Establishment of Oxysterol Biomarkers in a Mouse Model of Smith-Lemli-Opitz Syndrome and the Effect of Antioxidant Supplementation

Abstract

Establishment of Oxysterol Biomarkers in a Mouse Model of Smith-Lemli-Opitz Syndrome and the Effect of Antioxidant Supplementation Libin Xu, Zeljka Korade, Karoly Mirnics, and Ned A. Porter Vanderbilt University Levels of 7-dehydrocholesterol (7-DHC) are greatly elevated in patients with Smith-Lemli-Opitz syndrome (SLOS), which is caused by mutations in the gene encoding the last enzyme in cholesterol biosynthesis, 7-DHC reductase (DHCR7). SLOS is characterized by multiple congenital malformation and developmental disabilities (including autism). 7-DHC was found to be the most reactive lipid molecule toward free radical peroxidation, leading to over a dozen biologically active oxidation products (i.e., oxysterols). Here we demonstrated that in Neuro2a cells and human fibroblasts, the primary 7-DHC-derived oxysterols were readily metabolized to more stable oxysterols, including 3 ,5 -dihydroxycholest-7-en-6-one, 3 ,5 ,9 -trihydroxycholest-7-en-6-one, and 3 ,5 -dihydroxy-cholesta7,9(11)-dien-6-one. These three novel oxysterol biomarkers were also successfully identified in brain and liver tissues of a Dhcr7null mouse model of SLOS by HPLC-MS. In an attempt to develop novel therapy to SLOS, we fed Dhcr7-heterozygous mice with diets that are enriched with vitamin-E (400 IU vitamin-E/kg diet) during pregnancy. We found that levels of the oxysterol biomarkers in both brain and liver tissues of the newborn Dhcr7null pups were significantly lower in the group on high antioxidant diet than those on low antioxidant diet, indicating suppression of 7-DHC peroxidation by antioxidants in vivo during embryonic stage. This study points to antioxidant supplementation as a potential therapy to SLOS.