School of Biosciences, Cardiff University, Cardiff CF10 3AX, Wales, UK.
Int J Mol Sci. 2023 May 16;24(10):8838. doi: 10.3390/ijms24108838.
Polyunsaturated fatty acids (PUFAs) are important components of the diet of mammals. Their role was first established when the essential fatty acids (EFAs) linoleic acid and α-linolenic acid were discovered nearly a century ago. However, most of the biochemical and physiological actions of PUFAs rely on their conversion to 20C or 22C acids and subsequent metabolism to lipid mediators. As a generalisation, lipid mediators formed from n-6 PUFAs are pro-inflammatory while those from n-3 PUFAs are anti-inflammatory or neutral. Apart from the actions of the classic eicosanoids or docosanoids, many newly discovered compounds are described as Specialised Pro-resolving Mediators (SPMs) which have been proposed to have a role in resolving inflammatory conditions such as infections and preventing them from becoming chronic. In addition, a large group of molecules, termed isoprostanes, can be generated by free radical reactions and these too have powerful properties towards inflammation. The ultimate source of n-3 and n-6 PUFAs are photosynthetic organisms which contain Δ-12 and Δ-15 desaturases, which are almost exclusively absent from animals. Moreover, the EFAs consumed from plant food are in competition with each other for conversion to lipid mediators. Thus, the relative amounts of n-3 and n-6 PUFAs in the diet are important. Furthermore, the conversion of the EFAs to 20C and 22C PUFAs in mammals is rather poor. Thus, there has been much interest recently in the use of algae, many of which make substantial quantities of long-chain PUFAs or in manipulating oil crops to make such acids. This is especially important because fish oils, which are their main source in human diets, are becoming limited. In this review, the metabolic conversion of PUFAs into different lipid mediators is described. Then, the biological roles and molecular mechanisms of such mediators in inflammatory diseases are outlined. Finally, natural sources of PUFAs (including 20 or 22 carbon compounds) are detailed, as well as recent efforts to increase their production.
多不饱和脂肪酸（PUFAs）是哺乳动物饮食的重要组成部分。它们的作用最初是在近一个世纪前发现必需脂肪酸（EFAs）亚油酸和α-亚麻酸时确立的。然而，PUFAs 的大多数生化和生理作用依赖于它们转化为 20C 或 22C 酸，然后转化为脂质介质。一般来说，来自 n-6 PUFAs 的脂质介质是促炎的，而来自 n-3 PUFAs 的脂质介质是抗炎或中性的。除了经典的二十碳烷酸或二十二碳烷酸的作用外，许多新发现的化合物被描述为专门的促解决介质（SPM），它们被认为在解决感染等炎症情况并防止其发展为慢性方面发挥作用。此外，一大类被称为类异戊二烯的分子可以由自由基反应产生，这些分子也对炎症有强大的作用。n-3 和 n-6 PUFAs 的最终来源是含有 Δ-12 和 Δ-15 去饱和酶的光合生物，而这些酶几乎完全不存在于动物中。此外，从植物性食物中摄取的 EFA 相互竞争，以转化为脂质介质。因此，饮食中 n-3 和 n-6 PUFAs 的相对含量很重要。此外，哺乳动物中 EFA 转化为 20C 和 22C PUFAs 的效率相当低。因此，最近人们对藻类的利用产生了浓厚的兴趣，其中许多藻类大量产生长链 PUFAs，或者操纵油作物来制造这些酸。这一点尤其重要，因为鱼类油是人类饮食中它们的主要来源，正变得越来越有限。在这篇综述中，描述了 PUFAs 转化为不同脂质介质的代谢转化。然后，概述了这些介质在炎症性疾病中的生物学作用和分子机制。最后，详细介绍了 PUFAs 的天然来源（包括 20 或 22 碳化合物）以及最近增加其产量的努力。
