INSULIN RESTORES FATTY-ACID COMPOSITION EARLIER IN LIVER-MICROSOMES THAN ERYTHROCYTE-MEMBRANES IN STREPTOZOTOCIN-INDUCED DIABETIC RATS

Alterations of fatty acid composition have been observed in a number o f tissues in both experimental and human diabetes. Suppression of Delt a 6 desaturase in the liver, a key enzyme of fatty acid desaturation, has been reported to be responsible for these phenomena, We measured t he fatty acid composition of the liver and the erythrocytes, and exami ned Delta 6 desaturase activities to compare the effect of short-term insulin therapy on the tissues with and without Delta 6 desaturase, ie ., the liver and the erythrocytes using streptozotocin (STZ)-induced d iabetic rats. Linoleic (P < 0.05), palmitic (P < 0.01) and docosahexae noic (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 r ats when compared to those in control rats. These alterations were par tly reversed with insulin treatment. In the erythrocyte membrane, lino leic (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) we re lower in diabetic rats. In contrast to the case of the liver micros omes, however, these alterations were persistently observed after 48 h of insulin treatment. The activities of Delta 6 desaturase in diabeti c 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 tha n in the erythrocyte membrane in STZ-induced diabetic rats, The erythr ocyte membrane would not be suitable for the investigation dealing wit h rapid changes of fatty acid composition.