Zemniaçak Ângela Beatris, Ribeiro Rafael Teixeira, das Neves Gustavo Machado, Cunha Sâmela de Azevedo, Tavares Tailine Quevedo, Carvalho Andrey Vinícios Soares, Netto Carlos Alexandre, Castilho Roger Frigério, Wajner Moacir, Amaral Alexandre Umpierrez
Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Laboratório de Síntese Orgânica Medicinal (LaSOM), Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Neurochem Res. 2025 Jan 9;50(1):76. doi: 10.1007/s11064-024-04328-0.
Brain accumulation of the branched-chain α-keto acids α-ketoisocaproic acid (KIC), α-keto-β-methylvaleric acid (KMV), and α-ketoisovaleric acid (KIV) occurs in maple syrup urine disease (MSUD), an inherited intoxicating metabolic disorder caused by defects of the branched-chain α-keto acid dehydrogenase complex. Patients commonly suffer life-threatening acute encephalopathy in the newborn period and develop chronic neurological sequelae of still undefined pathogenesis. Therefore, this work investigated the in vitro influence of pathological concentrations of KIC (5 mM), KMV (1 mM), and KIV (1 mM) on mitochondrial bioenergetics in the cerebral cortex of neonate (one-day-old) rats. KIC, but not KMV and KIV, decreased phosphorylating (stimulated by ADP) and uncoupled (induced by CCCP) mitochondrial respiration supported by pyruvate, malate, and glutamate, indicating metabolic inhibition. These effects were less evident after supplementing the medium with succinate. KIC also mildly increased non-phosphorylating respiration (in the presence of oligomycin) using pyruvate plus malate or glutamate plus malate as substrates, suggesting an uncoupling effect. Moreover, KIC markedly inhibited the activity of α-ketoglutarate dehydrogenase noncompetitively and decreased ATP synthesis. Finally, docking simulations demonstrated that KIC preferentially interacts with E2 and E3 subunits of α-ketoglutarate dehydrogenase at the dihydrolipoamide binding site and into an allosteric site of E1. The present data strongly indicate that KIC compromises mitochondrial bioenergetics in the neonatal rat brain, supporting the hypothesis that disruption of energy homeostasis caused by brain KIC accumulation in the first days of life may be implicated in the neuropathology of MSUD.
支链α-酮酸α-酮异己酸（KIC）、α-酮-β-甲基戊酸（KMV）和α-酮异戊酸（KIV）在枫糖尿症（MSUD）中会在脑内蓄积，MSUD是一种由支链α-酮酸脱氢酶复合体缺陷引起的遗传性中毒性代谢紊乱疾病。患者通常在新生儿期会遭受危及生命的急性脑病，并出现发病机制仍不明确的慢性神经后遗症。因此，本研究调查了病理浓度的KIC（5 mM）、KMV（1 mM）和KIV（1 mM）对新生（1日龄）大鼠大脑皮质线粒体生物能量学的体外影响。KIC降低了由丙酮酸、苹果酸和谷氨酸支持的磷酸化（由ADP刺激）和解偶联（由CCCP诱导）线粒体呼吸，而KMV和KIV则没有，这表明存在代谢抑制。在培养基中添加琥珀酸后，这些影响不太明显。KIC还使用丙酮酸加苹果酸或谷氨酸加苹果酸作为底物，轻度增加了非磷酸化呼吸（在存在寡霉素的情况下），表明存在解偶联作用。此外，KIC显著非竞争性抑制α-酮戊二酸脱氢酶的活性并降低ATP合成。最后，对接模拟表明，KIC优先在二氢硫辛酰胺结合位点与α-酮戊二酸脱氢酶的E2和E3亚基相互作用，并进入E1的变构位点。目前的数据强烈表明，KIC损害了新生大鼠大脑中的线粒体生物能量学，支持了这样一种假设，即在生命的最初几天，大脑中KIC的积累导致的能量稳态破坏可能与MSUD的神经病理学有关。
