Role of reactive oxygen species (ROS) in the diabetes-induced anomalies inrat embryos in vitro: Reduction in antioxidant enzymes and low-molecular-weight antioxidants (LMWA) may be the causative factor for increased anomalies

A disturbed embryonic antioxidant defense mechanism may play a major role i n diabetes-induced teratogenesis. We therefore studied the antioxidant capa city of 10.5-day-old rat embryos and their yolk sacs after culture for 28 h r in vitro under diabetic conditions (3 mg/ml glucose, 2 mg/ml p-hydroxybut yrate (BHOB) and 10 mu g/ml of acetoacetate), as compared with control embr yos in vitro. We found a high rate of congenital anomalies, decreased growt h and protein content, and a decrease in the activity of both superoxide di smutase (SOD) and catalase (CAT) under diabetic conditions, as compared wit h controls. The reducing power, which reflects the concentration and type o f water-soluble and of lipid-soluble low-molecular-weight antioxidants (LMW A), was measured by cyclic voltammetry. Generally, LMWA were reduced in the embryos and yolk sacs under diabetic conditions. In the water-soluble frac tion of control embryos and yolk sacs, two peak potentials were found, indi cating two major groups of LMWA, while only one peak potential was found un der diabetic conditions, indicating that an entire group of LMWA is missing . HPLC studies have demonstrated a decrease in vitamin C (water-soluble fra ction) and in vitamin E (lipid-soluble fraction) under diabetic culture con ditions, and an increase in uric acid. Generally, the concentration of LMWA was higher in the embryos than in the yolk sac. LMWA concentration, protei n content, and antioxidant enzyme activity were lower in the malformed expe rimental embryos than in experimental embryos without anomalies. The additi on of vitamins C and E to the diabetic culture medium abolished the deleter ious effects of the diabetic serum on the embryos. The disturbed antioxidan t defense mechanism under diabetic conditions may be explained, at least in part, by a direct effect of diabetic metabolic factors on the activity of antioxidant enzymes and on the concentration of reducing equivalents. This, in turn, may be embryotoxic. (C) 1999 Wiley-Liss, Inc.