The effect of acute hyperglycaemia on brachial artery flow mediated dilatation in normal volunteers.

BACKGROUND Endothelial function is known to be abnormal in patients with diabetes and acute hyperglycaemia may play an aetiological role. AIMS The aim of this randomised controlled study was to determine if acute systemic hyperglycaemia impairs endothelial function in normal subjects. METHODS Endothelial function was assessed by the change in brachial artery diameter in response to forearm ischaemia using B-mode ultrasound in ten healthy subjects (eight male) aged 19-35 years. Brachial artery blood flow velocity and diameter were measured before and after five minutes of forearm ischaemia. Measurements were performed in the supine position after an overnight fast, before and after 60 minute infusions of 0.9% saline or 10% dextrose. Measurements were made on two separate occasions at least 24 hours apart, and subjects were randomised to saline first or dextrose first. The largest diameter measured after ischaemia was divided by the resting arterial diameter to calculate percent dilatation of the artery from baseline, and is reported as flow-mediated dilatation (FMD). RESULTS Dextrose infusion resulted in a significant rise in mean (SD) serum glucose 5.2 (0.1) to 9.2 (0.3) mmol/L and insulin concentration 6.3 (1.4) to 20.6 (3.7) mU/L p<0.002. Brachial artery blood flow velocity and diameter increased significantly from baseline after ischaemia (p<0.002). Mean FMD (SEM) before and after infusion were not, however, significantly different (p=0.4) (pre-saline 7.3 [1.0]%, post saline 5.2 [1.5]% and predextrose 8.1 [2.0]%, post dextrose 5.9 [1.7]%). CONCLUSIONS These data suggest that acute hyperglycaemia does not impair FMD in normal subjects.