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

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 x 10(5) (low), 3 x 10(7) (medium), or 3 x 10(9) (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.