Circadian clock and vascular disease

Abstract

Cardiovascular functions, including blood pressure and vascular functions, show diurnal oscillation. Circadian variations have been clearly shown in the occurrence of cardiovascular events such as acute myocardial infarction. Circadian rhythm strongly influences human biology and pathology. The identification and characterization of mammalian clock genes revealed that they are expressed almost everywhere throughout the body in a circadian manner. In contrast to the central clock in the suprachiasmatic nucleus (SCN), the clock in each tissue or cell is designated as a peripheral clock. It is now accepted that peripheral clocks have their own roles specific to each peripheral organ by regulating the expression of clock-controlled genes (CCGs), although the oscillation mechanisms of the peripheral clock are similar to that of the SCN. However, little was known about how the peripheral clock in the vasculature contributes to the process of cardiovascular disorders. The biological clock allows each organ or cell to anticipate and prepare for changes in external stimuli. Recent evidence obtained using genetically engineered mice with disrupted circadian rhythm showed a novel function of the internal clock in the pathogenesis of endothelial dysfunction, hypertension and hemostasis. Loss of synchronization between the central and peripheral clock also contributes to the pathogenesis of cardiovascular diseases, as restoration of clock homeostasis could prevent disease progression. Identification of CCGs in each organ, as well as discovery of tools to manipulate the phase of each biological clock, will be of great help in establishing a novel chronotherapeutic approach to the prevention and treatment of cardiovascular disorders.

Time-of-day of energy intake

“…B lood pressure follows a circadian rhythm which is coordinated by circadian Clock genes [1] and the diurnal rhythmicity of nitric oxide [2]. This circadian rhythm is lost in hypertension [1,2], and in insulin-resistant states such as obesity [3] and diabetes [4,5], and is associated with blunted endothelium vasodilation and adverse cardiovascular events [6].…”

24-hour Intraocular Pressure and Ocular Perfusion Pressure in Glaucoma

“…1). 82,104,113 For example, Millar-Craig et al 82 have shown that BP is lowest at around 3 AM and increases gradually during the early morning hours before waking, reaching a peak at midmorning. The BP rise that begins before waking was not associated with physical activity.…”

The influence of hepatitis B virus X protein on the clock genes in liver cells and its significance

“…A large epidemiological studies have found that circadian rhythm upset is associated with breast cancer for lighting effects. Women on the night shift and working in shifts have increasingly risk of developing breast cancer [8,12] . Elisabeth Filipski's research found the circadian clock disorders can speed up the development of liver cancer [13] .…”