Characterization and quantitative determination of gangliosides and neutral glycosphingolipids

The neutral and acidic glycolipids from the liver of an 1 1-year-old male were quantitatively isolated and characterized. The total concentration of gangliosides was also determined in samples from five other human livers. Lipid-bound sialic acid varied between 190-248 nmol/g with a mean value of 212 nmol/g. The major ganglioside was GM3, which represented 91.6% of the sialic acid. Besides GM3 and GMI, a wide variety of other minor monosialogangliosides were isolated. Gangliosides of the gangliotetraose series with up to four sialic acids were demonstrated in human liver for the first time. The composition of the ceramide portion of the gangliotetraose gangliosides was considerably different from that of the “visceral” gangliosides, G M ~ , GD3, and LM1 (sialosyl-lactoneotetraosylceramide), which suggests that these two groups of gangliosides are biosynthesized in two different pools. The concentration of the neutral glycolipids was approximately the same as that of the gangliosides. Lactosylceramide was the largest fraction, closely followed by galactosylceramide, glucosylceramide, and globotriaosylceramide. The ceramide composition of the neutral glycolipids resembled that of the “visceral” gangliosides, suggesting that they are metabolically related. 2-Hydroxy fatty acids were found in glucosyl-, galactosyl-, and lactosylceramides as well as in ganglioside G~3.-Nilsson, O., and L. Svennerholm. Characterization and quantitative determination of gangliosides and neutral glycosphingolipids in human liver. J . Lipid. Res. 1982. 23 327-334. Supplementary key words glucosylceramide galactosylceramide lactosylceramide globotriaosylceramide globotetraosylceramide normal fatty acids * 2-hydroxy fatty acids * sphingosine bases Our knowledge about the concentration and distribution of glycosphingolipids in human extraneural tissue is scanty (1, 2). T h e glycolipids in renal, splenic, and intestinal tissue have been the subject of a few studies (1, 2 ) , but the only comprehensive study of the liver glycolipids is the one published by Kwiterovich, Sloan, and Fredrickson in 1970 (3). This is remarkable since the liver is readily accessible to biopsy, which is useful in the diagnosis of inherited disorders of the glycolipid metabolism (4), and in assessment of the effect of enzymic replacement therapy (5, 6), and of the toxicity of certain drugs. Differentiation as well as malignant transformation of cells is accompanied by changes in the composition of the glycolipids in the cell membranes (7). In the light of the above observations, more accurate knowledge of the concentration of the glycosphingolipids in liver is necessary. During the last decade the methods for extracting and separating glycolipids have been improved (8, 9), and very sensitive chromatographic methods capable of measuring the concentrations of glycosphingolipids in even small biopsy specimens have been developed (10, 11). It was therefore decided to make a careful reinvestigation of the neutral and acidic glycolipids in liver tissue from young normal humans. T h e results could be used as reference values in the study of biopsy material from patients with metabolic disorders, and might at the same time shed some light on the possible function of the glycolipids as receptors, recognition substances, or adhesion molecules.