7-Dehydrocholesterol

7-dehydro Cholesterol (7-DHC) is an immediate precursor of cholesterol.¹ It is reduced to cholesterol by the enzyme 3β-hydroxysterol-Δ⁷-reductase (DHCR7) in the last step of cholesterol biosynthesis. 7-DHC accumulates in Smith-Lemli-Opitz syndrome (SLOS), a disorder characterized by a mutation in the DHCR7 gene and decreased cholesterol levels in bodily tissues and fluids, as well as microcephaly, intellectual disability, and distinctive dysmorphic features.^1,2 It is highly susceptible to free radical oxidation, giving rise to several oxysterols that may be involved in the pathogenesis of SLOS.¹ 7-DHC levels are increased in brain, liver, and serum in a rat model of SLOS induced by the DHCR7 inhibitor AY 9944 .¹ 7-DHC is a provitamin that is converted to vitamin D₃ by ultraviolet-B (UVB) light in a human skin equivalent system and in isolated human skin samples.^3,4

1.Xu, L., Liu, W., Sheflin, L.G., et al.Novel oxysterols observed in tissues and fluids of AY9944-treated rats: A model for Smith-Lemli-Opitz syndromeJ. Lipid Res.521810-1820(2011) 2.Xu, G., Salen, G., Shefer, S., et al.Reproducing abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome by inhibiting the conversion of 7-dehydrocholesterol to cholesterol in ratsJ. Clin. Invest.95(1)76-81(1995) 3.Lehmann, B., Genehr, T., Knuschke, P., et al.UVB-induced conversion of 7-dehydrocholesterol to 1α,25-dihydroxyvitamin D3 in an in vitro human skin equivalent modelJ. Invest. Dermatol.117(5)1179-1185(2001) 4.Chen, T.C., Chimeh, F., Lu, Z., et al.Factors that influence the cutaneous synthesis and dietary sources of vitamin DArch. Biochem. Biophys.460(2)213-217(2007)