The findings may explain why mice age at a slower pace when put on a low-calorie diet, say the researchers. They suggest that calorie restriction delays the changes in circadian functions that occur in cells during aging.
The research team, including members from the Institute for Research in Biomedicine (IRB) Barcelona in Spain and the University of California, Irvine, reports the findings in two papers published in the journal Cell.
The discovery appears to discount the widely held idea that, over time, stem cells lose their circadian rhythm – that is, the pattern of 24-hour activity held in a group of genes.
Instead, older stem cells “conserve circadian rhythm but now perform another set of functions to tackle the problems that arise with age,” says senior study author Prof. Salvador Aznar Benitah, who leads a group studying stem cells and cancer at IRB Barcelona.
The researchers examined changes in stem cells taken from the skin, muscle, and livers of young mice aged 3 months, as well as from older mice aged between 18 and 22 months. Stem cells are precursor cells that divide to generate tissues.
The team found that, over time, while the genes that controlled circadian rhythm were just as active in the older mice as in the younger mice, they were influencing different cell processes.