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Iron Status Modulates Circadian Rhythm and Cellular Metabolism in C2C12 Cells
Author(s) -
Soh Traces P.,
Fiddler Joanna L.,
Wu Lei,
Xin Gou,
Lin Dingbo,
Lucas Edralin A.,
Smith Brenda J.,
Clarke Stephen L.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1173.5
Subject(s) - myogenesis , circadian rhythm , biology , circadian clock , c2c12 , endocrinology , microbiology and biotechnology , medicine , myod , transcription factor , skeletal muscle , biochemistry , gene
In mammals iron deficiency (ID) can lead to hyperglycemia and dyslipidemia, though the factors responsible for these changes in glucose and lipid homeostasis remain unclear. Similar changes in glucose and lipid metabolism are also observed in response to abnormalities in circadian rhythm. Cellular oscillations in circadian rhythm are controlled through a network of negative feedback and feed‐forward loops that regulate the transcription of clock‐related and metabolic genes. The nuclear hormone receptors REV‐ERB and ROR are negative and positive regulators for Bmal1 , respectively. BMAL1:CLOCK dimers function not only to increase Per and Cry gene expression, but also increase the expression of REV‐ERB and ROR mRNA thereby forming a regulatory circuit to maintain circadian oscillations. REV‐ERBa and REV‐ERBb are heme‐regulated transcription factors, suggesting that alterations in heme synthesis may affect circadian rhythm. In the presence of heme, REV‐ERBs repress transcription of Bmal1 , G6pase , and Pepck in the liver and reduced heme levels leads to derepression of these genes. In the skeletal muscle, BMAL1 regulates cellular differentiation and mitochondrial function through the transcription of MyoD and Pgc1α/β. Dietary iron affects circadian signaling through REV‐ERB in the liver, though how iron status impacts REV‐ERB activity in skeletal muscle remains unknown. The aim of the study was to investigate the effect of iron status on the regulation of circadian rhythm and cellular metabolism in C2C12 myotubes. C2C12 myoblasts were differentiated into myotubes and synchronized prior to treatment. Cells were treated with the iron chelator desferroxamine (DFO) or iron in the form of ferric ammonium citrate (FAC). After 16 hr, RNA was extracted for gene expression analyses and cytosolic protein extracts were prepared for measurement of iron regulatory protein (IRP) RNA binding activity. FAC increased Rev‐erbβ and Pgc1β mRNA abundance by 1.5 and 1.7‐fold respectively. In DFO treated cells, the expression of Rorα and Bmal1 mRNA increased by 3.1‐fold and 1.7‐fold, respectively. In contrast, DFO decreased Pgc1α and Pgc1β mRNA abundance by 50%. Both FAC and DFO treatment reduced MyoD mRNA abundance by 40%. IRP‐RNA binding activity increased in DFO treated cells and was reduced over 50% when treated with FAC. These results suggest that REV‐ERBs are sensitive to iron status in C2C12. Additional studies are on‐going to determine the extent to which iron status contributes to altered glucose and lipid metabolism through REV‐ERB‐dependent mechanisms in muscle.