Saturated triglycerides and fatty acids activate neutrophils depending on carbon chain-length.

BACKGROUND: Unsaturated fatty acids are known as neutrophil activators. In the present study we investigated whether saturated triglycerides and fatty acids may also contribute to the previously observed activation of neutrophils by nutritional lipid emulsions. Furthermore we tested the hypothesis that carbon-chain length is of importance in this respect.
MATERIALS AND METHODS: Neutrophils (1 x 10(6) mL(-1)) were isolated from the blood of nine volunteers. Chemiluminescence was used to evaluate neutrophil activation, characterized by the production of oxygen radicals by neutrophils during incubation with 1 mmol L(-1) saturated fatty acid (6-20 carbon) or triglycerides (6-12 carbon fatty acid), dissolved in aqueous medium by preparing micelles with dipalmitoyl phosphatidylcholine (DPPC). Results were expressed as means +/- SEMs of the overall luminescence signal relative to the signal of cells incubated in medium.
RESULTS: Similar to a positive control, the polyunsaturated fatty acid arachidonic acid (C20 : 4), the triglycerides tricaproin (TC6 : 0), tricaprylin (TC8 : 0) and trilaurin (TC12 : 0) as well as the fatty acids lauric acid (C12 : 0), palmitic acid (C16 : 0), stearic acid (C18 : 0) and arachidic acid (C20 : 0) all induced oxygen radical production in neutrophils, while the medium-chain triglyceride tricaprin (TC10 : 0) and fatty acids caproic acid (C6 : 0), caprylic acid (C8 : 0) and capric acid (C10 : 0) exerted no clear effects, similar to negative controls (DPPC and glycerol).
CONCLUSIONS: Besides their (poly)-unsaturated counterparts, saturated triglycerides and fatty acids also activate neutrophils. Carbon chain-length is pivotal in the interaction of fatty acids and triglycerides and cells of the immune system.