Effect of exercise combined with glucagon-like peptide-1 receptor agonist treatment on cardiac function: A randomized double-blind placebo-controlled clinical trial

In patients with type 2 diabetes, both supervised exercise and treatment with the glucagon-like peptide-1 (GLP-1) receptor agonist (GLP-1RA) liraglutide may improve cardiac function. We evaluated cardiac function before and after 16 weeks of treatment with the GLP-1RA liraglutide or placebo, combined with supervised exercise, in 33 dysregulated patients with type 2 diabetes on diet and/or metformin. Early diastolic myocardial tissue velocity was improved by exercise in the placebo group (mean ± standard deviation [s.d.] -7.1 ± 1.6 to -7.7 ± 1.8 cm/s, P  = .01), but not in the liraglutide group (-7.1 ± 1.4 to -7.0 ± 1.4 cm/s, P  = .60; between groups, P  = .02). Similarly, the mean ± s.d. ratio of early and atrial mitral annular tissue velocities improved in the placebo group (1.0 ± 0.4 to 1.2 ± 0.4, P  = .003), but not in the liraglutide group (1.0 ± 0.3 to 1.0 ± 0.3, P  = .87; between groups, P  = .03). We found no significant differences in heart rate, left ventricular (LV) structure or function within or between the groups. In conclusion, the addition of liraglutide to exercise in sedentary patients with dysregulated type 2 diabetes may blunt the suggested beneficial effect of exercise on LV diastolic function.

Placebo-controlled, randomized trial of the addition of once-weekly glucagon-like peptide-1 receptor agonist dulaglutide to titrated daily insulin glargine in patients with type 2 diabetes (AWARD-9)

AIM

To compare the addition of weekly dulaglutide vs the addition of placebo to titrated glargine in patients with type 2 diabetes (T2D) with sub-optimum glycated haemoglobin (HbA1c) concentration.

MATERIALS AND METHODS

Patients (N = 300) from this phase III, double-blind, parallel-arm, placebo-controlled study were randomized to weekly subcutaneous injections of dulaglutide 1.5 mg or placebo with titrated daily glargine (mean ± standard deviation baseline dose: 39 ± 22 U), with or without metformin (≥1500 mg/d). The primary endpoint was superiority of dulaglutide/glargine to placebo/glargine with regard to change from baseline in HbA1c level at 28 weeks.

RESULTS

Least squares (LS) mean ± standard error (s.e.) HbA1c changes from baseline were -1.44 ± 0.09% (-15.74 ± 0.98 mmol/mol) with dulaglutide/glargine and -0.67 ± 0.09% (-7.32 ± 0.98 mmol/mol) with placebo/glargine at 28 weeks (LS mean difference [95% confidence interval] -0.77% [-0.97, -0.56]; P < .001). Body weight decreased with dulaglutide/glargine and increased with placebo/glargine (LS mean difference: -2.41 ± 0.39 kg; P < .001). Increases from baseline in mean glargine dose were significantly smaller with dulaglutide/glargine vs placebo/glargine (13 ± 2 U [0.1 ± 0.02 U/kg] vs 26 ± 2 U [0.3 ± 0.02 U/kg], respectively; P < .001; LS mean ± s.e. final dose: dulaglutide/glargine, 51 ± 2 U; placebo/glargine, 65 ± 2 U). The hypoglycaemia rate (≤3.9 mmol/L threshold) was 7.69 ± 15.15 and 8.56 ± 16.13 events/patient/year, respectively (P = .488). One episode of severe hypoglycaemia occurred in the dulaglutide/glargine group. Common gastrointestinal adverse events with dulaglutide were nausea (12.0%), diarrhoea (11.3%) and vomiting (6.0%).

CONCLUSIONS

Weekly dulaglutide 1.5 mg added to basal insulin is an efficacious and well tolerated treatment option for patients with T2D.

Treatment with GLP1 receptor agonists reduce serum CRP concentrations in patients with type 2 diabetes mellitus: A systematic review and meta-analysis of randomized controlled trials

AIM

To undertake a systematic review and meta-analysis of randomized controlled trials of the effect of glucagon-like peptide-1 receptor agonist (GLP-1 RAs) therapy on serum C-reactive protein (CRP) concentrations.

METHOD

PubMed-Medline, SCOPUS, Web of Science and Google Scholar databases were searched for the period up until March 16, 2016. Prospective studies evaluating the impact of GLP-1 RAs on serum CRP were identified. A random effects model (using the DerSimonian-Laird method) and generic inverse variance methods were used for quantitative data synthesis. Sensitivity analysis was conducted using the leave-one-out method. Heterogeneity was quantitatively assessed using the I² index. Random effects meta-regression was performed using unrestricted maximum likelihood method to evaluate the impact of potential moderator. International Prospective Register for Systematic Reviews (PROSPERO) number CRD42016036868.

RESULTS

Meta-analysis of the data from 7 treatment arms revealed a significant reduction in serum CRP concentrations following treatment with GLP-1 RAs (WMD -2.14 (mg/dL), 95% CI -3.51, -0.78, P=0.002; I² 96.1%). Removal of one study in the meta-analysis did not change the result in the sensitivity analysis (WMD -2.14 (mg/dL), 95% CI -3.51, -0.78, P=0.002; I² 96.1%), indicating that our results could not be solely attributed to the effect of a single study. Random effects meta-regression was performed to evaluate the impact of potential moderator on the estimated effect size. Changes in serum CRP concentration were associated with the duration of treatment (slope -0.097, 95% CI -0.158, -0.042, P<0.001).

CONCLUSIONS

This meta-analysis suggests that GLP-1 RAs therapy causes a significant reduction in CRP.

Baseline characteristics of patients enrolled in the Exenatide Study of Cardiovascular Event Lowering (EXSCEL)

BACKGROUND

EXSCEL is a randomized, double-blind, placebo-controlled trial examining the effect of exenatide once-weekly (EQW) versus placebo on time to the primary composite outcome (cardiovascular death, nonfatal myocardial infarction or nonfatal stroke) in patients with type 2 diabetes mellitus (DM) and a wide range of cardiovascular (CV) risk.

METHODS

Patients were enrolled at 688 sites in 35 countries. We describe their baseline characteristics according to prior CV event status and compare patients with those enrolled in prior glucagon-like peptide-1 receptor agonist (GLP-1RA) outcomes trials.

RESULTS

Of a total of 14,752 participants randomized between June 2010 and September 2015, 6,788 (46.0%) patients were enrolled in Europe; 3,708 (25.1%), North America; 2,727 (18.5%), Latin America; and 1,529 (10.4%), Asia Pacific. Overall, 73% had at least one prior CV event (70% coronary artery disease, 24% peripheral arterial disease, 22% cerebrovascular disease). The median (IQR) age was 63 years (56, 69), 38% were female, median baseline HbA1c was 8.0% (7.3, 8.9) and 16% had a prior history of heart failure. Those without a prior CV event were younger with a shorter duration of diabetes and better renal function than those with at least one prior CV event. Compared with prior GLP-1RA trials, EXSCEL has a larger percentage of patients without a prior CV event and a notable percentage who were taking a dipeptidyl peptidase-4 inhibitor at baseline (15%).

CONCLUSIONS

EXSCEL is one of the largest global GLP-1RA trials, evaluating the safety and efficacy of EQW with a broad patient population that may extend generalizability compared to prior GLP-1RA trials (ClinicalTrials.gov number, NCT01144338).

Critical role for GLP-1 in symptomatic post-bariatric hypoglycaemia

AIMS/HYPOTHESIS

Post-bariatric hypoglycaemia (PBH) is a rare, but severe, metabolic disorder arising months to years after bariatric surgery. It is characterised by symptomatic postprandial hypoglycaemia, with inappropriately elevated insulin concentrations. The relative contribution of exaggerated incretin hormone signalling to dysregulated insulin secretion and symptomatic hypoglycaemia is a subject of ongoing inquiry. This study was designed to test the hypothesis that PBH and associated symptoms are primarily mediated by glucagon-like peptide-1 (GLP-1).

METHODS

We conducted a double-blinded crossover study wherein eight participants with confirmed PBH were assigned in random order to intravenous infusion of the GLP-1 receptor (GLP-1r) antagonist. Exendin (9-39) (Ex-9), or placebo during an OGTT on two separate days at the Stanford University Clinical and Translational Research Unit. Metabolic, symptomatic and pharmacokinetic variables were evaluated. Results were compared with a cohort of BMI- and glucose-matched non-surgical controls (NSCs).

RESULTS

Infusion of Ex-9 decreased the time to peak glucose and rate of glucose decline during OGTT, and raised the postprandial nadir by over 70%, normalising it relative to NSCs and preventing hypoglycaemia in all PBH participants. Insulin AUC and secretion rate decreased by 57% and 71% respectively, and peak postprandial insulin was normalised relative to NSCs. Autonomic and neuroglycopenic symptoms were significantly reduced during Ex-9 infusion.

CONCLUSIONS/INTERPRETATION

GLP-1r blockade prevented hypoglycaemia in 100% of individuals, normalised beta cell function and reversed neuroglycopenic symptoms, supporting the conclusion that GLP-1 plays a primary role in mediating hyperinsulinaemic hypoglycaemia in PBH. Competitive antagonism at the GLP-1r merits consideration as a therapeutic strategy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02550145.

Novel Monoclonal Antibody Is an Allosteric Insulin Receptor Antagonist That Induces Insulin Resistance

A hallmark of type 2 diabetes is impaired insulin receptor (IR) signaling that results in dysregulation of glucose homeostasis. Understanding the molecular origins and progression of diabetes and developing therapeutics depend on experimental models of hyperglycemia, hyperinsulinemia, and insulin resistance. We present a novel monoclonal antibody, IRAB-B, that is a specific, potent IR antagonist that creates rapid and long-lasting insulin resistance. IRAB-B binds to the IR with nanomolar affinity and in the presence of insulin efficiently blocks receptor phosphorylation within minutes and is sustained for at least 3 days in vitro. We further confirm that IRAB-B antagonizes downstream signaling and metabolic function. In mice, a single dose of IRAB-B induces rapid onset of hyperglycemia within 6 h, and severe hyperglycemia persists for 2 weeks. IRAB-B hyperglycemia is normalized in mice treated with exendin-4, suggesting that this model can be effectively treated with a GLP-1 receptor agonist. Finally, a comparison of IRAB-B with the IR antagonist S961 shows distinct antagonism in vitro and in vivo. IRAB-B appears to be a powerful tool to generate both acute and chronic insulin resistance in mammalian models to elucidate diabetic pathogenesis and evaluate therapeutics.

Exendin-4 decreases ghrelin levels through mTOR signaling

Exendin-4 (EX-4), a long-acting glucagon-like peptide-1 receptor (GLP-1R) agonist, regulates feeding behavior through its ability to inhibit gastric emptying. Ghrelin, a gastric hormone, provides a hunger signal to the central nervous system to stimulate appetite. Here, we report that EX-4 suppresses ghrelin production through the mTORC1-dependent mechanism. Central administration of EX-4 reduces gastric, hypothalamic and plasma ghrelin in both C57BL/6J mice and diet induced obese mice. These changes were associated with a significant increase in mTORC1 activity. Both GLP-1 and EX-4 suppressed the expression and secretion of ghrelin in cultured mHypoE-42 cells, a hypothalamic cell line. These effects were associated with significant changes in mTOR signaling. Inhibition of mTORC1 activity by mTOR siRNA or rapamycin abolished the suppression of ghrelin production induced by GLP-1 and EX-4 in mHypoE-42 cells. Our results identify mTORC1 as a critical signaling pathway for the downregulation of ghrelin induced by activation of GLP-1R.

[Cardiovascular protection of patients with type 2 diabetes : from EMPA-REG OUTCOME to LEADER]

Two clinical trials demonstrate the superiority versus a placebo of two antidiabetic drugs in patients with type 2 diabetes and high cardiovascular risk. Empagliflozin, an inhibitor of sodium-glucose type 2 (SGLT2) cotransporters, in EMPA-REG OUTCOME, and liraglutide, an agonist of glucagon-like peptide-1 (GLP-1) receptors, in LEADER, showed a significant reduction in major cardiovascular events (- 14 and - 13 %, respectively), cardiovascular mortality (- 38 and - 22 %, respectively) and all-cause mortality (- 32 and - 15 %, respectively). A lower progression of kidney disease and less renal events were also reported. The underlying protective mechanisms remain controverted as the discussion whether the benefits are specific to each medication or could be extended to other molecules of these two pharmacological classes.

Quantification of the Contribution of GLP-1 to Mediating Insulinotropic Effects of DPP-4 Inhibition With Vildagliptin in Healthy Subjects and Patients With Type 2 Diabetes Using Exendin [9-39] as a GLP-1 Receptor Antagonist

We quantified the contribution of GLP-1 as a mediator of the therapeutic effects of dipeptidyl peptidase 4 (DPP-4) inhibition (vildagliptin) by using the GLP-1 receptor antagonist exendin [9-39] in patients with type 2 diabetes and in healthy subjects. Thirty-two patients with type 2 diabetes and 29 age- and weight-matched healthy control subjects were treated in randomized order with 100 mg once daily vildagliptin or placebo for 10 days. Meal tests were performed (days 9 and 10) without and with a high-dose intravenous infusion of exendin [9-39]. The main end point was the ratio of the areas under the curve (AUCs) of integrated insulin secretion rates (total AUCISR) and glucose (total AUCglucose) over 4 h after the meal. Vildagliptin treatment more than doubled responses of intact GLP-1 and glucose-dependent insulinotropic polypeptide and lowered glucose responses without changing AUCISR/AUCglucose in healthy subjects. Vildagliptin significantly increased this ratio by 10.5% in patients with type 2 diabetes, and exendin [9-39] reduced it (both P < 0.0001). The percentage reduction in the AUCISR/AUCglucose ratio achieved with exendin [9-39] was significantly smaller after vildagliptin treatment than after placebo treatment (P = 0.026) and was equivalent to 47 ± 5% of the increments due to vildagliptin. Thus, other mediators appear to contribute significantly to the therapeutic effects of DPP-4 inhibition.

Acute renal effects of the GLP-1 receptor agonist exenatide in overweight type 2 diabetes patients: a randomised, double-blind, placebo-controlled trial

AIMS/HYPOTHESIS

This study aimed to investigate the acute renal effects of the glucagon-like peptide-1 receptor agonist (GLP-1RA) exenatide in type 2 diabetes patients.

METHODS

We included overweight (BMI 25-40 kg/m(2)) men and postmenopausal women, aged 35-75 years with type 2 diabetes (HbA1c 48-75 mmol/mol; 6.5-9.0%) and estimated GFR ≥ 60 ml min(-1) 1.73 m(-2). Exenatide or placebo (NaCl solution, 154 mmol/l) was administrated intravenously in an acute, randomised, double-blind, placebo-controlled trial conducted at the Diabetes Center VU University Medical Center (VUMC). GFR (primary endpoint) and effective renal plasma flow (ERPF) were determined by inulin and para-aminohippurate clearance, respectively, based on timed urine sampling. Filtration fraction (FF) and effective renal vascular resistance (ERVR) were calculated, and glomerular hydrostatic pressure (PGLO) and vascular resistance of the afferent (RA) and efferent (RE) renal arteriole were estimated. Tubular function was assessed by absolute and fractional excretion of sodium (FENa), potassium (FEK) and urea (FEU), in addition to urine osmolality, pH and free water clearance. Renal damage markers, BP and plasma glucose were also determined.

RESULTS

Of the 57 patients randomised by computer, 52 were included in the final analyses. Exenatide (n = 24) did not affect GFR (mean difference +2 ± 3 ml min(-1) 1.73 m(-2), p = 0.489), ERPF, FF, ERVR or PGLO, compared with placebo (n = 28). Exenatide increased RA (p < 0.05), but did not change RE. Exenatide increased FENa, FEK, urine osmolality and pH, while FEU, urinary flow and free water clearance were decreased (all p < 0.05). Osmolar clearance and renal damage makers were not affected. Diastolic BP and mean arterial pressure increased by 3 ± 1 and 6 ± 2 mmHg, respectively, whereas plasma glucose decreased by 1.4 ± 0.1 mmol/l (all p < 0.05).

CONCLUSIONS/INTERPRETATION

Exenatide infusion does not acutely affect renal haemodynamics in overweight type 2 diabetes patients at normal filtration levels. Furthermore, acute GLP-1RA administration increases proximal sodium excretion in these patients.

TRIAL REGISTRATION

ClincialTrials.gov NCT01744236 FUNDING : The research leading to these results has been funded from: (1) the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement number 282521 - the SAFEGUARD project; and (2) the Dutch Kidney Foundation, under grant agreement IP12.87.

Glucagon orchestrates stress-induced hyperglycaemia

Hyperglycaemia is commonly observed on admission and during hospitalization for medical illness, traumatic injury, burn and surgical intervention. This transient hyperglycaemia is referred to as stress-induced hyperglycaemia (SIH) and frequently occurs in individuals without a history of diabetes. SIH has many of the same underlying hormonal disturbances as diabetes mellitus, specifically absolute or relative insulin deficiency and glucagon excess. SIH has the added features of elevated blood levels of catecholamines and cortisol, which are not typically present in people with diabetes who are not acutely ill. The seriousness of SIH is highlighted by its greater morbidity and mortality rates compared with those of hospitalized patients with normal glucose levels, and this increased risk is particularly high in those without pre-existing diabetes. Insulin is the treatment standard for SIH, but new therapies that reduce glucose variability and hypoglycaemia are desired. In the present review, we focus on the key role of glucagon in SIH and discuss the potential use of glucagon receptor blockers and glucagon-like peptide-1 receptor agonists in SIH to achieve target glucose control.

Role of lateral septum glucagon-like peptide 1 receptors in food intake

Hindbrain glucagon-like peptide 1 (GLP-1) neurons project to numerous forebrain areas, including the lateral septum (LS). Using a fluorescently labeled GLP-1 receptor (GLP-1R) agonist, Exendin 4 (Ex4), we demonstrated GLP-1 receptor binding throughout the rat LS. We examined the feeding effects of Ex4 and the GLP-1R antagonist Exendin (9-39) (Ex9) at doses subthreshold for effect when delivered to the lateral ventricle. Intra-LS Ex4 suppressed overnight chow and high-fat diet (HFD) intake, and Ex9 increased chow and HFD intake relative to vehicle. During 2-h tests, intra-LS Ex9 significantly increased 0.25 M sucrose and 4% corn oil. Ex4 can cause nausea, but intra-LS administration of Ex4 did not induce pica. Furthermore, intra-LS Ex4 had no effect on anxiety-like behavior in the elevated plus maze. We investigated the role of LS GLP-1R in motivation for food by examining operant responding for sucrose on a progressive ratio (PR) schedule, with and without a nutrient preload to maximize GLP-1 neuron activation. The preload strongly suppressed PR responding, but blockade of GLP-1R in the intermediate subdivision of the LS did not affect motivation for sucrose under either load condition. The ability of the nutrient load to suppress subsequent chow intake was significantly attenuated by intermediate LS Ex9 treatment. By contrast, blockade of GLP-1R in the dorsal subdivision of the LS increased both PR responding and overnight chow intake. Together, these studies suggest that endogenous activity of GLP-1R in the LS influence feeding, and dLS GLP-1Rs, in particular, play a role in motivation.

LEADER-4: blood pressure control in patients with type 2 diabetes and high cardiovascular risk: baseline data from the LEADER randomized trial

OBJECTIVE

As glucagon-like peptide-1 receptor agonists lower blood pressure (BP) in type 2 diabetes mellitus (T2DM), we examined BP control in relation to targets set by international bodies prior to randomization in the Liraglutide Effect and Action in Diabetes: Evaluation of cardiovascular outcome Results (LEADER) trial.

METHODS

We analyzed baseline data from LEADER (NCT01179048), an ongoing phase 3B, randomized, double-blind, placebo-controlled cardiovascular outcomes trial examining the cardiovascular safety of the glucagon-like peptide-1 receptor agonist liraglutide in 9340 people with T2DM from 32 countries [age (all mean ± SD) 64 ± 7.2 years, BMI 32.5 ± 6.3 kg/m, duration of diabetes 12.7 ± 8.0 years], all of whom were at high risk for cardiovascular disease (CVD).

RESULTS

A total of 81% (n = 7592) of participants had prior CVD and 90% (n = 8408) had a prior history of hypertension. Despite prescription of multiple antihypertensive agents at baseline, only 51% were treated to a target BP of less than 140/85 mmHg and only 26% to the recommended baseline BP target of less than 130/80 mmHg. In univariate analyses, those with prior CVD were prescribed more agents (P < 0.001) and had lower BP than those without (137 ± 18.8/78 ± 10.6 mmHg versus 140 ± 17.7/80 ± 9.9 mmHg; P < 0.001). In logistic regression analyses, residency in North America (64% treated to <140/85 mmHg; 38% treated to <130/80 mmHg) was the strongest predictor of BP control.

CONCLUSION

These contemporary data confirm that BP remains insufficiently controlled in a large proportion of individuals with T2DM at high cardiovascular risk, particularly outside North America. Longitudinal data from the LEADER trial may provide further insights into BP control in relation to cardiovascular outcomes in this condition.

Peripheral, but not central, GLP-1 receptor signaling is required for improvement in glucose tolerance after Roux-en-Y gastric bypass in mice

Roux-en-Y gastric bypass (RYGB) causes profound weight loss and remission of diabetes by influencing metabolic physiology, yet the mechanisms behind these clinical improvements remain undefined. After RYGB, levels of glucagon-like peptide-1 (GLP-1), a hormone that enhances insulin secretion and promotes satiation, are substantially elevated. Because GLP-1 signals in both the periphery and the brain to influence energy balance and glucose regulation, we aimed to determine the relative requirements of these systems to weight loss and improved glucose tolerance following RYGB surgery in mice. By pharmacologically blocking peripheral or central GLP-1R signaling, we examined whether GLP-1 action is necessary for the metabolic improvements observed after RYGB. Diet-induced obese mice underwent RYGB or sham operation and were implanted with osmotic pumps delivering the GLP-1R antagonist exendin-(9-39) (2 pmol·kg(-1)·min(-1) peripherally; 0.5 pmol·kg(-1)·min(-1) centrally) for up to 10 wk. Blockade of peripheral GLP-1R signaling partially reversed the improvement in glucose tolerance after RYGB. In contrast, fasting glucose and insulin sensitivity, as well as body weight, were unaffected by GLP-1R antagonism. Central GLP-1R signaling did not appear to be required for any of the metabolic improvements seen after this operation. Collectively, these results suggest a detectable but only modest role for GLP-1 in mediating the effects of RYGB and that this role is limited to its well-described action on glucose regulation.

Low incidence of anti-drug antibodies in patients with type 2 diabetes treated with once-weekly glucagon-like peptide-1 receptor agonist dulaglutide

Therapeutic administration of peptides may result in anti-drug antibody (ADA) formation, hypersensitivity adverse events (AEs) and reduced efficacy. As a large peptide, the immunogenicity of once-weekly glucagon-like peptide-1 (GLP-1) receptor agonist dulaglutide is of considerable interest. The present study assessed the incidence of treatment-emergent dulaglutide ADAs, hypersensitivity AEs, injection site reactions (ISRs), and glycaemic control in ADA-positive patients in nine phase II and phase III trials (dulaglutide, N = 4006; exenatide, N = 276; non-GLP-1 comparators, N = 1141). Treatment-emergent dulaglutide ADAs were detected using a solid-phase extraction acid dissociation binding assay. Neutralizing ADAs were detected using a cell-based assay derived from human endothelial kidney cells (HEK293). A total of 64 dulaglutide-treated patients (1.6% of the population) tested ADA-positive versus eight (0.7%) from the non-GLP-1 comparator group. Of these 64 patients, 34 (0.9%) had dulaglutide-neutralizing ADAs, 36 (0.9%) had native-sequence GLP-1 (nsGLP-1) cross-reactive ADAs and four (0.1%) had nsGLP-1 neutralization ADAs. The incidence of hypersensitivity AEs and ISRs was similar in the dulaglutide versus placebo groups. No dulaglutide ADA-positive patient reported hypersensitivity AEs. Because of the low incidence of ADAs, it was not possible to establish their effect on glycaemic control.

Molecular Characterisation of Small Molecule Agonists Effect on the Human Glucagon Like Peptide-1 Receptor Internalisation

The glucagon-like peptide receptor (GLP-1R), which is a G-protein coupled receptor (GPCR), signals through both Gαs and Gαq coupled pathways and ERK phosphorylation to stimulate insulin secretion. The aim of this study was to determine molecular details of the effect of small molecule agonists, compounds 2 and B, on GLP-1R mediated cAMP production, intracellular Ca2+ accumulation, ERK phosphorylation and its internalisation. In human GLP-1R (hGLP-1R) expressing cells, compounds 2 and B induced cAMP production but caused no intracellular Ca2+ accumulation, ERK phosphorylation or hGLP-1R internalisation. GLP-1 antagonists Ex(9-39) and JANT-4 and the orthosteric binding site mutation (V36A) in hGLP-1R failed to inhibit compounds 2 and B induced cAMP production, confirming that their binding site distinct from the GLP-1 binding site on GLP-1R. However, K334A mutation of hGLP-1R, which affects Gαs coupling, inhibited GLP-1 as well as compounds 2 and B induced cAMP production, indicating that GLP-1, compounds 2 and B binding induce similar conformational changes in the GLP-1R for Gαs coupling. Additionally, compound 2 or B binding to the hGLP-1R had significantly reduced GLP-1 induced intracellular Ca2+ accumulation, ERK phosphorylation and hGLP-1R internalisation. This study illustrates pharmacology of differential activation of GLP-1R by GLP-1 and compounds 2 and B.

Effects of endogenous GLP-1 and GIP on glucose tolerance after Roux-en-Y gastric bypass surgery

Exaggerated secretion of glucagon-like peptide 1 (GLP-1) is important for postprandial glucose tolerance after Roux-en-Y gastric bypass (RYGB), whereas the role of glucose-dependent insulinotropic polypeptide (GIP) remains to be resolved. We aimed to explore the relative importance of endogenously secreted GLP-1 and GIP on glucose tolerance and β-cell function after RYGB. We used DPP-4 inhibition to enhance concentrations of intact GIP and GLP-1 and the GLP-1 receptor antagonist exendin-(9-39) (Ex-9) for specific blockage of GLP-1 actions. Twelve glucose-tolerant patients were studied after RYGB in a randomized, placebo-controlled, 4-day crossover study with standard mixed-meal tests and concurrent administration of placebo, oral sitagliptin, Ex-9 infusion, or combined Ex-9-sitagliptin. GLP-1 receptor antagonism increased glucose excursions, clearly attenuated β-cell function, and aggravated postprandial hyperglucagonemia compared with placebo, whereas sitagliptin had no effect despite two- to threefold increased concentrations of intact GLP-1 and GIP. Similarly, sitagliptin did not affect glucose tolerance or β-cell function during GLP-1R blockage. This study confirms the importance of GLP-1 for glucose tolerance after RYGB via increased insulin and attenuated glucagon secretion in the postprandial state, whereas amplification of the GIP signal (or other DPP-4-sensitive glucose-lowering mechanisms) did not appear to contribute to the improved glucose tolerance seen after RYGB.

Glucagon-like peptide-1 regulates calcium homeostasis and electrophysiological activities of HL-1 cardiomyocytes

Glucagon like-peptide-1 (GLP-1) is an incretin hormone with antidiabetic effects through stimulating insulin secretion, β cell neogenesis, satiety sensation, and inhibiting glucagon secretion. Administration of GLP-1 provides cardioprotective effects through attenuating cardiac inflammation and insulin resistance. GLP-1 also modulates the heart rate and systolic pressure, which suggests that GLP-1 may have cardiac electrical effects. Therefore, the purposes of this study were to evaluate whether GLP-1 has direct cardiac effects and identify the underlying mechanisms. Patch clamp, confocal microscopy with Fluo-3 fluorescence, and Western blot analyses were used to evaluate the electrophysiological characteristics, calcium homeostasis, and calcium regulatory proteins in HL-1 atrial myocytes with and without GLP-1 (1 and 10nM) incubation for 24h. GLP-1 (1 and 10nM) and control cells had similar action potential durations. However, GLP-1 at 10nM significantly increased calcium transients and sarcoplasmic reticular Ca(2+) contents. Compared to the control, GLP-1 (10nM)-treated cells significantly decreased phosphorylation of the ryanodine receptor at S2814 and total phospholamban, but there were similar protein levels of sarcoplasmic reticular Ca(2+)-ATPase and the sodium-calcium exchanger. Moreover, exendin (9-39) amide (a GLP-1 receptor antagonist, 10nM) attenuated GLP-1-mediated effects on total SR content and phosphorylated ryanodine receptor S2814. This study demonstrates GLP-1 may regulate HL-1 cell arrhythmogenesis through modulating calcium handling proteins.

Nutrient-induced glucagon like peptide-1 release is modulated by serotonin

Glucagon like peptide-1 (GLP-1) and serotonin are both involved in food intake regulation. GLP-1 release is stimulated upon nutrient interaction with G-protein coupled receptors by enteroendocrine cells (EEC), whereas serotonin is released from enterochromaffin cells (ECC). The central hypothesis for the current study was that nutrient-induced GLP-1 release from EECs is modulated by serotonin through a process involving serotonin receptor interaction. This was studied by assessing the effects of serotonin reuptake inhibition by fluoxetine on nutrient-induced GLP-1, PYY and CCK release from isolated pig intestinal segments. Next, serotonin-induced GLP-1 release was studied in enteroendocrine STC-1 cells, where effects of serotonin receptor inhibition were studied using specific and non-specific antagonists. Casein (1% w/v), safflower oil (3.35% w/v), sucrose (50mM) and rebaudioside A (12.5mM) stimulated GLP-1 release from intestinal segments, whereas casein only stimulated PYY and CCK release. Combining nutrients with fluoxetine further increased nutrient-induced GLP-1, PYY and CCK release. Serotonin release from intestinal tissue segments was stimulated by casein and safflower oil while sucrose and rebaudioside A had no effect. The combination with fluoxetine (0.155μM) further enhanced casein and safflower oil induced-serotonin release. Exposure of ileal tissue segments to serotonin (30μM) stimulated GLP-1 release whereas it did not induce PYY and CCK release. Serotonin (30 and 100μM) also stimulated GLP-1 release from STC-1 cells, which was inhibited by the non-specific 5HT receptor antagonist asenapine (1 and 10μM). These data suggest that nutrient-induced GLP-1 release is modulated by serotonin through a receptor mediated process.

Distinct effects of dipeptidyl peptidase-4 inhibitor and glucagon-like peptide-1 receptor agonist on islet morphology and function

Although the two anti-diabetic drugs, dipeptidyl peptidase-4 inhibitors (DPP4is) and glucagon-like peptide-1 (GLP-1) receptor agonists (GLP1RAs), have distinct effects on the dynamics of circulating incretins, little is known of the difference in their consequences on morphology and function of pancreatic islets. We examined these in a mouse model of β cell injury/regeneration. The model mice were generated so as to express diphtheria toxin (DT) receptor and a fluorescent protein (Tomato) specifically in β cells. The mice were treated with a DPP4i (MK-0626) and a GLP1RA (liraglutide), singly or doubly, and the morphology and function of the islets were compared. Prior administration of MK-0626 and/or liraglutide similarly protected β cells from DT-induced cell death, indicating that enhanced GLP-1 signaling can account for the cytoprotection. However, 2-week intervention of MK-0626 and/or liraglutide in DT-injected mice resulted in different islet morphology and function: β cell proliferation and glucose-stimulated insulin secretion (GSIS) were increased by MK-0626 but not by liraglutide; α cell mass was decreased by liraglutide but not by MK-0626. Although liraglutide administration nullified MK-0626-induced β cell proliferation, their co-administration resulted in increased GSIS, decreased α cell mass, and improved glucose tolerance. The pro-proliferative effect of MK-0626 was lost by co-administration of the GLP-1 receptor antagonist exendin-(9-39), indicating that GLP-1 signaling is required for this effect. Comparison of the effects of DPP4is and/or GLP1RAs treatment in a single mouse model shows that the two anti-diabetic drugs have distinct consequences on islet morphology and function.

[Insulinization in type 2 diabetes mellitus. Intensification options]

Diabetes mellitus is associated with vascular complications and high rates of morbidity and mortality. Timely insulin therapy, intensified when necessary, represent appropriate measures to prevent or delay the onset of complications. However, the incidence of hypoglycemia and difficulties in treatment adherence represent barriers to achieve therapeutic success. Premixes analogs and, specially, combinations of insulin analogues are associated with pharmacokinetic and pharmacodynamic advantages, that translate into clinical benefits such as improved metabolic control, decreased hypoglycemic events and, for their simplicity, potentially greater adherence.

Examination of a Viral Infection Mimetic Model in Human iPS Cell-Derived Insulin-Producing Cells and the Anti-Apoptotic Effect of GLP-1 Analogue

Aims

Viral infection is associated with pancreatic beta cell destruction in fulminant type 1 diabetes mellitus. The aim of this study was to investigate the acceleration and protective mechanisms of beta cell destruction by establishing a model of viral infection in pancreatic beta cells.

Methods

Polyinosinic:polycytidylic acid was transfected into MIN6 cells and insulin-producing cells differentiated from human induced pluripotent stem cells via small molecule applications. Gene expression was analyzed by real-time PCR, and apoptosis was evaluated by caspase-3 activity and TUNEL staining. The anti-apoptotic effect of Exendin-4 was also evaluated.

Results

Polyinosinic:polycytidylic acid transfection led to elevated expression of the genes encoding IFNα, IFNβ, CXCL10, Fas, viral receptors, and IFN-inducible antiviral effectors in MIN6 cells. Exendin-4 treatment suppressed the elevated gene expression levels and reduced polyinosinic:polycytidylic acid-induced apoptosis both in MIN6 cells and in insulin-producing cells from human induced pluripotent stem cells. Glucagon-like peptide-1 receptor, protein kinase A, and phosphatidylinositol-3 kinase inhibitors counteracted the anti-apoptotic effect of Exendin-4.

Conclusions

Polyinosinic:polycytidylic acid transfection can mimic viral infection, and Exendin-4 exerted an anti-apoptotic effect both in MIN6 and insulin-producing cells from human induced pluripotent stem cells.

Hot Topics in Primary Care: Considerations in the Selection of Antihyperglycemic Therapy for Older Patients With Type 2 Diabetes Mellitus: A Focus on Newer Therapies

Treatment of type 2 diabetes mellitus (T2DM) in older patients is complicated by a variety of factors and requires an individualized approach. Benefits of intensive glycemic control must be weighed against associated risks. Dipeptidyl peptidase-4 inhibitors, glucagon-like peptide-1 receptor agonists, and sodium-glucose cotransporter-2 inhibitors are newer antihyperglycemic agents that effectively lower glycated hemoglobin levels, with a low risk of hypoglycemia, and have a neutral or beneficial effect on weight. The purpose of this review is to discuss challenges in treating older patients with T2DM, and the efficacy and safety of these newer classes based on clinical trials in older populations.

Overview of Glucagon-like Peptide-1 Receptor Agonists

Type 2 diabetes mellitus is an increasingly prevalent disease in the United States and globally. Multiple pharmacologic therapies are typically required over time to achieve and maintain target blood glucose levels. When first-line oral medications such as metformin (Glucophage) are not effective in achieving desired glycosylated hemoglobin (HbA1C) levels, glucagon-like peptide-1 receptor agonists may be used. This article provides an overview of this class of agents and provides implications for home healthcare clinicians.

Exendin-4 Prevents Vascular Smooth Muscle Cell Proliferation and Migration by Angiotensin II via the Inhibition of ERK1/2 and JNK Signaling Pathways

Angiotensin II (Ang II) is a main pathophysiological culprit peptide for hypertension and atherosclerosis by causing vascular smooth muscle cell (VSMC) proliferation and migration. Exendin-4, a glucagon-like peptide-1 (GLP-1) receptor agonist, is currently used for the treatment of type-2 diabetes, and is believed to have beneficial effects for cardiovascular diseases. However, the vascular protective mechanisms of GLP-1 receptor agonists remain largely unexplained. In the present study, we examined the effect of exendin-4 on Ang II-induced proliferation and migration of cultured rat aortic smooth muscle cells (RASMC). The major findings of the present study are as follows: (1) Ang II caused a phenotypic switch of RASMC from contractile type to synthetic proliferative type cells; (2) Ang II caused concentration-dependent RASMC proliferation, which was significantly inhibited by the pretreatment with exendin-4; (3) Ang II caused concentration-dependent RASMC migration, which was effectively inhibited by the pretreatment with exendin-4; (4) exendin-4 inhibited Ang II-induced phosphorylation of ERK1/2 and JNK in a pre-incubation time-dependent manner; and (5) U0126 (an ERK1/2 kinase inhibitor) and SP600125 (a JNK inhibitor) also inhibited both RASMC proliferation and migration induced by Ang II stimulation. These results suggest that exendin-4 prevented Ang II-induced VSMC proliferation and migration through the inhibition of ERK1/2 and JNK phosphorylation caused by Ang II stimulation. This indicates that GLP-1 receptor agonists should be considered for use in the treatment of cardiovascular diseases in addition to their current use in the treatment of diabetes mellitus.