A single administration of 'microbial' D-alanine to healthy volunteers augments reaction to negative emotions: A comparison with D-serine. (May 2020)

• Record Type: Journal Article
• Authors: Capitão, Liliana P; Forsyth, Jessica; Thomaidou, Mia A; Condon, Mark D; Harmer, Catherine J; Burnet, Philip WJ
• Is Part Of: Journal of psychopharmacology. Volume 34:Number 5(2020)
• Page Start: 557
• Page End: 566
• Publication Date: 2020-05
• Subjects: D-amino acids -- cognition -- emotional processing -- cortisol; Psychopharmacology -- Periodicals; 615.78
• DOI: 10.1177/0269881120908904
• Languages: English
• ISSNs: 0269-8811

Abstract

Background: Activation of the glutamate N-methyl-D-aspartate receptor with its co-agonist D-serine has been shown to improve subjective mood in healthy volunteers. D-alanine is another potent N-methyl-D-aspartate receptor co-agonist which arises from the natural breakdown of host gut microbes, and is predominantly sequestered in the pituitary. This may suggest that D-alanine influences the neuroendocrine stress response which may then impact on emotion. Aims: The current study explored the effects of D-serine and D-alanine on emotional processing, cognition and the levels of the stress hormone cortisol in healthy volunteers. Methods: In a double-blind, placebo-controlled randomised study, participants ( n =63) received a single oral dose of either D-serine, D-alanine (60 mg/kg) or placebo and then performed the Emotional Test Battery and N-back task (two hours post-administration) and provided saliva samples at fixed intervals. Results: Subjects administered with D-alanine were faster at identifying facial expressions of fear, surprise and anger, and at categorising negative self-referential words. Participants on D-alanine also showed a trend to recall more words than placebo in a memory task. D-serine did not have any meaningful effects in any of the tasks. Neither amino acid had a significant effect on salivary cortisol or working memory. Conclusion: This study is the first to suggest that D-alanine can modulate emotional cognitive processing after a single dose. The lack of findings for D-serine nevertheless contrasts a previous study, emphasising a need for further investigation to clarify discrepancies. A better understanding of the physiological actions of D-amino acids would be beneficial in evaluating their therapeutic potential.