(P20-009-23) Possible Roles of Aspergillus-Derived Enzymes in Gut-Brain Axis Modulation

Objectives: To examine roles of dietary Aspergillus-derived enzymes in gut and brain functions

Methods: Rodents were fed with a high-fat diet mixed with Aspergillus-derived enzymes, protease (PT) and lipase (LP), for 2-4 weeks. Gut microflora, amino acids, and homocarnosine were analyzed using qPCR, amino acid analyzer, and LC-MS/MS, respectively. Homocarnosine-deficient mice were subjected to light-dark transition and forced swimming tests for behavior analyses.

Results: We found that PT increased an abundance of probiotics, Bifidobacterium and Lactobacillus, and levels of short-chain fatty acids (p < 0.05). We further found that PT significantly increased cecal amino acids, threonine, alanine, proline, taurine, ornithine, phenylalanine, cysteine, and γ-aminobutyric acid (GABA)) (p < 0.05). Notably, phenylalanine, cysteine, and GABA were not detected in the group receiving no enzyme, suggesting that these amino acids were possibly produced from the elevated Bifidobacterium and Lactobacillus, which are well-known GABA producers. Moreover, we found that PT and LP, as well as a typical prebiotic fructo-oligosaccharides (FOS), exhibited a tendency increase in cecal GABA levels (p < 0.1) and a significant increase in hippocampal GABA level (p < 0.05). Since GABA is a constituent of a brain imidazole peptide, homocarnosine (GABA-L-histidine), we measured and found that PT (p = 0.045), LP (p = 0.084), and FOS (p = 0.014) increased hippocampal homocarnosine levels. Since homocarnosine is a putative neuromodulator, we examined if homocarnosine deficiency impacts behaviors and found that the homocarnosine-deficient mice exhibited hyperactive-, anxious-, and depressed-like behaviors (p < 0.05).

Conclusions: Aspergillus-derived enzymes exhibit prebiotic-like effects and possibly modulate the gut-brain axis through regulating postbiotic production such as GABA and the GABA-containing peptide homocarnosine, which possibly plays a role in regulating hyperactivity, anxiety, and depression. Dietary pre/probiotics that induce changes in GABA and homocarnosine in the brain may be the potential interventions for promoting brain health.

Funding Sources: Danone Institute of Japan Foundation and Amano Enzyme Inc.