Obesity plays such an important role in so many health problems in developed countries, and as such, is an important research topic. Recently, use of genetic sequencing allowed a team of researchers from Imperial College London to discover the first known person with a genetic deficiency formerly seen only in animal studies.

The study, published in PLOS ONE, adds to our growing knowledge of genetic factors that contribute to satiety, hunger, weight gain, and diabetes.

Genetic Inheritance Leads to the Lack of an Important Protein

The study focused on the genetic background of a young woman and six of her family members. The 20-year old woman at the center of the study suffered Type 2 diabetes, morbid obesity, learning problems, and reproductive difficulties. Members of her family were mildly obese, and her older brother (who exhibited similar symptoms) died when he was 21 from unknown causes. She came to the attention of study authors through a genetics-based obesity clinic.

By sampling genetic material from the woman and family members, researchers were able to determine she had received two copies of a mutated gene called carboxypeptidase (CPE). This protein is important for synthesis of hormones and neurotransmitters, as well as having a controlling effect on insulin, appetite, and hormones related to reproduction.

Previous evaluation of the effect of CPE deficiency and obesity has been conducted only with animal studies. In this study, researchers suggest the likelihood of her receiving two copies of the mutation were higher because the parents of the patient were distantly related. As a recessive trait, full expression of a CPE deficiency requires two copies of the defective gene.

Important findings of this study include:

  • This research identifies another gene-based cause of obesity. Already, there are approximately 30 different gene mutations known to contribute to a tendency to gain and retain weight, or become obese. One of the authors, Alexandra Blakemore, a specialist in diabetes and endocrinology, noted, "There are now an increasing number of single-gene causes of obesity and diabetes known, we don't know how many more have yet to be discovered, or what proportion of the severely obese people in our population have these diseases, it is not possible to tell just by looking." As a relatively new research method, genetic sequencing offers information to patients and families, as well as casting a brighter light on the development of methods to better understand, treat, or prevent the effects of genetic mutations.
  • Through identifying a human subject with CPE deficiency, the study authors are able to investigate its effects on humans. The condition is similar to any other genetically inherited disease. Blakemore adds, "These are serious disorders that affect the body's ability to regulate hunger and fullness signals. They are inherited in just the same way as other genetic diseases and the sufferers should not be stigmatised for their condition."
  • The study adds to information on inheritable obesity factors and illuminates the advantage of genetic testing for individuals who are interested. Another author on the study states, "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."

Individuals with a monogenic mutation, meaning only one copy of the damaged gene was inherited, may struggle with health problems other than weight gain and obesity. In the case of a CPE deficiency, the resulting physiological problems impact the body, and quality of life.

Besides genetic factors, there are other reasons you might gain weight and have difficulty losing it, including: thyroid issues, adrenal dysfunction, hormonal deficiencies and imbalances, hypothalamic problems, metabolic dysfunction, and menopause.

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