For more than a century, biologists have observed that lower ambient temperatures can lengthen the lifespans of animals ranging from worms and flies to fish and rodents. Now, researchers at the University of Cologne in Germany have mapped a specific biochemical mechanism that drives the phenomenon, showing that muscle tissue plays a central role in coordinating the anti-aging response across the body.
The study, published in the journal Nature, reveals that moderately cool environments prompt muscle cells to produce a vital metabolite called dihydrobiopterin, or BH2. Once released into circulation, the molecule protects distant organs from cellular damage and curbs the accumulation of harmful protein clumps associated with neurodegenerative diseases, ScienceAlert reported.
A chemical shield triggered by a chill
In experiments led by molecular biologist David Vilchez, scientists compared the roundworm Caenorhabditis elegans raised at a standard temperature of 20 degrees Celsius (68 degrees Fahrenheit) against worms kept at 15 degrees Celsius (59 degrees Fahrenheit). On average, the chilled worms lived about 15 percent longer, SingularityHub reported.
A metabolomics analysis identified 64 metabolites that surged at the cooler temperature, with BH2 showing the sharpest increase, according to BioTechniques. The researchers traced this surge to elevated production of an enzyme called CAT-4, predominantly inside the worms’ muscle tissue.
From the muscles, BH2 traveled to other tissues, including the intestine and the brain. Once there, it transformed into a bioactive molecule called tetrahydrobiopterin, or BH4, which activated an enzyme named PAH-1 to produce the amino acid tyrosine. When researchers disrupted the chemical cascade, the longevity advantage granted by cooler temperatures disappeared.
“We are excited to show that mildly cold temperatures trigger significant production of a specific metabolite, BH2, which is synthesized, stored, and subsequently released by muscle tissue,” Vilchez said, as quoted by ScienceAlert. “BH2 then goes to other parts of the body, where it helps to maintain protein homeostasis and contributes to tissue health during aging.”
Replicating cold benefits without the freeze
Crucially, the researchers demonstrated that an actual temperature drop might not be required to reap the benefits. By genetically elevating CAT-4 levels inside the worms’ muscles, the team extended the animals’ lifespan even when they remained at standard and warmer temperatures.
The findings also offered insights into age-related illness. In worm models of Huntington’s disease, the BH2 pathway preserved protein homeostasis, known as proteostasis, and prevented toxic proteins from clumping together. Subsequent laboratory tests on engineered human cells yielded comparable outcomes:
- Adding BH2 to human cells reduced the buildup of abnormal proteins tied to Huntington’s disease and amyotrophic lateral sclerosis, also known as ALS.
- Supplying both BH2 and tyrosine reduced programmed cell death in cultured human motor neurons carrying an ALS mutation.
- Feeding tyrosine directly to roundworms unable to synthesize BH2 extended their lifespans even in the absence of cold conditions.
“These findings suggest that specifically targeting a single tissue, such as muscle, could provide organism-wide protection,” Vilchez said, according to ScienceAlert. “This opens up new avenues for therapeutic approaches.”
A distant path to human therapies
Scientists caution that while the molecular mechanism is promising, practical applications for people remain far in the future. The findings so far rely on laboratory experiments in microscopic worms and cultured human cells, not living people, UA.NEWS reported.
Medical experts also warn against attempting self-treatment with over-the-counter supplements like tyrosine. In mammals, the delicate balance between BH2 and its active derivative regulates harmful reactive oxygen species. Flooding the system with uncalibrated doses could upset that balance, potentially accelerating cell damage or triggering unpredictable side effects across other enzymatic pathways, SingularityHub reported.
Moving forward, researchers aim to investigate whether existing medications that influence this metabolic cascade could provide clues for human health. Scientists also plan to conduct further tests to determine whether therapies targeting muscle tissue can safely replicate the life-extending power of cold exposure in larger mammals.
