New genetic cause of severe obesity and diabetes

2 July 2015

Following recent news that research has ruled out a link between the AMYI gene and obesity, a new study has identified a novel form of inherited diabetes and obesity.

The genetics of common forms of obesity and of type 2 diabetes are complex and inter-related since obesity itself predisposes individuals towards the subsequent development of type 2 diabetes. Variants in multiple genes have been implicated in both conditions. However, rare forms of ‘genetic’ inherited obesity, in which mutation in a single gene effectively causes obesity, also exist, and indeed can throw valuable light on the biological mechanisms that are involved in common obesity.  

New research from Imperial College London, published in the journal PLOS ONE, has identified the genetic cause of severe obesity and diabetes in a single family. A mutation in the gene for the carboxypeptidase-E (CPE) protein was found; CPE is known to be involved in signalling processes related to appetite, insulin and reproductive hormones – all consistent with patient symptoms. CPE deficiency has also been previously observed in mice – but not humans.

The condition is recessive, meaning that only individuals with two mutated (abnormal) copies of the CPE gene have the condition. However, researcher Dr Sanne Alsters said: “Finding a genetic cause for the patient’s problems has helped her and her family to understand and manage her condition better. We can also look at members of her family with one abnormal copy of the gene, to see they are affected in more subtle ways that could increase their risk of obesity”.

Study lead Professor Alex Blakemore said genetic tests should be widely available for patients with severe obesity, adding: “Diagnosis is very valuable to the patient. It helps to set realistic expectations, and can help them get the best possible treatment”. 

A 2013 PHG Foundation report, Genomics of Obesity, examines when and where genetic testing can be of value in the management of obesity, and notes that whilst inherited genetic disorders that cause obesity are individually very rare, they may be involved in up to 10% of cases of severe childhood obesity.

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