Negative effects of long-term feeding of high-grain diets to lactating goats on milk fat production and composition by regulating gene expression and DNA methylation in the mammary gland.
Negative effects of long-term feeding of high-grain diets to lactating goats on milk fat production and composition by regulating gene expression and DNA methylation in the mammary gland.
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长期饲喂高谷物饲料通过调节乳腺基因表达和 DNA 甲基化对泌乳山羊乳脂产生和成分产生负面影响
DOI：
10.1186/s40104-017-0204-2
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发表时间：
2017
影响因子：
7
通讯作者：
Zhao R
中科院分区：
文献类型：
--
作者：
Tian P;Luo Y;Li X;Tian J;Tao S;Hua C;Geng Y;Ni Y;Zhao R
背景众所周知，饲喂高精料（HC）日粮会引起反刍动物亚急性瘤胃酸中毒（SARA），并导致乳脂产量下降。然而，长期饲喂HC饲料对乳脂肪酸组成的影响以及乳脂下降的机制仍然知之甚少。本研究的目的是研究饲喂HC日粮对泌乳奶山羊乳脂产量和脂肪酸组成的影响，重点是乳脂下降的机制。17只泌乳中期奶山羊随机分为3组。对照组饲喂低浓缩饲料（35%浓缩饲料，n= 5，LC），有两个高浓缩饲料处理（65%浓缩饲料，HC），一个长期饲喂高浓缩饲料（19周，n= 7，HL），一个短期饲喂高浓缩饲料（4周，n= 5，HS）。测量乳脂产量和脂肪酸谱。为了探讨乳脂产量和组成变化的潜在机制，还分析了乳腺脂质代谢和DNA甲基化相关基因的表达。结果与LC饲料相比，HS和HL组饲喂HC饲料可提高产奶量高脂组乳脂率显著低于对照组（P<0.05），而高脂组乳脂率与对照组无显著差异（P> 0.05）。与对照组相比，高脂饲料组乳中饱和脂肪酸（SFA）总量无明显变化，而不饱和脂肪酸（乌法）和单不饱和脂肪酸（MUFA）含量显著降低（P< 0.05）。其中，HL组C15：0（P< 0.01）、C17：0（P <0.01）、C17：1（P<0.01）、C18：1 n-9 c（P< 0.05）、C18：3 n-3r（P< 0.01）和C20：0（P< 0.01）含量明显低于LC组; HS组C20：0（P< 0.05）和C18：3 n-3r（P< 0.01）含量明显低于LC组。但高渗组乳脂中C18：2n-6c（P< 0.05）和C20：4 n-6（P< 0.05）含量高于对照组。实时荧光定量PCR结果显示，与LC组相比，HL和HS组乳腺中参与乳脂产生的基因的mRNA表达普遍降低。其中，ACSL 1、ACSS1&2、ACACA、FAS、SCD、FADS 2和SREBP 1在HL组乳腺中表达下调（P<0. 05），ACSS 2、ACACA和FADS 2 mRNA在HS组乳腺中表达下调（P<0. 05）。HL组ACACA和SCD基因启动子区DNA甲基化水平较LC组增高（P< 0.05）。与LC组相比，HL组乳腺中ACSL 1蛋白表达水平和FAS酶活性也显著降低（P< 0.05）。结论长期饲喂HC日粮可导致泌乳山羊乳脂率下降，且随着饲喂HC日粮时间的延长，其脂肪酸谱发生变化，MUFAs降低，而SFAs升高。与乳脂产生有关的基因表达的普遍下调和乳腺中较高的DNA甲基化可能有助于长期饲喂HC饮食的山羊乳脂产生的减少。
BackgroundIt is well known that feeding a high concentrate (HC) diet to lactating ruminants likely induces subacute ruminal acidosis (SARA) and leads to a decrease in milk fat production. However, the effects of feeding a HC diet for long periods on milk fatty acids composition and the mechanism behind the decline of milk fat still remains poorly understood. The aim of this study was to investigate the impact of feeding a HC diet to lactating dairy goats on milk fat yield and fatty acids composition with an emphasis on the mechanisms underlying the milk fat depression. Seventeen mid-lactating dairy goats were randomly allocated to three groups. The control treatment was fed a low-concentrate diet (35% concentrate,n= 5, LC) and there were two high-concentrate treatments (65% concentrate, HC), one fed a high concentrate diet for a long period (19 wks,n= 7, HL); one fed a high concentrate diet for a short period of time (4 wk,n= 5, HS). Milk fat production and fatty acids profiles were measured. In order to investigate the mechanisms underlying the changes in milk fat production and composition, the gene expression involved in lipid metabolism and DNA methylation in the mammary gland were also analyzed.ResultsMilk production was increased by feeding the HC diet in the HS and HL groups compared with the LC diet (P< 0.01), while the percentage of milk fat was lower in the HL (P< 0.05) but not in the HS group. The total amount of saturated fatty acids (SFA) in the milk was not changed by feeding the HC diet, whereas the levels of unsaturated fatty acids (UFA) and monounsaturated fatty acids (MUFA) were markedly decreased in the HL group compared with the LC group (P< 0.05). Among these fatty acids, the concentrations of C15:0 (P< 0.01), C17:0 (P< 0.01), C17:1 (P< 0.01), C18:1n-9c (P< 0.05), C18:3n-3r (P< 0.01) and C20:0 (P< 0.01) were markedly lower in the HL group, and the concentrations of C20:0 (P< 0.05) and C18:3n-3r (P< 0.01) were lower in the HS group compared with the LC group. However, the concentrations of C18:2n-6c (P< 0.05) and C20:4n-6 (P< 0.05) in the milk fat were higher in the HS group. Real-time PCR results showed that the mRNA expression of the genes involved in milk fat production in the mammary gland was generally decreased in the HL and HS groups compared with the LC group. Among these genes,ACSL1,ACSS1&2,ACACA,FAS,SCD,FADS2,andSREBP1were down-regulated in the mammary gland of the HL group (P< 0.05), and the expressions ofACSS2,ACACA,andFADS2mRNA were markedly decreased in the HS goats compared with the LC group (P< 0.05). In contrast to the gene expression, the level of DNA methylation in the promoter regions of theACACAandSCDgenes was increased in the HL group compared with the LC group (P< 0.05). The levels of ACSL1 protein expression and FAS enzyme activity were also decreased in the mammary gland of the HL compared with the LC group (P< 0.05).ConclusionsLong-term feeding of a HC diet to lactating goats induced milk fat depression and FAs profile shift with lower MUFAs but higher SFAs. A general down-regulation of the gene expression involved in the milk fat production and a higher DNA methylation in the mammary gland may contribute to the decrease in milk fat production in goats fed a HC diet for long time periods.
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影响因子：
3.2
作者：
Benchaar, C.;Lettat, A.;Chouinard, P. Y.
通讯作者：
Chouinard, P. Y.
影响因子：
3.5
作者：
Ghazal, S.;Berthelot, V.;Schmidely, P.
通讯作者：
Schmidely, P.
影响因子：
3.7
作者：
Dong G;Qiu M;Ao C;Zhou J;Khas-Erdene;Wang X;Zhang Z;Yang Y
通讯作者：
Yang Y
DOI：
10.2174/1568008033340117
发表时间：
2003-12-01
期刊：
Current Drug Targets - Immune Endocrine and Metabolic Disorders
影响因子：
--
作者：
Cohen, Paul;Ntambi, James M.;Friedman, Jeffrey M.
通讯作者：
Friedman, Jeffrey M.
影响因子：
16.2
作者：
Diaz-Lopez, Andres;Babio, Nancy;Salas-Salvado, Jordi
通讯作者：
Salas-Salvado, Jordi