ORF26-05 - ODC Inhibition with DFMO Influences Gut Microbiota and Microbial Metabolites in Autoimmune Diabetes

Disease modifying therapies have been a recent focus for the treatment and prevention of type 1 diabetes (T1D). Inhibition of polyamine synthesis with oral difluoromethylornithine (DFMO) is currently in phase II clinical trials for the preservation of β cell function in T1D (NCT05594563). Although polyamines are highly abundant in pancreatic islets, they are also produced by gut bacteria, and the impact of DFMO on the gut microbiota is not well understood. We hypothesized that oral DFMO induces changes to the gut microbiota that contribute to its protective effects in T1D. We profiled microbiota composition and function by 16S rRNA sequencing and targeted metabolomics in prediabetic female NOD mice treated for 4 weeks with either 1% (w/v) DFMO in the drinking water or daily 100 mg/kg intraperitoneal injections. We found that 1% (w/v) DFMO (but not IP injections) augmented a bile acid-FXR axis that was characterized by an enrichment of Turicibacter, an altered bile acid (BA) pool, elevated deoxycholic acid (DCA), and increased serum FGF15. To interrogate the roles of elevated DCA and FGF19 (the human ortholog of FGF15) in the settings of islet inflammation and autoimmune diabetes, we performed paired bulk RNA-sequencing and proteomics in human islets pretreated with either 50 μM DCA or 100 nM FGF19 for 2 h before exposure to a proinflammatory cocktail (PIC; IL-1β and IFN-γ) for 24 h. When comparing DCA+PIC versus PIC alone, there were 296 differentially expressed genes (DEG) and 342 differentially abundant proteins (DAP), whereas in the comparison of FGF19+PIC versus PIC there were 114 DEGs and 169 DAPs. By Hallmark gene set enrichment analysis, DCA treatment decreased the Interferon Alpha Response when compared to PIC, while both Interferon Alpha Response and Interferon Gamma Response were decreased with FGF19 treatment. To study the role of DCA and FGF15/19 in vivo, we supplemented prediabetic, female NOD mice with 0.02% (w/v) DCA in the drinking water for 4 weeks and collected pancreata to assess immune infiltration by histology. NOD mice treated with DCA had elevated serum FGF15 levels and displayed less severe insulitis at the end of the 4-week treatment. Together, our data suggest that DCA and FGF19 are gut-derived factors altered by oral DFMO treatment and that they antagonize interferon responses in human islets. In conclusion, oral DFMO alters the microbiota to augment a BA-FXR axis that contributes to preserved beta cell function and modifies T1D pathogenesis.