Biochemical Correlates of Aortic Distensibility in vivo in Normal Subjects

Abstract

1. Non-invasive aortic compliance measurements have been used previously to assess the distensibility of the aorta in several pathological conditions associated with increased cardiovascular risk. In adult patients with familial hypercholesterolaemia and those with growth hormone deficiency, aortic compliance has been found to correlate inversely with plasma cholesterol levels and age. We set out to establish if a relationship existed between the biophysical measurement of aortic compliance and biochemical variables in normal healthy adult subjects. 2. Blood pressure-corrected aortic distensibility, fasting insulin, insulin-like growth factor-I, total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol and triacylgiycerol were measured in 38 (18 males, 20 females) normotensive healthy adults. 3. Blood pressure-corrected aortic distensibility was found to correlate inversely with age (r = −0.67, P <0.001), low-density lipoprotein-cholesterol (r = −0.37, P <0.02) and the low-density lipoprotein-/high density lipoprotein-cholesterol ratio (r = −0.33, P <0.05) and positively with insulin-like growth factor-I (r = 0.47, P <0.01). On separate analysis by sex, significant inverse correlations were observed in females between aortic distensbility and total cholesterol (r = −0.50, P <0.02), low-density lipoprotein-cholesterol (r = −0.55, P <0.01) and age (r = −0.74, P <0.001). A positive correlation was found between aortic distensibility and insulin-like growth factor-I (r = 0.48, P <0.05). On forced stepwise regression analysis, however, only age (P <0.02) was found to be significant. In males, an inverse correlation was found between aortic distensibility and age (r = −0.57, P <0.01), low-density lipoprotein-cholesterol (r = −0.51, P <0.05) and the low-density lipoprotein-/high-density lipoprotein-cholesterol ratio (r = −0.63, P <0.01). Positive correlations were observed between aortic distensibility and high-density lipoprotein-cholesterol (r = 0.48, P <0.05) and insulinlike growth factor-I (r = 0.48, P <0.05). On forced stepwise regression analysis the low-density lipoprotein-/high-density lipoprotein-cholesterol ratio (P <0.02) and age (P <0.04) were found to be the only significant independent predictors of aortic distensibility in males. 4. In normal adult subjects insulin-like growth factor-I and high-density lipoprotein-cholesterol are associated with increased aortic distensibility, whereas low-density lipoprotein-cholesterol is associated with aortic stiffening. We suggest that the measurement of blood pressure-corrected aortic distensibility in normal, healthy subjects may potentially be a useful, non-invasive research tool for investigating the effect of biochemical factors on the biophysical properties of the aortic wall.