Appetite Control
Appetite Control
复制标题
食欲控制
DOI：
10.1007/978-3-030-21573-6_21-1
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Joost H.G.
中科院分区：
文献类型：
--
作者：
Kleinridders A;Joost H.G.
抗氧化剂是以功能而不是常见结构基序为特征的分子。它们的共同特征是在生物系统中起“抗”氧化剂作用的能力。由于组织暴露于高浓度的物理溶解的分子氧以及含氮的生物分子，氧化剂通常被认为是与抗氧化剂相反的，是生物系统中产生的氧和/或氮衍生的反应物质（图1）。当然，还有大量其他生物相关的活性物质和氧化剂，包括硫中心自由基或氯化物质。因此，严格地说，我们在本条目中使用经常使用的首字母缩略词ROS（“活性氧物质”）来提及所有这些是不正确的。然而，它的优点是避免了两个不一致：如果图1中所示的化合物被简单地称为“氧化剂”或“自由基”，这将忽略并非所有这些化合物都必须是氧化剂（例如超氧阴离子，其可以在生物系统中充当还原剂）或自由基（例如非自由基反应性物质H2 O2、ONOO、HOCl）的事实。活性氧可能是内源性的，也可能是在暴露于外源性刺激后产生的。在存在氧气的情况下，电子沿着传递的任何地方都会发生内源性生成，例如在线粒体呼吸链中或在异生物质代谢过程中（Klotz和Steinbrenner 2017; Kehrer和Klotz 2015）。它可以由专用酶催化，包括还原氧以产生超氧化物或过氧化氢的氧化酶，并且ROS的内源性产生可以作为其他ROS的相互作用的（副）产物发生-例如过氧亚硝酸根，其通过超氧化物和一氧化氮自由基的组合产生，或羟基自由基，其可以通过金属离子诱导的过氧化物还原（芬顿反应）产生。引发ROS内源性产生的外源性刺激包括物理刺激，例如UV辐射或电离辐射和毒素。就像化学上的ROS不一定是氧化剂一样，相反的抗氧化剂不一定在生物学环境中充当还原剂：事实上，氧化剂可以引起适应性细胞反应，例如，通过刺激转录因子，因此是四种常见的抗氧化策略之一（Sies 1993; Klotz 2015）。这些策略包括（i）防止氧化剂形成，（ii）拦截氧化剂与其分子靶点之间的反应，（iii）修复氧化剂损伤的分子，以及（iv）通过上调内源性抗氧化剂防御，通过应激诱导的信号传导进行适应。
Antioxidants are molecules characterized by function rather than common structural motifs. Their common feature is the capability of acting “anti”-oxidants in biological systems. Owing to the exposure of tissues to high concentrations of physically dissolved molecular oxygen as well as to nitrogen-containing biomolecules, the oxidants, usually implied as being opposed by antioxidants, are oxygen-and/or nitrogen-derived reactive species generated in biological systems (Fig. 1). There is, of course, a plethora of other biologically relevant reactive species and oxidants, including sulfur-centered radicals or chlorinated species. Referring to all of these using the frequently employed acronym ROS (“reactive oxygen species”), as we will in this entry, is, therefore, strictly speaking, incorrect. It has, however, the advantage that two inconsistencies are being avoided: if the compounds shown in Fig. 1 were referred to simply as “oxidants” or “free radicals,” this would neglect the fact that not all of these compounds are necessarily oxidants (such as the superoxide anion, which may act as reductant in biological systems) or radicals (such as the non-radical reactive species H2O2, ONOO À, HOCl). ROS may be generated endogenously and upon exposure to exogenous stimuli. Endogenous generation occurs wherever electrons are passed along in the presence of oxygen, such as in the mitochondrial respiratory chain or during xenobiotic metabolism (Klotz and Steinbrenner 2017; Kehrer and Klotz 2015). It may be catalyzed by dedicated enzymes, including oxidases that reduce oxygen to generate superoxide or hydrogen peroxide, and endogenous generation of ROS may occur as (by) product of an interaction of other ROS–such as peroxynitrite, which is generated through a combination of superoxide and nitrogen monoxide radicals, or hydroxyl radical, which may be generated by a metal ion-induced reduction of peroxides (Fenton reaction). Exogenous stimuli eliciting the endogenous generation of ROS include physical stimuli such as UV radiation or ionizing radiation and toxins. Just as, chemically, ROS are not necessarily oxidants, the opposing antioxidants not necessarily act as reductants in a biological setting: in fact, oxidants can evoke an adaptive cellular response, for example, by stimulating transcription factors, and therefore serve one of the four commonly found antioxidative strategies (Sies 1993; Klotz 2015). These strategies include (i) the prevention of oxidant formation,(ii) interception of reactions between oxidants and their molecular targets,(iii) repair of molecules damaged by oxidants, and (iv) adaptation, through stress-induced signaling, by upregulating endogenous antioxidant defenses.
影响因子：
29
作者：
Zhao, Shangang;Zhu, Yi;Scherer, Philipp E.
通讯作者：
Scherer, Philipp E.