Male kidney-specific BMAL1 knockout mice are protected from K+-deficient, high-salt diet-induced blood pressure increases

High-Salt Diet Inhibits the Expression of Bmal1 and Promotes Atrial Fibrosis and Vulnerability to Atrial Fibrillation in Dahl Salt-Sensitive Rats

BACKGROUND

Hypertension is a risk factor for atrial fibrillation (AF), and brain and muscle arnt-like protein 1 (Bmal1) regulate circadian blood pressure and is implicated in several fibrotic disorders. Our hypothesis that Bmal1 inhibits atrial fibrosis and susceptibility to AF in salt-sensitive hypertension (SSHT) and our study provides a new target for the pathogenesis of AF induced by hypertension.

METHODS

The study involved 7-week-old male Dahl salt-sensitive that were fed either a high-salt diet (8% NaCl; DSH group) or a normal diet (0.3% NaCl; DSN group). An experimental model was used to measure systolic blood pressure (SBP), left atrial ejection fraction (LAEF), left atrial end-volume index (LAEVI), left atrial index (LAFI), AF inducibility, AF duration, and atrial fibrosis pathological examination and the expression of Baml1 and fibrosis-related proteins (TNF-α and α-SMA) in left atrial tissue.

RESULTS

DSH increased TNF-α and α-SMA expression in atrial tissue, level of SBP and LAESVI, atrial fibrosis, AF induction rate, and AF duration, and decreased Bmal1 expression in atrial tissue, the circadian rhythm of hypertension, and level of LAEF and LAFI. Our results also showed that the degree of atrial fibrosis was negatively correlated with Bmal1 expression, but positively correlated with the expression of TNF-α and α-SMA.

CONCLUSIONS

We demonstrated that a high-salt diet leads to circadian changes in hypertension due to a reduction of Bmal1 expression, which plays a crucial role in atrial fibrosis and increased susceptibility to AF in SSHT rats.

Circadian Influences on Myocardial Ischemia-Reperfusion Injury and Heart Failure

The impact of circadian rhythms on cardiovascular function and disease development is well established, with numerous studies in genetically modified animals emphasizing the circadian molecular clock's significance in the pathogenesis and pathophysiology of myocardial ischemia and heart failure progression. However, translational preclinical studies targeting the heart's circadian biology are just now emerging and are leading to the development of a novel field of medicine termed circadian medicine. In this review, we explore circadian molecular mechanisms and novel therapies, including (1) intense light, (2) small molecules modulating the circadian mechanism, and (3) chronotherapies such as cardiovascular drugs and meal timings. These promise significant clinical translation in circadian medicine for cardiovascular disease. (4) Additionally, we address the differential functioning of the circadian mechanism in males versus females, emphasizing the consideration of biological sex, gender, and aging in circadian therapies for cardiovascular disease.

Recent advances in understanding the kidney circadian clock mechanism

Circadian rhythms are endogenous biological oscillations that regulate various physiological processes in organisms, including kidney function. The kidney plays a vital role in maintaining homeostasis by regulating water and electrolyte balance, blood pressure, and excretion of metabolic waste products, all of which display circadian rhythmicity. For this reason, studying the circadian regulation of the kidney is important, and the time of day is a biological and experimental variable that must be considered. Over the past decade, considerable progress has been made in understanding the molecular mechanisms underlying circadian regulation within the kidney. In this review, the current knowledge regarding circadian rhythms in the kidney is explored, focusing on the molecular clock machinery, circadian control of renal functions, and the impact of disrupted circadian rhythms on kidney health. In addition, parameters that should be considered and future directions are outlined in this review.