Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, Cáceres, Spain.
Facility of Innovation and Analysis in Animal Source Foodstuffs, University of Extremadura, Cáceres, Spain.
Biol Reprod. 2021 Aug 3;105(2):519-532. doi: 10.1093/biolre/ioab073.
Energy metabolism in spermatozoa is complex and involves the metabolism of carbohydrate fatty acids and amino acids. The ATP produced in the electron transport chain in the mitochondria appears to be crucial for both sperm motility and maintaining viability, whereas glycolytic enzymes in the flagella may contribute to ATP production to sustain motility and velocity. Stallion spermatozoa seemingly use diverse metabolic strategies, and in this regard, a study of the metabolic proteome showed that Gene Ontology terms and Reactome pathways related to pyruvate metabolism and the Krebs cycle were predominant. Following this, the hypothesis that low glucose concentrations can provide sufficient support for motility and velocity, and thus glucose concentration can be significantly reduced in the medium, was tested. Aliquots of stallion semen in four different media were stored for 48 h at 18°C; a commercial extender containing 67 mM glucose was used as a control. Stallion spermatozoa stored in media with low glucose (1 mM) and high pyruvate (10 mM) (LG-HP) sustained better motility and velocities than those stored in the commercial extender formulated with very high glucose (61.7 ± 1.2% in INRA 96 vs 76.2 ± 1.0% in LG-HP media after 48 h of incubation at 18°C; P < 0.0001). Moreover, mitochondrial activity was superior in LG-HP extenders (24.1 ± 1.8% in INRA 96 vs 51.1 ± 0.7% in LG-HP of spermatozoa with active mitochondria after 48 h of storage at 18°C; P < 0.0001). Low glucose concentrations may permit more efficient sperm metabolism and redox regulation when substrates for an efficient tricarboxylic acid cycle are provided. The improvement seen using low glucose extenders is due to reductions in the levels of glyoxal and methylglyoxal, 2-oxoaldehydes formed during glycolysis; these compounds are potent electrophiles able to react with proteins, lipids, and DNA, causing sperm damage.
精子的能量代谢很复杂，涉及碳水化合物、脂肪酸和氨基酸的代谢。在线粒体电子传递链中产生的 ATP 似乎对精子的运动能力和活力维持都至关重要，而鞭毛中的糖酵解酶可能有助于产生 ATP 以维持运动能力和速度。种马精子似乎使用了不同的代谢策略，在这方面，一项代谢蛋白质组学的研究表明，与丙酮酸代谢和三羧酸循环相关的基因本体论术语和反应途径占主导地位。在此之后，人们提出了一个假设，即低葡萄糖浓度可以为运动能力和速度提供足够的支持，因此可以显著降低培养基中的葡萄糖浓度。将种马精液的等分试样分别储存在四种不同的培养基中 48 小时在 18°C；商业稀释剂含有 67 毫摩尔葡萄糖作为对照。在含有低葡萄糖（1 毫摩尔）和高丙酮酸（10 毫摩尔）的培养基（LG-HP）中储存的种马精子比在含有非常高葡萄糖的商业稀释剂（INRA 96 中的 76.2%±1.0%在孵育 48 小时后在 18°C；P<0.0001）中储存的精子具有更好的运动能力和速度。此外，LG-HP 稀释剂中的线粒体活性更高（INRA 96 中的 24.1%±1.8%与 LG-HP 中的 51.1%±0.7%相比，在 18°C 下储存 48 小时后具有活性线粒体的精子；P<0.0001）。当提供有效的三羧酸循环底物时，低葡萄糖浓度可能允许更有效的精子代谢和氧化还原调节。使用低葡萄糖稀释剂观察到的改善是由于糖酵解过程中形成的 2-氧代醛（glyoxal 和 methylglyoxal）水平降低所致；这些化合物是有效的亲电试剂，能够与蛋白质、脂质和 DNA 反应，导致精子损伤。
