{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T10:07:33Z","timestamp":1789380453014,"version":"build-2803163510"},"reference-count":45,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,12]],"date-time":"2026-09-12T00:00:00Z","timestamp":1789171200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Center of Technology Innovation for Dairy","award":["2023-JSGG-28"],"award-info":[{"award-number":["2023-JSGG-28"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>Background: Functional constipation is a common gastrointestinal disorder that impairs quality of life. Although probiotics have shown benefits in constipation, whether live and heat-killed forms of the same strain act through similar mechanisms remains unclear. This study compared the effects of live and heat-killed Lacticaseibacillus paracasei K56 in experimental constipation. Methods: Loperamide-treated mice received live or heat-killed L. paracasei K56. Gastrointestinal motility, colonic histology, neurotransmitters, aquaporin expression, gut microbiota, short-chain fatty acids, and metabolomic profiles were evaluated. Results: Both preparations relieved constipation, as reflected by shorter defecation latency, increased fecal output and moisture, and faster intestinal transit, with live K56 producing greater improvement. Colonic injury was alleviated, accompanied by reduced Aqp2 and Aqp3 expression and normalization of 5-hydroxytryptamine, substance P, and vasoactive intestinal peptide. The treatments increased Lactobacillus and Lachnospiraceae, promoted butyrate production, and altered tryptophan metabolism. Heat-killed K56 was mainly associated with changes in phenylalanine\/tyrosine- and methionine-related metabolism, whereas live K56 showed more pronounced alterations in arginine\/polyamine, tryptophan, and bile acid metabolism. Conclusions: Live and heat-killed L. paracasei K56 improved constipation through shared and distinct mechanisms involving gut microbiota, microbial metabolism, enteric neurotransmission, and intestinal water homeostasis. Live K56 produced stronger effects, whereas heat-killed K56 retained substantial biological activity.<\/jats:p>","DOI":"10.3390\/nu18182991","type":"journal-article","created":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T09:34:01Z","timestamp":1789378441000},"page":"2991","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Comparative Analysis of Live and Heat-Killed Lacticaseibacillus paracasei K56 in Alleviating Functional Constipation"],"prefix":"10.3390","volume":"18","author":[{"given":"Zhi","family":"Zhao","sequence":"first","affiliation":[{"name":"Department of Nutrition and Health, Key Laboratory of Functional Dairy, Co-Constructed by Ministry of Education and Beijing Government, China Agricultural University, Beijing 100190, China"},{"name":"College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-6893-8456","authenticated-orcid":false,"given":"Xinyi","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Nutrition and Health, Key Laboratory of Functional Dairy, Co-Constructed by Ministry of Education and Beijing Government, China Agricultural University, Beijing 100190, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"data-curation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"}]},{"given":"Jian","family":"He","sequence":"additional","affiliation":[{"name":"National Center of Technology Innovation for Dairy, Hohhot 100118, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"}]},{"given":"Ran","family":"Wang","sequence":"additional","affiliation":[{"name":"Department of Nutrition and Health, Key Laboratory of Functional Dairy, Co-Constructed by Ministry of Education and Beijing Government, China Agricultural University, Beijing 100190, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"given":"Lianhang","family":"Lan","sequence":"additional","affiliation":[{"name":"National Center of Technology Innovation for Dairy, Hohhot 100118, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"visualization","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2427-9064","authenticated-orcid":false,"given":"Jingjing","family":"He","sequence":"additional","affiliation":[{"name":"Department of Nutrition and Health, Key Laboratory of Functional Dairy, Co-Constructed by Ministry of Education and Beijing Government, China Agricultural University, Beijing 100190, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"data-curation","vocabulary":"credit"},{"role":"conceptualization","vocabulary":"credit"}]},{"given":"Jie","family":"Guo","sequence":"additional","affiliation":[{"name":"Department of Nutrition and Health, Key Laboratory of Functional Dairy, Co-Constructed by Ministry of Education and Beijing Government, China Agricultural University, Beijing 100190, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"}]},{"given":"Yixuan","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Nutrition and Health, Key Laboratory of Functional Dairy, Co-Constructed by Ministry of Education and Beijing Government, China Agricultural University, Beijing 100190, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"software","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0094-711X","authenticated-orcid":false,"given":"Wen","family":"Zhao","sequence":"additional","affiliation":[{"name":"National Center of Technology Innovation for Dairy, Hohhot 100118, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"software","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-5601-8539","authenticated-orcid":false,"given":"Xiaoxia","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Nutrition and Health, Key Laboratory of Functional Dairy, Co-Constructed by Ministry of Education and Beijing Government, China Agricultural University, Beijing 100190, China"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,12]]},"reference":[{"key":"ref_1","first-page":"532734","article-title":"Epidemiology Characteristics of Constipation for General Population, Pediatric Population, and Elderly Population in 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