Digital Gene-expression Profiling Analysis Of The Effect Of Alfalfa Saponins On Cholesterol Metabolism In Laying Hens

Background:To prevent cardiovascular disease, people are advised to limit their intake of dietary cholesterol to less than 300 mg/day. Egg consumption has been seriously reduced because of the high levels of cholesterol. The purpose of the present study was to evaluate the cholesterol-lowering effects of alfalfa saponins in yolk and the molecular mechanisms underlying these effects using digital gene-expression profiling analysis. Liver and ovary tissues were isolated from laying hens fed with alfalfa saponins for RNA sequencing.Results:The cholesterol content of the yolks of eggs from hens fed 120 mg/kg alfalfa saponins declined considerably on day 60. Other groups (60,240,480 mg/kg alfalfa saponins group) also showed decreases, but they were not significant. Digital gene expression generated over nine million reads per sample, producing expression data for least 12,384 genes. Among these genes,110 genes showed greater than normal expression in the liver and 107 genes showed greater than normal expression in the ovary. Cholesterol 7 alpha-hydroxylase(Cyp7al) and apolipoprotein H (Apoh), which act in the synthesis of bile acid and cholesterol efflux, showed more expression in the livers of hens given dietary alfalfa saponins supplementation. In the ovary, levels of very low density lipoprotein receptor (Vldlr), apolipoprotein B (Apob), apovitellenin 1 (Apovldâ…¢) and vitellogenin (Vtgâ… , Vtgâ…¡ and Vtgâ…¢) in ovary decreased with dietary alfalfa saponins supplementation.Conclusion:Transcriptome analysis revealed that the molecular mechanisms underlying the cholesterol-lowering effects of alfalfa saponins were partially mediated by enhancement of cholesterol efflux in the liver and this reduced of cholesterol deposition in the ovary.