Researchers find DNA-obesity link
Around 7 in every 1000 morbidly obese people are missing a section of their DNA (deoxyribonucleic acid) that contains around 30 genes, say the results of an EU-funded project published in the journal Nature. The authors of the study, from Imperial College London in the UK and 10 other European research centres, suggest that the missing DNA may have a dramatic effect on the weight of the affected people.
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Previous research studies have already shown several genetic variations, mostly single mutations in DNA, which can change the function of a gene, but the new research is the first to demonstrate that obesity can be caused by a rare genetic variation. The role of the missing genes is not yet known, but past studies suggest that they may be associated with delayed development, schizophrenia and autism.
EU support for the study came from the ENGAGE ('European network for genetic and genomic epidemiology') project, which is funded under the Health Theme of the Seventh Framework Programme (FP7), the BBMRI ('Biobanking and Biomolecular Resources Research Infrastructure') initiative, which is financed through the research infrastructures budget line of FP7, the ECOGENE ('Unlocking the European Union convergence region potential in genetics') project, which receives support via the Regions of knowledge Theme of FP7, and the EURO BLCS ('Biological, clinical and genetic markers of future risk of cardiovascular disease') project, which was funded through the Quality of life and management of living resources programme of the Fifth Framework Programme (FP5).
In the UK alone there are around 700,000 morbidly obese people, as indicated by a BMI (body mass index) of over 30 (normal weight is between 18.5 and 25). Researchers believe that up to 1 in 20 morbidly obese people have weight problems due to genetic variations including mutated genes and missing DNA.
The researchers speculate that there may be other genetic deletions or mutations that increase the chance of obesity in certain people. Their aim is to use the latest research to develop tests to find the best way to treat morbidly obese people with mutated or missing DNA.
Commenting on the findings, Imperial College London's Professor Philippe Froguel said: 'Although the recent rise in obesity in the developed world is down to an unhealthy environment, with an abundance of unhealthy food and many people taking very little exercise, the difference in the way people respond to this environment is often genetic.
'It is becoming increasingly clear that for some morbidly obese people, their weight gain has an underlying genetic cause. If we can identify these individuals through genetic testing, we can then offer them appropriate support and medical interventions, such as the option of weight loss surgery, to improve their long-term health.'
The researchers first identified the missing or mutated genes in teenagers and adults who had learning difficulties or were suffering from delayed development. They found 31 people who had nearly identical missing genes in 1 copy of their DNA. All of them had a BMI of over 30.
They then went on to study the genomes of more than 16,000 people, both obese and of normal weight, and found that 19 more people in the obese group had the same genetic deletion. This was not the case with the normal weight group.
The researchers now hope that that the results of the study may be used to identify genetic influences on other diseases such as type 2 diabetes.
Imperial College London:
Category: Project results
Information Source: Nature; Imperial College London
Document Reference: Walter, R.G., et al. (2010) A new highly penetrant form of obesity due to deletions on chromosome 16p11.2. Nature, 463, 671-675. DOI: 10.1038/nature08727.