Protective effects ofl-theanine on rats with dextran sulfate sodium-induced inflammatory bowel disease

The aim of this study is to evaluate the anti-inflammatory and protective effects ofl-theanine in inflammatory bowel disease (IBD) and to identify the underlying molecular mechanisms. Rats were pre-treated withl-theanine at 0, 50, 200, or 800 mg/kg/day. IBD was induced in rats using dextran sulfate sodium (DSS). Histopathological analysis suggests thatl-theanine can suppress DSS-induced IBD with significant inhibition of inflammation in large and small intestinal tissues. Moreover, the 200 mg/kg/dayl-theanine-treated DSS group had higher body and small intestine weights, a lower disease activity index and expression of inflammatory factors than the DSS group without pre-treatment. In RNA sequencing and tandem mass tag labeling analyses, large number of mRNAs and proteins expression level differed when compared with the DSS-induced rats with and without 200 mg/kg/dayl-theanine pre-treatment. Moreover, Kyoto Encyclopedia of Genes and Genomes pathway analysis indicates the anti-inflammatory activities ofl-theanine in DSS-induced IBD, with a high representation of genes in Cholesterol metabolism and Retinol metabolism pathways. Analysis of protein-protein interaction networks further indicates the involvement of these two pathways. These studies suggest that medium-dosel-theanine pre-treatment could ameliorate DSS-induced IBD through molecular mechanisms involving cholesterol and retinol metabolism.