Quadriceps metabolism during constant workrate cycling exercise in chronic obstructive pulmonary disease.

Abstract

Impaired resting metabolism in peripheral muscles potentially contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). This study investigated the cytosolic energy metabolism of the quadriceps, from glycogen degradation to lactate accumulation, in exercising patients with COPD, in comparison to healthy controls. We measured, in 12 patients with COPD and 10 control subjects, resting and post-cycling exercise quadriceps levels of 1) energy substrates and end products of glycolysis (glycogen, glucose, pyruvate, and lactate) and intermediate markers of glycolysis (glucose-6-phosphate, glucose-1-phosphate, fructose-6-phosphate) and 2) the activity of key enzymes involved in the regulation of glycolysis (phosphofructokinase, lactate dehydrogenase). Exercise intensity (P < 0.01), duration (P = 0.049), and total work (P < 0.01) were reduced in patients with COPD. The variations in energy substrates and end products of glycolysis after cycling exercise were of similar magnitude in patients with COPD and controls. Glucose-6-phosphate (P = 0.036) and fructose-6-phosphate (P = 0.042) were significantly elevated in patients with COPD after exercise. Phosphofructokinase (P < 0.01) and lactate dehydrogenase (P = 0.02) activities were greater in COPD. Muscle glycogen utilization (P = 0.022) and lactate accumulation (P = 0.025) per unit of work were greater in COPD. We conclude that cycling exercise induced changes in quadriceps metabolism in patients with COPD that were of similar magnitude to those of healthy controls. These intramuscular events required a much lower exercise work load and time to occur in COPD. Our data suggest a greater reliance on glycolysis during exercise in COPD, which may contribute to exercise intolerance in COPD.

• Authors: Didier Saey, Bruno B Lemire, Philippe Gagnon, Eric Bombardier, A Russell Tupling, Richard Debigaré, Claude H Côté, François Maltais
• Journal: Journal of applied physiology (Bethesda, Md. : 1985) (J Appl Physiol (1985)) Vol. 110 Issue 1 Pg. 116-24 (Jan 2011) ISSN: 1522-1601 [Electronic] United States
• PMID: 20966193 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Muscle Proteins
• Lactic Acid
• Glycogen

Topics

• Aged
• Exercise Test
• Exercise Tolerance
• Female
• Glycogen (metabolism)
• Humans
• Lactic Acid (metabolism)
• Male
• Muscle Contraction
• Muscle Proteins (metabolism)
• Muscle, Skeletal (metabolism)
• Physical Exertion
• Pulmonary Disease, Chronic Obstructive (physiopathology)
• Thigh