Effects of insulin and glucose metabolism on pancreatic exocrine function

Glucose metabolism is highly dependent on hormones secreted by the islets of La ngerhans, and most notably on insulin. Moreover, the endocrine and exocrine pancreas has a complex anatomical and functional interaction. The exocrine part of the pancreas is influenced by the islet hormones mainly through an islet-acinar portal system, for example, the periinsular acinar cells are larger and contain more zymogen and amylase. The insulo-acinar axis is also indicated by morphological evidences. Hypoinsulinemia causes pancreatic atrophy with fat replacement of the exocrine pancreas in different species. These results indirectly show the significant role of insulin on pancreatic exocrine function. However, direct evidence is also available to highlight the key role of insulin. Both endogenous and exogenous insulin evoke increases in pancreatic enzyme synthesis and growth. Insulin is not only important in healthy conditions, but is also involved in the regenerative processes during pancreatitis. Human studies have also proved the necessity of insulin in pancreatic exocrine function. In conclusion, insulin has long term effects on the regulation of the biosynthesis of pancreatic digestive enzymes and short term effects on the stimulation of pancreatic secretion. Other peptides, such as pancreatic polypeptide, glucagon and somatostatin seem to inhibit pancreatic secretion, although more experiments are needed to clarify this hypothesis. Despite our current knowledge, many other hypotheses and questions remained unanswered concerning the effects of hormones secreted by different cells of the islets of Langerhans, therefore, it seems to be of great importance to explore the effects of these hormones on pancreatic exocrine function.