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. 2023 Feb 18;15(4):1030. doi: 10.3390/nu15041030

Table 1.

Tryptophan, kynurenines, and the kynurenine pathway enzymes in experimental and clinical studies on anorexia nervosa.

Metabolites/Enzymes Conditions Type of Samples Results Reference Number
Tryptophan Four-day starvation in rats Brain ↓ [39,40]
Four-week starvation in rats Plasma ↓ [41]
Brain (hypothalamus) ↓ [41]
Caenorhabditis elegans, in culture, 2 h fasting Extracts from C. elegans ←→ [42]
AN (n = 35) Plasma ←→ [43]
AN (n = 16) Blood ←→ [44]
Anorectic, dialyzed (n = 13) Plasma ←→ [45]
AN (n = 26) Plasma ↓ [46]
Acute AN (n = 32),
Recovered AN (n = 32)		 Plasma ↓ [47]
AN (n = 42) Plasma ↓ [48]
AN (n = 19) Whole blood ↓ [49]
AN (n = 16) Serum ↓ [50]
Acute AN (n = 14),
Recovered AN (n = 14)		 Plasma ↓ acute AN vs. recovered
←→ vs. CTR		 [51]
Medication-free AN (n = 10) CSF ←→ [52]
Restrictive AN (n = 20) Serum ←→ [53]
Purging AN (n = 21) Serum ↑ [54]
Tryptophan/LNAA ratio AN (n = 16) Blood ↑ in more severe catabolic status [44]
Anorectic, dialyzed (n = 13) Plasma ←→ [45]
AN (n = 19) Whole blood ↓ [49]
Acute AN (n = 14),
Recovered AN (n = 14)		 Plasma ↑ [51]
AN (n = 42) Plasma ↓ [48]
L-kynurenine Caenorhabditis elegans, in culture, 2 h fasting Extracts from C. elegans ↓ [42]
Medication-free AN (n = 10) CSF ←→ [52]
Restrictive AN (n = 20) Serum ←→ [53]
Restrictive AN (n = 45), purging AN (n = 21) Serum ←→ [54]
3-OH-kynurenine Caenorhabditis elegans, in culture, 2 h fasting Extracts from C. elegans ↓ [42]
Restrictive AN (n = 20) Serum ←→ [53]
Kynurenic acid Medication-free AN (n = 10) CSF ↓ [52]
Restrictive AN (n = 20) Serum ←→ [53]
Quinolinic acid Medication-free AN (n = 10) CSF ←→ [52]
KAT1 gene expression Restrictive AN (n = 20) Serum ←→ [53]
KAT2 gene expression Restrictive AN (n = 20) Serum ←→ [53]
KAT3 gene expression C57BL/6 mice, activity-based anorexia Muscles ↑ [55]
Restrictive AN (n = 20) Serum ↑ [53]
KAT4 gene expression C57BL/6 mice, activity-based anorexia Muscles ↑ [55]

↓—decrease; ↑—increase; and ←→—no change. AN—anorexia nervosa; CSF—cerebrospinal fluid; CTR—control; KAT—kynurenine aminotransferase; and LNAA—large neutral amino acids.