Abstract
We investigated lipid metabolism in cultured skin fibroblasts from SLS patients and normal controls. Intact SLS fibroblasts incubated in the presence of 14C-palmitate accumulated more radioactive hexadecanol (HD) than normal, whereas incorporation of radioactivity into other neutral lipids and phospholipids was unaltered. The rate of HD synthesis and its utilization for glycerol ether synthesis were normal in SLS cells. The intracellular half-life of radioactive HD loaded into SLS fibroblasts was 70 minutes compared to 15 minutes in normal cells. Oxidation of HD to fatty acid was decreased in intact SLS fibroblasts to 12-32% of normal. Total FAO activity, the enzyme catalyzing this reaction, in normal cells was 59.8 ± 14.8 pmol/min/mg protein (range 36.6-79.6, n=9) and 7.8 ± 3.8 pmol/min/mg (range 4.3-13.1, n=4) in SLS cells. FAO is partially inhibited by palmitoyl CoA. Palmitoyl CoA-inhibitable FAO activity was decreased in SLS fibroblasts to 1% of normal (normal: 32.4 ± 8.3 pmol/min/mg protein; SLS: 0.4 ± 0.7 pmol/min /mg). Fibroblasts from two SLS heterozygotes had intermediate levels (46%;48%) of FAO activity. FAO was normal in cells from patients with X-linked ichthyosis, multiple sulfatase deficiency and Refsum disease. These studies suggest that SLS is due to FAO deficiency.
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