Enhanced expression of advanced glycosylation end products in skin of diabetic mice and the influence on collagen fibers

[Speaker] Shengju Yang:1
[Co-author] Guoliang Meng:2, Jianli Wang:1
1:Affiliated Hospital of Nantong University, China, 2:Nantong University, China

Background 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 Male C57BL/6J mice were divided into DM group and control group to receive multiple intraperitoneal injections of streptozotocin (50 mg/kg) and citric acid buffer (0.1 mol/L), respectively for 5 days. 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 measurement by an alkalinehydrolysis 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 was assessed by real-time quantitative PCR. The content of AGE was evaluated by fluorospectrophotometry and western blotting. The level of malondialdehvde (MDA) was estimated by using a thiobarbituric acid method.
Results 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 and in the levels of cross-linked collagen as well as mRNA expressions of collagen I and III, but a significant increase in the content of AGE and MDA in skin tissue. 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. Moreover, the contents of hydroxyproline and the expression levels of collagen I in skin were significantly lower, but the levels of AGE and MDA were significantly higher 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, which might be associated with increased AGE content and oxidative injury in skin.

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