Enhanced γ-aminobutyric acid and sialic acid in fermented deer antler velvet and immune promoting effects

Deer antler velvet is widely used in traditional medicine for its anti-aging, antioxidant, and immunity-enhancing effects. However, few studies have reported on the discovery of probiotic strains for deer antler fermentation to increase functional ingredient absorption. This study evaluated the ability of probiotic lactic acid bacteria to enhance the concentrations of bioactive molecules (e.g., sialic acid and gamma-aminobutyric acid [GABA]) in extracts of deer antler velvet. Seventeen strains of <italic>Lactobacillus </italic>spp<italic>. </italic>that were isolated from kimchi and infant feces, including <italic>L. sakei, L. rhamnosus, L. brevis, </italic>and<italic> L. plantarum</italic>, and those that improved the life span of <italic>Caenorhabditis elegans</italic> were selected for evaluation. Of the 17 strains, 2 (<italic>L. rhamnosus</italic> LFR20-004 and <italic>L. sakei</italic> LFR20-007) were selected based on data showing that these strains increased both the sialic acid and GABA contents of deer antler extract after fermentation for 2 d and significantly improved the life span of <italic>C. elegans</italic>. Co-fermentation with both strains further increased the concentrations of sialic acid, GABA, and metabolites such as short-chain fatty acids and amino acids. We evaluated the biological effects of the fermented antler velvet (FAV) on the antibacterial immune response in <italic>C. elegans</italic> by assessing worm survival after pathogen infection. The survival of the <italic>C. elegans</italic> conditioned with FAV for 24 h was significantly higher compared with that of the control worm group fed only normal feed (non-pathogenic <italic>E. coli</italic> OP50) exposed to <italic>E. coli O157:H7</italic>, <italic>Salmonella typhi, </italic>and<italic> Listeria monocytogenes.</italic> To evaluate the protective effects of FAV on immune response, cyclophosphamide (Cy), an immune-suppressing agent was treated to <italic>in vitro</italic> and <italic>in vivo</italic>. We found that FAV significantly restored viability of mice splenocytes and immune promoting-related cytokines (IL-6, IL-10, iNOS, IFN-γ, and TNF-α) were activated compared to non-fermented deer antlers. This finding indicated the protective effect of FAV against Cy-induced cell death and immunosuppressed mice. Taken together, our study suggests that immune-promoting antler velvet can be produced through fermentation using <italic>L. rhamnosus</italic> LFR20-004 and <italic>L. sakei</italic> LFR20-007.