Feedback inhibition of the cholesterol biosynthetic pathway in patients with Smith-Lemli-Opitz syndrome as demonstrated by urinary mevalonate excretion

Anuradha Pappu, Robert D. Steiner, Sonja L. Connor, Donna P. Flavell, Don S. Lin, Lauren Hatcher, D. Roger Illingworth, William E. Connor

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Smith-Lemli-Opitz syndrome (SLOS) is a genetic disorder characterized by low plasma cholesterol and high 7-dehydrocholesterol (7-DHC). Synthesis of cholesterol and 7-DHC and its metabolites is regulated by HMG-CoA reductase, whose activity can be measured by 24-h excretion of its product mevalonate. We devised a simple, non-invasive method for collecting 24-h urine in our subjects. With a background of a very low cholesterol diet, mean mevalonate excretion did not differ between controls and SLOS children, indicating that SLOS subjects have normal HMG-CoA reductase activity. In a short term feeding study, the effects of a high cholesterol diet in SLOS subjects include a significant 55% increase in plasma cholesterol levels and 39% decrease in mevalonate excretion and no change in plasma 7-DHC levels. However, in four SLOS subjects, fed a high cholesterol diet for 2-3 years, plasma cholesterol levels continued to increase, urinary mevalonate excretion remained low and total 7-DHC decreased significantly, likely from decreased total sterol synthesis. Thus, in SLOS subjects, HMG-CoA reductase activity was normal and was subject to normal cholesterol induced feedback inhibition. However, total sterol synthesis in SLOS may still be decreased because of increased diversion of mevalonate into the shunt pathway away from sterol synthesis.

Original languageEnglish (US)
Pages (from-to)1661-1669
Number of pages9
JournalJournal of Lipid Research
Volume43
Issue number10
DOIs
Publication statusPublished - Oct 1 2002

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Keywords

  • 24-h urine
  • 3-hydroxy-3-methylglutaryl-coenzyme A reductase
  • 3-methyl glutaconic acid
  • 7-dehydrocholesterol
  • 8-dehydrocholesterol
  • Mevalonate shunt pathway
  • Sterols

ASJC Scopus subject areas

  • Endocrinology

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