Celiac disease (gluten intolerance) is a curious autoimmune disease.
Upon exposure to gliaden (a gluten protein), the body instigates a
series of biochemical events that inflames the small intestine,
interferring with nutrient absorption.
If unrecognized, this condition will impede physical growth
in a child, and cause chronic diarrhea and fatigue.
The only known way to stop it is to avoid gluten in the diet.
As anyone who has gluten intolerance knows very well,
it is very challenging to adhere to this dietary remedy.
Gluten is present in wheat, rye, and barley (i.e. many common foods).
A treatment that is easier to follow would surely
be appreciated by people with gluten intolerance.
Eva Helmerhorst (Boston University, United States) and coworkers
have made a relevant discovery, namely their finding that microbes
in human saliva degrade gliaden.
Sifting through saliva.
The scientists collected dental plaque from a healthy volunteer
who had not brushed his/her teeth for 48 hours. Saliva was collected
from eight healthy volunteers who had most recently eaten
in the morning at least one hour previously.
As a side note, it was interesting to read that saliva production was
stimulated by chewing on a piece of Parafilm (plastic).
I presume this was done to ensure that the only microbes present
in the saliva reside in the mouth naturally, rather than to provide
a tasty treat.
Saliva was tested for its ability to digest gliadin.
The microbial enzymes within the saliva responsible for gliadin
processing were extensively characterized on a functional level.
Important findings.
The scientists report several useful findings.
The amino acid sequence (protein subunit)
tyrosine-proline-glutamine is preferentially degraded by the
gliaden-processing enzymes.
This amino acid sequence is common in gluten proteins.
This degradation information may be useful for designing
synthetic molecules (pharmaceuticals) which also degrade
gluten proteins.
Gliaden-processing enzymes retain their activity in both acidic
and basic pH, although most of the enzymes are acidic
(their presumed pH of maximal efficacy is between 2.5 and 4).
This suggests that gliaden-processing enzymes function
in many regions of the gastro-intestinal tract besides within
the mouth.
What are the specific microbes and enzymes responsible
for gliaden degradation in this research?
The scientists do not know yet (there are hundreds of
microbes in human saliva), but have narrowed it down to
four possibilities, which they report are the subject of
an upcoming publication.
Implications.
Enzymes which are not ordinarily present in the human mouth
are being investigated for treating gluten intolerance.
However, the use of resident enzymes is more likely to
be successful, due to long-term evolutionary adaptation.
Based on these findings, I suppose that a person with gluten
intolerance might be able to overcome the condition by sharing
a bunch of saliva with someone who can process gluten.
Assuming this remedy is less than desirable, research towards
identifying the responsible enzymes will hopefully enable scientists
to develop a formulation that can be ingested to
counteract gluten intolerance.
NOTE: The scientists' research was funded by the National Institutes
of Health.
Helmerhorst, E. J., Zamakhchari, M., Schuppan, D., & Oppenheim, F. G. (2010). Discovery of a Novel and Rich Source of Gluten-Degrading Microbial Enzymes in the Oral Cavity PLoS ONE, 5 (10) DOI: 10.1371/journal.pone.0013264
