The Mechanism Of FATP1 Regulating Skeletal Muscle Ectopic Fat Deposition In Stressed Broiler Chickens

As a fatty acid transporter,fatty acid transport protein 1(FATP1)plays an important role in fatty acid transport of broiler chickens.This study was conducted from the point of the important role of fatty acid transport in lipid accumulation.In levels of nucleic acid,protein,cell and tissue,we investigate the effect of FATP1 on lipid accumulation under glucocorticoids(DEX)treatment,using the experimental models of both in vivo and in vitro.1.The effect of FATP1 on skeletal muscle lipid accumulation in stressed broilers.DEX treatment was conducted according to broilers body weight.Results show triglyceride content in muscle tissue and VLDL and insulin in blood plasma were increased,meanwhile FATP1 gene expression was enhanced,and gene expressions of glucocorticoids receptor(GR),adiponectin receptor(ADPNR),peroxisome proliferator activated receptor alpha(PPARα)were simultaneously increased in thigh tissue.We can speculation that glucocorticoids regulate FATP1 expression to enhance lipid uptake and accumulation via GR-ADPNR-PPARαpathway.2.The effect of lipid levels on FATP1 regulation by glucocorticoids.Broilers were fed different fat levels diets,and treated with DEX at 35 days of age.Results show that DEX improved lipid accumulation in muscle under low fat diet,while DEX had no effect under high fat diet;Under low fat diets,Dex affected expressions of GR,ADPNR,PPARα and FATP1 of muscle tissues in a similar trend,but this trend was not existed in thigh tissue under DEX treatment with high fat diet.These results indicated that DEX has the different regulation on GR-ADPNR-PPARα-FATP1 pathway in muscle under different fat level diets.3.The effects of fatty acids type on the regulation of FATP1 by glucocorticoids.The myoblasts were cultured with the same concentration of oleic acid and palmitic acid,and different concentrations of DEX was added when cells were differentiated to about 80%.Results show lipid accumulation was increased under saturated fatty acid treatment while decreased under unsaturated fatty acid;DEX didn’t affect AKT phosphorylation;DEX with oleic acid exposure had no effect on gene expressions of GR,ADPNR,PPARα and FATP1,while DEX with palmitic acid exposure regulated TG content and expressions of GR,ADPNR,PPARα and FATP1 in a similarly rising trend.These results indicated that fatty acid typeinfluences the effects of DEX on the regulation of FATP1 and lipid accumulation in muscle.4.The pathway underling DEX regulating FATP1 and muscular lipid accumulation.In case of DEX only,it was found that the gene expression levels of FATP1 and PPAR had no significant change.The methods of the specific inhibitor were then used to confirm the potential role of GR,ERK2/MAPK and PPARα in glucocorticoids regulation,under the oleic acid or palmitic acid explosure.The results show that the inhibitors had effect on palmitic acid uptake rather than oleic acid,The results indicated that glucocorticoids regulate saturated fatty acid uptake through GR-PPARα or ERK2/MAPK-PPARα pathway.In summary,glucocorticoids facilitate lipid uptake and accumulation in muscle likely by improving FATP1 transcription.Different level and type of fatty acid could influence the effect of glucocorticoids on FATP1 and muscle lipid accumulation.Under stress conditions induced by glucocorticoids,myoblasts prefer to uptake saturated fatty acid through regulating GR-PPARα or ERK2/MAPK-PPARα pathway.This study reveals the targets of stress regulating lipid ectopic accumulation in skeletal muscles,and the interaction between the diet fat and glucocorticoids.