Figure 1.

(A). Classification of uremic metabolites based on origin. Uremic metabolites have three possible origins, either endogenous metabolism, microbial metabolism, or from exogenous intake. (B). Classification of uremic metabolites sourced from microbial metabolism. Uremic metabolites sourced from microbial metabolism are further classified according to the involvement of microbiota in their synthesis; they are either the result of dietary component metabolism, produced by host and biochemically modified by microbiota or synthesised de novo by the microbiota. SCFAs: short chain fatty acids; PSA: polysaccharide-A [4].