Menthol, a dietary bioactive monoterpene, alleviates LPS-induced intestinal inflammation in a weaned piglet model: potential involvement of the Piezo1/TPH1/5-HT axis

Menthol is a widely consumed dietary monoterpene found in peppermint oil, yet its effects on intestinal health under inflammatory conditions remain poorly understood. This study investigated the protective effects of dietary menthol against lipopolysaccharide (LPS)-induced intestinal inflammation in a weaned piglet model, focusing on the enteroendocrine Piezo1/TPH1/5-HT signaling axis. Sixty 28-day-old Duroc × (Landrace × Large White) weaned piglets were randomly assigned to five groups: a non-challenged control (CON), an LPS-challenged group, and three LPS-challenged groups receiving menthol at 12.5, 25, or 50 mg/kg of diet in a 22-day trail (21-day feeding +6 h post-LPS). Supplementation with 25 mg/kg menthol of diet significantly increased average daily body weight gain (ADG) and average daily feed intake (ADFI) while reducing the incidence of diarrhea before LPS challenge ( P < 0.05). After LPS administration, menthol markedly attenuated intestinal injury, as evidenced by reduced serum lactate dehydrogenase (LDH) activity and lower levels of pro-inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in both serum and intestinal tissues ( P < 0.05). Morphologically, menthol increased villus height and the villus height to crypt depth ratio (VH/CD), decreased crypt depth ( P < 0.05), and preserved microvilli density, tight junction integrity, and nuclear morphology of the small intestine. Notably, menthol partially restored the LPS-induced loss of enteroendocrine cells and normalized gut hormone profiles, specifically reducing serotonin (5-HT) and gastrin while increasing somatostatin. Mechanistically, menthol appeared to suppress the LPS-induced upregulation of the mechanosensor Piezo1, the 5-HT-synthesizing enzyme tryptophan hydroxylase 1 (TPH1), and the 5-HT3 receptor at both the gene and protein levels ( P < 0.05). These findings suggested that dietary menthol, particularly at 25 mg/kg of diet, alleviated intestinal inflammation, potentially by preserving enteroendocrine cell homeostasis and downregulating the Piezo1/TPH1/5-HT signaling pathway. This study provides new evidence for the potential application of menthol as a functional food ingredient to support gut health.