SUN-048 Maternal Caloric Restriction during Pregnancy Activates the Nrf2 Antioxidant Program in Embryonic Mouse Liver

Abstract

Obesity and type 2 diabetes in adult life are influenced by the intrauterine environment. The fetus adapts to the environment to which it was exposed, leading potentially to resistance to similar exposures experienced after birth. Studies in both mice and humans suggest that exposure of pregnant females to nutrient deprivation may lead their offspring to develop obesity, insulin resistance and ultimately cardiovascular disease in their adulthood. As the cytoprotective transcription factor Nrf2 (Nfe2l2) is known to be activated upon oxidative and electrophilic stress and has an emerging role in metabolism and specifically in hepatic gluconeogenesis and lipogenesis, we hypothesized that it should be important in the adaptation of the embryos to the metabolic stress induced by maternal caloric restriction. To this end, pregnant C57BL6 mice underwent calorie restriction (CR) by providing them with 50% of the necessary calories per body weight (assessed in pilot experiments) from gestation day 10 to gestation day 16. This CR scheme guarantees the delivery of viable pups that weigh 50% less than the pups whose mothers were fed ad libitum standard chow diet. This CR experiment was performed using either wild-type (WT) or Nrf2 knockout (Nrf2KO) parents. Pregnant females of both genotypes fed ad libitum were used as control. The pregnant females were sacrificed on gestational day 16 and embryos were extracted. Embryonic liver was used for DNA extraction for sex determination by PCR and for RNA preparation to be used for quantitative real-time PCR (qPCR). Statistical significance was set at p<0.05. 10 male embryonic livers were used in qPCR per each condition (CR or control) per each genotype (WT or Nrf2KO). The prototypical Nrf2 antioxidant target gene Nqo1 was increased 2-fold in CR mice. Nrf2-regulated glutathione transferases Gsta1 and Gsta4 were also induced 7.7-fold and 2-fold respectively after CR. Deletion of Nrf2 abrogated completely Nqo1 induction after CR and reduced Gsta1 induction to just 1.4-fold while Gsta1 induction remained unchanged. De novo lipogenesis genes Fasn and Acc2 expression was ~50% and ~90% lower after CR and this change was not significantly affected by Nrf2 deletion. The expression of G6Pase, one of the key gluconeogenic enzymes was also repressed 5-fold in CR mice while expression of Pepck remained unaffected. Lack of Nrf2 impaired the repression of G6Pase to 2-fold. Our study shows for the first time induction of Nrf2 pathway in embryonic liver exposed to CR. Molecular mechanisms and physiological significance of this effect in adult life of the CR WT and Nrf2KO embryos are currently investigated.