CMR12, a novel insulinotropic compound, enhances second-phase insulin secretion with metabolic changes in pancreatic β-cells.

Insulin secretion from pancreatic β-cells is primarily regulated by glucose stimulation, while cAMP-mediated amplifying pathways also play an important role. In this study, we identified compound 42 (C42) as an insulinotropic hit compound through an in silico similarity search using the cAMP analog Sp-cAMPS as a query. Further structural development by chemical synthesis yielded CMR12, a novel derivative with enhanced insulinotropic activity. This class of compounds enhances insulin secretion in MIN6-K8 cells in a glucose concentration-dependent and compound concentration-dependent manner, and shows a modest suppression of glucose excursion during oral glucose tolerance testing in mice. CMR12 also exhibited strong insulinotropic activity in isolated mouse islets and preferentially enhanced the sustained second phase of glucose-stimulated insulin secretion in perfused mouse pancreas. These compounds did not clearly increase Epac2-related FRET responses, intracellular cAMP, or cytosolic Ca2+ levels. CE-MS-based metabolomic analysis of C42-treated MIN6-K8 cells revealed selective metabolic alterations, including increased levels of 2-oxoglutarate and multiple amino acids, without a detectable increase in ATP levels. These findings suggest that CMR12 enhances glucose-stimulated insulin secretion, particularly second-phase secretion, through a mechanism that is not primarily dependent on canonical cAMP- or Ca2+-mediated pathways. CMR12 may serve as a seed compound for developing new therapeutic strategies targeting impaired insulin secretion.