EFFECT OF DIETARY FISH-OIL SUPPLEMENTATION ON PEROXIDATION OF SERUM-LIPIDS IN PATIENTS WITH NON-INSULIN-DEPENDENT DIABETES-MELLITUS

Lipid peroxidation may be important in the development of cardiovascul ar disease, a common cause of mortality and morbidity in non-insulin d ependent diabetes mellitus (NIDDM). We assessed the degree of lipid pe roxidation by measuring plasma malondialdehyde, as thiobarbituric acid reacting substances (TBARS), in 23 non-insulin dependent diabetic pat ients. Plasma levels of lipid standardised alpha-tocopherol (vitamin E ), lipid content of whole plasma and lipoprotein fractions, glycosylat ed haemoglobin, glycosylated low density lipoprotein (LDL) and fasting blood glucose were also measured. On completion of the baseline studi es patients randomly received either fish oil or matching olive oil ca psules in a double blind crossover fashion for 6 weeks followed by a 6 week washout period and a final 6 week treatment phase. Studies, iden tical to the initial baseline studies, were performed at the end of th e active treatment periods at 6 and 18 weeks. Treatment with olive oil did not change levels of TBARS, vitamin E or indices of glycaemic con trol compared with baseline. Total cholesterol and triglyceride (TG) c ontent of plasma and lipoprotein fractions were not significantly alte red. Treatment with fish oil resulted in elevation of TBARS (P<0.001) and reduction of vitamin E (P<0.01) compared with baseline and olive o il treatment. Plasma cholesterol was unchanged. A reduction in plasma TG compared with baseline occurred but failed to reach significance (P =0.07). Changes in apo B containing lipoproteins induced by fish oil f ailed to reach significance. No significant changes were observed in t he concentration or composition of high density lipoprotein (HDL). Fis h oil treatment showed no change in glycaemic control as assessed by g lycosylated haemoglobin and LDL although a rise in fasting blood gluco se just failed to reach significance (P=0.06). Lipid peroxidation in N IDDM can be exacerbated by dietary fish oil. This potentially adverse reaction may limit the therapeutic use of fish oils in such patients.