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Paracrine regulation of somatostatin secretion by insulin and glucagon in mouse pancreatic islets – published online 12/10/2020

Svendsen GA

Berit Svendsen, Jens J. Holst

The alpha and beta cells of the islets of Langerhans secrete glucagon and insulin, which play an important role in regulating plasma glucose concentration, whilst the islet delta cells produce somatostatin, which is known to be able to inhibit the secretion of the other two hormones. In the islets, the three cell types are arranged in a complex pattern that, together with the capillary network, seems to be consistent with extensive paracrine interactions. For example, insulin is thought to directly inhibit glucagon secretion and recent research has revealed that local glucagon secretion is also essential for protein-stimulated insulin secretion. However, whether somatostatin secretion is regulated by paracrine signalling from glucagon and insulin is less clear. In this issue, Svendsen and Holst (https://doi.org/10.1007/s00125-020-05288-0) describe how somatostatin powerfully inhibits glucagon secretion and, conversely, how  glucagon secretion provides a powerful local stimulus for somatostatin secretion, linking the two in a reciprocal feed-back circuit.  Insulin did not directly affect secretion of somatostatin in mouse islets. The authors conclude that the results underline the importance of paracrine intra-islet regulation and suggests that a defect in one hormone will affect the secretion of other islet hormones. Thus, knowledge about islet somatostatin secretion appears to be essential for the understanding of integrated islet function.

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