New York: Newly discovered genetic switches that increase lifespan and boost fitness in worms are also linked to increased lifespan in mammals, says a study that offers hope that drugs to flip these switches could improve human metabolic function and increase longevity. These so-called epigenetic switches are enzymes that are ramped up after mild stress during early development and continue to affect the expression of genes throughout the animal's life. When the researchers looked at strains of inbred mice that have radically different lifespans, those with the longest lifespans had significantly higher expression of these enzymes than did the short-lived mice. "Two of the enzymes we discovered are highly, highly correlated with lifespan; it is the biggest genetic correlation that has ever been found for lifespan in mice, and they're both naturally occurring variants," said one of the researchers Andrew Dillin, professor at University of California, Berkeley in the US. "Based on what we see in worms, boosting these enzymes could reprogramme your metabolism to create better health, with a possible side effect of altering lifespan," Dillin said. The discoveries were reported online in the journal Cell. The findings suggest that the reversal of ageing by epigenetic enzymes could also take place in humans. "It seems that, while extreme metabolic stress can lead to problems later in life, mild stress early in development says to the body, 'Whoa, things are a little bit off-kilter here, let's try to repair this and make it better.' These epigenetic switches keep this up for the rest of the animal's life," Dillin pointed out.