White H M, Carvalho E R, Koser S L, Schmelz-Roberts N S, Pezzanite L M, Slabaugh A C, Doane P H, Donkin S S
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907.
Archer Daniels Midland Company, Decatur, IL 62521.
J Dairy Sci. 2016 Jan;99(1):812-7. doi: 10.3168/jds.2015-9953. Epub 2015 Nov 5.
Nutritional status and glucose precursors are known regulators of gluconeogenic gene expression. Glycerol can replace corn in diets fed to dairy cows and use of glycerol is linked to increased rumen propionate production. The effect of dietary glycerol on the regulation of gluconeogenic enzymes is unknown. The objective of this study was to examine the effect of glycerol on expression of pyruvate carboxylase (PC), cytosolic and mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-C and PEPCK-M), and glucose-6-phosphatase. Twenty-six multiparous Holstein cows were fed either a control diet or a diet where high-moisture corn was replaced by glycerol from -28 through +56 d relative to calving (DRTC). Liver tissue was collected via percutaneous liver biopsy at -28, -14, +1, +14, +28, and +56 DRTC for RNA analysis. Expression of PC mRNA increased 6-fold at +1 and 4-fold at +14 DRTC relative to precalving levels. Dietary glycerol did not alter expression of PC mRNA expression. Expression of PEPCK-C increased 2.5-fold at +14 and 3-fold at +28 DRTC compared with +1 DRTC. Overall, dietary glycerol increased PEPCK-C expression compared with that of cows fed control diets. The ratio of PC to PEPCK-C was increased 6.3-fold at +1 DRTC compared with precalving and tended to be decreased in cows fed glycerol. We detected no effect of diet or DRTC on PEPCK-M or glucose-6-phosphatase mRNA, and there were no interactions of dietary treatment and DRTC for any transcript measured. Substituting corn with glycerol increased the expression of PEPCK-C mRNA during transition to lactation and suggests that dietary energy source alters hepatic expression. The observed increase in PEPCK-C expression with glycerol feeding may indicate regulation of hepatic gene expression by changes in rumen propionate production.
营养状况和葡萄糖前体是已知的糖异生基因表达调节因子。甘油可替代奶牛日粮中的玉米，甘油的使用与瘤胃丙酸产量增加有关。日粮甘油对糖异生酶调节的影响尚不清楚。本研究的目的是研究甘油对丙酮酸羧化酶（PC）、胞质和线粒体磷酸烯醇式丙酮酸羧激酶（PEPCK-C和PEPCK-M）以及葡萄糖-6-磷酸酶表达的影响。26头经产荷斯坦奶牛在产犊前-28天至产后+56天（干奶期至泌乳期），分别饲喂对照日粮或用甘油替代高水分玉米的日粮（日粮处理组）。在干奶期至泌乳期的-28、-14、+1、+14、+28和+56天，通过经皮肝活检采集肝脏组织进行RNA分析。与产犊前水平相比，PC mRNA表达在产后+1天增加了6倍，在+14天增加了4倍。日粮甘油未改变PC mRNA表达。与产后+1天相比，PEPCK-C表达在+14天增加了2.5倍，在+28天增加了3倍。总体而言，与饲喂对照日粮的奶牛相比，日粮甘油增加了PEPCK-C表达。与产犊前相比，产后+1天PC与PEPCK-C的比值增加了6.3倍，且日粮甘油组奶牛该比值有下降趋势。我们未检测到日粮或干奶期至泌乳期对PEPCK-M或葡萄糖-6-磷酸酶mRNA有影响，且所测任何转录本的日粮处理和干奶期至泌乳期之间均无相互作用。用甘油替代玉米增加了泌乳过渡期PEPCK-C mRNA的表达，表明日粮能量来源改变了肝脏表达。观察到的甘油饲喂使PEPCK-C表达增加可能表明瘤胃丙酸产量变化对肝脏基因表达有调节作用。
