Cynober Luc
Biochemistry Laboratory, Hôtel-Dieu Hospital-AP-HP and Laboratory of Biological Nutrition EA 2498, School of Pharmacy, Paris 5 University.
J Nutr. 2004 Oct;134(10 Suppl):2858S-2862S; discussion 2895S. doi: 10.1093/jn/134.10.2858s.
Ornithine alpha-ketoglutarate (OKG) is a salt formed of 2 molecules of ornithine and 1 alpha-ketoglutarate. Its administration improves nutritional status in chronically malnourished (e.g., elderly) and acutely malnourished patients (especially burn and trauma patients). There is evidence that OKG activity is not the simple addition of the effects of ornithine (Orn) and alpha-ketoglutarate (alphaKG), because the presence of both moieties is required to induce the generation of key metabolites such as glutamine, proline, and arginine (Arg), whereas this does not occur when one or the other is given separately. This observation is related to the fact that the main feature of Orn at the whole-body level is to be metabolized through the Orn aminotransferase-dependent pathway, whereas the simultaneous administration of Orn and alphaKG saturates this pathway, diverting Orn toward metabolism into Arg. For years, OKG activity has been associated with its ability to induce the secretion of anabolic hormones, such as insulin and growth hormone, and to increase glutamine and polyamine synthesis. Recent studies using chemical inhibitors of nitric oxide synthase (NOS) suggest that nitric oxide derived from Arg could be partly involved in OKG activity. The use of genetically modified animals (i.e., knockout for NOS expression) is required to confirm this hypothesis.
鸟氨酸α-酮戊二酸（OKG）是由2分子鸟氨酸和1分子α-酮戊二酸形成的盐。它的施用可改善慢性营养不良（如老年人）和急性营养不良患者（尤其是烧伤和创伤患者）的营养状况。有证据表明，OKG的活性并非鸟氨酸（Orn）和α-酮戊二酸（αKG）作用的简单相加，因为两个部分都存在时才能诱导关键代谢产物如谷氨酰胺、脯氨酸和精氨酸（Arg）的生成，而单独给予其中一种时则不会发生这种情况。这一观察结果与以下事实有关：在全身水平上，鸟氨酸的主要特征是通过依赖鸟氨酸转氨酶的途径进行代谢，而同时给予鸟氨酸和αKG会使该途径饱和，从而使鸟氨酸转向代谢生成精氨酸。多年来，OKG的活性一直与其诱导合成代谢激素（如胰岛素和生长激素）分泌以及增加谷氨酰胺和多胺合成的能力有关。最近使用一氧化氮合酶（NOS）化学抑制剂的研究表明，源自精氨酸的一氧化氮可能部分参与了OKG的活性。需要使用基因改造动物（即敲除NOS表达）来证实这一假设。
