Department of Human Nutrition, Ohio State University, Columbus, OH, USA.
J Lipid Res. 2013 Jul;54(7):1719-30. doi: 10.1194/jlr.R039537. Epub 2013 May 10.
Vitamin A was recognized as an essential nutrient 100 years ago. In the 1930s, it became clear that dietary β-carotene was cleaved at its central double to yield vitamin A (retinal or β-apo-15'-carotenal). Thus a great deal of research has focused on the central cleavage of provitamin A carotenoids to form vitamin A (retinoids). The mechanisms of formation and the physiological role(s) of noncentral (eccentric) cleavage of both provitamin A carotenoids and nonprovitamin A carotenoids has been less clear. It is becoming apparent that the apocarotenoids exert unique biological activities themselves. These compounds are found in the diet and thus may be absorbed in the intestine, or they may form from enzymatic or nonenzymatic cleavage of the parent carotenoids. The mechanism of action of apocarotenoids in mammals is not fully worked out. However, as detailed in this review, they have profound effects on gene expression and work, at least in part, through the modulation of ligand-activated nuclear receptors. Understanding the interactions of apocarotenoids with other lipid-binding proteins, chaperones, and metabolizing enzymes will undoubtedly increase our understanding of the biological roles of these carotenoid metabolites.
维生素 A 在 100 年前被认为是一种必需营养素。在 20 世纪 30 年代，人们清楚地认识到膳食中的β-胡萝卜素在其中心双键处被裂解，生成维生素 A（视黄醛或β-无环-15'-胡萝卜素）。因此，大量的研究集中在类维生素 A 胡萝卜素的中心裂解以形成维生素 A（类视黄醇）上。非中心（偏心）裂解形成维生素 A 的机制和生理作用（s）类维生素 A 胡萝卜素和非类维生素 A 胡萝卜素一直不太清楚。现在已经很明显，类胡萝卜素的开环产物本身具有独特的生物学活性。这些化合物存在于饮食中，因此可能在肠道中被吸收，或者它们可能通过母体类胡萝卜素的酶促或非酶促裂解形成。类胡萝卜素开环产物在哺乳动物中的作用机制尚未完全阐明。然而，正如本综述中详细介绍的那样，它们对基因表达有深远的影响，至少部分是通过调节配体激活的核受体来实现的。了解类胡萝卜素开环产物与其他脂质结合蛋白、伴侣蛋白和代谢酶的相互作用，无疑将增加我们对这些类胡萝卜素代谢物的生物学作用的理解。
