Bacterial SNPs in the human gut microbiome associate with host BMI

Area of Science:

• Microbiome research
• Human genetics
• Metagenomics

Background:

• Genome-wide association studies (GWASs) identify human single-nucleotide polymorphisms (SNPs) linked to health traits.
• Metagenome-wide association studies (MWASs) offer a parallel approach to link bacterial SNPs to host phenotypes, potentially revealing mechanistic insights.
• Few MWAS studies have been conducted to date.

Purpose of the Study:

• To develop and apply a framework for systematically detecting bacterial SNPs associated with host phenotypes.
• To investigate the association between bacterial SNPs and body mass index (BMI) in a large human cohort.

Main Methods:

• Recruitment of 7,190 healthy individuals for gut metagenomic sampling.
• Development of a metagenome-wide association study (MWAS) framework to identify bacterial SNPs associated with host phenotypes.
• Statistical analysis to detect significant SNP-phenotype associations and independent signals, controlling for covariates.

Main Results:

• Discovery of 1,358 statistically significant associations between bacterial SNPs and host BMI, with 40 independent associations identified.
• Replication of 17 associations in a geographically distinct cohort, independent of diet, medication, or exercise.
• Identification of BMI-associated SNPs in 27 bacterial species, including 12 not detected by standard relative abundance analysis.
• Uncovered specific SNP associations in *Bilophila wadsworthia* (inflammatory pathway) and *Faecalibacterium prausnitzii* (energy metabolism).

Conclusions:

• The study demonstrates the utility of MWAS for uncovering novel host-microbe interactions at the nucleotide level.
• Findings highlight the importance of considering bacterial genetic diversity beyond species-level abundance for understanding host phenotypes like BMI.
• The results provide a foundation for further research into the functional roles of specific bacterial SNPs in human health and disease.