Argov-Argaman Nurit, Raz Chen, Roth Zvi
Department of Animal Science, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Jerusalem, Israel.
Front Endocrinol (Lausanne). 2020 Sep 9;11:596. doi: 10.3389/fendo.2020.00596. eCollection 2020.
Progesterone plays a pivotal role during mammogenesis and serves as an inhibitor of the secretory activation of mammary cells in the last days of gestation. However, its role during lactogenesis, in particular its involvement in lipid metabolism, and milk fat content and composition, is unknown. Here, we provide new evidence of progesterone's involvement in the regulation of milk fat globule (MFG) synthesis and secretion. Findings from both and studies indicated that the concentration and the direction (increase vs. decrease) of progesterone concentration to which the mammary epithelial cells (MECs) are exposed affect MFG size. This was found to be very-low-density lipoprotein (VLDL) dependent: in the presence of VLDL, the proportion of MEC with small lipid droplets (<1 μm) increased 2.4-fold, and the proportion of large lipid droplets (>1 μm) increased 4-fold; in the absence of VLDL, no differences were found. The findings add to our understanding of the mechanism underlying the regulation of MFG size and provide new evidence for progesterone's role in lipid metabolism in the mammary gland during lactogenesis. The fact that the size, synthesis, and composition of MFG are affected by the cyclic pattern of progesterone concentration in the circulation might have physiologically relevant consequences, in particular on milk as a nutritional source.
孕酮在乳腺生成过程中起关键作用，并在妊娠后期作为乳腺细胞分泌激活的抑制剂。然而，其在泌乳生成过程中的作用，特别是其在脂质代谢以及乳脂肪含量和组成方面的参与情况尚不清楚。在此，我们提供了孕酮参与调节乳脂肪球（MFG）合成和分泌的新证据。体内和体外研究的结果均表明，乳腺上皮细胞（MECs）所接触的孕酮浓度及其变化方向（升高与降低）会影响MFG的大小。这一现象被发现依赖于极低密度脂蛋白（VLDL）：在有VLDL存在的情况下，含有小脂滴（<1μm）的MEC比例增加了2.4倍，而含有大脂滴（>1μm）的MEC比例增加了4倍；在没有VLDL的情况下，则未发现差异。这些发现增进了我们对MFG大小调节机制的理解，并为孕酮在泌乳生成过程中乳腺脂质代谢中的作用提供了新证据。MFG的大小、合成和组成受循环中孕酮浓度周期性模式影响这一事实可能具有生理相关后果，特别是对作为营养来源的乳汁而言。
