本试验旨在研究高脂血症奶牛乳腺组织中脂代谢相关生化指标和基因表达的变化。选取12头荷斯坦奶牛，采用全自动生化分析仪测定奶牛血清中主要生化指标，根据血清中甘油三酯（TG）、总胆固醇（TC）的含量是否升高将奶牛分为正常组和高脂组。取奶牛乳腺组织制作病理切片及油红O染色，观察乳腺组织病理形态学变化和脂滴蓄积情况。提取乳腺组织总RNA，应用实时荧光定量PCR（qRT-PCR）法检测乳腺组织脂代谢相关基因的相对表达量。结果表明：1）高脂组奶牛乳腺组织中脂代谢指标TC、TG、极低密度脂蛋白（VLDL）的含量显著升高（P<0.05），高密度脂蛋白胆固醇（HDL-C）的含量呈降低趋势，低密度脂蛋白胆固醇（LDL-C）的含量呈升高趋势，但差异均不显著（P>0.05）。2）病理学观察可见高脂组奶牛乳腺腺泡上皮细胞脱落，乳腺腺泡壁明显增厚，细胞肿胀，部分细胞脂滴增多，细胞核染色质浓缩、边移、细胞轮廓不清。油红O染色可见正常组奶牛乳腺组织细胞核明显呈蓝色，红色区域较少，主要集中在细胞边缘，仅有少量脂滴聚集，而高脂组奶牛乳腺组织有大片红色区域，小叶间结缔组织密度增加，乳腺上皮可见脂滴相互融合形成大的空泡状脂肪细胞。3）与正常组相比，高脂组奶牛乳腺脂代谢内源合成关键酶基因乙酰辅酶A羧化酶1（ACC1）以及活化相关基因乙酰辅酶A合成酶2（ACSS2）、长链脂酰辅酶A合成酶1（ACSL1）的相对表达量显著升高（P<0.05），摄取和转运关键基因脂肪酸结合蛋白3（FABP3）、分化抗原簇36（CD36）、脂蛋白脂肪酶（LPL），去饱和酶关键基因硬脂酰辅酶A去饱和酶（SCD）、脂肪酸去饱和酶1（FADS1）以及乳酯化关键基因乙酰甘油磷酸脂酰转移酶6（AGPAT6）的相对表达量显著降低（P<0.05）。综上所述，高脂血症促使奶牛血脂水平升高，引起乳腺组织出现明显的病理变化，同时，乳腺脂代谢相关基因表达发生明显变化。

This experiment was aimed to study the changes of biochemical indexes and gene expressions related to lipid metabolism in mammary tissue for hyperlipidemia dairy cows. Twelve Holstein dairy cows were selected and the main biochemical indexes in serum of dairy cows were determined by automatic biochemical analyzer. The dairy cows were divided into normal group and high lipid group according to whether the contents of total cholesterol (TC) and triglycerides (TG) in serum increased. Mammary tissue was selected for pathological sections and stained with oil red O, to observe pathological change and lipid droplet in mammary tissue. Total RNA of mammary tissue was isolated to detect the relative expression levels of lipid metabolism related genes by real time quantitive PCR (qRT-PCR). The results showed as follows:1) the lipid metabolism indexes of TC, TG and very low density lipoprotein (VLDL) contents in mammary tissue of high lipid group were significantly increased (P<0.05), the high density lipoprotein cholesterin (HDL-C) content was decreased, and the low density lipoprotein cholesterin (LDL-C) was increased, but no significant differences of them were found (P>0.05). 2)Pathological observation of dairy cows in the high lipid group showed that mammary epithelial cells shedding and mammary acinar wall was obviously thickened as well as cell swelling, some cell fat droplets increased, nuclear chromatin shrank, edge shift, cell contours unclear. Oil red O staining showed that the nuclei of dairy cows in the normal group was blue, and the red area was less, mainly concentrated on the edge of the cell, only a small amount of lipid droplets gathered. In the high lipid group, there were large red areas, and the connective tissue density increased. The lipid droplets were fused together to form large vacuolated fat cells. 3)Compared with the normal group, the relative expression levels of endogenous synthesis key enzyme gene acetyl-CoA carboxylase 1 (ACC1) and activation genes acetyl-CoA synthase 2 (ACSS2) and long chain lipid coenzyme A synthase 1 (ACSL1) of mammary fat metabolism in the high lipid group were significantly increased (P<0.05), while the relative expression levels of uptake and transport key genes fatty acid binding protein 3 (FABP3), differentiated antigen cluster 36 (CD36) and lipoprotein lipase (LPL), denaturize key genes stearyl coenzyme A desaturase (SCD) and fatty acid desaturase 1 (FADS1), lactamase key gene acetyl glycerol phosphatidyl transferase 6 (AGPAT6) were significantly reduced (P<0.05). It can be concluded from the present study that hyperlipidemia causes blood lipid level increasing and make obvious pathological changes of mammary tissue as well as mammary lipid metabolism related genes expression of dairy cows.