Izumi Hirohisa, Kosaka Nobuyoshi, Shimizu Takashi, Sekine Kazunori, Ochiya Takahiro, Takase Mitsunori
Nutritional Science Institute, Morinaga Milk Industry Co., Ltd., Zama, Kanagawa, Japan.
Division of Molecular and Cellular Medicine, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan.
PLoS One. 2014 Feb 12;9(2):e88843. doi: 10.1371/journal.pone.0088843. eCollection 2014.
Functional RNAs, such as microRNA (miRNA) and mRNA, are present in milk, but their roles are unknown. To clarify the roles of milk RNAs, further studies using experimental animals such as rats are needed. However, it is unclear whether rat milk also contains functional RNAs and what their time dependent expression profiles are. Thus, we prepared total RNA from whey isolated from rat milk collected on days 2, 9, and 16 postpartum and analyzed using microarrays and quantitative PCR. The concentration of RNA in colostrum whey (day 2) was markedly higher than that in mature milk whey (days 9 and 16). Microarray analysis detected 161 miRNAs and 10,948 mRNA transcripts. Most of the miRNAs and mRNA transcripts were common to all tested milks. Finally, we selected some immune- and development-related miRNAs and mRNAs, and analysed them by quantitative PCR (in equal sample volumes) to determine their time-dependent changes in expression in detail. Some were significantly more highly expressed in colostrum whey than in mature milk whey, but some were expressed equally. And mRNA expression levels of some cytokines and hormones did not reflect the protein levels. It is still unknown whether RNAs in milk play biological roles in neonates. However, our data will help guide future in vivo studies using experimental animals such as rats.
功能性RNA，如微小RNA（miRNA）和信使核糖核酸（mRNA），存在于乳汁中，但其作用尚不清楚。为了阐明乳汁RNA的作用，需要使用大鼠等实验动物进行进一步研究。然而，目前尚不清楚大鼠乳汁中是否也含有功能性RNA，以及它们随时间变化的表达谱是怎样的。因此，我们从产后第2天、第9天和第16天收集的大鼠乳汁中分离出乳清，制备了总RNA，并使用微阵列和定量PCR进行分析。初乳乳清（第2天）中的RNA浓度明显高于成熟乳乳清（第9天和第16天）。微阵列分析检测到161种miRNA和10948种mRNA转录本。大多数miRNA和mRNA转录本在所有测试乳汁中都有。最后，我们选择了一些与免疫和发育相关的miRNA和mRNA，并通过定量PCR（在等体积样品中）对其进行分析，以详细确定它们随时间变化的表达情况。一些在初乳乳清中的表达明显高于成熟乳乳清，但也有一些表达相当。一些细胞因子和激素的mRNA表达水平并不能反映其蛋白质水平。乳汁中的RNA是否在新生儿中发挥生物学作用仍然未知。然而，我们的数据将有助于指导未来使用大鼠等实验动物进行的体内研究。
