Table 3.

Changes in the kynurenine pathway in neurodegenerative diseases.

		AD	PD	ALS	HD
Brain	TRP	↓ [125]	↓ [181]	↑ [143]	↓ [182]
	QUIN	↑ [29]	↑ [138]	↑ [142]	↑ [6]
	KYNA	↑ [29]	↓ [138]	N [142]	N [145]
	K/T	↑ [5]	↑ [137]	↑ [142]	↑ [182]
	Melatonin	↓ [134]	↓ [134]	↓ [134]	↓ [146]
	IDO	↑ [183]	↑ [137]	↑ [184]	↑ [145]
	3-HK	↑ [130]	↑ [137]	↑ [142]	↑ [148]
Serum	TRP	↓ [125]	↓ [50]	↑ [143]	↓ [182]
	QUINA	↑ [29]	↑ [137]	↑ [142]	↑ [145]
	KYNA	↓ [132]	↓ [136]	↓ [142]	↓ [149]
	K/T	↑ [5]	↑ [185]	↑ [142]	↑ [182]
	3-HK	↓ [185]	N [185]	-	↓ [149]
	3- HAA	↑ [133]	↓ [138]	-	↓ [149]
	L-KYN	↑ [125]	↑ [186]	↑ [143]	↑ [6]

↑: increase; ↓: decrease; N: nonsignificant difference; -: uncertainty. Abbreviations: 3-HAA: 3-hydroxyanthrenillc acid; 3-HK: 3-hydroxykynurenine; 5-HT: 5-hydroxy tryptophan; AD: Alzheimer’s disease; ALS: amyotrophic lateral sclerosis; HD: Huntington’s disease; IDO: indoleamine 2,3-dioxygenase; K/T: L-KYN/TRP; KYNA: kynurenic acid; L-KYN: L-kynurenine; PD: Parkinson's disease; QUINA: quinolinic acid; TRP: L-tryptophan.