Dietary L-tryptophan leaves a lasting impression on the brain and the stress response

• Published in: British Journal of Nutrition
• Main Authors: Höglund, Erik, Øverli, Øyvind, Åberg Andersson, Madelene, Silva, Patricia, Laursen, Danielle Caroline, Moltesen, Maria Møller, Krogdahl, Åshild, Schjolden, Joachim, Winberg, Svante, Vindas, Marco A., Mayer, Ian, Hillestad, Marie
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: L-Tryptophan; Long-term effects; Monoamines; Atlantic salmon
• Online Access: https://curis.ku.dk/portal/da/publications/dietary-ltryptophan-leaves-a-lasting-impression-on-the-brain-and-the-stress-response(4cdd809d-c0ea-4d58-a42b-ea2628380120).html; https://doi.org/10.1017/S0007114517001428; http://www.scopus.com/inward/record.url?scp=85020518473&partnerID=8YFLogxK; http://orbit.dtu.dk/ws/files/133199371/Publishers_version.pdf

Comparative models suggest that effects of dietary tryptophan (Trp) on brain serotonin (5-hydroxytryptamine; 5-HT) neurochemistry and stress responsiveness are present throughout the vertebrate lineage. Moreover, hypothalamic 5-HT seems to play a central role in control of the neuroendocrine stress axis in all vertebrates. Still, recent fish studies suggest long-term effects of dietary Trp on stress responsiveness, which are independent of hypothalamic 5-HT. Here, we investigated if dietary Trp treatment may result in long-lasting effects on stress responsiveness, including changes in plasma cortisol levels and 5-HT neurochemistry in the telencephalon and hypothalamus of Atlantic salmon. Fish were fed diets containing one, two or three times the Trp content in normal feed for 1 week. Subsequently, fish were reintroduced to control feed and were exposed to acute crowding stress for 1 h, 8 and 21 d post Trp treatment. Generally, acute crowding resulted in lower plasma cortisol levels in fish treated with 3×Trp compared with 1×Trp- A nd 2×Trp-treated fish. The same general pattern was reflected in telencephalic 5-HTergic turnover, for which 3×Trp-treated fish showed decreased values compared with 2×Trp-treated fish. These long-term effects on post-stress plasma cortisol levels and concomitant 5-HT turnover in the telencephalon lends further support to the fact that the extrahypothalamic control of the neuroendocrine stress response is conserved within the vertebrate lineage. Moreover, they indicate that trophic/structural effects in the brain underlie the effects of dietary Trp treatment on stress reactivity.