Researchers have found that a low-calorie diet has effects on the stem cell circadian rhythm that could slow down the aging process. Experiments in mice have revealed that, with age, the biological clock in stem cells begins to focus on alternate cell processes. Instead of focusing on maintaining tissues, it begins to focus on DNA repair and other stress- and age-related functions.
Effects of Low-Calorie Diet on Stem Cells and Aging
The researchers found that when mice were placed on a low-calorie diet, they aged more slowly. The findings suggest that reduced caloric intake delays the circadian changes in stem cells that lead to tissue aging.
The team led by Professor Salvador Aznar Benitah and consisting of researchers from the University of California, Irvine, and the Institute for Research in Biomedicine in Barcelona, Spain, has published two papers in the scientific journal Cell.
Circadian rhythm is the pattern of activity over a 24-hour period. It is a widely held belief that stem cells suffer a loss in circadian rhythm when an individual becomes older. The new findings indicate that the circadian rhythm is conserved but is altered such that the stem cells perform a different set of functions related to aging.
Stem Cell Circadian Rhythm and Aging
The investigators took skin, liver, and muscle stem cells from 3-month-old mice as well as 18-22-month-old mice. These precursor cells have the ability to transform into different types of body tissues. The experiments showed that genes that control circadian rhythm in stem cells continue to be active in older mice but influence a different set of processes in the cells. In younger mice, the stem cells regulate tissue maintenance and wound healing through DNA replication. In older mice, the stem cell circadian rhythm machinery begins to control response to inflammation and other stress-related functions through DNA repair.
It is still unclear what triggers the change in circadian rhythm. However, the reprogramming is specific and different for each type of tissue. This indicates that each tissue in the body ages at a different pace. This finding is interesting for investigators looking at ways to slow down aging in humans.
Low-Calorie Diet and Aging
When the team compared mice fed on a calorie-restricted diet to mice fed on a normal diet, they found that mice who received a low-calorie diet did not experience a change in the circadian rhythm of stem cells. In mice who were fed a normal diet, circadian reprograming was evident. According to Professor Aznar Benitah, this indicates that a low-calorie diet can prevent stem cell reprogramming and physiological aging.
Previous experiments in fruit flies have shown that lifespan can be extended with calorie restriction. The new studies show that the link between calorie-restriction and cellular aging is the circadian rhythm of stem cells.
Stem cells renew and preserve tissues in day-night cycles. It remains to be seen whether a similar reprogramming occurs in humans and calorie restriction can slow aging. Testing in humans will be challenging, says Professor Aznar Benitah, because the eating regimen required for the experiments will require an extremely strong willpower to handle the constant hunger. Moreover, the experiments would entail a minimum energy supply to support only basic body functions, and this could negatively impact the person’s health and lifestyle.