Effects Of Low Protein Diets With Amino Acids Balanced On Growth Related Proteins Expression Profiling In The Skeletal Muscle Of Weaned Piglets

It is crucial that the dietary nitrogen being used efficiently by pig, this efficient utilization can not only save protein raw materials, but also reduce the emission of nitrogen to the environment, which could largely alleviate the burden of ecological environment. However, the main proteins involved in regulating the nitrogen deposition in muscles remain unclear. This study aims to explore the key differentially expressed protein as well as their interacted proteins response to the different protein-containing diets, to provide valuable data about the identification and function of key proteins which can affect the nitrogen utilization in piglet’s skeletal muscle.This study according to the NRC(2012) recommended protein levels CP(21%), dietary CP reduced by 7%(14%CP),4%(17%CP),1%(20%CP)and balance of the diet lysine(lys), methionine(Met), threonine(Thr) and tryptophan(Trp).Named 14%CP group 17%CP,20%CP group All the three diets were used to feed the weanling piglets on the day 25, piglets were slaughtered to collect the muscle samples for later studies. Hematoxylin and eosin(H&E) staining and transmission electron microscope(TEM) were used to observe the morphology of muscle samples induced by different diets. Moreover, the longissimus dorsi muscles form different piglet groups were lysed to extract the total proteins for the isobaric tags for relative and absolute quantitation(i TRAQ) experiment. By i TRAQ experiment, the differentially expressed proteins between different groups could be obtained.The H&E results showed that the area of longissimus dorsi muscle fibers from 20% CP group was increased than the other two groups. TEM observation showed that compared with the other two groups, sarcomeres of 17% CP group had clearer bright and dark bands alternating as well as the Z lines and M lines, which suggested that 17% CP group may have a better condition of sarcomeres. Additionally, i TRAQ experiment obtained a total of 1976 proteins among all the three samples. Among these 1976 proteins, In details, 138, 134, and proteins showed differential expression between 14% CP group and 17% CP group(17%/14%), 17% CP group and 20% CP group(20%/17%),respectively. GO analysis indicated that molecular function of most differentially expressed proteins were binding, catalytic activity, structural molecular activity, enzyme regulator activity, and transporter activity. We summarized that 38 and 69 proteins were related to sarcomere and mitochondrial function, respectively. KEGG pathway analysis revealed that there were 15 differentially expressed proteins(all down-regulated) in 17%/14% involved in oxidative phosphorylation(p = 8.68e-5), and 20 differentially expressed proteins(all up-regulated) in 20%/17% involved in oxidative phosphorylation(p = 1.96e-8), suggesting that the oxidative phosphorylation was decreased in 17% group compared with the other two groups, maybe due to the reason that the muscle metabolic ability was enhanced under 20% CP feeding,At last, two differentially expressed proteins MICAL3,ATP8, which was shared in 17%/14% and 20%/17%, was validated by western blot.In summary, our result showed that compared with the other two groups, the piglets fed with 17% dietary protein level got the more complete sarcomere morphology, lower mitochondrial damage and oxidative phosphorylation level.