Determinants of residential greenness and its association with prostate cancer risk: A case-control study in Singapore.

BACKGROUND: Exposure to greenness has been shown to be beneficial to health, but few studies have examined the association between residential greenness and prostate cancer (PCa) risk. Our main objectives were to identify the determinants of residential greenness, and to investigate if residential greenness was associated with PCa risk in Singapore. METHODS: The hospital-based case-control study was conducted between April 2007 and May 2009. The Singapore Prostate Cancer Study (SPCS) comprised 240 prostate cancer cases and 268 controls, whose demographics and residential address were collected using questionnaires. Residential greenness was measured by normalized difference vegetation index (NDVI) around the participants' homes using a buffer size of 1 km. Determinants of NDVI were identified using a multivariable linear regression model. Logistic regression models were used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) of associations between NDVI and PCa risk, adjusting for potential confounders. RESULTS: Having a BMI within the second quartile, as compared to the lowest quartile, was associated with higher levels of NDVI (ß-coefficient = 0.263; 95% CI = 0.040-0.485) after adjusting for covariates. Additionally, being widowed or separated, as compared to being married, was associated with lower levels of NDVI (ß-coefficient = -0.393; 95% CI = -0.723, -0.063). An interquartile range (IQR) increase in NDVI was positively associated with prostate cancer risk OR = 1.45; 95% CI = 1.02-2.07). Stratified analysis by tumour grade and stage showed that higher NDVI was associated with higher risk of low grade PCa. CONCLUSION: Our findings suggested that residential greenness was associated with higher risk of PCa in Singapore. Future studies on the quality and type of green spaces, as well as other factors of residential greenness, in association with PCa risk should be conducted to better understand this relationship.

Correlates, motivating factors, and barriers of engaging in regular self-reflection among public health students in higher education-A mixed methods approach.

Despite the wide implementation of self-reflection in higher education, the body of literature has predominantly focused on students from the clinical health sciences rather than public health. The objective of this study was to evaluate the correlates as well as to explore the motivating factors and barriers of engaging in regular self-reflection among public health students in higher education. We used a mixed methods approach (explanatory sequential design), comprising a cross-sectional survey (quantitative phase) followed by in-depth interviews (qualitative phase). We evaluated the association between reflection frequency as well as the perceptions and facilitators in reflection using the modified Breslow-Cox proportional hazards regression model. Prevalence ratio (PR) was generated. Thematic data analysis was carried out to analyse the qualitative data. Quantitative findings revealed being a regular reflector was positively associated with being more motivated to learn when one applied self-reflection (adjusted PR 1.60, 95% CI 1.17-2.20), the perception of being more prepared for a public health career in the future (adjusted PR 1.28, 95% CI 1.02-1.60), as well as being given enough opportunities to carry out self-reflection in the public health modules (adjusted PR 1.24, 95% CI 1.05-1.45). Qualitative findings revealed most students started their self-reflection mainly due to extrinsic factors such as institutional support, social support, teacher influence and environmental influence. Of these, the most prominent was teacher influence, indicating that they are key agents in promoting self-reflection. Students expressed that it would be important to cultivate intrinsic motivation to sustain their practice of self-reflection along the learning journey such as for the development of career-related professional skills. Other than intrinsic motivation, environmental influences were also important to promote continual reflection among students such as the availability of ample opportunities. Prominent barriers to address included external student factors such as the imbalanced power relationship between teacher and student, and internal student factors such as the perception that self-reflection was too cumbersome and time consuming.

An Integrative Approach to Needs Assessment and Curriculum Development of the First Public Health Major in Singapore.

Although public health undergraduate education is increasingly popular in the West, studies describing the needs assessment and curriculum development of public health undergraduate education programs are lacking in the Asia Pacific. The objective of this study was to describe the needs assessment and curriculum development of a second major in public health for undergraduates in the National University of Singapore, the first in Singapore. We used the integrated framework for curriculum development in higher education, which consisted of five stages. In Stage 1, the environment was assessed on the need for a new curriculum. Externally, there was a demand for public health workforce in Singapore based on a review of reports from the Ministry of Health and the job portals. Internally, there was a demand from existing students of the university, along with support from the faculty to offer a new curriculum. There was no university in Singapore offering an undergraduate major program in public health. In Stage 2, competencies to be developed were identified from public health job descriptions using job portals, the needs of public health stakeholders, and competencies listed in the public health curriculum accreditation frameworks such as the Council on Education for Public Health. In Stage 3, based on data triangulation, the curriculum was designed as a second major that is offered to all students of the university from year 2 onward. Students have to complete a total of 12 modules, of which 6 are core and 6 are elective. The capstone module is a 320-h internship module where students will be attached to public health-related agencies, organizations, or non-governmental organizations. Our curriculum is generally aligned with undergraduate public health programs in other established universities in the United States of America, United Kingdom, Australia, and Hong Kong. In Stage 4, various pedagogical strategies were identified for the core modules. We are currently at Stage 5 where implementation, monitoring, and evaluation are still being carried out. We hope that the lessons learnt will serve to inform other universities in the Asia Pacific that are considering implementing such programs and broadening their offerings in public health education.

Human breast milk sugars and polyols over the first 10 puerperium days.

OBJECTIVE: The transition from colostrum to mature breast milk during early puerperium is associated with significant concentration changes of numerous compounds. However, it is not known whether the free sugars, aminohexoses, and polyols are affected. Therefore, in this study, we aimed to determine their concentrations in human colostrum and milk during the first 10 days postpartum. METHODS: This prospective longitudinal study in a sample of normal consecutive obstetric patients was conducted as a collaboration between two academic centers-Polish and American. Participants were 13 women after uncomplicated pregnancy and delivery at term of a singleton, appropriate-for-gestational-age fetus. Lactose, galactose, glucose, mannose, galactosamine, glucosamine, glycerol, and myo-inositol concentrations were measured using high performance liquid chromatography. RESULTS: During the first 3 days postpartum, the concentrations of lactose and glucose increased significantly (P < 0.001), to steady-state values thereafter. In contrast, the concentrations of myo-inositol and glycerol decreased significantly (P < 0.001) over the first 4 days, to reach relatively low stable values. ANOVA analysis indicated that the postpartum day at which early changes ceased to be significantly different from their plateau values was Day 4. myo-Inositol concentrations were significantly higher (P = 0.022) in multiparas than in primiparas. CONCLUSIONS: The colostrum-to-milk transition is associated with significant changes in concentrations of free sugars and polyols, changes which are completed by the fourth postpartum day. Parity influences the concentrations of some compounds in the breast milk.

Placental TonEBP/NFAT5 osmolyte regulation in an ovine model of intrauterine growth restriction.

TonEBP/NFAT5 (the tonicity-responsive enhancer binding protein/nuclear factor of activated T cells) modulates cellular response to osmotic changes by accumulating inositol and sorbitol inside the cells. Our objective was to assess placental osmolytes, TonEBP/NFAT5 RNA and protein expression, and signaling molecules across gestation between control and intrauterine growth restriction (IUGR) ovine pregnancies. Pregnant sheep were placed in hyperthermic conditions to induce IUGR. Placental tissues were collected at 55, 95, and 130 days gestational age (dGA) to measure inositol, sorbitol, TonEBP/NFAT5 (NFAT5), sodium-dependent myo-inositol transporter (SMIT; official symbol SLC5A3), aldose reductase (AR), and NADPH (official symbol DE-CR1). Placental weight was reduced in IUGR compared to controls at 95 and 130 dGA. Osmolyte concentrations were similar between control and IUGR placentas, but both groups demonstrated a significant decrease in inositol concentration and an increase in sorbitol concentration with advancing gestation. Cytosolic NFAT5 protein decreased significantly from 55 to 95 dGA in both groups, and nuclear NFAT5 protein increased only at 130 dGA in the IUGR group, but no differences were seen between groups for either cytosolic or nuclear NFAT5 protein concentrations. DE-CR1 concentrations were similar between groups and increased significantly with advancing gestational age. AR was lowest at 55dGA, and SLC5A3 increased with advancing gestational age. We conclude that both placental osmolytes inositol and sorbitol (and their corresponding proteins SLC5A3 and AR) change with gestational age and are regulated, at least in part, by NFAT5 and DE-CR1 (NADPH). The inverse relationship between each osmolyte across gestation (e.g., inositol higher in early gestation and sorbitol higher in late gestation) may reflect nutritional needs that change across gestation.

The tissue and plasma concentration of polyols and sugars in sheep intrauterine growth retardation.

In an ovine model of placental insufficiency-induced intrauterine growth retardation (PI-IUGR), characterized by hypoxia, hypoglycemia and a significant reduction in fetal weight, we assessed alterations in fetal and placental polyols. Arterial maternal-fetal concentration differences of glucose and mannose were greater in the PI-IUGR fetus; glucose: C (n = 7), 2.68 +/- 0.14 mmol/L versus PI-IUGR (n = 9), 3.18 +/- 0.16 mmol/L (P < 0.02) and mannose: C, 42.9 +/- 8.1 micromol/L versus PI-IUGR, 68.5 +/- 19.1 micromol/L (P < 0.001). For PI-IUGR fetuses, fetal arterial plasma myo-inositol concentrations were significantly increased (P < 0.001). The concentrations of sorbitol, glucose and fructose were significantly reduced (P < 0.03, 0.01, 0.02, respectively). The cotyledons of IUGR placentas had a significantly increased concentration of myo-inositol (P < 0.003) and decreased concentrations of sorbitol, fructose and glycerol (P < 0.01, 0.02, 0.01, respectively). Fetal hepatic concentrations of sorbitol (P < 0.001) and fructose (P < 0.03) were also significantly reduced. These profound changes in both placental and fetal concentrations of polyols and sugars in sheep PI-IUGR pregnancies support the conclusion that within the PI-IUGR placenta there is an increased flux through the glucose 6-P:inositol 1-P cyclase system and decreased flux through the polyol dehydrogenase system, leading to increased placental myo-inositol production and decreased sorbitol production. The decreased placental supply of sorbitol to the fetal liver may lead to decreased fetal hepatic fructose production. These observations highlight that, in association with hypoxic and hypoglycemic PI-IUGR fetuses, there are major placental and fetal alterations in polyol production. The manner in which these alterations in fetoplacental carbohydrate metabolism contribute to the pathophysiology of PI-IUGR is currently unknown.

Effect of antenatal betamethasone on maternal and fetal amino acid concentration.

OBJECTIVE: To determine the concentration of amino acids in women receiving the first course of antenatal betamethasone and to evaluate the umbilical venous and arterial amino acid concentrations at the time of elective cesarean section after betamethasone administration. STUDY DESIGN: Blood samples were collected from 34 pregnant women at risk of premature delivery before and 24 and 48 hours after the first course of betamethasone. In addition, maternal and cord blood samples were collected in 13 women undergoing an elective cesarean section between 24 and 192 hours after betamethasone. RESULTS: Maternal amino acid concentrations were significantly increased after the first dose of betamethasone. Overall total amino nitrogen increased 17.5% 24 hours after betamethasone administration and 20.5% after 48 hours. The concentration of most amino acids was increased both in the umbilical vein and artery after maternal betamethasone administration. CONCLUSION: The concentration of maternal and fetal amino acids increases significantly after betamethasone administration.

Determination of the NFAT5/TonEBP transcription factor in the human and ovine placenta.

Osmotic stress results in the accumulation of osmolytes in tissues. Synthesis of these osmolytes is mediated by the transcription factor NFAT5/TonEBP in the human kidney. We tested for the presence of NFAT5 mRNA and protein in the human and ovine placenta and confirmed sorbitol and inositol osmolyte concentrations in these tissues. To determine NFAT5 protein, human and ovine placenta were tested for inositol, sorbitol and glucose using high performance liquid chromatography (HPLC). Additionally, RNA was extracted and cDNA was made from these tissues. PCR was performed and products were sequenced. Western blotting was used to assess the expression of the NFAT5 protein. Human and ovine placenta demonstrated: 1) high concentrations of sorbitol and inositol, 2) presence of NFAT5 mRNA, 3) confirmation by NFAT5 sequence identity, and 4) presence of NFAT5 protein. NFAT5 is present in the ovine and human placenta at the RNA and protein levels that suggest a role for this protein in the induction of these osmolytes. Further trophoblast studies of osmotic stress effects on osmolytes are planned.

Plasma concentrations of carbohydrates and sugar alcohols in term newborns after milk feeding.

Nonglucose carbohydrates such as galactose, mannose, and inositol play a clinically important role in fetal and neonatal nutrition, though little is known about their metabolism in the neonate. The aim of this study was to determine whether postprandial changes in plasma carbohydrate and sugar alcohol concentrations are affected by clinical variables such as postnatal age (PNA), milk type, feeding volume, or feeding duration in term newborns. Neonates (n = 26) taking intermittent enteral feedings were enrolled. Blood samples were obtained at baseline (immediately before the start of a feeding) and at 2-3 subsequent time points up to 110 min. Postprandial rise was only observed for plasma glucose concentrations [Glu] and plasma galactose concentrations [Gal] and clinical variables did not predict this change. Despite equimolar delivery in milk, the median of [Glu] rise minus [Gal] rise from baseline to second postprandial plasma sample was 674 microM (-38, 3333 microM; p < 0.0001), reflecting efficient hepatic first-pass metabolism of galactose. A significant PNA effect on [Gal] was observed such that for each day PNA there was an 18% decrease in [Gal] (p = 0.03). [Gal] are a function of PNA, suggesting maintenance of a significant ductus venosus shunt in term infants.

Concentrations of monosaccharides and their amino and alcohol derivatives in human preovulatory follicular fluid.

The study purpose was to compare sugar and polyol concentrations in preovulatory ovarian follicular fluid (FF) with those in the circulation. Samples of FF and peripheral venous blood were obtained after an overnight fast from 14 women attending an IVF program. High performance liquid chromatography measurements of seven polyols, two aminohexoses and four hexoses were the main outcome measures. Glucose concentrations in FF and plasma were 2781.26 +/- 205.64 and 4431.25 +/- 65.17 microM, respectively (P < 0.001). Mannose concentration in FF was 38.99 +/- 3.33 microM, significantly lower than plasma concentration (55.38 +/- 2.29 microM; P < 0.001). A concentration gradient from plasma to FF was also significant for glycerol (99.41 +/- 8.47 versus 74.32 +/- 6.54 microM; P < 0.002), galactose (31.69 +/- 1.58 versus 26.73 +/- 1.93 microM; P < 0.01) and galactosamine (11.49 +/- 0.69 versus 6.38 +/- 0.59 microM; P < 0.001). The plasma-to-FF concentration difference was greatest for glucose (1649.99 +/- 204.09 microM). There was a significant correlation between plasma and FF concentrations for galactose and glycerol. This study supports a substantial utilization of glucose by the oocyte/granulosa cells complex, and documents a significant concentration gradient from plasma to FF for glycerol, mannose, galactose and galactosamine. These plasma-FF differences may reflect both utilization of these carbohydrates by the cells of the preovulatory ovarian follicle and/or transport characteristics of these cells.

Amino acid, ammonia and urea concentrations in human pre-ovulatory ovarian follicular fluid.

BACKGROUND: This study aimed to determine amino acid (AA), ammonia and urea concentrations in human ovarian follicular fluid and to compare these concentrations with those in the circulation. METHODS: Samples of pre-ovulatory follicular fluid and peripheral venous blood were obtained from 14 IVF patients. High-performance liquid chromatography (HPLC) measurements of 25 AAs were the main outcome measures. RESULTS: There was a significant gradient of most AAs from plasma to follicular fluid, with the exception of glutamate, which demonstrated a three-fold increase in follicular fluid concentration (70.0 +/- 3.80 microM) compared with plasma (23.18 +/- 2.20 microM; P < 0.001). The plasma-to-follicular fluid concentration difference for glutamine (81.83 +/- 9.2 microM) was greatest among all AAs. Among essential AAs, this difference was greatest for the branched-chain AAs, isoleucine, leucine and valine. Ammonia concentrations in follicular fluid and blood were 38.87 +/- 2.23 and 22.11 +/- 1.96 microM, respectively (P < 0.001). Urea concentration in follicular fluid was 3.37 +/- 0.18 mM, a value not significantly different from plasma concentration (3.36 +/- 0.22 mM; P = 0.911). CONCLUSIONS: These plasma-follicular fluid differences may reflect both the utilization of AAs and the transport characteristics of the follicular cells. There is accumulation of glutamate and ammonia in pre-ovulatory follicular fluid. The data for urea are consistent with transport by passive diffusion, with no evidence of an active urea cycle in the cells of the follicle.

Free sugar and sugar alcohol concentrations in human breast milk.

OBJECTIVES: The goal was to determine the free sugars and polyols in human breast milk, both term and preterm, for comparison with formula milks. METHODS: Methodology was developed for the measurement of the free sugars and polyols in breast milk. There were 16 samples collected from women who delivered at term and 17 samples from women delivering preterm. For purposes of comparison, samples were also collected from four commercial formulas for term infants and eight from commercial formulas for preterm infants as well as one sample of cows' milk. All samples were frozen immediately and analyzed by high-performance liquid chromatography techniques. RESULTS: Except for lactose concentrations, no significant differences were detected for all other sugars and polyols between term and preterm breast milk samples. Within breast milk samples, two patterns emerged, with one group containing additional elution peaks for compounds not yet identified. A second group did not contain these compounds. There were a number of significant differences between breast milk and formulas, particularly for inositol, glycerol, glucose, and galactose. All milks contained significant concentrations of mannose. CONCLUSIONS: There are no significant differences among breast milk samples for free sugar and polyol concentrations except lactose. However, some milk contains additional peaks that could be of dietary or genetic origin. Formula milk has relatively high concentrations of glucose and galactose compared with breast milk, suggesting some lactose hydrolysis.

Fetal and maternal non-glucose carbohydrates and polyols concentrations in normal human pregnancies at term.

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 = 50) were studied at > or =37 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 -10.5 +/- 3.6 microM, for glycerol was 10 +/- 1.7 microM, for sorbitol was 3.8 +/- 0.5 microM (p < 0.001), and for mannose was 7.6 +/- 0.7 microM. There was a significant correlation between maternal concentration and umbilical venous concentration of mannose (UV(MAN) = 15.38 + 0.69 M(MAN); R(2) = 0.46; p < 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.

Maternal and fetal amino acid concentrations in normal pregnancies and in pregnancies with gestational diabetes mellitus.

OBJECTIVE: This study was undertaken to compare amino acid concentrations in normal pregnancies and pregnancies with gestational diabetes (GDM), a condition associated with altered fetal growth. STUDY DESIGN: Maternal and fetal amino acids were evaluated by high-performance liquid chromatograph at the time of delivery in 16 normal and 17 GDM pregnancies. Fetal weights were not different, but placental weights were significantly higher and fetal/placental weight ratios were significantly lower in GDM compared with normal. RESULTS: Ornithine was significantly increased in GDM mothers. In umbilical vein and artery of GDM significant increases were observed for valine, methionine, phenylalanine, isoleucine, leucine, ornithine, glutamate, proline, and alanine, whereas glutamine was significantly decreased. CONCLUSION: Placental amino acid exchange is altered in GDM pregnancies. Moreover, the changes observed for glutamine and glutamate in the umbilical samples suggest that in GDM the fetal hepatic production of glutamate is increased, likely as a consequence of the endocrine changes in the fetal compartment.

Polyol concentrations in the fluid compartments of the human conceptus during the first trimester of pregnancy: maintenance of redox potential in a low oxygen environment.

Polyols are sugar alcohols formed by the reduction of aldoses and ketoses. Production is favored under conditions of low oxygenation, when it may provide an alternative means to production of lactate for regulating the oxidation-reduction balance of pyridine nucleotides. Polyols also act as important organic osmolytes and as precursors of cell membrane components. We measured free sugar and polyol concentrations in matched samples of maternal serum, intervillous fluid, coelomic fluid, and amniotic fluid from normal human pregnancies at 5-12 wk gestational age. The concentrations of fructose, inositol, sorbitol, erythritol, and ribitol were significantly higher in coelomic and amniotic fluids than in maternal serum, but the reverse was the case for glucose and glycerol. Intervillous fluid concentrations of inositol, mannitol, and sorbitol were also significantly higher than those in maternal serum. These results demonstrate that the polyol pathway, considered vestigial in adult tissues, is highly active in the human conceptus during early pregnancy. The pathway may serve to maintain ATP concentrations and cellular redox potential while the embryo develops in a low oxygen environment. Polyols may also play important physiological roles in development of the human conceptus, possibly drawing water and solutes across the placenta and expanding the gestational sac.

Maternal and fetal blood ammonia concentrations in normal term human pregnancies.

BACKGROUND: The current evidence on the primary source of ammonia production in the human fetoplacental unit is potentially misleading. OBJECTIVE: The aim of the present investigation was to determine the concentration of ammonia in human maternal and fetal blood at birth and to compare them with published data in late gestation sheep. METHODS: In 12 normal human pregnancies, umbilical arterial and venous and maternal venous blood was sampled, and whole blood ammonia concentrations were measured. Data from 12 pregnant sheep and fetuses from our previous studies were utilized for comparison. RESULTS: The human fetus at delivery has higher concentrations of ammonia (60-80 microM) than the late gestation fetal lamb (25-35 microM). In the human, the arterial umbilical ammonia concentration exceeds the venous umbilical concentration, indicating a net ammonia production by fetal tissues. In sheep, the venous umbilical ammonia concentration exceeds the arterial umbilical concentration, indicating the net placental ammonia production. CONCLUSIONS: In contrast to fetal lambs, human fetuses exhibit a net production of ammonia, which may reflect differences in biologic state or a species difference.

Reciprocal inhibition of umbilical uptake within groups of amino acids.

Eight pregnant sheep were infused with two amino acid mixtures of different composition: essential amino acids only and the essentials plus some of the nonessentials. Uterine and umbilical uptakes of amino acids were measured before and during infusion. For most of the amino acids, the infusion increased both maternal plasma concentration and umbilical uptake. However, depending on the infusate composition, the increase in maternal concentration of some amino acids was associated with no change or a significant reduction in umbilical uptake. Data were pooled from this and other, similar studies to test the hypothesis that umbilical uptake of several amino acids can be inhibited by coinfused amino acids. The test consisted of fitting the data, by means of multiple regression analysis, to the linear transformation of a saturation kinetics equation in which uptake is assumed to depend on maternal arterial concentrations. The analysis showed significant inhibitory effects within the neutral essential amino acids group and within the lysine-arginine group, with no demonstrable interaction between the two groups. Uterine uptakes did not show clear evidence of saturability and inhibitory interactions, suggesting a large transport capacity and low transporter affinity on the maternal surface of the trophoblast. We conclude that the transport of any given amino acid from placenta to fetus is a function of both its own maternal concentration and the maternal concentration of inhibitory amino acids.

The effect of an elevated maternal lysine concentration on placental lysine transport in pregnant sheep.

OBJECTIVES: In a previous study, the coinfusion into the maternal circulation of lysine and several other amino acids failed to increase significantly lysine umbilical uptake. The purpose of this study was to determine whether umbilical lysine uptake can be increased by infusing a lysine solution that does not contain any other amino acid. STUDY DESIGN: Six late-gestation ewes were studied on 2 consecutive days. Samples were collected in both the control (first day) and experimental (second day) periods simultaneously from the maternal artery, uterine vein, fetal artery, and umbilical vein. In the control period, L-[1-(13)C] lysine was infused into the maternal circulation. During the experimental period, both L-[1-(13)C] lysine and L-(12)C lysine were infused to increase maternal lysine concentration. Uterine and umbilical blood flows were measured by the steady state diffusion technique. Uterine and umbilical uptake of lysine and of alpha-aminoaminoadipic acid (AAD, a biproduct of lysine oxidation) were calculated. RESULTS: In response to a 2.7-fold increase in maternal lysine concentration (P<.001), fetal lysine concentration increased approximately 70% (P<.05) and umbilical uptake 50% (P<.05). In the experimental period, there was a significant (P<.05) placental uptake of fetal AAD, and the fetal/maternal plasma (13)C-lysine-specific activity ratio increased from 0.221+/-0.026 to 0.294+/-0.029 (P<.05). In response to the increase in maternal lysine concentration, the maternal and fetal concentrations of several other amino acids were significantly decreased. CONCLUSION: This study establishes that the umbilical uptake of lysine can be increased by infusing lysine in the maternal circulation. However, the lysine infusion is associated with a decrease in the maternal concentration and umbilical uptake of other essential amino acids. These data, compared with the results of previous studies, indicate that attempts to increase the fetal uptake of an amino acid via maternal infusion may decrease the uptake of other amino acids by decreasing their maternal concentration and by inhibition of placental transport.

The effect of a maternal infusion of amino acids on umbilical uptake in pregnancies complicated by intrauterine growth restriction.

OBJECTIVE: To establish whether, in human pregnancies complicated by intrauterine growth restriction (IUGR), the maternal intravenous infusion of amino acids can increase fetal amino acid concentrations and umbilical uptake. STUDY DESIGN: Before elective cesarean delivery, a solution of amino acids was infused into a maternal vein in 8 patients with pregnancies complicated by IUGR (experimental group). At cesarean delivery, maternal, umbilical venous, and arterial blood samples were obtained. Ten comparable IUGR pregnancies were compared with those in the experimental group. RESULTS: In the experimental group, all maternal amino acid concentrations were increased significantly. In the umbilical vein, valine, methionine, isoleucine, leucine, phenylalanine, arginine, serine, glycine, and proline concentrations were elevated. Umbilical venoarterial differences of amino acid per mole of oxygen for leucine, isoleucine, methionine, arginine, glycine, serine, and proline were elevated but not for lysine, histidine, threonine, valine, and phenylalanine. CONCLUSION: In pregnancies complicated by IUGR, increasing the maternal concentration of amino acids leads to an increased umbilical uptake of some of the amino acids to the fetus. There was no evidence of a change in the uptake of 3 essential amino acids: lysine, histidine, and threonine.