A new enzyme originally developed for commercial
food processing turns out to also quickly and nearly-completely
break down whole gluten molecules as well as the T
cell stimulatory peptides that cause celiac disease,
a digestive disease with no current effective treatment
other than avoiding wheat, barley or rye products.
In addition, the enzyme operates best in just the
kind of physiological environment found in the human
stomach and works 60 times faster than an earlier
promising enzyme, which was not effective in acidic
conditions and was inactivated by pepsin, both of
which are found in the stomach.
"On the basis of our results, there now is a realistic
chance that oral supplementation with an enzyme can
ensure gluten degradation in the stomach before reaching
the small intestine, where it causes problems for
people with celiac disease," according to Frits Koning,
researcher at the Leiden University Medical Center,
The Netherlands, who headed the team that has published
a new research paper on its work.
The paper, "Highly efficient gluten degradation with
a newly identified prolyl endoprotease: implications
for celiac disease," is in the online American Journal
of Physiology- Gastrointestinal and Liver Physiology,
published by The American Physiological Society. Research
was by Dariusz Stepniak, Liesbeth Spaenij-Dekking,
Cristina Mitea, Martine Moester, Arnoud de Ru, Renee
Baak-Pablo, Peter van Veelen and Frits Koning of Leiden
University Medical Center, the Netherlands, and Luppo
Edens of DSM Food Specialties, Delft.
Clinical trials are likely next step
The new prolyl endoprotease (PEP) that was studied
is derived from Aspergillus niger (AN), a common fungus.
Strains of A. niger are used in industrial production
of citric and gluconic acid as well as producing several
food grade enzymes.
Because there are no animal models of celiac disease,
"the in vivo efficacy of AN-PEP for gluten detoxification
will ultimately have to be addressed in clinical studies
involving celiac patients. AN-PEP appears to be a
prime candidate for such clinical trials," the paper
concluded. As for the timing of any such trials, Koning
said: "This is an option the team hopes to explore
in the future."
A disease of many paradoxes
Celiac disease affects about 2 million Americans
and is also found in Europe, India and parts of the
Middle East. It's caused by an uncontrolled immune
response to wheat gluten and similar proteins of rye
and barley that cause diarrhea, malnutrition and failure
to thrive because it inhibits nutritional uptake.
"It's a Caucasian disease with a wide spectrum of
symptoms; not all patients are equally affected, but
we do not understand why this is the case," Koning
said. "It is known to be associated with the HLA-DQ2
gene," he noted, "but while about 25% of the white
population has this gene, only about one in 100 get
the disease, so it's really a quite puzzling disease
in many ways."
Currently the only way to elude the disease symptoms
is by avoiding wheat, barley and rye products. "It
sounds easy, but gluten especially is widespread in
Western diets," Koning said. Gluten is often used
as a food additive because it adds protein content
inexpensively and also gives dough its elasticity
and stickiness, which helps in manufacturing. For
instance, Koning said: "Celiac patients can eat potato
chips, but not if they have added paprika or other
spices because they're 'glued' to the chip with gluten."
AN-PEP outstrips earlier enzyme by 60-fold
Earlier attempts at finding non-human proteases for
gluten detoxification (first proposed in the late
1950s) focused on prolyl oligopeptidases (POP), most
notably FM-POP, which was able to break down gluten
sequences in vitro. However FM-POP's optimal operating
pH is between 7 and 8, so it didn't work well in the
more acidic stomach pH that goes down to 2 at one
stage. A combination of pH 2 and pepsin "immediately
inactivated FM-POP," the paper said. AN-PEP, on the
other hand, is active from pH 2-8, with optimum effect
around pH 4. The combination of pH 2 and pepsin didn't
affect AN-PEP activity.
"An effective enzymatic treatment for celiac diseases
requires means of destroying all or at least the vast
majority of gluten derived T cell stimulatory sequences,"
the paper said. The key to this is to break the large
gluten molecules (large peptides and intact proteins)
into smaller pieces before they leave the stomach.
Because food stays in the stomach one to four hours,
speed of protein degradation is also important. Mass
spectrometry comparisons showed that "degradation
of gluten peptides by AN-PEP was on average [about
4 minutes, or] 60 times faster than degradation by
FM-POP," the paper reported.
In addition to its ability to perform as a potential
oral enzymatic therapy because it "is capable of degrading
intact gluten molecules and T cell stimulatory epitopes
from gluten into harmless fragments" AN-PEP has several
additional commercial advantages, the paper said:
"The enzyme is extremely stable and can be produced
at acceptable cost at food grade quality in an industry
setting."
Celiac disease is an HLA-linked disease related to
Type 1 diabetes and rheumatoid arthritis in which
autoimmune reactions cause the disease; similarly,
immune reactions can lead to organ transplant rejection.
Koning said it "isn't likely that AN-PEP would be
of any therapeutic value in any of these HLA-associated
diseases" because Type 1 diabetes and rheumatoid arthritis
are real autoimmune diseases, where the immune system
attacks parts of the body. In celiac disease, it is
the gluten that is the target, not the body.
Reminder warning on early introduction of gluten
products
Koning said feeding wheat (or barley or rye) products
to infants before they're 6 months old isn't recommended
because once an immune response develops "immuno-memory
builds up and it doesn't go away." Indeed, Koning
noted that in Sweden some years ago gluten was introduced
into baby food, which led to a five-fold increase
in celiac disease. The problem disappeared when gluten
was removed.
