Selenium (Se) is an integral component of selenoproteins, with effective scavenging of harmful reactive oxygen species (ROS) by selenoproteins necessary to protect cells from oxidative stress. Due to the presence of Se-deficient soils in large portions of the US, including the southeast cow-calf producing states, grazed forages are insufficient in this trace mineral and dietary supplementation is recommended. We have investigated the effects of providing Se in an inorganic form (ISe, the industry standard) versus a 1:1 mixture (MIX) of ISe to organic Se (OSe), and have observed significant effects on luteal function, endometrial function and conceptus development. Herein, our objective was to determine the effect of form of Se on 1) clinical markers of total antioxidant capacity and liver function, and 2) the expression of mRNAs encoding selenoproteins in the liver. Following consecutive 45-d periods of Se-depletion then repletion, Angus-cross heifers were assigned to 90 d of treatment with a vitamin-mineral mix containing 35-ppm Se as ISe or MIX. Heifers were then inseminated at estrus (d 0) with serum collected at d 0, 7 and 17 to quantify albumin, beta-hydroxybutyrate (BHBA) and aspartate aminotransferase (AST). Liver samples were collected at euthanasia on d 17 (n = 6 pregnant heifers per treatment) for the quantification of the relative abundance of 25 selenoprotein mRNAs using qPCR. There was no effect of treatment on circulating albumin (P > 0.05). Hepatocyte-secreted albumin is the most prominent antioxidant in the circulation, with this result suggesting that albumin-driven redox capacity is not sensitive to the form of Se supplied to achieve a Se-adequate status. Systemic concentrations of BHBA and AST were increased (P < 0.05) in MIX- versus ISe-treated heifers at d 7 and 17 of pregnancy. Circulating BHBA is considered a primary indicator of liver function and the hepatic response to increased metabolic demands, whereas increased AST is conventionally considered a marker for liver damage. These results suggest increased demands on the liver in MIX versus ISe-treated heifers, however not at the level indicative of dysfunction or disease. Additionally, the serum concentration of urea nitrogen was quantified and determined to be reduced (P < 0.05) at estrus in MIX- versus ISe-treated heifers, indicative of form-induced changes in hepatic nitrogen metabolism. Targeted qPCR analysis to determine the effect of treatment on the abundance of encoding selenoproteins by mRNA, including the iodothyronine deiodinases, glutathione peroxidases and thioredoxin reductases, was largely unaffected by treatment, with only the abundance of mRNA encoding Selenoprotein V tending to differ (P = 0.07) with treatment. Overall, this study revealed form of Se-effects on markers of hepatic health and function, as well as blood urea nitrogen, but did not reveal form of Se-effects on the expression of hepatic selenoproteins mRNAs.

中文翻译：

---

131 硒形式对妊娠早期小母牛肝功能和硒蛋白 mRNA 的影响

硒 (Se) 是硒蛋白的重要组成部分，硒蛋白可有效清除有害的活性氧 (ROS)，从而保护细胞免受氧化应激。由于美国大部分地区（包括东南部的牛犊生产州）存在缺硒土壤，放牧的饲料中这种微量矿物质含量不足，建议补充膳食。我们研究了提供无机形式硒（ISe，行业标准）与 ISe 与有机硒 (OSe) 1:1 混合物 (MIX) 的影响，并观察到对黄体功能、子宫内膜功能和受孕的显着影响发展。在此，我们的目的是确定硒的形式对 1) 总抗氧化能力和肝功能的临床标志物，以及 2) 肝脏中编码硒蛋白的 mRNA 表达的影响。在连续 45 天的硒消耗和补充期后，安格斯杂交小母牛被分配接受 90 天的维生素矿物质混合物治疗，其中维生素矿物质混合物含有 35 ppm Se（ISe 或 MIX）。然后在发情期 (d 0) 对小母牛进行授精，并在 0、7 和 17 天收集血清以定量白蛋白、β-羟基丁酸 (BHBA) 和天冬氨酸转氨酶 (AST)。在第 17 天安乐死时收集肝脏样本（每次处理 n = 6 头怀孕小母牛），使用 qPCR 定量 25 种硒蛋白 mRNA 的相对丰度。治疗对循环白蛋白没有影响(P>0.05)。肝细胞分泌的白蛋白是循环中最重要的抗氧化剂，这一结果表明白蛋白驱动的氧化还原能力对为实现硒充足状态而提供的硒的形式不敏感。在妊娠第7天和第17天，MIX处理的小母牛与ISe处理的小母牛相比，BHBA和AST的全身浓度增加(P＜0.05)。循环 BHBA 被认为是肝功能和肝脏对代谢需求增加的反应的主要指标，而 AST 增加通常被认为是肝损伤的标志。这些结果表明，与 ISe 处理的小母牛相比，MIX 对肝脏的需求增加，但并未达到功能障碍或疾病的水平。另外，对MIX处理的小母牛与ISe处理的小母牛的发情期尿素氮浓度进行定量并确定其降低(P＜0.05)，表明形式诱导的肝氮代谢变化。靶向 qPCR 分析确定治疗对 mRNA 编码硒蛋白（包括碘甲腺原氨酸脱碘酶、谷胱甘肽过氧化物酶和硫氧还蛋白还原酶）丰度的影响，该分析在很大程度上不受治疗影响，只有编码硒蛋白 V 的 mRNA 丰度趋于不同（P = 0.07) 治疗。总体而言，这项研究揭示了硒对肝脏健康和功能标志物以及血液尿素氮的影响，但没有揭示硒对肝硒蛋白 mRNA 表达的影响。