L-theanine improves intestinal barrier functions by increasing tight junction protein expression and attenuating inflammatory reaction in weaned piglets

L-theanine, a characteristic non-protein amino acid first extracted from green tea leaves, has multiple biological functions, including antioxidant, immune and anti-inflammatory functions. However, the effect of L-theanine on intestinal barrier function of piglets remains unclear. This study aimed to investigate the role and underlying molecular mechanism of L-theanine in tight junction protein expression and intestinal mucosa inflammation in weaned piglets. Our data showed that L-theanine increased the expression of zonula occludens 1, claudin 1 and occludin in jejunum and ileum of piglets. In addition, L-theanine inhibited the mRNA expressions of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β), IL-6 and Toll-like receptor 4 (TLR4) and the protein expressions of TNF-α, phospho-p38 MAPK (mitogen-activated protein kinase), phospho-IĸB and nuclear NF-ĸB (nuclear factor-ĸB) p65. Taken together, our results indicated that L-theanine could improve intestinal barrier function in weaned piglets, and the effect might be mediated through inhibition of the TLR4/p38 MAPK/NF-κB signaling pathway.