1
|
Brun A, Magallanes ME, Karasov WH, Caviedes-Vidal E. Rapid and parallel changes in activity and mRNA of intestinal peptidase to match altered dietary protein levels in juvenile house sparrows ( Passer domesticus). J Exp Biol 2021; 224:jeb234708. [PMID: 33288529 DOI: 10.1242/jeb.234708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 11/16/2020] [Indexed: 11/20/2022]
Abstract
Although dietary flexibility in digestive enzyme activity (i.e. reaction rate) is widespread in vertebrates, mechanisms are poorly understood. When laboratory rats are switched to a higher protein diet, the activities of apical intestinal peptidases increase within 15 h, in some cases by rapid increase in enzyme transcription followed by rapid translation and translocation to the intestine's apical, brush-border membrane (BBM). Focusing on aminopeptidase-N (APN), we studied intestinal digestive enzyme flexibility in birds, relying on activity and mRNA data from the same animals. Our model was nestling house sparrows (Passer domesticus), already known to modulate intestinal peptidase activity when switching between lower and higher protein diets. Twenty-four hours after a switch from an adequate, lower protein diet to a higher protein diet, APN activity was increased in both whole intestinal tissue homogenates and in isolated BBM, but not at 12 h post-diet switch. Twenty-four hours after a reverse switch back to the lower protein diet, APN activity was decreased, but not at 12 h post-diet switch. Changes in APN activity in both diet switch experiments were associated with parallel changes in APN mRNA. Although transcriptional changes seem to be an important mechanism underlying dietary modulation of intestinal peptidase in both nestling house sparrows and laboratory rodents, the time course for modulation in nestlings seemed slower (taking approximately twice as long) compared with laboratory rodents. It may be ecologically advantageous if nestlings biochemically restructure their gut in response to a sustained increase in insects and protein intake rather than one or a few lucky insect meals.
Collapse
Affiliation(s)
- Antonio Brun
- University of Wisconsin-Madison, Department of Forest and Wildlife Ecology, Madison, WI 53706, USA
- Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto Multidisciplinario de Investigaciones Biológicas de San Luis, 5700 San Luis, Argentina
- Universidad Nacional de San Luis, Facultad de Ciencias de la Salud, 5700 San Luis, Argentina
| | - Melisa E Magallanes
- Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto Multidisciplinario de Investigaciones Biológicas de San Luis, 5700 San Luis, Argentina
| | - William H Karasov
- University of Wisconsin-Madison, Department of Forest and Wildlife Ecology, Madison, WI 53706, USA
| | - Enrique Caviedes-Vidal
- University of Wisconsin-Madison, Department of Forest and Wildlife Ecology, Madison, WI 53706, USA
- Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto Multidisciplinario de Investigaciones Biológicas de San Luis, 5700 San Luis, Argentina
- Universidad Nacional de San Luis, Departamento de Biología, 5700 San Luis, Argentina
| |
Collapse
|
2
|
Wang L, Caviedes-Vidal E, Karasov WH. Diet composition modulates intestinal hydrolytic enzymes in white-footed mice (Peromyscus leucopus). J Mammal 2019. [DOI: 10.1093/jmammal/gyz110] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
We tested whether white-footed mice (Peromyscus leucopus) modulate the activity of three key intestinal digestive enzymes (maltase, sucrase, and aminopeptidase-N [APN]) based on diet composition. To test the adaptive modulation hypothesis (AMH), we fed mice either of three kinds of synthetic diet, high starch (HS, 50% carbohydrate), high protein (HP, 60% protein), and high lipid (HL, 25% lipid), and determined their digestive responses. First, there was no effect of either diet itself, or time eating the diet, on body mass, or mass and length of small intestine. Second, the activity of both disaccharidases summed over the entire small intestine was highest on the HS diet, which was higher than on the HP diet by about 45% and higher than on the HL diet by 400%. This was consistent with our prediction that starch induces disaccharidase activity, and demonstrated induction of disaccharidase activities by high dietary carbohydrate in a wild mammal. Third, both summed and mass-specific activity of maltase and sucrase of HL mice were lower than those of HP mice, even though their diets had the same content of starch, which suggests that lipid in the HL diet inhibited disaccharidase activity. Finally, the summed activity of APN was highest on the HP diet, which was higher than on the HS diet or HL diet by ~100%, consistent with our prediction that high protein content induces peptidase activity. Taken together, our results support the AMH, though they also illustrate that high lipid content in the diet can confound some predicted patterns. Flexibility of digestive enzyme activity is likely important in allowing white-footed mice to cope with fluctuations in the environmental availability of different food types.
Probamos si el ratón de patas blancas (Peromyscus leucopus) modula las actividades de tres enzimas digestivas intestinales claves – maltasa, sacarasa y N-aminopeptidasa- al modificarse la composición de la dieta. Para someter a prueba la hipótesis de la modulación adaptativa, se alimentaron paralelamente ratones con tres tipos de dietas semi-sintéticas, una alta en almidón (HS, 50% carbohidratos), otra alta en proteína (HP, 60% proteínas), y una alta en lípidos (HL, 25% lípidos), y se determinaron sus respuestas digestivas. No se observó un efecto de la dieta o del tiempo que la consumieron sobre la masa corporal o la masa y el largo del intestino delgado (SI). La sumatoria de las actividades de cada una de las disacaridasas a lo largo de todo el intestino delgado fue más alta con la dieta HS que con las dietas HP y HL, un 45% y un 400% mayor, respectivamente. Esto fue consistente con nuestra predicción acerca de que el almidón induce la actividad disacaridásica, constituyendo el primer estudio que demuestra inequívocamente en un animal silvestre, que la inducción de las actividades de las disacaridasas intestinales es mediada por un incremento de los carbohidratos en la dieta. Las actividades hidrolíticas totales y masa-específicas de la maltasa y sacarasa de los ratones HL fueron más bajas que las de los alimentados con dieta HP, aun cuando sus dietas tenían el mismo contenido de almidón, lo que sugiere que los lípidos en la dieta HL inhiben la actividad de las disacaridasas. La actividad hidrolítica total de la N-aminopeptidasa fue mayor con la dieta HP, ~100% más alta que para las dietas HS y HL, de manera consistente con la predicción que propone que la presencia de mayor cantidad de proteína en la dieta induce la actividad peptidásica. En conjunto nuestros resultados dan soporte a la hipótesis de la modulación adaptativa, además de ilustrar que los lípidos en las dietas pueden confundir la predicción de patrones de procesamiento de alimentos. La flexibilidad de la actividad de las enzimas digestivas es probablemente importante para los ratones de patas blancas, ya que les permite adecuarse a las fluctuaciones ambientales de disponibilidad de diferentes tipos de recursos.
Collapse
Affiliation(s)
- Luping Wang
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, USA
| | - Enrique Caviedes-Vidal
- Departamento de Bioquimica y Ciencias Biologicas, Universidad Nacional de San Luis and Instituto Multidisciplinario de Investigaciones Biologicas de San Luis, Consejo Nacional de Investigaciones Cientificas y Tecnicas, San Luis, Argentina
| | - William H Karasov
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, USA
| |
Collapse
|
3
|
|
4
|
Clissold FJ, Tedder BJ, Conigrave AD, Simpson SJ. The gastrointestinal tract as a nutrient-balancing organ. Proc Biol Sci 2010; 277:1751-9. [PMID: 20129973 DOI: 10.1098/rspb.2009.2045] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Failure to provision tissues with an appropriate balance of nutrients engenders fitness costs. Maintaining nutrient balance can be achieved by adjusting the selection and consumption of foods, but this may not be possible when the nutritional environment is limiting. Under such circumstances, rebalancing of an imbalanced nutrient intake requires post-ingestive mechanisms. The first stage at which such post-ingestive rebalancing might occur is within the gastrointestinal tract (GIT), by differential release of digestive enzymes-releasing less of those enzymes for nutrients present in excess while maintaining or boosting levels of enzymes for nutrients in deficit. Here, we use an insect herbivore, the locust, to show for the first time that such compensatory responses occur within the GIT. Furthermore, we show that differential release of proteases and carbohydrases in response to nutritional state translate into differential extraction of macronutrients from host plants. The prevailing view is that physiological and structural plasticity in the GIT serves to maximize the rate of nutrient gain in relation to costs of maintaining the GIT; our findings show that GIT plasticity is integral to the maintenance of nutrient balance.
Collapse
|
5
|
Erickson RH, Yoon BC, Koh DY, Kim DH, Kim YS. Dietary induction of angiotensin-converting enzyme in proximal and distal rat small intestine. Am J Physiol Gastrointest Liver Physiol 2001; 281:G1221-7. [PMID: 11668031 DOI: 10.1152/ajpgi.2001.281.5.g1221] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Induction of angiotensin-converting enzyme was examined in proximal and distal intestinal segments of rats fed a low-protein (4%) diet and then switched to a high-protein (gelatin) diet. Animals were killed at varying time points, and brush-border membranes and total RNA were prepared from the segments. In the proximal intestine, there was a fivefold increase in angiotensin-converting enzyme levels after 14 days but only a twofold change in mRNA. In the distal intestine, there was no increase in enzyme activity but mRNA increased 2.4-fold. Organ culture was used to measure changes in enzyme biosynthesis. There was a 5- to 6-fold increase in the biosynthesis of angiotensin-converting enzyme in the proximal intestine 24 h after the switch to the gelatin diet and a 1.6-fold increase in mRNA levels. No change in biosynthesis was observed in the distal small intestine despite an increase in mRNA. These results support the conclusion that rapid dietary induction of intestinal angiotensin-converting enzyme is differentially regulated in proximal and distal segments of the small intestine.
Collapse
Affiliation(s)
- R H Erickson
- Gastrointestinal Research Laboratory, Department of Veterans Affairs Medical Center, San Francisco, California 94121, USA.
| | | | | | | | | |
Collapse
|
6
|
Affiliation(s)
- F Raul
- IRCAD, CJF INSERM 95-09, Strasbourg, France
| | | |
Collapse
|
7
|
Suzuki Y, Erickson RH, Yoon BC, Kim YS. Transcriptional regulation of rat intestinal angiotensin-converting enzyme and dipeptidyl peptidase IV by a high proline diet. Nutr Res 1995. [DOI: 10.1016/0271-5317(95)e0002-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
8
|
Sonoyama K, Kiriyama S, Niki R. Effect of dietary protein level on intestinal aminopeptidase activity and mRNA level in rats. J Nutr Biochem 1994. [DOI: 10.1016/0955-2863(94)90034-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
9
|
Quan R, Gray GM. Sucrase-alpha-dextrinase in the rat. Postinsertional conversion to inactive molecular species by a carbohydrate-free diet. J Clin Invest 1993; 91:2785-90. [PMID: 8514885 PMCID: PMC443345 DOI: 10.1172/jci116520] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Absence of dietary carbohydrate decreases both activities of intestinal brush border sucrase-alpha-dextrinase. We examined the molecular mechanism causing this decrease. Adult rats were fed chow (70% CHO) or matched carbohydrate-free (CHO-free) diet for 7 d. Sucrase activity decreased by 50% in whole homogenates and brush borders. Enzyme kinetics revealed no change in sucrose affinity (CHO-free Km = 18 mM, chow Km = 21 mM), but fewer active sites (CHO-free Vmax = 2,720, chow Vmax = 5,000 mumol/min per g protein). Intraintestinal pulse-labeling of [35S]methionine in vivo revealed no differences in incorporation into sucrase. Immunoreactive sucrase protein, assayed by ELISA and rocket immunoelectrophoresis, increased twofold per milliunit of sucrase enzymatic activity in CHO-free jejunum. Total immunosucrase (St), the sum of active and inactive enzyme (St = Sa+Si), was unchanged with carbohydrate withdrawal, but > 50% of the sucrase protein became inactive. SDS-PAGE of sucrase immunoprecipitates revealed alteration of alpha, beta, and gamma subunits in CHO-free animals: (a) alpha and beta subunits migrated farther (mass change--2 kD); and (b) the alpha subunit became diffuse or was a doublet and was less abundant than the beta subunit. Rather than representing loss of sucrase protein, the decline in sucrase activity is achieved with structural subunit changes, probably involving postinsertional processing.
Collapse
Affiliation(s)
- R Quan
- Department of Pediatrics (Gastroenterology/Nutrition), University of Texas Southwestern Medical Center, Dallas 75235-9063
| | | |
Collapse
|
10
|
Najjar SM, Hampp LT, Rabkin R, Gray GM. Altered intestinal and renal brush border amino-oligopeptidase structure in diabetes and metabolic acidosis: normal and biobreed (BB) rats. Metabolism 1992; 41:76-84. [PMID: 1538646 DOI: 10.1016/0026-0495(92)90194-f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Amino-oligopeptidase (AOP, aminopeptidase N), a major glycoprotein hydrolase in intestinal and kidney brush border membranes, plays a crucial role in digesting peptide nutrients and salvaging filtered peptides. The molecular structure of rat intestinal and kidney AOP was compared for normal Wistar and congenitally diabetic BB Wistar (BBd) rats. Brush border membranes were isolated, solubilized with Triton X-100, and the AOP specifically immunoprecipitated with polyvalent rabbit antiserum and analyzed on 7% sodium dodecyl sulfate (SDS)-acrylamide electrophoresis. While the specific hydrolytic activity was maintained, BBd rats displayed an altered migration of AOP on SDS gels. Intestinal AOP migrated as a smaller species (130 kd) in the BBd than in the normal Wistar (135 to 140 kd). In some BBd rats, additional intestinal AOP species were observed (a 130- to 135-kd doublet or a 125-, 130-, or 135-kd triplet). Kidney AOP migrated as a broader band (125 to 140 kd) than intestine for all rat groups, probably due to carbohydrate chain heterogeneity, and was approximately 5 kd smaller in the BBd rat than in the normal Wistar. In contrast, no mass change was found in diabetes induced by streptozotocin (STZ). The altered intestinal AOP in the BBd rat was present when first inserted into the brush border membrane (6 hours after intraperitoneal [35S]methionine labeling), and hence was not due to nonenzymatic glycosylation (NEG). Abnormal intestinal and kidney AOP structure appeared in early diabetes, irrespective of high plasma glucose levels or ketoacidosis, and was reversed following evolution of the diabetes under prolonged (21 to 120 days) insulin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- S M Najjar
- Department of Medicine, Stanford University School of Medicine, CA 94305
| | | | | | | |
Collapse
|
11
|
|
12
|
|
13
|
Whitt DD, Savage DC. Influence of indigenous microbiota on activities of alkaline phosphatase, phosphodiesterase I, and thymidine kinase in mouse enterocytes. Appl Environ Microbiol 1988; 54:2405-10. [PMID: 2849379 PMCID: PMC204272 DOI: 10.1128/aem.54.10.2405-2410.1988] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
An indigenous microflora introduced into the gastrointestinal tracts of animals in a population of germfree mice affected in different ways three enzymes in small bowel enterocytes. Cells were obtained by techniques designed for sequentially removing enterocytes from the tip of the villus to the crypts of Lieberkühn. The specific activity of alkaline phosphatase, a component of the enterocyte microvillous membrane, did not differ in cells isolated from germfree mice and from those associated with a microflora, while that of phosphodiesterase I, also a part of the microvillous membrane, was approximately 1.5-fold greater in the suspensions from all levels of the villi in germfree mice than in those from the associated animals. By contrast, the specific activity of thymidine kinase, a cytosol enzyme, in suspensions in which the cells were isolated from the lower portion of the villi and crypts was about one-half as great in cells from germfree mice as in those from the same regions of animals with a microbiota. These results support the hypothesis that activities of certain enzymes involved in metabolism, uptake, and incorporation by enterocytes of components of dietary nuclei acids are influenced by a microflora.
Collapse
Affiliation(s)
- D D Whitt
- Department of Microbiology, University of Illinois, Urbana 61801
| | | |
Collapse
|
14
|
Wanders RJ, van Roermund CW, van Wijland MJ, Schutgens RB, van den Bosch H, Schram AW, Tager JM. Direct demonstration that the deficient oxidation of very long chain fatty acids in X-linked adrenoleukodystrophy is due to an impaired ability of peroxisomes to activate very long chain fatty acids. Biochem Biophys Res Commun 1988; 153:618-24. [PMID: 3382393 DOI: 10.1016/s0006-291x(88)81140-9] [Citation(s) in RCA: 123] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A method was developed to prepare peroxisome-enriched fractions depleted of microsomes and mitochondria from cultured skin fibroblasts. The method consists of differential centrifugation of a postnuclear supernatant followed by density gradient centrifugation on a discontinuous Metrizamide gradient. The activity of hexacosanoyl-CoA synthetase was subsequently measured in postnuclear supernatants and peroxisome-enriched fractions prepared from cultured skin fibroblasts from control subjects and patients with X-linked adrenoleukodystrophy. Whereas the hexacosanoyl-CoA synthetase activity in postnuclear supernatants of X-linked adrenoleukodystrophy fibroblasts was only slightly decreased (77.8 +/- 4.4% of control (n = 15], enzyme activity was found to be much more markedly reduced in peroxisomal fractions isolated from the mutant fibroblasts (19.6 +/- 6.7% of control (n = 5]. This is a direct demonstration that the defect in X-linked adrenoleukodystrophy is at the level of a deficient ability of peroxisomes to activate very long chain fatty acids, as first suggested by Hashmi et al. [Hashmi, M., Stanley, W. and Singh, I. (1986) FEBS Lett. 86, 247-250].
Collapse
Affiliation(s)
- R J Wanders
- Department of Pediatrics, University Hospital Amsterdam, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
15
|
Biosynthesis, glycosylation, and intracellular transport of intestinal lactase-phlorizin hydrolase in rat. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45511-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
|
16
|
Raul F, Goda T, Gossé F, Koldovský O. Short-term effect of a high-protein/low-carbohydrate diet on aminopeptidase in adult rat jejunoileum. Site of aminopeptidase response. Biochem J 1987; 247:401-5. [PMID: 2892485 PMCID: PMC1148423 DOI: 10.1042/bj2470401] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The short-term effects of high-protein/low-carbohydrate diet on aminopeptidase N activity were studied in the brush-border membranes of proximal jejunum and proximal ileum of adult rats. The animals were starved overnight and re-fed for 15 h either with a standard diet (20% protein, 55% carbohydrate, in terms of energy content) or with a high-protein/low-carbohydrate diet of equal energy content (70% protein, 5% carbohydrate). All rats consumed similar amounts of diet, and measurements were made 15 h after initiation of re-feeding. In the proximal jejunum a slight increase in aminopeptidase activity was observed after the high-protein intake. In contrast, considerable stimulation (52%) of the enzyme specific activity was obtained in the proximal ileum. This increase in ileal aminopeptidase activity was more prominent in the mature cells of the upper villus. To determine if the increase of aminopeptidase activity was due to an increased amount of enzyme protein, rocket immunoelectrophoresis was performed with detergent-solubilized brush-border protein from ileum on agarose gels containing anti-(rat brush-border) antiserum. When the same amount of enzyme activity was loaded on the gels, the peaks of immunoprecipitate for aminopeptidase were similar for animals fed on a standard or a high-protein diet. When the same amount of protein was loaded, the peak of immunoprecipitate for aminopeptidase was higher (81%) after a high-protein diet. These results showed that the high protein intake evoked an increase in aminopeptidase activity, with a concomitant increase in the amount of immunoreactive protein.
Collapse
Affiliation(s)
- F Raul
- Institut National de la Santé ét de la Recherche Medicale, Unité 61, Strasbourg, France
| | | | | | | |
Collapse
|
17
|
Niederau C, Grendell JH, Rothman SS. Digestive end products release pancreatic enzymes from particulate cellular pools, particularly zymogen granules. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 881:281-91. [PMID: 2420368 DOI: 10.1016/0304-4165(86)90015-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effects of various amino acids and phosphorylated forms of glucose on the release of digestive enzymes from particulate cellular pools, particularly zymogen granules, were evaluated in rat pancreas. Whole tissue homogenates, as well as zymogen granules isolated either by differential centrifugation in 0.3 M sucrose or by preparation in buffered sucrose and subsequent centrifugation in a Percoll gradient, were studied. The basic amino acids L-arginine and L-lysine, sites of tryptic cleavage, caused the release of trypsinogen, but not chymotrypsinogen, whereas the aromatic amino acids L-phenylalanine and L-tryptophan, sites of chymotryptic cleavage, caused release of both trypsinogen and chymotrypsinogen. Neither led to the release of the starch-splitting enzyme amylase. All effects occurred within the range of normal plasma concentrations for these amino acids in the rat. Two amino acids, L-threonine and hydroxy-L-proline, that are not sites of cleavage by trypsin or chymotrypsin, and a nonmammalian amino acid, aminoadipic acid, did not lead to release of trypsinogen, chymotrypsinogen, or amylase. Two phosphorylated forms of glucose, glucose 1-phosphate and glucose 1,6-diphosphate, caused the release of amylase, but of neither trypsinogen nor chymotrypsinogen. Contrary to previous results, D-glucose was without effect, as was glucose 6-phosphate. We propose that certain digestive end products, by direct action on zymogen granules, cause the selective release of the enzymes involved in their evolution from polymeric substrates during digestion.
Collapse
|
18
|
Ferraris RP, Diamond JM. Use of phlorizin binding to demonstrate induction of intestinal glucose transporters. J Membr Biol 1986; 94:77-82. [PMID: 3806659 DOI: 10.1007/bf01901015] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We used specific binding of phlorizin to the intact intestinal mucosa in order to measure glucose transport site density in intestines of mice fed a high-carbohydrate or no-carbohydrate diet. Nonspecific binding varied with intestinal position but showed only modest dependence on diet. Specific binding to glucose transporters was 1.9 times greater in jejunum of high-carbohydrate mice than of no-carbohydrate mice; this ratio was the same as the ratio for Vmax values of active D-glucose uptake between the two diet groups. The gradient in specific binding of phlorizin along the intestine paralleled the gradient in Vmax of glucose transport. These results directly demonstrate that the increase in intestinal glucose transport caused by a high-carbohydrate diet is due to induction of glucose transporters. They also indicate that the normal positional gradient in glucose transport along the intestine arises from a gradient in transporters, induced by the normal gradient in luminal glucose concentration.
Collapse
|
19
|
Rothman SS. The biological functions and physiological effects of ingested inhibitors of digestive reactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1986; 199:19-31. [PMID: 3799277 DOI: 10.1007/978-1-4757-0022-0_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
|
20
|
Regulation of mucosal enzymes by their dietary substrates. Nutr Rev 1985; 43:212-3. [PMID: 4034114 DOI: 10.1111/j.1753-4887.1985.tb02426.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
|