Effect of gangliosides on diacylglycerol content and molecular species in nerve from diabetic rats

The effects of ganglioside treatment on 1,2-diacylglycerol content and on molecular species in 1,2-diacylglycerol, phosphatidic acid and total diacylglycerolipids, as well as Na⁺,K⁺-ATPase activity, were examined in sciatic nerves from streptozotocin-in-duced diabetic rats. Beginning 2 weeks after induction of diabetes, animals were administered mixed bovine brain gangliosides, AGF₁, an inner ester derivative of this mixture, or saline for 5 weeks. The levels of 1,2-diacylglycerol and arachidonyl-containing molecular species in age-matched non-diabetic animals were not affected by ganglioside treatment. In nerves from saline-treated diabetic animals, 1,2-diacylglycerol levels were not reduced, but both Na⁺,K⁺-ATPase activity and all arachidonoyl-containing species except for 18:0/20:4 1, 2-diacylglycerol were significantly decreased. The content of 1,2-diacylglycerol was lowered by 23 and 16% in bovine brain ganglioside and AGF₁-treated diabetic animals, respectively, and the quantity of 18:0/20:4 1,2-diacylglycerol was also selectively reduced. Ganglioside administration did not affect the diminished levels of arachidonoyl-containing molecular species in 1,2-diacylglycerol, phosphatidic acid or diacylglycerolipids in nerve from diabetic rats. In the same nerves, bovine brain gangliosides partially and AGF₁ completely restored Na⁺,K⁺-ATPase activity. The results suggest that gangliosides depress the content of total 1,2-diacylglycerol and the quantity of 18:0/20:4 1,2-diacylglycerol, specifically, in diabetic nerve. The possible relationship between the corrective action of gangliosides on Na⁺,K⁺-ATPase activity and the effect of these substances on 1,2-diacylglycerol molecular species composition and metabolism is discussed.