Sterol metabolism

M. C. Carey, in Enterohepatic Circulation of Bile Acids and Sterol Metabolism, G. Paumgartner, ed., MTP Press, Lancaster, Boston, 1984. 

Kishida, T., Kostetskii, I., Zhang, Z. et al. 2004. Targeted mutation of the MLN64 START domain causes only modest alterations in cellular sterol metabolism. J. Biol. Chem., 279( 18) 19276—19285. 

Many plants contain estrogenic compounds. Estrone (Fig. 11.11) is found in seeds of date palms, pomegranates, and apples, and estriol in willow. These may be merely by-products of sterol metabolism, or serve a particular function. Harborne (1993) proposed that plants synthesize steroid hormones to deter feeding by mammals. Estrogenic compounds in plants are thought to upset the delicate hormone balance of mammals. 

Smith LL, Gouron RE, Sterol metabolism. VI. Detection of 5P-cholestan-3P-ol... 

PO007 Gelissen, C., B. Brodie, and M. A. Eastwood. Effect of Plantago ovata (psyllium) husk and seeds on sterol metabolism studies in normal and ileostomy subjects, Amer J Clin Nutr 1994 59(2) 395-400. 

Beach DH, Holz GGJ, Singh BN, Lindmark DG (1990) Fatty acid and sterol metabolism of cultured Trichomonas vaginalis and Tritrichomonas foetus. Mol Biochem Parasitol 38 175-190... 

Smith LL, Teng JI, Kulig MJ, Hill FL. Sterol metabolism. XXIII. Cholesterol oxidation by radiation-induced processes. J Org Chem 1973 38 1763-1765. 

Kokke, W. C. M. C., Fenical, W., Bohlin, L., and Djerassi, C., Sterol synthesis by cultured zooxanthellae implications concerning sterol metabolism in the host-symbiont association in Caribbean gorgonians, Comp. Biochem. Physiol., 68B, 281, 1981. 

Lu TT, Repa JJ, Mangelsdorf DJ. Orphan nuclear receptors as eLiXiRs and FiXeRs of sterol metabolism. J Biol Chem 2001 276 37735-37738. 

Ridgway, N.D., Byers, D.M., Cook, H.W., Storey, M.K. 1999. Integration of phospholipids and sterol metabolism in mammalian cells. Prog. Lipid Res. 38, 337-360. 

He discovered vitamin K and its anticoagulant effects while studying the sterol metabolism of chicks in Copenhagen and was awarded the Nobel Prize in physiology or medicine in 1943 for this work. 

Silver, P.M., Oliver, B.G., and White, TC. (2004) Role of Candida albicans transcription factor Upc2p in drug resistance and sterol metabolism. Eukaryotic Cell, 3, 1391-1397. 

In addition, analysis of hormone levels in serum samples of white sucker Catostomus commersoni) in Lake Superior have been used to complement measurements of physiological response significant differences in the levels of testosterone and estradiol in females, and of testosterone levels in males have been associated with pollution by bleachery effluents (Munkittrick et al. 1991). It has been observed that feral fish captured from areas exposed to established contamination by PAHs, PCBs, and mercury did not exhibit the increased levels of hydrocortisone normally resulting from capture (Hontela et al. 1992). These results were interpreted as showing the adverse effect on sterol metabolism in fish chronically exposed to such pollutants. Collectively, such data draw attention to the subtler effects of exposure to xenobiotics. 

Trigg, P. I. (1968b). Sterol metabolism of Plasmodium knowlesi in vitro. Ann. Trop. Med. Parasitol. 62, 481-487. 

Hepatocytes show even more complicated pathways of CE metabohsm than macrophages do. As discussed elsewhere (see Chapter 2), they play a key role in sterol metabolism because they possess receptors that can bind and mediate the internalization of chylomicron remnants [99], VLDL remnants [99], LDL [99], and HDL [99,119]. In addition, they sa rete HDL and VLDL into the plasma, and in some species the VLDL can contain appreciable amounts of CE [120]. Hepatocytes also secrete LCAT into the plasma and thus control the formation of CE by this enzyme [121]. Finally, they convert UC into bile acids and secrete both UC and bile acids into the bile. 

Important elements of sterol metabolism can also be used to elucidate where in the cell a particular precursor has moved [7]. The arrival of cholesteryl esters within lysosomes is revealed by cleavage of the fatty acid to yield free cholesterol. The subsequent transport of cholesterol to the ER can be monitored by the action of acyl-CoA cholesterol acyltrans-ferase (Chapter 14) that results in the formation of new molecular species of cholesteryl esters. In addition, sphingomyelinase treatment of the cell surface induces cholesterol movement from the plasma membrane to the ER where its arrival can likewise be monitored by the action of acyl-CoA cholesterol acyltransferase. Import of cholesterol into mitochondria (usually restricted to steroidogenic cells) can be followed by side-chain cleavage reactions that produce pregnenolone [8]. Movement of pregnenolone out of mitochondria can be followed by oxidations at positions 3, 17, and 21, which occur in the ER. 

Kelley, R.I., L.E. Kratz, R.L. Glaser, M.L, Netzloff, L.M. Wolf, and E.W. Jabs (2002). Abnormal sterol metabolism in a patient with Antley-Bixler syndrome and ambiguous genitalia. Am. J. Med. Genet. 110, 95-102. 

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