Muscle atrophy and hypertrophy signaling in patients with chronic obstructive pulmonary disease.
BACKGROUND
The molecular mechanisms of muscle atrophy in chronic obstructive pulmonary disease (COPD) are poorly understood. In wasted animals, muscle mass is regulated by several AKT-related signaling pathways.


OBJECTIVE
To measure the protein expression of AKT, forkhead box class O (FoxO)-1 and -3, atrogin-1, the phosphophrylated form of AKT, p70(S6K) glycogen synthase kinase-3beta (GSK-3beta), eukaryotic translation initiation factor 4E binding protein-1 (4E-BP1), and the mRNA expression of atrogin-1, muscle ring finger (MuRF) protein 1, and FoxO-1 and -3 in the quadriceps of 12 patients with COPD with muscle atrophy and 10 healthy control subjects. Five patients with COPD with preserved muscle mass were subsequently recruited and were compared with six patients with low muscle mass.


METHODS
Protein contents and mRNA expression were measured by Western blot and quantitative polymerase chain reaction, respectively.


RESULTS
The levels of atrogin-1 and MuRF1 mRNA, and of phosphorylated AKT and 4E-BP1 and FoxO-1 proteins, were increased in patients with COPD with muscle atrophy compared with healthy control subjects, whereas atrogin-1, p70(S6K), GSK-3beta, and FoxO-3 protein levels were similar. Patients with COPD with muscle atrophy showed an increased expression of p70(S6K), GSK-3beta, and 4E-BP1 compared with patients with COPD with preserved muscle mass.


CONCLUSIONS
An increase in atrogin-1 and MuRF1 mRNA and FoxO-1 protein content was observed in the quadriceps of patients with COPD. The transcriptional regulation of atrogin-1 and MuRF1 may occur via FoxO-1, but independently of AKT. The overexpression of the muscle hypertrophic signaling pathways found in patients with COPD with muscle atrophy could represent an attempt to restore muscle mass.
Doucet
Mariève
M
Centre de Recherche de l'Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, Laval, Québec, Canada.
Russell
Aaron P
AP
Léger
Bertrand
B
Debigaré
Richard
R
Joanisse
Denis R
DR
Caron
Marc-André
MA
LeBlanc
Pierre
P
Maltais
François
F
D000368:Aged; D000886:Anthropometry; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000209:etiology / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D009133:Muscular Atrophy / Q000503:physiopathology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000378:metabolism*; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D009124:Muscle Proteins; D000070584:Tripartite Motif Proteins; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases; C440908:TRIM63 protein, human; D044767:Ubiquitin-Protein Ligases; D051057:Proto-Oncogene Proteins c-akt