How genetic mutation causes low blood sugar found

Scientists have found how a genetic mutation may lead to excess production of insulin which causes hypoglycemia, an advance that may pave the way for new therapies for low blood sugar.
Diabetes is characterised by a deficiency of insulin. The opposite is the case in congenital hyperinsulinism: patients produce the hormone too frequently and in excessive quantities, even if they have not eaten any carbohydrates.
Since the function of insulin is to metabolise sugars, excess production of insulin leads to chronic hypoglycaemia or low blood sugar.
The brain, which devours vast quantities of energy, is perpetually undernourished. The disorder can therefore lead to serious brain damage and even death in the worst cases.

Researchers from University of Geneva (UNIGE) in Switzerland focused on a genetic mutation known to be associated with hyperinsulinism.
This gene produces a protein known as GDH, which instructs the pancreas to release insulin. It normally behaves differently once the level of blood glucose passes a certain threshold, researchers said.

The GDH then opens up to receive a molecule known as an accelerator that binds to it. The protein moves into the active phase, which in turn sends a signal to the pancreas, causing it to produce more insulin.
In congenital hyperinsulinism the mutant gene causes the structure of the protein to change.

The protein remains permanently receptive to the accelerator molecule, whatever the level of glucose in the blood.
As a result, it constantly sends signals to the pancreas, telling it to release insulin, which it then does excessively, they said.
Insulin promotes the transfer of glucose to the muscles. If there is a constant surplus of insulin, it leads to undernourishment of the brain, which in turn results in brain damage and intellectual retardation, and to coma and even death in the most critical cases, researchers said.
"In these patients, even a meal consisting solely of protein will trigger the production of insulin," said Pierre Maechler, a researcher at UNIGE.

The finding, published in the journal Human Molecular Genetics, could pave the way for new therapies.