Characterization of hepatic fatty acids in mice with reduced liver fat by ultra‐short echo time 1H‐MRS at 14.1 T in vivo. (28th June 2015)

• Record Type: Journal Article
• Authors: Soares, Ana Francisca; Lei, Hongxia; Gruetter, Rolf
• Is Part Of: NMR in biomedicine. Volume 28:Number 8(2015:Aug.)
• Page Start: 1009
• Page End: 1020
• Publication Date: 2015-06-28
• Subjects: Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.3345
• Languages: English
• ISSNs: 0952-3480

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Alterations in the hepatic lipid content (HLC) and fatty acid composition are associated with disruptions in whole body metabolism, both in humans and in rodent models, and can be non‐invasively assessed by <sup>1</sup>H‐MRS <italic>in vivo</italic>. We used <sup>1</sup>H‐MRS to characterize the hepatic fatty‐acyl chains of healthy mice and to follow changes caused by streptozotocin (STZ) injection. Using STEAM at 14.1 T with an ultra‐short <italic>T</italic><sub>E</sub> of 2.8 ms, confounding effects from <italic>T</italic><sub>2</sub> relaxation and <italic>J</italic>‐coupling were avoided, allowing for accurate estimations of the contribution of unsaturated (UFA), saturated (SFA), mono‐unsaturated (MUFA) and poly‐unsaturated (PUFA) fatty‐acyl chains, number of double bonds, PU bonds and mean chain length. Compared with <italic>in vivo</italic><sup>1</sup>H‐MRS, high resolution NMR performed <italic>in vitro</italic> in hepatic lipid extracts reported longer fatty‐acyl chains (18 versus 15 carbons) with a lower contribution from UFA (61 ± 1% versus 80 ± 5%) but a higher number of PU bonds per UFA (1.39 ± 0.03 versus 0.58 ± 0.08), driven by the presence of membrane species in the extracts. STZ injection caused a decrease of HLC (from 1.7 ± 0.3% to 0.7 ± 0.1%), an increase in the contribution of SFA (from 21 ± 2% to 45 ± 6%) and a reduction of the mean length (from 15 to 13 carbons) of cytosolic fatty‐acyl chains. In addition, SFAs were also likely to have increased in membrane lipids of STZ‐induced diabetic mice, along with a decrease of the mean chain length. These studies show the applicability of <sup>1</sup>H‐MRS <italic>in vivo</italic> to monitor changes in the composition of the hepatic fatty‐acyl chains in mice even when they exhibit reduced HLC, pointing to the value of this methodology to evaluate lipid‐lowering interventions in the scope of metabolic disorders. Copyright © 2015 John Wiley & Sons, Ltd.</p> </abstract>