Effect of the glucagon-like peptide-1 receptor agonist lixisenatide on postprandial hepatic glucose metabolism in the conscious dog

The Future of Diabetes Therapies: New Insulins and Insulin Delivery Systems, Glucagon-Like Peptide 1 Analogs, and Sodium-Glucose Cotransporter Type 2 Inhibitors, and Beta Cell Replacement Therapy

As the prevalence of diabetes mellitus increases, so too does the number of available treatment modalities. Many diabetic therapies available in human medicine or on the horizon could hold promise in the management of small animal diabetes. However, it is important to consider how species differences in pathophysiology, management practices and goals, and lifestyle may affect the translation of such treatment modalities for veterinary use. This review article aimed to familiarize veterinarians with the more promising novel diabetic therapies and explore their possible applications in the treatment of canine and feline diabetes mellitus.

Physiological and pharmacological actions of glucagon like peptide-1 (GLP-1) in domestic animals

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GLP-1 improves peripheral glucose uptake in healthy dogs and cats.

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GLP-1 analogues administration in diabetic cats reduces exogenous insulin requirement.

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Dogs cardiomyocytes apoptosis is reduced by GLP-1-derived molecules action.

Analogues of glucagon like peptide-1 (GLP-1) and other drugs that increase this peptide half-life are used worldwide in human medicine to treat type 2 diabetes mellitus (DM) and obesity. These molecules can increase insulin release and satiety, interesting effects that could also be useful in the treatment of domestic animals pathologies, however their use in veterinary medicine are still limited. Considering the increasing incidence of DM and obesity in cats and dogs, the aim of this review is to summarize the available information about the physiological and pharmacological actions of GLP-1 in domestic animals and discuss about its potential applications in veterinary medicine. In diabetic dogs, the use of drugs based on GLP-1 actions reduced blood glucose and increased glucose uptake, while in diabetic cats they reduced glycemic variability and exogenous insulin administration. Thus, available evidence indicates that GLP-1 based drugs could become alternatives to DM treatment in domestic animals. Nevertheless, current data do not provide enough elements to recommend these drugs widespread clinical use.

Glucagon-like peptide-1 receptor agonists in non-alcoholic fatty liver disease: An update

Non-alcoholic fatty liver disease (NAFLD) is the predominant cause of chronic liver disease worldwide. NAFLD progresses in some cases to non-alcoholic steatohepatitis (NASH), which is characterized, in addition to liver fat deposition, by hepatocyte ballooning, inflammation and liver fibrosis, and in some cases may lead to hepatocellular carcinoma. NAFLD prevalence increases along with the rising incidence of type 2 diabetes mellitus (T2DM). Currently, lifestyle interventions and weight loss are used as the major therapeutic strategy in the vast majority of patients with NAFLD. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are used in the management of T2DM and do not have major side effects like hypoglycemia. In patients with NAFLD, the GLP-1 receptor production is down-regulated. Recently, several animal and human studies have emphasized the role of GLP-1RAs in ameliorating liver fat accumulation, alleviating the inflammatory environment and preventing NAFLD progression to NASH. In this review, we summarize the updated literature data on the beneficial effects of GLP-1RAs in NAFLD/NASH. Finally, as GLP-1RAs seem to be an attractive therapeutic option for T2DM patients with concomitant NAFLD, we discuss whether GLP-1RAs should represent the first line pharmacotherapy for these patients.

Effects of sequential treatment with lixisenatide, insulin glargine, or their combination on meal-related glycaemic excursions, insulin and glucagon secretion, and gastric emptying in patients with type 2 diabetes

AIM

To examine the glucose-lowering mechanisms of the glucagon-like peptide-1 receptor agonist lixisenatide after two subsequent meals and in combination with basal insulin.

MATERIALS AND METHODS

Twenty-eight metformin-treated patients with type 2 diabetes were randomly assigned to treatment sequences with either lixisenatide or insulin glargine alone for 4 weeks, and a combination of both treatments for 4 weeks. Metabolic examinations were performed before and after each treatment period following breakfast and a late lunch 8 hours later.

RESULTS

Lixisenatide mainly reduced postprandial glycaemia, while insulin glargine mainly reduced fasting glucose after breakfast (P < 0.05). This was partially preserved after a late lunch (P < 0.05). After breakfast, lixisenatide reduced insulin secretion and glucagon levels significantly. These effects were lost after a late lunch. Insulin glargine did not significantly reduce glucagon or insulin secretion. Gastric emptying was slowed by lixisenatide, but not by insulin glargine after breakfast. After the late lunch, lixisenatide slightly accelerated gastric emptying.

CONCLUSIONS

Lixisenatide decelerates gastric emptying after breakfast, thereby reducing glycaemic excursions, insulin secretion and glucagon levels. The glycaemic reduction persists until after a late lunch, despite accelerated gastric emptying. The combination with insulin glargine enhances the glucose-lowering effect because of complementary modes of action.

Glucagon-like peptide 1 (GLP-1)

BACKGROUND

The glucagon-like peptide-1 (GLP-1) is a multifaceted hormone with broad pharmacological potential. Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion, decrease of gastric emptying, inhibition of food intake, increase of natriuresis and diuresis, and modulation of rodent β-cell proliferation. GLP-1 also has cardio- and neuroprotective effects, decreases inflammation and apoptosis, and has implications for learning and memory, reward behavior, and palatability. Biochemically modified for enhanced potency and sustained action, GLP-1 receptor agonists are successfully in clinical use for the treatment of type-2 diabetes, and several GLP-1-based pharmacotherapies are in clinical evaluation for the treatment of obesity.

SCOPE OF REVIEW

In this review, we provide a detailed overview on the multifaceted nature of GLP-1 and its pharmacology and discuss its therapeutic implications on various diseases.

MAJOR CONCLUSIONS

Since its discovery, GLP-1 has emerged as a pleiotropic hormone with a myriad of metabolic functions that go well beyond its classical identification as an incretin hormone. The numerous beneficial effects of GLP-1 render this hormone an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, and neurodegenerative disorders.

Lixisenatide Reduces Chylomicron Triacylglycerol by Increased Clearance

CONTEXT

Glucagon-like peptide-1 (GLP-1) agonists control postprandial glucose and lipid excursion in type 2 diabetes; however, the mechanisms are unclear.

OBJECTIVE

To determine the mechanisms of postprandial lipid and glucose control with lixisenatide (GLP-1 analog) in type 2 diabetes.

DESIGN

Randomized, double-blind, cross-over study.

SETTING

Centre for Diabetes, Endocrinology, and Research, Royal Surrey County Hospital, Guildford, United Kingdom.

PATIENTS

Eight obese men with type 2 diabetes [age, 57.3 ± 1.9 years; body mass index, 30.3 ± 1.0 kg/m2; glycosylated hemoglobin, 66.5 ± 2.6 mmol/mol (8.2% ± 0.3%)].

INTERVENTIONS

Two metabolic studies, 4 weeks after lixisenatide or placebo, with cross-over and repetition of studies.

MAIN OUTCOME MEASURES

Study one: very-low-density lipoprotein (VLDL) and chylomicron (CM) triacylglycerol (TAG) kinetics were measured with an IV bolus of [2H5]glycerol in a 12-hour study, with hourly feeding. Oral [13C]triolein, in a single meal, labeled enterally derived TAG. Study two: glucose kinetics were measured with [U-13C]glucose in a mixed-meal (plus acetaminophen to measure gastric emptying) and variable IV [6,6-2H2]glucose infusion.

RESULTS

Study one: CM-TAG (but not VLDL-TAG) pool-size was lower with lixisenatide (P = 0.046). Lixisenatide reduced CM [13C]oleate area under the curve (AUC)60-480min concentration (P = 0.048) and increased CM-TAG clearance, with no effect on CM-TAG production rate. Study two: postprandial glucose and insulin AUC0-240min were reduced with lixisenatide (P = 0.0051; P < 0.05). Total glucose production (P = 0.015), rate of glucose appearance from the meal (P = 0.0098), and acetaminophen AUC0-360min (P = 0.006) were lower with lixisenatide than with placebo.

CONCLUSIONS

Lixisenatide reduced [13C]oleate concentrations, derived from a single meal in CM-TAG and glucose rate of appearance from the meal through delayed gastric emptying. However, day-long CM production, measured with repeated meal feeding, was not reduced by lixisenatide and decreased CM-TAG concentration resulted from increased CM-TAG clearance.

Morning Hyperinsulinemia Primes the Liver for Glucose Uptake and Glycogen Storage Later in the Day

We observed that a 4-h morning (AM) duodenal infusion of glucose versus saline doubled hepatic glucose uptake (HGU) and storage during a hyperinsulinemic-hyperglycemic (HIHG) clamp that afternoon (PM). To separate the effects of AM hyperglycemia versus AM hyperinsulinemia on the PM response, we used hepatic balance and tracer ([3-³H]glucose) techniques in conscious dogs. From 0 to 240 min, dogs underwent a euinsulinemic-hyperglycemic (GLC; n = 7) or hyperinsulinemic-euglycemic (INS; n = 8) clamp. Tracer equilibration and basal sampling occurred from 240 to 360 min, followed by an HIHG clamp (360-600 min; four times basal insulin, two times basal glycemia) with portal glucose infusion (4 mg ⋅ kg^-1 ⋅ min^-1). In the HIHG clamp, HGU (5.8 ± 0.9 vs. 3.3 ± 0.3 mg ⋅ kg^-1 ⋅ min^-1) and net glycogen storage (6.0 ± 0.8 vs. 2.9 ± 0.5 mg ⋅ kg^-1 ⋅ min^-1) were approximately twofold greater in INS than in GLC. PM hepatic glycogen content (1.9 ± 0.2 vs. 1.3 ± 0.2 g/kg body weight) and glycogen synthase (GS) activity were also greater in INS versus GLC, whereas glycogen phosphorylase (GP) activity was reduced. Thus AM hyperinsulinemia, but not AM hyperglycemia, enhanced the HGU response to a PM HIHG clamp by augmenting GS and reducing GP activity. AM hyperinsulinemia can prime the liver to extract and store glucose more effectively during subsequent same-day meals, potentially providing a tool to improve glucose control.

Lixisenatide as add-on treatment among patients with different β-cell function levels as assessed by HOMA-β index

BACKGROUND

The effect of lixisenatide-a prandial once-daily glucagon-like peptide-1 receptor agonist-on glycaemic control in patients with inadequately controlled type 2 diabetes mellitus (T2DM), stratified by baseline β-cell function, was assessed.

METHODS

The 24-week GetGoal-M, -P and -S trials evaluated the efficacy and safety of lixisenatide in combination with oral antidiabetic agents. This post hoc analysis used data from patients receiving lixisenatide in these trials, divided into matched cohorts by propensity scoring, and stratified according to baseline homeostasis model assessment of β-cell function (HOMA-β) index levels, high HOMA-β: > median HOMA-β (28.49%); low HOMA-β: ≤ median.

RESULTS

The matched "low" and "high" HOMA-β index cohorts (N = 546 patients) had comparable baseline parameters. Mean change from baseline in glycated haemoglobin (HbA_1c ) was -0.85% and -0.94% for low and high HOMA-β cohorts, respectively (P = .2607). Reductions from baseline in fasting plasma glucose (FPG; -0.77 vs -1.04 mmol/L; P = .1496) and postprandial plasma glucose (PPG; -5.82 vs -5.61 mmol/L; P = .7511) were similar in the low versus high HOMA-β index cohorts. Reduction in body weight was significantly greater in the low versus high HOMA-β index cohort (-2.06 vs -1.13 kg, respectively; P = .0006).

CONCLUSIONS

In patients with T2DM, lixisenatide was associated with reduction in HbA_1c and improvements in both FPG and PPG, regardless of β-cell function, indicating that lixisenatide is effective in reducing hyperglycaemia, even in patients with more advanced stages of T2DM and poor residual β-cell function.

High-protein breakfast promotes weight loss by suppressing subsequent food intake and regulating appetite hormones in obese Chinese adolescents

OBJECTIVE

A high-protein diet may decrease food intake through regulating satiety and appetite hormones and can be an effective strategy for weight loss. Few studies exist on obese Chinese adolescents.

METHODS AND MATERIALS

156 obese Chinese adolescents were enrolled and randomly assigned to one of two isoenergetic breakfasts, either with egg or steamed bread. Subsequent lunchtime food intake was recorded 4 h later. Appetite was assessed with a visual analog scale. Anorexigenic hormones peptide YY (PYY), glucagon-like peptide-1 (GLP-1) and orexigenic hormone ghrelin were determined with radioimmunoassay at 0, 30, and 180 min. Body weight was recorded. The tests were repeated 3 months later. Analysis was performed between two tests and then two groups. Pearson's correlation was used for association analysis.

RESULTS

Subsequent lunchtime food intake and body weight were decreased while satiety was increased in subjects on an egg breakfast, which is associated with an increase of serum PYY and GLP-1 (p < 0.001, respectively). There were strong correlations between weight loss, appetite, subsequent food intake and changes of appetite hormones.

CONCLUSION

A high-protein breakfast promotes weight loss in obese Chinese adolescents, possibly through its regulation of satiety, subsequent food intake and appetite hormones.

Lixisenatide improves recognition memory and exerts neuroprotective actions in high-fat fed mice

The metabolic benefits of lixisenatide as an anti-diabetic agent are recognized but potential extra-pancreatic effects of this glucagon-like peptide-1 (GLP-1) mimetic in the brain are less well known. This study examines actions within the hippocampus following chronic 40-day peripheral administration of lixisenatide to high-fat fed mice with established obesity, insulin resistance and impaired cognition. Lixisenatide (50 nmol/kg bw, twice-daily) resulted in marked improvements in glycemic status, insulin secretion and insulin sensitivity. Examination of pancreatic tissue revealed decreased islet area, increased islet number, and increased insulin content, with no evidence of pancreatic inflammation. Lixisenatide improved recognition memory during a novel object recognition task and this was associated with up-regulation of hippocampal expression of neurotrophic tyrosine kinase receptor type 2 (NTRK2) and mammalian target of rapamycin (mTOR) genes involved in modulating synaptic plasticity and long-term potentiation. Lixisenatide also enhanced progenitor cell proliferation and increased the number of immature neurons in the hippocampal dentate gyrus. These data indicate that lixisenatide is not only a new efficacious drug for treatment of diabetes but it also exerts favorable neuroprotective effects, reversing memory impairment in obesity-diabetes. Further clinical studies are necessary to fully assess potential beneficial actions of lixisenatide in the hippocampus and cognition in man.

Lixisenatide: evidence for its potential use in the treatment of type 2 diabetes

Lixisenatide is a once-daily glucagon-like peptide 1 (GLP-1) receptor agonist mimicking several favorable actions of endogenous GLP-1 that result in improved glycemic control with little or no hypoglycemia and weight loss. Phase II trials have shown that lixisenatide 20 μg once daily restores first-phase insulin release in patients with type 2 diabetes and improves the second-phase insulin response. Administered once or twice daily for 4 weeks, it significantly reduced postprandial and fasting blood glucose levels, and glycosylated hemoglobin (HbA_1c). The efficacy and safety of lixisenatide once daily is being assessed in the GETGOAL Phase III clinical trial program. Results have shown beneficial effects on HbA_1c compared with placebo in combination with commonly used antidiabetes agents, with no increased risk of hypoglycemia and with beneficial weight reduction. Adverse effects were similar to those observed for available GLP-1 receptor agonists, the most frequent being gastrointestinal. Both GLP-1 receptor agonists and long-acting insulin analogs have demonstrated protective effects on beta cells in preclinical studies. This, along with the pronounced effect of lixisenatide on postprandial plasma glucose, provides a rationale for combining it with long-acting basal insulin analogs, in the hope that the additive effects on glycemic control combined with a potential benefit on islet cells may lead to a new treatment approach to control blood glucose better and prevent long-term complications in patients with type 2 diabetes.

Endogenously released GLP-1 is not sufficient to alter postprandial glucose regulation in the dog

Glucagon-like peptide-1 (GLP-1) is secreted from the L cell of the gut in response to oral nutrient delivery. To determine if endogenously released GLP-1 contributes to the incretin effect and postprandial glucose regulation, conscious dogs (n = 8) underwent an acclimation period (t = -60 to -20 min), followed by a basal sampling period (t = -20 to 0 min) and an experimental period (t = 0-320 min). At the beginning of the experimental period, t = 0 min, a peripheral infusion of either saline or GLP-1 receptor (GLP-1R) antagonist, exendin (9-39) (Ex-9, 500 pmol/kg/min), was started. At t = 30 min, animals consumed a liquid mixed meal, spiked with acetaminophen. All animals were studied twice (± Ex-9) in random fashion, and the experiments were separated by a 1-2-week washout period. Antagonism of the GLP-1R did not have an effect, as indicated by repeated-measures MANOVA analysis of the Δ AUC from t = 45-320 min of arterial plasma glucose, GLP-1, insulin, glucagon, and acetaminophen levels. Therefore, endogenous GLP-1 is not sufficient to alter postprandial glucose regulation in the dog.