Examining the Biochemistry of Arctica Islandica Longevity
The clam species Arctica islandica is very long-lived, reaching at least four centuries in the wild. Researchers are comparing its biochemistry with similar but shorter-lived species to see if they can pinpoint the mechanisms that lead to its exceptional longevity. Here is recent research on this topic:
The observation of an inverse relationship between lifespan and mitochondrial H2 O2 production rate would represent strong evidence for the disputed oxidative stress theory of aging. Studies on this subject using invertebrates are surprisingly lacking, despite their significance in both taxonomic richness and biomass. Bivalve molluscs represent an interesting taxonomic group to challenge this relationship. They are exposed to environmental constraints such as microbial H2 S, anoxia/reoxygenation, and temperature variations known to elicit oxidative stress. Their mitochondrial electron transport system is also connected to an alternative oxidase that might improve their ability to modulate [the reactive oxygen species (ROS) generated by mitochondria and which produce oxidative stress].Here we compared H2 O2 production rates in isolated mantle mitochondria between the longest living metazoan - the bivalve Arctica islandica - and two taxonomically related species of comparable size. In an attempt to test mechanisms previously proposed to account for a reduction of ROS production in long-lived species, we compared oxygen consumption of isolated mitochondria and enzymatic activity of different complexes of the electron transport system in the two species with the greatest difference in longevity.
We found that A. islandica mitochondria produced significantly less [of the reactive oxygen species] H2 O2 than those of the two short-lived species in nearly all conditions of mitochondrial respiration tested, including forward, reverse, and convergent electron flow. Alternative oxidase activity does not seem to explain these differences. However, our data suggest that reduced complex I and III activity can contribute to the lower ROS production of A. islandica mitochondria, in accordance with previous studies.
Reduced activity within mitochondria in this sense shows up in some longevity-inducing mutations in laboratory animals. Mitochondrial activity and composition (how much damage they cause per unit time, and how resistant they are to damage) appears to be very important as a determinant of longevity differences between species. This should increase our interest in ways to repair mitochondrial damage in humans as a potential rejuvenation therapy.