This is very promising news as there is currently no treatment available for alleviating the long term symptoms of Duchenne muscular dystrophy (DMD).
DMD is a disorder that affects around 1 in 3,600 boys and is very rarely found among girls, it weakens the musculoskeletal system due to a mutation in the dystrophin gene - which is responsible for coding vital muscular proteins. It is characterized by respiratory and cardiovascular problems, fatigue, muscle weakness and progressive difficulty walking.
The researchers observed the effects of giving tamoxifen to a mouse model of DMD for a year. They were surprised at the end results, noting remarkable improvements in muscle force and cardiac structure. In the heart, fibrosis was reduced by nearly 50% and they noticed an increase in the thickness of the muscle fibers in the diaphragm, improving overall respiration.
People suffering from DMD have muscle fibers that are extremely susceptible to stress and experience decreased overall muscle function. Tamoxifen was found to greatly improve this and restore: muscle function, the structure of leg muscles and muscle contraction. The whole body strength of mice treated with tamoxifen doubled and even tripled in some instances.
The authors add:
"Our findings of a slower rate of contraction and an enhanced resistance to fatigue in muscles from tamoxifen-treated dystrophic mice are of significance for the pathophysiology of muscular dystrophy."
Tamoxifen restored muscular abilityThe study involved a wire test to assess the strength of mdx5Cv mice treated with tamoxifen versus mice receiving no treatment at all. They compared their ability to pull themselves up on a wire - an exercise that demands quite a bit of strength and energy - and observed how long they hung onto the wire with their forelimbs before falling.
The authors found that mice on the tamoxifen treatment were able to hold onto the wire for a few seconds longer compared to the mice not undergoing treatment. This reveals that tamoxifen treatment could indeed be very effective at restoring muscle strength among those with DMD.
Tamoxifen works by restoring plasma creatine kinase (CK) activity. Mice without DMD had levels of activity about three times greater than those with the condition - tamoxifen was able to normalize their activity. The authors believe that this effect is achieved because of an estrogen receptor mechanism, especially since the drug is able to significantly raise levels of estrogen receptor β2.
The authors note that tamoxifen has been shown to be effective at treating muscle tissue levels a lot lower than reported in previous studies - which were carried out on normal rodents. In conclusion, this finding suggests that tamoxifen way prove to be a very good treatment option for people suffering from DMD.
Another promising breakthrough regarding effective treatment for DMD was recently explored in a separate study which proposed a novel way of injecting protein into the muscles affected by DMD, successfully restoring strength among those affected.
Written by Joseph Nordqvist