title: Beta-carotene storage, conversion to retinoic acid, and induction of the lipocyte phenotype in hepatic stellate cells.
abstract: Hepatic stellate cells (HSCs) are the major site of retinol (ROH) metabolism and storage. GRX is a permanent murine myofibroblastic cell line, derived from HSCs, which can be induced to display the fat-storing phenotype by treatment with retinoids. Little is known about hepatic or serum homeostasis of beta-carotene and retinoic acid (RA), although the direct biogenesis of RA from beta-carotene has been described in enterocytes. The aim of this study was to identify the uptake, metabolism, storage, and release of beta-carotene in HSCs. GRX cells were plated in 25 cm(2) tissue culture flasks, treated during 10 days with 3 micromol/L beta-carotene and subsequently transferred into the standard culture medium. beta-Carotene induced a full cell conversion into the fat-storing phenotype after 10 days. The total cell extracts, cell fractions, and culture medium were analyzed by reverse phase high-performance liquid chromatography for beta-carotene and retinoids. Cells accumulated 27.48 +/- 6.5 pmol/L beta-carotene/10(6) cells, but could not convert it to ROH nor produced retinyl esters (RE). beta-Carotene was directly converted to RA, which was found in total cell extracts and in the nuclear fraction (10.15 +/- 1.23 pmol/L/10(6) cells), promoting the phenotype conversion. After 24-h chase, cells contained 20.15 +/- 1.12 pmol/L beta-carotene/10(6) cells and steadily released beta-carotene into the medium (6.69 +/- 1.75 pmol/ml). We conclude that HSC are the site of the liver beta-carotene storage and release, which can be used for RA production as well as for maintenance of the homeostasis of circulating carotenoids in periods of low dietary uptake.
authors.affiliation: Laboratório de Bioquímica Nutricional e de Alimentos, Instituto de Química, and Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Renata B
authors.initials: RB
authors.lastname: Martucci
authors.forename: Ana L
authors.initials: AL
authors.lastname: Ziulkoski
authors.forename: Vitor A
authors.initials: VA
authors.lastname: Fortuna
authors.forename: Regina M
authors.initials: RM
authors.lastname: Guaragna
authors.forename: Fátima C R
authors.initials: FC
authors.lastname: Guma
authors.forename: Luiz C
authors.initials: LC
authors.lastname: Trugo
authors.forename: Radovan
authors.initials: R
authors.lastname: Borojevic
mesh_terms: D000085:Acetates / Q000378:metabolism / Q000494:pharmacology; D017667:Adipocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002338:Carotenoids / Q000378:metabolism / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D010641:Phenotype; D014212:Tretinoin / Q000378:metabolism*; D019207:beta Carotene / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000085:Acetates; C436746:apo-8'-carotenoic acid; D019207:beta Carotene; D002338:Carotenoids; D014212:Tretinoin