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. 1986 Apr 1;235(1):19–24. doi: 10.1042/bj2350019

The metabolic route by which oleate is converted into cholesterol in rat hepatocytes.

G F Gibbons, C P Attwell Thomas, C R Pullinger
PMCID: PMC1146642  PMID: 3741380

Abstract

The effect of (-)-hydroxycitrate on the conversion of [1-14C]oleate into cholesterol was dependent on the time of day at which the cells were prepared and on the extracellular oleate concentration. In hepatocytes prepared during the light phase of the diurnal cycle (L2-hepatocytes), (-)-hydroxycitrate inhibited the conversion of L-[U-14C]lactate (2 mM) and of 0.13 mM-[1-14C]oleate into cholesterol. However, when [1-14C]oleate was present at 1.3 mM, most of the sterol carbon was derived from this source, and under these conditions (-)-hydroxycitrate had no inhibitory effect on [14C]cholesterol formation. In these cells, non-radioactive acetoacetate blocked the conversion of 1.3 mM-[1-14C]oleate, but not of 0.13 mM-[1-14C]oleate, into cholesterol. In cells prepared during the dark phase of the diurnal cycle (D6-hepatocytes), irrespective of the concentration of [1-14C]oleate, (-)-hydroxycitrate decreased its conversion into cholesterol. In both types of cell preparation, the inhibitory effect of (-)-hydroxycitrate on the conversion of L-[U-14C]lactate into cholesterol was greater than that on the overall rate of cholesterol production from all endogenous sources. These results provide evidence for the following. (1) The major metabolic route by which oleate is converted into cholesterol is dependent on its extracellular concentration. (2) When oleate is the major source of hepatic sterol carbon, the flux of substrate through citrate into cholesterol is dependent on the nutritional state of the animal. (3) When endogenous substrates are the sole source of sterol carbon, a substantial proportion of the carbon enters the cholesterol pathway through routes not involving citrate cleavage.

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Selected References

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

  1. Barth C., Hackenschmidt J., Ullmann H., Decker K. Inhibition of cholesterol synthesis by (-)-hydroxycitrate in perfused rat liver. Evidence for an extramitochondrial mevalonate synthesis from acetyl coenzyme A. FEBS Lett. 1972 May 15;22(3):343–346. doi: 10.1016/0014-5793(72)80266-7. [DOI] [PubMed] [Google Scholar]
  2. Bergstrom J. D., Robbins K. A., Edmond J. Acetoacetyl-coenzyme A synthetase activity in rat liver cytosol: a regulated enzyme in lipogenesis. Biochem Biophys Res Commun. 1982 Jun 15;106(3):856–862. doi: 10.1016/0006-291x(82)91789-2. [DOI] [PubMed] [Google Scholar]
  3. Bergstrom J. D., Wong G. A., Edwards P. A., Edmond J. The regulation of acetoacetyl-CoA synthetase activity by modulators of cholesterol synthesis in vivo and the utilization of acetoacetate for cholesterogenesis. J Biol Chem. 1984 Dec 10;259(23):14548–14553. [PubMed] [Google Scholar]
  4. Björnsson O. G., Pullinger C. R., Gibbons G. F. Diurnal changes in the rate of cholesterogenesis in hepatocytes from fed and starved rats: effects of precursors and pancreatic hormones in vitro. Arch Biochem Biophys. 1985 Apr;238(1):135–145. doi: 10.1016/0003-9861(85)90149-3. [DOI] [PubMed] [Google Scholar]
  5. Björnsson O. G., Pullinger C. R., Gibbons G. F. Effect of drugs, peptide hormones and lipogenic precursors on the relative incorporation of [3H]H2O and carbon into hepatic cholesterol. FEBS Lett. 1985 Aug 5;187(2):302–306. doi: 10.1016/0014-5793(85)81264-3. [DOI] [PubMed] [Google Scholar]
  6. Brunengraber H., Sabine J. R., Boutry M., Lowenstein J. M. 3- -Hydroxysterol synthesis by the liver. Arch Biochem Biophys. 1972 Jun;150(2):392–396. doi: 10.1016/0003-9861(72)90054-9. [DOI] [PubMed] [Google Scholar]
  7. Buckley B. M., Williamson D. H. Acetoacetyl-CoA synthetase; a lipogenic enzyme in rat tissues. FEBS Lett. 1975 Dec 1;60(1):7–10. doi: 10.1016/0014-5793(75)80406-6. [DOI] [PubMed] [Google Scholar]
  8. Edwards P. A. The influence of catecholamines and cyclic AMP on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and lipid biosynthesis in isolated rat hepatocytes. Arch Biochem Biophys. 1975 Sep;170(1):188–203. doi: 10.1016/0003-9861(75)90110-1. [DOI] [PubMed] [Google Scholar]
  9. Endemann G., Goetz P. G., Edmond J., Brunengraber H. Lipogenesis from ketone bodies in the isolated perfused rat liver. Evidence for the cytosolic activation of acetoacetate. J Biol Chem. 1982 Apr 10;257(7):3434–3440. [PubMed] [Google Scholar]
  10. Geelen M. J., Lopes-Cardozo M., Edmond J. Acetoacetate: a major substrate for the synthesis of cholesterol and fatty acids by isolated rat hepatocytes. FEBS Lett. 1983 Nov 14;163(2):269–273. doi: 10.1016/0014-5793(83)80833-3. [DOI] [PubMed] [Google Scholar]
  11. Gibbons G. F., Pullinger C. R., Björnsson O. G. Changes in the sensitivity of lipogenesis in rat hepatocytes to hormones and precursors over the diurnal cycle and during longer-term starvation of donor animals. J Lipid Res. 1984 Dec 1;25(12):1358–1367. [PubMed] [Google Scholar]
  12. Gibbons G. F., Pullinger C. R. Utilization of endogenous and exogenous sources of substrate for cholesterol biosynthesis by isolated hepatocytes. Biochem J. 1979 Jan 1;177(1):255–263. doi: 10.1042/bj1770255. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Goodridge A. G. Regulation of fatty acid synthesis in isolated hepatocytes. Evidence for a physiological role for long chain fatty acyl coenzyme A and citrate. J Biol Chem. 1973 Jun 25;248(12):4318–4326. [PubMed] [Google Scholar]
  14. Hamilton J. G., Sullivan A. C., Kritchevsky D. Hupolipidemic activity of (--)-hydroxycitrate. Lipids. 1977 Jan;12(1):1–9. doi: 10.1007/BF02532964. [DOI] [PubMed] [Google Scholar]
  15. Hems D. A., Rath E. A., Verrinder T. R. Fatty acid synthesis in liver and adipose tissue of normal and genetically obese (ob/ob) mice during the 24-hour cycle. Biochem J. 1975 Aug;150(2):167–173. doi: 10.1042/bj1500167. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Lane M. D., Mooney R. A. Tricarboxylic acid cycle intermediates and the control of fatty acid synthesis and ketogenesis. Curr Top Cell Regul. 1981;18:221–242. doi: 10.1016/b978-0-12-152818-8.50019-0. [DOI] [PubMed] [Google Scholar]
  17. Lowenstein J. M. Effect of (-)-hydroxycitrate on fatty acid synthesis by rat liver in vivo. J Biol Chem. 1971 Feb 10;246(3):629–632. [PubMed] [Google Scholar]
  18. Munday M. R., Williamson D. H. Diurnal variations in food intake and in lipogenesis in mammary gland and liver of lactating rats. Biochem J. 1983 Jul 15;214(1):183–187. doi: 10.1042/bj2140183. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Pullinger C. R., Gibbons G. F. Effects of hormones and pyruvate on the rates of secretion of very-low-density lipoprotein triacylglycerol and cholesterol by rat hepatocytes. Biochim Biophys Acta. 1985 Jan 9;833(1):44–51. doi: 10.1016/0005-2760(85)90251-6. [DOI] [PubMed] [Google Scholar]
  20. Pullinger C. R., Gibbons G. F. The relationship between the rate of hepatic sterol synthesis and the incorporation of [3H]water. J Lipid Res. 1983 Oct;24(10):1321–1328. [PubMed] [Google Scholar]
  21. Pullinger C. R., Gibbons G. F. The role of substrate supply in the regulation of cholesterol biosynthesis in rat hepatocytes. Biochem J. 1983 Mar 15;210(3):625–632. doi: 10.1042/bj2100625. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Rodwell V. W., Nordstrom J. L., Mitschelen J. J. Regulation of HMG-CoA reductase. Adv Lipid Res. 1976;14:1–74. doi: 10.1016/b978-0-12-024914-5.50008-5. [DOI] [PubMed] [Google Scholar]
  23. Salmon D. M., Bowen N. L., Hems D. A. Synthesis of fatty acids in the perused mouse liver. Biochem J. 1974 Sep;142(3):611–618. doi: 10.1042/bj1420611. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Scott D. F., Potter V. R. Metabolic oscillations in lipid metabolism in rats on controlled feeding schedules. Fed Proc. 1970 Jul-Aug;29(4):1553–1559. [PubMed] [Google Scholar]
  25. Seglen P. O. Preparation of isolated rat liver cells. Methods Cell Biol. 1976;13:29–83. doi: 10.1016/s0091-679x(08)61797-5. [DOI] [PubMed] [Google Scholar]
  26. Siess E. A., Kientsch-Engel R. I., Wieland O. H. Concentration of free oxaloacetate in the mitochondrial compartment of isolated liver cells. Biochem J. 1984 Feb 15;218(1):171–176. doi: 10.1042/bj2180171. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Siess E. A., Kientsch-Engel R. I., Wieland O. H. Role of free oxaloacetate in ketogenesis. Derivation from the direct measurement of mitochondrial [3-hydroxybutyrate]/[acetoacetate] ratio in hepatocytes. Eur J Biochem. 1982 Jan;121(3):493–499. doi: 10.1111/j.1432-1033.1982.tb05814.x. [DOI] [PubMed] [Google Scholar]
  28. Sullivan A. C., Triscari J., Hamilton J. G., Miller O. N., Wheatley V. R. Effect of (-)-hydroxycitrate upon the accumulation of lipid in the rat. I. Lipogenesis. Lipids. 1974 Feb;9(2):121–128. doi: 10.1007/BF02532136. [DOI] [PubMed] [Google Scholar]
  29. Triscari J., Sullivan A. C. Comparative effects of (--)-hydroxycitrate and (+)-allo-hydroxycitrate on acetyl CoA carboxylase and fatty acid and cholesterol synthesis in vivo. Lipids. 1977 Apr;12(4):357–363. doi: 10.1007/BF02533638. [DOI] [PubMed] [Google Scholar]
  30. Van Harken D. R., Dixon C. W., Heimberg M. Hepatic lipid metabolism in experimental diabetes. V. The effect of concentration of oleate on metabolism of triglycerides and on ketogenesis. J Biol Chem. 1969 May 10;244(9):2278–2285. [PubMed] [Google Scholar]
  31. Watson J. A., Fang M., Lowenstein J. M. Tricarballylate and hydroxycitrate: substrate and inhibitor of ATP: citrate oxaloacetate lyase. Arch Biochem Biophys. 1969 Dec;135(1):209–217. doi: 10.1016/0003-9861(69)90532-3. [DOI] [PubMed] [Google Scholar]

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