Combination therapy of dipeptidyl peptidase-4 inhibitors and metformin in type 2 diabetes: rationale and evidence

Efficacy of Alogliptin/Metformin Fixed-Dose Combination Tablets and Vildagliptin/Metformin Fixed-Dose Combination Tablets on Glycemic Control in Real-World Clinical Practice for the Patients with Type 2 Diabetes: A Multicenter, Open-Label, Randomized, Parallel Group, Comparative Trial

Background: This study was aimed to compare the efficacy of two combination tablets of dipeptidyl peptidase-4 (DPP-4) inhibitors and metformin with different dosages, alogliptin/metformin (AM) and vildagliptin/metformin (VM), on glycemic control in patients with type 2 diabetes (T2D). Methods: This was a prospective, multicenter, open-label, randomized, parallel group, comparative trial. After a run-in period of treatment with metformin alone, a total of 59 Japanese outpatients with T2D, aged 20-79 years with glycated hemoglobin (HbA1c) levels of 6.5%-10% were randomly assigned to 12-week AM treatment, alogliptin 25 mg/metformin 500 mg combination tablet orally once a day, or VM treatment, vildagliptin 50 mg/metformin 250 mg combination tablet orally twice a day. The primary endpoints were the changes in HbA1c and fasting plasma glucose (FPG) levels from baseline to week 12 between the two groups. Blinded intermittently scanned continuous glucose monitoring (isCGM) was performed between weeks 10 and 12. The incidence of adverse events during the study was also evaluated. Results: In all, 52 participants were analyzed. Significant decreases in HbA1c and FPG levels from baseline to week 12 were observed in both treatment groups. However, there were no significant differences between the AM and VM groups in the change in HbA1c level (-0.3% and -0.4%, P = 0.309) or the FPG level (-9.0 and -15.0 mg/dL, P = 0.789). The isCGM revealed that both treatments achieved the recommended glycemic target range. No adverse events, such as severe hypoglycemia, were observed in either group. Conclusions: We concluded that there were no significant differences in the efficacy of two combination tablets of DPP-4 inhibitors and metformin with different dosages on glycemic control in patients with T2D.

Pharmacokinetics of a Fixed-Dose Combination of Teneligliptin Hydrochloride Hydrate and Modified-Release Metformin Under Fasting and Fed Conditions in Healthy Subjects

Purpose

This study was performed to compare the pharmacokinetics of two fixed-dose combination (FDC) formulations of teneligliptin combined with modified-release metformin in healthy Korean subjects under fasting and fed conditions.

Patients and Methods

The study was a single-center, open-label, single-dose, 2-way, 2-period, crossover trial. A total of 72 eligible subjects (40 subjects in the fasting state study and 32 subjects in the fed study) were enrolled in the study and were randomized to treatment. After the administration of a single FDC tablet of the investigational products, blood samples were collected at specific time intervals from 0 to 96 hours. The plasma concentrations of teneligliptin and metformin were measured by ultra performance liquid chromatography-tandem mass spectrometry (UPLC‒MS/MS). Pharmacokinetic parameters were calculated, and 90% confidence intervals (CIs) of the geometric mean ratios (test/reference) of the parameters were obtained through analysis of variance of the logarithmically transformed data.

Results

The corresponding 90% CIs of area under the plasma concentration-time curve from time zero to the time of last measurable concentration (AUCt) and maximum plasma drug concentration (Cmax) for the test/reference geometric mean ratio (GMR) of teneligliptin were 94.81-101.32% and 86.03-97.63%, respectively, under fasting conditions. The corresponding 90% CIs of AUCt and Cmax for the test/reference GMR of metformin were 95.01-108.36% and 94.69-108.40%, respectively, under the fasting state and 98.82-107.56% and 97.25-106.99%, respectively, after feeding. All adverse events were of mild intensity, and the subjects recovered spontaneously without sequelae.

Conclusion

The test FDC drug is equivalent to the reference FDC drug in subjects under fasting and fed conditions within the Korean regulatory bioequivalence criteria. Both formulations were safe and well tolerated, and there were no differences in the safety profiles between the two single FDC formulation drugs.

Trial Registration No

Clinicaltrials.gov. KCT0007757, KCT0007759.

Effects of co-administration of metformin and evogliptin on cerebral infarct volume in the diabetic rat

Patients with diabetes suffer more severe ischemic stroke. A combination of metformin and dipeptidyl peptide-4 inhibitors is commonly prescribed to treat diabetes. Therefore, we aimed to determine if pretreatment with a combination of metformin and evogliptin, a dipeptidyl peptidase-4 inhibitor, could reduce cerebral infarct volume in rats with streptozotocin-induced diabetes. After confirming diabetes induction, the rats were treated with vehicle, evogliptin, metformin, or evogliptin/metformin combination for 30 days. Then, stroke was induced by transient middle cerebral artery occlusion (tMCAO). Infarct volume, oxidative stress, levels of methylglyoxal-modified protein, glucagon-like peptide-1 receptor (GLP-1R), AMPK, and Akt/PI3K pathway-related proteins, and post-stroke pancreatic islet cell volume were evaluated. Compared to vehicle, only the co-administration group had significantly reduced infarct volume from the effects of tMCAO; the regimen also improved glycemic control, whereas the individual treatments did not. Co-administration also significantly reduced methylglyoxal-modified protein level in the core of the brain cortex, and the expression of 4-HNE and 8-OHdG was reduced. Co-administration increased p-Akt levels in the ischemic core and mitigated the suppression of Bcl-2 expression. Plasma GLP-1 and dipeptidyl peptidase-4 levels and brain GLP-1R expression remained unaltered. In the pancreas, islet cell damage was reduced by co-administration. These results reveal that metformin and evogliptin co-administration ameliorates cerebral infarction associated with prolonged glycemic control and pancreatic beta cell sparing. Other potential protective mechanisms may be upregulation of insulin receptor signaling or reduction of methylglyoxal-induced neurotoxicity. The combination of metformin and evogliptin should be tested further for its potential against focal cerebral ischemia in diabetes patients.

Shift of Glucose Peak Time During Oral Glucose Tolerance Test is Associated with Changes in Insulin Secretion and Insulin Sensitivity After Therapy with Antidiabetic Drugs in Patients with Type 2 Diabetes

INTRODUCTION

Delay in peak blood glucose during an oral glucose tolerance test (OGTT) predicts declining β-cell function and poor ability to regulate glucose metabolism. Glucose peak time has not been used as a comparative indicator of the improvement in islet function after treatment with exenatide, insulin, or oral antidiabetic drugs (OADs). We evaluated the efficacy of three types of antidiabetic drugs on the basis of blood glucose peak time in patients with non-newly diagnosed type 2 diabetes.

METHODS

The data from 100 patients with diabetes who completed two OGTTs within 6 months were collected. Thirty-seven of them with type 2 diabetes were treated with Humalog Mix25, 28 patients with OADs (metformin, acarbose, and gliclazide), and 35 patients with exenatide.

RESULTS

Glycated hemoglobin improved in all three groups after treatment (P < 0.05). Subcutaneous adipose tissue (P < 0.01) and visceral adipose tissue (P < 0.0001) significantly decreased in the exenatide group. The insulinogenic index (IGI) (P = 0.01) and IGI × oral glucose insulin sensitivity (OGIS) (P = 0.01) improved in the exenatide group only. Homeostatic assessment of β-cell function (HOMA-β) and OGIS were greater in the exenatide and OAD groups than in the Humalog Mix25 group (all P < 0.05). A shift to an earlier peak was observed in 57.1%, 35.7%, and 27.0% of patients in the exenatide, OAD, and Humalog Mix25 groups, respectively (P = 0.029). OGIS (odds ratio [OR] 0.54, 95% confidence interval [CI] 0.33-0.89, P = 0.026) and IGI × OGIS (OR 1.72, 95% CI 0.44-6.68, P = 0.012) were independently related to shifts in glucose peak time.

CONCLUSION

Exenatide, Humalog Mix25, and OADs improved glycemic metabolism. However, exenatide exhibited superior efficacy in shifting blood glucose peak time to an earlier point, while it improved insulin secretion and insulin sensitivity. Hence, the shift of glucose peak time may be considered an indicator for the evaluation of the effect of hypoglycemic drugs.

Biguanides drugs: Past success stories and promising future for drug discovery

Biguanides have attracted much attention a century ago and showed resurgent interest in recent years after a long period of dormancy. They constitute an important class of therapeutic agents suitable for the treatment of a wide spectrum of diseases. Therapeutic indications of biguanides include antidiabetic, antimalarial, antiviral, antiplaque, and bactericidal applications. This review presents an extensive overview of the biological activity of biguanides and different mechanisms of action of currently marketed biguanide-containing drugs, as well as their pharmacological properties when applicable. We highlight the recent developments in research on biguanide compounds, with a primary focus on studies on metformin in the field of oncology. We aim to provide a critical overview of all main bioactive biguanide compounds and discuss future perspectives for the design of new drugs based on the biguanide fragment.

Metformin - its anti-cancer effects in hematologic malignancies

The main anti-diabetic effect of metformin mediated through stimulation of adenosine monophosphate (AMP)-activated protein kinase (AMPK) is the inhibition of hepatic gluconeogenesis and triggering glucose uptake in skeletal muscles. Additionally, some new pathways, besides the AMPK activation, were discovered, that can explain wide-range properties of metformin. All these properties are now attracting the attention of researchers in the fields other than diabetes and the drug has been reported to have anti-cancer, immunoregulatory and anti-aging effects. Among others, the beneficial effects of metformin in hematological disorders like leukemias, lymphomas, and multiple myeloma were reported. Despite a great progress in therapy, these diseases are still incurable in most cases. Thus, there is an urgent need to discover novel, less toxic and more effective drugs especially for older or chemotherapy-resistant patients. In this review article, the current findings on the anti-cancer effect of metformin together with underlying possible mechanisms in blood cancers are discussed. However. to evaluate precisely these promising effects of metformin, more studies are required, because many of the published results are preclinical.

Optimizing the treatment of newly diagnosed type 2 diabetes mellitus with combination of dipeptidyl peptidase-4 inhibitors and metformin: An expert opinion

The expanding burden of Type 2 Diabetes Mellitus (T2DM) in today's world, with respect to incidence, prevalence, and cost incurred, is an existential risk to society. Various guidelines recommend individualization of treatment. This expert opinion aims to review the recent evidences and reach a consensus on the preferable combination therapy for use in newly diagnosed Indian T2DM patients with HbA_1C >7.5%. The core committee included seventeen diabetes specialists. Three statements were developed, discussed, and rated by specialists and recommendations were noted. Specialists were requested to rate the statements using a 9-point Likert's scale with score of 1 being “Strongly Disagree” and 9 being “Strongly Agree”. Statement-specific scores of all the specialists were added and mean score of ≥7.00 was considered to have achieved a consensus. Statements used to meet the consensus were: Statement 1. Majority of newly-diagnosed Indian diabetics have HbA_1C >7.5%; Statement 2. Patients with HbA_1C >7.5% may be initiated with dual therapy of dipeptidyl peptidase-4 inhibitors (DPP4Is) + Metformin; and Statement 3. In Indian patients with HbA_1C >7.5% at diagnosis, DPP4Is + Metformin may be considered as a first-line therapy. Literature review revealed that HbA_1C level at the time of diagnosis in majority of Indian T2DM patients is >7.5%. Consensus was reached that dual anti-diabetic therapy should be initiated in patients with HbA_1C >7.5%. DPP4Is + Metformin is the preferred cost-effective option and may be considered as a first-line therapy in Indian T2DM patients with HbA_1C >7.5% at diagnosis.

SGLT2 Inhibitors as Add-On Therapy to Metformin for People with Type 2 Diabetes: A Review of Placebo-Controlled Trials in Asian versus Non-Asian Patients

Metformin remains the first pharmacological choice for treating hyperglycemia in type 2 diabetes (T2DM) in most international guidelines. Sodium-glucose cotransporter type 2 inhibitors (SGLT2is) are increasingly used as add-on therapy. T2DM pathophysiology is different in Asian and non-Asian (mainly Caucasian) patients. The aim of this systematic review is to compare the efficacy of SGLT2is vs placebo added to metformin in randomized controlled trials (RCTs: range 12-52 weeks) in Asian versus non-Asian patients with T2DM. The primary endpoint is the reduction in glycated hemoglobin (HbA1c) from baseline and key secondary endpoints are reductions in fasting plasma glucose (FPG), body weight (BW) and systolic blood pressure (SBP). Systematic literature search collected 7 RCTs (3 with 2 doses) in Asian patients (10 analyses, n=1164, iSGLT2: canagliflozin, dapagliflozin, ertugliflozin, ipragliflozin, tofogliflozin)) and 10 RCTs (6 with two doses) in non-Asian patients (16 analyses, n=2482, iSGLT2: canagliflozin, dapagliflozin, empagliflozin, ertugliflozin, ipragliflozin). Baseline values of HbA1c (7.98±0.19 vs 7.89±0.27%), FPG (8.80 ±0.46 vs 9.11±0.49 mmol/l) and SBP (128.4±1.6 vs 130.2±3.1 mmHg) were not significantly different in Asian vs non-Asian patients, but BW was lower in Asian patients (71.6±4.8 vs 88.0±2.5 kg, p<0.001). The placebo-adjusted weighed mean differences (WMD, 95% CI) were similar in Asian versus non-Asian patients regarding the reductions in HbA1c -0.60 (-0.68, -0.53) % versus -0.54 (-0.59, -0.49) % (p=0.568), FPG -1.37 (-1.53, -1.22) mmol/l vs -1.37 (-1.47, -1.27) mmol/l (p=0.627), BW when expressed in percentage of baseline BW -2.23 (-2.55, -1.90) % vs -2.16 (-2.37, -1.96) % (p=0.324), and SBP -4.53 (-5.53, -3.53) mmHg vs -4.06 (-4.83, -3.29) mmHg) (p=0.223). In conclusion, clinical efficacy of SGLT2i, as an add-on treatment to metformin monotherapy in patients with T2DM, is similar in Asian versus non-Asian patients, despite known ethnic differences in phenotype and pathophysiology of T2DM.

Reduction in HbA1c with SGLT2 inhibitors vs. DPP-4 inhibitors as add-ons to metformin monotherapy according to baseline HbA1c: A systematic review of randomized controlled trials

AIMS

This study compared the reduction of glycated haemoglobin (HbA1c) with sodium-glucose cotransporter type-2 inhibitors (SGLT2is) vs. dipeptidyl peptidase-4 inhibitors (DPP-4is) as add-ons to metformin in patients with type 2 diabetes mellitus (T2DM), with a specific focus on HbA1c changes according to baseline HbA1c.

MATERIALS AND METHODS

Electronic databases were scrutinized for randomized controlled trials (RCTs) evaluating the reduction of HbA1c from baseline (Δ HbA1c) with an SGLT2i or DPP-4i in patients with T2DM not well controlled by metformin monotherapy. The endpoint was Δ HbA1c using both indirect and direct comparisons.

RESULTS

Overall, Δ HbA1c was slightly greater with SGLT2is (-0.80±0.20% from 8.03±0.35%; 44 analyses, 29 RCTs, 15 with two doses, n=9321) than with DPP-4is (-0.71±0.23% from 8.05±0.43%; 61 analyses, 59 RCTs, n=17,914; P=0.0354). When the mean baseline HbA1c was<8% ([64mmol/mol] 7.79±0.15% vs. 7.71±0.23%), Δ HbA1c averaged -0.735±0.17% vs. -0.62±0.16% (P=0.0117) with SGLT2is vs. DPP-4is, respectively. However, this difference vanished when the mean baseline HbA1c was≥8% (-0.87±0.22% from 8.27±0.32% with SGLT2is vs. -0.80±0.24% from 8.35±0.33% with DPP-4is; P=0.2756). The relationship between Δ HbA1c and baseline HbA1c was only slightly stronger with SGLT2is (slope: -0.39, r²=-0.43; P<0.0001) than with DPP-4is (slope: -0.26, r²=-0.25; P<0.0001).

CONCLUSION

Because of the small difference in Δ HbA1c whatever the baseline HbA1c level with SGLT2is vs. DPP-4is as add-ons to metformin, choosing between these glucose-lowering agents in clinical practice should be based on other efficacy criteria (such as weight and blood pressure changes, cardiovascular and renal protection) or on safety profiles rather than on HbA1c levels.

Outcomes for Inappropriate Renal Dose Adjustment of Dipeptidyl Peptidase-4 Inhibitors in Patients With Type 2 Diabetes Mellitus: Population-Based Study

OBJECTIVES

To estimate inappropriate dosing of dipeptidyl peptidase-4 (DPP-4) inhibitors and to assess the risk of emergency department visits, hypoglycemia, and mortality in patients with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) prescribed inappropriate DPP-4 inhibitor doses because limited real-world information is available regarding rates of DPP-4 inhibitor dose adjustment and its safety in patients with T2DM and CKD.

PATIENTS AND METHODS

We performed a retrospective observational cohort study of 82,332 patients aged 30 to 75 years with T2DM and CKD being treated with DPP-4 inhibitors from January 1, 2012, through December 31, 2014, using the Korean National Health Information Database. We divided the patients according to the prescription of DPP-4 inhibitor with or without dose adjustment according to estimated glomerular filtration rate. The incidences of emergency department visits, hypoglycemia, and mortality were assessed using hazard ratios estimated using Cox proportional hazards regression modeling.

RESULTS

Approximately 40% of patients with T2DM and CKD were prescribed an inappropriate dose of DPP-4 inhibitor from 2009 through 2011; this proportion decreased to 24.4% in 2015. Hazard ratios (95% CIs) for inappropriate vs appropriate dosing of DPP-4 inhibitors were 1.115 (1.005-1.237) for mortality, 1.074 (1.018-1.133) for emergency department visits, and 1.192 (1.054-1.349) for severe hypoglycemia after multivariable adjustment for confounding factors.

CONCLUSION

One of every 3 patients with T2DM and CKD received inappropriate dosing of DPP-4 inhibitor, which was associated with high risk of emergency department visits, severe hypoglycemia, and mortality.

The Biological Impacts of Sitagliptin on the Pancreas of a Rat Model of Type 2 Diabetes Mellitus: Drug Interactions with Metformin

Sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, is a beneficial class of antidiabetic drugs. However, a major debate about the risk of developing pancreatitis is still existing. The aim of the work was to study the histological and immunohistochemical effects of sitagliptin on both endocrine and exocrine pancreases in a rat model of type 2 diabetes mellitus and to correlate these effects with the biochemical findings. Moreover, a possible synergistic effect of sitagliptin, in combination with metformin, was also evaluated. Fifty adult male rats were used and assigned into five equal groups. Group 1 served as control. Group 2 comprised of untreated diabetic rats. Group 3 diabetic rats received sitagliptin. Group 4 diabetic rats received metformin. Group 5 diabetic rats received both combined. Treatments were given for 4 weeks after the induction of diabetes. Blood samples were collected for biochemical assay before the sacrification of rats. Pancreases were removed, weighed, and were processed for histological and immunohistochemical examination. In the untreated diabetic group, the islets appeared shrunken with disturbed architecture and abnormal immunohistochemical reactions for insulin, caspase-3, and inducible nitric oxide synthase (iNOS). The biochemical findings were also disturbed. Morphometrically, there was a significant decrease in the islet size and islet number. Treatment with sitagliptin, metformin, and their combination showed an improvement, with the best response in the combined approach. No evidence of pancreatic injury was identified in the sitagliptin-treated groups. In conclusion, sitagliptin had a cytoprotective effect on beta-cell damage. Furthermore, the data didn't indicate any detrimental effects of sitagliptin on the exocrine pancreas.

Differential effect of concomitant antidiabetic agents on carotid atherosclerosis: a subgroup analysis of the PROLOGUE study

Accumulated evidence shows that some antidiabetic agents attenuate the progression of carotid atherosclerosis assessed as intima-media thickness (IMT). Although some studies have demonstrated an inhibitory effect of dipeptidyl peptidase-4 inhibitors on carotid IMT progression, in the PROLOGUE study sitagliptin failed to slow progression relative to conventional therapy for 24 months. We hypothesized that differences in the concomitant antidiabetic agents between the groups have influenced the progression of carotid IMT. We performed a post hoc analysis of the PROLOGUE study using subgroups stratified by concomitant antidiabetic agents. Although no subgroup with any combination of agents in the overall patients showed a significant difference between sitagliptin group and conventional therapy group in the changes from baseline in mean common carotid artery (CCA)-IMT at 24 months, a significant attenuation of mean CCA-IMT progression was observed in the sitagliptin group relative to conventional therapy group only in three combination subgroups aged < 70 years, namely no thiazolidinedione; no thiazolidinedione or biguanide; and no thiazolidinedione, biguanide or α-glucosidase inhibitor, even after adjustment for multiple confounding factors. In the three subgroups, no significant difference between sitagliptin group and conventional therapy group in the changes from baseline in HbA1c at 24 months was detected. Our data suggest that some concomitant agents, whose prescription frequencies were increased in the conventional therapy group, may have masked the inhibitory effect of sitagliptin on carotid IMT progression in the PROLOGUE study.

Efficacy and Safety of Initial Combination Therapy in Treatment-Naïve Type 2 Diabetes Patients: A Systematic Review and Meta-analysis

INTRODUCTION

The aim of this study was to evaluate the efficacy and safety of initial combination therapy compared with monotherapy in drug-naïve type 2 diabetes patients.

METHODS

MEDLINE, Embase and the Cochrane Central Register of Controlled Trials were searched for randomized clinical trials of initial combination therapy with hypoglycemic agents compared with monotherapy. Those which satisfied the search criteria were included in the meta-analysis. Weighted mean difference and relative risks were calculated.

RESULTS

A total of 36 studies were included in the meta-analysis. Compared with metformin monotherapy, initial combination therapy with metformin plus another anti-diabetes drug exhibited significant reductions in glycated hemoglobin (HbA1c) (p < 0.001). Most of the combination therapies had a similar risk of hypoglycemia (p > 0.05), with the exception of combinations of sulfonylurea/glinide and metformin or combinations of thiazolidinedione and metformin. Compared with dipeptidyl peptidase-4 (DPP-4) inhibitor monotherapy, initial combination therapy with DPP-4 inhibitor plus another anti-diabetes drug showed a significant decrease in HbA1c (p < 0.001) and a similar risk of hypoglycemia (p > 0.05). Compared with monotherapy with other anti-diabetes drugs, initial combination therapies also resulted in significant HbA1c reductions, a similar risk of hypoglycemia and similar risks of other adverse events.

CONCLUSION

Compared with monotherapy, all initial combination therapies resulted in significant HbA1c reductions. Compared with metformin monotherapy, initial combination therapies with DPP-4 inhibitors plus metformin, sodium/glucose cotransporter 2 inhibitors and metformin, respectively, were associated with similar risks of hypoglycemia, but initial combination therapies with sulfonylurea plus metformin, thiazolidinedione and metformin, respectively, were associated with higher risks of hypoglycemia.

FUNDING

AstraZeneca Ltd. (China).

TRIAL REGISTRATION

Registration number CRD42017060717 in PROSPERO.

Sitagliptin on carotid intima-media thickness in type 2 diabetes patients receiving primary or secondary prevention of cardiovascular disease: A subgroup analysis of the PROLOGUE study

BACKGROUND

Whether a dipeptidyl peptidase-4 (DPP-4) inhibitor can attenuate atherosclerosis is still controversial. Some clinical trials reported that DPP-4 inhibitors in diabetes patients without a previous history of cardiovascular (CV) events could reduce carotid intima-media thickness (IMT). However, in the PROLOGUE study, which enrolled diabetes patients both with and without previous CV events, sitagliptin failed to slow the progression of carotid IMT relative to conventional therapy.

AIM AND METHODS

We hypothesized that the effect of DPP-4 inhibitors on carotid atherosclerosis might be different between the primary and secondary prevention groups. We performed a post hoc analysis of the PROLOGUE study and compared the effects of sitagliptin and conventional therapy on changes in carotid IMT in subgroups with or without previous CV events.

RESULTS

No significant difference in the IMT changes between the treatment groups was found in the secondary prevention subgroup (sitagliptin, N = 102; conventional, 111). However, in the primary prevention subgroup (sitagliptin, 120; conventional, 109), we found significant inhibitory effects of sitagliptin on mean and max internal carotid artery IMT [estimated group difference: -0.096 mm (95% CI -0.175 to -0.018, p = 0.017) and -0.162 mm (95% CI -0.272 to -0.052, p = 0.004), respectively], although there was no significant difference in the common carotid artery IMT.

CONCLUSIONS

Our data suggest that there is a favorable effect of DPP-4 inhibitor treatment on carotid atherosclerosis in diabetes patients without previous CV events.

Cross-Talk Between Insulin Signaling and G Protein-Coupled Receptors

Diabetes is a major risk factor for the development of heart failure. One of the hallmarks of diabetes is insulin resistance associated with hyperinsulinemia. The literature shows that insulin and adrenergic signaling is intimately linked to each other; however, whether and how insulin may modulate cardiac adrenergic signaling and cardiac function remains unknown. Notably, recent studies have revealed that insulin receptor and β2 adrenergic receptor (β2AR) forms a membrane complex in animal hearts, bringing together the direct contact between 2 receptor signaling systems, and forming an integrated and dynamic network. Moreover, insulin can drive cardiac adrenergic desensitization via protein kinase A and G protein-receptor kinases phosphorylation of the β2AR, which compromises adrenergic regulation of cardiac contractile function. In this review, we will explore the current state of knowledge linking insulin and G protein-coupled receptor signaling, especially β-adrenergic receptor signaling in the heart, with emphasis on molecular insights regarding its role in diabetic cardiomyopathy.

Efficacy and safety of saxagliptin in combination with metformin as initial therapy in Chinese patients with type 2 diabetes: Results from the START study, a multicentre, randomized, double-blind, active-controlled, phase 3 trial

AIM

To assess the efficacy and safety of saxagliptin plus metformin over 24 weeks in pharmacotherapy-naïve Chinese patients with type 2 diabetes mellitus and inadequate glycaemic control (HbA1c, 8.0%-12.0%).

RESEARCH DESIGN AND METHODS

In this multicentre, double-blind, active-controlled study (The START study: NCT02273050, clinicaltrials.gov), patients were randomized (1:1:1) to saxagliptin 5 mg plus metformin, saxagliptin 5 mg plus placebo or metformin plus placebo. Saxagliptin was taken once daily; metformin was taken once/twice daily and was titrated from 500 mg to a maximum of 2000 mg/d over 8 weeks. The primary end point was change in HbA1c from baseline to Week 24.

RESULTS

Data from 630 patients (66.5% men; mean age, 50.1 years; mean body mass index, 26.6 kg/m² ; mean HbA1c, 9.4%; mean diabetes duration, 0.81 years) were analysed. Mean reduction in HbA1c was greater with saxagliptin plus metformin (-3.0%) than with saxagliptin plus placebo (-2.1%; P < .001) or metformin plus placebo (-2.8%; P = .034). Changes in mean fasting plasma glucose, 120-minute postprandial glucose, and 180-minute postprandial glucose area under the curve were greater, and more patients achieved a therapeutic glycaemic response, with saxagliptin plus metformin than with either monotherapy. Hypoglycaemic events were infrequent (<2%). Incidence of adverse events was similar among groups; upper respiratory tract infection and diarrhoea were most common.

CONCLUSIONS

Saxagliptin 5 mg plus metformin significantly improved glycaemic control compared with either monotherapy in treatment-naïve Chinese patients with type 2 diabetes, and was well tolerated.

Cardiovascular disease risk reduction in diabetes through conventional and natural approaches

Type 2 diabetes mellitus (DM) is a significant cause of premature complications and mortality in patients with cardiovascular disease (CVD). In addition to lifestyle modifications, conventional treatment of DM consists of oral hypoglycemic agents, insulin sensitizers, and subcutaneous insulin. In diabetic individuals with or at risk for CVD, aspirin and statin therapy reduce CVD morbidity and mortality. Several natural or herbal supplements have shown potential benefit in patients with CVD and DM. We provide an overview of the current guidelines for treatment of DM and CVD. We then review the literature to describe the efficacy of natural approaches to CVD risk reduction in diabetic patients, with a focus on physical activity, dietary modification, and natural/herbal supplements. Activity and diet improve cardiovascular outcomes in patients with CVD and DM. Natural and herbal supplements have potential for benefit but require further research to determine their efficacy and safety.

Pharmacogenetics of dipeptidyl peptidase 4 inhibitors in a Taiwanese population with type 2 diabetes

Dipeptidyl peptidase-4 (DPP-4) inhibitors are oral anti-hyperglycemic drugs enabling effective glycemic control in type 2 diabetes (T2D). Despite DPP-4 inhibitors' advantages, the patients' therapeutic response varies. In this retrospective cohort study, 171 Taiwanese patients with T2D were classified as sensitive or resistant to treatment based on the mean change in HbA1c levels. Using an assumption-free genome-wide association study, 45 single nucleotide polymorphisms (SNPs) involved in the therapeutic response to DPP-4 inhibitors (P < 1 × 10-4) were identified at or near PRKD1, CNTN3, ASK, and LOC10537792. A SNP located within the fourth intron of PRKD1 (rs57803087) was strongly associated with DPP-4 inhibitor response (P = 3.2 × 10-6). This is the first pharmacogenomics study on DPP-4 inhibitor treatment for diabetes in a Taiwanese population. Our data suggest that genes associated with β-cell function and apoptosis are involved in the therapeutic effect of DPP-4 inhibitors, even in the presence of additional oral anti-diabetic drugs. Our findings provide information on how genetic variants influence drug response and may benefit the development of personalized medicine.

Comparison of Antidiabetic Medications during the Treatment of Atherosclerosis in T2DM Patients

Type 2 diabetes is often associated with arterial atherosclerosis in large blood vessels. We set out to elucidate whether commonly used antidiabetic drugs metformin, sitagliptin, and pioglitazone will reduce atherosclerosis in T2DM patients. We enrolled 176 individuals with type 2 diabetes, which were divided into four treatment groups according to different oral drugs: metformin alone, sitagliptin alone, pioglitazone alone, or combination of metformin and sitagliptin. We assessed changes in glycometabolism, lipid metabolism, cytokine released, and carotid artery intima-media thickness as the readout for improvement in atherosclerosis. HbA1c levels were significantly decreased in all treatment groups (p < 0.05), and FBG levels were also decreased in metformin and combined groups (p < 0.05). In addition, we found IL-6 levels significantly decreased in all treatment groups (p < 0.05). Treatment with pioglitazone showed a significant increase in BMI, HDL, and ADPN levels (p < 0.05). We also observed a significant decrease in NHDL levels in the combined treatment group (p < 0.05). Our data revealed that in addition to hypoglycemic properties of metformin, sitagliptin, and pioglitazone, these drugs also have the potential to promote an anti-inflammatory response. Therefore, combination therapy may be more beneficial for reducing atherosclerosis in patients with type 2 diabetes. The clinical trial is registered with ChiCTR-ORC-17010835.

Synergistic effects of metformin with liraglutide against endothelial dysfunction through GLP-1 receptor and PKA signalling pathway

Metformin or glucagon-like peptide-1 (GLP-1) analogue liraglutide has cardiovascular benefits. However, it is not clear whether their combined treatment have additive or synergistic effects on the vasculature. In this study, human umbilical vein endothelial cells (HUVECs), exposed to palmitic acid (PA) to induce endothelial dysfunction, were incubated with metformin, liraglutide or their combination. High fat diet (HFD)-fed ApoE^−/− mice were randomized into control, metformin, liraglutide, and combination treatment groups. Results showed that in PA-treated HUVECs and HFD-fed ApoE^−/− mice, combination of metformin and liraglutide at lower dose significantly improved endothelial dysfunction compared with the single treatment. Metformin upregulated GLP-1 receptor (GLP-1R) level and protein kinase A (PKA) phosphorylation. However, PKA inhibition but not GLP-1R blockade eliminated the protective effects of metformin on endothelial function. Furthermore, AMPK inhibitor compound C abolished the metformin-mediated upregulation of GLP-1R level and PKA phosphorylation. In conclusion, combination of metformin and liraglutide has synergistic protective effects on endothelial function. Moreover, metformin stimulates GLP-1R and PKA signalling via AMPK-dependent pathway, which may account for its synergistic protective effects with liraglutide. Our findings provide new insights on the interaction between metformin and GLP-1, and provide important information for designing new GLP-1-based therapy strategies in treating type 2 diabetes.

Effectiveness of Vildagliptin in Clinical Practice: Pooled Analysis of Three Korean Observational Studies (the VICTORY Study)

The present observational study aimed to evaluate the clinical effectiveness of vildagliptin with metformin in Korean patients with type 2 diabetes mellitus (T2DM). Data were pooled from the vildagliptin postmarketing survey (PMS), the vildagliptin/metformin fixed drug combination (DC) PMS, and a retrospective observational study of vildagliptin/metformin (fixed DC or free DC). The effectiveness endpoint was the proportion of patients who achieved a glycemic target (HbA1c) of ≤7.0% at 24 weeks. In total, 4303 patients were included in the analysis; of these, 2087 patients were eligible. The mean patient age was 56.99 ± 11.25 years. Overall, 58.94% patients achieved an HbA1c target of ≤7.0% at 24 weeks. The glycemic target achievement rate was significantly greater in patients with baseline HbA1c < 7.5% versus ≥7.5% (84.64% versus 43.97%), receiving care at the hospital versus clinic (67.95% versus 52.33%), and receiving vildagliptin/metformin fixed DC versus free DC (70.69% versus 55.42%). Multivariate logistic regression analysis indicated that disease duration (P < 0.0001), baseline HbA1c (P < 0.0001), and DC type (P = 0.0103) had significant effects on drug effectiveness. Vildagliptin plus metformin appeared as an effective treatment option for patients with T2DM in clinical practice settings in Korea.

Effects of addition of a dipeptidyl peptidase IV inhibitor to metformin on sirolimus-induced diabetes mellitus

The guideline for the management of new-onset diabetes after transplantation recommends metformin (MET) as a first-line drug, and addition of a second-line drug is needed to better control of hyperglycemia. We tested the effect of addition of a dipeptidyl peptidase IV (DPP IV) inhibitor to MET on sirolimus (SRL)-induced diabetes mellitus (DM). In animal model of SRL-induced DM, MET treatment improved pancreatic islet function (blood glucose level and insulin secretion) and attenuated oxidative stress and apoptotic cell death. Addition of a DPP IV inhibitor to MET improved these parameters more than MET alone. An in vitro study showed that SRL treatment increased pancreas beta cell death and production of reactive oxygen species (ROS), and pretreatment of ROS inhibitor, or p38MAPK inhibitor effectively decreased SRL-induced islet cell death. Exendin-4 (EXD), a substrate of DPP IV or MET significantly improved cell viability and decreased ROS production compared with SRL treatment, and combined treatment with the 2 drugs improved both parameters. At the subcellular level, impaired mitochondrial respiration by SRL were partially improved by MET or EXD and much improved further after addition of EXD to MET. Our data suggest that addition of a DPP IV inhibitor to MET decreases SRL-induced oxidative stress and improves mitochondrial respiration. This finding provides a rationale for the combined use of a DPP IV inhibitor and MET in treating SRL-induced DM.

Serum Levels of Soluble CD26/Dipeptidyl Peptidase-IV in Type 2 Diabetes Mellitus and Its Association with Metabolic Syndrome and Therapy with Antidiabetic Agents in Malaysian Subjects

Background

A soluble form of CD26/dipeptidyl peptidase-IV (sCD26/DPP-IV) induces DPP-IV enzymatic activity that degrades incretin. We investigated fasting serum levels of sCD26/DPP-IV and active glucagon-like peptide-1 (GLP-1) in Malaysian patients with type 2 diabetes mellitus (T2DM) with and without metabolic syndrome (MetS), as well as the associations between sCD26/DPP-IV levels, MetS, and antidiabetic therapy.

Methods

We assessed sCD26/DPP-IV levels, active GLP-1 levels, body mass index (BMI), glucose, insulin, A1c, glucose homeostasis indices, and lipid profiles in 549 Malaysian subjects (including 257 T2DM patients with MetS, 57 T2DM patients without MetS, 71 non-diabetics with MetS, and 164 control subjects without diabetes or metabolic syndrome).

Results

Fasting serum levels of sCD26/DPP-IV were significantly higher in T2DM patients with and without MetS than in normal subjects. Likewise, sCD26/DPP-IV levels were significantly higher in patients with T2DM and MetS than in non-diabetic patients with MetS. However, active GLP-1 levels were significantly lower in T2DM patients both with and without MetS than in normal subjects. In T2DM subjects, sCD26/DPP-IV levels were associated with significantly higher A1c levels, but were significantly lower in patients using monotherapy with metformin. In addition, no significant differences in sCD26/DPP-IV levels were found between diabetic subjects with and without MetS. Furthermore, sCD26/DPP-IV levels were negatively correlated with active GLP-1 levels in T2DM patients both with and without MetS. In normal subjects, sCD26/DPP-IV levels were associated with increased BMI, cholesterol, and LDL-cholesterol (LDL-c) levels.

Conclusion

Serum sCD26/DPP-IV levels increased in T2DM subjects with and without MetS. Active GLP-1 levels decreased in T2DM patients both with and without MetS. In addition, sCD26/DPP-IV levels were associated with Alc levels and negatively correlated with active GLP-1 levels. Moreover, metformin monotherapy was associated with reduced sCD26/DPP-IV levels. In normal subjects, sCD26/DPP-IV levels were associated with increased BMI, cholesterol, and LDL-c.

Therapeutic Use of Metformin in Prediabetes and Diabetes Prevention

People with elevated, non-diabetic, levels of blood glucose are at risk of progressing to clinical type 2 diabetes and are commonly termed 'prediabetic'. The term prediabetes usually refers to high-normal fasting plasma glucose (impaired fasting glucose) and/or plasma glucose 2 h following a 75 g oral glucose tolerance test (impaired glucose tolerance). Current US guidelines consider high-normal HbA1c to also represent a prediabetic state. Individuals with prediabetic levels of dysglycaemia are already at elevated risk of damage to the microvasculature and macrovasculature, resembling the long-term complications of diabetes. Halting or reversing the progressive decline in insulin sensitivity and β-cell function holds the key to achieving prevention of type 2 diabetes in at-risk subjects. Lifestyle interventions aimed at inducing weight loss, pharmacologic treatments (metformin, thiazolidinediones, acarbose, basal insulin and drugs for weight loss) and bariatric surgery have all been shown to reduce the risk of progression to type 2 diabetes in prediabetic subjects. However, lifestyle interventions are difficult for patients to maintain and the weight loss achieved tends to be regained over time. Metformin enhances the action of insulin in liver and skeletal muscle, and its efficacy for delaying or preventing the onset of diabetes has been proven in large, well-designed, randomised trials, such as the Diabetes Prevention Program and other studies. Decades of clinical use have demonstrated that metformin is generally well-tolerated and safe. We have reviewed in detail the evidence base supporting the therapeutic use of metformin for diabetes prevention.

[Differential characteristics of type 2 diabetes in the elderly. Role of dipeptidyl peptidase 4 inhibitors]

The prevalence of type 2 diabetes mellitus increases with age, reaching rates around 30% in those over 75 years. The type 2 diabetes mellitus in the elderly has different pathophysiological and clinical characteristics from those of the younger diabetic patient. Some differential aspects in this population are the lower life expectancy and the frequent comorbidity, frailty and associated disability. Avoiding hypoglycemia is a therapeutic priority, given their increased risk of severe hypoglycemia. It is a situation in which the benefits of intensive glycemic control are virtually non-existent, thus prevention of side effects of treatments becomes a priority. Therefore, the goals of glycemic control should be less stringent than in the general population (glycated hemoglobin>7%), and the drugs of choice should be those with a low risk of side effects (especially hypoglycemia) and well tolerated. Dipeptidyl peptidase 4 inhibitors (iDPP4) are particularly useful in this age group, either as a second drug added to metformin monotherapy, or as first line when metformin is contraindicated or not tolerated. In this article the evidence available on the efficacy and tolerance of different pharmacological options available in population over 70 years is reviewed.

Efficacy and safety of teneligliptin, a dipeptidyl peptidase-4 inhibitor, combined with metformin in Korean patients with type 2 diabetes mellitus: a 16-week, randomized, double-blind, placebo-controlled phase III trial

The aim of the present study was to assess the efficacy and safety of teneligliptin in combination with metformin in Korean patients with type 2 diabetes mellitus who were inadequately controlled with metformin monotherapy. Patients [glycated haemoglobin (HbA1c) 7.0-10.0%, on stable metformin ≥1000 mg/day] were randomized 2 : 1 to receive 20 mg teneligliptin plus metformin (n = 136) or placebo plus metformin (n = 68). The primary endpoint was the change in HbA1c levels from baseline to week 16. The mean baseline HbA1c was 7.9% in the teneligliptin group and 7.8% in the placebo group. The differences between the teneligliptin and placebo groups regarding changes in HbA1c and fasting plasma glucose levels were -0.78 % and -1.24 mmol/l (22.42 mg/dl), respectively, at week 16. The incidence of adverse events was similar between the groups. The addition of teneligliptin once daily to metformin was effective and generally well tolerated in Korean patients with type 2 diabetes.

Clinical utility in the treatment of type 2 diabetes with the saxagliptin/metformin fixed combination

Fixed-dose combination (FDC) products represent a widely accepted approach to type 2 diabetes treatment, given that monotherapies sometimes fail to meet the treatment targets - obtaining a sustained reduction in micro- and macrovascular complications. Saxagliptin (SAXA)/metformin (MET) FDC tablets can be used either alone or in combination with glyburide, thiazolidinediones, or insulin. It has been proven that the SAXA/MET combination leads to a significant improvement in glycemic control compared to placebo in patients with type 2 diabetes that is inadequately controlled with MET alone. In addition, this FDC has been proven to be safe for people with diabetes mellitus and established cardiovascular disease, elderly patients, and patients with impaired renal function (>30 mL/minute), with dosage modification. Patient compliance, adherence, and persistence to the therapeutic regimen has been shown to be very good, while the titration of each compound according to the patient's profile is easy, given the availability of different formulations. The SAXA/MET FDC is a patient-friendly, dosage-flexible, and hypoglycemia-safe regimen with very few adverse events and a neutral or even favorable effect on body weight. It achieves significant glycosylated hemoglobin A1c reduction helping the patient to achieve his/her individual glycemic goals.