Abstract
Dehydroepiandrosterone (DHEA) and its sulfonated form dehydroepiandrosterone sulfate
(DHEAS) are the main circulating steroid hormones and many epidemiological studies
show an inverse relationship between DHEA/DHEAS levels and muscle loss for which the
primary cause is the accelerated protein breakdown. The aim of this work was to determine
whether DHEA/DHEAS supplementation in differentiating C2C12 skeletal muscle cells
might influence the expression of the atrophy-related ubiquitin ligase, MuRF-1, and
thereby impact key molecules of the differentiation program. DHEA is the prohormone
crucial for sex steroid synthesis, and DHEAS is thought to be its reservoir. However,
our preliminary experiments showed that DHEAS, but not DHEA, is able to influence
MuRF-1 expression. Therefore, we treated differentiating C2C12 cells with various
concentrations of DHEAS and analyzed the expression of MuRF-1, Hsp70, myosin heavy
chain (MHC), myogenin, and the activity of creatine kinase. We observed that DHEAS
at physiological concentrations downregulates MuRF-1 expression and affects muscle
differentiation, as shown by the increased levels of MHC, which is a sarcomeric protein
that undergoes MuRF-1-dependent degradation, and also by an increase in creatine kinase
activity and myogenin expression, which are two other well-known markers of differentiation.
Moreover, we found that DHEAS might have a protective effect on differentiating cells
as suggested by the augmented levels of Hsp70, a member of heat shock proteins family
that, besides its cytoprotective action, seems to have a regulatory role on key atrophy
genes such as MuRF-1. In conclusion, our data shed light on the role of DHEAS at physiologic
concentrations in maintaining muscle mass.
Key words
DHEAS - C2C12 differentiation - MuRF-1 - myosin heavy chain - heat shock proteins