Alzheimer’s-linked brain changes found in monkeys without memory loss

Researchers have identified molecular changes associated with Alzheimer’s disease in the brains of African green monkeys, without any signs of memory loss, after a year of exposure to amyloid-beta protein clusters.

The study, published in the journal Communications Biology, reported that five out of eight monkeys received lab-produced amyloid-beta clusters, while three others were given a control solution for comparison.

The animals received 12 doses over four weeks—three doses per week—administered through a port connected to the fluid surrounding the spinal cord.

Researchers monitored the monkeys’ performance in memory tests for a year and analyzed samples of cerebrospinal fluid. Despite the biological changes observed in the samples, no clear decline in memory was recorded in the monkeys that received amyloid-beta.

After 12 months, analyses showed increased levels of the protein C3, linked to immune response, and a decrease in certain proteins associated with neural connections.

Changes were also detected in blood vessel proteins and blood clotting processes, in addition to other protein alterations in extracellular vesicles.

Bianca Brown of Yale University emphasized that the results do not indicate the monkeys developed Alzheimer’s, but suggest the nervous system can retain long-term biological changes without behavioral symptoms or memory loss.

The researchers believe studying these changes could help understand the early stages of the disease in humans and support the future development of early indicators and treatments for Alzheimer’s.