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World J Diabetes. Apr 15, 2015; 6(3): 481-488
Published online Apr 15, 2015. doi: 10.4239/wjd.v6.i3.481
Birth defects in pregestational diabetes: Defect range, glycemic threshold and pathogenesis
Rinat Gabbay-Benziv, E Albert Reece, Fang Wang, Peixin Yang
Rinat Gabbay-Benziv, E Albert Reece, Fang Wang, Peixin Yang, Department of Obstetrics, Gynaecology and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, United States
E Albert Reece, Peixin Yang, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, United States
Author contributions: Gabbay-Benziv R and Wang F collected the data and wrote the manuscript; Reece EA contributed to the writing of the manuscript; Yang P designed the aim of the editorial and wrote the manuscript; all authors reviewed the manuscript, made their revision and finally approved it for publication.
Conflict-of-interest: None of the authors have a conflict of interest.
Supported by NIH R01DK083243, R01DK101972 and R56 DK095380 (to Yang P), R01DK103024 (to Yang P and Reece EA) and Basic Science Award (1-13-BS-220), American Diabetes Association (to Yang P).
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Peixin Yang, PhD, Department of Obstetrics, Gynaecology and Reproductive Sciences, University of Maryland School of Medicine, BRB11-039, 655 W. Baltimore Street, Baltimore, MD 21201, United States. pyang@fpi.umaryland.edu
Telephone: +1-410-7068402 Fax: +1-410-7065747
Received: August 29, 2014
Peer-review started: August 30, 2014
First decision: November 27, 2014
Revised: December 9, 2014
Accepted: January 9, 2015
Article in press: January 12, 2015
Published online: April 15, 2015
Processing time: 234 Days and 5.4 Hours
Abstract

Currently, 60 million women of reproductive age (18-44 years old) worldwide, and approximately 3 million American women have diabetes mellitus, and it has been estimated that this number will double by 2030. Pregestational diabetes mellitus (PGD) is a significant public health problem that increases the risk for structural birth defects affecting both maternal and neonatal pregnancy outcome. The most common types of human structural birth defects associated with PGD are congenital heart defects and central nervous system defects. However, diabetes can induce birth defects in any other fetal organ. In general, the rate of birth defects increases linearly with the degree of maternal hyperglycemia, which is the major factor that mediates teratogenicity of PGD. Stringent prenatal care and glycemic control are effective means to reduce birth defects in PGD pregnancies, but cannot reduce the incidence of birth defects to the rate of that is seen in the nondiabetic population. Studies in animal models have revealed that PGD induces oxidative stress, which activates cellular stress signalling leading to dysregulation of gene expression and excess apoptosis in the target organs, including the neural tube and embryonic heart. Activation of the apoptosis signal-regulating kinase 1 (ASK1)-forkhead transcription factor 3a (FoxO3a)-caspase 8 pathway causes apoptosis in the developing neural tube leading to neural tube defects (NTDs). ASK1 activates the c-Jun-N-Terminal kinase 1/2 (JNK1/2), which leads to activation of the unfolded protein response and endoplasmic reticulum (ER) stress. Deletion of the ASK1 gene, the JNK1 gene, or the JNK2 gene, or inhibition of ER stress by 4-Phenylbutyric acid abrogates diabetes-induced apoptosis and reduces the formation of NTDs. Antioxidants, such as thioredoxin, which inhibits the ASK1-FoxO3a-caspase 8 pathway or ER stress inhibitors, may prevent PGD-induced birth defects.

Keywords: Pregestational diabetes; Birth defects; Glycemic threshold; Diabetic embryopathy; Range of defects

Core tip: Pregestational diabetes is a rising problem with gravid impact on adverse pregnancy outcomes. This review concentrates on diabetes-induced birth defects and the underlying mechanism of diabetic embryopathy derived from animal studies. The main defects associated with pregestational diabetes are in the cardiovascular and central nervous systems, and are linearly related to maternal glycemic control. Animal studies reveal oxidative stress and stress kinase signalling-induced apoptosis as key factors in pathogenesis. However, many questions remain unanswered, and the rate of congenital defects in human diabetic pregnancies is still high. The cause of diabetic embryopathy warrants further investigations.