Department of Animal Science, Michigan State University, East Lansing 48824.
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907.
J Dairy Sci. 2020 Dec;103(12):11449-11460. doi: 10.3168/jds.2020-18914. Epub 2020 Oct 23.
Our objective was to determine the temporal effects of increasing supply of propionate on propionate metabolism in liver tissue of dairy cows in the postpartum (PP) period. A total of 6 dairy cows [primiparous: n = 3, 9.00 ± 1.00 d PP (mean ± SD) and multiparous: n = 3; 4.67 ± 1.15 d PP] were biopsied for liver explants in a block-design experiment. Explants were treated with 3 concentrations of [C]sodium propionate of 1, 2, or 4 mM. Explants were incubated in 2 mL of Medium 199 supplemented with 1% BSA, 0.6 mM oleic acid, 2 mM sodium l-lactate, 0.2 mM sodium pyruvate, and 0.5 mMl-glutamine at 38°C and sampled at 0.5, 15, and 60 min. Increasing the concentration of [C]propionate increased total C% enrichment of propionyl coenzyme A (CoA), succinate, fumarate, malate, and citrate with time. Concentration of propionate did not affect total C% enrichment of hepatic glucose or acetyl CoA, but total C% enrichment increased with time for hepatic glucose. The C labeling from propionate was incorporated into acetyl CoA, but increased concentrations of propionate did not result in greater labeling of acetyl CoA. However, increases in C% enrichment of [M+4]citrate and [M+5]citrate concentrations of [C]propionate indicate propionate conversion to acetyl CoA and subsequent entry of acetyl CoA into the tricarboxylic acid cycle in dairy cows in the PP period. This research presents evidence that despite an increase in hepatic acetyl CoA concentration and general consensus on the upregulation of gluconeogenesis of dairy cows during the PP period, carbon derived from propionate contributes to the pool of acetyl CoA, which increases as concentration of propionate increases, in addition to stimulating oxidation of acetyl CoA from other sources. Because of the hypophagic effects of propionate, but importance of propionate as a glucose precursor, a balance of propionate supply to dairy cows could lead to improvements in dry matter intake, and subsequently, health and production in dairy cows.
我们的目的是确定在产后（PP）期间，丙酸供应量的增加对奶牛肝组织中丙酸代谢的时间效应。总共对 6 头奶牛（初产牛：n = 3，9.00 ± 1.00 d PP（平均值 ± SD）和经产牛：n = 3；4.67 ± 1.15 d PP）进行了肝组织活检，以进行组织块实验。将组织块用 3 种浓度的[C]丙酸钠处理，浓度分别为 1、2 或 4 mM。组织块在含有 1% BSA、0.6 mM 油酸、2 mM 丙酸钠、0.2 mM 丙酮酸钠和 0.5 mM l-谷氨酰胺的 Medium 199 中于 38°C 孵育 2 mL，并在 0.5、15 和 60 min 时取样。随着时间的推移，增加[C]丙酸钠的浓度会增加丙酰辅酶 A（CoA）、琥珀酸、富马酸、苹果酸和柠檬酸的总 C%丰度。丙酸浓度不影响肝葡萄糖或乙酰辅酶 A 的总 C%丰度，但肝葡萄糖的总 C%丰度随时间增加。丙酸盐的 C 标记被掺入乙酰辅酶 A，但增加的丙酸浓度不会导致乙酰辅酶 A 的标记增加。然而，[C]丙酸钠的[M+4]柠檬酸和[M+5]柠檬酸浓度的 C 标记增加表明丙酸盐转化为乙酰辅酶 A，并且随后乙酰辅酶 A 进入奶牛 PP 期的三羧酸循环。这项研究提供了证据，表明尽管在 PP 期间奶牛的肝乙酰辅酶 A 浓度增加且普遍认为糖异生上调，但来自丙酸的碳有助于乙酰辅酶 A 的池，随着丙酸浓度的增加，该池增加，除了刺激其他来源的乙酰辅酶 A 的氧化。由于丙酸的低食欲作用，但丙酸作为葡萄糖前体的重要性，奶牛丙酸供应的平衡可能会改善干物质摄入量，随后改善奶牛的健康和生产。
