Sleep Basic Research on Verifying the Effects of Natural Compounds on Wakefulness or Sleep.

I studied at the Sleep and Circadian Neurobiology Laboratory, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, from April 2018 to March 2020. At Stanford University, I mainly researched the following themes: (1) sleep basic research using mice (administering compounds with sleep or wakefulness effects to mice and examining their effects), and (2) research on circadian rhythm disorders. There are only a few institutions in the world that can conduct sleep basic research using mice, and Stanford University is a wonderful environment to immerse yourself in research, as it is home to not only psychiatrists but also neurologists and many basic researchers. In this article, I would like to review the experiments I conducted during my study abroad, using mice to verify the effects of natural compounds on wakefulness or sleep. In one study, we evaluated the effects of ginkgolides (A, B, and C) and bilobalide on arousal, locomotion, and core body temperature. The results showed that only ginkgolide B dose-dependently increased the amount of arousal and decreased the amount of NREM sleep in the physiological sleep-wake cycle of mice. In another study, we tested the sleep-inducing effects of sake yeast in mice under an acute insomnia model. We showed that sake yeast dose-dependently increased REM and non-REM sleep, decreased arousal within 6 hours after oral administration of sake yeast, and decreased locomotion and core body temperature in a new cage.

Sake yeast induces the sleep-promoting effects under the stress-induced acute insomnia in mice.

Sleep deprivation induces adverse effects on the health, productivity, and performance. The individuals who could not get enough sleep temporarily experience the symptoms of an induced acute insomnia. This study investigated the efficacy of sake yeast in treatment of acute insomnia in mice. The results of this study showed that sake yeast induced a significant dose-dependent wake reduction, a rapid eye movement (REM) and a non-REM (NREM) sleep enhancement during the first 6 h after the oral administration of sake yeast with locomotor activity and core body temperature decreases under the stressful environment in a new cage. In fact, the wake amounts at 3 h and 6 h were significantly reduced after the oral administration of sake yeast compared with the vehicle. The NREM sleep amounts at 3 h and 6 h significantly increased after the administration of sake yeast compared with the vehicle. The REM amount at 6 h significantly increased after the administration of sake yeast compared with the vehicle, but not at 3 h. The previous study suggested that the sleep-promoting effects of sake yeast could be referred from the activating effect of adenosine A2A receptor (A2AR). In summary, the sake yeast is an A2AR agonist and may induce sleep due to its stress-reducing and anti-anxiety properties. Further verification of the involvement of adenosine in the pathophysiology of insomnia is needed.

Advances in the pharmacological management of non-24-h sleep-wake disorder.

Introduction: Melatonin, a hormone that regulates circadian rhythms and the sleep-wake cycle, is produced mainly during the dark period in the pineal gland and is suppressed by light exposure. Patients with non-24-h sleep-wake disorder (non-24) fail to entrain the master clock with the 24-h light-dark cycle due to the lack of light perception to the suprachiasmatic nucleus typically in totally blind individuals or other organic disorders in sighted individuals, causing a progressive delay in the sleep-wake cycle and periodic insomnia and daytime sleepiness.Areas covered: Herein, the authors review the pharmacological therapies including exogenous melatonin and melatonin receptor agonists for the management of non-24. They introduce a historical report about the effects of melatonin on the phase shift and entrainment for blind individuals with the free-running circadian rhythm.Expert opinion: Orally administered melatonin entrains the endogenous circadian rhythm and improves nighttime sleep and daytime alertness for non-24. Currently, tasimelteon is the only approved medication for non-24 by the US Food and Drug Administration and the European Medicines Agency. Treatments that focus only on sleep problems are insufficient for the treatment of non-24, and aids to entrain the free-running rhythm with the light-dark cycle are needed.

Use of skin advanced glycation end product levels measured using a simple noninvasive method as a biological marker for the diagnosis of neuropsychiatric diseases.

OBJECTIVES: The accumulation of advanced glycation end products (AGEs) may be involved in the pathophysiology of several neuropsychiatric diseases. In this study, the skin AGEs level of several neuropsychiatric diseases was assessed with a simple noninvasive method. Moreover, whether skin AGE level can be used as a biomarker for the diagnosis of these diseases was evaluated. METHODS: A total of 27 patients with schizophrenia, 26 with major depressive disorder, and 10 with major neurocognitive disorders (MNDs), such as Alzheimer's disease or dementia with Lewy body, as well as 26 healthy controls were enrolled in this study. The skin AGE levels of the patients were assessed with an AGE scanner, a fluorometric method used to assay skin AGE levels. RESULTS: One-way analysis of covariance was performed after adjusting for significant covariates, including age. Although the group with MNDs had higher skin AGE levels than the other groups, the main effect of diagnosis did not significantly affect the skin AGE levels of the groups. CONCLUSIONS: Skin AGE levels in neuropsychiatric diseases with mild symptoms did not significantly differ. Further large-scale studies using a simple noninvasive method for the early detection and treatment of MNDs must be conducted.

Intraperitoneal injection of ginkgolide B, a major active compound of Ginkgo biloba, dose-dependently increases the amount of wake and decreases non-rapid eye movement sleep in C57BL/6 mice.

The terpene lactones of Ginkgo biloba extract, namely ginkgolides (A, B, and C) and bilobalide, possess antioxidant, anti-inflammatory, and neuroprotective effects. They are widely prescribed for the treatment of cerebral dysfunctions and neurological impairments. In addition, they demonstrate antagonistic action at the gamma-aminobutyric acid type A and glycine receptors, which are members of the ligand-gated ion channel superfamily. In the present study, the effects of ginkgolides (A, B, and C) and bilobalide on sleep in C57BL/6 mice were investigated. Ginkgolide B was found to dose-dependently increase the amount of wake and decrease that of non-rapid eye movement sleep without changes in the electroencephalography power density of each sleep/wake stage, core body temperature and locomotor activity for the first 6 h after intraperitoneal injection. Of note, the amount of wake after injection of 5 mg/kg of ginkgolide B showed a significant increase (14.9 %) compared with that of vehicle (P = 0.005). In contrast, there were no significant differences in the amount of sleep, core body temperature, and locomotor activity in the mice injected with ginkgolide A and C. Bilobalide briefly induced a decrease in locomotor activity but did not exert significant effects on the amounts of sleep and wake. The modes of action of the wake-enhancing effects of ginkgolide B are unknown. However, it may act through the antagonism of gamma-aminobutyric acid type A and glycine receptors because it is established that these inhibitory amino acids mediate sleep and sleep-related physiology. It is of interest to further evaluate the stimulant and awaking actions of ginkgolide B on the central nervous system in clinical and basic research studies.

Tasimelteon for treating non-24-h sleep-wake rhythm disorder.

INTRODUCTION: Non-24-h sleep-wake rhythm disorder (non-24) is observed in approximately half of totally blind individuals, a condition caused by their circadian pacemaker in the suprachiasmatic nucleus not being entrained to 24 h due to a lack of light perceptions. These subjects have a progressively delayed circadian cycle each day, non-24 periodically inducing nighttime insomnia and daytime sleepiness. Tasimelteon is a dual melatonin receptor agonist with high affinity for the melatonin 2 receptor, and it entrains endogenous melatonin rhythms and sleep-wake cycles in individuals with non-24. Areas covered: Herein, the authors review the treatment of non-24 with tasimelteon. The authors further compare tasimelteon with other melatonin receptor agonists. Expert opinion: The treatment strategies for non-24 aim to resynchronize the free-running rhythm with the 24 h light-dark cycle. Tasimelteon entrains circadian rhythms and improves the sleep-wake functions of individuals with non-24. Furthermore, the RESET study demonstrated that 20% of patients that discontinued tasimelteon maintained circadian entrainment whereas 90% of those who continued it maintained circadian entrainment. Long-term administration of tasimelteon is safe and well tolerated, and it is the only pharmacological therapy approved by the US Food and Drug Administration and the European Medicines Agency for non-24.

Skin advanced glycation end products as biomarkers of photosensitivity in schizophrenia.

OBJECTIVES: Photosensitivity to ultraviolet A (UVA) radiation from sunlight is an important side effect of treatment with antipsychotic agents. However, the pathophysiology of drug-induced photosensitivity remains unclear. Recent studies demonstrated the accumulation of advanced glycation end products (AGEs), annotated as carbonyl stress, to be associated with the pathophysiology of schizophrenia. In this study, we investigated the relationship among skin AGE levels, minimal response dose (MRD) with UVA for photosensitivity, and the daily dose of antipsychotic agents in patients with schizophrenia and healthy controls. METHODS: We enrolled 14 patients with schizophrenia and 14 healthy controls. Measurement of skin AGE levels was conducted with AGE scanner, a fluorometric method for assaying skin AGE levels. Measurement of MRD was conducted with UV irradiation device. RESULTS: Skin AGE levels and MRD at 24, 48, and 72 hr in patients with schizophrenia showed a higher tendency for photosensitivity than in the controls, but the difference was statistically insignificant. Multiple linear regression analysis using skin AGE levels failed to show any influence of independent variables. MRD did not affect skin AGE levels. CONCLUSIONS: Photosensitivity to UVA in patients with schizophrenia receiving treatment with antipsychotic agents might not be affected by skin AGE levels.

Carbonyl Stress and Microinflammation-Related Molecules as Potential Biomarkers in Schizophrenia.

This literature review primarily aims to summarize our research, comprising both cross-sectional and longitudinal studies, and discuss the possibility of using microinflammation-related biomarkers as peripheral biomarkers in the diagnosis and monitoring of patients with schizophrenia. To date, several studies have been conducted on peripheral biomarkers to recognize the potential markers for the diagnosis of schizophrenia and to determine the state and effects of therapy in patients with schizophrenia. Research has established a correlation between carbonyl stress, an environmental factor, and the pathophysiology of neuropsychiatric diseases, including schizophrenia. In addition, studies on biomarkers related to these stresses have achieved results that are either replicable or exhibit consistent increases or decreases in patients with schizophrenia. For instance, pentosidine, an advanced glycation end product (AGE), is considerably elevated in patients with schizophrenia; however, low levels of vitamin B6 [a detoxifier of reactive carbonyl compounds (RCOs)] have also been reported in some patients with schizophrenia. Another study on peripheral markers of carbonyl stress in patients with schizophrenia revealed a correlation of higher levels of glyceraldehyde-derived AGEs with higher neurotoxicity and lower levels of soluble receptors capable of diminishing the effects of AGEs. Furthermore, studies on evoked microinflammation-related biomarkers (e.g., soluble tumor necrosis factor receptor 1) have reported relatively consistent results, suggesting the involvement of microinflammation in the pathophysiology of schizophrenia. We believe that our cross-sectional and longitudinal studies as well as various previous inflammation marker studies that could be interpreted from several perspectives, such as mild localized encephalitis and microvascular disturbance, highlighted the importance of early intervention as prevention and distinguished the possible exclusion of inflammations in schizophrenia.

High doses of antipsychotic polypharmacy are related to an increase in serum levels of pentosidine in patients with schizophrenia.

BACKGROUND: Carbonyl stress in patients with schizophrenia has been reported to be reflected by an increase in peripheral pentosidine levels. This cohort study tested whether the accumulation of pentosidine was related to the disease severity or the treatment (routine administration of high antipsychotic doses). METHODS: We followed up our original investigation using a new group of 137 patients with acute schizophrenia and 45 healthy subjects, and then pooled the two cohorts to conduct the following analysis on a total of 274 patients. The associations of serum pentosidine and pyridoxal levels with duration of education, estimated duration of medication, the severity of symptoms, and daily doses of antipsychotics, antiparkinsonian drugs, and anxiolytics were evaluated by multiple linear regression analysis. RESULTS: The combined cohort of 274 patients exhibited abnormally high serum levels of pentosidine, were associated with a higher daily dose of antipsychotic drugs and a longer estimated duration of medication without statistical significance of diagnosis. This was also observed in the patients treated with antipsychotic polypharmacy, but the serum pentosidine levels of patients treated with first- or second-generation antipsychotic monotherapy showed no relationship with these two variables. CONCLUSION: High levels of serum pentosidine were associated with high daily doses of antipsychotic drugs and a longer estimated duration of medication in patients treated with antipsychotic polypharmacy.

High serum soluble tumor necrosis factor receptor 1 predicts poor treatment response in acute-stage schizophrenia.

Inflammation may be involved in the pathophysiology of schizophrenia. However, few cross-sectional or longitudinal studies have examined changes in biomarker expression to evaluate diagnostic and prognostic efficacy in acute-stage schizophrenia. We compared serum inflammatory biomarker concentrations in 87 patients with acute-stage schizophrenia on admission to 105 age-, sex-, and body mass index (BMI)-matched healthy controls. The measured biomarkers were soluble tumor necrosis factor receptor 1 (sTNFR1) and adiponectin, which are associated with inflammatory responses, and pigment epithelium-derived factor (PEDF), which has anti-inflammatory properties. We then investigated biomarker concentrations and associations with clinical factors in 213 patients (including 42 medication-free patients) and 110 unmatched healthy controls to model conditions typical of clinical practice. Clinical symptoms were assessed using the Brief Psychiatric Rating Scale and Global Assessment of Function. In 121 patients, biomarker levels and clinical status were evaluated at both admission and discharge. Serum sTNFR1 was significantly higher in patients with acute-stage schizophrenia compared to matched controls while no significant group differences were observed for the other markers. Serum sTNFR1 was also significantly higher in the 213 patients compared to unmatched controls. The 42 unmedicated patients had significantly lower PEDF levels compared to controls. Between admission and discharge, sTNFR1 levels decreased significantly; however, biomarker changes did not correlate with clinical symptoms. The discriminant accuracy of sTNFR1 was 93.2% between controls and patients, showing no symptom improvement during care. Inflammation and a low-level anti-inflammatory state may be involved in both schizophrenia pathogenesis and acute-stage onset. High serum sTNFR1 in the acute stage could be a useful prognostic biomarker for treatment response in clinical practice.

Associations of common copy number variants in glutathione S-transferase mu 1 and D-dopachrome tautomerase-like protein genes with risk of schizophrenia in a Japanese population.

Oxidative-stress, genetic regions of interest (1p13 and 22q11), and common copy number variations (CNVs) may play roles in the pathophysiology of schizophrenia. In the present study, we confirmed associations between schizophrenia and the common CNVs in the glutathione (GSH)-related genes GSTT1, DDTL, and GSTM1 using quantitative real-time polymerase chain reaction analyses of 620 patients with schizophrenia and in 622 controls. No significant differences in GSTT1 copy number distributions were found between patient groups. However, frequencies of characterized CNVs and assumed gain alleles of DDTL and GSTM1 were significantly higher in patients with schizophrenia. In agreement with a previous report, the present data indicate that gains in the CNV alleles DDTL and GSTM1 are genetic risk factors in Japanese patients with schizophrenia, and suggest involvement of micro-inflammation and oxidative stress in the pathophysiology of schizophrenia.

Altered serum glyceraldehyde-derived advanced glycation end product (AGE) and soluble AGE receptor levels indicate carbonyl stress in patients with schizophrenia.

Recent cross-sectional and longitudinal studies indicate that measurements of peripheral blood carbonyl stress markers such as the advanced glycation end product (AGE) pentosidine and the reactive carbonyl-detoxifying B6 vitamin pyridoxal could be used as therapeutic biological markers in subpopulations of schizophrenia patients. Glyceraldehyde-derived AGEs (Glycer-AGE) have strong neurotoxicity, and soluble receptors for AGEs (sRAGE) may ameliorate the effects of AGEs. In the present study, we measured Glycer-AGEs and sRAGE levels to determine their potential as diagnostic, therapeutic, or clinical biological markers in patients with schizophrenia. After enrollment of 61 admitted Japanese patients with acute schizophrenia and 39 healthy volunteers, 54 patients were followed up from the acute stage to remission. Serum biomarkers were measured in blood samples taken before breakfast using competitive enzyme-linked immunosorbent assays, and Glycer-AGEs were significantly higher and sRAGE levels were significantly lower in patients with acute schizophrenia than in healthy controls. Glycer-AGEs/sRAGE ratios were also higher in schizophrenia patients and were stable during the clinical course. Furthermore, discriminant analyses confirmed that Glycer-AGEs and Glycer-AGEs/sRAGE ratios are significant diagnostic markers for schizophrenia, and distinguished between patients and healthy controls in 70.0% of cases. However, these markers of carbonyl stress were not correlated with clinical features, including disease severity, or with daily chlorpromazine doses. These data indicate the potential of Glycer-AGEs, RAGEs, and their relative ratios as diagnostic markers for patients with schizophrenia.

Significance of measurements of peripheral carbonyl stress markers in a cross-sectional and longitudinal study in patients with acute-stage schizophrenia.

Altered peripheral carbonyl stress markers, high levels of serum pentosidine, which accumulates following carbonyl stress, and low levels of pyridoxal (vitamin B6), which detoxifies reactive carbonyl compounds, have been reported in a cross-sectional study of chronic schizophrenia. However, changes in the levels of these compounds in patients with schizophrenia have not been investigated in a longitudinal study. To clarify whether these markers may be biological markers that reflect the clinical course of the disease, the serum levels of these compounds were investigated in a cross-sectional and a longitudinal study. One hundred and thirty-seven acute-stage Japanese patients were enrolled. Among these, 53 patients were followed from the acute stage to remission. A portion of patients in the acute stage (14 cases, 10.2%) showed extremely high pentosidine levels. These levels were not associated with the severity of symptoms but were associated with antipsychotic dose amounts. Pyridoxal levels were lower in schizophrenia and increased according to the clinical course of the illness. Furthermore, 18 patients with decreased pyridoxal levels according to the clinical course showed that the greater the decrease in pyridoxal levels, the lesser the improvement in symptoms. Thus, extremely high pentosidine levels in a portion of patients may be caused by higher daily antipsychotic doses, whereas pyridoxal levels were lower in schizophrenia and increased according to the clinical course. Patients with decreasing pyridoxal levels during the clinical course showed less improvement in symptoms. Carbonyl stress markers may also be therapeutic biological markers in some patients with schizophrenia.