Older type 2 diabetic males do not exhibit abnormal pulmonary oxygen uptake and muscle oxygen utilization dynamics during submaximal cycling exercise

Am J Physiol Regul Integr Comp Physiol. 2011 Mar;300(3):R685-92. doi: 10.1152/ajpregu.00479.2010. Epub 2010 Dec 22.

Abstract

There are reports of abnormal pulmonary oxygen uptake (Vo(2)) and deoxygenated hemoglobin ([HHb]) kinetics in individuals with Type 2 diabetes (T2D) below 50 yr of age with disease durations of <5 yr. We examined the Vo(2) and muscle [HHb] kinetics in 12 older T2D patients with extended disease durations (age: 65 ± 5 years; disease duration 9.3 ± 3.8 years) and 12 healthy age-matched control participants (CON; age: 62 ± 6 years). Maximal oxygen uptake (Vo(2max)) was determined via a ramp incremental cycle test and Vo(2) and [HHb] kinetics were determined during subsequent submaximal step exercise. The Vo(2max) was significantly reduced (P < 0.05) in individuals with T2D compared with CON (1.98 ± 0.43 vs. 2.72 ± 0.40 l/min, respectively) but, surprisingly, Vo(2) kinetics was not different in T2D compared with CON (phase II time constant: 43 ± 17 vs. 41 ± 12 s, respectively). The Δ[HHb]/ΔVo(2) was significantly higher in T2D compared with CON (235 ± 99 vs. 135 ± 33 AU·l(-1)·min(-1); P < 0.05). Despite a lower Vo(2max), Vo(2) kinetics is not different in older T2D compared with healthy age-matched control participants. The elevated Δ[HHb]/ΔVo(2) in T2D individuals possibly indicates a compromised muscle blood flow that mandates a greater O(2) extraction during exercise. Longer disease duration may result in adaptations in the O(2) extraction capabilities of individuals with T2D, thereby mitigating the expected age-related slowing of Vo(2) kinetics.

MeSH terms

  • Adaptation, Physiological
  • Age Factors
  • Aged
  • Bicycling*
  • Case-Control Studies
  • Diabetes Mellitus, Type 2 / metabolism*
  • Diabetes Mellitus, Type 2 / physiopathology
  • Exercise*
  • Hemoglobins / metabolism
  • Humans
  • Kinetics
  • Male
  • Middle Aged
  • Muscle Contraction*
  • Muscle, Skeletal / blood supply
  • Muscle, Skeletal / metabolism*
  • Muscle, Skeletal / physiopathology
  • Oxygen Consumption*
  • Pulmonary Gas Exchange*
  • Regional Blood Flow

Substances

  • Hemoglobins
  • deoxyhemoglobin