Evidence of increased flux to n-6 docosapentaenoic acid in phospholipids of pancreas from cftr À/À knockout mice Mario Ollero a,b,1 , Michael Laposata c, 4 , Munir M. Zaman b , Paola G Blanco b , Charlotte Andersson b , John Zeind d , Yana Urman b , Geraldine Kent e , Juan G. Alvarez 2 , Steven D. Freedman b a Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA b Department of Obstetrics, Gynecology and Reproductive Biology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA c Department of Pathology, Division of Laboratory Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA d GCRC, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA e Department of Pathology and Pediatrics, The Hospital for Sick Children, Toronto, ON, Canada Received 15 November 2005; accepted 11 May 2006 Abstract An association has been reported between alterations in fatty acid metabolism and cystic fibrosis (CF). We hypothesized that these alterations are specific for a particular lipid component(s) and are the result of a specific metabolic defect. The different lipid classes were examined for fatty acid changes by using pancreatic homogenates and primary cultures of pancreatic acini from cftr À/À (CF) and wild-type mice. Lipid classes and phospholipids were separated by aminopropyl column chromatography and high-performance liquid chromatography, and fatty acid methyl esters were analyzed. The results indicate that in CF mice (1) linoleate was decreased in phospholipids but not in neutral lipids; (2) there was an increase in dihomo-c -linolenate and in docosapentaenoate, the terminal fatty acid of the n-6 pathway, in total lipids and total phospholipids, but not in the neutral lipid class; and (3) the docosapentaenoate (n-6)/ docosahexaenoate (n-3) ratio was significantly elevated in neutral phospholipids. This suggests an enhanced flux through the n-6 pathway beyond arachidonate. This study provides a more in-depth understanding of the fatty acid alterations found in CF, as reflected by the cftr À/À mouse model. D 2006 Elsevier Inc. All rights reserved. 1. Introduction Cystic fibrosis (CF) is the most prevalent lethal autosomal recessive disorder among Caucasians [1]. The typical patient experiences pancreatic insufficiency and recurrent pulmonary infections. These infections are accom- panied by excessive inflammation in the respiratory system that can ultimately lead to progressive bronchiectasis, respiratory failure, and death [2]. The CF transmembrane regulator (CFTR) is a cyclic adenosine monophosphate– regulated chloride channel [3]. Mutations of the gene for CFTR are integral to the development of CF [3,4]. However, the links between impairment of CFTR function and many of the pathologic manifestations of CF remain unknown. For several decades, an association has been made between alterations in fatty acid metabolism and the presence of CF. A report was published in 1977 showing abnormal fatty acid composition in the plasma of CF patients with pancreatic insufficiency [5]. It was presumed at that time that a decrease in fatty acid absorption was responsible for fatty acid changes found in the plasma of patients with CF. In 1985, Farrell et al [5] demonstrated that fatty acid composition was abnormal in both plasma and solid tissues in patients with CF, with the major changes being a decrease in linoleate (LA, 18:2 n-6) and an increase in palmitoleate (16:1 n-7) (see Fig. 1 for a 0026-0495/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.metabol.2006.05.002 4 Corresponding author. Massachusetts General Hospital, Boston, MA 02114, USA. Tel.: +1 617 726 8172; fax: +1 617 726 3256. E-mail address: mlaposata@partners.org (M. Laposata). 1 Current address: Universite ´ Rene ´ Descartes-Paris 5, INSERM U467, Paris, France. 2 Current address: Centro de Infertilidad Masculina ANDROGEN, La Corun ˜a, Spain. Metabolism Clinical and Experimental 55 (2006) 1192 – 1200 www.elsevier.com/locate/metabol