Lows amounts of a brain protein called RbAp48 may be responsible for the memory loss that normally occurs in older individuals, a US study said Wednesday.

The findings offer "compelling evidence" that age-related memory loss is a condition distinct from Alzheimer's disease, researchers at the Columbia University Medical Center reported online in the journal Science Translational Medicine.

According to the researchers, the study suggests that this form of memory loss may be reversible and that therapies designed to boost the protein could benefit some older individuals.

The researchers examined eight healthy brains, a mix of young and old, from the New York Brain Bank at the Columbia University. The brains came from individuals who chose to donate their brains to science after death.

They found 17 genes that did not work properly in old brains compared with young brains in a part of the hippocampus, a brain region that plays a vital role in memory.

From these 17 genes, the gene that was most severely affected was RbAp48. Its expression, as well as the amount of the RbAp48 protein produced by the gene, was reduced by almost 50 percent in the so-called dentate gyrus of old brains, the researchers said.

To determine whether RbAp48 plays an active role in age-related memory loss, the researchers turned to mouse studies. They found that switching off the protein in younger mice made them forgetful, while increasing the protein in older mice restored their memory.

"We were astonished that not only did this (increasing the RbAp48 protein) improve the mice's performance on the memory tests, but their performance was comparable to that of young mice," lead author Elias Pavlopoulos, an associate research scientist at the Columbia University Medical Center, said in a statement.



The researchers described the findings that age-related memory loss in mice may be reversible as being "very encouraging."

"Of course, it's possible that other changes in the DG (dentate gyrus) contribute to this form of memory loss. But at the very least, it shows that this protein is a major factor, and it speaks to the fact that age-related memory loss is due to a functional change in neurons of some sort," said Nobel laureate Eric Kandel, who led the Columbia University team.

"Unlike with Alzheimer's, there is no significant loss of neurons," said Kandel.

Further research is needed to uncover exactly how aging reduces the amount of RbAp48 in the brain, and to determine if the protein can be targeted in the human brain, the researchers added.