Urd Kielgast

An overview of once-weekly glucagon-like peptide-1 receptor agonists—available efficacy and safety data and perspectives for the future

Incretin‐based therapies, such as the injectable glucagon‐like peptide‐1 (GLP‐1) receptor agonists and orally administered dipeptidyl peptidase‐4 (DPP‐4) inhibitors, have recently been introduced into clinical practice. At present, the GLP‐1 receptor agonists need to be administered once or twice daily. Several once‐weekly GLP‐1 receptor agonists are in phase 3 development. This review examines the efficacy, safety and perspective for the future of the once‐weekly GLP‐1 receptor agonists: exenatide once weekly, taspoglutide, albiglutide, LY2189265 and CJC‐1134‐PC, and compared them to the currently available agonists, exenatide BID and liraglutide QD. A greater reduction in haemoglobin A1c (HbA1c) and fasting plasma glucose was found with the once‐weekly GLP‐1 receptor agonists compared with exenatide BID, while the effect on postprandial hyperglycaemia was modest with the once‐weekly GLP‐1 receptor agonist. The reduction in HbA1c was in most studies greater compared to oral antidiabetic drugs and insulin glargine. The reduction in weight did not differ between the short‐ and long‐acting agonists. The gastrointestinal side effects were less with the once‐weekly agonists compared with exenatide BID, except for taspoglutide. Antibodies seem to be most frequent with exenatide once weekly, while hypersensitivity has been described in few patients treated with taspoglutide. Injection site reactions differ among the long‐acting GLP‐1 receptor agonists and are observed more frequently than with exenatide BID and liraglutide. In humans, no signal has been found indicating an association between the once‐weekly agonists and C‐cell cancer. The cardiovascular safety, durability of glucose control and effect on weight will emerge from several ongoing major long‐term trials. The once‐weekly GLP‐1 receptor analogues are promising candidates for the treatment of type 2 diabetes, although their efficacy may not be superior to once‐daily analogue liraglutide.

Four Weeks of Treatment With Liraglutide Reduces Insulin Dose Without Loss of Glycemic Control in Type 1 Diabetic Patients With and Without Residual β-Cell Function

OBJECTIVE To investigate the effect of 4 weeks of treatment with liraglutide on insulin dose and glycemic control in type 1 diabetic patients with and without residual β-cell function. RESEARCH DESIGN AND METHODS Ten type 1 diabetic patients with residual β-cell function (C-peptide positive) and 19 without (C-peptide negative) were studied. All C-peptide–positive patients were treated with liraglutide plus insulin, whereas C-peptide–negative patients were randomly assigned to liraglutide plus insulin or insulin monotherapy. Continuous glucose monitoring with identical food intake and physical activity was performed before (week 0) and during (week 4) treatment. Differences in insulin dose; HbA1c; time spent with blood glucose <3.9, >10, and 3.9–9.9 mmol/L; and body weight were evaluated. RESULTS Insulin dose decreased from 0.50 ± 0.06 to 0.31 ± 0.08 units/kg per day (P < 0.001) in C-peptide–positive patients and from 0.72 ± 0.08 to 0.59 ± 0.06 units/kg per day (P < 0.01) in C-peptide–negative patients treated with liraglutide but did not change with insulin monotherapy. HbA1c decreased in both liraglutide-treated groups. The percent reduction in daily insulin dose was positively correlated with β-cell function at baseline, and two patients discontinued insulin treatment. In C-peptide–positive patients, time spent with blood glucose <3.9 mmol/L decreased from 3.0 to 1.0 h (P = 0.03). A total of 18 of 19 patients treated with liraglutide lost weight during treatment (mean [range] −2.3 ± 0.3 kg [−0.5 to −5.1]; P < 0.001). Transient gastrointestinal adverse effects occurred in almost all patients treated with liraglutide. CONCLUSIONS Treatment with liraglutide in type 1 diabetic patients reduces insulin dose with improved or unaltered glycemic control.

Gut hormones, early dumping and resting energy expenditure in patients with good and poor weight loss response after Roux-en-Y gastric bypass

Objective:To identify factors contributing to the variation in weight loss after Roux-en-Y gastric bypass (RYGB).Design:Cross-sectional study of patients with good (excess body mass index lost (EBL) >60%) and poor weight loss response (EBL <50%) >12 months after RYGB and a lean control group matched for age and gender.Materials and methods:Sixteen patients with good weight loss response, 17 patients with poor weight loss response, and eight control subjects were included in the study. Participants underwent dual energy X-ray absorptiometry scan, indirect calorimetry and a 9 h multiple-meal test with measurements of glucose, insulin, total bile acids (TBA), glucagon-like peptide (GLP)-1, peptide YY3–36 (PYY), cholecystokinin (CCK), ghrelin, neurotensin and pancreatic polypeptide (PP) as well as assessment of early dumping and appetite.Results:Suppression of hunger was more pronounced in the good than the poor responders in response to the multiple-meal test (P=0.006). In addition, the good responders had a larger release of GLP-1 (P=0.009) and a greater suppression of ghrelin (P=0.037) during the test, whereas the postprandial secretion of CCK was highest in the poor responders (P=0.005). PYY, neurotensin, PP and TBA release did not differ between the RYGB-operated groups. Compared with control subjects, patients had exaggerated release of GLP-1 (P<0.001), PYY (P=0.008), CCK (P=0.010) and neurotensin (P<0.001). Early dumping was comparable in the good and poor responders, but more pronounced than in controlled subjects. Differences in resting energy expenditure between the three groups were entirely explained by differences in body composition.Conclusion:Favorable meal-induced changes in hunger and gut hormone release in patients with good compared with poor weight loss response support the role of gut hormones in the weight loss after RYGB.

Antidiabetic Actions of Endogenous and Exogenous GLP-1 in Type 1 Diabetic Patients With and Without Residual β-Cell Function

OBJECTIVE To investigate the effect of exogenous as well as endogenous glucagon-like peptide 1 (GLP-1) on postprandial glucose excursions and to characterize the secretion of incretin hormones in type 1 diabetic patients with and without residual β-cell function. RESEARCH DESIGN AND METHODS Eight type 1 diabetic patients with (T1D+), eight without (T1D−) residual β-cell function, and eight healthy matched control subjects were studied during a mixed meal with concomitant infusion of GLP-1 (1.2 pmol/kg/min), saline, or exendin 9-39 (300 pmol/kg/min). Before the meal, half dose of usual fast-acting insulin was injected. Plasma glucose (PG), glucagon, C-peptide, total GLP-1, intact glucose-dependent insulinotropic polypeptide (GIP), free fatty acids, triglycerides, and gastric emptying rate (GE) by plasma acetaminophen were measured. RESULTS Incretin responses did not differ between patients and control subjects. Infusion of GLP-1 decreased peak PG by 45% in both groups of type 1 diabetic patients. In T1D+ patients, postprandial PG decreased below fasting levels and was indistinguishable from control subjects infused with saline. In T1D− patients, postprandial PG remained at fasting levels. GLP-1 infusion reduced GE and glucagon levels in all groups and increased fasting C-peptide in T1D+ patients and control subjects. Blocking endogenous GLP-1 receptor action increased endogenous GLP-1 secretion in all groups and increased postprandial glucose, glucagon, and GE in T1D+ and T1D− patients. The insulinogenic index (the ratio of insulin to glucose) decreased in T1D+ patients during blockade of endogenous GLP-1 receptor action. CONCLUSIONS Type 1 diabetic patients have normal incretin responses to meals. In type 1 diabetic patients, exogenous GLP-1 decreases peak postprandial glucose by 45% regardless of residual β-cell function. Endogenous GLP-1 regulates postprandial glucose excursions by modulating glucagon levels, GE, and β-cell responsiveness to glucose. Long-term effects of GLP-1 in type 1 diabetic patients should be investigated in future clinical trials.

Regulation of glucagon secretion by incretins

Glucagon secretion plays an essential role in the regulation of hepatic glucose production, and elevated fasting and postprandial plasma glucagon concentrations in patients with type 2 diabetes (T2DM) contribute to their hyperglycaemia. The reason for the hyperglucagonaemia is unclear, but recent studies have shown lack of suppression after oral but preserved suppression after isoglycaemic intravenous glucose, pointing to factors from the gut. Gastrointestinal hormones that are secreted in response to oral glucose include glucagon‐like peptide‐1 (GLP‐1) that strongly inhibits glucagon secretion, and GLP‐2 and GIP, both of which stimulate secretion. When the three hormones are given together on top of isoglycaemic intravenous glucose, glucagon suppression is delayed in a manner similar to that observed after oral glucose. Studies with the GLP‐1 receptor antagonist, exendin 9–39, suggest that endogenous GLP‐1 plays an important role in regulation of glucagon secretion during fasting as well as postprandially. The mechanisms whereby GLP‐1 regulates glucagon secretion are debated, but studies in isolated perfused rat pancreas point to an important role for a paracrine regulation by somatostatin from neighbouring D cells. Clinical studies of the antidiabetic effect of GLP‐1 in T2DM suggest that the inhibition of glucagon secretion is as important as the stimulation of insulin secretion.

Fast pouch emptying, delayed small intestinal transit, and exaggerated gut hormone responses after Roux-en-Y gastric bypass.

Roux‐en‐Y gastric bypass (RYGB) causes extensive changes in gastrointestinal anatomy and leads to reduced appetite and large weight loss, which partly is due to an exaggerated release of anorexigenic gut hormones.

Treatment of type 1 diabetic patients with glucagon-like peptide-1 (GLP-1) and GLP-1R agonists.

GLP-1 (glucagon-like peptide-1) is a peptide hormone secreted from endocrine cells in the intestinal mucosa in response to meals. The major effects of GLP-1 are to increase glucose-induced insulin secretion and reduce glucagon release, but GLP-1 also inhibits gastric emptying rate and reduces appetite and bodyweight in obese subjects. In vivo studies using animal models of type 2 diabetes and in vitro studies using human islet cells have suggested that GLP-1 or GLP-1 analogues are also able to increase beta-cell mass, but in animal models of type 1 diabetes, there is much less evidence for a beta-cell preserving effect. This review summarizes the present knowledge of GLP-1 and its analogues regarding its role as a possible treatment in patients with type 1 diabetes. The studies that address the effect of GLP-1 and GLP-1 analogues on beta-cell mass in both type 2 and type 1 diabetes, as well as the potential of GLP-1 as an adjuvant therapy in islet cell transplantation, will be reviewed. Suggestions for future studies of GLP-1 treatment in type 1 diabetes may include early treatment in order to preserve beta-cell mass and prolong the remission period, but should also take a potential insulin sparing effect and changes in the risk of hypoglycemia into account.

Effect of Glucagon-Like Peptide-1 on α- and β-Cell Function in C-Peptide-Negative Type 1 Diabetic Patients

Context: The mechanism by which glucagon-like peptide-1 (GLP-1) suppresses glucagon secretion is uncertain, and it is not determined whether endogenous insulin is a necessary factor for this effect. Objective: Our objective was to characterize the and -cell responses to GLP-1 in type 1 diabetic patients without residual -cell function. Methods: Nine type 1 diabetic patients, classified as C-peptide negative by a glucagon test, were clamped at plasma glucose of 20 mmol/liter for 90 min with arginine infusion at time 45 min and concomitant infusion of GLP-1 (1.2 pmol/kg min) or saline. Results: Infusion with GLP-1 increased C-peptide concentration just above the detection limit of 33 pmol/liter in one patient, but C-peptide remained immeasurable in all other patients. In the eight remaining patients, total area under the curve of glucagon was significantly decreased with GLP-1 compared with saline: 485 72 vs. 760 97 pmol/liter min (P 0.001). In addition, GLP-1 decreased the arginine-stimulated glucagon release (incremental AUC of 103 21 and 137 16 pmol/liter min, with GLP-1 and saline, respectively, P 0.05). Conclusions: In type 1 diabetic patients without endogenous insulin secretion, GLP-1 decreases the glucagon secretion as well as the arginine-induced glucagon response during hyperglycemia. GLP-1 induced endogenous insulin secretion in one of nine type 1 diabetic patients previously classified as being without endogenous insulin secretion. Mol Endocrinol, April 2010, 24(4):873–875 mend.endojournals.org 875