Studying more than 2,000 anonymous samples from three ethnically distinct groups of people, the scientists found that having two copies of a less-common version of klotho is twice as prevalent in infants as in people over age 65. These results suggest that people born with the two copies die sooner than others, although the gene's exact influence on health and aging are not known, the scientists say.
Previously, Japanese scientists discovered klotho in mice, noticing that without klotho's protein, the mice developed atherosclerosis, osteoporosis, emphysema and other conditions common in elderly humans. Because of their interest in accelerated aging diseases, Dietz and his colleagues began studying klotho in people.
The first thing to do when you discover a mechanism that accelerates age-related degeneration in mice is to turn it around and see if can extend healthy life span - as a general rule, gerontologists are unexcited by processes that reduce life span. There are all too many of those, and most have no association with any way of extending life span - application of blunt force is one example, as a certain wag noted.
The time elapsed between the 2002 work and the present day is just about long enough to set up a decent set of life span experiments with laboratory mice and get a good sense as to how it will all turn out. In the case of the Klotho gene, this indeed came to pass. It is pleasing to see that Klotho has now been welcomed into that small, select circle of known ways to significantly extend healthy life span in mice:
In the new study, a group led by Kuro-o, now an assistant professor of pathology at the University of Texas Southwestern Medical Center at Dallas, created transgenic mice with overactive versions of the Klotho gene. Those mice proved to have life spans 20 percent or more longer than mice with the ordinary version of the gene, Kuro-o said.
"These are still animal experiments, but potentially it might be possible to use the hormone in humans," he said. "But we still don't know if the protein can be used to extend life span in humans."
A lot must still be learned about the Klotho hormone, starting with the way it works, Muro-o said. "We speculate that it blocks insulin action," he said. Specifically, it appears to block the insulin-like growth factor-1 pathway. Studies have shown that blocking that pathway extends the life span of worms, flies and mice, he said, and the same may well be true of humans.
The upper bound of life span extension in the study was 30% or so, in the same ballpark as the results of calorie restriction. The association with insulin suggests that both overexpression of Klotho and the gene expression changes caused by calorie restriction may work on an overlapping set of biochemical mechanisms - which certainly shouldn't prevent industrious researchers from trying both at once to see how that goes. I certainly would if I had the funds and a group of gene engineered Klotho mice.
I predict that this will be grist for the mill for those funded groups and companies - such as Elixir, Sirtris, etc - already working hard on metabolic science resulting from calorie restriction studies. Good news all round for those interested in near term (next five to ten years) results from currently funded longevity research.