title: Measuring short-term liver metabolism non-invasively: postprandial and post-exercise ¹H and ³¹P MR spectroscopy.
abstract: OBJECTIVE
  The objective of this study was to determine the effects of a standardized fat rich meal and subsequent exercise on liver fat content by ¹H MRS and on liver adenosine triphosphate (ATP) content by ³¹P MRS in healthy subjects.
  
  
  METHODS
  Hepatic ¹H and proton decoupled ³¹P MRS were performed on nine healthy subjects on a clinical 3.0 T MR imager three times during a day: after (1) an overnight fast, (2) a following standardized fat rich meal and (3) a subsequent exercise session. Blood parameters were followed during the day to serve as a reference to MRS.
  
  
  RESULTS
  Liver fat content increased gradually over the day (p = 0.0001) with an overall increase of 30 %. Also γ-NTP changed significantly over the day (p = 0.005). γ-NTP/tP decreased by 9 % (p = 0.019, post hoc) from the postprandial to the post-exercise state.
  
  
  CONCLUSIONS
  Our study shows that in vivo MRS can depict short lived physiological changes; entering of fat into liver cells and consumption of ATP during exercise can be measured non-invasively in healthy subjects. The physiological state may have an impact on fat and energy metabolite levels. Hepatic ¹H and ³¹P MRS studies should be performed under standardized conditions.
authors.affiliation: Department of Radiology, HUS Medical Imaging Center, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland, antti.hakkarainen@gmail.com.
authors.forename: Antti
authors.initials: A
authors.lastname: Hakkarainen
authors.forename: Jesper
authors.initials: J
authors.lastname: Lundbom
authors.forename: Esa K
authors.initials: EK
authors.lastname: Tuominen
authors.forename: Marja-Riitta
authors.initials: MR
authors.lastname: Taskinen
authors.forename: Kirsi H
authors.initials: KH
authors.lastname: Pietiläinen
authors.forename: Nina
authors.initials: N
authors.lastname: Lundbom
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D050154:Adiposity / Q000502:physiology; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics; D019518:Postprandial Period / Q000502:physiology*; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D010759:Phosphorus Isotopes; D000255:Adenosine Triphosphate