The objective of this study was to investigate the effects of different Se sources and concentrations on glutathione forms and cholesterol metabolism in beef cattle. Sixty-three Nellore bulls (412 ± 19 kg body weight (BW); 24 mo old) were randomly assigned to a completely randomized design in a 2 × 3 + 1 factorial arrangement (63 pens; one animal/pen) with two Se sources (sodium selenite, ING and Se-yeast, ORG), three concentrations (0.3, 0.9, and 2.7 mg supplemental Se/kg dry matter (DM)), and control treatment (without Se supplementation) fed for 90 d. Blood samples were collected on day 0, 28, 56, and 84. Muscle and liver samples were collected at harvest. Hepatic GSSG (P = 0.004), GSH/GSSG ratio (P = 0.030), and GSH-Px (P = 0.004) were affected by Se source × concentration interaction. Oxidized glutathione was higher in the ORG group vs. ING at concentration 2.7 mg supplemental Se/kg DM, but at 0.3 mg supplemental Se/kg DM the ING group was higher than ORG. The liver GSH-Px activity was higher in the ORG group vs. ING at concentration 0.9 and 2.7 mg supplemental Se/kg DM. The GSH/GSSG ratio was the highest in animals fed 0.3 mg supplemental Se/kg DM of ORG. Selenium liver concentration increased linearly with the supplemental Se concentration in the diet (y = 0.0583 + 0.4254x, R2 = 0.92, P < 0.0001), regardless of source. Total meat cholesterol was greater (P < 0.001) in CON (control) vs. SUP (supplemented, regardless source) group. The muscle GSH-Px activity was higher (P < 0.001) in SUP vs. CON and increased (P < 0.004) with increasing supplemental Se concentrations. There was an increase on very low-density lipoprotein (VLDL), glucose, and triglycerides in ORG vs. ING (P ≤ 0.035). In general, serum Se was higher (P < 0.001) in SUP vs. CON and increased with increasing supplemental Se concentration. Lastly, the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) concentration was lower (P = 0.002) in SUP (0.39 ng/mL) vs. CON (0.55 ng/mL). Selenium supplementation with different sources and concentrations has the potential to affect cholesterol metabolism by affecting GSH/GSSG ratio, GSH-Px, and the HMGCR.

中文翻译：

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不同硒源和浓度对肉牛谷胱甘肽过氧化物酶活性和胆固醇代谢的影响

本研究的目的是研究不同硒来源和浓度对肉牛谷胱甘肽形式和胆固醇代谢的影响。63 头 Nellore 公牛（412 ± 19 千克体重 (BW)；24 个月大）被随机分配到一个完全随机设计的 2 × 3 + 1 析因排列（63 只围栏；一只动物/围栏），具有两种硒源（亚硒酸钠、ING 和硒酵母，ORG）、三种浓度（0.3、0.9 和 2.7 mg 补充硒/千克干物质 (DM)）和对照处理（不补充硒）喂食 90 天。在第 0、28、56 和 84 天收集血样。在收获时收集肌肉和肝脏样本。肝脏 GSSG (P = 0.004)、GSH/GSSG 比率 (P = 0.030) 和 GSH-Px (P = 0.004) 受硒源 × 浓度相互作用的影响。ORG 组的氧化型谷胱甘肽高于对照组。ING 在浓度为 2.7 mg 补充 Se/kg DM 时，但在 0.3 mg 补充 Se/kg DM 时，ING 组高于 ORG。在浓度为 0.9 和 2.7 mg 补充 Se/kg DM 时，ORG 组的肝脏 GSH-Px 活性高于 ING。GSH/GSSG 比率在喂食 0.3 mg 补充 Se/kg DM ORG 的动物中最高。无论来源如何，肝脏硒浓度随饮食中硒浓度的增加呈线性增加（y = 0.0583 + 0.4254x，R2 = 0.92，P < 0.0001）。CON（对照）与 SUP（补充，无论来源）组相比，肉类总胆固醇更高 (P < 0.001)。与 CON 相比，SUP 的肌肉 GSH-Px 活性更高 (P < 0.001)，并且随着补充硒浓度的增加而增加 (P < 0.004)。极低密度脂蛋白 (VLDL)、葡萄糖、ORG 与 ING 中的甘油三酯 (P ≤ 0.035)。一般而言，SUP 与 CON 相比血清硒更高 (P < 0.001)，并且随着补充硒浓度的增加而增加。最后，SUP (0.39 ng/mL) 与 CON (0.55 ng/mL) 中的 3-hydroxy-3-methyl-glutaryl-coenzyme A 还原酶 (HMGCR) 浓度较低 (P = 0.002)。不同来源和浓度的硒补充剂有可能通过影响 GSH/GSSG 比率、GSH-Px 和 HMGCR 来影响胆固醇代谢。