Obesity Found to Age the Liver Faster

Posted October 13th, 2014 at 6:59 pm (UTC-4)
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The patterns of the figures provides a microscopic view of liver cells from lean (left  and obese subjects (right), respectively. (UCLA)

The patterns of the figures provides a microscopic view of liver cells from lean (left and obese subjects (right), respectively. (UCLA)

U.S. and German scientists have found, for the first time, that obesity significantly quickens the aging process of the liver and have revealed that carrying excessive weight can negatively impact certain human tissues.

While scientists have suspected that obesity does play a significant role in aging a person faster the American/German team said that their research marked the first time they were able to prove the concept.

The international team’s findings have been published today by the journal, the Proceedings of the National Academy of Sciences.

The researchers used an ‘epigenetic clock’, which is a unique age prediction method developed in 2013 by Steve Horvath, a professor of human genetics at the David Geffen School of Medicine at the University of California, Los Angeles (UCLA).   Horvath is also first author of the PNAS study.

“This is the first study that evaluated the effect of body weight on the biological ages of a variety of human tissues,” Horvath said in a press release.  “Given the obesity epidemic in the Western world, the results of this study are highly relevant for public health.”

The aging clock has been shown to precisely measure the age of a variety of human tissues, organs and cell types, by employing a time-keeping device that had been previously unknown.

In developing his ‘epigenetic clock’ Horvath and his colleagues focused on a naturally occurring process called methylation, which is a chemical modification of the DNA molecule.

Body Mass Index - BMI Chart (National Heart, Lung and Blood Institute)

Body Mass Index – BMI Chart (National Heart, Lung and Blood Institute)

To reach their findings in this study and examine the connection between increased body weight and epigenetic acceleration, the US and German scientists worked with and used Horvath’s aging clock method on almost 1,200 human tissue samples, 140 of which were liver samples.

The researchers found that the aging clock was quite accurate and was able to match the biological age with the chronological age of liver tissue samples taken from subjects with little body fat.

On the other hand, the scientists found that liver tissues taken from subjects who were obese had a tendency of having a higher biological age than their chronological age than they had expected.

While they found that obesity has no affect the epigenetic age of human tissues such as fat, muscle or blood, Horvath and his colleagues found that the epigenetic age of the liver, on average, increased by 3.3 years for every 10 units of Body Mass Index (BMI).

In their published study the researchers gave an example by comparing the biogenetic age of the liver of a 1.65 meter tall woman who weighs 63.5 kg, with a BMI of 23.3 with another woman who of the same height, but instead weighs 27.1 additional kg and a body mass index of 33.3.

This figure overlays aging clocks on the Vitruvian man created by Leonardo da Vinci circa 1490. This diagram illustrates the epigenetic clock (also known as biological aging clock), which can be used to measure the age of different parts of the human body. (Steve Horvath via Wikimedia Commons)

This figure overlays aging clocks on the Vitruvian man created by Leonardo da Vinci circa 1490. This diagram illustrates the epigenetic clock (also known as biological aging clock), which can be used to measure the age of different parts of the human body. (Steve Horvath via Wikimedia Commons)

Horvath and his team found that the heavier woman’s liver would be about three years older than the woman who weighed less.

“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.”

The researchers also found that overweight or obese people who had rapidly lost weight with measures such as bariatric surgery were unable, at least in the short term, to reverse the accelerated aging process in the liver.

Horvath said that he and his colleagues will continue their work to find if this obesity driven early-onset aging of the liver could be prevented and if the risk of diabetes and liver cancer could also be avoided.

The researchers said that their findings not only support previously held theories that obesity plays a role with the accelerated aging effects of the human body and is yet another important reason for people to maintain a healthy weight.

Rick Pantaleo
Rick Pantaleo maintains the Science World blog and writes stories for VOA’s web and radio on a variety of science, technology and health topics. He also occasionally appears on various VOA programs to talk about the latest scientific news. Rick joined VOA in 1992 after a 20 year career in commercial broadcasting.

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