|
|
Filipski, E., Li, X. M., & Levi, F. (2006). Disruption of circadian coordination and malignant growth. Cancer Causes Control, 17(4), 509–514.
Abstract: Altered circadian rhythms predicted for poor survival in patients with metastatic colorectal or breast cancer. An increased incidence of cancers has been reported in flying attendants and in women working predominantly at night. To explore the contribution of circadian structure to tumor growth we ablated the 24-h rest-activity cycle and markedly altered the rhythms in body temperature, serum corticosterone and lymphocyte count in mice by complete stereotaxic destruction of the suprachiasmatic nuclei (SCN) or by subjecting the mice to experimental chronic jet-lag. Such disruption of circadian coordination significantly accelerated malignant growth in two transplantable tumor models, Glasgow osteosarcoma and Pancreatic adenocarcinoma. The mRNA expression of clock genes per2 and reverb-alpha in controls displayed significant circadian rhythms in the liver (Cosinor, p=0.006 and p=0.003, respectively) and in the tumor (p=0.04 and p<0.001, respectively). Both rhythms were suppressed in the liver and in the tumor of jet lagged mice. This functional disturbance of molecular clock resulted in down regulation of p53 and overexpression of c-Myc, two effects which may favor cancer growth. CONCLUSIONS: These results indicate that circadian system could play an important role in malignant growth control. This should be taken into consideration in cancer prevention and therapy.
|
|
|
|
Gubin, D., Weinert, D., Solovieva, S. V., Durov, A. M., Litvinova, N. S., Danilova, L. A., et al. (2020). Melatonin attenuates light-at-night effects on systolic blood pressure and body temperature but does not affect diastolic blood pressure and heart rate circadian rhythms. Biological Rhythm Research, 51(5), 780–793.
Abstract: Aim of the present study is to assess whether 1.5mg of exogenous melatonin provided under modified CR in constant light (~400 lx) is capable to mimic effects of dark phase. Forty-six young adults (YA), 17–24 years old of both genders were studied under amodified CR protocol for 26 h. Initially, participants were investigated under constant light (CR-LL) and 2 weeks later under the same conditions though 1.5mg melatonin (Melaxen) was given orally at 22:30. Systolic blood pressure (SBP) and diastolic blood pressure (DBP), heart rate (HR) and body temperature (BT) were measured every 2 h. To verify the effect of constant light, formerly published results obtained under light-dark conditions (CR-LD) were reanalyzed.
Administration of 1.5 mg of exogenous melatonin modified the 24 h patterns of BT and SBP within short 3.5 h time window but did not influence DBP and HR. A short-term reduction of SBP and BT for 1.5–3.5 hours was observed. The values in the CR-LL+M group were significantly lower than in CR-LL at 2:00 h. Hence, exogenous melatonin did mimic the scotophase. Though this effect was gender-specific and found only in female YA.
Results of this study prompt further research to qualify and quantify dosage-, duration- and time-dependent differences of melatonin effects, to discern between short-term (acute) and long-term (chronic) melatonin administration, and to clarify its underlying mechanisms.
|
|
|
|
Hozer, C., & Pifferi, F. (2020). Physiological and cognitive consequences of a daily 26 h photoperiod in a primate: exploring the underlying mechanisms of the circadian resonance theory. Proc Biol Sci, 287(1931), 20201079.
Abstract: The biological clock expresses circadian rhythms, whose endogenous period (tau) is close to 24 h. Daily resetting of the circadian clock to the 24 h natural photoperiod might induce marginal costs that would accumulate over time and forward affect fitness. It was proposed as the circadian resonance theory. For the first time, we aimed to evaluate these physiological and cognitive costs that would partially explain the mechanisms of the circadian resonance hypothesis. We evaluated the potential costs of imposing a 26 h photoperiodic regimen compared to the classical 24 h entrainment measuring several physiological and cognitive parameters (body temperature, energetic expenditure, oxidative stress, cognitive performances) in males of a non-human primate (Microcebus murinus), a nocturnal species whose endogenous period is about 23.5 h. We found significant higher resting body temperature and energy expenditure and lower cognitive performances when the photoperiodic cycle length was 26 h. Together these results suggest that a great deviation of external cycles from tau leads to daily greater energetic expenditure, and lower cognitive capacities. To our knowledge, this study is the first to highlight potential mechanisms of circadian resonance theory.
|
|
|
|
Issad, S. M., Benhafri, N., El Allali, K., Farsi, H., Ouali-Hassenaoui, S., & Dekar-Madoui, A. (2021). Effects of prolonged night-time light exposure and traffic noise on the behavior and body temperature rhythmicity of the wild desert rodent, Gerbillus tarabuli. Chronobiol Int, in press.
Abstract: The aim of this study was to demonstrate for the first time in Tarabul's gerbils (Gerbillus tarabuli), the effects of simultaneous exposure to two major environmental stressors – light and noise pollutions – on the body temperature rhythm and anxious behavior. Seven groups, each consisting of 6 adult male gerbils, were subjected to a standard LD cycle (12 L:12D) with lights on at 08:00 h and off at 20:00 h, constant conditions (total darkness, DD), prolonged nighttime exposure to light (PEL: 18 L:6D) with lights on at 08:00 h and off at 02:00 h, mimicking prolonged exposure to light pollution in peri-urban areas, exposure to auditory stress (TNS) of 80 dB, and conditions combining PEL&TNS. The body temperature circadian rhythm was recorded, and behavioral tests were performed at the end of experimental phases. The results revealed the existence, for the first time in Gerbilus tarabuli, of an endogenous circadian rhythm of body temperature with a period of 23.8 +/- 0.04 h. Prolonged exposure to light at night (PEL) induced a significant phase delay (02 h 09 min +/- 0.16 h) of the rhythm, with an acrophase (peak time) occurring at 04:42 +/- 0.13 h instead of 02:33 +/- 0.21 h. Exposure to TNS for 4 hours per night induced a significant increase of the amplitude of the rhythm and a decrease of the rhythm regularity (robustness of 73.26% in TNS vs. 82.32 in control condition). While combining TNS and PEL significantly delayed the phase of the Tb rhythm by 3 h 10 min (acrophase at 06:39 +/- 0.37 h instead of 02:33 +/- 0.21 h), increased the amplitude, and significantly reduced the stability of the rhythm (robustness of 67.25% in PEL&TNS vs. 82.32 in control condition). PEL&TNS and TNS environments induce an important stress in gerbils highlighted by a significant decrease of the number of line crossings and time spent in the center area of the open field test. Furthermore, elevated plus maze test revealed gerbils of the PEL&TNS and TNS conditions significantly visited the lowest number of open arms and spent a shorter amount of time in it. In addition, these conditions were responsible for less activity (total number of entries in arms) than in the control and PEL conditions. These results indicate clearly that in the desert area, peri-urban light and noise pollutions disturb the circadian rhythm components and alter the behavior of Tarabul's gerbils inducing an anxious state.
|
|
|
|
Lack, L. C., Gradisar, M., Van Someren, E. J. W., Wright, H. R., & Lushington, K. (2008). The relationship between insomnia and body temperatures. Sleep Med Rev, 12(4), 307–317.
Abstract: Sleepiness and sleep propensity are strongly influenced by our circadian clock as indicated by many circadian rhythms, most commonly by that of core body temperature. Sleep is most conducive in the temperature minimum phase, but is inhibited in a “wake maintenance zone” before the minimum phase, and is disrupted in a zone following that phase. Different types of insomnia symptoms have been associated with abnormalities of the body temperature rhythm. Sleep onset insomnia is associated with a delayed temperature rhythm presumably, at least partly, because sleep is attempted during a delayed evening wake maintenance zone. Morning bright light has been used to phase advance circadian rhythms and successfully treat sleep onset insomnia. Conversely, early morning awakening insomnia has been associated with a phase advanced temperature rhythm and has been successfully treated with the phase delaying effects of evening bright light. Sleep maintenance insomnia has been associated not with a circadian rhythm timing abnormality, but with nocturnally elevated core body temperature. Combination of sleep onset and maintenance insomnia has been associated with a 24-h elevation of core body temperature supporting the chronic hyper-arousal model of insomnia. The possibility that these last two types of insomnia may be related to impaired thermoregulation, particularly a reduced ability to dissipate body heat from distal skin areas, has not been consistently supported in laboratory studies. Further studies of thermoregulation are needed in the typical home environment in which the insomnia is most evident.
|
|
