The green tea polyphenol EGCG alleviates maternal diabetes–induced neural tube defects by inhibiting DNA hypermethylation

Abstract

BACKGROUND Maternal diabetes increases the risk of neural tube defects in offspring. Our previous study demonstrated that the green tea polyphenol, Epigallocatechin gallate, inhibits high glucose-induced neural tube defects in cultured embryos. However, the therapeutic effect of Epigallocatechin gallate on maternal diabetes–induced neural tube defects is still unclear. OBJECTIVE We aimed to examine whether Epigallocatechin gallate treatment can reduce maternal diabetes–induced DNA methylation and neural tube defects. STUDY DESIGN Nondiabetic and diabetic pregnant mice at embryonic day 5.5 were given drinking water with or without 1 or 10 μM Epigallocatechin gallate. At embryonic day 8.75, embryos were dissected from the visceral yolk sac for the measurement of the levels and activity of DNA methyltransferases, the levels of global DNA methylation, and methylation in the CpG islands of neural tube closure essential gene promoters. embryonic day 10.5 embryos were examined for neural tube defect incidence. RESULTS Epigallocatechin gallate treatment did not affect embryonic development because embryos from nondiabetic dams treated with Epigallocatechin gallate did not exhibit any neural tube defects. Treatment with 1 μM Epigallocatechin gallate did not reduce maternal diabetes–induced neural tube defects significantly. Embryos from diabetic dams treated with 10 μM Epigallocatechin gallate had a significantly lower neural tube defect incidence compared with that of embryos without Epigallocatechin gallate treatment. Epigallocatechin gallate reduced neural tube defect rates from 29.5% to 2%, an incidence that is comparable with that of embryos from nondiabetic dams. Ten micromoles of Epigallocatechin gallate treatment blocked maternal diabetes–increased DNA methyltransferases 3a and 3b expression and their activities, leading to the suppression of global DNA hypermethylation. Additionally, 10 μM Epigallocatechin gallate abrogated maternal diabetes–increased DNA methylation in the CpG islands of neural tube closure essential genes, including Grhl3, Pax3, and Tulp3. CONCLUSION Epigallocatechin gallate reduces maternal diabetes–induced neural tube defects formation and blocks the enhanced expression and activity of DNA methyltransferases, leading to the suppression of DNA hypermethylation and the restoration of neural tube closure essential gene expression. These observations suggest that Epigallocatechin gallate supplements could mitigate the teratogenic effects of hyperglycemia on the developing embryo and prevent diabetes–induced neural tube defects.

Superoxide dismutase 2 overexpression alleviates maternal diabetes-induced neural tube defects, restores mitochondrial function and suppresses cellular stress in diabetic embryopathy

“…In our published data [43] and current finding, maternal diabetes increased ROS, apoptosis and defective mitochondria only in the neuroepithelium but not in the adjacent non-neural tissues. Based on published findings [66] that antioxidant supplements ameliorate NTDs in diabetic pregnancy, our current findings support the hypothesis that SOD2 overexpression-blocked mitochondrial dysfunction and ROS production may contribute to the inhibitory effect of SOD2 overexpression on maternal diabetes-induced NTDs.…”

The increased activity of a transcription factor inhibits autophagy in diabetic embryopathy

“…It has been shown that maternal diabetes induces oxidative stress by enhancing the production of endogenous reactive oxygen species and decreasing cellular antioxidant defense enzyme activity. 8,9,17,25–27 Studies using the transgenic mouse model that overexpresses the antioxidant enzyme, superoxide dismutase 1, have demonstrated that eliminating reactive oxygen species caused by maternal diabetes can effectively resolve cellular stress and proapoptotic signaling. 28–30 In complementary with the previous findings that FoxO3a mediates the proapoptotic effect of maternal diabetes, the present study further discovered that the transcription activity of FoxO3a is essential for cell apoptosis because deletion of the FoxO3a transactivation domain abolished maternal diabetes-induced neuroepithelial cell apoptosis and NTD formation.…”

“…Supplements containing natural antioxidants, such as curcumin (found in the spice turmeric) and epigallocatechin-3-gallate (EGCG) (found in green tea), also effectively suppress cellular stress, apoptosis, and NTD formation in diabetic pregnancy. 9,26,31 Specifically, EGCG can block maternal diabetes-induced FoxO3a activation. 31 This experimental evidence supports the hypothesis that FoxO3a is a true downstream effector of oxidative stress in diabetic embryopathy.…”

Pregestational type 2 diabetes mellitus induces cardiac hypertrophy in the murine embryo through cardiac remodeling and fibrosis

“…The animal model described in this study allows deep mechanistic studies; however, it may not faithfully reflect the human conditions. This concern is significantly alleviated because both diabetic animal models and human pregestational diabetes induce a same set of structural birth defects 62, 63, 72, 73, 75–77, 97–99 .…”