Total Parenteral Nutrition Decreases Liver Oxidative Metabolism and Antioxidant Defenses in Healthy Rats: Comparative Effect of Dietary Olive and Soybean Oil

BACKGROUND Total parenteral nutrition (TPN) is used for critically ill patients undergoing surgery, after trauma, or during disease conditions that favor oxidative stress. We studied the effect of TPN on liver oxidative metabolism and antioxidant defenses in rats, and we compared the effect of soybean oil- and olive oil-based diets. METHODS Seven-week-old rats (n = 28) were divided into four groups. Two experimental groups received a TPN solution containing soybean oil (TPN-S) or a mixture of olive/soybean oil, 80/20 (TPN-O), IV for 6 days. Orally fed animals received a solid diet including soybean oil (Oral-S) or olive/soybean oil, 80/20 (Oral-O). The following parameters were measured: DL-alpha-tocopherol, vitamin A, malondialdehyde and thiobarbituric acid reactive substances (MDA-TBARS), and total radical-trapping antioxidant parameter (TRAP) in serum; DL-alpha-tocopherol, vitamin A, glutathione (GSH), and catalase (Cat) activity in liver homogenate; fatty acids from phospholipid, cytochrome P-450 content, NADPH-cytochrome c2 reductase activity in liver microsomes; superoxide dismutase (SOD), glutathione peroxidase (Gpx), glutathione reductase (GR), glutathione transferase (GST), and glucose-6-phosphate dehydrogenase (G6PD) in liver cytosol. RESULTS The soybean or olive oil diets modified the liver microsomal fatty acid phospholipid composition, but the unsaturation index remained unchanged. TPN specifically increased the saturation of the membrane. The cytochrome P-450 level and the NADPH-cytochrome c2 reductase, SOD, Gpx, Cat, and GST activities were unchanged by soybean oil or olive oil diet but decreased receiving TPN. CONCLUSIONS In rats, TPN decreased the liver oxidative metabolism and enzymatic antioxidant defenses. This may be related to saturation of the liver microsomal fatty acids.