Pan Xia, Köberle Martin, Ghashghaeinia Mehrdad
Physiological Institute, Department of Vegetative and Clinical Physiology, Eberhard Karls University of Tübingen, 72074 Tübingen, Germany.
Department of Dermatology and Allergology, School of Medicine and Health, Technical University of Munich, Biedersteinerstr. 29, 80802 München, Germany.
Antioxidants (Basel). 2024 Aug 9;13(8):968. doi: 10.3390/antiox13080968.
In the small intestine, nutrients from ingested food are absorbed and broken down by enterocytes, which constitute over 95% of the intestinal epithelium. Enterocytes demonstrate diet- and segment-dependent metabolic flexibility, enabling them to take up large amounts of glutamine and glucose to meet their energy needs and transfer these nutrients into the bloodstream. During glycolysis, ATP, lactate, and H ions are produced within the enterocytes. Based on extensive but incomplete glutamine oxidation large amounts of alanine or lactate are produced. Lactate, in turn, promotes hypoxia-inducible factor-1α (Hif-1α) activation and Hif-1α-dependent transcription of various proton channels and exchangers, which extrude cytoplasmic H-ions into the intestinal lumen. In parallel, the vitamin C-dependent and duodenal cytochrome b-mediated conversion of ferric iron into ferrous iron progresses. Finally, the generated electrochemical gradient is utilized by the divalent metal transporter 1 for H-coupled uptake of non-heme Fe-ions. Iron efflux from enterocytes, subsequent binding to the plasma protein transferrin, and systemic distribution supply a wide range of cells with iron, including erythroid precursors essential for erythropoiesis. In this review, we discuss the impact of vitamin C on the redox capacity of human erythrocytes and connect enterocyte function with iron metabolism, highlighting its effects on erythropoiesis.
在小肠中，摄入食物中的营养物质被肠上皮细胞吸收并分解，肠上皮细胞构成了超过95%的肠上皮。肠上皮细胞表现出饮食和节段依赖性的代谢灵活性，使其能够摄取大量谷氨酰胺和葡萄糖以满足其能量需求，并将这些营养物质转运到血液中。在糖酵解过程中，肠上皮细胞内产生ATP、乳酸和氢离子。基于广泛但不完全的谷氨酰胺氧化，会产生大量丙氨酸或乳酸。乳酸反过来又促进缺氧诱导因子-1α（Hif-1α）的激活以及各种质子通道和交换体的Hif-1α依赖性转录，这些质子通道和交换体将细胞质中的氢离子挤出到肠腔中。与此同时，维生素C依赖和十二指肠细胞色素b介导的三价铁向二价铁的转化过程在进行。最后，二价金属转运体1利用产生的电化学梯度进行H耦合摄取非血红素铁离子。铁从肠上皮细胞流出，随后与血浆蛋白转铁蛋白结合，并进行全身分布，为包括红细胞生成所必需的红系前体细胞在内的广泛细胞提供铁。在这篇综述中，我们讨论了维生素C对人类红细胞氧化还原能力的影响，并将肠上皮细胞功能与铁代谢联系起来，强调其对红细胞生成的影响。
