The Norwegian Microbiota Study in Anorexia Nervosa (NORMA): Integrating a clinical trial with preclinical experiments-A study protocol.

Anorexia nervosa is associated with gut microbiota dysbiosis and dysregulation in the gut-brain axis, but research examining gut microbiota as a potential driver of AN-related pathologies remains limited.

• Individuals with AN exhibit gut microbiota dysbiosis and dysregulation in the gut-brain axis (GBA).
• Co-occurring mental health challenges and gastrointestinal symptoms contribute to the difficulty of treating AN.
• The study identifies a gap in research examining the role of gut microbiota as a potential driver of AN-related pathologies.

NORMA consists of three work packages: a clinical observational trial (WP1), in vitro fermentation experiments (WP2), and animal experiments (WP3).

• WP1 is a clinical observational trial recruiting 90 AN patients and 90 healthy controls.
• WP2 involves growing fecal microorganisms from patients and HCs in vitro to assess the influence of prebiotics.
• WP3 involves transferring fecal microbiota from AN and HC donors to mice to determine if and how AN-related microbiota affects AN-relevant phenotypes.
• NORMA is a collaboration between the Norwegian University of Life Sciences and seven Norwegian specialized eating disorder inpatient treatment units.
• The study is registered as a clinical trial at clinicaltrials.gov (NCT06144905).

WP1 will recruit 90 AN patients and 90 healthy controls with specific eligibility criteria for each group.

• AN patients must be aged 16–50 and have a BMI < 18.5 and be admitted for treatment.
• Healthy controls must be aged 16–50 and have a BMI of 18.5–27.
• Data collected will include mental and physical health, dietary intake, and blood and fecal samples for biomarker and microbiota analyses.
• Data for AN patients will be collected at baseline, 6 weeks, and 12 weeks after start of treatment, while HCs will be assessed once.
• Outcomes will be compared between groups, and longitudinal effects of standard treatment examined within the AN group.

WP2 will use in vitro fermentation experiments to assess the influence of prebiotics on fecal microorganisms from AN patients and healthy controls.

• Fecal microorganisms from both AN patients and healthy controls will be grown in vitro.
• The primary aim is to assess the influence of prebiotics on these microbial communities.
• This work package is designed to complement the clinical and animal experiment components of NORMA.

WP3 will use a fecal microbiota transplantation mouse model to determine whether AN-related microbiota affects AN-relevant phenotypes.

• Mice will receive fecal microbiota transplants from AN patients or healthy control donors.
• The experiment aims to determine if and how AN-related microbiota affects AN-relevant phenotypes.
• This preclinical component is integrated with the clinical trial to provide mechanistic insight.

NORMA is described as pioneering in its integration of clinical, in vitro, and animal studies, representing the most comprehensive gut microbiota study of AN conducted so far.

• The study aims to investigate the role of gut microbiota in AN and the effects of standardized treatment on gut microbiota composition.
• The study aims to inform the development of 'innovative therapeutic strategies' and improve treatment outcomes and quality of life for individuals with AN.
• The integration of three distinct methodological approaches (clinical, in vitro, animal) is identified as a novel feature of NORMA.