title: Noninvasive measurements of glycogen in perfused mouse livers using chemical exchange saturation transfer NMR and comparison to (13)C NMR spectroscopy.
abstract: Liver glycogen represents an important physiological form of energy storage. It plays a key role in the regulation of blood glucose concentrations, and dysregulations in hepatic glycogen metabolism are linked to many diseases including diabetes and insulin resistance. In this work, we develop, optimize, and validate a noninvasive protocol to measure glycogen levels in isolated perfused mouse livers using chemical exchange saturation transfer (CEST) NMR spectroscopy. Model glycogen solutions were used to determine optimal saturation pulse parameters which were then applied to intact perfused mouse livers of varying glycogen content. Glycogen measurements from serially acquired CEST Z-spectra of livers were compared with measurements from interleaved natural abundance (13)C NMR spectra. Experimental data revealed that CEST-based glycogen measurements were highly correlated with (13)C NMR glycogen spectra. Monte Carlo simulations were then used to investigate the inherent (i.e., signal-to-noise-based) errors in the quantification of glycogen with each technique. This revealed that CEST was intrinsically more precise than (13)C NMR, although in practice may be prone to other errors induced by variations in experimental conditions. We also observed that the CEST signal from glycogen in liver was significantly less than that observed from identical amounts in solution. Our results demonstrate that CEST provides an accurate, precise, and readily accessible method to noninvasively measure liver glycogen levels and their changes. Furthermore, this technique can be used to map glycogen distributions via conventional proton magnetic resonance imaging, a capability universally available on clinical and preclinical magnetic resonance imaging (MRI) scanners vs (13)C detection, which is limited to a small fraction of clinical-scale MRI scanners.
authors.affiliation: †Merck Research Laboratories, 2000 Galloping Hill Rd., Kenilworth, New Jersey 07033, United States.
authors.forename: Corin O
authors.initials: CO
authors.lastname: Miller
authors.affiliation: †Merck Research Laboratories, 2000 Galloping Hill Rd., Kenilworth, New Jersey 07033, United States.
authors.forename: Jin
authors.initials: J
authors.lastname: Cao
authors.affiliation: ‡Vanderbilt University, Institute of Imaging Science, Nashville, Tennessee 37232, United States.|§Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.
authors.forename: Eduard Y
authors.initials: EY
authors.lastname: Chekmenev
authors.affiliation: ‡Vanderbilt University, Institute of Imaging Science, Nashville, Tennessee 37232, United States.|§Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.|∥Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Damon
authors.affiliation: ∥Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.
authors.forename: Alan D
authors.initials: AD
authors.lastname: Cherrington
authors.affiliation: ‡Vanderbilt University, Institute of Imaging Science, Nashville, Tennessee 37232, United States.|§Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.|∥Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States.
authors.forename: John C
authors.initials: JC
authors.lastname: Gore
mesh_terms: D000818:Animals; D002623:Chemistry Techniques, Analytical / Q000379:methods* / Q000592:standards*; D006003:Glycogen / Q000032:analysis*; D008099:Liver / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D051379:Mice
chemical_list: D006003:Glycogen