AGE-related cross-linking of collagen is associated with aortic wall matrix stiffness in the pathogenesis of drug-induced diabetes in rats

Abstract

Diabetes mellitus is major risk factor for cardiovascular disease, and atherosclerosis accounts for most of the morbidity and mortality of diabetic patients. To examine the effects of diabetes on the vessel wall, we examined the association of collagen cross-linking in relation to matrix stiffness of the descending aorta in streptozotocin-induced diabetic rats. The matrix stiffness of the vessel was determined by measuring the tensile properties of the tissue. Seven weeks following the establishment of diabetes, both control and diabetic rats were killed and the descending aortas were excised and analyzed. The findings from biomechanical analysis indicated a significant increase in maximum load (26%), stress (22%), Young's modulus of elasticity (60%), and toughness (32%) in diabetic aortas compared to control. In contrast, the maximum strain of the diabetic rat aorta was significantly reduced by 20% compared to control rats, suggesting stiffening of the blood vessel. The results from biochemical analysis showed that the amount of total collagen increased by 21% in diabetic tissues compared to the control. The sequential extractions of collagen showed that the diabetic specimens yielded 34% more neutral salt-soluble collagen (NSC) than the control. The amount of pepsin-soluble collagen was 31% less in diabetic tissues than in the control group, whereas the amount of insoluble collagen (ISC) increased by 56%. A significant accumulation in advanced glycation end products (AGEs) were seen in pepsin- and collagenase-soluble collagen in diabetic vessel. Furthermore, the altered biomechanical properties of the vessel wall were strongly correlated with the biochemistry of collagen. Overall, these results provide evidence that the diabetic state is associated with the changes in collagen biochemistry and in the biomechanics of the blood vessel.