With medium-chain triglycerides, higher and faster oxygen radical production by stimulated polymorphonuclear leukocytes occurs

Background: Parenteral lipid emulsions are suspected of suppressing the imm une function. However, study results are contradictory and mainly concern t he conventional long-chain triglyceride Emulsions, Methods: Polymorphonucle ar leukocytes were preincubated with parenteral lipid emulsions. The influe nce of the lipid emulsions on the production of oxygen radicals by these st imulated leukocytes was studied by measuring chemiluminescence. Three diffe rent parenteral lipid emulsions were tested: long-chain triglycerides, a ph ysical mixture of medium- and long-chain triglycerides, and structured trig lycerides. Structured triglycerides consist of triglycerides where the medi um- and long-chain fatty acids are attached to the same glycerol molecule. Results: Stimulated polymorphonuclear leukocytes preincubated with the phys ical mixture of medium- and long-chain triglycerides showed higher levels o f oxygen radicals (p <.005) and faster production of oxygen radicals (p <.0 05) compared with polymorphonuclear leukocytes preincubated with long-chain triglycerides or structured triglycerides. Additional studies indicated th at differences in results of various lipid emulsions were not caused by dif ferences in emulsifier. The overall production of oxygen radicals was signi ficantly lower after preincubation with the three lipid emulsions compared with controls without lipid emulsion. Conclusions: A physical mixture of me dium- and long-chain triglycerides induced faster production of oxygen radi cals, resulting in higher levels of oxygen radicals, compared with long-cha in triglycerides or structured triglycerides. This can be detrimental in ca ses where oxygen radicals play either a pathogenic role or a beneficial one , such as when rapid phagocytosis and killing of bacteria is needed. The ob served lower production of oxygen radicals by polymorphonuclear leukocytes in the presence of parenteral lipid emulsions may result in immunosuppressi on by these lipids.