Metabolic Rates and Aging

June 12, 2004

Live Fast, Die Old
    Tonight's Science News features a study that looked at metabolic rates versus longevity in mice. Intuitive wear-and-tear theories of aging lead us to expect that the higher an organism's metabolic rate, the more calories it burns. The more calories it burns, the more damaging free radicals it generates. And the faster it generates free radicals, the faster it should age.
    Not so. A study of fruit flies found no relationship between metabolic rates and lifespans. Now, tonight's study of metabolic rates in mice indicates that, within a given species of mouse, the higher the metabolic rate, the longer the mouse will live. "'It was a complete surprise,' says Speakman." Carrying this over to people, it would suggest that highly energetic people tend to be the longest-lived. (Of course, high levels of energy could signify a well-functioning organism.)
    This finding is in keeping with the idea that aging is controlled by genes, and that organisms don't have to age at all. But then, we know that some organisms, such as the rough-eyed rockfish and the red sea urchin, show no signs of aging up to at least 200 years of age. As mentioned in last night's article, 
    "Plants like the quaking aspens and the box huckleberry[1], or the baobab tree that spreads by runners, don't seem to ever grow old   Some liverwort clumps may be millions of years old. “Wear-and-tear” theories of aging have been intuitively popular[2], but life is digital and self-repairing, and evidently, may be potentially capable of total self-repair. (We are dealing with technology that, if we didn’t have living organisms to serve as templates, is probably a century or two beyond today’s technology.)
    "Also, animals have been discovered that show no signs of aging. For example, the calico species of rockfish has a lifespan of the order of 12 years, while the rough-eyed rockfish reaches at least 205 (see reference 31), and shows no signs of aging even at this age. Recently, the red sea urchin has also been shown to reach at least 200 with no signs of aging. Of course, these species may actually age if they live long enough, but there's certainly a huge difference in rates of aging between, for example, the calico rockfish and their kissing cousins, the rough-eyed rockfish."
    Trees like the Joshua Tree and the giant redwoods may die not from aging but from growing too large for the osmotic mechanisms that nourish them to keep up.
    It would seem that Mother Nature can keep organisms young and vibrant as long as she chooses.