Parenteral lipids impair pneumococcal elimination by human neutrophils.
BACKGROUND
Lipid-induced modulation of phagocyte function seems to contribute to increased susceptibility to infections in patients on parenteral nutrition, and an increased risk for development of pneumonia has been observed in this group. The role of various structurally different lipid emulsions, however, remains unclear. In this study, we therefore assessed phagocyte function, as the capacity of neutrophils to eliminate Streptococcus pneumoniae (i.e. combined result of phagocytosis and killing), in the presence of these lipids.


METHODS
Neutrophils from six healthy volunteers were incubated for 1 h in emulsions (5 mmol L(-1)) derived from soybean- (LCT), fish- (VLCT), olive- (LCT-MUFA), mixed soybean/coconut oils (LCT/MCTs) or structured lipids (SL). After opsonization of the pneumococci (strain OREP-4) by human immunoglobulins, bacteria and neutrophils were incubated in the presence of complement. Next, pneumococcal elimination was evaluated and expressed as the percentage of bacteria eliminated relative to the initial bacterial numbers in neutrophil-free samples.


RESULTS
Neutrophils that were not exposed to lipids showed a pneumococcal elimination capacity of 75 +/- 3% (mean +/- SD). This significantly decreased after exposure to LCT-MUFA (70 +/- 6%), VLCT (67 +/- 2%), SL (63 +/- 9%), LCT (66 +/- 10%) and LCT/MCT (47 +/- 15%).


CONCLUSIONS
These data demonstrate that parenteral lipids impair the microbial elimination capacity of neutrophils in a structure-dependent manner. In accordance with our previously reported in vitro effect on a range of phagocyte functions, LCT/MCT is by far the most potent in this respect.
Versleijen
Michelle W
MW
Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands.
Roelofs
Hennie M
HM
te Morsche
Rene H
RH
Simonetti
Elles R
ER
Hermans
Peter W
PW
Wanten
Geert J
GJ
D000328:Adult; D002478:Cells, Cultured; D015169:Colony Count, Microbial; D005260:Female; D005395:Fish Oils; D006801:Humans; D008055:Lipids / Q000494:pharmacology*; D008297:Male; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D010587:Phagocytosis / Q000187:drug effects*; D010936:Plant Extracts; D013296:Streptococcus pneumoniae / Q000502:physiology*; D055815:Young Adult
D005395:Fish Oils; D008055:Lipids; D010936:Plant Extracts