scholarly journals Effects of oocyte maturation regimen on the relative abundance of gene transcripts in bovine blastocysts derived in vitro or in vivo

Reproduction ◽  
2002 ◽  
pp. 365-375 ◽  
Author(s):  
HM Knijn ◽  
C Wrenzycki ◽  
PJ Hendriksen ◽  
PL Vos ◽  
D Herrmann ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Relative Abundance ◽  
Glucose Transporter ◽  
Expression Patterns ◽  
Marker Genes ◽  
Glucose Transporter 1 ◽  
Lh Surge ◽  
Preovulatory Follicles

Bovine embryos produced in vitro differ substantially from embryos produced in vivo in the mRNA expression patterns of genes important for development. Several factors in the in vitro production systems have profound effects on embryonic mRNA expression patterns. The effects of the type of maturation on the expression pattern of genes important for development in blastocysts produced in vitro have not yet been investigated. The aim of the present study was to investigate the effects of various maturational protocols on the relative abundance of a panel of six marker genes, indicative of compaction and cavitation, metabolism, stress susceptibility and RNA processing, in bovine blastocysts produced in vitro. Four groups of blastocysts were analysed by a sensitive semi-quantitative RT-PCR assay. Blastocysts were produced in vitro from oocytes of different origin from: (1) 3-8 mm follicles; (2) preovulatory follicles before the LH surge; and (3) preovulatory follicles 24 h after the LH surge. The first two groups were matured in vitro, whereas the third group had undergone maturation in vivo. A fourth group comprised blastocysts developed entirely in vivo. Expression of glucose transporter 1 was significantly (P < 0.05) higher, and expression of desmocollin 2 and plakophilin tended to be higher (P < 0.1) for in vivo (group 4) compared with in vitro blastocysts (group 1), whereas no differences were found for heat shock protein 70.1, E-cadherin and poly(A) polymerase. Expression of the six transcripts did not differ among blastocysts produced in vitro from oocytes of groups 1, 2 and 3. Results indicate that alterations in the relative abundance of these transcripts in blastocysts produced in vitro cannot primarily be attributed to the origin of the oocyte, but are likely to have been induced by post-maturation or fertilization culture conditions.

Expression of early development-related genes in bovine nuclear transferred and fertilized embryos

Zygote ◽  
2003 ◽  
Vol 11 (4) ◽  
pp. 355-360 ◽  
Author(s):  
Sang Hyun Park ◽  
Soo-Bong Park ◽  
Nam-Hyung Kim
Keyword(s):  
Mrna Expression ◽  
Early Development ◽  
Interleukin 6 ◽  
Nuclear Transfer ◽  
Glucose Transporter ◽  
Expression Patterns ◽  
Glucose Transporter 1 ◽  
E Cadherin

Cloning efficiency following somatic cell nuclear transfer is very low. In order to obtain insights into this problem, mRNA expression patterns of early development-related genes in nuclear transferred embryos were compared with those obtained from in vivo and in vitro fertilization. Semiquantitative reverse-transcription polymerase chain reaction assay was used to compare the gene expression of, the cell adhesion protein E-cadherin, interleukin -6, heat-shock protein 70.1 and bos taurus apoptosis regulator box-a (Bax). The relative abundances of glucose transporter-1, E-cadherin and interleukin-6 were significantly (P<0.05) higher in in vitro fertilized morulae than in vivo derived morulae. Transcription of the gene encoding octamer-binding transcription factor 4 was higher in blastocysts obtained from in vivo fertilization than in those from in vivo blastocysts. The transcript for Bax was markedly upregulated in blastocysts derived from in vitro production and nuclear transfer procedures compared with in vivo fertilization. These results suggest that alterations in mRNA expression of early development genes are more associated with in vitro culture condition than the nuclear transfer procedure itself.

In vitro and in vivo culture effects on mRNA expression of genes involved in metabolism and apoptosis in bovine embryos

2005 ◽  
Vol 17 (8) ◽  
pp. 775 ◽  
Author(s):  
Hiemke M. Knijn ◽  
Christine Wrenzycki ◽  
Peter J. M. Hendriksen ◽  
Peter L. A. M. Vos ◽  
Elly C. Zeinstra ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Mrna Expression ◽  
Critical Period ◽  
Glucose Transporter ◽  
Expression Patterns ◽  
Culture Conditions ◽  
Glut 4 ◽  
Gene Transcripts

Bovine blastocysts produced in vitro differ substantially from their in vivo-derived counterparts with regard to glucose metabolism, level of apoptosis and mRNA expression patterns. Maternal embryonic genomic transition is a critical period in which these changes could be induced. The goals of the present study were twofold: (1) to identify the critical period of culture during which the differences in expression of gene transcripts involved in glucose metabolism are induced; and (2) to identify gene transcripts involved in apoptosis that are differentially expressed in in vitro- and in vivo-produced blastocysts. Relative abundances of transcripts for the glucose transporters Glut-1, Glut-3, Glut-4 and Glut-8, and transcripts involved in the apoptotic cascade, including BAX, BCL-XL, XIAP and HSP 70.1, were analysed by a semiquantitative reverse transcription–polymerase chain reaction assay in single blastocysts produced in vitro or in vivo for specific time intervals, that is, before or after maternal embryonic transition. Whether the culture environment was in vitro or in vivo affected the expression of glucose transporter transcripts Glut-3, Glut-4 and Glut-8. However, the critical period during culture responsible for these changes, before or after maternal embryonic transition, could not be determined. With the exception of XIAP, no effects of culture system on the mRNA expression patterns of BAX, BCL-XL and HSP 70.1 could be observed. These data show that expression of XIAP transcripts in expanded blastocysts is affected by in vitro culture. These findings add to the list of bovine genes aberrantly expressed in culture conditions, but do not support the hypothesis that maternal embryonic transition is critical in inducing the aberrations in gene expression patterns studied here.

247 MESSENGER RNA EXPRESSION PATTERNS OF DNA AND HISTONE METHYLTRANSFERASES IN PREIMPLANTATION DEVELOPMENT OF IN VIVO- AND IN VITRO-PRODUCED BOVINE EMBRYOS

2006 ◽  
Vol 18 (2) ◽  
pp. 231 ◽  
Author(s):  
K. Höffmann ◽  
H. Niemann ◽  
K.-G. Hadeler ◽  
D. Herrmann ◽  
C. Wrenzycki
Keyword(s):  
Developmental Stage ◽  
Mrna Expression ◽  
Relative Abundance ◽  
Expression Patterns ◽  
Bovine Embryos ◽  
Histone Methyltransferases ◽  
Embryonic Genome ◽  
Uterine Flushing

The effects of in vitro production (IVP) and/or somatic nuclear transfer on mRNA expression patterns have mostly been determined in morulae and blastocysts, i.e. after embryonic genome activation. Comparative data regarding mRNA expression patterns throughout the oviductal phase of pre-implantation development are scarce. Here we studied mRNA expression for genes related to DNA methylation and modification of histones which account for the major epigenetic reprogramming during development. Pertubated epigenetic reprogramming of the genome is a likely cause of developmental abnormalities and epigenetic diseases associated with assisted reproduction technologies. The objective of the present study was to compare mRNA expression of DNA methyltransferases Dnmt1, -3a, and -3b and histone methyltransferases SUV39-h1 and G9a between in vivo-derived bovine embryos and their IVP counterparts using a semiquantitative RT-PCR assay (Wrenzycki et al. 2002 Biol. Reprod. 66, 127-134) employing two embryos for each assay. In vivo-derived embryos were collected from 28 superovulated heifers by endoscopic flushing of oviducts (zygotes to 8-cell stages) (Besenfelder et al. 2001 Theriogenology 55, 837-845) or by uterine flushing (16-cell stages to blastocysts). Endoscopic flushing at different time points after AI (Days 1, 1.5, 2, 3, 4, and 4.5) yielded 31 zygotes; 15 two-cell, 5 three-cell, 13 four-cell, 1 five-cell, 2 six-cell, and 11 eight-cell embryos; 4 degenerated embryos; and 18 unfertilized ova. The recovery rate (corpora lutea counted per recovered embryos) was 58% and 62% for the endoscopic and uterine flushing, respectively. Differences in the relative abundance of each gene transcript between groups were tested using ANOVA with the main effects being origin (in vivo/in vitro) and developmental stage (zygote to blastocyst) and their interactions followed by multiple pairwise comparisons using a Tukey test (P < 0.05). Origin of embryos affected the relative abundance of transcripts for Dnmt1, Dnmt3a, and SUV39-h1, and developmental stage affected the relative abundance of transcripts for Dnmt1, -3a, -3b, SUV39-h1, and G9a. No interactive effects were observed for origin and developmental stage in the relative abundance of all transcripts. The relative abundance of Dnmt1 transcripts differed significantly between in vivo- and in vitro-produced morulae and blastocysts. For Dnmt3a, mRNA differences were determined between in vivo- and in vitro-produced 10-16-cell stages and morulae. Suv39-h1 transcripts differed significantly between in vivo- and in vitro-derived zygotes, 2-cell embryos, 8-cell embryos, 10-16-cell embryos, and blastocysts. The results suggest that IVP alters mRNA expression of genes related to epigenetic modifications very early in development, even before the embryonic genome has been activated.

121 DIFFERENTIAL mRNA EXPRESSION BETWEEN IN VIVO AND IN VITRO-DERIVED BOS INDICUS AND BOS TAURUS EMBRYOS

2009 ◽  
Vol 21 (1) ◽  
pp. 160
Author(s):  
L. Nasser ◽  
P. Stranieri ◽  
A. Gutiérrez-Adán ◽  
M. Clemente ◽  
L. Jorge de Souza ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Repeated Measures ◽  
Bos Taurus ◽  
Receptor Gene ◽  
Expression Patterns ◽  
Bos Indicus ◽  
Growth Factor Receptor ◽  
P53 Gene

Brazil is a leading country in the world of commercial use of in vitro-produced bovine embryos with 200 000 transfers per year. The majority of in vitro-produced embryos are pure breed Nelore and are transferred fresh with 40% pregnancy rate. However, pregnancies are drastically reduced with frozen in vitro embryos. This experiment is part of our effort to learn more about molecular composition and morphology of in vitro-derived embryos that may be responsible for such discrepancy. We examined molecular expression of mRNA transcripts of 6 selected genes; apoptosis Bax,TP53(p53), SHC1SHC(p66), insulin growth factor receptor (IGF2R), stabilization of the plasma membrane PLAC8 and glucose conversion H6PD in in-vivo (control) and in-vitro Nelore and Bos taurus embryos. In vivo embryos were collected from superovulated cows at Day 7. In vitro embryo was produced from oocytes aspirated from live cows. A total of 284 oocytes (4 replicates) were matured and fertilized by standard IVF procedures. Presumptive zygotes were cultured in CR2 medium with 5% BSA in 50 μL drops (25 zygotes per drop) at 39°C under paraffin oil and 5% CO2 in humidified air. Embryos that developed on Days 7 to blastocyst were transferred to recipients, and 10 blastocysts from each replicate were frozen for evaluation of gene expression patterns. Poly(A) mRNA was prepared from 3 groups of pools of 10 in vitro embryos and 10 of control in vivo-derived embryos. The quantification of all gene transcripts was carried out by real-time quantitative RT-PCR using the comparative CT method. Data on mRNA expression were normalized to the endogenous H2a.z and was analyzed by one-way repeated-measures ANOVA. The cleavage rates at Day 2 and number of blastocysts developed at Day 7 were 80.3 ± 3.2 and 42.2 ± 6.4, respectively. The level of expression of IGF2R was significantly (P < 0.05) higher in in vivo-derived embryos than in both groups of in vitro embryos. The expression of all 3 apoptosis genes were lower (P < 0.05) in in vivo than in vitro embryos with exception of p53 gene that was not different between Nelore in vitro and in vivo embryos but was significantly higher (P < 0.05) in Bos taurus in vitro embryos. There was no difference in expression of PLAC8 gene among any tested group of embryos and in expression of H6PD gene between Nelore in vitro and in vivo embryos. We concluded that significant differences in molecular makeup between in vitro and in vivo-derived Nelore embryos exist. Of particular importance seems to be pattern of expression of IGF2R receptor gene known as a good indicator of embryo quality, which promotes proliferation and differentiation. Similarly, higher expression of 2 BAX and p66 genes of apoptosis in in vitro embryos seems to be a further indication of inferior quality of Nelore in vitro-derived embryos that showed to be more profound in Bos taurus in vitro-derived embryos.

Effects of the antiandrogen hydroxyflutamide on progesterone secretion by preovulatory rat follicles in vivo and in vitro

1991 ◽  
Vol 69 (9) ◽  
pp. 1288-1293 ◽  
Author(s):  
Yallampalli Chandrasekhar ◽  
David T. Armstrong
Keyword(s):  
Luteinizing Hormone ◽  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
Serum Progesterone ◽  
Antagonistic Action ◽  
Lh Surge ◽  
Progesterone Secretion ◽  
Preovulatory Follicles

Serum and ovarian progesterone levels and in vitro production of progesterone by preovulatory follicles were measured on proestrus in pregnant mare's serum gonadotropin (PMSG) primed immature rats in which the luteinizing hormone (LH) surge and ovulation were blocked by administration of the antiandrogen hydroxyflutamide. Serum progesterone levels observed at 12:00 on proestrus were significantly elevated, twofold above those observed in vehicle-treated controls, by in vivo administration of 5 mg hydroxyflutamide 4 h earlier. In control rats, proestrous progesterone did not increase until 16:00, in parallel with rising LH levels of the LH surge. No LH surge occurred in the hydroxyflutamide-treated rats, ovulation was blocked, and serum progesterone declined throughout the afternoon of proestrus, from the elevated levels present at 12:00. Administration of human chorionic gonadotropin (hCG) at 11:00 advanced the elevation of serum progesterone by 2 h in vehicle-treated controls and prevented the decline in progesterone levels in hydroxyfiutamide-treated rats. The patterns of change in ovarian tissue concentrations with time and treatment were essentially similar to those observed for serum progesterone. In in vitro experiments, progesterone secretion during 24 h culture of preovulatory follicles obtained on PMSG-induced proestrus was significantly increased, sixfold, by addition to the culture media of 370 μM but not of 37 μM hydroxyflutamide. Testosterone (50 nM) and hCG (20 mIU/mL) caused 26- and 14-fold increases, respectively, in progesterone secretion by cultured follicles. Hydroxyflutamide significantly reduced the stimulatory effect of testosterone but not of hCG on progesterone secretion in vitro. These results suggest that the antiandrogen hydroxyflutamide stimulates progesterone secretion, both in vivo and in vitro, through an initial androgen-agonistic action, before its antagonistic action is expressed. Its androgen-antagonistic action is responsible for its ability to inhibit testosterone-induced progesterone secretion in vitro. Its failure to reduce hCG-stimulated progesterone secretion in vivo and in vitro indicates that the latter stimulation is exerted independently of, and not as a consequence of, androgen action. The decrease in serum progesterone levels on the afternoon of proestrus therefore appears to be a consequence rather than a cause of the absence of an LH surge in the hydroxyflutamide-treated rats. It is concluded that the inhibitory effect of hydroxyflutamide on the preovulatory LH surge and ovulation is due not to inhibition of progesterone secretion at the ovarian level but most likely to neuroendocrine site(s) of action of the inhibitor.Key words: antiandrogen, hydroxyflutamide, progesterone, luteinizing hormone, ovulation, human chorionic gonadotropin.

scholarly journals Glucosamine Interferes With Myelopoiesis and Enhances the Immunosuppressive Activity of Myeloid-Derived Suppressor Cells

2021 ◽  
Vol 8 ◽  
Author(s):  
Eric Chang-Yi Lin ◽  
Shuoh-Wen Chen ◽  
Luen-Kui Chen ◽  
Ting-An Lin ◽  
Yu-Xuan Wu ◽  
...  
Keyword(s):  
Glucose Transporter ◽  
Immune Cell ◽  
Suppressor Cells ◽  
Therapeutic Benefit ◽  
Myeloid Derived Suppressor Cells ◽  
Hematopoietic Stem ◽  
Glucose Transporter 1 ◽  
Arginase 1

Glucosamine (GlcN) is the most widely consumed dietary supplement and exhibits anti-inflammatory effects. However, the influence of GlcN on immune cell generation and function is largely unclear. In this study, GlcN was delivered into mice to examine its biological function in hematopoiesis. We found that GlcN promoted the production of immature myeloid cells, known as myeloid-derived suppressor cells (MDSCs), both in vivo and in vitro. Additionally, GlcN upregulated the expression of glucose transporter 1 in hematopoietic stem and progenitor cells (HSPCs), influenced HSPC functions, and downregulated key genes involved in myelopoiesis. Furthermore, GlcN increased the expression of arginase 1 and inducible nitric oxide synthase to produce high levels of reactive oxygen species, which was regulated by the STAT3 and ERK1/2 pathways, to increase the immunosuppressive ability of MDSCs. We revealed a novel role for GlcN in myelopoiesis and MDSC activity involving a potential link between GlcN and immune system, as well as the new therapeutic benefit.

scholarly journals Epigenetic upregulation by valproic acid of transferrin receptor 1, and not glucose transporter 1 or CD98hc, at the blood-brain barrier

2022 ◽  
Author(s):  
Steinunn Sara Helgudóttir ◽  
Kasper Bendix Johnsen ◽  
Lisa Juul Routhe ◽  
Charlotte L.M. Rasmussen ◽  
Azra Karamehmedovic ◽  
...  
Keyword(s):  
Valproic Acid ◽  
Endothelial Cells ◽  
Protein Expression ◽  
Transferrin Receptor ◽  
Glucose Transporter ◽  
Brain Capillaries ◽  
Glucose Transporter 1 ◽  
Transferrin Receptor 1

Abstract BackgroundThe objectives of the present study were to investigate whether the expression of transferrin receptor 1 (TfR1), glucose transporter 1 (Glut1), or Cluster of Differentiation 98 Heavy Chain (CD98hc) is epigenetically regulated in brain capillary endothelial cells (BCECs) denoting the blood-brain barrier (BBB).MethodsThe expression of these targets was investigated both in vitro and in vivo following treatment with the histone deacetylase inhibitor (HDACi) valproic acid (VPA). Mice were injected intraperitoneally with VPA followed by analysis of isolated brain capillaries, and the capillary depleted brain samples. Brain tissue, isolated brain capillaries, and cultured primary endothelial cells were analyzed by RT-qPCR, immunolabeling and ELISA for expression of TfR1, Glut1 and CD98hc. We also studied the vascular targeting in VPA-treated mice injected with monoclonal anti-transferrin receptor (Ri7) conjugated with 1.4 nm gold nanoparticles. ResultsValidating the effects of VPA on gene transcription in BCECs, transcriptomic analysis identified 24,371 expressed genes, of which 305 were differentially expressed with 192 upregulated and 113 downregulated genes. In vitro using BCECs co-cultured with glial cells, the mRNA expression of Tfrc was significantly higher after VPA treatment for 6 h with its expression returning to baseline after 24 h. Conversely, the mRNA expression of Glut1 and Cd98hc was unaffected by VPA treatment. In vivo, the TfR1 protein expression in brain capillaries increased significantly after treatment with both 100 mg/kg and 400 mg/kg VPA. Conversely, VPA treatment did not increase GLUT1 or CD98hc. Using ICP-MS-based quantification, the brain uptake of nanogold conjugated anti-TfR1 antibodies was non-significant in spite of increased expression of TfR1. ConclusionsWe report that VPA treatment upregulates TfR1 at the BBB both in vivo and in vitro in isolated primary endothelial cells. In contrast, VPA treatment does not influence the expression of GLUT1 and CD98hc. The increase in the overall TfR1 protein expression however does not increase transport of TfR-targeted monoclonal antibody and indicates that targeted delivery using the transferrin receptor should aim for increased mobilization of already available transferrin receptor molecules to improve trafficking through the BBB.

20 ALTERED GENE EXPRESSION IN BOVINE SOMATIC CELL NUCLEAR-TRANSFERRED EMBRYOS AFTER TRICHOSTATIN A TREATMENT

2012 ◽  
Vol 24 (1) ◽  
pp. 121
Author(s):  
L. S. A. Camargo ◽  
M. M. Pereira ◽  
S. Wohlres-Viana ◽  
C. R. C. Quintão ◽  
L. T. Iguma ◽  
...  
Keyword(s):  
Gene Expression ◽  
Somatic Cell ◽  
Chromatin Remodeling ◽  
Relative Abundance ◽  
Glucose Transporter ◽  
Trichostatin A ◽  
Rna Extraction ◽  
Calf Serum ◽  
Glucose Transporter 1

Trichostatin A is a histone deacetylase inhibitor that improves histone acetylation and chromatin remodeling of somatic cell nuclear-transferred embryos (Iager et al. 2008 Cloning Stem Cells 10, 371–379; Maalouf et al. 2009 BMC Dev. Biol. 9, 11). We have previously observed that it also improves quality of bovine cloned embryos, which may increase pregnancy rates. This study aimed to evaluate the effect of trichostatin A treatment of zygotes on relative abundance of 9 transcripts in bovine nuclear-transferred blastocysts. In vitro matured oocytes were enucleated, fused to somatic cells and activated with ionomycin (Camargo et al. 2011 Reprod. Fertil. Dev. 23, 122). After activation, putative zygotes were randomly separated into 2 groups: NT-TRICHO, zygotes were cultured for 4 h in 6-DMAP followed by 7 h in CR2 aa medium plus with 2.5% fetal calf serum (FCS; Nutricell, Campinas, Brazil), both supplemented with 50 nM trichostatin A (Sigma); NT-CONT, zygotes were cultured in the same described conditions without thichostatin A supplementation. In vitro-fertilized embryos (IVF group) were used as a calibrator for relative transcript quantification. Embryos from the 3 groups were cultured in CR2 aa supplemented with 2.5% FCS under 5% CO2, 5% O2 and 90% N2 at 38.5°C. At 168 h postactivation, the embryos were rapidly frozen in liquid nitrogen. Pools of 10 blastocysts for each group were subject to RNA extraction and reverse transcription, in which cDNA was amplified by real-time PCR using the β-actin and GAPDH genes as endogenous references. The transcripts analysed encode high mobility group N1 (HMGN1), peroxiredoxin 1 (PRDX1), octamer-binding protein 4 (OCT4), insulin-like growth factor 1 and 2 receptors (IGF1r and IGF2r), glucose transporter 1 and 5 (GLUT1 and GLUT5), histone acetyltransferase (HAT) and heat shock protein 70.1 (HSP70) genes. Results were analysed by a pair-wise fixed reallocation randomization test using the REST software v.2. Data from NT-TRICHO and NT-CONT were compared with the IVF group and between themselves. The relative abundance of HSP70, PRDX1, IGF2r and HMGN1 transcripts was higher (P < 0.05) in NT-TRICHO compared with the IVF group and no difference was detected for the other transcripts. In the NT-CONT group, the relative abundance of IGF2r and HAT was higher (P < 0.05), whereas IGF1r and OCT4 were lower (P < 0.05) compared with IVF embryos. When data from NT-TRICHO and NT-CONT were compared, a higher amount (P < 0.05) of stress-associated transcripts (HSP70 and PRDX1) were found in NT-TRICO blastocysts. These results suggest that although trichostatin A may improve chromatin remodeling, alterations on gene expression still persist in bovine somatic cell nuclear-transferred blastocysts in comparison with IVF embryos. Financial support: Embrapa Project 01.07.01.002, CNPq 403019/2008–7 and Fapemig.

scholarly journals Gene expression of GLUT3 glucose transporter regulated by glucose in vivo in mouse brain and in vitro in neuronal cell cultures from rat embryos

1994 ◽  
Vol 300 (1) ◽  
pp. 125-131 ◽  
Author(s):  
S Nagamatsu ◽  
H Sawa ◽  
N Inoue ◽  
Y Nakamichi ◽  
H Takeshima ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mrna Expression ◽  
Mouse Brain ◽  
Glucose Transporter ◽  
Neuronal Cultures ◽  
Protective Mechanism ◽  
Rat Embryos ◽  
Glut1 Mrna

This study was designed to determine whether glucose regulates the gene expression of glucose transporter GLUT3 in neurons. We examined the regulation of GLUT3 mRNA by glucose in vivo in mouse brain and in vitro by using neuronal cultures from rat embryos. Hypoglycaemia (< 30 mg/dl), produced by 72 h of starvation, increased GLUT3 mRNA in mouse brain by 2-fold. Hybridization studies in situ demonstrated that hypoglycaemia-induced increases in GLUT3 mRNA expression were observed selectively in brain regions including the hippocampus, dentate gyrus, cerebral cortex and piriform cortex, but not the cerebellum. Primary neuronal cultures from rat embryos deprived of glucose for 48 h also showed an increase (4-fold over control) in GLUT3 mRNA, indicating that glucose can directly regulate expression of GLUT3 mRNA. In contrast with hypoglycaemia, hyperglycaemia produced by streptozotocin did not alter the expression of GLUT3 mRNA. We also confirmed previous findings that hypoglycaemia increases GLUT1 mRNA expression in brain. The increase in GLUT1 expression was probably limited to the blood-brain barrier in vivo, since GLUT1 mRNA could not be detected in neurons of the mouse cerebrum. Thus we conclude that up-regulation of neuronal GLUT3 in response to glucose starvation represents a protective mechanism against energy depletion in neurons.

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