Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Shaanxi, China; Laboratory of Reproductive Endocrinology, Graduate School of Integrated Sciences for Life, Hiroshima University, Hiroshima, Japan.
Laboratory of Reproductive Endocrinology, Graduate School of Integrated Sciences for Life, Hiroshima University, Hiroshima, Japan.
Free Radic Biol Med. 2020 Nov 1;159:44-53. doi: 10.1016/j.freeradbiomed.2020.07.008. Epub 2020 Aug 1.
Mammalian cells improve redox homeostasis under reactive oxygen species (ROS) stress conditions via the enhancement of the pentose phosphate pathway (PPP). However, it is not clear how the cell reprograms glucose metabolism from glycolysis to the PPP. Hence, in the present study, we used boar sperm as a model to elucidate the mechanism by which the glycolysis/PPP transition occurs under ROS stress. The boar sperm treated with moderate glucose levels for 3 h exhibited increased sperm linear motility patterns, ATP levels and GSH/GSSG ratios and decreased ROS levels compared to the boar sperm treated without glucose. In addition, the hexokinase activity, glucose-6-phosphate dehydrogenase (G6PD) activity, NADPH level, NADPH/NADP ratio and mitochondrial activity were higher in the sperm treated with moderate glucose than in those not treated with glucose. Interestingly, the enzyme activity of fructose-1,6-bisphosphate aldolase (ALDOA) was not significantly changed during the incubation. The sperm linear motility patterns were decreased by treatment with the G6PD inhibitor 6-aminonicotinamide. Moreover, moderate glucose treatment significantly increased the itaconate levels in sperm. Both endogenous and exogenous itaconate increased the total itaconate modifications and the itaconate-modified ALDOA levels in sperm, suggesting that under moderate-glucose conditions, glycolysis in the sperm was suppressed by an increase in the itaconate levels. Furthermore, the addition of itaconate improved the sperm linear motility patterns by suppressing glycolysis and enhancing oxidative phosphorylation (OXPHOS). Therefore, the itaconate generated from OXPHOS regulates the glycolysis/PPP transition to maintain redox homeostasis. In sperm, this itaconate-dependent mechanism plays an important role in maintaining their high linear motility.
哺乳动物细胞通过增强磷酸戊糖途径（PPP）在活性氧（ROS）应激条件下改善氧化还原稳态。然而，细胞如何将葡萄糖代谢从糖酵解重新编程为 PPP 尚不清楚。因此，在本研究中，我们使用公猪精子作为模型，阐明在 ROS 应激下糖酵解/PPP 转变发生的机制。与未用葡萄糖处理的精子相比，用中等葡萄糖水平处理 3 小时的公猪精子表现出增加的精子线性运动模式、ATP 水平和 GSH/GSSG 比值以及降低的 ROS 水平。此外，中等葡萄糖处理的精子中的己糖激酶活性、葡萄糖-6-磷酸脱氢酶（G6PD）活性、NADPH 水平、NADPH/NADP 比和线粒体活性高于未用葡萄糖处理的精子。有趣的是，在孵育过程中果糖-1,6-二磷酸醛缩酶（ALDOA）的酶活性没有明显变化。用 G6PD 抑制剂 6-氨基烟酰胺处理会降低精子的线性运动模式。此外，中等葡萄糖处理可显著增加精子中的衣康酸水平。内源性和外源性衣康酸均可增加精子中的总衣康酸修饰和衣康酸修饰的 ALDOA 水平，这表明在中等葡萄糖条件下，精子中的糖酵解受到衣康酸水平升高的抑制。此外，衣康酸的添加通过抑制糖酵解和增强氧化磷酸化（OXPHOS）来改善精子的线性运动模式。因此，由 OXPHOS 产生的衣康酸调节糖酵解/PPP 转变以维持氧化还原稳态。在精子中，这种依赖衣康酸的机制在维持其高线性运动中起着重要作用。
