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Abstract Considerable research efforts have been expended to study the factors that are associated with fat deposition in poultry production. Dehydroepiandrosterone (DHEA, 3b-hydroxy-5-androsterone-17-one) is a steroidal compound that is secreted by the mammalian adrenal cortex gland. It is known to be a fat-reducing agent by activation of the steroid hormone receptors. In the present study, cultured primary chicken hepatocytes exposed to DHEA (0, 0.01, 0.1, 1.0 10 and 100 μmol/L, respectively) dissolved in medium were left for 20 min for cAMP assay by RIA(radioimmunoassay) kit. We found that the levels of cAMP were significantly higher in 0.1~100 μmol/L DHEA groups(P<0.05), especially a maximum accumulation in 0.1 μmol/L DHEA group that compared with the control group(P<0.01). Chicken hepatocytes pre-incubated with 0.25 mmol/L IBMX(3-isobutyl-1-methylxanthine) or vehicle for 5 min, followed by the addition of 0.1 μmol/L DHEA, 20 μmol/L forskolin or vehicle for 20 min at 37℃ were tested for adenylate cyclase (AC) activity. Cell lysates isolated from hepatocytes exposed to 0.1 μmol/L DHEA, 0.25 mmol/L IBMX or vehicle were tested for phosphodiesterase (PDE) and cAMP-dependent kinase A (PKA) activity. Additionally, chicken hepatocytes cultured in media as described above were exposed to 0.1 μmol/L DHEA, 20 μmol/L forskolin or vehicle for 1 h at 37℃. The cells were also exposed to 10 μmol/L H89(PKA- selective inhibitor), 2 μmol/L PKA inhibitor peptide (PKI) or vehicle for 30 min at 37℃. Then, 0.1 μmol/L DHEA was added, the cells were cultured for another 1 h, and scraped for the measurement of CREB phosphorylation levels. The results showed that, no significant differences were found in AC activity in both the DHEA and control groups(P>0.05). As expected, a full stimulation was achieved at 20 μmol/L forskolin(P<0.05), a powerful agonist of AC activity. In contrast, 0.1 μmol/L DHEA markedly suppressed PDE activity at 20 min as compared with the control group(P<0.05). The inhibitor IBMX was also potent in suppressing PDE activity during the incubation period(P<0.05). Cells incubated with 0.1 μmol/L DHEA for 20 min exhibited a significant increase in PKA activity(P<0.05). 0.1 μmol/L DHEA treatment lead to a significant increase in CREB phosphorylation(P<0.05). No significant differences was observed in hepatocytes pretreated with PKA inhibitors(P>0.05). The results suggest that DHEA can activate the cAMP/PKA signaling pathway and regulate lipid metabolism by enhancing CREB phosphorylation level, and provide a better understanding for improvements proposed for DHEA in decrease of body fat in broiler chickens.
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Received: 21 October 2011
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