GCG and diabetes mellitus: Hepatocytes prepared from db/db mice showed higher levels of glucagon-induced nuclear Ca2+ signals and gluconeogenic gene expression when compared to hepatocytes from m + /db mice, which was reduced by 8-Br-ADPR (Fig. 7b, c), implicating the potential role of ADPR-mediated nuclear Ca2+ signals in the pathogenesis of diabetes in association with gluconeogenesis.