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Breast milk is the safest and most complete natural food for babies. Although breast milk is crucial to the health and development of infants, the metabolites in breast milk during lactation period have not been characterized. Therefore, we examined and compared the metabolites in breast colostrum and mature breast milk using gas chromatography-time-of-flight-mass spectrometry-based metabolomics. A total of 159 metabolites were characterized, of which 72 were differentially expressed metabolites (DEMs), including 17 upregulated and 55 downregulated DEMs in breast colostrum compared to those in mature breast milk. Metabolic pathway analysis revealed that these DEMs were related to glycine, serine, and threonine metabolism; glyoxylate and dicarboxylate metabolism; alanine, aspartate, and glutamate metabolism; pentose and glucuronate interconversions; and aminoacyl-tRNA biosynthesis. Our results improve the understanding of breast milk composition and provide a theoretical basis for optimizing infant formula to closely imitate the nutrients required for proper growth and development of babies.

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OBJECTIVE: The study aimed to investigate the contents and isomer composition of vitamin E in mature milk in different regions of China. METHODS: Simultaneously recruited 604 lactating mothers aged(29.58±3.43) from Shanghai, Guangzhou, Tianjin, Chengdu, Lanzhou and Changchun cities. They were mainly primiparas with good education background. A total number of 604 mature milk samples was collected. The contents of α-, γ-, δ-tocopherols and the stereoisomers of α-tocopherol were determined by high performance liquid chromatography(HPLC). RESULTS: The M(P25, P75) concentrations of α-tocopherol, RRR-α-tocopherol, γ-tocopherol and δ-tocopherol in Chinese mature milk were 3.16(2.29, 4.16)mg/L, 2.57(1.77, 3.48)mg/L, 0.89(0.58, 1.27)mg/L and 0.17(0.09, 0.27)mg/L, respectively. The total α-TE level was 3.09(2.22, 4.10)mg/L with statistically regional differences(P<0.001). RRR-α-tocopherol was the predominated stereoisomers of α-tocopherol, accounting for 83.17%(76.36%, 88.43%). The proportion of RRR in Tianjin mature milk was significantly lower than that in Lanzhou(77.11% vs. 86.16%, P<0.001) while breast milk samples from other regions had similar RRR-α-tocopherol proportions(82.82%-85.39%). CONCLUSION: Vitamin E content in mature milk was mainly composed of α-tocopherol. Even though the contents of tocopherols have large regional differences, RRR-α-tocopherol was predominated form in all breast milk samples. It is suggested that RRR-α-tocopherol was the main active form of vitamin E in the early stage of life.

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Background: We aimed to evaluate irisin and SREBP-1c levels in serum, colostrum and mature breast milk in women with and without gestational diabetes (GDM); and to relate them with maternal glucose, lipid profile and weight status of babies. Methods: GDM positive women (n = 33) and normal glucose tolerant women (NGT) (n = 33) were recruited. Maternal blood samples were collected at 28th week of gestation and later at 6-week post-partum while breast milk samples of the lactating mothers were collected within 72 hours of birth (colostrum) and at 6 weeks post-partum (mature milk). Irisin and SREBP-1c levels were analyzed by commercially available ELISA kits for all maternal samples. Results: Lower levels of irisin were seen in serum, colostrum and mature breast milk of GDM females (p < .01). SREBP-1c profile showed a similar trend of low serum levels in GDM, however, they were undetectable in colostrum and mature breast milk. Weak to moderate correlations of serum irisin with BMI (r = 0.439; p < .001), GTT 0 hours (r = 0.403; p = .01), HbA1c (r = -0.312; p = .011), Fasting blood glucose (r = 0.992; p = .008), and baby weight at birth (r = 0.486; p < .001). Colostrum and mature breast milk irisin showed positive associations with baby weight at 6 weeks (r = 0.325; p = .017; r = 0.296; p = .022, respectively). Serum SREBP-1c at 6 weeks correlated with random blood glucose (r = 0.318; p = .009), and HbA1c (r= -0.292; p = .011). All correlations were lost once we adjusted for maternal BMI. Conclusions: Low irisin and SREBP1-c levels may favor development of GDM in pregnant subjects. Further, low mature breast milk levels may act as a continued stressor from fetal to infant life as long as breast-feeding is continued. Further studies are required to identify the mechanistic relationship between these biomarkers and GDM.

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Introducción: La leche materna es el alimento ideal para niños desde el nacimiento hasta los seis meses de edad. Muchas madres interrumpen la lactancia materna por diversas causas, por lo que la administración de leche materna procedente de bancos de leche surge como alternativa a ser evaluada. Objetivo: Determinar las variaciones en la composición proteica de la leche materna durante el almacenamiento bajo congelación. Materiales y Métodos: Fueron colectadas 31 muestras de leche madura de mujeres entre 17 a 35 años. Las muestras se almacenaron en congelación (–20°C), durante períodos de 15, 30, 60, y 90 días. Una alícuota de cada muestra fue analizada como control basal. La concentración de proteínas totales (g/dl) fue determinada por el método de Lowry, se transformó en g/día y calculó las calorías proteicas, considerando el consumo de 850 ml de leche. Se caracterizaron las fracciones proteicas de la leche con la técnica de electroforesis en geles de poliacrilamida (SDS-PAGE). Resultados: Los resultados mostraron una concentración proteica de 1,58 g/dl al inicio y de 1,61 g/dl a los 90 días. No se encontraron variaciones significativas al comparar el contenido de proteínas, ni en el aporte proteico y calórico de la leche durante el almacenamiento bajo congelación (P>0,05). El perfil electroforético sólo demostró variaciones en fracciones proteicas de bajo peso molecular. Conclusiones: La estabilidad de los componentes proteicos ratifica como segura la forma de almacenamiento de la leche materna humana bajo congelación por un período de 3 meses en bancos de leche.

Introduction: Breast milk is the ideal food for children from birth to age six months. For various reasons many mothers stop breastfeeding early, for which reason supply of breast milk from milk banks is an alternative that should be evaluated. Objective: To determine variations in protein composition of breast milk during frozen storage. Materials and Methods: We collected 31 samples of mature milk of women between ages 17 and 35. Samples were stored frozen (-20° C) for periods of 15, 30, 60, and 90 days. An aliquot of each sample was analyzed for baseline control. Total protein concentration (g/dl) was determined by Lowry method and protein calories as g/day were calculated based on a consumption of 850 ml of milk. Protein fractions of milk were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Results: Results showed a protein concentration of 1.58 g/dl at baseline and 1.61 g/dl at 90 days. Comparison found no significant differences in protein content or protein and calorie value of the milk during frozen storage (P>0.05). The electrophoretic profile showed changes only in low molecular weight protein fractions. Conclusions: The stability of the protein components demonstrates safe storage of frozen human milk in milk banks for a period of 3 months.

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