New research, published Friday in the journal Science Advances, identifies a common genetic mutation that is linked to longer lifespan in males. While the mutation appeared to have no effect on women, it adds to a list of several gene variants which scientists have found to influence human lifespan. Scientists hope to eventually create drugs which can mimic the effects of such genes, potentially slowing the aging process. However, scientific progress has moved slowly when it comes to identifying these genes.
Additionally, history has shown that environmental factors tend to have a dramatic effect on lifespan. In Germany in 1875, life expectancy was less than 39 years, but has today more than doubled to 80. This improvement can be attributed to clean water, advances in medical care, and other factors. Yet genes have been proven to play a role in lifespan, with identical twins often sharing more similar lifespans than fraternal twins.
One 2001 study found that close relatives were more likely to have similar lifespans than distant relatives.
Despite these findings, large-scale studies of DNA have identified few genes with links to lifespan.
Albert Einstein College of Medicine geneticist Nir Barzilai said “It’s been a real disappointment.”
Basic biology has yielded more clues to what influences lifespan. Gil Atzmon, a geneticist at University of Haifa who works with Barzilai, said:
“If you look at dogs, flies, mice, whatever it is, smaller lives longer.”
These trends have led scientists to examine molecules which are linked to growth, including growth hormone, which is produced in the brain. It binds to a surface molecule on cells called a growth hormone receptor, triggering cells to grow faster. About one quarter of people have a mutation in the gene for these receptors, in which a chunk of DNA is missing. Studies have also shown this could be linked to shorter height in children, leading Atzmon to wonder whether it might also influence lifespan, given the link between size and longevity.
Atzmon and colleagues sequenced the gene for growth hormone receptors in 567 Ashkenazi Jews over the age of 60, and in their children. They found that the mutation was present in 12 percent of men over the age of 100, a rate about three times as high as in 70 year old men. In women, the mutation was present at the same rate in both age groups.
They followed up by examining the gene in three other populations, and found the same results.
The researchers hope to mimic the effect of the mutation, by finding ways to reduce levels of the growth hormone in older people.