Heat stress can play a negative effect on milk yield and composition of dairy cattle, leading to immeasurable economic loss. The basic components of the mammary gland are the alveoli; these alveolar mammary epithelial cells reflect the milk producing ability of dairy cows. In this study, we exposed bovine mammary epithelial cells to heat stress and compared them to a control group using isobaric tags for relative and absolute quantitation combined with liquid chromatography coupled with tandem mass spectrometry. Compared with a control group, 104 differentially elevated proteins (>1.3-fold) and 167 decreased proteins (<0.77-fold) were identified in the heat treatment group. Gene Ontology analysis identified a majority of the differentially expressed proteins are associated in cell-substrate junction assembly, catabolic processes and metabolic processes. Some of these significantly regulated proteins were related to the synthesis and secretion of milk, such as milk protein and fat. This finding was further supported by the results obtained from the reduced β-casein expression through the system of plasminogen activator - plasminogen - plasmin and decreased fatty acid synthase could partly explain why milk fat synthesis ability of dairy cows decreased under heat stress. Our results highlight the effects of heat stress on synthesis of milk protein and fat, thus providing additional clues for further studies of heat stress on dairy milk production.

中文翻译：

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蛋白质组学分析可揭示热应激对牛乳腺上皮细胞基因表达和牛奶合成的影响。

热应激会对牛奶的产量和奶牛的组成产生负面影响，导致不可估量的经济损失。乳腺的基本成分是肺泡。这些肺泡的乳腺上皮细胞反映了奶牛的产奶能力。在这项研究中，我们将牛乳腺上皮细胞暴露于热应激条件下，并使用等压标记进行相对和绝对定量结合液相色谱与串联质谱联用，将它们与对照组进行比较。与对照组相比，在热处理组中鉴定出104种差异升高的蛋白（> 1.3倍）和167种降低的蛋白（<0.77倍）。基因本体分析确定了大多数差异表达的蛋白质与细胞-底物连接组装相关，分解代谢过程和代谢过程。这些显着调节的蛋白质中的一些与牛奶的合成和分泌有关，例如牛奶蛋白质和脂肪。通过纤溶酶原激活物-纤溶酶原-纤溶酶系统降低的β-酪蛋白表达和降低的脂肪酸合酶得到的结果进一步支持了这一发现，这可以部分解释为什么热应激下奶牛的乳脂合成能力下降。我们的研究结果突出了热应激对乳蛋白和脂肪合成的影响，从而为进一步研究热应激对乳汁生产提供了其他线索。通过纤溶酶原激活物-纤溶酶原-纤溶酶系统降低的β-酪蛋白表达和降低的脂肪酸合酶得到的结果进一步支持了这一发现，这可以部分解释为什么热应激下奶牛的乳脂合成能力下降。我们的研究结果突出了热应激对乳蛋白和脂肪合成的影响，从而为进一步研究热应激对乳汁生产提供了其他线索。通过纤溶酶原激活物-纤溶酶原-纤溶酶系统降低的β-酪蛋白表达和降低的脂肪酸合酶得到的结果进一步支持了这一发现，这可以部分解释为什么热应激下奶牛的乳脂合成能力下降。我们的研究结果突出了热应激对乳蛋白和脂肪合成的影响，从而为进一步研究热应激对乳汁生产提供了其他线索。