Regional and Overall Aortic Function In Nondiabetic Individuals With Insulin Resistance and Normal Glucose Tolerance

Abstract

Context: Insulin resistance is associated with altered vascular function in diabetes. Objective: The objective of the study was to define the overall and regional aortic function as well as the changes of aortic function over time in nondiabetic individuals with insulin resistance and a normal oral glucose tolerance test (OGTT). Design: This was a cross-sectional and longitudinal analysis with 12 months follow-up. Setting: The setting of the study was in primary care. Patients: Nondiabetic individuals (n = 181, mean age 42 ± 8 y) with a normal OGTT and insulin resistance as defined by the insulin sensitivity index (ISI) participated in the study. Interventions: ISI was estimated from serial measurements of plasma insulin and glucose during an iv glucose tolerance test. Ascending and abdominal aortic distensibility (AoD) and stiffness index-β (AoSI) were assessed using echocardiography. Carotid-to-femoral artery pulse wave velocity (PWVc-f; an index of overall aortic function) was measured from carotid and femoral arteries Doppler flow velocities recorded simultaneously with an electrocardiogram. Associations between ISI, AoD, AoSI, and PWVc-f were assessed using linear regression analyses and ANOVA. Differences between baseline and 12 months were compared using a paired t test. Main Outcome Measures: AoD and AoSI associations as well as changes over a 12-month period in relation to ISI were measured. Results: Ascending AoD (P = .01) and ascending AoSI (P = .025) were significantly associated with ISI; in contrast, abdominal AoD and AoSI and PWVc-f did not. Changes in AoD, AoSI, and PWVc-f over time were more prominent in individuals with low ISI compared with those with high ISI. Conclusions: The significant associations between ISI and aortic function suggest that insulin resistance may affect the cardiovascular system, even when OGTT is normal.