Aberrant lipid accumulation in the mouse visceral yolk sac resulting from maternal diabetes and obesity

Vitamin E supplementation prevents obesogenic diet-induced developmental abnormalities in SR-B1 deficient embryos

Introduction

Genetic and environmental factors influence the risk of neural tube defects (NTD), congenital malformations characterized by abnormal brain and spine formation. Mouse embryos deficient in Scavenger Receptor Class B Type 1 (SR-B1), which is involved in the bidirectional transfer of lipids between lipoproteins and cells, exhibit a high prevalence of exencephaly, preventable by maternal vitamin E supplementation. SR-B1 knock-out (KO) embryos are severely deficient in vitamin E and show elevated reactive oxygen species levels during neurulation.

Methods

We fed SR-B1 heterozygous female mice a high-fat/high-sugar (HFHS) diet and evaluated the vitamin E and oxidative status in dams and embryos from heterozygous intercrosses. We also determined the incidence of NTD.

Results and discussion

HFHS-fed SR-B1 HET females exhibited altered glucose metabolism and excess circulating lipids, along with a higher incidence of embryos with developmental delay and NTD. Vitamin E supplementation partially mitigated HFHS-induced maternal metabolic abnormalities and completely prevented embryonic malformations, likely through indirect mechanisms involving the reduction of oxidative stress and improved lipid handling by the parietal yolk sac.

Diabetes Mellitus and Pregnancy: An Insight into the Effects on the Epigenome

Worldwide, diabetes mellitus represents a growing health problem. If it occurs during pregnancy, it can increase the risk of various abnormalities in early and advanced life stages of exposed individuals due to fetal programming occurring in utero. Studies have determined that maternal conditions interfere with the genotypes and phenotypes of offspring. Researchers are now uncovering the mechanisms by which epigenetic alterations caused by diabetes affect the expression of genes and, therefore, the development of various diseases. Among the numerous possible epigenetic changes in this regard, the most studied to date are DNA methylation and hydroxymethylation, as well as histone acetylation and methylation. This review article addresses critical findings in epigenetic studies involving diabetes mellitus, including variations reported in the expression of specific genes and their transgenerational effects.

Differential responses to maternal diabetes in embryo and visceral yolk sac

Introduction: Maternal diabetes during pregnancy is well known to be associated with a higher risk for structural birth defects in the offspring. Recent searches for underlying mechanisms have largely focused on aberrant processes in the embryo itself, although prior research in rodent models implicated dysfunction also of the visceral yolk sac. The objective of our research was to investigate both tissues within the conceptus simultaneously. Methods: We conducted unbiased transcriptome profiling by RNA sequencing on pairs of individual yolk sacs and their cognate embryos, using the non-obese diabetic (NOD) mouse model. The analysis was performed at gestational day 8.5 on morphologically normal specimen to circumvent confounding by defective development. Results: Even with large sample numbers (n = 33 in each group), we observed considerable variability of gene expression, primarily driven by exposure to maternal diabetes, and secondarily by developmental stage of the embryo. Only a moderate number of genes changed expression in the yolk sac, while in the embryo, the exposure distinctly influenced the relationship of gene expression levels to developmental progression, revealing a possible role for altered cell cycle regulation in the response. Also affected in embryos under diabetic conditions were genes involved in cholesterol biosynthesis and NAD metabolism pathways. Discussion: Exposure to maternal diabetes during gastrulation changes transcriptomic profiles in embryos to a substantially greater effect than in the corresponding yolk sacs, indicating that despite yolk sac being of embryonic origin, different mechanisms control transcriptional activity in these tissues. The effects of maternal diabetes on expression of many genes that are correlated with developmental progression (i.e. somite stage) highlight the importance of considering developmental maturity in the interpretation of transcriptomic data. Our analyses identified cholesterol biosynthesis and NAD metabolism as novel pathways not previously implicated in diabetic pregnancies. Both NAD and cholesterol availability affect a wide variety of cellular signaling processes, and can be modulated by diet, implying that prevention of adverse outcomes from diabetic pregnancies may require broad interventions, particularly in the early stages of pregnancy.