The effect of L-tryptophan on hemorrhagic shock induced bacterial translocation1

Enhanced Intestinal Barriers by Puerarin in Combination with Tryptophan

The intestinal barrier is essential for maintaining human intestinal health. The growing number of studies has shown that both puerarin and tryptophan and its metabolites have a beneficial effect on the intestinal barrier. This study aims at the combination of puerarin and tryptophan or its metabolites for improving the intestinal barrier. In our study, 40 female Sprague-Dawley rats were randomly divided into five groups (n = 8) for a 4-week experiment and dextran sodium sulfate was used to induce an intestinal barrier injury in rats. Our results showed that puerarin combined with tryptophan or its metabolites (indole-3-propionic acid, IPA) improved the intestinal barrier by enhancing the mucus layer barrier, which was mainly achieved by increasing the number of goblet cells and promoting the secretion of MUC2. Both TRPM5 and VAMP8 promoted MUC2 secretion in goblet cells through exocytosis, but their mechanisms of action are different. In our study, we found that puerarin and tryptophan showed different effects on TRPM5 and VAMP8, respectively. Puerarin enhances the expression of TRPM5, and tryptophan inhibits the expression of TRPM5; however, puerarin and tryptophan have no significant effect on the expression of VAMP8.

Melatonin independent protective role of l-tryptophan in experimental reflux esophagitis in rats

Melatonin is implicated in sustaining the esophageal integrity in gastro-esophageal reflux disease. However, the role of its synthetic precursor l-tryptophan is not clear in this pathology. The present study was designed to explore the effects of l-tryptophan on esophageal damage following reflux esophagitis (RE)-establishment and concurrent alterations in factors possibly influencing esophageal integrity such as esophageal melatonin level, luminal acidity, H(+)K(+)-ATPase activity, mucin and gastric PGE(2) levels. RE was established in rats by simultaneous ligation of pylorus region and fore-stomach. RE significantly decreased the esophageal-melatonin level and the expression of its synthesizing enzymes: arylalkylamine-N-acetyltransferase (AA-NAT) and hydroxyindole-O-methyltransferase (HIOMT). Administration of l-tryptophan significantly decreased the RE-induced esophageal mucosal damage, without altering the levels of melatonin. l-Tryptophan pretreatment also normalized the esophageal mucosal damage caused by melatonin receptor antagonist-luzindole. Simultaneously, l-tryptophan significantly increased the RE-decreased expression of AA-NAT with insignificant effect on HIOMT gene expression. In contrast, l-tryptophan per se caused a significant elevation in the esophageal melatonin level, with no significant effect on the expression of AA-NAT and HIOMT enzymes. Further, l-tryptophan significantly normalized the RE-induced changes in the gastric juice volume, acidity and pH. However, it did not significantly inhibit the H(+)K(+)-ATPase activity in vitro. Also, l-tryptophan significantly increased the RE-reduced mucin level, COX-2 activity and thereby PGE(2) levels. Interestingly, indomethacin (PGE(2) synthesis blocker), aggravated the RE-induced tissue injury with simultaneous changes in the gastric volume, acidity, pH and mucin content, which l-tryptophan failed to reverse, suggesting that the attenuating effect of l-tryptophan on gastric secretions could be PGE(2) driven. Thus the current study provide evidences that protective functions of l-tryptophan against RE is independent of its conversion into melatonin, and possibly involve mobilization of factors such as COX-2 derived PGE(2) and mucin that counterbalance the detrimental effect of gastric acid on esophageal mucosa, signifying the therapeutic efficacy of l-tryptophan against the esophageal pathologies.