Department of Biochemistry, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, 20-950 Lublin, Poland.
Centre for Interdisciplinary Research, The John Paul II Catholic University of Lublin, 20-708 Lublin, Poland.
Animal. 2021 Nov;15(11):100377. doi: 10.1016/j.animal.2021.100377. Epub 2021 Oct 5.
Tryptophan (Trp) is an essential amino acid which metabolises via the kynurenine pathway to generate a number of bioactive substances referred to as kynurenines. Among those are 3-hydroxykynurenine (3-HKyn) and quinolinic acid, which are neurotoxic, as well as kynurenic acid (Kyna) and xanthurenic acid (XA), which, similarly to nicotinamide (NAm), show neuroprotective and anti-depressive effects. Routine exercise is known to modulate Trp metabolism in skeletal muscle and is thus believed to reduce the risk of depressive states in humans and laboratory animals. Analogously, it was hypothesised that exercise can influence Trp metabolism in horses as well. The aim of this study was to evaluate the influence of two different types of exercise on Trp metabolism in horses of the same breed. A total of 32 purebred Arabian horses were involved in the study. The 22 three-year-old racehorses were subjected to short-time intense exercise. Ten other horses were made to perform endurance competitions at a distance of 80 km. Blood samples were collected at rest and following the end of the exercise period. Plasma concentrations of Trp, kynurenine (Kyn), Kyna, 3-HKyn, XA and NAm were determined using Ultra-High Performance Liquid Chromatography-Electrospray Ionisation-Tandem Mass Spectrometry. Short-time intense exercise led to an increase in plasma concentrations of Kyn, Kyna and XA. The endurance effort induced an increase in Kyna and a decrease in Trp and NAm levels. Both types of exercise, short-time intensive exercise and endurance exercise induced an increase in Trp metabolites, especially Kyna, and did not induce an increase in Trp level. Thus, from a pathophysiological perspective of the kynurenine pathway's influence on mental state, both types of exercise induced beneficial effects in horses.
色氨酸（Trp）是一种必需氨基酸，它通过犬尿氨酸途径代谢，生成多种生物活性物质，称为犬尿氨酸。其中包括 3-羟基犬尿氨酸（3-HKyn）和喹啉酸，它们具有神经毒性，而犬尿酸（Kyna）和黄尿酸（XA）与烟酰胺（NAm）类似，具有神经保护和抗抑郁作用。常规运动已知可调节骨骼肌中的 Trp 代谢，因此被认为可以降低人类和实验动物出现抑郁状态的风险。类似地，人们假设运动也可以影响马的 Trp 代谢。本研究的目的是评估两种不同类型的运动对同一品种马的 Trp 代谢的影响。共有 32 匹纯血阿拉伯马参与了这项研究。22 匹三岁的赛马进行了短时间的剧烈运动，另外 10 匹马进行了 80 公里的耐力比赛。在休息和运动结束后采集血样。使用超高效液相色谱-电喷雾串联质谱法测定 Trp、犬尿氨酸（Kyn）、Kyna、3-HKyn、XA 和 NAm 的血浆浓度。短时间剧烈运动导致 Kyn、Kyna 和 XA 的血浆浓度升高。耐力运动诱导 Kyna 增加和 Trp 和 NAm 水平降低。短时间剧烈运动和耐力运动都会增加 Trp 代谢物，尤其是 Kyna，而不会增加 Trp 水平。因此，从犬尿氨酸途径对精神状态影响的病理生理学角度来看，两种类型的运动都对马产生了有益的影响。
