Effect of glucose on the biomechanical function of arterial elastin

Abstract

Elastin is essential to provide elastic support for blood vessels. As a remarkably long-lived protein, elastin can suffer from cumulative effects of exposure to biochemical damages, which can greatly compromise its biomechanical properties. Non-enzymatic glycation is one of the main mechanisms of aging and its effect is magnified in diabetic patients. The purpose of this study is to investigate the effects of glucose on mechanical properties of isolated porcine aortic elastin. Elastin samples were incubated in 2 M glucose solution and were allowed to equilibrate for 4, 7, 14, 21 or 28 days at 37°C. Equibiaxial tensile tests were performed to study the changes of elastic properties of elastin due to glycation. Significant decreases in tissue dimension were observed after 7 days glucose incubation. Elastin samples treated for 14, 21 or 28 days demonstrate a significant increase in hysteresis in the stress-stretch curves, indicating a greater energy loss due to glucose treatment. Both the longitudinal and the circumferential directions show significant increases in tangent modulus with glucose treatment, however only significant increases are observed after 7 days for the circumferential direction. An eight-chain statistical mechanics based microstructural model was used to study the hyperelastic and orthotropic behavior of the glucose-treated elastin and the material parameters were estimated using a nonlinear least squares method. Material parameters in the model were related to elastin density and fiber orientation, and, hence, the possible microstructural changes in glucose-treated elastin. Estimated material parameters show a general increasing trend in elastin density per unit volume with glucose incubation. The simulation results also indicate that more elastic fibers are aligned in the longitudinal and circumferential directions, rather than in the radial direction.

The coupled bio-chemo-electro-mechanical behavior of glucose exposed arterial elastin

“…These observations suggest that glucose also reduces the piezoelectric response of elastin substantially, which could be related to crosslinking that stiffens elastic fibers and reduces their piezoelectricity. Indeed, we also found increase of tangent modulus in glucose treated elastin (Wang et al 2015; Zou and Zhang 2012). The structural and functional alterations of elastin with glucose exposure may have important physiological implications.…”

“…In vitro studies have shown that glucose treatments stiffens arterial elastin (Winlove et al 1996), increases the storage and loss modulus (Lillie and Gosline 1996), and also changes the viscoelastic stress relaxation behavior of elastin (Zou and Zhang 2011). Elastin was found to become markedly stiffer and more viscoelastic with excessive glucose exposure (Wang et al 2015; Zou and Zhang 2012). Mechanical testing results (Figure 4) show that the stiffness of elastin increases gradually with glucose treatment.…”

“…Moreover, the amount of hysteresis also increases with treatment times. Transmission electron microscopy (TEM) studies revealed no obvious structural changes in elastin due to glucose treatment, suggesting molecular level structural modifications due to the interactions between elastin and glucose (Wang et al 2015). …”

Mechanical, structural, and dynamical modifications of cholesterol exposed porcine aortic elastin

“…The experiments showed that under uniaxial strain the surrounding waters of hydration of elastin upon extension undergo more rapid tumbling, pointing to an increase in the entropy of water; this finding indicated that the entropic recoil of hydrated elastin does not arise from a change in water entropy 32 . In a separate study, we investigated the effects of glucose on the elastic recoil of elastin through a combined experimental and computational approach 24,64 . In glucose, elastin is found to exhibit stiffer characteristics as well as viscoelastic behavior.…”

Multi-scale Modeling of the Cardiovascular System: Disease Development, Progression, and Clinical Intervention

“…Cytoskeletal mechanics figure courtesy P. Alford; cytoskeletal model figure courtesy W. Ronan; tissue model figure courtesy G. Holzapfel. For further reference, see 9, 19, 21, 49, 72, 160–162 .…”