Modulation of the diet and gastrointestinal microbiota normalizes systemic inflammation and β-cell chemokine expression associated with autoimmune diabetes susceptibility. Rattus norvegicus

The incidence of Type 1 diabetes (T1D), a T-cell mediated autoimmunity that targets the insulin secreting β-cells, has significantly increased, suggesting greater environmental pressure. In studies of T1D families and the BioBreeding rat model, we have identified a peripheral innate inflammatory state that is associated with diabetes susceptibility, consistent with pattern recognition receptor (PRR) ligation, but independent of disease progression. Here, compared to control strains, islets of spontaneously diabetic BB DRlyp/lyp and nondiatetic BB DR+/+ weanlings provided a standard cereal diet were found to temporally express a proinflammatory transcriptional program consistent with microbial antigen exposure that included numerous cytokines/chemokines. Dependence of this proinflammatory phenotype on the diet and gastrointestinal microbiota was investigated by transitioning DR+/+ weanlings to a hydrolyzed casein diet (HCD) or treating them with antibiotics to respectively alter or reduce PRR ligand exposure. Sequencing of the bacterial 16S rRNA gene revealed that these treatments significantly altered the ileal and cecal microbiota, resulting in increases in the Firmicutes:Bacteriodetes ratio, and abundances of lactobacilli and butyrate producing genera. Both treatments partially normalized the peripheral inflammatory state, reducing plasma cytokine, chemokine and TLR-4 activity levels. The proinflammatory islet transcriptome was more extensively normalized by HCD and immune-fluorescent staining revealed reductions in β-cell chemokine expression. HCD and antibiotic treatment did not normalize BB rat PBMC hyper-responsiveness to ex vivo mitogen stimulation. Combined, these studies link islet-level T1D susceptibility in BB rats to a genetically controlled innate inflammatory state that is influenced by environmental determinants encompassing the diet and the intestinal microbiota. Overall design: Pancreatic islet gene expression in DR (ND, HCD, and B/S) and F+/+ (ND) rat at day40 (+/-5 days) which is prior to insulitis. Islet transcriptomes of 40 day old F+/+ ND (CEL files labeled RT1uu,1 RNA pool, 6-8 equal contibutors per pool, 2 technical replicates per pool) rats, DR+/+ HCD (1 RNA pool, 6-8 equal contibutors per pool, 2 technical replicates per pool) rats, and DR+/+ B/S (1 RNA pool, 6-8 equal contibutors per pool, 2 technical replicates per pool) rats were compared to those of age matched DR+/+ ND (2 RNA pools, 6-8 equal contibutors per pool, 2 technical replicates per pool) rats.