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Home > 16 Biosynthesis of Cholesterol and Steroids > VITAMIN D3 > Summary
Summary
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  • Cholesterol is a vital constituent of cell membranes and the precursor molecule for bile acids, steroid hormones and vitamin D.
  • Cholesterol is derived both from the diet and also synthesized de novo from acetyl-CoA. Cholesterol biosynthesis is strictly regulated. The rate limiting enzyme is the HMG-CoA reductase.
  • The metabolism of cholesterol into bile acids and steroid hormones involves several hydroxylation reactions catalyzed by cytochrome P450 mono-oxygenase enzymes.
  • Several clinical disorders are associated with abnormalities in the regulation of cholesterol homeostasis or metabolism.
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ACTIVE LEARNING
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  1. Describe the regulation of intracellular cholesterol concentration.
  2. How does SR-BI receptor differ from the LDL receptor?
  3. Which are the secondary bile acids?
  4. Discuss the enterohepatic circulation of bile acids.
  5. Discuss the role of monooxygenases in steroid synthesis.
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Further reading
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1. Sakai J, Rawson RB. The sterol regulatory element-binding protein pathway: control of lipid homeostasis through regulated intracellular transport. Curr Opin Lipidol 2001;12:261-6. Full articleGo to this article on the publisher's site
Body_ID: R016001
2. Angelin B, Eriksson M and Rudling M. Bile acids and lipoprotein metabolism: a renaissance for bile acids in the post-statin era? Curr Opin Lipidol 1999;10:269-74. Full articleGo to this article on the publisher's site
Body_ID: R016002
3. Repa JJ, Mangelsdorf DJ. The liver X receptor gene team: Potential new players in atherosclerosis. Nature 2002;8(11):1243-8. Full articleGo to this article on the publisher's site
Body_ID: R016003
4. Marcil M, Brooks-Wilson A, Clee SM, et al. Mutations in the ABC1 gene in familial HDL deficiency with defective cholesterol efflux. Lancet 1999;354:1341-6. Full articleGo to this article on the publisher's site
Body_ID: R016004
5. Janowski BA Willy PJ, Devi TR, Falck JR, Mangelsdorf DJ. An oxysterol signaling pathway mediated by the nuclear receptor LXRa. Nature 1996;383: 728-31. Full articleGo to this article on the publisher's site
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6. Thomas MK, Demay MB. Vitamin D deficiency and disorders of vitamin D metabolism. Endocrinology and Metabolism Clinics of North America 2000;29:611-627.
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7. White PC, Speiser PW. Congenital adrenal hyperplasia due to 21hydroxylase deficiency. Endocrine Reviews 2000;21:245-291. Full articleGo to this article on the publisher's site
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