A variation of a gene that has been linked to increased physical and social activity appears to indirectly favor longevity, genetic studies in mice and humans confirm.
The study concerns a variation (allele) of the DRD4 gene, which is found in disproportionately high rates in those who survive beyond the age of 90. Furthermore, it is associated with increased lifespan in laboratory animals, the researchers report in The Journal of Neuroscience.
The DRD4 gene contains the information for the production of a dopamine receptor, which is present on the surface of certain brain cells and mediates communication between them.
The dopamine system in the brain, which is affected by many drugs such as cocaine, is known to play an important role in focusing attention and pursuing pleasurable activities.
This particular variant of DRD4, called 7R, suppresses the receptor's activity. The likely result is that carriers must stimulate the brain's reward system more intensely to feel the same satisfaction.
People who carry the 7R allele, the researchers report, tend to be more active and more sociable, although the same variety has also been linked to attention deficit disorder, as well as a tendency toward addiction and risky behaviors.
The new study now links the 7R to longevity, but cannot clarify whether there is a causal relationship: "Although this genetic variation probably does not directly affect longevity, it is associated with personality traits that are known to be important for a long, healthy life," says Robert Moises, a professor at the University of California, Irving and director of the US National Institute on Substance Abuse.
Indeed, previous studies have shown that increased physical and social activity tend to provide health and prolong life.
In the new study, Moises' team first looked at 310 of the volunteers who were taking part in a large, broader study of longevity. The analysis showed that volunteers over 90% were 66% more likely to carry the 7R variant, compared with a control group of nearly 3,000 people aged 7 to 45.
The study continued in mice, where it was found that experimental animals that did not carry the specific allele had a reduction in lifespan of 7.0 to 9.7 percent.
According to previous work by the same research group, the 7R allele of the receptor was favored by natural selection during a wave of migration from Africa to Europe 30,000 years ago.
