# Identification and characterization of tryptophan metabolism-related genes in carotid artery plaques

**Authors:** Xiaodong Jia, Zhen Wang, Lin Bai, Jianmei Wei, Xizi Wang, Zhaona Song, Xianchao Guo, Runze Jiang, Qiang Zhang, Adeyemi Stephen Stephen Oluyomi, Adeyemi Stephen Stephen Oluyomi, Ram Nagaraj, Ram Nagaraj

PMC · DOI: 10.1371/journal.pone.0341122 · PLOS One · 2026-02-02

## TL;DR

This study identifies genes related to tryptophan metabolism in carotid artery plaques, which could help predict and manage atherosclerosis.

## Contribution

The study identifies six key tryptophan metabolism-related genes and develops a predictive model for carotid plaque risk.

## Key findings

- Six tryptophan metabolism-related genes (TPH1, MAOB, TDO2, KMO, KYNU, CYP1B1) are differentially expressed in carotid plaques.
- A logistic regression model using these genes achieves an AUC of 0.75 for predicting plaque risk.
- The genes influence plaque development through tryptophan metabolism, lipid biosynthesis, and inflammation.

## Abstract

Cardiovascular and cerebrovascular diseases, often caused by atherosclerosis, are the stern cause of death worldwide, and carotid plaque play a crucial role in the development of these diseases. Tryptophan metabolism is an important pathway involved in the regulation of immune response, inflammation and vascular health. In this study, we analyzed bulk and scRNA data from carotid plaque to investigate the relevance between tryptophan metabolism and plaque formation. We identified 446 differentially expressed genes that are enriched in immune and tryptophan-related pathways. Focusing on tryptophan metabolism, we identified six key tryptophan-related differentially expressed genes: TPH1, MAOB, TDO2, KMO, KYNU, and CYP1B1. Using the six genes, we constructed a logistic regression model with an AUC of 0.75, which successfully predicted the risk of carotid plaque formation. Analysis of global and single-cell data revealed differential expression patterns and related modes of action of the six genes in carotid plaque, suggesting that they influence the development of carotid plaque through their involvement in tryptophan metabolism, lipid biosynthesis, and inflammatory responses. These tryptophan-related differentially expressed genes can be used as potential biomarkers to assess plaque risk and as therapeutic targets to manage carotid atherosclerosis by regulating tryptophan metabolism and reducing inflammation.

## Linked entities

- **Genes:** TPH1 (tryptophan hydroxylase 1) [NCBI Gene 7166], MAOB (monoamine oxidase B) [NCBI Gene 4129], TDO2 (tryptophan 2,3-dioxygenase) [NCBI Gene 6999], KMO (kynurenine 3-monooxygenase) [NCBI Gene 8564], KYNU (kynureninase) [NCBI Gene 8942], CYP1B1 (cytochrome P450 family 1 subfamily B member 1) [NCBI Gene 1545]
- **Diseases:** atherosclerosis (MONDO:0005311)

## Full-text entities

- **Genes:** TDO2 (tryptophan 2,3-dioxygenase) [NCBI Gene 6999] {aka HYPTRP, TDO, TO, TPH2, TRPO}, CD68 (CD68 molecule) [NCBI Gene 968] {aka GP110, LAMP4, SCARD1}, IDO1 (indoleamine 2,3-dioxygenase 1) [NCBI Gene 3620] {aka IDO, IDO-1, INDO}, MAOB (monoamine oxidase B) [NCBI Gene 4129], CD4 (CD4 molecule) [NCBI Gene 920] {aka CD4mut, IMD79, Leu-3, OKT4D, T4}, KMO (kynurenine 3-monooxygenase) [NCBI Gene 8564] {aka dJ317G22.1}, KYNU (kynureninase) [NCBI Gene 8942] {aka KYNUU, VCRL2}, CD8A (CD8 subunit alpha) [NCBI Gene 925] {aka CD8, CD8alpha, IMD116, Leu2, p32}, TPH1 (tryptophan hydroxylase 1) [NCBI Gene 7166] {aka TPRH, TRPH}, AHR (aryl hydrocarbon receptor) [NCBI Gene 196] {aka FVH3, RP85, bHLHe76}, IDO2 (indoleamine 2,3-dioxygenase 2) [NCBI Gene 169355] {aka INDOL1}, CYP1B1 (cytochrome P450 family 1 subfamily B member 1) [NCBI Gene 1545] {aka ASGD6, CP1B, CYPIB1, GLC3A, P4501B1}
- **Diseases:** endothelial dysfunction (MESH:D014652), disorder of tryptophan metabolism (MESH:D008659), TRDEGs (MESH:D001039), vascular calcification (MESH:D061205), chronic inflammation (MESH:D007249), Atherosclerotic (MESH:D050197), diabetes (MESH:D003920), atherosclerotic plaques (MESH:D058226), immune disorder (MESH:D007154), calcification (MESH:D002114), coronary heart disease (MESH:D003327), Cardiovascular and cerebrovascular diseases (MESH:D002318), death (MESH:D003643), plaque (MESH:D003773), hyperlipidemia (MESH:D006949), artery plaques (MESH:D016893), stroke (MESH:D020521), hypertension (MESH:D006973), immune dysregulation (OMIM:614878), carotid atherosclerosis (MESH:D002340)
- **Chemicals:** 5-HTP (MESH:D006916), 5-HT (MESH:D012701), cholesterol (MESH:D002784), indole (MESH:C030374), 3-HK (-), 3-hydroxykynurenine (MESH:C005045), calcium (MESH:D002118), lipid (MESH:D008055), aromatic amino acid (MESH:D024322), N-formylkynurenine (MESH:C007772), Tryptophan (MESH:D014364), amino acid (MESH:D000596), Kyn (MESH:D007737)
- **Species:** Homo sapiens (human, species) [taxon 9606], Mus musculus (house mouse, species) [taxon 10090]
- **Cell lines:** LM22 — Homo sapiens (Human), Astrocytoma, Cancer cell line (CVCL_A1IU)

## Full text

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## Figures

6 figures with captions in the complete paper: https://tomesphere.com/paper/PMC12863520/full.md

## References

36 references — full list in the complete paper: https://tomesphere.com/paper/PMC12863520/full.md

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Source: https://tomesphere.com/paper/PMC12863520