A synbiotic consisting of Lactiplantibacillus plantarum S58 and β-glucan ameliorates exertional heat stroke-induced intestinal barrier injury via modulating the MAPK pathway and gut microbiota in rats

S58 and β-glucan (S58/βG) in a rat model of EHS. Rats received S58/βG pretreatment for 14 or 28 days before EHS induction, and a range of indicators including core temperature, intestinal histopathology, tight junction protein expression, MAPK signaling pathway activation, epithelial apoptosis, and gut microbiota composition were systematically assessed. The results demonstrated that S58/βG effectively enhanced thermotolerance, maintained intestinal integrity, and mitigated systemic organ injury. Mechanistically, it inhibited the phosphorylation of p38 and ERK, attenuated epithelial apoptosis, and maintained the expression of ZO-1, occludin, and E-cadherin. Moreover, S58/βG modulated the gut microbiota by progressively increasing beneficial bacteria and reducing potentially pathogenic bacteria over time. These findings demonstrate, for the first time, that S58/βG confers protection against EHS by concurrently modulating the gut microbiota and MAPK pathway, highlighting its potential as a dietary intervention to prevent EHS in vulnerable populations.