Van den Top A Marc, Van Tol Arie, Jansen Hans, Geelen Math J H, Beynen Anton C
Department of Nutrition, Graduate School of Animal Health, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80.152, 3508 TD Utrecht, The Netherlands.
J Dairy Res. 2005 May;72(2):129-37. doi: 10.1017/s0022029905000774.
Cholesterol and phospholipid concentrations in serum lipoproteins, plasma activities of lecithin:cholesterol acyltransferase (LCAT) and phospholipid transfer protein (PLTP) and lipoprotein lipase (LPL) activity in adipose tissue biopsies were measured ante and post partum in dairy cows given either free or restricted access to feed during the dry period. After parturition, all cows were fed ad libitum. The purpose of this study was to try to understand the earlier observed marked drop post partum in plasma triacylglycerol (TAG) in terms of lipoprotein metabolism in cows developing fatty liver post partum. As would be expected, free access to feed during the dry period induced a rise of hepatic TAG concentrations post partum associated with a decrease in plasma TAG levels. Total and free cholesterol concentrations in the VLDL, IDL, LDL and HDL2 fractions fell immediately after parturition. VLDL and IDL cholesterol concentrations remained at a constant, low level during the entire sampling period post partum, whereas the drop in LDL and HDL2 cholesterol post partum was followed by a rebound rise. Plasma LCAT and PLTP activities decreased by on average 19% and 33%, respectively, after parturition and then rose to values seen before parturition, but there was no effect of feeding regimen during the dry period. Activities of LCAT and PLTP were significantly correlated with cholesterol and phospholipid concentrations in LDL and HDL2. Plasma LCAT activity, as measured with exogenous substrate, and PLTP activity were both positively correlated with HDL3 phospholipid levels. LPL activity in adipose tissue dropped after parturition, the drop being smaller after feeding ad libitum during the dry period. It is concluded that the drop in adipose tissue LPL activity post partum is at variance with the simultaneous fall in plasma TAG. Possibly, the decrease in adipose tissue LPL activity helps to channel fatty acids away from adipose tissue into the udder. The post-partum changes in lipid transfer proteins in the blood are in line with the changes observed in the levels of the lipoproteins.
在干奶期给予自由采食或限饲的奶牛中，在产前和产后测定了血清脂蛋白中的胆固醇和磷脂浓度、卵磷脂胆固醇酰基转移酶（LCAT）和磷脂转运蛋白（PLTP）的血浆活性以及脂肪组织活检中的脂蛋白脂肪酶（LPL）活性。分娩后，所有奶牛均自由采食。本研究的目的是试图从产后发生脂肪肝的奶牛的脂蛋白代谢角度，理解早期观察到的产后血浆三酰甘油（TAG）的显著下降。正如预期的那样，干奶期自由采食导致产后肝脏TAG浓度升高，同时血浆TAG水平降低。产后，极低密度脂蛋白（VLDL）、中间密度脂蛋白（IDL）、低密度脂蛋白（LDL）和高密度脂蛋白2（HDL2）组分中的总胆固醇和游离胆固醇浓度立即下降。产后整个采样期间，VLDL和IDL胆固醇浓度保持在恒定的低水平，而产后LDL和HDL2胆固醇下降后出现反弹上升。产后血浆LCAT和PLTP活性分别平均下降了19%和33%，然后升至产前水平，但干奶期的饲养方案对此没有影响。LCAT和PLTP的活性与LDL和HDL2中的胆固醇和磷脂浓度显著相关。用外源性底物测定的血浆LCAT活性和PLTP活性均与HDL3磷脂水平呈正相关。产后脂肪组织中的LPL活性下降，干奶期自由采食后下降幅度较小。结论是，产后脂肪组织LPL活性的下降与血浆TAG的同时下降不一致。可能是脂肪组织LPL活性的降低有助于将脂肪酸从脂肪组织引导至乳房。血液中脂质转运蛋白的产后变化与脂蛋白水平的变化一致
