Piglet Nutrition and Cognition Laboratory, University of Illinois , Urbana, IL , USA.
Department of Food Science and Technology, University of California Davis , Davis, CA , USA.
Front Nutr. 2016 Sep 8;3:39. doi: 10.3389/fnut.2016.00039. eCollection 2016.
Milk oligosaccharides (OSs) are bioactive components known to influence neonatal development. These compounds have specific physiological functions acting as prebiotics, immune system modulators, and enhancing intestine and brain development.
The pig is a commonly used model for studying human nutrition, and there is interest in quantifying OS composition of porcine milk across lactation compared with human milk. In this study, we hypothesized that OS and sialic acid (SA) composition of porcine milk would be influenced by stage of lactation.
Up to 250 mL of milk were collected from seven sows at each of three time points: day 0 (colostrum), days 7-9 (mature), and days 17-19 (weaning). Colostrum was collected within 6 h of farrowing and 3-day intervals were used for mature and weaning milk to ensure representative sampling. Milk samples were analyzed for OS profiles by Nano-LC Chip-QTOF MS, OS concentrations via HPAEC-PAD, and SA (total and free) was assessed by enzymatic reaction fluorescence detection.
Sixty unique OSs were identified in porcine milk. Neutral OSs were the most abundant at each lactation stage (69-81%), followed by acidic-sialylated OSs (16-29%) and neutral-fucosylated OSs (2-4%). As lactation progressed, acidic OSs decreased (P = 0.003), whereas neutral-fucosylated (P < 0.001) and neutral OSs (P = 0.003) increased throughout lactation. Six OSs were present in all samples analyzed across lactation [lacto-N-difucohexaose I (LNDFH-I), 2'-fucosyllactose (2'-FL), lacto-N-fucopentaose I (LNFP-I), lacto-N-neohexaose (LNnH), α1-3,β-4-d-galactotriose (3-Hex), 3'-sialyllactose (3'-SL)], while LDFT was present only in colostrum samples. Analysis of individual OS concentrations indicated differences (P = 0.023) between days 0 and 7. Conversely, between days 7 and 18, OS concentrations remained stable with only LNnH (P < 0.001) and LNDFH-I (P = 0.002) decreasing over this period. Analysis of free SA indicated a decrease (P < 0.001) as lactation progressed, while bound (P < 0.001) and total (P < 0.001) SA increased across lactation.
Concentrations of OS differ between colostrum and mature milk in the pig, and SA concentrations shift from free to bound forms as lactation progresses. Our results suggest that although porcine milk OS concentration and the number of structures is lower than human milk, the OS profile appears to be closer to human milk rather than to bovine milk, based on previously published profiles.
牛奶低聚糖（OS）是具有生物活性的成分，已知会影响新生儿的发育。这些化合物具有特定的生理功能，可作为益生元、免疫系统调节剂，并增强肠道和大脑发育。
猪是研究人类营养的常用模型，人们对定量比较猪乳和人乳在整个泌乳期的 OS 组成很感兴趣。在这项研究中，我们假设 OS 和唾液酸（SA）的组成会受到泌乳阶段的影响。
在三个时间点从七头母猪中每头收集多达 250 毫升奶：第 0 天（初乳）、第 7-9 天（成熟）和第 17-19 天（断奶）。初乳是在分娩后 6 小时内收集的，为确保代表性采样，成熟和断奶奶使用 3 天间隔。通过纳升液相芯片-QTOF MS 分析 OS 谱，通过 HPAEC-PAD 分析 OS 浓度，通过酶反应荧光检测评估 SA（总 SA 和游离 SA）。
在猪乳中鉴定出 60 种独特的 OS。在每个泌乳阶段，中性 OS 最为丰富（69-81%），其次是酸性唾液酸化 OS（16-29%）和中性岩藻糖基化 OS（2-4%）。随着泌乳的进行，酸性 OS 减少（P=0.003），而中性岩藻糖基化 OS（P<0.001）和中性 OS 增加（P=0.003）。有六种 OS 在整个泌乳期的所有分析样本中均存在（LNDFH-I、2'-FL、LNFP-I、LNnH、3-Hex、3'-SL），而 LDFT 仅存在于初乳样本中。分析个体 OS 浓度表明，在第 0 天和第 7 天之间存在差异（P=0.023）。相反，在第 7 天和第 18 天之间，OS 浓度保持稳定，仅 LNnH（P<0.001）和 LNDFH-I（P=0.002）在此期间减少。分析游离 SA 表明，随着泌乳的进行，SA 浓度降低（P<0.001），而结合（P<0.001）和总（P<0.001）SA 增加。
猪乳中的 OS 浓度在初乳和成熟乳之间存在差异，随着泌乳的进行，SA 浓度从游离形式转变为结合形式。我们的结果表明，尽管猪乳的 OS 浓度和结构数量低于人乳，但基于之前发表的谱图，其 OS 谱似乎更接近人乳而不是牛乳。
