Gut microbiota in experimental murine model of Graves' orbitopathy established in different environments may modulate clinical presentation of disease

BACKGROUND

Variation in induced models of autoimmunity has been attributed to the housing environment and its effect on the gut microbiota. In Graves' disease (GD), autoantibodies to the thyrotropin receptor (TSHR) cause autoimmune hyperthyroidism. Many GD patients develop Graves' orbitopathy or ophthalmopathy (GO) characterized by orbital tissue remodeling including adipogenesis. Murine models of GD/GO would help delineate pathogenetic mechanisms, and although several have been reported, most lack reproducibility. A model comprising immunization of female BALBc mice with a TSHR expression plasmid using in vivo electroporation was reproduced in two independent laboratories. Similar orbital disease was induced in both centers, but differences were apparent (e.g., hyperthyroidism in Center 1 but not Center 2). We hypothesized a role for the gut microbiota influencing the outcome and reproducibility of induced GO.

RESULTS

We combined metataxonomics (16S rRNA gene sequencing) and traditional microbial culture of the intestinal contents from the GO murine model, to analyze the gut microbiota in the two centers. We observed significant differences in alpha and beta diversity and in the taxonomic profiles, e.g., operational taxonomic units (OTUs) from the genus Lactobacillus were more abundant in Center 2, and Bacteroides and Bifidobacterium counts were more abundant in Center 1 where we also observed a negative correlation between the OTUs of the genus Intestinimonas and TSHR autoantibodies. Traditional microbiology largely confirmed the metataxonomics data and indicated significantly higher yeast counts in Center 1 TSHR-immunized mice. We also compared the gut microbiota between immunization groups within Center 2, comprising the TSHR- or βgal control-immunized mice and naïve untreated mice. We observed a shift of the TSHR-immunized mice bacterial communities described by the beta diversity weighted Unifrac. Furthermore, we observed a significant positive correlation between the presence of Firmicutes and orbital-adipogenesis specifically in TSHR-immunized mice.

CONCLUSIONS

The significant differences observed in microbiota composition from BALBc mice undergoing the same immunization protocol in comparable specific-pathogen-free (SPF) units in different centers support a role for the gut microbiota in modulating the induced response. The gut microbiota might also contribute to the heterogeneity of induced response since we report potential disease-associated microbial taxonomies and correlation with ocular disease.

Chilled food systems. Effects of chilled holding on quality of beef loaves

Following storage at 32 degrees or 42 degrees +/- 1 degrees F. for zero (4 hr.), and one, two, four, seven, and nine days, beef loaves which had either been cooked; cooked and pasteurized; or cooked, frozen, and thawed prior to storage were compared with a freshly prepared, freshly cooked loaf. Loaves were initially cooked to an internal temperature of 165 degrees F. and reheated to the same temperature prior to testing. A freshly prepared loaf cooked immediately prior to evaluation statistically had a shorter heating time, less cooking losses, higher moisture content, lower thiobarbituric acid (TBA) scores, and higher taste panel scores for odor, juiciness, flavor, and appearance. In all quality-related properties evaluated, the reference loaf rated higher. Pasteurized loaves were not significantly different from refrigerated loaves. Frozen, thawed loaves had significantly different values for TBA scores for all taste panel evaluations; these differences were indicative of reduced quality. Taste panel scores decreased and TBA scores increased significantly over nine-day storage. The hypothesis that changes over time were linear was not rejected. The only significant difference noted for the two storage temperatures of 32 degrees and 42 degrees F. was for total heating time. Standard plate counts for aerobic bacteria were extremely low when samples were taken after storage and after reheating. Only two loaves sampled had counts per gram above 100. The absence of microbial growth pattern indicated that increases in TBA scores and decreases in odor and flavor scores were produced by autoxidation of lipids.