{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,24]],"date-time":"2026-09-24T21:05:54Z","timestamp":1790283954771,"version":"4.1.0"},"reference-count":35,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2025,6,15]],"date-time":"2025-06-15T00:00:00Z","timestamp":1749945600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["23K10959"],"award-info":[{"award-number":["23K10959"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Aminopeptidase N (APN), an enzyme expressed in the small intestinal mucosa, is involved in dietary protein digestion. Previous studies have shown that oral administration of fermented milk containing lactic acid bacteria (LAB) enhances mucosal APN activity in young mice. This study aimed to investigate whether LAB strains stimulate mucosal APN activity in aged mice and to evaluate its relevance to age-related changes in body composition. The underlying molecular mechanisms were also explored in vitro. Experiment 1: Aged C57BL\/6J mice were fed diets supplemented with heat-killed LAB strains\u2014Enterococcus faecalis OU-23 (EF), Leuconostoc mesenteroides OU-03 (LM), or Lactiplantibacillus plantarum SNK12 (LP). Compared to the aged Control group, the ileal APN activity was significantly higher in the LP group. LP administration also elevated serum Gla-osteocalcin levels and decreased serum CTX-1 levels. Experiment 2: IEC-6 cells were co-cultured with LP that had been treated with RNase, DNase, or lysozyme. APN activity was significantly lower in cells co-cultured with DNase- or lysozyme-treated LP compared to those co-cultured with untreated LP. A specific LAB strain may enhance mucosal APN activity in the aged intestine, potentially contributing to improved bone metabolism. This effect may be mediated by bacterial DNA and peptidoglycan.<\/jats:p>","DOI":"10.3390\/ijms26125742","type":"journal-article","created":{"date-parts":[[2025,6,16]],"date-time":"2025-06-16T10:47:22Z","timestamp":1750070842000},"page":"5742","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Specific Heat-Killed Lactic Acid Bacteria Enhance Mucosal Aminopeptidase N Activity in the Small Intestine of Aged Mice"],"prefix":"10.3390","volume":"26","author":[{"given":"Takeshi","family":"Tsuruta","sequence":"first","affiliation":[{"name":"Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 7008530, Japan"},{"name":"Research Center for Intestinal Health Science, Okayama University, Okayama 7008530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mami","family":"Wakisaka","sequence":"additional","affiliation":[{"name":"Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 7008530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4607-0747","authenticated-orcid":false,"given":"Takumi","family":"Watanabe","sequence":"additional","affiliation":[{"name":"Bio-Lab Co., Ltd., Hidaka-shi 350-1249, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aoi","family":"Nishijima","sequence":"additional","affiliation":[{"name":"Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 7008530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Akihito","family":"Ikeda","sequence":"additional","affiliation":[{"name":"Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 7008530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mao","family":"Teraoka","sequence":"additional","affiliation":[{"name":"Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 7008530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tianyang","family":"Wang","sequence":"additional","affiliation":[{"name":"Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 7008530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kuiyi","family":"Chen","sequence":"additional","affiliation":[{"name":"Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 7008530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6105-8124","authenticated-orcid":false,"given":"Naoki","family":"Nishino","sequence":"additional","affiliation":[{"name":"Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama 7008530, Japan"},{"name":"Research Center for Intestinal Health Science, Okayama University, Okayama 7008530, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,6,15]]},"reference":[{"key":"ref_1","first-page":"3","article-title":"The biology of aging","volume":"70","author":"Troen","year":"2003","journal-title":"Mt. 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