Introduction
metabolic syndrome
METABOLIC SYNDROME, INSULIN SENSITIVITY
The metabolic syndrome (MetSyn) constitutes a major global health concernPreviously reported microbial effects on human health have been mainly attributed to the bacterial component of the microbiotaConsidering their ability to modulate gut bacteria and their functionModulation of gut microbiota composition through FMT has been shown to improve peripheral insulin sensitivity in individuals with MetSynTo study the effect of faecal phages on glucose metabolism, comparing a clean and concentrated faecal virome transplant with a phage-inactivated transplant would be most desirable. Unfortunately, the IRB only allowed us to minimally process the faecal suspension that is usually used for FMT, so we chose an FFT approach. We were hence not able to remove components other than bacteria from the filtrate. However, since phages are self-propagating entities with presumed longer effects on the microbial ecosystem than a single administration of metabolites, peptides or debris, we considered it justified to use the FFT to study phage-bacteria interactions and subsequent effects on glucose metabolism.In this double-blind, randomised, placebo-controlled pilot study, we provide proof of concept that a faecal filtrate from lean healthy donors containing gut virions can be safely administered to MetSyn recipients. Moreover, gut phages have the potential to improve glycemic variability and alter phage-microbe dynamics. Although follow-up studies with cleaner, better defined and better-matched donor-recipient pairs are needed, this study provides a critical basis to do so and move the field forward.