Variability of Lipids in Human Milk

Lipidomic Characterization of Whey Concentrates Rich in Milk Fat Globule Membranes and Extracellular Vesicles

Lipids from milk fat globule membranes (MFGMs) and extracellular vesicles (EVs) are considered beneficial for cognitive development and human health. Milk-derived whey concentrates rich in these lipids are therefore used as ingredients in infant formulas to mimic human milk and in medical nutrition products to improve the metabolic fitness of adults and elderly people. In spite of this, there is no consensus resource detailing the multitude of lipid molecules in whey concentrates. To bridge this knowledge gap, we report a comprehensive and quantitative lipidomic resource of different whey concentrates. In-depth lipidomic analysis of acid, sweet, and buttermilk whey concentrates identified 5714 lipid molecules belonging to 23 lipid classes. The data show that the buttermilk whey concentrate has the highest level of fat globule-derived triacylglycerols and that the acid and sweet whey concentrates have the highest proportions of MFGM- and EV-derived membrane lipids. Interestingly, the acid whey concentrate has a higher level of cholesterol whereas sweet whey concentrate has higher levels of lactosylceramides. Altogether, we report a detailed lipid molecular compendium of whey concentrates and lay the groundwork for using in-depth lipidomic technology to profile the nutritional value of milk products and functional foods containing dairy-based concentrates.

Selective extraction of phospholipids from human milk using glass fabric modified with zirconium-based metal organic framework

Phospholipids (PLs) are important and complex trace lipids in milk, which have positive effects on the infants' nervous and immune system development. Herein, a new method for selective extraction of PLs using glass fabric @ MOF-808 was proposed. Based on Lewis acid-base interaction, MOF-808 containing abundant Zr-OH groups was selected as the adsorption body, and glass fabric was used as a substrate to make the adsorbent easy to remove and reuse. The influencing factors such as loading solution, extraction time, eluent and elution time were further investigated. The adsorbent showed high adsorption capacity (3.31-6.54 mg/g for PLs) and good reusability (reused at least five times). The method showed low detection limits (1.61 μg/L - 10.24 μg/L) and quantification limits (5.24 μg/L-51.21 μg/L) for eight classes of PLs. The analysis of PLs in human milk at different lactation stages by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry could obtain up to 206 PLs, indicating that the method has extremely high extraction and anti-interference capabilities. This work is the first time to introduce MOF materials to selectively extract PLs and use glass fabric as a substrate for MOF-808, which has the advantages of easy recovery and high sensitivity. It provides technical support for the discovery of more PL species and has potential applications in phospholipidomics.

Defining the lipid profiles of human milk, infant formula, and animal milk: implications for infant feeding

Background

Breastfed infants have lower disease risk compared to formula-fed infants, however, the mechanisms behind this protection are unknown. Human milk has a complex lipidome which may have many critical roles in health and disease risk. However, human milk lipidomics is challenging, and research is still required to fully understand the lipidome and to interpret and translate findings. This study aimed to address key human milk lipidome knowledge gaps and discuss possible implications for early life health.

Methods

Human milk samples from two birth cohorts, the Barwon Infant Study (n = 312) and University of Western Australia birth cohort (n = 342), were analysed using four liquid chromatography-mass spectrometry (LC-MS) methods (lipidome, triacylglycerol, total fatty acid, alkylglycerol). Bovine, goat, and soy-based infant formula, and bovine and goat milk were analysed for comparison. Composition was explored as concentrations, relative abundance, and infant lipid intake. Statistical analyses included principal component analysis, mixed effects modelling, and correlation, with false discovery rate correction, to explore human milk lipidome longitudinal trends and inter and intra-individual variation, differences between sample types, lipid intakes, and correlations between infant plasma and human milk lipids.

Results

Lipidomics analysis identified 979 lipids. The human milk lipidome was distinct from that of infant formula and animal milk. Ether lipids were of particular interest, as they were significantly higher, in concentration and relative abundance, in human milk than in formula and animal milk, if present in the latter samples at all. Many ether lipids were highest in colostrum, and some changed significantly through lactation. Significant correlations were identified between human milk and infant circulating lipids (40% of which were ether lipids), and specific ether lipid intake by exclusively breastfed infants was 200-fold higher than that of an exclusively formula-fed infant.

Conclusion

There are marked differences between the lipidomes of human milk, infant formula, and animal milk, with notable distinctions between ether lipids that are reflected in the infant plasma lipidome. These findings have potential implications for early life health, and may reveal why breast and formula-fed infants are not afforded the same protections. Comprehensive lipidomics studies with outcomes are required to understand the impacts on infant health and tailor translation.

Progress of Mass Spectrometry-Based Lipidomics in the Dairy Field

Lipids play important biological roles, such as providing essential fatty acids and signaling. The wide variety and structural diversity of lipids, and the limited technical means to study them, have seriously hampered the resolution of the mechanisms of action of lipids. With advances in mass spectrometry (MS) and bioinformatic technologies, large amounts of lipids have been detected and analyzed quickly using MS-based lipidomic techniques. Milk lipids, as complex structural metabolites, play a crucial role in human health. In this review, the lipidomic techniques and their applications to dairy products, including compositional analysis, quality identification, authenticity identification, and origin identification, are discussed, with the aim of providing technical support for the development of dairy products.

Comparative Analysis of Docosahexaenoic Acid (DHA) Content in Mother's Milk of Term and Preterm Mothers

Objectives and Study: Docosahexaenoic acid (DHA) plays an essential role in infants’ development. Maternal diet and breastmilk are the primary DHA sources for newborns. This single-center observational study aimed to compare the DHA content in mother’s milk of preterm mothers with that of term ones, and to investigate the changes in mother’s milk DHA content according to the week of the gestational age. Methods: A food frequency questionnaire (FFQ) was submitted to each mother to estimate the DHA intake during the last trimester of pregnancy, and the mother’s milk was collected between 24 and 96 h post-partum. Results: Women who gave birth prematurely showed a lower content of mother’s milk DHA than the term ones (0.51; IQR 0.38−0.6% FA vs. 0.71; IQR 0.52−0.95% FA; p = 0.001). In the multivariate linear regression analyses, for each additional week of gestational age, there was an increase in DHA content in the mother’s milk (0.046% FA; CI 95% 0.018−0.074; p < 0.001). Conclusions: Our results suggest that breast milk may not be sufficient to fully satisfy the recommended DHA intake in preterm infants. This study may represent a starting point to investigate new possible DHA supplementation strategies, especially for the late and moderate preterm infants.

Milk polar lipids composition and functionality: a systematic review

Polar lipids including glycerophospholipids and sphingophospholipids are important nutrients and milk is a major source, particularly for infants. This systematic review describes the human and bovine milk polar lipid composition, structural organization, sources for formulation, and physiological functionality. A total of 2840 records were retrieved through Scopus, 378 were included. Bovine milk is a good source of polar lipids, where yield and composition are highly dependent on the choice of dairy streams and processing. In milk, polar lipids are organized in the milk fat globule membrane as a tri-layer encapsulating triglyceride. The overall polar lipid concentration in human milk is dependent on many factors including lactational stage and maternal diet. Here, reasonable ranges were determined where possible. Similar for bovine milk, where differences in milk lipid concentration proved the largest factor determining variation. The role of milk polar lipids in human health has been demonstrated in several areas and critical review indicated that brain, immune and effects on lipid metabolism are best substantiated areas. Moreover, insights related to the milk fat globule membrane structure-function relation as well as superior activity of milk derived polar lipid compared to plant-derived sources are emerging areas of interest regarding future research and food innovations.

The Role of Human Milk Lipids and Lipid Metabolites in Protecting the Infant against Non-Communicable Disease

Non-communicable diseases continue to increase globally and have their origins early in life. Early life obesity tracks from childhood to adulthood, is associated with obesity, inflammation, and metabolic dysfunction, and predicts non-communicable disease risk in later life. There is mounting evidence that these factors are more prevalent in infants who are formula-fed compared to those who are breastfed. Human milk provides the infant with a complex formulation of lipids, many of which are not present in infant formula, or are present in markedly different concentrations, and the plasma lipidome of breastfed infants differs significantly from that of formula-fed infants. With this knowledge, and the knowledge that lipids have critical implications in human health, the lipid composition of human milk is a promising approach to understanding how breastfeeding protects against obesity, inflammation, and subsequent cardiovascular disease risk. Here we review bioactive human milk lipids and lipid metabolites that may play a protective role against obesity and inflammation in later life. We identify key knowledge gaps and highlight priorities for future research.

Comprehensive Analysis of Lipid Composition in Human Foremilk and Hindmilk

Precision nutrition, also referred to as personalized nutrition, focuses on the individual to determine the individual's most effective eating plan to prevent or treat disease. A precision nutrition for infants requires the determination of the profile of human milk. We compared the lipid profiles of the foremilk (i.e., the initial milk of a breastfeed) and hindmilk (the last milk) of six Japanese subjects and evaluated whether a human milk lipid profile is useful for precision nutrition even though the fat concentration fluctuates during lactation. We detected and quantified 527 species with a lipidome analysis by liquid chromatography-tandem mass spectrometry. The fat concentration in hindmilk (120.6 ± 66.7 μmol/mL) was significantly higher than that in foremilk (68.6 ± 33.3 μmol/mL). While the total carbon number of fatty acids in triglyceride (TG) was highest in C52 for all subjects, the second or third number differed among the subjects. Both the distribution of total carbon number of fatty acids included in TG and the distribution of fatty acids in TG classified by the number of double bonds were almost the same in the foremilk and hindmilk in each subject. The lipids levels containing docosahexaenoic acid and arachidonic acid in total lipids of the foremilk and the hindmilk were almost the same in each subject. Among the sphingolipids and glycerophospholipids, the level of sphingomyelin was the highest in four subjects' milk, and phosphatidylcholine was the highest in the other two subjects' milk. The order of their major species was the same in each foremilk and hindmilk. A clustering heatmap revealed the differences between foremilk and hindmilk in the same subject were smaller than the differences among individuals. Our analyses indicate that a human-milk lipid profile reflects individual characteristics and is a worthwhile focus for precision nutrition.

Detailed knowledge of maternal and infant factors and human milk composition could inform recommendations for optimal composition

Breastfeeding is best for infants, but quantitative associations between specific milk components and infant biomarkers remain unclear. Methodological limitations include missing milk volume intake, variable milk composition and that standardised, fasted state blood sampling is impossible in infants. Milk protein and fat content appear marginally related to infant serum amino acid and phospholipid concentrations, with some association between milk fatty acid composition and lipid species levels. CONCLUSION: Detailed simultaneous examinations of maternal factors, milk composition and infant biomarkers or outcomes could identify the mechanistic basis of human milk effects and help develop dietary recommendations for optimal human milk composition.

Total Fatty Acid and Polar Lipid Species Composition of Human Milk

Human milk lipids are essential for infant health. However, little is known about the relationship between total milk fatty acid (FA) composition and polar lipid species composition. Therefore, we aimed to characterize the relationship between the FA and polar lipid species composition in human milk, with a focus on differences between milk with higher or lower milk fat content. From the Norwegian Human Milk Study (HUMIS, 2002–2009), a subset of 664 milk samples were analyzed for FA and polar lipid composition. Milk samples did not differ in major FA, phosphatidylcholine, or sphingomyelin species percentages between the highest and lowest quartiles of total FA concentration. However, milk in the highest FA quartile had a lower phospholipid-to-total-FA ratio and a lower sphingomyelin-to-phosphatidylcholine ratio than the lowest quartile. The only FAs associated with total phosphatidylcholine or sphingomyelin were behenic and tridecanoic acids, respectively. Milk FA and phosphatidylcholine and sphingomyelin species containing these FAs showed modest correlations. Associations of arachidonic and docosahexaenoic acids with percentages of phosphatidylcholine species carrying these FAs support the conclusion that the availability of these FAs limits the synthesis of phospholipid species containing them.

Healthy Breastfeeding Infants Consume Different Quantities of Milk Fat Globule Membrane Lipids

The human milk fat globule membrane (MFGM) contains important lipids for growing infants. Anthropometric measurements, milk samples, and infant milk intake were collected in a cohort of eleven healthy mother–infant dyads during exclusive breastfeeding from birth to six months. One hundred and sixty-six MFGM lipids were analysed using liquid chromatography-mass spectrometry, and the infant intake was calculated. The concentrations and intake were compared and associations between infant intake and growth characteristics explored. The lipid concentrations and infant intake varied widely between mother–infant dyads and between months one and three. The infant intake for many species displayed positive correlations with infant growth, particularly phospholipid species. The high variation in lipid intake is likely an important factor in infant growth, with strong correlations identified between the intake of many MFGM lipids and infant head circumference and weight. This study highlights the need for intake measurements and inclusion in cohort studies to elucidate the role of the human milk lipidome in infant growth and development.

Human milk sphingomyelins and metabolomics: an enigma to be discovered

Sphingomyelins, the most abundant sphingolipids in most mammalian cells, appear to be among the most represented polar lipids in breast milk. Despite the variability of the data reported in the literature, human milk sphingomyelins are qualitatively unique and their quantities are five times higher than in most formula milk. The structural and functional role within the milk fat globule membranes, the involvement in neonatal neurological maturation both in neuro-typical development and in some pathological circumstances, together with the possible contribution in the intestinal development of newborns, are certainly among the main characteristics that have fueled the curiosity of the scientific world. Metabolomics studies, providing a unique metabolic fingerprint, allow an in-depth analysis of the role of these molecules in the extreme variability and uniqueness of breast milk. In the perspective of preventive medicine, at the base of which there is certainly personalized nutrition, it is possible, in the presence of particular conditions, such as neonatal growth retardation or in preterm infants, to consider supplementation of some target nutrients, such as certain sphingomyelins. Nevertheless, further studies are needed to more accurately assess whether and how the type and quantity of sphingomyelins present in breast milk could affect the metabolic health of newborns.HIGHLIGHTSBreast milk is the golden standard for infants' nutritionSphingomyelins are the most represented polar lipids in breast milkThese molecules are involved in both intestinal and neural developments of newbornsMetabolomics is a very useful tool to investigate their precise roleFurther studies are needed to provide eventual nutritional treatment.