Tuesday, October 14, 2014
Despite numerous psychiatric, genetic and neurobiological studies, the molecular mechanisms behind eating disorders including anorexia, bulimia and, binge eating disorder are poorly understood. The different eating disorders (ED) are commonly characterised by dysregulation of appetite. The latest piece of evidence showed that a protein produced by gut bacteria may be involved in the regulation of appetite.
The latest study issued in the journal Translational Psychiatry found that a protein called ClpB produced by the gut bacteria Escherichia coli mimics the human satiety hormone melanotropin. In response to this bacterial protein, the body produces antibodies. These antibodies bind to the protein as well as to melanotropin due to its structural homology to ClpB, modifying its satietogenic effect. As a result, the sensation of satiety is either reached as seen in anorexia, or not reached as noted in bulimia or binge eating disorder.
In order to arrive at these findings, the researchers modified the gut bacterial composition in 2 groups of mice. The 1st group was exposed to mutant E. coli that did not produce ClpB, while the other group was exposed to E .coli that produced the protein. The researchers found that the food intake and antibody level in the 1st group of mice remained unchanged, whereas a variation in these parameters was observed in the 2nd group of mice.
To confirm these findings in humans, the researchers analysed data from 60 patients. The standardised scale "Eating Disorders Inventory-2" was used to diagnose these patients. The severity of their disorders was evaluated based on a questionnaire that covered topics pertaining to their behaviour and emotions such as wish to lose weight, bulimia, maturity fears, etc.
Upon testing, it was found that these patients had high plasma levels of antibodies to ClpB protein and melanotropin. Additionally, their immunological response helped determine whether they would develop anorexia or bulimia. These findings confirm the involvement of the bacterial protein ClpB in regulating appetite.
Commenting on the study findings, the researchers said, "We are presently working to develop a blood test based on detection of the bacterial protein ClpB. If we are successful in this, we will be able to establish specific and individualised treatments for eating disorders." The researchers are simultaneously testing the role of certain antibodies in neutralising the bacterial protein in mice to remedy the action of the protein and prevent dysregulation of appetite.
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