Konjac Oligosaccharide Alleviates Constipation in Mice via 5-HT4R/cAMP/PKA/p-CREB Pathway Activation

Background: Konjac oligosaccharide (KOS), which is produced through the degradation of konjac glucomannan via enzymatic, chemical, or physical treatments, has been found to have laxative effects. The current study aimed to elucidate the mechanisms underlying the laxative effect of KOS.

Methods: KOS was administered by gavage to wild-type and 5-hydroxytryptamine 4 receptor (5-HT4R)-knockout C57BL/6 mice subjected to loperamide-induced constipation for four weeks. Following treatment, feces, blood, small intestine, colonic tissue, and intestinal contents were collected. Constipation-related parameters, gastrointestinal Hormones, and CA²⁺ concentrations were evaluated. Histopathological changes were examined via hematoxylin and eosin staining. Immunofluorescence staining, Western blotting, and immunohistochemical staining were performed to detect the 5-HT4R/cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway. Isolated smooth muscle cells (SMCs) were treated with KOS and GR113808 (a 5-HT4R antagonist), morphologically observed under an inverted microscope, and identified by α-SMA immunofluorescence staining. Cell viability was assessed via CCK-8 assays. 5-HT4R/cAMP/PKA/p-CREB pathway activity in SMCs was detected via Western blotting.

Results: KOS alleviated loperamide-induced constipation in mice. KOS activated the 5-HT4R/cAMP/PKA/p-CREB pathway in loperamide-induced constipated mice. The protective effect of KOS was significantly diminished in 5-HT4R^-/- mice. KOS promoted the proliferation of SMCs by activating the 5-HT4R/cAMP/PKA/p-CREB signaling pathway.

Conclusion: KOS improves loperamide-induced constipation by activating the 5-HT4R/cAMP/PKA/p-CREB signaling pathway.

5-HT4 receptor; CAMP/PKA signaling; Colonic motility; Functional constipation; Gut motility; Konjac oligosaccharide (KOS); Loperamide; Smooth muscle cells.