title: Nucleoprotein supplementation enhances the recovery of rat soleus mass with reloading after hindlimb unloading-induced atrophy via myonuclei accretion and increased protein synthesis.
abstract: Hindlimb unloading results in muscle atrophy and a period of reloading has been shown to partially recover the lost muscle mass. Two of the mechanisms involved in this recovery of muscle mass are the activation of protein synthesis pathways and an increase in myonuclei number. The additional myonuclei are provided by satellite cells that are activated by the mechanical stress associated with the reloading of the muscles and eventually incorporated into the muscle fibers. Amino acid supplementation with exercise also can increase skeletal muscle mass through enhancement of protein synthesis and nucleotide supplements can promote cell cycle activity. Therefore, we hypothesized that nucleoprotein supplementation, a combination of amino acids and nucleotides, would enhance the recovery of muscle mass to a greater extent than reloading alone after a period of unloading. Adult rats were assigned to 4 groups: control, hindlimb unloaded (HU; 14 days), reloaded (5 days) after hindlimb unloading (HUR), and reloaded after hindlimb unloading with nucleoprotein supplementation (HUR + NP). Compared with the HUR group, the HUR + NP group had larger soleus muscles and fiber cross-sectional areas, higher levels of phosphorylated rpS6, and higher numbers of myonuclei and myogenin-positive cells. These results suggest that nucleoprotein supplementation has a synergistic effect with reloading in recovering skeletal muscle properties after a period of unloading via rpS6 activation and satellite cell differentiation and incorporation into the muscle fibers. Therefore, this supplement may be an effective therapeutic regimen to include in rehabilitative strategies for a variety of muscle wasting conditions such as aging, cancer cachexia, muscular dystrophy, bed rest, and cast immobilization.
authors.affiliation: Rehabilitation Science, Graduate School of Health Sciences, Kobe University, 7-10-2 Tomogaoka, Kobe 654-0142, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Nakanishi
authors.affiliation: Rehabilitation Science, Graduate School of Health Sciences, Kobe University, 7-10-2 Tomogaoka, Kobe 654-0142, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Hirayama
authors.affiliation: Rehabilitation Science, Graduate School of Health Sciences, Kobe University, 7-10-2 Tomogaoka, Kobe 654-0142, Japan; Department of Physical Therapy, Osaka Yukioka College of Health Science, 1-1-41 Soujiji, Ibaraki 567-0801, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Rehabilitation Science, Graduate School of Health Sciences, Kobe University, 7-10-2 Tomogaoka, Kobe 654-0142, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Maeshige
authors.affiliation: Department of Food Science and Nutrition, Nagoya Women's University, 3-40 Shiojicho, Nagoya 467-8611, Japan.
authors.forename: Hiroyo
authors.initials: H
authors.lastname: Kondo
authors.affiliation: Laboratory of Cell Biology and Life Science, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsucho, Kyoto 606-8501, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ishihara
authors.affiliation: Brain Research Institute and Department of Integrative Biology and Physiology, University of California, Los Angeles, CA 90095-7239, USA.
authors.forename: Roland R
authors.initials: RR
authors.lastname: Roy
authors.affiliation: Rehabilitation Science, Graduate School of Health Sciences, Kobe University, 7-10-2 Tomogaoka, Kobe 654-0142, Japan. Electronic address: fujino@phoenix.kobe-u.ac.jp.
authors.forename: Hidemi
authors.initials: H
authors.lastname: Fujino
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002467:Cell Nucleus; D019587:Dietary Supplements; D005260:Female; D006614:Hindlimb; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009133:Muscular Atrophy / Q000188:drug therapy* / Q000534:rehabilitation; D018008:Myogenin / Q000378:metabolism; D009698:Nucleoproteins / Q000494:pharmacology / Q000627:therapeutic use*; D009929:Organ Size / Q000187:drug effects; D010805:Physical Conditioning, Animal; D014176:Protein Biosynthesis / Q000187:drug effects*; D017208:Rats, Wistar; D032496:Satellite Cells, Skeletal Muscle / Q000187:drug effects / Q000502:physiology; D013314:Stress, Mechanical
chemical_list: D009124:Muscle Proteins; D018008:Myogenin; D009698:Nucleoproteins
keywords: Cell differentiation; Hindlimb suspension; Nucleoproteins; Rat; rpS6