Yujiro Yamanaka - Academia.edu (original) (raw)

Papers by Yujiro Yamanaka

Research paper thumbnail of Differential responses to artificial photoperiods of the rising and falling phases of human melatonin rhythm are consistent with a dual oscillator hypothesis

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology

The present study demonstrated differential light responsiveness of the rising and falling phases... more The present study demonstrated differential light responsiveness of the rising and falling phases of nocturnal melatonin secretion in human subjects exposed to artificial long (LD 16:8) and short days (LD 8:16) and suggested the involvement of different oscillators under these phases. The findings well mimicked the seasonality of the circadian rhythms in nature and consisted with the evening/morning dual oscillator hypothesis proposed originally for nocturnal rodents, providing a new concept for the human circadian system.

Research paper thumbnail of Figure_S2 – Supplemental material for Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice

Supplemental material, Figure_S2 for Two Coupled Circadian Oscillators Are Involved in Nonphotic ... more Supplemental material, Figure_S2 for Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice by Yujiro Yamanaka, Sato Honma and Ken-ichi Honma in Journal of Biological Rhythms

Research paper thumbnail of Figure_S1 – Supplemental material for Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice

Supplemental material, Figure_S1 for Two Coupled Circadian Oscillators Are Involved in Nonphotic ... more Supplemental material, Figure_S1 for Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice by Yujiro Yamanaka, Sato Honma and Ken-ichi Honma in Journal of Biological Rhythms

Research paper thumbnail of Symposia Abstracts

Sleep and Biological Rhythms, 2005

Research paper thumbnail of Two oscillatory components detected by forced splitting of the sleep-wake cycle in humans

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology

The sleep-wake cycle of human subjects was artificially split into two episodes by imposing an 8-... more The sleep-wake cycle of human subjects was artificially split into two episodes by imposing an 8-h light and 4-h dark cycle (LD 8:4) twice a day for 7 days, which was followed by a 3 day free-running session. Sleep was permitted only in the dark period. The subjects in the ordinary group were exposed to ordinary light (ca. 500 lux) in the 8-h light period, and those in the bright light group to bright (ca. 5,000 lux) and ordinary light alternatively with bright light after the 1st dark period (24:00 - 4:00 h). Split sleeps persisted in the free-running session with the major episode around the 1st dark period and the minor episode around the 2nd dark. By contrast, circadian melatonin rhythm in the free-running session significantly phase-delayed in the ordinary light group, but phase-advanced in the bright light group, keeping the melatonin rhythm un-split. The length of nocturnal melatonin secretion (NMS) was significantly shortened in the bright light group. Interestingly, the fal...

Research paper thumbnail of Impacts of mastication frequency on circadian rhythm of glucose metabolism

Folia Pharmacologica Japonica

Research paper thumbnail of Menstrual phase-dependency of physiological indices and qualities of life

IEICE Technical Report; IEICE Tech. Rep., Oct 22, 2020

Research paper thumbnail of 生活環境と生物時計

Japanese Journal of Biometeorology / Nihon Seikisho Gakkai Zasshi, 2016

Twenty-four hour rhythmicity (circadian rhythm) is observed in our physiology (blood pressure and... more Twenty-four hour rhythmicity (circadian rhythm) is observed in our physiology (blood pressure and endocrine function etc.) and behavior (sleep-wake cycle) under the real world. Circadian rhythm is driven by internal autonomous clock, so called as circadian pacemaker. In mammals including humans, circadian system is organized in hierarchical multi-oscillators which consist of central circadian pacemaker in the suprachiasmatic nucleus (SCN) of hypothalamus and peripheral organs. The SCN entrains to an external light-dark cycle with a period of 24 h and adjusts autonomously our physiology and behavior. In the modern world, some people are forced to live with an irregular work schedule that becomes desynchronization between his or her circadian clock and sleep-wake cycle. Such abnormal sleep-wake cycle and poor sleep are reported to be a risk factor for metabolic dysfunction and mood disorders. In this review, I will introduce a formal property of circadian clock in humans and effect of our living environment, such as light, meal and exercise, on our internal body clock.

Research paper thumbnail of Effects of Lactococcus lactis subsp. cremoris YRC3780 daily intake on the HPA axis response to acute psychological stress in healthy Japanese men

European Journal of Clinical Nutrition, 2021

Background Lactococcus lactis subsp. cremoris (YRC3780), which is isolated from kefir, has been a... more Background Lactococcus lactis subsp. cremoris (YRC3780), which is isolated from kefir, has been associated with anti-allergic effects in humans. However, it remains unknown whether daily intake of YRC3780 attenuates the response to psychological stress in humans in parallel with changes to the gut microbiome. We examined the fundamental role of YRC3780 in the gut microbiome, stress response, sleep, and mental health in humans. Methods Effects of daily intake of YRC3780 on the hypothalamic-pituitary-adrenal (HPA) axis response to acute psychological stress were investigated in a double-blind, placebo-controlled clinical trial involving 27 healthy young men (mean age and body mass index: 23.5 years and 21.5 kg/m2) who were randomly assigned to placebo (n = 13) or YRC3780 (n = 14) groups. The HPA axis response to acute psychological stress, the diurnal rhythm of HPA axis activity, and gut microbiome were assessed and compared between the two groups. Results The results showed that dail...

Research paper thumbnail of Chronobiology: Human circadian pacemaker and circadian rhythms

Japanese Journal of Physical Fitness and Sports Medicine, 2020

Research paper thumbnail of Circadian rhythm disturbances in bipolar disorder: approaches using animal models

Research paper thumbnail of Time of Day of Vaccination Does Not Associate With SARS–CoV–2 Antibody Titer Following First Dose of mRNA COVID–19 Vaccine

Journal of Biological Rhythms

The immune system exhibits circadian rhythms, and its response to viral infection is influenced b... more The immune system exhibits circadian rhythms, and its response to viral infection is influenced by the circadian clock system. Previous studies have reported associations between the time of day of vaccination against COVID-19 and production of anti-SARS-CoV-2 antibody titer. We examined the effect of vaccination time of day on anti-SARS-CoV-2 antibody titer after the first dose of vaccination with the mRNA-1273 (Moderna) COVID-19 vaccine in an adult population. A total of 332 Japanese adults participated in the present study. All participants were not infected with SARS-CoV-2 and had already received the first dose of mRNA-1273 2 to 4 weeks prior to participating in the study. The participants were asked to provide basic demographic characteristics (age, sex, medical history, allergy, medication, and mean sleep duration), the number of days after the first dose of vaccination, and the time of day of vaccination. Blood was collected from the participants, and SARS-CoV-2 antibody tit...

Research paper thumbnail of Morning Mastication Enhances Postprandial Glucose Metabolism in Healthy Young Subjects

The Tohoku Journal of Experimental Medicine, 2019

Postprandial glucose concentration is dependent on the time of day and its concentration in the m... more Postprandial glucose concentration is dependent on the time of day and its concentration in the morning is lower than in the evening. However, whether it is dependent on mastication at different times of the day has not been studied before. We hypothesized that mastication affects insulin-mediated glucose metabolism differently in the morning and evening in healthy individuals. Firstly, nine healthy male volunteers (22.0 ± 0.7 SEM years, body mass index 22.0 ± 1.0 kg/m 2) performed a 75-g oral glucose tolerance test (OGTT). One week after the OGTT, they participated in a high-carbohydrate food (rice) consumption test with 10 or 40 chews per mouthful. Each experiment was conducted in the morning (0800 h) and evening (2000 h) on the same day. Blood samples were collected before and at 30-min intervals for 120 min after glucose or rice consumption. The incremental area under the curve (iAUC) for glucose in the OGTT was significantly lower in the morning than in the evening, whereas the iAUC for insulin was similar at both times. In participants who chewed 40 times, the iAUC for glucose after rice consumption was significantly lower in the morning than in the evening but was similar at both times in individuals who chewed 10 times. Chewing 40 times in the morning (but not the evening) significantly increased insulin secretion at 30 min. This suggests that morning mastication improves early-phase insulin secretion after rice consumption. This novel finding may aid in reducing the incidence of obesity and type 2 diabetes mellitus.

Research paper thumbnail of in young subjects under fixed sleep schedule phase nocturnal melatonin rise and maintain circadian Repeated exposures to daytime bright light increase

Research paper thumbnail of Differential effects of scheduled novel environment with a running-wheel on re-entrainment of circadian clocks in the suprachiasmatic nuclei and peripheral tissues in mice subjected to an 8 h shifted light-dark cycles

Research paper thumbnail of Non-photic entrainment to scheduled 3-h wheel running activity in the mice circadian rhythm

Research paper thumbnail of Basic concepts and unique features of human circadian rhythms: implications for human health

Nutrition Reviews, 2020

Most physiological functions and behaviors exhibit a robust approximately 24-hour rhythmicity (ci... more Most physiological functions and behaviors exhibit a robust approximately 24-hour rhythmicity (circadian rhythm) in the real world. These rhythms persist under constant conditions, but the period is slightly longer than 24 hours, suggesting that circadian rhythms are endogenously driven by an internal, self-sustained oscillator. In mammals, including humans, the central circadian pacemaker is located in the hypothalamic suprachiasmatic nucleus. The primary zeitgeber for this pacemaker is bright sunlight, but nonphotic time cues also affect circadian rhythms. The human circadian system uniquely exhibits spontaneous internal desynchronization between the sleep-wake cycle and core body temperature rhythm under constant conditions and partial entrainment of the sleep-wake cycle in response to nonphotic time cues. Experimental and clinical studies of human circadian rhythms must take into account these unique features. This review covers the basic concepts and unique features of the huma...

Research paper thumbnail of Hypothalamic-pituitary-adrenal axis differentially responses to morning and evening psychological stress in healthy subjects

Neuropsychopharmacology Reports, 2018

Aim: The hypothalamic-pituitary-adrenal (HPA) axis responds to changing environmental demands inc... more Aim: The hypothalamic-pituitary-adrenal (HPA) axis responds to changing environmental demands including psychological stressors. The aim of the present study was to assess whether the time of day effects on the acute response of HPA axis activity to acute psychological stress. Method: We studied 27 healthy young subjects. The subjects were participated two experiments as follows. In the first experiment, subjects were instructed to keep their regular sleep schedule for 2 weeks which were measured by using a wrist-worn activity monitor. Afterward, to evaluate a diurnal rhythm of salivary cortisol, eight saliva samples were collected during waking period every 2 hours from when the subjects woke up. In the second experiment, the subjects were randomly assigned to two groups. The Trier Social Stress Test (TSST) was performed either in the morning (n = 14) or in the evening (n = 13). We measured diurnal rhythm of salivary cortisol and stress response of salivary cortisol and heart rate by the TSST. Morning and evening tests were started at 2 hours and 10 hours after woke up, respectively. Results: All subjects showed a normal diurnal rhythm of salivary cortisol concentration, with a peak in the morning immediately after awaking and a minimum in the evening. The salivary cortisol response after the TSST was significantly increased from the prestress level in the morning but not in the evening. Conclusion: The HPA response to acute psychological stress was more pronounced in the morning than in the evening, correlating with the circadian regulation of cortisol synthesis.

Research paper thumbnail of Cryptochrome deficiency enhances transcription but reduces protein levels of pineal Aanat

Journal of Molecular Endocrinology, 2018

Cryptochrome (Cry)1and2are essential for circadian rhythm generation, not only in the suprachiasm... more Cryptochrome (Cry)1and2are essential for circadian rhythm generation, not only in the suprachiasmatic nucleus, the site of the mammalian master circadian clock, but also in peripheral organs throughout the body. CRY is also known as a repressor of arylalkylamine-N-acetyltransferase (Aanat) transcription; therefore,Crydeficiency is expected to induce constantly high pineal melatonin content. Nevertheless, we previously found that the content was consistently low in melatonin-proficientCry1andCry2double-deficient mice (Cry1−/−/Cry2−/−) on C3H background. This study aims to clarify the mechanism underlying this discrepancy. In theCry1−/−/Cry2−/−pineal, expression levels ofAanatand clock genePer1were consistently high with no circadian fluctuation on the first day in constant darkness, demonstrating that CRY actsin vivoas a repressor of the pineal circadian clock and AANAT. In contrast, the enzyme activity and protein levels of AANAT remained low throughout the day, supporting our previ...

Research paper thumbnail of Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice

Journal of Biological Rhythms, 2018

The onset and offset of an activity band in the circadian behavioral rhythm are known to differen... more The onset and offset of an activity band in the circadian behavioral rhythm are known to differentially reentrain to shifted light-dark cycles (LD). Differential reentrainment could be explained by different light responsivities of circadian oscillators underlying these phase-markers. In contrast, reentrainment is accelerated by exposure to nonphotic time cues such as timed wheel-running. However, the relationship between the 2 oscillators and nonphotic acceleration of reentrainment is largely unknown. We examined phase-shifts of the mouse behavioral rhythm in response to an 8-h phase-advanced shift of LD and effects of behavioral interventions: maintained in a home cage (HC), exposed to a running wheel (RW) in HC (HC+RW), transferred to a new cage (NC), and exposed to RW in NC (NC+RW). Each intervention was given for 3h from the beginning of the shifted dark period and repeated for 4 days. Following the last dark period, the mice were released into constant darkness (DD). As a resu...

Research paper thumbnail of Differential responses to artificial photoperiods of the rising and falling phases of human melatonin rhythm are consistent with a dual oscillator hypothesis

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology

The present study demonstrated differential light responsiveness of the rising and falling phases... more The present study demonstrated differential light responsiveness of the rising and falling phases of nocturnal melatonin secretion in human subjects exposed to artificial long (LD 16:8) and short days (LD 8:16) and suggested the involvement of different oscillators under these phases. The findings well mimicked the seasonality of the circadian rhythms in nature and consisted with the evening/morning dual oscillator hypothesis proposed originally for nocturnal rodents, providing a new concept for the human circadian system.

Research paper thumbnail of Figure_S2 – Supplemental material for Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice

Supplemental material, Figure_S2 for Two Coupled Circadian Oscillators Are Involved in Nonphotic ... more Supplemental material, Figure_S2 for Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice by Yujiro Yamanaka, Sato Honma and Ken-ichi Honma in Journal of Biological Rhythms

Research paper thumbnail of Figure_S1 – Supplemental material for Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice

Supplemental material, Figure_S1 for Two Coupled Circadian Oscillators Are Involved in Nonphotic ... more Supplemental material, Figure_S1 for Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice by Yujiro Yamanaka, Sato Honma and Ken-ichi Honma in Journal of Biological Rhythms

Research paper thumbnail of Symposia Abstracts

Sleep and Biological Rhythms, 2005

Research paper thumbnail of Two oscillatory components detected by forced splitting of the sleep-wake cycle in humans

American Journal of Physiology-Regulatory, Integrative and Comparative Physiology

The sleep-wake cycle of human subjects was artificially split into two episodes by imposing an 8-... more The sleep-wake cycle of human subjects was artificially split into two episodes by imposing an 8-h light and 4-h dark cycle (LD 8:4) twice a day for 7 days, which was followed by a 3 day free-running session. Sleep was permitted only in the dark period. The subjects in the ordinary group were exposed to ordinary light (ca. 500 lux) in the 8-h light period, and those in the bright light group to bright (ca. 5,000 lux) and ordinary light alternatively with bright light after the 1st dark period (24:00 - 4:00 h). Split sleeps persisted in the free-running session with the major episode around the 1st dark period and the minor episode around the 2nd dark. By contrast, circadian melatonin rhythm in the free-running session significantly phase-delayed in the ordinary light group, but phase-advanced in the bright light group, keeping the melatonin rhythm un-split. The length of nocturnal melatonin secretion (NMS) was significantly shortened in the bright light group. Interestingly, the fal...

Research paper thumbnail of Impacts of mastication frequency on circadian rhythm of glucose metabolism

Folia Pharmacologica Japonica

Research paper thumbnail of Menstrual phase-dependency of physiological indices and qualities of life

IEICE Technical Report; IEICE Tech. Rep., Oct 22, 2020

Research paper thumbnail of 生活環境と生物時計

Japanese Journal of Biometeorology / Nihon Seikisho Gakkai Zasshi, 2016

Twenty-four hour rhythmicity (circadian rhythm) is observed in our physiology (blood pressure and... more Twenty-four hour rhythmicity (circadian rhythm) is observed in our physiology (blood pressure and endocrine function etc.) and behavior (sleep-wake cycle) under the real world. Circadian rhythm is driven by internal autonomous clock, so called as circadian pacemaker. In mammals including humans, circadian system is organized in hierarchical multi-oscillators which consist of central circadian pacemaker in the suprachiasmatic nucleus (SCN) of hypothalamus and peripheral organs. The SCN entrains to an external light-dark cycle with a period of 24 h and adjusts autonomously our physiology and behavior. In the modern world, some people are forced to live with an irregular work schedule that becomes desynchronization between his or her circadian clock and sleep-wake cycle. Such abnormal sleep-wake cycle and poor sleep are reported to be a risk factor for metabolic dysfunction and mood disorders. In this review, I will introduce a formal property of circadian clock in humans and effect of our living environment, such as light, meal and exercise, on our internal body clock.

Research paper thumbnail of Effects of Lactococcus lactis subsp. cremoris YRC3780 daily intake on the HPA axis response to acute psychological stress in healthy Japanese men

European Journal of Clinical Nutrition, 2021

Background Lactococcus lactis subsp. cremoris (YRC3780), which is isolated from kefir, has been a... more Background Lactococcus lactis subsp. cremoris (YRC3780), which is isolated from kefir, has been associated with anti-allergic effects in humans. However, it remains unknown whether daily intake of YRC3780 attenuates the response to psychological stress in humans in parallel with changes to the gut microbiome. We examined the fundamental role of YRC3780 in the gut microbiome, stress response, sleep, and mental health in humans. Methods Effects of daily intake of YRC3780 on the hypothalamic-pituitary-adrenal (HPA) axis response to acute psychological stress were investigated in a double-blind, placebo-controlled clinical trial involving 27 healthy young men (mean age and body mass index: 23.5 years and 21.5 kg/m2) who were randomly assigned to placebo (n = 13) or YRC3780 (n = 14) groups. The HPA axis response to acute psychological stress, the diurnal rhythm of HPA axis activity, and gut microbiome were assessed and compared between the two groups. Results The results showed that dail...

Research paper thumbnail of Chronobiology: Human circadian pacemaker and circadian rhythms

Japanese Journal of Physical Fitness and Sports Medicine, 2020

Research paper thumbnail of Circadian rhythm disturbances in bipolar disorder: approaches using animal models

Research paper thumbnail of Time of Day of Vaccination Does Not Associate With SARS–CoV–2 Antibody Titer Following First Dose of mRNA COVID–19 Vaccine

Journal of Biological Rhythms

The immune system exhibits circadian rhythms, and its response to viral infection is influenced b... more The immune system exhibits circadian rhythms, and its response to viral infection is influenced by the circadian clock system. Previous studies have reported associations between the time of day of vaccination against COVID-19 and production of anti-SARS-CoV-2 antibody titer. We examined the effect of vaccination time of day on anti-SARS-CoV-2 antibody titer after the first dose of vaccination with the mRNA-1273 (Moderna) COVID-19 vaccine in an adult population. A total of 332 Japanese adults participated in the present study. All participants were not infected with SARS-CoV-2 and had already received the first dose of mRNA-1273 2 to 4 weeks prior to participating in the study. The participants were asked to provide basic demographic characteristics (age, sex, medical history, allergy, medication, and mean sleep duration), the number of days after the first dose of vaccination, and the time of day of vaccination. Blood was collected from the participants, and SARS-CoV-2 antibody tit...

Research paper thumbnail of Morning Mastication Enhances Postprandial Glucose Metabolism in Healthy Young Subjects

The Tohoku Journal of Experimental Medicine, 2019

Postprandial glucose concentration is dependent on the time of day and its concentration in the m... more Postprandial glucose concentration is dependent on the time of day and its concentration in the morning is lower than in the evening. However, whether it is dependent on mastication at different times of the day has not been studied before. We hypothesized that mastication affects insulin-mediated glucose metabolism differently in the morning and evening in healthy individuals. Firstly, nine healthy male volunteers (22.0 ± 0.7 SEM years, body mass index 22.0 ± 1.0 kg/m 2) performed a 75-g oral glucose tolerance test (OGTT). One week after the OGTT, they participated in a high-carbohydrate food (rice) consumption test with 10 or 40 chews per mouthful. Each experiment was conducted in the morning (0800 h) and evening (2000 h) on the same day. Blood samples were collected before and at 30-min intervals for 120 min after glucose or rice consumption. The incremental area under the curve (iAUC) for glucose in the OGTT was significantly lower in the morning than in the evening, whereas the iAUC for insulin was similar at both times. In participants who chewed 40 times, the iAUC for glucose after rice consumption was significantly lower in the morning than in the evening but was similar at both times in individuals who chewed 10 times. Chewing 40 times in the morning (but not the evening) significantly increased insulin secretion at 30 min. This suggests that morning mastication improves early-phase insulin secretion after rice consumption. This novel finding may aid in reducing the incidence of obesity and type 2 diabetes mellitus.

Research paper thumbnail of in young subjects under fixed sleep schedule phase nocturnal melatonin rise and maintain circadian Repeated exposures to daytime bright light increase

Research paper thumbnail of Differential effects of scheduled novel environment with a running-wheel on re-entrainment of circadian clocks in the suprachiasmatic nuclei and peripheral tissues in mice subjected to an 8 h shifted light-dark cycles

Research paper thumbnail of Non-photic entrainment to scheduled 3-h wheel running activity in the mice circadian rhythm

Research paper thumbnail of Basic concepts and unique features of human circadian rhythms: implications for human health

Nutrition Reviews, 2020

Most physiological functions and behaviors exhibit a robust approximately 24-hour rhythmicity (ci... more Most physiological functions and behaviors exhibit a robust approximately 24-hour rhythmicity (circadian rhythm) in the real world. These rhythms persist under constant conditions, but the period is slightly longer than 24 hours, suggesting that circadian rhythms are endogenously driven by an internal, self-sustained oscillator. In mammals, including humans, the central circadian pacemaker is located in the hypothalamic suprachiasmatic nucleus. The primary zeitgeber for this pacemaker is bright sunlight, but nonphotic time cues also affect circadian rhythms. The human circadian system uniquely exhibits spontaneous internal desynchronization between the sleep-wake cycle and core body temperature rhythm under constant conditions and partial entrainment of the sleep-wake cycle in response to nonphotic time cues. Experimental and clinical studies of human circadian rhythms must take into account these unique features. This review covers the basic concepts and unique features of the huma...

Research paper thumbnail of Hypothalamic-pituitary-adrenal axis differentially responses to morning and evening psychological stress in healthy subjects

Neuropsychopharmacology Reports, 2018

Aim: The hypothalamic-pituitary-adrenal (HPA) axis responds to changing environmental demands inc... more Aim: The hypothalamic-pituitary-adrenal (HPA) axis responds to changing environmental demands including psychological stressors. The aim of the present study was to assess whether the time of day effects on the acute response of HPA axis activity to acute psychological stress. Method: We studied 27 healthy young subjects. The subjects were participated two experiments as follows. In the first experiment, subjects were instructed to keep their regular sleep schedule for 2 weeks which were measured by using a wrist-worn activity monitor. Afterward, to evaluate a diurnal rhythm of salivary cortisol, eight saliva samples were collected during waking period every 2 hours from when the subjects woke up. In the second experiment, the subjects were randomly assigned to two groups. The Trier Social Stress Test (TSST) was performed either in the morning (n = 14) or in the evening (n = 13). We measured diurnal rhythm of salivary cortisol and stress response of salivary cortisol and heart rate by the TSST. Morning and evening tests were started at 2 hours and 10 hours after woke up, respectively. Results: All subjects showed a normal diurnal rhythm of salivary cortisol concentration, with a peak in the morning immediately after awaking and a minimum in the evening. The salivary cortisol response after the TSST was significantly increased from the prestress level in the morning but not in the evening. Conclusion: The HPA response to acute psychological stress was more pronounced in the morning than in the evening, correlating with the circadian regulation of cortisol synthesis.

Research paper thumbnail of Cryptochrome deficiency enhances transcription but reduces protein levels of pineal Aanat

Journal of Molecular Endocrinology, 2018

Cryptochrome (Cry)1and2are essential for circadian rhythm generation, not only in the suprachiasm... more Cryptochrome (Cry)1and2are essential for circadian rhythm generation, not only in the suprachiasmatic nucleus, the site of the mammalian master circadian clock, but also in peripheral organs throughout the body. CRY is also known as a repressor of arylalkylamine-N-acetyltransferase (Aanat) transcription; therefore,Crydeficiency is expected to induce constantly high pineal melatonin content. Nevertheless, we previously found that the content was consistently low in melatonin-proficientCry1andCry2double-deficient mice (Cry1−/−/Cry2−/−) on C3H background. This study aims to clarify the mechanism underlying this discrepancy. In theCry1−/−/Cry2−/−pineal, expression levels ofAanatand clock genePer1were consistently high with no circadian fluctuation on the first day in constant darkness, demonstrating that CRY actsin vivoas a repressor of the pineal circadian clock and AANAT. In contrast, the enzyme activity and protein levels of AANAT remained low throughout the day, supporting our previ...

Research paper thumbnail of Two Coupled Circadian Oscillators Are Involved in Nonphotic Acceleration of Reentrainment to Shifted Light Cycles in Mice

Journal of Biological Rhythms, 2018

The onset and offset of an activity band in the circadian behavioral rhythm are known to differen... more The onset and offset of an activity band in the circadian behavioral rhythm are known to differentially reentrain to shifted light-dark cycles (LD). Differential reentrainment could be explained by different light responsivities of circadian oscillators underlying these phase-markers. In contrast, reentrainment is accelerated by exposure to nonphotic time cues such as timed wheel-running. However, the relationship between the 2 oscillators and nonphotic acceleration of reentrainment is largely unknown. We examined phase-shifts of the mouse behavioral rhythm in response to an 8-h phase-advanced shift of LD and effects of behavioral interventions: maintained in a home cage (HC), exposed to a running wheel (RW) in HC (HC+RW), transferred to a new cage (NC), and exposed to RW in NC (NC+RW). Each intervention was given for 3h from the beginning of the shifted dark period and repeated for 4 days. Following the last dark period, the mice were released into constant darkness (DD). As a resu...