Expression Of Hexose Transporters Research Articles

Drug resistance in diploid yeast is acquired through dominant alleles,haploinsufficiency, gene duplication and aneuploidy.

Previous studies of adaptation to the glucose analog, 2-deoxyglucose, by Saccharomyces cerevisiae have utilized haploid cells. In this study, diploid cells were used in the hope of identifying the distinct genetic mechanisms used by diploid cells to acquire drug resistance. While haploid cells acquire resistance to 2-deoxyglucose primarily through recessive alleles in specific genes, diploid cells acquire resistance through dominant alleles, haploinsufficiency, gene duplication and aneuploidy. Dominant-acting, missense alleles in all three subunits of yeast AMP-activated protein kinase confer resistance to 2-deoxyglucose. Dominant-acting, nonsense alleles in the REG1 gene, which encodes a negative regulator of AMP-activated protein kinase, confer 2-deoxyglucose resistance through haploinsufficiency. Most of the resistant strains isolated in this study achieved resistance through aneuploidy. Cells with a monosomy of chromosome 4 are resistant to 2-deoxyglucose. While this genetic strategy comes with a severe fitness cost, it has the advantage of being readily reversible when 2-deoxyglucose selection is lifted. Increased expression of the two DOG phosphatase genes on chromosome 8 confers resistance and was achieved through trisomies and tetrasomies of that chromosome. Finally, resistance was also mediated by increased expression of hexose transporters, achieved by duplication of a 117 kb region of chromosome 4 that included the HXT3, HXT6 and HXT7 genes. The frequent use of aneuploidy as a genetic strategy for drug resistance in diploid yeast and human tumors may be in part due to its potential for reversibility when selection pressure shifts.

Non-structural carbohydrates and sugar export in grapevine leaves exposed to different light regimes.

Light is a main environmental factor that determines leaf microclimate within the vine, as well as its photosynthesis and carbohydrate metabolism. This study aimed to examine the relationships between photosynthesis, carbohydrate metabolism, and the expression of related genes in leaves of grapevine grown under different radiation regimes. During the 2014/2015 growing season, an experiment was conducted on a Malbec vineyard (Vitis vinifera L.) in which four radiation exposure treatments were established on the leaves: (1) East, (2) West, (3) Sun, and (4) Shade (i.e., reduction in light intensity). Diurnal dynamics of photosynthesis and non-structural carbohydrates were measured and leaf export rates were calculated. Transcript profiles of leaf sugar transporters (VvHT1, VvHT3, VvSUC27), a sucrose phosphate synthase enzyme (VvSPS), and invertases (VvGIN1, VvCWI) were also examined. We showed that East and Sun leaves had higher daily photosynthetic and export rates than West leaves, which was mainly explained by the environmental conditions (air and leaf temperature, VPDleaf-air ) and leaf water status. Shade leaves accumulated less starch and soluble sugars than exposed leaves, which correlated with a higher expression of hexose transporters and invertases. The hypotheses that these sugars in Shade leaves would play a role as signaling molecules and/or have increased sink strength and phloem unloading are discussed. These results allow us to understand the physiological and molecular behavior of leaves exposed to different radiation regimes, which can be used to design appropriate vineyard management practices.

Mucosal Monosaccharide Transporter Expression in Newborns With Jejunoileal Atresia and Along the Adult Intestine.

In newborn rodents, intestinal maturation involves delayed fructose transporter GLUT5 expression until weaning. In jejunoileal atresia (JIA), distal intestinal segments lack exposure to amniotic fluid-containing carbohydrates. We assessed in human newborns, the impact of intestinal maturation and obstruction on mucosal monosaccharide transporter expression. Samples were obtained from 10 newborns operated for small intestinal atresia and from 17 adults undergoing gastroduodenoscopy and/or ileocolonoscopy. mRNA expression of the transporters SGLT1, GLUT1, GLUT2, GLUT5, and GLUT7 was measured in neonate samples proximal and distal of the atresia as well as in adult duodenum, ileum, and colon. Protein expression and localization was assessed using immunofluorescence. Although mRNA expression of monosaccharide transporters did not significantly differ between newborn and adult samples, luminal fructose transporter GLUT5 protein was absent in 0- to 4-day-old neonates, but expressed in adults. The mRNA expression of the 5 tested monosaccharide transporters was unchanged distal from the JIA relative to proximal. Similarly, luminal sodium-dependent glucose transporter SGLT1 and basolateral GLUT2 were expressed proximal and distal to JIA as visualized by immunofluorescence staining. With the exception of glucose transporter GLUT1 that showed highest expression levels in colon, all investigated hexose transporters showed strongest expression in duodenum, lower levels in ileum and lowest in colon. Human newborns lack small intestinal fructose transporter GLUT5 protein expression and small intestinal atresia does not affect the expression of hexose transporters.

Iron regulates hexose transporters in Schizosaccharomyces pombe.

This study focuses on the effect of iron on hexose transporters which perform glucose uptake. For this aim, we investigated the role of iron in glucose utilization and expression of hexose transporters in Schizosaccharomyces pombe. We applied different iron concentrations (1, 2, 5, 10 mM) to the cells grown up to mid-logarithmic phase. According to analysis of cell viability and morphology, we determined 2 mM and 5 mM as non-toxic and toxic doses, respectively. Besides, glucose consumption efficiency increased (1.5-fold) in the cells which were exposed to these iron concentrations. qRT-PCR analysis of hexose transporter genes showed that the expression of ght2 and ght8 genes were downregulated under both non-toxic and toxic iron conditions, but that of ght5 gene was significantly decreased only by toxic iron dose. In conclusion, it was suggested for the first time in this study that the Ght5 protein, as being high affinity hexose transporter, might play a role in sensing and signaling of iron stress.

Yeast phospholipase C is required for stability of casein kinase I Yck2p and expression of hexose transporters.

Phospholipase C (Plc1p) in Saccharomyces cerevisiae is required for normal degradation of repressor Mth1p and expression of the HXT genes encoding cell membrane transporters of glucose. Plc1p is also required for normal localization of glucose transporters to the cell membrane. Consequently, plc1Δ cells display histone hypoacetylation and transcriptional defects due to reduced uptake and metabolism of glucose to acetyl-CoA, a substrate for histone acetyltransferases. In the presence of glucose, Mth1p is phosphorylated by casein kinase I Yck1/2p, ubiquitinated by the SCFGrr1 complex and degraded by the proteasome. Here, we show that while Plc1p does not affect the function of the SCFGrr1 complex or the proteasome, it is required for normal protein level of Yck2p. Since stability of Yck1/2p is regulated by a glucose-dependent mechanism, PLC1 inactivation results in destabilization of Yck1/2p and defect in Mth1p degradation. Based on our results and published data, we propose a model in which plc1Δ mutation causes increased internalization of glucose transporters, decreased transport of glucose into the cells, and consequently decreased stability of Yck1/2p, increased stability of Mth1p and decreased expression of the HXT genes.

Improved Xylose Metabolism by a CYC8 Mutant of Saccharomyces cerevisiae.

Engineering Saccharomyces cerevisiae for the utilization of pentose sugars is an important goal for the production of second-generation bioethanol and biochemicals. However, S. cerevisiae lacks specific pentose transporters, and in the presence of glucose, pentoses enter the cell inefficiently via endogenous hexose transporters (HXTs). By means of in vivo engineering, we have developed a quadruple hexokinase deletion mutant of S. cerevisiae that evolved into a strain that efficiently utilizes d-xylose in the presence of high d-glucose concentrations. A genome sequence analysis revealed a mutation (Y353C) in the general corepressor CYC8, or SSN6, which was found to be responsible for the phenotype when introduced individually in the nonevolved strain. A transcriptome analysis revealed altered expression of 95 genes in total, including genes involved in (i) hexose transport, (ii) maltose metabolism, (iii) cell wall function (mannoprotein family), and (iv) unknown functions (seripauperin multigene family). Of the 18 known HXTs, genes for 9 were upregulated, especially the low or nonexpressed HXT10, HXT13, HXT15, and HXT16 Mutant cells showed increased uptake rates of d-xylose in the presence of d-glucose, as well as elevated maximum rates of metabolism (Vmax) for both d-glucose and d-xylose transport. The data suggest that the increased expression of multiple hexose transporters renders d-xylose metabolism less sensitive to d-glucose inhibition due to an elevated transport rate of d-xylose into the cell.IMPORTANCE The yeast Saccharomyces cerevisiae is used for second-generation bioethanol formation. However, growth on xylose is limited by pentose transport through the endogenous hexose transporters (HXTs), as uptake is outcompeted by the preferred substrate, glucose. Mutant strains were obtained with improved growth characteristics on xylose in the presence of glucose, and the mutations mapped to the regulator Cyc8. The inactivation of Cyc8 caused increased expression of HXTs, thereby providing more capacity for the transport of xylose, presenting a further step toward a more robust process of industrial fermentation of lignocellulosic biomass using yeast.

Postnatal developmental changes of the small intestinal villus height, crypt depth and hexose transporter mRNA expression in supplemental feeding and grazing goats

This trial was conducted to investigate the effects of feeding system and age on morphological development (including villus height, crypt depth, and ratio of villus height to crypt depth) and expression of hexose transporters (i.e., SGLT1, GLUT2 and GLUT5) in different segments of the small intestine of goat kids. A total of 40 Liuyang black goat kids were randomly slaughtered at 0, 7, 28, 42, 56 and 70days of age. There were two feeding systems [i.e., supplemental feeding (S) and grazing (G)] from 28 to 70days of age. Duodenal, jejunal and ileal tissues were collected to measure the villus height and crypt depth. Mucosa samples were taken to quantify mRNA or protein expression of sodium-dependent glucose-linked transporter-1 (SGLT1), facilitated glucose/fructose transporter 2 (GLUT2), and facilitated glucose transporter 5 (GLUT5). Villus height was not affected (P>0.05) by feeding system, and crypt depth was only affected (P<0.001) by feeding system within the jejunum. Moreover, villus height increased (P=0.006) with increasing age in the duodenum, whereas it decreased as age increased in the jejunum (P=0.040) and ileum (P<0.001). Additionally, the jejunal and ileal crypt depth linearly increased (P<0.001) with increasing age in both S and G groups. The feeding system had a significant effect (P<0.05) on mRNA expression of SGLT1, GLUT2 and GLUT5 in the intestine, except for GLUT2 expression within the ileum. The mRNA and protein expression of SGLT1 and the mRNA expression of GLUT2 and GLUT5 declined (P<0.001) with increasing age in the jejunum and ileum. The present results indicate that supplemental feeding at an early age is beneficial to activate expression of SGLT1, GLUT2 and GLUT5 transporters in goats for an improved ability to absorb hexose.

Tissue localization of GM-CSF receptor in bovine ovarian follicles and its role on glucose uptake by mural granulosa cells

The granulocyte-macrophage colony stimulating factor (GM-CSF) is a multifunctional cytokine implicated in proliferation, differentiation, and activation of several cell types including those involved in hematopoiesis and reproduction. In the present study, the expression of the α- and β-subunit genes of GM-CSF receptor during follicular development in cattle was assessed. The spatial association of α- and β-subunits of GM-CSF with follicle stimulating hormone receptor (FSHR) and 3β-hydroxysteroid dehydrogenase (3β-HSD), and the temporal associations with gene expression of hexose transporters (GLUTs) in granulosa cells of cattle were also evaluated. The effect of GM-CSF on the functionality of hexose transporters was also determined in an in vitro primary culture of granulosa cells. The spatial association of subunits of the GM-CSF receptor with 3β-HSD and FSHR suggests a potential steroidogenic regulation of GM-CSF in granulosa cells. Immunodetection of GLUTs and uptake kinetic assays confirmed expression and functionality of these genes for hexose transporters in granulosa cells of cattle. Treatment of granulosa cells with GM-CSF, FSH or insulin- like growth factor-I (IGF-I) alone increased 2-deoxyglucose (DOG) or 3-0-methylglucose (OMG) uptake; however, when cells were treated with various combination of these factors there were no additive effect. Unexpectedly, the combination of GM-CSF and FSH decreased DOG uptake compared to FSH treatment alone. Thus, the expression pattern of GM-CSF receptor subunit genes during follicle development in cattle and promotion of DOG and OMG uptake in granulosa cells indicate a role for GM-CSF, FSH and/or IGF-I alone in regulating granulosa cell metabolic activity, specifically by promoting glucose uptake.

Molecular and Kinetic Characterization of the Fermentative Behavior of &lt;i&gt;Saccharomyces cerevisiae&lt;/i&gt; Strains Isolated from North Patagonia

At present, Argentina does not count with a production of indigenous yeast strains with suitable technological and oenological features to be used in the regional winery industry. Isolation and molecular characterization of these microorganisms and its fermentation attributes would be relevant to the sustainable development of the activity in the country and to recognize and preserve the biodiversity of the region. Eight strains isolated from grapes and musts from the North Patagonian region and genetically identified as Saccharomyces cerevisiae, were studied for their fermentation behavior, emphasizing in hexose transport through the plasma membrane, which is the limiting step of the process. Thus, sugar consumption profiles were analyzed in different media at laboratory scale, to be subsequently applied to the fermentation of natural musts. Three of the eight initial strains were selected, named NNM10, NIF8 and NMN16 according to their fermentation profiles. The expression of hexose transporters during fermentations revealed interesting differences in the response of each strain to sugar consumption, where transporters HXT2 and HXT5 showed significant changes in expression in Patagonian strains, which are normally associated to endurance to culture stress conditions. The results obtained by combining the characteristics studied, at molecular and physiological level, are extremely encouraging. Native strain NMN16, showed a high potential for application in local winemaking. Assays carried out on a pilot scale will determine the feasibility of applying this strain with promising technological features at industrial scale.

Cooking enhances beneficial effects of pea seed coat consumption on glucose tolerance, incretin, and pancreatic hormones in high-fat-diet-fed rats.

Pulses, including dried peas, are nutrient- and fibre-rich foods that improve glucose control in diabetic subjects compared with other fibre sources. We hypothesized feeding cooked pea seed coats to insulin-resistant rats would improve glucose tolerance by modifying gut responses to glucose and reducing stress on pancreatic islets. Glucose intolerance induced in male Sprague-Dawley rats with high-fat diet (HFD; 10% cellulose as fibre) was followed by 3 weeks of HFD with fibre (10%) provided by cellulose, raw-pea seed coat (RP), or cooked-pea seed coat (CP). A fourth group consumed low-fat diet with 10% cellulose. Oral and intraperitoneal glucose tolerance tests (oGTT, ipGTT) were done. CP rats had 30% and 50% lower glucose and insulin responses in oGTT, respectively, compared with the HFD group (P < 0.05) but ipGTT was not different. Plasma islet and incretin hormone concentrations were measured. α- and β-cell areas in the pancreas and density of K- and L-cells in jejunum and ileum were quantified. Jejunal expression of hexose transporters was measured. CP feeding increased fasting glucagon-like peptide 1 and glucose-stimulated gastric inhibitory polypeptide responses (P < 0.05), but K- and L-cells densities were comparable to HFD, as was abundance of SGLT1 and GLUT2 mRNA. No significant difference in β-cell area between diet groups was observed. α-cell area was significantly smaller in CP compared with RP rats (P < 0.05). Overall, our results demonstrate that CP feeding can reverse adverse effects of HFD on glucose homeostasis and is associated with enhanced incretin secretion and reduced α-cell abundance.

Improved use of a public good selects for the evolution of undifferentiated multicellularity

We do not know how or why multicellularity evolved. We used the budding yeast, Saccharomyces cerevisiae, to ask whether nutrients that must be digested extracellularly select for the evolution of undifferentiated multicellularity. Because yeast use invertase to hydrolyze sucrose extracellularly and import the resulting monosaccharides, single cells cannot grow at low cell and sucrose concentrations. Three engineered strategies overcame this problem: forming multicellular clumps, importing sucrose before hydrolysis, and increasing invertase expression. We evolved populations in low sucrose to ask which strategy they would adopt. Of 12 successful clones, 11 formed multicellular clumps through incomplete cell separation, 10 increased invertase expression, none imported sucrose, and 11 increased hexose transporter expression, a strategy we had not engineered. Identifying causal mutations revealed genes and pathways, which frequently contributed to the evolved phenotype. Our study shows that combining rational design with experimental evolution can help evaluate hypotheses about evolutionary strategies. DOI:http://dx.doi.org/10.7554/eLife.00367.001.

Comparative expression of hexose transporters (SGLT1, GLUT1, GLUT2 and GLUT5) throughout the mouse gastrointestinal tract

Hexose transporters play a pivotal role in the absorption of food-derived monosaccharides in the gastrointestinal tract. Although a basic knowledge of the hexose transporters has already been gained, their detailed distribution and comparative intensities of expression throughout the gastrointestinal tract have not been fully elucidated. In this study, we quantitatively evaluated the expression of SGLT1, GLUT1, GLUT2, and GLUT5 by in situ hybridization and real-time PCR techniques using a total of 28 segments from the gastrointestinal tract of 9-week-old mice. GLUT2 and GLUT5 mRNA expressions were detected predominantly from the proximal to middle parts of the small intestine, showing identical expression profiles, while SGLT1 mRNA was expressed not only in the small intestine but also in the large intestine. Notably, GLUT1 mRNA was expressed at a considerable level in both the stomach and large intestine but was negligible in the small intestine. Immunohistochemistry demonstrated the polarized localization of hexose transporters in the large intestine: SGLT1 on the luminal surface and GLUT1 on the basal side of epithelial cells. The present study provided more elaborate information concerning the localization of hexose transporters in the small intestine. Furthermore, this study revealed the significant expression of glucose transporters in the large intestine, suggesting the existence of the physiological uptake of glucose in that location in mice.

Increased hexose transport in the roots of tomato plants submitted to prolonged hypoxia

We investigated the effects of prolonged hypoxia on the sugar uptake in tomato (Solanum lycopersicum L. var. MP-1) roots. Hydroponic cultures of whole tomato plants were submitted to hypoxic treatment for 1 week, and the roots were analyzed for sugar concentrations, hexose uptake and hexose transporter expression level. Contrary to what has been observed after anoxic shock or short-term hypoxic treatment, we show that sugar concentrations increase and hexose uptake is up-regulated in the roots after 1 week of hypoxic treatment. Increased hexose transport is concomitant with the induction of the hexose transporter gene LeHT2. These responses may be due either to a direct effect of low O(2) supply, or to a secondary effect associated with the increase in sugar concentrations, which, typically, develops in most hypoxic plants.

Expression and function of intestinal hexose transporters after small intestinal denervation

The role of neural regulation in expression and function of intestinal hexose transporters is unknown. The aim of this study is to determine the role of intestinal innervation in gene expression and function of the membrane hexose transporters, SGLT1, GLUT2, and GLUT5 in the enterocyte. We hypothesize that denervation of the small intestine decreases expression of hexose transporters, which leads to decreased glucose absorption. Six groups of Lewis rats were studied (n = 6 each) as follows: control, 1 week after sham laparotomy, 1 and 8 weeks after syngeneic (no immune rejection) orthotopic small-bowel transplantation (SBT) (SBT1 and SBT8) to induce complete extrinsic denervation, and 1 and 8 weeks after selective disruption of intrinsic neural continuity to jejunoileum by gut transection and reanastomosis (T/A1 and T/A8). All tissue was harvested between 8 AM and 10 AM. In duodenum, jejunum, and ileum, mucosal messenger RNA (mRNA) levels were quantitated by real-time polymerase chain reaction (PCR), protein by Western blotting, and transporter-mediated glucose absorption using the everted sleeve technique. Across the 6 groups, the relative gene expression of hexose transporter mRNA and protein levels were unchanged, and no difference in transporter-mediated glucose uptake was evident in any region. The glucose transporter affinity (K(m)) and functional transporter levels (V(max)) calculated for duodenum and jejunum showed no difference among the 6 groups. Baseline regulation of hexose transporter function is not mediated tonically by intrinsic or extrinsic neural continuity to the jejunoileum.

Clay ingestion enhances intestinal triacylglycerol hydrolysis and non-esterified fatty acid absorption

Consumption by animals and humans of earthy materials such as clay is often related to gut pathologies. Our aim was to determine the impact of kaolinite ingestion on glucose and NEFA transport through the intestinal mucosa. The expression of hexose transporters (Na/glucose co-transporter 1 (SGLT1), GLUT2, GLUT5) and of proteins involved in NEFA absorption (fatty acid transporter/cluster of differentiation 36 (FAT/CD36), fatty acid transport protein 4 (FATP4) and liver fatty acid binding protein (L-FABP)) was measured (1) in rats whose jejunum was perfused with a solution of kaolinite, and (2) in rats who ate spontaneously kaolinite pellets during 7 and 28 d. Also, we determined TAG and glucose absorption in the kaolinite-perfused group, and pancreatic lipase activity, gastric emptying and intestinal transit in rats orally administered with kaolinite. Glucose absorption was not affected by kaolinite perfusion or ingestion. However, kaolinite induced a significant increase in intestinal TAG hydrolysis and NEFA absorption. The cytoplasmic expression of L-FABP and FATP4 also increased due to kaolinite ingestion. NEFA may enter the enterocytes via endocytosis mainly since expression of NEFA transporters in the brush-border membrane was not affected by kaolinite. After uptake, rapid binding of NEFA by L-FABP and FATP4 could act as an intracellular NEFA buffer to prevent NEFA efflux. Increased TAG hydrolysis and NEFA absorption may be due to the adsorption properties of clay and also because kaolinite ingestion caused a slowing down of gastric emptying and intestinal transit.

Hexose Transporter Expression and Function in Mouse Small Intestine: Role of Diurnal Rhythm

BackgroundExpression and function of hexose transporters vary diurnally in rat small intestine; however, this subject remains unexplored in mice. AimThe aim of the study was to investigate the diurnal expression and function of hexose transporters SGLT1, GLUT2, and GLUT5 in mouse small bowel. MethodsTwenty-four c57bl6 mice maintained in a 12-h light/dark room (6 am–6 pm) were sacrificed at 9 am, 3 pm, 9 pm, and 3 am (n = 6 each). In duodenal, jejunal, and ileal mucosa, total cellular mRNA and protein levels were quantitated by real-time PCR and semiquantitative Western blotting, respectively. The everted sleeve technique measured transporter-mediated glucose uptake at 9 am and 9 pm. ResultsmRNA expression of SGLT1, GLUT2, and GLUT5 varied diurnally in all three intestinal segments (p ≤ 0.03). SGLT1, GLUT2, and GLUT5 protein levels varied diurnally in duodenum and jejunum (p < 0.05) but not in ileum. Transporter-mediated glucose uptake was greater at 9 pm than 9 am (p ≤ 0.04) in all three segments. Vmax was greater in duodenum (10 vs 6 nmol/cm/s) and jejunum (8 vs 5 nmol/cm/s) at 9 pm compared to 9 am (p = 0.01); Km remained unchanged. SummarymRNA levels of intestinal hexose transporters varied diurnally. Protein levels peaked 6–12 h later during dark cycle when >70% of food intake occurred; glucose transport followed a similar pattern with increased uptake at 9 pm. ConclusionHexose transporter expression and function vary diurnally with nocturnal feeding patterns of mice.

Fructose the odd man out. Why is the genomic control of intestinal GLUT5 expression different?

Fructose the odd man out. Why is the genomic control of intestinal GLUT5 expression different?

27. Induction of Diurnal Expression of Intestinal Hexose Transporter SGLT1 in Rat Ileum After Massive Small Bowel Resection

Diurnal patterns in gene expression (mRNA protein) of the intestinal hexose transporters sodium glucose transporter 1 (SGLT1) and glucose transporters-2 and −5 (GLUT2 and GLUT5) are well-established in the rat duodenum and jejunum. In contrast, in ileum, mRNA but not protein expression varies diurnally. We hypothesized that diurnal expressions of intestinal hexose transporters are inducible in the ileum after massive proximal small bowel resection. Aim: To determine whether 70% jejunoileal resection can induce a diurnal rhythm in protein expression of hexose transporters. Methods: Diurnal expressions of mRNA (SGLT1, GLUT2, GLUT5) and protein (SGLT1) were studied in ileum of rats 1 and 8 wk after 70% mid-small bowel resection at four time points (3AM, 9AM, 3PM, and 9PM; n=6 rats at each time point; 24 rats were studied similarly at 1 wk after sham celiotomy with bowel manipulation only. Mucosal scrapings of rat ileum were obtained. RT-PCR was used to measure mRNA, and protein levels were determined by semi-quantitative Western blotting. Both RNA and protein levels are expressed as a ratio to the housekeeping gene GAPDH for standardization. Continuous data (weight) are x±SEM. Results: At 1 wk after 70% resection, rats lost 5±1% body weight but by 8 wk had gained 48±4% over preoperative weight. During the postoperative period, rats continued to eat primarily at night time (65% to 74% intake 6PM to 6AM). Our previous studies in normal rats showed that mRNA of SGLT1 peaked at 9PM (3.1 fold), but protein levels had no diurnal variation (Surgery, 2007). Similarly, this pattern persisted in sham-operated rats 1 wk postoperatively (p<0.03). In rats 1 wk after 70% jejunoileal resection, SGLT1 mRNA levels continued to demonstrate a diurnal rhythm with peak expression at 9PM in the remnant ileum (p<0.002); however, 70% resection was also associated with a diurnal rhythm of SGLT1 protein expression in the remnant ileum (peak expression at 9PM, p<0.03). The diurnal rhythms in RNA and protein expression disappeared in the remnant ileum 8 wk after resection (p≤0.08). mRNA for GLUT2 varied similarly to SGLT1, while mRNA for GLUT5 continued to cycle diurnally at both 1 and 8 wk postoperatively (p<0.003). Protein data for GLUT2 and GLUT5 are pending. Summary: Massive (70%) mid-small bowel resection induced a dirunal rhythm in SGLT1 protein expression in the remnant ileum that disappeared by 8 wk postoperatively. Conclusion: Ileum responds early on to the effects of extensive small bowel resection (? more intraluminal nutrients) by adopting a diurnal expression in SGLT1 protein via a post-translational process; chronic adaptation reverses this diurnal variation of SGLT1 gene and protein expression in the remnant ileum. Loss of diurnal variation after 8 wk suggests that other mechanisms, such as jejunal mucosal hyperplasia, are activated because of loss of absorptive surface to increase absorption proximally via intestinal adaptation.

Coordinated, diurnal hexose transporter expression in rat small bowel: Implications for small bowel resection

Hexose transporter mRNA and protein levels follow a diurnal rhythm in rat jejunum. Their coordinated expression and resultant function throughout the small bowel is not well understood. We hypothesized that hexose transporter levels and glucose absorption follow a coordinated, site-specific diurnal rhythm in rat duodenum and jejunum, but not in ileum. Sprague-Dawley rats were housed in a strictly maintained, 12-h, light/dark room [light 6 am to 6 pm] with free access to water and chow. Mucosa was harvested from duodenum, jejunum, and ileum at 3 am, 9 am, 3 pm, and 9 pm, and full thickness 1-cm segments were harvested at 9 am, and 9 pm (n = 6 for each segment at each time point). mRNA levels were determined by reverse-transcription, real-time polymerase chain reaction (n > or = 5), protein levels by semiquantitative Western blotting (n > or = 5), and transporter-mediated glucose uptake by everted sleeve technique (n = 6). mRNA levels of SGLT1 and GLUT5 followed a temporally coordinated, diurnal rhythm in all 3 segments (P < .01), while mRNA for GLUT2 and protein levels for SGLT1 and GLUT2 varied diurnally only in duodenum and jejunum (P > .05) but not in ileum (P > .10). SGLT1 and GLUT5 mRNA induction decreased aborally. Baseline SGLT1 and GLUT5 mRNA levels and SLGT1 and GLUT2 protein levels did not vary aborally (P > .05 for all). GLUT2 mRNA baseline levels were decreased in ileum (P < .01). Glucose uptake varied diurnally in duodenum and jejunum with no difference in ileum. Transporter-mediated glucose uptake was greater in duodenum and jejunum compared with ileum. Regulation of hexose absorption in rat small bowel seems to be site-specific and mediated by multiple mechanisms.

P44

Background: In rat small intestine, mRNA and protein expression levels of hexose transporters follow a diurnal variation. Whether a diurnal rhythm exists in mice is unknown. Aim: To investigate diurnal variation in expression levels of SGLT1, GLUT2 and GLUT5 mRNA and protein in mouse duodenum, jejunum, and ileum. Hypothesis: Hexose transporter expression exhibits diurnal rhythm in mouse small intestine. Methods: c57bl6 mice (n=24) maintained in a 12 hour light/dark room (light from 6AM to 6PM) had free access to mouse chow and water.