Somatostatin-14 modulates postprandial glucose levels and release of gastrointestinal and pancreatic hormones

Ingestion of a 4, 500-kcal mixed meal by healthy volunteers resulted in a significant rise of plasma somatostatin-14-like immunoreactivity (9 ± 1 pmol 1^-1). Whether this peptide has a role as a humoral agent or not is still controversial and, until recently, most studies investigating its effects by exogenous administration have produced vastly supraphysiological circulating plasma levels. In order to reproduce the rise obtained following the large meal, synthetic somatostatin-14 was infused at a dose of 0.8 pmol kg^-1 min^-1 before and during a 530-kcal test breakfast. This resulted in a rise of 8 + 2 pmol 1^-1 in the peripheral circulation. This infusion produced a significant reduction in the postprandial release of insulin, gastric inhibitory polypeptide, pancreatic polypeptide and in the preprandial motilin levels. In contrast, blood glucose levels following the breakfast were elevated when compared to the control saline infusion. This suggests that somatostatin possesses true endocrine functions and is capable of profoundly altering the postprandial glucose and hormone response.