Taurine, biosynthesized from methionine or cysteine in the liver, plays a crucial regulatory role in bile acid conjugation, antioxidant effects, and glucose and cholesterol metabolism. This may influence the metabolic changes associated with fat accumulation in beef cattle. However, the physiological role of taurine in this species has not been fully elucidated. In this study, we explored the physiological role of taurine in Japanese Black steers (Bos taurus) in different phases during the fattening period. To examine the correlation among plasma taurine concentrations, various physiological parameters, and genes related to taurine synthesis in the liver, we used biopsied liver tissues, blood samples, and rumen fluids collected from 21 steers at three different stages, i.e., early (T1; 13 months of age), middle (T2; 20 months of age), and late (T3; 28 months of age) phases. Additionally, to investigate the regulatory mechanisms underlying the expression profile of taurine synthesis genes, primary bovine hepatocytes obtained from 4-week-old Holstein calves were treated with palmitate, oleate, acetate, propionate, or β-hydroxybutyrate (BHBA). Plasma taurine and cholesterol concentrations significantly (P < 0.001) increased in the T2 phase, which is potentially attributable to increased energy intake and assimilation induced by increased intake of concentrated feed. Cysteine sulfinic acid decarboxylase (CSAD) expression significantly increased (P < 0.01) in T2 than in other phases. The expression levels of cysteine dioxygenase type 1 (CDO1) and cholesterol 7 alpha-hydroxylase (CYP7A1) were significantly higher (P < 0.001) in T2 than in T3; moreover, the CDO1/glutamate-cysteine ligase catalytic subunit (GCLC) ratio was higher (P < 0.05) in T2 than in T1. Plasma taurine concentrations were positively correlated with plasma methionine (r = 0.51; P < 0.05) and total cholesterol (r = 0.56; P < 0.05) concentrations at T2. Relative CDO1 mRNA expression was upregulated in cultured bovine hepatocytes treated with oleate and propionate, whereas it was downregulated upon acetate treatment. These findings indicate that the increase in plasma taurine concentrations in the T2 phase is associated with changes in lipid and methionine metabolism in Japanese Black steers.

中文翻译：

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黑毛牛育肥期血牛磺酸浓度动态及其与营养生理状况的相关性


牛磺酸由肝脏中的蛋氨酸或半胱氨酸生物合成，在胆汁酸结合、抗氧化作用以及葡萄糖和胆固醇代谢中起着至关重要的调节作用。这可能会影响与肉牛脂肪堆积相关的代谢变化。然而，牛磺酸在该物种中的生理作用尚未完全阐明。在这项研究中，我们探讨了牛磺酸在日本黑阉牛 （Bos taurus） 育肥期不同阶段的生理作用。为了检查血浆牛磺酸浓度、各种生理参数和与肝脏牛磺酸合成相关的基因之间的相关性，我们使用了从三个不同阶段的 21 头公牛收集的活检肝组织、血液样本和瘤胃液，即早期 （T1;13 个月大）、中期 （T2;20 个月大） 和晚期 （T3;28 个月大） 阶段。此外，为了研究牛磺酸合成基因表达谱的调控机制，用棕榈酸酯、油酸酯、乙酸盐、丙酸盐或 β-羟基丁酸盐 （BHBA） 处理从 4 周龄荷斯坦犊牛获得的原代牛肝细胞。血浆牛磺酸和胆固醇浓度在 T2 期显著增加 （P < 0.001），这可能是由于浓缩饲料摄入量增加引起的能量摄入增加和同化。半胱氨酸亚磺酸脱羧酶 （CSAD） 在 T2 中的表达显著高于其他阶段 （P < 0.01）。T2 中半胱氨酸双加氧酶 1 型 （CDO1） 和胆固醇 7 α-羟化酶 （CYP7A1） 的表达水平显著高于 T3 （P < 0.001）;此外，T2 中的 CDO1/谷氨酸-半胱氨酸连接酶催化亚基 （GCLC） 比率 （P < 0.05） 高于 T1。 血浆牛磺酸浓度与血浆蛋氨酸呈正相关 （r = 0.51;P < 0.05） 和总胆固醇 （r = 0.56;P < 0.05） 浓度。在用油酸盐和丙酸盐处理的培养牛肝细胞中，CDO1 mRNA 的相对表达上调，而在乙酸盐处理后下调。这些发现表明，T2 期血浆牛磺酸浓度的增加与日本黑阉牛脂质和蛋氨酸代谢的变化有关。