This application proposes to study human placental metabolism, specifically, energy and carbohydrate metabolism which are fundamental processes necessary to ensure normal fetal well being. Previous reports, as well as our own studies, indicate the placenta favors oxidative phosphorylation under aerobic conditions, but its large glucose consumption and lactate production suggest glycolysis is also an important pathway. However, the amount of lactate and the low total energy produced could not support glycolysis as the major metabolic pathway. The relative importance of each in normal and abnormal placentas is unknown. We would like to test the hypothesis that oxidative phosphorylation and glycolysis are both active metabolic pathways in normal placentas but that diabetic placentas may favor increased glycolysis because of chronic exposure to high levels of glucose and localized hypoxia. Changes in energy metabolism in diabetic placentas may be associated with altered placental functions leading to clinically observed poor fetal outcomes. Placental metabolism studies will be performed using magnetic resonance spectroscopy (MRS) a technique which allows noninvasive, continuous observations of dynamic biochemical processes. Our laboratory has established the use of MRS to study placental villi within a perifusion apparatus. The villi are suspended in medium and viably maintained for several hours by continuous oxygenation, nutrient perifusion, pH and temperature control. Changes in the ATP, inorganic phosphate, and sugar phosphate peaks representing ongoing oxidative phosphorylation and glycolysis have been observed. We have also monitored tissue function by evaluating glucose and oxygen consumption, lactate production. and estradiol, progesterone and chorionic gonadotropin secretion. We will begin by characterizing the roles of oxidative phosphorylation and glycolysis in normal placentas. Metabolic behavior will be monitored under baseline conditions and stressed conditions such as hypoxia, hyper and hypoglycemia, and acidosis. Additional observations will be made of the responses to inhibitors such as cyanide and iodoacetate. We will observe spectroscopic changes in the viable tissue as well as in perchloric acid tissue extracts which yield better resolved spectra at fixed time points. Parallel assessment of placental function will include monitoring chorionic gonadotropin, estradiol and progesterone secretion, glucose and oxygen consumption and lactate production. Once the behavior of normal villi is established under these conditions, diabetic placentas will be studied under the same conditions and comparative analysis will be performed. We hope to acquire a better understanding of normal and diabetic placental energy and carbohydrate metabolism by using the powerful noninvasive method of MRS. Information gained will not only have potential clinical significance but may also represent important complements to future in vivo spectroscopic studies of the placenta.
