Daily Rhythms Of Body Temperature Research Articles

Rhythmicity of locomotor behavior and body temperature in Felis catus maintained under controlled microclimate conditions

Rhythmicity of locomotor behavior and body temperature in Felis catus maintained under controlled microclimate conditions

ASIC1a affects hypothalamic signaling and regulates the daily rhythm of body temperature in mice

The body temperature of mice is higher at night than during the day. We show here that global deletion of acid-sensing ion channel 1a (ASIC1a) results in lower body temperature during a part of the night. ASICs are pH sensors that modulate neuronal activity. The deletion of ASIC1a decreased the voluntary activity at night of mice that had access to a running wheel but did not affect their spontaneous activity. Daily rhythms of thyrotropin-releasing hormone mRNA in the hypothalamus and of thyroid-stimulating hormone β mRNA in the pituitary, and of prolactin mRNA in the hypothalamus and pituitary were suppressed in ASIC1a−/− mice. The serum thyroid hormone levels were however not significantly changed by ASIC1a deletion. Our findings indicate that ASIC1a regulates activity and signaling in the hypothalamus and pituitary. This likely leads to the observed changes in body temperature by affecting the metabolism or energy expenditure.

Social isolation increases metabolic rate in the transition of light- to dark- phase and advances Rev-erb-α expression in brown adipose tissue to regulate daily rhythm of core body temperature in mice

Mammals use social thermoregulation to maintain the core body temperature (Tc) at a lower energy cost. Brown adipose tissue (BAT) plays a crucial role in thermoregulation. This study tested the hypothesis that social isolation induces alterations in thermogenesis and metabolism to maintain the rhythm of Tc throughout the day. Adult male mice (C57BLJ/6) were maintained in groups of 4–5 (group-housed) or isolated (single-housed) for 28 days. Telemetric probes recorded spontaneous locomotor activity (SLA) and Tc to analyze SLA and Tc daily rhythms. Body weight was measured weekly. VO2 consumption was analyzed at zeitgeber time (ZT) 1–3 (beginning of light phase) or ZT10–14 (beginning of dark phase). The expression of thermogenic-related and clock genes in the BAT occurred at ZT2, ZT8, ZT14, and ZT20. The β3 adrenergic agonist CL-316,243 was i.p. injected in the group- or single-housed mice. Social isolation increased the amplitude of Tc rhythm but decreased the amplitude of SLA oscillation. Nevertheless, in single-housed mice, the circadian peak of Tc and SLA was unaltered, with reduced body weight gain, increased VO2 consumption, and BAT Ucp1 expression at ZT14. Isolation advanced the BAT Rev-erb-ɑ peak of expression and phased-shift the peak of expression in BAT Bmal1, while it abolished the daily BAT Per2 oscillation. Isolation also abolished the BAT Ucp1 and hormone-sensitive lipase (Hsl) expression induced by stimulation of the β3ADR, but it increased Rev-erb-ɑ and Pgc1α. Thus, alterations in Ucp1, Reverb-α, Bmal1, and Per2 daily expression may favor an increased metabolic rate at the beginning of the dark, which, in turn, contributes to maintaining the daily Tc rhythm at the expense of reduced body weight gain in isolated mice. In addition, at least at the transcription level, the response of BAT from isolated mice to adrenergic agonist seems to be via a non-canonical mechanism involving Rev-erb-α and Pgc1α.

Sustained effect of habitual feeding time on daily rhythm of core body temperature in mice.

Background and aimCircadian clocks in most peripheral tissues are entrained mainly by feeding. Therefore, this study aimed to investigate whether the daily rhythm of core body temperature (CBT), including the effect of diet-induced thermogenesis, varies according to habitual feeding time.MethodsWild-type and uncoupling protein 1 (UCP1) knockout mice were fed only during the first 4 h (Breakfast group) or the last 4 h of the dark period (Dinner group) for 17 days. On day 18, both groups were fed twice for 2 h, at the same starting times. Locomotor activity and CBT were measured continuously during the experiment.ResultsOn day 18, CBT increased at the beginning of each feeding period, regardless of the group and strain. However, the CBT increase induced by the first meal decreased sharply in the Breakfast group and mildly in the Dinner group; the opposite was observed after the second meal. In UCP1 knockout, but not wild-type, mice, the total amount of CBT was significantly lower in the Dinner group than in the Breakfast group. These effects were mostly independent of the locomotor activity and food intake.ConclusionThese results reveal that the effect of habitual feeding time on the daily rhythm of CBT is sustained at least until the following day. These effects may be mediated by both UCP1-dependent and -independent mechanisms.

Roles of the Circadian Clock Mechanism in the Regulation of Daily Rhythms of Body Temperature

Body temperature of thermostatic animals does not stay constant but displays a regular circadian fluctuation, which has a role in maintaining homeostasis of sleep and metabolism as well as entraining the peripheral circadian clocks in the body. Following the discovery of clock genes that generate the circadian rhythm and the master clock structure in the brain and recent advances in infrared temperature imaging, there is a greater opportunity to investigate the mechanism underlying body temperature regulation, which currently remains unclear. In this review, we summarize our recent findings on a mechanism of body temperature regulation through a non-coding cis-element of the core clock gene Per2. The body temperature during siesta is controlled by the calcitonin receptors, which exhibit restricted expression in the suprachiasmatic nucleus, the locus of the central circadian clock in the brain. This review also refers to a recent machine learning-assisted thermography recording procedure, a technique that enables real-time simultaneous monitoring of circadian fluctuations in body temperature, locomotor activity, feeding, and drinking behaviors of animals. We will discuss the current challenges and open questions in understanding the molecular and circuit level mechanisms that give rise to circadian rhythms in body temperature.

Activity–Rest and Body Temperature Rhythms in Mice with Knockout of the Panx1 Gene

Pannexins are a family of three proteins which play an important role in intercellular communications. This study shows that mice with knockout of the Panx1 gene(Panx1–/–) have elevated levels of movement activity and increased proportions of waking, due to decreases in slow-wave sleep, as compared with control animals, as a result of decreases in the adenosine content of the brain. We suggest that these mice may also show impairments to thermoregulation and the daily temperature curve rhythm. To test this suggestion, eight adult male C57BL/6J mice and eight adult male Panx1–/– mice, derived from them, underwent i.p. implantation of autonomous temperature and movement activity sensors. Recordings were made over several months at an environmental temperature of 23 ± 1°C. The results confirmed our previous data indicating higher movement activity in Panx1–/– mice compared with controls. The daily body temperature rhythm in Panx1–/– mice persisted and was no different from that in control animals. The first series of experiments showed an increased tendency to fall into torpor in Panx1–/– mice as compared with controls. However, no onset of torpor occurred in the next series, using a further four pairs of animals. Thus, the role of the Panx1 gene in the diurnal activity-rest rhythm was confirmed, while its role in the temperature rhythm and thermoregulatory reactions remains unclear and requires further study.

Altered metabolic and hormonal responses in male rats exposed to acute bright light-at-night associated with global DNA hypo-methylation

The association between light pollution and disruption of daily rhythms, metabolic and hormonal disorders, as well as cancer progression is well-recognized. These adverse effects could be due to nocturnal melatonin suppression. The signaling pathway by which light pollution affects metabolism and endocrine responses is unclear. We studied the effects of artificial light at night (ALAN11Artificial light at night.) on body mass, food and water intake, daily rhythms of body temperature, serum glucose and insulin in male rats. Daily rhythms of urine production and urinary 6-sulfatoxymelatonin (6-SMT226-sulfatoxymelatonin.), as well as global DNA methylation in pancreas and liver tissues were also assessed. Mass gain was higher in ALAN rats compared with controls. Food intake, water consumption, glucose, insulin, and 6-SMT levels markedly lessened in response to ALAN. Conversely, urine production and body temperature were elevated in ALAN rats compared with controls. Significant 24-h rhythms were detected for all variables that were altered in mesor, amplitude, and acrophase occurrences under ALAN conditions. DNA hypo-methylation was detected in ALAN pancreatic tissue compared with controls, but not in hepatic tissue. Overall, ALAN affects metabolic and hormonal physiology in different levels in which flexible crosstalk between melatonin and both epigenetics and metabolic levels expressed as body temperature rhythm, is suggested to mediate the environmental exposure at the molecular level and subsequently physiology is altered. The flexibility of epigenetic modifications provides a potential therapeutic target for rectifying ALAN adverse effects by epigenetic markers such as melatonin and behavioral lifestyle interventions for confining ALAN exposures as much as possible.

Daily rhythms of body temperature around lambing in sheep measured non-invasively

ABSTRACT Fifteen ewes had data-loggers affixed under the tail, programmed to record temperature (T) every 5 min, storing up to 72 h of data. Ewes were monitored to identify time of lambing (time 0). Lambing period lasted 5 d; thereafter seven ewes which yielded data for 24 h before and after lambing were selected. Mean T (±S.E.M.) was 39.03±0.02°C. Mean T in the 24 h preceding lambing (38.68±0.02°C) was lower than it was in the 24 h following parturition (39.38±0.03°C) (P< 0.0001). T was lower in the 12 h preceding lamb birth (38.56±0.10°C) than it was in the previous 12 h (−24 to −12, 38.76±0.02°C) (P<0.0001); thereafter, T was lowest precisely at parturition (mean T = 38.18±0.03°C) and increases rapidly and peaked (mean T = 39.70±0.04°C) 2 h after lambing. In the 12 h following delivery (39.28±0.02°C), T increased, especially in the window +12 to +24 h (39.51±0.03°C). In conclusion, T of ewes changed around parturition, with a reduction 12 h before lambing, followed by a rapid increase in the hours following parturition. The data-loggers used proved a high degree of sensitivity to detect physiological T changes, which confirmed that they are appropriate for use in sheep studies.

Locomotor activity and body temperature rhythms in the Mahali mole-rat (C. h. mahali): The effect of light and ambient temperature variations

African mole-rats (family: Bathyergidae) are strictly subterranean mammals that reside in extensive networks of underground tunnels. They are rarely, if ever, exposed to light and experience muted temperature ranges. Despite these constant conditions, the presence of a functional circadian clock capable of entraining to external light cues has been reported for a number of species. In this study, we examine a social mole-rat species, Cryptomys hottentotus mahali, to determine if it possesses a functional circadian clock that is capable of perceiving light and ambient temperature cycles, and can integrate these cues into circadian rhythms of locomotor activity and core body temperature. Eight male and eight female, non-reproductive individuals were subjected to six cycles of varying light and temperature regimes. The majority of the individuals displayed daily rhythms of locomotor activity and body temperature that are synchronised to the external light and temperature cycles. Furthermore, endogenous rhythms of both locomotor activity and core body temperature were displayed under constant conditions. Thus, we can conclude that C. h. mahali possesses a functional circadian clock that can integrate external light and temperature cues into circadian rhythms of locomotor activity and core-body temperature.

Time-shifting effects of methylphenidate on daily rhythms in the diurnal rodent Arvicanthis ansorgei.

People suffering of attention-deficit/hyperactivity disorder (ADHD) and treated with the psychostimulant methylphenidate (MPH) show sleep-wake cycle and daily rhythm alterations despite the beneficial effects of MPH on behavioral symptoms (i.e., hyperactivity, attention). In nocturnal rodents (i.e., mice), chronic exposure to MPH alters the neural activity of the circadian clock in the suprachiasmatic nucleus (SCN), behavioral rhythms, and the sleep-wake cycle. Here, we studied the effects of MPH on daily rhythms of behavior and body temperature of the diurnal rodent Arvicanthis ansorgei. Under a light-dark cycle, chronic exposure to MPH in drinking water delayed the onset of both activity and body temperature rhythms. Interestingly, delays were larger when MPH access was restricted to the first 6h of the light phase (i.e., activity phase) of the 24-h cycle. Since MPH effects are dependent on animal's fluid intake, in a last experiment, we controlled the time and dose of MPH delivery in Arvicanthis using an intraperitoneal perfusion method. Similarly to the experiment with MPH in drinking water, Arvicanthis showed a delay in the onset of general activity and body temperature when MPH infusions, but not vehicle, were during the first 6h of the light phase. This study indicates that MPH alters daily rhythms in a time-dependent manner and proposes the use of a diurnal rodent for the study of the effects of MPH on the circadian clock. Knowing the circadian modulation on the effects of MPH in behavior could give new insights in the treatment of ADHD.

Calcitonin receptors are ancient modulators for rhythms of preferential temperature in insects and body temperature in mammals.

Daily body temperature rhythm (BTR) is essential for maintaining homeostasis. BTR is regulated separately from locomotor activity rhythms, but its molecular basis is largely unknown. While mammals internally regulate BTR, ectotherms, including Drosophila, exhibit temperature preference rhythm (TPR) behavior to regulate BTR. Here, we demonstrate that the diuretic hormone 31 receptor (DH31R) mediates TPR during the active phase in Drosophila DH31R is expressed in clock cells, and its ligand, DH31, acts on clock cells to regulate TPR during the active phase. Surprisingly, the mouse homolog of DH31R, calcitonin receptor (Calcr), is expressed in the suprachiasmatic nucleus (SCN) and mediates body temperature fluctuations during the active phase in mice. Importantly, DH31R and Calcr are not required for coordinating locomotor activity rhythms. Our results represent the first molecular evidence that BTR is regulated distinctly from locomotor activity rhythms and show that DH31R/Calcr is an ancient specific mediator of BTR during the active phase in organisms ranging from ectotherms to endotherms.

Heterothermy is associated with reduced fitness in wild rabbits.

An increase in variation in the 24 h pattern of body temperature (heterothermy) in mammals can be induced by energy and water deficits. Since performance traits such as growth and reproduction also are impacted by energy and water balance, we investigated whether the characteristics of the body temperature rhythm provide an indication of the reproductive success of an individual. We show that the amplitude of the daily rhythm of body temperature in wild rabbits (Oryctolagus cuniculus) prior to breeding is inversely related to the number of pregnancies in the subsequent seven months, while the minimum daily body temperature is positively correlated to the number of pregnancies. Because reproductive output could be predicted from characteristics of the core body temperature rhythm prior to the breeding season, we propose that the pattern of the 24 h body temperature rhythm could provide an index of animal fitness in a given environment.

Short communication: The effects of morning compared with evening feed delivery in lactating dairy cows during the summer

Delivering fresh feed in the evening is a management strategy sometimes used during periods of heat stress, but previous experiments have observed that night feeding increased feed intake during the 2 h after feeding and did not change intake during the overnight period. The objective of this study was to determine the effect of night feeding on daily rhythms of the dairy cow during the summer season. Twelve Holstein cows were used in a crossover design with 14-d periods. An automated system recorded the timing of feed intake over the last 7 d of each period. Treatments were ad libitum feeding with fresh feed delivery 1×/d at 0830 h or 2030 h. Milk yield and composition were not changed by treatment, but night feeding decreased the concentration of preformed fatty acids in milk fat. Night feeding decreased feed intake 1.7 kg/d, and decreased total-tract dry matter and neutral detergent fiber (NDF) digestibility by 0.7 and 0.8 percentage units, respectively. The amount of feed consumed in the first 2 h after feeding was 64% greater with night feeding, but intake did not differ between treatments during the night or early afternoon. A treatment by time of day interaction was observed for fecal NDF and indigestible NDF concentration and plasma glucose, insulin, and urea concentrations. Night feeding resulted in an increase in plasma insulin after feeding, which decreased plasma glucose. The daily rhythm of core body temperature was entrained by treatment, with the phase shifted and the amplitude decreased by night feeding indicating alteration of the central clock. In conclusion, feeding cows once per day in the evening during the summer caused a similar increase in feed intake and plasma insulin after feeding as previously observed during non-heat stress seasons. Night feeding also decreased intake and total-tract digestibility. The daily pattern of feed intake and other behaviors should be considered before initiation of night feeding.

Activity, sleep and ambient light have a different impact on circadian blood pressure, heart rate and body temperature rhythms

ABSTRACTThe aim of the present study was to investigate the impact of endogenous and exogenous factors for the expression of the daily rhythms of body temperature (BT), blood pressure (BP) and heart rate (HR). One hundred and seventy-three young adults (YA), 17–24 years old (y.o.), of both genders were studied under a modified constant-routine (CR) protocol for 26 h. Participants were assigned randomly to groups with different lighting regimens: CR-LD, n = 77, lights (>400 l×) on from 09:00 to 17:00 h and off (<10 l×) from 17:00 to 09:00 next morning; CR-LL, n = 81, lights on (>400 l×) during the whole experimental session; CR-DD, n = 15, constant dim light (<10 l×) during the whole experiment. Systolic (SBP) and diastolic (DBP) BP, HR and BT were measured every 2 h. For comparison, the results of the former studies performed under conditions of regular life with an activity period from 07:00 to 23:00 h and sleep from 23:00 till 07:00 h (Control) were reanalyzed. Seven-day Ambulatory Blood Pressure Monitoring (ABPM) records from 27 YA (16–38 y.o.) and BT self-measurement data from 70 YA (17–30 y.o.) taken on ≥ 3 successive days at 08:00, 11:00, 14:00, 17:00, 20:00, 23:00 and 03:00 were available.The obtained daily patterns were different between Control and CR-DD groups, due to effects of activity, sleep and light. The comparison of Control and CR-LD groups allowed the effects of sleep and activity to be estimated since the lighting conditions were similar. The activity level substantially elevated SBP, but not DBP. Sleep, on the other hand, lowered the nighttime DBP, but has no effect on SBP. HR was affected both by activity and sleep. In accordance with previous studies, these results confirm that the steep BP increase in the morning is not driven by the circadian clock, but rather by sympathoadrenal factors related to awakening and corresponding anticipatory mechanisms. The effect on BT was not significant.To investigate the impact of light during the former dark time and darkness during the former light time, the CR-LL and CR-DD groups were each compared with the CR-LD group. Light delayed the evening decrease of BT, most likely via a suppression of the melatonin rise. Besides, it had a prominent arousal effect on SBP both in the former light and dark phases, a moderate effect on DBP and no effect on HR. Darkness induced decline in BT. BP values were decreased during the former light time. No effects on HR were found. Altogether, the results of the present paper show that BT, BP and HR are affected by exogenous factors differently. Moreover, the effect was gender-specific. Especially, the response of BT and BP to ambient light was evident only in females.We suppose that the distinct, gender-specific responses of SBP, DBP and HR to activity, sleep and ambient light do reflect fundamental differences in the circadian control of various cardiovascular functions. Furthermore, the presented data are important for the elaboration of updated reference standards, the interpretation of rhythm disorders and for personalized chronotherapeutic approaches to prevent adverse cardiovascular events more effectively.

Circadian Variations of Serum Mitochondrial Uncoupling Protein 1 (UCP1) Levels and Rectal Temperature in Capra Hircus

The daily rhythm of body temperature is an important process to be studied not only to advance knowledge on the temporal variability of thermal homeostasis but also has a means to facilitate the study of biological rhythmicity in general. The aim of the present study was to study the daily rhythm of rectal temperature and the changes in the serum levels of mitochondrial uncoupling protein 1 (UCP1) in goat

健康と生活習慣病予防における時間栄養学の役割

Almost all metabolic activities of nutrients are under control of the endocrine system, and among them the adrenocortical activity is the most typical example that shows circadian rhythmic changes. We examined relationships between the plasma corticosterone rhythm and feeding schedules in rats. The plasma corticosterone rhythm corresponding to feeding time appears regardless of whether the rats were kept on a light-dark cycle, or in constant light or were blinded. Therefore, it can be concluded that food, more than illumination, is a potent trigger of the circadian adrenocortical rhythm in rats. In addition to the experiments in rats, we also investigated roles of feeding schedulesinformation of the adrenocortical rhythm in human subjects. The corticosterone rhythm disappeared when rats were given a liquid diet intravenously, but not orally, suggesting a necessary role of the oro-gastro-intestinal tract. In addition to the studies in rats, influence to feeding schedules on adrenocortical rhythms was also examined in hospitalized human subjects under a normal light-dark cycle. A clear plasma cortisol rhythm was observed in patients who had been fed on a liquid diet into-duodenum during a restricted time of day, suggest that the circadian cortisol rhythm in man is more closely related to feeding rhythms than cycles of light-dark and sleep-wakefulness. As far as we know, this is the first report demonstrating the important of food in entraining human circadian cortisol rhythm. Next, we measured daily rhythm ofbody temperature in hospitalized patients under continuous and cyclic TEN（totalenteral nutrition）. In the diurnal TEN group, body temperature was low at night and early morning and high in the afternoon early evening. In the continuous TEN group, however, body temperature did not show any significant change with clock-time. In conclusion, the timing of diet intake remarkably modifies the circadian rhythm of body temperature and adrenocortical activity in man. We examined relationship between the feeding time of high salt diet intake and urinary excretion of sodium and chloride. The urinary excretion of sodium and chloride were higher in evening than morning and daytime in woman, is more closely related to the circadian plasma aldosterone rhythm. Furthermore, the clock time difference in endocrine and metabolic responses after physical exercise was assessed according to biorhythm. Physical capacity changed to the time of evaluation, and was greater in the evening than in the morning. Among physiological functions that determine was development of physical strength, plasma growth hormone was higher evening exercise than morning exercise. Further studies are needed on this intriguing idea.

Arabian Oryx (Oryx leucoryx) Respond to Increased Ambient Temperatures with a Seasonal Shift in the Timing of Their Daily Inactivity Patterns.

The Arabian oryx inhabits an environment where summer ambient temperatures can exceed 40 °C for extended periods of time. While the oryx uses a suite of adaptations that aid survival, the effects of this extreme environment on inactivity are unknown. To determine how the oryx manages inactivity seasonally, we measured the daily rhythm of body temperature and used fine-grain actigraphy, in 10 animals, to reveal when the animals were inactive in relation to ambient temperature and photoperiod. We demonstrate that during the cooler winter months, the oryx was inactive during the cooler parts of the 24-h day (predawn hours), showing a nighttime (nocturnal) inactivity pattern. In contrast, in the warmer summer months, the oryx displayed a bimodal inactivity pattern, with major inactivity bouts (those greater than 1 h) occurring equally during both the coolest part of the night (predawn hours) and the warmest part of the day (afternoon hours). Of note, the timing of the daily rhythm of body temperature did not vary seasonally, although the amplitude did change, leading to a seasonal alteration in the phase relationship between inactivity and the body temperature rhythm. Because during periods of inactivity the oryx were presumably asleep for much of the time, we speculate that the daytime shift in inactivity may allow the oryx to take advantage of the thermoregulatory physiology of sleep, which likely occurs when the animal is inactive for more than 1 h, to mitigate environmentally induced increases in body temperature.

Streptozotocin-induced diabetes disrupts the body temperature daily rhythm in rats.

BackgroundIn mammals, the temperature rhythm is regulated by the circadian pacemaker located in the suprachiasmatic nuclei, and is considered a “marker rhythm”. Melatonin, the pineal gland hormone, is a major regulator of the endogenous rhythms including body temperature. Its production is influenced by many factors, such as type 1 diabetes mellitus. In rats, diabetes leads to hypothermia and reduced melatonin synthesis; insulin treatment reestablishes both.AimTo study the body temperature daily rhythm of diabetic animals and the effects of insulin and/or melatonin treatment on its structure.MethodsWe studied the effects of streptozotocin-induced diabetes (60 mg/kg) on the body temperature rhythm of Wistar rats and the possible modifications resulting from early and late treatments with insulin (6U/day) and/or melatonin (daily 0.5 mg/kg). We monitored the daily body temperature rhythm, its rhythmic parameters (MESOR, amplitude and acrophase), glycemia and body weight for 55 days. Data were classified by groups and expressed as mean ± SEM. One-way ANOVA analysis was performed followed by Bonferroni posttest. Statistical significance was set at p < 0.05.ResultsDiabetes led to complete disruption of the temperature rhythm and hypothermia, which were accentuated over time. All early treatments (insulin or/and melatonin) prevented the temperature rhythm disruption and hypothermia. Insulin plus melatonin restored the body temperature rhythm whereas insulin alone resulted less efficient; melatonin alone did not restore any of the parameters studied; however, when supplemented close to diabetes onset, it maintained the temperature rhythmicity. All these corrective effects of the early treatments were dependent on the continuous maintenance of the treatment.ConclusionsTaken together, our findings show the disruption of the body temperature daily rhythm, a new consequence of insulin-dependent diabetes, as well as the beneficial effect of the complementary action of melatonin and insulin restoring the normal rhythmicity.Electronic supplementary materialThe online version of this article (doi:10.1186/s13098-015-0035-2) contains supplementary material, which is available to authorized users.

Estimation of body temperature rhythm based on heart activity parameters in daily life.

Body temperature contains valuable health related information such as circadian rhythm and menstruation cycle. Also, it was discovered from previous studies that body temperature rhythm in daily life is related with sleep disorders and cognitive performances. However, monitoring body temperature with existing devices during daily life is not easy because they are invasive, intrusive, or expensive. Therefore, the technology which can accurately and nonintrusively monitor body temperature is required. In this study, we developed body temperature estimation model based on heart rate and heart rate variability parameters. Although this work was inspired by previous research, we originally identified that the model can be applied to body temperature monitoring in daily life. Also, we could find out that normalized Mean heart rate (nMHR) and frequency domain parameters of heart rate variability showed better performance than other parameters. Although we should validate the model with more number of subjects and consider additional algorithms to decrease the accumulated estimation error, we could verify the usefulness of this approach. Through this study, we expect that we would be able to monitor core body temperature and circadian rhythm from simple heart rate monitor. Then, we can obtain various health related information derived from daily body temperature rhythm.

The nuclear receptor Rev-erbα controls circadian thermogenic plasticity

Circadian oscillation of body temperature is a basic, evolutionary-conserved feature of mammalian biology1. Additionally, homeostatic pathways allow organisms to protect their core temperatures in response to cold exposure2. However, the mechanism responsible for coordinating daily body temperature rhythm and adaptability to environmental challenges is unknown. Here we show that the nuclear receptor Rev-erbα, a powerful transcriptional repressor, links circadian and thermogenic networks through the regulation of brown adipose tissue (BAT) function. Mice exposed to cold fare dramatically better at 5 AM (Zeitgeber time 22) when Rev-erbα is barely expressed than at 5 PM (ZT10) when Rev-erbα is abundant. Deletion of Rev-erbα markedly improves cold tolerance at 5 PM, indicating that overcoming Rev-erbα-dependent repression is a fundamental feature of the thermogenic response to cold. Physiological induction of uncoupling protein 1 (UCP1) by cold temperatures is preceded by rapid down-regulation of Rev-erbα in BAT. Rev-erbα represses UCP1 in a brown adipose cell-autonomous manner and BAT UCP1 levels are high in Rev-erbα-null mice even at thermoneutrality. Genetic loss of Rev-erbα also abolishes normal rhythms of body temperature and BAT activity. Thus, Rev-erbα acts as a thermogenic focal point required for establishing and maintaining body temperature rhythm in a manner that is adaptable to environmental demands.