A great deal of work in the aging research community focuses on trying to untangle the relationship between genes, epigenetic patterns of gene expression, metabolism, and natural variations in human longevity. It's an enormously complex task, far harder than just trying to repair the known biochemical damage of aging - analogous to producing a general theory and full mathematical model of paint peeling rather than just repainting a wall.
In the dimly lit, chilly hallway outside Passarino's university office stand several freezers full of tubes containing centenarian blood. The DNA from this blood and other tissue samples has revealed additional information about the [study population]. For example, people who live into their 90s and beyond tend to possess a particular version, or allele, of a gene important to taste and digestion. This allele not only gives people a taste for bitter foods like broccoli and field greens, which are typically rich in compounds known as polyphenols that promote cellular health, but also allows cells in the intestine to extract nutrients more efficiently from food as it's being digested.
Passarino has also found in his centenarians a revved-up version of a gene for what is called an uncoupling protein. The protein plays a central role in metabolism - the way a person consumes energy and regulates body heat - which in turn affects the rate of aging.
"We have dissected five or six pathways that most influence longevity," says Passarino. "Most of them involve the response to stress, the metabolism of nutrients, or metabolism in general - the storage and use of energy." His group is currently examining how environmental influences - everything from childhood diet to how long a person attends school - might modify the activity of genes in a way that either promotes or curtails longevity.
If nothing else, the plethora of new studies indicates that longevity researchers are pushing the scientific conversation to a new level. [But] genes alone are unlikely to explain all the secrets of longevity. Passarino made the point while driving back to his laboratory after visiting the centenarians in Molochio. "It's not that there are good genes and bad genes," he said. "It's certain genes at certain times. And in the end, genes probably account for only 25 percent of longevity. It's the environment too, but that doesn't explain all of it either. And don't forget chance."