1980
DOI: 10.3109/00365518009091522
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Effect of natural oestrogens on tryptophan metabolism: evidence for interference of oestrogens with kynureninase

Abstract: Urinary excretion of metabolites of the tryptophan-nicotinic acid ribonucleotide pathway, urinary excretion of 4-pyridoxic acid and blood concentrations of oestradiol and pyridoxal phosphate were studied in groups of post-menopausal women before or during treatment with natural oestrogens, i.e. oestradiol and oestriol, before and after loading doses of 9800 mumol L-tryptophan or 700 mumol L-kynurenine sulphate. Natural oestrogens induced abnormalities of tryptophan metabolism similar to those induced by synthe… Show more

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Cited by 8 publications
(7 citation statements)
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“…Vitamin B 6 is an essential cofactor for several enzymes in the kynurenine pathway, which is often abnormal in women receiving oestrogens as contraceptives or as hormone‐replacement therapy (HRT). This effect has often been interpreted as resulting from oestrogen‐induced vitamin B 6 deficiency or depletion, 62–64 although there may also be direct competition with pyridoxal phosphate binding to kynureninase 65,66 . It may be that vitamin B 6 supplements should accompany the long‐term use of HRT in an attempt to preserve normality in the kynurenine pathway and prevent the potentially damaging changes in the levels of 3‐hydroxyanthranilic acid and/or anthranilic acid.…”
Section: Discussionmentioning
confidence: 99%
“…Vitamin B 6 is an essential cofactor for several enzymes in the kynurenine pathway, which is often abnormal in women receiving oestrogens as contraceptives or as hormone‐replacement therapy (HRT). This effect has often been interpreted as resulting from oestrogen‐induced vitamin B 6 deficiency or depletion, 62–64 although there may also be direct competition with pyridoxal phosphate binding to kynureninase 65,66 . It may be that vitamin B 6 supplements should accompany the long‐term use of HRT in an attempt to preserve normality in the kynurenine pathway and prevent the potentially damaging changes in the levels of 3‐hydroxyanthranilic acid and/or anthranilic acid.…”
Section: Discussionmentioning
confidence: 99%
“…Literature data regarding the effect of estrogens and testosterone on TDO is controversial: both adrenalectomy and ovariectomy reduced TDO activity in homogenates of liver from mature rats. However, administration of estrogens and testosterone had no effect on TDO 6 although they inhibited activity of the key enzymes of the KYN–NAD pathway 37–40 …”
Section: Regulation Of Rate‐limiting Enzymes Of Try–kyn Pathwaymentioning
confidence: 98%
“…However, administration of estrogens and testosterone had no effect on TDO 6 although they inhibited activity of the key enzymes of the KYN-NAD pathway. [37][38][39][40] Regulation of indoleamine 2,3-dioxygenase Cytokines and IDO. IDO is a cytokine-inducible enzyme (Fig.…”
Section: Regulation Of Rate-limiting Enzymes Of Try-kyn Pathwaymentioning
confidence: 99%
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“…L-Kynurenine hydrolase, an enzyme involved in the pathway of tryptophan metabolism, was downregulated by 169.3-fold at 48 h. L-Kynurenine hydrolase activity is inhibited by natural and exogenous estrogen, as evidenced by increased urinary excretion of tryptophan metabolites upon treatment with estrogen (57). Evidence suggests that this inhibition is an estrogenmediated decrease in the availability of vitamin B 6 , the coenzyme of kynureninase, although estrogen may also exhibit a direct effect on kynureninase activity (57). The roles in endometrium for this interesting gene may involve upregulation of vitamin B6 availability in this tissue during the secretory phase of the menstrual cycle.…”
Section: Downregulated Genesmentioning
confidence: 99%