Prolonged QT intervals in mice with cardiomyocyte-specific deficiency of the molecular clock
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Prolonged QT intervals in mice with cardiomyocyte-specific deficiency of the molecular clock. / Gottlieb, Lisa A.; Larsen, Karin; Halade, Ganesh; Young, Martin E.; Thomsen, Morten B.
I: Acta Physiologica, Bind 233, Nr. 1, e13707, 09.07.2021.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › fagfællebedømt
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T1 - Prolonged QT intervals in mice with cardiomyocyte-specific deficiency of the molecular clock
AU - Gottlieb, Lisa A.
AU - Larsen, Karin
AU - Halade, Ganesh
AU - Young, Martin E.
AU - Thomsen, Morten B.
PY - 2021/7/9
Y1 - 2021/7/9
N2 - Aim Cardiac arrhythmias and sudden deaths have diurnal rhythms in humans. The underlying mechanisms are unknown. Mice with cardiomyocyte-specific disruption of the molecular clock genes have lower heart rate than control. Because changes in the QT interval on the electrocardiogram is a clinically used marker of risk of arrhythmias, we sought to test if the biological rhythms of QT intervals are dependent on heart rate and if this dependency is changed when the molecular clock is disrupted. Methods We implanted radio transmitters in male mice with cardiomyocyte-specific Bmal1 knockout (CBK) and in control mice and recorded 24-h ECGs under diurnal and circadian conditions. We obtained left ventricular monophasic action potentials during pacing in hearts ex vivo. Results Both RR and QT intervals were longer in conscious CBK than control mice (RR: 117 +/- 7 vs 110 +/- 9 ms, P < .05; and QT: 53 +/- 4 vs 48 +/- 2 ms, P < .05). The prolonged QT interval was independent of the slow heart rate in CBK mice. The QT interval exhibited diurnal and circadian rhythms in both CBK and control mice. The action potential duration was longer in CBK than in control mice, indicating slower repolarization. Action potential alternans occurred at lower pacing rate in hearts from CBK than control mice (12 +/- 3 vs 16 +/- 2 Hz, respectively, P < .05). Conclusion The bradycardic CBK mice have prolonged ventricular repolarization independent of the heart rate. Diurnal and circadian rhythms in repolarization are preserved in CBK mice and are not a consequence of the 24-h rhythm in heart rate. Arrhythmia vulnerability appears to be increased when the cardiac clock is disrupted.
AB - Aim Cardiac arrhythmias and sudden deaths have diurnal rhythms in humans. The underlying mechanisms are unknown. Mice with cardiomyocyte-specific disruption of the molecular clock genes have lower heart rate than control. Because changes in the QT interval on the electrocardiogram is a clinically used marker of risk of arrhythmias, we sought to test if the biological rhythms of QT intervals are dependent on heart rate and if this dependency is changed when the molecular clock is disrupted. Methods We implanted radio transmitters in male mice with cardiomyocyte-specific Bmal1 knockout (CBK) and in control mice and recorded 24-h ECGs under diurnal and circadian conditions. We obtained left ventricular monophasic action potentials during pacing in hearts ex vivo. Results Both RR and QT intervals were longer in conscious CBK than control mice (RR: 117 +/- 7 vs 110 +/- 9 ms, P < .05; and QT: 53 +/- 4 vs 48 +/- 2 ms, P < .05). The prolonged QT interval was independent of the slow heart rate in CBK mice. The QT interval exhibited diurnal and circadian rhythms in both CBK and control mice. The action potential duration was longer in CBK than in control mice, indicating slower repolarization. Action potential alternans occurred at lower pacing rate in hearts from CBK than control mice (12 +/- 3 vs 16 +/- 2 Hz, respectively, P < .05). Conclusion The bradycardic CBK mice have prolonged ventricular repolarization independent of the heart rate. Diurnal and circadian rhythms in repolarization are preserved in CBK mice and are not a consequence of the 24-h rhythm in heart rate. Arrhythmia vulnerability appears to be increased when the cardiac clock is disrupted.
KW - chronobiology
KW - circadian rhythm
KW - heart rate
KW - mouse model
KW - QT interval
KW - telemetry
KW - HEART-RATE-VARIABILITY
KW - CIRCADIAN GENE-EXPRESSION
KW - CONTRACTILE FUNCTION
KW - K+ CURRENTS
KW - PHYSIOLOGY
KW - RHYTHMS
KW - REPOLARIZATION
KW - CONTRIBUTES
KW - METABOLISM
KW - FAILURE
U2 - 10.1111/apha.13707
DO - 10.1111/apha.13707
M3 - Journal article
C2 - 34176211
VL - 233
JO - Acta Physiologica
JF - Acta Physiologica
SN - 1748-1708
IS - 1
M1 - e13707
ER -
ID: 274431317