Correlative study of advanced glycation end products (AGE) and diabetic skin with microangiopathy

Objective To explore the relationship of advanced glycation end products (AGE) and diabetic skin with microangiopathy and the mechanism of impaired wound healing. Methods 18 male Sprague-Dawley(SD) rats weighing 200～220 g were randomized into the control and STZ-induced diabetic groups. The shaved skin specimens from the back of rats were collected at 12 w after STZ-inducing. Skin AGE concentrations were assessed by detecting the total fluorescence in tissue collagen with F-3010 spectrofluorometer and immunohistochemistry assay. The ultrastructural changes of skin microvessels were observed by electronmicroscopy. Human umbilical vein endothelial cells ECV304 were cultured in vitro with AGE modified human serum albumin (AGE-HSA) at the concentrations of 12.5, 25, 50, and 100 μg/ml for 6, 12, 24, and 48 hours. The cells incubated with HSA of the same concentrations were used as controls. The cell vitality at each time point was analyzed by MTT assay and fluorescence microscopy. Results Skin fluorescence of diabetic rats increased significantly in comparing with age-matched controls thoughout the course of the study (P0.05). Consistent with collagen fluorescence, the positive expression of skin AGE in diabetic animals was much stronger than the weak expression in healthy controls. Furthermore, skin microangiopathy was easily detected in the diabetic group, manifesting as the degenerated vascular endothelial cells and thickening of basement membrane. The absorption of ECV304 cells cultured with AGE-HSA at the concentration of 100 μg/ml for 6 h was significantly lower than that in the control group (P0.01). Meanwhile, flow cytometry and fluorescence microscopy showed higher proportions of apoptotic cells among the ECV304 cells cultured with 100 μg/ml AGE-HSA than those among the control cells at each time point (P0.01). Conclusion AGE is an important cause of diabetic skin microangiopathy. Furthermore, AGE modification-induced pathobiological cascade may be involved in the mechanism of impaired wound healing in diabetes neoangiogenesis impairment or retardation. (Shanghai Med J, 2004,27:532-535)