Eating in 10-hour window can override disease-causing genetic defects
Scientists at the Salk Institute found that mice lacking the biological clocks thought to be necessary for a healthy metabolism could still be protected against obesity and metabolic diseases by having their daily access to food restricted to a 10-hour window.
The work, which appeared in the journal Cell Metabolism on August 30, 2018, suggests that the health problems associated with disruptions to animals' 24-hour rhythms of activity and rest -- which in humans is linked to eating for most of the day or doing shift work -- can be corrected by eating all calories within a 10-hour window.
"For many of us, the day begins with a cup of coffee first thing in the morning and ends with a bedtime snack 14 or 15 hours later," says Satchidananda Panda, a professor in Salk's Regulatory Biology Laboratory and the senior author of the new paper.
"But restricting food intake to 10 hours a day, and fasting the rest, can lead to better health, regardless of our biological clock."
Every cell in mammals' bodies operates on a 24-hour cycle known as the circadian rhythm -- cellular cycles that govern when various genes are active. For example, in humans, genes for digestion are more active earlier in the day while genes for cellular repair are more active at night.
Previously, the Panda lab discovered that mice allowed 24-hour access to a high-fat diet became obese and developed a slew of metabolic diseases including high cholesterol, fatty liver and diabetes.
But these same mice, when restricted to the high-fat diet for a daily 8- to 10-hour window became lean, fit and healthy. The lab attributed the health benefits to keeping the mice in better sync with their cellular clocks -- for example, by eating most of the calories when genes for digestion were more active.
In the current study, the team aimed to better understand the role of circadian rhythms in metabolic diseases by disabling genes responsible for maintaining the biological clock in mice, including in the liver, which regulates many metabolic functions.
The genetic defects in these clock-less mice make them prone to obesity, diabetes, fatty liver disease, and elevated blood cholesterol. These diseases further escalate when the animals are allowed to eat fatty and sugary food.