Overeating disrupts networks of genes in the body, causing obesity, diabetes and heart disease, in ways that may be possible to predict, according to reports in Nature (here and here). Researchers developed a new method of analyzing DNA and used it to discover that obesity is not only complex - something already known - but complex in ways that had not been previously understood.
"Obesity is not a disease that is the result of a single change to a single gene. It changes entire networks," Eric Schadt, Merck's executive director of genetics, tells Reuters. His team, which conducted the research, identified networks of hundreds of genes that were thrown off base when mice are fed a high-fat diet. "This network is completely rocked by exposure to a high-fat, Western-type diet," Schadt says. They then turned to a database of Icelandic people being studied by Decode Genetics and found people have the same networks.
The joint teams did a detailed study of 1,000 blood samples and almost 700 samples of fat tissues from some of the volunteers in Iceland. And this showed that people who have a higher body mass index have characteristic patterns of gene activation in their fatty tissues not seen in DNA taken from blood, Reuters writes.
"What it says it that the common forms of these diseases are very complex," Schadt tells the wire. "Simple genetic tests cannot detect these networks...(But) good diet and exercise is still probably the best treatment or way to prevent the onset of obesity. If you are not going to alter your lifestyle, we can identify what network is going to be most significantly altered. Then we can bring that network more into a state to where it looks like when you are on a normal diet."
Schadt's team, writing in two studies published in the journal, said the diseases of obesity appear to originate in the immune system. "The network is enriched for genes that are involved in macrophages," Schadt tells Reuters. "In a normal state these things are keeping you free of infection and fighting off things that want to harm your body. This network is also significantly changed when you are on a high-fat diet," he added.
Some people have networks that predispose them to diabetes when they become obese, others to high cholesterol and clogged arteries. Some network patterns appeared to predispose some people to so-called metabolic syndrome, in which patients develop a cluster of symptoms including high blood sugar, high blood pressure and clogged arteries. And a lucky few can become obese with no apparent direct health consequences, at least as concerns heart disease and diabetes.