title: Characterization of the peak at 2.06 ppm in (31) P magnetic resonance spectroscopy of human liver: phosphoenolpyruvate or phosphatidylcholine?
abstract: High field MR scanners can resolve a metabolite resonating at 2.06 ppm in the in vivo proton-decoupled liver (31) P MR spectrum. Traditionally this peak has been assigned to phosphoenolpyruvate (PEP), the key metabolite for gluconeogenesis. However, recent evidence supported the assignment to biliary phosphatidylcholine (PtdCh), which is produced in the liver and stored in the gall bladder. To elucidate the respective contributions of PtdCh and PEP to the in vivo resonance at 2.06 ppm (PEP-PtdCh), we made phantom measurements that confirmed that both biliary PtdCh and PEP resonate approximately at 2 ppm. The absolute quantification of PEP-PtdCh yielded concentrations ranging from 0.6 to 2.0 mmol/l, with mean coefficients of variation of 4.8% for intraday and 7.2% for interday reproducibility in healthy volunteers. The T1 relaxation time of PEP-PtdCh was 0.97 ± 0.30 s in the liver and 0.44 ± 0.11 s in the gallbladder. Ingestion of a mixed meal decreased the concentration of PtdCh-PEP by approximately 12%. In the retrospective analysis, PEP-PtdCh was 68% higher in the liver of subjects with gallbladder infiltration of the volume of interest (VOI) compared with those without gallbladder infiltration. PEP-PtdCh was also significantly higher in the liver of cholecystectomy patients compared with volunteers without gallbladder infiltration, which suggests increased intrahepatic bile fluid as a compensation for gall bladder removal. These results show that liver PtdCh is the major component of the resonance at 2.06 ppm and that careful VOI positioning is mandatory to avoid interference from the gallbladder.
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.|German Center for Diabetes Research, Partner, Düsseldorf, Germany.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bierwagen
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.|German Center for Diabetes Research, Partner, Düsseldorf, Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Begovatz
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.|German Center for Diabetes Research, Partner, Düsseldorf, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Nowotny
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.|German Center for Diabetes Research, Partner, Düsseldorf, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Markgraf
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.|German Center for Diabetes Research, Partner, Düsseldorf, Germany.|Department of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Nowotny
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.|German Center for Diabetes Research, Partner, Düsseldorf, Germany.|Department of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Chrysi
authors.initials: C
authors.lastname: Koliaki
authors.affiliation: German Center for Diabetes Research, Partner, Düsseldorf, Germany.|Institute for Biometry and Epidemiology, German Diabetes Center, Düsseldorf, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Giani
authors.affiliation: German Center for Diabetes Research, Partner, Düsseldorf, Germany.|Institute for Biometry and Epidemiology, German Diabetes Center, Düsseldorf, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Klüppelholz
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.|German Center for Diabetes Research, Partner, Düsseldorf, Germany.
authors.forename: Jesper
authors.initials: J
authors.lastname: Lundbom
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.|German Center for Diabetes Research, Partner, Düsseldorf, Germany.|Department of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Roden
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D005260:Female; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008111:Liver Function Tests / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010713:Phosphatidylcholines / Q000378:metabolism*; D010728:Phosphoenolpyruvate / Q000378:metabolism*; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D015415:Biomarkers; D010713:Phosphatidylcholines; D010759:Phosphorus Isotopes; D019275:Radiopharmaceuticals; D010728:Phosphoenolpyruvate
keywords: 31P liver spectroscopy; bile; gall bladder; phosphatidylcholine; phosphoenolpyruvate