In vitro mucosal digestion of synthetic gliadin-derived peptides in celiac disease

Abstract

Two celiac-active synthetic peptides derived from the A-gliadin structure corresponding to residues 8-19 (LQPQNPSQQQPQ) and to 11-19 were digested in vitro with small intestinal mucosa from children with celiac disease in remission and from normal children. The products of digestion were separated into two fractions on the basis of M(r) < 400 and M(r) > 400 by gel permeation chromatography and subjected to amino acid analysis. After digestion of the dodecapeptide with celiac mucosa, 71 +/- 14% (molar) of the total digestion products remained in the M(r) > 400 fraction. Glutamine, proline, serine, and asparagine were the major amino acids present. Glutamine, proline, and leucine were the major amino acids in the M(r) < 400 fraction. The M(r) > 400 fraction from the celiac mucosal digestion of the nonapeptide was of similar composition to the corresponding fraction from the dodecapeptide and represented 78 +/- 15% of the total products. Digestion of the two peptides with normal mucosa gave lower amounts of products in the M(r) > 400 fraction, but they were of similar composition to the corresponding fractions from the celiac mucosal digestion. Peptides such as NPSQQP and QNPSQQQ may be present in the M(r) > 400 fractions since glutamine and proline are present in the approximate ratio of 2:1, respectively. The results indicate a defect in the mucosal digestion of peptides which are active in an animal model of celiac disease.

Enzyme Therapy that Can Digest the Toxic Motifs of Gluten as an Aid in the Management of Celiac Disease

“…If patients on placebo who dropped out (mostly because they developed symptoms relating to gluten exposure) were included, such an intention to treat analysis would be even stronger. Furthermore, the results verified the in vitro work on toxic epitopes of gluten referred to earlier in the papers [5,6] and lead to better understanding of enzyme therapy.…”

“…The disease occurs almost exclusively in people with the DQ2 or DQ8 HLA haplotype. Celiac patients with these HLA haplotypes are unable to break down gluten to smaller peptides which do not induce immunological responses or direct epithelial damage [5,6].…”

Enzyme Therapy for Coeliac Disease: Is It Ready For Prime Time?

“…When these peptides were subjected to specific deletions of amino acids it was found that the most active peptide was the nonapeptide 11-19 while the dodecapeptide 75-86 was seen to be close to the maximum activity in this group of peptides (Cornell & Mothes,1993. f. Coeliac mucosal digestion of each of these peptides showed that undigested residues of octapeptides were obtained in greater amounts than those obtained from digestion with mucosa from normal individuals (Cornell & Rivett, 1995;. g. Importantly, these undigested octapeptides were found to contain sequences of amino acids found by ourselves and others to be associated with toxicity (De Ritis et al1988;McLachlan et al, 2002).…”

“…Moreover, these residues still retained the serine residue, presumably associated the PSQQ motif, because the amino acid composition of the residues matched the octapeptide sequence 12-19, QNPSQQQPQ (Cornell & Rivett, 1995). It is interesting that peptide 206-217, has been shown to be toxic in vivo (Mantzaris & Jewell, 1991).…”

Effect of Prolyl Endopeptidase on Digestive-Resistant Gliadin Peptides in Vivo

“…Regardless of the primary mechanism, the essential prerequisite is the initiating role of the digestive-resistant intact gliadin peptide fragments, which must persist in the intestinal lumen to have deleterious effects. Previous in vitro studies have suggested digestive resistance of gliadin in Celiac Sprue patients (Cornell and Rivett, 1995;Cornell, 1998). More recent studies have demonstrated that a region of ␣-gliadin harboring tandem repeat sequences of PQPQLPY is resistant to digestion by gastric, pancreatic, and intestinal brush-border peptidases, and harbors multiple copies of highly immunogenic epitopes Shan et al, 2002).…”