Role of exercise-sensitive microbial-derived aromatic amino acid metabolites in modifying monocyte physiology

Lin, Chia-Hao

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https://hdl.handle.net/2142/120090 Copy

Description

Title

Role of exercise-sensitive microbial-derived aromatic amino acid metabolites in modifying monocyte physiology

Author(s)

Lin, Chia-Hao

Issue Date

2023-04-24

Director of Research (if dissertation) or Advisor (if thesis)

Allen, Jacob M

Department of Study

Kinesiology & Community Health

Discipline

Kinesiology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

Gut microbiome, exercise, immunometabolism, monocyte, inflammation, microbial metabolite, chemotaxis

Abstract

Exercise induces a myriad of health benefits, but not all mechanisms are fully elucidated. Emerging evidence suggests that exercise can also modify the gut microbiome. Prior work in our laboratory revealed that exercise training for 6 weeks increases serum concentrations of microbiota metabolites derived from aromatic amino acids (ArAA), indole-3-lactic acid (ILA) and 4-hydroxyphenyllactic acid (4-HPLA), termed aryl-lactates. We hypothesized aryl-lactates play a role in regulating host immune function. Monocytes are key innate immune cells and express receptors for both ILA and 4-HPLA. ILA binds to a nuclear receptor, aryl-hydrocarbon receptor (AhR), and both ILA and 4-HPLA potentially bind to a G protein-coupled receptor, hydroxycarboxylic acid receptor-3 (HCAR3). We hypothesized that through binding of these two receptors, ILA and 4-HPLA would alter monocyte immunometabolism, attenuate inflammatory signaling, and alters chemotactic response of monocytes. Transformed human monocytes (THP-1) and primary monocytes were cultured with 50 μM of ILA, 4-HPLA or PBS-Control, with added immune challenges (lipopolysaccharide (LPS) or Flagellin (FLG)). Cells were collected and analyzed for inflammatory cytokines (TNFa, IL-10, IL-6) and AhR target genes (CYP1A1) by rtPCR. Chemotaxis was measured in THP-1 monocytes using a transwell migration assay. To determine HCAR3 activation, cAMP levels were measured in THP-1 cell lysates with a competitive ELISA. Extracellular lactate was measured to determine the effect of aryl-lactates on modifying the immunometabolism of primary human monocytes. ILA and 4-HPLA’s alteration of inflammatory cytokine expression is cell type dependent. Evidence of AhR binding by ILA was confirmed in primary monocytes from by increased expression of CYP1A1. cAMP levels were elevated by ILA, but reduced by 4-HPLA, indicating divergent mechanisms by which microbial-derived aryl-lactates activates HCAR3 and alters cellular energy status. Extracellular lactate was increased by ILA, indicating altered glycolysis. Our in vitro and ex vivo work indicate that aryl-lactates alters inflammatory gene expression, chemotactic response, and immunometabolism of monocytes.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Chia-Hao Lin

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