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. 2013 Jan;33(2):194-212.
doi: 10.1128/MCB.01036-12. Epub 2012 Oct 29.

Genomic and proteomic profiling reveals reduced mitochondrial function and disruption of the neuromuscular junction driving rat sarcopenia

Chikwendu Ibebunjo  1 , Joel M Chick, Tracee Kendall, John K Eash, Christine Li, Yunyu Zhang, Chad Vickers, Zhidan Wu, Brian A Clarke, Jun Shi, Joseph Cruz, Brigitte Fournier, Sophie Brachat, Sabine Gutzwiller, QiCheng Ma, Judit Markovits, Michelle Broome, Michelle Steinkrauss, Elizabeth Skuba, Jean-Rene Galarneau, Steven P Gygi, David J Glass
Affiliations

Genomic and proteomic profiling reveals reduced mitochondrial function and disruption of the neuromuscular junction driving rat sarcopenia

Chikwendu Ibebunjo et al. Mol Cell Biol. 2013 Jan.

Abstract

Molecular mechanisms underlying sarcopenia, the age-related loss of skeletal muscle mass and function, remain unclear. To identify molecular changes that correlated best with sarcopenia and might contribute to its pathogenesis, we determined global gene expression profiles in muscles of rats aged 6, 12, 18, 21, 24, and 27 months. These rats exhibit sarcopenia beginning at 21 months. Correlation of the gene expression versus muscle mass or age changes, and functional annotation analysis identified gene signatures of sarcopenia distinct from gene signatures of aging. Specifically, mitochondrial energy metabolism (e.g., tricarboxylic acid cycle and oxidative phosphorylation) pathway genes were the most downregulated and most significantly correlated with sarcopenia. Also, perturbed were genes/pathways associated with neuromuscular junction patency (providing molecular evidence of sarcopenia-related functional denervation and neuromuscular junction remodeling), protein degradation, and inflammation. Proteomic analysis of samples at 6, 18, and 27 months confirmed the depletion of mitochondrial energy metabolism proteins and neuromuscular junction proteins. Together, these findings suggest that therapeutic approaches that simultaneously stimulate mitochondrogenesis and reduce muscle proteolysis and inflammation have potential for treating sarcopenia.

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Figures

Fig 1
Fig 1
Body, organ, and muscle weights and EDL muscle contractile properties. The percent body weight change over the last 4 weeks before study (A) and the weights of the heart (B), kidneys (C), and tibialis (D), gastrocnemius (E), and quadriceps (F) muscles of rats aged 6, 12, 18, 21, 24, and 27 months. The wet weight of the EDL muscle declined with age (G) in association with approximately twice as much decline in evoked peak tetanic strength (Po) (H); hence, specific strength tended to decline, but not significantly (I). *, **, ***, and **** indicate P < 0.05, 0.01, 0.001, and 0.0001 versus 6 months, respectively. 6M, 6 months; 12M, 12 months, etc.
Fig 2
Fig 2
Plantaris muscle fiber histomorphometry. The age-dependent decline in plantaris muscle mass (A) was associated with a proportional decrease in fiber cross-sectional area (B), a leftward shift of the fiber cross-sectional area histogram (C), and increased deformation of fibers (D and E). Analysis of the individual fiber types indicated no significant differences in the degree (F and G) or patterns (I to K) of atrophy between types 1, 2A, and 2B fiber types. *, **, ***, and **** indicate P < 0.05, 0.01, 0.001, 0.0001 versus 6 months, respectively. 6M, 6 months; 12M, 12 months, etc.
Fig 3
Fig 3
Representative photomicrographs of 6-month and 27-month plantaris muscles stained for picrosirius red (PSR), alkaline phosphatase (AlkPhos), acetylcholinesterase (Ache), and succinate dehydrogenase (SDH). Analysis (right column) revealed that muscles from 24- and 27-month-old rats have more intense picrosirius staining, a tendency for increased capillary density, increased acetylcholinesterase-stained area per fiber cross-sectional area, and an increase in fibers weakly stained for and a corresponding decrease in fibers strongly stained for SDH activity. *, **, ***, and **** indicate P < 0.05, 0.01, 0.001, and 0.0001 versus 6 months, respectively. 6M, 6 months; 12M, 12 months, etc.
Fig 4
Fig 4
Cluster analysis of the 3,890 genes significantly regulated in sarcopenia. The optimal number of clusters, K, was determined to be 6 by the Elbow method after plotting the cluster score against number of clusters (A). (B) K-means clustering of the 3,890 significantly regulated genes into six clusters and expression profiles along the time point in months. (C) The number of genes within each of the six clusters.
Fig 5
Fig 5
Map of enriched gene sets for genes in cluster 2 based on DAVID output. Each node represents a gene set. Clusters of functionally related gene sets were manually framed and summarized into key findings in the text frame with the same color. (A) Functional annotation analysis of the genes in cluster 2 indicates that pathways and processes involved in energy metabolism are depressed in sarcopenia. (B) Quantitative PCR analyses verified downregulation of some genes in cluster 2 and other genes involved in energy metabolism (B) and mitochondrial dynamics (C). *, **, ***, and **** indicate P < 0.05, 0.01, 0.001, and 0.0001 versus 6 months, respectively. 6M, 6 months; 12M, 12 months, etc.
Fig 6
Fig 6
(A) Functional annotation analysis of genes in cluster 3 indicates that pathways and processes involved in regulating the cell cycle, protein metabolism, immune response, and cell death/apoptosis are enriched in sarcopenia. (B) Quantitative PCR analyses verified upregulation of some of the genes in cluster 3 and candidate genes involved in apoptosis. *, **, ***, and **** indicate P < 0.05, 0.01, 0.001, and 0.0001 versus 6 months, respectively. 6M, 6 months; 12M, 12 months, etc.
Fig 7
Fig 7
Gene ontology analysis of differentially regulated proteins in gastrocnemius muscles from 6-, 18-, and 27-month-old rats. (A) Cluster analysis identified four profiles. (B to D) Proteins in clusters 1 and 2, comprising many mitochondrial (B) and muscle structural proteins (C), were mostly repressed, whereas proteins in clusters 3 and 4, comprising ribosomal and translation proteins, were enriched (D) in muscles from 27-month-old rats relative to 6-month-old rats. (E and F) The expression of some of these (E) and other proteins (F) was verified by Western blotting. M, months.
Fig 8
Fig 8
Mitochondrial DNA content and activity. (A to D) Mitochondrial DNA content (A), muscle weight (B), and protein yield in the soluble (S20 [C]) and pellet (P20 [D]) fractions of proportionately pooled gastrocnemius muscle samples from the 6-, 18-, and 24-month-old age groups. (E to H) The activities of citrate synthase, complex I, complex II, and complex IV of the electron transport chain were determined and normalized to the muscle weight. The pooled samples for the 6-, 18-, and 24-month-old groups were analyzed three times, and the mean plus the standard error of the mean plotted. *, **, ***, and **** indicate P < 0.05, 0.01, 0.001, and 0.0001 versus 6 months, respectively. M, months.
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References

    1. Janssen I, Baumgartner RN, Ross R, Rosenberg IH, Roubenoff R. 2004. Skeletal muscle cutpoints associated with elevated physical disability risk in older men and women. Am. J. Epidemiol. 159:413–421 - PubMed
    1. Metter EJ, Talbot LA, Schrager M, Conwit R. 2002. Skeletal muscle strength as a predictor of all-cause mortality in healthy men. J. Gerontol. A Biol. Sci. Med. Sci. 57:B359–B365 - PubMed
    1. Balagopal P, Rooyackers OE, Adey DB, Ades PA, Nair KS. 1997. Effects of aging on in vivo synthesis of skeletal muscle myosin heavy- chain and sarcoplasmic protein in humans. Am. J. Physiol. 273:E790–E800 - PubMed
    1. Gray C, MacGillivray TJ, Eeley C, Stephens NA, Beggs I, Fearon KC, Greig CA. 2011. Magnetic resonance imaging with K-means clustering objectively measures whole muscle volume compartments in sarcopenia/cancer cachexia. Clin. Nutr. 30:106–111 - PubMed
    1. Lexell J. 1995. Human aging, muscle mass, and fiber type composition. J. Gerontol. A Biol. Sci. Med. Sci. 50(Spec No):11–16 - PubMed

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