The Intestinal Microbiota in Acute Anorexia Nervosa and During Renourishment

Abstract

Objective The relevance of the microbe-gut-brain axis to psychopathology is of interest in anorexia nervosa (AN), as the intestinal microbiota plays a critical role in metabolic function and weight regulation. Methods We characterized the composition and diversity of the intestinal microbiota in AN, using stool samples collected at inpatient admission (T1) (n=16) and discharge (T2) (n=10). At T1, participants completed the Beck Depression and Anxiety Inventories and the Eating Disorder Examination-Questionnaire. Patients with AN were compared to healthy individuals who participated in a previous study (healthy comparison group; HCG). Genomic DNA was isolated from stool samples, and bacterial composition was characterized by 454 pyrosequencing of the 16S rRNA gene. Sequencing results were processed by the Quantitative Insights Into Microbial Ecology pipeline. We compared T1 vs. T2 samples, samples from both points were compared to HCG (n=12), and associations between psychopathology and T1 samples were explored. Results In patients with AN, significant changes emerged between T1 and T2 in taxa abundance and beta (between-sample) diversity. Patients with AN had significantly lower alpha (within-sample) diversity than HCG at both T1 (p=0.0001) and T2 (p=0.016), and differences in taxa abundance were found between AN patients and HCG. Levels of depression, anxiety, and eating disorder psychopathology at T1 were associated with composition and diversity of the intestinal microbiota. Conclusions We provide evidence of intestinal dysbiosis in AN and an association between mood and the enteric microbiota in this patient population. Future directions include mechanistic investigations of the microbe-gut-brain axis in animal models and association of microbial measures with metabolic changes and recovery indices.

The Gut-Brain Axis in Healthy Females: Lack of Significant Association between Microbial Composition and Diversity with Psychiatric Measures

“…Mixed evidence has emerged from investigations comparing the intestinal microbiotas of individuals with major depressive disorder to healthy controls, with one study failing to find significant between-group differences in microbial diversity or taxonomic composition [64], while the other found increased diversity and significant taxonomic differences at the phylum, family, and genus levels [11]. In patients with acute anorexia nervosa, which is frequently comorbid with depression, work from our laboratory has shown that microbial diversity was both associated with depression and significantly lower than in healthy controls [12]. Composition and diversity of the intestinal microbiota may also be associated with temperament in young children, but how such links may evolve during the development of adult personality is unclear [65].…”

Weight Gain after Fecal Microbiota Transplantation in a Patient with Recurrent Underweight following Clinical Recovery from Anorexia Nervosa

“…One often proposed hypothesis is the varying degree to which certain microbes can extract calories from food, for example through the production of short-chain fatty acids (SCFAs) from indigestible carbohydrates (see below), resulting in an increased extraction of energy despite stable dietary intake [6]. Furthermore, studies have assigned a role for gut microbes in host metabolic rates, the latter of which was found altered in AN patients [3]. In this case, the resting energy metabolism decreased after FMT, possibly contributing to the gain in bodyweight.…”

“…Fecal microbiota transplantation (FMT) from obese to nonobese subjects has led to weight gain despite unchanged dietary intake in animals as well as humans [2]. It has been repeatedly shown that short- and long-term dietary patterns including undernutrition and dieting in patients with AN can change the microbiota composition [3]. The notion that the gut microbiome can also affect nervous system functions through the gut-brain axis makes its involvement in eating behavior and psychiatric disorders plausible [4].…”

The Role of Psychotropic Medications in the Management of Anorexia Nervosa: Rationale, Evidence and Future Prospects

“…Those peptides are often altered during the ill state of an eating disorder and normalize with recovery, but is it largely unknown whether they contribute mechanistically to AN [177]. A new area of research is the intestinal microbiome and one small study suggested that the bacterial composition in the intestine is altered in AN and that weight recovery is associated in changes in the microbiome [178]. Future research may identify pharmacological interventions that could be beneficial for the recovery from AN.…”