MOE Joint International Research Laboratory of Animal Health & Food Safety, Nanjing Agricultural University, Nanjing 210095, PR China; Key Laboratory of Animal Physiology & Biochemistry, Nanjing Agricultural University, Nanjing 210095, PR China; Faculty of Veterinary Science, University of Genenia, Genenia, Sudan.
MOE Joint International Research Laboratory of Animal Health & Food Safety, Nanjing Agricultural University, Nanjing 210095, PR China; Key Laboratory of Animal Physiology & Biochemistry, Nanjing Agricultural University, Nanjing 210095, PR China.
Poult Sci. 2022 Jun;101(6):101871. doi: 10.1016/j.psj.2022.101871. Epub 2022 Mar 24.
Corticosterone is critical for the maturation and survival of chicken fetus around hatching. Betaine is used as a feed additive in poultry industry to promote growth and mitigate stress. However, it remains unknown whether betaine could affect adrenal corticosterone synthesis in pre-hatching chicken fetuses. In this study, betaine (2.5 mg/egg) was injected into developing chicken fetuses at d 11 of incubation (E11) and its impact on adrenal steroidogenesis was investigated at day 19 (E19). Plasma corticosterone concentration was significantly (P < 0.05) elevated in betaine-treated fetuses, together with increased adrenal expression of melanocortin 2 receptor and steroidogenic acute regulatory protein. Accordingly, the corticosterone biosynthetic enzymes, such as cytochrome P450 family 11 subfamily A member 1, 3β-hydroxysteroid dehydrogenase and cytochrome P450 family 21 subfamily A member 2, as well as cholesterol biosynthesis or regulation-related genes, such as sterol regulatory element-binding protein 1, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase and low-density lipoprotein receptor, were all significantly (P < 0.05) upregulated in betaine group. Meanwhile, steroidogenic factor-1 and glucocorticoid receptor were significantly (P < 0.05) enhanced, whereas expression of dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome gene, a nuclear receptor known as a repressor of adrenal steroidogenesis, was significantly (P < 0.05) downregulated. Betaine significantly (P < 0.05) increased adrenal expression of genes involved in one-carbon metabolism and DNA methylation, such as S-adenosyl homocysteine hydrolase, betaine-homocysteine-methyltransferase, methionine adenosyl transferase and DNA methyltransferases, yet the promoter regions of most steroidogenic genes were significantly (P < 0.05) hypomethylated. These results indicate that in ovo injection of betaine promotes adrenal glucocorticoid synthesis in chicken fetuses before hatching, which involves alterations in DNA methylation.
皮质酮对于孵化前小鸡胎儿的成熟和存活至关重要。甜菜碱被用作家禽养殖业的饲料添加剂，以促进生长和减轻应激。然而，目前尚不清楚甜菜碱是否会影响孵化前小鸡胎儿的肾上腺皮质酮合成。在这项研究中，在孵化第 11 天（E11）向发育中的鸡胎儿注射甜菜碱（2.5mg/蛋），并在第 19 天（E19）研究其对肾上腺类固醇生成的影响。与对照组相比，甜菜碱处理的胎鸡血浆皮质酮浓度显著升高（P < 0.05），同时肾上腺黑素皮质素 2 受体和类固醇生成急性调节蛋白的表达也增加。相应地，皮质酮生物合成酶，如细胞色素 P450 家族 11 亚家族 A 成员 1、3β-羟类固醇脱氢酶和细胞色素 P450 家族 21 亚家族 A 成员 2，以及胆固醇生物合成或调节相关基因，如固醇调节元件结合蛋白 1、3-羟-3-甲基戊二酰基辅酶 A 还原酶和低密度脂蛋白受体，在甜菜碱组中均显著上调（P < 0.05）。同时，类固醇生成因子-1 和糖皮质激素受体显著增强（P < 0.05），而作为肾上腺类固醇生成抑制剂的核受体剂量敏感性别逆转-肾上腺发育不良综合征关键区 X 染色体基因的表达显著下调（P < 0.05）。甜菜碱显著上调与一碳代谢和 DNA 甲基化相关的肾上腺基因表达，如 S-腺苷同型半胱氨酸水解酶、甜菜碱-同型半胱氨酸-甲基转移酶、蛋氨酸腺苷转移酶和 DNA 甲基转移酶，但大多数类固醇生成基因的启动子区域显著低甲基化（P < 0.05）。这些结果表明，在鸡胚中注射甜菜碱可促进孵化前胎儿肾上腺糖皮质激素的合成，这涉及 DNA 甲基化的改变。
