Differences in oligosaccharide pattern of a sample of polar bear colostrum and mid-lactation milk

Creation of a milk oligosaccharide database, MilkOligoDB, reveals common structural motifs and extensive diversity across mammals

The carbohydrate fraction of most mammalian milks contains a variety of oligosaccharides that encompass a range of structures and monosaccharide compositions. Human milk oligosaccharides have received considerable attention due to their biological roles in neonatal gut microbiota, immunomodulation, and brain development. However, a major challenge in understanding the biology of milk oligosaccharides across other mammals is that reports span more than 5 decades of publications with varying data reporting methods. In the present study, publications on milk oligosaccharide profiles were identified and harmonized into a standardized format to create a comprehensive, machine-readable database of milk oligosaccharides across mammalian species. The resulting database, MilkOligoDB, includes 3193 entries for 783 unique oligosaccharide structures from the milk of 77 different species harvested from 113 publications. Cross-species and cross-publication comparisons of milk oligosaccharide profiles reveal common structural motifs within mammalian orders. Of the species studied, only chimpanzees, bonobos, and Asian elephants share the specific combination of fucosylation, sialylation, and core structures that are characteristic of human milk oligosaccharides. However, agriculturally important species do produce diverse oligosaccharides that may be valuable for human supplementation. Overall, MilkOligoDB facilitates cross-species and cross-publication comparisons of milk oligosaccharide profiles and the generation of new data-driven hypotheses for future research.

Chemical structures of oligosaccharides in milks of the American black bear (Ursus americanus americanus) and cheetah (Acinonyx jubatus)

The milk oligosaccharides were studied for two species of the Carnivora: the American black bear (Ursus americanus, family Ursidae, Caniformia), and the cheetah, (Acinonyx jubatus, family Felidae, Feliformia). Lactose was the most dominant saccharide in cheetah milk, while this was a minor saccharide and milk oligosaccharides predominated over lactose in American black bear milk. The structures of 8 neutral saccharides from American black bear milk were found to be Gal(β1-4)Glc (lactose), Fuc(α1-2)Gal(β1-4)Glc (2'-fucosyllactose), Gal(α1-3)Gal(β1-4)Glc (isoglobotriose), Gal(α1-3)[Fuc(α1-2)]Gal(β1-4)Glc (B-tetrasaccharide), Gal(α1-3)[Fuc(α1-2)]Gal(β1-4)[Fuc(α1-3)]Glc (B-pentasaccharide), Fuc(α1-2)Gal(β1-4)[Fuc(α1-3)]GlcNAc(β1-3)Gal(β1-4)Glc (difucosyl lacto-N-neotetraose), Gal(α1-3)Gal(β1-4)[Fuc(α1-3)]GlcNAc(β1-3)Gal(β1-4)Glc (monogalactosyl monofucosyl lacto-N-neotetraose) and Gal(α1-3)Gal(β1-4)GlcNAc(β1-3)Gal(β1-4)Glc (Galili pentasaccharide). Structures of 5 acidic saccharides were also identified in black bear milk: Neu5Ac(α2-3)Gal(β1-4)Glc (3'-sialyllactose), Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1-3)[Fuc(α1-2)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (monosialyl monofucosyl lacto-N-neohexaose), Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1-3)[Gal(α1-3)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (monosialyl monogalactosyl lacto-N-neohexaose), Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1-3){Gal(α1-3)Gal(β1-4)[Fuc(α1-3)]GlcNAc(β1-6)}Gal(β1-4)Glc (monosialyl monogalactosyl monofucosyl lacto-N-neohexaose), and Neu5Ac(α2-6)Gal(β1-4)GlcNAc(β1-3){Gal(α1-3)[Fuc(α1-2)]Gal(β1-4)[Fuc(α1-3)]GlcNAc(β1-6)}Gal(β1-4)Glc (monosialyl monogalactosyl difucosyl lacto-N-neohexaose). A notable feature of some of these milk oligosaccharides is the presence of B-antigen (Gal(α1-3)[Fuc(α1-2)]Gal), α-Gal epitope (Gal(α1-3)Gal(β1-4)Glc(NAc)) and Lewis x (Gal(β1-4)[Fuc(α1-3)]GlcNAc) structures within oligosaccharides. By comparison to American black bear milk, cheetah milk had a much smaller array of oligosaccharides. Two cheetah milks contained Gal(α1-3)Gal(β1-4)Glc (isoglobotriose), while another cheetah milk did not, but contained Gal(β1-6)Gal(β1-4)Glc (6'-galactosyllactose) and Gal(β1-3)Gal(β1-4)Glc (3'-galactosyllactose). Two cheetah milks contained Gal(β1-4)GlcNAc(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (lacto-N-neohexaose), and one cheetah milk contained Gal(β1-4)Glc-3'-O-sulfate. Neu5Ac(α2-8)Neu5Ac(α2-3)Gal(β1-4)Glc (disialyllactose) was the only sialyl oligosaccharide identified in cheetah milk. The heterogeneity of milk oligosaccharides was found between both species with respect of the presence/absence of B-antigen and Lewis x. The variety of milk oligosaccharides was much greater in the American black bear than in the cheetah. The ratio of milk oligosaccharides-to-lactose was lower in cheetah (1:1-1:2) than American black bear (21:1) which is likely a reflection of the requirement for a dietary supply of N-acetyl neuraminic acid (sialic acid), in altricial ursids compared to more precocial felids, given the role of these oligosaccharides in the synthesis of brain gangliosides and the polysialic chains on neural cell adhesion.

Chemical structures of oligosaccharides in milk of the raccoon (Procyon lotor)

In this study on milk saccharides of the raccoon (Procyonidae: Carnivora), free lactose was found to be a minor constituent among a variety of neutral and acidic oligosaccharides, which predominated over lactose. The milk oligosaccharides were isolated from the carbohydrate fractions of each of four samples of raccoon milk and their chemical structures determined by ¹H-NMR and MALDI-TOF mass spectroscopies. The structures of the four neutral milk oligosaccharides were Fuc(α1-2)Gal(β1-4)Glc (2'-fucosyllactose), Fuc(α1-2)Gal(β1-4)GlcNAc(β1-3)Gal(β1-4)Glc (lacto-N-fucopentaose IV), Fuc(α1-2)Gal(β1-4)GlcNAc(β1-3)Gal(β1-4)GlcNAc(β1-3)Gal(β1-4)Glc (fucosyl para lacto-N-neohexaose) and Fuc(α1-2)Gal(β1-4)GlcNAc(β1-3)[Fuc(α1-2)Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc (difucosyl lacto-N-neohexaose). No type I oligosaccharides, which contain Gal(β1-3)GlcNAc units, were detected, but type 2 saccharides, which contain Gal(β1-4)GlcNAc units were present. The monosaccharide compositions of two of the acidic oligosaccharides were [Neu5Ac]₁[Hex]₆[HexNAc]₄[deoxy Hex]₂, while those of another two were [Neu5Ac]₁[Hex]₈[HexNAc]₆[deoxy Hex]_3. These acidic oligosaccharides contained α(2-3) or α(2-6) linked Neu5Ac, non reducing α(1-2) linked Fuc, poly N-acetyllactosamine (Gal(β1-4)GlcNAc) and reducing lactose.

Changes in the Milk Metabolome of the Giant Panda (Ailuropoda melanoleuca) with Time after Birth--Three Phases in Early Lactation and Progressive Individual Differences

Ursids (bears) in general, and giant pandas in particular, are highly altricial at birth. The components of bear milks and their changes with time may be uniquely adapted to nourish relatively immature neonates, protect them from pathogens, and support the maturation of neonatal digestive physiology. Serial milk samples collected from three giant pandas in early lactation were subjected to untargeted metabolite profiling and multivariate analysis. Changes in milk metabolites with time after birth were analysed by Principal Component Analysis, Hierarchical Cluster Analysis and further supported by Orthogonal Partial Least Square-Discriminant Analysis, revealing three phases of milk maturation: days 1–6 (Phase 1), days 7–20 (Phase 2), and beyond day 20 (Phase 3). While the compositions of Phase 1 milks were essentially indistinguishable among individuals, divergences emerged during the second week of lactation. OPLS regression analysis positioned against the growth rate of one cub tentatively inferred a correlation with changes in the abundance of a trisaccharide, isoglobotriose, previously observed to be a major oligosaccharide in ursid milks. Three artificial milk formulae used to feed giant panda cubs were also analysed, and were found to differ markedly in component content from natural panda milk. These findings have implications for the dependence of the ontogeny of all species of bears, and potentially other members of the Carnivora and beyond, on the complexity and sequential changes in maternal provision of micrometabolites in the immediate period after birth.

Milk oligosaccharides over time of lactation from different dog breeds

The partnership of humans and dogs goes back to over 10'000 years, yet relatively little is known about a dog's first extra-uterine nutrition particularly when it comes to milk oligosaccharides. We set out to identify and quantify milk oligosaccharides over the course of lactation from different dog breeds (Labrador retriever, Schnauzer and 3 Alaskan husky crossbreeds). To this end, 2 different chromatographic methods with fluorescence and mass spectrometry detection were developed and one was validated for quantification. Besides lactose and lactose-sulphate, we identified 2 different trisaccharides composed of 3 hexose units, 3'sialyllactose (3'SL), 6'sialyllactose (6'SL), 2'fucosyllactose (2'FL), and a tetrasaccharide composed of 2 hexoses, an N-acetylhexosamine and a deoxyhexose. 3'SL was present at the highest levels in milk of all dog breeds starting at around 7.5 g/L and dropping to about 1.5 g/L in the first 10 days of lactation. 6'SL was about 10 times less abundant and 2'FL and the tetrasaccharide had rather varying levels in the milk of the different breeds with the tetrasaccharide only detectable in the Alaskan husky crossbreeds. The longitudinal and quantitative data of milk oligosaccharides from different dog breeds are an important basis to further our understanding on their specific biological roles and also on the specific nutritional requirements of lactating puppies.

Neutral and acidic milk oligosaccharides of the striped skunk (Mephitidae: Mephitis mephitis)

The biological significance of the tremendous variation in proportions of oligosaccharides and lactose among mammalian milks is poorly understood. We investigated milk oligosaccharides of the striped skunk (Mephitis mephitis) and compared these results to other species of the clade Mustelida. Individual oligosaccharides were identified by proton nuclear magnetic resonance spectroscopy. In the striped skunk, six oligosaccharides were identified: isoglobotriose, 2'-fucosyllactose, A-tetrasaccharide, Galili pentasaccharide, 3'-sialyllactose and monosialyl monogalactosyl lacto-N-neohexaose. Four of these have been found in related Mustelida and the other two in more distantly related carnivorans. The neutral and acidic oligosaccharides derive from three core structures: lactose (Gal(β1-4)Glc), lacto-N-neotetraose (Gal(β1-4)GlcNAc(β1-3)Gal(β1-4)Glc) and lacto-N-neohexaose (Gal(β1-4)GlcNAc(β1-3)[Gal(β1-4)GlcNAc(β1-6)]Gal(β1-4)Glc).

Milk composition in free-ranging polar bears (Ursus maritimus) as a model for captive rearing milk formula

The goals of this study were to have an improved understanding of milk composition and to help create a suitable milk formula for cubs raised in captivity. Milk samples were evaluated for fat, fatty acids, carbohydrate, vitamin D(3), 25(OH)D(3), vitamin A (retinol), vitamin E (α-tocopherol), protein, and amino acids. Total lipids in milk did not differ for cubs (mean ± SEM = 26.60 ± 1.88 g/100 ml vs. yearlings 27.80 ± 2.20 g/100 ml). Milk lipids were of 23.6% saturated fatty acid for cubs and 22.4% for yearlings. Milk consumed by cubs and yearlings contained 43.8 and 42.0% mono-unsaturated fatty acids and 23.4 and 21.9% polyunsaturated fatty acids, respectively. Carbohydrate content was higher in milk for cubs (4.60 ± 0.64 g/100 ml) than for yearlings (2.60 ± 0.40 g/100 ml). Vitamin D(3) concentration of milk was 18.40 ± 5.00 ng/ml in early lactation compared with 7.60 ± 2.00 ng/ml for mid-lactation. 25(OH)D(3) was lower in milk consumed by cubs (162.00 ± 6.70 pg/ml) than in milk consumed by yearlings (205.00 ± 45.70 pg/ml). Vitamin A concentrations were 0.06 ± 0.01 and 0.03 ± 0.01 µg/ml for cubs and yearlings, respectively. Vitamin E was higher in milk consumed by cubs (20.16 ± 4.46 µg/ml) than by yearlings (7.30 ± 1.50 µg/ml). Protein content did not differ in milk available to cubs (11.40 ± 0.80 g/100 ml compared with milk for yearlings 11.80 ± 0.40 g/100 ml). Taurine was the most abundant free amino acid at 3,165.90 ± 192.90 nmol/ml (0.04% as fed basis).

Structural determination of the oligosaccharides in the milk of an Asian elephant (Elephas maximus)

Milk of an Asian elephant (Elephas maximus), collected at 11 days post partum, contained 91 g/L of hexose and 3 g/L of sialic acid. The dominant saccharide in this milk sample was lactose, but it also contained isoglobotriose (Glc(alpha1-3)Gal(beta1-4)Glc) as well as a variety of sialyl oligosaccharides. The sialyl oligosaccharides were separated from neutral saccharides by anion exchange chromatography on DEAE-Sephadex A-50 and successive gel chromatography on Bio Gel P-2. They were purified by high performance liquid chromatography (HPLC) using an Amide-80 column and characterized by 1H-NMR spectroscopy. Their structures were determined to be those of 3'-sialyllactose, 6'-sialyllactose, monofucosyl monosialyl lactose (Neu5Ac(alpha2-3)Gal(beta1-4)[Fuc(alpha1-3)]Glc), sialyl lacto-N-neotetraose c (LST c), galactosyl monosialyl lacto-N-neohexaose, galactosyl monofucosyl monosialyl lacto-N-neohexaose and three novel oligosaccharides as follows: Neu5Ac(alpha2-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc, Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc, and Neu5Ac(alpha2-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc. The higher oligosaccharides contained only the type II chain (Gal(beta1-4)GlcNAc); this finding differed from previously published data on Asian elephant milk oligosaccharides.

Characterization of oligosaccharides in milk of a mink, Mustela vison

Carbohydrates were extracted from a sample of milk from a mink, Mustela vison (Family Mustelidae). Free neutral and acidic oligosaccharides were isolated from the carbohydrate fraction and their chemical structures were compared with those of white-nosed coati (Nasua narica, Procyonidae) and harbour seal (Phoca vitulina, Phocidae) that we had studied previously. The ratio of free lactose to milk oligosaccharides was similar to that in milk of the white-nosed coati; in both species, this ratio was much lower than that in the milk of most eutherians. The neutral oligosaccharides of mink milk had alpha(1-3)-linked Gal or alpha(1-2)-linked Fuc residues at their non-reducing ends, as in the neutral oligosaccharides of white-nosed coati milk. Some of the neutral and acidic oligosaccharides, determined here, had been found also in harbour seal milk, but the harbour seal oligosaccharides did not contain alpha(1-3)-linked Gal residues.

Characterization of oligosaccharides in milk of bearded seal (Erignathus barbatus)

Carbohydrates were extracted from milk of a bearded seal, Erignathus barbatus (Family Phocidae). Free neutral oligosaccharides were separated by gel filtration, anion-exchange chromatography and preparative thin layer chromatography, while free acidic oligosaccharides were separated by gel filtration and then purified by ion exchange chromatography, gel filtration and high performance liquid chromatography. Oligosaccharide structures were determined by 1H-NMR spectroscopy. The structures of the neutral oligosaccharides were as follows; lactose, 2'-fucosyllactose, lacto-N-fucopentaose IV, difucosyl lacto-N-neohexaose and difucosyl decasaccharide which contained a lacto-N-neohexaose unit as well as an additional Gal(beta1-4)GlcNAc(beta1-3) unit and two residues of non-reducing Fuc(alpha1-2). The acidic oligosaccharides were thought to contain an Neu5Ac(alpha2-6) residue linked to GlcNAc or a sulfate linked to Gal at OH-3. The sialyl oligosaccharides and sulfated oligosaccharides had a lacto-N-neohexaose unit and two non-reducing Fuc(alpha1-2) residues and some of them had in addition one or two Gal(beta1-4)GlcNAc(beta1-3) units. The milk oligosaccharides of the bearded seal were compared to those of the harbour seal, which had been studied previously.

Chemical characterization of sialyl oligosaccharides in milk of the Japanese black bear, Ursus thibetanus japonicus

Sialyl oligosaccharides were separated from two samples of Japanese black bear milk by extraction with chloroform/methanol, gel filtration on Bio Gel P-2, ion exchange chromatography on DEAE-Sephadex A-50 and high-performance liquid chromatography (HPLC) on a TSK gel Amido-80 column. They were characterized by (1)H-NMR spectroscopy. The structures of four sialyl oligosaccharides separated from the milk were the following: Neu5Ac(alpha2-3)Gal(beta1-4)Glc. Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)[Gal(alpha1-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-6)]Gal(beta1-4)Glc. Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)[Gal(alpha1-3)[Fuc(alpha1-2)]Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-6)]Gal(beta1-4)Glc. Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)[Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-6)Gal(beta1-4)Glc.