Comprehensive Characterization of Bovine Milk Lipids: Phospholipids, Sphingolipids, Glycolipids, and Ceramides

Comprehensive Characterization of Serum Lipids of Dairy Cows: Effects of Negative Energy Balance on Lipid Remodelling

BACKGROUND

The presence and concentration of lipids in serum of dairy cows have significant implications for both animal health and productivity and are potential biomarkers for several common diseases. However, information on serum lipid composition is rather fragmented, and lipid remodelling during the transition period is only partially understood.

METHODS

Using a combination of reversed-phase liquid chromatography-mass spectrometry (RP-LC-MS), hydrophilic interaction-mass spectrometry (HILIC-MS), and lipid annotation software, we performed a comprehensive identification and quantification of serum of dairy cows in pasture-based Holstein-Friesian cows. The lipid remodelling induced by negative energy balance was investigated by comparing the levels of all identified lipids between the fresh lactation (5-14 days in milk, DIM) and full lactation (65-80 DIM) stages.

RESULTS

We identified 535 lipid molecular species belonging to 19 classes. The most abundant lipid class was cholesteryl ester (CE), followed by phosphatidylcholine (PC), sphingomyelin (SM), and free fatty acid (FFA), whereas the least abundant lipids included phosphatidylserine (PS), phosphatidic acid (PA), phosphatidylglycerol (PG), acylcarnitine (AcylCar), ceramide (Cer), glucosylceramide (GluCer), and lactosylceramide (LacCer).

CONCLUSIONS

A remarkable increase in most lipids and a dramatic decrease in FFAs, AcylCar, and DHA-containing species were observed at the full lactation compared to fresh lactation stage. Several serum lipid biomarkers for detecting negative energy balance in cows were also identified.

Global Levels and Variations of Cholesterol and Polar Lipids of Human Milk: A Systematic Review and Meta-analysis

Polar lipids and cholesterol are vital structural components of the milk fat globule membrane, playing a crucial role in infant growth and development; however, systematic global reports on their content in human milk are currently lacking. This study conducted a systematic literature search in Chinese and English databases, including 69,392 human milk samples from 96 studies. A random-effects model based on global data was used to assess the content of total lipids, cholesterol, gangliosides, and phospholipids in human milk and their variations with the lactation stage, geographical region, and sample year. The mean contents of total lipids, cholesterol, and total phospholipids were 2774.15 mg/100 g (95% CI: 2614.88, 2933.42 mg/100 g), 21.15 mg/100 g (18.35, 23.95 mg/100 g), and 70.72 mg/100 g (68.84, 72.60 mg/100 g), respectively, with gangliosides GM3 and GD3 at 0.63 mg/100 g (0.54, 0.72 mg/100 g) and 0.34 mg/100 g (0.32, 0.36 mg/100 g). The major phospholipids SM, PC, PE, PS, and PI averaged 24.19 mg/100 g (23.17 and 25.21 mg/100 g), 21.27 mg/100 g (19.92 and 22.62 mg/100 g), 18.28 mg/100 g (17.46 and 19.10 mg/100 g), 2.86 mg/100 g (2.32 and 3.40 mg/100 g), and 2.12 mg/100 g (1.75 and 2.49 mg/100 g). With the progression of lactation, total lipids, gangliosides, and most phospholipids (SM, PC, PS, PI) increased, while cholesterol and PE decreased. Over the years, total lipids, gangliosides, and PE showed an upward trend, whereas cholesterol and most phospholipids declined. Human milk from Europe had lower total lipid and cholesterol levels compared with other regions. While the total phospholipid content did not show significant regional differences (P > 0.05), variations in phospholipid composition were observed. These findings emphasize the importance of understanding spatiotemporal changes in human milk lipids to develop personalized nutrition strategies that support optimal infant growth and development.

Yes-associated protein 1 is essential for maintaining lactation via regulating mammary epithelial cell dynamics and secretion capacity

Understanding the physiology and molecular mechanisms of lactogenesis is crucial for enhancing mammalian milk production. Yes-associated protein 1 (YAP1) regulated mammary epithelial cell survival during pregnancy, but its role in lactation maintenance remains unclear. We found that YAP1 was highly expressed in mammary gland across specie, with elevated expression levels during murine gestation and lactation, particularly localized in alveoli epithelial cells. In vivo administration of a YAP1 inhibitor impaired murine milk yield, mammary gland weight, alveolar structure, and mammary epithelial cell dynamics. In vitro, YAP1 positively affected mammary epithelial cell growth and the synthesis of triglyceride and α-casein. Notably, the primary lactogenesis hormone Prolactin induced cell growth and triglyceride secretion while enhancing YAP1 expression and activity. In contrast, Melatonin inhibited cell growth and triglyceride synthesis, decreasing YAP1 expression and activity. YAP1 knockdown compromised prolactin induced effects, whereas YAP1 overexpression partially rescued cell functions inhibited by melatonin. Finally, Bioinformatics analyses revealed that YAP1 regulated multiple biological processes related to lactogenesis, including cell cycle, apoptosis, endoplasmic reticulum, amino acid transport and biosynthesis, etc. These finding indicated that YAP1 is essential for mammary epithelial cells growth and secretion and played an essential role in the lactating endocrine network by mediating key hormone functions.

Integrating the milk microbiome signatures in mastitis: milk-omics and functional implications

Mammalian milk contains a variety of complex bioactive and nutritional components and microorganisms. These microorganisms have diverse compositions and functional roles that impact host health and disease pathophysiology, especially mastitis. The advent and use of high throughput omics technologies, including metagenomics, metatranscriptomics, metaproteomics, metametabolomics, as well as culturomics in milk microbiome studies suggest strong relationships between host phenotype and milk microbiome signatures in mastitis. While single omics studies have undoubtedly contributed to our current understanding of milk microbiome and mastitis, they often provide limited information, targeting only a single biological viewpoint which is insufficient to provide system-wide information necessary for elucidating the biological footprints and molecular mechanisms driving mastitis and milk microbiome dysbiosis. Therefore, integrating a multi-omics approach in milk microbiome research could generate new knowledge, improve the current understanding of the functional and structural signatures of the milk ecosystem, and provide insights for sustainable mastitis control and microbiome management.

Multi-omics analysis of five species of milk and specific composition links within each species

The gold standard of milk is human milk, not cow milk. The present study expects to explored the comprehensive nutritional value of different kinds of milk and the differences between them through multi-omics analysis and found functional components that are more similar to human milk. This study employed untargeted LC-MS/MS metabolomics, untargeted LC-MS/MS lipidomics, and 4D label-free proteomics analysis techniques. The findings revealed substantial disparities in metabolites, lipids, and proteins among the five types of milk. Notably, pig milk exhibited a remarkable abundance of N-acetylneuraminic acid (Neu5Ac) and specific polar lipids. Yak milk stood out with significantly elevated levels of creatine and lipoprotein lipase (LPL) compared to other species. Buffalo milk boasted the highest concentrations of L-isoleucine, echinocystic acid, and alkaline phosphatase, tissue-nonspecific isozyme (ALPL). The concentrations of iminostilbene and osteopontin (OPN) were higher in cow milk.

Omega-3 Long-Chain Polyunsaturated Fatty Acids in Nonseafood and Estimated Intake in the USA: Quantitative Analysis by Covalent Adduct Chemical Ionization Mass Spectrometry

Omega-3 long-chain polyunsaturated fatty acids (LCPUFA) play critical roles in human development and health. Their intake is often effectively estimated solely based on seafood consumption, though the high intake of terrestrial animal-based foods with minor amounts of LCPUFA may be significant. Covalent adduct chemical ionization (CACI) tandem mass spectrometry is one approach for de novo structural and quantitative analysis of minor unsaturated fatty acids (FA), for which standards are unavailable. Here, CACI-MS and MS/MS are used to identify and quantify minor omega-3 LCPUFA of terrestrial animal foods based on the application of measured response factors (RFs) to various FA. American mean intakes of pork, beef, chicken, and eggs contribute 20, 27, 45, and 71 mg/day of docosahexaenoic acid (DHA), respectively. The estimated intake of omega-3 DHA, eicosapentaenoic acid, and docosapentaenoic acid from nonseafood sources is significant, at 164, 103, and 330 mg/day, greater than most existing estimates of omega-3 LCPUFA intake.

The ZmNF-YC1-ZmAPRG pathway modulates low phosphorus tolerance in maize

Phosphorus (P) is an essential nutrient for plant growth and yield. Low phosphate use efficiency makes it important to clarify the molecular mechanism of low P stress. In our previous studies, a P efficiency gene ZmAPRG was identified. Here, we further screened the upstream regulator ZmNF-YC1 of ZmAPRG by yeast one hybrid (Y1H) assay, and found it was a low inorganic phosphorus (Pi)-inducible gene. The results of dual luciferase assays, expression analysis, and ChIP-qPCR assays showed that ZmNF-YC1 is a positive regulator of ZmAPRG. Overexpression of ZmNF-YC1 improved low P tolerance, whereas knockout of ZmNF-YC1 decreased low P tolerance in maize. Bimolecular fluorescence complementation (BiFC), yeast two hybrid (Y2H) assay, and yeast three hybrid (Y3H) assay further showed that ZmNF-YC1 can interact with ZmNF-YB14, and recruit ZmNF-YA4/10 to form NF-Y complexes. Transcriptional activation assay confirmed that the NF-Y complexes can activate the promoters of ZmAPRG. Meanwhile, transcriptome and metabolome analyses indicated that overexpression of ZmAPRG improves low P tolerance by regulating lipid composition and photosynthetic capacity, and chlorophyll fluorescence parameters provided evidence in support of this hypothesis. Furthermore, overexpression of ZmAPRG increased grain yield in inbred and hybrid maize under low P conditions. Taken together, our research revealed a low P tolerance mechanism of the ZmNF-YC1-ZmAPRG pathway.

Effect of consumption of sheep and cow milk on rat brain fatty acid and phospholipid composition

The effect of sheep milk and cow milk on the lipid composition of rat brain was investigated in two feeding experiments of 28-days duration. Total lipids of the rat brain were extracted using ethanol-hexane, and the fatty acids and phospholipid contents analysed using gas chromatography with flame ionization detection (GC-FID) and phosphorus-31 nuclear magnetic resonance (31P NMR). Furthermore, freeze-dried pooled samples were analysed using attenuated total reflectance Fourier Transform Infrared and Fourier Transform Raman Spectroscopy and analysed with multivariate methods. A significantly (P < 0.05) higher C18:2 content was found in the cow milk group compared with sheep milk-treated groups in Study one. In Study two, a significantly (P < 0.05) lower C16:0 content was present in the sheep milk-treated group compared to the control low Ca/P group. No significant (P > 0.05) differences were observed in the spectroscopy analyses. It is concluded that sheep and cow milks fed to rats for 28-days had a low effect on the brain lipidome.

Comprehensive analysis of phospholipid in milk and their biological roles as nutrients and biomarkers

Phospholipids (PL) have garnered significant attention due to their physiological activities. Milk and other dairy products are important dietary sources for humans and have been extensively used to analyze the presence of PL by various analytical techniques. In this paper, the analysis techniques of PL were reviewed with the eight trigrams of phospholipidomics and a comprehensive fingerprint of 1295 PLs covering 8 subclasses in milk and other dairy products, especially. Technology is the primary productive force. Based on phospholipidomics technology, we further review the relationship between the composition of PL and factors that may be involved in processing and experimental operation, and emphasized the significance of the biological role played by PL in dietary supplements and biomarkers (production, processing and clinical research), and providing the future research directions.

Microwave-Assisted Extraction/UHPLC-Q-Orbitrap-MS-Based Lipidomic Workflow for Comprehensive Study of Lipids in Soft Cheese

In this work, Microwave-Assisted Extraction (MAE) was proposed as an alternative and environmentally friendly technique in lipidomics to study the lipid fingerprint of soft cheeses, such as mozzarella. For method development, a first step concerning an evaluation of extraction solvents was carried out via testing three different mixtures, including methanol/ethyl acetate, isopropanol/ethyl acetate, and ethanol/ethyl acetate, at a 1:2 v/v ratio. The latter was chosen as a solvent mixture for subsequent method optimization. MAE conditions, in terms of solvent volume, time, and temperature, were explored to define their effects on extraction capability through a full factorial experimental design. The best compromise to extract more lipids at the same time was obtained with 24 mL g-1 for solvent-to-solid ratio, 65 °C for temperature, and 18 min for time. Lipid analyses were conducted by UHPLC-Q-Orbitrap-MS associated with multivariate statistics. The developed lipidomic workflow allowed for the extraction of over 400 lipids grouped into 18 different subclasses. The results confirmed that MAE is a suitable technique for lipid extraction in the omics approach with high efficiency, even using low-cost and less toxic solvents. Moreover, a comprehensive structure characterization of extracted lipids, in terms of fatty acid composition and regiochemistry, was carried out.

Effects of dietary forage-to-concentrate ratio and forage type on milk phospholipids and fatty acid composition of polar lipids

The effects of grass silage and red clover silage on milk fatty acid (FA) composition are extensively studied, but little is known of their effects on minor lipid constituents of milk fat globule membrane. We investigated the effects of forage:concentrate (FC) ratio in grass silage-based diets and forage type (grass silage vs. red clover silage) on selected molecular species of milk phospholipids (PL) and the FA composition of PL. Ten multiparous Nordic Red cows were offered following dietary treatments: grass silage-based diets containing 70:30 (HG) or 30:70 (LG) FC ratio or a red clover silage-based diet (RC) comprising 50:50 FC ratio on a dry matter basis. The most abundant molecular species within the phosphatidylcholines was 16:0-18:1 phosphatidylcholine that was increased by 18% in HG compared with LG milk. Dietary treatments did not affect the relative proportion of 18:1-18:1+18:0-18:2 phosphatidylethanolamine that was the most prevalent species (ca. 44%-45%) in that class. We identified the d18:1-22:0 sphingomyelin as the most abundant sphingomyelin species that tended to increase in HG milk compared with LG. The FC ratio did not affect the relative proportions of saturated FA nor monounsaturated FA in PL, but the proportion of cis-9 18:1 was elevated in HG versus LG milk, whereas the proportion of 18:2n-6 was 50% higher in LG versus HG milk. The RC diet increased monounsaturated FA and 18:3n-3 levels in PL compared with grass silage-based diets and decreased the relative proportion of saturated FA. However, the RC diet did not affect the relative proportion of polyunsaturated FA in PL, although red clover silage typically increases the proportion of polyunsaturated FA in milk fat. This study provides valuable knowledge of the minor lipid components in milk on species level in relation to common feeding strategies in high-forage systems.

Defining the Ceramide Composition of Bovine and Human Milk Gangliosides by Direct Infusion ESI-CID Tandem Mass Spectrometry of Native and Permethylated Molecular Species

Gangliosides are glycosphingolipids composed of an oligosaccharide that contains one or more sialic acid residues and is linked to a ceramide, a lipid composed of a long chain base (LCB) that bears an amide-linked fatty acyl group (FA). The ceramide portions of gangliosides are embedded in cell membranes; the exposed glycans interact with the extracellular environment. Gangliosides play a myriad of roles in activities such as cell-cell communication, formation of lipid rafts, cellular adhesion, calcium homeostasis, host-pathogen interaction, and viral invasion. Although the epitopes responsible for the interactions of gangliosides are located in the glycan, the epitope presentation is strongly influenced by the orientation of the attached ceramide within the lipid membrane, a feature that depends on the details of its structure, that is, the specific LCB and FA. Since the identities of both the glycan and the ceramide affect the activity of gangliosides, it is important to characterize the individual intact molecular forms. We report here a mass spectrometry-based method that combines the information gained from low-energy collision-induced dissociation (CID) measurements for the determination of the glycan with tandem mass spectra obtained at stepped higher-energy CID for the detailed characterization of the LCB and FA components of intact gangliosides. We provide results from applications of this method to the analysis of gangliosides present in bovine and human milk in order to demonstrate the assignment of LCB and FA for intact gangliosides and differential detection of isomeric ceramide structures.

Bioactive Functions of Lipids in the Milk Fat Globule Membrane: A Comprehensive Review

The milk fat globule membrane (MFGM) is a complex tri-layer membrane that wraps droplets of lipids in milk. In recent years, it has attracted widespread attention due to its excellent bioactive functions and nutritional value. MFGM contains a diverse array of bioactive lipids, including cholesterol, phospholipids, and sphingolipids, which play pivotal roles in mediating the bioactivity of the MFGM. We sequentially summarize the main lipid types in the MFGM in this comprehensive review and outline the characterization methods used to employ them. In this comprehensive review, we sequentially describe the types of major lipids found in the MFGM and outline the characterization methods employed to study them. Additionally, we compare the structural disparities among glycerophospholipids, sphingolipids, and gangliosides, while introducing the formation of lipid rafts facilitated by cholesterol. The focus of this review revolves around an extensive evaluation of the current research on lipid isolates from the MFGM, as well as products containing MFGM lipids, with respect to their impact on human health. Notably, we emphasize the clinical trials encompassing a large number of participants. The summarized bioactive functions of MFGM lipids encompass the regulation of human growth and development, influence on intestinal health, inhibition of cholesterol absorption, enhancement of exercise capacity, and anticancer effects. By offering a comprehensive overview, the aim of this review is to provide valuable insights into the diverse biologically active functions exhibited by lipids in the MFGM.

Recent Approaches for Analytical Characterization of Phospholipids in Food Matrices. Is the Phospholipid Fraction Exploited in the Authentication of Food Lipids?

Phospholipids (PhLs) are essential components of cell membranes, characterized by a hydrophobic tail and a hydrophilic headgroup. They play several roles in biological systems, including energy storage, protection, and antioxidant properties. PhLs are found naturally in foods such as egg yolks, milk, or vegetable oils. The composition and concentration of PhLs observed in these foods vary according to the analytical methodology applied, mainly in the extraction and sample treatment process. Analytical targeted approaches for characterized PhLs involve liquid chromatography and mass spectrometry techniques. These methods provide insights into the composition and content of PhLs in food matrices. However, there is limited research on using PhL profiles for food quality evaluation and authentication purposes. Untargeted approaches, such as fingerprinting, have the potential to assess the authenticity of food products by capturing analytical signals linked to the PhL fraction. This review focusses on recent analytical strategies used in characterizing PhLs in distinctive foodstuffs (eggs, milk, and vegetable oils). It discusses sample preparation, analytical separation, and detection techniques. The review also highlights the potential of multivariate approaches to incorporate information on PhL composition to assess the authenticity of food products, an area that has been largely overlooked in previous studies.

Untargeted Lipidomics and Chemometric Tools for the Characterization and Discrimination of Irradiated Camembert Cheese Analyzed by UHPLC-Q-Orbitrap-MS

In this work, an investigation using UHPLC-Q-Orbitrap-MS and multivariate statistics was conducted to obtain the lipid fingerprint of Camembert cheese and to explore its correlated variation with respect to X-ray irradiation treatment. A total of 479 lipids, categorized into 16 different lipid subclasses, were measured. Furthermore, the identification of oxidized lipids was carried out to better understand the possible phenomena of lipid oxidation related to this technological process. The results confirm that the lipidomic approach adopted is effective in implementing the knowledge of the effects of X-ray irradiation on food and evaluating its safety aspects. Furthermore, Partial Least Squares-Discriminant Analysis (PLS-DA) and Linear Discriminant Analysis (LDA) were applied showing high discriminating ability with excellent values of accuracy, specificity and sensitivity. Through the PLS-DA and LDA models, it was possible to select 40 and 24 lipids, respectively, including 3 ceramides (Cer), 1 hexosyl ceramide (HexCer), 1 lysophosphatidylcholine (LPC), 1 lysophosphatidylethanolamine (LPE), 3 phosphatidic acids (PA), 4 phosphatidylcholines (PC), 10 phosphatidylethanolamines (PE), 5 phosphatidylinositols (PI), 2 phosphatidylserines (PS), 3 diacylglycerols (DG) and 9 oxidized triacylglycerols (OxTG) as potential markers of treatment useful in food safety control plans.

Effects of extended transition milk feeding on blood metabolites of female Holstein dairy calves at 3 weeks of age: a liquid chromatography with tandem mass spectrometry-based metabolomics approach

Transition milk (TRM) is a rich source of bioactive components that promotes intestinal development and growth, and reduces the susceptibility to diarrhoea in calves. The objective of this study was to characterise the effects of replacing pasteurised waste milk (none-saleable milk containing antibiotic and/or drug residues) with pasteurised TRM for 3 wk on blood metabolites of dairy calves at 21 d of age. A total of 84 healthy newborn female Holstein calves was blocked by birth order and assigned randomly to four treatment groups with partial replacement of pasteurised waste milk by TRM (second milking after parturition) at 0 (0 L/day TRM + 6 L/day milk), 0.5 (0.5 L/day TRM + 5.5 L/day milk), 1 (1 L/day TRM + 5 L/day milk), or 2 L (2 L/day TRM + 4 L/day milk) for a 21-day period. Serum metabolome was determined by liquid chromatography with tandem mass spectrometry-based metabolomics analysis on a subset of 26 randomly selected individuals from calves fed pasteurised waste milk (CON, 6 L/d milk; n = 13) or TRM (2 L/d TRM + 4 L/d milk; n = 13) at 21 d of age. The identified metabolites (194 out of 265) were categorised according to chemical class and the number of metabolites per class in the serum, amongst which glycerophospholipids 16% (n = 43), fatty acyls 7% (n = 19), organic acids 7% (n = 18), organic heterocyclic compounds 5% (n = 13), benzenoids 5% (n = 12), sphingolipids 5% (n = 12), organic oxygen compounds 4% (n = 11), and nucleic acids 3% (n = 9), were the predominant types. Significant differences in metabolites were determined by the volcano plot. Applying the volcano plot, only two metabolites (ceramide and phosphatidylserine) were significantly different between CON and TRM. Overall, our results suggested that prolonged TRM feeding for 3 wk had little effect on the serum metabolome of the dairy calves. We speculate that the potential effects of feeding TRM for 3 wk compared with waste milk were spatially limited to affect the composition of the local gut microbial community and the growth or function of the intestinal epithelium, not allowing detection of the likely effects in the serum through a metabolomic approach.

High-sensitivity qualitative and quantitative analysis of human, bovine and goat milk glycosphingolipids using HILIC-MS/MS with internal standards

Glycosphingolipids (GSLs) in human milk regulate the immune system, support intestinal maturation, and prevent gut pathogens. The structural complexity and low abundance of GSLs limits their systematic analysis. Here, we coupled the use of monosialoganglioside 1-2-amino-N-(2-aminoethyl) benzamide (GM1-AEAB) derivatives as internal standards with HILIC-MS/MS to qualitatively and quantitatively compare GSLs in human, bovine, and goat milk. One neutral glycosphingolipid (GB) and 33 gangliosides were found in human milk, of which 22 were newly detected and three were fucosylated. Five GB and 26 gangliosides were identified in bovine milk, of which 21 were newly discovered. Four GB and 33 gangliosides were detected in goat milk, 23 of them newly reported. GM1 was the main GSL in human milk; whereas disialoganglioside 3 (GD3) and monosialogangloside 3 (GM3) were dominant in bovine and goat milk, respectively; N-acetylneuraminic acid (Neu5Ac) was detected in >88 % of GSLs in bovine and goat milk. N-hydroxyacetylneuraminic acid (Neu5Gc)-modified GSLs were 3.5 times more abundant in goat than in bovine milk; whereas GSLs modified with both Neu5Ac and Neu5Gc were 3 times more abundant in bovine than in goat milk. Given the health benefits of different GSLs, these results will facilitate the development of custom-designed human milk-based infant formula.

Ganglioside analysis in body fluids by liquid-phase separation techniques hyphenated to mass spectrometry

The expression of gangliosides in central nervous system is a few times higher than in the extraneural tissue, a characteristic highlighting their major role at this level. Although in very low amounts, gangliosides are ubiquitously distributed in body fluids too, where, depending on many factors, including pathological states, their composition fluctuates, thus having diagnostic value. Ganglioside investigation in biological fluids, which, except for cerebrospinal fluid (CSF), may be sampled noninvasively, was for years impeded by the limited sensitivity of the analytical instrumentation available in glycomics. However, because the last decade has witnessed significant developments in biological mass spectrometry (MS) and the hyphenated separation techniques, marked by a major increase in sensitivity, reproducibility, and data reliability, ganglioside research started to be focused on biofluid analysis by separation techniques coupled to MS. In this context, our review presents the achievements in this emerging field of gangliosidomics, with a particular emphasis on modern liquid chromatography (LC), thin-layer chromatography, hydrophilic interaction LC, and ion mobility separation coupled to high-performance MS, as well as the results generated by these systems and allied experimental procedures in profiling and structural analysis of gangliosides in healthy or diseased body fluids, such as CSF, plasma/serum, and milk.

The influence of MPL addition on structure, interfacial compositions and physicochemical properties on infant formula fat globules

The lack of milk fat globule membrane phospholipids (MPL) at the interface of infant formula fat globules has an impact on the stability of fat globules, compared to human milk. Therefore, infant formula powders with different MPL contents (0%, 10%, 20%, 40%, 80%, w/w of MPL/whey protein mixture) were prepared, and the effect of interfacial compositions on the stability of globules was investigated. With increasing MPL amount, the particle size distribution had two peaks and returned to a uniform state when 80% MPL was added. At this composition, the MPL at the oil-water interface formed a continuous thin layer. Moreover, the addition of MPL improved the electronegativity and the emulsion stability. In terms of the rheological properties, increasing the concentration of MPL improved the elastic properties of the emulsion and the physical stability of the fat globules, while reducing the aggregation and agglomeration between fat globules. However, the potential for oxidation increased. Based on these results, the interfacial properties and stability on infant formula fat globules was significantly influenced by the level of MPL, which should be considered in the design of infant milk powders.

Comparative Genomic Analysis of the Thiolase Family and Functional Characterization of the Acetyl-Coenzyme A Acyltransferase-1 Gene for Milk Biosynthesis and Production of Buffalo and Cattle

Cattle and buffalo served as the first and second largest dairy animals, respectively, providing 96% milk products worldwide. Understanding the mechanisms underlying milk synthesis is critical to develop the technique to improve milk production. Thiolases, also known as acetyl-coenzyme A acetyltransferases (ACAT), are an enzyme family that plays vital roles in lipid metabolism, including ACAT1, ACAT2, ACAA1, ACAA2, and HADHB. Our present study showed that these five members were orthologous in six livestock species including buffalo and cattle. Transcriptomic data analyses derived from different lactations stages showed that ACAA1 displayed different expression patterns between buffalo and cattle. Immunohistochemistry staining revealed that ACAA1 were dominantly located in the mammary epithelial cells of these two dairy animals. Knockdown of ACAA1 inhibited mammary epithelial cell proliferation and triglyceride and β-casein secretion by regulating related gene expressions in cattle and buffalo. In contrast, ACAA1 overexpression promoted cell proliferation and triglyceride secretion. Finally, three novel SNPs (g.-681A>T, g.-23117C>T, and g.-24348G>T) were detected and showed significant association with milk production traits of Mediterranean buffaloes. In addition, g.-681A>T mutation located in the promoter region changed transcriptional activity significantly. Our findings suggested that ACAA1 play a key role in regulating buffalo and cattle milk synthesis and provided basic information to further understand the dairy animal lactation physiology.

Effects of various thermal treatments on interfacial composition and physical properties of bovine milk fat globules

This study aimed to investigate changes of milk fat globules (MFG) and their membranes after thermal treatments, and further analyzed the relationship between the stability of MFG and interfacial compositions of milk fat globule membrane (MFGM). We characterized the influence of three kinds of thermal treatments on fat globule interfacial components (including interfacial phospholipids and interfacial protein) and physical properties using phospholipidomics and several microscopy techniques. The results showed that size of MFG increased from 2.96 μm to 3.59 μm and ζ-potential decreased from -9.71 mV to -13.23 mV after thermal treatment, suggesting that MFGM was damaged and MFG occurred coalescence. Thermal treatment increased the Young's modulus of MFGM and made membranes more fragile. The abundance of MFGM proteins decreased while casein and β-lactoglobulin increased after thermal treatment. Results of phospholipidomics showed that 27 phospholipid species could be used to distinguish the samples. Pasteurization reduced mainly SM and PC located in the outer bilayer of MFGM, while ultra-pasteurization reduced not only SM and PC but also PI and PE located in the inner leaflet. Based on correlation analysis, the increase in Young's modulus of MFGM during thermal treatment might be related to changes in chemical components on the membrane, suggesting a potential link between the change of MFGM components and fat globule coalescence behavior.

Acute Stress-Induced Changes in the Lipid Composition of Cow's Milk in Healthy and Pathological Animals

Producers of milk and dairy products have been faced with the challenge of responding to European society's demand for guaranteed animal welfare production. In recent years, measures have been taken to improve animal welfare conditions on farms and evaluation systems have been developed to certify them, such as the Welfare Quality^® protocol. Among the markers used for this purpose, acute phase proteins stand out, with haptoglobin being one of the most relevant. However, the diagnostic power of these tools is limited and more sensitive and specific technologies are required to monitor animal health status. Different factors such as diet, stress, and diseases modify the metabolism of the animals, altering the composition of the milk in terms of oligosaccharides, proteins, and lipids. Thus, in order to study oxidative-stress-associated lipids, a collection of well-characterized milk samples, both by veterinary diagnosis and by content of the acute stress biomarker haptoglobin, was analyzed by mass spectrometry and artificial intelligence. Two lipid species (sphingomyelin and phosphatidylcholine) were identified as potential biomarkers of health status in dairy cows. Both lipids allow for the discrimination of milk from sick animals and also milk from those with stress. Moreover, lipidomics revealed specific lipid profiles depending on the origin of the samples and the degree of freedom of the animals on the farm. These data provide evidence for specific lipid changes in stressed animals and open up the possibility that haptoglobin could also affect lipid metabolism in cow's milk.

Quantification of phospholipids and glycerides in human milk using ultra-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry

Human milk lipids, which are an important source of energy and affect growth and development of infants, require a comprehensive method for its qualitative and quantitative analysis. This work describes a method for the analysis of phospholipids, glycerides, free fatty acids and gangliosides in human milk by ultra-performance liquid chromatography using a C18 column with quadrupole-time-of-flight mass spectrometry (Q-TOF-MS). The lipids were extracted by liquid-liquid extraction and phospholipids were separated by solid phase extraction (SPE). The chromatographic columns with two different specifications (4.6 mm × 150 mm, and 3 mm × 50 mm) were used to detect phospholipids and glycerides in human milk, respectively. The sphingolipids and glycerides were analyzed in positive ion mode, and the glycerophospholipids and free fatty acids were analyzed in negative ion mode. Both internal and external standards were used for absolute quantification in this experiment. 483 species of lipids, including phospholipids, glycerides, free fatty acids and gangliosides, in human milk were analyzed using UPLC-Q-TOF-MS with high sensitivity and good linearity, with coefficient of correlation above 0.99, the relative standard deviation of accuracy and precision less than 10%. The results in a large number of human milk samples showed that this method was suitable for qualitative and quantitative analysis of lipids in human milk, even for other mammalian milk and infant formulae.

Comparison of Workflows for Milk Lipid Analysis: Phospholipids

Milk is a rich source of lipids, with the major components being triglycerides (TAG) and phospholipids (mainly phosphatidylcholine (PC), sphingomyelin (SM), phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI)). Liquid chromatography-mass spectrometry (LC-MS) is the predominant technique for lipid identification and quantification across all biological samples. While fatty acid (FA) composition of the major lipid classes of milk can be readily determined using tandem MS, elucidating the regio-distribution and double bond position of the FA remains difficult. Various workflows have been reported on the quantification of lipid species in biological samples in the past 20 years, but no standard or consensus methods are currently available for the quantification of milk phospholipids. This study will examine the influence of several common factors in lipid analysis workflow (including lipid extraction protocols, LC stationary phases, mobile phase buffers, gradient elution programmes, mass analyser resolution and isotope correction) on the quantification outcome of bovine milk phospholipids. The pros and cons of the current LC-MS methods as well as the critical problems to be solved will also be discussed.

Comprehensive lipidomic analysis of milk polar lipids using ultraperformance supercritical fluid chromatography-mass spectrometry

Polar lipids in milk are receiving increasing interest due to their bioactivities. However, milk polar lipids present a wide range of physical-chemical properties at different concentrations, making their analysis challenging. In this study, we presented a comprehensive lipidomic method using ultraperformance supercritical fluid chromatography (UPSFC)-quadrupole-time of flight-mass spectrometry (Q-TOF-MS), which enabled the separation of 18 lipid classes (including nonpolar lipids, cholesterol, ceramide, glycerophospholipids, sphingomyelin, and gangliosides) within 10 min. The method was used to analyze the polar lipids in seven samples, including human milk, other mammalian milk and milk fat globule membrane ingredients, identifying 14 lipid classes containing 219 lipid molecular species. A mass spectrometry data processing strategy applicable for high-throughput studies was also developed and validated.

Quantifying Sphingomyelin in Dairy through Infusion-Based Shotgun Mass Spectrometry with Lithium-Ion-Induced Fragmentation

Quantifying sphingomyelin (SM) species by infusion-based mass spectrometry (MS) is complicated by the presence of isobaric phosphatidylcholine (PC) species, which generate a common m/z 184 product ion in the presence of ammonium ions as a result of the phosphocholine headgroup. Lithium ion adducts of SM undergo a selective dehydration [Li + H₂O + (CH₃)₃NC₂H₄PO₄] with a corresponding neutral loss of -207 Da. This neutral loss was employed to create a SM-selective method for identifying target species, which were quantitated using multiple reaction monitoring (MRM). SM-selective fragments in MS³ were used to characterize the sphingosine base and acyl chain. These methods were used to identify 50 individual SM species in bovine milk ranging from SM 28:1 to SM 44:2, with d16:1, d17:1, d18:1, d19:1, and d20:1 bases, and acyl fatty acids ranging from 10 to 25 carbons and 0-1 desaturations. Spiked SM standards into milk had a recovery of 99.7%, and endogenous milk SM had <10% coefficient of variation for both intra- and interday variability, with limits of detection of 1.4-5.55 nM and limits of quantitation of 11.8-178.1 nM. This MS-MRM method was employed to accurately and precisely quantify SM species in dairy products, including bovine-derived whole milk, half and half, whipping cream, and goat milk.

The nutritional functions of dietary sphingomyelin and its applications in food

Sphingolipids are common structural components of cell membranes and are crucial for cell functions in physiological and pathophysiological conditions. Sphingomyelin and its metabolites, such as sphingoid bases, ceramide, ceramide-1-phosphate, and sphingosine-1-phosphate, play signaling roles in the regulation of human health. The diverse structures of sphingolipids elicit various functions in cellular membranes and signal transduction, which may affect cell growth, differentiation, apoptosis, and maintain biological activities. As nutrients, dietary sphingomyelin and its metabolites have wide applications in the food and pharmaceutical industry. In this review, we summarized the distribution, classifications, structures, digestion, absorption and metabolic pathways of sphingolipids, and discussed the nutritional functioning of sphingomyelin in chronic metabolic diseases. The possible implications of dietary sphingomyelin in the modern food preparations including dairy products and infant formula, skin improvement, delivery system and oil organogels are also evaluated. The production of endogenous sphingomyelin is linked to pathological changes in obesity, diabetes, and atherosclerosis. However, dietary supplementations of sphingomyelin and its metabolites have been shown to maintain cholesterol homeostasis and lipid metabolism, and to prevent or treat these diseases. This seemly paradoxical phenomenon shows that dietary sphingomyelin and its metabolites are candidates for food additives and functional food development for the prevention and treatment of chronic metabolic diseases in humans.

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.

Lipidomic Signatures of Dairy Consumption and Associated Changes in Blood Pressure and Other Cardiovascular Risk Factors Among Chinese Adults

BACKGROUND

Omics data may provide a unique opportunity to discover dairy-related biomarkers and their linked cardiovascular health.

METHODS

Dairy-related lipidomic signatures were discovered in baseline data from a Chinese cohort study (n=2140) and replicated in another Chinese study (n=212). Dairy intake was estimated by a validated food-frequency questionnaire. Lipidomics was profiled by high-coverage liquid chromatography-tandem mass spectrometry. Associations of dairy-related lipids with 6-year changes in cardiovascular risk factors were examined in the discovery cohort, and their causalities were analyzed by 2-sample Mendelian randomization using available genome-wide summary data.

RESULTS

Of 350 lipid metabolites, 4 sphingomyelins, namely sphingomyelin (OH) C32:2, sphingomyelin C32:1, sphingomyelin (2OH) C30:2, and sphingomyelin (OH) C38:2, were identified and replicated to be positively associated with total dairy consumption (β=0.130 to 0.148; P<1.43×10^-4), but not or weakly with nondairy food items. The score of 4 sphingomyelins showed inverse associations with 6-year changes in systolic (-2.68 [95% CI, -4.92 to -0.43]; P=0.019), diastolic blood pressures (-1.86 [95% CI, -3.12 to -0.61]; P=0.004), and fasting glucose (-0.25 [95% CI, -0.41 to -0.08]; P=0.003). Mendelian randomization analyses further revealed that genetically inferred sphingomyelin (OH) C32:2 was inversely associated with systolic (-0.57 [95% CI, -0.85 to -0.28]; P=9.16×10^-5) and diastolic blood pressures (-0.39 [95% CI, -0.59 to -0.20]; P=7.09×10^-5).

CONCLUSIONS

The beneficial effects of dairy products on cardiovascular health might be mediated through specific sphingomyelins among Chinese with overall low dairy consumption.

Novel Insight Into the Role of ACSL1 Gene in Milk Production Traits in Buffalo

Understanding the genetic mechanisms underlying milk production traits contribute to improving the production potential of dairy animals. Long-chain acyl-CoA synthetase 1 (ACSL1) plays a key role in fatty acid metabolism and was highly expressed in the lactating mammary gland epithelial cells (MGECs). The objectives of the present study were to detect the polymorphisms within ACSL1 in Mediterranean buffalo, the genetic effects of these mutations on milk production traits, and understand the gene regulatory effects on MGECs. A total of twelve SNPs were identified by sequencing, including nine SNPs in the intronic region and three in the exonic region. Association analysis showed that nine SNPs were associated with one or more traits. Two haplotype blocks were identified, and among these haplotypes, the individuals carrying the H2H2 haplotype in block 1 and H5H1 in block 2 were superior to those of other haplotypes in milk production traits. Immunohistological staining of ACSL1 in buffalo mammary gland tissue indicated its expression and localization in MGECs. Knockdown of ACSL1 inhibited cell growth, diminished MGEC lipid synthesis and triglyceride secretion, and downregulated CCND1, PPARγ, and FABP3 expression. The overexpression of ACSL1 promoted cell growth, enhanced the triglyceride secretion, and upregulated CCND1, PPARγ, SREBP1, and FABP3. ACSL1 was also involved in milk protein regulation as indicated by the decreased or increased β-casein concentration and CSN3 expression in the knockdown or overexpression group, respectively. In summary, our present study depicted that ACSL1 mutations were associated with buffalo milk production performance. This may be related to its positive regulation roles on MGEC growth, milk fat, and milk protein synthesis. The current study showed the potential of the ACSL1 gene as a candidate for milk production traits and provides a new understanding of the physiological mechanisms underlying milk production regulation.

Advances in analysis, metabolism and mimicking of human milk lipids

Human milk lipids differ from the milk lipids of other mammals in composition and positional distribution of fatty acids. Analysis and detection technology of lipids is key to understanding milk lipids, and thus the concentrations, compositions and distribution characteristics of milk lipids are discussed. Differences between human milk lipids and their substitutes in form, composition and structure affect their digestion, absorption and function in infants. Characteristics and mimicking of human milk lipids have been intensively studied with the objective of narrowing the gap between human milk and infant formulae. Based on the existing achievements, further progress may be made by improving detection techniques, deepening knowledge of metabolic pathways and perfecting fat substitutes. This review detailed the characteristics of human milk lipids and related detection technologies with a view towards providing a clear direction for research on mimicking human milk lipids in formulae to further improve infant nutrition.

Feeding hydrogenated palm fatty acids and rumen-protected protein to lactating Holstein-Friesian dairy cows modifies milk fat triacylglycerol composition and structure, and solid fat content

The aim of this study was to analyze the effect of fat and protein supplementation to dairy cattle rations on milk fat triacylglycerol (TAG) composition, fatty acid (FA) positional distribution in the TAG structure, and milk solid fat content (SFC). Fifty-six lactating Holstein-Friesian cows were blocked into 14 groups of 4 cows and randomly assigned 1 of 4 dietary treatments fed for 28 d: (1) low protein, low fat, (2) high protein, low fat, (3) low protein, high fat, and (4) high protein, high fat. The high protein and high fat diets were obtained by isoenergetically supplementing the basal ration (low protein, low fat) with rumen-protected soybean meal and rumen-protected rapeseed meal, and hydrogenated palm FA (mainly C16:0 and C18:0), respectively. Fat supplementation modified milk TAG composition more extensively compared with protein supplementation. Fat supplementation resulted in decreased concentrations of the low molecular weight TAG carbon number (CN) 26 to CN34 and medium molecular weight TAG CN40, CN44, and CN46, and increased concentrations of CN38 and the high molecular weight TAG CN50 and CN52. Increased contents of C16:0, C18:0, and C18:1cis-9 in TAG in response to fat supplementation were related to increases in the relative concentrations of C16:0 and C18:0 at the sn-2 position and C18:0 and C18:1cis-9 at the sn-1(3) positions of the TAG structure. Increased concentrations of high molecular weight TAG species CN50 and CN52 in response to fat supplementation was associated with increased milk SFC at 20, 25, and 30°C. Our study shows that important alterations in milk TAG composition and structure occur when feeding hydrogenated palm FA to lactating dairy cattle, and that these alterations result in an increased SFC of milk fat. These changes in milk SFC and TAG composition and structure may improve absorption of both fat and minerals in milk-based products for infants and may affect processing of milk fat.

Cardiometabolic health benefits of dairy-milk polar lipids

Low-quality dietary patterns impair cardiometabolic health by increasing the risk of obesity-related disorders. Cardiometabolic risk relative to dairy-food consumption continues to be a controversial topic, due to recommendations that endorse low-fat and nonfat dairy foods over full-fat varieties despite accumulated evidence that does not strongly support these recommendations. Controlled human studies and mechanistic preclinical investigations support that full-fat dairy foods decrease cardiometabolic risk by promoting gut health, reducing inflammation, and managing dyslipidemia. These gut- and systemic-level cardiometabolic benefits are attributed, at least in part, to milk polar lipids (MPLs) derived from the phospholipid- and sphingolipid-rich milk fat globule membrane that is of higher abundance in full-fat dairy milk. The controversy surrounding full-fat dairy food consumption is discussed in this review relative to cardiometabolic health and MPL bioactivities that alleviate dyslipidemia, shift gut microbiota composition, and reduce inflammation. This summary, therefore, is expected to advance the understanding of full-fat dairy foods through their MPLs and the need for translational research to establish evidence-based dietary recommendations.

Regio-distribution and double bond locations of unsaturated fatty acids in phospholipids of bovine milk

Hundreds of phospholipid (PL) species with defined fatty acid (FA) composition have been identified previously in bovine milk using liquid chromatography tandem mass spectrometry (LC-MS/MS). Paterno-Buchi photochemical reaction coupled with LC-MS/MS was applied in this study to further unravel the regio-distribution and double bond (DB) locations of FAs. Using SPE-purified PLs and 2-acetylpyridine as the photochemical derivatization reagent, we were able to reveal the non-specific regio-distribution of unsaturated FAs and the widespread occurrence of regioisomers in milk PLs. Although Δ9 and Δ9,12 were found to be the predominant DB location(s) for C18:1 and C18:2 respectively, other DB positional isomers such as C18:1Δ11, C18:1Δ12 and C18:1Δ13 and C18:2Δ9,11 were widely detected in PL structures, implying that the minor isomers of C18:1 and C18:2 equally participate in the synthesis of PLs. Our study provides novel information on the fine structure of milk PLs and further underlines the complexity of milk lipid composition.

MILK LIPIDS AND SUBCLINICAL MASTITIS

This article deals with the process of obtaining quality raw milk by analyzing its lipid composition. The lipid composition of raw milk depends on many factors, among which, first of all, is the species, the composition of the diet and the physiological state of the breast. In recent years, a large amount of data has accumulated on the fluctuations of certain lipid parameters of milk depending on the type, age, lactation, diet, time of year, exercise, animal husbandry technology, physiological state of the lactating organism in general and breast status in particular. Factors of regulation of fatty acid composition of raw milk: genetically determined parameters of quality and safety; fatty acid composition of the diet; synthesis of fatty acids by microorganisms of the digestive tract; synthesis of fatty acids in the breast; physiological state of the breast. The milk of each species of productive animals has its own specific lipid profile and is used in the formulation of certain dairy products to obtain the planned technological and nutritional parameters. Diagnosis of productive animals for subclinical mastitis involves the use of auxiliary (thermometry, thermography, electrical conductivity) and laboratory research methods: counting the number of somatic cells; use of specialized tests; microbiological studies of milk; biochemical studies of milk. The biochemical component in the diagnosis of subclinical forms of mastitis is underestimated. An increase in body temperature implies an increase in the intensity of heat release during the oxidation of substrates, sometimes due to a decrease in the intensity of synthesis of energy-intensive compounds. There are simply no other sources of energy in the body. The situation is the same with certain parts of the metabolism, which are aimed at the development of protective reactions to the etiological factor aimed at the defeat of the breast. That is why the biochemical composition of breast secretions in the absence of clinical signs of mastitis undergoes biochemical changes and the task of scientists is to develop mechanisms for clear tracking of such changes, identification of animals with subclinical forms of mastitis and effective treatment.

Seasonal variation in fatty acid and triacylglycerol composition of bovine milk fat

The aim of this study was to assess the effects of seasonal variation on the changes of the fatty acid (FA) and triacylglycerol (TAG) composition of bovine milk fat (MF) in a nonseasonal milking system. Weekly milk samples were collected from 14 dairy factories and pooled per week as representative samples of the average Dutch bovine milk. The sample collection started in May 2017 and finished in April 2018, resulting in a total of 52 samples, corresponding to each week of the year. The samples were analyzed for MF content (%) and FA and TAG composition using gas chromatography with flame-ionization detection. The increased intake of C18:3 cis-9,12,15 through grass feeding in spring and summer was associated with major changes in MF FA composition, including reduced proportions of de novo synthesized FA and presence of several rumen biohydrogenation products and conjugated linoleic acid isomers in MF. These changes in seasonal FA composition had an effect on TAG seasonal variation. The TAG seasonal variation showed that all TAG groups were significantly different between months. The low molecular weight and the medium molecular weight TAG groups increased in winter and decreased in summer, whereas the high molecular weight TAG groups increased in summer and decreased in winter. Based on pooled monthly samples, MALDI-TOF-mass spectrometry allowed the analysis of even- and odd-chain TAG species in MF based on their total carbon number and number of double bonds. These analyses indicated saturated TAG species to be greatest in winter, whereas monounsaturated, polyunsaturated, and odd-chain TAG species were greatest in summer. Our study showed that TAG seasonal variation in a nonseasonal milking system is influenced by the variation in FA composition throughout the seasons.

Milk Phospholipid Profiling Among Japanese Women with Differing Docosahexaenoic Acid Levels

To characterize the milk phospholipids (PLs) profile using phosphorus-31 nuclear magnetic resonance (³¹P-NMR) and to investigate the effect of elevated milk docosahexaenoic acid (DHA) levels on PLs profiles in Japanese mothers.

Methods

Milk samples from eligible patients with high and low DHA from a former cross-sectional study (n = 20; n = 10 for each group) were included. Fifteen milk PLs were analyzed using ³¹P-NMR, and the profiles were compared group-wise using Mann-Whitney U-test. The P value of <0.05 was considered statistically significant.

Results

The median DHA content in milk was 1.13% and 0.29% for the high and low milk DHA groups, respectively. Twelve PLs, excluding lysophosphatidylserine, cardiolipin, and phosphatidylglycerol, were detected in all participants with 100% positive results. The median concentrations and proportions of total PLs, sphingophospholipids, and glycerophospholipids were comparable between groups. The proportions of choline-containing glycerophospholipid were significantly higher in the high milk DHA group than that in the low milk DHA group (24.09% [median, interquartile range: 23.08%-26.38%] and 21.41% [20.74%-22.84%], P = 0.019). Although the proportions of phosphatidylinositol were significantly lower in the high milk DHA group than that in the low milk DHA group (6.62% [5.75%-6.72%] versus 7.63% [7.11%-8.16%], P = 0.002), while that of phosphatidylcholine (21.90% [18.51%-23.22%] versus 19.78% [18.17%-20.26%], P = 0.059) and alkyl-acyl phosphatidylcholine (0.60% [0.40%-0.74%] versus 0.33% [0.14%-0.51%], P = 0.059) were higher in the former than that in the latter.

Conclusions

Our results were comparable to that of the previous literature. Large variations in the milk DHA might affect the composition of choline-containing glycerophospholipids in Japanese mothers. However, possible confounders were not excluded in the study populations.

Simultaneous Determination of Typical Chlorinated, Oxygenated, and European Union Priority Polycyclic Aromatic Hydrocarbons in Milk Samples and Milk Powders

An increasing number of studies have suggested that PAH contamination in dairy products demands high concern. This study established an efficient determination method for the European Union 15 + 1 PAHs and four PAH derivatives in dairy samples using a QuEChERS method coupled with GC-QqQ-MS. The optimized method obtained a recovery of 63.38-109.17% with a precision of 3.82-15.62%, and the limit of detection and limit of quantification were 0.08-0.78 and 0.27-2.59 μg/kg, respectively. The validated method was then successfully applied to identify the 20 PAHs in 82 dairy samples, including 43 commercial milk samples and 39 milk powders. The total PAH concentrations ranged from 2.37 to 11.83 μg/kg, and benzo[a]pyrene was only quantified in one milk and one milk powder sample at 0.35 and 0.42 μg/kg, respectively. The concentrations of PAH4 in milk samples and milk powders were not quantified (nq)-3.99 and nq-4.51 μg/kg, respectively. The results confirmed the appreciable occurrence of PAHs in dairy products, especially in infant formula. The data in this study provide a scientific basis for assessment on origin tracing, dietary exposure, and health risk of PAHs and their derivatives.

Deciphering the Importance of Glycosphingolipids on Cellular and Molecular Mechanisms Associated with Epithelial-to-Mesenchymal Transition in Cancer

Every living cell is covered with a dense and complex layer of glycans on the cell surface, which have important functions in the interaction between cells and their environment. Glycosphingolipids (GSLs) are glycans linked to lipid molecules that together with sphingolipids, sterols, and proteins form plasma membrane lipid rafts that contribute to membrane integrity and provide specific recognition sites. GSLs are subdivided into three major series (globo-, ganglio-, and neolacto-series) and are synthesized in a non-template driven process by enzymes localized in the ER and Golgi apparatus. Altered glycosylation of lipids are known to be involved in tumor development and metastasis. Metastasis is frequently linked with reversible epithelial-to-mesenchymal transition (EMT), a process involved in tumor progression, and the formation of new distant metastatic sites (mesenchymal-to-epithelial transition or MET). On a single cell basis, cancer cells lose their epithelial features to gain mesenchymal characteristics via mechanisms influenced by the composition of the GSLs on the cell surface. Here, we summarize the literature on GSLs in the context of reversible and cancer-associated EMT and discuss how the modification of GSLs at the cell surface may promote this process.

Cow's Milk and Dairy Consumption: Is There Now Consensus for Cardiometabolic Health?

Cow's milk and dairy products derived from this complex food source have long been proposed as beneficial to human health, yet underlying clinical evidence of direct benefit continues to raise controversy. Limited evidence supports positive cardiometabolic effects of a number of dairy macro- and micronutrient components including whey protein and casein, unsaturated fats, milk fat globule membrane (MFGM) and polar phospholipids, vitamin D and calcium, in addition to non-bovine components including bacterial and yeast probiotics. More controversial remain lipid components trans fats, including trans vaccenic acid, trans palmitoleic acid, and conjugated cis trans linoleic acid (CLA), plus medium-chain and odd-chain dairy fats. New evidence is rapidly identifying multiple pathways by which these dairy nutrients may effect health. Processing, including fermentation and homogenization, may also have positive effects. Conversely, the high saturated fat content of dairy has long raised concern, aligned with international guidelines to minimize dietary intake of animal-origin saturated fatty acids (SFA) to achieve better cardiometabolic health. However, led in part by observational studies and meta-analyses showing dairy to have no or even an inverse association with cardiometabolic health, evidence from randomized controlled trials (RCTs) has been scrutinized over the last 5 years, and focus on low-fat dairy has been challenged. Recent evidence supports the hypothesis that adverse effects of SFAs on metabolic health may be ameliorated when these fats are consumed within a complex matrix such as milk, cheese or yogurt, and that dairy food categories may influence outcomes as much as total fat content. For example, yogurt and high-fat, high-SFA cheese have a negative association with risk of type 2 diabetes (T2D) in many, not all, published trials. However, large sample dairy RCTs of long duration with CVD or T2D incidence as primary endpoints are lacking. This is a clear research gap, with these clinical studies required if a causative link between dairy and improved cardiometabolic health is to be confirmed and in turn promoted through dietary guidelines. Current advisories from national guidance groups such as American Heart Association (AHA) and European Society of Cardiology (ESC) continue to promote consumption of low-fat dairy products, whilst liquid milk and yogurt remain part of nutrition guidelines from joint American Diabetes Association (ADA)/European Association for Study of Diabetes (EASD) reports, and as part of a "no-one-size-fits-all" answer to diet and T2D by the ADA in their most recent 2019 Consensus Report.