Abnormal n-6 fatty acid metabolism in cystic fi brosis is caused by activation of AMP-activated protein kinase

Abstract

Cystic fi brosis (CF) patients and model systems exhibit consistent abnormalities in PUFA metabolism, including increased metabolism of linoleate to arachidonate. Recent studies have connected these abnormalities to increased expression and activity of the 6- and 5-desaturase enzymes. However, the mechanism connecting these changes to the CF transmembrane conductance regulator ( CFTR ) mutations responsible for CF is unknown. This study tests the hypothesis that increased activity of AMP-activated protein kinase (AMPK), previously described in CF bronchial epithelial cells, causes these changes in fatty acid metabolism by driving desaturase expression. Using CF bronchial epithelial cell culture models, we confi rm elevated activity of AMPK in CF cells and show that it is due to increased phosphorylation of AMPK by Ca 2+ /calmodulin-dependent protein kinase kinase (CaMKK). We also show that inhibition of AMPK or CaMKK reduces desaturase expression and reverses the metabolic alterations seen in CF cells. These results signify a novel AMPK-dependent mechanism linking the genetic defect in CF to alterations in PUFA metabolism. -Umunakwe, O. C., and A. C. Seegmiller. Abnormal n-6 fatty acid metabolism in cystic fi brosis is caused by activation of AMP-activated protein kinase. J. Lipid Res. 2014. 55: 1489 - 1497 . © 2014 by the American Society for Biochemistry and Molecular Biology, Inc.