A study in Nature Aging led by UC San Francisco researchers has identified an iron-associated protein that appears to drive age-related memory decline in mice. The protein, called FTL1, increased in the hippocampus as mice aged. When scientists reduced it in older animals, brain-cell connections improved and the mice performed better on memory tests.
The findings point to a specific molecular change inside the aging brain. The hippocampus is central to learning and memory and it is especially vulnerable as animals grow older. In this study, FTL1 stood out because its levels rose with age and tracked with poorer cognitive performance.
The work is still early-stage. The experiments were performed in mice and in lab-grown neurons, so the results do not yet show that lowering FTL1 would restore memory in people. Even so, the study gives aging researchers a sharper target for future work on cognitive decline.
FTL1 Rises in the Aging Hippocampus
UC San Francisco scientists began by looking for molecular changes in the hippocampus. They compared young mice with older mice and tracked age-related shifts in genes and proteins. Among the many signals they examined, FTL1 in the hippocampus emerged as a consistent difference between the two age groups.
FTL1 stands for ferritin light chain 1. Ferritin proteins help cells handle iron, an essential metal that must be carefully controlled. In the aging mouse hippocampus, higher levels of FTL1 appeared alongside weaker neural connections and worse performance on cognitive tests.
That pattern gave the researchers a clue. If FTL1 simply rose during aging, it might have been a marker of age. The study went further by changing FTL1 levels directly and watching how the brain responded. Those experiments made the protein look like an active driver of decline.
The study focused on neurons, the brain cells that send and receive information. In older mice, neuronal FTL1 increased in a region that supports memory formation. This link between an iron-associated protein and memory circuits suggests that iron biology may be tied closely to how the aging brain loses flexibility.
Young Brains Took on Aging Traits
To test whether FTL1 could push the brain toward an older state, the team increased FTL1 levels in young mice. The result was striking. Their brains began to show features normally associated with aging, including reduced synaptic connections in the hippocampus.
Synapses are the contact points where neurons communicate. Dense and healthy synaptic networks help the brain store information and adapt to new experiences. When FTL1 rose in young mice, the researchers observed changes linked to poorer synaptic function and weaker cognition.
Lab experiments added another layer of evidence. Nerve cells engineered to produce high amounts of FTL1 developed simpler shapes. Instead of forming complex branching structures, these neurons grew shorter and less elaborate extensions. That kind of reduced branching can limit how well neurons connect with one another.
This matters because brain aging in mice involves more than a single memory score. It includes structural changes in neural circuits, molecular shifts inside cells and changes in how neurons use energy. Raising FTL1 touched several of these features at once.
The study also connected FTL1 to iron chemistry inside neurons. Increased FTL1 altered labile iron oxidation states, according to the paper. In plain terms, the protein seems to affect the form and handling of reactive iron inside brain cells. That finding may help explain why too much FTL1 can disrupt normal neuronal function.
Old Mice Regained Memory Function
The most important test came in older mice. When researchers reduced FTL1 in the hippocampus, the animals showed signs of recovery. Their synaptic connections increased and their performance on memory tests improved.
Saul Villeda, PhD, associate director of the UCSF Bakar Aging Research Institute and senior author of the paper, described the result in unusually strong terms. “It is truly a reversal of impairments,” he said.
That quote captures why the finding drew attention. Many aging studies focus on slowing damage or protecting cells before decline appears. Here, the researchers changed a protein in already old mice and saw improvement in brain features that had declined with age.
Villeda added, “It’s much more than merely delaying or preventing symptoms.” The statement refers to the mouse results. It should be read in that context, because the work has not yet reached clinical testing in humans.
The recovery involved both behavior and biology. The older mice did better on memory tasks and their hippocampal neurons showed more synaptic-related molecular changes. Together, those findings suggest that reducing FTL1 may reopen some capacity for repair in aging neural circuits.
A Metabolism Clue Points to Treatment Ideas
Further experiments linked FTL1 to the way neurons use energy. In the aging hippocampus, higher FTL1 was associated with changes in metabolic processes, including ATP synthesis. ATP is the main energy currency cells use to power their work.
When neurons have less efficient energy metabolism, they may struggle to maintain synapses and support memory. The study suggests that FTL1 can contribute to that problem. Elevated FTL1 made brain cells behave in ways that resembled older neurons, including a slower metabolic profile.
The researchers then tested whether boosting metabolism could counter those effects. In the study, NADH supplementation helped mitigate the pro-aging effects of neuronal FTL1 on cognition. NADH is involved in cellular energy production, so this result points to metabolism as one possible route for intervention.
This does not mean NADH is ready as a treatment for memory decline. The study’s evidence comes from preclinical work and the brain is far more complex in people. Still, the result gives scientists a useful path to follow. If FTL1 harms neurons partly by changing energy use, therapies could aim at neuronal metabolism, FTL1 itself, or both.
The metabolism finding also makes the story broader than one protein alone. FTL1 may sit inside a network that includes iron balance, synaptic maintenance and energy production. Each part of that network could become a clue for future brain-aging research.
What This Could Mean for Brain Aging Research
The study offers a concrete target for a difficult problem. Age-related cognitive decline affects learning and memory and the hippocampus is one of the brain regions most tied to those abilities. By identifying FTL1 as a pro-aging neuronal factor in mice, the researchers have narrowed the search for mechanisms that might be modifiable.
For general readers, the central point is simple. Higher FTL1 in older mouse brains was linked with weaker connections and poorer memory. Increasing it in young mice produced aging-like changes. Lowering it in older mice improved memory performance and synaptic features.
Those three lines of evidence make the case stronger than a simple age comparison. The researchers observed FTL1 rising with age, then changed FTL1 levels experimentally. That approach helps move the finding closer to cause and effect within the limits of mouse research.
The limits remain important. Mice are powerful models for studying the brain, yet human aging involves decades of biology, lifestyle, disease risk and genetics. A future therapy would need to reach the right cells safely, adjust FTL1 carefully and avoid disrupting iron handling elsewhere in the brain or body.
Even with those caveats, Villeda sees real promise in the biology. “We’re seeing more opportunities to alleviate the worst consequences of old age,” he said. The study supports that optimism by showing that some aging-linked brain changes can be shifted in living animals.
Study Authors and Funding
The paper was led by researchers connected with UC San Francisco and published in Nature Aging in 2025. The senior author was Saul A. Villeda, whose work focuses on mechanisms that influence aging and rejuvenation in the brain.
Other UCSF authors listed in the supplied source material include Laura Remesal, Juliana Sucharov-Costa, Karishma J. B. Pratt, Gregor Bieri, Amber Philp, Mason Phan, Turan Aghayev, Charles W. White III, Elizabeth G. Wheatley, Brandon R. Desousa, Isha H. Jian, Jason C. Maynard and Alma L. Burlingame. The paper includes the full author list.
The work used several approaches to connect FTL1 with brain aging. These included gene and protein analyses in the hippocampus, experiments that increased FTL1 in young mice, experiments that reduced FTL1 in old mice and cell studies that examined neuron structure and metabolism.
Funding came in part from the Simons Foundation, the Bakar Family Foundation, the National Science Foundation, the Hillblom Foundation, the Bakar Aging Research Institute, Marc and Lynne Benioff and the National Institutes of Health. The NIH grant numbers listed in the supplied material include AG081038, AG067740, AG062357 and P30 DK063720.
Taken together, the study frames FTL1 protein as a key experimental target in mouse brain aging. It also highlights the value of looking inside specific brain regions, rather than treating aging as one uniform process across the body. For memory research, the hippocampus remains one of the clearest places to search for molecular changes that can be tested and, someday, possibly targeted.
