Abnormal Pulmonary Oxygen Uptake and Skeletal Muscle Deoxygenation Kinetics are not Obligatory Features of the Type II Diabetic Condition

Abstract

PURPOSE: There are several reports of slower VO2 kinetics in Type 2 diabetic patients compared to healthy age-matched controls. It has been suggested that the principle limitation to VO2 kinetics in this group might be related to O2 delivery, based on the observation of an initial transient increase in the near infrared spectroscopy (NIRS) derived deoxygenated hemoglobin/myoglobin ([HHb]) response above the steady state level in the first 90-120s of exercise. To date, these observations have principally been made in adults below the age of 50-years who have had the disease for less than 5-years. This study was conducted to compare the VO2 and muscle deoxygenation kinetics of older Type II diabetic patients who have had the disease for an extended period vs. age matched healthy control participants. METHODS: Pulmonary VO2 kinetics and muscle [HHb] dynamics were determined in 12 older Type II diabetic (age: 65 ± 5 years; disease duration 9.3 ± 3.8 years) and 12 healthy aged-matched control participants (age: 62 ± 6 years) during transitions from "unloaded" to moderate intensity exercise. RESULTS: The time course of the VO2 kinetics was not different in Type II diabetic patients compared with control participants (phase II t: 43 ± 17 s vs. 41 ± 12 s, P > 0.05). The initial [HHb] response exceeded the steady state level in only 4 out of the 24 participants (2 in each group). There was no difference in the time course of the [HHb] response between the Type II diabetic patients and the control group (primary phase [HHb] t:17 ± 8 vs. 14 ± 3 s, P > 0.05). There was a significant elevation in the Δ[HHb]/ΔVO2 in the Type II diabetic patients compared to the control participants (235 ± 135 vs 135 ± 42 AU·L·min-1, P < 0.05). CONCLUSION: The similar VO2 kinetic responses may be related to the healthy individuals experiencing an aging/detraining-related slowing of their VO2 kinetics, whilst beyond the early predations of Type 2 diabetes, the patients do not. The higher Δ[HHb]/ΔVO2 possibly indicates a compromised blood flow in the Type II diabetic that mandates a greater O2 extraction to meet the metabolic demand during moderate intensity exercise. It is possible that those who have had type II diabetes for an extended period have experienced an adaptation in their O2 extraction capabilities to account for any blood flow perturbations.