Tsepkova P M, Artiukhov A V, Boyko A I, Aleshin V A, Mkrtchyan G V, Zvyagintseva M A, Ryabov S I, Ksenofontov A L, Baratova L A, Graf A V, Bunik V I
Lomonosov Moscow State University, Faculty of Bioengineering and Bioinformatics, Moscow, 119234, Russia.
Biochemistry (Mosc). 2017 Jun;82(6):723-736. doi: 10.1134/S0006297917060098.
Molecular mechanisms of long-term changes in brain metabolism after thiamine administration (single i.p. injection, 400 mg/kg) were investigated. Protocols for discrimination of the activities of the thiamine diphosphate (ThDP)-dependent 2-oxoglutarate and 2-oxoadipate dehydrogenases were developed to characterize specific regulation of the multienzyme complexes of the 2-oxoglutarate (OGDHC) and 2-oxoadipate (OADHC) dehydrogenases by thiamine. The thiamine-induced changes depended on the brain-region-specific expression of the ThDP-dependent dehydrogenases. In the cerebral cortex, the original levels of OGDHC and OADHC were relatively high and not increased by thiamine, whereas in the cerebellum thiamine upregulated the OGDHC and OADHC activities, whose original levels were relatively low. The effects of thiamine on each of the complexes were different and associated with metabolic rearrangements, which included (i) the brain-region-specific alterations of glutamine synthase and/or glutamate dehydrogenase and NADP+-dependent malic enzyme, (ii) the brain-region-specific changes of the amino acid profiles, and (iii) decreased levels of a number of amino acids in blood plasma. Along with the assays of enzymatic activities and average levels of amino acids in the blood and brain, the thiamine-induced metabolic rearrangements were assessed by analysis of correlations between the levels of amino acids. The set and parameters of the correlations were tissue-specific, and their responses to the thiamine treatment provided additional information on metabolic changes, compared to that gained from the average levels of amino acids. Taken together, the data suggest that thiamine decreases catabolism of amino acids by means of a complex and long-term regulation of metabolic flux through the tricarboxylic acid cycle, which includes coupled changes in activities of the ThDP-dependent dehydrogenases of 2-oxoglutarate and 2-oxoadipate and adjacent enzymes.
研究了硫胺素给药（单次腹腔注射，400mg/kg）后大脑代谢长期变化的分子机制。开发了用于区分硫胺二磷酸（ThDP）依赖性2-氧代戊二酸和2-氧代己二酸脱氢酶活性的方案，以表征硫胺素对2-氧代戊二酸（OGDHC）和2-氧代己二酸（OADHC）脱氢酶多酶复合物的特异性调节。硫胺素诱导的变化取决于ThDP依赖性脱氢酶的脑区特异性表达。在大脑皮层中，OGDHC和OADHC的原始水平相对较高，且未因硫胺素而增加，而在小脑中，硫胺素上调了OGDHC和OADHC的活性，其原始水平相对较低。硫胺素对每种复合物的作用不同，且与代谢重排相关，其中包括：（i）谷氨酰胺合成酶和/或谷氨酸脱氢酶以及NADP+依赖性苹果酸酶的脑区特异性改变；（ii）氨基酸谱的脑区特异性变化；（iii）血浆中多种氨基酸水平降低。除了酶活性测定以及血液和大脑中氨基酸的平均水平外，还通过分析氨基酸水平之间的相关性来评估硫胺素诱导的代谢重排。相关性的集合和参数具有组织特异性，与从氨基酸平均水平获得的信息相比，它们对硫胺素治疗的反应提供了有关代谢变化的额外信息。综上所述，数据表明硫胺素通过对三羧酸循环代谢通量进行复杂且长期的调节来降低氨基酸的分解代谢，这包括2-氧代戊二酸和2-氧代己二酸的ThDP依赖性脱氢酶以及相邻酶活性的耦合变化。
