The Role of Short-chain Fatty Acids in Malnutrition on Stress, Eating Behavior, and Nutritional State

This clinical trial aims to test the psychobiological effects of certain substances produced by gut bacteria, known as short-chain fatty acids (SCFAs), in people with anorexia nervosa.

Objective This protocol proposes investigating the effects of short-chain fatty acids (SCFAs), produced by gut bacterial fermentation of dietary fiber, as mediators of microbiota-gut-brain interactions on the acute stress response, eating behavior, and nutritional state in malnourished patients with anorexia nervosa (AN). SCFAs have recently been proposed as crucial mediators of the microbiome's effects on the host. Emerging evidence suggests that SCFAs impact human physiology through various physiological pathways and may regulate stress responses and eating behavior.

Method The investigators will conduct a randomized, triple-blind, placebo-controlled trial in 92 AN patients. Patients will receive either a placebo or a mixture of SCFAs (acetate propionate, butyrate) using colon-delivery capsules (CDCs) for six weeks. This clinical trial is an add-on to the standard inpatient psychotherapeutic program focusing on nutritional rehabilitation.

Hypotheses The investigators hypothesize that colonic SCFAs delivery will modulate neuroendocrine, cardiovascular, and subjective responses to an acute laboratory psychosocial stress task. As secondary outcome measures, the investigators will assess alterations in restrictive eating behavior and nutritional status, as reflected by changes in body mass index (BMI). Additionally, the investigators will explore changes in microbiota composition, gastrointestinal symptoms, eating disorder psychopathology, and related comorbidities.

Discussion The findings of this study can enhance our understanding of how gut microbiota-produced metabolites, particularly SCFAs, impact the stress response and eating behavior of individuals with AN. It has the potential to provide essential insights into the complex interplay between the gut, stress system, and eating behavior and facilitate new therapeutic targets for stress-related psychiatric disorders.

Eligibility Criteria:
Inclusion Criteria:

* Participants are female.
* Participants are at least 16 years of age.
* Participants are Dutch-speaking.
* Participants meet the diagnostic criteria of anorexia nervosa based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association, 2013). The first time the participant met these criteria was less than seven years ago.
* Participants have a current BMI \< 17,5 (kg/m2).
* Participants are on the waiting list for a psychiatric/psychotherapeutic inpatient treatment program with nutritional rehabilitation on the eating disorder ward of the University Psychiatric Hospital Leuven.
* Participants can access a -18°C home freezer for stool storage.

Exclusion Criteria:

* Any medical or psychiatric disorder, which in the Investigator's opinion, might jeopardize the participant's safety or compliance with the protocol.
* Any prior or concomitant treatment(s) that might jeopardize the participant's safety or that would compromise the integrity of the Trial.
* Substance/alcohol/illegal drug abuse or dependence or evidence for chronic uses of sedatives, drugs and/or sleep medication.
* High caffeine intake (\> 1000 ml coffee daily or equivalent quantities of other caffeine-containing substances).
* Use of pre- or probiotics within the last month before the start of the study.
* Use of antibiotics within the last three months before the start of the study.
* Pregnancy or intention to become pregnant.
* Previous experience with one of the tasks used in the study.
* Use of antipsychotics
* Use of selective serotonin reuptake inhibitors (SSRIs), oral contraceptives, or other drugs is allowed if patients are on a stable dosage for at least four weeks.