A drug pairing that's become popular in longevity circles has blindsided researchers with evidence of severe brain damage in mice. The findings, published in the Proceedings of the National Academy of Sciences, could reshape how scientists approach treatments aimed at extending lifespan and delaying age-related disease.
The culprit is dasatinib plus quercetin, a combination known in research circles as D+Q. These drugs have attracted widespread attention for their theoretical ability to clear out senescent cells, which accumulate with age and trigger chronic inflammation linked to diabetes, heart disease, and neurodegeneration. Yet myelin, the insulating layer that wraps nerve fibers and allows electrical signals to travel through the brain and body, took a beating when exposed to D+Q in the University of Connecticut study.
"When you administer this cocktail to an animal, young or old, the myelin is damaged, which makes it disappear," said Stephen Crocker, an immunologist at UConn School of Medicine. "Even worse in the young animals."
Myelin loss translates to real neurological consequences: numbness, pain, walking difficulties, and cognitive problems. The damage mirrors what happens in multiple sclerosis, a disease that targets myelin-producing cells.
The research team, led by scientists now at Dartmouth and Anna Maria College, initially set out to test whether D+Q might repair brain damage associated with MS. Instead, they found the opposite. Both young mice (6 to 9 months old) and older mice (22 months old) showed dramatic thinning of myelin layers after treatment. The younger animals suffered worse degradation than their aged counterparts, an unexpected result that contradicts typical assumptions about how drugs affect different age groups.
The brain's corpus callosum, the major connector between the two cerebral hemispheres, deteriorated noticeably in treated animals. The pattern mirrors damage seen in cancer patients experiencing chemotherapy side effects colloquially known as "chemo brain."
What happened to the myelin-producing cells themselves reveals an intriguing mechanism. The oligodendrocytes didn't die. Instead, they regressed into a juvenile, less functional state. The cells appeared starved of energy, forcing them to shed complexity as a survival strategy.
"We suspect the drugs are choking off energy the cells need, and the cells respond by reducing complexity, reverting to a younger state, but less functional," Crocker said.
The reverted cells bore striking resemblance to abnormal populations found in people with multiple sclerosis, opening a new avenue for understanding how the disease progresses. If myelin-producing cells enter a dormant state rather than dying, they might retain the capacity for recovery, Crocker and his team theorize. Current work focuses on whether these damaged cells can be coaxed back to health and encouraged to rebuild myelin.
The discovery carries immediate implications beyond the lab. D+Q is being tested clinically for type 2 diabetes and Alzheimer's disease. Outside formal clinical trials, some people interested in longevity have experimented with the drugs on their own, despite medical warnings. The new evidence suggests such self-administration carries unknown brain risks.
Author Jessica Williams: "This is a stark reminder that a drug's theoretical benefits don't automatically translate to safety in a living brain."
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