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.

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.

The insulinotropic activity of the novel imidazoline compound BL11282 was investigated. Intravenous administration of BL11282 (0.3 mg ⅐ kg -1 ⅐ min -1 ) to anesthetized rats did not change blood glucose and insulin levels under basal conditions, but produced a higher increase in blood insulin levels and a faster glucose removal from the blood after glucose infusion. Similarly, in isolated Wistar rat pancreatic islets, 0.1-100 mol/l BL11282 potently stimulated glucose-induced insulin secretion but did not modulate basal insulin secretion. Unlike previously described imidazolines, BL11282 did not block ATP-dependent K ؉ channels. Furthermore, the compound stimulated insulin secretion in islets depolarized with high concentrations of KCl or permeabilized with electric shock. Insulinotropic activity of BL11282 was dependent on activity of protein kinases A and C. In pancreatic islets from spontaneously diabetic GK rats, the imidazoline compound restored the impaired insulin response to glucose. In conclusion, the imidazoline BL11282 constitutes a new class of insulinotropic compounds that exerts an exclusive glucose-dependent insulinotropic activity in pancreatic islets by stimulating insulin exocytosis. Diabetes 50:797-802, 2001 C ompounds with imidazoline structure are potent stimulators of insulin secretion in pancreatic ␤-cells (1). This effect is thought to be due to the blockade of ATP-dependent K ϩ channel (K ATP ) activity and the increase in cytosolic free Ca 2ϩ concentration ([Ca 2ϩ ] i ) (2). Recently, we have shown that the imidazoline compound RX871024, in addition to blocking K ATP channels and increasing [Ca 2ϩ ] i , exerts its insulinotropic effect by enhancing insulin exocytosis at stages distal to the increase in [Ca 2ϩ ] i (3-5). This direct stimulation of exocytosis was only observed at elevated glucose concentrations and required activation of protein kinases A and C.Sulfonylurea drugs, which are currently used in the treatment of type 2 diabetes, block K ATP channels in ␤-cells and stimulate insulin secretion at both low and high glucose concentrations (6). The strong insulinotropic effect of sulfonylureas observed at low glucose concentrations often provokes pronounced hypoglycemia in patients treated with these drugs (7). Therefore, agents that do not stimulate basal insulin secretion but augment glucoseinduced insulin secretion by modulating Ca 2ϩ -stimulated insulin exocytosis could provide a better therapeutic alternative to sulfonylureas.We now demonstrate that an imidazoline compound, BL11282 (Fig. 1A, insert), represents a new class of insulinotropic compounds that do not stimulate basal insulin secretion and lack the effect on K ATP channel activity, but markedly potentiate glucose-induced insulin secretion. RESEARCH DESIGN AND METHODS BL11282 and LY333531 were obtained from Eli Lilly (Indianapolis, IN).Rp-cAMPS was from Calbiochem (San Diego, CA). All other reagents were from Sigma (St. Louis, MO). Intravenous glucose tolerance test. The intravenous glucose tolerance test ...

Rational treatment of primary hypertension remains elusive, owing to a lack of knowledge about the pathogenesis of blood pressure elevation. Established hypertension is associated with well-described cardiovascular hemodynamic changes. Because the cardiovascular system is self-regulating, the action of an antihypertensive on one of the regulatory mechanisms induces changes in others. A drug-induced decrease of the elevated peripheral resistance leads to compensatory reflex mechanisms. The use of centrally acting drugs avoids compensatory neural reflexes. Furthermore, the participation of the central and autonomic nervous systems in the pathogenesis of hypertension is probable. The development of drugs aimed at controlling the central nervous system (CNS) would, therefore, be reasonable. The use of a,-adrenoceptor agonists, such as clonidine, as antihypertensive agents has declined. The mean reason being a high rate of side effects such as sedation, dry mouth with marked reduction in salivary flow, and other nonspecific effects. The mode of action was explained by stimulation of both pre-and postsynaptic a,-adrenoceptors within the CNS . However, recent investigations have clearly demonstrated that centrally acting drugs like clonidine and moxonidine induce their antihypertensive effects primarily by high affinity binding at the imidazoline receptors. Most of the side effects are induced by an action at aw,-receptors. The difference between clonidine and moxonidine is moxonidine's pronounced selectivity for imidazoline rather than ctzreceptors. Moxonidine and other related compounds may reestablish the use of centrally active drugs in antihypertensive therapy.~ ~~~

The imidazoline compound RX871024 glucose-dependently potentiates the release of insulin in pancreatic islets and beta-cell lines. This activity of the compound is not related to its action by stimulating alpha 2-adrenoceptors and I1- and I2-imidazoline receptors. There are at least three modes of action of RX871024 in beta-cells: (1) RX871024 blocks the ATP-dependent, Ca(2+)-activated, and delayed rectifier K+ channel activity; (2) RX871024 causes mobilization of Ca2+ from thapsigargin-sensitive intracellular stores, the effect probably controlled by cytochrome P450; and (3) the stimulatory activity of RX871024 on insulin release involves interaction of the compound with the exocytotic machinery, unrelated to the changes in membrane potential and cytoplasmic-free Ca2+ concentration, whereas protein phosphorylation plays an important role in this process. The maximal insulinotropic effect of RX871024 is much higher than that of the sulfonylurea glibenclamide. RX871024 stimulates insulin release and normalizes blood glucose levels in rats in vivo without affecting blood pressure and heart rate.