Pine pollen fiber alleviates constipation induced by loperamide in mice: focus on gastrointestinal motility-related hormones, short-chain fatty acids, and gut microbiota changes

Constipation, a prevalent gastrointestinal disorder, urgently requires safe and effective intervention strategies. Natural dietary fibers have gained attention for their potential to alleviate constipation through multiple mechanisms. This study investigated the therapeutic effects of pine pollen fiber (PPF), a by-product from pine pollen processing, on loperamide-induced constipation in mice. The mice were administered low or high doses of PPF for 14 consecutive days, and we evaluated constipation-related indicators, serum levels of gastrointestinal peptides and neurotransmitters, gut microbiota composition, and short-chain fatty acid (SCFA) production. The results showed that PPF supplementation significantly improved defecation function by increasing the fecal moisture content and intestinal propulsion rate. The PPF intervention restored the balance of neuroendocrine factors by upregulating excitatory neurotransmitters (substance P, motilin, gastrin, and acetylcholine) and downregulating inhibitory peptides (vasoactive intestinal peptide and somatostatin). 16S rRNA sequencing revealed that PPF modulated the gut microbiota structure and enhanced microbial diversity. Notably, PPF administration significantly promoted the production of SCFAs, particularly acetate, propionate and butyrate. These microbial metabolites may in turn influence the secretion of gastrointestinal hormones and neurotransmitters, as evidenced by the restored balance of excitatory and inhibitory factors in serum. Collectively, these findings indicate that the alleviation of constipation by PPF involves multi-pathway mechanisms linking gut microbiota modulation, SCFA production, and neuroendocrine regulation, supporting its potential application as a functional food ingredient for intestinal health.