From the Department of Biochemistry.
J Biol Chem. 2013 Dec 13;288(50):36129-40. doi: 10.1074/jbc.M113.507285. Epub 2013 Nov 1.
Transport of pyruvate into mitochondria by the mitochondrial pyruvate carrier is crucial for complete oxidation of glucose and for biosynthesis of amino acids and lipids. Zaprinast is a well known phosphodiesterase inhibitor and lead compound for sildenafil. We found Zaprinast alters the metabolomic profile of mitochondrial intermediates and amino acids in retina and brain. This metabolic effect of Zaprinast does not depend on inhibition of phosphodiesterase activity. By providing (13)C-labeled glucose and glutamine as fuels, we found that the metabolic profile of the Zaprinast effect is nearly identical to that of inhibitors of the mitochondrial pyruvate carrier. Both stimulate oxidation of glutamate and massive accumulation of aspartate. Moreover, Zaprinast inhibits pyruvate-driven O2 consumption in brain mitochondria and blocks mitochondrial pyruvate carrier in liver mitochondria. Inactivation of the aspartate glutamate carrier in retina does not attenuate the metabolic effect of Zaprinast. Our results show that Zaprinast is a potent inhibitor of mitochondrial pyruvate carrier activity, and this action causes aspartate to accumulate at the expense of glutamate. Our findings show that Zaprinast is a specific mitochondrial pyruvate carrier (MPC) inhibitor and may help to elucidate the roles of MPC in amino acid metabolism and hypoglycemia.
丙酮酸通过线粒体丙酮酸载体转运进入线粒体对于葡萄糖的完全氧化和氨基酸及脂质的生物合成至关重要。扎普司特是一种众所周知的磷酸二酯酶抑制剂，也是西地那非的先导化合物。我们发现扎普司特改变了视网膜和大脑中线粒体中间产物和氨基酸的代谢组学特征。扎普司特的这种代谢作用不依赖于磷酸二酯酶活性的抑制。通过提供（13）C 标记的葡萄糖和谷氨酰胺作为燃料，我们发现扎普司特的代谢作用谱与线粒体丙酮酸载体的抑制剂几乎相同。两者都刺激谷氨酸的氧化和天冬氨酸的大量积累。此外，扎普司特抑制脑线粒体中的丙酮酸驱动的 O2 消耗，并阻断肝线粒体中的线粒体丙酮酸载体。在视网膜中，天冬氨酸-谷氨酸载体的失活并不能减轻扎普司特的代谢作用。我们的结果表明，扎普司特是一种有效的线粒体丙酮酸载体（MPC）抑制剂，这种作用导致天冬氨酸积累，而谷氨酸减少。我们的发现表明，扎普司特是一种特异性的线粒体丙酮酸载体（MPC）抑制剂，可能有助于阐明 MPC 在氨基酸代谢和低血糖中的作用。
