Figure 1.

Circulating metabolites. Metabolites are small molecules that act locally, in the tissue where they are produced, or systemically, when released to the extracellular environment. In the latter case, metabolites can circulate and be identified in different biofluids, such as plasma serum, urine, and cerebral spinal fluid. Circulating metabolites can be released as free molecules or inside vesicles. The production of metabolites can be influenced by changes in the external or internal environment, such as the microbiome, as well as by the occurrence of disease. In this last case, the disease processes may impact metabolite production and, thus, make it possible to use metabolites as disease biomarkers. The figure was created with Biorender.com.