Riddet Institute, Massey University, Te Ohu Rangahau Kai Facility, Palmerston North, New Zealand; Food Experience and Sensory Testing (Feast) Laboratory, School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand.
Riddet Institute, Massey University, Te Ohu Rangahau Kai Facility, Palmerston North, New Zealand; Smart Foods and Bioproducts, Te Ohu Rangahau Kai Facility, AgResearch Limited, Palmerston North, New Zealand.
J Nutr. 2024 Oct;154(10):2948-2962. doi: 10.1016/j.tjnut.2024.07.010. Epub 2024 Jul 15.
Absorption of tryptophan (TRP) across the gut epithelium is potentially modulated by competing large neutral amino acids (LNAAs), which could affect the appearance of TRP and its metabolites in the bloodstream.
This study aimed to determine, in a growing pig model of an adult human, the absorption of TRP and other LNAAs from the gastrointestinal tract, and plasma appearance of TRP, LNAAs, and TRP metabolites, in response to dietary proteins varying in TRP content.
Pigs were adapted for 7 d to each of 4 diets that differed in their protein source and TRP content: 1) alpha-lactalbumin (AL; 9.95 mg TRP/g diet DM), 2) whey protein (6.59 mg TRP/g), 3) casein (3.73 mg TRP/g), or 4) zein (0.14 mg TRP/g). On day 8, pigs were euthanised after a 12-h fast (baseline), or 1, 2, 3, 4, or 6 h after they received a test meal consisting of 45 g protein, or a protein-free meal (n = 6 pigs at each time in each meal group). Tryptophan and LNAA absorption from the small intestine, and appearance of TRP, LNAAs, and TRP metabolites (melatonin, serotonin, kynurenine pathway metabolites), in the portal vein and systemic circulation, were determined.
AL intake resulted in sustained elevated plasma TRP concentrations after an overnight fast. The amount of TRP absorbed was dose-dependently related to protein TRP content (P = 0.028), with fastest rates for pigs fed AL (371 mg/h). Portal and systemic plasma TRP, TRP/LNAA, and the TRP metabolites were highest (P ≤ 0.05) after AL intake, and remained above baseline levels for ∼4 h postprandially. Absorption rates of TRP correlated with postprandial plasma TRP and TRP metabolites (P ≤ 0.05).
In adult humans, postprandial plasma TRP and TRP metabolite concentrations can likely be modulated by the TRP content of the meal.
色氨酸（TRP）在肠道上皮细胞的吸收可能受到竞争的大中性氨基酸（LNAAs）的调节，这可能会影响血液中 TRP 及其代谢物的出现。
本研究旨在确定在成年猪模型中，从胃肠道吸收 TRP 和其他 LNAAs，并根据膳食蛋白质中 TRP 含量的不同，测定 TRP、LNAAs 和 TRP 代谢物在血浆中的出现情况。
猪适应了 7 天的 4 种不同的饮食，这些饮食的蛋白质来源和 TRP 含量不同：1）α-乳白蛋白（AL；9.95mg TRP/g 日粮 DM），2）乳清蛋白（6.59mg TRP/g），3）酪蛋白（3.73mg TRP/g）或 4）玉米蛋白（0.14mg TRP/g）。第 8 天，禁食 12 小时后（基础），或接受含有 45g 蛋白质的测试餐或无蛋白质餐（每餐组每个时间点各 6 头猪）1、2、3、4 或 6 小时后，处死猪。从小肠吸收 TRP 和 LNAAs，以及门静脉和全身循环中 TRP、LNAAs 和 TRP 代谢物（褪黑素、血清素、犬尿氨酸途径代谢物）的出现情况。
AL 摄入导致夜间禁食后持续升高的血浆 TRP 浓度。TRP 的吸收量与蛋白质 TRP 含量呈剂量依赖性相关（P=0.028），饲喂 AL 的猪的吸收速度最快（371mg/h）。门静脉和全身血浆 TRP、TRP/LNAA 和 TRP 代谢物在 AL 摄入后最高（P≤0.05），并在餐后约 4 小时内保持在基线以上。TRP 的吸收速率与餐后血浆 TRP 和 TRP 代谢物相关（P≤0.05）。
在成年人中，餐后血浆 TRP 和 TRP 代谢物浓度可能可以通过膳食中的 TRP 含量来调节。
