Abstract
AIMS/HYPOTHESIS: Neural tube defects (NTDs) are a common malformation associated with diabetic embryopathy. Maternal hyperglycaemia-induced oxidative stress inhibits the expression of Pax3, a gene that is essential for neural tube closure, and increases the incidence of NTDs. Because oxidative stress can stimulate AMP-activated kinase (AMPK) activity, and AMPK can regulate gene transcription, we hypothesised that increased AMPK activity would mediate the adverse effects of maternal hyperglycaemia-induced oxidative stress on Pax3 expression and NTDs. METHODS: Pregnant mice were made transiently hyperglycaemic by glucose injection, or hypoxic by housing in a hypoxic chamber, or were treated with antimycin A to induce oxidative stress, and AMPK activity in the embryos was assayed. The effects of stimulating AMPK activity with 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) on Pax3 expression and NTDs were determined. Vitamin E or glutathione ethyl ester was used to reduce oxidative stress, and compound C was used to inhibit AMPK activation. Murine embryonic stem cells were employed as an in vitro model to study the effects of oxidative stress on AMPK activity and the effects of AMPK stimulation on Pax3 expression. RESULTS: Maternal hyperglycaemia stimulated AMPK activity, and stimulation of AMPK with AICAR inhibited Pax3 expression (in vivo and in vitro) and increased NTDs (in vivo). Stimulation of AMPK by hyperglycaemia, hypoxia or antimycin A was inhibited by antioxidants. The AMPK inhibitor compound C blocked the effects of hyperglycaemia or AA on Pax3 expression and NTDs. CONCLUSIONS/INTERPRETATION: Stimulation of AMPK in embryos during a diabetic pregnancy mediates the effects of hyperglycaemia-induced oxidative stress to disturb the expression of the critical Pax3 gene, thereby causing NTDs.