NO SIGNIFICANT EFFECT OF VITAMIN-E-DEFICIENCY OR SUPPLEMENTATION ON COLLAGEN-LINKED FLUORESCENCE IN SKIN OF DIABETIC RATS

It is speculated that oxidative stress in vivo may have some influence on advanced, nonenzymatic, glycosylation end products. However, this has not been demonstrated yet. We assessed changes in collagen-linked fluorescence in the skin of nondiabetic and streptozotocin-induced diabetic rats fed three different diets for 4 weeks that could modify oxidative stress: vitamin E-deficient (D), vitamin E-supplemented (S), and control (C). The serum lipid peroxide level expressed as thiobarbituric acid (TBA) activity in diabetic rats on the S diet (9.6 ± 1.0 [SE] nmol/L/mL) was significantly (P < .01) lower than that in rats on the D diet (111.4 ± 22.4), and similar to that in nondiabetic rats on the C diet (12.4 ± 2.2). The collagen-linked fluorescence level was significantly (P < .01) higher in diabetic rats than in nondiabetic rats, which corresponded to the serum glucose and glycosylated hemoglobin levels. However, there were no significant differences in the fluorescence levels among three groups classified by three different diets in both nondiabetic and diabetic rats (21.7 ± 1.7 arbitrary U/mg collagen for D, 22.3 ± 2.0 for C, and 22.8 ± 2.5 for S in nondiabetic rats v 41.2 ± 4.1 for D, 40.1 ± 4.7 for C, and 39.3 ± 3.5 for S in diabetic rats), despite significant changes in serum lipid peroxide levels. Consequently, there were no significant changes found in collagen-linked fluorescence levels in diabetic rats wherein oxidative stress was modified by vitamin E deficiency and supplementation. It is suggested that the fluorescence level related to nonenzymatic glycosylation is scarcely affected in vivo by oxidative stress, at least in the case of lipid-mediated peroxidative reactions. © 1992.