What We Can Learn from a Clam
Most of us would be hard pressed to imagine what similarities the human body would have to a hard-shell clam. Scientists, however, know that aquatic invertebrate animals such as clams, oysters, and mussels have a bi-valve heart that functions very much like the human heart. Unlike humans, some clams live centuries. Now researchers are studying clams to see if they have something to teach us about heart health.
The mollusk under examination is a hard-shell North Atlantic clam that lives hundreds of years. Because we know that heart and blood vessel disease are the main causes of illness and death in human beings, the scientists decided to investigate the Arctica islandica, or ocean quahog, the longest-living, non-colony dwelling animal known to exist. So far, the oldest identified specimen of this clam lived to age 508, a fact determined by counting the shell growth rings.
The research examined age-related changes in the hearts of these clams. The study was funded by the National Center for Complementary and Integrative Health (formerly NCCAM), the American Heart Association, and the National Institute on Aging, among others. The team of scientists published their findings from the initial study in The Journals of Gerontology, Series A, Biological Sciences and Medical Sciences.
For the study, the researchers obtained Arctica islandica specimens from an inlet near Belfast, Northern Ireland. The scientists put the specimens into four age groups (the oldest among them was 182 years) and conducted a cross-sectional study. They then correlated their findings to existing hypotheses about biological and cardiovascular aging in mammals, including humans. Hypotheses relating to mammals suggest that aging is characterized by accumulation of proteins modified through oxidation, decreased ability to break down and removed the proteins damaged by oxidation through the ubiquitin-proteasome system, a diminishing of the heat shock proteins that govern stress resistance and life span, and decay in the mitochondria.
The researchers identified a number of chemical markers and tracked their rise and fall over time. Their findings, along with results of previous research on extremely long-lived bivalves, add weight to the hypothesis that successfully aging species have developed “more efficient cellular stress resistance mechanisms than shorter-living ones and can maintain long-term protein homeostasis and mitochondrial integrity, which may contribute to successful cardiac aging across the phyla.” The authors of the study have called for further research into cardiovascular aging in animals with extreme longevity.