Skip to main content
NCBI home page
Biochemical Journal logoLink to Biochemical Journal
. 1989 Dec 1;264(2):495–502. doi: 10.1042/bj2640495

Regulation of hepatic cholesterol biosynthesis. Effects of a cytochrome P-450 inhibitor on the formation and metabolism of oxygenated sterol products of lanosterol.

J Iglesias 1, G F Gibbons 1
PMCID: PMC1133607  PMID: 2604729

Abstract

The involvement of oxygenated cholesterol precursors in the regulation of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity was studied by examining the effect of ketoconazole on the metabolism of mevalonic acid, lanosterol and the lanosterol metabolites, lanost-8-ene-3 beta,32-diol,3 beta-hydroxylanost-8-en-32-al and 4,4-dimethylcholesta-8,14-dien-3 beta-ol, in liver subcellular fractions and hepatocyte cultures. Inhibition of cholesterol synthesis from mevalonate by ketoconazole at concentrations up to 30 microM was due exclusively to a suppression of cytochrome P-450LDM (LDM = lanosterol demethylase) activity, resulting in a decreased rate of lanosterol 14 alpha-demethylation. No enzyme after the 14 alpha-demethylase step was affected. When [14C]mevalonate was the cholesterol precursor, inhibition of cytochrome P450LDM was accompanied by the accumulation of several labelled oxygenated sterols, quantitatively the most important of which was the C-32 aldehyde derivative of lanosterol. There was no accumulation of the 24,25-oxide derivative of lanosterol, nor of the C-32 alcohol. Under these conditions the activity of HMG-CoA reductase declined. The C-32 aldehyde accumulated to a far greater extent when lanost-8-ene-3 beta,32-diol rather than mevalonate was used as the cholesterol precursor in the presence of ketoconazole. With both precursors, this accumulation was reversed at higher concentrations of ketoconazole in liver subcellular fractions. A similar reversal was not observed in hepatocyte cultures.

Full text

PDF
495

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Akhtar M., Alexander K., Boar R. B., McGhie J. F., Barton D. H. Chemical and enzymic studies on the characterization of intermediates during the removal of the 14alpha-methyl group in cholesterol biosynthesis. The use of 32-functionalized lanostane derivatives. Biochem J. 1978 Mar 1;169(3):449–463. doi: 10.1042/bj1690449b. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Aoyama Y., Yoshida Y., Sonoda Y., Sato Y. Metabolism of 32-hydroxy-24,25-dihydrolanosterol by purified cytochrome P-45014DM from yeast. Evidence for contribution of the cytochrome to whole process of lanosterol 14 alpha-demethylation. J Biol Chem. 1987 Jan 25;262(3):1239–1243. [PubMed] [Google Scholar]
  3. BUCHER N. L., McGARRAHAN K., GOULD E., LOUD A. V. Cholesterol biosynthesis in preparations of liver from normal, fasting, x-irradiated, cholesterol-fed, triton, or delta 4-cholesten-3-one-treated rats. J Biol Chem. 1959 Feb;234(2):262–267. [PubMed] [Google Scholar]
  4. Bartlett S. M., Gibbons G. F. Short- and longer-term regulation of very-low-density lipoprotein secretion by insulin, dexamethasone and lipogenic substrates in cultured hepatocytes. A biphasic effect of insulin. Biochem J. 1988 Jan 1;249(1):37–43. doi: 10.1042/bj2490037. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Cavenee W. K., Chen H. W., Kandutsch A. A. Regulation of cholesterol biosynthesis in enucleated cells. J Biol Chem. 1981 Mar 25;256(6):2675–2681. [PubMed] [Google Scholar]
  6. Dawson P. A., Van der Westhuyzen D. R., Goldstein J. L., Brown M. S. Purification of oxysterol binding protein from hamster liver cytosol. J Biol Chem. 1989 May 25;264(15):9046–9052. [PubMed] [Google Scholar]
  7. Favata M. F., Trzaskos J. M., Chen H. W., Fischer R. T., Greenberg R. S. Modulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase by azole antimycotics requires lanosterol demethylation, but not 24,25-epoxylanosterol formation. J Biol Chem. 1987 Sep 5;262(25):12254–12260. [PubMed] [Google Scholar]
  8. Gibbons F. G., Pullinger C. R., Mitropoulos K. A. Studies on the mechanism of lanosterol 14 alpha-demethylation. A requirement for two distinct types of mixed-function-oxidase systems. Biochem J. 1979 Nov 1;183(2):309–315. doi: 10.1042/bj1830309. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Gibbons G. F., Attwell Thomas C. P., Pullinger C. R. The metabolic route by which oleate is converted into cholesterol in rat hepatocytes. Biochem J. 1986 Apr 1;235(1):19–24. doi: 10.1042/bj2350019. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Gibbons G. F., Mitropoulos K. A., Pullinger C. R. Lanosterol 14alpha-demethylase. The metabolism of some potential intermediates by cell-free systems from rat liver. Biochem Biophys Res Commun. 1976 Apr 5;69(3):781–789. doi: 10.1016/0006-291x(76)90943-8. [DOI] [PubMed] [Google Scholar]
  11. Gibbons G. F., Mitropoulos K. A. The effect of carbon monoxide on the nature of the accumulated 4,4-dimethyl sterol precursors of cholesterol during its biosynthesis from (2-14C)mevalonic acid in vitro. Biochem J. 1973 Mar;132(3):439–448. doi: 10.1042/bj1320439. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Gibbons G. F., Mitropoulos K. A. The rôle of cytochrome P-450 in cholesterol biosynthesis. Eur J Biochem. 1973 Dec 3;40(1):267–273. doi: 10.1111/j.1432-1033.1973.tb03194.x. [DOI] [PubMed] [Google Scholar]
  13. Gibbons G. F., Pullinger C. R., Chen H. W., Cavenee W. K., Kandutsch A. A. Regulation of cholesterol biosynthesis in cultured cells by probable natural precursor sterols. J Biol Chem. 1980 Jan 25;255(2):395–400. [PubMed] [Google Scholar]
  14. Gibbons G. F. The metabolic sequence by which some 4,4-dimethyl sterols are converted into cholesterol. Biochem J. 1974 Oct;144(1):59–68. doi: 10.1042/bj1440059. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Gupta A., Sexton R. C., Rudney H. Modulation of regulatory oxysterol formation and low density lipoprotein suppression of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity by ketoconazole. A role for cytochrome P-450 in the regulation of HMG-CoA reductase in rat intestinal epithelial cells. J Biol Chem. 1986 Jun 25;261(18):8348–8356. [PubMed] [Google Scholar]
  16. Iglesias J., Gibbons G. F. Oxidative metabolism of cholesterol precursors: sensitivity to ketoconazole, an inhibitor of cytochrome P-450. Steroids. 1989 Mar-May;53(3-5):311–328. doi: 10.1016/0039-128x(89)90017-2. [DOI] [PubMed] [Google Scholar]
  17. Kandutsch A. A., Chen H. W., Heiniger H. J. Biological activity of some oxygenated sterols. Science. 1978 Aug 11;201(4355):498–501. doi: 10.1126/science.663671. [DOI] [PubMed] [Google Scholar]
  18. Kandutsch A. A., Chen H. W. Inhibition of sterol synthesis in cultured mouse cells by 7alpha-hydroxycholesterol, 7beta-hydroxycholesterol, and 7-ketocholesterol. J Biol Chem. 1973 Dec 25;248(24):8408–8417. [PubMed] [Google Scholar]
  19. Kandutsch A. A., Chen H. W. Inhibition of sterol synthesis in cultured mouse cells by cholesterol derivatives oxygenated in the side chain. J Biol Chem. 1974 Oct 10;249(19):6057–6061. [PubMed] [Google Scholar]
  20. Kempen H. J., van Son K., Cohen L. H., Griffioen M., Verboom H., Havekes L. Effect of ketoconazole on cholesterol synthesis and on HMG-CoA reductase and LDL-receptor activities in Hep G2 cells. Biochem Pharmacol. 1987 Apr 15;36(8):1245–1249. doi: 10.1016/0006-2952(87)90077-3. [DOI] [PubMed] [Google Scholar]
  21. Kühn-Velten N., Lessmann M., Förster M. E., Staib W. Specific accumulation of 17 alpha-hydroxyprogesterone in microsomal membranes during the process of cytochrome P-450(C-17)-catalysed androgen biosynthesis. A dynamic study of intermediate formation and turnover. Biochem J. 1988 Nov 15;256(1):53–59. doi: 10.1042/bj2560053. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Miettinen T. A. Cholesterol metabolism during ketoconazole treatment in man. J Lipid Res. 1988 Jan;29(1):43–51. [PubMed] [Google Scholar]
  23. Panini S. R., Sexton R. C., Gupta A. K., Parish E. J., Chitrakorn S., Rudney H. Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and cholesterol biosynthesis by oxylanosterols. J Lipid Res. 1986 Nov;27(11):1190–1204. [PubMed] [Google Scholar]
  24. Panini S. R., Sexton R. C., Rudney H. Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase by oxysterol by-products of cholesterol biosynthesis. Possible mediators of low density lipoprotein action. J Biol Chem. 1984 Jun 25;259(12):7767–7771. [PubMed] [Google Scholar]
  25. Rudney H., Sexton R. C. Regulation of cholesterol biosynthesis. Annu Rev Nutr. 1986;6:245–272. doi: 10.1146/annurev.nu.06.070186.001333. [DOI] [PubMed] [Google Scholar]
  26. Saucier S. E., Kandutsch A. A., Phirwa S., Spencer T. A. Accumulation of regulatory oxysterols, 32-oxolanosterol and 32-hydroxylanosterol in mevalonate-treated cell cultures. J Biol Chem. 1987 Oct 15;262(29):14056–14062. [PubMed] [Google Scholar]
  27. Schroepfer G. J., Jr Sterol biosynthesis. Annu Rev Biochem. 1981;50:585–621. doi: 10.1146/annurev.bi.50.070181.003101. [DOI] [PubMed] [Google Scholar]
  28. Taylor F. R., Kandutsch A. A. Oxysterol binding protein. Chem Phys Lipids. 1985 Aug 30;38(1-2):187–194. doi: 10.1016/0009-3084(85)90066-0. [DOI] [PubMed] [Google Scholar]
  29. Taylor F. R., Saucier S. E., Shown E. P., Parish E. J., Kandutsch A. A. Correlation between oxysterol binding to a cytosolic binding protein and potency in the repression of hydroxymethylglutaryl coenzyme A reductase. J Biol Chem. 1984 Oct 25;259(20):12382–12387. [PubMed] [Google Scholar]
  30. Trzaskos J. M., Bowen W. D., Shafiee A., Fischer R. T., Gaylor J. L. Cytochrome P-450-dependent oxidation of lanosterol in cholesterol biosynthesis. Microsomal electron transport and C-32 demethylation. J Biol Chem. 1984 Nov 10;259(21):13402–13412. [PubMed] [Google Scholar]
  31. Trzaskos J. M., Favata M. F., Fischer R. T., Stam S. H. In situ accumulation of 3 beta-hydroxylanost-8-en-32-aldehyde in hepatocyte cultures. A putative regulator of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity. J Biol Chem. 1987 Sep 5;262(25):12261–12268. [PubMed] [Google Scholar]
  32. Trzaskos J. M., Fischer R. T., Favata M. F. Mechanistic studies of lanosterol C-32 demethylation. Conditions which promote oxysterol intermediate accumulation during the demethylation process. J Biol Chem. 1986 Dec 25;261(36):16937–16942. [PubMed] [Google Scholar]
  33. Van den Bossche H., Willemsens G., Cools W., Marichal P., Lauwers W. Hypothesis on the molecular basis of the antifungal activity of N-substituted imidazoles and triazoles. Biochem Soc Trans. 1983 Dec;11(6):665–667. doi: 10.1042/bst0110665. [DOI] [PubMed] [Google Scholar]

Articles from Biochemical Journal are provided here courtesy of The Biochemical Society

RESOURCES