Effects of glucose tolerance on the changes provoked by glucose ingestion in microvascular function

Abstract

Aims/hypothesis Hyperglycaemia and hyperinsulinaemia have opposite effects on endothelium-dependent vasodilatation in microcirculation, but the net effect elicited by glucose ingestion and the separate influence of glucose tolerance are unknown. Methods In participants with normal glucose tolerance (NGT), impaired glucose tolerance (IGT) or diabetic glucose tolerance, multiple plasma markers of both oxidative stress and endothelial activation, and forearm vascular responses (plethysmography) to intra-arterial acetylcholine (ACh) and sodium nitroprusside (SNP) infusions were measured before and after glucose ingestion. In another IGT group, we evaluated the time-course of the skin vascular responses (laser Doppler) to ACh and SNP (by iontophoresis) 1, 2 and 3 h into the OGTT; the plasma glucose profile was then reproduced by means of a variable intravenous glucose infusion and the vascular measurements repeated. Results Following oral glucose, plasma antioxidants were reduced by 5% to 10% (p<0.01) in all patient groups. The response to acetylcholine was not affected by glucose ingestion in any group, while the response to SNP was attenuated, particularly in the IGT group. The ACh:SNP ratio was slightly improved therefore in all groups, even in diabetic participants, in whom it was impaired basally. A time-dependent improvement in ACh:SNP ratio was also observed in skin microcirculation following oral glucose; this improvement was blunted when matched hyperglycaemia was coupled with lower hyperinsulinaemia (intravenous glucose). Conclusions/interpretation Regardless of glucose tolerance, oral glucose does not impair endothelium-dependent vasodilatation either in resistance arteries or in the microcirculation, despite causing increased oxidative stress; the endogenous insulin response is probably responsible for countering any inhibitory effect on vascular function.

Repeatability of a dual gradient‐recalled echo MRI method for monitoring post‐isometric contraction blood volume and oxygenation changes

“…The RC indicates the 95% confidence interval for the mean difference between study days (31). Studies evaluating forearm blood flow using cuff occlusion plethysmography in response to infusion of acetylcholine or reactive hyperemia by cuff occlusion have shown that peak blood flow is about 45% lower in diabetic patients when compared to healthy age matched individuals (6,7,21,38-41). If this difference in blood flow between diabetics and healthy individuals is also true for changes in blood volume, we would expect that diabetic individuals would have a change in blood volume following MVC isometric contractions of about 1.27.…”

Acute Hyperglycemia Impairs Vascular Function in Healthy and Cardiometabolic Diseased Subjects

“…Fourteen of these articles reported vascular data for multiple subgroups of a given or diverse health status; thus, they were assessed as individual studies. 22,[25][26][27][28]31,37,38,45,52,[56][57][58][59] The main characteristics and clinical data for these studies are shown in Tables 1 and 2, respectively. Three potentially relevant studies were not available for full text reading and thus could not be included.…”

Effect of mild hyperisulinemia on conduit vessel endothelial function

“…However, in each and all these studies, hyperglycemia is combined to hyperinsulinemia that, according to the two above mentioned studies, should cause per se a much more persistent and more severe depression of endothelial function that was never reported. Although the body of evidence linking chronic hyperglycemia to endothelial dysfunction is large and extended also to resistance arteries and microcirculation [28], interestingly acute hyperglycemia induced by intravenous glucose infusion had no effect both in conductance arteries [29] and in resistance vessels [30], and the effect was evident only when hyperinsulinemia was prevented to confirm that glucose and insulin have opposite effects on the endothelium.…”