Obesity has become an epidemic in the West. It’s linked to many chronic diseases. UCLA researchers and a German team went further and found for the first time that obesity greatly accelerates aging of the liver.
This finding could explain the early onset of many age-related diseases, including liver cancer, in obese subjects.
Although it had long been suspected that obesity ages a person faster, it hadn’t been possible to prove the theory, said study first author Steve Horvath, a professor of human genetics at UCLA.
Using the epigenetic clock Horvath developed last year, he and Jochen Hampe from the University Hospital Dresden showed that carrying excessive weight can negatively impact select human tissues.
“This is the first study that evaluated the effect of body weight on the biological ages of a variety of human tissues,” Horvath said. “Given the obesity epidemic in the Western world, the results of this study are highly relevant for public health.”
Horvath’s aging clock uses a previously unknown time-keeping mechanism in the body to accurately gauge the age of diverse human organs, tissues and cell types.
The researchers used the epigenetic clock to measure the biological age of several tissues. The aging clock proved accurate in matching biological to chronological age in lean subjects. But liver tissues from obese subjects tended to have a higher biological age than expected.
While obesity doesn’t affect the epigenetic age of fat, muscle or blood tissue, they found that, on average, the epigenetic age of the liver increased by 3.3 years for every 10 Body Mass Index (BMI) units.
For example, a woman who is 5 feet 5 and weighs 140 pounds has a BMI of 23.3. A woman the same height but weighing 200 pounds would have a body mass index of 33.3. Her liver would be about three years older than the woman who weighed 140 pounds, the study found.
“This does not sound like a lot, but it is actually a very strong effect,” Horvath said. “For some people, the age acceleration due to obesity will be much more severe, even up to 10 years older.”
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Horvath also found that rapid weight loss induced by bariatric surgery did not reverse the accelerated aging, at least in the short term.
“The increased epigenetic age of liver tissue in obese individuals should provide insights into common liver-related comorbidities of obesity, such as insulin resistance and liver cancer,” the study states.
“Obesity accelerates epigenetic aging of human liver Steve Horvath, ”Wiebke Erhart, Mario Brosch, Ole Ammerpohl, Witigo von Schönfels, Markus Ahrens, Nils Heits, Jordana T. Bell, Pei-Chien Tsai, Tim D. Spector, Panos Deloukas, Reiner Siebert, Bence Sipos, Thomas Becker, Christoph Röcken, Clemens Schafmayer, Jochen Hampe, Proceedings of the National Academy of Sciences, online Oct. 13, 2014