OR14-6 Probiotic Supplementation with Lactiplantibacillus Plantarum 299v Modulates β-Cell Endoplasmic Reticulum Stress and Prevents Type 1 Diabetes in Biobreeding Rats

Abstract Type 1 diabetes (T1D) is a complex disease characterized by the loss of pancreatic beta-cells and lifelong dependence on insulin replacement therapy. As the worldwide incidence of T1D has increased and the prevalence of high-risk HLA haplotypes has declined among new diagnoses, a greater focus has been placed on environmental factors contributing to T1D pathogenesis. Lactiplantibacillus plantarum 299v (Lp299v) supplement is reported to increase plasma and stool levels of anti-inflammatory short-chain fatty acids (SCFAs) and promote IL-10 signaling in colonic derived macrophages and T-cells. Therefore, we investigated the effect of Lp299v supplement on T1D pathogenesis in diabetes-prone BioBreeding DRlyp/lyp rats. Rats were weaned at 21 days of age (D21) onto a normal cereal diet (ND) or a gluten-free hydrolyzed casein diet (HCD), with or without daily Lp299v supplementation. All rats provided ND developed diabetes by D83 and supplementing ND with Lp299v did not significantly delay progression. Rats provided HCD showed a significant delay in diabetes onset over ND, while progression was even more delayed in the HCD+Lp299v group, with 25% of animals remaining diabetes-free to D130 (study end). Relative to the other groups, HCD+Lp299v rats exhibited significant increases in the plasma levels of the SCFAs propionate and butyrate (beneficial metabolites produced by intestinal bacteria). In addition, stool microbiota showed increased abundances of SCFA-producing taxa at D40. Gene expression analysis of pancreatic islets was conducted at D40, prior to insulitis. Lp299v supplementation favorably modulated islet expression levels of pathways related to endoplasmic reticulum (ER) stress, and the major arms of the unfolded protein response (UPR), especially in combination with the HCD. Notably, ER stress has been implicated in the formation of islet neoantigens that may underlie the initial loss of immune tolerance in T1D. Lp299v supplement differentially modulated the UPR to favor the expression of the transcription factor Atf6, increase expression of transcripts related to cell survival/proliferation, and the ER-associated protein degradation (ERAD) pathway of the UPR. This contrasted with HCD alone, which promoted a transcriptional program related to autophagy. To colocalize and confirm activities detected in the transcriptional analyses to β-cells, pancreata of D40 rats were subjected to dual immunofluorescence staining for insulin and UPR-related proteins. Consistent with elevated ERAD activity, significantly greater EIF4G1 and OS9 expression were observed in HCD+Lp299v islets. Phospho-PERK staining was significantly higher in islets of the HCD-alone group, consistent with the elevated expression of autophagy transcripts. Analysis of plasma proinsulin: C-peptide ratios revealed that Lp299v alone could improve islet function, as significant decreases were measured in all groups relative to ND. While ongoing studies aim to define the bacterial metabolites underlying the favorable outcomes, these studies suggest that Lp299v supplementation improves proteostasis capacity in β-cells and slows T1D progression in DRlyp/lyp rats. Presentation: Sunday, June 12, 2022 12:15 p.m. - 12:30 p.m.