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Kim HS, Kim ET, Eom JS, Choi YY, Lee SJ, Lee SS, Chung CD, Lee SS. Exploration of metabolite profiles in the biofluids of dairy cows by proton nuclear magnetic resonance analysis. PLoS One 2021; 16:e0246290. [PMID: 33513207 PMCID: PMC7845951 DOI: 10.1371/journal.pone.0246290] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 01/15/2021] [Indexed: 11/26/2022] Open
Abstract
Studies that screen for metabolites produced in ruminants are actively underway. We aimed to evaluate the metabolic profiles of five biofluids (ruminal fluid, serum, milk, urine, and feces) in dairy cow by using proton nuclear magnetic resonance (1H-NMR) and provide a list of metabolites in each biofluid for the benefit of future research. We analyzed the metabolites in five biofluids from lactating cows using proton nuclear magnetic resonance imaging; 96, 73, 88, 118, and 128 metabolites were identified in the five biofluids, respectively. In addition, 8, 6, 9, and 17 metabolites were unique to ruminal fluid, serum, milk, and urine, respectively. The metabolites present at high concentrations were: acetate, propionate, and butyrate in ruminal fluid; lactate, glucose, and acetate in serum; and lactose, guanidoacetate, and glucitol in milk. In addition, the following metabolites were present at high concentrations: hippurate, urea, and trimethylamine N-oxide in urine and acetate, propionate, and butyrate in feces. The score plots of the principal component analysis did not show clear distinctions among the five biofluid samples. The purpose of this study was to verify the ability of our metabolomics approaches to identify metabolites in the biofluids of dairy cows.
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Affiliation(s)
- Hyun Sang Kim
- Division of Applied Life Science (BK21Four), Gyeongsang National University, Jinju, Korea
| | - Eun Tae Kim
- National Institute of Animal Science, Rural Development Administration, Cheonan, Korea
| | - Jun Sik Eom
- Division of Applied Life Science (BK21Four), Gyeongsang National University, Jinju, Korea
| | - You Young Choi
- Division of Applied Life Science (BK21Four), Gyeongsang National University, Jinju, Korea
| | - Shin Ja Lee
- Institute of Agriculture and Life Science & University-Centered Labs, Gyeongsang National University, Jinju, Korea
| | - Sang Suk Lee
- Ruminant Nutrition and Anaerobe Laboratory, College of Bio-industry Science, Sunchon National University, Suncheon, Korea
| | - Chang Dae Chung
- Ruminant Nutrition and Anaerobe Laboratory, College of Bio-industry Science, Sunchon National University, Suncheon, Korea
| | - Sung Sill Lee
- Division of Applied Life Science (BK21Four), Gyeongsang National University, Jinju, Korea
- Institute of Agriculture and Life Science & University-Centered Labs, Gyeongsang National University, Jinju, Korea
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Jeckelmann JM, Erni B. The mannose phosphotransferase system (Man-PTS) - Mannose transporter and receptor for bacteriocins and bacteriophages. Biochim Biophys Acta Biomembr 2020; 1862:183412. [PMID: 32710850 DOI: 10.1016/j.bbamem.2020.183412] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 07/08/2020] [Accepted: 07/14/2020] [Indexed: 02/06/2023]
Abstract
Mannose transporters constitute a superfamily (Man-PTS) of the Phosphoenolpyruvate Carbohydrate Phosphotransferase System (PTS). The membrane complexes are homotrimers of protomers consisting of two subunits, IIC and IID. The two subunits without recognizable sequence similarity assume the same fold, and in the protomer are structurally related by a two fold pseudosymmetry axis parallel to membrane-plane (Liu et al. (2019) Cell Research 29 680). Two reentrant loops and two transmembrane helices of each subunit together form the N-terminal transport domain. Two three-helix bundles, one of each subunit, form the scaffold domain. The protomer is stabilized by a helix swap between these bundles. The two C-terminal helices of IIC mediate the interprotomer contacts. PTS occur in bacteria and archaea but not in eukaryotes. Man-PTS are abundant in Gram-positive bacteria living on carbohydrate rich mucosal surfaces. A subgroup of IICIID complexes serve as receptors for class IIa bacteriocins and as channel for the penetration of bacteriophage lambda DNA across the inner membrane. Some Man-PTS are associated with host-pathogen and -symbiont processes.
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Affiliation(s)
- Jean-Marc Jeckelmann
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
| | - Bernhard Erni
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland.
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3
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Abstract
Rumen microbes produce cellular protein inefficiently partly because they do not direct all ATP toward growth. They direct some ATP toward maintenance functions, as long-recognized, but they also direct ATP toward reserve carbohydrate synthesis and energy spilling (futile cycles that dissipate heat). Rumen microbes expend ATP by vacillating between (1) accumulation of reserve carbohydrate after feeding (during carbohydrate excess) and (2) mobilization of that carbohydrate thereafter (during carbohydrate limitation). Protozoa account for most accumulation of reserve carbohydrate, and in competition experiments, protozoa accumulated nearly 35-fold more reserve carbohydrate than bacteria. Some pure cultures of bacteria spill energy, but only recently have mixed rumen communities been recognized as capable of the same. When these communities were dosed glucose in vitro, energy spilling could account for nearly 40% of heat production. We suspect that cycling of glycogen (a major reserve carbohydrate) is a major mechanism of spilling; such cycling has already been observed in single-species cultures of protozoa and bacteria. Interconversions of short-chain fatty acids (SCFA) may also expend ATP and depress efficiency of microbial protein production. These interconversions may involve extensive cycling of intermediates, such as cycling of acetate during butyrate production in certain butyrivibrios. We speculate this cycling may expend ATP directly or indirectly. By further quantifying the impact of reserve carbohydrate accumulation, energy spilling, and SCFA interconversions on growth efficiency, we can improve prediction of microbial protein production and guide efforts to improve efficiency of microbial protein production in the rumen.
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Affiliation(s)
| | - Jeffrey L. Firkins
- Department of Animal Sciences, The Ohio State UniversityColumbus, OH, USA
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Denton BL, Diese LE, Firkins JL, Hackmann TJ. Accumulation of reserve carbohydrate by rumen protozoa and bacteria in competition for glucose. Appl Environ Microbiol 2015; 81:1832-8. [PMID: 25548053 DOI: 10.1128/AEM.03736-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The aim of this study was to determine if rumen protozoa could form large amounts of reserve carbohydrate compared to the amounts formed by bacteria when competing for glucose in batch cultures. We separated large protozoa and small bacteria from rumen fluid by filtration and centrifugation, recombined equal protein masses of each group into one mixture, and subsequently harvested (reseparated) these groups at intervals after glucose dosing. This method allowed us to monitor reserve carbohydrate accumulation of protozoa and bacteria individually. When mixtures were dosed with a moderate concentration of glucose (4.62 or 5 mM) (n = 2 each), protozoa accumulated large amounts of reserve carbohydrate; 58.7% (standard error of the mean [SEM], 2.2%) glucose carbon was recovered from protozoal reserve carbohydrate at time of peak reserve carbohydrate concentrations. Only 1.7% (SEM, 2.2%) was recovered in bacterial reserve carbohydrate, which was less than that for protozoa (P < 0.001). When provided a high concentration of glucose (20 mM) (n = 4 each), 24.1% (SEM, 2.2%) of glucose carbon was recovered from protozoal reserve carbohydrate, which was still higher (P = 0.001) than the 5.0% (SEM, 2.2%) glucose carbon recovered from bacterial reserve carbohydrate. Our novel competition experiments directly demonstrate that mixed protozoa can sequester sugar away from bacteria by accumulating reserve carbohydrate, giving protozoa a competitive advantage and stabilizing fermentation in the rumen. Similar experiments could be used to investigate the importance of starch sequestration.
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Hackmann TJ, Diese LE, Firkins JL. Quantifying the responses of mixed rumen microbes to excess carbohydrate. Appl Environ Microbiol 2013; 79:3786-95. [PMID: 23584777 DOI: 10.1128/AEM.00482-13] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The aim of this study was to determine if a mixed microbial community from the bovine rumen would respond to excess carbohydrate by accumulating reserve carbohydrate, energy spilling (dissipating excess ATP energy as heat), or both. Mixed microbes from the rumen were washed with N-free buffer and dosed with glucose. Total heat production was measured by calorimetry. Energy spilling was calculated as heat production not accounted by (i) endogenous metabolism (heat production before dosing glucose) and (ii) synthesis of reserve carbohydrate (heat from synthesis itself and reactions yielding ATP for it). For cells dosed with 5 mM glucose, synthesis of reserve carbohydrate and endogenous metabolism accounted for nearly all heat production (93.7%); no spilling was detected (P = 0.226). For cells dosed with 20 mM glucose, energy spilling was not detected immediately after dosing, but it became significant (P < 0.05) by approximately 30 min after dosing with glucose. Energy spilling accounted for as much as 38.7% of heat production in one incubation. Nearly all energy (97.9%) and carbon (99.9%) in glucose were recovered in reserve carbohydrate, fermentation acids, CO2, CH4, and heat. This full recovery indicates that products were measured completely and that spilling was not a methodological artifact. These results should aid future research aiming to mechanistically account for variation in energetic efficiency of mixed microbial communities.
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Das S, Sen R. Kinetic modeling of sporulation and product formation in stationary phase by Bacillus coagulans RK-02 vis-à-vis other Bacilli. Bioresour Technol 2011; 102:9659-9667. [PMID: 21852126 DOI: 10.1016/j.biortech.2011.07.067] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 07/17/2011] [Accepted: 07/19/2011] [Indexed: 05/31/2023]
Abstract
A logistic kinetic model was derived and validated to characterize the dynamics of a sporogenous bacterium in stationary phase with respect to sporulation and product formation. The kinetic constants as determined using this model are particularly important for describing intrinsic properties of a sporogenous bacterial culture in stationary phase. Non-linear curve fitting of the experimental data into the mathematical model showed very good correlation with the predicted values for sporulation and lipase production by Bacillus coagulans RK-02 culture in minimal media. Model fitting of literature data of sporulation and product (protease and amylase) formation in the stationary phase by some other Bacilli and comparison of the results of model fitting with those of Bacillus coagulans helped validate the significance and robustness of the developed kinetic model.
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Affiliation(s)
- Subhasish Das
- Department of Biotechnology, Indian Institute of Technology, Kharagpur 721 302, West Bengal, India.
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Janssen PH. Influence of hydrogen on rumen methane formation and fermentation balances through microbial growth kinetics and fermentation thermodynamics. Anim Feed Sci Technol 2010; 160:1-22. [DOI: 10.1016/j.anifeedsci.2010.07.002] [Citation(s) in RCA: 413] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Atasoglu C, Gäbel G, Aschenbach JR. Apical sodium–glucose co-transport can be regulated by blood-borne glucose in the ruminal epithelium of sheep (Ovis aries, Merino breed). Br J Nutr 2007; 92:777-83. [PMID: 15533266 DOI: 10.1079/bjn20041265] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The intestinal Na-dependent D-glucose co-transporter (SGLT)-1 in sheep is under dietary regulation by luminal substrates. The aim of the present study was to find out whether the SGLT-1 in the forestomach of sheep is also regulated by sugars. Furthermore, the location of a possible glucosensor (luminalv.intracellularv.basolateral) was to be elucidated. Ruminal epithelia of sheep (Ovis aries, Merino breed) were pre-incubated in Ussing chambers with various substrates on the mucosal (i.e. luminal) or serosal (i.e. blood) side. This pre-incubation period was followed by a second pre-incubation period without the tested substrates (washout period). Thereafter, apical D-glucose uptake by ruminal epithelial cells was determined with 200 μmol D-[14C]glucose/l in the absence or co-presence of the SGLT-1 inhibitor, phlorizin. Pre-incubation with D-glucose on the mucosal side had no significant effect on apical D-glucose uptake (P>0.05). In contrast, pre-incubation with D-glucose, D-mannose, 3-O-methyl-D-glucose or sucrose on the serosal side significantly increased D-glucose uptake compared with mannitol-treated controls (P<0.05). Serosal pre-incubation with cellobiose or D-xylose had no effect. The stimulation of D-glucose uptake by serosal D-glucose pre-incubation was concentration dependent, with maximal stimulation at about 10 mmol/l. We conclude that the ruminal SGLT-1 can be up-regulated in a concentration-dependent manner by blood-borne D-glucose via an extracellular sugar-sensing mechanism.
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Affiliation(s)
- Cengiz Atasoglu
- Institute of Veterinary Physiology, Leipzig University, D-04103 Leipzig, Germany
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Medina VF, Larson SL, Agwaramgbo L, Perez W, Escalon L. Treatment of trinitrotoluene by crude plant extracts. Chemosphere 2004; 55:725-732. [PMID: 15013677 DOI: 10.1016/j.chemosphere.2003.12.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2003] [Revised: 08/18/2003] [Accepted: 12/29/2003] [Indexed: 05/24/2023]
Abstract
Crude plant extract solutions (spinach and parrotfeather) were prepared and spiked with 2,4,6-trinitrotoluene (TNT) (20 mgl(-1)). 90-h TNT removal by these solutions was compared to controls. Spinach and parrotfeather extract solutions removed 99% and 50% of the initial TNT, respectively; TNT was not eliminated in the controls or in extract solutions where removal activity was deactivated by boiling. A first-order removal constant of 0.052 h(-1) was estimated for spinach extract solutions treating 20 mgl(-1) TNT concentrations, which compared favorably to intact plant removal. Concentration variation was described by Michaelis-Menton kinetics. Detectable TNT degradation products represented only a fraction of the total TNT transformed, and the transformation favored the formation of 4-aminodinitrotoluene. The results indicated that crude plant extracts transform TNT, without the presence of the live plant.
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Affiliation(s)
- Victor F Medina
- Environmental Engineering Branch, EP-E, Environmental Laboratory, ERDC, US Army Corps of Engineers, 3909 Halls Ferry Road, Vicksburg, MS 39180, USA.
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10
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Gäbel G, Aschenbach JR. Influence of food deprivation on the transport of 3-O-methyl-α-D-glucose across the isolated ruminal epithelium of sheep. J Anim Sci 2002. [DOI: 10.1093/ansci/80.10.2740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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11
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Abstract
Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.
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Affiliation(s)
- Lee R Lynd
- Chemical and Biochemical Engineering, Thayer School of Engineering and Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
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12
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Abstract
Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.
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Affiliation(s)
- Lee R Lynd
- Chemical and Biochemical Engineering, Thayer School of Engineering and Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
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Abstract
Mixed ruminal bacteria were incubated in vitro with glucose, xylose, cellobiose, and various protein amino acids replaced isonitrogenously with 25% (i.e., 25 mg of N/L) of ammonia-N, to determine the growth rate and the amount of sugar consumed in the exponential growth phase. The growth rate and efficiency (grams of bacteria per gram of sugars) increased by 46 and 15%, respectively, when a mixture of 20 amino acids was added. On the other hand, neither growth rate nor efficiency increased when any one of these amino acids was added singly, except for Glu and Gln, each of which produced significant but small improvements. The stimulatory effect of the combined amino acids on bacterial growth declined when each of Leu, Trp, Tyr, Glu, Met, Phe, and Val was removed from the original group of 20. When a mixture of only these seven amino acids was used as a supplement, their stimulatory effects on growth rate and efficiency were only 21 and 25%, respectively, of the effects that the mixture of 20 amino acids showed. The effects increased to 76 and 72% on growth rate and efficiency, respectively, when Gly, Cys, and His were supplied in addition to the seven amino acids. The growth rate and efficiency of the ruminal bacteria were inhibited by an addition of each of Ile, Thr, Cys, Phe, Leu, Lys, or Val to ammonia-N, and the effects of the first five of these amino acids were highly significant. Isoleucine, threonine, and phenylalanine were each inhibitory even at a low concentration (1 mg of NL), while cysteine and leucine showed inhibitory effects at higher concentrations (more than 10 mg of N/L). A higher growth rate of the ruminal bacteria when supplemented with amino acid mixtures was accompanied with a higher growth efficiency, which was attributable to a relatively smaller proportion of energy expended on maintenance according to the Pirt derivation.
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Affiliation(s)
- H Kajikawa
- National Institute of Livestock and Grassland Science, Tsukuba Norindanchi, Ibaraki, Japan.
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14
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Abstract
Glucose absorption via the sodium glucose-linked transporter (SGLT)-1, decreases the glucose concentration in the ruminant forestomach and may ameliorate or prevent ruminal lactic acidosis. Because acidotic ruminants show increased sympathetic activity, the possibility of adrenergic modulation of SGLT-1 was investigated. Glucose uptake into ovine ruminal epithelia was measured in Ussing chambers after the addition of 200 micromol/L (14)C-labeled glucose to the mucosal solution. Glucose uptake decreased (P < 0.05) by >50% in comparison with control after mucosal addition of the SGLT-1 inhibitor, phlorizin (100 micromol/L). Serosal preincubation with 100 micromol/L epinephrine increased (P < 0.05) the phlorizin-sensitive glucose uptake in the absence and presence of indomethacin (10 micromol/L). The effect of epinephrine was simulated by beta- (100 micromol/L isoproterenol) and beta(2)-receptor agonists (10 micromol/L terbutaline), as well as by direct stimulation of adenylyl cyclase (10 micromol/L forskolin). The serosal addition of methoxamine, clonidine, dobutamine or BRL 37344 had no effect. Inhibition of protein kinase A with 2 micromol/L H 89 completely abolished the stimulation of glucose uptake by epinephrine. We conclude that ruminal SGLT-1 can be stimulated via beta(2)-dependent generation of cyclic adenosine monophosphate.
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Affiliation(s)
- Jörg R Aschenbach
- Department of Veterinary Physiology, Leipzig University, D-04103 Leipzig, Germany.
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15
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Abstract
The ruminal epithelium has an enormous capacity for the absorption of short-chain fatty acids (SCFAs). This not only delivers metabolic energy to the animal but is also an essential regulatory mechanism that stabilizes the intraruminal milieu. The epithelium itself, however, is endangered by the influx of SCFAs because the intracellular pH (pHi) may drop to a lethal level. To prevent severe cytosolic acidosis, the ruminal epithelium is able to extrude (or buffer) protons by various mechanisms: (i) a Na+/H+ exchanger, (ii) a bicarbonate importing system and (iii) an H+/monocarboxylate cotransporter (MCT). Besides pHi regulation, the MCT also provides the animal with ketone bodies derived from the intraepithelial breakdown of SCFAs. Ketone bodies, in turn, can serve as an energy source for extrahepatic tissues. In addition to SCFA uptake, glucose absorption has recently been identified as a potential way of eliminating acidogenic substrates from the rumen. At least with respect to SCFAs, absorption rates can be elevated when adapting animals to energy-rich diets. Although they are very effective under physiological conditions, the absorptive and regulatory mechanisms of the ruminal epithelium also have their limits. An increased number of protons during the state of ruminal acidosis can be eliminated neither from the lumen nor the cytosol, thus worsening dysfermentation and finally leading to functional and morphological alterations of the epithelial lining.
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Affiliation(s)
- G Gäbel
- Veterinär-Physiologisches Institut, Universität Leipzig, Germany.
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16
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Abstract
Intraruminal glucose is thought to be completely converted to short-chain fatty acids (SCFA) by symbiotic microorganisms. Nevertheless, earlier in vitro studies evidenced the expression of the sodium glucose-linked transporter (SGLT)-1, in the ovine ruminal epithelium. The present study aimed to determine whether the ruminal SGLT-1 is functionally important in vivo. In a first experimental series using the emptied, washed, and isolated reticulorumen of sheep, 6.3% of glucose was absorbed from an intraruminal buffer solution (2 L, 128 mmol/L Na(+), 0.5 mmol/L glucose, 0 mmol/L galactose) within 30 min (P < 0.001). Reducing Na(+) concentration to 10 mmol/L resulted in complete inhibition of glucose absorption, and the addition of 10 mmol/L galactose (at 128 mmol/L Na(+)) induced a small but insignificant inhibition. In a second experimental series, the addition of 12 mmol/L glucose to an initially glucose-free buffer led to an increase in the transruminal potential difference from 34.4 to 37.1 mV within 4 min (P < 0.001). From the 12 mmol/L glucose-containing buffer, 11.0% of glucose was absorbed within 30 min (P < 0.05). In all experiments, microbial glucose degradation in the reticulorumen was prevented by adding cefuroxime (100 mg/L) and colistin methanesulfonate (25 mg/L) to the buffer solution. The effectiveness of antimicrobial treatment was verified by ex vivo incubations of buffer samples drawn from the reticulorumen. We conclude that glucose is absorbed in a sodium-dependent manner from the reticulorumen at low and high glucose concentrations. Absorption at high glucose concentrations is of nutritional importance because it counteracts the genesis of ruminal lactic acidosis.
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Affiliation(s)
- J R Aschenbach
- Department of Veterinary Physiology, Leipzig University, D-04103 Leipzig, Germany
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Aschenbach JR, Wehning H, Kurze M, Schaberg E, Nieper H, Burckhardt G, Gäbel G. Functional and molecular biological evidence of SGLT-1 in the ruminal epithelium of sheep. Am J Physiol Gastrointest Liver Physiol 2000; 279:G20-7. [PMID: 10898743 DOI: 10.1152/ajpgi.2000.279.1.g20] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Because of the effective catabolism of D-glucose to short-chain fatty acids by intraruminal microorganisms, the absorption of D-glucose from the rumen was thought to be of minor importance. However, clinical studies suggested that significant quantities of D-glucose are transported from the ruminal contents to the blood. We therefore tested the ruminal epithelium of sheep for the presence of Na(+)-glucose cotransporter 1 (SGLT-1) on both the functional and mRNA levels. In the absence of an electrochemical gradient, 3-O-methylglucose (3-OMG) was net absorbed across isolated ruminal epithelia mounted in Ussing chambers. The net transport of 3-OMG followed Michaelis-Menten kinetics and was sensitive to phlorizin or decreasing Na(+) concentrations. The mucosal addition of 10 mM D-glucose induced an immediate, phlorizin-sensitive increase in short-circuit current (I(sc)). I(sc) could also be increased by serosal addition of D-glucose or D-mannose, but electrogenic uptake of D-glucose or 3-OMG added on the mucosal side was still detectable after serosal stimulation of I(sc). RT-PCR using primers specific for the ovine intestinal SGLT-1 with subsequent TA cloning and sequencing revealed 100% identity between the cloned cDNA and mRNA fragment 187-621 of ovine intestinal SGLT-1. In conclusion, the ruminal epithelium has a high-affinity SGLT-1, which indicates that it maintains the capacity for D-glucose absorption.
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Affiliation(s)
- J R Aschenbach
- Veterinär-Physiologisches Institut, Universität Leipzig, Germany
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18
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Abstract
We examined microbial activity in the rumen to cleave benzyl ether bonds of lignin model compounds that fluoresced when the bonds were cleaved. 4-Methylumbelliferone veratryl ether dimer was degraded completely within 8 h even in the presence of fungicidal antibiotics, but no significant degradation occurred with bactericidal antibiotics. Degradation of a phenolic beta-O-4 trimer incorporating 4-methylumbelliferone by a benzyl ether linkage was stimulated by ruminal microbes, although its corresponding non-phenolic model compound, 1-(4-ethoxy-3-methoxyphenyl)-1-O-(4-methylumbelliferyl)-2-(2-methoxyp henoxy)-3-propanol, was not degraded. A coniferyl dehydrogenation polymer bearing fluorescent beta-O-4 benzyl ether that contains both phenolic and non-phenolic benzyl ether bonds was partially degraded (about 20%) in 48 h. These results suggest that ruminal microbes decompose benzyl ether linkages of lignin polymers under anaerobic conditions.
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Affiliation(s)
- H Kajikawa
- National Institute of Animal Industry, Tsukuba Norindanchi, Ibaraki, Japan
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Abstract
The transport of cellobiose in mixed ruminal bacteria harvested from a holstein cow fed an Italian ryegrass hay was determined in the presence of nojirimycin-1-sulfate, which almost inhibited cellobiase activity. The kinetic parameters of cellobiose uptake were 14 microM for the Km and 10 nmol/min/mg of protein for the Vmax. Extracellular and cell-associated cellobiases were detected in the rumen, with both showing higher Vmax values and lower affinities than those determined for cellobiose transport. The proportion of cellobiose that was directly transported before it was extracellularly degraded into glucose increased as the cellobiose concentration decreased, reaching more than 20% at the actually observed levels of cellobiose in the rumen, which were less than 0.02 mM. The inhibitor experiment showed that cellobiose was incorporated into the cells mainly by the phosphoenolpyruvate phosphotransferase system and partially by an ATP-dependent and proton-motive-force-independent active transport system. This finding was also supported by determinations of phosphoenolpyruvate phosphotransferase-dependent NADH oxidation with cellobiose and the effects of artificial potentials on cellobiose transport. Cellobiose uptake was sensitive to a decrease in pH (especially below 6.0), and it was weakly but significantly inhibited in the presence of glucose.
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Affiliation(s)
- H Kajikawa
- Department of Animal Nutrition, National Institute of Animal Industry, Tsukuba Norindanchi, Ibaraki 305-0901, Japan.
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