Skeletal muscle microvascular exchange capacity is associated with hyperglycaemia in subjects with central obesity

Aims Poor glycaemic control is associated with increased risk of microvascular disease in various organs including the eye and kidney, but the relationship between glycated haemoglobin (HbA_1c) and microvascular function in skeletal muscle has not been described. We tested the association between HbA_1c and a measure of microvascular exchange capacity (K_f) in skeletal muscle in people with central obesity at risk of developing Type 2 diabetes. Methods Microvascular function was measured in 28 women and 19 men mean (± sd ) age 51 ± 9 years] with central obesity who did not have diabetes. We estimated insulin sensitivity by hyperinsulinaemic–euglycaemic clamp, visceral and total fatness by magnetic resonance imaging, fitness (VO₂ max by treadmill testing), physical activity energy expenditure metabolic equivalents of tasks (METS) by use of the SenseWear Pro armband] and skeletal muscle microvascular exchange capacity (K_f) by venous occlusion plethysmography. Results In regression modelling, age, sex and fasting plasma glucose accounted for 30.5% of the variance in HbA_1c (r² = 0.31, P = 0.001). Adding K_f to this model explained an additional 26.5% of the variance in HbA_1c (r² = 0.57, P = 0.0001 and K_f was strongly and independently associated with HbA_1c (standardized B coefficient ?0.45 (95% confidence interval ?0.19, ?0.06), P = 0.001). Conclusions We found a strong negative independent association between a measure of skeletal muscle microvascular exchange capacity (K_f) and HbA_1c. K_f was associated with almost as much of the variance in HbA_1c as fasting plasma glucose.