Abstract 18130: Acute Changes of Glucose and Insulin Levels During Oral Glucose Tolerance Test are Related to Changes in Arterial Stiffness and Wave Reflection

Abstract

Background: Hyperglycemia is linked with arterial stiffness, a factor with significant prognostic value. We investigated whether the acute changes of glucose and insulin levels during oral glucose tolerance test (OGTT) are related with acute changes in arterial stiffness. Methods: In 60 consecutive subjects without known diabetes a standard 75-gr oral glucose tolerance test (OGTT) was performed and glucose and insulin levels were measured at 0, 30, 60, 90 and 120min after glucose loading. At the same time intervals, we measured the carotid- femoral pulse wave velocity (PWVc) using the Complior and aortic PWV (PWVa) and augmentation index (AI) using an oscillometric method (Arteriograph,TensioMed). We categorized patients in those with normal (n=21) and those with abnormal OGTT. Results: During OGTT, we found that increasing glucose levels were related with increasing PWVc and PWVa (r=0.28, r=0.42, p<0.01) and increasing insulin levels were related with decreasing AI (r=-0.27) in all patients. Patients with abnormal OGTT had higher baseline PWVc (10.4±2 vs. 9.1±1.8 m/sec), PWVa (9.4±1.9 vs. 6.9±1.8 m/sec), AI (24±9 vs. 17±11 %), insulin (14±6 vs. 11±4μU/ml) and glucose(114±26 vs. 93±7 mg/dl) and similar age sex and BMI than those with normal OGTT (p<0.05).Compared to baseline, AI was reduced by 44% at 30 min and 17% at 60 min in patients with normal OGTT (p<0.01) compared to 7.8% and 11 % in abnormal OGTT (p=0.7). In all patients, the % decrease in AI at 30 min was related with the corresponding %increase in insulin (r=-0.46, p<0.05) but not with % change in glucose. The % increase in glucose levels at 60, 90 and 120 min during abnormal OGTT was related to the % increase in PWVa (r=0.46, r=0.34, r=0.55, p<0.05), PWVc (r=0.40, r=0.32, r=0.33, p<0.05) and AI (r=0.36, r=0.34, r=-0.35, p<0.05). Conclusions. Patients with normal OGTT show an acute decrease in AI related with the increase in insulin level likely because of insulin stimulation of endothelial NO synthesis. During abnormal OGTT, this beneficial effect of insulin on AI is blunted likely because of insulin resistance and the acute changes in glucose levels are linked with an increase in arterial stiffness. Thus, insulin resistance determines the acute changes of arterial stiffness after postprandial hypeglycemia.