Randomised clinical study: Aspergillus niger-derived enzyme digests gluten in the stomach of healthy volunteers

Abstract

Background: Aspergillus niger prolyl endoprotease (AN-PEP) efficiently degrades gluten molecules into non-immunogenic peptides in vitro.

Aim: To assess the efficacy of AN-PEP on gluten degradation in a low and high calorie meal in healthy subjects.

Methods: In this randomised, double-blind, placebo-controlled, cross-over study 12 healthy volunteers attended to four test days. A liquid low or high calorie meal (4 g gluten) with AN-PEP or placebo was administered into the stomach. Via a triple-lumen catheter gastric and duodenal aspirates were sampled, and polyethylene glycol (PEG)-3350 was continuously infused. Acetaminophen in the meals tracked gastric emptying time. Gastric and duodenal samples were used to calculate 240-min area under the curve (AUC0-240 min ) of ?-gliadin concentrations. Absolute ?-gliadin AUC0-240 min was calculated using duodenal PEG-3350 concentrations.

Results: AN-PEP lowered α-gliadin concentration AUC0-240 min, compared to placebo, from low and high calorie meals in stomach (low: 35 vs. 389 μg × min/mL; high: 53 vs. 386 μg × min/mL; P < 0.001) and duodenum (low: 7 vs. 168 μg × min/mL; high: 4 vs. 32 μg × min/mL; P < 0.001) and absolute α-gliadin AUC0-240 min in the duodenum from low (2813 vs. 31 952 μg × min; P < 0.001) and high (2553 vs. 13 095 μg × min; P = 0.013) calorie meals. In the placebo group, the high compared to low calorie meal slowed gastric emptying and lowered the duodenal α-gliadin concentration AUC0-240 min (32 vs. 168 μg × min/mL; P = 0.001).

Conclusions: AN-PEP significantly enhanced gluten digestion in the stomach of healthy volunteers. Increasing caloric density prolonged gastric residence time of the meal. Since AN-PEP already degraded most gluten from low calorie meals, no incremental effect was observed by increasing meal caloric density. ClinicalTrials.gov, Number: NCT01335503; www.trialregister.nl, Number: NTR2780.

© 2015 John Wiley & Sons Ltd.

Figures

Figure 1

(a) DQ2.5‐glia‐α3 concentration (mean ± SEM) over time in the stomach in low calorie meals. (b) DQ2.5‐glia‐α3 concentration (mean ± S.E.M.) over time in the stomach in high calorie meals. (c) DQ2.5‐glia‐α3 concentration (mean ± S.E.M.) over time in the duodenum in low calorie meals. (d) DQ2.5‐glia‐α3 concentration (mean ± S.E.M.) over time in the duodenum in high calorie meals. (e) Absolute DQ2.5‐glia‐α3 output (mean ± S.E.M.) over time in the duodenum in low calorie meals. (f) Absolute DQ2.5‐glia‐α3 output (mean ± S.E.M.) over time in the duodenum in high calorie meals.

Figure 2

DQ2.5‐glia‐α3 concentration over time in the duodenum of the individual subjects in low calorie meals (LCM) and high calorie meals (HCM). (a) + (b): subject 5. (c) + (d): subject 6. (e) + (f): subject 7. (g) + (h): subject 10. (i) + (j): subject 11. (k) + (l): subject 12. (m) + (n): subject 13. (o) + (p): subject 14. (q) + (r): subject 15. (s) + (t): subject 16. (u): subject 17. (v) + (w): subject 19.

Figure 3

Representative western blot showing degradation of water‐insoluble DQ2.5‐glia‐α1 over time in the stomach and duodenum in low and high calorie meals with and without AN‐PEP.

Figure 4

Representative SDS‐PAGE gel showing the presence of AN‐PEP protein in gastric and duodenal aspirates.