Cold Temperatures and Longevity

When it comes to health, not all temperatures have the same impact.

Research indicates that cold temperatures might actually promote longevity, helping to boost metabolism and offering positive effects on a cellular level. In contrast, excessive heat tends not to be beneficial for the human body.

But what is it about cold that makes it advantageous in this regard?

A recent study published in Nature identified a mechanism behind these benefits, linked to a metabolic substance called dihydrobiopterin (BH2).

David Vilchez, a molecular biologist from the University of Cologne, expressed excitement at the findings, stating that mildly cold temperatures significantly boost the production of BH2, which is created, stored, and released by muscle tissue. This metabolite then travels to various parts of the body, playing a role in maintaining protein homeostasis and tissue health as we age.

Historically, scientists have known for over a century that cold conditions can increase lifespan in various animals, but the exact process was somewhat of a mystery.

Initial theories suggested it might be passive thermodynamic effects, but recent studies propose that cold-induced longevity is a result of actively regulated biological pathways that help organisms thrive.

In previous research, Vilchez and colleagues found that exposure to cold prompted the removal of harmful protein aggregates in the nematode worm Caenorhabditis elegans, initiating cellular structures known as proteasomes to break down protein waste.

In this latest study, the researchers explored the signals behind such reactions, considering that metabolites—small molecules produced through metabolism—might play a role.

Experiments with C. elegans showed that exposure to moderately cold temperatures (about 15 °C, or 59 °F) increased the production of an enzyme called CAT-4 in the worms’ muscles, which then stimulated the creation of BH2.

Once generated, BH2 is transported to other tissues where it’s transformed into another molecule, tetrahydrobiopterin (BH4), which enables an enzyme called PAH-1 to produce the amino acid tyrosine.

Disrupting this pathway, as they found, diminished the lifespan benefits associated with cold exposure, suggesting that the positive effects of lower temperatures are not merely due to a passive slowing of metabolism but are facilitated by an actively regulated process beginning in muscle cells.

In additional experiments, the pathway also seemed to enhance healthy protein balance, helping suppress harmful protein agglomeration in a model of Huntington’s disease.

Vilchez noted that targeting specific tissues, like muscle, might offer widespread protection, opening avenues for new therapeutic approaches.

Interestingly, the researchers discovered that cold temperatures might not be essential for the pathway to function. By genetically increasing CAT-4 levels in the worms’ muscles, they managed to extend their lifespan even at normal or warmer temperatures, hinting that some benefits of cold might be replicated without actually lowering body temperature.

“We were genuinely surprised to see such significant lifespan extension, even at standard and warmer temperatures,” Vilchez remarked.

Further experiments involving human cells that developed proteins related to Huntington’s and amyotrophic lateral sclerosis (ALS) indicated that adding BH2 reduced the buildup of these abnormal proteins.

Moreover, another study suggested that supplementing with BH2 and tyrosine minimized signs of programmed cell death in human motor neurons affected by an ALS-associated mutation, implying that this pathway could provide some protection against neurodegeneration.

It’s essential to note that these findings have only been observed in laboratory settings with nematodes and human cells, and there’s still a long way to go before considering any potential human applications.

However, the results bring us closer to deciphering how cold contributes to longevity, and one day, we may be able to harness these effects for ourselves.

The findings are discussed in Nature.