title: Lactobacillus reuteri 6475 Increases Bone Density in Intact Females Only under an Inflammatory Setting.
abstract: OBJECTIVE
  We previously demonstrated that short-term oral administration of the probiotic Lactobacillus reuteri 6475 enhanced bone density in male but not female mice. We also established that L. reuteri 6475 enhanced bone health and prevented bone loss in estrogen-deficient female mice. In this study, we tested whether a mild inflammatory state and/or a long-term treatment with the probiotic was required to promote a positive bone effect in estrogen-sufficient female mice.
  
  
  METHODS
  A mild inflammatory state was induced in female mice by dorsal surgical incision (DSI). Following DSI animals were orally supplemented with L. reuteri or vehicle control for a period of 8 weeks. Gene expression was measured in the intestine and bone marrow by qPCR. Distal femoral bone density and architecture was analyzed by micro-CT.
  
  
  RESULTS
  We report that 8 weeks after DSI there is a significant increase in the weight of spleen, thymus and visceral (retroperitoneal) fat pads. Expression of intestinal cytokines and tight junction proteins are also altered 8 weeks post-DSI. Interestingly, L. reuteri treatment was found to display both intestinal region- and inflammation-dependent effects. Unexpectedly we identified that 1) L. reuteri treatment increased bone density in females but only in those that underwent DSI and 2) DSI benefited cortical bone parameters. In the bone marrow, dorsal surgery induced CD4+ T cell numbers, a response that was unaffected by L. reuteri treatment, whereas expression of RANKL, OPG and IL-10 were significantly affected by L. reuteri treatment.
  
  
  CONCLUSIONS
  Our data reveals a previously unappreciated effect of a mild surgical procedure causing a long-lasting effect on inflammatory gene expression in the gut and the bone. Additionally, we demonstrate that in intact female mice, the beneficial effect of L. reuteri on bone requires an elevated inflammatory status.
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America.
authors.forename: Fraser L
authors.initials: FL
authors.lastname: Collins
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America.
authors.forename: Regina
authors.initials: R
authors.lastname: Irwin
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America.
authors.forename: Hayley
authors.initials: H
authors.lastname: Bierhalter
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Schepper
authors.affiliation: Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Britton
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America.
authors.forename: Narayanan
authors.initials: N
authors.lastname: Parameswaran
authors.affiliation: Department of Physiology, Michigan State University, East Lansing, Michigan, United States of America.|Department of Radiology, Michigan State University, East Lansing, Michigan, United States of America.|Biomedical Imaging Research Centre, Michigan State University, East Lansing, Michigan, United States of America.
authors.forename: Laura R
authors.initials: LR
authors.lastname: McCabe
mesh_terms: D000818:Animals; D015519:Bone Density; D001854:Bone Marrow Cells / Q000276:immunology / Q000378:metabolism; D016723:Bone Remodeling / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000235:genetics; D004967:Estrogens / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D007249:Inflammation / Q000235:genetics / Q000378:metabolism / Q000628:therapy*; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000276:immunology; D052200:Limosilactobacillus reuteri / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D019936:Probiotics / Q000008:administration & dosage / Q000627:therapeutic use*; D055114:X-Ray Microtomography
chemical_list: D016207:Cytokines; D004967:Estrogens