Brain injury protein in the blood could help estimate biological age in animals

The protein "neurofilament light chain" (NfL) – studied in humans in the context of neurodegenerative diseases and aging – is also detectable in the blood of numerous animals, and NfL levels increase with age in mice, cats, dogs, and horses. Experts from the DZNE and the Hertie Institute for Clinical Brain Research (HIH) at the University of Tübingen report these findings in the scientific journal "PLOS Biology". In their view, this biomarker could help to assess the biological age of animals and estimate their life expectancy.

The protein NfL is an indicator of nerve damage. It is released when neurons undergo change or degenerate, either as a result of disease or with normal aging. NfL can then enter the bloodstream and be detected using sensitive analysis techniques.

In neurodegenerative diseases such as Alzheimer's and ALS, NfL is found at elevated levels in the blood. However, the concentration also rises in healthy people with age. We have now observed a very similar age-related increase in mice, cats, dogs, and horses."

Prof. Mathias Jucker, research group leader at DZNE and HIH

Marker with predictive power

Studies have revealed that the concentration of NfL in the blood of elderly people is associated with an increased risk of death, suggesting a link between neurological aging and mortality. Dr. Carina Bergman, a scientist in Jucker's team, now came across similar findings in mice. The blood of 44 older animals was monitored regularly over 4 months. Those with slowly rising NfL levels lived comparatively longer, while faster increases were linked to shorter lifespans.

"Our data therefore suggest that life expectancy of mice can be estimated from the rate of change of NfL levels – similar to what has been reported for aging humans," says Bergmann.

Over 50 animal species

In addition to cats, dogs, horses, and mice (with the latter being studied in particular detail), a further 53 animal species were examined on a sampling basis. This included rabbits, lions, monkeys, elephants, reptiles, and birds. This was done in collaboration with the zoo in Stuttgart, Germany, the Vetsuisse Faculty at the University of Zurich, and a veterinary diagnostics laboratory. The NfL protein was detected in the blood of all mammals, but only in some reptiles and birds, such as a crocodile and a parrot. A possible explanation is that the NfL protein sequence in these animals differs slightly from its human counterpart, and therefore could not be detected by the assay used in the present study. "Overall, however, our data show that analysis methods from dementia research are also promising for veterinary medicine, when it comes to assessing the biological age, neurological health, and life expectancy of animals, says Jucker.