Fetal and Maternal Non-glucose Carbohydrates and Polyols Concentrations in Normal Human Pregnancies at Term

Abstract

The objective of the present investigation was to determine fetal and maternal plasma concentrations of nonglucose carbohydrates and polyols in normal human pregnancies at term. Uncomplicated human pregnancies (n ϭ 50) were studied at Ն37 wk gestation. Blood samples were obtained from umbilical artery, umbilical vein, and maternal peripheral blood at the time of elective cesarean section. Plasma concentrations of inositol, glycerol, erythritol, sorbitol, and mannose were determined by HPLC analysis. Differences between umbilical venous, umbilical arterial, and maternal concentration were tested by the two-tailed t test for paired samples. Correlations between umbilical and maternal concentration and between umbilical venoarterial concentration difference and umbilical arterial concentration were assessed by Pearson's correlation and multiple regression analysis. All newborns were appropriate for gestational age, and oxygenation and acid-base balance were within the normal range for all fetuses studied. For most of the polyols (inositol, sorbitol, and erythritol), the fetal concentration was significantly higher than the maternal concentration. The umbilical venoarterial concentration difference for inositol was Ϫ10.5 Ϯ 3.6 M, for glycerol was 10 Ϯ 1.7 M, for sorbitol was 3.8 Ϯ 0.5 M (p Ͻ 0.001), and for mannose was 7.6 Ϯ 0.7 M. There was a significant correlation between maternal concentration and umbilical venous concentration of mannose (UV MAN ϭ 15.38 ϩ 0.69 M MAN ; R 2 ϭ 0.46; p Ͻ 0.001). These results indicate that in normal human pregnancies at term, inositol is produced by the fetus, sorbitol is produced by the placenta, and there is a significant umbilical uptake of mannose from the maternal circulation. The transport of glucose across the human placenta has been well studied in both normal and high-risk pregnancies (1-4). However, the study of the other carbohydrates and sugar alcohols in plasma has received far less attention. In part, this may reflect the untested assumption that other carbohydrates and polyols can be produced from glucose in sufficient amounts to meet fetal requirements. One might assume, then, that there is little need for a supply of these other compounds to the fetus by placental transport. However, studies of the nutritional supply of amino acids in early development have emphasized that many amino acids that are considered "nonessential" may be required in the dietary supply to the fetus or the newborn (5,6). The same may be true of some carbohydrates. Recent studies have suggested that mammalian cells may require an exogenous supply of mannose to meet mannose 6-phosphate requirements for glycoprotein synthesis (7). Furthermore, the biologic importance of the polyols has received attention with respect to their accumulation in reproductive tissues (8 -10) and to their roles in complications of diabetes (11,12). A recent study demonstrated that a low maternal serum inositol concentration is associated with a 2.6-fold increased risk for offspring with spina bifida (13). In additio...

Urinary Excretion of Pentose Phosphate Pathway-Associated Polyols in Early Postnatal Life

“…Similar observations were reported for normal human pregnancies at term [12] . Initially, fetal polyol formation was considered as a possibly phylogenetic old vestigial metabolic pathway [11] .…”

“…In most previous studies, a rather extended spectrum of polyols has been analyzed [1,[10][11][12] . The present study focused on the four primary pentose phosphate pathwayassociated polyols, which are elevated in ribose 5-phosphate isomerase and transaldolase deficiency, in order to provide a basis for a rational interpretation of pentose phosphate pathway-associated polyol profiles in neonates.…”

“…erythritol, treitol, ribitol, arabitol) with age suggesting an age-dependence for polyol formation [1,10] . In addition, a few studies on polyol profiles during fetal development showed that the concentrations of most of the investigated polyols (inositol, D -sorbitol, erythritol, ribitol) were significantly higher in amniotic fluid than in maternal plasma [11,12] . These findings indicate that polyols might play a significant biological role during fetal development.…”

Blood Galactose and Glucose Levels in Mothers, Cord Blood, and 48-Hour-Old Breast-Fed Full-Term Infants

“…A new approach studying carbohydrates other than glucose and sugar alcohols has focused on the fetus and placenta [8,12] . Also, a recent study has shown that mannose, a sugar required for glycoprotein and glycophospholipid synthesis can be synthesized by the human fetus [12] .…”

“…Also, a recent study has shown that mannose, a sugar required for glycoprotein and glycophospholipid synthesis can be synthesized by the human fetus [12] . An important approach requiring investigation is the role of fetal galactose in the synthesis of several complex glycosphingolipids (GSL), mainly the GSL derived from galactosylceramide (GalCer).…”