Comparative effects of β-glucan and mannan oligosaccharides on heat stress-induced inflammation: associations with gut barrier integrity and intestinal microbiota in mice.

Heat stress poses serious threats to human and animal health by inducing systemic inflammation, oxidative stress, and intestinal barrier damage, yet the potential of functional food components in mitigating heat stress-associated health impairments remains insufficiently explored. This study used a chronic heat stress model in C57BL/6 J mice to compare the protective effects of β-glucan (BG) and mannan oligosaccharides (MOS) against heat stress-induced injury. The underlying mechanisms of each supplement were also systematically investigated. The results demonstrated that both BG and MOS effectively attenuated heat stress-induced body weight loss, elevated liver index, and systemic inflammatory responses, significantly reduced serum levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and heat shock protein 70 (HSP70), and restored antioxidant enzyme activity. Notably, BG exhibited superior efficacy in suppressing pro-inflammatory cytokines and restoring serum immunoglobulin A (IgA) levels. Regarding intestinal barrier integrity, both oligosaccharides markedly upregulated the colonic expression of tight junction proteins zonula occludens-1 (ZO-1), Claudin-1, and Occludin, decreased serum diamine oxidase (DAO) and lipopolysaccharide (LPS) levels, and partially alleviated heat stress-induced intestinal barrier disruption. Hepatic tissue analysis revealed that both BG and MOS ameliorated heat stress-induced hepatic inflammation and lipid metabolism dysfunction. This was achieved by suppressing TLR4 and iNOS expression while restoring the balance of CD36 and PPARα expression. Furthermore, fecal microbial diversity analysis revealed that MOS was associated with increased abundance of Lachnospiraceae-related taxa, which are known to include short-chain fatty acid-producing bacteria. These microbial changes may contribute to the maintenance of gut microecological homeostasis via distinct microbiota-associated pathways. Collectively, these findings suggest that BG and MOS may alleviate multi-level heat stress-induced damage, potentially in association with improved intestinal barrier-related markers, altered gut microbiota composition, and modulation of gut-liver axis-related responses, thereby providing preliminary evidence for their potential application as functional food components to address heat stress-related health challenges.