In a rodent study, scientists have found that a drug called rapamycin can help restore blood flow to the brain that is lost during aging and can help modify the memory loss that accompanies this change. The findings, which have been reported in Aging Cell, may help create new treatments for the health problems that come with aging and could offer a way to prevent dementia that’s related to Alzheimer’s disease.
In this study, the researchers exposed rats to rapamycin past their middle age, when they were about 19 months old. The rats continued to receive the drug in their food until they reached an advanced (rat) age of 34 months old.
"Essentially this is as old as these rats can get. These animals were very old but still, blood circulation in the brain was exactly the same as when they started treatment," noted the senior study author Veronica Galvan, Ph.D., a professor of cellular and integrative physiology at University of Texas (UT) Health San Antonio.
Rats that were not treated with rapamycin behaved as was expected for older adults; they began to lose blood flow to the brain and had memory loss. "In contrast, the old rats treated with rapamycin looked like middle-aged rats in our study," Van Skike revealed.
"Aging is the strongest risk factor for dementia, so it is exciting that rapamycin, a drug known to promote longevity, may also help preserve the integrity of brain circulation and memory performance in older adults," said Sudha Seshadri, M.D., a professor of neurology at UT Health San Antonio and director of the Glenn Biggs Institute. "We are already studying the safety of the drug in persons with mild cognitive impairment, a precursor to dementia as a collaboration among Biggs and Barshop researchers."
The researchers did not use a dementia or disease animal model to study the impacts of the drug. "We were looking at just regular aging," said Van Skike. "These rats had natural cognitive decline that was not provoked by a forced disease process."
An enzyme that is known to play a critical role in regulating aging and cell growth is known as target of rapamycin (TOR). Galvan noted that this work provides "very good evidence" that TOR triggers the loss of neural connections known as synapses and blood flow to the brain during aging.
Blood flow to the brain is critical; it provides enormous amounts of energy in the form of glucose and oxygen to support function. Recent research led by Seshadri has suggested that disruption in cerebral blood flow is an early risk factor for Alzheimer's disease.