The mechanisms leading to weight loss in patients with chronic obstructive pulmonary disease (COPD) are poorly understood, but may involve alterations in macronutrient metabolism. Changes in muscle oxidative capacity and lactate production during exercise suggest glucose metabolism may be altered in COPD subjects. The objective of this study was to determine differences in the rates of glucose production and clearance, the rate of glycolysis (pyruvate production), and oxidative and non-oxidative pyruvate disposal in subjects with severe COPD compared to healthy controls. The in vivo rates of glucose production and clearance were measured in fourteen stable outpatients with severe COPD (seven with low and seven with preserved body mass indices) and seven healthy controls using an intravenous infusion of 2H2-glucose. Additionally, pyruvate production and oxidative and non-oxidative pyruvate disposal were measured using intravenous infusions of 13C-bicarbonate and 13C-pyruvate. Endogenous glucose flux and glucose clearance were significantly faster in the combined COPD subjects (p=0.002 and p<0.001 respectively). This difference remained significant when COPD subjects were separated by body mass index. Pyruvate flux and oxidation were significantly higher in the combined COPD subjects than controls (p=0.02 for both), but there was no difference in non-oxidative pyruvate disposal or plasma lactate concentrations between the two groups. In subjects with severe COPD, there are alterations in glucose metabolism, leading to increased glucose production and faster glucose metabolism by glycolysis and oxidation compared to controls. However, no difference in glucose conversion to lactate via pyruvate reduction is observed.
- Copyright © 2011, Journal of Applied Physiology