Heat stress (HS) triggers oxidative stress, systemic inflammation, and disrupts growth efficiency of livestock. β-adrenergic agonists supplemented to ruminant livestock improve growth performance, increase skeletal muscle mass and decrease carcass fat. The objective of this study was to understand the independent and interacting effects of HS and zilpaterol hydrochloride (ZH) supplementation on the transcriptome of subcutaneous white adipose tissue and the longissimus dorsi muscle in steers. Twenty-four Red Angus-based steers were assigned to thermoneutral (TN; Temperature Humidity Index (THI)=68) or HS (THI=73-85) conditions and were not supplemented or supplemented with ZH (8.33 mg/kg/day) for 21 d in a 2x2 factorial. Steers in the TN condition were pair-fed to the average daily feed intake of HS steers. RNA was isolated from adipose tissue and skeletal muscle samples collected via biopsy on 3, 10, and 21 d and sequenced using 3’ Tag-Seq to an achieved average depth of 3.6 million reads/sample. Transcripts, mapped to ARS-UCD1.2, were quantified. Differential expression (DE) analyses were performed in DESeq2 with a significance threshold for false discovery rate of 0.05. In adipose, 4 loci (MISP3, APOL6, SLC25A4, S100A12) were DE due to ZH on d 3, and 2 (RRAD, ALB) were DE due to the interaction of HS and ZH on d 10 (Padj<0.05). In muscle, 40 loci (including TENM4 and OAZ1) were DE due to ZH on d 10 and 6 loci (HIF1A, LOC101903734, PDZD9, HNRNPU, MTUS1, TMCO6) were DE due to environment on d 21 (Padj<0.05). To explore biological pathways altered by environment, supplement, and their interaction, loci with DE (Praw<0.05) were evaluated in Ingenuity Pathway Analysis. In adipose, 509 pathways were predicted to be altered (P<0.01): 202 due to HS, 126 due to ZH, and 181 due to the interaction; these included inflammatory pathways predicted to be upregulated due to HS but downregulated due to the interaction of HS and ZH. In muscle, 113 pathways were predicted to be altered (P<0.01): 23 due to HS, 66 due to ZH, and 24 due to the interaction of HS and ZH. Loci and pathway data in muscle suggest HS induced oxidative stress and that the stress response was moderated by ZH. Metabolic pathways were predicted to be altered due to HS, ZH, and their interaction in both tissues. These data provide evidence that HS and ZH interact to alter expression of genes in metabolic and immune function pathways and that ZH moderates some adverse effects of HS.

中文翻译：

---

转录组分析表明，在肉牛中补充齐帕特罗可部分缓解白色脂肪组织中热应激诱导的炎症和骨骼肌中的氧化应激

热应激 (HS) 会引发氧化应激、全身性炎症，并破坏家畜的生长效率。补充给反刍家畜的 β-肾上腺素能激动剂可改善生长性能，增加骨骼肌质量并减少胴体脂肪。本研究的目的是了解补充 HS 和盐酸齐帕特罗 (ZH) 对皮下白色脂肪组织和背最长肌转录组的独立和相互作用影响。二十四头基于红安格斯的阉牛被分配到热中性（TN；温度湿度指数（THI）=68）或 HS（THI=73-85）条件，并且未补充或补充 ZH（8.33 mg/kg/天）在 2x2 阶乘中持续 21 天。TN 条件下的牛被配对喂养到 HS 牛的平均每日采食量。从第 3、10 和 21 天通过活检收集的脂肪组织和骨骼肌样本中分离出 RNA，并使用 3' Tag-Seq 进行测序，平均深度达到 360 万读数/样本。映射到 ARS-UCD1.2 的转录本被量化。在 DESeq2 中进行差异表达 (DE) 分析，错误发现率的显着性阈值为 0.05。在脂肪中，4 个基因座（MISP3、APOL6、SLC25A4、S100A12）是由于第 3 天的 ZH 而导致的 DE，而 2 个（RRAD、ALB）是由于第 10 天的 HS 和 ZH 的相互作用而导致的 DE（Padj < 0.05）。在肌肉中，40 个基因座（包括 TENM4 和 OAZ1）在第 10 天因 ZH 而出现 DE，6 个基因座（HIF1A、LOC101903734、PDZD9、HNRNPU、MTUS1、TMCO6）在第 21 天因环境而出现 DE（Padj<0.05）。为了探索被环境、补充剂及其相互作用改变的生物途径，基因座与 DE (Praw < 0. 05) 在 Ingenuity Pathway Analysis 中进行了评估。在脂肪中，预计有 509 条通路发生改变 (P<0.01)：202 条是由于 HS，126 条是由于 ZH，181 条是由于相互作用；这些包括预测由于 HS 而上调但由于 HS 和 ZH 的相互作用而下调的炎症通路。在肌肉中，预测有 113 条通路发生改变 (P<0.01)：23 条是由于 HS，66 条是由于 ZH，24 条是由于 HS 和 ZH 的相互作用。肌肉中的位点和通路数据表明 HS 诱导氧化应激，并且应激反应由 ZH 调节。由于 HS、ZH 及其在两种组织中的相互作用，预计代谢途径会发生改变。这些数据提供的证据表明 HS 和 ZH 相互作用以改变代谢和免疫功能途径中的基因表达，并且 ZH 缓和 HS 的一些不利影响。