Table 3.
Assignments Related to Microbial Metabolites with p < 0.1 Between OA Cases vs Controls
| Compound Name | Ontology Level | VIP | p-value | Fold Change |
|---|---|---|---|---|
| Indole | PDa | 1.0 | 0.003 | 1.5 |
| Propionic Acid | PDc | 1.7 | 0.007 | −2.6 |
| Indole | PDa | 1.2 | 0.022 | 2.1 |
| Indole-3-Acetate | OL1 | 1.3 | 0.025 | 2.0 |
| Suberate | OL2b | 0.9 | 0.026 | −1.3 |
| Phenylacetate | PDc | 1.0 | 0.030 | 1.5 |
| Beta-L-Fucose | PDc | 0.9 | 0.031 | 2.6 |
| Tryptophanol | PDd | 1.0 | 0.032 | 1.9 |
| Phenylethanolamine | OL2a | 0.8 | 0.034 | 1.3 |
| Hippuric Acid | PDb | 1.5 | 0.034 | −2.4 |
| Pyruvic Acid | PDc | 1.0 | 0.056 | −1.4 |
| Epinephrine Sulfate | PDd | 1.4 | 0.060 | −1.8 |
| Shikimic Acid | OL2a | 0.7 | 0.061 | −1.3 |
| Aspartyl-Serine | PDc | 1.1 | 0.062 | −1.6 |
| Sarcosine | OL2a | 1.0 | 0.071 | 1.5 |
| Indole | PDa | 0.7 | 0.071 | 1.3 |
| P-Hydroxybenzylalcohol | PDc | 0.5 | 0.075 | −1.2 |
| Shikimic Acid | PDc | 1.1 | 0.079 | 1.4 |
| Hypoxanthine | OL1 | 0.7 | 0.080 | −1.3 |
| Hypoxanthine | OL2a | 0.6 | 0.084 | −1.3 |
| 4-Ethylphenol | PDd | 0.5 | 0.084 | −1.2 |
| N-Acetyl-D-Glucosamine | OL1 | 0.7 | 0.084 | −1.3 |
| Beta-D-Glucose | PDc | 1.1 | 0.087 | −1.3 |
| N-Acetyl-D-Glucosamine | OL2a | 0.8 | 0.093 | −1.5 |
| Indolepyruvate | PDb | 0.9 | 0.094 | 15.1 |
| Indoleacetaldehyde | OL2b | 1.6 | 0.094 | 1.2 |
| 3-Methylindole | PDc | 0.7 | 0.096 | −1.3 |
Displayed metabolites are peaks that matched to the microbial metabolite list in Table S3. VIP (variable importance to projection) scores were calculated using the PLS-DA model from Figure 1. P-values were calculated using a two-sided t-test with Satterwaite correction. Positive fold changes indicate a higher value in OA as compared to non-OA. OL1 refers to an in-house library match by MS, MS/MS, and RT; OL2a refers to an in-house library match by MS and RT; OL2b refers to an in-house library match by MS and MS/MS; PDa refers to a public database match by MS and experimental MS/MS (NIST orMETLIN); PDb refers to a public database match by MS and theoretical MS/MS (HMDB); PDc refers to a public database match by MS and isotopic similarity; PDd refers to a public database match by MS only. Ontology levels OL1, OL2a, and OL2b correspond to level 1 of the Metabolomics Standards Initiative (MSI) standards (identification using two independent and orthogonal data), whereas levels PDa, PDb, PDc, and PDd correspond to level 2 of the MSI standards (putatively annotated compounds)59. Repeated metabolite names indicate multiple peaks matched to the same metabolite.