Liver fat content and lipid metabolism in dairy cows during early lactation and during a mid-lactation feed restriction
Liver fat content and lipid metabolism in dairy cows during early lactation and during a mid-lactation feed restriction
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DOI：
10.3168/jds.2012-6245
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发表时间：
2013-08-01
影响因子：
3.5
通讯作者：
Bruckmaier, R. M.
中科院分区：
文献类型：
--
作者：
Gross, J. J.;Schwarz, F. J.;Bruckmaier, R. M.
在过渡期，奶牛的脂肪代谢明显受能量状态的影响。脂肪肝是产后的主要健康障碍之一。本研究的目的是评估负能量平衡(NEB)在哺乳期的两个阶段的影响[NEB在产后开始哺乳期(P.P.)以及基于相关基因mRNA丰度的肝脏甘油三酯含量和血浆和肝脏脂代谢参数的故意限制饲料诱导的NEB。对50头经产奶牛从产前第3周到大约第17周进行了研究。分两期进行。根据第一阶段(分娩至产后12周)的能量平衡，奶牛被分配到对照组(CON；n=25)或限制组(RES，能量需要量的70%；n=25)，从哺乳中期100d左右开始(第二阶段)，持续3wk。肝脏甘油三酯(TG)、血浆非酯化脂肪酸(NEFA)和β-羟丁酸含量在第1周最高。此后又有所下降。在第二阶段，限饲对肝脏甘油三酯和β-羟基丁酸浓度没有影响，但与对照奶牛相比，RES奶牛的NEFA浓度升高。肝脏肿瘤坏死因子α、三磷酸腺苷柠檬酸裂解酶、线粒体甘油-3-磷酸酰基转移酶和甘油-3-磷酸脱氢酶2的mRNA丰度在两个实验期间均未因哺乳和能量状态而改变。脂肪酸合酶在周期2的表达高于周期1，但在Res组和Con组之间无差异。乙酰辅酶A-羧基酶的mRNA丰度在周期2比周期1有升高的趋势，溶质载体家族27(脂肪酸转运蛋白)成员1(SLC27A1)在周期1上调。在限饲期间，RESS奶牛也是如此。综上所述，本研究表明，NEB对奶牛哺乳早期和后期的肝脂代谢和肝脏中甘油三酯浓度有不同的影响。因此，围产期的顺势适应引发了代谢的过度反应，而在建立哺乳后内分泌和代谢系统的动态平衡控制期间，如本研究的限饲期间，器官对代谢和环境的变化具有很好的适应能力。
During the transition period, the lipid metabolism of dairy cows is markedly affected by energy status. Fatty liver is one of the main health disorders after parturition. The aim of this study was to evaluate the effects of a negative energy balance (NEB) at 2 stages in lactation [NEB at the onset of lactation postpartum (p.p.) and a deliberately induced NEB by feed restriction near 100 d in milk] on liver triglyceride content and parameters of lipid metabolism in plasma and liver based on mRNA abundance of associated genes. Fifty multiparous dairy cows were studied from wk 3 antepartum to approximately wk 17 p.p. in 2 periods. According to their energy balance in period 1 (parturition to wk 12 p.p.), cows were allocated to a control (CON; n = 25) or a restriction group (RES; 70% of energy requirements; n = 25) for 3 wk in mid lactation starting at around 100 d in milk (period 2). Liver triglyceride (TG) content, plasma nonesterified fatty acids (NEFA), and beta-hydroxybutyrate were highest in wk 1 p.p. and decreased thereafter. During period 2, feed restriction did not affect liver TG and beta-hydroxybutyrate concentration, whereas NEFA concentration was increased in RES cows as compared with CON cows. Hepatic mRNA abundances of tumor necrosis factor alpha, ATP citrate lyase, mitochondrial glycerol-3-phosphate acyltransferase, and glycerol-3-phosphate dehydrogenase 2 were not altered by lactational and energy status during both experimental periods. The expression of fatty acid synthase was higher in period 2 compared with period 1, but did not differ between RES and CON groups. The mRNA abundance of acetyl-coenzyme A-carboxylase showed a tendency toward higher expression during period 2 compared with period 1. The solute carrier family 27 (fatty acid transporter), member 1 (SLC27A1) was upregulated in wk 1 p.p. and also during feed restriction in RES cows. In conclusion, the present study shows that a NEB has different effects on hepatic lipid metabolism and TG concentration in the liver of dairy cows at early and later lactation. Therefore, the homeorhetic adaptations during the periparturient period trigger excessive responses in metabolism, whereas during the homeostatic control of endocrine and metabolic systems after established lactation, as during the period of feed restriction in the present study, organs are well adapted to metabolic and environmental changes.