scholarly journals The sweet life: diet sugar concentration influences paracellular glucose absorption

2008 ◽  
Vol 4 (5) ◽  
pp. 530-533 ◽  
Author(s):  
Kathryn R Napier ◽  
Cromwell Purchase ◽  
Todd J McWhorter ◽  
Susan W Nicolson ◽  
Patricia A Fleming
Keyword(s):  
Glucose Absorption ◽  
Paracellular Permeability ◽  
Sugar Concentration ◽  
Dynamic State ◽  
Intestinal Lumen ◽  
Future Studies ◽  
Relative Contribution ◽  
Rapid Absorption ◽  
Paracellular Absorption ◽  
Total Glucose

Small birds and bats face strong selection pressure to digest food rapidly in order to reduce digesta mass carried during flight. One mechanism is rapid absorption of a high proportion of glucose via the paracellular pathway (transfer between epithelial cells, not mediated by transporter proteins). Intestinal paracellular permeability to glucose was assessed for two nectarivorous passerines, the Australian New Holland honeyeater ( Phylidonyris novaehollandiae ) and African white-bellied sunbird ( Cinnyris talatala ) by measuring the bioavailability of radiolabelled, passively absorbed l -glucose. Bioavailability was high in both species and increased with diet sugar concentration (honeyeaters, 37 and 81% and sunbirds, 53 and 71% for 250 and 1000 mmol l −1 sucrose diets, respectively). We conclude that the relative contribution of paracellular to total glucose absorption increases with greater digesta retention time in the intestine, and paracellular absorption may also be modulated by factors such as intestinal lumen osmolality and interaction with mediated glucose uptake. The dynamic state of paracellular absorption should be taken into account in future studies.

Paracellular glucose transport plays a minor role in the unanesthetized dog

1999 ◽  
Vol 276 (3) ◽  
pp. G789-G794 ◽  
Author(s):  
John S. Lane ◽  
Edward E. Whang ◽  
David A. Rigberg ◽  
Oscar J. Hines ◽  
David Kwan ◽  
...  
Keyword(s):  
Water Absorption ◽  
Infusion Pump ◽  
Glucose Absorption ◽  
Paracellular Transport ◽  
Constant Infusion ◽  
Minor Role ◽  
Solvent Drag ◽  
Relative Contribution ◽  
High Concentrations ◽  
Total Glucose

Traditionally, intestinal glucose absorption was thought to occur through active, carrier-mediated transport. However, proponents of paracellular transport have argued that previous experiments neglected effects of solvent drag coming from high local concentrations of glucose at the brush-border membrane. The purpose of this study was to evaluate glucose absorption in the awake dog under conditions that would maximize any contribution of paracellular transport. Jejunal Thiry-Vella loops were constructed in six female mongrel dogs. After surgical recovery, isotonic buffers containingl-glucose as the probe for paracellular permeability were given over 2-h periods by constant infusion pump. At physiological concentrations ofd-glucose (1–50 mM), the fractional absorption ofl-glucose was only 4–7% of total glucose absorption. Infusion of supraphysiological concentrations (150 mM) of d-glucose,d-maltose, ord-mannitol yielded low-fractional absorptions ofl-glucose (2–5%), so too did complex or nonabsorbable carbohydrates. In all experiments, there was significant fractional water absorption (5–19%), a prerequisite for solvent drag. Therefore, with even up to high concentrations of luminal carbohydrates in the presence of significant water absorption, the relative contribution of paracellular glucose absorption remained low.

scholarly journals Absorption and metabolism of glucose by the mesenteric-drained viscera of sheep fed on dried-grass or ground, maize-based diets

1985 ◽  
Vol 54 (2) ◽  
pp. 449-458 ◽  
Author(s):  
A. N. Janes ◽  
T. E. C. Weekes ◽  
D. G. Armstrong
Keyword(s):  
Small Intestine ◽  
Turnover Rate ◽  
Glucose Utilization ◽  
Venous Blood ◽  
Glucose Production ◽  
Glucose Absorption ◽  
Endogenous Glucose Production ◽  
Whole Body ◽  
Glucose Turnover ◽  
Total Glucose

1. Sheep fitted with re-entrant canulas in the proximal duodenum and terminal ileum were used to determine the amount of α-glucoside entering, and apparently disappearing from, the small intestine when either dried-grass or ground maize-based diets were fed. The fate of any α-glucoside entering the small intestine was studied by comparing the net disappearance of such a-glucoside from the small intestine with the absorption of glucose into the mesenteric venous blood.2. Glucose absorption from the small intestine was measured in sheep equipped with catheters in the mesenteric vein and carotid artery. A continuous infusion of [6-3H]glucose was used to determine glucose utilization by the mesenteric-drained viscera and the whole-body glucose turnover rate (GTR).3. The amounts of α-glucoside entering the small intestine when the dried-grass and maize-based diets were given were 13.9 (SE 1.5) and 95.4 (SE 16.2) g/24 h respectively; apparent digestibilities of such α-glucoside in the small intestine were 60 and 90% respectively.4. The net absorption of glucose into the mesenteric venous blood was —2.03 (SE 1.20) and 19.28 (SE 0.75) mmol/h for the dried-grass and maize-based diets respectively. Similarly, total glucose absorption amounted to 1.52 (SE 1.35) and 23.33 (SE 1.86) mmol/h (equivalent to 7 and 101 g/24 h respectively). These values represented 83 and 11 1% of the a-glucoside apparently disappearing from the small intestine, determined using the re-entrant cannulated sheep.5. Total glucose absorption represented 8 and 61% of the whole-body GTR for the dried-grass and maize-based diets respectively. Endogenous glucose production was significantly lower when the sheep were fed on the maize-based diet compared with the dried-grass diet.6. The mesenteric-drained viscera metabolized a small amount of glucose, equivalent to 234 and 17% of the total glucose absorbed for the dried-grass and maize-based diets respectively.7. It is concluded that a large proportion of the starch entering the small intestine of sheep given a maize-based diet is digested and absorbed as glucose, and thus contributes to the whole-body GTR.

scholarly journals Delphinidin-Rich Maqui Berry Extract (Delphinol®) Lowers Fasting and Postprandial Glycemia and Insulinemia in Prediabetic Individuals during Oral Glucose Tolerance Tests

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Jorge L. Alvarado ◽  
Andrés Leschot ◽  
Álvaro Olivera-Nappa ◽  
Ana-María Salgado ◽  
Hernán Rioseco ◽  
...  
Keyword(s):  
Glucose Tolerance ◽  
Tolerance Test ◽  
Glucose Absorption ◽  
Oral Glucose ◽  
Oral Glucose Tolerance ◽  
Postprandial Glycemia ◽  
Glucose Intake ◽  
Rice Consumption ◽  
Maqui Berry ◽  
Total Glucose

Delphinidin anthocyanins have previously been associated with the inhibition of glucose absorption. Blood glucose lowering effects have been ascribed to maqui berry (Aristotelia chilensis) extracts in humans after boiled rice consumption. In this study, we aimed to explore whether a standardized delphinidin-rich extract from maqui berry (Delphinol) affects glucose metabolism in prediabetic humans based on glycemia and insulinemia curves obtained from an oral glucose tolerance test (OGTT) after a challenge with pure glucose. Volunteers underwent four consecutive OGTTs with at least one week washout period, in which different doses of Delphinol were administered one hour before glucose intake. Delphinol significantly and dose-dependently lowered basal glycemia and insulinemia. Lower doses delayed postprandial glycemic and insulinemic peaks, while higher doses reversed this tendency. Glycemia peaks were dose-dependently lowered, while insulinemia peaks were higher for the lowest dose and lower for other doses. The total glucose available in blood was unaffected by treatments, while the total insulin availability was increased by low doses and decreased by the highest dose. Taken together, these open exploratory results suggest that Delphinol could be acting through three possible mechanisms: by inhibition of intestinal glucose transporters, by an incretin-mediated effect, or by improving insulin sensitivity.

scholarly journals Does apical membrane GLUT2 have a role in intestinal glucose uptake?

F1000Research ◽  
2014 ◽  
Vol 3 ◽  
pp. 304 ◽  
Author(s):  
Richard J. Naftalin
Keyword(s):  
Brush Border ◽  
Prolonged Exposure ◽  
Apical Membrane ◽  
Sugar Transport ◽  
Glucose Absorption ◽  
Intestinal Lumen ◽  
Sugar Transporter ◽  
Transport Component ◽  
Intestinal Glucose Absorption ◽  
Paracellular Flow

It has been proposed that the non-saturable component of intestinal glucose absorption, apparent following prolonged exposure to high intraluminal glucose concentrations, is mediated via the low affinity glucose and fructose transporter, GLUT2, upregulated within the small intestinal apical border.The evidence that the non-saturable transport component is mediated via an apical membrane sugar transporter is that it is inhibited by phloretin, after exposure to phloridzin. Since the other apical membrane sugar transporter, GLUT5, is insensitive to inhibition by either cytochalasin B, or phloretin, GLUT2 was deduced to be the low affinity sugar transport route.As in its uninhibited state, polarized intestinal glucose absorption depends both on coupled entry of glucose and sodium across the brush border membrane and on the enterocyte cytosolic glucose concentration exceeding that in both luminal and submucosal interstitial fluids, upregulation of GLUT2 within the intestinal brush border will usually stimulate downhill glucose reflux to the intestinal lumen from the enterocytes; thereby reducing, rather than enhancing net glucose absorption across the luminal surface.These states are simulated with a computer model generating solutions to the differential equations for glucose, Na and water flows between luminal, cell, interstitial and capillary compartments. The model demonstrates that uphill glucose transport via SGLT1 into enterocytes, when short-circuited by any passive glucose carrier in the apical membrane, such as GLUT2, will reduce transcellular glucose absorption and thereby lead to increased paracellular flow. The model also illustrates that apical GLUT2 may usefully act as an osmoregulator to prevent excessive enterocyte volume change with altered luminal glucose concentrations.

scholarly journals Direct and indirect cues can enable dual-adaptation, but through different learning processes

2021 ◽  
Author(s):  
Marion Forano ◽  
Raphael Schween ◽  
Jordan A Taylor ◽  
Mathias Hegele ◽  
David W Franklin
Keyword(s):  
Task Complexity ◽  
Dynamic State ◽  
Small Subset ◽  
Adaptation Studies ◽  
Dual Adaptation ◽  
Relative Contribution ◽  
Sensorimotor Transformations ◽  
Computer Mouse ◽  
Indirect Cues ◽  
Implicit And Explicit

Switching between motor tasks requires accurate adjustments for changes in dynamics (grasping a cup) or sensorimotor transformations (moving a computer mouse). Dual-adaptation studies have investigated how learning of context-dependent dynamics or transformations is enabled by sensory cues. However, certain cues, such as color, have shown mixed results. We propose that these mixed results may arise from two major classes of cues: "direct" cues, which are part of the dynamic state and "indirect" cues, which are not. We hypothesized that explicit strategies would primarily account for adaptation for an indirect color cue but would be limited to simple tasks while a direct visual separation cue would allow implicit adaptation regardless of task complexity. To test this idea, we investigated the relative contribution of implicit and explicit learning in relation to contextual cue type (colored or visually shifted workspace) and task complexity (one or eight targets) in a dual-adaptation task. We found that the visual workspace location cue enabled adaptation across conditions primarily through implicit adaptation. In contrast, we found that the color cue was largely ineffective for dual adaptation, except in a small subset of participants who appeared to use explicit strategies. Our study suggests that the previously inconclusive role of color cues in dual-adaptation may be explained by differential contribution of explicit strategies across conditions.

scholarly journals L-arabinose co-ingestion delays glucose absorption derived from sucrose in healthy men and women: a double-blind, randomized crossover trial

2021 ◽  
pp. 1-29
Author(s):  
Kenneth Pasmans ◽  
Ruth C.R. Meex ◽  
Jorn Trommelen ◽  
Joan M.G. Senden ◽  
Elaine E. Vaughan ◽  
...  
Keyword(s):  
Plasma Glucose ◽  
Glucose Production ◽  
Glucose Absorption ◽  
Endogenous Glucose Production ◽  
Dietary Interventions ◽  
Glucose Kinetics ◽  
Double Blind ◽  
Exogenous Glucose ◽  
Total Glucose ◽  
Glucose Output

Abstract Dietary interventions to delay carbohydrate digestion or absorption can effectively prevent hyperglycemia in the early postprandial phase. L-arabinose can specifically inhibit sucrase. It remains to be assessed whether co-ingestion of L-arabinose with sucrose delays sucrose digestion, attenuates subsequent glucose absorption, and impacts hepatic glucose output. In this double-blind, randomized crossover study, we assessed blood glucose kinetics following ingestion of a 200-mL drink containing 50 g sucrose with 7.5 g L-arabinose (L-ARA) or without L-arabinose (CONT) in twelve young, healthy participants (24±1 y; BMI: 22.2±0.5 kg/m2). Plasma glucose kinetics were determined by a dual stable isotope methodology involving ingestion of [U-13C6]-glucose-enriched sucrose, and continuous intravenous infusion of [6,6-2H2]-glucose. Peak glucose concentrations reached 8.18±0.29 mmol/L for CONT 30 min after ingestion. In contrast, the postprandial rise in plasma glucose was attenuated for L-ARA, because peak glucose concentrations reached 6.62±0.18 mmol/L only 60 min after ingestion. The rate of exogenous glucose appearance for L-ARA was 67 and 57% lower compared with CONT at t = 15 min and 30 min, respectively, whereas it was 214% higher at t = 150 min, indicating a more stable absorption of exogenous glucose for L-ARA compared with CONT. Total glucose disappearance during the first hour was lower for L-ARA compared with CONT (11±1 versus 17±1 g, p<0.0001). Endogenous glucose production was not differentially affected at any time point (p=0.27). Co-ingestion of L-arabinose with sucrose delays sucrose digestion, resulting in a slower absorption of sucrose-derived glucose without causing adverse effects in young, healthy adults.

scholarly journals Estimation of the Relative Contribution of Postprandial Glucose Exposure to Average Total Glucose Exposure in Subjects with Type 2 Diabetes

2016 ◽  
Vol 2016 ◽  
pp. 1-4
Author(s):  
Bo Ahrén ◽  
James E. Foley
Keyword(s):  
Type 2 Diabetes ◽  
Plasma Glucose ◽  
Glycated Haemoglobin ◽  
Small Contribution ◽  
Postprandial Plasma Glucose ◽  
Relative Contribution ◽  
Glucose Exposure ◽  
Total Glucose ◽  
Average Glucose

We hypothesized that the relative contribution of fasting plasma glucose (FPG) versus postprandial plasma glucose (PPG) to glycated haemoglobin (HbA1c) could be calculated using an algorithm developed by the A1c-Derived Average Glucose (ADAG) study group to make HbA1c values more clinically relevant to patients. The algorithm estimates average glucose (eAG) exposure, which can be used to calculate apparent PPG (aPPG) by subtracting FPG. The hypothesis was tested in a large dataset (comprising 17 studies) from the vildagliptin clinical trial programme. We found that 24 weeks of treatment with vildagliptin monotherapy (n=2523) reduced the relative contribution of aPPG to eAG from 8.12% to 2.95% (by 64%,p<0.001). In contrast, when vildagliptin was added to metformin (n=2752), the relative contribution of aPPG to eAG insignificantly increased from 1.59% to 2.56%. In conclusion, glucose peaks, which are often prominent in patients with type 2 diabetes, provide a small contribution to the total glucose exposure assessed by HbA1c, and the ADAG algorithm is not robust enough to assess this small relative contribution in patients receiving combination therapy.

scholarly journals Passage Performance of Potamodromous Cyprinids over an Experimental Low-Head Ramped Weir: The Effect of Ramp Length and Slope

2019 ◽  
Vol 11 (5) ◽  
pp. 1456 ◽  
Author(s):  
Susana Amaral ◽  
Paulo Branco ◽  
Christos Katopodis ◽  
Maria Ferreira ◽  
António Pinheiro ◽  
...  
Keyword(s):  
Cost Effective ◽  
Fish Passage ◽  
Habitat Connectivity ◽  
Intermediate Level ◽  
Fish Movements ◽  
Future Studies ◽  
Relative Contribution ◽  
Low Head ◽  
Passage Efficiency

Low-head ramped weirs are a common instream obstacle to fish movements. Fish passability of these structures, where water passes over but does not generate a waterfall, is primarily related to ramp length and slope, but their relative contribution has seldom been considered. This study aims to assess the passage performance of a potamodromous cyprinid, the Iberian barbel (Luciobarbus bocagei), negotiating an experimental ramped weir with varying ramp length (L) and slope (S). Four configurations were tested, with a constant discharge of 110 L∙s−1. Results suggest that both factors influenced passage performance of fish. Attraction efficiency (AE) increased with increasing L and S, whereas the number of successes (N) and passage efficiency (PE) decreased upon increasing L. For S, it was found that both N and PE peaked at the intermediate level (20%). These results suggest that configurations with the lowest slopes may not necessarily be the best option because they may be less attractive for the fish and their demand for space is higher. Higher slopes (but not excessive) could be more attractive to fish, less space-demanding, and therefore, more cost-effective. Future studies should investigate how discharge and boulder placement influence fish passage across ramped weirs, to improve habitat connectivity.

scholarly journals Reinvestigating the Determinants of Lifelong Learning: Can Pedagogy for Critical Thinking Contribute to Developing Lifelong Learners?

2015 ◽  
Vol 7 (1) ◽  
pp. 1-14
Author(s):  
Maryam Homayounzadeh
Keyword(s):  
Critical Thinking ◽  
Potential Effect ◽  
Freshman English ◽  
Lifelong Learners ◽  
Future Studies ◽  
Relative Contribution ◽  
English Majors ◽  
Determining Factor ◽  
Qualitative Analyses ◽  
Intrinsic Motivation Inventory

Abstract The aim of the current study is to investigate practically the determining factor(s) affecting the students’ inclination to become lifelong learners and further to verify the potential effect of pedagogy for critical thinking to play a significant role in this respect. Participants in the study were 80 freshman English majors, found mostly through the Intrinsic Motivation Inventory (IMI) questionnaire to be amotivated as learners. Primarily, significant variables, identified in the literature to affect the students’ inclination to grow as lifelong learners, were specified. The criteria were applied in practice to investigate their relative contribution in making a group of amotivated freshman English majors motivated as lifelong learners. Various instruments and materials from questionnaires to student writings were used to collect data concerning the identified variables so as to identify through both quantitative and qualitative analyses the most determining one(s) in educating lifelong learners. The results suggested critical thinking as the most consequential variable involved. Implications of the study for pedagogy in higher education were discussed and questions were raised for future studies to take into account.

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