Endocrine Abstracts

The neurotransmitter Serotonin (5-hydroxytrympatmine (5-HT), influences hormone secretion from human and rodent islets of Langerhans. Given its confirmed local production in the insulin producing beta (β)-cells, this monoamine has been shown to modulate insulin secretion by both intra- and extracellular mechanisms. However, the precise mechanisms by which 5-HT its effects on insulin release and whole-body glucose metabolism is yet to be fully understood. Fourteen different 5-HT receptors are present in human islets, localized in the different hormone-secreting cell types (e.g., α-and β-cells). The receptors activate a number of intracellular signaling pathways. In fact, both stimulatory and inhibitory actions on insulin release by 5-HT have been observed. Recent advances have pinpointed specific receptors as being crucial for regulation of β-cell mass and compensatory insulin release during pregnancy. Under such circumstances, changes in metabolic status appear to alter both the synthesis of β-cell 5-HT as well as expression of specific 5-HT receptors. Whether actions of 5-HT are implicated in β-cell dysfunction in Type 2 Diabetes is yet to be clarified, but cannot be excluded. Indeed, 5-HT may be an important modulator that fine tunes the release of insulin both and glucagon, the two main hormones that control glucose and lipid homoeostasis.