Body language: Altered genes

Overeating disrupts entire networks of genes in the body, causing not only obesity but diabetes and heart disease, in ways that may be possible to predict, US-based researchers said.

Researchers at Merck Research Laboratories in Washington developed a new method of analysing 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," said Eric Schadt, Executive Director of Genetics at Merck Research Laboratories.

His team identified networks of hundreds of genes that appear to be thrown out of kilter when mice are fed a high-fat diet.

"This network is completely rocked by exposure to a high-fat, Western-type diet," Schadt said.

They then turned to a database of Icelandic people being studied by Decode Genetics Inc 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 tissue from some of the Icelandic volunteers.

This showed that people who have a higher body mass index, a measurement of obesity, have characteristic patterns of gene activation in their fatty tissues not seen in DNA taken from blood.

"What it says is that the common forms of these diseases are very complex. Simple genetic tests cannot detect these networks," said Schadt, who also works at Rosetta Inpharmatics, a subsidiary of Merck Research Laboratories in Seattle.

Schadt said his team hoped to study these networks and identify the genes most likely to cause disease. New drugs can be designed to target their activity, he said.

Companies can also profit from making tests to detect an individual’s particular pattern and his or her risk of various diseases arising from overeating.

"Good diet and exercise are 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," he said.

Different strokes

Obese and overweight individuals are less likely to die in five years after suffering a stroke than their normal peers, a new study shows.

Researchers at Hvidovre University Hospital analysed data from 21,884 stroke patients in Denmark who had their body mass index (BMI) determined.

Patients were placed into one of five BMI groups: underweight (BMI less than 18.5), normal weight (18.5 to 24.9), overweight (25.0 to 29.9), obese (30.0 to 34.9) and severely obese (35 and greater) and were followed for up to five years after a stroke.

Overweight, obese and severely obese subjects were 27 per cent, 16 per cent and 16 per cent less likely, respectively, to die during follow-up, researchers led by Dr Tom Skyhoj Olsen discovered. Underweight patients, by contrast, were 63 per cent more likely to die, the researchers reported in the online edition of Neuroepidemiology.