Image taken on May 6, 2015 shows an overweight woman in a mall in Tijuana City, northeast of Mexico. (Photo/Xinhua)
Night shifts and other lifestyle changes that subject yourself to jet lag on a regular basis may put you at a higher risk of not only developing obesity, but also incurable liver cancer, a new study said Wednesday.
Researchers from the Baylor College of Medicine modeled the effects of chronic jet lag in normal mice who were fed a healthy diet by changing the times the lights went on and off during the night each week.
They found that the mice gained weight and fat, and developed fatty liver disease, which progressed to chronic inflammation and eventually liver cancer in some cases.
The study showed that the jetlagged mice lost normal control of liver metabolism, which included not only the buildup of fat, but also increased production of bile acids, which are produced by the liver to help us digest our food.
Earlier studies have linked high bile acid levels to liver cancer, not only in mice but also in humans.
The researchers found that repeated jet lag disabled one gene called FXR, which keeps bile acid level in the liver within a normal physiological range.
As a result, jetlagged mice lacking the gene had higher bile acid levels and much more liver cancer.
In addition, chronic jet lag overexpressed another gene called CAR that regulates bile acid breakdown and is also known to promote liver cancer. Mice lacking this gene did not get any liver tumors.
The researchers didn't directly study jetlag in humans but they believed these receptors work in a similar manner in humans.
"There is evidence that sleep disruption increases both fatty liver disease and liver cancer risk in humans," said the study, which appeared in the U.S. journal Cancer Cell.
Therefore, "lifestyle changes that generate chronic jet lag can also disrupt the body's internal homeostasis and increase liver cancer risk in humans."
The findings highlighted the importance of healthy lifestyles, said study author Loning Fu, associate professor at Baylor.
"Recent studies have shown that more than 80 percent of the population in the United States adopt a lifestyle that leads to chronic disruption in their sleep schedules," said Fu. "This has also reached an epidemic level in other developed countries, which is coupled with the increase in obesity and liver cancer risk."
The scientists hoped to continue their research to further examine whether drugs interacting with the genes can help to prevent jet lag from affecting bile acid levels in the liver, with the ultimate goal of potentially using them as pharmaceutical strategies to prevent liver cancer in humans.
