Abstract: Yang Shengju*, Meng Guoliang, Gu Lixiong, Wang Jianli. *Department of Dermatology and Venereology, Affiliated Hospital of Nantong University, Nantong 226001, Jiangsu, China Corresponding author: Wang Jianli, Email: pfkwang@163.com 【Abstract】 Objective To investigate the expressions of advanced glycosylation end products （AGE） in skin of mice with diabetes mellitus （DM） for different durations, and to evaluate their influence on collagen fibers. Methods Forty healthy 8-week-old male C57BL/6J mice were divided into DM group （n = 20） and control group （n = 20） to receive multiple intraperitoneal injections of low dose streptozotocin （50 mg/kg） and citric acid buffer （0.1 mol/L）, respectively, for 5 consecutive days. Ten mice were sacrificed in each group on week 4 and 12 respectively after the last intraperitoneal injection, and full-thickness skin tissue samples were harvested from the middorsal region of each mouse. Then, hematoxylin-eosin （HE） staining was performed to observe histological changes, and total collagen content was estimated according to hydroxyproline content measured by an alkaline-hydrolysis method. The cross-linking degree of collagen was determined by Edman degradation method using pepsin, the mRNA expression level of collagen type I and Ⅲ by real-time quantitative PCR, the content of AGE by fluorospectrophotometry and Western blotting, and the level of malondialdehyde （MDA） by using a thiobarbituric acid method. Statistical analysis was carried out by t test. Results As light microscopy showed, the skin became obviously thinner in the diabetic mice with a progressive decrease in the number of collagen fibers in comparison with the control mice. On week 4 and 12 after the last injection, the diabetic mice exhibited a significant reduction in the content of hydroxyproline （（684.5 ± 76.7） vs. （787.7 ± 87.7） mg/g, （558.1 ± 73.1） vs. （757.8 ± 75.3） mg/g, both P < 0.01） and in the levels of cross-linked collagen as well as mRNA expressions of collagen I and III （P < 0.01 or 0.05）, but a significant increase in the content of AGE （（37.47 ± 10.65） vs. （26.39 ± 3.74） AUF/mg hydroxyproline, （47.70 ± 5.66） vs. （29.91 ± 6.50） AUF/mg hydroxyproline, both P < 0.01） and MDA （（6.62 ± 0.47） vs. （4.82 ± 0.56） μmol/L, （8.63 ± 0.36） vs. （5.15 ± 0.46） μmol/L, both P < 0.01） in skin tissue , compared with the control mice. The level of non-cross-linked collagen in skin tissue was also lower in the diabetic mice than in the control mice on week 12 （P < 0.05）. Moreover, the contents of hydroxyproline and the expression levels of collagen I in skin were significantly lower （P < 0.05）, but the levels of AGE and MDA were significantly higher （P < 0.01） in the diabetic mice on week 12 than in those on week 4. Conclusions The characteristics of collagen fibers in skin are altered in diabetic mice when compared with normal control mice, which may be associated with increased AGE content and oxidative injury in skin.

Key words: Skin, Diabetes mellitus, Collagen typeⅠ, Collagen typeⅢ, Glycosylation end products, advanced