Functional alterations of human neutrophils by medium-chain triglyceride emulsions: evaluation of phagocytosis, bacterial killing, and oxidative activity

Abstract

Medium-chain triglyceride (MCT) and long-chain triglyceride (LCT) emulsions currently used in nutritional therapy were evaluated for their in vitro effect on neutrophil oxidative metabolism, phagocytosis, and bacterial killing activities. Neutrophils from healthy adult male volunteers were assessed after blood incubation with commercially available fat emulsions containing LCT, MCT, or a mixture of 50% MCT and 50% LCT at a final triglyceride concentration of 20 mg/ml. It was observed that MCT-containing emulsions stimulated nitroblue tetrazolium (NBT) dye reduction by neutrophils as determined by a cytochemical NBT test performed directly on whole blood. This effect was dose dependent. However, after lipid removal by cell washing, the MCT-treated neutrophils showed decreased production of hydrogen peroxide (H2O2) and NBT reduction in response to bacterial lipopolysaccharide or phorbol myristate acetate stimuli as well as impaired phagocytosis and killing of Staphylococcus aureus. In contrast, the LCT emulsion did not alter any of the neutrophil functions evaluated. The present data suggest that MCTs elicit the oxidative metabolism of neutrophils, probably by phagocytosis of fat particles and, depending on the lipid concentration, this effect may not be reversible, leading to impairment of the cellular response to subsequent membrane stimuli.

Studies on Polymorphonuclear Leukocyte Bactericidal Function III: The Role of Extracellular Matrix Proteins

“…6, bottom). receptors is supported by previous studies demonstrating the need for adequate opsonic receptor expression to support bactericidal and fungicidal activity in vitro DISCUSSION [20,21]. Taken together, our results demonstrate a complex The process of bacterial phagocytosis and killing is a key component of the host immune response.…”

Effect of fatty acids on leukocyte function

“…The presence of medium-chain fatty acidcontaining phospholipids in neutrophil culture increases the production of reactive oxygen species, whereas in vivo treatment with these fatty acids reduces hydrogen peroxide production, nitroblue tetrazolium reduction, and impairs phagocytosis and Staphylococcus aureus killing (15).…”

“…Macrophages and neutrophils -Fatty acid-fed animals show decreased cell activation, production of reactive oxygen species (ROS), phagocytosis and antigen presentation (by macrophages) (5,(13)(14)(15)19,21,28). -The addition of fatty acids to the cell medium increases ROS formation and phagocytosis (12,15,20).…”

“…-The addition of fatty acids to the cell medium increases ROS formation and phagocytosis (12,15,20). -Omega-3-rich diets decrease IL-1beta, IL-6 and IL-8 production, whereas omega-6-rich diets increase the production of these cytokines (6,(22)(23)(24)(25)27).…”

Assessment of Oxidative Metabolism

“…For example, the Nitroblutetrasolium precipitation reduction test is a crude method that evaluates high levels of oxidative activity and it requires large sample volumes (6).…”