ABSTRACT
Racemic cis-1,1-dioxo-5,6-dihydro-[4,1,2]oxathiazine derivative 4a was isolated as an impurity in a sample of a hit from a HTS campaign on 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1). After separation by chiral chromatography the 4a-S, 8a-R enantiomer of compound 4a was identified as the true, potent enzyme inhibitor. The cocrystal structure of 4a with human and murine 11ß-HSD1 revealed the unique binding mode of the oxathiazine series. SAR elucidation and optimization in regard to metabolic stability led to monocyclic tetramethyloxathiazines as exemplified by compound 21g.
Subject(s)
11-beta-Hydroxysteroid Dehydrogenase Type 1/antagonists & inhibitors , Diabetes Mellitus/drug therapy , Enzyme Inhibitors/chemical synthesis , Models, Molecular , Thiazines/chemical synthesis , Animals , Binding Sites , Enzyme Activation/drug effects , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Enzyme Stability , Humans , Hypoglycemic Agents/chemistry , Hypoglycemic Agents/pharmacology , Inhibitory Concentration 50 , Mice , Molecular Structure , Stereoisomerism , Structure-Activity Relationship , Thiazines/chemistry , Thiazines/pharmacologyABSTRACT
BACKGROUND: In diabetic patients, the pharmacokinetics of injected human insulin does not permit optimal control of glycemia. Fast and slow acting insulin analogues have been developed, but they may have adverse properties, such as increased mitogenic or anti-apoptotic signaling. Insulin/IGF1 hybrid receptors (IR/IGF1R), present in most tissues, have been proposed to transmit biological effects close to those of IGF1R. However, the study of hybrid receptors is difficult because of the presence of IR and IGF1R homodimers. Our objective was to perform the first study on the pharmacological properties of the five marketed insulin analogues towards IR/IGF1R hybrids. METHODOLOGY: To study the effect of insulin analogues on IR/IGF1R hybrids, we used our previously developed Bioluminescence Resonance Energy Transfer (BRET) assay that permits specific analysis of the pharmacological properties of hybrid receptors. Moreover, we have developed a new, highly sensitive BRET-based assay to monitor phophatidylinositol-3 phosphate (PIP(3)) production in living cells. Using this assay, we performed a detailed pharmacological analysis of PIP(3) production induced by IGF1, insulin and insulin analogues in living breast cancer-derived MCF-7 and MDA-MB231 cells. RESULTS: Among the five insulin analogues tested, only glargine stimulated IR/IGF1R hybrids with an EC50 that was significantly lower than insulin and close to that of IGF1. Glargine more efficiently stimulated PIP(3) production in MCF-7 cells but not in MDA-MB231 cells as compared to insulin. In contrast, glargine metabolites M1 and M2 showed lower potency for hybrid receptors stimulation, PIP(3) production, Akt and Erk1/2 phosphorylation and DNA synthesis in MCF-7 cells, compared to insulin. CONCLUSION: Glargine, possibly acting through IR/IGF1R hybrids, displays higher potency, whereas its metabolites M1 and M2 display lower potency than insulin for the stimulation of proliferative/anti-apoptotic pathways in MCF-7 cells.
Subject(s)
Insulin, Long-Acting/metabolism , Insulin, Long-Acting/pharmacology , Receptor, IGF Type 1/metabolism , Receptor, Insulin/metabolism , Recombinant Fusion Proteins/metabolism , HEK293 Cells , Humans , Insulin Glargine , MCF-7 Cells , Phosphatidylinositol Phosphates/biosynthesis , Signal Transduction/drug effectsABSTRACT
BACKGROUND: Insulin glargine (Lantus) is a long-acting basal insulin analog that demonstrates effective day-long glycemic control and a lower incidence of hypoglycemia than NPH insulin. After subcutaneous injection insulin glargine is partly converted into the two main metabolites M1 ([Gly(A21)]insulin) and M2 ([Gly(A21),des-Thr(B30)]insulin). The aim of this study was to characterize the glargine metabolites in vitro with regard to their insulin receptor (IR) and IGF-1 receptor (IGF1R) binding and signaling properties as well as their metabolic and mitogenic activities. METHODS: The affinity of human insulin, insulin glargine and its metabolites to the IR isoforms A and B or IGF1R was analyzed in a competitive binding assay using SPA technology. Receptor autophosphorylation activities were studied via In-Cell Western in CHO and MEF cells overexpressing human IR-A and IR-B or IGF1R, respectively. The metabolic response of the insulins was studied as stimulation of lipid synthesis using primary rat adipocytes. Thymidine incorporation in Saos-2 cells was used to characterize the mitogenic activity. CONCLUSIONS: The binding of insulin glargine and its metabolites M1 and M2 to the IR were similar and correlated well with their corresponding autophosphorylation and metabolic activities in vitro. No differences were found towards the two IR isoforms A or B. Insulin glargine showed a higher affinity for IGF1R than insulin, resulting in a lower EC(50) value for autophosphorylation of the receptor and a more potent stimulation of thymidine incorporation in Saos-2 cells. In contrast, the metabolites M1 and M2 were significantly less active in binding to and activation of the IGF1R and their mitogenicity in Saos-2 cells was equal to human insulin. These findings strongly support the idea that insulin glargine metabolites contribute with the same potency as insulin glargine to blood glucose control but lead to significantly reduced growth-promoting activity.
