Dallas David C, Smink Christina J, Robinson Randall C, Tian Tian, Guerrero Andres, Parker Evan A, Smilowitz Jennifer T, Hettinga Kasper A, Underwood Mark A, Lebrilla Carlito B, German J Bruce, Barile Daniela
Department of Food Science and Technology Foods for Health Institute
Dairy Science and Technology Group, Wageningen University and Research Centre, Wageningen, The Netherlands.
J Nutr. 2015 Mar;145(3):425-33. doi: 10.3945/jn.114.203646. Epub 2014 Dec 24.
Hundreds of naturally occurring milk peptides are present in term human milk. Preterm milk is produced before complete maturation of the mammary gland, which could change milk synthesis and secretion processes within the mammary gland, leading to differences in protein expression and enzymatic activity, thereby resulting in an altered peptide profile.
This study examined differences in peptides present between milk from women delivering at term and women delivering prematurely.
Nano-LC tandem mass spectrometry was employed to identify naturally occurring peptides and compare their abundances between term and preterm human milk samples at multiple time points over lactation. Term milk samples were collected from 8 mothers and preterm milk was collected from 14 mothers. The 28 preterm and 32 term human milk samples were divided into 4 groups based on day of collection (<14, 14-28, 29-41, and 42-58 d).
Preterm milk peptide counts, ion abundance, and concentration were significantly higher in preterm milk than term milk. Bioinformatic analysis of the cleavage sites for peptides identified suggested that plasmin was more active in preterm milk than term milk and that cytosol aminopeptidase and carboxypeptidase B2 likely contribute to extensive milk protein breakdown. Many identified milk peptides in both term and preterm milk overlapped with known functional peptides, including antihypertensive, antimicrobial, and immunomodulatory peptides.
The high protein degradation by endogenous proteases in preterm milk might attenuate problems because of the preterm infant's immature digestive system. This trial was registered at clinicaltrials.gov as NCT01817127.
足月人乳中存在数百种天然存在的乳肽。早产母乳是在乳腺完全成熟之前产生的，这可能会改变乳腺内的乳汁合成和分泌过程，导致蛋白质表达和酶活性的差异，从而导致肽谱改变。
本研究检测了足月分娩女性和早产女性乳汁中肽的差异。
采用纳升液相色谱串联质谱法鉴定天然存在的肽，并比较足月和早产人乳样本在哺乳期多个时间点的丰度。从8名母亲处收集足月乳汁样本，从14名母亲处收集早产乳汁样本。根据收集日期（<14、14 - 28、29 - 41和42 - 58天）将28份早产和32份足月人乳样本分为4组。
早产乳汁中的肽计数、离子丰度和浓度显著高于足月乳汁。对鉴定出的肽的切割位点进行生物信息学分析表明，纤溶酶在早产乳汁中比足月乳汁中更活跃，并且胞质氨基肽酶和羧肽酶B2可能有助于乳汁蛋白质的广泛分解。足月和早产乳汁中许多鉴定出的乳肽与已知的功能肽重叠，包括抗高血压、抗菌和免疫调节肽。
早产乳汁中内源性蛋白酶对蛋白质的高降解可能减轻由于早产儿消化系统不成熟而产生的问题。该试验已在clinicaltrials.gov上注册，注册号为NCT01817127。
