Loss of intestinal alkaline phosphatase leads to distinct chronic changes in bone phenotype Florian Kuehn, MD, a,b Fatemeh Adiliaghdam, MD, a Sulaiman R. Hamarneh, MD, a Robin Vasan, MD, a Enyu Liu, MD, a Yang Liu, MD, a Juan M. Ramirez, MD, a Raza S. Hoda, MD, c Alexander R. Munoz, MD Candidate, a Frank C. Ko, PhD, d Michael Armanini, MSc, d Daniel J. Brooks, MSc, d Mary L. Bouxsein, PhD, d Marie B. Demay, MD, d and Richard A. Hodin, MD a, * a Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts b Department of General, Visceral, Vascular and Transplant Surgery, Hospital of the University of Munich, Munich, Germany c Pathology Department, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts d Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts article info Article history: Received 29 March 2018 Received in revised form 2 June 2018 Accepted 19 June 2018 Available online xxx Keywords: IAP Gut-bone axis Inflammation Bone remodeling abstract Background: The gut is becoming increasingly recognized as the source of various systemic diseases, and recently, it has been linked to bone metabolism via the so-called gut-bone axis. The microbiome and gut-derived mediators are thought to impact upon bone meta- bolism, and administration of probiotics has been shown to have beneficial effects in bone. The gut brush border enzyme intestinal alkaline phosphatase (IAP) plays an important role in controlling calcium absorption, inhibiting lipopolysaccharides, and other inflammatory mediators responsible for endotoxemia and appears to preserve the normal gut microbiota. Interestingly, IAP-deficient mice (AKP3 / ) also display a significant decrease in fecal Lactobacillus, the genus shown to be beneficial to bone. Materials and methods: IAP mRNA levels in mouse bone were measured using quantitative real-time polymerase chain reaction. Femurs of IAP-knockout (KO) and wild-type (WT) mice were analyzed by microcomputed tomography and histopathology. Serum levels of alkaline phosphatase, calcium, and phosphorus were measured. Target cell response upon exposure to serum from IAP-KO and WT mice was quantified using primary bone marrow macrophages. Results: IAP was not significantly expressed in bones of WT or KO animals. IAP (alkaline phosphatase 3) expression in bone was vanishingly low compared to the duodenum (bone versus duodenum, 56.9  17.7 versus 25,430.3  10,884.5 relative expression, P ¼ 0.01). Bone histology of younger IAP-KO and WT animals was indistinguishable, whereas older IAP- deficient mice showed a distinctly altered phenotype on histology and computed tomog- raphy scan. Younger KO mice did not display any abnormal levels in blood chemistry. Older IAP-KO animals showed an isolated increase in serum alkaline phosphatase levels The article has been presented as an oral presentation at the 13th Academic Surgical Congress 2018 in Jacksonville, Florida, USA, and at the 135th Congress of the German Society of Surgery (DGCH) 2018 in Berlin, Germany. * Corresponding author. Professor of Surgery, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, 15 Parkman Street, Boston, MA 02114. Tel.: 617-724-2570; fax: 617-724-2574. E-mail address: rhodin@mgh.harvard.edu (R.A. Hodin). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.JournalofSurgicalResearch.com journal of surgical research  december 2018 (232) 325 e331 0022-4804/$ e see front matter ª 2018 Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jss.2018.06.061