Fibroblast growth factor 21 (FGF21) has been identified as an important regulator of carbohydrate and lipid metabolism, which plays an important role for metabolic regulation, particularly under conditions of energy deprivation or stress conditions. Dairy cows are subjected to a negative energy balance and various kinds of stress particularly during the periparturient phase and during early lactation. It has been shown that the plasma concentration of FGF21 in dairy cows is dramatically increased at parturition and remains high during the first weeks of lactation. This finding suggests that FGF21 might exert similar functions in dairy cows than in other species, such as mice or humans. However, the role of FGF21 in dairy cows has been less investigated so far. Following a brief summary of the previous findings about the function of FGF21 in humans and mice, the present review aims to present the current state of knowledge about the role of FGF21 in dairy cows. The first part of the review deals with the tissue localization of FGF21 and with conditions leading to an upregulation of FGF21 expression in the liver of dairy cows. In the second part, the influence of nutrition on FGF21 expression and the role of FGF21 for metabolic diseases in dairy cows is addressed. In the third part, findings of exogenous FGF21 application on metabolism in dairy cows are reported. Finally, the potential relevance of FGF21 in dairy cows is discussed. It is concluded that FGF21 might be of great importance for metabolic adaptation to negative energy balance and stress conditions in dairy cows. However, further studies are needed for a better understanding of the functions of FGF21 in dairy cows.

中文翻译：

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奶牛成纤维细胞生长因子 21：当前知识和潜在相关性

成纤维细胞生长因子 21 (FGF21) 已被确定为碳水化合物和脂质代谢的重要调节剂，在代谢调节中发挥着重要作用，特别是在能量匮乏或应激条件下。奶牛承受能量负平衡和各种压力，特别是在围产期和泌乳早期。研究表明，奶牛的 FGF21 血浆浓度在分娩时急剧增加，并在哺乳期的头几周内保持较高水平。这一发现表明，FGF21 在奶牛中可能发挥与其他物种（例如小鼠或人类）类似的功能。然而，迄今为止，FGF21在奶牛中的作用研究较少。在简要总结之前关于 FGF21 在人类和小鼠中的功能的发现之后，本综述旨在介绍有关 FGF21 在奶牛中的作用的当前知识状况。综述的第一部分涉及 FGF21 的组织定位以及导致奶牛肝脏中 FGF21 表达上调的条件。第二部分阐述了营养对 FGF21 表达的影响以及 FGF21 在奶牛代谢疾病中的作用。第三部分报道了外源FGF21应用对奶牛代谢的影响。最后，讨论了 FGF21 在奶牛中的潜在相关性。结论是，FGF21 可能对于奶牛负能量平衡和应激条件的代谢适应具有重要意义。然而，需要进一步的研究来更好地了解 FGF21 在奶牛中的功能。