Maternal diabetes-associated neural tube defects: evidence for β-hydroxybutyrate-related HDAC1/3-H3K27ac-MEST-LRP6...

Maternal diabetes is an important risk factor for embryonic developmental defects, including neural tube defects (NTDs). Elevated β-hydroxybutyrate (BHB), a major ketone body increased under diabetic metabolic conditions, has been implicated in abnormal embryonic development, but its relationship with epigenetic regulation during neurulation remains incompletely defined. In this study, maternal diabetes was induced in pregnant ICR mice by intraperitoneal streptozotocin (STZ; 200 mg/kg) at embryonic day 5.5. In the final in vivo model, 18 control dams produced 216 embryos, whereas 20 diabetic dams produced 250 embryos, including 43 NTD-affected embryos (17.2%). Diabetic pregnancies showed elevated maternal serum BHB, and BHB levels were also increased in brain tissue from diabetic NTD embryos. Ex vivo whole-embryo culture of E8.5 embryos in rat serum supplemented with BHB (2 or 4 mM) showed impaired embryonic growth and NTD-like morphological abnormalities at 4 mM BHB, together with increased embryonic brain BHB content. At the molecular level, diabetic NTD brain tissue and BHB-treated HT-22 neuronal cells showed reduced HDAC1/3 expression and increased H3K27ac. MEST expression was increased whereas mature LRP6 was decreased. HDAC1 or HDAC3 overexpression in BHB-treated HT-22 cells reduced H3K27ac and partially reversed MEST and mature LRP6 changes. These findings support an association between elevated BHB and HDAC1/3-H3K27ac-MEST-LRP6 dysregulation in maternal diabetes-associated NTDs. Because direct chromatin-occupancy and MEST functional manipulation experiments were not performed, the proposed pathway should be interpreted as a potential mechanism requiring further validation.