Horizontal gene transfer after faecal microbiota transplantation in adolescents with obesity

BACKGROUND

Horizontal gene transfer (HGT) describes the transmission of DNA outside of direct ancestral lineages. The process is best characterised within the bacterial kingdom and can enable the acquisition of genetic traits that support bacterial adaptation to novel niches. The adaptation of bacteria to novel niches has particular relevance for faecal microbiota transplantation (FMT), a therapeutic procedure which aims to resolve gut-related health conditions of individuals, through transplanted gut microbiota from healthy donors.

RESULTS

Three hundred eighty-one stool metagenomic samples from a placebo-controlled FMT trial for obese adolescents (the Gut Bugs Trial) were analysed for HGT, using two complementary methodologies. First, all putative HGT events, including historical HGT signatures, were quantified using the bioinformatics application WAAFLE. Second, metagenomic assembly and gene clustering were used to assess and quantify donor-specific genes transferred to recipients following the intervention. Both methodologies found no difference between the level of putative HGT events in the gut microbiomes of FMT and placebo recipients, post-intervention. HGT events facilitated by engrafted donor species in the FMT recipient gut at 6 weeks post-intervention were identified and characterised. Bacterial strains contributing to this subset of HGT events predominantly belonged to the phylum Bacteroidetes. Engraftment-dependent horizontally transferred genes were retained within recipient microbiomes at 12 and 26 weeks post-intervention.

CONCLUSION

Our study suggests that novel microorganisms introduced into the recipient gut following FMT have no impact on the basal rate of HGT within the human gut microbiome. Analyses of further FMT studies are required to assess the generalisability of this conclusion across different FMT study designs and for the treatment of different gut-related conditions. Video Abstract.

Protocol for the Gut Bugs in Autism Trial: a double-blind randomised placebo-controlled trial of faecal microbiome transfer for the treatment of gastrointestinal symptoms in autistic adolescents and adults

INTRODUCTION

Autism (formally autism spectrum disorder) encompasses a group of complex neurodevelopmental conditions, characterised by differences in communication and social interactions. Co-occurring chronic gastrointestinal symptoms are common among autistic individuals and can adversely affect their quality of life. This study aims to evaluate the efficacy of oral encapsulated faecal microbiome transfer (FMT) in improving gastrointestinal symptoms and well-being among autistic adolescents and adults.

METHODS AND ANALYSIS

This double-blind, randomised, placebo-controlled trial will recruit 100 autistic adolescents and adults aged 16-45 years, who have mild to severe gastrointestinal symptoms (Gastrointestinal Symptoms Rating Scale (GSRS) score ≥2.0). We will also recruit eight healthy donors aged 18-32 years, who will undergo extensive clinical screening. Recipients will be randomised 1:1 to receive FMT or placebo, stratified by biological sex. Capsules will be administered over two consecutive days following an overnight bowel cleanse with follow-up assessments at 6, 12 and 26 weeks post-treatment. The primary outcome is GSRS score at 6 weeks. Other assessments include anthropometry, body composition, hair cortisol concentration, gut microbiome profile, urine/plasma gut-derived metabolites, plasma markers of gut inflammation/permeability and questionnaires on general well-being, sleep quality, physical activity, food diversity and treatment tolerability. Adverse events will be recorded and reviewed by an independent data monitoring committee.

ETHICS AND DISSEMINATION

Ethics approval for the study was granted by the Central Health and Disability Ethics Committee on 24 August 2021 (reference number: 21/CEN/211). Results will be published in peer-reviewed journals and presented to both scientific and consumer group audiences.

TRIAL REGISTRATION NUMBER

ACTRN12622000015741.

Protocol for the Gut Bugs Trial: a randomised double-blind placebo-controlled trial of gut microbiome transfer for the treatment of obesity in adolescents

INTRODUCTION

Animal studies showed that germ-free mice inoculated with normal mouse gut bacteria developed obesity, insulin resistance and higher triglyceride levels, despite similar food intake. In humans, an association has been found between obesity and gut microbiome dysbiosis. However, gut microbiome transfer has not been evaluated for the treatment of human obesity. We will examine the effectiveness of gut microbiome transfer using encapsulated material for the treatment of obesity in adolescents.

METHODS AND ANALYSIS

A two-arm, double-blind, placebo-controlled, randomised clinical trial of a single course of gut microbiome transfer will be conducted in 80 obese [body mass index (BMI) ≥30 kg/m²] adolescents (males and females, aged 14-18 years) in Auckland, New Zealand. Healthy lean donors (males and females, aged 18-28 years) will provide fresh stool samples from which bacteria will be isolated and double encapsulated. Participants (recipients) will be randomised at 1:1 to control (placebo) or treatment (gut microbiome transfer), stratified by sex. Recipients will receive 28 capsules over two consecutive mornings (~14 mL of frozen microbial suspension or saline). Clinical assessments will be performed at baseline, 6, 12 and 26 weeks, and will include: anthropometry, blood pressure, fasting metabolic markers, dietary intake, physical activity levels and health-related quality of life. Insulin sensitivity (Matsuda index), gut microbiota population structure characterised by 16S rRNA amplicon sequencing and body composition (using dual-energy X-ray absorptiometry) will be assessed at baseline, 6, 12 and 26 weeks. 24-hour ambulatory blood pressure monitoring will be performed at baseline and at 6 weeks. The primary outcome is BMI SD scores (SDS) at 6 weeks, with BMI SDS at 12 and 26 weeks as secondary outcomes. Other secondary outcomes include insulin sensitivity, adiposity (total body fat percentage) and gut microbial composition at 6, 12 and 26 weeks. Statistical analysis will be performed on the principle of intention to treat.

ETHICS AND DISSEMINATION

Ethics approval was provided by the Northern A Health and Disability Ethics Committee (Ministry of Health, New Zealand; 16/NTA/172). The trial results will be published in peer-reviewed journals and presented at international conferences.

TRIAL REGISTRATION NUMBER

ACTRN12615001351505; Pre-results.