Sea Squirt Compounds Show Promise for Brain Aging in Mouse Studies

A marine animal eaten in parts of Asia has given researchers an unexpected window into how the aging brain changes. Sea squirts—known as meongge in Korea and hoya in Japan—contain unusually high levels of plasmalogens, a type of lipid that forms part of cell membranes. Scientists from Xi'an Jiaotong-Liverpool University, Stanford University, Shanghai Jiao Tong University, and the University of Chinese Academy of Sciences decided to test whether these compounds might slow or reverse some of the cognitive decline that comes with age.

Plasmalogens occur naturally throughout the human body, concentrated especially in the brain, heart, and immune cells. But as people grow older, plasmalogen levels drop steadily. The same decline appears in patients with Alzheimer's disease and Parkinson's disease, a pattern that prompted researchers to ask whether restoring these molecules might help restore lost function. They turned to aged mice to find out.

The experiment was straightforward. Researchers placed aged mice in a pool containing a hidden platform and measured how quickly they could learn to find it. After five days of training, the mice that had received plasmalogen supplements reached the platform significantly faster than untreated aged mice. Their performance resembled that of younger animals. When the researchers examined the brains of the treated mice, they found more synapses—the tiny junctions where nerve cells communicate—and those connections appeared to be in better structural condition than in untreated animals. Synapses are the physical basis of learning and memory; more of them, and healthier ones, should mean better cognitive function.

The treated mice also showed substantially lower levels of inflammation in their brains. This matters because while inflammation is part of the body's normal immune response, chronic or excessive inflammation in the aging brain can damage nerve cells and disrupt communication between synapses. As the brain ages, immune activity can become dysregulated, potentially accelerating cognitive decline. The reduction in inflammation in the plasmalogen-treated mice offered a plausible explanation for their improved performance in learning tests.

The researchers identified several possible mechanisms by which plasmalogens might produce these effects, though they do not yet know which one is primary. Plasmalogens significantly increased molecules associated with the growth and development of neurons and synapses, suggesting they may promote neuroregeneration. Professor Lei Fu noted that plasmalogens may also affect the structural properties of synapses by increasing the fluidity and flexibility of synaptic membranes, which could enhance the transmission of impulses between neurons. A third pathway involves the gut-brain connection: some studies show that dietary plasmalogens affect the microorganisms in the gut, and the researchers suggested that this effect on the gut-brain axis could contribute to the improvements in learning and memory they observed.

But the findings remain confined to mice. The study does not establish that eating sea squirts or taking plasmalogen supplements can reverse aging in people. Researchers would need to conduct human trials to determine whether similar effects occur in humans, what doses might be effective, and whether long-term supplementation is safe. For now, the work offers scientists a new avenue for investigating how plasmalogens might influence the changes associated with aging—and a reminder that the answer to some of medicine's oldest questions might be hiding in foods that have been eaten for centuries in other parts of the world.