The Effect of Hypoxia and Work Intensity on Insulin Resistance in Type 2 Diabetes

Abstract

Context:Hypoxia and muscle contraction stimulate glucose transport in vitro. We have previously demonstrated that exercise and hypoxia have an additive effect on insulin sensitivity in type 2 diabetics.Objectives:Our objective was to examine the effects of three different hypoxic/exercise (Hy Ex) trials on glucose metabolism and insulin resistance in the 48 h after acute hypoxia in type 2 diabetics.Design, Participants, and Interventions:Eight male type 2 diabetics completed 60 min of hypoxic [mean (sem) O2 = ∼14.7 (0.2)%] exercise at 90% of lactate threshold [Hy Ex60; 49 (1) W]. Patients completed an additional two hypoxic trials of equal work, lasting 40 min [Hy Ex40; 70 (1) W] and 20 min [Hy Ex20; 140 (12) W].Main Outcome Measures:Glucose rate of appearance and rate of disappearance were determined using the one-compartment minimal model. Homeostasis models of insulin resistance (HOMAIR), fasting insulin resistance index and β-cell function (HOMAβ-cell) were calculated at 24 and 48 h after trials.Results:Peak glucose rate of appearance was highest during Hy Ex20 [8.89 (0.56) mg/kg · min, P < 0.05]. HOMAIR and fasting insulin resistance index were improved in the 24 and 48 h after Hy Ex60 and Hy Ex40 (P < 0.05). HOMAIR decreased 24 h after Hy Ex20 (P < 0.05) and returned to baseline values at 48 h.Conclusions:Moderate-intensity exercise in hypoxia (Hy Ex60 and Hy Ex40) stimulates acute- and moderate-term improvements in insulin sensitivity that were less apparent in Hy Ex20. Results suggest that exercise duration and not total work completed has a greater influence on acute and moderate-term glucose control in type 2 diabetics.