title: Effects of 1,25(OH)2 D3 and 25(OH)D3 on C2C12 Myoblast Proliferation, Differentiation, and Myotube Hypertrophy.
abstract: An adequate vitamin D status is essential to optimize muscle strength. However, whether vitamin D directly reduces muscle fiber atrophy or stimulates muscle fiber hypertrophy remains subject of debate. A mechanism that may affect the role of vitamin D in the regulation of muscle fiber size is the local conversion of 25(OH)D to 1,25(OH)2 D by 1α-hydroxylase. Therefore, we investigated in a murine C2C12 myoblast culture whether both 1,25(OH)2 D3 and 25(OH)D3 affect myoblast proliferation, differentiation, and myotube size and whether these cells are able to metabolize 25(OH)D3 and 1,25(OH)2 D3 . We show that myoblasts not only responded to 1,25(OH)2 D3 , but also to the precursor 25(OH)D3 by increasing their VDR mRNA expression and reducing their proliferation. In differentiating myoblasts and myotubes 1,25(OH)2 D3 as well as 25(OH)D3 stimulated VDR mRNA expression and in myotubes 1,25(OH)2 D3 also stimulated MHC mRNA expression. However, this occurred without notable effects on myotube size. Moreover, no effects on the Akt/mTOR signaling pathway as well as MyoD and myogenin mRNA levels were observed. Interestingly, both myoblasts and myotubes expressed CYP27B1 and CYP24 mRNA which are required for vitamin D3 metabolism. Although 1α-hydroxylase activity could not be shown in myotubes, after treatment with 1,25(OH)2 D3 or 25(OH)D3 myotubes showed strongly elevated CYP24 mRNA levels compared to untreated cells. Moreover, myotubes were able to convert 25(OH)D3 to 24R,25(OH)2 D3 which may play a role in myoblast proliferation and differentiation. These data suggest that skeletal muscle is not only a direct target for vitamin D3 metabolites, but is also able to metabolize 25(OH)D3 and 1,25(OH)2 D3 . J. Cell. Physiol. 231: 2517-2528, 2016. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.
authors.affiliation: Department of Internal Medicine/Endocrinology, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: van der Meijden
authors.affiliation: Department of Clinical Chemistry, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
authors.forename: N
authors.initials: N
authors.lastname: Bravenboer
authors.affiliation: Department of Clinical Chemistry, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
authors.forename: N F
authors.initials: NF
authors.lastname: Dirks
authors.affiliation: Department of Clinical Chemistry, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
authors.forename: A C
authors.initials: AC
authors.lastname: Heijboer
authors.affiliation: Department of Internal Medicine/Endocrinology, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: den Heijer
authors.affiliation: Laboratory for Myology, MOVE Research Institute Amsterdam, Department of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
authors.forename: G M J
authors.initials: GM
authors.lastname: de Wit
authors.affiliation: Laboratory for Myology, MOVE Research Institute Amsterdam, Department of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
authors.forename: C
authors.initials: C
authors.lastname: Offringa
authors.affiliation: Department of Clinical Chemistry, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: Lips
authors.affiliation: Laboratory for Myology, MOVE Research Institute Amsterdam, Department of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
authors.forename: R T
authors.initials: RT
authors.lastname: Jaspers
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002112:Calcifediol / Q000494:pharmacology*; D002117:Calcitriol / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D006984:Hypertrophy; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D018008:Myogenin / Q000235:genetics / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism; D038601:Ribosomal Protein S6 / Q000378:metabolism
chemical_list: D018008:Myogenin; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D038601:Ribosomal Protein S6; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D051057:Proto-Oncogene Proteins c-akt; D018995:Myosin Heavy Chains; D002117:Calcitriol; D002112:Calcifediol