Degradation of memory functions is one of the main signs of decline in patients with Alzheimer's disease. However, in a new study involving mice, researchers from Kyushu University have found that a fragment of protein derived from soybeans can reduce memory impairment in mice that have been induced with the disease.
By breaking down proteins from soybeans, the memory-improving molecule was derived. It is classified as a dipeptide as it contains only two amino acids, which are building blocks of proteins. The dipeptide studied here is known as Tyr-Pro. It is unique as it was able to reach the mice's brain successfully and enabled the improvement of impaired memory functions.
"While our previous studies were the first to identify a dipeptide able to make the journey, our new studies now show that it can actually affect memory in mice," said Toshiro Matsui, lead author of the study.
Feeding Mice The Dipeptide
For the study, the researchers analyzed the effects of the dipeptide. It is named Tyr-Pro because it consists of two amino acids —Tyrosine and Proline. Peptides often fail to make the journey to the brain due to several layers of barriers that they pass. However, Tyr-Pro was able to make its way to the brains of the mice.
"On top of the possibility of being broken down during digestion, peptides then face the challenge of crossing a highly selectively barrier to get from the blood into the brain," explained Matsui.
Tyr-Pro was fed to mice several days prior to injecting them with a chemical that is used to simulate the effects of Alzheimer's disease by impeding memory functions. Tyr-Pro was fed to the mice after the injection of the chemical as well for several days.
Noticeable Improvement In Memory Functions
Tests to evaluate short-term memory of the mice were carried out using a simple maze where the ability of the mice to explore different arms of the maze was compared. Impaired mice that had consumed the dipeptide over the duration of two weeks performed better than those who had not. However, the mice that did not have induced memory impairment outshined both the groups.
During the tests to evaluate long-term memory, the results were similar. The test measured the duration for which a mouse stayed in the illuminated area of an enclosure to avoid receiving a mild electrical shock in the dark area after being trained in the box the previous day.
Offering New Evidence
There have been studies that have suggested that certain peptides can diminish the rate at which brain functions decline. Nevertheless, the current study is the first to provide evidence that peptides have the ability to enter the brain intact.
The scientists are hopeful that the results of the study can be replicated in human beings someday. "We still need studies to see if these benefits carry over to humans, but we hope that this is a step toward functional foods that could help prevent memory degradation or even improve our memories," concluded Matsui.