Antidiabetic Activity of a Highly Potent and Selective Nonpeptide Somatostatin Receptor Subtype-2 Agonist

Abstract

Somatostatin inhibits both glucagon and insulin secretion. Glucagon significantly contributes to hyperglycemia in type 2 diabetes. Despite its function in the inhibition of glucagon secretion, somatostatin fails to reduce hyperglycemia in type 2 diabetes, due to a parallel suppression of insulin secretion. Five pharmacologically distinct somatostatin receptor subtypes (sst1–sst5) mediate the effects of somatostatin on a cellular level. Pancreatic A cells express sst2, whereas B cells express sst5. In this study, we describe a novel approach to the treatment of type 2 diabetes using a highly sst2-selective, nonpeptide agonist (compound 1). Compound 1 effectively inhibited glucagon secretion from pancreatic islets isolated from wild-type mice, whereas glucagon secretion from sst2-deficient islets was not suppressed. Compound 1 did not influence nonfasted insulin concentration. In sst2-deficient mice, compound 1 did not have any effects on glucagon or glucose levels, confirming its sst2 selectivity. In animal models of type 2 diabetes in the nonfasted state, circulating glucagon and glucose levels were decreased after treatment with compound 1. In the fasting state, compound 1 lowered blood glucose by approximately 25%. In summary, small-molecule sst2-selective agonists that suppress glucagon secretion offer a novel approach toward the development of orally bioavailable drugs for treatment of type 2 diabetes.