Structural characterization and bioactivity of a novel α-(1 → 4)-glucan from Lentinus edodes with immunomodulatory and gut microbiota-modulating potential

Lentinus edodes, commonly known as shiitake mushrooms, is widely cultivated for its nutritional and medicinal properties. It has been traditionally used for enhancing immune function, reducing inflammation, and providing antioxidant protection. Among its bioactive components, polysaccharides, particularly β-glucans, have attracted considerable attention for their anti-inflammatory, immunomodulatory, and anticancer effects. However, less is known about α-glucans, which differ in structure and biological activity from β-glucans. This study aims to isolate and characterize an α-glucan from L. edodes (LEP1), investigating its effects on lipopolysaccharide (LPS)-induced systemic inflammation and its potential to modulate gut microbiota in mice. Crude polysaccharides were extracted from L. edodes and purified to obtain LEP1. LEP1 was characterized using various analytical techniques, including scanning electron microscopy (SEM), molecular weight determination, and nuclear magnetic resonance (NMR) analysis. The effects of LEP1 were evaluated in a mouse model of LPS-induced systemic inflammation. Mice were treated with low- and high-doses of LEP1, and various parameters such as body weight, organ indices, and histopathological changes were assessed. The levels of inflammatory cytokines and oxidative stress markers were analyzed, and gut microbiota composition was studied using 16S ribosomal RNA (rRNA) sequencing. LEP1 significantly alleviated LPS-induced weight loss, reduced organ atrophy, and improved colon length. Treatment with LEP1 reduced pro-inflammatory cytokines [interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α] and restored antioxidant enzyme activities [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)] in liver and colon tissues. Histopathological analysis showed that LEP1 alleviated liver and colon damage caused by LPS, including inflammation and epithelial disruption. LEP1 inhibited the activation of nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) and NLR family pyrin domain containing 3 (NLRP3) inflammasome pathways while upregulating the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) antioxidant pathway. In addition, LEP1 reshaped the gut microbiota by increasing beneficial bacteria, such as Lactobacillus and Allobaculum, while decreasing harmful taxa such as Escherichia-Shigella. LEP1, an α-glucan derived from L. edodes, exhibits significant anti-inflammatory and antioxidant effects in LPS-induced mice, partly through the modulation of key signaling pathways, such as NF-κB/NLRP3 and Nrf2/HO-1. In addition, LEP1 positively affects gut microbiota composition, contributing to its systemic anti-inflammatory effects. These findings indicate that LEP1 shows potential as a functional food ingredient that may mitigate inflammation and oxidative stress, potentially through modulation of immune signaling and microbiota composition. Further studies are required to fully understand the clinical implications of these effects.