Hyperglycemia, hypoxia and their combination exert oxidative stress and changes in antioxidant gene expression: Studies on cultured rat embryos

Hyperglycemia and hypoxia are well-known teratogens that may affect many animal species, including man. We hypothesize that a combination of hypoxia and hyperglycemia will increase embryonic damage produced by either factor individually. We investigated the interrelationship between hyperglycemia and hypoxia and their effects on genes involved in the balance of embryonic redox status. METHODS: Rat embryos (10.5-day-old) were cultured for 28hr in culture medium with about 6mg/ml of glucose and 20% oxygen (hyperglycemia), with 10% oxygen (hypoxia) and 2.4g/ml glucose (normal) or a combination of both 6mg/ml glucose and 10% oxygen. Antioxidant capacity was determined by activity and gene expression of antioxidant enzymes: Cu/Zn SOD, Mn-SOD, CAT, and GSH-px using real time PCR. RESULTS: Hyperglycemia, hypoxia, or their combination, decreased embryonic growth and induced a high rate (62-78%) of anomalies mainly of the nervous system, heart, and limbs. CAT mRNA and GSH-px mRNA were decreased in the malformed embryos exposed to hyperglycemia, to hypoxia or their combination. CAT mRNA was also decreased in the nonmalformed embryos subjected to hyperglycemia and hypoxia. Cu/Zn SOD mRNA was increased in all experimental embryos whether malformed or not, whereas Mn-SOD was drastically decreased. Total SOD and CAT like activity were changed very little in the experimental embryos compared to controls. CONCLUSIONS: Both hyperglycemia, hypoxia, and their combination reduce embryonic growth and development, induce embryonic anomalies, and modify the expression of the principle antioxidant genes. However, hypoxia does not seem to enhance the damaging effects of hyperglycemia except its effects of embryonic growth.