In this study, aortic distensibility was significantly lower in the prediabetes group than in the control group. We also found a significant negative correlation between aortic distensibility and the levels of HbA1C. Impaired glucose tolerance alters the mechanical properties of the interstitial tissue of the vascular wall; moreover, it enhances nonenzymatic glycation of proteins. Nonenzymatic glycation leads to the formation of increased collagen crosslinks that result in increased arterial stiffness [10,11,12].
In the current study, all patients’ ages were between the 3rd and 5th decades to avoid age effects on aortic elastic properties; that is, in individuals ≥ 55 years of age, PP increased more markedly and strain continued to decline, leading to lesser sensitivity of aortic distensibility as a marker of arterial aging beyond this age [13].
The current study showed that BMI and WC were higher in the study group than in the control group. These findings are consistent with the results of Marini et al., who assessed cardiometabolic risk profiles in individuals with prediabetes [12]. In our study, there was no significant difference in systolic blood pressure (SBP) between the study and control groups; on the contrary, diastolic blood pressure (DBP) and pulse pressure were different, which was not consistent with a randomized controlled trial that assessed BP variability in individuals with prediabetes that showed higher SBP and DBP, which may be explained by the nonuse of ambulatory BP monitoring in our study [13].
In the current study, aortic distensibility (AD) values at different locations (aortic root, ascending aorta, and descending aorta) had significant negative correlations with waist circumference, which was consistent with another study that assessed AD in untreated essential hypertension patients, although they had measured aortic PWV with the SphygmoCor VX system for aortic stiffness assessment [14].
Our control group demonstrated AA distensibility of 28.10 ± 8.33 Kpa-1 × 10-3 (P < 0.001) and DA distensibility of 33.08 ± 7.57 Kpa-1 × 10-3 (P < 0.001), which is consistent with the values reported by Redheuil et al. in a cross-sectional randomized controlled trial that assessed distensibility by MRI (21.3 ± 2 Kpa-1 × 10-3, P < 0.0001) [8].
In our study, aortic distensibility at the aortic root and descending aorta was not significantly correlated with the age of the subjects, AR (r = − 0.03, P < 0.83), and DA (r = − 0.08, P < 0.56); however, the distensibility of the ascending aorta had a moderate significant correlation with age, which may be attributed to the higher elastin content of the ascending aorta that may decrease with age [15].
Our results were also consistent with the MESA study that used fasting glucose levels to diagnose glucose intolerance and its effect on proximal thoracic aortic distensibility by MRI, which found that glucose status had no effect on AD in subjects aged > 65 years old, while aortic distensibility values in the age-matched subgroup were similar to our results (2.11 × 10-3 mmHg-1 for IFG, P = 0.01) [15].
The present study showed that patients with metabolic syndrome have lower AD and that waist circumference, BMI, and HbA1C were stronger predictors of worse AD. Metabolic syndrome increases the risk of CV disease in many ways and increases arterial stiffness in all ages [16,17,18]. The sympathetic nervous system, renin-angiotensin system, inflammatory cytokines, and hyperdynamic circulation play an important pathophysiologic role in metabolic syndrome [19].
Aortic elasticity indices have been linked to the occurrence of CV events and target organ damage in prediabetics, diabetics, and hypertensives, which emphasizes the importance of assessing aortic distensibility (as one of aortic elasticity markers) in these patients [20, 21].