Potential Chonobiological Triggering Factors of Acute Heart Attack

Abstract: The immediate triggers of acute heart attack or acute coronary syndrome (ACS) are not known exactly. There is a marked increase in sympathetic activity, neuroendocrino-logical dysfunction, oxidative stress and deficiency of 3 fatty acids, vitamins, minerals, as well as antioxidants during ACS. Energy intake and expenditure have diurnal variation throughout 24-hour cycle and any disturbance in this cycle may result into disruption of the endogenous clock and neurohumoral dysfunctions. Clinical studies have reported an increased incidence of reinfarction, sudden death, coronary constriction, myocardial ischaemia, vascular variability disorders and angina, during second quarter of the 24 hour cycle, at the point where there is rapid withdrawal of vagal activity and increase in sympathetic tone. In several studies, among patients with heart attack, there was a significant 2-3 fold increase in cardiac events in the second quarter of the day (6-12 hours) compared to other quarters respectively. Triggers of heart attack were noted in up to 80.0% of patients in various studies. Brain related and psychological mechanisms, i.e., emotional stress, sleep deprivation, cold climate, hot climate, large meals and physical exertion were observed among 30-50% of patients. Such triggers have also been reported in Europe, North America and Asia. These triggering factors are known to enhance sympathetic activity and decrease vagal tone, resulting into increased secretion of plasma cortisol, noradrenaline, aldosterone, angiotensin converting enzyme, interleukin-1, 2, 6, 18 and tumor necrosis factor-alpha, that are proinflammatory. There is also a deficiency in the serum levels of 3 fatty acids, vitamin A, E, C, coenzyme Q10, magnesium, potassium, melatonin, interleukin-10 (antiinflammatory) and increase in TBARS, MDA, diene conjugates, TNF-alpha and IL-6, which are indicators of oxidative damage and inflammation, respectively. It is not clear whether the predisposition of ACS is due to size of the meals or other proinflammatory factors of meals

Daytime Exposure to Blue Light Alters Cardiovascular Circadian Rhythms, Electrolyte Excretion and Melatonin Production

Artificial light is characterized by certain features of its impact on the body in terms of its spectral distribution of power, duration of exposure and intensity. Short waves, perceived as blue light, are the strongest synchronizing agent for the circadian system. In the present work, we investigated the features of the circadian rhythms of blood pressure (BP), heart rate (HR), the excretion of electrolytes and the secretion of melatonin in normotensive (Wistar–Kyoto) and hypertensive (SHR) rats under the action of monochromatic blue light in the daytime period. It was found that the exposure of Wistar–Kyoto rats to monochromatic blue light was accompanied by a significant decrease in nighttime and 24 h systolic BP. The most remarkable changes are characteristic of the HR in SHR rats under monochromatic light. A significant decrease in HR in each time period was found, but the predominance of nighttime over daytime values remained in SHR animals. There was also a significant increase in the mesor of the HR in SHR rats. Additionally, the amplitude of diastolic BP and HR, as well as the range of oscillations in HR, were significantly increased compared with the standard light pattern. In contrast to SHR rats, the regulation of the circadian rhythms in Wistar–Kyoto rats was more flexible and presented more changes, which may be aimed at the adaptation of the body to environmental conditions. For Wistar–Kyoto rats, an increase in the level of excreted electrolytes was observed under the action of monochromatic light, but no similar changes were found in SHR rats. For Wistar–Kyoto rats, a significant decrease in the urine concentration of aMT6s in the daytime and nighttime periods is characteristic, which results in the loss of the circadian rhythm. In SHR rats, there was a significant decrease in the nighttime content of aMT6s in the urine, while the daytime concentration, on the contrary, increased. The obtained data demonstrate that prolonged exposure to monochromatic blue light in the daytime period affects the circadian structure of the rhythms of the cardiovascular system, the rhythm of electrolyte excretion and the production of epiphyseal melatonin in wild-type and hypertensive animals. In SHR rats, the rhythms of BP and HR exhibit a more rigid pattern

Chronobiological data: advantages of telemetric monitoring and prospects of mathematical modeling

Chronobiology and chronomedicine is a special part of biomedical sciences studying rhythmical patterns in physiological and pathological processes. In order to analyse probability of some pathology and to make forecasts concerning possibility of some diseases based on the signs of rhythmicity disorders it is necessary to perform continuous monitoring of different physiological functions for a certain period of time. Since 1984 until now we have had an excellent opportunity of studying biological rhythms and their disorders in animals using the method of radio-telemetric monitoring. A huge amount of continuous data obtained in telemetric monitoring could be used for mathematical modeling of different pathological processes on the basis of rhythmic patterns. In this work we have presented some preliminary results of the chronobiological study in which the effects of bright light on blood pressure and heart rate were investigated. The experiment was carried out on male rats of genetic strains: Wistar-Kyoto – normotensive rats and SHR – spontaneously hypertensive rats. The animals were exposed to 1 hour exposure of ∼ 10000 lux white LED light from 10.00 to 11.00 a.m. For the analysis of daily profiles of blood pressure and heart rate we used the method of radio-telemetric monitoring of blood pressure and heart rate. It was shown that systolic blood pressure significantly increased in both Wistar-Kyoto and SHR rats under the action of bright during the time of bright light exposure (from 10.00 to 11.00 a.m.) and within the whole daytime period. For SHR rats an increase in diastolic blood pressure during the period of bright light action was also typical. But there were no significant changes in heart rate in the animals of either strain. These results require further and more detailed chronobiological studies to provide additional evidence. However traditional statistical methods seem to be important but not sufficient for further investigations. Moreover we could lose a considerable part of data without using contemporary methods of computer and mathematical modeling