Dietary Lactic Acid Bacteria Modulate Yolk Components and Cholesterol Metabolism by Hmgr Pathway in Laying Hens

ABSTRACT This study aimed to investigate the effect of dietary lactic acid bacteria (LAB) on egg production, yolk components, cholesterol metabolism, and enterohepatic circulation of bile acids in hens. Four treatment diets included a control and LAB added at 3 × 105 (low), 3 × 107 (medium), or 3 × 109 (high) cfu/kg. The treatment LAB contained equal amounts of Lactobacillus acidophilus, Lactobacillus plantarum, and Enterococcus faecium. Results showed that high LAB increased (p<0.05) laying rate, egg mass, and yolk phospholipid, but decreased (p<0.05) yolk triglyceride and phosvitin. Diets with LAB decreased (p<0.05) yolk and serum cholesterol content, and serum bile acid by 9.3 to 39.9%. In liver, high LAB downregulated (p<0.05) mRNA expression of serine/threonine kinase 11 (STK11), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), AMP-activated protein kinase catalytic subunit (PRKAA1, 2), and protein phosphatase catalytic subunits (PPP2CA, PPP2CB and PPP3CA) by 49.5 to 175.4%. In mucosa, high LAB downregulated (p<0.05) PRKAA1 and HMGR by 68.2 and 69.6%, respectively; but upregulated (p<0.05) PPP2CA and PPP2CB by 51.2 and 45%, respectively. Linear decreasing (p≤0.035) responses to LAB doses were found on cholesterol, phosvitin, bile acid, and hepatic gene expressions, and quadratic (p≤0.006) effects on yolk cholesterol and hepatic STK11. It is concluded that probiotic LAB can improve yolk components and decrease hepatic cholesterol synthesis by regulating HMGR pathway in hens.

摘要 本研究旨在探究日粮乳酸菌（lactic acid bacteria, LAB）对蛋鸡产蛋性能、卵黄成分、胆固醇代谢以及胆汁酸肠肝循环的影响。
试验设置4组日粮，分别为对照组，以及添加3×10⁵（低剂量）、3×10⁷（中剂量）、3×10⁹（高剂量）菌落形成单位每千克（cfu/kg）的LAB组。所使用的试验LAB由嗜酸乳杆菌（Lactobacillus acidophilus）、植物乳杆菌（Lactobacillus plantarum）和粪肠球菌（Enterococcus faecium）按等量配比组成。
研究结果显示，高剂量LAB可显著提升（p<0.05）蛋鸡的产蛋率、蛋重以及卵黄磷脂含量，同时显著降低（p<0.05）卵黄甘油三酯与卵黄高磷蛋白含量。添加LAB的日粮可显著降低（p<0.05）卵黄与血清胆固醇含量，以及血清胆汁酸水平，降幅达9.3%至39.9%。
在肝脏组织中，高剂量LAB可显著下调（p<0.05）丝氨酸/苏氨酸激酶11（serine/threonine kinase 11, STK11）、3-羟基-3-甲基戊二酰辅酶A还原酶（3-hydroxy-3-methylglutaryl-CoA reductase, HMGR）、AMP活化蛋白激酶催化亚基（AMP-activated protein kinase catalytic subunit, PRKAA1、PRKAA2）以及蛋白磷酸酶催化亚基（protein phosphatase catalytic subunits, PPP2CA、PPP2CB与PPP3CA）的mRNA表达量，下调幅度为49.5%至175.4%。
在肠道黏膜组织中，高剂量LAB可显著下调（p<0.05）PRKAA1与HMGR的mRNA表达量，下调幅度分别为68.2%与69.6%；但可显著上调（p<0.05）PPP2CA与PPP2CB的mRNA表达量，上调幅度分别为51.2%与45%。
研究发现，胆固醇、卵黄高磷蛋白、胆汁酸以及肝脏基因表达水平随LAB添加剂量呈线性降低趋势（p≤0.035）；而卵黄胆固醇与肝脏STK11的表达则呈二次曲线效应（p≤0.006）。
综上，益生菌型LAB可通过调控蛋鸡体内HMGR通路，改善卵黄成分并降低肝脏胆固醇合成。