Institute of Animal Science, Physiology & Hygiene Unit, University of Bonn, Katzenburgweg 7 - 9, 53115 Bonn, Germany.
J Dairy Sci. 2013 Jul;96(7):4508-13. doi: 10.3168/jds.2012-6363. Epub 2013 May 16.
Aquaglyceroporins act as channel proteins and regulate water and glycerol exchange through cell membranes. The aquaglyceroporin aquaporin-7 (AQP7) is abundantly expressed in adipose tissue (AT) and regulates the release of glycerol produced by lipolysis. We aimed to investigate the expression of AQP7 mRNA during lactation in subcutaneous (s.c.) and visceral (v.c.) adipose depots of primiparous and pluriparous dairy cows. In 2 independent experiments, Holstein cows were supplemented with conjugated linoleic acids (CLA) or a control (CON) fat supplement at 100g/d. Pluriparous cows were supplemented starting with the first day in milk (DIM) up to 182 DIM and biopsies from s.c. AT were collected at d -21, 1, 21, 70, 105 182 196, 224, and 252 relative to calving (CLA=11; CON=10). Samples from 3s.c. and v.c. adipose depots were investigated in primiparous cows (n=25) receiving the supplements from 1 DIM until slaughter at 1, 42, or 105 DIM. The AQP7 mRNA abundance decreased from d -21 to 1 in s.c. AT of pluriparous cows without further increase to d 252 of lactation. In primiparous cows of the CON group, the AQP7 mRNA abundance increased from 1 to 105 DIM in s.c. AT from the tail head and in mesenteric AT. In retroperitoneal AT, the only depot for which a significant decrease in mass was observed with DIM, AQP7 mRNA abundance was greater at 42 and 105 than 1 DIM. Comparing the different fat depots, retroperitoneal AT had the highest and mesenterial AT had the lowest AQP7 mRNA abundance, but no general difference was observed between v.c. and s.c. fat depots. The values were not affected by CLA treatment with the exception of mesenteric AT, for which lower AQP7 mRNA abundance values were recorded in the CLA than in the CON group. The longitudinal characterization of the AQP7 mRNA expression profile throughout lactation revealed differences between primiparous and pluriparous cows, with an increase of AQP7 mRNA abundance up to 105 DIM only in the primiparous cows. Due to a lack of CLA effects in pluriparous cows and the limitation to just one fat depot in primiparous cows, a modulatory effect of CLA on AQP7 mRNA abundance in dairy cows is not supported by our study.
水甘油通道蛋白作为通道蛋白，调节水和甘油通过细胞膜的交换。水甘油通道蛋白水通道蛋白 7（AQP7）在脂肪组织（AT）中大量表达，并调节脂肪分解产生的甘油的释放。我们旨在研究初产和经产奶牛皮下（s.c.）和内脏（v.c.）脂肪组织中 AQP7mRNA 在哺乳期的表达。在 2 个独立的实验中，荷斯坦奶牛每天补充共轭亚油酸（CLA）或对照（CON）脂肪补充剂 100g/d。经产奶牛从产犊前 21 天（d -21）开始补充，直至 182 天产犊，并采集 s.c.AT 的活检样品。-21、1、21、70、105、182、196、224 和 252 天相对产犊（CLA=11；CON=10）。在接受补充剂从 1 天产犊至 1、42 或 105 天产犊的初产奶牛（n=25）中，对 3 个 s.c.和 v.c.脂肪组织进行了研究。在无进一步增加的情况下，多产奶牛的 s.c.AT 中 AQP7mRNA 丰度从 d -21 减少到 1。在初产奶牛的 CON 组中，s.c.尾部和肠系膜 AT 的 AQP7mRNA 丰度从 1 增加到 105 天产犊。在腹膜后 AT 中，唯一观察到随着 DIM 质量下降的脂肪组织，42 天和 105 天的 AQP7mRNA 丰度高于 1 天产犊。与不同的脂肪组织比较，腹膜后 AT 的 AQP7mRNA 丰度最高，肠系膜 AT 的 AQP7mRNA 丰度最低，但 v.c.和 s.c.脂肪组织之间没有观察到一般差异。CLA 处理对这些值没有影响，除了肠系膜 AT，CLA 组的 AQP7mRNA 丰度值低于 CON 组。整个哺乳期 AQP7mRNA 表达谱的纵向特征表明初产和经产奶牛之间存在差异，只有初产奶牛的 AQP7mRNA 丰度增加到 105 天产犊。由于多产奶牛缺乏 CLA 作用以及初产奶牛仅局限于一个脂肪组织，CLA 对奶牛 AQP7mRNA 丰度的调节作用未得到本研究的支持。
