Yonekura Shinichi, Sakamoto Kazuhito, Komatsu Tokushi, Hagino Akihiko, Katoh Kazuo, Obara Yoshiaki
Department of Animal Physiology, Graduate School of Agriculture, Tohoku University, Aoba-ku, Sendai 981-8555, Japan.
Domest Anim Endocrinol. 2006 Jul;31(1):88-96. doi: 10.1016/j.domaniend.2005.09.002. Epub 2005 Sep 21.
Leptin mRNA is expressed in not only adipocytes but also mammary epithelial cells and leptin protein is present in milk. Although milk leptin is thought to influence metabolism or the immune system in neonates, there is little information about the regulation of leptin expression in mammary epithelial cells. We examined the effect of growth hormone (GH) and/or lactogenic hormone complex (DIP; dexamethasone, insulin and prolactin) on leptin mRNA expression in mammary epithelial cells. We used a bovine mammary epithelial cell (BMEC) clonal line, which was established from a 26-day pregnant Holstein heifer. We confirmed that the mRNA was expressed in BMECs and the expression was significantly reduced by GH and/or DIP, when the cells were cultured on both plastic plates and cell culture inserts at days 2 and 7 after stimulation with lactogenic hormones. GH and/or DIP significantly increased level of alpha-casein mRNA in BMECs after 7 days on the cell culture inserts, but no mRNA expression was detected at day 2. GH and DIP significantly stimulated the secretion of alpha-casein from BMEC on cell culture inserts at 3.5 and 7 days. However, neither alpha-casein mRNA expression nor secretion was observed in the BMECs cultured on plastic dishes, even in the presence of GH or/and DIP. These results indicate that GH and DIP can directly reduce leptin mRNA expression in both undifferentiated and functionally differentiated bovine mammary epithelial cell.
瘦素mRNA不仅在脂肪细胞中表达，也在乳腺上皮细胞中表达，且乳汁中存在瘦素蛋白。尽管乳汁中的瘦素被认为会影响新生儿的新陈代谢或免疫系统，但关于乳腺上皮细胞中瘦素表达的调控信息却很少。我们研究了生长激素（GH）和/或催乳激素复合物（DIP；地塞米松、胰岛素和催乳素）对乳腺上皮细胞中瘦素mRNA表达的影响。我们使用了一种牛乳腺上皮细胞（BMEC）克隆系，该克隆系是从一头怀孕26天的荷斯坦小母牛建立的。我们证实该mRNA在BMEC中表达，并且当细胞在催乳激素刺激后第2天和第7天在塑料板和细胞培养插入物上培养时，GH和/或DIP可显著降低其表达。在细胞培养插入物上培养7天后，GH和/或DIP可显著提高BMEC中α-酪蛋白mRNA的水平，但在第2天未检测到mRNA表达。在细胞培养插入物上培养3.5天和7天时，GH和DIP可显著刺激BMEC分泌α-酪蛋白。然而，即使存在GH或/和DIP，在塑料培养皿中培养的BMEC中既未观察到α-酪蛋白mRNA表达，也未观察到其分泌。这些结果表明，GH和DIP可直接降低未分化和功能分化的牛乳腺上皮细胞中瘦素mRNA的表达。
