TY - JOUR
T1 - The mechanisms of skeletal muscle atrophy in response to transient knockdown of the vitamin D receptor in vivo
AU - Bass, Joseph J.
AU - Kazi, Abid A.
AU - Deane, Colleen S.
AU - Nakhuda, Asif
AU - Ashcroft, Stephen P.
AU - Brook, Matthew S.
AU - Wilkinson, Daniel J.
AU - Phillips, Bethan E.
AU - Philp, Andrew
AU - Tarum, Janelle
AU - Kadi, Fawzi
AU - Andersen, Ditte
AU - Garcia, Amadeo Muñoz
AU - Smith, Ken
AU - Gallagher, Iain J.
AU - Szewczyk, Nathaniel J.
AU - Cleasby, Mark E.
AU - Atherton, Philip J.
N1 - Funding Information:
We would like to thank Professor Martin Hewison (Institute of Metabolism and Systems Research, University of Birmingham) for assistance on bioinformatic and pathway analysis. This work was supported by the Medical Research Council (grant number MR/J500495/1). D.J.W. was a post‐doctoral research fellow funded through the MRC‐ARUK Centre for Musculoskeletal Ageing Research awarded to the Universities of Nottingham and Birmingham. This work was supported by a grant from the Physiological Society (to P.J.A. and K.S.). The authors declare no competing interests.
Publisher Copyright:
© 2020 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society
PY - 2021/2/1
Y1 - 2021/2/1
N2 - Key points: Reduced vitamin D receptor (VDR) expression prompts skeletal muscle atrophy. Atrophy occurs through catabolic processes, namely the induction of autophagy, while anabolism remains unchanged. In response to VDR-knockdown mitochondrial function and related gene-set expression is impaired. In vitro VDR knockdown induces myogenic dysregulation occurring through impaired differentiation. These results highlight the autonomous role the VDR has within skeletal muscle mass regulation. Abstract: Vitamin D deficiency is estimated to affect ∼40% of the world's population and has been associated with impaired muscle maintenance. Vitamin D exerts its actions through the vitamin D receptor (VDR), the expression of which was recently confirmed in skeletal muscle, and its down-regulation is linked to reduced muscle mass and functional decline. To identify potential mechanisms underlying muscle atrophy, we studied the impact of VDR knockdown (KD) on mature skeletal muscle in vivo, and myogenic regulation in vitro in C2C12 cells. Male Wistar rats underwent in vivo electrotransfer (IVE) to knock down the VDR in hind-limb tibialis anterior (TA) muscle for 10 days. Comprehensive metabolic and physiological analysis was undertaken to define the influence loss of the VDR on muscle fibre composition, protein synthesis, anabolic and catabolic signalling, mitochondrial phenotype and gene expression. Finally, in vitro lentiviral transfection was used to induce sustained VDR-KD in C2C12 cells to analyse myogenic regulation. Muscle VDR-KD elicited atrophy through a reduction in total protein content, resulting in lower myofibre area. Activation of autophagic processes was observed, with no effect upon muscle protein synthesis or anabolic signalling. Furthermore, RNA-sequencing analysis identified systematic down-regulation of multiple mitochondrial respiration-related protein and genesets. Finally, in vitro VDR-knockdown impaired myogenesis (cell cycling, differentiation and myotube formation). Together, these data indicate a fundamental regulatory role of the VDR in the regulation of myogenesis and muscle mass, whereby it acts to maintain muscle mitochondrial function and limit autophagy.
AB - Key points: Reduced vitamin D receptor (VDR) expression prompts skeletal muscle atrophy. Atrophy occurs through catabolic processes, namely the induction of autophagy, while anabolism remains unchanged. In response to VDR-knockdown mitochondrial function and related gene-set expression is impaired. In vitro VDR knockdown induces myogenic dysregulation occurring through impaired differentiation. These results highlight the autonomous role the VDR has within skeletal muscle mass regulation. Abstract: Vitamin D deficiency is estimated to affect ∼40% of the world's population and has been associated with impaired muscle maintenance. Vitamin D exerts its actions through the vitamin D receptor (VDR), the expression of which was recently confirmed in skeletal muscle, and its down-regulation is linked to reduced muscle mass and functional decline. To identify potential mechanisms underlying muscle atrophy, we studied the impact of VDR knockdown (KD) on mature skeletal muscle in vivo, and myogenic regulation in vitro in C2C12 cells. Male Wistar rats underwent in vivo electrotransfer (IVE) to knock down the VDR in hind-limb tibialis anterior (TA) muscle for 10 days. Comprehensive metabolic and physiological analysis was undertaken to define the influence loss of the VDR on muscle fibre composition, protein synthesis, anabolic and catabolic signalling, mitochondrial phenotype and gene expression. Finally, in vitro lentiviral transfection was used to induce sustained VDR-KD in C2C12 cells to analyse myogenic regulation. Muscle VDR-KD elicited atrophy through a reduction in total protein content, resulting in lower myofibre area. Activation of autophagic processes was observed, with no effect upon muscle protein synthesis or anabolic signalling. Furthermore, RNA-sequencing analysis identified systematic down-regulation of multiple mitochondrial respiration-related protein and genesets. Finally, in vitro VDR-knockdown impaired myogenesis (cell cycling, differentiation and myotube formation). Together, these data indicate a fundamental regulatory role of the VDR in the regulation of myogenesis and muscle mass, whereby it acts to maintain muscle mitochondrial function and limit autophagy.
KW - atrophy
KW - metabolism
KW - skeletal muscle
KW - vitamin D
U2 - 10.1113/JP280652
DO - 10.1113/JP280652
M3 - Article
C2 - 33258480
AN - SCOPUS:85099511610
SN - 0022-3751
VL - 599
SP - 963
EP - 979
JO - The Journal of Physiology
JF - The Journal of Physiology
IS - 3
ER -