Signal Transduction Mechanism Of Quercetin Regulating Lipid Metabolism In Broilers

480 of healthy AA broilers?1 day old,similar body weight?were randomly divided into four groups,with six replicates per group and twenty broilers per replicate.Four groups included control and three experimental groups,fed with basic diet supplemented with 0.00%,0.02%,0.04%,0.06%quercetin for 42 days,respectively.In this study,the effects of quercetin on lipid metabolism were investigated by measuring growth performance,carcass traits,chicken quality,parameters of blood fat and hormones relating to lipid metabolism,and RNA-seq of ileal mucosa and gene expression relating to adenosine monophosphate activated protein kinase/peroxisome proliferators activated receptor?AMPK/PPAR?signaling pathway and signal transduction mechanism.Effects of quercetin on growth performance in AA broilers:there were no significant difference in growth performance at 0.02%,0.04%and 0.06%quercetin groups?P>0.05?,compared with control.Effects of quercetin on carcass traits in AA broilers:compared with control,percentage of breast muscle was significantly decreased?P<0.01?by 0.02%quercetin,percentage of abdominal fat was significantly decreased?P<0.05?by 0.06%quercetin.However,there were no significant effect on other indexes by quercetin?P>0.05?.Effects of quercetin on chicken quality in AA broilers:compared with control,0.06%quercetin significantly increased p H_45min of breast muscle?P<0.01?,0.04%and 0.06%quercetin significantly improved p H_45min of thigh muscle?P<0.05,P<0.01?,and p H_45min of thigh muscle was the highest at 0.06%quercetin group.0.04%and 0.06%quercetin significantly increased L*value of thigh muscles?P<0.05?;0.02%and 0.04%quercetin significantly reduced shear force of breast muscles?P<0.05,P<0.01?,0.04%quercetin significantly reduced shear force of thigh muscles?P<0.05?;0.04%and 0.06%quercetin significantly decreased drip loss of thigh muscles?P<0.05?.0.06%quercetin significantly increased scores of color and tenderness of chicken?P<0.01,P<0.05?,scores of chicken color and tenderness were increased with increasing quercetin;0.04%and 0.06%quercetin significantly increased score of juiciness?P<0.01?,and score of juicinesswas the highest at 0.06%quercetin group.However,quercetin did not significantly affect other indexes?P>0.05?.Effect of quercetin on blood fat and hormones relating to lipid metabolism in AA broilers:comparing with control,0.04%and 0.06%quercetin significantly decreased serum content of triglyceride?TG??P<0.01?,total cholesterol?TC??P<0.01?,and low density lipoprotein-cholesterol?LDL-C??P<0.05?;Content of serum TG,TC and LDL-C was the lowest at 0.06%quercetin group;However,0.02%,0.04%and 0.06%quercetin did not significantly affect high density lipoprotein-cholesterol?HDL-C?content?P>0.05?in serum.0.04%and 0.06%quercetin significantly increased serum content of leptin?LEP?and adiponectin?ADPN??P<0.01?,and content of serum leptin and adiponectin was the highest at 0.06%quercetin group.Effect of quercetin on lipids metabolism in ileal mucosa of AA broilers:compared with control,KEGG database revealed that differential gene enrichment pathway included glycerophospholipid metabolism?P<0.01?,AMPK signaling pathway?P<0.01?,cholesterol metabolism?P<0.01?,steroid hormone biosynthesis?P<0.01?,insulin resistance?P<0.05?,bile secretion?P<0.01?and metabolic pathway?P<0.05?at 0.02%quercetin group;Differential gene enrichment pathway included cholesterol metabolism?P<0.01?,insulin resistance?P<0.05?and fatty acid metablism?P<0.05?at 0.04%quercetin group;Differential gene enrichment pathway included fat digestion and absorption?P<0.01?,glycerophospholipid metabolism?P<0.01?,fatty acid degradation?P<0.05?,metabolic pathways?P<0.05?and ether lipid metabolism?P<0.05?at0.06%quercetin group.m RNA expression of genes were determined using RT-q PCR,these selected genes were expressed in a similar patterns between RT-q PCR and RNA-seq.It indicated that RNA-seq and expression abundance of these genes were highly accurate.Effect of quercetin on AMPK/PPAR signaling pathway in AA broilers:in liver,comparing with control,0.02%quercetin significantly increased m RNA expression of phosphatidylinositol3-kinase?PI3K?,AMPK?1,AMPK?2,AMPK?2?P<0.01,P<0.01,P<0.05,P<0.05?;0.04%quercetin significantly increased expression of protein kinase B?PKB/AKT?m RNA?P<0.01?;0.06%quercetin significantly increased m RNA expression of liver kinase B1?LKB1?,carnitine Palmitoyl?CPT1?,PPAR?,AMPK??P<0.01,P<0.01,P<0.05,P<0.01?;0.04%and 0.06%quercetin significantly increased expression of Apo A1 m RNA?P<0.05?,and expression of Apo A1 m RNA was the highest at 0.06%quercetin group;0.04%and 0.06%quercetin significantly reduced m RNA expression of acetyl Co A carboxylase?ACC?and 3-hydroxy-3-methylglutary Co A reductase?HMGR??P<0.05,P<0.05,P<0.01,P<0.01?;0.02%,0.04%and 0.06%quercetin significantly reduced m RNA expression of PPAR?and sterol regulatory element-binding proteins?SREBP1??P<0.05,P<0.05,P<0.01,P<0.01,P<0.01,P<0.01?,m RNA expression of PPAR?and SREBP1 was the lowest at 0.06%quercetin group;In breast muscle,comparing with control,0.04%and 0.06%quercetin significantly increased m RNA expression of PKB and AMPK?1?P<0.05?,m RNA expression of PKB and AMPK?1 was the highest at 0.06%quercetin group;0.06%quercetin significantly increased m RNA expression of CPT1 and PPAR??P<0.05,P<0.01?;0.06%quercetin significantly decreaded m RNA expression of HMGR and SREBP1?P<0.05?;0.02%,0.04%and 0.06%quercetin significantly reduced expression of L-FABP m RNA?P<0.05,P<0.01,P<0.01?.Comparing with control,0.02%quercetin significantly increased protein expression of AMPK,PI3K,PKB,CPT1?P<0.01,P<0.05,P<0.05,P<0.01?;0.06%quercetin significantly increased protein expression of LKB1,PI3K,PKB and CPT1?P<0.01?;0.02%and0.06%quercetin significantly decreased protein expression of SREBP1 and ACC?P<0.01?.However,there were no significant effect on m RNA expression of other genes by quercetin?P>0.05?.In summary,the present results showed that dietary quercetin supplementation regulated lipid metabolism by affecting glycerophospholipid metabolism,AMPK signaling pathway,cholesterol metabolism,steroid hormone biosynthesis,insulin resistance,bile secretion,metabolic pathway,fatty acid metablismat,fat digestion and absorption,fatty acid degradation,ether lipid metabolism,thus reduced the percentage of abodominal fat and improved chicken quality,and AMPK/PPAR signaling pathway was the most dominant signaling pathway.Quercetin increased lipid oxidation,enhanced transport of lipids from liver and reduced fat deposition through the LKB1-AMPK?-PPAR?signaling pathway in liver;And increased lipid oxidation,reduced transport of lipids to breast muscle and fat deposition through the PI3K-PKB-AMPK?1-PPAR?signaling pathway in breast muscle and it was tissue-specific.In this study,the optimum level of dietary quercetin supplementation is 0.06%for decreasing fat deposition.