Insulin restores fatty acid composition earlier in liver microsomes than erythrocyte membranes in streptozotocin-induced diabetic rats

Abstract

Alterations of fatty acid composition have been observed in a number of tissues in both experimental and human diabetes. Suppression of Δ6 desaturase in the liver, a key enzyme of fatty acid desaturation, has been reported to be responsible for these phenomena. We measured the fatty acid composition of the liver and the erythrocytes, and examined Δ6 desaturase activities to compare the effect of short-term insulin therapy on the tissues with and without Δ6 desaturase, ie., the liver and the erythrocytes using streptozotocin (STZ)-induced diabetic rats. Linoleic ( P < 0.05), palmitic ( P < 0.01) and docosahexaenoic (DHA) acid ( P < 0.01) were higher and arachidonic ( P < 0.01) and oleic acid ( P < 0.01) were lower in the liver microsomes of diabetic rats when compared to those in control rats. These alterations were partly reversed with insulin treatment. In the erythrocyte membrane, linoleic ( P < 0.01) and stearic acid ( P < 0.05) were higher, and palmitic ( P < 0.05), palmitoleic ( P < 0.01), and arachidonic acid ( P < 0.01) were lower in diabetic rats. In contrast to the case of the liver microsomes, however, these alterations were persistently observed after 48 h of insulin treatment. The activities of Δ6 desaturase in diabetic rats were 68% of those of controls ( P < 0.05), and increased to 119% of controls after insulin treatment. These results show that insulin restores the fatty acid composition earlier in the liver microsome than in the erythrocyte membrane in STZ-induced diabetic rats. The erythrocyte membrane would not be suitable for the investigation dealing with rapid changes of fatty acid composition.