Carotenoids exert a rich variety of physiological functions in mammals and are beneficial for human health. These lipids are acquired from the diet and metabolized to apocarotenoids, including retinoids (vitamin A and its metabolites). The small intestine is a major site for their absorption and bioconversion. From here, carotenoids and their metabolites are distributed within the body in triacylglycerol-rich lipoproteins to support retinoid signaling in peripheral tissues and photoreceptor function in the eyes. In recent years, much progress has been made in identifying carotenoid metabolizing enzymes, transporters, and binding proteins. A diet-responsive regulatory network controls the activity of these components and adapts carotenoid absorption and bioconversion to the bodily requirements of these lipids. Genetic variability in the genes encoding these components alters carotenoid homeostasis and is associated with pathologies. We here summarize the advanced state of knowledge about intestinal carotenoid metabolism and its impact on carotenoid and retinoid homeostasis of other organ systems, including the eyes, liver, and immune system. The implication of the findings for science-based intake recommendations for these essential dietary lipids is discussed.

This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

类胡萝卜素在哺乳动物中发挥着丰富多样的生理功能，对人体健康有益。这些脂质从饮食中获得并代谢为类胡萝卜素，包括类视黄醇（维生素 A 及其代谢物）。小肠是它们吸收和生物转化的主要场所。从这里开始，类胡萝卜素及其代谢物以富含三酰基甘油的脂蛋白的形式分布在体内，以支持外周组织中的类视黄醇信号传导和眼睛中的光感受器功能。近年来，在鉴定类胡萝卜素代谢酶、转运蛋白和结合蛋白方面取得了很大进展。饮食响应调节网络控制这些成分的活性，并使类胡萝卜素的吸收和生物转化适应这些脂质的身体需求。编码这些成分的基因的遗传变异会改变类胡萝卜素的稳态并与病理相关。我们在此总结了有关肠道类胡萝卜素代谢及其对其他器官系统（包括眼睛、肝脏和免疫系统）的类胡萝卜素和类维生素 A 稳态的影响的先进知识状态。讨论了这些发现对这些必需膳食脂质的基于科学的摄入建议的影响。

本文是由 Johannes von Lintig 和 Loredana Quadro 编辑的题为类胡萝卜素在细胞和分子生物学方面的最新进展特刊的一部分。