cp-91149 and Diabetes-Mellitus--Type-2

Contributions of gluconeogenesis suppression in liver, kidney, and intestine as major gluconeogenic organs to the glucose-lowering effect of CS-917, a fructose 1,6-bisphosphatase inhibitor, was evaluated in overnight-fasted Goto-Kakizaki (GK) rats. CS-917 decreased plasma glucose by suppressing glucose release and lactate uptake from liver but not from kidney and intestine. These results suggest that hepatic gluconeogenesis suppression predominantly contributes to the glucose-lowering effect of CS-917 in GK rats. Moreover, the mechanism by which CS-917 decreased plasma glucose more in overnight-fasted GK rats than in non-fasted ones was investigated. Lactate uptake from liver was suppressed by 15 mg/kg of CS-917 in both states, but glucose release from liver and plasma glucose were decreased only in the overnight-fasted state. CS-917 at 30 mg/kg decreased hepatic glycogen content in both states and depleted it in the overnight-fasted state. In the non-fasted GK rats, co-administration of CS-917 with CP-91149, a glycogen phosphorylase inhibitor, suppressed hepatic glycogen reduction by CS-917 and decreased plasma glucose more than single administration of CS-917. These results suggest that gluconeogenesis suppression by CS-917 was counteracted by hepatic glycogenolysis especially in the non-fasted state and that combination therapy with CS-917 and CP-91149 is efficacious to decrease plasma glucose in GK rats.

Topics: Alanine; Amides; Animals; Blood Glucose; Diabetes Mellitus, Type 2; Drug Evaluation, Preclinical; Fasting; Gluconeogenesis; Glucose; Glycogenolysis; Hypoglycemic Agents; Indoles; Lactic Acid; Male; Organophosphonates; Organophosphorus Compounds; Peptide Hydrolases; Rats

Intraportal infusion of serotonin (5-hydroxytryptamine, 5-HT) or inhibitors of its cellular uptake stimulate hepatic glucose uptake in vivo by either direct or indirect mechanisms. The aims of this study were to determine the direct effects of 5-HT in hepatocytes and to test the hypothesis that atypical antipsychotic drugs that predispose to type 2 diabetes counter-regulate the effects of 5-HT.. Rat hepatocytes were studied in short-term primary culture.. Serotonin (5-HT) stimulated glycogen synthesis at nanomolar concentrations but inhibited it at micromolar concentrations. The stimulatory effect was mimicked by alpha-methyl-5-HT, a mixed 5-HT1/5-HT2 receptor agonist, whereas the inhibition was counteracted by a 5-HT2B/2C receptor antagonist. alpha-Methyl-5-HT stimulated glycogen synthesis additively with insulin, but unlike insulin, did not stimulate glucose phosphorylation and glycolysis, nor did it cause Akt (protein kinase B) phosphorylation. Stimulation of glycogen synthesis by alpha-methyl-5-HT correlated with depletion of phosphorylase a. This effect could not be explained by elevated levels of glucose 6-phosphate, which causes inactivation of phosphorylase, but was explained, at least in part, by decreased phosphorylase kinase activity in situ. The antipsychotic drugs clozapine and olanzapine, which bind to 5-HT receptors, counteracted the effect of alpha-methyl-5-HT on phosphorylase inactivation.. This study provides evidence for both stimulation and inhibition of glycogen synthesis in hepatocytes by serotonergic mechanisms. The former effects are associated with the inactivation of phosphorylase and are counteracted by atypical antipsychotic drugs that cause hepatic insulin resistance. Antagonism of hepatic serotonergic mechanisms may be a component of the hepatic dysregulation caused by antipsychotic drugs that predispose to type 2 diabetes.

Topics: Amides; Animals; Antipsychotic Agents; Benzodiazepines; Blotting, Western; Cells, Cultured; Clozapine; Diabetes Mellitus, Type 2; Enzyme Activation; Glycogen; Hepatocytes; Immunoblotting; Indoles; Male; Olanzapine; Phosphorylases; Rats; Rats, Wistar; Serotonin; Serotonin 5-HT1 Receptor Agonists; Serotonin 5-HT2 Receptor Agonists; Serotonin 5-HT2 Receptor Antagonists

Topics: Administration, Oral; Animals; Blood Glucose; Cell Line; Diabetes Mellitus, Type 2; Enzyme Inhibitors; Glycogen; Humans; Hypoglycemic Agents; Indoles; Liver; Mice; Mice, Obese; Phosphorylases; Recombinant Proteins; Stereoisomerism; Structure-Activity Relationship

An inhibitor of human liver glycogen phosphorylase a (HLGPa) has been identified and characterized in vitro and in vivo. This substance, [R-(R*, S*)]-5-chloro-N-[3-(dimethylamino)-2-hydroxy-3-oxo-1-(phenylmethyl)pr opyl]-1H-indole-2-carboxamide (CP-91149), inhibited HLGPa with an IC50 of 0.13 microM in the presence of 7.5 mM glucose. CP-91149 resembles caffeine, a known allosteric phosphorylase inhibitor, in that it is 5- to 10-fold less potent in the absence of glucose. Further analysis, however, suggests that CP-91149 and caffeine are kinetically distinct. Functionally, CP-91149 inhibited glucagon-stimulated glycogenolysis in isolated rat hepatocytes (P < 0.05 at 10-100 microM) and in primary human hepatocytes (2.1 microM IC50). In vivo, oral administration of CP-91149 to diabetic ob/ob mice at 25-50 mg/kg resulted in rapid (3 h) glucose lowering by 100-120 mg/dl (P < 0.001) without producing hypoglycemia. Further, CP-91149 treatment did not lower glucose levels in normoglycemic, nondiabetic mice. In ob/ob mice pretreated with 14C-glucose to label liver glycogen, CP-91149 administration reduced 14C-glycogen breakdown, confirming that glucose lowering resulted from inhibition of glycogenolysis in vivo. These findings support the use of CP-91149 in investigating glycogenolytic versus gluconeogenic flux in hepatic glucose production, and they demonstrate that glycogenolysis inhibitors may be useful in the treatment of type 2 diabetes.

Topics: Amides; Animals; Blood Glucose; Caffeine; Cells, Cultured; Diabetes Mellitus, Type 2; Enzyme Inhibitors; Humans; Indoles; Liver; Liver Glycogen; Male; Mice; Mice, Obese; Phosphorylases; Rats; Recombinant Proteins