DIABETES-INDUCED AND AGE-RELATED-CHANGES IN FATTY-ACID PROPORTIONS OFPLASMA-LIPIDS IN RATS

Diabetes-induced and age-related proportional changes in plasma fatty acids of triglycerides (TG), phospholipids (PL), and cholesteryl ester s (CE) were investigated using streptozotocin-induced diabetic and con trol rats. Among n-6 fatty acids from diabetic rat plasma, increased p roportions of 18:2n-6 and 20:3n-6 in all three lipid classes and of 18 :3n-6 in PL at 1-3 months old and in TG at 3-5 months old were observe d. The proportions of 20:4n-6 decreased in both PL and CE, but were un changed in diabetic TG. Among the n-3 fatty acids, in the early stage, diabetes caused increases in the proportions of 18:3n-3 in PL and CE and of 20:5n-3 and 22:6n-3 in TG, while 22:5n-3 was decreased later in the disease course. These results suggest reduced Delta 5-desaturase activities on 20:3n-6 but not on 20:4n-3, while Delta 6-desaturase act ivity on 18:2n-6 was essentially unaffected. Furthermore, the reductio n in Delta 9-desaturase activity in diabetic rats may well explain the decreases in the proportions of 16:1n-7 and 18:1n-7. However, the pro portion of 18:1n-9, another product of Delta 9-desaturase, was signifi cantly increased in CE and PL as compared to the controls. Thus, there was a discrepancy between our results and those of earlier studies wi th respect to the n-9, n-6, and n-3 fatty acid proportions of plasma l ipids in diabetic rats. We also investigated age-related changes in th e proportions of plasma fatty acids. Although rather small, age-relate d changes were evident in both diabetic and control rats.