A specific<i>Streptococcus mutans</i>strain aggravates non‐alcoholic fatty liver disease

<jats:sec><jats:title>Objective</jats:title><jats:p><jats:italic>Streptococcus mutans</jats:italic>, a major dental caries pathogen, has shown to be associated with the aggravation of cerebral hemorrhage and inflammatory bowel diseases. In this study, we evaluated the effects of<jats:italic>S. mutans</jats:italic>on the development of non‐alcoholic steatohepatitis (<jats:styled-content style="fixed-case">NASH</jats:styled-content>) in a mouse model.</jats:p></jats:sec><jats:sec><jats:title>Materials and methods</jats:title><jats:p><jats:italic>Streptococcus mutans</jats:italic>oral strain<jats:styled-content style="fixed-case">MT</jats:styled-content>8148 (serotype<jats:italic>c</jats:italic>) and a blood isolate<jats:styled-content style="fixed-case">TW</jats:styled-content>871 (<jats:italic>k</jats:italic>) were used. C57BL/6J mice (6 weeks old) were fed a high‐fat diet for 4 weeks; the test strains or phosphate‐buffered saline was then intravenously administered. Mice were euthanized after 8 or 12 weeks. Whole body, extirpated liver, and visceral fat weights were determined, and histopathological evaluations of the liver specimens were performed.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Mice infected with<jats:styled-content style="fixed-case">TW</jats:styled-content>871 showed significantly greater body and liver weights than those administered<jats:styled-content style="fixed-case">MT</jats:styled-content>8148 or phosphate‐buffered saline. Histopathological analyses revealed prominent infiltration of inflammatory cells and adipocellular deposition in livers extirpated 8 weeks after an infection with<jats:styled-content style="fixed-case">TW</jats:styled-content>871; fibrosis was also observed in livers extirpated after 12 weeks.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>These results suggest that a specific strain of<jats:italic>S. mutans</jats:italic>could induce<jats:styled-content style="fixed-case">NASH</jats:styled-content>.</jats:p></jats:sec>