Effects of dietary curcumin or N-acetylcysteine on NF-κB activity and contractile performance in ambulatory and unloaded murine soleus

We used hindlimb suspension to unload the hindlimb muscles of adult mice. Animals had free access to drinking water or drinking water supplemented with 1% NAC and to standard laboratory diet or diet supplemented with 1% curcumin. For 11 days, half the animals in each dietary group were suspended by the tail (unloaded) and half were allowed to ambulate freely.Unloading caused a 51–53% loss of soleus muscle weight and cross-sectional area relative to freely-ambulating controls. Unloading also decreased total force and force per cross-sectional area developed by soleus. Curcumin supplementation decreased NF-κB activity measured in peripheral tissues of ambulatory mice by gel shift analysis. In unloaded animals, curcumin supplementation did not inhibit NF-κB activity or blunt the loss of muscle mass in soleus. In contrast, NAC prevented the increase in NF-κB activity induced by unloading but did not prevent losses of muscle mass or function.In conclusion, neither dietary curcumin nor dietary NAC prevents unloading-induced skeletal muscle dysfunction and atrophy, although dietary NAC does prevent unloading induced NF-κB activation.Prolonged exposure to microgravity causes muscle atrophy, resulting in weakness and predisposition to fatigue. Such changes can markedly degrade astronauts' performance, especially upon return to Earth [1]. Atrophy starts as early as 4 days into space flight [2] and becomes more significant in long-term space missions [3]. In addition to atrophy, weight-bearing skeletal muscles lose their contractile force per cross-sectional area [4]. Since atrophy in space flight and disuse atrophy share similar pathophysiologic mechanisms [5], countermeasures to microgravity-induced muscle wasting may also be effective for the prevention of disuse atrophy and muscle weakness in long term bedridden patients. Thus, there is considerable interest in the development of countermeasures that oppose the complications of muscle disuse.Hindlimb unloading, a commonly