Metabolic activity in skeletal muscles of patients with non-hypoxaemic chronic obstructive pulmonary disease studied by 31P-magnetic resonance spectroscopy.
OBJECTIVE
An alteration of high energy phosphate metabolism in muscles may contribute to exercise intolerance. The objective of this study was to clarify the changes in high energy phosphate metabolites in muscles during exercise in patients with non-hypoxaemic chronic obstructive pulmonary disease (COPD), which influences the impairment of muscle metabolism.


METHODS
Calf muscle energy metabolism was studied in eight stable non-hypoxaemic COPD patients and eight control subjects, using 31P-magnetic resonance spectroscopy (MRS). MRS spectra were acquired at rest, during exercise at two levels of intensity, and during recovery. The control subjects exercised under both normoxic and hypoxic conditions. The intensity of exercise was standardized by the maximal isometric voluntary contraction (MVC) of the calf muscle and the cross-sectional area (CSA) of calf muscle.


RESULTS
MVC and CSA were lower in COPD patients. No significant differences in intracellular pH, inorganic phosphate/phosphocreatine ratio or percentage recovery in inorganic phosphate/phosphocreatine ratio were observed between the two groups in muscles at rest, during exercise or during recovery.


CONCLUSIONS
Muscle metabolites, during exercise standardized by muscle CSA and MVC, did not differ between non-hypoxaemic COPD patients and control subjects. MVC, CSA or both, are assumed to be closely related to muscle metabolism, as no difference in high energy phosphate metabolites was observed for COPD patients compared to control subjects when the load was standardized for MVC and CSA. This suggests that high energy metabolites are consumed to a similar extent in the same muscle volume in non-hypoxaemic COPD patients and control subjects.
Hamaoka
Tomoko
T
Department of Respirology, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Tatsumi
Koichiro
K
Saito
Yoshiichito
Y
Arai
Yasuhiro
Y
Horie
Yoshimasa
Y
Masuyama
Shigeru
S
Tanabe
Nobuhiro
N
Takiguchi
Yuichi
Y
Ikehira
Hiroo
H
Obata
Takayuki
T
Sasaki
Yasuhito
Y
Tanada
Syuzi
S
Kuriyama
Takayuki
T
D000368:Aged; D015444:Exercise / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D007564:Japan; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology; D010710:Phosphates / Q000032:analysis; D010725:Phosphocreatine / Q000032:analysis; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism* / Q000503:physiopathology
D010710:Phosphates; D010725:Phosphocreatine