Bienholz Anja, Al-Taweel Ahmad, Roeser Nancy F, Kribben Andreas, Feldkamp Thorsten, Weinberg Joel M
Division of Nephrology, Department of Internal Medicine, Veterans Affairs Ann Arbor Healthcare System and University of Michigan, Ann Arbor, Michigan, United States of America; Division of Nephrology, Department of Internal Medicine, University Duisburg-Essen, Essen, Germany.
Division of Nephrology, Department of Internal Medicine, Veterans Affairs Ann Arbor Healthcare System and University of Michigan, Ann Arbor, Michigan, United States of America.
PLoS One. 2014 Apr 11;9(4):e94584. doi: 10.1371/journal.pone.0094584. eCollection 2014.
Kidney proximal tubules subjected to hypoxia/reoxygenation develop a nonesterified fatty acid-induced energetic deficit characterized by persistent partial mitochondrial deenergization that can be prevented and reversed by citric acid cycle substrates. To further assess the role of competition between fatty acids and substrates on inner membrane substrate carriers in the deenergization and the contribution to deenergization of fatty acid effects on respiratory function, digitonin-permeabilized rabbit and mouse tubules were studied using either addition of exogenous oleate after control normoxic incubation or increases of endogenous fatty acids produced by hypoxia/reoxygenation. The results demonstrated major effects of matrix oxaloacetate accumulation on succinate-supported energization and respiration and their modification by fatty acids. Improvements of energization in the presence of fatty acids by glutamate were shown to result predominantly from lowering matrix oxaloacetate rather than from amelioration of transmembrane cycling of fatty acids and uncoupling. Mouse tubules had 2.5 fold higher rates of succinate utilization, which resulted in stronger effects of oxaloacetate accumulation than rabbit tubules. Hypoxia/reoxygenation induced respiratory inhibition that was more severe for complex I-dependent substrates. Fatty acids themselves did not acutely contribute to this respiratory inhibition, but lowering them during 60 min. reoxygenation to allow recovery of ATP during that period alleviated it. These data clarify the basis for the nonesterified fatty acid-induced mitochondrial energetic deficit in kidney proximal tubules that impairs structural and functional recovery and provide insight into interactions that need to be considered in the design of substrate-based interventions to improve mitochondrial function.
经历缺氧/复氧的肾近端小管会出现非酯化脂肪酸诱导的能量不足，其特征为线粒体持续部分去极化，而柠檬酸循环底物可预防并逆转这种情况。为了进一步评估脂肪酸与底物在内膜底物载体上的竞争对去极化的作用以及脂肪酸对呼吸功能去极化作用的贡献，我们使用了两种方法对皂角苷通透的兔和小鼠肾小管进行了研究：一种是在正常氧孵育后添加外源性油酸，另一种是增加缺氧/复氧产生的内源性脂肪酸。结果表明，基质草酰乙酸的积累对琥珀酸支持的能量化和呼吸有主要影响，且脂肪酸会对其产生修饰作用。结果显示，在脂肪酸存在的情况下，谷氨酸对能量化的改善主要是由于降低了基质草酰乙酸，而不是改善了脂肪酸的跨膜循环和解偶联。小鼠肾小管的琥珀酸利用率比兔肾小管高2.5倍，这导致草酰乙酸积累的影响比兔肾小管更强。缺氧/复氧诱导的呼吸抑制对依赖复合体I的底物更为严重。脂肪酸本身并不会对这种呼吸抑制产生急性影响，但在复氧60分钟期间降低脂肪酸水平以使ATP在此期间得以恢复，则可减轻这种抑制。这些数据阐明了肾近端小管中非酯化脂肪酸诱导的线粒体能量不足的基础，这种能量不足会损害结构和功能的恢复，并为基于底物的干预措施设计中需要考虑的相互作用提供了见解，以改善线粒体功能。
