Lacticaseibacillus paracasei NCU-04 relieves constipation and the depressive-like behaviors induced by loperamide in mice through the microbiome-gut-brain axis

Constipation is a prevalent gastrointestinal condition that significantly affects patients' physical and mental well-being, yet current treatments often lack safety and efficacy. Emerging evidence highlights the critical role of the microbiota-gut-brain axis (MBGA) in managing constipation, paving the way for probiotics as an adjuvant treatment to improve constipation symptoms. In this study, we isolated a gut probiotic strain, Lacticaseibacillus paracasei NCU-04, and investigated its improvement effects on loperamide-induced constipation in mice. We demonstrated that L. paracasei NCU-04 exhibited excellent probiotic properties, including robust growth, strong antibacterial and antioxidant capacities, and a lack of hemolytic activity in vitro. The administration of L. paracasei NCU-04 effectively improved the defecation-related indicators such as the fecal water content, time to the first black stool defecation, and intestine transit rate, suggesting enhanced gut immobility in constipated mice. Additionally, L. paracasei NCU-04 significantly reduced colon inflammation induced by loperamide. Further, L. paracasei NCU-04 increased levels of colonic motilin, 5-hydroxytryptamine (5-HT), and c-kit, while decreased that of aquaporin 3, vasoactive intestinal peptide, and peptide YY. Notably, L. paracasei NCU-04 effectively upregulated the expression of 5-HT and its receptor (i.e., 5-HT4R) in the brains of constipated mice. High-throughput sequencing revealed that L. paracasei NCU-04 restored the diversity and composition of the gut microbiota disturbed by loperamide, and significantly increased the relative abundance of Prevotella and Lactobacillus genera in the stool, while decreased that of Odoribacter, Rikenella, and Parabacteroides. Importantly, L. paracasei NCU-04 also effectively improved the depression-like behaviors associated with constipation, possibly through 5-HT mediated MGBA. These results suggest that L. paracasei NCU-04 may offer a promising approach for treating constipation and its related depressive symptoms, supporting its potential as a functional food or adjuvant therapy for human health.