The role of tryptophan-niacin key enzymes in brain's immune system

l -色氨酸（Trp）代谢产物如l -犬尿氨酸（Kyn）、l -犬尿酸、喹啉酸（QA）和吡啶酸（PA）在中枢神经和免疫系统中具有重要的生理作用。膳食中的脱氢异雄酮（DHEA）影响喹啉酸（QA）的产生。本研究提示脱氢表雄酮降低ACMSD mRNA表达的机制与wy - 14643不同，脱氢表雄酮调节ACMSD表达的途径可能不只是ppar - α介导的途径。在stz诱导的糖尿病组中，[5-3H]L-Trp转化为氚化水、L-Kyn和QA的量分别是对照组的3倍以上。提示stz型糖尿病引起肝脏中L-Kyn和QA代的增加，而PA和Nam代的增加不引起，提示胰岛素依赖性糖尿病的免疫和神经系统可能受L-Kyn和QA代的增加而不受PA和Nam代的增加的影响。炎症诱导的色氨酸分解酶吲哚胺2,3-双加氧酶（IDO）的激活导致QA的产生增加。我们研究了哪些饮食成分会影响小胶质细胞中的IDO表达。本研究提示，一些膳食多酚影响lps诱导的小胶质细胞IDO表达。

The L-tryptophan (Trp) metabolites such as L-kynurenine(Kyn), L-kinurenic acid, quinolinic acid (QA) and picolinic acid (PA) have been shown physiologically important in central nervous and immune system. Dietary dehydroisoandrosterone (DHEA) affects quinolinic acid (QA) production. The present study suggesting that the mechanism of decrease in ACMSD mRNA level by DHEA was different from that by WY-14,643, and that there would be any pathway other than PPARalpha mediated one for DHEA to regulate ACMSD expression.In the STZ-induced diabetes group, the amount of [5-3H]L-Trp converted to tritiated water, L-Kyn or QA were found to be more than 3 times of that in the control group, respectively. It is suggested that STZ-diabetes mellitus causes augmentations of both L-Kyn and QA generations but not those of PA and Nam in liver, indicating the possibility that the immune and neuronal systems of insulin dependent diabetes mellitus would be influenced by the increased amounts of L-Kyn and QA but not by those of PA and Nam.Inflammation-induced activation of the tryptophan catabolizing enzyme indoleamine 2,3-dioxygenase (IDO) causes increase of QA production. We investigated which dietary components affect IDO expression in microglial cells. This study suggests that some dietary polyphenols affected LPS-induced IDO expression in microglial cells.