| 1. |
- Jansson, Nina, 1976, et al.
(författare)
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Leptin stimulates the activity of the system A amino acid transporter in human placental villous fragments.
- 2003
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Ingår i: The Journal of clinical endocrinology and metabolism. - 0021-972X. ; 88:3, s. 1205-11
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Tidskriftsartikel (refereegranskat)abstract
- The activity and expression of placental nutrient transporters are primary determinants for the supply of nutrients to the fetus, and these nutrients in turn regulate fetal growth. We developed an experimental system to assess amino acid uptake in single primary villous fragments to study hormonal regulation of the amino acid transporter system A in term human placenta. Validation of the method, using electron microscopy and studies of hormone production, indicated that fragments maintained ultrastructural and functional integrity for at least 3 h. The activity of system A was measured as the Na(+)-dependent uptake of methylaminoisobutyric acid (MeAIB), and the effect of 1 h incubation in various hormones was investigated. Uptake of MeAIB into villous fragments in the presence of Na(+) was linear up to at least 30 min. Insulin (300 ng/ml, n = 14) increased system A activity by 56% (P < 0.05). This effect was also present at insulin concentrations in the physiological range (+47% at 0.6 ng/ml, n = 10, P < 0.05). Leptin (500 ng/ml, n = 14) increased Na(+)-dependent MeAIB uptake by 37% (P < 0.05). System A activity increased in a concentration-dependent fashion in response to leptin (n = 10). However, neither epidermal GF (600 ng/ml), cortisol (340 ng/ml), nor GH (500 ng/ml) altered system A activity significantly (n = 14). We conclude that primary single isolated villous fragments can be used in studies of hormonal regulation of nutrient uptake into the syncytiotrophoblast. These data suggest that leptin regulates system A, a key amino acid transporter.
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| 2. |
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Ericsson, Anette, 1975, et al.
(författare)
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Hormonal regulation of glucose and system A amino acid transport in first trimester placental villous fragments.
- 2005
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Ingår i: American journal of physiology. Regulatory, integrative and comparative physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 288:3
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Tidskriftsartikel (refereegranskat)abstract
- Alterations in placental nutrient transfer have been implicated in fetal growth abnormalities. In pregnancies complicated by diabetes and accelerated fetal growth, upregulations of glucose transporter 1 (GLUT1) and amino acid transporter system A have been shown in the syncytiotrophoblast of term placenta. In contrast, intrauterine growth restriction is associated with a downregulation of placental system A transporters. However, underlying mechanisms of transporter regulation are poorly understood, particularly in early pregnancy. In this study, hormonal regulation of placental glucose and system A transporters was investigated. The uptake of 3-O-[methyl-(14)C]-d-glucose was studied in villous fragments isolated from first trimester (6-13 wk of gestation) and term human placenta. Villous fragments were incubated in buffer containing insulin, leptin, cortisol, growth hormone (GH), prolactin, IGF-I, or under hypo/hyperglycemic conditions for 1 h. Subsequently, 3-O-[methyl-(14)C]-D-glucose uptake was measured with and without phloretin for 70 s in first trimester tissue and 20 s in term tissue. Methylaminoisobutyric uptake was measured with and without Na+ for 20 min. Glucose uptake was unaltered by hormones or hypo/hyperglycemia. GH decreased system A activity by 31% in first trimester (P < 0.05). The uptake of glucose was 50% higher in term compared with first trimester fragments and increased markedly between 6 and 13 wk of gestation (P < 0.05). We conclude that placental glucose transporter activity is not regulated by short exposures to the hormones or glucose concentrations tested. In contrast to term placental villous fragments, system A activity was not regulated by insulin or leptin in first trimester but was downregulated by GH.
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| 7. |
- Gaccioli, F., et al.
(författare)
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Expression and functional characterisation of System L amino acid transporters in the human term placenta
- 2015
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Ingår i: Reproductive Biology and Endocrinology. - : Springer Science and Business Media LLC. - 1477-7827. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Background: System L transporters LAT1 (SLC7A5) and LAT2 (SLC7A8) mediate the uptake of large, neutral amino acids in the human placenta. Many System L substrates are essential amino acids, thus representing crucial nutrients for the growing fetus. Both LAT isoforms are expressed in the human placenta, but the relative contribution of LAT1 and LAT2 to placental System L transport and their subcellular localisation are not well established. Moreover, the influence of maternal body mass index (BMI) on placental System L amino acid transport is poorly understood. Therefore the aims of this study were to determine: i) the relative contribution of the LAT isoforms to System L transport activity in primary human trophoblast (PHT) cells isolated from term placenta; ii) the subcellular localisation of LAT transporters in human placenta; and iii) placental expression and activity of System L transporters in response to maternal overweight/obesity. Methods: System L mediated leucine uptake was measured in PHT cells after treatment with si-RNA targeting LAT1 and/or LAT2. The localisation of LAT isoforms was studied in isolated microvillous plasma membranes (MVM) and basal membranes (BM) by Western blot analysis. Results were confirmed by immunohistochemistry in sections of human term placenta. Expression and activity System L transporters was measured in isolated MVM from women with varying pre-pregnancy BMI. Results: Both LAT1 and LAT2 isoforms contribute to System L transport activity in primary trophoblast cells from human term placenta. LAT1 and LAT2 transporters are highly expressed in the MVM of the syncytiotrophoblast layer at term. LAT2 is also localised in the basal membrane and in endothelial cells lining the fetal capillaries. Measurements in isolated MVM vesicles indicate that System L transporter expression and activity is not influenced by maternal BMI. Conclusions: LAT1 and LAT2 are present and functional in the syncytiotrophoblast MVM, whereas LAT2 is also expressed in the BM and in the fetal capillary endothelium. In contrast to placental System A and beta amino acid transporters, MVM System L activity is unaffected by maternal overweight/obesity.
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| 8. |
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| 9. |
- Jansson, Nina, 1976, et al.
(författare)
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Activation of Placental mTOR Signaling and Amino Acid Transporters in Obese Women Giving Birth to Large Babies.
- 2013
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 98:1, s. 105-13
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Tidskriftsartikel (refereegranskat)abstract
- Context: Babies of obese women are often large at birth, which is associated with perinatal complications and metabolic syndrome later in life. The mechanisms linking maternal obesity to fetal overgrowth are largely unknown. Objective: We tested the hypothesis that placental insulin/IGF-I and mammalian target of rapamycin (mTOR) signaling is activated and amino acid transporter activity is increased in large babies of obese women. Design and Setting: Pregnant women were recruited prospectively for collection of placental tissue at a university hospital and academic biomedical center. Patients or Other Participants: Twenty-three Swedish pregnant women with first trimester body mass index ranging from 18.5 to 44.9 kg/m(2) and with uncomplicated pregnancies participated in the study. Interventions: There were no interventions. Main Outcome Measures: We determined the phosphorylation of key signaling molecules (including Akt, IRS-1, S6K1, 4EBP-1, RPS6, and AMPK) in the placental insulin/IGF-I, AMPK, and mTOR signaling pathways. The activity and protein expression of the amino acid transporter systems A and L were measured in syncytiotrophoblast microvillous plasma membranes. Results: Birth weights (range, 3025-4235 g) were positively correlated to maternal body mass index (P < 0.05). The activity of placental insulin/IGF-I and mTOR signaling was positively correlated (P < 0.001), whereas AMPK phosphorylation was inversely (P < 0.05) correlated to birth weight. Microvillous plasma membrane system A, but not system L, activity and protein expression of the system A isoform SNAT2 were positively correlated to birth weight (P < 0.001). Conclusions: Up-regulation of specific placental amino acid transporter isoforms may contribute to fetal overgrowth in maternal obesity. This effect may be mediated by activation of insulin/IGF-I and mTOR signaling pathways, which are positive regulators of placental amino acid transporters.
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| 10. |
- Jansson, Nina, 1976, et al.
(författare)
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Down-regulation of placental transport of amino acids precedes the development of intrauterine growth restriction in rats fed a low protein diet.
- 2006
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Ingår i: The Journal of physiology. - : Wiley. - 0022-3751. ; 576:Pt 3, s. 935-46
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Tidskriftsartikel (refereegranskat)abstract
- Intrauterine growth restriction (IUGR) represents an important risk factor for perinatal complications and for adult disease. IUGR is associated with a down-regulation of placental amino acid transporters; however, whether these changes are primary events directly contributing to IUGR or a secondary consequence is unknown. We investigated the time course of changes in placental and fetal growth, placental nutrient transport in vivo and the expression of placental nutrient transporters in pregnant rats subjected to protein malnutrition, a model for IUGR. Pregnant rats were given either a low protein (LP) diet (n = 64) or an isocaloric control diet (n = 66) throughout pregnancy. Maternal insulin, leptin and IGF-I levels decreased, whereas maternal amino acid concentrations increased moderately in response to the LP diet. Fetal and placental weights in the LP group were unaltered compared to control diet at gestational day (GD) 15, 18 and 19 but significantly reduced at GD 21. Placental system A transport activity was reduced at GD 19 and 21 in response to a low protein diet. Placental protein expression of SNAT2 was decreased at GD 21. In conclusion, placental amino acid transport is down-regulated prior to the development of IUGR, suggesting that these placental transport changes are a cause, rather than a consequence, of IUGR. Reduced maternal levels of insulin, leptin and IGF-1 may link maternal protein malnutrition to reduced fetal growth by down-regulation of key placental amino acid transporters.
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| 11. |
- Jansson, Nina, 1976, et al.
(författare)
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Maternal hormones linking maternal body mass index and dietary intake to birth weight.
- 2008
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Ingår i: American Journal of Clinical Nutrition. - Bethesda, USA : American Society for Nutrition. - 0002-9165 .- 1938-3207. ; 87:6, s. 1743-9
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Obese women often give birth to large-for-gestational age infants (typically defined as a birth weight greater than the 90th percentile), who are at risk of birth injuries and of developing metabolic syndrome later in life. The mechanisms underlying increased fetal growth remain to be established. OBJECTIVE: We aimed to identify maternal hormones that can explain the link between dietary intake, body mass index (BMI), and birth weight. DESIGN: Pregnant women with BMIs (in kg/m(2)) ranging from 17 to 44 (n = 49) were recruited in gestational weeks 8-12. Serum hormone concentrations were measured and dietary history interviews were performed in the first and third trimesters. Multiple regression models were produced to identify hormones that correlate with birth weight and are influenced by BMI or dietary factors. RESULTS: We found a strong positive correlation between BMI and first- and third-trimester insulin and leptin concentrations and a negative correlation between BMI and first-trimester adiponectin and first- and third-trimester insulin-like growth factor binding protein-1 (IGFBP-1). Maternal total fat intake in the first trimester was positively correlated with maternal leptin and inversely correlated with adiponectin. In addition, third-trimester total fat intake was positively correlated with circulating resistin concentrations. First-trimester maternal serum resistin was positively correlated with birth weight, whereas third-trimester maternal IGFBP-1 was negatively correlated with birth weight. CONCLUSIONS: High first-trimester maternal serum resistin and low third-trimester IGFBP-1 were correlated with increased birth weight. We propose that low serum concentrations of IGFBP-1 represent a link between high BMI and increased fetal growth by increasing the bioavailability of insulin-like growth factor-I, which up-regulates placental nutrient transport.
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| 12. |
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| 13. |
- Jansson, Thomas, 1955, et al.
(författare)
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Placental transport and metabolism in fetal overgrowth -- a workshop report.
- 2006
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Ingår i: Placenta. - : Elsevier BV. - 0143-4004. ; 27 Suppl A
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Tidskriftsartikel (refereegranskat)abstract
- Fetal overgrowth in pregnancies complicated by diabetes is the result of an increased substrate availability which stimulates fetal insulin secretion and fetal growth. However, despite strict glycemic control in modern clinical management of the pregnant woman with diabetes, fetal overgrowth remains an important clinical problem. Recent studies in vivo provide evidence for increased delivery of amino acids to the fetus in gestational diabetes (GDM) even when metabolic control is strict. This could be due to that truly normal maternal substrate levels cannot be achieved in diabetic pregnancies and/or caused by altered placental nutrient transport and metabolism. Studies in vitro demonstrate an up-regulation of placental transport systems for certain amino acids in GDM associated with fetal overgrowth. GDM is also characterized by changes in placental gene expression, including up-regulation of inflammatory mediators and Leptin. In type-I diabetes with fetal overgrowth the in vitro activity of placental transporters for both glucose and certain amino acids as well as placental lipoprotein lipase is increased. Furthermore, both clinical observations in type-I diabetic pregnancies and preliminary animal experimental studies suggest that even brief periods of metabolic perturbation early in pregnancy may affect placental growth and transport function for the remainder of pregnancy, thereby contributing to fetal overgrowth. Ultrasound measurements of fetal fat deposits and abdominal circumference as well as 3D ultrasound assessment of placental volume represent non-invasive techniques for in utero diagnosis of fetal and placental overgrowth. It is proposed that these methods represent valuable additions to the clinical management of the diabetic pregnancy. In conclusion, altered placental function may be a mechanism contributing to fetal overgrowth in diabetic pregnancies with apparent optimal metabolic control. It is proposed that detailed information on placental metabolism and transport functions obtained in vitro and in vivo represent a placental phenotype that provides important information and may facilitate diagnosis and improve clinical management of fetal overgrowth.
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| 14. |
- Johansson, M, et al.
(författare)
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Non-gastric H+/K+ ATPase is present in the microvillous membrane of the human placental syncytiotrophoblast
- 2004
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Ingår i: PLACENTA. - : Elsevier BV. - 0143-4004. ; 25:6, s. 505-511
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Tidskriftsartikel (refereegranskat)abstract
- In humans, the non-gastric H+/K+ATPase (ATP1AL1) has previously been shown to be expressed in the epithelia of skin, kidney and colon. In this study we tested the hypothesis that the non-gastric H+/K+ATPase is localized to the syncytiotrophoblast, the transporting epithelium of the human placenta. Microvillous (MVM) and basal plasma membranes (BM) of the syncytiotrophoblast were isolated from term placenta and membrane proteins were separated using SDS–PAGE. The ATP1AL1 protein was identified as a 114 kD band in both MVM and BM by Western blot, however, the protein was more abundant in the MVM. Using immunocytochemistry H+/K+ATPase protein was localized in MVM but not BM. We constructed primers specific for ATP1AL1 and performed RT–PCR on RNA isolated from human placenta and human kidney. A product of the expected size could be detected in both tissues after 30 cycles of amplification. The sequence identity of this 517 nucleotide product was confirmed by sequencing and found to be identical to the human non-gastric H+/K+ATPase. The activity of this proton pump appears to be low in normal healthy placental at term, however, it is speculated that MVM non-gastric H+/K+ATPase may be important in pathological states. In conclusion, non-gastric H+/K+ATPase is present in the microvillous plasma membrane of the transporting epithelia of the human placenta. Author Keywords: Non-gastric H+/K+-ATPase; Syncytiotrophoblast; Placenta; Human
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| 15. |
- Lager, Susanne, 1978, et al.
(författare)
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Effect of IL-6 and TNF-α on fatty acid uptake in cultured human primary trophoblast cells.
- 2011
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Ingår i: Placenta. - : Elsevier BV. - 1532-3102 .- 0143-4004. ; 32:2, s. 121-7
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Tidskriftsartikel (refereegranskat)abstract
- Maternal obesity and gestational diabetes (GDM) are conditions associated with fetal overgrowth and excessive fat accumulation in the fetus, implicating an increased placental nutrient transfer in these pregnancies. Obese and GDM mothers have altered metabolism and hormone levels, including elevation of maternal circulatory lipids and pro-inflammatory cytokines. We tested the hypothesis that interleukin (IL)-6 and tumor necrosis factor (TNF)-α stimulate placental fatty acid transport, as these pro-inflammatory cytokines have been shown to affect lipid metabolism in other tissues. In cultured primary human trophoblast cells IL-6, but not TNF-α, stimulated fatty acid accumulation, as measured by BODIPY fluorescence. The increased fatty acid accumulation could not be explained by an increased expression of key components in placental fatty acid transport, such as adipophilin, fatty acid transport protein (FATP)1, FATP4, or lipoprotein lipase. In a cohort of lean and overweight/obese pregnant women, increasing maternal third trimester IL-6 plasma concentrations correlated with decreasing placental lipoprotein lipase activity. However, as no effect on lipoprotein lipase activity was observed in cultured trophoblast cells after exposure to either IL-6 or TNF-α, the correlation between maternal circulatory IL-6 levels and placental lipoprotein lipase activity at term is unlikely to represent a cause-and-effect relationship. In conclusion, high levels of IL-6 stimulate trophoblast fatty acid accumulation, which could contribute to an excessive nutrient transfer in conditions associated with elevated maternal IL-6 such as obesity and gestational diabetes.
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| 16. |
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| 17. |
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| 18. |
- Lager, Susanne, 1978, et al.
(författare)
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Oleic acid stimulates system A amino acid transport in primary human trophoblast cells mediated by toll-like receptor 4
- 2013
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Ingår i: Journal of Lipid Research. - 0022-2275. ; 54:3, s. 725-733
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Tidskriftsartikel (refereegranskat)abstract
- Obese women have an increased risk to deliver large babies. However, the mechanisms underlying fetal overgrowth in these pregnancies are not well understood. Obese pregnant women typically have elevated circulating lipid levels. We tested the hypothesis that fatty acids stimulate placental amino acid transport, mediated via toll-like receptor 4 (TLR4) and mammalian target of rapamycin (mTOR) signaling pathways. Circulating NEFA levels and placental TLR4 expression were assessed in women with varying prepregnancy body mass index (BMI). The effects of oleic acid on system A and system L amino acid transport, and on the activation of the mTOR (4EBP1, S6K1, rpS6), TLR4 (IĸBɑ, JNK, p38 MAPK), and STAT3 signaling pathways were determined in cultured primary human trophoblast cells. Maternal circulating NEFAs (n = 33), but not placental TLR4 mRNA expression (n = 16), correlated positively with BMI (P < 0.05). Oleic acid increased trophoblast JNK and STAT3 phosphorylation (P < 0.05), whereas mTOR activity was unaffected. Furthermore, oleic acid doubled trophoblast system A activity (P < 0.05), without affecting system L activity. siRNA-mediated silencing of TLR4 expression prevented the stimulatory effect of oleic acid on system A activity. Our data suggest that maternal fatty acids can increase placental nutrient transport via TLR4, thereby potentially affecting fetal growth.
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| 19. |
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| 20. |
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| 21. |
- Magnusson, AnneLiese, et al.
(författare)
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Glucose metabolism in the human preterm and term placenta tusof IUGR fees
- 2004
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Ingår i: Placenta. ; 25:4, s. 337-46
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Tidskriftsartikel (refereegranskat)abstract
- Many fetuses suffering from intrauterine growth restriction (IUGR) are hypoglycaemic. However, the underlying mechanisms are not well established. An increased placental glucose consumption in IUGR could impair glucose transfer across the placenta. In this study we used two different approaches to investigate glucose metabolism in preterm and term placentae of IUGR fetuses. We determined activity and protein expression of the three rate-limiting glycolytic enzymes phosphofructo kinase (PFK), pyruvate kinase (PK) and hexokinase (HXK) in a cytoplasmic fraction of homogenates of placentae obtained from IUGR and appropriate for gestational age (AGA) pregnancies. Protein expression was assessed using Western blot and enzyme activities were determined in a spectrophotometer by measuring the rate of NADH oxidation (PFK and PK) or NADP reduction (HXK) in enzyme reactions coupled to the respective enzyme. To determine the distribution of the glycolytic enzymes immunocytochemistry was performed. We also measured glucose consumption and lactate production in fresh placental villous tissue using a perifusion system. The expression of PFK, PK and HXK as well as the activity of PK and HXK was unaltered in IUGR placentae. The activity of PFK on the other hand was 32 per cent lower in IUGR placentae (n=24, P<0.05). Immunocytochemistry confirmed the distribution of the enzymes to the cytoplasm of the syncytiotrophoblast. Placental glucose consumption in IUGR [0.06+/-0.01 micromol/(min*g), n=5] was not different from AGA [0.06+/-0.005 micromol/(min*g), n=12], whereas lactate production was decreased by 28 per cent in IUGR. These results do not support the hypothesis of increased placental glucose consumption but suggest an altered glycolytic pathway in the IUGR placenta.
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| 22. |
- Magnusson, AnneLiese, et al.
(författare)
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Triglyceride hydrolase activities and expression of fatty acid binding proteins in the human placenta in pregnancies complicated by intrauterine growth restriction and diabetes
- 2004
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Ingår i: J Clin Endocrinol Metab. ; 89:9, s. 4607-14
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Tidskriftsartikel (refereegranskat)abstract
- Triglyceride (TG) hydrolases in the placental microvillous plasma membrane (MVM) release fatty acids from circulating lipoproteins and represent the critical initial step in transplacental fatty acid transfer. We investigated the activity of two TG hydrolases in MVM isolated from placentas of appropriately grown for gestational age pregnancies and pregnancies complicated by intrauterine growth restriction (IUGR), insulin-dependent diabetes mellitus (IDDM) or gestational diabetes mellitus (GDM). In addition, we measured protein expression of lipoprotein lipase (LPL) in MVM and two fatty acid binding proteins (L- and C-FABP) in placental homogenates. The TG hydrolase activities were assessed by measuring hydrolysis of (3)H-trioleic acid incorporated into intralipid micelles after incubation with MVM. The placenta-specific TG hydrolase activity (optimum at pH 6) did not differ in the patient groups studied. MVM LPL activity (optimum at pH 8) was reduced by 47% in preterm IUGR (n = 8, P < 0.05), compared with gestational age-matched controls. The LPL activity in placentas of IDDM pregnancies was increased by 39% (n = 8, P < 0.05), compared with controls. No significant differences were observed in cases of GDM. We found no alteration in protein expression of LPL or C-FABP. The expression of L-FABP was increased by 112% (n = 8, P < 0.05) in IDDM and 64% (n = 8, P < 0.05) in GDM. These results indicate that alterations in MVM LPL activity and expression of L-FABP may contribute to the altered lipid deposition and metabolism in IUGR and diabetic pregnancies.
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| 23. |
- Magnusson-Olsson, AnneLiese, et al.
(författare)
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Effect of maternal triglycerides and free fatty acids on placental LPL in cultured primary trophoblast cells and in a case of maternal LPL deficiency.
- 2007
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Ingår i: Am J Physiol Endocrinol Metab. ; 293:1
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Tidskriftsartikel (refereegranskat)abstract
- Maternal hypertriglyceridemia is a normal condition in late gestation and is an adaptation to ensure an adequate nutrient supply to the fetus. Placental lipoprotein lipase (LPL) is involved in the initial step in transplacental fatty acid transport as it hydrolyzes maternal triglycerides (TG) to release free fatty acids (FFA). We investigated LPL activity and protein (Western blot) and mRNA expression (real-time RT-PCR) in the placenta of an LPL-deficient mother with marked hypertriglyceridemia. The LPL activity was fourfold lower, LPL protein expression 50% lower, and mRNA expression threefold higher than that of normal, healthy placentas at term (n = 4-7). To further investigate the role of maternal lipids in placental LPL regulation, we isolated placental cytotrophoblasts from term placentas and studied LPL activity and protein and mRNA expression after incubation in Intralipid (as a source of TG) and oleic, linoleic, and a combination of oleic, linoleic, and arachidonic acids as well as insulin. Intralipid (40 and 400 mg/dl) decreased LPL activity by approximately 30% (n = 10-14, P < 0.05) and 400 microM linoleic and linoleic-oleic-arachidonic acid (n = 10) decreased LPL activity by 37 and 34%, respectively. No major changes were observed in LPL protein or mRNA expression. We found no effect of insulin on LPL activity or protein expression in the cultured trophoblasts. To conclude, the activity of placental LPL is reduced by high levels of maternal TG and/or FFA. This regulatory mechanism may serve to counteract an excessive delivery of FFA to the fetus in conditions where maternal TG levels are markedly increased.
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| 24. |
- Magnusson-Olsson, AnneLiese, et al.
(författare)
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Gestational and hormonal regulation of human placental lipoprotein lipase
- 2006
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Ingår i: J Lipid Res. ; 47:11, s. 2551-61
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Tidskriftsartikel (refereegranskat)abstract
- The fetal demand for FFA increases as gestation proceeds, and LPL represents one potential mechanism for increasing placental lipid transport. We examined LPL activity and protein expression in first trimester and term human placenta. The LPL activity was 3-fold higher in term (n = 7; P < 0.05) compared with first trimester (n = 6) placentas. The LPL expression appeared lower in microvillous membrane from first trimester (n = 2) compared with term (n = 2) placentas. We incubated isolated placental villous fragments with a variety of effectors [GW 1929, estradiol, insulin, cortisol, epinephrine, insulin-like growth factor-1 (IGF-1), and tumor necrosis factor-alpha] for 1, 3, and 24 h to investigate potential regulatory mechanisms. Decreased LPL activity was observed after 24 h of incubation with estradiol (1 micro g/ml), insulin, cortisol, and IGF-1 (n = 12; P < 0.05). We observed an increase in LPL activity after 3 h of incubation with estradiol (20 ng/ml) or hyperglycemic medium plus insulin (n = 7; P < 0.05). To conclude, we suggest that the gestational increase in placental LPL activity represents an important mechanism to enhance placental FFA transport in late pregnancy. Hormonal regulation of placental LPL activity by insulin, cortisol, IGF-1, and estradiol may be involved in gestational changes and in alterations in LPL activity in pregnancies complicated by altered fetal growth.
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| 25. |
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| 26. |
- Roos, Sara, 1979, et al.
(författare)
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Expression of placental mammalian target of rapamycin (mTOR) is altered in relation to fetal growth and mTOR regulates leucine transport
- 2005
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Ingår i: Placenta. - 0143-4004. ; 26:8-9
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Konferensbidrag (refereegranskat)abstract
- Placental transport functions are altered in pregnancies complicated by restricted (IUGR) or accelerated fetal growth (LGA; large-for-gestational-age). We have suggested that the placenta may function as a nutrient sensor, regulating its nutrient transport in response to changes in substrate supply, and consequently altering fetal growth. mTOR is a protein kinase involved in regulating protein translation in response to nutrient stimuli. mTOR mRNA has been shown to be expressed in the placenta, its functional role however is unknown. To test the hypothesis that mTOR is involved in placental nutrient sensing we investigated mTOR protein expression in the human placenta in relation to fetal growth and we assessed the effect of the mTOR inhibitor rapamycin on amino acid transporter activity. Methods: mTOR expression was studied by immunohistochemistry and Western blotting and amino acid transporter activity was measured in term villous fragments. Results: mTOR protein was expressed in the cytoplasm of the syncytiotrophoblast. mTOR protein expression was up-regulated by 51% (p < 0.05) in homogenates of IUGR placentas (n = 9, controls n = 12) and down-regulated by 42% (p < 0.05) in placentas of LGA infants (n = 6, controls n = 15). Rapamycin (100 nM) decreased system L activity by 35% (n = 7, p < 0.05) but did not affect the activity of system A or taurine transporters. Conclusion: Placental mTOR protein expression is inversely related to fetal growth. Inhibition of placental mTOR decreases placental leucine transport, representing a novel regulatory mechanism for the L amino acid transporter. These findings are compatible with the hypothesis that the mTOR signaling system may play a role in placental nutrient sensing.
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| 27. |
- Roos, Sara, 1979, et al.
(författare)
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Human placental taurine transporter in uncomplicated and IUGR pregnancies: cellular localization, protein expression, and regulation
- 2004
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Ingår i: Am J Physiol Regul Integr Comp Physiol. - : American Physiological Society. - 0363-6119. ; 287:4
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Tidskriftsartikel (refereegranskat)abstract
- Transplacental transfer is the fetus' primary source of taurine, an essential amino acid during fetal life. In intrauterine growth restriction (IUGR), placental transport capacity of taurine is reduced and fetal taurine levels are decreased. We characterized the protein expression of the taurine transporter (TAUT) in human placenta using immunocytochemistry and Western blotting, tested the hypothesis that placental protein expression of TAUT is reduced in IUGR, and investigated TAUT regulation by measuring the Na(+)-dependent taurine uptake in primary villous fragments after 1 h of incubation with different effectors. TAUT was primarily localized in the syncytiotrophoblast microvillous plasma membrane (MVM). TAUT was detected as a single 70-kDa band, and MVM TAUT expression was unaltered in IUGR. The PKC activator PMA and the nitric oxide (NO) donor 3-morpholinosydnonimine decreased TAUT activity (P < 0.05, n = 7-15). However, none of the tested hormones, e.g., leptin and growth hormone, altered TAUT activity significantly. PKC activity measured in MVM from control and IUGR placentas was not different. In conclusion, syncytiotrophoblast TAUT is strongly polarized to the maternal-facing plasma membrane. MVM TAUT expression is unaltered in IUGR, suggesting that the reduced MVM taurine transport in IUGR is due to changes in transporter activity. NO release downregulates placental TAUT activity, and it has previously been shown that IUGR is associated with increased fetoplacental NO levels. NO may therefore play an important role in downregulating MVM TAUT activity in IUGR.
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| 28. |
- Roos, Sara, 1979, et al.
(författare)
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Mammalian target of rapamycin in the human placenta regulates leucine transport and is down-regulated in restricted fetal growth.
- 2007
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Ingår i: The Journal of physiology. - : Wiley. - 0022-3751. ; 582:Pt 1, s. 449-59
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Tidskriftsartikel (refereegranskat)abstract
- Pathological fetal growth is associated with perinatal morbidity and the development of diabetes and cardiovascular disease later in life. Placental nutrient transport is a primary determinant of fetal growth. In human intrauterine growth restriction (IUGR) the activity of key placental amino acid transporters, such as systems A and L, is decreased. However the mechanisms regulating placental nutrient transporters are poorly understood. We tested the hypothesis that the mammalian target of rapamycin (mTOR) signalling pathway regulates amino acid transport in the human placenta and that the activity of the placental mTOR pathway is reduced in IUGR. Using immunohistochemistry and culture of trophoblast cells, we show for the first time that the mTOR protein is expressed in the transporting epithelium of the human placenta. We further demonstrate that placental mTOR regulates activity of the l-amino acid transporter, but not system A or taurine transporters, by determining the mediated uptake of isotope-labelled leucine, methylaminoisobutyric acid and taurine in primary villous fragments after inhibition of mTOR using rapamycin. The protein expression of placental phospho-S6K1 (Thr-389), a measure of the activity of the mTOR signalling pathway, was markedly reduced in placentas obtained from pregnancies complicated by IUGR. These data identify mTOR as an important regulator of placental amino acid transport, and provide a mechanism for the changes in placental leucine transport in IUGR previously demonstrated in humans. We propose that mTOR functions as a placental nutrient sensor, matching fetal growth with maternal nutrient availability by regulating placental nutrient transport.
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| 29. |
- Roos, Sara, 1979, et al.
(författare)
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Placental mTOR links maternal nutrient availability to fetal growth.
- 2009
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Ingår i: Biochemical Society transactions. - 1470-8752. ; 37:Pt 1, s. 295-8
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Tidskriftsartikel (refereegranskat)abstract
- The mTOR (mammalian target of rapamycin) signalling pathway functions as a nutrient sensor, both in individual cells and, more globally, in organs such as the fat body in Drosophila and the hypothalamus in the rat. The activity of placental amino acid transporters is decreased in IUGR (intrauterine growth restriction), and recent experimental evidence suggests that these changes contribute directly to the restricted fetal growth. We have shown that mTOR regulates the activity of the placental L-type amino acid transporter system and that placental mTOR activity is decreased in IUGR. The present review summarizes the emerging evidence implicating placental mTOR signalling as a key mechanism linking maternal nutrient and growth factor concentrations to amino acid transport in the human placenta. Since fetal growth is critically dependent on placental nutrient transport, placental mTOR signalling plays an important role in the regulation of fetal growth.
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| 30. |
- Roos, Sara, 1979, et al.
(författare)
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Regulation of amino acid transporters by glucose and growth factors in cultured primary trophoblast cells is mediated by mTOR signaling
- 2009
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Ingår i: American Journal of Physiology - Cell Physiology. - : American Physiological Society. - 0363-6143 .- 1522-1563. ; 298, s. C723-C731
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Tidskriftsartikel (refereegranskat)abstract
- Inhibition of mammalian target of rapamycin (mTOR) signaling in cultured human primary trophoblast cells reduces the activity of key placental amino acid transporters. However, the upstream regulators of placental mTOR are unknown. We hypothesized that glucose, insulin, and IGF-I regulate placental amino acid transporters by inducing changes in mTOR signaling. Primary human trophoblast cells were cultured for 24 h with media containing various glucose concentrations, insulin, or IGF-I, with or without the mTOR inhibitor rapamycin, and, subsequently, the activity of system A, system L, and taurine (TAUT) transporters was measured. Glucose deprivation (0.5 mM glucose) did not significantly affect Thr172-AMP-activated protein kinase phosphorylation or REDD1 expression but decreased S6 kinase 1 phosphorylation at Thr389. The activity of system L decreased in a dose-dependent manner in response to decreasing glucose concentrations. This effect was abolished in the presence of rapamycin. Glucose deprivation had two opposing effects on system A activity: 1) an “adaptive” upregulation mediated by an mTOR-independent mechanism and 2) downregulation by an mTOR-dependent mechanism. TAUT activity was increased after incubating cells with glucose-deprived media, and this effect was largely independent of mTOR signaling. Insulin and IGF-I increased system A activity and insulin stimulated system L activity, effects that were abolished by rapamycin. We conclude that the mTOR pathway represents an important intracellular regulatory link between nutrient and growth factor concentrations and amino acid transport in the human placenta.intrauterine growth restriction (IUGR) and accelerated fetal growth represent two important clinical conditions that occur in 15% of all pregnancies (1, 2). Aberrant fetal growth is associated with an increased risk of perinatal morbidity (7) as well as metabolic abnormalities in adult life, such as obesity, type 2 diabetes, and cardiovascular disease (6, 12, 46). The most important determinant of fetal growth is nutrient availability, which is highly dependent on placental transport capacity. The mechanisms underlying altered fetal growth remain to be established, but accumulating evidence implicates changes in the activity of specific placental amino acid transporters as a critical factor contributing to abnormal fetal growth (27, 54). Experimental evidence supports the hypothesis that changes in placental nutrient transporter activity are a cause of rather than a response to altered fetal growth. For example, in pregnant rats subjected to protein malnutrition, it is likely that downregulation of the placental system A amino acid transporter directly contributes to the development of IUGR (26).In IUGR, fetuses may be hypoglycemic (15) and have reduced circulating levels of insulin (43) and IGF-I (4, 34). The maternal levels of glucose (15) and IGF-I (40, 41) may also be reduced in this condition. The placenta of the IUGR fetus could therefore be exposed to decreased levels of glucose, hormones, and growth factors. Both insulin and IGF-I stimulate placental system A activity (24, 30, 31). These results suggest that extracellular cues regulate placental nutrient transporters and, as a consequence, fetal nutrient supply, but the cellular mechanisms remain to be fully established.The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that is regulated by a multitude of intracellular and extracellular signals. For example, mTOR is activated by growth factors and nutrient levels, such as amino acids (59), and inhibited by numerous stress conditions, such as cellular energy depletion (13, 17). Glucose may also regulate mTOR signaling through energy production in the form of ATP (13, 17). The AMP-activated protein kinase (AMPK) is regulated by the AMP-to-ATP ratio, which rises under nutrient deprivation and activates AMPK (10). Activated AMPK can in turn phosphorylate tuberous sclerosis complex 2 (TSC2), leading to mTOR inactivation (23). AMPK is phosphorylated and activated by LKB1 (52), and it has been shown that phosphorylation of LKB1 at Ser428 is essential for AMPK activation by metformin, and the authors speculate that LKB1-Ser428 phosphorylation may be a common pathway required for AMPK activation (60). There might also be additional, AMPK-independent, pathways involved in energy depletion. A recent report has shown that REDD1 (regulated in development and DNA damage responses 1) in mouse embryonic fibroblasts is induced by chronic energy depletion, and this in turn leads to inactivation of mTOR complex 1 (mTORC1) measured as phosphorylation of S6 kinase 1 (S6K1) at Thr389, independent of AMPK (55).Insulin and IGF-I activate the tyrosine kinase activity of its receptors to phosphorylate the insulin receptor substrate 1, which in turn activates phosphatidylinositol 3-kinase (PI3K) to generate PI(3,4,5)P3. Phosphatidylinositol 3,4,5-trisphosphate (PIP3) binding to Akt leads to the translocation of Akt to the plasma membrane, where it is phosphorylated and activated. The activation of Akt positively modulates mTORC1 function, by phosphorylating, and inhibiting, TSC2 (reviewed in Ref. 59).We have previously shown that inhibition of mTOR reduces the activity of placental system L, system A, and the taurine transporter (TAUT) (50). Since the activity of these amino acid transporter systems is downregulated in the placenta in association to IUGR (14, 19, 28, 37, 45) and placental mTOR activity has been reported to be decreased in IUGR (49, 62), it is possible that mTOR signaling plays an important role in regulating placental amino acid transporters in vivo. However, the upstream regulators of placental mTOR are unknown. We hypothesized that glucose, insulin, and IGF-I regulate placental amino acid transporter activity by inducing changes in mTOR signaling. To test this hypothesis, human primary trophoblast cells were incubated with media containing various concentrations of glucose, insulin, or IGF-I in the presence or absence of the specific mTOR inhibitor rapamycin. Subsequently, the activity of system L, system A, and the taurine transporter was measured. To investigate whether the AMPK pathway and/or REDD1 is activated in glucose-deprived primary trophoblasts, the protein expression of phosphorylated (P)-Thr172-AMPKα, total AMPK, P-Ser428-LKB1, and REDD1 in control and glucose-deprived cells was also studied.
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| 31. |
- Roos, Sara, 1979, et al.
(författare)
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Regulation of placental amino acid transporter activity by mammalian target of rapamycin.
- 2009
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Ingår i: American journal of physiology. Cell physiology. - : American Physiological Society. - 0363-6143 .- 1522-1563. ; 296:1
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Tidskriftsartikel (refereegranskat)abstract
- The activity of placental amino acid transporters is decreased in intrauterine growth restriction (IUGR), but the underlying regulatory mechanisms have not been established. Inhibition of the mammalian target of rapamycin (mTOR) signaling pathway has been shown to decrease the activity of the system L amino acid transporter in human placental villous fragments, and placental mTOR activity is decreased in IUGR. In the present study, we used cultured primary trophoblast cells to study mTOR regulation of placental amino acid transporters in more detail and to test the hypothesis that mTOR alters amino acid transport activity by changes in transporter expression. Inhibition of mTOR by rapamycin significantly reduced the activity of system A (-17%), system L (-28%), and taurine (-40%) amino acid transporters. mRNA expression of isoforms of the three amino acid transporter systems in response to mTOR inhibition was measured using quantitative real-time PCR. mRNA expression of l-type amino acid transporter 1 (LAT1; a system L isoform) and taurine transporter was reduced by 13% and 50%, respectively; however, mTOR inhibition did not alter the mRNA expression of system A isoforms (sodium-coupled neutral amino acid transporter-1, -2, and -4), LAT2, or 4F2hc. Rapamycin treatment did not significantly affect the protein expression of any of the transporter isoforms. We conclude that mTOR signaling regulates the activity of key placental amino acid transporters and that this effect is not due to a decrease in total protein expression. These data suggest that mTOR regulates placental amino acid transporters by posttranslational modifications or by affecting transporter translocation to the plasma membrane.
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| 32. |
- Roos, Sara, 1979, et al.
(författare)
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The human placental taurine transporter in uncomplicated and IUGR pregnancies: cellular localization, protein expression, and regulation
- 2004
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Ingår i: Placenta. - 0143-4004. ; 25:8-9
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Konferensbidrag (refereegranskat)abstract
- Transplacental transfer is the fetus’ primary source of taurine, an essential amino acid during fetal life. In intrauterine growth restriction (IUGR) placental transport capacity of taurine is reduced and fetal taurine levels are decreased. Methods: Immunocytochemistry was used to study cellular localization of the taurine transporter (TAUT), protein expression was studied by Western blotting, and TAUT regulation by measuring the sodium-dependent taurine uptake in primary villous fragments after 1 h incubation with different effectors. Results: TAUT was primarily detected in the syncytiotrophoblast microvillous plasma membrane (MVM). In Western blot analysis TAUT was detected as a single 70kDa band and MVM TAUT expression was unaltered in IUGR (n=8). Phorbol 12-myristate 13-acetate, a stimulator of protein kinase C, and the NO donor 3-morpholinosydnonimine decreased TAUT activity (n= 7-15, p<0.05). However, none of the tested hormones, such as leptin, cortisol, and insulin, altered TAUT activity significantly (n=6-15). PKC activity measured in MVM isolated from AGA and IUGR placentas was found to be similar (n=8). Conclusions: TAUT in the transporting epithelium of the human placenta is strongly polarized to the maternal-facing plasma membrane. MVM TAUT expression is unaltered in IUGR suggesting that the reduction in MVM taurine transport in association to IUGR is due to changes in transporter activity. PKC-mediated phosphorylation and NO release downregulate TAUT activity. MVM PKC-activity is unaltered in IUGR, but NO levels have previously been shown to be higher in IUGR, suggesting a possible mechanism for the reduced taurine uptake across MVM in IUGR.
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| 33. |
- Rosario, FJ, et al.
(författare)
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Maternal Protein Restriction in the Rat Inhibits Placental Insulin, mTOR, and STAT3 Signaling and Down-Regulates Placental Amino Acid Transporters
- 2011
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Ingår i: ENDOCRINOLOGY. - 0013-7227. ; 152:3, s. 1119-1129
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: The mechanisms underlying reduced fetal growth in response to maternal protein restriction are not well established. Maternal levels of insulin, IGF-I, and leptin are decreased in rats fed a low protein (LP) diet. Because these hormones stimulate placental amino acid transporters in vitro, we hypothesized that maternal protein restriction inhibits placental leptin, insulin/IGF-I, and mammalian target of rapamycin signaling and down-regulates the expression and activity of placental amino acid transporters. Pregnant rats were fed either an isocaloric low protein (LP, 4% protein) or control diet (18% protein) and studied at gestational day (GD) 15, GD19, or GD21 (term 23). At GD19 and GD21, placental expression of phosphorylated eukaryotic initiation factor 4E binding protein 1 (Thr-36/46 or Thr-70) and phosphorylated S6 ribosomal protein (Ser-235/236) was decreased in the LP group. In addition, placental expression of phosphorylated S6 kinase 1 (Thr-389), phosphorylated Akt (Thr-308), and phosphorylated signal transducer and activator of transcription 3 (Tyr-705) was reduced at GD21. In microvillous plasma membranes(MVM) isolated from placentas of LP animals, protein expression of the sodium-coupled neutral amino acid transporter (SNAT)2 and the large neutral amino acid transporters 1 and 2 was reduced at GD19 and GD21. MVM SNAT1 protein expression was reduced at GD21 in LP rats. SNAT4 and 4F2 heavy chain expression in MVM was unaltered. System A and L amino acid transporter activity was decreased in MVM from LP animals at GD19 and GD21. In conclusion, maternal protein restriction inhibits placental insulin, mammalian target of rapamycin signaling, and signal transducer and activator of transcription 3 signaling, which is associated with a down-regulation of placental amino acid transporters. We speculate that maternal endocrine and metabolic control of placental nutrient transport reduces fetal growth in response to protein restriction. (Endocrinology 152: 1119-1129, 2011)
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| 34. |
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