Dietary regulation of intestinal brush-border sugar and amino acid transport in carnivores

1991 ◽  
Vol 261 (4) ◽  
pp. R793-R801 ◽  
Author(s):  
R. K. Buddington ◽  
J. W. Chen ◽  
J. M. Diamond
Keyword(s):  
Brush Border ◽  
Sugar Transport ◽  
Nutrient Transporters ◽  
Sugar Transporters ◽  
Dietary Regulation ◽  
Leopard Frogs ◽  
Intestinal Brush Border ◽  
Carbohydrate Levels

The ability of omnivores and herbivores to regulate reversibly their intestinal brush-border nutrient transporters is functionally related to the unpredictably variable composition of their natural diets. To determine whether carnivores are able similarly to regulate the activities of their intestinal nutrient transporters, we fed to three species of vertebrates that are carnivorous as adults (cats, mink, and leopard frogs) diets with either at least 50% digestible carbohydrate or with negligible carbohydrate levels. Rates of transport for the sugars glucose and fructose and the amino acids (AAs) aspartate, leucine, lysine, and proline were measured throughout the intestine (only proline and glucose in the frogs) by an in vitro everted-sleeve method. Although all three species consume much carbohydrate during early development, only the mink was able to regulate sugar transporter activity in response to changes in levels of dietary carbohydrate. In contrast, the sugar transporters of the cat were unresponsive to varying carbohydrate levels, and long-term feeding of a high-carbohydrate diet caused down-regulation of sugar transport in frogs. Of the three species, only the mink is a member of a family that includes omnivorous species, whereas all members of the families to which the cat and frog belong are carnivorous as adults. All three species were able to regulate rates of AA transport, though the patterns and magnitude of the responses differed between species as well as between AAs, suggesting independent regulation of some AA transporters.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary regulation of intestinal ascorbate uptake in guinea pigs

1991 ◽  
Vol 260 (1) ◽  
pp. G108-G118 ◽  
Author(s):  
W. H. Karasov ◽  
B. W. Darken ◽  
M. C. Bottum
Keyword(s):  
Ascorbic Acid ◽  
Vitamin C ◽  
Brush Border ◽  
Guinea Pigs ◽  
Dietary Regulation ◽  
Intestinal Brush Border ◽  
Pregnancy And Lactation ◽  
Human Adults ◽  
Ascorbate Uptake

We measured ascorbic acid (AA) uptake across the intestinal brush border in vitro in intact tissue from guinea pigs fed maintenance AA (200 mg/kg diet) or made hypervitaminotic (5,000 mg/kg diet) or hypovitaminotic (chronically and acutely). Total uptake per centimeter ileum was 25-50% lower in hypervitaminotic juvenile, adult male, and lactating guinea pigs compared with their respective controls, whereas carrier-mediated D-glucose uptake and Na(+)-independent AA uptake were similar. High dietary ascorbate specifically reduced the Vmax for carrier-mediated AA uptake. Hypovitaminosis had no significant effect on uptake of AA or other solutes. We performed diet-switching experiments (high-AA diet to maintenance diet) with young and adult guinea pigs to determine the reversibility of the downregulation. In adult guinea pigs, the downregulation of AA uptake was reversible within 7 days. In the young of mothers fed high AA during pregnancy and lactation, and which fed on high AA for 14 days after weaning, the downregulation was reversible within 14 days. Thus regulation of AA uptake is reversible and therefore probably does not play a significant role in the development of vitamin C dependency in human adults, or their young, after ingestion of megadoses of ascorbic acid.

Cubilin and megalin expression and their interaction in the rat intestine: effect of thyroidectomy

2001 ◽  
Vol 281 (5) ◽  
pp. E900-E907 ◽  
Author(s):  
Raghunatha R. Yammani ◽  
Shakuntla Seetharam ◽  
Bellur Seetharam
Keyword(s):  
Brush Border ◽  
Intrinsic Factor ◽  
Immunoblot Analysis ◽  
Rat Intestine ◽  
Complement Components ◽  
Protein Levels ◽  
Intestinal Brush Border ◽  
Molecular Masses ◽  
Epidermal Growth

Cubilin is a 460-kDa multipurpose, multidomain receptor that contains an NH2-terminal 110-residue segment followed by 8 epidermal growth factor (EGF)-like repeats and a contiguous stretch (representing nearly 88% of its mass) of 27 CUB (initially found in complement components C1r/C1s, Uegf, and bone morphogenic protein-1) domains. Cubilin binds to intrinsic factor (IF)-cobalamin (cbl, vitamin B12) complex and promotes the ileal transport of cbl. The 460-kDa form of cubilin is the predominant form present in the apical brush-border membranes of rat intestine, kidney, and yolk sac, but a 230-kDa form of cubilin is also noted in the intestinal membranes. In thyroidectomized (TDX) rats, levels of intestinal brush-border IF-[57Co]-labeled cbl binding, 460-kDa cubilin protein levels and tissue (kidney) accumulation of cbl were reduced by ∼70%. Immunoblot analysis using cubilin antiserum of intestinal total membranes from TDX rats revealed cubilin fragments with molecular masses of 200 and 300 kDa. Both of these bands, along with the 230-kDa band detected in the total membranes of control rats and unlike the 460-kDa form, failed to react with antiserum to EGF. Mucosal membrane cubilin associated with megalin was reduced from ∼12% in control to ∼4% in TDX rats, and this decreased association was not due to altered megalin levels. Thyroxine treatment of TDX rats resulted in reversal of all of these effects, including an increase to nearly 24% of cubilin associated with megalin. In vitro, megalin binding to cubilin occurred with the NH2-terminal region that contained the EGF-like repeats and CUB domains 1 and 2 but not with a downstream region that contained CUB domains 2–10. These studies indicate that thyroxine deficiency in rats results in decreased uptake and tissue accumulation of cbl caused mainly by destabilization and deficit of cubilin in the intestinal brush border.

Hemileaflet susceptibility to oxidative damage in the intestinal brush-border membrane

1995 ◽  
Vol 268 (2) ◽  
pp. G260-G269
Author(s):  
D. Jourd'heuil ◽  
S. Mehta ◽  
J. B. Meddings
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Peroxyl Radical ◽  
Tissue Injury ◽  
Biological Membranes ◽  
First Order ◽  
Intestinal Brush Border Membrane ◽  
Outer Leaflet ◽  
Intestinal Brush Border

Oxidation of biological membranes is characteristic of many types of tissue injury, including those observed with inflammatory bowel disease. The lipid compositions of the inner and outer leaflets of biological membranes differ significantly, making one leaflet theoretically more susceptible to oxidative stress than the other. In this study, we evaluated the susceptibility of each membrane hemileaflet for peroxyl radical-mediated oxidation. In vitro peroxidation of intestinal brush-border membrane was initiated with the peroxyl radical-generator 2,2'-azobis-(2-amidinopropane)hydrochloric acid (AAPH). Oxidation events were monitored by following the oxidation-sensitive degradation of the lipid-soluble fluorescent probe cis-parinaric acid (PnA). The degradation patterns were clearly distinct in the inner and outer hemileaflet. PnA degradation in the inner hemileaflet was consistent with a slow first-order reaction, whereas degradation in the outer leaflet appeared as two first-order processes delayed in time. The results suggest that the sum of available antioxidants and endogenous substrates for oxidation are consumed more rapidly in the outer membrane hemileaflet, making this leaflet more susceptible to peroxidation compared with the cytofacial leaflet.

In vitro Gastrointestinal Models for Prebiotic Carbohydrates: A Critical Review

2019 ◽  
Vol 25 (32) ◽  
pp. 3478-3483 ◽  
Author(s):  
Oswaldo Hernandez-Hernandez
Keyword(s):  
Small Intestine ◽  
Gastrointestinal Tract ◽  
Brush Border ◽  
Critical Review ◽  
In Vitro Digestibility ◽  
Human Gastrointestinal Tract ◽  
Intestinal Brush Border ◽  
Small Intestinal ◽  
Existing Data

Background: In the last decade, various consortia and companies have created standardized digestion protocols and gastrointestinal simulators, such as the protocol proposed by the INFOGEST Consortium, the simulator SHIME, the simulator simgi®, the TIM, etc. Most of them claim to simulate the entire human gastrointestinal tract. However, few results have been reported on the use of these systems with potential prebiotic carbohydrates. Methods: This critical review addresses the existing data on the analysis of prebiotic carbohydrates by different in vitro gastrointestinal simulators, the lack of parameters that could affect the results, and recommendations for their enhancement. Results: According to the reviewed data, there is a lack of a realistic approximation of the small intestinal conditions, mainly because of the absence of hydrolytic conditions, such as the presence of small intestinal brush border carbohydrases that can affect the digestibility of different carbohydrates, including prebiotics. Conclusion: There is a necessity to standardize and enhance the small intestine simulators to study the in vitro digestibility of carbohydrates.

Comparison of different dietary sugars as inducers of intestinal sugar transporters

1987 ◽  
Vol 252 (4) ◽  
pp. G574-G584 ◽  
Author(s):  
D. H. Solberg ◽  
J. M. Diamond
Keyword(s):  
Small Intestine ◽  
Unit Length ◽  
Sugar Transport ◽  
Dietary Carbohydrate ◽  
Feeding Rates ◽  
Sugar Transporters ◽  
Mouse Small Intestine ◽  
Dietary Fructose ◽  
Carbohydrate Levels ◽  
Dietary Sugars

Intestinal sugar transport increases with dietary carbohydrate levels, but the specific regulatory signals involved have been little studied. Hence we compared rations containing one of five sugars [D-glucose, D-galactose, 3-O-methyl-D-glucose (3-O-MG), D-fructose, and maltose] in their effects on brush-border uptake of five transported solutes (D-glucose, D-galactose, 3-O-MG, D-fructose, and L-proline) by everted sleeves of mouse small intestine. As confirmed by transepithelial potential difference (PD) measurements, there is a distinct fructose transporter that does not evoke a PD, along with one or more aldohexose transporters that do evoke a PD. Galactose and 3-O-MG rations cause a twofold increase in feeding rates, mucosal hyperplasia, and hence nonspecific increases in uptake per unit length of intestine for all transported solutes. Dietary fructose is by far the best specific inducer of the fructose transporter. The five dietary sugars are of fairly similar potency as specific inducers of aldohexose transport, but dietary galactose and fructose may be slightly more potent than glucose. Regulatory signals need not be transported substrates, or vice versa, and need not be metabolizable. Variation in uptake ratios of pairs of aldohexoses with ration and intestinal position suggest multiple aldohexose transporters of overlapping specificity, with different relative activities at different positions and with different susceptibilities to induction by different dietary sugars.

scholarly journals Lysine Transport across Isolated Rabbit Ileum

1969 ◽  
Vol 53 (2) ◽  
pp. 157-182 ◽  
Author(s):  
B. G. Munck ◽  
Stanley G. Schultz
Keyword(s):  
Brush Border ◽  
Maximal Velocity ◽  
Transport Capacity ◽  
Rabbit Ileum ◽  
Mucosal Membrane ◽  
Intestinal Brush Border

Lysine transport by in vitro distal rabbit ileum has been investigated by determining (a) transmural fluxes across short-circuited segments of the tissue; (b) accumulation by mucosal strips; and (c) influx from the mucosal solution across the brush border into the epithelium. Net transmural flux of lysine is considerably smaller than that of alanine. However, lysine influx across the brush border and lysine accumulation by mucosal strips are quantitatively comparable to alanine influx and accumulation. Evidence is presented that the "low transport capacity" of rabbit ileum for lysine is due to: (a) a carrier-mediated process responsible for efflux of lysine out of the cell across the serosal and/or lateral membranes that is characterized by a low maximal velocity; and (b) a high "backflux" of lysine out of the cell across the mucosal membrane. A possible explanation for the latter observation is discussed with reference to the relatively low Na dependence of lysine transport across the intestinal brush border.

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