Introduction: DHEA and its sulfated form (DHEAS) are the most abundant steroid in humans, produced mainly by the adrenal cortex, converted to androgens and estrogens in peripheral tissues by tissue-specific steroidogenic enzymes. There are experimental evidences indicating DHEA anti-obesity, anti-inflammatory, and anti-oxidative effects in cell lines, animal models, and human.
Aim: The aim of this study was analyse the protective effect of DHEA in the skeletal muscle cell line, L6 myotubes, treated with palmitate toward the AKT, mTORC1/p70S6k, and ATF4/GADD34 pathways.
Methods: Differenciated L6 myotubes were incubated with DHEA 10 or 100 nM for 36 h plus 0.5 mM palmitate incubation for the last 12 h. The samples were used for typical immunoblotting with antibodies against the mentioned proteins above, and morphological analysis of cell death. Data are represented as mean±S.E.M. Statistical analyses were performed using one-way ANOVA (P<0.05).
Results: DHEA (10 nM) was able to increase the protein level of AKT (~10%), mTORC1 (~36%), p70S6K (~80%), ATF4 by 30%, and GADD34 by 30% compared to control (P<0.05). Furthermore, 100 nM DHEA induced enhanced of mTORC1 to 160%, ATF4 to 120%, and GADD34 to 130% compared to control (P<0.05). The 12 h incubation with palmitate induced reduction of all analyzed proteins except the p70S6K to ~30% compared to control (P<0.05). Despite no effect of DHEA in the protein expression change due to palmitate, the 10 nM DHEA was able to improve the survival of the cells incubated with palmitate to an extent of 10% apoptosis, similar to controls.
Conclusion: The physiological DHEA concentration was able to increase the expression of proteins involved in the both protein synthesis and UPR pathways. It was also able to have a protective effect upon lipotoxicity.