Study on the characteristics of glycerides and phospholipids in human milk from Tibet

Comparison of lipidome profiles in human milk from Chinese Han and Korean ethnic groups based on high-throughput lipidomic techniques

The composition of milk lipids varies across different ethnic sources. The lipidome profiles of Chinese Han human milk (HHM) and Chinese Korean human milk (KHM) were investigated in this study. A total of 741 lipids were identified in HHM and KHM. Twenty-eight differentially expressed lipids (DEL) were screened between the 2 milk groups; among these, 6 triacylglycerols (TG), 13 diacylglycerols (DG), 7 free fatty acids (FFA), and 1 monoglyceride (MG) were upregulated in KHM. Carnitine (CAR) was upregulated in HHM. Most DEL showed a single peak distribution in both groups. The correlations, related pathways and diseases of these DEL were further analyzed. The results demonstrated that DG, MG, and FFA showed highly positive correlations with each other (r > 0.8). The most enriched Kyoto Encyclopedia of Genes and Genomes (https://www.kegg.jp/kegg/) and Human Metabolome Database (http://www.hmdb.ca) pathways were inositol phosphate metabolism, and α-linolenic acid and linolenic acid metabolism, respectively. Major depressive disorder-related FFA (20:5) and FFA (22:6) were more abundant in KHM, whereas HHM showed more obesity-related CAR. These data potentially provide lipidome information regarding human milk from different ethnicities in China.

Impact of manufacturing processes on glycerolipid and polar lipid composition and ultrastructure in infant formula

The introduction of exogenous lipids in the production of infant formula induces significant alterations in milk lipid composition, content, and membrane structure, thus affecting the lipid digestion, absorption, and utilization. This study meticulously tracks these changes throughout the manufacturing process. Pasteurization has a significant effect on phosphatidylcholine and sphingomyelin in the outer membrane, decreasing their relative contents to total polar lipids from 12.52% and 17.34% to 7.72% and 12.59%, respectively. Subsequent processes, including bactericidal-concentration and spray-drying, demonstrate the thermal stability of sphingomyelin and ceramides, while glycerolipids with arachidonic acid/docosahexaenoic acid and glycerophospholipids, particularly phosphatidylethanolamine, diminish significantly. Polar lipids addition and freeze-drying technology significantly enhance the polar lipid content and improve microscopic morphology of infant formula. These findings reveal the diverse effects of technological processes on glycerolipid and polar lipid compositions, concentration, and ultrastructure in infant formulas, thus offering crucial insights for optimizing lipid content and structure within infant formula.

SpecLipIDA: a pseudotargeted lipidomics approach for polyunsaturated fatty acids in milk

Polyunsaturated fatty acids (PUFAs), such as arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), play an important role in the nutritional value of milk lipids. However, a comprehensive analysis of PUFAs and their esters in milk is still scarce. In this study, we developed a novel pseudotargeted lipidomics approach, named SpecLipIDA, for determining PUFA lipids in milk. Triglycerides (TGs) and phospholipids (PLs) were separated using NH2 cartridges, and mass spectrometry data in the information-dependent acquisition (IDA) mode were preprocessed by MS-DIAL, leading to improved identification in subsequent targeted analysis. The target matching algorithm, based on specific lipid cleavage patterns, demonstrated enhanced identification of PUFA lipids compared to the lipid annotations provided by MS-DIAL and GNPS. The approach was applied to identify PUFA lipids in various milk samples, resulting in the detection of a total of 115 PUFA lipids. The results revealed distinct differences in PUFA lipids among different samples, with 44 PUFA lipids significantly contributing to these differences. Our study indicated that SpecLipIDA is an efficient method for rapidly and specifically screening PUFA lipids.

Effects of lipids from multiple sources on glyceride composition, concentration, and structure of infant formulas benchmarked to human milk

The important parameters affecting the nutritional properties of lipids were analyzed and compared between human milk (HM), infant formulas (IFs), mammalian milk, and substitute fat, including molecular species, fatty acid composition, glyceride content, and important structural triacylglycerols (TAGs). The molecular species of triacylglycerols with functional fatty acids were significantly different between HM and IFs, and their contents in HM were significantly higher than those in IFs. Accordingly, the evaluation scores of fatty acid composition and glyceride content in IFs were less than 50 compared to HM. Although the introduction of vegetable oils effectively improved the unsaturation of IF lipid, the excessive addition of TAGs rich in oleic and linoleic acid resulted in an imbalance of TAG composition and structure. Only 36.84 % of IFs were supplemented with structured lipids, but those still lacked sn-2 palmitate TAGs. The adoption of multiple lipids and novel processing technologies is required for novel IFs to match the composition, content, positional structure and spherical membrane structure of HM as closely as possible.

Development and Application of Feature-Based Molecular Networking for Phospholipidomics Analysis

Phospholipids are small but critical lipids in milk. Conventional lipidomics is a powerful method for the analysis of lipids in milk. Although the number of lipidomics software has drastically increased over the past five years, reducing false positives and obtaining structurally accurate annotations of phospholipids remain a significant challenge. In this study, we developed a rapid and accurate method for measuring a wide spectrum of phospholipids in milk. The developed approach that employed information-dependent acquisition (IDA) mode and feature-based molecular networking has exhibited better performance on data processing and lipid annotation when compared with sequential window acquisition of all theoretical mass spectra (SWATH) and MS-DIAL. This validated method was further evaluated using three kinds of sheep milk. A total of 150 phospholipids were identified, including rarely reported phospholipids containing ethers or vinyl ethers. The result indicated that phospholipids could be used as potential markers to distinguish sheep milk from different varieties and origins. The experimental and computational methods provide a rapid and reliable method for the investigation of phospholipids in milk.