163-OR: RNAseq Analysis Reveals Temporal Dynamics of Colonic Immune Response to High-Fat Diet in Mice

Introduction & Objective: We previously showed that 1 week of high-fat diet (HFD) increases pro-inflammatory colonic macrophages (Mϕ) and that their depletion was associated with improved glycemic control. The current study aimed to elucidate the temporal changes of gene expression of intestinal immune cells in mice fed a HFD compared to chow.

Methods: Male C57BL/6N mice were fed either a HFD or chow for 1 week or 3 months. GTTs assessed the metabolic status. Colon CD45+ cells were isolated, subjected to single-cell RNA sequencing (analyzed by the Bioinformatics Core Facility), and used for flow cytometry analysis. Rectal inhibition of the cGAS-STING pathway was performed using H-151 (STING inhibitor). To compare chow with HFD, an unpaired Mann-Whitney U test with a two-sided distribution was done.

Results: After 1 week of HFD, glucose tolerance was impaired, and pro-inflammatory Mϕ of the colon increased, which were no longer elevated after 3 months of HFD. ScRNA-seq revealed an early increase in T-cells, which remained after 3 months, while B cells were only increased and activated after 3 months of HFD. Enrichment analysis showed an increased IFN-γ and IFN-α response in monocytes (Mono) and Mϕ after 1 week of HFD, while after 3 months EMT and ROS pathways were downregulated. Pseudo-bulk RNA-seq unveiled an upregulation of the cGAS-STING pathway within Mono and Mϕ after 1 week of HFD, which was no longer present after 3 months. Local STING inhibition for 1 week led to improved glucose tolerance and downregulation of IFN-α gene expression in the colon but did not protect against the increase of inflammatory Mϕ upon HFD.

Conclusion: 1 week of HFD resulted in profound changes in the immune cell landscape of the colon with an early innate and late adaptive immune response upon HFD feeding. The cGAS-STING pathway was upregulated early after initiation of the HFD, suggesting its initiating role in the disease. Indeed, interfering with the cGAS-STING pathway led to improved glycemia in HFD-fed mice.