Abstract
BackgroundOmega (n)-3 polyunsaturated fatty acids (PUFA) are converted to bioactive lipid components that are important mediators in metabolic and physiological pathways; however, which bioactive compounds are metabolically active, and their mechanisms of action are still not clear. We investigated using lipidomic techniques, the effects of diets high in n-3 PUFA on the fatty acid composition of various bioactive lipids in plasma and liver.Methodology and Principal FindingsFemale C57BL/6 mice were fed semi-purified diets (20% w/w fat) containing varying amounts of n-3 PUFA before mating, during gestation and lactation, and until weaning. Male offspring were continued on their mothers’ diets for 16 weeks. Hepatic and plasma lipids were extracted in the presence of non-naturally occurring internal standards, and tandem electrospray ionization mass spectrometry methods were used to measure the fatty acyl compositions. There was no significant difference in total concentrations of phospholipids in both groups. However, there was a significantly higher concentration of eicosapentaenoic acid containing phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and cholesteryl esters (CE) (p < 0.01) in the high n-3 PUFA group compared to the low n-3 PUFA group in both liver and plasma. Plasma and liver from the high n-3 PUFA group also had a higher concentration of free n-3 PUFA (p < 0.05). There were no significant differences in plasma concentrations of different fatty acyl species of phosphatidylethanolamine, triglycerides, sphingomyelin and ceramides.Conclusions/SignificanceOur findings reveal for the first time that a diet high in n-3 PUFA caused enrichment of n-3 PUFA in PC, LPC, CE and free fatty acids in the plasma and liver of C57BL/6 mice. PC, LPC, and unesterified free n-3 PUFA are important bioactive lipids, thus altering their fatty acyl composition will have important metabolic and physiological roles.
Highlights
Essential polyunsaturated fatty acids (PUFA) of the omega-3 (n-3) and n-6 classes are important in the regulation of metabolic processes
There were no significant differences in the total concentrations of phospholipids in both plasma and liver between high and low n-3 PUFA fed mice (Table S2 in File S1)
The high n-3 PUFA group showed higher incorporation of docosahexaenoic acid (DHA) into hepatic PC compared to the low n-3 PUFA group (p < 0.05; Figure 1B); there were no differences in plasma DHA containing PC in both groups (Figure 1A)
Summary
Essential polyunsaturated fatty acids (PUFA) of the omega-3 (n-3) and n-6 classes are important in the regulation of metabolic processes. Membrane fluidity can be influenced by the incorporation of dietary long chain n-3 PUFA into membrane PL, which enhances the functions of transmembrane proteins and their interactions with extracellular ligands [14,15,16] This indirectly affects signalling pathways and other physiological functions of the membrane. We investigated using lipidomic techniques, the effects of diets high in n-3 PUFA on the fatty acid composition of various bioactive lipids in plasma and liver. Conclusions/Significance: Our findings reveal for the first time that a diet high in n-3 PUFA caused enrichment of n-3 PUFA in PC, LPC, CE and free fatty acids in the plasma and liver of C57BL/6 mice. PC, LPC, and unesterified free n-3 PUFA are important bioactive lipids, altering their fatty acyl composition will have important metabolic and physiological roles
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