Tocopherol isoforms in parenteral lipid emulsions and neutrophil activation

Background and Aims: Tocopherol is a lipid-soluble anti-oxidant that exists in several isoforms. Patients on total parenteral nutrition depend on lipid emulsions for their tocopherol intake. In the present study, we analysed the content of tocopherol isoforms in various lipid emulsions. We also tested the hypothesis that immune-modulating effects of lipid emulsions could be attributed to different concentrations of α-tocopherol (α-toc) or peroxidation products. Method: α-, β-, γ- and δ-toc were measured in emulsions containing long-chain triglycerides (LCT), mixed long- and medium-chain triglycerides (LCT/MCT), structured lipids (SL), olive oil (OO) or fish oil (FO). As a measure for cellular activation, neutrophil membrane adhesion markers were assessed after exposure to two LCT/MCT emulsions that differ only in α-toc content. Results: Various emulsions differed widely in tocopherol contents, especially with respect to the α- isoform. The latter isomer also was subject to considerable degradation despite adequate storage conditions. The previously observed activation of neutrophils by LCT/MCT was not influenced by the increased concentration of α-toc or the decreased concentration of lipid peroxidation products in a new LCT/MCT emulsion. Conclusions: Tocopherol supplementation by parenteral lipid emulsions strongly depends on the lipid source and the storage lifetime of the emulsion. The effects of LCT/MCT on the immune system are not modulated by α-toc or by lipid peroxidation products.