Saturday, January 9, 2010

Severe Childhood Obesity Linked To Missing DNA

Researchers in the UK have linked cases of severe childhood obesity to missing DNA that runs in families, whereby members missing the vital genetic chunk are severely obese from a young age, have a strong drive to eat and put on weight very easily; the missing DNA, called SH2B1, is located on chromosome 16 and plays an important role in regulating weight and blood sugar.

The finding has implications for the diagnosis and care of severely obese children, whose condition may be misattributed to abuse, said the researchers.

The study, thought to be the first to show this kind of genetic deletion can cause obesity, is the work of Dr Sadaf Farooqi from the University of Cambridge and Dr Matt Hurles from the Wellcome Trust Sanger Institute, and colleagues, and was published online in the journal Nature on 6 December.

Obesity is on the rise and has become a major public health concern all over the world. Although the increase in the last 30 years is most likely driven by environmental factors such as diet and lifestyle, our genes also play an important part, for instance in determining why some of us are more likely to put on weight than others.

For the study, which was funded by the Wellcome Trust, Farooqi, Hurles and colleagues scanned the entire genomes of 300 severely obese children for mutations in copy number variants (CNVs), large segments of DNA that are either copied or missing in our genes, and which scientists suggest play a vital role in the development of genetic diseases.

They compared them to the genome information of over 7,000 controls, apparently healthy volunteers from the Wellcome Trust Case Control Consortium 2.

The results showed that the children with severe obesity had some CNVs that were different to the controls. The researchers wrote that:

"We identified several rare copy number variants that were recurrent in patients but absent or at much lower prevalence in controls."

Farooqi told the media:

"We found that part of chromosome 16 can be deleted in some families, and that people with this deletion have severe obesity from a young age."

"Our results suggest that one particular gene on chromosome 16 called SH2B1 plays a key role in regulating weight and also in handling blood sugar levels. People with deletions involving this gene had a strong drive to eat and gained weight very easily," he added.

Hurles said:

"This is the first evidence that copy number variants have been linked to a metabolic condition such as obesity. They are already known to cause other disorders such as autism and learning difficulties."

The finding has implications for the diagnosis and social care of severely obese children, whose condition may incorrectly be attributed to abuse by their parents or carers.

For instance, some of the children in the study had been placed on the Social Services "at risk" register because it was assumed that their parents were deliberately overfeeding them: they are now no longer on the register, according to a press statement from the University of Cambridge.

Farooqi said that their findings show that severe obesity is a "serious medical issue that deserves scientific investigation".

"It adds to the growing weight of evidence that a wide range of genetic variants can produce a strong drive to eat," he added, explaining that they hoped this discovery will change "attitudes and practices amongst those with professional responsibility for the health and well-being of children".

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Severe Childhood Obesity Linked To Missing DNA

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