Glutamate–glutamine cycle and exchange in the placenta–fetus unit during late pregnancy

Abstract

The present review focuses on the physiological functions of glutamate-glutamine exchange involving placental amino acid transport and umbilical amino acid uptake in mammals (particularly in sows), with special emphasis on the associated regulating mechanisms. Glutamate plus glutamine are among the most abundant and the most utilized amino acids in fetus during late gestation. During pregnancy, amino acids, notably as precursors of macromolecules including proteins and nucleotides are involved in fetal development and growth. Amino acid concentrations in fetus are generally higher than in the mother. Among amino acids, the transport and metabolism of glutamate and glutamine during fetal development exhibit characteristics that clearly emphasize the importance of the interaction between the placenta and the fetal liver. Glutamate is quite remarkable among amino acids, which originate from the placenta, and is cleared from fetal plasma. In addition, the flux of glutamate through the placenta from the fetal plasma is highly correlated with the umbilical glutamate delivery rate. Glutamine plays a central role in fetal carbon and nitrogen metabolism and exhibits one of the highest fetal/maternal plasma ratio among all amino acids in human and other mammals. Glutamate is taken up by placenta from the fetal circulation and then converted to glutamine before being released back into the fetal circulation. Works are required on the glutamate-glutamine metabolism during late pregnancy in physiological and pathophysiological situations since such works may help to improve fetal growth and development both in humans and other mammals. Indeed, glutamine supplementation appears to ameliorate fetal growth retardation in sows and reduces preweaning mortality of piglets.

Chitosan oligosaccharide affects antioxidant defense capacity and placental amino acids transport of sows

“…Jones et al (2010) found that dexamethasone reduced Ucp2 expression of placenta in the rat during late gestation in labyrinth zone [25], and is consistent with similar effects observed in bovine mammary epithelial cell cultures [26]. Consequently, the lower mRNA level of Ucp2 in the COS group may serve to enhance antioxidant protection in the late gestation placenta, and impact on placental nutrient metabolism, especially at times of increased energy demand [27]. …”

Brucella Genital Tropism: What's on the Menu

“…While it appears that neutral and basic amino acids are transported from the ovine placenta into fetal blood, the acidic amino acids glutamate and aspartate are not. In fact, glutamate is delivered by the fetal lamb to the placenta in large amounts and then converted to glutamine before being released back into the fetal circulation (Battaglia and Meschia, 1978; Wu et al, 2015). Glutamate is also the main free amino acid in the testis and semen of most mammalian species, where it occurs mainly in the seminal plasma (Setchell et al, 1967; Keil et al, 1979).…”

Association of maternal prepregnancy BMI with metabolomic profile across gestation

“…50 Glutamate and aspartate are the only AA 309 which are not actively transported across the placenta 48 and glutamate from the fetal circulation is taken 310 up into the placenta. 51 Thus, higher maternal levels of glutamate are not depleted via fetal transport 311 similar to other AA but likewise, higher maternal glutamate levels may not influence fetal growth. 312…”