The islet beta-cell.

The beta-cell is one of four major types of cells present in the islets of Langerhans, which are islands of cells distributed throughout the endocrine pancreas in most mammals. The beta-cell synthesizes and secretes the hormone insulin mainly in response to glucose but also in response to several nutrients, hormones and nervous stimuli. In adult rodents the beta-cell has a slow mitotic rate. Recent studies provide novel insights into the functions of the beta-cell. The presence of functional insulin-like growth factor-1 and insulin receptors and components of their signaling pathway indicate an important role for insulin/IGF-1 signaling in the regulation of beta-cell function. Further, the recent discovery of glucokinase (GK) and the ATP-dependent potassium channels on insulin secretory granules, the detection of AMP-protein kinase in the beta-cell and the identification of a new beta-cell transcription factor, mMafA, are some exciting new areas of research currently underway to further understand the complex pathways that regulate the functions of beta-cells.