Potential role of the CD38/cADPR signaling pathway as an underlying mechanism of the effects of medetomidine on insulin and glucose homeostasis

Objective: To investigate the CD38/cADPR signaling pathway as possible underlying mechanism of the effects of medetomidine on insulin and glucose homeostasis. Animals: Thirty-two C57BL/6 mice of both sexes. Methods: Wild-type (WT) and CD38-knockout (CD38^-/-) mice received medetomidine (50 μg kg^-1) or a similar volume of 0.9% NaCl (control) by intraperitoneal (IP) injection (each group n = 8). The mice were euthanized 45 minutes later with sodium pentobarbital IP and blood was sampled via cardiac puncture. Insulin and glucose concentrations were measured by radioimmunoassay and by the oxygen rate method, respectively. Data were analyzed with anova and Bonferroni post hoc (5% significance) and are shown as mean ± SD. Results: Plasma insulin and glucose concentrations were similar between WT and CD38^-/- mice under control conditions. As compared to controls, medetomidine administration produced a statistically significant decrease in plasma insulin concentrations in the WT mice whereas the decrease in the CD38^-/- mice was not statistically significant. Correspondingly, medetomidine caused a significantly greater increase in plasma glucose concentrations in the WT than in the CD38^-/- mice. Conclusion: The CD38/cADPR signaling pathway may be one underlying mechanism of the glucose and insulin effects of the alpha-2 adrenergic receptor agonist medetomidine and likely other drugs of its' class.