Reduced exercise arteriovenous O2 difference in Type 2 diabetes

Maximal O-2 consumption ((V)O-2max) is lower in individuals with Type 2 diabetes than in sedentary nondiabetic individuals. This study aimed to determine whether the lower (V)overO(2) (max) in diabetic patients was due to a reduction in maximal cardiac output ((Q)over dot(max)) and/or peripheral O-2 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)over dotO(2max), submaximal cardiac output, (Q)over dot(max), and arterial-mixed venous O-2 (a-(v) over bar O-2) difference were assessed. Maximal workload, (V)over dotO(2max), and maximal a-(v) over barO(2) difference were lower in Type 2 diabetic patients (P < 0.05). (Q)over dot(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 O-2 uptake and heart rate were lower at several workloads in diabetic patients; respiratory exchange ratio was similar between groups at all workloads. (V)over dotO(2max) was linearly correlated with a-(v) over bar O-2 difference, but not (Q)over dot(max) in diabetic patients. These data suggest that a reduction in maximal a-(v) over bar O-2 difference contributes to a decreased (V)over dotO(2max) in Type 2 diabetic patients.