Figure 1.

Alterations of amino acids and amines for sepsis diagnosis (Table 1), septic shock diagnosis (Table 2), prognostication of sepsis (Table 3), prognostication of septic shock (Table 4), and monitoring the treatment response (Table 5). A down-sided triangle (▼) represents a decreased level, whereas an up-sided triangle (▲) represents vice versa. (A) Aromatic amino acids (AAAs) and its down-stream amino acid are illustrated. Phenylalanine is converted to tyrosine before metabolizing to dihydroxyphenylalanine (DOPA) and catecholamines, respectively. Tryptophan is another AAA that can change to either kynurenine or serotonin and melatonin. (B) Branched-chain amino acids (BCAAs) including leucine, isoleucine, and valine are catabolized to S-(3-methylbutanoyl)-dihydrolipoamide-E and amino acid-derived acylcarnitines (C3-5), respectively. (C) A substrate of glutathione synthesis begins with methionine that converts into homocysteine, cystathionine, and cysteine, respectively. Moreover, serine is involved in the cystathionine production with an exchange of α-ketoglutarate. Cysteine can also turn into taurine, which has an anti-oxidant effect. (D) Glutamate is an intermediate substrate between glutathione production and urea cycle-related metabolites. Glutamate can be converted into glutamine and pyrroline-5-carboxylate (P5C). The latter metabolite is a precursor for proline synthesis. Moreover, glutamate can interchange with the urea cycle pathway metabolites. (E) The urea cycle pathway metabolites included citrulline, arginine, and ornithine. Arginine is a key amino acid for nitric oxide (NO) synthesis and NO inhibitors, including symmetric dimethylarginine (SMDA), asymmetric dimethylarginine (ADMA), total dimethylarginine (total DMA), and dimethylamine. (F) Polyamines are converted from ornithine. The polyamine metabolites include putrescine, spermidine, and spermine.