Effect of Intravenous Infusion of Exenatide (Synthetic Exendin-4) on Glucose-Dependent Insulin Secretion and Counterregulation During Hypoglycemia

Abstract

This study assessed whether glucose-dependent insulin secretion and overall counterregulatory response are preserved during hypoglycemia in the presence of exenatide. Twelve healthy fasted volunteers were randomized in a triple-blind crossover study to receive either intravenous exenatide (0.066 pmol ⅐ kg ؊1 ⅐ min ؊1 ) or placebo during a 270-min stepwise hyperinsulinemichypoglycemic clamp (insulin infusion 0.8 mU ⅐ kg ؊1 ⅐ min ؊1 ). Plasma glucose was clamped sequentially at 5.0 (0 -120 min), 4.0 (120 -180 min), 3.2 (180 -240 min), and 2.7 mmol/l (240 -270 min). At 270 min, insulin infusion was terminated and plasma glucose increased to ϳ3.2 mmol/l. The time to achieve plasma glucose >4 mmol/l thereafter was recorded. Insulin secretory rates (ISRs) and counterregulatory hormones were measured throughout. Glucose profiles were superimposable between the exenatide and placebo arms. In the presence of euglycemic hyperinsulinemia, ISRs in the exenatide arm were ϳ3.5-fold higher than in the placebo arm (353 ؎ 29 vs. 100 ؎ 29 pmol/min [least-square means ؎ SE]). However, ISRs declined similarly and rapidly at all hypoglycemic steps (<4 mmol/l) in both groups. Glucagon was suppressed in the exenatide arm during euglycemia and higher than placebo during hypoglycemia. Plasma glucose recovery time was equivalent for both treatments. The areas under the concentration-time curve from 270 to 360 min for cortisol, epinephrine, norepinephrine, and growth hormone were similar between treatment arms. There were no differences in adverse events. In the presence of exenatide, there was a preserved, glucose-dependent insulin secretory response and counterregulatory response during hypoglycemia. Diabetes 53:2397-2403, 2004 T he pathogenesis of type 2 diabetes is characterized by peripheral insulin resistance and progressive failure of pancreatic ␤-cell function, ultimately resulting in deficient insulin secretion. Furthermore, an excessive glucagon secretion and an impaired incretin response to meals contribute to the metabolic derangement of the disease (1-4). Control of circulating glucose levels is rarely optimal, and many currently available therapies also have unfavorable side effects and restrictions, limiting the extent of their use (5-8). This emphasizes the need for novel antidiabetic agents.Glucagon-like peptide (GLP)-1 is an incretin hormone secreted from the intestinal mucosa in response to meal ingestion. Physiological GLP-1 exhibits several glucoregulatory functions, such as glucose-dependent enhancement of insulin secretion, suppression of glucagon secretion, delayed gastric emptying, and reduction of food intake. It may even promote ␤-cell preservation and improved neogenesis (9). GLP-1 has an extremely short half-life in plasma.Exenatide (synthetic exendin-4) is a 39 -amino acid peptide incretin mimetic that demonstrates the above glucoregulatory actions of GLP-1 (10,11), and it has been shown to be a potent agonist to the GLP-1 receptor in vitro (12). Clinical studies in humans have demonstrated markedly improved ...

Alpha cell function in health and disease: influence of glucagon-like peptide-1

“…As illustrated in Fig. 4b, exenatide infusion suppressed plasma glucagon during euglycaemia, did not affect glucagon during moderate hypoglycaemia, and significantly increased plasma glucagon during more severe hypoglycaemia [83]. In a similar study of stepped hypoglycaemic clamps during GLP-1 infusion, GLP-1 suppressed glucagon levels during euglycaemia but had no detectable effect on plasma glucagon during hypoglycaemia [84].…”

GLP-1 for type 2 diabetes

“…GLP-1 receptor agonists and DPP-4 inhibitors stimulate insulin secretion and inhibit glucagon secretion, as has been demonstrated in several studies with different methods for judging islet function [1,10,[22][23][24][25][26]28]. Interestingly, as demonstrated for vildagliptin [31] and exenatide [32], during hypoglycaemia, the counterregulatory increase in glucagon levels is preserved, showing that even though GLP-1 based therapy inhibits glucagon secretion as a part of the antidiabetic action, the defence by increasing glucagon in hypoglycaemia is not compromised. This further illustrates the safety of this treatment in relation to hypoglycaemia.…”

Addition of vildagliptin to insulin improves glycaemic control in type 2 diabetes

“…As discussed in a recent review [12], the effects of glucagon-like peptide-1 do not appear to be limited to suppression of glucagon release in the presence of hyperglycaemia; rather, during hypoglycaemia, activation of the glucagon-like peptide-1 receptor (by agonists such as exenatide) increases glucagon levels, enhancing the stimulatory effect of low glucose levels on the alpha cell [13].…”