Hopes were raised that diabetes drugs could be developed as treatments for Alzheimer’s disease after scientists demonstrated the beneficial effect of insulin on the brain.

A US-led research team found the hormone, released by the pancreas to help control levels of sugar in the blood, protected memory-forming parts of the brain. The study, published in the Proceedings of the National Academy of Sciences, concluded that insulin may slow or prevent the memory loss caused by toxic proteins which attack the brains of Alzheimer’s sufferers.

It boosts theories the disease — characterised by progressively catastrophic dementia — could be due to a type of brain diabetes.

People with diabetes either fail to produce insulin, do not produce enough or fail to use what is produced effectively.

Researchers from Northwestern University in Illinois and the Federal University of Rio de Janeiro in Brazil carried out a study that involved treating neurons taken from one of the brain’s memory centres — the hippocampus — with insulin and diabetes drug rosiglitazone.

Cells in the hippocampus are susceptible to damage caused by ADDLs, toxic proteins that build up in people with Alzheimer’s disease.

ADDLs (amyloid beta-derived diffusible ligands) are known to attack memory-forming synapses, according to the scientists.

After the proteins have attached, the synapses lose their capacity to respond to incoming information, resulting in memory loss.

The researchers discovered damage to neurons exposed to ADDLs was blocked by insulin, which stopped the proteins from attaching to the cells.

The insulin-sensitising drug rosiglitazone enhanced protection by low levels of insulin, the study found.