Mixtures of the two major conjugated linoleic acid (CLA) isomers trans-10,cis-12-CLA and cis-9,trans-11-CLA are used as over the counter supplements for weight loss. Because of the reported adverse effects of CLA on insulin sensitivity in some mouse studies, we sought to compare the impact of dietary t10c12-CLA and c9t11-CLA on liver, adipose tissue, and systemic metabolism of adult lean mice. We fed 8 week-old C57Bl/6J male mice with low fat diets (10.5% Kcal from fat) containing 0.8% t10c12-CLA or c9t11-CLA for 9 or 38 days. Diets containing c9t11-CLA had minimal impact on the endpoints studied. However, 7 days after starting the t10c12-CLA diet, we observed a dramatic reduction in fat mass measured by NMR spectroscopy, which interestingly rebounded by 38 days. This rebound was apparently due to a massive accumulation of lipids in the liver, because adipose tissue depots were visually undetectable. Hepatic steatosis and the disappearance of adipose tissue after t10c12-CLA feeding was associated with elevated plasma insulin levels and insulin resistance, compared to mice fed a control diet or c9t11-CLA diet. Unexpectedly, despite being insulin resistant, mice fed t10c12-CLA had normal levels of blood glucose, without signs of impaired glucose clearance. Hepatic gene expression and fatty acid composition suggested enhanced hepatic de novo lipogenesis without an increase in expression of gluconeogenic genes. These data indicate that dietary t10c12-CLA may alter hepatic

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Commensal bacteria are critical regulators of both tissue homeostasis and the development and exacerbation of autoimmunity. However, it remains unclear how the intestinal microbiota contributes to inflammation in tissues such as the central nervous system (CNS) where these microbes are typically absent and whether T cell receptor (TCR) specificity for commensal-derived antigens is important to the development of tissue inflammation-related outcomes. Here, we found that ileum- and cecum-colonizing segmented filamentous bacteria (SFB)-specific T cells (clone TCR7B8) can infiltrate the CNS wherein they can be reactivated and produce high levels of inflammatory cytokines including IFNg, IL-17A, TNFa, and GM-CSF in the absence of regulatory T cells. In contrast, other SFB-specific T cells (clone TCR1A2) recognizing an epitope in which 8/9 amino acids overlap with those recognized by TCR7B8 failed to induce such neuroinflammation. Despite their similar SFB-derived peptide antigen targets, TCR7B8 was found to recognize peptides derived from host proteins including receptor tyrosine-protein kinase ErbB2, trophinin 1, and anaphase-promoting complex subunit 2 in vitro, whereas TCR1A2 did not, indicating that TCR7B8 induces CNS inflammation via molecular mimicry. Immune checkpoint blockade accelerated TCR7B8-mediated CNS inflammation, suggesting a potential cause of immune-related adverse events induced in cancer patients undergoing such treatment. Together, our findings reveal a potential mechanism whereby gut commensal-specific T cells are dysregulated and contribute to extraintestinal inflammation.