英文科普：心跳节奏与生物钟一致

（单词翻译:单击）

Sudden cardiac death -catastrophic and unexpected fatal heart stoppage -- is more likely to occur shortly after waking in the morning and in the late night. In a report in the journal Nature, an international consortium of researchers that includes Case Western Reserve University School of Medicine in Cleveland and Baylor College of Medicine explains the molecular¹ linkage² between the circadian clock and the deadly heart rhythms that lead to sudden death.

The answer begins with a controller of the circadian clock -- krüppel-like factor 15 (Klf15), which has been a long-time target of the laboratory of Dr. Mukesh Jain of Case Western, said Dr. Xander Wehrens, professor of molecular physiology³ and biophysics and cardiology at BCM, also an author.

Klf15, in turn, controls the level of a potassium（钾） channel-interacting protein (KChIP2), which affects how potassium flows out of heart muscle cells called cardiac myocytes（肌细胞） .

Changes affect potassium current

Because the level of this KChIP2 protein fluctuates（波动） during the circadian or daily cycle, it can change the size of the potassium current in cardiac myocytes. Changes in this subunit or Klf15 can affect the potassium current that governs repolarization of the cardiac myocyte. Overall, this can shorten or lengthen⁴ the time the heart muscle has to empty the heart's pumping chamber⁵ (ventricle) of blood. This time interval⁶ for repolarization（极化恢复） is critical. Too much or too little can result in abnormal heart rhythms called arrhythmias. As the heart loses the regularity⁷ of the beat, it cannot pump blood efficiently⁸.

Studies of mice that lacked Klf15 and mice with a genetic⁹ change that caused them to make more Klf15 than normal increased the risk of deadly arrhythmias（心率失常） .

This was a proof of principle, said Wehrens.

"It is the first example of a molecular mechanism¹⁰ for the circadian change in susceptibility to cardiac arrhythmias," he said.

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