In vitro effects of deoxynivalenol on electrical properties of intestinal mucosa of laying hens

Early Biomarkers for Detecting Subclinical Exposure to Fumonisin B1, Deoxynivalenol, and Zearalenone in Broiler Chickens

Identifying biomarkers of mycotoxin effects in chickens will provide an opportunity for early intervention to reduce the impact of mycotoxicosis. This study aimed to identify whether serum enzyme concentrations, gut integrity, and liver miRNAs can be potential biomarkers for fumonisin B1 (FB1), deoxynivalenol (DON), and zearalenone (ZEA) toxicity in broiler birds as early as 14 days after exposure. A total of 720 male broiler chicks were distributed to six treatment groups: T1: control group (basal diet), T2 (2 FB1 + 2.5 DON + 0.9 ZEA), T3 (5 FB1 + 0.4 DON + 0.1 ZEA), T4 (9 FB1 + 3.5 DON + 0.7 ZEA), T5 (17 FB1 + 1.0 DON + 0.2 ZEA), and T6 (21 FB1 + 3.0 DON + 1.0 ZEA), all in mg/kg diet. On d14, there were no significant differences in the body weight gain (BWG) of mycotoxin treatment groups when compared to the control (p > 0.05), whereas on d21, T6 birds showed significantly reduced BWG compared to the control (p < 0.05). On d14, birds in T6 showed significant upregulation of liver miRNAs, gga-let-7a-5p (14.17-fold), gga-miR-9-5p (7.05-fold), gga-miR-217-5p (16.87-fold), gga-miR-133a-3p (7.41-fold), and gga-miR-215-5p (6.93-fold) (p < 0.05) and elevated serum fluorescein isothiocyanate-dextran (FITC-d) concentrations, aspartate aminotransferase (AST), and creatine kinase (CK) levels compared to the control (p < 0.05). On d21, T2 to T6 birds exhibited reduced serum phosphorus, glucose, and potassium, while total protein, FITC-d, AST, and CK levels increased compared to control (p < 0.05). These findings suggest that serum FITC-d, AST, CK, and liver miRNAs could serve as biomarkers for detecting mycotoxin exposure in broiler chickens.

Nutritional impact of mycotoxins in food animal production and strategies for mitigation

Mycotoxins are toxic secondary metabolites produced by filamentous fungi that are commonly detected as natural contaminants in agricultural commodities worldwide. Mycotoxin exposure can lead to mycotoxicosis in both animals and humans when found in animal feeds and food products, and at lower concentrations can affect animal performance by disrupting nutrient digestion, absorption, metabolism, and animal physiology. Thus, mycotoxin contamination of animal feeds represents a significant issue to the livestock industry and is a health threat to food animals. Since prevention of mycotoxin formation is difficult to undertake to avoid contamination, mitigation strategies are needed. This review explores how the mycotoxins aflatoxins, deoxynivalenol, zearalenone, fumonisins and ochratoxin A impose nutritional and metabolic effects on food animals and summarizes mitigation strategies to reduce the risk of mycotoxicity.

Feeding of deoxynivalenol increases the intestinal paracellular permeability of broiler chickens

In recent years, the deleterious effects attributed to mycotoxins, in particular on the intestine, faced increased attention and it was shown that deoxynivalenol (DON) causes adverse effects on gut health. In this context, it has been repeatedly reported that DON can alter the intestinal morphology, disrupt the intestinal barrier and reduce nutrient absorption. The underlying mechanism of a compromised intestinal barrier caused by DON in chickens has yet to be illustrated. Although, DON is rapidly absorbed from the upper parts of the small intestine, the effects on the large intestine cannot be excluded. Additionally, a damaging effect of DON on the gut epithelium might decrease the resistance of the gut against infectious agents. Consequently, the objectives of the present studies were: (1) to investigate the impact of DON on the epithelial paracellular permeability by demonstrating the mucosal to serosal flux of ¹⁴C-mannitol in the small and large intestine applying Ussing chambers and (2) to delineate the effects of DON on the colonization and translocation of Escherichia coli. Both parameters are well suited as potential indicators for gut barrier failure. For this, a total of 75 one-day-old Ross 308 broiler chickens were housed in floor pens on wood shavings with feed and water provided ad libitum. Birds were randomly allocated to three different groups (n = 25 with 5 replicates/group) and were fed for 5 weeks with either contaminated diets (5 or 10 mg DON/kg feed) or basal diets (control). Body weight (BW) and BW gain of birds in the group fed with 10 mg/kg DON were significantly lower than in group with 5 mg/kg DON and the control group. Moreover, the mannitol flux in jejunum and cecum was significantly (P < 0.05) higher in DON-fed groups compared to control birds. Consistent with this, DON enhanced the translocation of E. coli with a higher number of bacteria encountered in the spleen and liver. Altogether, the actual results verified that DON can alter the intestinal paracellular permeability in broiler chickens and facilitates the translocation of enteric microorganisms such as E. coli to extra-intestinal organs. Considering that moderate levels of DON are present in feed, the consumption of DON-contaminated feed can induce an intestinal breakdown with negative consequences on broiler health.

Deoxynivalenol decreased the growth performance and impaired intestinal physical barrier in juvenile grass carp (Ctenopharyngodon idella)

Deoxynivalenol (DON) is one of the most common mycotoxin contaminants of animal feed worldwide and brings significant threats to the animal production. However, studies concerning the effect of DON on fish intestine are scarce. This study explored the effects of DON on intestinal physical barrier in juvenile grass carp (Ctenopharyngodon idella). A total of 1440 juvenile grass carp (12.17 ± 0.01 g) were fed six diets containing graded levels of DON (27, 318, 636, 922, 1243 and 1515 μg/kg diet) for 60 days. This study for the first time documented that DON caused body malformation in fish, and histopathological lesions, oxidative damage, declining antioxidant capacity, cell apoptosis and destruction of tight junctions in the intestine of fish. The results indicated that compared with control group (27 μg/kg diet), DON: (1) increased the reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC) content, and up-regulated the mRNA levels of Kelch-like-ECH-associated protein 1 (Keap1: Keap1a but not Keap1b), whereas decreased glutathione (GSH) content and antioxidant enzymes activities, and down-regulated the mRNA levels of antioxidant enzymes (except GSTR in MI) and NF-E2-related factor 2 (Nrf2), as well as the protein levels of Nrf2 in fish intestine. (2) up-regulated cysteinyl aspartic acid-protease (caspase) -3, -7, -8, -9, apoptotic protease activating factor-1 (Apaf-1), Bcl2-associated X protein (Bax), Fas ligand (FasL) and c-Jun N-terminal protein kinase (JNK) mRNA levels, whereas down-regulated B-cell lymphoma-2 (bcl-2) and myeloid cell leukemia-1 (Mcl-1) mRNA levels in fish intestine. (3) down-regulated the mRNA levels of ZO-1, ZO-2b, occludin, claudin-c, -f, -7a, -7b, -11 (except claudin-b and claudin-3c), whereas up-regulated the mRNA levels of claudin-12, -15a (not -15b) and myosin light chain kinase (MLCK) in fish intestine. All above data indicated that DON caused the oxidative damage, apoptosis and the destruction of tight junctions via Nrf2, JNK and MLCK signaling in the intestine of fish, respectively. Finally, based on PWG, FE, PC and MDA, the safe dose of DON for grass carp were all estimated to be 318 μg/kg diet.

Dietary deoxynivalenol does not affect mineral element accumulation in breast and thigh muscles of broiler chicken

Deoxynivalenol (DON), a well-known contaminant of feed, can have negative effects on gut permeability and function in poultry, which then could affect major and trace element content of the broilers’ breast and thigh muscles, and ultimately reduce meat quality. To study this hypothesis, DON-contaminated diet was fed to broiler chicks. Two groups of birds were housed in metabolic cages with free access to water and feed, with or without DON (10 mg/kg). After 5 weeks, birds were dissected and samples of the breast and thigh muscles, feed and droppings were analysed for five macro (Ca, K, Mg, Na, and P) and ten micro elements (Al, Cr, Cu, Fe, Mn, Li, Mo, Ni, Pb, Rb, and Zn) by inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometer (ICP-MS) methods. In both groups, increased (p < 0.05) concentrations of Ca Na, Fe, Mn, and Zn were found in thigh muscles compared with the breast, whereas the concentrations of Mg, P, and Rb were higher in the breast muscles. DON had no effect on the elemental contents of the broilers’ breast and thigh muscles. In conclusion, DON at a level of 10 mg/kg feed to broiler chicken over of 5 weeks did not alter the macro or micro element composition in muscle meat.

Phosphoproteome Analysis Reveals the Molecular Mechanisms Underlying Deoxynivalenol-Induced Intestinal Toxicity in IPEC-J2 Cells

Deoxynivalenol (DON) is a widespread trichothecene mycotoxin that commonly contaminates cereal crops and has various toxic effects in animals and humans. DON primarily targets the gastrointestinal tract, the first barrier against ingested food contaminants. In this study, an isobaric tag for relative and absolute quantitation (iTRAQ)-based phosphoproteomic approach was employed to elucidate the molecular mechanisms underlying DON-mediated intestinal toxicity in porcine epithelial cells (IPEC-J2) exposed to 20 μM DON for 60 min. There were 4153 unique phosphopeptides, representing 389 phosphorylation sites, detected in 1821 phosphoproteins. We found that 289 phosphopeptides corresponding to 255 phosphoproteins were differentially phosphorylated in response to DON. Comprehensive Gene Ontology (GO) analysis combined with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment revealed that, in addition to previously well-characterized mitogen-activated protein kinase (MAPK) signaling, DON exposure altered phosphatidylinositol 3-kinase/Akt (PI3K/Akt) and Janus kinase/signal transducer, and activator of transcription (JAK/STAT) pathways. These pathways are involved in a wide range of biological processes, including apoptosis, the intestinal barrier, intestinal inflammation, and the intestinal absorption of glucose. DON-induced changes are likely to contribute to the intestinal dysfunction. Overall, identification of relevant signaling pathways yielded new insights into the molecular mechanisms underlying DON-induced intestinal toxicity, and might help in the development of improved mechanism-based risk assessments in animals and humans.

Impacts of the feed contaminant deoxynivalenol on the intestine of monogastric animals: poultry and swine

Deoxynivalenol (DON) is one of the most prevalent cereal contaminants with major public health concerns owing to its high toxigenic potentials. Once ingested, DON first and foremost targets epithelial cells of the gastrointestinal tract, whose proper functioning, as the first line of defence, is of paramount importance for the host's health. Emerging evidences, summarized in this article, suggest that DON produces its toxicity primarily via activation of the mitogen-activated protein kinases (MAPKs) signalling pathway and alteration in the expression of genes responsible for key physiological and immunological functions of the intestinal tissue of chickens and pigs. The activation of MAPKs signalling cascade results in disruption of the gut barrier function and an increase in the permeability by reducing expression of the tight junction proteins. Exposure to DON also down-regulates the expression of multiple transporter systems in the enterocytes with subsequent impairment of the absorption of key nutrients. Other major intestinal cytotoxic effects of DON described herein are modulation of mucosal immune responses, leading to immunosupression or stimulation of local immune cells and cytokine release, and also facilitation of the persistence of intestinal pathogens in the gut. Both of the last events potentiate enteric infections and local inflammation in pigs and poultry, rendering enterocytes and the host more vulnerable to luminal toxic compounds. This review highlights the cytotoxic risks associated with the intake of even low levels of DON and also identifies gaps of knowledge that need to be addressed by future research.

The feed contaminant deoxynivalenol affects the intestinal barrier permeability through inhibition of protein synthesis

Deoxynivalenol (DON) has critical health effects if the contaminated grains consumed by humans or animals. DON can have negative effects on the active transport of glucose and amino acids in the small intestine of chickens. As the underlying mechanisms are not fully elucidated, the present study was performed to delineate more precisely the effects of cycloheximide (protein synthesis inhibitor, CHX) and DON on the intestinal absorption of nutrients. This was to confirm whether DON effects on nutrient absorption are due to an inhibition of protein synthesis. Changes in ion transport and barrier function were assessed by short-circuit current (Isc) and transepithelial ion conductance (Gt) in Ussing chambers. Addition of D-glucose or L-glutamine to the luminal side of the isolated mucosa of the jejunum increased (P < 0.001) the Isc compared with basal conditions in the control tissues. However, the Isc was not increased by the glucose or glutamine addition after pre-incubation of tissues with DON or CHX. Furthermore, both DON and CHX reduced Gt, indicating that the intestinal barrier is compromised and consequently induced a greater impairment of the barrier function. The remarkable similarity between the activity of CHX and DON on nutrient uptake is consistent with their common ability to inhibit protein synthesis. It can be concluded that the decreases in transport activity by CHX was evident in this study using the chicken as experimental model. Similarly, DON has negative effects on the active transport of some nutrients, and these can be explained by its influence on protein synthesis.

Effect of deoxynivalenol and other Type B trichothecenes on the intestine: a review

The natural food contaminants, mycotoxins, are regarded as an important risk factor for human and animal health, as up to 25% of the world's crop production may be contaminated. The Fusarium genus produces large quantities of fusariotoxins, among which the trichothecenes are considered as a ubiquitous problem worldwide. The gastrointestinal tract is the first physiological barrier against food contaminants, as well as the first target for these toxicants. An increasing number of studies suggest that intestinal epithelial cells are targets for deoxynivalenol (DON) and other Type B trichothecenes (TCTB). In humans, various adverse digestive symptoms are observed on acute exposure, and in animals, these toxins induce pathological lesions, including necrosis of the intestinal epithelium. They affect the integrity of the intestinal epithelium through alterations in cell morphology and differentiation and in the barrier function. Moreover, DON and TCTB modulate the activity of intestinal epithelium in its role in immune responsiveness. TCTB affect cytokine production by intestinal or immune cells and are supposed to interfere with the cross-talk between epithelial cells and other intestinal immune cells. This review summarizes our current knowledge of the effects of DON and other TCTB on the intestine.

Effects of feeding deoxynivalenol (DON)-contaminated wheat to laying hens and roosters of different genetic background on the reproductive performance and health of the newly hatched chicks

A total of 216 23-week-old laying hens from two different genetic backgrounds (half of the birds were Lohmann brown [LB] and [LSL] hens, respectively) and 24 adult roosters were assigned to a feeding trial to study the effect of increasing concentrations of deoxynivalenol (DON) in the diet (0, 5, 10 mg/kg) on the reproductive performance of hens and roosters, and the health of the newly hatched chicks. Hatchability was adversely affected by the presence of DON in LB hens' diet, while the hatchability of the LSL chicks was significantly higher than LB chicks. An interaction effect between DON in the hens' diet and the breed was noticed on fertility, as the fertility was decreased in the eggs of LB hens receiving 10 mg/kg DON in their diet and increased in the eggs of LSL hens fed 10 mg/kg DON. Moreover, spleen relative weight was significantly decreased in the chicks hatched from eggs of hens fed contaminated diets, while gizzard relative weight was significantly decreased in LB chicks with 10 mg/kg DON in their diet compared with the control group. On the other hand, the chicks' haematology and organ histopathology were not affected by the dietary treatment. Additionally, the presence of DON in the roosters' diet had no effect on fertility (the percentage of fertile eggs of all laid eggs). Consequently, the current results indicate a negative impact of DON in LB hens' diet on fertility and hatchability, indicating that the breed of the hens seems to be an additional factor influencing the effect of DON on reproductive performance of the laying hens.

Modulation of intestinal functions following mycotoxin ingestion: meta-analysis of published experiments in animals

Mycotoxins are secondary metabolites of fungi that can cause serious health problems in animals, and may result in severe economic losses. Deleterious effects of these feed contaminants in animals are well documented, ranging from growth impairment, decreased resistance to pathogens, hepato- and nephrotoxicity to death. By contrast, data with regard to their impact on intestinal functions are more limited. However, intestinal cells are the first cells to be exposed to mycotoxins, and often at higher concentrations than other tissues. In addition, mycotoxins specifically target high protein turnover- and activated-cells, which are predominant in gut epithelium. Therefore, intestinal investigations have gained significant interest over the last decade, and some publications have demonstrated that mycotoxins are able to compromise several key functions of the gastrointestinal tract, including decreased surface area available for nutrient absorption, modulation of nutrient transporters, or loss of barrier function. In addition some mycotoxins facilitate persistence of intestinal pathogens and potentiate intestinal inflammation. By contrast, the effect of these fungal metabolites on the intestinal microbiota is largely unknown. This review focuses on mycotoxins which are of concern in terms of occurrence and toxicity, namely: aflatoxins, ochratoxin A and Fusarium toxins. Results from nearly 100 published experiments (in vitro, ex vivo and in vivo) were analyzed with a special attention to the doses used.

Effects of deoxynivalenol and lipopolysaccharide on electrophysiological parameters in growing pigs

Deoxynivalenol (DON) is a major B-trichothecene that draws importance from its natural occurrence in cereals worldwide. It has many effects on rapidly dividing cells. Lipopolysaccharide (LPS) is an endotoxin released from most Gram-negative bacteria, which plays a major role in induction of inflammation and sepsis under certain conditions. In our experiments we aimed to study the effects of different concentrations of DON (up to 8,000 ng/ml) on the electrogenic transport of nutrients and on tissue conductances in growing pigs using the Ussing chamber technique. The effect of DON-contaminated feed (2.9 mg/kg feed) on the respective parameters, as well as the interactions between DON and intraperitoneal (i.p.) LPS were assessed using porcine jejunal tissues. In vitro DON inhibited the absorption of alanine and glucose across the pig jejunum at concentrations of 4,000 and 8,000 ng/ml, suggesting that DON had an inhibitory effect on the electrogenic transport of nutrients across porcine small intestines. Electrogenic transport of alanine and glucose across porcine small intestines varied regionally among intestinal segments with higher response in ileal tissues. A synergistic effect was observed between DON in feed and injected LPS on tissue conductance. In response, glucose with higher short circuit currents was observed across porcine jejunal mucosa in nutrient stimulated conditions.

A nutritional approach for the management of deoxynivalenol (DON) toxicity in the gastrointestinal tract of growing chickens

It has been shown that DON has negative effects on the active transport of some nutrients in the small intestine of chickens. The plausible interactions between food contaminants and natural components could be high. The present study investigated the effects of DON on the presence or absence of dietary inulin on the electrophysiological response of the gut to glucose. Ussing chamber studies were conducted with isolated jejunal epithelia at the age of 35 days. Electrophysiology of the epithelia was recorded and the changes of the short-circuit current (Isc) were determined. The addition of d-glucose on the luminal side of the isolated mucosa increased (P < 0.05) the Isc in the control group and inulin supplemented group. The oligosaccharides did not increase glucose absorption in young healthy chickens compared with the controls. In the second experiment, after preincubation of tissues with DON, the addition of glucose did not increase the Isc in jejunum and colon in the control group (P > 0.05). However, in the dietary inulin supplemented group in both jejunum and colon, the addition of glucose after preincubation of tissues with DON increased the Isc, suggesting that the dietary inulin supplementation of the broilers regulated and improved the glucose absorption in the presence of DON and kept it at normal levels.

Effects of feeding blends of grains naturally contaminated with Fusarium mycotoxins on small intestinal morphology of turkeys

An experiment was conducted to investigate the effects of feeding grains naturally contaminated with Fusarium mycotoxins on morphometric indices of duodenum, jejunum, and ileum in turkeys. The possible preventative effect of a polymeric glucomannan mycotoxin adsorbent (GMA) was also determined. Three hundred 1-d-old male turkey poults were fed wheat, corn, and soybean meal-based starter (0 to 3 wk), grower (4 to 6 wk), developer (7 to 9 wk), and finisher (10 to 12 wk) diets formulated with control grains, contaminated grains, and contaminated grains + 0.2% GMA. Morphometric indices were measured at the end of each growth phase and included villus height (VH), crypt depth, villus width, thicknesses of submucosa and muscularis, villus-to-crypt ratio, and apparent villus surface area (AVSA). At the end of the starter phase, feedborne mycotoxins significantly decreased the VH in the duodenum, and supplementation of the contaminated diet with GMA prevented this effect. The feeding of contaminated grains also reduced (P < 0.05) VH and AVSA in jejunum, whereas none of the variables were affected in the ileum. Villus width and AVSA of duodenum, VH, and AVSA of jejunum and submucosa thickness of ileum were significantly reduced when birds were fed contaminated grains at the end of the grower phase, and supplementation with GMA prevented these effects in jejunum and ileum. No effects of diets were seen on morphometric variables at the end of the developer and finisher phases. It was concluded that consumption of grains naturally contaminated with Fusarium mycotoxins results in adverse effects on intestinal morphology during early growth phases of turkeys, and GMA can prevent many of these effects.

Effects of B-trichothecenes on luminal glucose transport across the isolated jejunal epithelium of broiler chickens

Trichothecenes are closely-related sesquiterpenoids (ring structure) with a 12, 13 epoxy ring and a variable number of hydroxyl, acetyl or other substituents. In chickens, D-glucose and amino acid absorption occurs via carrier-mediated transport. Recently, it has been observed that deoxynivalenol (DON) alters the gut function and impairs glucose and amino acid transport in chickens. The purpose of this work was to determine the effects of different B-trichothecenes [DON, Nivalenol (NIV), 15-Ac-DON and Fusarenon X (FUS X)] on intestinal carrier-mediated sodium co-transport of D-glucose in the small intestine of broiler chickens. Intestinal transport was determined by changes in the short-circuit current (Isc), proportional to ion transmembrane flux, in the middle segment of the jejunum of broilers with the Ussing chamber technique. D-glucose produced an increase of the Isc, and this effect was reverted by different B-trichothecene mycotoxins, indicating that the glucose induced Isc was altered by B-trichothecenes. The addition of glucose after pre-incubation of the tissues with B-trichothecenes had no effect (p > 0.05) on the Isc, suggesting that B-trichothecenes afflicted the Na(+)-D-glucose co-transport. However, FUX had no obvious effect on the measured parameters. It could be concluded from the present study that the glucose co-transporter activity appears to be more sensitive to DON, NIV and 15-Ac-DON suppression than by FUS X in the jejunum of broilers.

Influence of deoxynivalenol on the D-glucose transport across the isolated epithelium of different intestinal segments of laying hens

Deoxynivalenol (DON) decreases glucose absorption in the proximal jejunum of laying hens in vitro and this effect is apparently mediated by the inhibition of the sodium D-glucose co-transporter. DON could modulate the sugar transport of other intestinal regions of chickens. For this purpose, we have measured the effects of DON on the Na(+) D-glucose co-transporter, by addition of DON after and before a glucose addition in the isolated epithelium from chicken duodenum, jejunum, ileum, caecum and colon by using the Ussing chamber technique in the voltage clamp technique. The data showed in all segments of the gut that the addition of D-glucose on the mucosal side produced an increase in the current (Isc) compared with the basal values, the Isc after glucose addition to the small intestine was greater than the Isc of the large intestine compared with the basal values, specially of the jejunum (p < 0.002), indicating that the jejunum is the segment that is the best prepared for Na(+)-D-glucose co-transport. Further addition of 10 microg DON/ml to the mucosal solution decreased the Isc in all segments and the Isc returned to the basal value, especially in the duodenum and mid jejunum (p < 0.05). In contrast, the addition of 5 mmol D-glucose/l on the mucosal side after incubation of the tissues with DON in all segments had no effect on the Isc (p > 0.05), suggesting that DON previously inhibited the Na(+)D-glucose co-transport. The blocking effects of DON in duodenum and jejunum were greater than the other regions of the gut. It can be concluded that the small intestine of laying hens has the most relevant role in the carrier mediated glucose transport and the large intestine, having non-significant capacity to transport sugars, appears to offer a minor contribution to glucose transport because the surface area is small. The effect of D-glucose on the Isc was reversed by DON in all segments, especially in the duodenum and jejunum, suggesting that DON entirely inhibited Na(+)-D-glucose co-transport. This finding indicates that the inhibition of Na(+) co-transport system in all segments could be an important mode of action for DON toxicity of hens.

In vitro effects of deoxynivalenol on small intestinal D-glucose uptake and absorption of deoxynivalenol across the isolated jejunal epithelium of laying hens

Deoxynivalenol (DON) is a common mycotoxin contaminant in feedstuffs. It has been shown to cause diverse toxic effects in animals. The aim of the present study was to evaluate the effects of DON on the glucose transport capacity in chickens' jejunum and to investigate the permeation of DON itself by the Ussing chamber technique. Glucose uptake into chicken jejunal epithelia was measured after the addition of 200 mumol/L of (14)C-labeled glucose to the mucosal solution. Glucose uptake under control condition was 3.28 +/- 0.53 nmol/cm(2) x min. The contribution of sodium glucose-linked transporter 1 (SGLT-1) to total glucose uptake was estimated by inhibiting SGLT-1 with phlorizin (100 micromol/L). In the presence of phlorizin, glucose uptake was reduced (P < 0.05) to 1.21 +/- 0.19 nmol/cm(2) x min. Deoxynivalenol decreased (P < 0.05) the glucose uptake in the absence of phlorizin to 1.81 +/- 0.24 nmol/cm(2) x min but had no additional effect on the glucose uptake in the presence of phlorizin (0.97 +/- 0.17 nmol/cm(2) x min). Mucosal-to-serosal permeation of DON was proportional to the initial DON concentration over a concentration range from 1 to 10 mug/mL on the mucosal side. Apparent permeability at 10 microg/mL of DON measured 60 to 90 min after DON application was 1.7 x 10(-05) cm/s. It can be concluded that DON (10 mg/L) decreases glucose uptake almost as efficiently as phlorizin. The similarity between the effects of phlorizin and DON on glucose uptake evidences their common ability to inhibit Na(+)-D-glucose cotransport. In addition to local effects, DON can be absorbed from the jejunum. A predominant part of DON passes across the chicken intestinal epithelium by passive diffusion, which is likely on the paracellular pathway. The results imply that the exposure to DON-contaminated feeds may negatively affect animal health and performance by local (i.e., inhibition of intestinal SGLT-1) and systemic effects.

Clostridium perfringens alpha toxin affects electrophysiological properties of isolated jejunal mucosa of laying hens

Bacteria that colonize the intestinal tract can invade epithelial cells or produce toxins that cause diarrhoeal diseases. Proliferation of Clostridium perfringens and production of alpha-toxin, a phospholipase C, is the major factor for necrotic enteritis in poultry. However, little is known about the functional importance of luminal alpha-toxin during intestinal infection. The purpose of this study was to investigate the effects of purified alpha toxin of Clostridium perfringens on the electrophysiology of the laying hen's stripped jejunum in Ussing chambers. The effects were investigated in Experiment 1 after toxin addition to the mucosal and serosal side of the tissue, and a second experiment was performed to study the effect of the toxin on sodium-dependent glucose transport. Mucosal exposure of jejunal tissue sheets to 100 units of alpha toxin/L did not elicit electrophysiologic changes. The addition of purified alpha toxin to the serosal side induced a biphasic increase in short-circuit current (ISC) after 15 and 100 min. The magnitude of the increase of ISC of both peaks was similar, but the second phase response lasted longer. The tissue conductivity tended (P = 0.07) to be lower after 2 h of toxin addition compared with basal value when no toxin was added. In the second experiment, adding D-glucose on the mucosal side of the jejunum increased (P < 0.05) the ISC from a baseline value of 42 +/- 28 microA/cm2 to a maximal value of 103 +/- 27 microA/cm2. Preincubation with alpha-toxin almost fully inhibited this stimulation of ISC by D-glucose. The conductance of the tissues was not affected by the toxin addition. These findings indicate that alpha toxin not only causes electrogenic secretion of anions, probably due to the stimulation of chloride secretion, but also diminishes electrogenic Na+/glucose cotransport from the mucosal to serosal side in the small intestine of poultry.

Effects of luminal deoxynivalenol and L-proline on electrophysiological parameters in the jejunums of laying hens

Most amino acids are cotransported with sodium. Deoxynivalenol (DON) decreases glucose absorption in the chicken small intestine in vivo and in vitro, and this effect is apparently mediated by the inhibition of the sodium D-glucose cotransporter. DON could selectively modulate the activities of other intestinal transporters. In order to assess this hypothesis, a study was conducted to characterize the in vitro effects of DON in the presence of mucosal amino acids, using L-proline as a model, on the electrophysiological parameters in the jejunums of laying hens. L-Proline (mucosal concentration of 1 mmol/L) was added to a stripped proximal part of jejunum sheets mounted in Ussing chambers in Ringer buffer, and the electrical properties were measured. The transmural potential difference (PD) was nearly constant between the treatments. The tissue resistance (Rt) was higher (P < 0.05) in the tissues exposed to DON compared with basal values and the values after addition of L-proline. Addition of L-proline on the luminal side of the isolated mucosa increased (P < 0.05) the short circuit-current (Isc), and it decreased (P < 0.05) after addition of DON, indicating that the proline-induced Isc was altered by DON. The addition of proline after incubation of the tissues with DON had no effect (P > 0.05) on PD or Rt. Proline did not increase the Isc under these conditions. DON decreased (P < 0.1) the Isc after addition of proline, indicating that DON inhibited the Na+-amino acid co-transport. We concluded from the present study that the amino acid cotransporter activity appears to be highly sensitive to DON suppression.