Individualised incretin-based treatment for type 2 diabetes

A comprehensive review on the glucoregulatory properties of food-derived bioactive peptides

Diabetes mellitus, a group of metabolic disorders characterized by persistent hyperglycemia, affects millions of people worldwide and is on the rise. Dietary proteins, from a wide range of food sources, are rich in bioactive peptides with antidiabetic properties. Notable examples include AGFAGDDAPR, a black tea-derived peptide, VRIRLLQRFNKRS, a β-conglycinin-derived peptide, and milk-derived peptide VPP, which have shown antidiabetic effects in diabetic rodent models through variety of pathways including improving beta-cells function, suppression of alpha-cells proliferation, inhibiting food intake, increasing portal cholecystokinin concentration, enhancing insulin signaling and glucose uptake, and ameliorating adipose tissue inflammation. Despite the immense research on glucoregulatory properties of bioactive peptides, incorporation of these bioactive peptides in functional foods or nutraceuticals is widely limited due to the existence of several challenges in the field of peptide research and commercialization. Ongoing research in this field, however, is fundamental to pave the road for this purpose.

Efficacy and Safety of Short- and Long-Acting Glucagon-Like Peptide 1 Receptor Agonists on a Background of Basal Insulin in Type 2 Diabetes: A Meta-analysis

PURPOSE

To compare the efficacy and safety of short- and long-acting glucagon-like peptide 1 receptor agonists (GLP-1 RAs), both used in combination with basal insulin, in patients with type 2 diabetes.

DATA SOURCES AND STUDY SELECTION

Randomized controlled trials comparing the coadministration of short- or long-acting GLP-1 RAs and basal insulin with basal insulin ± placebo were identified (PubMed search). Of 974 identified publications, 14 clinical trials were included. Eight trials examined short-acting and six long-acting GLP-1 RAs.

DATA EXTRACTION AND DATA SYNTHESIS

Differences in HbA_1c, fasting plasma glucose, body weight, and adverse events were compared between studies using short- or long-acting GLP-1 RAs by random-effects meta-analysis.

LIMITATIONS

There were relatively small numbers of available publications, some heterogeneity regarding protocols, and differences in the GLP-1 RA compound used.

CONCLUSIONS

Long-acting GLP-1 RAs more effectively reduced HbA_1c (∆ -6 mmol/mol [95% CI -10; -2], P = 0.007), fasting plasma glucose (∆ -0.7 mmol/L [-1.2; -0.3], P = 0.007), and body weight (∆ -1.4 kg [-2.2; -0.6], P = 0.002) and raised the proportion of patients achieving an HbA_1c target <7.0% (<53 mmol/mol) (P = 0.03) more than the short-acting ones. Patients reporting symptomatic (P = 0.048) but not severe (P = 0.96) hypoglycemia were fewer with long- versus short-acting GLP-1 RAs added to insulin. A lower proportion of patients reported nausea (-52%, P < 0.0001) or vomiting (-36%, P = 0.0002) with long-acting GLP-1 RAs. Overall, GLP-1 RAs improved HbA_1c, fasting plasma glucose, and body weight when added to basal insulin. However, long-acting GLP-1 RAs were significantly more effective for glycemic and body weight control and displayed better gastrointestinal tolerability.

Relative contribution of basal and postprandial hyperglycaemia stratified by HbA1c categories before and after treatment intensification with dulaglutide

AIM

To assess the effect of dulaglutide on the relative contribution of basal hyperglycaemia (BHG) and postprandial hyperglycaemia (PPHG) to overall hyperglycaemia across HbA1c categories in patients with type 2 diabetes.

METHODS

Data from five phase 3 studies (N = 673) were pooled to assess the change in relative contributions of BHG and PPHG to overall hyperglycaemia across different HbA1c categories after 6 months of treatment intensification with dulaglutide 1.5 mg as monotherapy or with 1 or 2 oral medication(s) in patients with type 2 diabetes. BHG and PPHG were calculated using the area under the curve (AUC) of 7-point self-monitored plasma glucose concentration profiles. As a secondary objective, relative contribution of BHG and PPHG for dulaglutide versus liraglutide, exenatide BID and insulin glargine was assessed by individual studies at 6 months.

RESULTS

In pooled data, after 6 months of treatment intensification with dulaglutide 1.5 mg, there was a significant reduction from baseline in overall hyperglycaemia (AUC_overall ) [(mean ± SE) -466.31 ± 18.32 mg*h/dL (P < 0.001)], BHG (AUC_basal ) [(mean ± SE) -371.46 ± 16.36 mg*h/dL (P < 0.001)] and PPHG (AUC_postprandial ) [(mean ± SE) -94.84 ± 7.97 mg*h/dL (P < 0.001)]. At baseline, relative contributions of BHG increased and PPHG decreased with increasing HbA1c levels. This pattern was maintained at 6 months, even as overall glycaemia improved with decreasing HbA1c values.

CONCLUSIONS

In patients with type 2 diabetes, dulaglutide reduces HbA1c by lowering both basal and postprandial hyperglycaemia across various HbA1c levels.

Design of Glucagon-Like Peptide-1 Receptor Agonist for Diabetes Mellitus from Traditional Chinese Medicine

Glucagon-like peptide-1 (GLP-1) is a promising target for diabetes mellitus (DM) therapy and reduces the occurrence of diabetes due to obesity. However, GLP-1 will be hydrolyzed soon by the enzyme dipeptidyl peptidase-4 (DPP-4). We tried to design small molecular drugs for GLP-1 receptor agonist from the world's largest traditional Chinese medicine (TCM) Database@Taiwan. According to docking results of virtual screening, we selected 2 TCM compounds, wenyujinoside and 28-deglucosylchikusetsusaponin IV, for further molecular dynamics (MD) simulation. GLP-1 was assigned as the control compound. Based on the results of root mean square deviation (RMSD), solvent accessible surface (SAS), mean square deviation (MSD), Gyrate, total energy, root mean square fluctuation (RMSF), matrices of smallest distance of residues, database of secondary structure assignment (DSSP), cluster analysis, and distance of H-bond, we concluded that all the 3 compounds could bind and activate GLP-1 receptor by computational simulation. Wenyujinoside and 28-deglucosylchikusetsusaponin IV were the TCM compounds that could be GLP-1 receptor agonists.

Clinical application of glucagon-like Peptide 1 receptor agonists for the treatment of type 2 diabetes mellitus

Glucagon-like peptide 1 (GLP-1) is secreted from enteroendocrine L-cells in response to oral nutrient intake and elicits glucose-stimulated insulin secretion while suppressing glucagon secretion. It also slows gastric emptying, which contributes to decreased postprandial glycemic excursions. In the 1990s, chronic subcutaneous infusion of GLP-1 was found to lower blood glucose levels in patients with type 2 diabetes. However, GLP-1's very short half-life, arising from cleavage by the enzyme dipeptidyl peptidase 4 (DPP-4) and glomerular filtration by the kidneys, presented challenges for clinical use. Hence, DPP-4 inhibitors were developed, as well as several GLP-1 analogs engineered to circumvent DPP-4-mediated breakdown and/or rapid renal elimination. Three categories of GLP-1 analogs, are being developed and/or are in clinical use: short-acting, long-acting, and prolonged-acting GLP-1 analogs. Each class has different plasma half-lives, molecular size, and homology to native GLP-1, and consequently different characteristic effects on glucose metabolism. In this article, we review current clinical data derived from each class of GLP-1 analogs, and consider the clinical effects reported for each category in recent head to head comparison studies. Given the relatively brief clinical history of these compounds, we also highlight several important efficacy and safety issues which will require further investigation.

GLP-1 receptor agonists for individualized treatment of type 2 diabetes mellitus

In healthy humans, the incretin glucagon-like peptide 1 (GLP-1) is secreted after eating and lowers glucose concentrations by augmenting insulin secretion and suppressing glucagon release. Additional effects of GLP-1 include retardation of gastric emptying, suppression of appetite and, potentially, inhibition of β-cell apoptosis. Native GLP-1 is degraded within ~2-3 min in the circulation; various GLP-1 receptor agonists have, therefore, been developed to provide prolonged in vivo actions. These GLP-1 receptor agonists can be categorized as either short-acting compounds, which provide short-lived receptor activation (such as exenatide and lixisenatide) or as long-acting compounds (for example albiglutide, dulaglutide, exenatide long-acting release, and liraglutide), which activate the GLP-1 receptor continuously at their recommended dose. The pharmacokinetic differences between these drugs lead to important differences in their pharmacodynamic profiles. The short-acting GLP-1 receptor agonists primarily lower postprandial blood glucose levels through inhibition of gastric emptying, whereas the long-acting compounds have a stronger effect on fasting glucose levels, which is mediated predominantly through their insulinotropic and glucagonostatic actions. The adverse effect profiles of these compounds also differ. The individual properties of the various GLP-1 receptor agonists might enable incretin-based treatment of type 2 diabetes mellitus to be tailored to the needs of each patient.

SUMO downregulates GLP-1-stimulated cAMP generation and insulin secretion

Glucagon-like peptide-1 (GLP-1)-based incretin therapy is becoming central to the treatment of type 2 diabetes. Activation of incretin hormone receptors results in rapid elevation of cAMP followed by enhanced insulin secretion. However, the incretin effect may be significantly impaired in diabetes. The objective of this study is to investigate downregulation of GLP-1 signaling by small ubiquitin-related modifier protein (SUMO). Mouse islets exposed to high glucose showed increased expression of endogenous SUMO transcripts and its conjugating enzyme Ubc-9. Overexpression of SUMO-1 in mouse insulinoma 6 (MIN6) cells and primary mouse β-cells resulted in reduced static and real-time estimates of intracellular cAMP upon receptor stimulation with exendin-4, a GLP-1 receptor (GLP-1R) agonist. GLP1-R was covalently modified by SUMO. Overexpression of SUMO-1 attenuated cell surface trafficking of GLP-1R, which resulted in significantly reduced insulin secretion when stimulated by exendin-4. Partial knock down of SUMO-conjugating enzyme Ubc-9 resulted in enhanced exendin-4-stimulated insulin secretion in mouse islets exposed to high glucose. Thus, SUMO modification of the GLP-1R could be a contributing factor to reduced incretin responsiveness. Elucidating mechanisms of GLP-1R regulation by sumoylation will help improve our understanding of incretin biology and of GLP-1-based treatment of type 2 diabetes.

Noninsulin treatment of type 2 diabetes mellitus in geriatric patients: a review

BACKGROUND

Currently, 42% of the US population with diabetes is aged ≥65 years.

OBJECTIVE

The aim of this review was to discuss the efficacy and tolerability of noninsulin therapies for type 2 diabetes mellitus (T2DM), with an emphasis on patients aged ≥65 years.

METHODS

PubMed and EMBASE (1977-2010) were searched using the terms geriatric, elderly patients, type 2 diabetes mellitus, metformin, secretagogues, thiazolidinediones (TZDs), alpha-glucosidase inhibitors, dipeptidyl peptidase-4 (DPP-4) inhibitors, and glucagon-like peptide-1 (GLP-1) receptor agonists. Articles were included if they were clinical trials, reviews, or meta-analyses.

RESULTS

More than 10 classes of noninsulin treatments are available for T2DM. However, most treatments have been evaluated only in trials in patients aged <65 years, and trials in older populations are scarce. Therefore, health care providers should consider the overall benefit to risk, with a focus on risk factors in older patients. A1C reductions range from 0.6% to 2%, with similar decreases observed for metformin, TZDs, sulfonylureas (SUs), glinides, and GLP-1 receptor agonists Treatment-associated adverse events vary. The prevalence of hypoglycemia is high with the secretagogues, SUs, and glinides (20% with glibenclamide or glipizide, 16% with repaglinide). The TZDs have been associated with an increased risk for heart failure (adjusted ratio = 1.60; 95% CI, 1.21-2.10; P < 0.001) compared with the other oral therapies. Gastrointestinal adverse events have been commonly reported with metformin (38% of patients), which is contraindicated in cases of renal insufficiency. Use of the GLP-1 RAs liraglutide and exenatide have been associated with comparable weight reductions of ∼3 kg and with a low risk for hypoglycemia (prevalence, 4% with exenatide 10 μg; ∼5% with liraglutide 1.2 or 1.8 mg). Treatment with the GLP-1 RAs has been associated with transient gastrointestinal reactions, mainly nausea.

CONCLUSIONS

The selection of noninsulin treatments in older patients with T2DM should be individualized based on patient assessment and on careful evaluation of the potential benefits (glycemic and extraglycemic) and risks (ie, hypoglycemia, weight gain, cardiovascular risks). More clinical trials in older patients, especially those aged ≥65 years, with T2DM are needed.