Quantification of the glycogen 13C-1 NMR signal during glycogen synthesis in perfused rat liver

• Published in: NMR in biomedicine Vol. 16; no. 1; pp. 36 - 46
• Main Authors: Bergans, N., Dresselaers, T., Vanhamme, L., Van Hecke, P., Van Huffel, S., Vanstapel, F.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.02.2003; Wiley
• Subjects: 13C NMR spectroscopy; Algorithms; Animals; Biological and medical sciences; Carbon Isotopes; Dihydropyridines - pharmacology; Food Deprivation - physiology; Furans - pharmacology; futile cycling; glycogen synthesis; glycogenolysis; Investigative techniques, diagnostic techniques (general aspects); Liver - chemistry; Liver - drug effects; Liver - metabolism; Liver Glycogen - analysis; Liver Glycogen - biosynthesis; Liver Glycogen - chemistry; Magnetic Resonance Spectroscopy - methods; Male; Medical sciences; Miscellaneous. Technology; Models, Biological; perfused liver; Perfusion; quantification; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Rats; Rats, Wistar; Signal Processing, Computer-Assisted; spectral analysis in time domain; Rat; Glycogen; Liver; Rodentia; Quantization; Glucose; Experimental study; Nuclear magnetic resonance imaging; Vertebrata; Mammalia; Synthesis; Perfusion; Spectrum analysis; Animal; Medical imagery; Glycogenolysis; Technique
• ISSN: 0952-3480; 1099-1492
• DOI: 10.1002/nbm.812

We studied glycogen synthesis from glucose in perfused livers of fed (n = 4) and 24 h starved (n = 7) rats. Glycogenolysis was inhibited by BAY R3401 (150 µM) and proglycosyn (100 µM). After 60 min, we replaced 99% 13C‐1 glucose by natural abundance glucose. This pulse‐chase design allowed us to recognize residual ongoing futile glycogen turnover from the release of initially deposited 13C‐label, into the 13C‐free chase medium. Net residual turnover was less than 2 ± 0.7% and 0.6 ± 0.2% of 1‐13C glycogen deposition rates of 0.31 ± 0.04 and 0.99 ± 0.04 µmol glucose g−1 min−1, in starved and fed livers, respectively. The 1‐13C glycogen signal was monitored throughout the experiment with proton‐decoupled 13C NMR spectroscopy and analyzed in the time domain using AMARES. We noticed progressive line‐broadening in any single experiment in the chase phase. One or a sum of two to three overlapping Lorentzians, with different exponential damping factors, were fitted to the signal. When the S/N was better than 40, the fit always delivered a small and a broad component. In the chase phase, the fit with a single Lorentzian resulted in a decline of glycogen signal by about 15 ± 4 and 12 ± 2% in starved and fed rats, respectively. This apparent decline in 1‐13C glycogen signal could not be accounted for by the appearance of equivalent amounts of 13C‐labeled metabolites in the perfusate. The fit with a sum of two Lorentzians resulted in a decline of glycogen signal intensity of 7 ± 5 and 5 ± 3% in starved and fed rats, respectively, which reduced the apparent turnover to 8 ± 9% and 6 ± 4%, respectively. Quantification of the growing 13C‐1 glycogen signal requires a model function that accommodates changes in line shape throughout the period under study. Copyright © 2003 John Wiley & Sons, Ltd.