Mechanisms for the antihyperglycemic effect of sitagliptin in patients with type 2 diabetes

Rationale and Design of the Study to Investigate the Metabolic Action of Imeglimin on Patients with Type 2 Diabetes Mellitus (SISIMAI)

INTRODUCTION

Imeglimin is a first-in-class, novel, oral glucose-lowering agent for the treatment of type 2 diabetes mellitus. The efficacy and safety of imeglimin as an antidiabetic agent have been investigated in clinical trials. However, its metabolic effects in humans have not yet been fully elucidated.

METHODS

The Study to InveStIgate the Metabolic Action of Imeglimin on patients with type 2 diabetes mellitus (SISIMAI) is a single-arm intervention study. In this study, we have recruited 25 patients with type 2 diabetes to receive 2000 mg/day imeglimin for 20 weeks. We perform a 75-g oral glucose tolerance test (OGTT) with double-glucose tracers, a two-step hyperinsulinemic-euglycemic clamp with glucose tracer, ectopic fat measurement by proton magnetic resonance spectroscopy, visceral/subcutaneous fat area measurement by magnetic resonance imaging, muscle biopsy, and evaluation of fitness level by cycle ergometer before and after imeglimin administration.

PLANNED OUTCOMES

The primary outcome is the change in area under the curve of glucose levels during the OGTT after 20 weeks of imeglimin treatment. We also calculate the endogenous glucose production, rate of oral glucose appearance, and rate of glucose disappearance from the data during the 75-g OGTT and compare them between pre- and post-treatment. Additionally, we will compare other parameters, such as the changes in tissue-specific insulin sensitivity, ectopic fat accumulation, visceral/subcutaneous fat area accumulation, and fitness level between each point. This is the first study to investigate the organ-specific metabolic action of imeglimin in patients with type 2 diabetes mellitus using the 75-g OGTT with the double tracer method. The results of this study are expected to provide useful information for drug selection based on the pathophysiology of individual patients with type 2 diabetes mellitus.

TRIAL REGISTRATION

jRCTs031210600.

β-Cell Function, Incretin Effect, and Glucose Kinetics in Response to a Mixed Meal in Patients With Type 2 Diabetes Treated With Dapagliflozin Plus Saxagliptin

OBJECTIVE

To explore the complementary effects of a combination of dipeptidyl peptidase 4 and sodium-glucose cotransporter 2 inhibitors added to metformin on hormonal and metabolic responses to meal ingestion.

RESEARCH DESIGN AND METHODS

Forty-five patients (age 58 ± 8 years; HbA1c 58 ± 6 mmol/mol; BMI 30.7 ± 3.2 kg/m2) with type 2 diabetes uncontrolled with metformin were evaluated at baseline and 3 and 28 days after 5 mg saxagliptin (SAXA), 10 mg dapagliflozin (DAPA), or 5 mg saxagliptin plus 10 mg dapagliflozin (SAXA+DAPA) using a mixed-meal tolerance test (MMTT) spiked with dual-tracer glucose to assess glucose metabolism, insulin secretion, and sensitivity.

RESULTS

At day 3, fasting and mean MMTT glucose levels were lower with SAXA+DAPA (-31.1 ± 1.6 and -91.5 ± 12.4 mg/dL) than with SAXA (-7.1 ± 2.1 and -53 ± 10.5 mg/dL) or DAPA (-17.0 ± 1.1 and -42.6 ± 10.0 mg/dL, respectively; P < 0.001). Insulin secretion rate (SAXA+DAPA +75%; SAXA +11%; DAPA +3%) and insulin sensitivity (+2.2 ± 1.7, +0.4 ± 0.7, and +0.4 ± 0.4 mg ⋅ kg-1⋅ min-1, respectively) improved with SAXA+DAPA (P < 0.007). Mean glucagon-like peptide 1 (GLP-1) was higher with SAXA+DAPA than with SAXA or DAPA. Fasting glucagon increased with DAPA and SAXA+DAPA but not with SAXA. Fasting endogenous glucose production (EGP) increased with SAXA+DAPA and DAPA. During MMTT, EGP suppression was greater (48%) with SAXA+DAPA (vs. SAXA 44%; P = 0.02 or DAPA 34%; P = 0.2). Metabolic clearance rate of glucose (MCRglu) increased more with SAXA+DAPA. At week 4, insulin secretion rate, β-cell glucose sensitivity, and insulin sensitivity had further increased in the SAXA+DAPA group (P = 0.02), with no additional changes in GLP-1, glucagon, fasting or MMTT EGP, or MCRglu.

CONCLUSIONS

SAXA+DAPA provided superior glycemic control compared with DAPA or SAXA, with improved β-cell function, insulin sensitivity, GLP-1 availability, and glucose clearance.

The Therapeutic Effects of Baicalein on the Hepatopulmonary Syndrome in the Rat Model of Chronic Common Bile Duct Ligation

Background and Aims

Hepatopulmonary syndrome (HPS) is characterized by arterial oxygenation defects due to pulmonary vascular dilation in liver disease. To date, liver transplantation remains the only effective treatment for HPS. This study aimed to explore the preventative role of baicalein in HPS development.

Methods

Sixty male rats were randomly assigned to three groups: sham, common bile duct ligation (CBDL), and baicalein, receiving intraperitoneal injections of baicalein (40 mg·kg-1·d-1, diluted in saline) for 21 days. Survival rate, liver and kidney function, and bile acid metabolism levels were evaluated. Liver and lung angiogenesis and hepatic glycogen staining were assessed, and the expression of relevant proteins was evaluated by immunohistochemistry.

Results

Baicalein improved survival rates and hypoxemia in rats post-CBDL, reducing angiogenic protein levels and enhancing glucose homeostasis. Compared to the untreated group, baicalein suppressed the expression of vascular endothelial growth factor, placental growth factors, matrix metalloprotease 9 and C-X-C motif chemokine 2, and it increased the expression of glycemic regulatory proteins, including dipeptidyl peptidase-4, sirtuin 1, peroxisome proliferator-activated receptor gamma co-activator 1α, and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3.

Conclusion

Baicalein significantly improves hepatic function and hypoxia in HPS rats by attenuating pathological angiogenesis in the liver and lungs, showing promise as a treatment for HPS.

Hepatic glucose metabolism in the steatotic liver

The liver is central in regulating glucose homeostasis, being the major contributor to endogenous glucose production and the greatest reserve of glucose as glycogen. It is both a target and regulator of the action of glucoregulatory hormones. Hepatic metabolic functions are altered in and contribute to the highly prevalent steatotic liver disease (SLD), including metabolic dysfunction-associated SLD (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). In this Review, we describe the dysregulation of hepatic glucose metabolism in MASLD and MASH and associated metabolic comorbidities, and how advances in techniques and models for the assessment of hepatic glucose fluxes in vivo have led to the identification of the mechanisms related to the alterations in glucose metabolism in MASLD and comorbidities. These fluxes can ultimately increase hepatic glucose production concomitantly with fat accumulation and alterations in the secretion and action of glucoregulatory hormones. No pharmacological treatment has yet been approved for MASLD or MASH, but some antihyperglycaemic drugs approved for treating type 2 diabetes have shown positive effects on hepatic glucose metabolism and hepatosteatosis. A deep understanding of how MASLD affects glucose metabolic fluxes and glucoregulatory hormones might assist in the early identification of at-risk individuals and the use or development of targeted therapies.

Identification of Risk Factors for Gliptin-associated Bullous Pemphigoid among Diabetic Patients

Drug-associated bullous pemphigoid has been shown to follow long-term gliptin (dipeptidyl-peptidase 4 inhibitors) intake. This study aimed at identifying risk factors for gliptin-associated bullous pemphigoid among patients with type 2 diabetes. A retrospective study was conducted in a tertiary centre among diabetic patients exposed to gliptins between the years 2008-2021. Data including demographics, comorbidities, medications, and laboratory results were collected using the MDClone platform. Seventy-six patients with type 2 diabetes treated with dipeptidyl-peptidase 4 inhibitors who subsequently developed bullous pemphigoid were compared with a cohort of 8,060 diabetic patients exposed to dipeptidyl-peptidase 4 inhibitors who did not develop bullous pemphigoid. Based on a multivariable analysis adjusted for age and other covariates, Alzheimer's disease and other dementias were significantly more prevalent in patients with bullous pemphigoid (p = 0.0013). Concomitant use of either thiazide or loop diuretics and gliptin therapy was associated with drug-associated bullous pemphigoid (p < 0.0001 for both). While compared with sitagliptin, exposure to linagliptin and vildagliptin were associated with bullous pemphigoid with an odds ratio of 5.68 and 6.61 (p < 0.0001 for both), respectively. These results suggest gliptins should be prescribed with caution to patients with type 2 diabetes with coexisting Alzheimer's and other dementias, or patients receiving long-term use of thiazides and loop diuretics. The use of sitagliptin over linagliptin and vildagliptin should be preferred in these patients.

Impact of dipeptidyl peptidase-4 inhibitors on glucose-dependent insulinotropic polypeptide in type 2 diabetes mellitus: a systematic review and meta-analysis

Aims

Glucose-dependent insulinotropic polypeptide (GIP) confers a variety of metabolic benefits in type 2 diabetes mellitus (T2DM). This meta-analysis was conducted to investigate the impact of dipeptidyl peptidase 4 (DPP4) inhibitors on GIP levels in T2DM patients.

Methods

Medline (PubMed), CENTER (Cochrane Library), and Embase (Ovid) were searched and randomized controlled trials (RCTs) evaluating the impact of DPP4 inhibitors on fasting and postprandial GIP levels were obtained. For postprandial GIP, only studies with the data of GIP changes reported as the total area under the curve (AUCGIP) using a meal or oral glucose tolerance test were included. A random-effects model was used for data pooling after incorporating heterogeneity.

Results

Overall, 14 RCTs with 541 T2DM patients were included. Compared to placebo/no treatment, the use of DPP4 inhibitors significantly increased the fasting GIP level (standard mean difference [SMD]: 0.77, 95% confidence interval [CI]: 0.48-1.05, P<0.001; I2 = 52%) and postprandial AUCGIP (SMD: 1.33, 95% CI: 1.02-1.64, P<0.001; I2 = 65%). Influence analysis by excluding one dataset at a time showed consistent results. Sensitivity analyses only including studies with radioimmunoassay showed also consistent results (fasting GIP: SMD: 0.75, 95% CI: 0.51-1.00, P<0.001; I2 = 0%; and postprandial AUCGIP: SMD: 1.48, 95% CI: 1.18-1.78, P<0.001; I2 = 54%). Further subgroup analyses demonstrated that the influence of DPP4 inhibitors on fasting and postprandial GIP levels in T2DM patients was not significantly changed by study characteristics such as study design, patient mean age, baseline glycated hemoglobin (HbA1c) concentration, body mass index (BMI), background treatment, treatment duration, or method for postprandial GIP measurement (all P for subgroup effects <0.05).

Conclusion

The use of DPP4 inhibitors effectively increases the fasting and postprandial GIP concentrations in T2DM patients.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022356716.

Does glucose lowering restore GIP effects on insulin secretion?

AIMS

Some studies have shown that in type 2 diabetic patients the potentiation of insulin secretion by glucose-dependent insulinotropic polypeptide (GIP) is compromised but can be partially restored if glucose is lowered. Renewed interest for this phenomenon has been expressed in the context of the new dual GIP-GLP-1 (glucagon-like peptide-1) receptor agonists, which have shown greater efficacy of this drug class compared with single GLP-1 receptor agonists, including on insulin secretion. However, contrasting evidence has been reported on the recovery of GIP action with glucose lowering. In our study, we reconsider all publications relevant for the problem and analyze the results using a uniform methodology.

DATA SYNTHESIS

We show that, while some contradictions might be explained by heterogeneous analysis methods, it is possible to interpret all the available data coherently and conclude that the effect of glucose lowering is relevant only when glucose concentration is virtually normalized.

CONCLUSIONS

While a significant restoration of GIP action may not occur with some traditional diabetes treatments, GIP action improvement might become relevant when glucose is virtually normalized and could explain part of the success of the double GIP-GLP-1 receptor agonists.

Incretin and Pancreatic β-Cell Function in Patients with Type 2 Diabetes

To maintain normal glucose homeostasis after a meal, it is essential to secrete an adequate amount of insulin from pancreatic β-cells. However, if pancreatic β-cells solely depended on the blood glucose level for insulin secretion, a surge in blood glucose levels would be inevitable after the ingestion of a large amount of carbohydrates. To avoid a deluge of glucose in the bloodstream after a large carbohydrate- rich meal, enteroendocrine cells detect the amount of nutrient absorption from the gut lumen and secrete incretin hormones at scale. Since insulin secretion in response to incretin hormones occurs only in a hyperglycemic milieu, pancreatic β-cells can secrete a "Goldilocks" amount of insulin (i.e., not too much and not too little) to keep the blood glucose level in the normal range. In this regard, pancreatic β-cell sensitivity to glucose and incretin hormones is crucial for maintaining normal glucose homeostasis. In this Namgok lecture 2022, we review the effects of current anti-diabetic medications on pancreatic β-cell sensitivity to glucose and incretin hormones.

Hepatocyte-derived DPP4 regulates portal GLP-1 bioactivity, modulates glucose production, and when absent influences NAFLD progression

Elevated circulating dipeptidyl peptidase-4 (DPP4) is a biomarker for liver disease, but its involvement in gluconeogenesis and metabolic associated fatty liver disease progression remains unclear. Here, we identified that DPP4 in hepatocytes but not TEK receptor tyrosine kinase-positive endothelial cells regulates the local bioactivity of incretin hormones and gluconeogenesis. However, the complete absence of DPP4 (Dpp4-/-) in aged mice with metabolic syndrome accelerates liver fibrosis without altering dyslipidemia and steatosis. Analysis of transcripts from the livers of Dpp4-/- mice displayed enrichment for inflammasome, p53, and senescence programs compared with littermate controls. High-fat, high-cholesterol feeding decreased Dpp4 expression in F4/80+ cells, with only minor changes in immune signaling. Moreover, in a lean mouse model of severe nonalcoholic fatty liver disease, phosphatidylethanolamine N-methyltransferase mice, we observed a 4-fold increase in circulating DPP4, in contrast with previous findings connecting DPP4 release and obesity. Last, we evaluated DPP4 levels in patients with hepatitis C infection with dysglycemia (Homeostatic Model Assessment of Insulin Resistance > 2) who underwent direct antiviral treatment (with/without ribavirin). DPP4 protein levels decreased with viral clearance; DPP4 activity levels were reduced at long-term follow-up in ribavirin-treated patients; but metabolic factors did not improve. These data suggest elevations in DPP4 during hepatitis C infection are not primarily regulated by metabolic disturbances.

The Implication of Mechanistic Approaches and the Role of the Microbiome in Polycystic Ovary Syndrome (PCOS): A Review

As a complex endocrine and metabolic condition, polycystic ovarian syndrome (PCOS) affects women's reproductive health. These common symptoms include hirsutism, hyperandrogenism, ovulatory dysfunction, irregular menstruation, and infertility. No one knows what causes it or how to stop it yet. Alterations in gut microbiota composition and disruptions in secondary bile acid production appear to play a causative role in developing PCOS. PCOS pathophysiology and phenotypes are tightly related to both enteric and vaginal bacteria. Patients with PCOS exhibit changed microbiome compositions and decreased microbial diversity. Intestinal microorganisms also alter PCOS patient phenotypes by upregulating or downregulating hormone release, gut-brain mediators, and metabolite synthesis. The human body's gut microbiota, also known as the "second genome," can interact with the environment to improve metabolic and immunological function. Inflammation is connected to PCOS and may be caused by dysbiosis in the gut microbiome. This review sheds light on the recently discovered connections between gut microbiota and insulin resistance (IR) and the potential mechanisms of PCOS. This study also describes metabolomic studies to obtain a clear view of PCOS and ways to tackle it.

A Rare Case Report of Sitagliptin-Induced Angioedema

Sitagliptin, a dipeptidyl peptidase-4 inhibitor, is used for the treatment of type 2 diabetes mellitus. Sitagliptin-induced angioedema has increased with the simultaneous use of angiotensin receptor blockers and angiotensin-converting enzyme inhibitors. We present a rare case of a 50-year-old female diagnosed with sitagliptin-induced angioedema. On examination, she had both upper and lower lip swelling without any respiratory compromise. On further investigation, her C1 esterase inhibitor level was normal. After stopping sitagliptin, her symptoms resolved. Thus, cautious use of dipeptidyl peptidase-4 inhibitor is advised.

Effects of GLP-1 and GIP on Islet Function in Glucose-Intolerant, Pancreatic-Insufficient Cystic Fibrosis

Impaired insulin and incretin secretion underlie abnormal glucose tolerance (AGT) in pancreatic insufficient cystic fibrosis (PI-CF). Whether the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) can enhance pancreatic islet function in cystic fibrosis (CF) is not known. We studied 32 adults with PI-CF and AGT randomized to receive either GLP-1 (n = 16) or GIP (n = 16) during glucose-potentiated arginine (GPA) testing of islet function on two occasions, with either incretin or placebo infused, in a randomized, double-blind, cross-over fashion. Another four adults with PI-CF and normal glucose tolerance (NGT) and four matched control participants without CF underwent similar assessment with GIP. In PI-CF with AGT, GLP-1 substantially augmented second-phase insulin secretion but without effect on the acute insulin response to GPA or the proinsulin secretory ratio (PISR), while GIP infusion did not enhance second-phase or GPA-induced insulin secretion but increased the PISR. GIP also did not enhance second-phase insulin in PI-CF with NGT but did so markedly in control participants without CF controls. These data indicate that GLP-1, but not GIP, augments glucose-dependent insulin secretion in PI-CF, supporting the likelihood that GLP-1 agonists could have therapeutic benefit in this population. Understanding loss of GIP's insulinotropic action in PI-CF may lead to novel insights into diabetes pathogenesis.

Signaling pathways in obesity: mechanisms and therapeutic interventions

Obesity is a complex, chronic disease and global public health challenge. Characterized by excessive fat accumulation in the body, obesity sharply increases the risk of several diseases, such as type 2 diabetes, cardiovascular disease, and nonalcoholic fatty liver disease, and is linked to lower life expectancy. Although lifestyle intervention (diet and exercise) has remarkable effects on weight management, achieving long-term success at weight loss is extremely challenging, and the prevalence of obesity continues to rise worldwide. Over the past decades, the pathophysiology of obesity has been extensively investigated, and an increasing number of signal transduction pathways have been implicated in obesity, making it possible to fight obesity in a more effective and precise way. In this review, we summarize recent advances in the pathogenesis of obesity from both experimental and clinical studies, focusing on signaling pathways and their roles in the regulation of food intake, glucose homeostasis, adipogenesis, thermogenesis, and chronic inflammation. We also discuss the current anti-obesity drugs, as well as weight loss compounds in clinical trials, that target these signals. The evolving knowledge of signaling transduction may shed light on the future direction of obesity research, as we move into a new era of precision medicine.

Loss of the Incretin Effect in Type 2 Diabetes: A Systematic Review and Meta-analysis

CONTEXT

Loss of the incretin effect (IE) in type 2 diabetes (T2D) contributes to hyperglycemia and the mechanisms underlying this impairment are unclear.

OBJECTIVE

To quantify the IE impairment in T2D and to investigate the factors associated with it using a meta-analytic approach.

METHODS

PubMed, Scopus, and Web-of-Science were searched. Studies measuring IE by the gold-standard protocol employing an oral glucose tolerance test (OGTT) and an intravenous glucose infusion at matched glucose levels were selected. We extracted IE, sex, age, body mass index (BMI), and hemoglobin A1c, fasting values, and area under curve (AUC) of glucose, insulin, C-peptide, glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 (GLP-1). In subjects with T2D, we also recorded T2D duration, age at diagnosis, and the percentage of subjects taking antidiabetic medications.

RESULTS

The IE weighted mean difference between subjects with T2D and those with normal glucose tolerance (NGT) was -27.3% (CI -36.5% to -18.1%; P < .001; I2 = 86.6%) and was affected by age (P < .005). By meta-regression of combined NGT and T2D data, IE was inversely associated with glucose tolerance (lower IE in T2D), BMI, and fasting GIP (P < .05). By meta-regression of T2D studies only, IE was associated with the OGTT glucose dose (P < .0001). IE from insulin was larger than IE from C-peptide (weighted mean difference 11.2%, CI 9.2-13.2%; P < .0001; I2 = 28.1%); the IE difference was inversely associated with glucose tolerance and fasting glucose.

CONCLUSION

The IE impairment in T2D vs NGT is consistent though considerably variable, age being a possible factor affecting the IE difference. Glucose tolerance, BMI, and fasting GIP are independently associated with IE; in subjects with T2D only, the OGTT dose is a significant covariate.

Effect of free fatty acids on insulin secretion, insulin sensitivity and incretin effect - a narrative review

Deleterious effects of free fatty acids, FFAs, on insulin sensitivity are observed in vivo studies in humans. Mechanisms include impaired insulin signaling, oxidative stress, inflammation, and mitochondrial dysfunction, but the effects on insulin secretion are less well known. Our aim was to review the relationship of increased FFAs with insulin resistance, secretion and mainly with the incretin effect in humans. Narrative review. Increased endogenous or administered FFAs induce insulin resistance. FFAs effects on insulin secretion are debatable; inhibition and stimulation have been reported, depending on the type and duration of lipids exposition and the study subjects. Chronically elevated FFAs seem to decrease insulin biosynthesis, glucose-stimulated insulin secretion and β-cell glucose sensitivity. Lipids infusion decreases the response to incretins with unchanged incretin levels in volunteers with normal glucose tolerance. In contrast, FFAs reduction by acipimox did not restore the incretin effect in type-2 diabetes, probably due to the dysfunctional β-cell. Possible mechanisms of FFAs excess on incretin effect include reduction of the expression and levels of GLP-1 (glucagon like peptide-1) receptor, reduction of connexin-36 expression thus the coordinated secretory activity in response to GLP-1, and GIP (glucose-dependent insulinotropic polypeptide) receptors downregulation in islets cells. Increased circulating FFAs impair insulin sensitivity. Effects on insulin secretion are complex and controversial. Deleterious effects on the incretin-induced potentiation of insulin secretion were reported. More investigation is needed to better understand the extent and mechanisms of β-cell impairment and insulin resistance induced by increased FFAs and how to prevent them.

New Insights on the Interactions Between Insulin Clearance and the Main Glucose Homeostasis Mechanisms

OBJECTIVE

Endogenous insulin clearance (EIC) is physiologically reduced at increasing insulin secretion rate (ISR). Computing EIC at the prevailing ISR does not distinguish the effects of hypersecretion from those of other mechanisms of glucose homeostasis. We aimed to measure EIC in standardized ISR conditions (i.e., at fixed ISR levels) and to analyze its associations with relevant physiologic factors.

RESEARCH DESIGN AND METHODS

We estimated standardized EIC (EIC_ISR) by mathematical modeling in nine different studies with insulin and glucose infusions (N = 2,067). EIC_ISR association with various traits was analyzed by stepwise multivariable regression in studies with both euglycemic clamp and oral glucose tolerance test (OGTT) (N = 1,410). We also tested whether oral glucose ingestion, as opposed to intravenous infusion, has an independent effect on EIC (N = 1,555).

RESULTS

Insulin sensitivity (as M/I from the euglycemic clamp) is the strongest determinant of EIC_ISR, approximately four times more influential than insulin resistance-related hypersecretion. EIC_ISR independently associates positively with M/I, fasting and mean OGTT glucose or type 2 diabetes, and β-cell glucose sensitivity and negatively with African American or Hispanic race, female sex, and female age. With oral glucose ingestion, an ISR-independent ∼10% EIC reduction is necessary to explain the observed insulin concentration profiles.

CONCLUSIONS

Based on EIC_ISR, we posit the existence of two adaptive processes involving insulin clearance: the first reduces EIC_ISR with insulin resistance (not with higher BMI per se) and is more relevant than the concomitant hypersecretion; the second reduces EIC_ISR with β-cell dysfunction. These processes are dysregulated in type 2 diabetes. Finally, oral glucose ingestion per se reduces insulin clearance.

The Role of the α Cell in the Pathogenesis of Diabetes: A World beyond the Mirror

Type 2 Diabetes Mellitus (T2DM) is one of the most prevalent chronic metabolic disorders, and insulin has been placed at the epicentre of its pathophysiological basis. However, the involvement of impaired alpha (α) cell function has been recognized as playing an essential role in several diseases, since hyperglucagonemia has been evidenced in both Type 1 and T2DM. This phenomenon has been attributed to intra-islet defects, like modifications in pancreatic α cell mass or dysfunction in glucagon's secretion. Emerging evidence has shown that chronic hyperglycaemia provokes changes in the Langerhans' islets cytoarchitecture, including α cell hyperplasia, pancreatic beta (β) cell dedifferentiation into glucagon-positive producing cells, and loss of paracrine and endocrine regulation due to β cell mass loss. Other abnormalities like α cell insulin resistance, sensor machinery dysfunction, or paradoxical ATP-sensitive potassium channels (KATP) opening have also been linked to glucagon hypersecretion. Recent clinical trials in phases 1 or 2 have shown new molecules with glucagon-antagonist properties with considerable effectiveness and acceptable safety profiles. Glucagon-like peptide-1 (GLP-1) agonists and Dipeptidyl Peptidase-4 inhibitors (DPP-4 inhibitors) have been shown to decrease glucagon secretion in T2DM, and their possible therapeutic role in T1DM means they are attractive as an insulin-adjuvant therapy.

Effect of Sitagliptin on Islet Function in Pancreatic Insufficient Cystic Fibrosis With Abnormal Glucose Tolerance

PURPOSE

Impaired incretin secretion may contribute to the defective insulin secretion and abnormal glucose tolerance (AGT) that associate with worse clinical outcomes in pancreatic insufficient cystic fibrosis (PI-CF). The study objective was to test the hypothesis that dipeptidyl peptidase-4 (DPP-4) inhibitor-induced increases in intact incretin hormone [glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP)] concentrations augment insulin secretion and glucagon suppression and lower postprandial glycemia in PI-CF with AGT.

METHODS

26 adults from Children's Hospital of Philadelphia and University of Pennsylvania CF Center with PI-CF and AGT [defined by oral glucose tolerance test glucose (mg/dL): early glucose intolerance (1-h ≥ 155 and 2-h < 140), impaired glucose tolerance (2-h ≥ 140 and < 200 mg/dL), or diabetes (2-h ≥ 200)] were randomized to a 6-month double-blind trial of DPP-4 inhibitor sitagliptin 100 mg daily or matched placebo; 24 completed the trial (n = 12 sitagliptin; n = 12 placebo). Main outcome measures were mixed-meal tolerance test (MMTT) responses for intact GLP-1 and GIP, insulin secretory rates (ISRs), glucagon suppression, and glycemia and glucose-potentiated arginine (GPA) test-derived measures of β- and α-cell function.

RESULTS

Following 6-months of sitagliptin vs placebo, MMTT intact GLP-1 and GIP responses increased (P < 0.001), ISR dynamics improved (P < 0.05), and glucagon suppression was modestly enhanced (P < 0.05) while GPA test responses for glucagon were lower. No improvements in glucose tolerance or β-cell sensitivity to glucose, including for second-phase insulin response, were found.

CONCLUSIONS

In glucose intolerant PI-CF, sitagliptin intervention augmented meal-related incretin responses with improved early insulin secretion and glucagon suppression without affecting postprandial glycemia.

Effect of Nigella sativa oil on pharmacokinetics and pharmacodynamics of gliclazide in rats

Nigella sativa oil (NSO) has been used widely for its putative anti-hyperglycemic activity. However, little is known about its potential effect on the pharmacokinetics and pharmacodynamics of antidiabetic drugs, including gliclazide. This study aimed to investigate herb-drug interactions between gliclazide and NSO in rats. Plasma concentrations of gliclazide (single oral and intravenous dose of 33 and 26.4 mg/kg, respectively) in the presence and absence of co-administration with NSO (52 mg/kg per oral) were quantified in healthy and insulin resistant rats (n = 5 for each group). Physiological and treatment-related factors were evaluated as potential influential covariates using a population pharmacokinetic modeling approach (NONMEM version 7.4). Clearance, volume of distribution and bioavailability of gliclazide were unaffected by disease state (healthy or insulin resistant). The concomitant administration of NSO resulted in higher systemic exposures of gliclazide by modulating bioavailability (29% increase) and clearance (20% decrease) of the drug. A model-independent analysis highlighted that pre-treatment with NSO in healthy rats was associated with a higher glucose lowering effect by up to 50% compared with that of gliclazide monotherapy, but not of insulin resistant rats. Although a similar trend in glucose reductions was not observed in insulin resistant rats, co-administration of NSO improved the sensitivity to insulin of this rat population. Natural product-drug interaction between gliclazide and NSO merits further evaluation of its clinical importance.

Glucose-lowering action through targeting islet dysfunction in type 2 diabetes: Focus on dipeptidyl peptidase-4 inhibition

Dipeptidyl peptidase-4 (DPP-4) inhibition is a glucose-lowering medication for type 2 diabetes. It works through stimulation of insulin secretion and inhibition of glucagon secretion in a glucose-dependent manner, resulting in lowered fasting and postprandial glycemia with low risk of hypoglycemia. As impaired insulin secretion and augmented glucagon secretion are key factors underlying hyperglycemia in type 2 diabetes, DPP-4 inhibition represents a therapy that targets the underlying mechanisms of the disease. If insufficient in monotherapy, it can preferably be used in combination with metformin, which targets insulin resistance, and also in combination with sodium-glucose cotransporter 2 inhibition, thiazolidinediones and insulin, which target other mechanisms. In individuals of East Asian origin, islet dysfunction is of particular importance for the development of type 2 diabetes. Consequently, it has been shown in several studies that DPP-4 is efficient in these populations. This mini-review highlights the islet mechanisms of DPP-4 inhibition, islet dysfunction as a key factor for hyperglycemia in type 2 diabetes and that, consequently, DPP-4 is of particular value in populations where islet dysfunction is central, such as in individuals of East Asian origin.

Effects of Sustained Treatment With Lixisenatide on Gastric Emptying and Postprandial Glucose Metabolism in Type 2 Diabetes: A Randomized Controlled Trial

OBJECTIVE

Tachyphylaxis for slowing of gastric emptying is seen with continuous exposure to glucagon-like peptide 1 (GLP-1). We therefore aimed to establish whether prolonged use of a "short-acting" GLP-1 receptor agonist, lixisenatide, achieves sustained slowing of gastric emptying and reduction in postprandial glycemia.

RESEARCH DESIGN AND METHODS

A total of 30 patients with metformin-treated type 2 diabetes underwent assessment of gastric emptying (scintigraphy) and glucose metabolism (dual tracer technique) after a 75-g glucose drink, before and after 8 weeks' treatment with lixisenatide (20 μg subcutaneously daily) or placebo, in a double-blind randomized parallel design.

RESULTS

Gastric retention of the glucose drink was markedly increased after lixisenatide versus placebo (ratio of adjusted geometric means for area under the curve [AUC] over 240 min of 2.19 [95% CI 1.82, 2.64], P < 0.001), associated with substantial reductions in the rate of systemic appearance of oral glucose (P < 0.001) and incremental AUC for blood glucose (P < 0.001). Lixisenatide suppressed both glucagon (P = 0.003) and insulin (P = 0.032), but not endogenous glucose production, over 120 min after oral glucose intake. Postprandial glucose lowering over 240 min was strongly related to the magnitude of slowing of gastric emptying by lixisenatide (r = -0.74, P = 0.002) and to the baseline rate of emptying (r = 0.52, P = 0.048) but unrelated to β-cell function (assessed by β-cell glucose sensitivity).

CONCLUSIONS

Eight weeks' treatment with lixisenatide is associated with sustained slowing of gastric emptying and marked reductions in postprandial glycemia and appearance of ingested glucose. Short-acting GLP-1 receptor agonists therefore potentially represent an effective long-term therapy for specifically targeting postprandial glucose excursions.

Persistent whole day meal effects of three dipeptidyl peptidase-4 inhibitors on glycaemia and hormonal responses in metformin-treated type 2 diabetes

AIM

Dipeptidyl peptidase-4 (DPP-4) inhibition has effects on both fasting and postprandial glucose. However, the extent of this effect over the whole day and whether different DPP-4 inhibitors have the same effects have not been established. We therefore explored the whole day effects of three different DPP-4 inhibitors versus placebo on glucose, islet and incretin hormones after ingestion of breakfast, lunch and dinner in subjects with metformin-treated and well-controlled type 2 diabetes.

METHODS

The study was single-centre and crossover designed, involving 24 subjects [12 men, 12 women, mean age 63 years, body mass index 31.0 kg/m² , glycated haemoglobin 44.7 mmol/mol (6.2%)], who underwent four test days in random order. Each whole day test included ingestion of standardized breakfast (525 kcal), lunch (780 kcal) and dinner (560 kcal) after intake of sitagliptin (100 mg) or vildagliptin (50 mg twice), or saxagliptin (5 mg) or placebo.

RESULTS

Compared with placebo, DPP-4 inhibition reduced glucose levels, increased beta-cell function (insulin secretory rate in relation to glucose), suppressed glucagon, increased intact glucagon-like-peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) but suppressed total GLP-1 and GIP after all three meals. The effects were sustained throughout the daytime period with similar changes after each meal and did not differ between the DPP-4 inhibitors.

CONCLUSIONS

DPP-4 inhibition has persistent daytime effects on glucose, islet and incretin hormones with no difference between three different DPP-4 inhibitors.

GIP and GLP-1 Receptor Antagonism During a Meal in Healthy Individuals

CONTEXT

The actions of both endogenous incretin hormones during a meal have not previously been characterized.

OBJECTIVE

Using specific receptor antagonists, we investigated the individual and combined contributions of endogenous glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) to postprandial glucose metabolism, energy expenditure, and gallbladder motility.

DESIGN

Randomized, double-blinded, placebo-controlled, crossover design.

SETTING

On four separate days, four liquid mixed meal tests (1894 kJ) over 270 minutes (min).

PATIENTS OR OTHER PARTICIPANTS

Twelve healthy male volunteers.

INTERVENTIONS

Infusions of the GIP receptor antagonist GIP(3-30)NH2 (800 pmol/kg/min), the GLP-1 receptor antagonist exendin(9-39)NH2 (0-20 min: 1000 pmol/kg/min; 20-270 min: 450 pmol/kg/min), GIP(3-30)NH2+exendin(9-39)NH2, or placebo/saline.

MAIN OUTCOME MEASURE

Baseline-subtracted area under the curve (bsAUC) of C-peptide.

RESULTS

Infusion of GIP(3-30)NH2+exendin(9-39)NH2 significantly increased plasma glucose excursions (bsAUC: 261 ± 142 mmol/L × min) during the liquid mixed meals compared with GIP(3-30)NH2 (180 ± 141 mmol/L × min; P = 0.048), exendin(9-39)NH2 (171 ± 114 mmol/L × min; P = 0.046), and placebo (116 ± 154 mmol/L × min; P = 0.015). Correspondingly, C-peptide:glucose ratios during GIP(3-30)NH2+exendin(9-39)NH2 infusion were significantly lower than during GIP(3-30)NH2 (P = 0.0057), exendin(9-39)NH2 (P = 0.0038), and placebo infusion (P = 0.014). GIP(3-30)NH2 resulted in significantly lower AUCs for glucagon than exendin(9-39)NH2 (P = 0.0417). Gallbladder ejection fraction was higher during GIP(3-30)NH2 compared with placebo (P = 0.004). For all interventions, energy expenditure and respiratory quotient were similar.

CONCLUSIONS

Endogenous GIP and GLP-1 lower postprandial plasma glucose excursions and stimulate insulin secretion but only endogenous GIP affects gallbladder motility. The two incretin hormones potentiate each other's effects in the control of postprandial glycemia in healthy men.

Evaluation of the incretin effect in humans using GIP and GLP-1 receptor antagonists

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) potentiate glucose-induced insulin secretion and are therefore thought to be responsible for the incretin effect. The magnitude of the incretin effect, defined as the fraction of postprandial insulin secretion stimulated by intestinal factors, has been reported to be up to ∼60% in healthy individuals. In several pathological conditions but especially in patients with type 2 diabetes, the incretin effect is severely reduced or even absent. In line with this, the insulinotropic effects of GIP and GLP-1 are impaired in patients with type 2 diabetes, even when administered in supraphysiological doses. In healthy individuals, GIP has been proposed to be the most important incretin hormone of the two, but the individual contribution of the two is difficult to determine. However, using incretin hormone receptor antagonists: the novel GIP receptor antagonist GIP(3-30)NH₂ and the widely used GLP-1 receptor antagonist exendin(9-39)NH₂, we can now distinguish between the effects of the two hormones. In this review, we present and discuss studies in which the individual contribution of GIP and GLP-1 to the incretin effect in healthy individuals have been estimated and discuss the limitations of using incretin hormone receptor antagonists.

Association of Dipeptidyl Peptidase 4 Inhibitor Use With Risk of Bullous Pemphigoid in Patients With Diabetes

Importance

Recent studies suggest that dipeptidyl peptidase 4 (DPP-4) inhibitors are associated with an increased risk of developing bullous pemphigoid (BP). Population-based studies on the association between DPP-4 inhibitors and BP are limited.

Objective

To characterize the potential association between the use of DPP-4 inhibitors and an increased risk of developing BP.

Design, Setting, and Participants

This retrospective, nationwide, population-based, case-control study using Korean insurance claims data from January 1, 2012, to December 31, 2016, included patients with newly diagnosed BP and diabetes. Control patients with diabetes (and without BP) were randomly obtained after matching for age, sex, and year of diagnosis within the same period.

Main Outcomes and Measures

The number of patients with newly diagnosed BP and diabetes per year and annual changes in the proportion of patients with diabetes among all patients with BP were measured. The association between use of DPP-4 inhibitors and risk of developing BP was analyzed using univariate and multivariate logistic regression analyses.

Results

The study included 670 case patients (with diabetes and BP) and 670 control patients (with only diabetes) (mean [SD] age, 75.3 [10.0] years in each group; 342 [51.0%] male in each group). The number of patients with diabetes and BP more than doubled during the study period (from 77 in 2012 to 206 in 2016). The proportion of patients with diabetes among all patients with BP also increased (from 0.18 in 2012 to 0.33 in 2016). The use of DPP-4 inhibitors was associated with a significant increase in the risk of developing BP (adjusted odds ratio [aOR], 1.58; 95% CI, 1.25-2.00; P < .001); among all DPP-4 inhibitors used in Korea, the highest aOR was associated with the use of vildagliptin (aOR, 1.81; 95% CI, 1.31-2.50; P < .001). Subgroup analyses revealed a significant association in male patients (aOR, 1.91; 95% CI, 1.39-2.63; P < .001) and that vildagliptin was the most high-risk DPP-4 inhibitor (aOR, 2.70; 95% CI, 1.73-4.34; P < .001).

Conclusions and Relevance

The findings suggest that DPP-4 inhibitors are associated with a significantly increased risk of the development of BP in patients with diabetes. Of the DPP-4 inhibitors available in Korea, vildagliptin was associated with the highest risk, particularly in male patients. Practitioners should consider that DPP-4 inhibitors, particularly vildagliptin, may be associated with the development of BP in patients with diabetes. These nationwide, population-based results may serve as a foundation for further studies seeking to understand how DPP-4 inhibitors contribute to the development of BP.

DPP-4 is expressed in human pancreatic beta cells and its direct inhibition improves beta cell function and survival in type 2 diabetes

It has been reported that the incretin system, including regulated GLP-1 secretion and locally expressed DPP-4, is present in pancreatic islets. In this study we comprehensively evaluated the expression and role of DPP-4 in islet alpha and beta cells from non-diabetic (ND) and type 2 diabetic (T2D) individuals, including the effects of its inhibition on beta cell function and survival. Isolated islets were prepared from 25 ND and 18 T2D organ donors; studies were also performed with the human insulin-producing EndoC-βH1 cells. Morphological (including confocal microscopy), ultrastructural (electron microscopy, EM), functional (glucose-stimulated insulin secretion), survival (EM and nuclear dyes) and molecular (RNAseq, qPCR and western blot) studies were performed under several different experimental conditions. DPP-4 co-localized with glucagon and was also expressed in human islet insulin-containing cells. Furthermore, DPP-4 was expressed in EndoC-βH1 cells. The proportions of DPP-4 positive alpha and beta cells and DPP-4 gene expression were significantly lower in T2D islets. A DPP-4 inhibitor protected ND human beta cells and EndoC-βH1 cells against cytokine-induced toxicity, which was at least in part independent from GLP1 and associated with reduced NFKB1 expression. Finally, DPP-4 inhibition augmented glucose-stimulated insulin secretion, reduced apoptosis and improved ultrastructure in T2D beta cells. These results demonstrate the presence of DPP-4 in human islet alpha and beta cells, with reduced expression in T2D islets, and show that DPP-4 inhibition has beneficial effects on human ND and T2D beta cells. This suggests that DPP-4, besides playing a role in incretin effects, directly affects beta cell function and survival.

Effects on the glucagon response to hypoglycaemia during DPP-4 inhibition in elderly subjects with type 2 diabetes: A randomized, placebo-controlled study

AIMS

Maintainance of glucagon response to hypoglycaemia is important as a safeguard against hypoglycaemia during glucose-lowering therapy in type 2 diabetes. During recent years, DPP-4 (dipeptidyl peptidase-4) inhibition has become more commonly used in elderly patients. However, whether DPP-4 inhibition affects the glucagon response to hypoglycaemia in the elderly is not known and was the aim of this study.

METHODS

In a single-centre, double-blind, randomized, placebo-controlled crossover study, 28 subjects with metformin-treated type 2 diabetes (17 male, 11 female; mean age, 74 years [range 65-86]; mean HbA1c, 51.5 mmol/mol [6.9%]) received sitagliptin (100 mg once daily) as add-on therapy or placebo for 4 weeks with a 4-week washout period in between. After each treatment period, the subjects underwent a standard breakfast test, followed by a 2-step hyperinsulinaemic hypoglycaemic clamp (target 3.5 and 3.0 mmol/L), followed by lunch.

RESULTS

Glucagon levels after breakfast and lunch, and the glucagon response at 3.5 mmol/L, were lower after sitagliptin than after placebo. However, the glucagon response to hypoglycaemia at 3.1 mmol/L did not differ significantly between the two. Similarly, the noradrenaline, adrenaline and cortisol responses were lower with sitagliptin than with placebo at 3.5 mmol/L, but not at 3.1 mmol/L glucose. Responses in pancreatic polypeptide did not differ between the two.

CONCLUSIONS

Elderly subjects with metformin-treated type 2 diabetes have lower glucagon levels at 3.5 mmol/L glucose, but maintain the glucagon response to hypoglycaemia at 3.1 mmol/L during DPP-4 inhibition, which safeguards against hypoglycaemia and may contribute to decreasing the risk of hypoglycaemia by DPP-4 inhibition in this age group.

Effects of acute NEFA manipulation on incretin-induced insulin secretion in participants with and without type 2 diabetes

AIMS/HYPOTHESIS

Incretin effect-the potentiation of glucose-stimulated insulin release induced by the oral vs the i.v. route-is impaired in dysglycaemic states. Despite evidence from human islet studies that NEFA interfere with incretin function, little information is available about the effect in humans. We tested the impact of acute bidirectional NEFA manipulation on the incretin effect in humans.

METHODS

Thirteen individuals with type 2 diabetes and ten non-diabetic volunteers had a 3 h OGTT, and, a week later, an i.v. isoglycaemic glucose infusion (ISO; OGTT matched). Both pairs of studies were repeated during an exogenous lipid infusion in the non-diabetic volunteers, and following acipimox administration (to inhibit lipolysis) in people with diabetes. Mathematical modelling of insulin secretion dynamics assessed total insulin secretion (TIS), beta cell glucose sensitivity (β-GS), glucose-induced potentiation (P_GLU) and incretin-induced potentiation (P_INCR); the oral glucose sensitivity index was used to estimate insulin sensitivity.

RESULTS

Lipid infusion increased TIS (from 61 [interquartile range 26] to 78 [31] nmol/m² on OGTT and from 29 nmol/m² [26] to 57 nmol/m² [30] on ISO) and induced insulin resistance. P_INCR decreased from 1.6 [1.1] to 1.3 [0.1] (p < 0.05). β-GS, P_GLU and glucagon, glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP) responses were unaffected. Acipimox (lowering NEFA by ~55%) reduced plasma glucose and TIS and enhanced insulin sensitivity, but did not change β-GS, P_INCR, P_GLU or glucagon, GLP-1 or GIP responses. As the per cent difference, incretin effect was decreased in non-diabetic participants and unchanged in those with diabetes.

CONCLUSIONS/INTERPRETATION

Raising NEFA selectively impairs incretin effect and insulin sensitivity in non-diabetic individuals, while acute NEFA reduction lowers plasma glucose and enhances insulin sensitivity in people with diabetes but does not correct the impaired incretin-induced potentiation.

Roux-en-Y gastric bypass compared with equivalent diet restriction: Mechanistic insights into diabetes remission

AIMS

To investigate the physiological mechanisms leading to rapid improvement in diabetes after Roux-en-Y gastric bypass (RYGB) and specifically the contribution of the concurrent peri-operative dietary restrictions, which may also alter glucose metabolism.

MATERIALS AND METHODS

In order to assess the differential contributions of diet and surgery to the mechanisms leading to the rapid improvement in diabetes after RYGB we enrolled 10 patients with type 2 diabetes scheduled to undergo RYGB. All patients underwent a 10-day inpatient supervised dietary intervention equivalent to the peri-operative diet (diet-only period), followed by, after a re-equilibration (washout) period, an identical period of pair-matched diet in conjunction with RYGB (diet and RYGB period). We conducted extensive metabolic assessments during a 6-hour mixed-meal challenge test, with stable isotope glucose tracer infusion performed before and after each intervention.

RESULTS

Similar improvements in glucose levels, β-cell function, insulin sensitivity and post-meal hepatic insulin resistance were observed with both interventions. Both interventions led to significant reductions in fasting and postprandial acyl ghrelin. The diet-only intervention induced greater improvements in basal hepatic glucose output and post-meal gastric inhibitory polypeptide (GIP) secretion. The diet and RYGB intervention induced significantly greater increases in post-meal glucagon-like peptide-1 (GLP-1), peptide YY (PYY) and glucagon levels.

CONCLUSIONS

Strict peri-operative dietary restriction is a main contributor to the rapid improvement in glucose metabolism after RYGB. The RYGB-induced changes in the incretin hormones GLP-1 and PYY probably play a major role in long-term compliance with such major dietary restrictions through central and peripheral mechanisms.

Different glucagon effects during DPP-4 inhibition versus SGLT-2 inhibition in metformin-treated type 2 diabetes patients

AIMS

Previous studies have shown that dipeptidyl peptidase (DPP)-4 inhibition lowers glucagon levels whereas sodium-glucose co-transporter 2 (SGLT-2) inhibition increases them. This study evaluated the extent of these opposite effects in a direct comparative head-to-head study.

METHODS

In a single-centre, randomized study with a cross-over design, 28 metformin-treated patients with type 2 diabetes (T2D) (mean age, 63 years; baseline HbA1c, 6.8%) were treated with vildagliptin (50 mg twice daily) or dapagliflozin (10 mg once daily) for 2 weeks, with a 4-week wash-out period between the two separate treatments. After each treatment period, a meal test was undertaken, with measurements of islet and incretin hormones and 4-hour area under the curve (AUC) levels were estimated.

RESULTS

Fasting glucagon (35.6 ± 2.5 vs 39.4 ± 3.4 pmoL/L; P = .032) and postprandial glucagon (4-hour AUC_glucagon , 32.1 ± 2.3 vs 37.5 ± 2.7 nmoL/L min; P = .001) were ~15% lower after vildagliptin compared to dapagliflozin treatment. This was associated with stronger early (15 minute) C-peptide response and higher 4-hour AUC_C-peptide (P < .010), higher 4-hour AUC of the intact form of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) (P < .001) and lower 4-hour AUC of total GIP and GLP-1 (P < .001).

CONCLUSION

Treatment with DPP-4 inhibition with vildagliptin results in 15% lower fasting and postprandial glucagon levels compared to SGLT-2 inhibition with dapagliflozin. DPP-4 inhibition also induces more rapid insulin secretion and higher levels of intact incretin hormones, resulting in stronger feedback inhibition of incretin hormone secretion than SGLT-2 inhibition.

Effect of single-dose DPP-4 inhibitor sitagliptin on β-cell function and incretin hormone secretion after meal ingestion in healthy volunteers and drug-naïve, well-controlled type 2 diabetes subjects

To explore the effects of a single dose of the DPP-4 inhibitor sitagliptin on glucose-standardized insulin secretion and β-cell glucose sensitivity after meal ingestion, 12 healthy and 12 drug-naïve, well-controlled type 2 diabetes (T2D) subjects (mean HbA1c 43 mmol/mol, 6.2%) received sitagliptin (100 mg) or placebo before a meal (525 kcal). β-cell function was measured as the insulin secretory rate at a standardized glucose concentration and the β-cell glucose sensitivity (the slope between glucose and insulin secretory rate). Incretin levels were also monitored. Sitagliptin increased standardized insulin secretion, in both healthy and T2D subjects, compared to placebo, but without increasing β-cell glucose sensitivity. Sitagliptin also increased active glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) and reduced total (reflecting the secretion) GIP, but not total GLP-1 levels. We conclude that a single dose of DPP-4 inhibition induces dissociated effects on different aspects of β-cell function and incretin hormones after meal ingestion in both healthy and well-controlled T2D subjects.

Performance of individually measured vs population-based C-peptide kinetics to assess β-cell function in the presence and absence of acute insulin resistance

AIMS

To compare the performance of population-based kinetics with that of directly measured C-peptide kinetics when used to calculate β-cell responsivity indices, and to study people with and without acute insulin resistance to ensure that population-based kinetics apply to all conditions where β-cell function is measured.

METHODS

Somatostatin was used to inhibit endogenous insulin secretion in 56 people without diabetes. Subsequently, a C-peptide bolus was administered and the changing concentrations were used to calculate individual kinetic measures of C-peptide clearance. In addition, the participants were studied on 2 occasions in random order using an oral glucose tolerance test (OGTT). On one occasion, free fatty acid elevation, to cause insulin resistance, was achieved by infusion of Intralipid + heparin. The Disposition Index (DI) was then estimated by the oral minimal model using either population-based or individual C-peptide kinetics.

RESULTS

There were marked differences in the exchange variables (k ₁₂ and k ₂₁ ) of the model describing C-peptide kinetics, but smaller differences in the fractional clearance; that is, the irreversible loss from the accessible compartment (k ₀₁ ), obtained from population-based estimates compared with experimental measurement. Because it is predominantly influenced by k ₀₁ , DI estimated using individual kinetics correlated well with DI estimated using population-based kinetics.

CONCLUSIONS

These data support the use of population-based measures of C-peptide kinetics to estimate β-cell function during an OGTT.

The Role of Glucagon in the Pathophysiology and Treatment of Type 2 Diabetes

Type 2 diabetes is a disease involving both inadequate insulin levels and increased glucagon levels. While glucagon and insulin work together to achieve optimal plasma glucose concentrations in healthy individuals, the usual regulatory balance between these 2 critical pancreatic hormones is awry in patients with diabetes. Although clinical discussion often focuses on the role of insulin, glucagon is equally important in understanding type 2 diabetes. Furthermore, an awareness of the role of glucagon is essential to appreciate differences in the mechanisms of action of various classes of glucose-lowering therapies. Newer drug classes such as dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists improve glycemic control, in part, by affecting glucagon levels. This review provides an overview of the effect of glucose-lowering therapies on glucagon on the basis of an extensive PubMed literature search to identify clinical studies of glucose-lowering therapies in type 2 diabetes that included assessment of glucagon. Clinical practice currently benefits from available therapies that impact the glucagon regulatory pathway. As clinicians look to the future, improved treatment strategies are likely to emerge that will either use currently available therapies whose mechanisms of action complement each other or take advantage of new therapies based on an improved understanding of glucagon pathophysiology.

Do we know the true mechanism of action of the DPP-4 inhibitors?

The prevalence of type 2 diabetes is increasing, which is alarming because of its serious complications. Anti-diabetic treatment aims to control glucose homeostasis as tightly as possible in order to reduce these complications. Dipeptidyl peptidase-4 (DPP-4) inhibitors are a recent addition to the anti-diabetic treatment modalities, and have become widely accepted because of their good efficacy, their benign side-effect profile and their low hypoglycaemia risk. The actions of DPP-4 inhibitors are not direct, but rather are mediated indirectly through preservation of the substrates they protect from degradation. The two incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide, are known substrates, but other incretin-independent mechanisms may also be involved. It seems likely therefore that the mechanisms of action of DPP-4 inhibitors are more complex than originally thought, and may involve several substrates and encompass local paracrine, systemic endocrine and neural pathways, which are discussed here.

Bullous Pemphigoid Associated with the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin in a Patient with Liver Cirrhosis Complicated with Rapidly Progressive Hepatocellular Carcinoma

A 78-year-old man presented with cutaneous blisters of the limbs and abdominal distension. He had been treated for various diseases, including liver cirrhosis. He had begun receiving sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, for diabetes mellitus three years before the hospitalization. A skin biopsy demonstrated bullous pemphigoid. Ultrasonography (US) revealed multiple liver tumors, although he had been receiving regular US studies. We stopped sitagliptin and started insulin and corticosteroids. However, his renal dysfunction progressed, and he died 14 days after the hospitalization. We should therefore be careful of various complications, including bullous pemphigoid and progression of tumors, when using DPP-4 inhibitors.

Sitagliptin down-regulates retinol-binding protein 4 and reduces insulin resistance in gestational diabetes mellitus: a randomized and double-blind trial

Gestational diabetes mellitus (GDM) is a condition that affects increasing number of pregnant women worldwide. Sitagliptin was reported to alleviate symptoms of type 2 diabetes mellitus by reducing serum levels of retinol-binding protein 4 (RBP-4). We investigated the effectiveness of sitagliptin on insulin sensitivity parameters in GDM patients. Pregnant GDM women in the 2nd trimester were recruited for this study. Participants were then assigned randomly to sitagliptin treatment group or placebo treatment group, and administered sitagliptin or placebo daily for 16 weeks. Glucose and insulin profiles, as well as serum RBP-4 level, were measured at both baseline and end of the study. After 16 weeks of treatment, participants in the STL group exhibited significantly improved levels of fasting plasma glucose and serum insulin, homeostasis model of assessment of β cell function (HOMA-β) and insulin resistance (HOMA-IR), compared with those in the placebo group. Serum levels of RBP-4 were also markedly decreased in the sitagliptin treatment group, and more importantly it was positively correlated with improved insulin resistance parameters. Our study supports a potentially promising role of sitagliptin in improving insulin resistance by decreasing RBP-4 in GDM-affected women.

Efficacy and safety of repaglinide added to sitagliptin in Japanese patients with type 2 diabetes: A randomized 24-week open-label clinical trial

Although sitagliptin and repaglinide monotherapies improve postprandial hyperglycemia, the long-term effects and safety of their combination has not been examined. In this randomized 24-week trial of Japanese patients with poor control (HbA1c 7.0-8.5%) by sitagliptin, we divided 40 patients randomly into two equal groups of the repaglinide add-on to sitagliptin (ADD-ON, n=20), or sitagliptin switched to repaglinide (SWITCH, n=20). The meal tolerance test was carried out at weeks 0 and 24. The primary outcomes were changes in HbA1c and area under the curves (AUC) of glucose from the baseline to week 24. The mean change in HbA1c from baseline to week 24 was larger in the ADD-ON (-0.87±0.63%, mean±SD), compared with the SWITCH (0.03±0.65%, p=0.000). Significant improvements were noted in the mean changes in fasting glucose and AUCs of glucose in the ADD-ON vs. SWITCH (p=0.007 and p=0.000). Insulin secretion relative to glucose elevation (ISG; defined as AUC insulin/AUC glucose) increased significantly in the ADD-ON, although the mean change in fasting insulin level was significantly decreased in the ADD-ON (p=0.015 and p=0.026). The AUC of glucagon was significantly lower at 24-week relative to baseline in the ADD-ON, but was not significant in the two groups (p=0.047 and p=0.056, respectively). The combination therapy produced significant reductions in HbA1c, AUC of glucose and fasting glucose compared with switching to repaglinide without weight gain or severe hypoglycemia. The improved glycemic control with this combination therapy may be at least in part due to augmentation of repaglinide-induced insulin secretion by sitagliptin.

β-Cell Glucagon-Like Peptide-1 Receptor Contributes to Improved Glucose Tolerance After Vertical Sleeve Gastrectomy

Vertical sleeve gastrectomy (VSG) produces high rates of type 2 diabetes remission; however, the mechanisms responsible for this remain incompletely defined. Glucagon-like peptide-1 (GLP-1) is a gut hormone that contributes to the maintenance of glucose homeostasis and is elevated after VSG. VSG-induced increases in postprandial GLP-1 secretion have been proposed to contribute to the glucoregulatory benefits of VSG; however, previous work has been equivocal. In order to test the contribution of enhanced β-cell GLP-1 receptor (GLP-1R) signaling we used a β-cell-specific tamoxifen-inducible GLP-1R knockout mouse model. Male β-cell-specific Glp-1r(β-cell+/+) wild type (WT) and Glp-1r(β-cell-/-) knockout (KO) littermates were placed on a high-fat diet for 6 weeks and then switched to high-fat diet supplemented with tamoxifen for the rest of the study. Mice underwent sham or VSG surgery after 2 weeks of tamoxifen diet and were fed ad libitum postoperatively. Mice underwent oral glucose tolerance testing at 3 weeks and were euthanized at 6 weeks after surgery. VSG reduced body weight and food intake independent of genotype. However, glucose tolerance was only improved in VSG WT compared with sham WT, whereas VSG KO had impaired glucose tolerance relative to VSG WT. Augmentation of glucose-stimulated insulin secretion during the oral glucose tolerance test was blunted in VSG KO compared with VSG WT. Therefore, our data suggest that enhanced β-cell GLP-1R signaling contributes to improved glucose regulation after VSG by promoting increased glucose-stimulated insulin secretion.

The incretin effect in healthy individuals and those with type 2 diabetes: physiology, pathophysiology, and response to therapeutic interventions

The incretin effect describes the phenomenon whereby oral glucose elicits higher insulin secretory responses than does intravenous glucose, despite inducing similar levels of glycaemia, in healthy individuals. This effect, which is uniformly defective in patients with type 2 diabetes, is mediated by the gut-derived incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). The importance of the incretin effect for the maintenance of glucose homoeostasis is clearly established, and incretin-based therapies are among the most promising new therapies for type 2 diabetes. However, despite the effectiveness of these therapies in many patients, the idea that they restore the incretin effect is a common misconception. In type 2 diabetes, the endocrine pancreas remains responsive to GLP-1 but is no longer responsive to GIP, which is the most likely reason for a reduced or absent incretin effect. Incretin-based drugs, including GLP-1 receptor agonists and dipeptidyl peptidase 4 (DPP-4) inhibitors, stimulate GLP-1 receptors and thus augment insulin secretion in response to both oral and intravenous glucose stimulation, thereby abolishing any potential difference in the responses to these stimuli. These drugs therefore do not restore the defective incretin effect in patients. By contrast, some bariatric surgical procedures enhance GLP-1 responses and also restore the incretin effect in obese individuals with type 2 diabetes. Thus, not all biological actions elicited by the stimulation of GLP-1 receptors lead to quantitative changes to the incretin effect.

Impact of a mild decrease in fasting plasma glucose on β-cell function in healthy subjects and patients with type 2 diabetes

Restoring euglycaemia for weeks or months improves insulin secretion in patients with type 2 diabetes (T2D). We tested whether mild decrements in fasting glucose (FPG) acutely affect β-cell function and insulin sensitivity. Thirteen normotolerant (NGT) and 10 T2D patients volunteered in pairs. In an isoglycemic test (Iso), after 100 min of stabilization, an incremental glucose infusion over 3 h was applied to raise plasma glucose to >22 mmol/l, followed by an arginine challenge; in a subisoglycemic test (Sub), a glucose infusion matching the plasma glucose time course of Iso was preceded by an insulin infusion period (100 min) aimed at maintaining a mild FPG reduction while avoiding hypoglycaemia. β-Cell function was assessed by mathematical modeling, whereas the acute insulin response (AIR) to arginine was determined from C-peptide levels. In the Sub, FPG was lowered by 17% in NGT and 31% in T2D patients. On the glucose ramp, total insulin release was lower in Sub than in Iso in both groups [from 106 (43) to 75 (39) nmol/m(-2) in NGT and from 71 (63) to 64 (41) nmol/m(-2) in T2D, P = 0.001]. In the Sub, β-cell glucose sensitivity was significantly (P = 0.008) reduced in NGT [from 50 (31) to 43 (21) pmol·min(-1)·m(-2)·mM(-1)] but not in T2D [19 (20) to 20 (20) pmol·min(-1)·m(-2)·mM(-1)]. Likewise, AIR was lowered in NGT [8.9 (4.6) to 7.1 (4.4) nmol/l, P = 0.048] but not in T2D [4.7 (3.3) to 5.3 (3.2) nmol/l]. Insulin sensitivity improved in NGT but only marginally in T2D. Prestimulatory glucose levels acutely influence both β-cell function and insulin sensitivity differentially in nondiabetic and type 2 diabetic individuals.

Improved glucose regulation in type 2 diabetic patients with DPP-4 inhibitors: focus on alpha and beta cell function and lipid metabolism

Inhibition of dipeptidyl peptidase-4 (DPP-4) is an established glucose-lowering strategy for the management of type 2 diabetes mellitus. DPP-4 inhibitors reduce both fasting and postprandial plasma glucose levels, resulting in reduced HbA1c with low risk for hypoglycaemia and weight gain. They act primarily by preventing inactivation of the incretin hormones glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1, thereby prolonging the enhanced endogenous levels of these hormones after meal ingestion. This in turn causes islet and extrapancreatic effects, including increased glucose sensing in islet alpha and beta cells. These effects result in increased insulin secretion and decreased glucagon secretion being more effective in hyperglycaemic states and reduced insulin secretion and increased glucagon secretion being more effective during hypoglycaemia. Other secondary pharmacological actions of DPP-4 inhibitors include mobilisation and burning of fat during meals, decrease in fat extraction from the gut, reduction of fasting lipolysis and liver fat and increase in LDL particle size. These actions contribute to the clinical effects of DPP-4 inhibition, and the reduced demand for insulin could also lead to a durability benefit. This review summarises the current knowledge of the secondary pharmacological actions of DPP-4 inhibitors that lead to improved glucose regulation in patients with type 2 diabetes, focusing on alpha and beta cell function and lipid metabolism.

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.

Very short-term effects of the dipeptidyl peptidase-4 inhibitor sitagliptin on the secretion of insulin, glucagon, and incretin hormones in Japanese patients with type 2 diabetes mellitus: analysis of meal tolerance test data

Background

Sitagliptin inhibits dipeptidyl peptidase-4, which inactivates the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide. To assess its antidiabetic potency, we used meal tolerance tests (MTTs) to determine the very short-term effects of sitagliptin on plasma concentrations of insulin and glucagon.

Methods

On day 1, patients with newly diagnosed or uncontrolled type 2 diabetes mellitus started a calorie-restricted diet. On day 2, the first MTT was performed, before treatment with sitagliptin 50 mg/day started later the same day. On day 5, a second MTT was performed. Area under the concentration–time curves (AUCs) of relevant laboratory values were calculated [AUC from time zero to 2 h (AUC_0–2h) and from time zero to 4 h (AUC_0–4h)].

Results

Fifteen patients were enrolled. AUCs for postprandial plasma glucose were decreased after 3 days of sitagliptin treatment [AUC_0–2h 457 ± 115 mg/dL·h (25.4 ± 6.4 mmol/L·h) to 369 ± 108 mg/dL·h (20.5 ± 6.0 mmol/L·h); AUC_0–4h 896 ± 248 mg/dL·h (49.7 ± 13.8 mmol/L·h) to 701 ± 246 mg/dL·h (38.9 ± 13.7 mmol/L·h); both p < 0.001]. AUC_0–2h and AUC_0–4h for postprandial plasma glucagon also decreased: 195 ± 57 to 180 ± 57 pg/mL·h (p < 0.05) and 376 ± 105 to 349 ± 105 pg/mL·h (p < 0.01), respectively. The AUC_0–2h [median with quartile values (25 %, 75 %)] for active GLP-1 increased: 10.5 (8.5, 15.2) to 26.4 (16.7, 32.4) pmol/L·h (p = 0.03).

Conclusions

Very short-term (3-day) treatment with sitagliptin decreases postprandial plasma glucose significantly. This early reduction in glucose may result partly from suppression of excessive glucagon secretion, through a direct effect on active GLP-1. Improvement in postprandial plasma glucose, through suppression of glucagon secretion, is believed to be an advantage of sitagliptin for the treatment of patients with type 2 diabetes.

Mechanisms by which cocoa flavanols improve metabolic syndrome and related disorders

Dietary administration of cocoa flavanols may be an effective complementary strategy for alleviation or prevention of metabolic syndrome, particularly glucose intolerance. The complex flavanol composition of cocoa provides the ability to interact with a variety of molecules, thus allowing numerous opportunities to ameliorate metabolic diseases. These interactions likely occur primarily in the gastrointestinal tract, where native cocoa flavanol concentration is high. Flavanols may antagonize digestive enzymes and glucose transporters, causing a reduction in glucose excursion, which helps patients with metabolic disorders maintain glucose homeostasis. Unabsorbed flavanols, and ones that undergo enterohepatic recycling, will proceed to the colon where they can exert prebiotic effects on the gut microbiota. Interactions with the gut microbiota may improve gut barrier function, resulting in attenuated endotoxin absorption. Cocoa may also positively influence insulin signaling, possibly by relieving insulin-signaling pathways from oxidative stress and inflammation and/or via a heightened incretin response. The purpose of this review is to explore the mechanisms that underlie these outcomes, critically review the current body of literature related to those mechanisms, explore the implications of these mechanisms for therapeutic utility, and identify emerging or needed areas of research that could advance our understanding of the mechanisms of action and therapeutic potential of cocoa flavanols.

Empagliflozin/linagliptin single-tablet combination: first-in-class treatment option

BACKGROUND

The availability of a dual sodium glucose co-transporter 2/dipeptidyl peptidase-4 inhibitor combination in a single-tablet combination (STC) represents a new therapeutic option for patients with type 2 diabetes. Empagliflozin/linagliptin STC has been recently approved by the US Food and Drug Administration for the treatment of type 2 diabetes mellitus (T2DM).

AIM

The aim of this study was to describe the latest clinical evidence on the efficacy and safety profiles of empagliflozin/linagliptin STCs in comparison with the individual components. Juxtaposition of the STC with dapagliflozin/saxagliptin combination was also presented.

RESULTS

Empagliflozin/linagliptin STC given as initial therapy or on metformin background lowered mean glycated haemoglobin (HbA1c) by approximately 1.1% (mean baseline HbA1c, 8.0%). Furthermore, the STC reduced mean body weight by 2.0-3.0 kg from baseline. With the STC treatment, no confirmed incidents of hypoglycaemia were reported in drug-naïve patients; in patients taking metformin hypoglycaemia occurred at low rates which were comparable with monotherapy. Use of STCs in the treatment of T2DM can simplify drug dosing regimen, reduce pill burden and increase treatment adherence. Empagliflozin/linagliptin STC is a combination that offers potential additional benefits such as body weight loss and moderate reductions in blood pressure, without increasing risk of hypoglycaemia.

CONCLUSION

Empagliflozin/linagliptin STC appears to be a rational choice for a wide range of patients in need of multiple agents for controlling hyperglycaemia. The STC should be particularly useful in patients in whom hypoglycaemia, weight gain and treatment adherence are of concern.

Increased plasma dipeptidyl peptidase-4 activities are associated with high prevalence of subclinical atherosclerosis in Chinese patients with newly diagnosed type 2 diabetes: a cross-sectional study

OBJECTIVE

Hyperglycemia, insulin resistance, dislipidemia, oxidative stress and inflammation are well-documented risk factors for subclinical atherosclerosis. Dipeptidyl peptidase-4(DPP4) is a newly identified adipokine related to these risk factors. Hence, we aimed to investigate the association between plasma DPP4 activities and subclinical atherosclerosis in type 2 diabetes.

METHODS

A total of 985 newly diagnosed type 2 diabetic subjects were studied. Plasma DPP4 activity, mannose 6-phosphate receptor (M6P-R), oxidative stress parameters, inflammatory markers and common carotid artery Intima-Media Thickness (c-IMT) were measured in all participants.

RESULTS

Participants in the highest quartile of DPP4 activity had higher HbA1c, homeostatic model assessment of insulin resistance(HOMA-IR), triglyceride, low-density lipoprotein cholesterol(LDL-C), oxidized LDL, nitrotyrosine, 8-iso-PGF2a, interleukin-6 (IL-6), high-sensitivity C-reactive protein (hs-CRP), M6P-R, c-IMT compared with participants in the lowest quartile (all P < 0.001). DPP4 activities were associated positively with HbA1c, HOMA-IR, triglyceride, LDL-C, oxidized LDL, nitrotyrosine, 8-iso-PGF2a, IL-6, hs-CRP, M6P-R and c-IMT (all P < 0.05). The ORs for insulin resistance, dislipidemia, oxidative stress and inflammation were higher with increasing DPP4 quartiles (P < 0.001 for trend). In the highest DPP4 quartile, subclinical atherosclerosis risk was significantly higher (OR 4.97; 95% CI 3.03-8.17) than in the lowest quartile. This association remained strong (2.17; 1.21-3.89) after further controlling for HbA1c, HOMA-IR, triglyceride, oxidized LDL, nitrotyrosine, and IL-6.

CONCLUSIONS

This study shows that increased DPP4 activities are positively and independently associated with subclinical atherosclerosis in type 2 diabetes. Our findings suggest of potential role of DPP4 in the pathogenesis of subclinical atherosclerosis and in the prevention and management of this disease.

Single-pill combination therapy for type 2 diabetes mellitus: linagliptin plus empagliflozin

BACKGROUND

Treatment of type 2 diabetes mellitus invariably requires the use of multiple daily medications which can impact negatively on patient adherence. As a result, there is growing interest in the use of single-pill combinations that can reduce the pill burden. Many such formulations incorporate metformin, although this agent is not suitable for all patients. The single-pill combination of the dipeptidyl peptidase-4 inhibitor linagliptin with the sodium glucose co-transporter 2 inhibitor empagliflozin offers a new and attractive option, given their complementary mechanisms of action.

SCOPE

Publications with titles containing the keywords 'linagliptin' or 'empagliflozin' were identified from a non-systematic search of PubMed without date restrictions, together with abstracts presented at the annual meetings of the American Diabetes Association and the European Association for the Study of Diabetes 2012-2014. ClinicalTrials.gov was searched for entries containing these two keywords. Additional references known to the author were included.

FINDINGS

The efficacy and safety of linagliptin and empagliflozin as monotherapy or in combination with other oral antidiabetic drugs has been established through extensive clinical trial programs. Studies specifically evaluating the efficacy/safety of a dipeptidyl peptidase-4 inhibitor/sodium glucose co-transporter 2 inhibitor in combination are limited, but do include two studies of linagliptin/empagliflozin of up to 52 weeks in duration. These studies show that the single-pill combination of linagliptin and empagliflozin produced clinical improvements in glycemic control that were generally superior to the improvements seen with linagliptin and empagliflozin alone, but with a safety profile comparable to that of the individual constituents.

CONCLUSIONS

The single-pill combination of linagliptin and empagliflozin, with their complementary mechanisms of action, is a promising treatment option for patients with type 2 diabetes mellitus. It would reduce the daily pill burden in this population, potentially improving adherence to, and optimizing the benefits of, treatment of diabetes mellitus.

Potential for dipeptidyl peptidase-4 inhibitor and sodium glucose cotransporter 2 inhibitor single-pill combinations

With prolonged duration of Type 2 diabetes mellitus, most patients need a combination of antihyperglycemic drugs to reach their target HbA1c. Evidence shows that single-pill combinations (SPCs) may increase patient satisfaction, adherence, and reduce overall health-care costs. Several SPCs containing metformin and another oral antidiabetic drug (OAD) are available on the market. Although well established in clinical practice, long-term durability and tolerability of traditional OADs can be inadequate. Dipeptidyl peptidase (DPP)-4 inhibitors and sodium glucose cotransporter (SGLT) 2 inhibitors are two newer classes of OADs that are efficacious and are less likely to induce adverse effects such as gastrointestinal reactions, hypoglycemia and weight gain when compared with metformin, sulfonylureas, and thiazolidinediones. This article describes current efficacy and safety data of DPP-4/SGLT2 inhibitor combination therapy. Pharmacokinetics, mechanism-of-action based rationale for the combination and timing of the addition of a SPC to the treatment regimen are discussed.