Microbiome Transfer Partly Overrides Lack of IL-1RI Signaling to Alter Hepatic but not Adipose Tissue Phenotype and Lipid Handling following a High-Fat Diet Challenge

Scope: IL-1RI-mediated inflammatory signaling alters metabolic tissue responses to dietary challenges (e.g., high-fat diet [HFD]). Recent work suggests that metabolic phenotype is transferrable between mice in a shared living environment (i.e., co-housing) due to gut microbiome exchange. The authors examine whether the metabolic phenotype of IL-1RI^−/− mice fed HFD or low-fat diet (LFD) could be transferred to wild-type (WT) mice through gut microbiome exchange facilitated by co-housing. Methods and results: Male WT (C57BL/J6) and IL-1RI^−/− mice are fed HFD (45% kcal) or LFD (10% kcal) for 24 weeks and housed i) by genotype (single-housed) or ii) with members of the other genotype in a shared microbial environment (co-housed). The IL-1RI^−/− gut microbiome is dominant to WT, meaning that co-housed WT mice adopted the IL-1RI^−/− microbiota profile. This is concomitant with greater body weight, hepatic lipid accumulation, adipocyte hypertrophy, and hyperinsulinemia in co-housed WT mice, compared to single-housed counterparts. These effects are most evident following HFD. Primary features of microbiome differences are Lachnospiraceae and Ruminococcaceae (known producers of SCFA). Conclusion: Transfer of SCFA-producing microbiota from IL-1RI^−/− mice highlights a new connection between diet, inflammatory signaling, and the gut microbiome, an association that is dependent on the nature of the dietary fat challenge.