Structural characterization and immune-enhancing properties of an acidic heteroglycan from Protaetia brevitarsis seulensis larvae
Ju-Hwi Park, Jong Jin Park, Jongbeom Chae, Seong Do Lee, Subin Gwon, Hunseong Kim, Ju Hyun Min, Young Hoon Jung, Joon Ha Lee, Won‐Young Lee, Jae Sam Hwang, Ibukunoluwa Fola Olawuyi, Ju‐Ock Nam, Dongyup Hahn
Abstract
Edible insects are a promising source of bioactive compounds with diverse health benefits. This study investigated the immunomodulatory properties of polysaccharides isolated from Protaetia brevitarsis seulensis larvae (PBSL). Polysaccharides were fractionated using a molecular weight cutoff membrane, and among these fractions, the higher molecular weight fraction (H-PBSL, 666.84 kDa) demonstrated significant immunomodulatory activity. Methylation and NMR structural analyses revealed H-PBSL to be an acidic heteroglycan with a complex structure, consisting of a backbone of repeating (1→4)-linked α-glucan units highly branched at O-6 positions with T-α-Glcp, T-α-GlcpA, and T-β-Galp. The immunomodulatory effects of H-PBSL were evaluated using RAW264.7 macrophage cells. H-PBSL treatment enhanced phagocytic activity and increased the expression of immune modulators and macrophage activation surface molecules. In addition, H-PBSL activated the NF-κB signaling pathway, evidenced by increased phosphorylation of IκB and NF-κB, and translocation of NF-κB from cytosol to nucleus. Moreover, inhibition of Toll-like receptor 4 (TLR4) reduced H-PBSL-induced nitric oxide synthesis, indicating TLR4′s pivotal role in H-PBSL-mediated macrophage activation. These findings highlight the potential of H-PBSL as a novel immunomodulatory agent derived from an edible insect, with possible applications in functional foods and nutraceuticals.