Table 1.
Altered levels of tryptophan-derived metabolites and associations with clinical outcomes in metabolic, cardiovascular, and chronic kidney diseases.
| Metabolic Disorders | |||
| Metabolite | Increased/Decreased/Association | Patient Group | Reference |
| Kynurenine/tryptophan ratio | Increased | Obese/metabolic syndrome | [76] |
| Kynurenine | + associated with BMI, HOMA-index | Diabetes | [147] |
| Kynurenine | Increased | Type 2 diabetes/obese | [148] |
| Indole | Decreased (feces) | Type 2 diabetes/obese | [149] |
| Indole-3 acetic acid | Decreased (feces) | Type 2 diabetes/obese | [149] |
| 3-methyl-indole | Decreased (feces) | Type 2 diabetes/obese | [149] |
| Tryptamine | Decreased (feces) | Type 2 diabetes/obese | [149] |
| Indole-3 propionic acid | + associated with insulin sensitivity | Type 2 diabetes | [150] |
| Indole-3 propionic acid | Decreased | Type 2 diabetes/obese | [94] |
| 5-hydroxyindole-3-acetic acid | Increased | Metabolic syndrome | [151] |
| Chronic Kidney and Cardiovascular Diseases | |||
| Metabolite | Increased/Decreased/Association | Patient Group | Reference |
| Indoxyl sulfate | Increased | CKD, ESRD | [32,152] |
| Indoxyl sulfate | + associated with mortality | CKD | [153] |
| Indoxyl sulfate | + associated with hearth failure | CKD hemodyalysis | [154] |
| Indoxyl sulfate | + associated with aortic calcification | CKD | [155] |
| Indoxyl sulfate | + associated with arterial stiffness | CKD | [155] |
| Kynurenine | + associated with myocardial infarction | Coronary artery disease | [71] |
| Kynurenine | Increased (in unstable atherosclerotic plaques) | Coronary artery disease | [71] |