Institute of Animal Science, Physiology Unit, University of Bonn, 53115 Bonn, Germany.
Department of Life Sciences and Engineering, Animal Nutrition and Hygiene Unit, University of Applied Sciences Bingen, 55411 Bingen am Rhein, Germany.
J Dairy Sci. 2024 Oct;107(10):8688-8708. doi: 10.3168/jds.2024-24844. Epub 2024 Jun 13.
Bile acids (BA) play a crucial role not only in lipid digestion but also in the regulation of overall energy homeostasis, including glucose and lipid metabolism. The aim of this study was to investigate BA profiles and mRNA expression of BA-related genes in the liver of high versus normal body condition in dairy cows. We hypothesized that body condition and the transition from gestation to lactation affect hepatic BA concentrations as well as the mRNA abundance of BA-related receptors, regulatory enzymes, and transporters. Therefore, we analyzed BA in the liver as well as the mRNA abundance of BA-related synthesizing enzymes, transporters, and receptors in the liver during the transition period in cows with different body conditions around calving. In a previously established animal model, 38 German Holstein cows were divided into groups with high body condition score (HBCS; n = 19) or normal body condition score (NBCS; n = 19) based on BCS and backfat thickness (BFT). Cows were fed diets aimed at achieving the targeted differences in BCS and BFT (NBCS: BCS <3.5, BFT <1.2 cm; HBCS: BCS >3.75, BFT >1.4 cm) until they were dried off at wk 7 before parturition. Both groups were fed identical diets during the dry period and subsequent lactation. Liver biopsies were taken at wk -7, 1, 3, and 12 relative to parturition. For BA measurement, a targeted metabolomics approach with liquid chromatography electrospray ionization MS/MS was used to analyze BA in the liver. The mRNA abundance of targeted genes related to BA synthesizing enzymes, transporters, and receptors in the liver was analyzed using microfluidic quantitative PCR. In total, we could detect 14 BA in the liver: 6 primary and 8 secondary BA, with glycocholic acid (GCA) being the most abundant one. The increase of glycine-conjugated BA after parturition, in parallel to increasing serum glycine concentrations may originate from an enhanced mobilization of muscle protein to meet the high nutritional requirements in early lactating cows. Higher DMI in NBCS cows compared with HBCS cows was associated with higher liver BA concentrations such as GCA, deoxycholic acid, and cholic acid. The mRNA abundance of BA-related enzymes measured herein suggests the dominance of the alternative signaling pathway in the liver of HBCS cows. Overall, BA profiles and BA metabolism in the liver depend on both, the body condition and lactation-induced effects in periparturient dairy cows.
胆汁酸 (BA) 不仅在脂质消化中发挥着关键作用，还在整体能量稳态的调节中发挥着作用，包括葡萄糖和脂质代谢。本研究旨在探讨奶牛高体况和正常体况下肝脏中 BA 谱和 BA 相关基因的 mRNA 表达。我们假设体况和妊娠到泌乳的过渡会影响肝脏 BA 浓度以及 BA 相关受体、调节酶和转运体的 mRNA 丰度。因此，我们分析了围产前期不同体况奶牛肝脏中的 BA 以及肝脏中 BA 合成酶、转运体和受体的 mRNA 丰度。在之前建立的动物模型中，38 头德国荷斯坦奶牛根据体况评分 (BCS) 和背膘厚 (BFT) 分为高体况评分组 (HBCS; n = 19) 和正常体况评分组 (NBCS; n = 19)。奶牛被喂食旨在实现 BCS 和 BFT 差异目标的日粮 (NBCS: BCS <3.5, BFT <1.2 cm; HBCS: BCS >3.75, BFT >1.4 cm)，直到分娩前的第 7 周干奶。两组在干奶期和随后的泌乳期都喂食相同的日粮。在分娩前的第-7、1、3 和 12 周时取肝脏活检。采用液相色谱电喷雾电离 MS/MS 的靶向代谢组学方法分析肝脏中的 BA。使用微流控定量 PCR 分析肝脏中与 BA 合成酶、转运体和受体相关的靶向基因的 mRNA 丰度。总共可以检测到肝脏中的 14 种 BA:6 种初级和 8 种次级 BA，其中甘氨胆酸 (GCA) 含量最丰富。分娩后甘氨酸结合 BA 的增加，与血清甘氨酸浓度的增加平行，可能源于肌肉蛋白的动员增加，以满足早期泌乳奶牛的高营养需求。NBCS 奶牛的 DMI 高于 HBCS 奶牛，与 GCA、脱氧胆酸和胆酸等更高的肝脏 BA 浓度相关。本文测量的 BA 相关酶的 mRNA 丰度表明，HBCS 奶牛肝脏中替代信号通路占主导地位。总体而言，肝脏中 BA 谱和 BA 代谢既取决于体况，也取决于围产前期奶牛的泌乳诱导作用。
