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// Cecilia Roux 1, 2 , Chiara Riganti 3 , Sammy Ferri Borgogno 1, 2 , Roberta Curto 1, 2 , Claudia Curcio 1, 2 , Valeria Catanzaro 4 , Giuseppe Digilio 4 , Sergio Padovan 5 , Maria Paola Puccinelli 6 , Monica Isabello 6 , Silvio Aime 2, 7 , Paola Cappello 1, 2, 7, * and Francesco Novelli 1, 2, 7, * 1 Center for Experimental Research and Medical Studies, Citta della Salute e della Scienza di Torino, 10126 Turin, Italy 2 Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy 3 Department of Oncology, University of Turin, 10126 Turin, Italy 4 Department of Science and Technologic Innovation, Universita del Piemonte Orientale “A. Avogadro”, 15121 Alessandria, Italy 5 Institute for Biostructures and Bioimages (CNR) c/o Molecular Biotechnology Center, 10126 Turin, Italy 6 Clinical Biochemistry Laboratory, Citta della Salute e della Scienza di Torino, 10126 Turin, Italy 7 Molecular Biotechnology Center, University of Turin, 10126 Turin, Italy * These authors have contributed equally to this work Correspondence to: Francesco Novelli, email: franco.novelli@unito.it Paola Cappello, email: paola.cappello@unito.it Keywords: PDAC; amino acid; circulating biomarkers; pancreatitis; diagnosis Received: March 24, 2017 Accepted: August 04, 2017 Published: August 24, 2017 ABSTRACT Pancreatic ductal adenocarcinoma (PDAC) is becoming the second leading cause of cancer-related death in the Western world. The mortality is very high, which emphasizes the need to identify biomarkers for early detection. As glutamine metabolism alteration is a feature of PDAC, its in vivo evaluation may provide a useful tool for biomarker identification. Our aim was to identify a handy method to evaluate blood glutamine consumption in mouse models of PDAC. We quantified the in vitro glutamine uptake by Mass Spectrometry (MS) in tumor cell supernatants and showed that it was higher in PDAC compared to non-PDAC tumor and pancreatic control human cells. The increased glutamine uptake was paralleled by higher activity of most glutamine pathway-related enzymes supporting nucleotide and ATP production. Free glutamine blood levels were evaluated in orthotopic and spontaneous mouse models of PDAC and other pancreatic-related disorders by High-Performance Liquid Chromatography (HPLC) and/or MS. Notably we observed a reduction of blood glutamine as much as the tumor progressed from pancreatic intraepithelial lesions to invasive PDAC, but was not related to chronic pancreatitis-associated inflammation or diabetes. In parallel the increased levels of branched-chain amino acids (BCAA) were observed. By contrast blood glutamine levels were stable in non-tumor bearing mice. These findings demonstrated that glutamine uptake is measurable both in vitro and in vivo . The higher in vitro avidity of PDAC cells corresponded to a lower blood glutamine level as soon as the tumor mass grew. The reduction in circulating glutamine represents a novel tool exploitable to implement other diagnostic or prognostic PDAC biomarkers.