Comparative proteomics and phosphoproteomics analyses of DHEA-induced on hepatic lipid metabolism in broiler chickens

Dehydroepiandrosterone (DHEA) is a precursor of the adrenocorticosteroid hormones that are common to all animals, including poultry. The study described herein was undertaken to investigate the effect of DHEA on lipid metabolism in broiler chickens during embryonic development and to determine the regulatory mechanisms involved in its physiological action. Treatment group eggs were injected with 50mg DHEA diluted in 50 μL dimethyl sulfoxide (DMSO) per kg, while control group eggs (arbor acres [AA] fertilized) were injected with 50 μL DMSO per kg prior to incubation. Liver samples were collected on days 9, 14 and 19 of embryonic development as well as at hatching. Extracted proteins were analyzed by two dimensional gel electrophoresis (2-DE) in combination with western blotting for specific anti-phosphotyrosine. The differential spots were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) or MALDI-TOF-TOF-MS. Peptide mass fingerprinting (PMF) of the differentially-expressed proteins were performed using the MASCOT, Prospector or proFound server. Thirty-seven proteins and twenty-two tyrosine phosphorylation proteins were successfully identified. All 37 proteins and 22 tyrosine phosphorylation proteins exhibited a significant volume difference from the control group. These results demonstrated that DHEA increased the expression and level of tyrosine phosphorylation and sulfotransferase proteins in broilers (at pI 5.9), therefore promoting the biotransformation of DHEA. The expression of apolipoproteinA-I was increased in the DHEA treatment group, which facilitated the conversion of cholesterol to cholesterol esters. Also, DHEA increased the expression of peroxiredoxin-6 and its tyrosine phosphorylation protein levels, thus enhancing its anti-oxidative activity. Furthermore, pyruvate dehydrogenase expression was decreased and the level of its tyrosine phosphorylation proteins increased in the DHEA treatment group. Take together, those data indicate that DHEA reduces the supply of acetyl-CoA by inhibiting the activity of its target enzyme (i.e., pyruvate dehydrogenase), thus affecting both protein synthesis and phosphorylation level and decreasing fat deposition in broiler chickens during embryonic development, which could reflect a physiologically-relevant DHEA fat-reduction mechanism in the broiler chicken.