Contrary to what many people may think, anorexia nervosa is not simply about wanting to be thin. In fact, it is a complex mental disorder that changes the way the brain regulates appetite and body image.
In people with anorexia nervosa, the brain’s reward system changes and weight loss becomes its number one priority. This leads to extreme behavioral changes. Among other things, people suffering from anorexia nervosa radically reduce their calorie consumption. About one percent of all young people develop anorexia nervosa, and in about one in five, it becomes a chronic and often fatal illness. Nine out of 10 of those diagnosed with anorexia nervosa are women in adolescence or early adulthood.
The incidence of anorexia nervosa is increasing.
The disease is caused by a complex interaction between several so-called vulnerability genes and environmental influences. However, it now also appears to be the result of a serious imbalance in the intestinal ecosystem of trillions of bacteria and viruses.
This is the conclusion of a new study by an international team led by Danish scientists. The study involved 77 Danish girls and young women suffering from anorexia nervosa and 70 healthy individuals of the same sex. The results suggest that severe changes in gut microbes and metabolites produced by the corresponding gut microbiome in the blood may directly affect the development of anorexia nervosa.
To demonstrate this, the researchers transplanted feces from anorexia cases and healthy individuals, respectively, into bacteria-free mice, explains professor and lead researcher Oluf Borbye Pedersen from the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen.
“Mice given feces from people with anorexia nervosa had trouble gaining weight, and analyzes of genetic activities in certain parts of their brain revealed changes in several genes that regulate appetite. Furthermore, mice that had been given feces from people affected with anorexia nervosa showed greater activity of the genes that regulate fat combustion, which probably contributes to their lower body weight," explains Oluf Pedersen, principal investigator of the study together with clinical professor René Støvring, who specializes in anorexia nervosa.
Intestinal bacteria produce small amounts of important vitamins
Using DNA technology and advanced bioinformatic analysis, researchers identified distinct and marked changes in the composition and function of the trillions of bacteria and viruses in the intestines in cases of anorexia nervosa.
The researchers compared alterations in the gut microbiome with blood molecules (metabolites) produced by the gut microbiome, demonstrating associations between specific changes in gut bacteria, blood bacterial molecules, and a number of personality traits, such as distorted body image. , the drive for thinness and the refusal to eat in those affected by anorexia nervosa.
“We also found that specific gut bacteria in women with anorexia nervosa produce less vitamin B1 . B1 deficiency can lead to loss of appetite, various intestinal symptoms, anxiety and withdrawn social behavior,” says Assistant Professor Yong Fan of the Novo Nordisk Foundation Basic Metabolic Research Center, a young investigator leading the study.
“In addition, our analysis of the intestinal microbiome revealed in cases of anorexia different virus particles capable of breaking down lactic acid-producing bacteria in the intestines. “Both findings may form the basis of future controlled clinical trials with vitamin B1 supplements and fermented foods or probiotics containing various types of lactic acid bacteria,” he says.
Years of clinically controlled studies lie ahead
The new study is an example of basic research aimed at exploring whether an altered gut microbial ecosystem is a contributing factor to the development or retention of chronic disease. And this can potentially be the case with anorexia nervosa.
The next question is whether basic research can lay the groundwork for clinically controlled trials that explore whether current treatment for anorexia nervosa, which includes psychotherapy, family counseling, and attempts to change the patient’s eating and exercise habits, can benefit from a additional treatment aimed at normalizing the intestinal microbiome.
“A complex disease like anorexia nervosa requires personalized and multifactorial treatment. Our findings, which suggest that alterations of intestinal bacterial and viral communities and their functions reflected in blood metabolites synthesized by altered microbiomes may be involved in disease development and retention, provide a rationale for initiating clinically controlled trials. In such trials, clinical investigators will likely test the potential effects of an initial antibiotic intervention to restore the aberrant gut microbiome followed by weekly fecal microbiota transplantation (FMT) from healthy young donors for months. These FMTs can be supplemented with vitamin B1 and multi-strain probiotics. Whether interventions such as those suggested will qualify for future therapies complementary to the current conventional intervention."
