Suppressive effect of a selective increase in plasma linoleic acid concentration and intravascular lipolysis on peripheral T cell activation

Department of Gastroenterology and Hepatology
Radboud University Nijmegen Medical Centre
PO Box 9101
6500 HB Nijmegen
Netherlands
E-mail: g.wanten{at}mdl.umcn.nl

Dear Sir:

With interest we read in the Journal the findings of a recent study by Larbi et al (1), in which the authors reported on the suppressive effects on T cell activation and function, together with changes in the membrane properties of these cells, that are brought about by the intravenous administration of a soybean oil-based lipid emulsion (Intralipid 20%; Baxter, Mississauga, Canada). The authors concluded that these results should have serious implications for nutritional therapy in patients at high risk of septic complications.

We have several concerns with regard to the latter statement. First, the investigation by Larbi et al was performed in healthy subjects, and, therefore, their results cannot be extrapolated to patients with an inflammatory condition. Second, several reviews focused on immune modulation by parenteral lipids in general (2) and by soybean oil-based emulsions in particular (3) concluded that no clear picture exists, because of the very disparate outcomes of the studies reviewed. For instance, our group has consistently found that Intralipid, an emulsion that is rich in long-chain triacylglycerols, does not affect human neutrophil and mononuclear cell functions, including oxygen radical production, adhesion, chemotaxis, pathogen killing, and cytokine production (4-8). As in the study by Larbi et al, these observations were made in cells obtained from healthy volunteers and in studies with both in vitro and in vivo designs. It is important that, in our hands, Intralipid did not alter membrane fluidity, as measured by the same technique that Larbi et al used, or signal transduction of leukocytes (9, 10). In contrast, the administration of an emulsion containing medium-chain triacylglycerols in these investigations resulted in cell activation, altered cytokine responses, increased membrane fluidity, and attenuation of calcium signaling in neutrophils and mononuclear cells (4-10). In our opinion, these conflicting outcomes show that, at present, we do not fully comprehend the nature of the interaction of immune cells and parenteral lipids and the circumstances influencing that interaction.

ACKNOWLEDGMENTS

The author had no personal or financial conflict of interest with respect to the study of Larbi et al or the report on that study.

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