Changes of the human liver GM3 ganglioside molecular species during aging

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Abstract
Sialosyl-lactosylceramide, GM3, is the major ganglioside of human liver, where it constitutes more than 90% of the total lipid-bound sialic acid. When analyzed by thin-layer chromatography, human liver GM3 migrates as two main spots. They are representative of ganglioside molecular species which differ in the acyl moiety. The faster running spot is mainly composed of molecular species with non-hydroxylated C22-C24 acyl chains; the other contains mainly molecular species bearing non-hydroxylated C16-C18 and alpha-hydroxylated C16-C24 acyl chains. In this study the content of the two GM3 molecular species groups was investigated in 31 subjects ranging from 19 to 85 years of age. By thin-layer chromatography we observed that the group of molecular species containing non-hydroxylated C22-C24 acyl chains, decreased linearly with subject age, while that of non-hydroxylated C16-C18 acyl chains and hydroxylated C16-C24 acyl chains increased linearly. Fast-atom-bombardment mass spectrometry performed on seven samples from subjects ranging from 21 to 78 years of age demonstrated that the age-dependent increase of the lower spot is caused by an increase in the hydroxylated fatty acid form of GM3, the content of non-hydroxylated C16-C18 fatty acid species remaining constant with age.