Effects of Parenterally Infused Fish Oil on Lipid Metabolism in Total Parenteral Nutrition Wei Jao Chen, MD Department of Surgery, College of Medicine, National Taiwan University, Taipei, Taiwan Although many studies have been conducted to examine the effect of dietary n-3 fatty acids (FAs) on plasma lipids and lipoproteins, the effects of n-3 FAs on lipid metabolism in total parenteral nutrition (TPN) remains unclear. TPN differs from oral feeding not only in the route of administration but also in the composition of nutrients, the influences of dietary n-3 FAs on lipid metabolism, therefore, may not apply to TPN patients. During the last several years, we have carried out a series of studies in rats receiving TPN to see the effect of n-3 FAs on lipid metabolism. The effects of fat emulsions prepared with fish oil (n-3 FAs rich) and safflower oil (n-6 FAs rich) on lipid metabolism in TPN rats was compared and found that 1) compared with safflower oil, TPN with fish oil emulsion does not cause hyperlipidemia nor induce hepatic steatosis in normal rats, 2) fish oil infusion ameliorated the severity of hepatic steatosis induced by high fat diet, 3) fish oil infusion resulted in a lower plasma prostacyclin I2 and thromboxane A2 concentrations than did safflower oil, suggesting that TPN with fish oil may be beneficial in preventing platelet aggregation. 4) lipid peroxidation products were not higher and antioxidanat enzyme activities were lower in the fish oil group than in the safflower oil group, indicating that lipid peroxidation products were less accumulated in the liver in the fish oil group. We also examined the effects of fish oil infusion on diseases with abnormal lipid metabolism and inflammatory reaction, such as diabetes mellitus and sepsis. The results showed that compared with soybean oil, diabetic rats with fish oil did not lead to lower plasma levels of triglyceride and free fatty acids, also no differences in plasma glucose and insulin levels between the 2 groups were observed. As for the septic condition, parenterally administered fish oil had no beneficial effect in lowering inflammatory-related mediators in the location of injurious stimulus. However, catabolic reaction in septic rats preinfused with fish oil is less obvious than those preinfused with safflower oil. Since the effects of parenterally infused fish oil on diseases are not totally comparable to those of dietary supplementation, the exact pharmacologic effect of administration of fish oil to TPN patients complicated with diseases required further exploration. From "The 6th Congress of the PENSA Program & Abstract" Taipei, Taiwan, November 9-12, 2000 : Page 2