Ganglioside Expression in Human Pancreatic Islets

Recent biochemical studies have shown that the cytoplasmic islet cell–antibody autoantigen has properties of a monosialoganglioside (G_M). To characterize islet glycolipids and ascertain whether islets express unique gangliosides, we determined the pattern of ganglioside expression in whole human pancreas and isolated human islets using high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC). The major gangliosides detected in glycolipid extracts of whole human pancreas were G_M3, G_D3 (disialoganglioside), and in a lesser amount, a G_D1a-comigrating ganglioside. In contrast to whole human pancreas, isolated human islets were found to predominantly express G_M3, an acidic glycolipid comigrating with G_M2, and a ganglioside with mobility between G_M2 and G_M1 by both HPLC and HPTLC. Quantitation of the major ganglioside UV peaks seen on HPLC gave the following results. In whole pancreas, G_M3 represented 66.7% of total gangliosides detected; an asialoglycolipid comigrating with G_M2, 2.0%; a ganglioside migrating between G_M2 and G_M1, 2.6%; G_D3, 22.6%; and a G_D1a-comigrating ganglioside, 6.1%. In isolated islets, these components were found at the following levels: G_M3, 14.9%; G_M2-comigrating glycolipid, 74.2%; a ganglioside migrating between G_M2 and G_M1, 9.8%; G_D3, 1.1%; and the G_D1a-comigrating ganglioside, not detectable.