efficiency and costs (experience in Bulgaria) of oral antidiabetic therapies based on glitazones and gliptins

Type 2 diabetes mellitus is a serious, chronic, progressive and widespread disease. Metformin is the most commonly prescribed initial therapy, but combination with other antidiabetic agents usually becomes necessary due to the progression of the disease. Pioglitazone is recommended as a second-line therapy because of its strong antihyperglycemic effect and its ability to reduce insulin resistance. Treatment with pioglitazone is associated with a significantly lower risk of cardiovascular complications and hypoglycemia, while simultaneously improving the lipid profile and the symptomatic and histological changes in the liver. Gliptins (sitagliptin and vildagliptin) are a new class of oral antidiabetic drugs which reduce glycated hemoglobin by a different mechanism. Although the efficacy of sitagliptin and vildagliptin is close to that of pioglitazone, the lack of long-term safety data and the higher price question their predominant use. The objective of this review is to highlight the advantages of mono- and combination therapy with pioglitazone in comparison with gliptins and to underline the inconsistencies in the medicinal and reimbursement policy in Bulgaria.

Pharmacological treatment of diabetes in older people

The pharmacological management of diabetes in older people is complex and challenging. It requires a comprehensive understanding of the individual beyond the diabetes itself. Through the ageing years, the older individual presents with diabetes-related and non-related comorbidities and complications, develops functional limitations and psychological issues, and may lack social support and access to care. A disturbance in these categories, known as the four geriatric domains, will negatively affect diabetes self-management and self-efficacy, leading to poor outcomes and complications. Furthermore, older people with diabetes may be more interested in the management of other chronic conditions such as pain or impaired mobility, and diabetes may be lower in their list of priorities. Proper education must be provided to the older individual and caregivers, with continuous monitoring and counselling, especially when pharmacological interventions offer risks of side effects, adverse reactions and interactions with other medications. Informed shared medical decisions will help to improve adherence to the regimen; however, such discussions ought to be based on the best evidence available, which is unfortunately limited in this age group. We performed a review focused on pharmacological agents and summarize current evidence on their use for the treatment of diabetes in older people. We encourage clinicians to investigate and incorporate the four geriatrics domains in the selection and monitoring of these agents.

The effect of alogliptin and pioglitazone combination therapy on various aspects of β-cell function in patients with recent-onset type 2 diabetes

OBJECTIVE

Type 2 diabetes mellitus (T2DM) management requires continuous treatment intensification due to progressive decline in β-cell function in insulin resistant individuals. Initial combination therapy of a dipeptidyl peptidase (DPP)-4 inhibitor with a thiazolidinedione (TZD) may be rational. We assessed the effects of the DPP4 inhibitor alogliptin (ALO) combined with the TZD pioglitazone (PIO), vs ALO monotherapy or placebo (PBO), on β-cell function and glycemic control in T2DM.

MATERIAL AND METHODS

A 16-week, two-center, randomized, double-blind, PBO-controlled, parallel-arm intervention study in 71 patients with well-controlled T2DM (age 59.1±6.3 years; A1C 6.7±0.1%) treated with metformin, sulfonylurea, or glinide monotherapy was conducted. Patients were treated with combined ALO 25 mg and PIO 30 mg daily or ALO 25 mg daily monotherapy or PBO. Main outcome measures included change in A1C and fasting plasma glucose (FPG) from baseline to week 16. In addition, change in β-cell function parameters obtained from standardized meal tests at baseline and at week 16 was measured.

RESULTS

ALO/PIO and ALO decreased A1C from baseline by 0.9±0.1 and 0.4±0.2% respectively (both P<0.001 vs PBO). FPG was decreased to a greater extent by ALO/PIO compared with ALO monotherapy (P<0.01). ALO/PIO treatment improved β-cell glucose sensitivity (vs PBO; P<0.001) and fasting secretory tone (vs PBO; P=0.001), while ALO monotherapy did not change β-cell function parameters. All treatments were well tolerated.

CONCLUSION

Short-term treatment with ALO/PIO or ALO improved glycemic control in well-controlled T2DM patients, but only combined ALO/PIO improved β-cell function. These data support that initial combination therapy with a DPP4 inhibitor and TZD to address multiple core defects in T2DM may be a sensible approach.

Insulin plus incretin agent combination therapy in type 2 diabetes: a systematic review

BACKGROUND

Insulin and incretin agents (dipeptidyl peptidase-4 inhibitors [DPP4is] and glucagon-like peptide-1 receptor agonists [GLP1 RAs]) are second-line treatment options in patients with type 2 diabetes (T2D) not achieving glycemic targets with metformin. Combinations of insulin with incretin agents have been explored in randomized controlled trials (RCTs) and retrospective studies. However, the optimal approach is still elusive; numerous combination regimens can be envisioned, differing in composition and in order of addition.

SCOPE

A systematic survey was conducted of RCTs testing insulin/DPP4i or insulin/GLP1 RA regimens. PubMed and other online databases were queried using 'insulin' and the names of all incretin agents available in Canada, along with 'combination', 'concomitant', 'concurrent', and 'add-on'. Web of Science and clinicaltrials.gov were searched to identify unpublished trials.

FINDINGS

Fifteen placebo-controlled or active-comparator RCTs were identified, reporting outcomes for regimens combining insulins and incretin agents available in Canada. DPP4i add-on to insulin therapy (six trials) leads to modest A1c lowering, with weight neutrality. GLP1 RA and insulin combination therapy (GLP1 RA add-on, five trials; insulin add-on, two trials) is associated with significant A1c lowering, with beneficial effects on body weight. A single proof-of-concept trial compared GLP1 RA to DPP4i add-on to insulin, and only one RCT examined simultaneous introduction of an incretin agent with insulin. Adding an incretin agent to established basal insulin therapy may represent a useful alternative to insulin intensification with prandial or premixed insulin. Initial introduction of an incretin agent, with subsequent introduction of insulin, offers potential practical advantages. No study directly comparing order of addition has yet been reported.

CONCLUSIONS

Insulin/incretin combination therapy comprises a variety of efficacious, weight-sparing regimens and may be considered for many patients who do not achieve glycemic targets when treated with insulin or an incretin agent.

Assessment of pancreatic β-cell function: review of methods and clinical applications

Type 2 diabetes mellitus (T2DM) is characterized by a progressive failure of pancreatic β-cell function (BCF) with insulin resistance. Once insulin over-secretion can no longer compensate for the degree of insulin resistance, hyperglycemia becomes clinically significant and deterioration of residual β-cell reserve accelerates. This pathophysiology has important therapeutic implications. Ideally, therapy should address the underlying pathology and should be started early along the spectrum of decreasing glucose tolerance in order to prevent or slow β-cell failure and reverse insulin resistance. The development of an optimal treatment strategy for each patient requires accurate diagnostic tools for evaluating the underlying state of glucose tolerance. This review focuses on the most widely used methods for measuring BCF within the context of insulin resistance and includes examples of their use in prediabetes and T2DM, with an emphasis on the most recent therapeutic options (dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists). Methods of BCF measurement include the homeostasis model assessment (HOMA); oral glucose tolerance tests, intravenous glucose tolerance tests (IVGTT), and meal tolerance tests; and the hyperglycemic clamp procedure. To provide a meaningful evaluation of BCF, it is necessary to interpret all observations within the context of insulin resistance. Therefore, this review also discusses methods utilized to quantitate insulin-dependent glucose metabolism, such as the IVGTT and the euglycemic-hyperinsulinemic clamp procedures. In addition, an example is presented of a mathematical modeling approach that can use data from BCF measurements to develop a better understanding of BCF behavior and the overall status of glucose tolerance.

Extra-pancreatic effects of incretin-based therapies: potential benefit for cardiovascular-risk management in type 2 diabetes

Development of cardiovascular disease is one of the major complications of type 2 diabetes mellitus (T2DM). The chronic hyperglycaemic state is often accompanied by dyslipidaemia, hypertension, low-grade systemic inflammation and oxidative stress which collectively result in a high risk of micro- and macrovascular complications. Current glucose-lowering agents do not sufficiently address fore-mentioned macrovascular-risk factors. Recently, new therapeutic agents were introduced, based on the incretin hormone glucagon-like peptide-1 (GLP-1), that is, the GLP-1 receptor agonists (GLP-1RA) and dipeptidyl-peptidase 4 (DPP-4) inhibitors. Beside its effect on pancreatic insulin secretion, GLP-1 exerts several extra-pancreatic effects such as slowing down gastric emptying, promoting satiety and reducing food intake and weight loss. Also, GLP-1 and GLP-1RA were shown to improve cardiovascular-risk profiles, by reducing body fat content, blood pressure, circulating lipids and inflammatory markers in patients with T2DM. This review summarizes the presently known evidence with regard to extra-pancreatic effects of the incretin-based agents, focusing on the actions that improve the cardiovascular-risk profile. We present available data from clinical trials of at least 24 week duration, but also findings from small-sized clinical 'proof of principle' studies. We conclude that GLP-1 RA and to a lesser extent DPP-4 inhibitors are promising agents with regard to their effects on body weight, blood pressure and lipids, which collectively ameliorate the cardiovascular-risk profile and as such may have added value in the treatment of T2DM. However, large-sized long-term outcome studies are warranted to show the true added value of these agents in the treatment of patients with T2DM.

Cardiovascular effects of gliptins

Dipeptidyl peptidase 4 (DPP-4) inhibitors (commonly referred to as gliptins) are a novel class of oral antihyperglycaemic agents with demonstrated efficacy in the treatment of type 2 diabetes mellitus (T2DM). Preclinical data and mechanistic studies have indicated a possible beneficial action on blood vessels and the heart, via both glucagon-like peptide 1 (GLP-1)-dependent and GLP-1-independent effects. DPP-4 inhibition increases the concentration of many peptides with potential vasoactive and cardioprotective effects. Clinically, DPP-4 inhibitors improve several risk factors in patients with T2DM. They improve blood glucose control (mainly by reducing postprandial glycaemia), are weight neutral (or even induce modest weight loss), lower blood pressure, improve postprandial lipaemia, reduce inflammatory markers, diminish oxidative stress, and improve endothelial function. Some positive effects on the heart have also been described in patients with ischaemic heart disease or congestive heart failure, although their clinical relevance requires further investigation. Post-hoc analyses of phase II-III, controlled trials suggest a possible cardioprotective effect with a trend for a lower incidence of major cardiovascular events with gliptins than with placebo or active agents. However, the actual relationship between DPP-4 inhibition and cardiovascular outcomes remains to be proven. Major prospective clinical trials with predefined cardiovascular outcomes and involving various DPP-4 inhibitors are now underway in patients with T2DM and a high-risk cardiovascular profile.

Longer term safety of dipeptidyl peptidase-4 inhibitors in patients with type 2 diabetes mellitus: systematic review and meta-analysis

Dipeptidyl peptidase-4 (DPP-4) inhibitors are oral antidiabetic agents that hold the potential of slowing the progress of type 2 diabetes mellitus. Their long-term safety is still a subject of debate. A systematic review of randomized, controlled trials was undertaken to comprehensively profile the safety of chronic treatment of type 2 diabetes mellitus with DPP-4 inhibitors. We searched data sources including MEDLINE, CENTRAL, publishers' and manufacturers' databases. Eligible trials were double-blind, randomized, placebo or active-controlled trials with ≥18 weeks duration in patients with type 2 diabetes reporting safety outcomes. Meta-analysis was performed separately for trials in which the control group received placebo (44 studies), another gliptin (3 studies) and any other antidiabetic drug (20 studies). Risk ratios with 95% confidence intervals were computed using a Mantel-Haenszel fixed-effect model for general safety outcomes, hypoglycaemia and adverse events by system organ class. Of 307 publications retrieved, 67 randomized, controlled trials met the eligibility criteria and were included in this review (4 alogliptin, 8 linagliptin, 8 saxagliptin, 20 sitagliptin, and 27 vildagliptin trials). Adverse events with gliptin treatment were at placebo level (relative risk (RR) 1.02 [0.99, 1.04]). No increased risk of infections was detectable (RR 0.98 [0.93, 1.05] compared to placebo and 1.02 [0.97, 1.07] compared to other antidiabetic drugs). Asthenia (RR 1.57 [1.09, 2.27]) as well as cardiac (RR 1.37 [1.00, 1.89]) and vascular disorders (RR 1.74 [1.05, 2.86] for linagliptin) emerged as adverse events associated with DPP-4 inhibitor treatment. The risk of hypoglycaemia was low with DPP-4 inhibitor treatment (RR 0.92 [0.74, 1.15] compared to placebo, RR 0.20 [0.17, 0.24] compared to sulphonylureas) in the absence of sulphonylurea or insulin co-therapy, but significantly elevated for combination therapy of sulphonylurea or insulin with sitagliptin or linagliptin (RR 1.86 [1.46, 2.37] compared to placebo). A large body of data supports the long-term safety of gliptin treatment and refutes an increased risk of infections. Further research is needed to clarify a possible link to asthenia, cardiac and vascular events. For combination therapy with insulin or insulin secretagogues, a careful choice of the agent used may limit the risk of hypoglycaemia.

Linagliptin/Metformin fixed-dose combination treatment: a dual attack to type 2 diabetes pathophysiology

Combination therapies are a widely accepted approach to type 2 diabetes treatment, considering that monotherapies fail to provide adequate glycemic control in the majority of cases. The combination of oral antidiabetic agents into a single tablet would significantly simplify the therapeutic regimen and maximize patients' adherence to treatment. Recently, a fixed-dose, single-tablet, combined formulation of linagliptin (a dipeptidyl peptidase-4 inhibitor) and metformin has been approved for use in type 2 diabetic patients, and is indicated as an adjunct to diet and exercise for those patients who remain inadequately controlled despite maximal tolerated doses of metformin, metformin and sulfonylurea, or linagliptin and metformin monotherapies. The combination tablet is administered twice daily and can be used either alone or combined with sulfonylureas. Clinical trials suggest that this fixed-dose combination provides significantly superior glycemic control compared to linagliptin and metformin monotherapy, in terms of improving key parameters of glucose homeostasis such as glycosylated hemoglobin, fasting and postprandial glucose levels. It also exhibits an excellent tolerability profile, without promoting weight gain and hypoglycemic episodes. The compounds of this formulation do not display clinically relevant pharmacokinetic interactions with each other, and exert synergistic (complementary) pharmacodynamic effects, including an enhanced incretin effect, suppressed hepatic glucose production, and improved peripheral insulin sensitivity. As a result, a linagliptin/metformin fixed-dose combination offers the potential to address multiple defects of type 2 diabetes pathophysiology (pancreatic islet dysfunction, insulin resistance, increased hepatic glucose output), and most importantly, in the context of a safe, efficacious, flexible, and convenient therapeutic regimen.

What next after metformin? A retrospective evaluation of the outcome of second-line, glucose-lowering therapies in people with type 2 diabetes

CONTEXT

After failure of metformin monotherapy, many second-line, glucose-lowering therapies are available to treat people with type 2 diabetes.

OBJECTIVE

The objective of the study was to compare clinical outcomes using common alternative regimens.

DESIGN AND SETTING

This was a retrospective cohort study using data from the U.K.-based General Practice Research Database.

PATIENTS

These were primary care patients with type 2 diabetes who had metformin monotherapy as their first treatment and who then initiated on relevant second-line, glucose-lowering regimens during the study period 2000-2010. A total of 27,457 patients were prescribed a second-line therapy, of whom 26,278 (95.7%) were prescribed a regimen with 1,000 or more observations.

MAIN OUTCOME MEASURES

All-cause mortality, major adverse cardiovascular events (MACE), cancer, and a combined end point of any of these were measured. Secondary end points were change in glycosylated hemoglobin between baseline and 12 months. Time to clinical end points was compared using Cox proportional hazards models.

RESULTS

Sulfonylurea monotherapy had significantly higher hazard ratios (HRs) for all-cause mortality (HR 1.459, 1.207-1.763); MACE (HR 1.578, 1.187-2.099); stroke (HR 1.444, 1.050-1.987); and the combined end point (HR 1.381, 1.194-1.597). Metformin plus pioglitazone had significantly lower adjusted HRs for all-cause mortality (HR 0.707, 0.515-0.970) and the combined end point (HR 0.747, 0.612-0.911). Mean glycosylated hemoglobin improved between baseline and 12 months for all regimens other than sulfonylurea monotherapy.

CONCLUSION

The combination of metformin plus pioglitazone appears to provide superior clinical outcomes compared with the most commonly used regimen, metformin plus sulfonylurea. Sulfonylurea monotherapy resulted in worse outcome.

Unraveling oxyntomodulin, GLP1's enigmatic brother

Oxyntomodulin (OXM) is a peptide secreted from the L cells of the gut following nutrient ingestion. OXM is a dual agonist of the glucagon-like peptide-1 receptor (GLP1R) and the glucagon receptor (GCGR) combining the effects of GLP1 and glucagon to act as a potentially more effective treatment for obesity than GLP1R agonists. Injections of OXM in humans cause a significant reduction in weight and appetite, as well as an increase in energy expenditure. Activation of GCGR is classically associated with an elevation in glucose levels, which would be deleterious in patients with T2DM, but the antidiabetic properties of GLP1R agonism would be expected to counteract this effect. Indeed, OXM administration improved glucose tolerance in diet-induced obese mice. Thus, dual agonists of the GCGR and GLP1R represent a new therapeutic approach for diabetes and obesity with the potential for enhanced weight loss and improvement in glycemic control beyond those of GLP1R agonists.

Comparative clinical pharmacokinetics of dipeptidyl peptidase-4 inhibitors

Dipeptidyl peptidase-4 (DPP-4) inhibitors collectively comprise a presently unique form of disease management for persons with type 2 diabetes mellitus. The aim of this review is to compare the clinical pharmacokinetics of available DPP-4 inhibitors (alogliptin, linagliptin, saxagliptin, sitagliptin and vildagliptin) for the purpose of identifying potential selection preferences according to individual patient variables and co-morbidities. DPP-4 inhibitors are readily absorbed orally. Following oral ingestion, absorption occurs mainly in the small intestine, with median times to maximum (peak) plasma concentration ranging from 1 to 3 hours. The fraction of each dose absorbed ranges from approximately 30% with linagliptin to 75-87% for all others. Numerical differences in maximum (peak) plasma drug concentrations and areas under the plasma concentration-time curve among the DPP-4 inhibitors vary by an order of magnitude. However, functional capacity measured in terms of glucose-lowering ability remains comparable among all available DPP-4 inhibitors. Distribution of DPP-4 inhibitors is strongly influenced by both lipophilicity and protein binding. Apparent volumes of distribution (V(d)) for most agents range from 70 to 300 L. Linagliptin exhibits a V(d) of more than 1000 L, indicating widespread distribution into tissues. Binding to target proteins in plasma and peripheral tissues exerts a major influence upon broadening linagliptin distribution. DPP-4 inhibitor metabolism is widely variable, with reported terminal half-lives ranging from approximately 3 to more than 200 hours. Complex relationships between rates of receptor binding and dissociation appear to strongly influence the durations of action of those DPP-4 inhibitors with comparatively shorter half-lives. Durations of activity often are not reflective of clearance and, with the exception of vildagliptin which may be administered either once daily in the evening or twice daily, these medications are effective when used with a once-daily dosing schedule. Saxagliptin and, to a lesser extent, sitagliptin are largely metabolized by hepatic cytochrome P450 (CYP) 3A4 and 3A5 isoforms. With the exception of the primary hydroxylated metabolite of saxagliptin, which is 2-fold less potent than its parent molecule, metabolic products of hepatic biotransformation are minimally active and none appreciably contribute to either the therapeutic or the toxic effects of DPP-4 inhibitors. No DPP-4 inhibitor has been shown to inhibit or to induce hepatic CYP-mediated drug metabolism. Accordingly, the number of clinically significant drug-drug interactions associated with these agents is minimal, with only saxagliptin necessitating dose adjustment if administered concurrently with medications that strongly inhibit CYP3A4. Linagliptin undergoes enterohepatic cycling with a large majority (85%) of the absorbed dose eliminated in faeces via biliary excretion. Other DPP-4 inhibitors predominantly undergo renal excretion, with 60-85% of each dose eliminated as unchanged parent compound in the urine. Systematic reviews of clinical trials suggest that the overall efficacy of DPP-4 inhibitors in patients with type 2 diabetes generally is similar. Apart from these generalizations, pharmacokinetic distinctions that potentially influence product selection are tentative. When considered in total, data reviewed in this report suggest that the best overall balance between potency and the clinical pharmacokinetic characteristics of distribution, metabolism and elimination may be observed with linagliptin followed closely by vildagliptin, saxagliptin, sitagliptin and alogliptin.