Glucagon-like peptide 1 (GLP-1) is a potent glucoselowering agent of potential interest for the treatment of type 2 diabetes. To evaluate actions of NN2211, a long-acting GLP-1 derivative, we examined 11 patients with type 2 diabetes, age 59 ؎ 7 years (mean ؎ SD), BMI 28.9 ؎ 3.0 kg/m 2 , HbA 1c 6.5 ؎ 0.6%, in a double-blind, placebo-controlled, crossover design. A single injection (10 g/kg) of NN2211 was administered at 2300 h, and profiles of circulating insulin, C-peptide, glucose, and glucagon were monitored during the next 16.5 h. A standardized mixed meal was served at 1130 h. Efficacy analyses were performed for the fasting (7-8 h) and mealtime (1130 -1530 h) periods. Insulin secretory rates (ISR) were estimated by C-peptide deconvolution analysis. Glucose pulse entrainment (6 mg ⅐ kg ؊1 ⅐ min P atients with type 2 diabetes experience relative insulin deficiency as well as delayed and blunted meal-related insulin response (1). Glucagon excess contributes to the elevated fasting and postprandial glycemia (2). Because of a marked and glucosedependent insulinotropic action and a restraining effect on glucagon release, glucagon like peptide-1 (GLP-1) is an obvious candidate for the treatment of type 2 diabetes (3). In addition, GLP-1 delays gastric emptying and reduces appetite in patients with type 2 diabetes also in nonemetic doses (4). Continuous intravenous infusion and repeated subcutaneous injections of GLP-1 (7-36 amide) effectively reduce fasting plasma glucose as well as meal-related glycemia (3,5). Even in patients with type 2 diabetes and secondary failure of sulfonylurea treatment, GLP-1 has been demonstrated to reduce glycemia effectively (6).Increased ␤-cell function has been reported after overnight GLP-1 infusion, as measured by homeostasis model assessment (HOMA) and by first-and second-phase insulin secretion (7). The secretagogue effect is achieved by a concomitant increase of basal (nonpulsatile) and highfrequency pulsatile insulin release in patients with type 2 diabetes (8). In a study of ultradian insulin pulsatility, GLP-1 was reported to restore glucose entrainment in individuals with impaired glucose tolerance (9), indicating preferential effects on the coordination of insulin release.GLP-1 is rapidly cleaved by dipeptidyl-peptidase IV after both intravenous and subcutaneous injections, and the development of long-acting derivatives is needed for clinical use. NN2211 is an acylated GLP-1 derivative with prolonged action due to a combination of albumin binding, metabolic stability, and slow release from the injection site. NN2211 has shown a favorable pharmacokinetic

Background Glucagon-like peptide-1 (GLP-1) receptor agonists are novel agents for type 2 diabetes treatment, offering glucose-dependent insulinotropic effects, reduced glucagonemia and a neutral bodyweight or weight-reducing profile. However, a short half-life (minutes), secondary to rapid inactivation by dipeptidyl peptidase-IV (DPP-IV) and excretion, limits the therapeutic potential of the native GLP-1 hormone. Recently, the GLP-1 receptor agonist exenatide injected subcutaneously twice daily established a novel therapy class. Developing long-acting and efficacious GLP-1 analogues represents a pivotal research goal. We developed a GLP-1 immunoglobulin G (IgG4) Fc fusion protein (LY2189265) with extended pharmacokinetics and activity.

Insulin concentrations oscillate at a periodicity of 5-15 min per oscillation. These oscillations are due to coordinate insulin secretory bursts, from millions of islets. The generation of common secretory bursts requires strong within-islet and within-pancreas coordination to synchronize the secretory activity from the ␤-cell population. The overall contribution of this pulsatile mechanism dominates and accounts for the majority of insulin release. This review discusses the methods involved in the detection and quantification of periodicities and individual secretory bursts. The mechanism by which overall insulin secretion is regulated through changes in the pulsatile component is discussed for nerves, metabolites, hormones, and drugs. The impaired pulsatile secretion of insulin in type 2 diabetes has resulted in much focus on the impact of the insulin delivery pattern on insulin action, and improved action from oscillatory insulin exposure is demonstrated on liver, muscle, and adipose tissues. Therefore, not only is the dominant regulation of insulin through changes in secretory burst mass and amplitude, but the changes may affect insulin action. Finally, the role of impaired pulsatile release in early type 2 diabetes suggests a predictive value of studies on insulin pulsatility in the development of this disease. Diabetes 51 (Suppl. 1): S245-S254, 2002

The purpose of the present study was to determine the contributions of discrete insulin secretory bursts vs. basal insulin release to total insulin secretion in vivo. Quantification of the partitioning of pulsatile and basal insulin secretion is complicated by physiological delivery of these pulses into the portal vein and the absence of validated methods of measuring the rates of pulsatile and basal insulin secretion in vivo. We therefore 1) developed a canine model with chronically implanted portal vein catheters, 2) validated an established deconvolution technique as well as a novel direct catheterization technique (Clustcath) for measurement of pulsatile and nonpulsatile insulin secretion rates in this model, and 3) applied these methods to study insulin secretion in the overnight-fasted dog in vivo to determine the contribution of pulsatile vs. basal insulin secretion to total rates of endogenous insulin secretion. Rates of total, pulsatile, and nonpulsatile endogenous insulin secretion measured by Cluscath closely parallel those measured by deconvolution analysis (54 +/- 15 vs. 51 +/- 11, 38 +/- 12 vs. 36 +/- 11, and 16 +/- 4 vs. 14 +/- 4 pmol/min, respectively). Clustcath and deconvolution indicated that the majority of insulin was secreted as pulses (70 +/- 6 and 66 +/- 7%, respectively). These data infer that any process that selectively decreases the pulsatile component of insulin secretion (e.g., diabetes mellitus) will likely have a major impact on total insulin secretion.

Uncontrolled hepatic glucose production contributes significantly to hyperglycemia in patients with type 2 diabetes. Hyperglucagonemia is implicated in the etiology of this condition; however, effective therapies to block glucagon signaling and thereby regulate glucose metabolism do not exist. To determine the extent to which blocking glucagon action would reverse hyperglycemia, we targeted the glucagon receptor (GCGR) in rodent models of type 2 diabetes using 2′-methoxyethyl-modified phosphorothioate-antisense oligonucleotide (ASO) inhibitors. Treatment with GCGR ASOs decreased GCGR expression, normalized blood glucose, improved glucose tolerance, and preserved insulin secretion. Importantly, in addition to decreasing expression of cAMP-regulated genes in liver and preventing glucagon-mediated hepatic glucose production, GCGR inhibition increased serum concentrations of active glucagon-like peptide-1 (GLP-1) and insulin levels in pancreatic islets. Together, these studies identify a novel mechanism whereby GCGR inhibitors reverse the diabetes phenotype by the dual action of decreasing hepatic glucose production and improving pancreatic β cell function.

In 1922, Karen Hansen [1] measured two series of blood glucose concentrations and reported oscillations in the peripheral concentrations of this substrate, results which were validated by simultaneous sampling from two sites to exclude the possibility that assay variability was a cause of the observed variations. Furthermore she studied the glucose concentrations in diabetic patients, and described both rapid and slower oscillations [1]. Half a century later the observation of rapid oscillations was shown to correlate with oscillations in the peripheral insulin concentrations [2±6], with glucose concentration increases slightly out of phase with insulin secretion pulses [7]. The pulsatile secretion of insulin was shown to coincide with islet pulsatile release of glucagon [4,6,8,9], and somatostatin [9±11]. A number of studies have reported importance of this release pattern for optimal insulin action [10, 12±21, 21±25], for overall insulin secretion [26±35], and for possible development of disease [36±43]. Studies on pulsatile insulin secretion could therefore be important for appreciating how insulin release is regulated overall and how Diabetologia (2002) 45: 3±20 ReviewsThe in vivo regulation of pulsatile insulin secretion

Impaired insulin secretion in type 2 diabetes is characterized by decreased first-phase insulin secretion, an increased proinsulin-to-insulin molar ratio in plasma, abnormal pulsatile insulin release, and heightened disorderliness of insulin concentration profiles. In the present study, we tested the hypothesis that these abnormalities are at least partly reversed by a period of overnight suspension of beta-cell secretory activity achieved by somatostatin infusion. Eleven patients with type 2 diabetes were studied twice after a randomly ordered overnight infusion of either somatostatin or saline with the plasma glucose concentration clamped at approximately 8 mmol/l. Controls were studied twice after overnight saline infusions and then at a plasma glucose concentration of either 4 or 8 mmol/l. We report that in patients with type 2 diabetes, 1) as in nondiabetic humans, insulin is secreted in discrete insulin secretory bursts; 2) the frequency of pulsatile insulin secretion is normal; 3) the insulin pulse mass is diminished, leading to decreased insulin secretion, but this defect can be overcome acutely by beta-cell rest with somatostatin; 4) the reported loss of orderliness of insulin secretion, attenuated first-phase insulin secretion, and elevated proinsulin-to-insulin molar ratio also respond favorably to overnight inhibition by somatostatin. The results of these clinical experiments suggest the conclusion that multiple parameters of abnormal insulin secretion in patients with type 2 diabetes mechanistically reflect cellular depletion of immediately secretable insulin that can be overcome by beta-cell rest.

Detection of insulin secretory bursts in peripheral blood is hampered by hepatic insulin extraction, dilution in the systemic insulin pool, and time-delayed damping of secretory burst amplitude. Previous studies in dogs in vivo and other experiments in vitro have shown that ∼70% of all insulin is released within distinct insulin secretory bursts. To establish a method for detection and quantification of pulsatile insulin release in humans on the basis of peripheral insulin concentration measurements, we used a high-sensitivity, -specificity, and -precision insulin enzyme-linked immunosorbent assay (ELISA) and optimized an established deconvolution methodology to quantify the frequency, mass, and amplitude of insulin secretory bursts as well as to estimate the relative contribution of pulsatile insulin release to overall insulin secretion. By use of minutely sampled serum insulin concentrations measured by a highly sensitive insulin ELISA, and insulin kinetics of 2.8 min (first half-life), 5.0 min (second half-life), and a fractional slow component of 0.28, the deconvolved insulin secretion rates in 20 healthy subjects during glucose infusion (4.5 mg ⋅ kg−1 ⋅ min−1) could be resolved into a series (4.7 ± 0.1 min/pulse) of approximately symmetric insulin secretory bursts with a mean mass of 87 ± 12 pmol ⋅ l−1 ⋅ pulse−1and a mean amplitude (maximal release rate) of 35 ± 4.7 pmol ⋅ l−1 ⋅ min−1. The relative contribution of pulsatile to overall insulin secretion was 75 ± 1.6% (range 59–85%). We conclude that in vivo insulin secretion in humans during nominal glucose stimulation consists of a series of punctuated insulin secretory bursts accounting for ≥75% of total insulin secretion.