Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061.
Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213.
Poult Sci. 2018 Jun 1;97(6):2053-2063. doi: 10.3382/ps/pey037.
Common dietary supplemental methionine (Met) sources include DL-methionine (DL-Met) and the Met precursor DL-2-hydroxy-4-(methylthio) butanoic acid (DL-HMTBA). For bio-utilization, D-Met and DL-HMTBA are converted into L-Met through oxidation and transamination. The objective of this study was to determine the effect of different dietary supplemental Met sources on gene expression and enzyme activity of Met oxidases in male broiler chickens. Liver, muscle, duodenum, jejunum, and ileum were collected at days 10 (d 10), 21 (d 21), and 26 (d 26) post-hatch from male broiler chickens that were fed a basal diet deficient in sulfur amino acids (SAA) (control), or the control diet supplemented with DL-Met, L-Met, or DL-HMTBA to meet SAA requirements. The mRNA abundance of D-Met oxidase, L-HMTBA oxidase, and D-HMTBA oxidase was measured by real-time PCR, and oxidase activities were measured using colorimetric assays (n = 5). Liver expressed more D- and L-HMTBA oxidase mRNA, while breast muscle and liver expressed more D-Met oxidase mRNA than other tissues. In the liver, DL-HMTBA and L-Met supplementation were associated with greater mRNA abundance of L-HMTBA oxidase compared to the control diet-fed group at d 10 but not d 21 or d 26. DL-HMTBA supplementation, however, was not associated with changes in the mRNA abundance of D-HMTBA oxidase. The Met-deficient diet at d 26 was associated with greater hepatic abundance of DAO mRNA, which is responsible for oxidation of amino acids. Oxidase activities were similar among the Met deficient and Met-supplemented groups. In conclusion, dietary Met supplementation influenced the transcriptional regulation and activity of Met oxidases in a tissue and age-specific manner. Met oxidases may thus act as a determining factor in the bioefficacy of different dietary supplemental Met sources.
常见的膳食补充蛋氨酸（Met）来源包括 DL-蛋氨酸（DL-Met）和 Met 前体 DL-2-羟基-4-（甲基硫代）丁酸（DL-HMTBA）。对于生物利用，D-Met 和 DL-HMTBA 通过氧化和转氨作用转化为 L-Met。本研究旨在确定不同膳食补充 Met 来源对肉鸡雄性鸡肝脏、肌肉、十二指肠、空肠和回肠中 Met 氧化酶基因表达和酶活性的影响。在孵化后第 10 天（d 10）、第 21 天（d 21）和第 26 天（d 26），从喂食缺乏硫氨基酸（SAA）的基础日粮（对照组）或补充 DL-Met、L-Met 或 DL-HMTBA 以满足 SAA 需求的对照组日粮的雄性肉鸡中收集肝脏、肌肉、十二指肠、空肠和回肠。通过实时 PCR 测量 D-Met 氧化酶、L-HMTBA 氧化酶和 D-HMTBA 氧化酶的 mRNA 丰度，并使用比色测定法测量氧化酶活性（n = 5）。肝脏表达更多的 D-和 L-HMTBA 氧化酶 mRNA，而胸肌和肝脏表达的 D-Met 氧化酶 mRNA 多于其他组织。在肝脏中，与对照组日粮喂养组相比，在 d 10 时，DL-HMTBA 和 L-Met 补充与 L-HMTBA 氧化酶的 mRNA 丰度增加相关，但在 d 21 或 d 26 时则不然。然而，DL-HMTBA 补充与 D-HMTBA 氧化酶的 mRNA 丰度变化无关。在 d 26 时，Met 缺乏日粮与肝脏中 DAO mRNA 的丰度增加有关，DAO 负责氨基酸的氧化。氧化酶活性在 Met 缺乏和 Met 补充组之间相似。总之，膳食 Met 补充以组织和年龄特异性的方式影响 Met 氧化酶的转录调控和活性。因此，Met 氧化酶可能是不同膳食补充 Met 来源生物功效的决定因素。
