Reduced exercise arteriovenous O2 difference in Type 2 diabetes

Abstract

Maximal O2 consumption (V˙o 2 max) is lower in individuals with Type 2 diabetes than in sedentary nondiabetic individuals. This study aimed to determine whether the lowerV˙o 2 max in diabetic patients was due to a reduction in maximal cardiac output (Q˙max) and/or peripheral O2 extraction. After 11 Type 2 diabetic patients and 12 nondiabetic subjects, matched for age and body composition, who had not exercised for 2 yr, performed a bicycle ergometer exercise test to determine V˙o 2 max, submaximal cardiac output, Q˙max, and arterial-mixed venous O2 (a-v̄ O2) difference were assessed. Maximal workload, V˙o 2 max, and maximal a-v̄ O2 difference were lower in Type 2 diabetic patients ( P < 0.05). Q˙max was low in both groups but not significantly different: 11.2 and 10.0 l/min for controls and diabetic patients, respectively ( P > 0.05). Submaximal O2 uptake and heart rate were lower at several workloads in diabetic patients; respiratory exchange ratio was similar between groups at all workloads.V˙o 2 max was linearly correlated with a-v̄ O2 difference, but not Q˙max in diabetic patients. These data suggest that a reduction in maximal a-v̄ O2 difference contributes to a decreasedV˙o 2 max in Type 2 diabetic patients.