Once a hormone is released it can stimulate its own production. This principle was previously proven by Professor Berggren’s group in relation to insulin. Now the same group shows the generality of the approach: glucagon secreting cells increase their production when they sense increasing levels of glucagon. The results are published in PNAS in December 2012.
Hormones are powerful regulators of various biological processes. To ensure that there is always enough supply of the hormones, their secretion and production must be coupled. A simple but efficient way to provide such regulation is through an autocrine signalling, in which the molecules are sensed by those cells that produce them. Secretion and production of insulin by the pancreatic beta cells are connected via this positive autocrine feedback mechanism. It has though been considered to be an exception more than a rule due to the role that insulin plays in controlling blood sugar concentrations.
Glucagon is a peptide hormone secreted by alpha cells in the islets of Langerhans. This hormone has a role opposite to that of insulin: glucagon increases levels of blood sugar to avoid a dangerous state of hypoglycemia*. It is therefore of vital importance to have an absolute control of the blood glucagon levels.
Researchers in Professor Berggren’s group have recently shown that as in the case with insulin production, glucagon production is also regulated via autocrine signalling. Alpha cell have special receptors that sense secreted glucagon and translate the signal into increased production levels to ‘stock up’ the hormone for future use. Therefore, the positive autocrine feedback mechanism is a more general principle for hormone-secreting cells than previously anticipated.
* Hypoglycemia – dangerously low blood sugar concentration, a state that heavily affects the brain’s functions and possibly results in death.
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