Hyperglycemia-induced embryonic dysmorphogenesis correlates with genomic DNA mutation frequency in vitro and in vivo

Congenital malformations affecting multiple organ systems are at least thre e times more common in infants of mothers with IDDM than in infants born to nondiabetic mothers. Numerous studies have confirmed the teratogenic effec t of hyperglycemia on the developing embryo, although no direct mechanism h as been determined. In this study, we aimed to correlate the frequency of l acI mutations with degree of hyperglycemic exposure and severity of malform ations in mouse embryos from in vitro cultures. Day 8 transgenic mouse embr yos cultured in 30 or 50 mmol/l glucose for 48 h exhibited a higher inciden ce of morphological abnormalities, as well as an increase in lacI mutation frequency, compared with embryos cultured in 10 mmol/l glucose with no abno rmalities and a lower frequency of lacI mutations. We also used a transgeni c lacI rat system to evaluate the relationship between abnormal embryonic d evelopment and DNA mutation frequency in day 11 embryos of severely diabeti c rats (serum glucose >20 mmol/l). Compared with control embryos, the embry os from diabetic rats displayed significantly more malformations, shorter c rown-rump lengths, fewer somites, and more than six times greater genomic D NA mutation frequency. Genetic analysis of the mutated lacI gene from both in vitro cultured mouse embryos and in vivo developed rat embryos revealed that the majority of mutations were due to base substitutions (transitions and transversions), but that the rate of large DNA mutations tended to incr ease in embryos exposed to a diabetic environment. Our results support the interrelationship between increased rates of congenital malformations and D NA mutations in the offspring of diabetic pregnancy.