In this study we set out to understand is sleep fragmentation affects the cardiovascular regulation and circadian variability of core body temperature more or less than sleep deprivation. 50 healthy men (age 29.0±3.1 years; BMI 24.3±2.1 kg/m2) participated in a 3-day study that included one adaptative night and one experimental night involving randomization to: sleep deprivation (SD) and sleep fragmentation (SF). The evaluation included hemodynamic parameters, measures of the spectral analysis of heart rate and blood pressure variability, and the sensitivity of arterial baroreflex function. Core body temperature (CBT) was measured with a telemetric system. SF affects heart rate (61.9±5.6 vs. 56.2±7.6, p<0.01) and stroke index (52.7±11.1 vs. 59.8±12.2, p<0.05) with significant changes in the activity of the ANS (LF-sBP: 6.0±5.3 vs. 3.4±3.7, p<0.05; HF-sBP: 1.8±1.8 vs. 1.0±0.7, p<0.05; LF-dBP: 5.9±4.7 vs. 3.5±3.2, p<0.05) more than SD. Post hoc analysis revealed that after SD mean value of CBT from 21:30 to 06:30 was significantly higher compared to normal night’s sleep and SF. In healthy men SF affects the hemodynamic and autonomic changes more than SD. Sympathetic overactivity is the proposed underlying mechanism., J. Słomko, M. Zawadka-Kunikowska, J. J. Klawe, M. Tafil-Klawe, J. Newton, P. Zalewski., and Obsahuje bibliografii
Glucose is molecule usually studied in relation to metabolism. Except for this traditional view, it is known that under certain conditions glucose can serve as a signal molecule for the circadian system. The circadian system is entrained by relevant synchronizing cues that can be tissue-dependent. Central oscillator is synchronized mainly by light-dark cycle, while peripheral oscillators can be entrained by food intake. Glucose transport in the organism is controlled by insulin dependent and independent mechanism. Therefore, we employed streptozotocin- induced diabetes to elucidate the influence of metabolic changes on glucose transporter ( glut1, glut4 ) 24-h expression profile in peripheral oscillators in tissues, inside (frontal cortex, cerebellum) and outside (heart) the blood-b rain barrier. Diabetes was induced by streptozotocin inje ction. Seventeen days later, sampling was performed during a 24-h cycle. Gene expression was measured using real-time PCR. We observed down- regulation of glut1 and glut4 expression in the heart of diabetic rats. The expression of glut1 and glut4 in brain areas was not down-regulated, however, we ob served trend to phase advance in glut1 expression in the cerebellum. These results may indicate higher glucose levels in diabetic brain, which might influence regulation of clock gene expressi on in different manner in brain compared to periphery., D. Šoltésová ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Angiotensin-converting enzyme 2 (ACE2) was identified as a molecule that mediates the cellular entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Several membrane molecules of the host cell must cooperate in this process. While ACE2 serves in a membrane receptor-mediating interaction with the surface spike (S) glycoprotein of SARS-CoV-2 located on the virus envelope, enzyme A disintegrin and metalloproteinase 17 (ADAM17) regulates ACE2 availability on the membrane and transmembrane protease serine 2 (TMPRSS2) facilitates virus-cell membrane fusion. Interestingly, ACE2, ADAM17 and TMPRSS2 show a daily rhythm of expression in at least some mammalian tissue. The circadian system can also modulate COVID-19 progression via circadian control of the immune system (direct, as well as melatonin-mediated) and blood coagulation. Virus/ACE2 interaction causes ACE2 internalization into the cell, which is associated with suppressed activity of ACE2. As a major role of ACE2 is to form vasodilatory angiotensin 1-7 from angiotensin II (Ang II), suppressed ACE2 levels in the lung can contribute to secondary COVID-19 complications caused by up-regulated, pro-inflammatory vasoconstrictor Ang II. This is supported by the positive association of hypertension and negative COVID-19 prognosis although this relationship is dependent on numerous comorbidities. Hypertension treatment with inhibitors of renin-angiotensin system does not negatively influence prognosis of COVID-19 patients. It seems that tissue susceptibility to SARS-CoV-2 shows negative correlation to ACE2 expression. However, in lungs of infected patient, a high ACE2 expression is associated with better outcome, compared to low ACE2 expression. Manipulation of soluble ACE2 levels is a promising COVID-19 therapeutic strategy
The aim of our study was to verify the relationship between heart rate (HR) and ventricular fibrillation threshold (VFT) during different types of ventilation in female Wistar rats from the circadian point of view. The ex-periments were performed under pentobarbital anesthesia (40 mg/kg i.p., adaptation to a light-dark cycle 12:12 h, open chest experiments) and the obtained results were averaged independently of the seasons. The VFT measure-ments were performed during normal ventilation (17 animals) and hypoventilation (10 animals). The HR was re-corded immediately before the rise of ventricular arrhy-thmias. Results are expressed as arithmetic means ± S.D. and differences are considered significant when p<0.05. The basic pe-riodic characteristics were calculated using single and population mean cosinor tests. The results from our experiments have demonstrate that 1) the VFT and HR respond identically to hypoventilation by a decrease in the light and also in the dark phases, and 2) hypoventilation changes the 24-h course of the VFT without a change in the 24-h rhythm of the HR. It is concluded that the HR and VFT behave as two independent functional systems without apparent significant circadian dependence during both types of ventilation., P. Švorc, I. Bračoková, I. Podlubný., and Obsahuje bibliografii
Disturbed circadian activity of the sympathetic system may be involved in negative consequences of chronodisruption on the cardiovascular system. We studied daily changes in pressure response to adrenergic stimulation in rats exposed to repeated phase advance shifts (PAS) of light/dark (LD) regimen. Blood pressure (BP), heart rate (HR) and locomotor activity was measured by radiotelemetry in normotensive Wistar rats exposed to repeated PAS (three 8-h shifts per week) lasting for 12 weeks. Norepinephrine was administered subcutaneously in the middle of L and D during week 12 of PAS exposure. In the control LD cycle, cardiovascular parameters exhibited significant daily rhythms with expected higher values during D than L phase. Rats exposed to PAS showed disturbed rhythms without a BP and HR increase. Administration of norepinephrine to control rats revealed daily variability in the cardiovascular response with higher stimulation of BP during L than D. This daily pattern of BP response to norepinephrine was diminished in the PAS group. The damped daily variability in pressure response to norepinephrine and augmented response during the light phase of the day suggest that the increased and desynchronized activity of the sympathetic system may worsen responses of the cardiovascular system to load in individuals exposed to irregular LD conditions., L. Molcan, A. Vesela, M. Zeman., and Obsahuje bibliografii