CHARACTERIZATION AND CHANGES OF GLYCOSPHINGOLIPIDS IN THE AORTA OF THE WATANABE HEREDITABLE HYPERLIPIDEMIC RABBIT

Characterization and elucidation of the changes of glycosphingolipids in the aorta along with the progression of atherosclerosis were performed in the Watanabe hereditable hyperlipidemic (WHHL) rabbit, an animal model for human familial hypercholesterolemia, as compared with in the normal rabbit. Neutral glycosphingolipids in aortae of both normal and WHHL rabbits were composed of glucosylceramide, galactosylceramide, lactosylceramide, globotriaosylceramide, globotetraosylceramide, and galactosylneolactotetraosylceramide. The total amount of neutral glycosphingolipids in the aorta of the WHHL rabbit (557 nmol/g tissue) was increased about 5-fold compared to the normal level (107 nmol/g tissue). Prominent increases were observed in glucosylceramide (13-fold the normal level) and lactosylceramide (12-fold the normal level). The amount of total gangliosides in the aorta of the WHHL rabbit (207-mu-g NeuAc/g tissue) was markedly increased, being about 12-fold the normal level (17-mu-g NeuAc/g tissue). GM3 ganglioside was increased about 11-fold compared to normal. GD3 ganglioside, which was almost undetectable in normal aorta, also showed a marked increase in that of the WHHL rabbit (51.7-mu-g NeuAc/g tissue). Sulfatide, which was absent in the aorta of the normal rabbit, was markedly accumulated in that of the WHHL rabbit (280 nmol/g tissue). The fatty acid composition of neutral glycosphingolipids of WHHL rabbit was found to include a higher amount of C23:0, which is the major fatty acid of glycolipids in serum lipoproteins. Gangliosides in the aorta of the WHHL rabbit contained more C16:0 than in the normal rabbit. Sphingosine of sulfatide in the aorta of the WHHL rabbit was composed of sphingenine (86%), sphinganine (9%), 4-D-hydroxysphinganine (4%), and 4-D-hydroxyeicosasphinganine (less than 1%). The results of fatty acid analysis of glycosphingolipids in the aorta of WHHL rabbit suggested that the various glycosphingolipids mostly derived from serum lipoproteins were accumulated in the aorta of the WHHL rabbit along with the progression of atherosclerosis, and that most of these glycolipids were hydrolyzed into less polar glycolipids such as glucosylceramide or lactosylceramide. On the other hand, the moderate increases in globotriaosylceramide, globotetraosylceramide, and galactosylneolactotetraosylceramide, which are ordinary constituents of the normal aorta, indicated the marked intimal thickening of the aorta of the WHHL rabbit. It is also suggested that GM3 and GD3 gangliosides were derived not only from sera but also from new-type cell populations, such as foam cells or macrophages in the atherosclerotic lesions, because the fatty acids of these gangliosides included more palmitic acid than those of either serum lipoproteins or the normal aorta. The most interesting finding was that the occurrence of sulfatide and GD3 ganglioside in the aorta of the WHHL rabbit could be a useful indicator of the degree of progression of atherosclerosis, since these glycosphingolipids were hardly detected in the normal aorta.