Background: In healthy subjects insulin induces microcirculatory vasodilation by stimulating endothelial nitric oxide release (Fig. A). Whether insulin would modulate large artery flow mediated dilation (FMD) in the early postprandial phase has not been investigated, yet.

Methods: In six healthy volunteers (age 28±3 yrs, BMI 26±5 kg/m^2), we measured blood glucose and brachial artery FMD during fasting conditions and 30 minutes after consumption of a 75g glucose solution. FMD with reactive hyperemia was obtained by simultaneous Doppler/B-mode echo and beat-to-beat video analysis, providing smoothed velocity and diameter curves (Fig. B).

Results: Blood glucose increased from 4.5±0.2 to 7.5±0.9 mmol/l (p<0.001). With glucose loading, FMD, when defined as the peak increase in diastolic diameter relative to baseline (ΔD_peak/D_baseline), increased from 3.2±2.6 to 7.4±4.9% (p=0.011). FMD, when normalized for the relative mean flow velocity increase (Δv_mean/v_baseline), showed a more pronounced increase from 0.047±0.042 to 0.113±0.047 (p<0.001).

Conclusions: Glucose loading leads to an increased brachial artery FMD response in the early postprandial phase, which is most likely related to the endothelial insulin-NO pathway.