6th December 2009

Genetic studies reveal new causes of severe obesity in childhood

Representation of copy number variation (CNVs) in the genome.

Representation of copy number variation (CNVs) in the genome.

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Scientists in Cambridge have discovered that the loss of a key segment of DNA can lead to severe childhood obesity. This is the first study to show that this kind of genetic alteration can cause obesity. The results are published today in Nature.

The study, led by Dr Sadaf Farooqi from the University of Cambridge and Dr Matt Hurles from the Wellcome Trust Sanger Institute, looked at 300 children with severe obesity.

The team scanned each child's entire genome looking for types of mutation known as copy number variants (CNVs). CNVs are large chunks of DNA either duplicated or deleted from our genes. Scientists believe this type of mutation may play an important role in genetic diseases.

By looking for CNVs that were unique in children with severe obesity, compared with over 7,000 controls (apparently healthy volunteers from the Wellcome Trust Case Control Consortium 2), they found that certain parts of the genome were missing in some patients with severe obesity.

According to Dr Farooqi: "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"

" 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. "

Dr Matt Hurles

"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."

Dr Matt Hurles adds: "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 findings also have implications for diagnosing severe childhood obesity, which has on occasion been misattributed to abuse. Some of the children in the study had been formally placed on the Social Services 'at risk' register on the assumption that the parents were deliberately overfeeding their children and causing their severe obesity. They have now been removed from the register.

"This study shows that severe obesity is a serious medical issue that deserves scientific investigation," says Dr Farooqi. "It adds to the growing weight of evidence that a wide range of genetic variants can produce a strong drive to eat. We hope that this will alter attitudes and practices amongst those with professional responsibility for the health and well-being of children."

Obesity is increasing throughout the world and is now recognised as a major global public health concern. Although the increased prevalence of obesity over the past 30 years is undoubtedly driven by environmental factors, genetic factors play a major role in determining why some people are more likely to gain weight than others.

Notes to Editors

Publication details

Funding

This work was supported by the Wellcome Trust.

Participating Centres

  • University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, UK
  • Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
  • Bristol Children's Hospital, Bristol, UK
  • Genetic Medicine, St Mary's Hospital, Oxford Road, Manchester, UK

The mission of the University of Cambridge Metabolic Research Laboratories (MRL) is to undertake basic and translational research relevant to the understanding, prevention and treatment of diabetes, obesity and other related endocrine and metabolic disorders.

The Wellcome Trust Sanger Institute

The Wellcome Trust Sanger Institute, which receives the majority of its funding from the Wellcome Trust, was founded in 1992. The Institute is responsible for the completion of the sequence of approximately one-third of the human genome as well as genomes of model organisms and more than 90 pathogen genomes. In October 2006, new funding was awarded by the Wellcome Trust to exploit the wealth of genome data now available to answer important questions about health and disease.

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The Wellcome Trust

The Wellcome Trust is a global charitable foundation dedicated to achieving extraordinary improvements in human and animal health. We support the brightest minds in biomedical research and the medical humanities. Our breadth of support includes public engagement, education and the application of research to improve health. We are independent of both political and commercial interests.

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