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- Jansson, Nina, 1976, et al.
(author)
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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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In: The Journal of clinical endocrinology and metabolism. - 0021-972X. ; 88:3, s. 1205-11
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Journal article (peer-reviewed)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. |
- Johansson, M, et al.
(author)
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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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In: PLACENTA. - : Elsevier BV. - 0143-4004. ; 25:6, s. 505-511
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Journal article (peer-reviewed)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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| 4. |
- Magnusson, AnneLiese, et al.
(author)
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Glucose metabolism in the human preterm and term placenta tusof IUGR fees
- 2004
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In: Placenta. ; 25:4, s. 337-46
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Journal article (peer-reviewed)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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| 5. |
- Magnusson, AnneLiese, et al.
(author)
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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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In: J Clin Endocrinol Metab. ; 89:9, s. 4607-14
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Journal article (peer-reviewed)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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| 6. |
- Roos, Sara, 1979, et al.
(author)
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Human placental taurine transporter in uncomplicated and IUGR pregnancies: cellular localization, protein expression, and regulation
- 2004
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In: Am J Physiol Regul Integr Comp Physiol. - : American Physiological Society. - 0363-6119. ; 287:4
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Journal article (peer-reviewed)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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| 7. |
- Roos, Sara, 1979, et al.
(author)
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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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In: Placenta. - 0143-4004. ; 25:8-9
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Conference paper (peer-reviewed)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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