Chromogranin-B regulation of IAPP and insulin secretion

In the endocrine pancreas, chromogranin-A and pancreastatin have been suggested to inhibit islet insulin secretion, whereas chromogranin-B has not been studied in this context. Furthermore, a putative effect by chromogranins on IAPP secretion is unknown. We aimed to elucidate the endogenous effect of chromogranin-A, pancreastatin and chromogranin-B on islet insulin and IAPP secretion from pancreatic NMRI mouse islets. In acute experiments, there was a tendency towards an increase in insulin release, which became more manifest after a 48-h exposure. Moreover, 48 h exposure to chromogranin-B antiserum resulted in a significant increase in (pro)insulin synthesis. Neither antibodies against chromogranin-A nor pancreastatin had any effect on islet hormone secretion. None of the antibodies tested had any effect on islet IAPP or insulin content. We suggest that chromogranin-B released from islets may have an autocrine inhibitory effect on islet IAPP and insulin secretion. Our data imply a regulatory role of chromogranin-B in islet IAPP and insulin secretion.