Vitamin A and lipid metabolism: relationship between hepatic stellate cells (HSCs) and adipocytes
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MINI REVIEW
Vitamin A and lipid metabolism: relationship between hepatic stellate cells (HSCs) and adipocytes Patrick Sauvant & Maud Cansell & Claude Atgié
Received: 25 January 2011 / Accepted: 11 May 2011 / Published online: 31 May 2011 # University of Navarra 2011
Abstract Vitamin A or retinol plays a major role in the regulation of cellular homeostasis. Retinyl palmitate remains the main chemical form of vitamin A storage and is mainly located in hepatic stellate cells (HSCs) in lipid droplets resembling those found in adipose cells. White adipose tissue (WAT), is essentially involved in the regulation of lipid metabolism, through its role in lipid storage, and might also be considered as a vitamin A storage and metabolism site. WAT contains all the intracellular equipment for vitamin A metabolism and signaling pathways which allows retinol to be metabolized into retinoic acid, known to control genomic expression in WAT. The description of molecular mechanisms involved in the activation of HSCs and the differentiation of preadipocytes reveal similar cellular and molecular mechanisms. Indeed HSCs and adipocytes share a common expression of key transcription factors like PPAR-γ and RXR known to influence perilipin expression, which play fundamental roles in lipid droplet metabolism. Both cells are also sources of important endocrine signaling secretions influencing the expression of these transcription factors. The morphological and functional characteristics of HSCs and adipoP. Sauvant (*) : M. Cansell : C. Atgié UMR 5248 CBMN “Chimie et Biologie des Membranes et des Nanoobjets”, CNRS, Université de Bordeaux, Institut Polytechnique de Bordeaux (IPB), Allée Geoffroy de St Hilaire, Pessac, 33 600 Bordeaux, France e-mail: [email protected]
cytes, including the metabolism of vitamin A and other lipids and their related signaling pathways, are summarized and compared in this review. We highlight the complexity of the interrelationship between lipids and vitamin A metabolism and the role of the complex communication existing between HSCs and WAT in diseases such as non-alcoholic fatty liver disease which is the hepatic manifestation of the metabolic syndrome. Keywords PAV-1 . Non-alcoholic fatty liver diseases (NAFLD) . Metabolic syndrome . Adipokines . Perilipin . PPAR . ADRP
Introduction Vitamin A deficiency was without doubt the first nutrient deficiency disease to be clearly recognized. Indeed, empirically used to cure night blindness in Egyptians (−1,500 BC), one of the first hypothesized roles of vitamin A was its main role in vision. This essential function was clearly elucidated by George Wald in 1968 [70], about 50 years after its discovery by Elmer McCollum for its role in normal growth and development in cattle [37, 38] which allowed McCollum to define vitamin A as a fat-soluble factor essential for life. This whole fascinating story was reported by George Wolf [73]. Since its discovery and the discovery of retinoic acid receptors (RAR) and retinoid X receptors (RXR) [13, 33, 34, 47],
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