Alteration in aortic wall stiffness and accumulation of collagen during the prediabetic stage of type II diabetes mellitus in rats

Aortic damage during the prediabetic stage of diabetes mellitus (DM) was in vestigated in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, as an animal model of type II DM. In 30 OLETF and 30 nonDM rats, an oral glucose toleran ce test was performed at 10, 20 and 30 weeks of age. At 15 and 30 weeks, in travascular ultrasound images and aortic pressure were recorded and the sti ffness parameter beta was calculated. The aortic walls were excised at 5, 1 5 and 30 weeks for histopathology and the measurement of hydroxyproline. At 10 weeks, blood glucose (mg/dl) and insulin concentrations (ng/ml) of the OLETF rats (2h; 168+/-30 and 0.82+/-0.15) were significantly high (nonDM: 1 18+/-15; p=0.02 and 0.16+/-0.64; p=0.003). At the prediabetic stage (15 wee ks), beta in the OLETF rats (2.5+/-0.9) was larger than in nonDM rats (1.4/-0.4; p=0.0006), and the collagen (hydroxyproline) content/dry weight (mg/ g) of the aortic wall was significantly higher in OLETF (33.5+/-3.1) than i n nonDM rats (28.7+/-3.5; p<.05). Histopathological examination showed that from 15 weeks of age the medial wall thickness increased gradually. In the prediabetic stage, collagen accumulation may contribute to impairment of a ortic wall stiffness in the OLETF rats, which would accelerate the aging pr ocess in the aortic wall.