The impact of chronic TMAO administration on liver oxidative stress, inflammation, and fibrosis

Abstract Purpose TMAO, a gut microbiota derived byproduct, has been associated with various cardiometabolic diseases by promoting oxidative stress and inflammation. The liver is the main organ for TMAO production and chronic exposure to high doses of TMAO could alter its function. In the present study we evaluated the effect of chronic exposure of high TMAO doses on liver oxidative stress, inflammation and fibrosis. Methods TMAO was administered daily via gastric gavage to 24 male Wistar rats for 3 months. The animals were divided in three groups, a high-dosage group that received 40 mg of TMAO/day, a low-dose group that received 20 mg of TMAO/day and a control group treated with vehicle. Blood was drawn for the quantification of TMAO and liver tissues were harvested for the assessment of oxidative stress (MDA, GSH, GSSG, GPx, CAT, and 8-oxo-dG) and inflammation by quantification of NOS and COX-2 expression. The evaluation of fibrosis was made by western blot analysis of α-SMA and Collagen-3 protein expression. Moreover, histological investigation and immunohistochemical staining of iNOS were performed in order to assess the liver damage. Results After 3 months of TMAO exposure, TMAO serum levels enhanced in parallel with significant increases in MDA and GSSG levels in liver and lower values of GSH and GSH/GSSG ratio as well as significant decrease in GPx and CAT activities. Inflammation was also highlighted, with a significant increase in iNOS and COX-2 expression, but without structural changes and without induction of liver fibrosis. Conclusion Chronic administration of TMAO for 3 months induced liver oxidative stress and inflammation without the appearance of fibrosis or liver structural changes.