Preclinical and Clinical Data on Extraglycemic Effects of GLP-1 Receptor Agonists

Thymoquinone activates imidazoline receptor to enhance glucagon-like peptide-1 secretion in diabetic rats

INTRODUCTION

Thymoquinone (TQ) is one of the principal bioactive ingredients proven to exhibit anti-diabetic effects. Recently, glucagon-like peptide-1 (GLP-1) has been found to be involved in antidiabetic effects in rats. The aim of this study was to evaluate the mediation of GLP-1 in the antidiabetic effect of TQ and to understand the possible mechanisms.

MATERIAL AND METHODS

NCI-H716 cells and CHO-K1 cells were used to investigate the effects of TQ on GLP-1 secretion in vitro. In type 1 diabetic rats, the changes in plasma glucose and GLP-1 levels were evaluated with TQ treatment.

RESULTS

The direct effect of TQ on imidazoline receptors (I-Rs) was identified in CHO-K1 cells overexpressing I-Rs. Additionally, in the intestinal NCI-H716 cells that may secrete GLP-1, TQ treatment enhanced GLP-1 secretion in a dose-dependent manner. However, these effects of TQ were reduced by ablation of I-Rs with siRNA in NCI-H716 cells. Moreover, these effects were inhibited by BU224, the imidazoline I2 receptor (I-2R) antagonist. In diabetic rats, TQ increased plasma GLP-1 levels, which were inhibited by BU-224 treatment. Functionally, TQ-attenuated hyperglycemia is also evidenced through GLP-1 using pharmacological manipulations.

CONCLUSIONS

This report demonstrates that TQ may promote GLP-1 secretion through I-R activation to reduce hyperglycemia in type-1 diabetic rats.

Divergent Effect of Central Incretin Receptors Inhibition in a Rat Model of Sporadic Alzheimer's Disease

The incretin system is an emerging new field that might provide valuable contributions to the research of both the pathophysiology and therapeutic strategies in the treatment of diabetes, obesity, and neurodegenerative disorders. This study aimed to explore the roles of central glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) on cell metabolism and energy in the brain, as well as on the levels of these incretins, insulin, and glucose via inhibition of the central incretin receptors following intracerebroventricular administration of the respective antagonists in healthy rats and a streptozotocin-induced rat model of sporadic Alzheimer's disease (sAD). Chemical ablation of the central GIP receptor (GIPR) or GLP-1 receptor (GLP-1R) in healthy and diseased animals indicated a region-dependent role of incretins in brain cell energy and metabolism and central incretin-dependent modulation of peripheral hormone secretion, markedly after GIPR inhibition, as well as a dysregulation of the GLP-1 system in experimental sAD.

The Glucagon-Like Peptide-1 Analog Exenatide Increases Blood Glucose Clearance, Lactate Clearance, and Heart Rate in Comatose Patients After Out-of-Hospital Cardiac Arrest

OBJECTIVES

To investigate the effects of the glucagon-like peptide-1 analog exenatide on blood glucose, lactate clearance, and hemodynamic variables in comatose, resuscitated out-of-hospital cardiac arrest patients.

DESIGN

Predefined post hoc analyzes from a double-blind, randomized clinical trial.

SETTING

The ICU of a tertiary heart center.

PATIENTS

Consecutive sample of adult, comatose patients undergoing targeted temperature management after out-of-hospital cardiac arrest from a presumed cardiac cause, irrespective of the initial cardiac rhythm.

INTERVENTIONS

Patients were randomized 1:1 to receive 6 hours and 15 minutes of infusion of either 17.4 μg of the glucagon-like peptide-1 analog exenatide (Byetta; Lilly) or placebo within 4 hours from sustained return of spontaneous circulation. The effects of exenatide were examined on the following prespecified covariates within the first 6 hours from study drug initiation: lactate level, blood glucose level, heart rate, mean arterial pressure, and combined dosage of norepinephrine and dopamine.

MEASUREMENTS AND MAIN RESULTS

The population consisted of 106 patients receiving either exenatide or placebo. During the first 6 hours from study drug initiation, the levels of blood glucose and lactate decreased 17% (95% CI, 8.9-25%; p = 0.0004) and 21% (95% CI, 6.0-33%; p = 0.02) faster in patients receiving exenatide versus placebo, respectively. Exenatide increased heart rate by approximately 10 beats per minute compared to placebo (p < 0.0001). There was no effect of exenatide on other hemodynamic variables.

CONCLUSIONS

In comatose out-of-hospital cardiac arrest patients, infusion with exenatide lowered blood glucose and resulted in increased clearance of lactate as well as increased heart rate. The clinical importance of these physiologic effects remains to be investigated.

Cardiovascular risk in chronic kidney disease: what is new in the pathogenesis and treatment?

The prevalence of chronic kidney disease (CKD) has increased markedly over past decades due to the aging of the worldwide population. Despite the progress in the prevention and treatment, the cardiovascular (CV) morbidity and mortality remain high among patients with CKD. Although CKD is a progressive and irreversible condition, it is possible to slow decreasing kidney function, as well as the development and progression of associated with kidney disease comorbidities. Diabetes mellitus has become major cause of CKD worldwide. It is estimated that the prevalence of diabetes will increase from 425 million worldwide in 2017 to 629 million by 2045, substantially the percentage of diabetic nephropathy among CKD patients is set to rise markedly. The results of multicenter trials concerning novel antidiabetic drugs suggest that efficacy in reducing CV risk is independent of the improvement in glycemic control. This review discusses underlying causes of high CV risk and strategies reducing individual burden among CKD patients.

Exenatide Add-on to Continuous Subcutaneous Insulin Infusion Therapy Reduces Bolus Insulin Doses in Patients with Type 2 Diabetes: A Randomized, Controlled, Open-Label Trial

INTRODUCTION

The objective of this study was to investigate the effect of adding exenatide to continuous subcutaneous insulin infusion (CSII) therapy on the precise insulin doses required by type 2 diabetic patients to maintain glycemic control.

METHODS

This was a single-center, randomized, controlled, open-label trial. Uncontrolled T2D patients were recruited between March 2010 and November 2011 at Nanjing First Hospital, China. Subjects were randomly assigned (1:1) to either an exenatide add-on to CSII group or a CSII therapy only (i.e., control) group (n = 18, respectively) for 5 weeks. Patients were subjected to 3 days of continuous glucose monitoring (CGM) during the screening period and after therapy. The precise insulin doses, the times taken by the patients to achieve euglycemic control, and the mean amplitude of glycemic excursion (MAGE) at the endpoint were compared between the two groups. The primary endpoint was precise insulin dose differences between groups from baseline to the endpoint.

RESULTS

A total of 36 subjects were admitted as inpatients. Patients in the exenatide add-on therapy group needed less insulin titration time to achieve glycemic control (3.67 ± 1.33 vs. 4.78 ± 1.00 days, P = 0.028) and significantly lower bolus insulin doses than the control group at the endpoint (total bolus, 0.13 ± 0.03 vs. 0.17 ± 0.04 U/kg, P = 0.02, breakfast bolus, 0.05 ± 0.01 vs. 0.06 ± 0.01 U/kg, P = 0.01, lunch bolus, 0.04 ± 0.01 vs. 0.06 ± 0.01 U/kg, P = 0.01, dinner bolus, 0.04 ± 0.01 vs. 0.05 ± 0.01 U/kg, P = 0.01, respectively). Moreover, the CGM data showed that patients in the exenatide add-on therapy group exhibited a significant reduction in MAGE as compared to the control group (2.96 ± 1.14 vs. 4.21 ± 1.39 mmol/L, P = 0.012).

CONCLUSION

Our data suggest that adding exenatide therapy to CSII therapy leads to an improvement in glycemic excursions and the use of smaller bolus insulin doses.

TRIAL REGISTRATION

Chinese Clinical Trial Registry identifier, ChiCTR-PPR-15007045.

Comparative effectiveness of incretin-based therapies and the risk of death and cardiovascular events in 38,233 metformin monotherapy users

There is limited comparative effectiveness evidence to guide approaches to managing diabetes in individuals failing metformin monotherapy. Our aim was to compare the incidence of all-cause mortality and major adverse cardiovascular events (MACEs) among new metformin monotherapy users initiating a dipeptidyl-peptidase-4 inhibitor (DPP4i), glucagon-like peptide-1 receptor agonist (GLP-1RA), sulfonylurea (SU), thiazolidinedione, or insulin.We conducted a cohort study using the UK-based Clinical Practice Research Datalink. Participants included a cohort of 38,233 new users of metformin monotherapy who initiated a 2nd antidiabetic agent between January 1, 2007 and December 31, 2012 with follow-up until death, disenrollment, therapy discontinuation, or study end-date. A subcohort of 21,848 patients with linked hospital episode statistics (HES) and Office of National Statistics (ONS) data were studied to include MACE and cardiovascular-related death. The primary exposure contrasts, defined a priori, were initiation of a DPP4i versus an SU and initiation of a GLP-1RA versus an SU following metformin monotherapy. Cox proportional hazards models were used to assess the relative differences in time to mortality and MACE between exposure contrasts, adjusting for important baseline patient factors and comedications used during follow-up.The main study cohort consisted of 6213 (16%) patients who initiated a DPP4i, 25,916 initiated an SU (68%), 4437 (12%) initiated a TZD, 487 (1%) initiated a GLP-1RA, 804 (2%) initiated insulin, and 376 (1%) initiated a miscellaneous agent as their 2nd antidiabetic agent. Mean age was 62 years, 59% were male, and mean glycated hemoglobin was 8.8% (92.6 mmol/mol). Median follow-up was 2.7 years (interquartile range 1.3-4.2). Mortality rates were 8.2 deaths/1000 person-years for DPP4i and 19.1 deaths/1000 person-years for SU initiators. Adjusted hazards ratio (aHR) for mortality in DPP4i versus SU initiators = 0.58, 95% CI 0.46 to 0.73, P < 0.001. MACE rates were 19.1/1000 person-years for DPP4i initiators, 15.9/1000 person-years for GLP1-RA initiators versus 33.1/1000 person-years for SU initiators (aHR: DPP4i vs SU initiators = 0.64, 95%CI 0.52-0.80; GLP1RA vs SU initiators = 0.73, 95% CI 0.34-1.55).In this cohort of metformin monotherapy users, 2nd-line DPP4i use was associated with a 42% relative reduction in all-cause mortality and 36% reduction in MACE versus SUs, the most common 2nd-line therapy in our study. GLP-1RAs were not associated with adverse events in this cohort.

Safety and Tolerability of Glucagon-Like Peptide-1 Receptor Agonists Utilizing Data from the Exenatide Clinical Trial Development Program

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have demonstrated benefits for patients with type 2 diabetes including A1C reduction and weight loss with minimal risk of hypoglycemia. This article provides an evidence-based update of safety and tolerability considerations for the clinical use of GLP-1RAs as a class, with a specific detailed review of data from the exenatide clinical trial development program, which has the longest history and availability of safety and tolerability data as the first-approved GLP-1RA. Specific areas covered include comparative risk of hypoglycemia, as well as pancreatic, thyroid, and cardiovascular safety data; clinical guidance regarding current safety and tolerability data is also reviewed.

Beat it early: putative renoprotective haemodynamic effects of oral hypoglycaemic agents

Diabetic kidney disease represents a considerable burden; around one-third of patients with type 2 diabetes develop chronic kidney disease. In health, the kidneys play an important role in the regulation of glucose homeostasis via glucose utilization, gluconeogenesis and glucose reabsorption. In patients with diabetes, renal glucose homeostasis is significantly altered with an increase in both gluconeogenesis and renal tubular reabsorption of glucose. Environmental factors, both metabolic (hyperglycaemia, obesity and dyslipidaemia) and haemodynamic, together with a genetic susceptibility, lead to the activation of pro-oxidative, pro-inflammatory and pro-fibrotic pathways resulting in kidney damage. Hyperfiltration and its haemodynamic-driven insult to the kidney glomeruli is an important player in proteinuria and progression of kidney disease towards end-stage renal failure. Control of glycaemia and blood pressure are the mainstays to prevent kidney damage and slow its progression. There is emerging evidence that some hypoglycaemic agents may have renoprotective effects which are independent of their glucose-lowering effects. Sodium-glucose co-transporter-2 (SGLT-2) inhibitors may exert a renoprotective effect by a number of mechanisms including restoring the tubuloglomerular feedback mechanism and lowering glomerular hyperfiltration, reducing inflammatory and fibrotic markers induced by hyperglycaemia thus limiting renal damage. Simultaneous use of an SGLT-2 inhibitor and blockade of the renin-angiotensin-aldosterone system may be a strategy to slow progression of diabetic nephropathy more than either drug alone. The use of dipeptidyl peptidase-4 inhibitors and glucagon-like peptide 1 receptor agonists may exert a renoprotective effect by reducing inflammation, fibrosis and blood pressure. Given the burden of diabetic kidney disease, any additional renoprotective benefit with hypoglycaemic therapy is to be welcomed. Large randomized controlled trials are currently underway investigating if these new anti-diabetic agents can provide renoprotection in diabetes.

Comparative Assessment of Lixisenatide, Exenatide, and Liraglutide Pen Devices: A Pilot User-Based Study

BACKGROUND

Glucagon-like peptide-1 (GLP-1) receptor agonists are a relatively recent addition to the treatment options for type 2 diabetes mellitus (T2DM) and are administered using prefilled pen devices.

METHOD

In this open-label task and interview-based pilot study, 3 GLP-1 receptor agonist pen devices-exenatide (Byetta^®, Bristol-Myers Squibb/AstraZeneca), liraglutide (Victoza^®, Novo Nordisk), and lixisenatide (Lyxumia^®, Sanofi-Aventis)-were comparatively assessed in a randomized order in 30 participants with T2DM for ease of use, using a series of key performance measures (time taken to complete a series of tasks, number of user errors [successful performance], and user satisfaction rating). Linear and logistic regression analysis was conducted for the lixisenatide and liraglutide pens versus the exenatide pen. Participants' mean age was 60 years; 27% and 20% of the participants had visual impairments and reduced manual dexterity, respectively.

RESULTS

Tasks were completed faster (P < .001) and with higher successful performance (P = .001) with the lixisenatide pen than with the exenatide pen, whereas the liraglutide pen was not statistically significant versus the exenatide pen on these parameters. Overall, user satisfaction was statistically higher for the lixisenatide and liraglutide pens versus the exenatide pen (P < .001 for both).

CONCLUSIONS

Lixisenatide and liraglutide pens are associated with higher user satisfaction compared with the exenatide pen. In addition, the lixisenatide pen is faster and results in fewer errors than its comparator (exenatide). The lixisenatide pen may therefore be a suitable choice for patients with T2DM, including older and pen device-naïve patients, and those with visual impairments and reduced manual dexterity.

Mechanisms and clinical efficacy of lixisenatide for the management of type 2 diabetes

INTRODUCTION

"Incretin-based" therapies, such as the glucagon-like peptide-1 (GLP-1) receptor agonists, represent a major advance in type 2 diabetes mellitus (T2DM) treatment. GLP-1 receptor agonists differ substantially in their duration of action, frequency of administration and clinical profile.

METHODS

This article reviews the mechanisms of action and clinical evidence for GLP-1 receptor targeting and discusses differences between GLP-1 therapies, focusing particularly on clinical data for the GLP-1 receptor agonist, lixisenatide.

RESULTS

GLP-1 therapies target islet cell "defects" of insufficient insulin and excessive glucagon secretion in T2DM, in a glucose-dependent manner, with minimal risk of hypoglycemia. Different GLP-1 therapies exert differential effects on fasting and postprandial glycemia (both being major determinants of glycemic control). They also slow gastric emptying to different extents, probably accounting for different effects to reduce postprandial glycemia. The GetGoal phase 3 studies in T2DM have confirmed the efficacy of once-daily lixisenatide in reducing plasma glucose and glycated hemoglobin (HbA1c), with a pronounced lowering of postprandial plasma glucose (PPG), as monotherapy and as add-on to oral antidiabetic drugs and to basal insulin. Lixisenatide's ability to diminish PPG is probably partly mediated by its marked ability to delay gastric emptying. Lixisenatide is generally well tolerated, with possibly better gastrointestinal tolerability and lower risk of hypoglycemia than exenatide immediate release. Lixisenatide is associated with a beneficial effect on weight, with either no change or a decrease in body weight when administered as add-on therapy to basal insulin in overweight patients with T2DM.

CONCLUSIONS

Lixisenatide improves glycemic control, by primarily affecting PPG, while preventing weight gain or reducing body weight with a low risk of hypoglycemia in T2DM. Lixisenatide is likely to represent a significant advance in the management of T2DM, perhaps particularly in those patients with relatively faster gastric emptying and lower levels of HbA1c, including those receiving basal insulin.

Effects of HbA1c and weight reduction on blood pressure in patients with type 2 diabetes mellitus treated with exenatide*

AIM

Treatment of patients with type 2 diabetes with glucagon-like peptide-1 (GLP-1) receptor agonist exenatide has showed improvements in glycaemic control coupled with weight loss and lowered blood pressure (BP). We examined the synergy between improved glycaemia and weight loss on BP reduction in patients treated with either exenatide twice daily (BID) or once weekly (QW).

METHODS

Combining data from three controlled trials, 686 (53% male) patients [baseline mean ± SD: age 55 ± 10 years, weight 95 ± 20 kg, systolic blood pressure (SBP)/diastolic blood pressure (DBP) 130/79 ± 15/9 mmHg, HbA(1c) 8.3 ± 1.1%] treated with exenatide QW (n = 541) or BID (n = 145) were observed over 26 weeks. Using weighted means (WMs) of the longitudinal measures of HbA(1c) and weight, patients were subdivided into four groups at each visit by glycaemic and weight responses; patients who failed to reduce both HbA(1c) and weight below WMs became the reference group (R). The other three groups corresponded to patients with HbA(1c) reduction (A), weight reduction (W) and both HbA(1c) and weight reduction (AW).

RESULTS

Compared with R, patients in AW, A and W groups had a significantly higher likelihood of improving SBP <130 mmHg by 88, 30 and 61%, respectively. Compared with R, patients in AW, A and W had 63, 13 and 45% higher likelihood of improving DBP <80 mmHg.

CONCLUSION

Although the mechanism of BP-lowering effect of exenatide is not established, it appears that the short-term dynamics of BP is related to concomitant effects on glycaemia and body weight. These data offer a preliminary insight into the possible cardiometabolic effects of GLP-1 receptor agonism.

Exendin-4 attenuates lipopolysaccharides induced inflammatory response but does not protects H9c2 cells from apoptosis

BACKGROUND

Glucagon-like peptide-1 (GLP-1) and its analogues are reported to exert wide-ranging cardiovascular actions in preclinical and clinical studies. We thus investigated whether the GLP-1 receptor agonist, exendin-4, has inhibitory effects on LPS-stimulated inflammatory response in cardiomyoblasts.

METHODS

H9c2 cardiomyoblasts were exposed to LPS and treated with exendin-4. Expressions of proinflammatory mediators were assessed using quantitative real-time PCR. Nuclear localization of NF-κB was examined using immunoblotting. mRNA expression of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production were evaluated by q PCR and NO assay. Furthermore, anti-apoptotic effect of exendin-4 in LPS-stimulated H9c2 cells was determined using qPCR and immunoblot.

RESULTS

Exposure to LPS increased mRNA expressions of TNF-α, COX-2 and MMP-9 in H9c2 cells. It also caused increases in iNOS mRNA expression and NF-κB nuclear translocation. Exendin-4 dose-dependently downregulated mRNA levels of TNF-α, COX-2 and MMP-9 in LPS-stimulated H9c2 cells. It also reduced NF-κB nuclear translocation. Treatment with exendin-4 showed no effect on LPS-induced apoptosis in H9c2 cells.

CONCLUSIONS

Exendin-4 exerts an effect on cardiomyoblast exposed to LPS by inhibiting mRNA expression of inflammatory mediators and suppressing NF-κB activation. These effects are consistent with some of the observed anti-inflammatory properties of exendin-4, as well as its beneficial actions on the cardiovascular system.

The role of incretin therapy at different stages of diabetes

The pathogenetic mechanisms causing type 2 diabetes are complex, and include a significant reduction of the incretin effect. In patients with type 2 diabetes, GLP-1 secretion may be impaired, while GIP secretion seems unaffected. In contrast, the insulinotropic activity of GIP is severely altered, whereas that of GLP-1 is maintained to a great extent. Better understanding of the role of incretin hormones in glucose homeostasis has led to the development of incretin-based therapies that complement and offer important advantages over previously used agents. Incretin-based agents have significant glucose-lowering effects, promote weight loss (or are weight-neutral), inhibit glucagon secretion while maintaining counter-regulatory mechanisms, exhibit cardiovascular benefits, and protect β-cells while possessing a low risk profile. At present, incretin-based therapies are most widely used as add on to metformin to provide sufficient glycemic control after metformin failure. However, they are also recommended as monotherapy early in the disease course, and later in triple combination. These agents may also be a promising therapeutic tool in prediabetic subjects. Therefore, a therapeutic algorithm is needed for their optimal application at different stages of diabetes, as suggested in this article.

Liraglutide Therapy for Type 2 Diabetes: Overcoming Unmet Needs

Although advances have been achieved in the management of type 2 diabetes, current treatment options for patients with this disease still fail to address disease progression, glycaemic control remains suboptimal and therapies are often associated with weight gain and hypoglycaemia. Thus, new antidiabetes therapies are being sought. Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones that have been the recent focus of research. The physiological action of GLP-1, in particular, has demonstrated its potential in addressing the therapeutic needs of patients with type 2 diabetes. To exploit this action, liraglutide, a human GLP-1 analogue that shares 97% of its amino acid sequence identity with native GLP-1, has been developed. In a recent phase 3 trial programme (LEAD, Liraglutide Effect and Action in Diabetes), treatment with liraglutide was associated with substantial improvements in glycaemic control and low risk of hypoglycaemia. In addition, reductions in weight and systolic blood pressure were reported. There is also an indication that liraglutide is capable of improving β-cell function and increasing β-cell mass. Thus, liraglutide may overcome the limitations with current therapies and help to address the unmet clinical needs of patients with type 2 diabetes.