Production and utilization of amino  acids by ovine placenta in vivo

Chung, Misoo; Teng, Cecilia; Timmerman, Michelle; Meschia, Giacomo; Battaglia, Frederick C.

doi:10.1152/ajpendo.1998.274.1.e13

Cited by 71 publications

(86 citation statements)

References 17 publications

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“…Discussions on uteroplacental and fetal uptake of AA can be primarily divided into two areas of interest focusing on either metabolic pathways or transport systems (Battaglia and Regnault, 2001;Jansson, 2001;Fowden et al, 2006). From a metabolic standpoint, previous research has shown consistent uterine and fetal uptakes of essential AA (Chung et al, 1998). Contradictory to previous research we observed an increased uptake for the majority of AA in the fetus compared with the uterus, which resulted in many AA being released from the uteroplacenta.…”

Section: Discussionmentioning

confidence: 57%

Dietary melatonin supplementation alters uteroplacental amino acid flux during intrauterine growth restriction in ewes

Lemley

Camacho

Meyer

et al. 2013

Animal

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Dietary melatonin supplementation during mid-to late-gestation increased umbilical artery blood flow and caused disproportionate fetal growth. This melatonin-induced increase in umbilical artery blood flow may alter nutrient availability to the fetus, which may lead to alterations in fetal size. The objectives of the current experiment were to determine amino acid (AA) and glucose concentrations as well as AA and glucose flux across the uteroplacenta using a mid-to late-gestation model of intrauterine growth restriction supplemented with dietary melatonin as a 2 3 2 factorial design. At day 50 of gestation, 32 ewes were supplemented with 5 mg of melatonin (MEL) or no melatonin (CON) and were allocated to receive 100% (adequate; ADQ) or 60% (restricted; RES) of nutrient requirements. On day 130 of gestation, uterine and umbilical blood flows were determined via Doppler ultrasonography during a non-survival surgery. Blood samples were collected under general anesthesia from the maternal saphenous artery, gravid uterine vein, umbilical artery, and umbilical vein for AA analysis and glucose. Total a-AA concentrations in maternal artery and gravid uterine vein were decreased (P , 0.05) in RES v. ADQ fed ewes. Maternal arterial 2 venous difference in total a-AA was increased ( P < 0.01) in RES v. ADQ fed ewes, while total uterine a-AA flux was not different (P . 0.40) across all treatment groups. Fetal venous 2 arterial difference in total a-AA as well as uteroplacental flux of total a-AA were decreased (P , 0.05) in CON-RES v. CON-ADQ, and similar (P . 0.20) in MEL-RES v. CON-ADQ. Maternal concentrations and uterine flux of branched-chain AA (BCAA) were not different across all treatment groups; however, fetal uptake of BCAA was decreased (P , 0.05) in CON-RES v. CON-ADQ, and similar (P . 0.20) in MEL-RES v. CON-ADQ. Uterine uptake of glucose was not different (P > 0.08) across all treatment groups, while uteroplacental uptake of glucose was increased (P < 0.05) in RES v. ADQ ewes. In conclusion, maternal nutrient restriction increased maternal arterial 2 venous difference in total a-AA, while total uterine a-AA flux was unaffected by maternal nutrient restriction. Melatonin supplementation did not impact maternal serum concentrations or uterine flux of glucose or AA; however, melatonin did improve fetal BCAA uptake during maternal nutrient restriction.

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Section: Discussionmentioning

confidence: 57%

Dietary melatonin supplementation alters uteroplacental amino acid flux during intrauterine growth restriction in ewes

Lemley

Camacho

Meyer

et al. 2013

Animal

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“…This also included comparisons between essential and non-essential AA, where only limited information is available (e.g. Biolo et al [17]; Chung et al [24]). The data at 1.5 M were similar to those from a comparable intake in an earlier study [10], but were lower for some non essential AA (plasma ILR = 10.34 mmol·h -1 vs. 6.95 mmol·h -1 for glycine, 17.12 mmol·h -1 vs. 12.26 mmol·h -1 for glutamate, 5.43 mmol·h -1 vs. 2.81 mmol·h -1 for aspartate).…”

Section: Discussionmentioning

confidence: 99%

“…The extent of synthesis and inter-conversion varies with species as well as the nutritional and physiological state (e.g. Wolff et al [18]; Chung et al [24]). For sheep, although serine is converted to glycine [41], the converse does not occur ( [42] and unpublished results).…”

Section: Discussionmentioning

confidence: 99%

Effect of intake on whole body plasma amino acid kinetics in sheep

Savary-Auzeloux¹,

Hoskin

Lobley³

2003

Reprod. Nutr. Dev.

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-While both the quantity and quality of food ingested are potent regulators of whole body protein metabolism in ruminants, little data are available on responses across a wide range of intakes. The current study examined the responses in whole body protein flux (PrF) to such intake changes and compared these with the responses across the hind-quarters (in a companion study). Six growing sheep (6-8 months, 30-35 kg) received each of four intakes of dried grass pellets (0.5, 1.0, 1.5 and 2.5 times maintenance energy; M) for a minimum of 7 days. At each intake, a mixture of U-13 C amino-acids (AA) was infused intravenously for 10 h. Arterial plasma and blood were obtained over the last 4 h of infusion and the concentrations and the enrichments of thirteen 13 C labelled AA were determined. The absolute values for plasma Irreversible Loss Rate (ILR) but also converted PrF varied between the AA. PrF values were lower for histidine, methionine, aspartate, glycine and proline (range 68 to 174 g·d -1 at 1.5 M) than for isoleucine, leucine, valine and glutamate (range 275 to 400 g·d -1 at 1.5 M). These discrepancies may be explained by (1) the differential AA removal by the splanchnic tissues, (2) the de novo synthesis of the non-essential AA, (3) the transfer of AA from the erythrocytes or plasma to the tissues. The first two assumptions require further investigation whereas recent work has shown a minor role for AA transfers between erythrocytes and tissues. For most AA, ILR and PrF responded linearly to intake but curvilinear responses were observed for phenylalanine, lysine, leucine, isoleucine and tyrosine. These differences were not due to hind-quarter metabolism and may involve the digestive tract and liver.intake / whole body / kinetics / ovine / amino acid Reprod. Nutr. Dev. 43 (2003) 117-129 117

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“…Glutamate is another amino acid that is not significantly taken up by the uterine circulation (2,7). This is accompanied by a net release from the fetus toward the placenta, opposite in direction to the flux of most other amino acids and similar to the net flux of serine into the placenta, suggesting a unique role for both of these two nonessential amino acids (Fig.…”

mentioning

confidence: 99%

Amino Acid Interconversions in the Fetal-Placental Unit: The Animal Model and Human Studies In Vivo

Cetin

2001

Pediatr Res

103

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Fetal growth and development are dependent upon the adequate provision of oxygen and substrates from the maternal circulation. The need for amino acids is related to protein synthesis, interconversion to other substrates, and oxidation. Amino acids cross the placenta by active transport systems, and their concentrations in the fetus are higher than in the mother. In addition, most amino acids are extensively metabolized within the placenta, and, for some nonessential amino acids, placental synthesis has been demonstrated in chronically catheterized fetal lambs. Interorgan cycling between the fetal liver and placenta has been hypothesized for nonessential amino acids like glycine and serine. Amino acids are oxidized within the fetal tissues, particularly in liver and muscle, with differences between amino acids and in relation to metabolic state. In human pregnancies, maternal-fetal transfer rates have been investigated in vivo by stable isotope methodologies performed at fetal blood sampling. The transfer rate of nonessential amino acids like glycine is significantly lower than for essential amino acids like leucine, confirming glycine synthesis in the fetoplacental unit also in human pregnancies. Moreover, when a steady state model is applied, the fetal-maternal ratio for [1-13 C]leucine is significantly reduced in pregnancies associated with intrauterine growth restriction, reflecting a decrease in leucine placental transfer and/or an increase in protein catabolism in the fetoplacental unit. This reduction is proportional to the degree of severity of intrauterine growth restriction but is significant also in those intrauterine growthrestricted fetuses with normal oxygenation and acid-base status. Amino acids represent key nutrients during intrauterine life. Placental mechanisms accounting for amino acid transfer from the mother to the fetus have been thoroughly described in the last 20 y. The relevance of these mechanisms to fetal growth is strongly suggested by a number of studies demonstrating differences in amino acid placental transfer and metabolism occurring in human pregnancies associated with IUGR. The primary objective of this review is to integrate this recent information obtained in human pregnancies with the wide knowledge that has developed around the animal model. Some years ago, it seemed adventurous to propose the concept that pregnancy represented a metabolic state of not just a mother and a fetus but a three-compartment model of motherplacenta-fetus. The most-used animal model to study the relative contributions of each of these compartments to amino acid metabolism has been the pregnant sheep, principally because it is feasible in this species to catheterize chronically the maternal and fetal circulations.Uterine and umbilical uptakes can be calculated using an application of the Fick principle (1) as the product of concentration differences across the uterine circulation (uterine arterial concentration-uterine venous concentration) or the umbilical circulation (umbilical venous concentratio...

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Production and utilization of amino acids by ovine placenta in vivo

Cited by 71 publications

References 17 publications

Dietary melatonin supplementation alters uteroplacental amino acid flux during intrauterine growth restriction in ewes

Dietary melatonin supplementation alters uteroplacental amino acid flux during intrauterine growth restriction in ewes

Effect of intake on whole body plasma amino acid kinetics in sheep

Amino Acid Interconversions in the Fetal-Placental Unit: The Animal Model and Human Studies In Vivo

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