In a new study, Dutch researchers have found how changes in the gut microbiome, microorganisms inhabiting the digestive tract, may play a role in the development and progression of anorexia nervosa (AN), an eating disorder that is characterised by restrictive food intake and severe weight loss.
This is the latest in a long line of health conditions like anxiety, Alzheimer’s disease, cancer, heart ailments and inflammatory disorders that have been linked with the gut microbiome. The primary mode of action is thought to be through the gut-brain-axis, which can affect “brain functions including regulation of appetite, behaviour and emotions.”
To study this, researchers from the University of Copenhagen analysed the stool samples of young women with AN to study a disrupted gut microbiome and its metabolites, materials produced by gut bacteria after they feed on substances like fibre.
“The new study is an example of basic research meant to explore whether a disturbed microbial ecosystem of the gut a contributory factor in the development or retention of a chronic disease,” Oluf Borbye Pedersen, professor and principal investigator at the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen said.
“And this may potentially be the case for anorexia nervosa,” he added.
Connecting the gut microbiome to AN
Anorexia nervosa is a complex eating disorder that has a high mortality rate compared to other mental disorders. Some of the symptoms of the disorder include extreme restrictive eating, fear of gaining weight and a distorted perception of one’s body.
In the new study published in Nature Microbiology, a team of scientists from the University of Copenhagen found changes in some of the species of microbes in the gut and correlated it to how AN develops.
The study involved a cohort of 77 Danish girls who had AN. Scientists used a variety of techniques like DNA sequencing technology and bioinformatics analyses to track the changes in the bacteria and viruses that live in the gut.
The metabolites or blood molecules released by the disrupted microbiome demonstrate a connect between the gut and 12 personality traits associated with eating and social behaviour such as reduced food intake, need for thinness and body dissatisfaction.
“We also discovered that specific gut bacteria in women with anorexia nervosa produce less vitamin B1. Deficiency of B1 may lead to loss of appetite, various intestinal symptoms, anxiety and isolating social behaviour,” says assistant professor Yong Fan, another researcher from the study.
Studies in mice
To further understand how the microbiome affects AN, the researchers transplanted the stools from individuals with AN into germ-free mice.
“The mice receiving stools from individuals with anorexia nervosa had trouble gaining weight, and analyses of gene activities in certain parts of their brain revealed changes in various genes regulating appetite,” explains Pedersen in a statement.
Additionally, these mice also showed increased activity of genes regulating fat combustion likely contributing to their lower body weight.
Significance of findings and what lies ahead
“A complex disease like anorexia nervosa calls for personalised and multifactorial treatment. Our findings suggesting that disruptions of the communities of gut bacteria and viruses and their functions may be involved in the development and retention of the disease,” said Pedersen.
He adds that this could provide a rationale for initiating clinically controlled trials. In such trials, clinical investigators will likely test the potential effects of an initial antibiotics intervention to reset the aberrant gut microbiome followed by weekly faecal microbiota transplantation (FMT) from young healthy donors for months.
To replenish the B1 vitamin that is lost, the FMTs might be supplemented with multistrain probiotics.
“Whether interventions like the suggested will qualify for future adjunctive therapy to current conventional intervention, remains to be shown,” Pedersen concluded.
