Lipidome analysis of milk composition in humans, monkeys, bovids, and pigs

A metabolomics analysis of interspecies and seasonal trends in ruminant milk: The molecular difference between bovine, caprine, and ovine milk

Ruminant milk composition can be affected by many factors, primarily interspecies differences, but also environmental factors (e.g., season, feeding system, and feed composition). Pasture-based feeding systems are known to be influenced by seasonal effects on grass composition. Spring pasture is rich in protein and low in fiber compared with late-season pasture, potentially inducing variability in the composition of some milk metabolites across the season. This study aimed to investigate interspecies and seasonal differences in the milk metabolome across the 3 major commercial ruminant milk species from factories in New Zealand: bovine, caprine, and ovine milk. Samples of bovine (n = 41) and caprine (n = 44) raw milk were collected monthly for a period of 9 mo (August 2016-April 2017), and ovine milk samples (n = 20) were collected for a period of 5 mo (August 2016-January 2017). Milk samples were subjected to biphasic extraction, and untargeted metabolite profiling was performed using 2 separate liquid chromatography high-resolution mass spectrometry analytical methods (polar metabolites and lipids). Major differences in the milk metabolome were observed between the 3 ruminant species, with 414 of 587 (71%) polar metabolite features and 210 of 233 (87%) lipid features being significantly different between species. Significant seasonal trends were observed in the polar metabolite fraction for bovine, caprine, and ovine milk (17, 24, and 32 metabolites, respectively), suggesting that the polar metabolite relative intensities of ovine and caprine milk were more susceptible to changes within seasons than bovine milk. We found no significant seasonal difference for the triglycerides (TG) species measured in bovine milk, whereas 3 and 52 TG species changed in caprine and ovine milk, respectively, across the seasons. In addition, 4 phosphatidylcholines and 2 phosphatidylethanolamines varied in caprine milk within the season, and 8 diglycerides varied in ovine milk. The interspecies and seasonal metabolite differences reported here provide a knowledge base of components potentially linked to milk physiochemical properties, and potential health benefits of New Zealand pasture-fed dairy ingredients.

Analysis for lipid nutrient differences in the milk of 13 species from a quantitative non-targeted lipidomics perspective

Lipids are essential organic components in milk and have been associated with various health benefits for newborns. However, a comprehensive analysis of lipid profiles across multiple species and levels has been lacking. In this study, we employed liquid chromatography-tandem mass spectrometry (LC-MS/MS) to accurately determine the absolute content of lipid molecules. It revealed that ruminants exhibit a higher concentration of short-chain fatty acids compared to non-ruminants. Additionally, we identified ALC (camel), MGH (horse), and DZD (donkey) as species that display similarities to components found in human milk fat. Remarkably, it reveals that porcine milk fat is characterized by long chain lengths, low saturation, and a high proportion of essential fatty acids. PS (22:5_18:2) could potentially serve as a biomarker in porcine milk. These unique characteristics present potential opportunities for the utilization of porcine milk. Overall, our findings provide valuable insights into the lipidomics profiles of milk from different species.

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.

Analysis of Muscle Lipidome in Juvenile Rainbow Trout Fed Rapeseed Oil and Cochayuyo Meal

This study aimed to analyze the effects on the lipidome of juvenile Oncorhynchus mykiss muscle fed 90% Brassica napus “rapeseed” oil and different amounts of Durvillaea antarctica “Cochayuyo” meal (1.5, 3 and 6%) as a replacement for cellulose. The analysis allowed for the identification of 329 lipids, mainly represented by phospholipids and fatty esters. The inclusion of Brassica napus oil significantly increased the levels of C18:2 species and fatty esters of hydroxylated fatty acids, which could play a bioactive role in human health. One of the most abundant lipids in all fillets was Phosphatidylcholine 33:6, which, according to the literature, could be considered a biomarker for the identification of Oncorhynchus mykiss. In all experimental diets, the species Phosphatidylethanolamine 15:1-18:24 showed four-fold higher levels than the control; increments of n-3- and n-6-rich phospholipids were also observed. Diets containing Durvillaea antarctica meal did not generate more significant variation in fish muscle phospholipids relative to the muscle of the rapeseed-oil-only group. These lipid species consist of medium- and long-chain fatty acids with different degrees of unsaturation. Still, it appears that the rapeseed oil masks the lipid contribution of the meal, possibly due to the low levels of total lipids in the macroalgae.

Mechanisms underlying neonate-specific metabolic effects of volatile anesthetics

Volatile anesthetics (VAs) are widely used in medicine, but the mechanisms underlying their effects remain ill-defined. Though routine anesthesia is safe in healthy individuals, instances of sensitivity are well documented, and there has been significant concern regarding the impact of VAs on neonatal brain development. Evidence indicates that VAs have multiple targets, with anesthetic and non-anesthetic effects mediated by neuroreceptors, ion channels, and the mitochondrial electron transport chain. Here, we characterize an unexpected metabolic effect of VAs in neonatal mice. Neonatal blood β-hydroxybutarate (β-HB) is rapidly depleted by VAs at concentrations well below those necessary for anesthesia. β-HB in adults, including animals in dietary ketosis, is unaffected. Depletion of β-HB is mediated by citrate accumulation, malonyl-CoA production by acetyl-CoA carboxylase, and inhibition of fatty acid oxidation. Adults show similar significant changes to citrate and malonyl-CoA, but are insensitive to malonyl-CoA, displaying reduced metabolic flexibility compared to younger animals.

Changes in sow milk lipidome across lactation occur in fatty acyl residues of triacylglycerol and phosphatidylglycerol lipids, but not in plasma membrane phospholipids

Milk fats are vital to neonate survival and development, but vary highly by diet, maternal metabolic state and stage of lactation. To gain a better understanding of changes in lipid composition of sow milk across lactation, milk was collected from nine multiparous sows on days 0, 3, 7, and 14, relative to birth and lipids were profiled using multiple reaction monitoring (MRM) profiling. Percent fat was determined by creamatocrit, and found to be different (P < 0.05) between day 0 (12.36 ± 5.90%) and day 3 (16.22 ± 3.65%) but not between day 7 (13.13 ± 2.19%) and day 14 (12.13 ± 2.45%). Fat was extracted from milk (n = 6/day) using the Bligh-Dyer method and profiled using tandem mass spectrometry MRM to determine the abundance of lipids defined by class and fatty acyl residue composition. Lipid species relative concentration was calculated from internal standards, and data analysis was performed using Metaboanalyst 4.0. Concentration of phosphatidyl-choline, -serine, -ethanolamine, -inositol, cholesteryl ester and sphingomyelin did not vary across lactation days, nor did the distribution of associated fatty acyl residues. The total abundance of triacylglycerides (TGs) and phosphatidylglycerols (PGs) increased (P < 0.05) from colostrum (day 0) to transitional (days 3 and 7) and mature milk (day 14). As lactation days increased from day 0 to day 14, the number of carbons and unsaturation within fatty acyl residues decreased (P < 0.05) in both TGs and PGs. The proportion of TGs and PGs increased (P < 0.05) relative to other lipid classes. Changes in composition of milk triglycerides and phosphatidylglycerols likely reflect the metabolic activity of the mammary gland and developmental needs of neonates.

The untargeted lipidomic profile of quarter milk from dairy cows with subclinical intramammary infection by non-aureus staphylococci

This observational study determined the lipidome of cow milk during subclinical intramammary infection (IMI) by non-aureus staphylococci (NAS), also defined as coagulase-negative staphylococci, using an untargeted approach. Among the pathogens causing bovine IMI, NAS have become the most frequently isolated bacteria from milk samples. Although the application of system biology approaches to mastitis has provided pivotal information by investigating the transcriptome, proteome, peptidome, and metabolome, the milk lipidome during mammary gland inflammation remains undisclosed. To cover this gap, we determined the milk lipidome of 17 dairy cows with IMI caused by NAS (NAS-IMI), and we compared the results with those of healthy quarter milk from 11 cows. The lipidome was determined following a liquid chromatography-quadrupole time-of-flight mass spectrometry approach. Sixteen subclasses of lipids were identified in both groups of animals. From 2,556 measured lipids, the abundance of 597 changed more than 10-fold in quarter milk with NAS-IMI compared with healthy quarters. The results demonstrate the influence of NAS-IMI on the milk lipidome, implying significant changes in lipid species belonging to the family of triacylglycerols and sphingomyelins, and contribute to the understanding of inflammatory processes in the bovine udder, highlighting potential novel biomarkers for improving mastitis diagnostics.

Quantification of Nonpersistent Pesticides in Small Volumes of Human Breast Milk with Ultrahigh Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry

Existing methods for the analysis of pesticides in human breast milk involve multiple extraction steps requiring large sample and solvent volumes, which can be a major obstacle in large epidemiologic studies. Here, we developed a simple, low-volume method for extracting organophosphates, pyrethroids, carbamates, atrazine, and imidacloprid from 100 to 200 μL of human breast milk. Multiple extraction protocols were tested including microwave-assisted acid/base digestion and double-solvent extraction with 2 or 20 mL of 2:1 (v/v) dichloromethane/hexane, with or without subsequent solid-phase extraction (SPE) cleanup. Samples were analyzed by liquid chromatography tandem mass spectrometry. Analyte recoveries and reproducibility were highest when 100-200 μL of milk were extracted with 2 mL of dichloromethane/hexane without subsequent SPE steps. Analysis of 79 breast milk samples using this method revealed the presence of carbamates, organophosphates, pyrethroids, and imidacloprid at detection frequencies of 79-96, 53-90, 1-7, and 61%, respectively. This study demonstrates the feasibility of a simple low-volume extraction method for measuring pesticides in human breast milk.