Placental Amino Acids Transport in Intrauterine Growth Restriction

Abstract

The placenta represents a key organ for fetal growth as it acts as an interface between mother and fetus, regulating the fetal-maternal exchange of nutrients, gases, and waste products. During pregnancy, amino acids represent one of the major nutrients for fetal life, and both maternal and fetal concentrations are significantly different in pregnancies with intrauterine growth restriction when compared to uncomplicated pregnancies. The transport of amino acids across the placenta is a complex process that includes the influx of neutral, anionic, and cationic amino acids across the microvilluos plasma membrane of the syncytiotrophoblast, the passage through the cytoplasm of the trophoblasts, and the transfer outside the trophoblasts across the basal membrane into the fetal circulation. In this paper, we review the transport mechanisms of amino acids across the placenta in normal pregnancies and in pregnancies complicated by intrauterine growth restriction.

Enteric and serological distribution of serotonin and its precursor tryptophan in perinatal low and normal weight piglets

“…These lower concentrations of 5-HT in SGA piglets might be attributed to a fall in the number of platelets, as already described in low birth weight infants (Christensen et al, 2006). Another study in foetal piglets also described lower foetal tryptophan concentrations in IUGR (Lin et al, 2012) and suggested this might be because of impaired amino acid transport through the placenta (Avagliano et al, 2012). Although the previous proposition correlates with our data describing lower total tryptophan levels in SGA piglets, we cannot rule out that this latter finding is owing to a lower feed intake in these piglets (Devillers et al, 2007).…”

Placental regulation of fetal nutrient supply

“…It is possible that the trophoblast mTOR signaling links maternal nutrient availability to fetal growth by modulating the flux of amino acids across the placenta. [36] and [37].…”

“…Amino acids are transferred across the placenta by active transport using a complex system with more than 10 different families of amino acid carriers: systems A, L, yþ, yþL, T, X -AG and ASC (Table 1) [36,37]. These carriers can be classified in two classes: accumulative amino acid transporters (mainly represented by system A and X -AG ) and amino acid exchangers (LAT1, LAT2, yþLAT1, yþLAT2 and ASC) [37].…”

Low female birth weight and advanced maternal age programme alterations in next-generation blastocyst development

“…Glutamate has been reported to be important for placental and fetal metabolism as it generates NADPH for placental fatty acid steroid synthesis (Moores et al 1994, Vaughn et al 1995. Human intrauterine growth restriction studies are characterised by reduced fetal plasma concentrations of essential amino acids such as valine, leucine, isoleucine and lysine (Cetin et al 1988, Avagliano et al 2012. A reduction in uptake of lysine in the placenta due to reduced system A amino acid transport activity has also been demonstrated in pregnancies complicated by intrauterine growth restriction (Dicke & Henderson 1988, Jansson et al 1998.…”