Hepatic iron loading in mice increases cholesterol biosynthesis

Authors

  • Ross M. Graham,

    Corresponding author
    1. School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia
    2. Western Australian Institute for Medical Research, University of Western Australia, Perth, WA, Australia
    • M704, School of Medicine and Pharmacology, The University of Western Australia, PO Box 480, Fremantle Hospital, Fremantle, 6959, Western Australia, Australia
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    • fax: +61-8-9431-2977

  • Anita C. G. Chua,

    1. School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia
    2. Western Australian Institute for Medical Research, University of Western Australia, Perth, WA, Australia
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  • Kim W. Carter,

    1. Telethon Institute for Child Health Research, University of Western Australia Centre for Child Health Research, University of Western Australia, Perth, WA, Australia
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  • Roheeth D. Delima,

    1. School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia
    2. Western Australian Institute for Medical Research, University of Western Australia, Perth, WA, Australia
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  • Daniel Johnstone,

    1. School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, Australia
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  • Carly E. Herbison,

    1. School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia
    2. Western Australian Institute for Medical Research, University of Western Australia, Perth, WA, Australia
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  • Martin J. Firth,

    1. Telethon Institute for Child Health Research, University of Western Australia Centre for Child Health Research, University of Western Australia, Perth, WA, Australia
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  • Rebecca O'Leary,

    1. Telethon Institute for Child Health Research, University of Western Australia Centre for Child Health Research, University of Western Australia, Perth, WA, Australia
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  • Elizabeth A. Milward,

    1. School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, Australia
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  • John K. Olynyk,

    1. School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia
    2. Western Australian Institute for Medical Research, University of Western Australia, Perth, WA, Australia
    3. Department of Gastroenterology, Fremantle Hospital, Fremantle, WA, Australia
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  • Debbie Trinder

    1. School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia
    2. Western Australian Institute for Medical Research, University of Western Australia, Perth, WA, Australia
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  • Potential conflict of interest: Nothing to report.

Abstract

Iron and cholesterol are both essential metabolites in mammalian systems, and too much or too little of either can have serious clinical consequences. In addition, both have been associated with steatosis and its progression, contributing, inter alia, to an increase in hepatic oxidative stress. The interaction between iron and cholesterol is unclear, with no consistent evidence emerging with respect to changes in plasma cholesterol on the basis of iron status. We sought to clarify the role of iron in lipid metabolism by studying the effects of iron status on hepatic cholesterol synthesis in mice with differing iron status. Transcripts of seven enzymes in the cholesterol biosynthesis pathway were significantly up-regulated with increasing hepatic iron (R2 between 0.602 and 0.164), including those of the rate-limiting enzyme, 3-hydroxy-3-methylglutarate-coenzyme A reductase (Hmgcr; R2 = 0.362, P < 0.002). Hepatic cholesterol content correlated positively with hepatic iron (R2 = 0.255, P < 0.007). There was no significant relationship between plasma cholesterol and either hepatic cholesterol or iron (R2 = 0.101 and 0.014, respectively). Hepatic iron did not correlate with a number of known regulators of cholesterol synthesis, including sterol-regulatory element binding factor 2 (Srebf2; R2 = 0.015), suggesting that the increases seen in the cholesterol biosynthesis pathway are independent of Srebf2. Transcripts of genes involved in bile acid synthesis, transport, or regulation did not increase with increasing hepatic iron. Conclusion: This study suggests that hepatic iron loading increases liver cholesterol synthesis and provides a new and potentially important additional mechanism by which iron could contribute to the development of fatty liver disease or lipotoxicity. (HEPATOLOGY 2010;)

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