PubMed Health⌕ Search

Biomedical subjects

Thomas Marti

Publications and source records attributed to Thomas Marti.

6 recordsLinked to original sources
PubMed2005

Low-dose gluten challenge in celiac sprue: malabsorptive and antibody responses.

BACKGROUND & AIMS: Undiagnosed patients with symptoms of celiac sprue often present to physicians after establishing dietary gluten exclusion. Although they must resume a gluten-containing diet for evaluation, there are no guidelines regarding duration of the gluten challenge, gluten dose, or monitoring parameters. We investigated the effects of a short-term gluten challenge in asymptomatic treated adult celiac patients on intestinal absorption and celiac antibody tests. METHODS: Eight adult asymptomatic celiac patients consumed either 5 or 10 g of partially hydrolyzed gluten per day in an orange juice mixture for 21 days while maintaining their usual gluten-free diet. A symptom questionnaire, serum antibodies (antigliadin immunoglobulin [Ig]A and antitransglutaminase IgA and IgG), D-xylose urine excretion test, and 72-hour quantitative fecal fat test were monitored. RESULTS: Two patients (25%) had at least 1 abnormal celiac antibody test at baseline. There was no increase in antibodies during gluten exposure compared with baseline for any of the patients (P > .05). At baseline, 1 patient had abnormal urine xylose excretion, and 3 patients had abnormal fecal fat values. At day 15 of gluten challenge, all patients had reduced xylose absorption compared with baseline (P = .0019), and 5 of 8 participants (63%) reduced their xylose excretion to the abnormal range. Seven of 8 patients (88%) had increased fecal fat excretion at day 15 (P = .026), and 6 of these (75%) had steatorrhea by day 15. CONCLUSIONS: Short-term gluten challenge in asymptomatic adult celiac patients produces carbohydrate and fat malabsorption but does not increase transglutaminase and antigliadin antibody titers.

Aged↗
PubMed2005

Effect of pretreatment of food gluten with prolyl endopeptidase on gluten-induced malabsorption in celiac sprue.

BACKGROUND & AIMS: We sought to determine whether prolyl endopeptidase (PEP) treatment of food gluten would obviate the intestinal dysfunction produced by small amounts of dietary gluten supplement in patients with celiac sprue. METHODS: Twenty asymptomatic patients with histologically proven celiac sprue completed a randomized, double-blind, cross-over study involving two 14-day stages. Each patient consumed a low dose of a gluten supplement daily (5 g; equivalent to 1 slice of bread) in 1 stage and gluten pretreated with PEP in the other stage. Patients completed a daily symptom questionnaire and a D-xylose urine excretion and a 72-hour quantitative fecal fat were monitored before and after each stage. RESULTS: Despite clinical remission at baseline, 40% of patients had at least 1 abnormal celiac antibody, 20% had an abnormal urine xylose, and 63% had an abnormal fecal fat test result. There was no difference in symptoms as a function of the type of gluten consumed. In response to gluten not treated with PEP, an appreciable proportion of patients developed malabsorption of fat (7 of 17, 41%) or xylose (8 of 14, 57%). When the gluten was pretreated with PEP, fat malabsorption was avoided in 5 of 7 and xylose malabsorption in 4 of 8 of these same patients. CONCLUSIONS: A significant proportion of asymptomatic patients with celiac sprue have abnormal celiac antibodies and fat or carbohydrate malabsorption. Pretreatment of gluten with PEP avoided the development of fat or carbohydrate malabsorption in the majority of those patients who developed fat or carbohydrate malabsorption after a 2-week gluten challenge.

Adult↗
PubMed2004

Comparative biochemical analysis of three bacterial prolyl endopeptidases: implications for coeliac sprue.

Prolyl endopeptidases have potential for treating coeliac sprue, a disease of the intestine caused by proteolytically resistant peptides from proline-rich prolamins of wheat, barley and rye. We compared the properties of three similar bacterial prolyl endopeptidases, including the known enzymes from Flavobacterium meningosepticum (FM) and Sphingomonas capsulate (SC) and a novel enzyme from Myxococcus xanthus (MX). These enzymes were interrogated with reference chromogenic substrates, as well as two related gluten peptides (PQPQLPYPQPQLP and LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF), believed to play a key role in coeliac sprue pathogenesis. In vitro and in vivo studies were conducted to evaluate the activity, specificity and acid/protease stability of the enzymes. All peptidases were relatively resistant to acid, pancreatic proteases and membrane peptidases of the small intestinal mucosa. Although their activities against reference substrates were similar, the enzymes exhibited substantial differences with respect to chain length and subsite specificity. SC hydrolysed PQPQLPYPQPQLP well, but had negligible activity against LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF. In contrast, the FM and MX peptidases cleaved both substrates, although the FM enzyme acted more rapidly on LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF than MX. Whereas the FM enzyme showed a preference for Pro-Gln bonds, SC cleaved both Pro-Gln and Pro-Tyr bonds with comparable efficiency, and MX had a modest preference for Pro-(Tyr/Phe) sites over Pro-Gln sites. While a more comprehensive understanding of sequence and chain-length specificity may be needed to assess the relative utility of alternative prolyl endopeptidases for treating coeliac sprue, our present work has illustrated the diverse nature of this class of enzymes from the standpoint of proteolysing complex substrates such as gluten.

Amino Acid Sequence↗
PubMed2004

Prolyl endopeptidase-mediated destruction of T cell epitopes in whole gluten: chemical and immunological characterization.

Celiac Sprue is a widely prevalent immune disease of the small intestine induced by dietary gluten intake in genetically susceptible individuals. It has been suggested that prolyl endopeptidases (PEPs) may be useful catalysts for gluten detoxification. We have investigated this hypothesis using food-grade gluten as the target antigen, and a combination of mass spectrometry and patient-derived T cells as quantitative assay systems. Spectrometric characterization of physiologically proteolyzed gluten revealed a number of 10 to 50 residue peptides containing known T cell epitopes involved in Celiac Sprue pathogenesis. Several of these peptides were multivalent, suggesting they may be potent triggers of the inflammatory response to gluten in celiac patients. Treatment of proteolyzed gluten with recombinant bacterial PEP decreased the number of potentially immunostimulatory peptides. Substantially reduced immunogenicity was also quantified in 12 of 14 intestinal polyclonal T cell lines from celiac patients. Kinetic investigations using eight T cell clones showed rapid destruction of alpha-gliadin epitopes, but less complete processing of gamma-gliadin epitopes. Given the difficulty associated with a strict lifelong gluten-exclusion diet, the ability of a single enzyme to greatly reduce the antigenic burden of grocery store gluten reinforces the case for developing oral peptidase therapy against Celiac Sprue.

Chromatography, High Pressure Liquid↗
PubMed2002

Pore-forming polypeptides of the pathogenic protozoon Naegleria fowleri.

The free-living amoeboflagellate and potential human pathogen Naegleria fowleri causes the often fatal disease primary amoebic meningoencephalitis. The molecular repertoire responsible for the cytolytic and tissue-destructive activity of this amoeboid protozoon is largely unknown. We isolated two pore-forming polypeptides from extracts of highly virulent trophozoites of N. fowleri by measuring their membrane-permeabilizing activity. N-terminal sequencing and subsequent molecular cloning yielded the complete primary structures and revealed that the two polypeptides are isoforms. Both polypeptides share similar structural properties with antimicrobial and cytolytic polypeptides of the protozoon Entamoeba histolytica (amoebapores) and of cytotoxic natural killer (NK) and T cells of human (granulysin) and pig (NK-lysin), all characterized by a structure of amphipathic alpha-helices and an invariant framework of cysteine residues involved in disulfide bonds. In contrast to the aforementioned proteins, the Naegleria polypeptides both are processed from large precursor molecules containing additional isoforms of substantial sequence divergence. Moreover, biochemical characterization of the isolated polypeptides in combination with mass determination showed that they are N-glycosylated and variably processed at the C terminus. The biological activity of the purified polypeptides of Naegleria was examined toward human cells and bacteria, and it was found that these factors, named naegleriapores, are active against both types of target cells, which is in good agreement with their proposed biological role as a broad-spectrum effector molecule.

Amino Acid Sequence↗