Effect of Dietary Leucine Supplementation on Plasma Leptin Level and Protein Metabolism of Skeletal Muscles in Rats

To explore the effects of dietary leucine supplementation on the growth performance,leptin production,and protein metabolism of skeletal muscle in growing rats,24 male Sprague-Dawley rats aged 4 weeks were randomly allotted to feed one of the two diets added 2.04% alanine(control diet) or 3% leucine(experimental diet) for 12 days.There were 12 replicates per treatment.On the evening of d 11,all rats were food-deprived.On the morning of d 12,all rats were injected intraperitoneally with L-phenylalanine containing L-[ring-2H5] phenylalanine in 1.5 h after refed.The growth performance was not significantly affected by dietary leucine supplementation(P0.10).However,plasma leptin concentrations of the rats fed the experimental diet were significantly increased(P0.01).The protein breakdown of gastrocnemius and soleus of rats fed the experimental diet was significantly lower than that of rats fed the control diet(P0.01).The protein synthesis of gastrocnemius of rats fed the experimental diet was significantly higher than that of rats fed the control diet(P0.01).In conclusion,dietary leucine supplementation significantly increased the plasma leptin levels,and significantly regulated the protein metabolism of skeletal muscles in growing rats.