Anoxia Tolerance and Species Longevity
I noticed a paper on longevity in turtles today that speculates on a link between species life span and tolerance of low-oxygen environments. It seems to be as interesting a line of research as any opened up by the comparison of differences in biochemistry and longevity between species. Why are long-lived species long-lived, and can we expect the answers to translate, as for calorie restriction research, into potential benefits for human health?
Forever young: mechanisms of natural anoxia tolerance and potential links to longevity
While mammals cannot survive oxygen deprivation for more than a few minutes without sustaining severe organ damage, some animals have mastered anaerobic life. Freshwater turtles belonging to the Trachemys and Chrysemys genera are the champion facultative anaerobes of the vertebrate world, often surviving without oxygen for many weeks at a time. The physiological and biochemical mechanisms that underlie anoxia tolerance in turtles include profound metabolic rate depression, post-translational modification of proteins, strong antioxidant defenses, activation of specific stress-responsive transcription factors, and enhanced expression of cytoprotective proteins. Turtles are also known for their incredible longevity and display characteristics of "negligible senescence".We propose that the robust stress-tolerance mechanisms that permit long term anaerobiosis by turtles may also support the longevity of these animals. Many of the mechanisms involved in natural anoxia tolerance, such as hypometabolism or the induction of various protective proteins/pathways, have been shown to play important roles in mammalian oxygen-related diseases and improved understanding of how cells survive without oxygen could aid in the understanding and treatment of various pathological conditions that involve hypoxia or oxidative stress.
When reading this my first thought was of another unusually long-lived species that has a high tolerance for low-oxygen life: the naked mole-rat. As researchers noted in past years:
Here we report that brain tissue from naked mole-rats, rodents that live in a chronically low-oxygen environment, is remarkably resistant to hypoxia: naked mole-rat neurons maintain synaptic transmission much longer than mouse neurons and can recover from periods of anoxia exceeding 30 min.
It is possibly a coincidence that some whale species are also very long-lived; consider their exposure to anoxia during feeding dives. On the whole, and if considered from the perspective of researchers interested in metabolic manipulation to slow aging, the anoxia angle seems well worth pursuing.
Krivoruchko A, & Storey KB (2010). Forever young: mechanisms of natural anoxia tolerance and potential links to longevity. Oxidative medicine and cellular longevity, 3 (3), 186-98 PMID: 20716943
My son is interested in free diving and often practices holding his breath for extended periods. I know this post was about species, not individuals, but it is fun to speculate whether a trained ability to handle low oxygen could affect longevity. I suppose it would be possible to test this with mice but do not of any human population that one could look to...
There are several cultures of humans in the Caribbean and South Pacific who practice fishing methods that deprive them from oxygen for long periods of time, up to 7 minutes in the best divers. Most of us would be dead from going 7 minutes without breathing, or at least unconscious from hypoxia. I was a diver as well and a swimmer, but my maximum underwater time was under 3 minutes. I'm bigger than most of those men, in terms of chest wall size, but they seem to have a mechanism that prevents damage from hypoxia.