Nucleoprotein-enriched diet enhances the protein synthesis pathway and satellite cell activation via ERK1/2 phosphorylation in the unloaded rat muscle.

New findings What is the central question of this study? The purpose of this study was to determine if the nucleotides in a nucleoprotein diet could ameliorate the unloading-associated decrease in soleus muscle mass and fiber size. What is the main finding and its importance? The results indicate that the nucleotides in the nucleoprotein-enriched diet could ameliorate the unloading-associated decrease in type I fiber size and muscle mass most likely due to the activation of protein synthesis pathways and satellite cell proliferation and differentiation via ERK1/2 phosphorylation. Thus nucleotide supplementation appears to be an effective countermeasure for muscle atrophy. Abstract Hindlimb unloading decreases both protein synthesis pathway and satellite cell activation results in muscle atrophy. Nucleotides are included in nucleoprotein and provide the benefits of increasing ERK1/2 phosphorylation. ERK 1/2 phosphorylation is also important in the activation of satellite cells, especially for myoblast proliferation and stimulating protein synthesis pathways. Therefore, we hypothesized that nucleotide in the nucleoproteins would ameliorate muscle atrophy via increasing the protein synthesis pathways and satellite cell activation during hindlimb unloading in rat soleus. Twenty-four female Wistar rats were divided into four groups: control rats fed a basal diet without nucleoprotein (CON), control rats fed a nucleoprotein-enriched diet (CON+NP), hindlimb unloaded rats fed a basal diet (HU), or hindlimb unloaded rats fed a NP diet (HU+NP). HU for two-weeks resulted in decreases in p70S6K- and rpS6-phosphorylation, the numbers of MyoD and myogenin, type I muscle fiber size, and muscle mass. Both CON and HU rats fed the NP diet showed an increase in ERK1/2, p70S6K- and rpS6-phosphorylation, and in the number of MyoD and myogenin compared to their basal diet groups. The NP diet also ameliorated the unloading-associated decrease in type I muscle fiber size and muscle mass. The results indicate that the nucleotides in the nucleoprotein-enriched diet could ameliorate the unloading-associated decrease in type I fiber size and muscle mass most likely due to the activation of protein synthesis pathways and satellite cell proliferation and differentiation via ERK1/2 phosphorylation. Thus nucleotide supplementation appears to be an effective countermeasure for muscle atrophy. This article is protected by copyright. All rights reserved.