Increasing numbers of dietary supplements with
ecdysteroids are marketed as "natural
anabolic agents". Results of recent studies suggested that their
anabolic effect is mediated by
estrogen receptor (ER) binding. Within this study the anabolic potency of
ecdysterone was compared to well characterized anabolic substances. Effects on the fiber sizes of the soleus muscle in rats as well the diameter of C2C12 derived myotubes were used as
biological readouts.
Ecdysterone exhibited a strong hypertrophic effect on the fiber size of rat soleus muscle that was found even stronger compared to the test compounds
metandienone (
dianabol), estradienedione (trenbolox), and SARM S 1, all administered in the same dose (5 mg/kg
body weight, for 21 days). In C2C12 myotubes
ecdysterone (1 µM) induced a significant increase of the diameter comparable to
dihydrotestosterone (1 µM) and IGF 1 (1.3 nM). Molecular docking experiments supported the ERĪ² mediated action of
ecdysterone. To clarify its status in sports,
ecdysterone should be considered to be included in the class "S1.2 Other
Anabolic Agents" of the list of prohibited substances of the World Anti-Doping Agency.