Hyperglycemia induces regional hemodynamic changes, as suggested by animal studies. These hemodynamic changes may play an initiating role in the pathogenesis of diabetic microangiopathy. The aim of the present study was to evaluate the effects of acute local hyperglycemia for 24 h on basal human forearm muscle and skin blood flow and endothelium-dependent and -independent vasoreactivity. Local hyperglycemia (approximately 15 mM) was induced by infusion of 5% glucose into the brachial artery of the nondominant arm. In control experiments, the same individual amount of glucose was infused intravenously in the dominant arm to correct for possible systemic effects of the infused glucose. Vasoreactivity of the forearm vasculature was evaluated by local infusion of acetylcholine (ACh), sodium nitroprusside (SNP), NG-monomethyl-L-arginine (L-NMMA), and norepinephrine (NE) into the brachial artery. Regional hemodynamic measurements were performed at baseline and after 6, 12, and 24 h of local hyperglycemia. Median (with interquartile range) basal forearm (muscle) blood flow (FBF) was not influenced by the 24-h local hyperglycemia [infused-to-contralateral arm FBF ratio for glucose 1.32 (1.16-1.64) vs. control 1.54 (1.34-1.69)]. Skin microcirculatory blood flow (laser Doppler flowmetry, LDF) was not influenced by the 24-h local hyperglycemia [LDF ratio for glucose 1.00 (0.62-1.56) vs control 0.80 (0.58-1.14)]. In addition, the vasoreactivity of both muscle and skin (not shown) vasculature to ACh [percent change in FBF ratio for glucose 167% (81-263) vs. control 148% (94-211)], SNP [for glucose 486% (178-586) vs. control 293% (196-454)], L-NMMA [for glucose -36% (-56 to -22) vs. control -41% (-51 to -24)], and NE [for glucose -48% (-72 to -41) vs. control -66% (-79 to -33)] was also not affected by the local hyperglycemia. Thus, in contrast to animal studies, our results suggest that a moderate-to-severe hyperglycemia does not affect the regulation of basal blood flow or endothelium-dependent or -independent vasoreactivity in humans.

A possible hypotensive action of regular endurance exercise in normotensive sedentary subjects still remains a matter of debate. This is partly caused by the fact that the anticipated fall in resting blood pressure is rather small and fluctuations in blood pressure during the day can be large. The benefits of ambulatory blood pressure monitoring (ABP) originate to a great deal from the fact that the repeatability on different occasions of the ambulatory blood pressure average is improved by the greater number of readings. In this context we evaluated the effect of moderate exercise training in 19 sedentary male subjects, aged 22 to 44 years, with normal or slightly elevated blood pressure. They entered a randomized cross-over study. Measurements were performed before the study, after 6 weeks of sedentary life style (S) and after 6 weeks of training (T) on a cycle ergometer 3 times a week for 45 min at 75% VO2max. ABP was measured with a Spacelabs 90207 monitor and cardiac output at rest with echo-Doppler. Training increased VO2max from 3.13 +/- 0.09 to 3.40 +/- 0.08 l/min (p < 0.01). Resting heart rate decreased from 60 +/- 2 to 57 +/- 2 bpm (p < 0.05). Resting blood pressure was unchanged after training. Resting stroke volume increased from 82 +/- 3 to 89 +/- 3 ml (p < 0.02). Systemic vascular resistance index was significantly decreased due to conditioning (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal studies suggest that hyperglycaemia directly affects local blood flow and vascular reactivity. We studied the effects of 7 h of local forearm hyperglycaemia, on forearm (muscle) and skin microcirculatory blood flow in 12 healthy men. Furthermore, the effects of this local hyperglycaemia on forearm vasoreactivity to noradrenaline were studied. Using the perfused forearm technique, a local hyperglycaemia of approximately 16 mmol/l was induced by continuous intraarterial infusion of 5% glucose. All subjects received both glucose and placebo (0.9% NaCl) infusions on two different occasions, in random order and blinded for the subjects. Forearm (muscle) blood flow and vascular reactivity to noradrenaline were measured using venous occlusion plethysmography. Skin microcirculatory blood flow was evaluated using intravital capillary microscopy (nutritive blood flow) and laser-Doppler fluxmetry (thermoregulatory blood flow). Measurements were performed at baseline, after 4 h, and after 7 h of intraarterial glucose or placebo infusion. During local glucose infusion there was a slight increase in the levels of insulin, C-peptide, systemic glucose, and blood pressure, compared to the placebo experiments. No differences were observed in forearm blood flow and laser-Doppler flux ratio (infused: contralateral arm), as well as in capillary blood cell velocity between glucose and placebo experiments. Noradrenaline produced similar reductions in forearm blood flow ratio during glucose and placebo experiments. We conclude that in contrast to animal studies, local hyperglycaemia (approximately 16 mmol/l) for 7 h does not affect forearm macro and microcirculatory blood flow or vascular reactivity to noradrenaline in man.

Regional forearm physiological hyperinsulinemia has a vasodilator effect on resistance vessels in skeletal muscle, but is slow in onset (180 min). However, skin vasculature and peripheral veins are not affected by this hyperinsulinemia.

No abstract