Abstract

Coronavirus disease 2019 (COVID-19) has poorer clinical outcomes in males than in females, and immune responses underlie these sex-related differences. Because immune responses are, in part, regulated by metabolites, we examined the serum metabolomes of COVID-19 patients. In male patients, kynurenic acid (KA) and a high KA–to–kynurenine (K) ratio (KA:K) positively correlated with age and with inflammatory cytokines and chemokines and negatively correlated with T cell responses. Males that clinically deteriorated had a higher KA:K than those that stabilized. KA inhibits glutamate release, and glutamate abundance was lower in patients that clinically deteriorated and correlated with immune responses. Analysis of data from the Genotype-Tissue Expression (GTEx) project revealed that the expression of the gene encoding the enzyme that produces KA, kynurenine aminotransferase, correlated with cytokine abundance and activation of immune responses in older males. This study reveals that KA has a sex-specific link to immune responses and clinical outcomes in COVID-19, suggesting a positive feedback between metabolites and immune responses in males.

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This work is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/. This license does not apply to figures/photos/artwork or other content included in the article that is credited to a third party; obtain authorization from the rights holder before using such material.

Cite as

Cai, Y., Kim, D., Takahashi, T., Broadhurst, D., Yan, H., Ma, S., Rattray, N., Casanovas-Massana, A., Israelow, B., Klein, J., Lucas, C., Mao, T., Moore, A., Muenker, M., Oh, J., Silva, J., Wong, P., Yale IMPACT Research Team, Ko, A., Khan, S., Iwasaki, A. & Johnson, C. 2021, 'Kynurenic acid may underlie sex-specific immune responses to COVID-19', Science Signaling, 14(690), article no: eabf8483. https://doi.org/10.1126/scisignal.abf8483

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Last updated: 16 June 2022
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