Vitamin D Mitochondria ~ Shauna Bloom Vigor

Vitamin D Mitochondria

. 2020 Mar 1;318(3):C536-C541.

doi: 10.1152/ajpcell.00568.2019. Epub 2020 Jan 15.

The vitamin D receptor regulates mitochondrial function in C2C12 myoblasts

Affiliations

PMID: 31940245
PMCID: PMC7099523
DOI: 10.1152/ajpcell.00568.2019

Free PMC article

The vitamin D receptor regulates mitochondrial function in C2C12 myoblasts

Stephen P Ashcroft et al. Am J Physiol Cell Physiol. 2020 .

Free PMC article

Abstract

Vitamin D deficiency has been linked to a reduction in skeletal muscle function and oxidative capacity; however, the mechanistic bases of these impairments are poorly understood. The biological actions of vitamin D are carried out via the binding of 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃) to the vitamin D receptor (VDR). Recent evidence has linked 1α,25(OH)₂D₃ to the regulation of skeletal muscle mitochondrial function in vitro; however, little is known with regard to the role of the VDR in this process. To examine the regulatory role of the VDR in skeletal muscle mitochondrial function, we used lentivirus-mediated shRNA silencing of the VDR in C2C12 myoblasts (VDR-KD) and examined mitochondrial respiration and protein content compared with an shRNA scrambled control. VDR protein content was reduced by ~95% in myoblasts and myotubes (P < 0.001). VDR-KD myoblasts displayed a 30%, 30%, and 36% reduction in basal, coupled, and maximal respiration, respectively (P < 0.05). This phenotype was maintained in VDR-KD myotubes, displaying a 34%, 33%, and 48% reduction in basal, coupled, and maximal respiration (P < 0.05). Furthermore, ATP production derived from oxidative phosphorylation (ATP_Ox) was reduced by 20%, suggesting intrinsic impairments within the mitochondria following VDR-KD. However, despite the observed functional decrements, mitochondrial protein content, as well as markers of mitochondrial fission were unchanged. In summary, we highlight a direct role for the VDR in regulating skeletal muscle mitochondrial respiration in vitro, providing a potential mechanism as to how vitamin D deficiency might impact upon skeletal muscle oxidative capacity.

Keywords: adaptation; metabolism; mitochondria; skeletal muscle; vitamin D.

Conflict of interest statement

No conflicts of interest, financial or otherwise, are declared by the authors.

Figures

**Fig. 1.**
Generation of vitamin D receptor (VDR) loss of function C2C12 myoblasts. A: quantification of VDR protein content in VDR-knockdown (KD) compared with control myoblasts and myotubes. B: representative immunoblot images of VDR protein content in VDR-KD myoblasts and myotubes. **P < 0.005, independent t test. Data are means ± SD (n = 5-6 lanes/group) and represented as a fold change from control.

**Fig. 2.**
Vitamin D receptor-knockdown (VDR-KD) myoblasts display reduced mitochondrial respiration compared with control. A: oxygen consumption rate (OCR) during analysis of respiratory control in control and VDR-KD myoblasts. B: respiratory control parameters from control and VDR-KD myoblasts. C: OCR during analysis of respiratory control in control and VDR-KD myotubes. D: respiratory control parameters from control and VDR-KD myotubes. E: estimations of total ATP production (ATP_Total), oxidative phosphorylation (ATP_Ox), and glycolysis (ATP_Glyc) in control and VDR-KD myoblasts. F: mitochondrial membrane potential assessed via TMRE (tetramethylrhodamine ethyl ester) fluorescence in control and VDR-KD myoblasts. *P < 0.05, **P < 0.005, independent t test. Data are means ± SD (A–E: n = 9–10 wells/group. F: n = 5 wells/group).

**Fig. 3.**
No change in markers of mitochondrial protein content in vitamin D receptor-knockdown (VDR-KD) myoblasts and myotubes compared with control. A–D: protein abundance of mitochondrial subunits complex I (CI; NDUFB8), complex II (CII; SDHB), complex IV (CIV; MTCO1), complex V (CV; ATP5A), as well as citrate synthase (CS) and cytochrome c (Cyt c) in control and VDR-KD myoblasts (A and B) and myotubes (C and D). Data are expressed as means ± SD (n = 6 lanes/group) and represented as a fold change from control.

**Fig. 4.**
Markers of mitochondrial fission remain unchanged while optic atrophy-1 (OPA1) protein abundance is increased in vitamin D receptor-knockdown (VDR-KD) myoblasts and myotubes compared with control. A–D: protein abundance of markers of mitochondrial fusion (MFN2 and OPA1) and fission [mitofilin, fission protein 1 (Fis1), and dynamin-like protein 1 (DRP1)] in control and VDR-KD myoblasts (A and B) and myotubes (C and D). *P < 0.05, independent t tests. Data are means ± SD (n = 6 lanes/group) and represented as a fold change from control.

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Vitamin D Mitochondria

Source: https://pubmed.ncbi.nlm.nih.gov/31940245/

Shauna Bloom Vigor