Li Ran, Ibeagha-Awemu Eveline M
Agriculture and Agri-Food Canada,Sherbrooke Research and Development Centre,Sherbrooke,Quebec J1M 0C8,Canada.
J Dairy Res. 2017 May;84(2):119-123. doi: 10.1017/S002202991700022X.
Recently we showed that 5% linseed oil (LSO) and 5% safflower oil (SFO) supplementation of cow's diets reduced milk fat yield by 30·38 and 32·42% respectively, accompanied by differential expression of genes and regulation by microRNAs (miRNA). This research communication addresses the hypothesis that epigenetic regulation could be involved in the observed milk fat reduction. Thus, this study investigated the gene expression pattern of major epigenetic modifying enzymes in response to dietary supplementation with LSO or SFO. Twenty-six Canadian Holstein cows in mid lactation were randomly assigned to two groups (13/group) and fed a control diet for 28 d (day -28 to -1) (control period- CP) followed by a treatment period (TP) (control diet supplemented with 5% LSO (LSO treatment) or 5% SFO (SFO treatment) of 28 d (day +1 to +28). After treatment, cows in the two groups were returned to the control diet for another 28 d (day +29 to +56) (post treatment period-PTP). Milk samples were collected on day -1 (CP), +7, +28 (TP) and +56 (PTP) for RNA isolation and measurement of the expression of thirteen epigenetic modifying genes including two DNA methytrasferases (DNMT1, DNMT3A), four histone acetylases (HAT1, KAT2A, KAT5 and CREBBP), five histone deacetylases (HDAC1, HDAC2, HDAC3, SIRT1 and SIRT2) and two histone methytransferases (EHMT2 and PRMT1) by qPCR. Linseed oil supplementation significantly repressed the expression of EHMT2, HDAC2 and HDAC3 on day +7 (P < 0·05) and KAT2A and SIRT2 on day +28 (P < 0·05) as compared with the control period (day -1) while SFO had no effect. When LSO was withdrawn, the expression of some of the genes increased slightly but did not reach control (day -1) levels at the end of the PTP. Our study demonstrated a significant role of LSO in the epigenetic regulation of fatty acid synthesis as compared to SFO. The effect of LSO may be related to its higher degree of unsaturation and might represent a different regulatory mechanism which needs further investigation.
最近我们发现，在奶牛日粮中添加5%的亚麻籽油（LSO）和5%的红花油（SFO），分别使乳脂产量降低了30.38%和32.42%，同时伴随着基因的差异表达以及微小RNA（miRNA）的调控。本研究通讯探讨了表观遗传调控可能与观察到的乳脂减少有关这一假设。因此，本研究调查了在补充LSO或SFO日粮的情况下，主要表观遗传修饰酶的基因表达模式。26头处于泌乳中期的加拿大荷斯坦奶牛被随机分为两组（每组13头），先饲喂对照日粮28天（第-28天至-1天）（对照期 - CP），随后进入为期28天的处理期（TP）（对照日粮分别补充5%的LSO（LSO处理组）或5%的SFO（SFO处理组），即第+1天至+28天）。处理结束后，两组奶牛再回归对照日粮，持续28天（第+29天至+56天）（处理后期 - PTP）。在第-1天（CP）、+7天、+28天（TP）和+56天（PTP）采集牛奶样本用于RNA提取，并通过qPCR测定13个表观遗传修饰基因的表达，这些基因包括两种DNA甲基转移酶（DNMT1、DNMT3A）、四种组蛋白乙酰转移酶（HAT1、KAT2A、KAT5和CREBBP）、五种组蛋白去乙酰化酶（HDAC1、HDAC2、HDAC3、SIRT1和SIRT2）以及两种组蛋白甲基转移酶（EHMT2和PRMT1）。与对照期（第-1天）相比，添加亚麻籽油在第+7天显著抑制了EHMT2、HDAC2和HDAC3的表达（P < 0.05），在第+28天显著抑制了KAT2A和SIRT2的表达（P < 0.05），而添加红花油则没有影响。当停止添加LSO后，一些基因的表达略有增加，但在PTP结束时未达到对照（第-1天）水平。我们的研究表明，与SFO相比，LSO在脂肪酸合成的表观遗传调控中发挥了重要作用。LSO的作用可能与其更高的不饱和度有关，可能代表一种不同的调控机制，需要进一步研究。
