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Effects of Aging on Markers of Ribosome Biogenesis in Fast‐ and Slow‐Twitch Skeletal Muscle in Rodents Aged 3 to 24 Months
Author(s) -
Mobley Christopher Brooks,
Mumford Petey W.,
Kephart Wesley C.,
Haun Cody T.,
Holland A. Maleah,
Osburn Shelby C.,
Beck Darren T.,
Martin Jeffrey S.,
Young Kaelin C.,
Kavazis Andreas N.,
Lowery Ryan P.,
Wilson Jacob M.,
Roberts Michael D.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.lb626
Subject(s) - skeletal muscle , plantaris muscle , medicine , endocrinology , soleus muscle , biology , ribosome biogenesis , chemistry , ribosome , rna , biochemistry , gene
OBJECTIVE Ribosome biogenesis is an essential process for regulating skeletal muscle mass by facilitating muscle protein synthesis. Aging results in numerous alterations in skeletal muscle; specifically, a decline in protein synthesis in skeletal muscle. However, less is known about the functional impact of the ribosome in aging skeletal muscle. Therefore, we sought to investigate the effects of sequential aging on various markers of ribosome biogenesis in fast‐ and slow‐twitch skeletal muscle in rodents. METHODS Male Fischer 344 rats (300–600 g) were sequentially aged to 3, 6, 12, 18, & 24 months (mo). Plantaris (Type II, fast‐twitch) and soleus (Type I, slow‐twitch) skeletal muscle were harvested from each respective animal and subjected to RNA isolation and analyses and Western blotting. RESULTS Compared to 3 mo old rats, plantaris ribosome content (total RNA) was 40% lower in 6 mo rats (p<0.05), 59% lower in 12 mo old rats (p<0.05), 69% lower in 18 mo old rats (p<0.05) and 55% lower in 24 mo old rats. There were no age‐related differences in soleus ribosome content. Plantaris c‐myc protein significantly paradoxically increased across age groups; specifically, 12 mo rats were 3.05‐fold greater (p<0.05), 18 mo rats were 5.28‐fold greater (p<0.05) and 24 mo old rats were 5.44‐fold greater (p<0.05) than 3 mo old rats. There were no age‐related differences in soleus c‐myc protein levels. Plantaris upstream binding factor (UBF) protein was 76% greater in 24 mo old rats versus 3 mo old rats (p<0.05). Soleus UBF was only different between the 18 mo old rats and 24 mo old rats (specifically ~3‐fold greater in 18 mo versus 24 mo old rats; p<0.05). Compared to 3 mo old rats, plantaris eukaryotic initiation factor (eIF)2Bɛ protein was 34% lower in 6 mo old rats (p<0.05), 49% lower in 18 mo old rats (p<0.05) and 68% lower in 24 mo old rats (p<0.05). There were no age‐related differences in soleus eIF2Bɛ protein levels. Plantaris eukaryotic elongation factor 2 (eEF2) was not different between age groups. Compared to 3 mo old rats, soleus eEF2 was 32% lower (p<0.05) in 18 mo rats and 66% lower in 24 mo old rats (p<0.05). CONCLUSION Aging clearly decreases ribosome content in fast‐twitch but not slow‐twitch skeletal muscle. Furthermore, there is a compensatory up‐regulation in plantaris c‐myc and UBF protein expression to potentially offset the decline in ribosome content. Identifying other intracellular mechanisms and/or co‐factors that contribute to decrements in ribosome biogenesis in skeletal muscle is warranted. Support or Funding Information This study is supported in part by a contract from the University of Tampa (to M.D.R. from J.M.W) as well as laboratory start‐up funds from M.D.R.