Glucose metabolism in the fetal liver during hypoxia

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PROJECT SUMMARY The goal of this proposal is to test the metabolic and molecular effects of hypoxia during late gestation on the early activation of fetal hepatic glucose production rate (GPR). This is important because pregnancies complicated by placental ischemic disease and specifically placental insufficiency induced intrauterine growth restriction (IUGR) expose the fetus to hypoxia. We have shown that the fetal liver during IUGR has increased GPR, which is resistant to suppression by insulin, a hallmark of diabetes pathogenesis. The IUGR fetus also has limited glucose oxidation (GOX) capacity, which may re-direct carbon for GPR. Our published data in the IUGR fetus supports a mechanism whereby FOXO1 increases PCK1 to increase glucose production, and PDK4 to limit glucose oxidation. Importantly, the expression of both PCK1 and PDK4 are inversely related to fetal pO2 indicating that hypoxia is a common regulator of GPR and GOX. Our goal is to understand the hypoxia induced mechanisms for the early activation of fetal GPR. We hypothesize that fetal hypoxia locks FOXO1 into an active nuclear state. This event produces increased PCK1, which increases GPR, and increased PDK4, which decreases GOX to re-direct carbon substrates for GPR and maintain glucose and energy supply for the fetus. I will selectively test the effects of late gestation hypoxia on the fetal liver by precisely reducing fetal arterial pO2 to 11-14 mmHg from 0.8 to 0.9 gestation, which mimics fetal pO2 in age-matched IUGR fetuses. Aim 1 will determine the role of fetal hypoxia in the development of increased GPR and decreased GOX and define novel molecular mechanisms regulating this metabolic adaptation in the fetus. I will measure glucose uptake, utilization, production, and oxidation rates in the alive fetus using metabolic tracer studies. In the fetal liver, I will measure the FOXO1 signaling pathway and expect to identify that hypoxia induces FOXO1 activation to increase PCK1 and PDK4. Coordinated changes in the fetal hepatic metabolome will be determined to support increased carbon substrates for GPR. Aim 2 will determine the fetal hepatocyte substrate preference for GPR and GOX produced by hypoxia. I will measure the oxygen consumption rate of primary fetal hepatocytes to determine if amino acids are preferentially oxidized during hypoxia to compensate for decreased GOX. I will interrogate how hypoxia-induced FOXO1 signaling coordinates GPR and GOX by selectively inducing hypoxia and inhibiting FOXO1. Expected outcomes: Fetal hypoxia will activate GPR and limit GOX through FOXO1 specific mechanisms. Impact: I will define the fetal metabolic and molecular adaptations to hypoxia, which is key to understanding how hypoxia promotes early activation of GPR in the fetal liver, establishing a direct risk for developing type 2 diabetes later in life. The metabolism training plan accompanying these research aims will provide integrative training in metabolic and molecular techniques at the whole-body (fetal), tissue (liver), and cellular (hepatocyte) level to promote my independence as a researcher in fetal metabolism.