Effects of chemically defined structured lipid emulsions on reticuloendothelial system function and morphology of liver and lung in a continuous low-dose endotoxin rat model.

Abstract

This study was undertaken to determine the effect of chemically defined structured lipids on nonspecific host defense and on histologic patterns of liver and lungs compared with a physical mixture of long-chain triglycerides and medium-chain triglycerides in a continuous low-dose endotoxin rat model. Forty male Sprague-Dawley rats, divided into four feeding groups (structured lipids, structured lipids+endotoxin, physical mixture, physical mixture+endotoxin), received total parenteral nutrition for 48 hours. During the first part of the study, 24 animals were given an injection of live Escherichia coli labeled with radioactive iron (59Fe) to investigate the function of the reticuloendothelial system. During the second part of the study, the liver and lungs of 16 animals were histologically examined using light and electron microscopy. Despite the similar values in the control groups, the animals receiving structured lipids+endotoxin sequestered a significantly greater percentage of bacteria in the liver and spleen (p < or = .01) and a significantly lesser percentage in the lung (p < or = .05) compared with the animals given physical mixture+endotoxin as part of their diet. Moreover, rats in the physical mixture+endotoxin group showed a microscopically evaluated higher fatty infiltration in the liver than did the structured lipids+endotoxin group. The results of this study indicate that chemically defined structured lipids reduce fatty infiltration of the liver compared with a physical mixture of the same compounds in an animal model of metabolic stress. They were accompanied by a better function of the reticuloendothelial system and a lesser bacterial sequestration in the lungs.