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PubMed2000

Degradation of gluten by proteases from dry and germinating wheat (Triticum durum) seeds: An in vitro approach to storage protein mobilization.

Vital gluten was used as an ideal substrate to investigate the role of some proteases in storage protein degradation. Aspartic proteinase and carboxypeptidase were identified as endogenous enzymes adsorbed on gluten and their optimum pH values determined. SDS-PAGE of soluble products released by gluten digestion revealed that the activity of these proteases plays a minor role in protein mobilization, whereas cysteine proteinase, purified from wheat seeds at the fourth day of germination, is extremely effective, producing a remarkable protein degradation in short times. Synergistic effects of aspartic and cysteine proteinase were not observed. Spin labeling of the sulfhydryl groups of gluten proteins enabled a comparative EPR investigation of the consequences of proteolytic degradation on gluten elasticity. It was found that storage protein mobilization brings a loss of elasticity to the polymeric network of gluten, which is particularly marked when the hydrolysis is performed by cysteine proteinase.

Endopeptidases↗
PubMed2001

Physicochemical studies of caroubin: a gluten-like protein.

It has been reported that caroubin, a protein mixture obtained from carob seeds, has rheological properties similar to those of gluten. Comparative studies of the effects of hydration and temperature on caroubin and gluten were carried out with the aid of NMR, FTIR, scanning electron microscopy, and differential scanning calorimetry techniques. The results show that caroubin has a more ordered structure than gluten and that hydration has little effect on its secondary structure when compared to gluten. Caroubin is more easily accessible to water than gluten, suggesting that caroubin is more hydrophilic in nature. On hydration, caroubin, like gluten, forms fibrillar structures and sheets.

Calorimetry, Differential Scanning↗
PubMed2006

Thermoformed wheat gluten biopolymers.

The quantity of available wheat gluten exceeds the current food use markets. Thermoforming is an alternative technical means for transforming wheat gluten. Thermoforming was applied here to wheat gluten under chemically reductive conditions to form pliable, translucent sheets. A wide variety of conditions, i.e., temperature, reducing agents, plasticizers and additives were tested to obtain a range of elastic properties in the thermoformed sheets. These properties were compared to those of commercially available polymers, such as polypropylene. Elasticity of the gluten formulations were indexed by Young's modulus and were in the range measured for commercial products when tested in the 30-70% relative humidity range. Removal of the gliadin subfraction of gluten yielded polymers with higher Young's modulus since this component acts as a polymer-chain terminator. At relative humidity less than 30% all whole gluten-based sheets were brittle, while above 70% they were highly elastic.

Biopolymers↗
PubMed2000

Protein insolubilization and thiol oxidation in sulfite-treated wheat gluten films during aging at various temperatures and relative humidities.

Gluten films were prepared by casting an acidic and ethanolic solution of gluten previously treated with sodium sulfite. The effects of sulfitolysis on proteins were investigated by SE-HPLC and thiol/disulfide content measurements. During sulfitolysis, insoluble glutenin macropolymer was converted into its constitutive subunits. About 10% of gluten disulfide bonds were cleaved, of which three-fourths originated from interchain disulfide bonds. Oxidation of thiol groups released during sulfitolysis was followed for various temperatures (T) and relative humidities. Oxidation was shown to be a second-order rate process occurring below the glass transition temperature (T(g)) and related to T - T(g). Thiol oxidation ensured the formation of interchain bonds between specific classes of gluten proteins according to an ordered process. Intrachain bonds were also formed and through thiol/disulfide-exchange reactions were finally converted to interchain bonds. Thus, fully oxidized gluten films had more insoluble glutenin macropolymers than native gluten.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Identification and analysis of multivalent proteolytically resistant peptides from gluten: implications for celiac sprue.

Dietary gluten proteins from wheat, rye, and barley are the primary triggers for the immuno-pathogenesis of Celiac Sprue, a widespread immune disease of the small intestine. Recent molecular and structural analyses of representative gluten proteins, most notably alpha- and gamma-gliadin proteins from wheat, have improved our understanding of these pathogenic mechanisms. In particular, based on the properties of a 33-mer peptide, generated from alpha-gliadin under physiological conditions, a link between digestive resistance and inflammatory character of gluten has been proposed. Here, we report three lines of investigation in support of this hypothesis. First, biochemical and immunological analysis of deletion mutants of alpha-2 gliadin confirmed that the DQ2 restricted T cell response to the alpha-2 gliadin are directed toward the epitopes clustered within the 33-mer. Second, proteolytic analysis of a representative gamma-gliadin led to the identification of another multivalent 26-mer peptide that was also resistant to further gastric, pancreatic and intestinal brush border degradation, and was a good substrate of human transglutaminase 2 (TG2). Analogous to the 33-mer, the synthetic 26-mer peptide displayed markedly enhanced T cell antigenicity compared to monovalent control peptides. Finally, in silico analysis of the gluten proteome led to the identification of at least 60 putative peptides that share the common characteristics of the 33-mer and the 26-mer peptides. Together, these results highlight the pivotal role of physiologically generated, proteolytically stable, TG2-reactive, multivalent peptides in the immune response to dietary gluten in Celiac Sprue patients. Prolyl endopeptidase treatment was shown to abolish the antigenicity of both the 33-mer and the 26-mer peptides, and was also predicted to have comparable effects on other proline-rich putatively immunotoxic peptides identified from other polypeptides within the gluten proteome.

Amino Acid Sequence↗
PubMed1995

Digestion of wheat gluten and potato protein by the preruminant calf: digestibility, amino acid composition and immunoreactive proteins in ileal digesta.

Three milk substitute diets, in which the protein was either provided exclusively by skim milk powder or partially (52%) substituted by a native wheat gluten or a potato protein concentrate, were given to intact or ileo-caecal cannulated preruminant calves. The apparent faecal nitrogen digestibility was lower (P < 0.05) with the potato than with the gluten and control diets (0.90, 0.93 and 0.95, respectively). The same trend was observed at the ileal level (0.83, 0.87 and 0.91, respectively). Apparent digestibilities of most amino acids were lower with the potato than with the control diet (P < 0.05 for glutamic acid, proline, cystine, methionine, isoleucine, leucine, tyrosine and lysine). The same trend was observed with the gluten diet. Apparent digestibilities of glutamic acid and cystine were also lower (P < 0.05) with the potato than with the gluten diet. Protein fractions of Mr 43,000 and below 14,000 were detected immunochemically in ileal digesta corresponding to the potato diet, but no immunoreactivity was found in digesta with the gluten diet. However, the considerable enrichment of digesta in glutamic acid and proline with gluten indicates that dietary protein fractions rich in these 2 amino acids escaped digestion in the small intestine. With the potato diet, the undigested fractions contained high levels of aspartic acid, glutamic acid and cystine.

Amino Acids↗
PubMed2006

A unique dendritic cell subset accumulates in the celiac lesion and efficiently activates gluten-reactive T cells.

BACKGROUND & AIMS: Celiac disease is a chronic inflammation of the duodenal mucosa driven by gluten-reactive T cells restricted by the disease-associated HLA-DQ2 molecule. The mechanisms that regulate the activation of mucosal T cells are, however, understood poorly. The aim of this study was to identify the antigen-presenting cells that are responsible for the activation of gluten-reactive T cells in the celiac lesion. METHODS: Intestinal biopsy specimens obtained from untreated and treated celiac patients and normal controls were either snap-frozen directly or incubated for 24 hours with or without gluten peptides. Cryosections were subjected to multicolor immunofluorescence applying monoclonal antibodies to a range of antigen-presenting cell markers. Macrophages and dendritic cells were isolated from enzymatically digested small intestinal biopsies of untreated patients and incubated with gluten-reactive T-cell clones to measure their antigen-presenting capacity. RESULTS: HLA-DQ2+ cells in the normal duodenal mucosa consisted of 2 distinct cell populations: about 80% were CD68+ DC-lysosome intercellular adhesion molecule-3-grabbing nonintegrin+ macrophages and 20% were CD11c+ dendritic cells. Importantly, the CD11c+ dendritic cells accumulated in the celiac lesion and revealed an activated phenotype expressing CD86 and DC-specific-associated membrane protein. Moreover, when isolated from challenged biopsy specimens, the CD11c+ dendritic cells efficiently activated gluten-reactive T cells. CONCLUSIONS: Our results suggest that a unique subset of dendritic cells are responsible for local activation of gluten-reactive T cells in the celiac lesion.

Adolescent↗
PubMed2004

Structural basis for HLA-DQ2-mediated presentation of gluten epitopes in celiac disease.

Celiac disease, also known as celiac sprue, is a gluten-induced autoimmune-like disorder of the small intestine, which is strongly associated with HLA-DQ2. The structure of DQ2 complexed with an immunogenic epitope from gluten, QLQPFPQPELPY, has been determined to 2.2-A resolution by x-ray crystallography. The glutamate at P6, which is formed by tissue transglutaminase-catalyzed deamidation, is an important anchor residue as it participates in an extensive hydrogen-bonding network involving Lys-beta71 of DQ2. The gluten peptide-DQ2 complex retains critical hydrogen bonds between the MHC and the peptide backbone despite the presence of many proline residues in the peptide that are unable to participate in amide-mediated hydrogen bonds. Positioning of proline residues such that they do not interfere with backbone hydrogen bonding results in a reduction in the number of registers available for gluten peptides to bind to MHC class II molecules and presumably impairs the likelihood of establishing favorable side-chain interactions. The HLA association in celiac disease can be explained by a superior ability of DQ2 to bind the biased repertoire of proline-rich gluten peptides that have survived gastrointestinal digestion and that have been deamidated by tissue transglutaminase. Finally, surface-exposed proline residues in the proteolytically resistant ligand were replaced with functionalized analogs, thereby providing a starting point for the design of orally active agents for blocking gluten-induced toxicity.

Celiac Disease↗
PubMed2004

Effect of an oats-containing gluten-free diet on symptoms and quality of life in coeliac disease. A randomized study.

BACKGROUND: Evidence suggests the acceptability of oats in a gluten-free diet in coeliac disease. We investigated the impact of an oats-containing diet on quality of life and gastrointestinal symptoms. METHODS: Thirty-nine coeliac disease patients on a gluten-free diet were randomized to take either 50 g of oats-containing gluten-free products daily or to continue without oats for 1 year. Quality of life was assessed using the Psychological General Well-Being questionnaire and gastrointestinal symptoms using the Gastrointestinal Symptom Rating Scale. Small-bowel mucosal villous architecture, CD3+, alphabeta+, gammadelta+ intraepithelial lymphocytes, serum endomysial and tissue transglutaminase antibodies were investigated. RESULTS: Twenty-three subjects were randomized to the oats-containing diet and 16 to the traditional gluten-free diet. All adhered strictly to their respective diet. Quality of life did not differ between the groups. In general, there were more gastrointestinal symptoms in the oats-consuming group. Patients taking oats suffered significantly more often from diarrhoea, but there was a simultaneous trend towards a more severe average constipation symptom score. The villous structure did not differ between the groups, but the density of intraepithelial lymphocytes was slightly but significantly higher in the oats group. The severity of symptoms was not dependent on the degree of inflammation. Antibody levels did not increase during the study period. CONCLUSION: The oats-containing gluten-free diet caused more intestinal symptoms than the traditional diet. Mucosal integrity was not disturbed, but more inflammation was evident in the oats group. Oats provide an alternative in the gluten-free diet, but coeliac patients should be aware of the possible increase in intestinal symptoms.

Adult↗
PubMed2006

Urinary nitric oxide during one year of gluten-free diet with or without oats in children with coeliac disease.

OBJECTIVE: Although in both adults and children with coeliac disease (CD) it is now recommended that oats be added to their gluten-free diet, there is still some controversy concerning the possible harmful effects of oats in some individuals. In this study concentrations of nitric oxide metabolites were repeatedly measured in the urine of children under investigation for CD, when on a gluten-free diet with or without oats. MATERIAL AND METHODS: The study included 116 children, randomized to a standard gluten-free diet (GFD-std) or a gluten-free diet supplemented with wheat-free oat products (GFD-oats), over a one-year period. Small-bowel biopsy was performed at the beginning and end of the study. Morning urine samples were collected from 87 children and urinary nitrite/nitrate concentrations were monitored at 0, 3, 6, 9 and 12 months. RESULTS: All patients were in clinical remission after the study period. There was a rapid decline in urinary nitrite/nitrate concentrations in both groups as early as after 3 months. No differences were seen between the study groups at any of the checkpoints. However, at the end of the study, the nitrite/nitrate values of 9 children in the GFD-oats group and 8 children in the GFD-std group had not normalized. CONCLUSIONS: Children with CD on a gluten-free diet with oats display a similar reduction in urinary nitrite/nitrate as those on a traditional gluten-free diet. Some children, however, still demonstrate high nitrite/nitrate excretion after one year on either diet, indicating that long-term follow-up studies of children on an oats-containing diet are needed.

Adolescent↗
PubMed1999

Persistent mucosal abnormalities in coeliac disease are not related to the ingestion of trace amounts of gluten.

BACKGROUND: It is expected that in patients with coeliac disease the small-bowel mucosal mucosa will return to normal if they adhere to a gluten-free diet (GFD). However, in many this is not the case. This study aims to determine whether this persistent villous atrophy (VA) could be due to continued ingestion of the trace amounts of gluten in 'gluten-free' foods, as defined by the WHO/FAO Codex Alimentarius. METHODS: Duodenal biopsy specimens from 89 adults with long-standing coeliac disease were examined, and the findings correlated with their form of gluten-free diet. RESULTS: In 51 subjects the duodenal specimen was normal, whereas in 38 there was villous atrophy (partial, 28; subtotal, 8; total, 2). There was no relationship between the presence or absence of VA and ingestion of either a GFD as defined by the Codex Alimentarius (Codex-GFD; 39 patients) or a GFD that contained no detectable gluten (NDG diet: 50 patients). Intraepithelial lymphocyte counts were higher, and lactase levels lower, in subjects with an abnormal biopsy specimen than in those in whom it was normal. However, within each of these biopsy groups there was no difference in these variables between patients on a Codex-GFD and those on an NDG-GFD. IgA antigliadin antibody was detected in 4 of 29 patients on a Codex-GFD and in 3 of 13 on a NDG-GFD (NS). CONCLUSION: The persistent mucosal abnormalities seen in patients with coeliac disease on a GFD are not due to the ingestion of trace amounts of gluten. The consequences of these abnormalities have yet to be determined.

Adult↗
PubMed2006

Immunochemical determination of gluten in malts and beers.

The gluten content in different varieties of barley and malts, and in different types of beers, was determined by a 'sandwich' enzyme immunoassay (RIDASCREEN Gliadin kit). The gluten levels in barley wheat, rye and spelt malts ranged 18.8-45.0, 44.0-68.0, 41.6 and 21.2 g kg-1, respectively. When various types of beer were compared, the gluten concentration increased as follows: alcohol-free beer (<3.0), lager beers (<3.0-8.7 mg l-1), stouts (9.0-15.2 mg l-1) and wheat beers (10.6-41.2 mg l-1). When 10 Czech lager beers were analysed, using both sandwich and competitive ELISA, the results showed that the latter method provided values several times higher than the former. Gluten balance was carried out during the brewing process, starting from the raw materials and terminating at the final beer. Gluten levels decreased due to precipitation during the mashing process, primary and secondary fermentation and, lastly, as a result of adsorption during beer stabilization. The gluten content in beer is, thus, approximately three orders of magnitude lower than in the raw malt.

Alcoholic Beverages↗
PubMed2004

Effect of a gluten-free diet on gastrointestinal symptoms in celiac disease.

BACKGROUND: Atypical presentations of celiac disease appear to be at least as common as is the classic presentation of steatorrhea, diarrhea, and weight loss. OBJECTIVE: We examined the effect of a gluten-free diet on gastrointestinal symptoms in a cohort of US patients with celiac disease. DESIGN: A follow-up survey was conducted in 215 patients who were evaluated at the University of Iowa from 1990 through 1997 as having biopsy-confirmed celiac disease. The systematic survey asked detailed questions regarding gastrointestinal symptoms before and after the institution of a gluten-free diet in the patients, all of whom had been given the same dietary advice. RESULTS: The group consisted of 160 female and 55 male patients. Although diarrhea was the most frequent symptom in untreated celiac disease, steatorrhea occurred in only one-fifth of patients. Other complaints were common, and most responded to gluten exclusion. The benefit of gluten exclusion was equally apparent in men and women. Diarrhea responded in most patients, usually within days, and the mean time to resolution was 4 wk. Many patients had alternating diarrhea and constipation, both of which were responsive to the gluten-free diet. Most patients had abdominal pain and bloating, which resolved with the diet. CONCLUSIONS: Celiac disease causes a wide range of gastrointestinal symptoms. Clinicians must have a high level of suspicion to detect the atypical forms of celiac disease. With a gluten-free diet, patients have substantial and rapid improvement of symptoms, including symptoms other than the typical ones of diarrhea, steatorrhea, and weight loss.

Body Mass Index↗
PubMedDate not supplied

Reaction of rectal mucosa of celiac patients to direct contact with gluten.

It is assumed that the colonic mucosa of celiac patients is not sensitive to gluten. This assumption has been supported by the absence of clinical manifestations of colonic involvement in patients with active celiac disease which, by itself, does not confirm insensitivity to gluten. Eight children, aged from 11 to 25 months, with an initial diagnosis of celiac disease were studied: in five children a definite diagnosis has already been confirmed. Rectal gluten challenge was done by means of retention enemas. A volume of 100 ml of a 10% gluten suspension in water was introduced into the rectum three times per day for 8 days; each enema was retained at least 1 h. Rectosigmoidoscopies and rectal biopsies were done before and at the end of the challenge period. The endoscopic appearance of rectal mucosa was normal in all the children either before or after gluten challenge. The means of total mucosal thickness, intraepithelial lymphocyte counts, mitotic crypt cell activity, and cellular infiltration of lamina propria increased after challenge; the mean of goblet cell/epithelial cell ratio in the surface epithelium decreased. The differences between each pair of means (before and after challenge), however, were not significant except for total mucosal thickness (p less than 0.05), the meaning of which is unclear. This study did not definitely demonstrate that the rectal mucosa of celiacs is insensitive to gluten. For practical clinical purposes, however, it behaves as such. This makes the rectal mucosa a useless tool for the final diagnosis of celiac disease.

Administration, Rectal↗
PubMed1991

Routine measurements of gluten antibodies in children of short stature.

Serum IgA and IgG gluten antibody levels were measured prospectively in 168 children without abdominal symptoms referred to the outpatient clinic for short stature. Elevated (greater than 0.30 units) gluten IgA antibody levels (0.82 +/- 0.22 units) were detected in five children (aged 8.5 +/- 1.6 years, height standard deviation score -2.14 +/- 0.26). They had probable celiac disease based on villus atrophy at duodenal biopsy, in vitro toxicity of wheat gluten, and disappearance of serum gluten antibodies after gluten withdrawal from the diet. Three of these children had elevated IgG antibody levels (greater than 0.25 units). Elevated IgG antibody levels with normal IgA levels were demonstrated in 11 short children who had normal duodenal biopsy results. It is concluded that measurement of gluten antibodies, especially of the IgA type, should be included in the diagnostic evaluation of children with short stature.

Adolescent↗
PubMed1998

The gluten-free diet: a nutritional risk factor for adolescents with celiac disease?

BACKGROUND: The gluten-free diet is the standard therapy for patients affected by celiac disease, although compliance with the diet is not optimal in adolescents or adults. Moreover, the gluten-free diet may induce nutritional imbalances. METHODS: Alimentary habits and diet composition were examined in 47 adolescents with celiac disease and 47 healthy aged-matched control subjects. All subjects compiled a 3-day alimentary record that allowed determination of their energy intakes: the macronutrient composition of their diets; and their iron, calcium, and fiber intakes. To evaluate compliance with the gluten-free diet, immunoglobulin A antigliadin and antiendomysium antibodies were assessed in all with celiac disease. RESULTS: The analysis of the records and the results of antibody levels showed that 25 subjects strictly followed dietetic prescriptions (group 1A), whereas 22 patients consumed gluten-containing food (group 1B). Those with celiac disease and control subjects (group 2) consumed a normocaloric diet. Lipid and protein consumption was high, however, and the consumption of carbohydrates low. Moreover, dietary levels of calcium, fiber, and especially in girls, iron, were low. These nutritional imbalances were significantly more evident in group 1A than in group 1B, as a consequence of poor alimentary choices. Moreover, in group 1A overweight and obesity were more frequent (72%) than in group 1B (51%) and in the control subjects (47%). CONCLUSIONS: In people with celiac disease, adherence to a strict gluten-free diet worsens the already nutritionally unbalanced diet of adolescents, increasing elevated protein and lipid consumption. In the follow-up of patients with celiac disease, considerable effort has yet to be made to improve compliance with a gluten-free diet, and especially to control the nutritional balance of the diet in compliant patients.

Adolescent↗
PubMed2003

Innovative approach to low-level gluten determination in foods using a novel sandwich enzyme-linked immunosorbent assay protocol.

OBJECTIVES: There is currently much call for a reliable enzyme-linked immunosorbent assay (ELISA) protocol for determining gluten in foods to serve as a basis for further Codex Alimentarius regulations. Given its ability to recognize the potential coeliac-toxic epitope QQPFP, which occurs repeatedly in alpha-, gamma- and omega-gliadins, hordeins and secalins, the monoclonal antibody R5 raised against a secalin extract may prove to be an essential tool for gluten analysis. This study was designed to develop a highly sensitive and specific sandwich ELISA to quantify low levels of wheat, barley and rye prolamins in foods for coeliacs. METHODS: Simple sandwich ELISA based on the use of a single monoclonal antibody (R5) as both the coating and detection was developed. A quantitative cocktail gluten-extraction procedure for heat-processed foods was also tested. RESULTS: R5-ELISA was able to identify gliadins, hordeins and secalins with assay sensitivities of 0.78, 0.39 and 0.39 ng/ml, respectively. The assay's detection limit was 1.5 ng gliadins/ml (1.56 ppm gliadins, 3.2 ppm gluten). The system proved insensitive to the non-coeliac-toxic cereals maize, rice and oats, and was non-cultivar-dependent. It was also able to detect gliadins and hordeins in unprocessed and heat-processed wheat- and barley-based products, and to estimate the gluten content of hydrolysed foods. CONCLUSION: We present a new generation of a robust sandwich R5-ELISA with good reproducibility (8.7%) and repeatability (7.7%). Its gluten-detection limit of 3.2 ppm is lower than the existing threshold of 20-200 ppm. The ELISA, which is equally sensitive to barley, wheat and rye prolamins, is compatible with the quantitative cocktail extraction procedure for heat-processed foods. Along with the cocktail procedure, the Working Group on Prolamin Analysis and Toxicity is currently evaluating an R5-ELISA system as proposed by the Codex Alimentarius Commission.

Antibodies, Monoclonal↗
PubMed1983

Class-specific antibodies to gluten in dermatitis herpetiformis.

An immune reaction to wheat protein has been previously proposed to explain the pathogenesis of dermatitis herpetiformis. In order to detect and characterize antibodies to gluten in human sera, we developed an enzyme immunoassay for class-specific antibodies. Results of this assay in 49 patients with dermatitis herpetiformis were compared with those of 38 normal control subjects, 11 patients with celiac disease, and 6 small-bowel bypass patients. IgA antibodies to gluten were significantly more frequent in dermatitis herpetiformis sera (28/49) than in normal control sera (4/38). IgG antibodies to gluten were significantly more frequent in both celiac disease (10/11) and dermatitis herpetiformis (16/49) sera than in control (5/38) sera. Dermatitis herpetiformis sera also had an increased prevalence of IgM antibodies to gluten (19/49). Small-bowel bypass patients demonstrated no antibody to gluten. Antibodies to gluten in dermatitis herpetiformis objectively mark a state of immune reactivity to wheat protein and may be involved in the genesis of the cutaneous IgA immune deposits and the skin disease.

Adult↗