Decreased microvascular functional vasodilatory reserve and features of the metabolic syndrome

Abstract

We have investigated insulin‐induced changes in microvascular conductance in individuals with features of the metabolic syndrome using laser Doppler fluximetry (LDF) and a novel 785 nm, 20 mW, 4 mm separation probe (Moor Instruments Ltd, UK). 33 volunteers [52±9 y (mean ±SD); 15 men)] were studied. All gave written informed consent. LDF was measured above the anterior tibialis muscle of the non‐dominant lower limb and insulin sensitivity by hyperinsulinaemic euglycaemic clamp. Measurements were made at rest and during reactive hyperaemia (RH) to arterial occlusion, before and during the clamp. Vascular conductance (VC) calculated as LDF/MABP (arbitrary units), at baseline and during RH, decreased with >3 features of the metabolic syndrome (p=0.01) and calculated overall CVD risk (p=0.01). VC at was significantly increased by insulin at baseline (0.8±0.4 vs 1.1±0.6, p=0.001) but reduced during peak RH (before insulin: 413±32 vs high dose insulin: 363±35 %baseline, p=0.01). The impaired RH response (peak VC and rate of recovery from peak) was associated with plasma total cholesterol (r2=0.51, p=0.01) and LDL cholesterol concentrations (r2=0.49, p=0.05). We conclude that individuals with features of the metabolic syndrome show a reduced functional vasodilatory reserve and that this impaired response contributes to a reduced insulin sensitivity and glucose handling by muscle.