Functional PET imaging of gut microbiota with [¹⁸F]fluorodeoxyglucose, [¹⁸F]fluorodeoxysorbitol and [¹¹C]choline reflects Clostridia and Lactobacillales abundance in caecum and small intestine and host metabolic interactions.

Abstract

Interaction of gut microbiota (GM) with dietary sugars (glucose, sorbitol) and choline has been transversely implicated in the pathogenesis of multiple chronic diseases. Our aim was to develop functional PET imaging of GM, using a multi-tracer approach to capture bacteria classes involved in sugar fermentation and choline catabolism at their gastrointestinal (GI) location. Adult and young sex-balanced groups of mice underwent oral administration of [¹⁸F]FDG, [¹⁸F]FDS or [¹¹C]choline ([¹¹C]cho) and repeated PET imaging over 4-5 h. Antibiotics, probiotic or faecal microbiota transplantation (FMT) served to quantify the specific role and site of bacteria action. GM was sequenced ex-vivo; gut histology and metabolic profiles were assessed in subsets. [¹⁸F]FDG and [¹⁸F]FDS reflected caecum abundance of Clostridia and Bacteroidia fermenters, with [¹⁸F]FDG exhibiting strongest and broadest relations. Clearance of [¹¹C]cho from small gut reflected Bacilli and Lactobacilli abundance. In vitro cultures supported these relationships. Urinary ¹¹C-excretion was nearly abolished by antibiotics. PET imaging was able to differentiate and predict gut bacteria classes in mice receiving FMT from two age-extreme human donors. Urinary [¹⁸F]FDS excretion reflected small-gut goblet cell activation; high caecum [¹⁸F]FDG retention and small gut [¹¹C]cho clearance predicted body glucose use and low systemic inflammation. Imaging of ingested probes is simple and effective to map GM characteristics in situ and the functional crosstalk with host processes in mice in real-time. Our data confirm that the GI ecosystem is highly diversified, pointing to small intestine and caecum GM as dominant players in gut-body handling of our target nutrients.