Scientists have discovered a new inherited form of obesity¹ and type 2 diabetes² in humans. A large number of genes³ are involved in regulating body weight, and there are now over 30 genes known in which people with harmful changes in DNA⁴ sequence become extremely overweight. Similarly, there are a number of genes that can, when altered, cause type 2 diabetes. These conditions are inherited through families in exactly the same way as disorders⁵ such as cystic fibrosis or Huntington's disease.

 

It is unclear what proportion of severe obesity and type 2 diabetes is caused by genetic⁶ disease.

 

Researchers at Imperial College London discovered the new defect by sequencing the DNA of an extremely obese⁷ young woman and members of her family. In addition to an increased appetite leading to severe weight problems from childhood, she had type 2 diabetes, learning difficulties, and reproductive problems. 

 

They found that she had inherited two copies of a harmful genetic change that meant she could not make a protein called carboxypeptidase-E (CPE). This is an enzyme⁸ that is important in the proper processing of a number of hormones⁹ and brain transmitters controlling appetite, insulin and other hormones important in the reproductive system.

 

Studies have previously¹⁰ shown that CPE deficiency causes obesity, diabetes, and impaired¹¹ memory in mice, but no humans with the condition have been found before. CPE deficiency is a recessive¹² condition, so a person would need to inherit the altered genetic sequence from both parents to be affected¹³.

 

The study, published in the journal PLOS ONE, was funded by the NIHR Imperial Biomedical Research Centre and Diabetes UK.

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