Measurement of resistance of barriers to solute transport in vivo in rat jejunum

1986 ◽  
Vol 250 (6) ◽  
pp. G727-G735 ◽  
Author(s):  
H. Westergaard ◽  
K. H. Holtermuller ◽  
J. M. Dietschy
Keyword(s):  
Glucose Transport ◽  
Diffusion Barrier ◽  
Saturated Fatty Acids ◽  
Water Layer ◽  
Rat Jejunum ◽  
Transport Parameters ◽  
Live Animal ◽  
Diffusion Limited ◽  
Barrier Resistance

Assessment of intestinal absorptive function requires techniques for correcting transport constants for diffusion barrier resistance. These studies were done to develop such techniques for use in vivo. In one method the functional thickness of the unstirred water layer (d) in rat jejunum was quantitated electrically, and its minimal surface area (Sw) was measured directly. From these values the diffusion barrier resistance (d/Sw) decreased from 0.041 to 0.022 as the perfusion rate of the intestine was increased from 1.5 to 15 ml/min. In the second method apparent passive permeability coefficients (*P) were measured for a series of saturated fatty acids, and these increased with chain length. However, at the longest chain lengths tested, *P became proportional to their free diffusion coefficients, indicating that uptake was limited by the rate of diffusion up to the microvillus surface. From the rates of uptake of such diffusion-limited probes, the diffusion barrier resistance was again calculated and found to decrease from 0.041 to 0.022 as the rate of perfusion was increased from 1.5 to 15 ml/min. Over this same range of perfusion rates, the apparent Michaelis constant (*Km) for D-glucose transport decreased from 18.2 to 10.0 mM. Using either set of resistance terms and these apparent Km values, the true Km value for glucose transport in vivo was found to equal 0.8 mM when the barrier resistance was extrapolated to zero. Thus these data indicate that diffusion-limited probes can be utilized to measure unstirred layer resistance in the intestine of a live animal so that absolute transport parameters can be determined in vivo in experimental animals and, presumably, in humans.

Intestinal glucose transport using perfused rat jejunum in vivo: model analysis and derivation of corrected kinetic constants

1989 ◽  
Vol 76 (4) ◽  
pp. 403-413 ◽  
Author(s):  
Jonathan B. Meddings ◽  
Henrik Westergaard
Keyword(s):  
Linear Regression ◽  
Glucose Transport ◽  
Diffusion Barrier ◽  
Transport Model ◽  
Kinetic Constants ◽  
Rat Jejunum ◽  
Single Carrier ◽  
Barrier Resistance ◽  
And Diffusion

1. The transport model that best describes intestinal glucose transport in vivo remains unsettled. Three models have been proposed: (1) a single carrier, (2) a single carrier plus passive diffusion, and (3) a two-carrier system. The objectives of the current studies were to define the transport model that best fits experimental data and to devise methods to obtain the kinetic constants, corrected for diffusion barrier resistance, with this model. 2. Intestinal glucose uptake was measured during perfusion of rat jejunum in vivo over a wide range of perfusate concentrations and diffusion barrier resistance was determined under identical experimental conditions. The data were fitted to the transport equations that describe the three models with appropriate diffusion barrier corrections, and the kinetic constants were derived by non-linear regression techniques. The fit of each model to the data was assessed using six statistical tests, five of which favoured a model described by a single carrier and passive diffusion. 3. The main conclusions of these studies are: (1) kinetic constants uncorrected for diffusion barrier resistance are seriously in error; (2) values for the derived kinetic constants are strongly dependent on the transport model selected for the data analysis which underscores the need for rigorous model analysis; (3) corrected kinetic constants may be obtained by either non-linear regression or by a simpler graphical analysis once the correct transport model has been selected and diffusion barrier resistance determined; (4) only corrected kinetic constants should be used for inter-species comparisons or to study the effect of specific interventions on intestinal glucose transport.

Vitamin K1 intestinal absorption in vivo: influence of luminal contents on transport.

1977 ◽  
Vol 232 (1) ◽  
pp. E69 ◽  
Author(s):  
D Hollander ◽  
E Rim ◽  
K S Muralidhara
Keyword(s):  
Intestinal Absorption ◽  
Absorption Rate ◽  
Saturated Fatty Acids ◽  
Sodium Taurocholate ◽  
Water Layer ◽  
Vitamin K1 ◽  
Unstirred Water Layer ◽  
Saturation Kinetics ◽  
Nonionic Detergent

Intestinal absorption of [3H]phylloquinone was investigated in the unanesthetized rat by the use of a technique of recirculating perfused isolated intestinal segments. Apparent saturation kinetics were found as the concentration of the vitamin in the perfusate was increased in a stepwise fashion from 15 nM to 300 muM. Alkalinization of the perfusate or the addition of 2.5 mM linoleic acid to the perfusate caused a significant (P less than 0.05) decrease in the absorption rate of phylloquinone. Modifications in the perfusate concentration of sodium taurocholate, the substitution of a nonionic detergent (Pluronic F-68) for sodium taurocholate, the addition of medium- and long-chain saturated fatty acids, or the addition of vitamins K2 and K3 to the perfusate did not alter the absorption rate of the vitamin. Decreasing the thickness of the unstirred water layer by increasing the perfusion rate caused a significant increase in phylloquinone absorption rate. In vivo absorption of vitamin K1 appears to be mediated by an energy requiring saturable transport mechanism. The composition of the perfusate, its pH, and its rate of flow are all important determinants of vitamin K1 absorption rate.

A compartmental model to quantitate in vivo glucose transport in the human forearm

1989 ◽  
Vol 257 (6) ◽  
pp. E943-E958 ◽  
Author(s):  
C. Cobelli ◽  
M. P. Saccomani ◽  
E. Ferrannini ◽  
R. A. Defronzo ◽  
R. Gelfand ◽  
...  
Keyword(s):  
Glucose Transport ◽  
Compartmental Model ◽  
Nonlinear Least Squares ◽  
Normal Subjects ◽  
Glucose Disposal ◽  
Good Precision ◽  
Transport Parameters ◽  
Tracer Injection ◽  
Identifiability Analysis

Glucose transport is a critical step in the control of glucose disposal that, until presently, has not been quantitated in vivo in humans. We have employed the perfused forearm and euglycemic insulin-clamp techniques in combination with a dual-tracer injection to measure basal and insulin-mediated glucose transport in six normal subjects. L-[3H]glucose, which is not transported, was used to trace extracellular glucose kinetics; 3-O-[14C]-methyl-D-glucose, transportable but not metabolizable, was used to monitor glucose movement across the cell membrane. After bolus intra-arterial injection of the two tracers, plasma samples were obtained every 15-30 s for 10 min from a deep forearm vein to determine the washout curves. A linear compartmental model was developed that accounts for blood flow heterogeneity. It consists of three parallel, two-compartment chains merging into the sampling compartment to which cellular compartments are appended. A priori identifiability analysis was performed. The uniquely identifiable parameterization includes the transport rate constants of glucose into and out of the cell. The model was identified using nonlinear least-squares parameter estimation. Transport parameters are estimated with very good precision, and their reproducibility is satisfactory. The model also allows the estimation of the mean arteriovenous transit times of both the extracellular and the transported tracer. The compartmental model provides a novel approach to investigate glucose transport in vivo in humans.

Insulin modulates rat intestinal glucose transport: effect of hypoinsulinemia and hyperinsulinemia

1989 ◽  
Vol 256 (5) ◽  
pp. G911-G918 ◽  
Author(s):  
H. Westergaard
Keyword(s):  
Glucose Transport ◽  
Plasma Insulin ◽  
Diabetic Rats ◽  
Kinetic Constants ◽  
Maximal Velocity ◽  
Intestinal Epithelial ◽  
Intravenous Glucose ◽  
Uptake Rates ◽  
Barrier Resistance

The current studies were designed to evaluate the role of plasma insulin and glucose as regulators of intestinal glucose transport in vivo. Initially, rats received either intravenous glucose infusion or intraperitoneal streptozotocin to induce sustained hyperglycemic hyperinsulinemia or hyperglycemic hypoinsulinemia. Net jejunal uptake rates of glucose were measured in vivo at several perfusate concentrations, and the kinetic constants, corrected for diffusion barrier resistance, were derived. Maximal velocity (Jmax) was increased 1.8-fold by hyperglycemic hyperinsulinemia and 2.6-fold by hyperglycemic hypoinsulinemia compared with controls, whereas Km and passive permeability of glucose were unchanged. The rate of L-proline uptake at saturation conditions was not increased by these experimental interventions. The corrected kinetic constants for jejunal glucose transport in streptozotocin diabetic rats kept normoglycemic and normoinsulinemic with insulin were similar to controls. Finally, induction of normoglycemic hyperinsulinemia by intravenous glucose-insulin infusion increased Jmax 1.8-fold, similar to hyperglycemic hyperinsulinemia, but induction of hyperglycemic normoinsulinemia by intravenous glucose-somatostatin infusion did not change Jmax. In conclusion, changes in plasma insulin but not glucose concentration cause a specific and reversible increase in Jmax of intestinal glucose transport. Hypoinsulinemia is a more potent signal than hyperinsulinemia. The membrane level, microvillus or basolateral, at which insulin induces an increased number of glucose transporters in intestinal epithelial cells remains to be defined.

COVID-19: Opinion in Prevention and dietary based management hypothesis

Coronaviruses ◽  
2020 ◽  
Vol 01 ◽  
Author(s):  
Ashraf Talaat Youssef
Keyword(s):  
Fatty Acids ◽  
Saturated Fatty Acids ◽  
Lung Damage ◽  
Gastric Aspirate ◽  
Enveloped Viruses ◽  
Multiple Organs ◽  
Fold Reduction ◽  
Antiviral Activities

The pandemic of COVID-19 had started in Wuhan city china in late 2019 with a subsequent worldwide spread. The viral infection can seriousely affect multiple organs mainly lungs, kidneys, heart, liver and brain and may lead to respiratory, renal, cardiac or hepatic failure.Vascular thrombosis of unexplained mechanism that may lead to widespread blood clots in multiple organs and cytokine storms that result of overstimulation of the immune system subsequent of lung damage may lead to sudden decompensation due to hypotension and more damage to liver, kidney, brain or lungs.Until now no drug had proved efficient in getting rid of the problem and controlling the pandemic mainly depends on preventive measures.Many preventive measures can be considered to prevent the worldwide spread of viral transmission. Polyunsaturated long chain fatty acids (PUFAs) and the medium chain saturated fatty acids (MCSFAs) and their corresponding monoglycerides had high antiviral activities against the enveloped viruses which reach to more than 10,000 -fold reduction in the viral titres in vitro and in vivo after testing of its gastric aspirate, and can contribute to the systemic immunity against the enveloped viruses.

scholarly journals Functional expression, quantification and cellular localization of the Hxt2 hexose transporter of Saccharomyces cerevisiae tagged with the green fluorescent protein

1999 ◽  
Vol 339 (2) ◽  
pp. 299-307 ◽  
Author(s):  
Arthur L. KRUCKEBERG ◽  
Ling YE ◽  
Jan A. BERDEN ◽  
Karel van DAM
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Green Fluorescent Protein ◽  
Glucose Transport ◽  
Cellular Localization ◽  
Fluorescent Protein ◽  
Hexose Transporter ◽  
High Concentrations ◽  
Green Fluorescent

The Hxt2 glucose transport protein of Saccharomyces cerevisiae was genetically fused at its C-terminus with the green fluorescent protein (GFP). The Hxt2-GFP fusion protein is a functional hexose transporter: it restored growth on glucose to a strain bearing null mutations in the hexose transporter genes GAL2 and HXT1 to HXT7. Furthermore, its glucose transport activity in this null strain was not markedly different from that of the wild-type Hxt2 protein. We calculated from the fluorescence level and transport kinetics that induced cells had 1.4×105 Hxt2-GFP molecules per cell, and that the catalytic-centre activity of the Hxt2-GFP molecule in vivo is 53 s-1 at 30 °C. Expression of Hxt2-GFP was induced by growth at low concentrations of glucose. Under inducing conditions the Hxt2-GFP fluorescence was localized to the plasma membrane. In a strain impaired in the fusion of secretory vesicles with the plasma membrane, the fluorescence accumulated in the cytoplasm. When induced cells were treated with high concentrations of glucose, the fluorescence was redistributed to the vacuole within 4 h. When endocytosis was genetically blocked, the fluorescence remained in the plasma membrane after treatment with high concentrations of glucose.

scholarly journals Polyunsaturated ω-3 fatty acids inhibit ACE2-controlled SARS-CoV-2 binding and cellular entry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anna Goc ◽  
Aleksandra Niedzwiecki ◽  
Matthias Rath
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Eicosapentaenoic Acid ◽  
Linolenic Acid ◽  
Cathepsin L ◽  
Saturated Fatty Acids ◽  
Monounsaturated Fatty Acids ◽  
In Vivo Experiments ◽  
Lipid Compounds

AbstractThe strain SARS-CoV-2, newly emerged in late 2019, has been identified as the cause of COVID-19 and the pandemic declared by WHO in early 2020. Although lipids have been shown to possess antiviral efficacy, little is currently known about lipid compounds with anti-SARS-CoV-2 binding and entry properties. To address this issue, we screened, overall, 17 polyunsaturated fatty acids, monounsaturated fatty acids and saturated fatty acids, as wells as lipid-soluble vitamins. In performing target-based ligand screening utilizing the RBD-SARS-CoV-2 sequence, we observed that polyunsaturated fatty acids most effectively interfere with binding to hACE2, the receptor for SARS-CoV-2. Using a spike protein pseudo-virus, we also found that linolenic acid and eicosapentaenoic acid significantly block the entry of SARS-CoV-2. In addition, eicosapentaenoic acid showed higher efficacy than linolenic acid in reducing activity of TMPRSS2 and cathepsin L proteases, but neither of the fatty acids affected their expression at the protein level. Also, neither reduction of hACE2 activity nor binding to the hACE2 receptor upon treatment with these two fatty acids was observed. Although further in vivo experiments are warranted to validate the current findings, our study provides a new insight into the role of lipids as antiviral compounds against the SARS-CoV-2 strain.

scholarly journals Current Knowledge on Functionality and Potential Therapeutic Uses of Donkey Milk

Animals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1382
Author(s):  
Mina Martini ◽  
Iolanda Altomonte ◽  
Domenico Tricò ◽  
Riccardo Lapenta ◽  
Federica Salari
Keyword(s):  
Animal Models ◽  
Randomized Clinical Trials ◽  
Current Knowledge ◽  
Saturated Fatty Acids ◽  
Cow Milk ◽  
Donkey Milk ◽  
Alpha Linolenic Acid ◽  
High Concentration

The increase of knowledge on the composition of donkey milk has revealed marked similarities to human milk, which led to a growing number of investigations focused on testing the potential effects of donkey milk in vitro and in vivo. This paper examines the scientific evidence regarding the beneficial effects of donkey milk on human health. Most clinical studies report a tolerability of donkey milk in 82.6–98.5% of infants with cow milk protein allergies. The average protein content of donkey milk is about 18 g/L. Caseins, which are main allergenic components of milk, are less represented compared to cow milk (56% of the total protein in donkey vs. 80% in cow milk). Donkey milk is well accepted by children due to its high concentration of lactose (about 60 g/L). Immunomodulatory properties have been reported in one study in humans and in several animal models. Donkey milk also seems to modulate the intestinal microbiota, enhance antioxidant defense mechanisms and detoxifying enzymes activities, reduce hyperglycemia and normalize dyslipidemia. Donkey milk has lower calorie and fat content compared with other milks used in human nutrition (fat ranges from 0.20% to 1.7%) and a more favourable fatty acid profile, being low in saturated fatty acids (3.02 g/L) and high in alpha-linolenic acid (about 7.25 g/100 g of fat). Until now, the beneficial properties of donkey milk have been mostly related to whey proteins, among which β-lactoglobulin is the most represented (6.06 g/L), followed by α-lactalbumin (about 2 g/L) and lysozyme (1.07 g/L). So far, the health functionality of donkey milk has been tested almost exclusively on animal models. Furthermore, in vitro studies have described inhibitory action against bacteria, viruses, and fungi. From the literature review emerges the need for new randomized clinical trials on humans to provide stronger evidence of the potential beneficial health effects of donkey milk, which could lead to new applications as an adjuvant in the treatment of cardiometabolic diseases, malnutrition, and aging.

scholarly journals N-palmitoyl-D-glucosamine, A Natural Monosaccharide-Based Glycolipid, Inhibits TLR4 and Prevents LPS-Induced Inflammation and Neuropathic Pain in Mice

2021 ◽  
Vol 22 (3) ◽  
pp. 1491 ◽  
Author(s):  
Monica Iannotta ◽  
Carmela Belardo ◽  
Maria Consiglia Trotta ◽  
Fabio Arturo Iannotti ◽  
Rosa Maria Vitale ◽  
...  
Keyword(s):  
Sciatic Nerve ◽  
Inflammatory Cytokines ◽  
Lipid A ◽  
Saturated Fatty Acids ◽  
Structural Similarity ◽  
Antagonistic Activity ◽  
Critical Function ◽  
Anti Inflammatory

Toll-like receptors (TLRs) are key receptors through which infectious and non-infectious challenges act with consequent activation of the inflammatory cascade that plays a critical function in various acute and chronic diseases, behaving as amplification and chronicization factors of the inflammatory response. Previous studies have shown that synthetic analogues of lipid A based on glucosamine with few chains of unsaturated and saturated fatty acids, bind MD-2 and inhibit TLR4 receptors. These synthetic compounds showed antagonistic activity against TLR4 activation in vitro by LPS, but little or no activity in vivo. This study aimed to show the potential use of N-palmitoyl-D-glucosamine (PGA), a bacterial molecule with structural similarity to the lipid A component of LPS, which could be useful for preventing LPS-induced tissue damage or even peripheral neuropathies. Molecular docking and molecular dynamics simulations showed that PGA stably binds MD-2 with a MD-2/(PGA)3 stoichiometry. Treatment with PGA resulted in the following effects: (i) it prevented the NF-kB activation in LPS stimulated RAW264.7 cells; (ii) it decreased LPS-induced keratitis and corneal pro-inflammatory cytokines, whilst increasing anti-inflammatory cytokines; (iii) it normalized LPS-induced miR-20a-5p and miR-106a-5p upregulation and increased miR-27a-3p levels in the inflamed corneas; (iv) it decreased allodynia in peripheral neuropathy induced by oxaliplatin or formalin, but not following spared nerve injury of the sciatic nerve (SNI); (v) it prevented the formalin- or oxaliplatin-induced myelino-axonal degeneration of sciatic nerve. SIGNIFICANCE STATEMENT We report that PGA acts as a TLR4 antagonist and this may be the basis of its potent anti-inflammatory activity. Being unique because of its potency and stability, as compared to other similar congeners, PGA can represent a tool for the optimization of new TLR4 modulating drugs directed against the cytokine storm and the chronization of inflammation.

scholarly journals Using the Microwell-mesh to culture microtissues in vitro and as a carrier to implant microtissues in vivo into mice

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Melissa E. Monterosso ◽  
Kathryn Futrega ◽  
William B. Lott ◽  
Ian Vela ◽  
Elizabeth D. Williams ◽  
...  
Keyword(s):  
Hair Follicles ◽  
Live Animal ◽  
Nsg Mice ◽  
Animal Imaging ◽  
Organ Specific ◽  
Bioluminescence Signal ◽  
Serial Transplantation ◽  
Live Animal Imaging

AbstractProstate cancer (PCa) patient-derived xenografts (PDXs) are commonly propagated by serial transplantation of “pieces” of tumour in mice, but the cellular composition of pieces is not standardised. Herein, we optimised a microwell platform, the Microwell-mesh, to aggregate precise numbers of cells into arrays of microtissues, and then implanted the Microwell-mesh into NOD-scid IL2γ−/− (NSG) mice to study microtissue growth. First, mesh pore size was optimised using microtissues assembled from bone marrow-derived stromal cells, with mesh opening dimensions of 100×100 μm achieving superior microtissue vascularisation relative to mesh with 36×36 μm mesh openings. The optimised Microwell-mesh was used to assemble and implant PCa cell microtissue arrays (hereafter microtissues formed from cancer cells are referred to as microtumours) into mice. PCa cells were enriched from three different PDX lines, LuCaP35, LuCaP141, and BM18. 3D microtumours showed greater in vitro viability than 2D cultures, but neither proliferated. Microtumours were successfully established in mice 81% (57 of 70), 67% (4 of 6), 76% (19 of 25) for LuCaP35, LuCaP141, and BM18 PCa cells, respectively. Microtumour growth was tracked using live animal imaging for size or bioluminescence signal. If augmented with further imaging advances and cell bar coding, this microtumour model could enable greater resolution of PCa PDX drug response, and lead to the more efficient use of animals. The concept of microtissue assembly in the Microwell-mesh, and implantation in vivo may also have utility in implantation of islets, hair follicles or other organ-specific cells that self-assemble into 3D structures, providing an important bridge between in vitro assembly of mini-organs and in vivo implantation.

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