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 mo of age), middle (T2; 20 mo of age), and late (T3; 28 mo of age) phases. Additionally, to investigate the regulatory mechanisms underlying the expression profile of taurine synthesis genes, primary bovine hepatocytes obtained from 4-wk-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 < 0.05) 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.
Keywords: Japanese Black cattle; fattening period; lipid metabolism; taurine.
The biological role of taurine under various physiological conditions of several animal species remains unclear. In this study, we assessed the physiological functions of taurine in Japanese Black steers (Bos taurus), focusing on the regulatory mechanisms underlying the expression of taurine-related genes using biopsied livers and cultured hepatocytes. In the middle fattening phase of these steers, plasma taurine concentrations exhibited a positive correlation with plasma methionine concentrations, which coincided with the increased expression of the cysteine dioxygenase 1 (CDO1) and cysteine-sulfinic acid decarboxylase (CSAD) enzymes in the liver; these enzymes are considered markers for taurine biosynthesis from methionine. In cultured bovine hepatocytes, the expression of the CDO1 gene was enhanced by oleate and propionate treatments and reduced by acetate. The plasma taurine concentrations were markedly increased in the middle fattening phase, which potentially plays a role in reducing oxidative stress in the liver and optimizing lipid metabolism in response to increased energy intake during this phase. Our findings revealed the complex interactions between taurine and lipid metabolism during the fattening period of Japanese Black steers, emphasizing the significance of specific enzymes and metabolites that induce taurine biosynthesis.
© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.