Background; The Smith-Lemli-Opitz Syndrome (frequency ca 1:20,000) is a major public health problem which is described by a constellation of severe birth defects, including profound mental retardation and severe failure to thrive heretofore diagnosed only from its characteristic facies and limb and organ defects. We have recently reported, for the first time, a major biochemical defect in the syndrome. In 28 children plasma cholesterol levels (4 to 132 mg/dl) are below the fifth percentile for age matched controls while concentrations (6 to 61 mg/dl) of the cholesterol precursor 7-dehydrocholesterol (cholest-5,7-dien-3beta-ol) are elevated 2500 to 6000- fold above normal. Although not detected in controls, 7-dehydrocholesterol is also found in high concentrations in all tissues as well as in cultured fibroblasts. Abnormally low plasma cholesterol concentrations combined with high levels of 7-dehydrocholesterol demonstrate major block in cholesterol biosynthesis at the step in which the C-7,8 double bond of 7- dehydrocholesterol is reduced to form cholesterol. This may be sufficient to cause cholesterol deprivation in the embryo and fetus and prevent its proper development while the incorporation of 7-dehydrocholesterol in cells is likely to interfere with proper membrane function. We have also affected a prenatal diagnosis in two women by detecting elevated 7- dehydrocholesterol in amniotic fluid. An isotope incorporation assay in fibroblasts suggest that a test for carriers might be possible. Planned Studies: Our goals are to further define the biochemical defect in the syndrome by measurements of tissue lipids, by carrying out in vitro measurements of appropriate enzymes in the cholesterol biosynthetic pathway (3beta-hydroxy-delta 5.7-steroid delta7--reductase and HMG-CoA reductase) in affected, carrier and control fibroblasts cultured under various conditions and to examine cellular function and membrane properties under conditions of reduced C-7 reductase activity. An animal model of the disease is being developed and has already been used to plan and test treatment strategies and to further study the biochemistry of the disease. Four children have been placed on controlled high cholesterol diets (replacement therapy). As a results, their plasma cholesterol levels appeared to increase and they seem to progress a little more rapidly. Finally a collaborative effort is being planned to purify the C-7 reductase enzyme, sequence it and clone the cDNA. Eventually, it is hoped that an efficient test for carriers will be developed.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD031932-03
Application #
2403400
Study Section
Metabolism Study Section (MET)
Project Start
1995-05-01
Project End
1998-04-30
Budget Start
1997-05-01
Budget End
1998-04-30
Support Year
3
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of Medicine & Dentistry of NJ
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
605799469
City
Newark
State
NJ
Country
United States
Zip Code
07107
Honda, A; Salen, G; Matsuzaki, Y et al. (2001) Differences in hepatic levels of intermediates in bile acid biosynthesis between Cyp27(-/-) mice and CTX. J Lipid Res 42:291-300
Honda, A; Salen, G; Matsuzaki, Y et al. (2001) Side chain hydroxylations in bile acid biosynthesis catalyzed by CYP3A are markedly up-regulated in Cyp27-/- mice but not in cerebrotendinous xanthomatosis. J Biol Chem 276:34579-85
Honda, M; Tint, G S; Honda, A et al. (2000) Regulation of cholesterol biosynthetic pathway in patients with the Smith-Lemli-Opitz syndrome. J Inherit Metab Dis 23:464-74
Honda, A; Salen, G; Shefer, S et al. (2000) Regulation of 25- and 27-hydroxylation side chain cleavage pathways for cholic acid biosynthesis in humans, rabbits, and mice. Assay of enzyme activities by high-resolution gas chromatography;-mass spectrometry. J Lipid Res 41:442-51
Honda, A; Salen, G; Honda, M et al. (2000) 3-Hydroxy-3-methylglutaryl-coenzyme A reductase activity is inhibited by cholesterol and up-regulated by sitosterol in sitosterolemic fibroblasts. J Lab Clin Med 135:174-9
Honda, A; Salen, G; Shefer, S et al. (1999) Bile acid synthesis in the Smith-Lemli-Opitz syndrome: effects of dehydrocholesterols on cholesterol 7alpha-hydroxylase and 27-hydroxylase activities in rat liver. J Lipid Res 40:1520-8
Nguyen, L B; Shefer, S; Salen, G et al. (1998) Competitive inhibition of hepatic sterol 27-hydroxylase by sitosterol: decreased activity in sitosterolemia. Proc Assoc Am Physicians 110:32-9
Honda, A; Salen, G; Nguyen, L B et al. (1998) Regulation of early cholesterol biosynthesis in rat liver: effects of sterols, bile acids, lovastatin, and BM 15.766 on 3-hydroxy-3-methylglutaryl coenzyme A synthase and acetoacetyl coenzyme A thiolase activities. Hepatology 27:154-9
Honda, A; Salen, G; Nguyen, L B et al. (1998) Down-regulation of cholesterol biosynthesis in sitosterolemia: diminished activities of acetoacetyl-CoA thiolase, 3-hydroxy-3-methylglutaryl-CoA synthase, reductase, squalene synthase, and 7-dehydrocholesterol delta7-reductase in liver and mononuclear leu J Lipid Res 39:44-50
Honda, M; Tint, G S; Shefer, S et al. (1998) Accurate detection of Smith-Lemli-Opitz syndrome carriers by measurement of the rate of reduction of the ergosterol C-7 double bond in cultured skin fibroblasts. J Inherit Metab Dis 21:761-8

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