Abstract
BackgroundThe fatty acid mixture of human milk is ideal for the newborn but little is known about its composition in the first few weeks of lactation. Of special interest are the levels of long-chain PUFAs (LCPUFAs), since these are essential for the newborn’s development. Additionally, the LCPUFAs arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are precursors for lipid mediators which regulate inflammation.MethodsWe determined the composition of 94 human milk samples from 30 mothers over the first month of lactation for fatty acids using GC-MS and quantified lipid mediators using HPLC-MS/MS.ResultsOver the four weeks period, DHA levels decreased, while levels of γC18:3 and αC18:3 steadily increased. Intriguingly, we found high concentrations of lipid mediators and their hydroxy fatty acid precursors in human milk, including pro-inflammatory leukotriene B4 (LTB4) and anti-inflammatory and pro-resolving lipoxin A4 (LXA4), resolvin D1 (RvD1) and resolvin E1 (RvE1). Lipid mediator levels were stable with the exception of two direct precursors.ConclusionsElevated levels of DHA right after birth might represent higher requirements of the newborn and the high content of anti-inflammatory and pro-resolving lipid mediators and their precursors may indicate their role in neonatal immunity and may be one of the reasons for the advantage of human milk over infant formula.
Highlights
The fatty acid mixture of human milk is ideal for the newborn but little is known about its composition in the first few weeks of lactation
Oxygenation of arachidonic acid (AA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) occurs in a concerted action of lipoxygenases, cyclooxygenases and cytochrome-P-450 dependent oxygenases to result in the pro-inflammatory leukotrienes and the anti-inflammatory lipoxins from AA and resolvins and protectins from DHA and EPA [29,30,31,32,33,34]
All of the investigated lipid mediators leukotriene B4 (LTB4), lipoxin A4 (LXA4), resolvin E1 (RvE1) and resolvin D1 (RvD1) were found at considerable concentrations, which were higher than the concentrations reported for plasma of healthy individuals
Summary
The fatty acid mixture of human milk is ideal for the newborn but little is known about its composition in the first few weeks of lactation. The fatty acid composition of the membrane influences membrane properties and immune-regulatory processes through the metabolization of free and membrane bound LCPUFAs to lipid mediators [28] These lipid mediators are signaling molecules that initiate and resolve inflammation and they derive from oxygenation of the omega-6 fatty acid AA and the two omega-3 fatty acids DHA and EPA [29,30]. Apart from being anti-inflammatory, lipoxins, resolvins and protectins initiate inflammation-resolving actions like recruitment of nonphlogistic monocytes and clearance of apoptotic polymorphonuclear neutrophils by macrophages [35,36,37] Due to their potent immune-regulatory functions, these lipid mediators are thought to play a role in chronic inflammatory diseases like atherosclerosis, rheumatoid arthritis and inflammatory bowel disease [31,38,39,40]. We surmised that a supply of anti-inflammatory and pro-resolving lipid mediators to the newborn by breast milk could be one of the explanations for the lower incidence of intestinal inflammation in breast-fed compared to formula-fed infants [41,42]
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