title: Monitoring creatine and phosphocreatine by (13)C MR spectroscopic imaging during and after (13)C4 creatine loading: a feasibility study.
abstract: Creatine (Cr) supplementation to enhance muscle performance shows variable responses among individuals and different muscles. Direct monitoring of the supplied Cr in muscles would address these differences. In this feasibility study, we introduce in vivo 3D (13)C MR spectroscopic imaging (MRSI) of the leg with oral ingestion of (13)C4-creatine to observe simultaneously Cr and phosphocreatine (PCr) for assessing Cr uptake, turnover, and the ratio PCr over total Cr (TCr) in individual muscles. (13)C MRSI was performed of five muscles in the posterior thigh in seven subjects (two males and two females of ~20 years, one 82-year-old male, and two neuromuscular patients) with a (1)H/(13)C coil in a 3T MR system before, during and after intake of 15 % (13)C4-enriched Cr. Subjects ingested 20 g Cr/day for 4 days in four 5 g doses at equal time intervals. The PCr/TCr did not vary significantly during supplementation and was similar for all subjects and investigated muscles (average 0.71 ± 0.07), except for the adductor magnus (0.64 ± 0.03). The average Cr turnover rate, assessed in male muscles, was 2.1 ± 0.7 %/day. The linear uptake rates of Cr were variable between muscles, although not significantly different. This assessment was possible in all investigated muscles of young male volunteers, but less so in muscles of the other subjects due to lower signal-to-noise ratio. Improvements for future studies are discussed. In vivo (13)C MRSI after (13)C-Cr ingestion is demonstrated for longitudinal studies of Cr uptake, turnover, and PCr/TCr ratios of individual muscles in one exam.
authors.affiliation: Department of Radiology, Radboud University Medical Center, Nijmegen, The Netherlands. Barbara.Janssen@radboudumc.nl.
authors.forename: Barbara H
authors.initials: BH
authors.lastname: Janssen
authors.affiliation: Department of Neurology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Saskia
authors.initials: S
authors.lastname: Lassche
authors.affiliation: Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Maria T
authors.initials: MT
authors.lastname: Hopman
authors.affiliation: Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Ron A
authors.initials: RA
authors.lastname: Wevers
authors.affiliation: Department of Neurology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Baziel G M
authors.initials: BG
authors.lastname: van Engelen
authors.affiliation: Department of Radiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Arend
authors.initials: A
authors.lastname: Heerschap
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D002247:Carbon Isotopes / Q000493:pharmacokinetics / Q000494:pharmacology; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D010725:Phosphocreatine
keywords: 13C; Creatine; Human muscle; MR spectroscopy