Reduced plasma orexin-A levels in patients with bipolar disorder

Baseline prepulse inhibition dependency of orexin A and REM sleep deprivation

RATIONALE

Prepulse inhibition (PPI) impairment reflects sensorimotor gating problems, i.e. in schizophrenia. This study aims to enlighten the role of orexinergic regulation on PPI in a psychosis-like model.

OBJECTIVES

In order to understand the impact of orexinergic innervation on PPI and how it is modulated by age and baseline PPI (bPPI), chronic orexin A (OXA) injections was carried on non-sleep-deprived and sleep-deprived rats that are grouped by their bPPI.

METHODS

bPPI measurements were carried on male Wistar rats on P45 or P90 followed by grouping into low-PPI and high-PPI rats. The rats were injected with OXA twice per day for four consecutive days starting on P49 or P94, while the control groups received saline injections. 72 h REMSD was carried on via modified multiple platform technique on P94 and either OXA or saline was injected during REMSD. PPI tests were carried out 30 min. after the last injection.

RESULTS

Our previous study with acute OXA injection after REMSD without bPPI grouping revealed that low OXA doses might improve REMSD-induced PPI impairment. Our current results present three important conclusions: (1) The effect of OXA on PPI is bPPI-dependent and age-dependent. (2) The effect of REMSD is bPPI-dependent. (3) The effect of OXA on PPI after REMSD also depends on bPPI.

CONCLUSION

Orexinergic regulation of PPI response with and without REMSD can be predicted by bPPI levels. Our findings provide potential insights into the regulation of sensorimotor gating by sleep/wakefulness systems and present potential therapeutic targets for the disorders, where PPI is disturbed.

Evaluation of Peripheral Blood Concentrations of Phoenixin, Spexin, Nesfatin-1 and Kisspeptin as Potential Biomarkers of Bipolar Disorder in the Pediatric Population

There are some initial suggestions in the literature that phoenixin, spexin, nesfatin-1 and kisspeptin may play a role in the pathogenesis of affective disorders. Therefore, they may also be cautiously considered as potential diagnostic or predictive biomarkers of BD. This study aimed to evaluate the levels of the aforementioned neuropeptides in the peripheral blood of children and adolescents with bipolar. This study included 122 individuals: 67 persons with diagnosed bipolar disorder types I and II constituted the study group, and 55 healthy persons were included in the control group. Statistically significant differences in the concentrations of neuropeptides between the control and study groups were noted in relation to nesfatin-1 and spexin (although spexin lost statistical significance after introducing the Bonferroni correction). In a logistic regression analysis, an increased risk of bipolar disorder was noted for a decrease in nesfatin-1 concentration. Lower levels of nesfatin-1 seemed to be a significant risk factor for the development of bipolar disorder types I and II. Furthermore, the occurrence of bipolar disorder was associated with significantly elevated levels of spexin. None of the analyzed neuropeptides was significantly correlated with the number of symptoms of bipolar disorder.

Association between peripheral orexin A/B levels and depression with childhood trauma

BACKGROUND

Orexin dysfunction has previously been demonstrated to be associated with depression. However, no studies reported the different effects of orexin A/B on depression with and without childhood trauma (CT). In this study，we assessed the correlation between expression of orexin A/B and depression severity in major depressive disorder (MDD) patients and healthy controls.

METHODS

A total of 97 MDD patients and 51 healthy controls were recruited in this study. According to the total scores of childhood trauma questionnaire (CTQ), the MDD patients were further divided into two subgroups, MDD with CT and MDD without CT. The 17-item Hamilton Depression Scale (HAMD-17), and plasma orexin A and orexin B concentrations were measured in all participants using enzyme-linked immunosorbent assay.

RESULTS

Orexin B plasma levels were significantly higher in MDD patients with CT and without CT than that in the healthy control group (P < 0.05), whereas there was no statistical difference between the two depression groups. After adjusting age and BMI for covariates, the LASSO regression revealed significant association between the plasma orexin B levels and the total scores of HAMD (β = 3.348), CTQ (β = 2.005). There was no difference in plasma orexin A levels among three groups (P > 0.05).

CONCLUSIONS

Although peripheral orexin B levels are associated with the depression, rather than orexin A, CT appear to play a role in the association between orexin B levels and depression. China Clinical Trial Registration Center (Registration No.: ChiCTR2000039692).

Decreased plasma neuropeptides in first-episode schizophrenia, bipolar disorder, major depressive disorder: associations with clinical symptoms and cognitive function

Background

There is an urgent need to identify differentiating and disease-monitoring biomarkers of schizophrenia, bipolar disorders (BD), and major depressive disorders (MDD) to improve treatment and management.

Methods

We recruited 54 first-episode schizophrenia (FES) patients, 52 BD patients, 35 MDD patients, and 54 healthy controls from inpatient and outpatient clinics. α-Melanocyte Stimulating Hormone (α-MSH), β-endorphin, neurotensin, orexin-A, oxytocin, and substance P were investigated using quantitative multiplex assay method. Psychotic symptoms were measured using the Brief Psychiatric Rating Scale (BPRS) and Positive and Negative Syndrome Scale (PANSS), manic symptoms using the Young Mania Rating Scale (YMRS), and depressive symptoms using 17 item-Hamilton Depression Rating Scale (HAMD). We additionally measured cognitive function by using a battery of tests given to all participants.

Results

α-MSH, neurotensin, orexin-A, oxytocin, and substance P were decreased in the three patient groups compared with controls. Neurotensin outperformed all biomarkers in differentiating patient groups from controls. There were no significant differences for 6 neuropeptides in their ability to differentiate between the three patient groups. Higher neurotensin was associated with better executive function across the entire sample. Lower oxytocin and higher substance p were associated with more psychotic symptoms in FES and BD groups. β-endorphin was associated with early morning wakening symptom in all three patient groups.

Conclusion

Our research shows decreased circulating neuropeptides have the potential to differentiate severe mental illnesses from controls. These neuropeptides are promising treatment targets for improving clinical symptoms and cognitive function in FES, BD, and MDD.

Nasal administration of orexin A partially rescues dizocilpine-induced cognitive impairments in female C57BL/6J mice

Sex difference has been reported in several behavioural endophenotypes of neuropsychiatric disorder in both rodents and humans. However, sex difference in cognitive symptoms associated with neuropsychiatric disorders has not been studied in detail. In this study, we induced cognitive impairment using the NMDA receptor antagonist, dizocilpine (MK-801), in male and female C57BL/6J mice and performed a visual discrimination task in an automated touchscreen system. We found that discrimination performance decreased with increased doses of MK-801 in both sexes. However, female mice showed stronger deficit in discrimination performance than the male mice especially after administration of low (0.01mg/kg) and high (0.15mg/kg) doses of MK-801. Furthermore, we tested if administration of orexin A, orexin-1 receptor antagonist SB-334867 or orexin-2 receptor antagonist EMPA rescued MK-801 (0.15mg/kg) induced cognitive impairment in visual discrimination. We found that nasal administration of orexin A partially rescued the cognitive impairment induced by MK-801 in females but not in males. Taken together, our data show that female C57BL/6J mice are more sensitive compared to males to some doses of MK-801 in discrimination learning task and that orexin A partially rescues this cognitive impairment in females.

Targeting the orexin/hypocretin system for the treatment of neuropsychiatric and neurodegenerative diseases: from animal to clinical studies

Orexins (also known as hypocretins) are neuropeptides located exclusively in hypothalamic neurons that have extensive projections throughout the central nervous system and bind two different G protein-coupled receptors (OX1R and OX2R). Since its discovery in 1998, the orexin system has gained the interest of the scientific community as a potential therapeutic target for the treatment of different pathological conditions. Considering previous basic science research, a dual orexin receptor antagonist, suvorexant, was the first orexin agent to be approved by the US Food and Drug Administration to treat insomnia. In this review, we discuss and update the main preclinical and human studies involving the orexin system with several psychiatric and neurodegenerative diseases. This system constitutes a nice example of how basic scientific research driven by curiosity can be the best route to the generation of new and powerful pharmacological treatments.

Associations between daytime and nighttime plasma orexin A levels and cognitive function in patients with obstructive sleep apnea

The relationship between plasma orexin A (OXA) levels and cognitive function in patients with obstructive sleep apnea (OSA) remains unclear. This study aimed to evaluate associations between daytime and nighttime plasma OXA levels and cognitive function in patients with OSA. Subjects with suspected OSA underwent overnight polysomnography (PSG), Montreal Cognitive Assessment (MoCA), and Epworth Sleepiness Scale (ESS) assessment. Subjects were considered controls or having OSA according to the apnea-hypopnea index (AHI). Daytime and nighttime plasma OXA levels were determined by ELISA. Receiver-operating characteristics curves were used to evaluate the diagnostic value of plasma OXA levels for assessing cognitive impairment in OSA patients. One hundred and six subjects met the inclusion criteria. MoCA scores and plasma OXA concentrations were significantly lower in OSA patients than controls (p < 0.01). Patients with moderate and severe OSA had significantly lower MoCA scores than controls and mild OSA patients (p < 0.01). Daytime and nighttime OXA levels were significantly lower in OSA patients with cognitive impairment than those without cognitive impairment (p < 0.01). Both daytime and nighttime plasma OXA levels in patients with OSA were positively correlated with MoCA scores and nadir SaO2, negatively correlated with AHI, oxygen desaturation index, and percentage of time spent with an SaO2 below 90% (all p < 0.05), and not correlated with ESS scores. The optimal threshold of daytime plasma OXA to diagnose OSA with cognitive impairment was 49.34 pg/ml, with a sensitivity of 80.0% and a specificity of 74.3%. We concluded that plasma OXA concentrations might be related to cognitive function and daytime plasma OXA levels have diagnostic value for assessing cognitive impairment in OSA patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-022-00387-4.

Orexin-a elevation in antipsychotic-treated compared to drug-free patients with schizophrenia: A medication effect independent of metabolic syndrome

BACKGROUND/PURPOSE

Orexin-A levels are reportedly increased in antipsychotic (APD)-treated patients with schizophrenia compared to healthy controls and have been associated with metabolic abnormalities. It is not clear whether the orexin-A elevation is related specifically to the drug (APDs) effect, which should be clarified by including a drug-free group for comparison, or related to drug-induced metabolic abnormalities.

METHODS

Blood orexin-A levels and metabolic profiles were compared between 37 drug-free, 45 aripiprazole-treated, and 156 clozapine-treated patients with schizophrenia. The association between orexin-A and metabolic outcomes were examined. We explored the effects of APDs treatment and metabolic status on orexin-A levels by linear regression.

RESULTS

Patients under APDs treatment had increased orexin-A levels compared to drug-free patients, with aripiprazole-treated group having higher orexin-A levels than clozapine-treated group. Higher orexin-A levels reduced the risks of metabolic syndrome (MS) and type 2 diabetes mellitus, indicating a relationship between orexin-A levels and metabolic problems. After adjusting the effect from metabolic problems, we found APD treatment is still associated with orexin-A regulation, with aripiprazole more significantly than clozapine.

CONCLUSION

With the inclusion of drug-free patients rather than healthy controls for comparison, we demonstrated that orexin-A is upregulated following APD treatment even after we controlled the potential effect from MS, suggesting an independent effect of APDs on orexin-A levels. Furthermore, the effect differed between APDs with dissimilar obesogenicity, i.e. less obesogenicity likely associated with higher orexin-A levels. Future prospective studies exploring the causal relationship between APDs treatment and orexin-A elevation as well as the underlying mechanisms are warranted.

The role of neuropeptide Y, orexin-A, and ghrelin in differentiating unipolar and bipolar depression: a preliminary study

BACKGROUND

When depressive symptoms in bipolar and unipolar patients were compared, a number of studies reported that atypical vegetative features such as hypersomnia and hyperphagia were more common in bipolar patients. Moreover, neuropeptides such as orexin-A (ORX-A), ghrelin (GRL), and neuropeptide Y (NPY) are involved in the regulation of these vegetative functions.

MATERIALS AND METHODS

A total of 45 unipolar and 24 bipolar depressive patients, and 36 euthymic healthy controls were included in the study. The groups were compared in terms of peripheral blood samples of ORX-A, GRL, and NPY levels, as well as HAM-D, Epworth Sleepiness Scale, Three-Factor Eating Questionnaire-Revised, and Suicide Probability Scale scores.

RESULTS

Both unipolar and bipolar patients had lower ORX-A, GRL, and NPY levels compared to the controls, whereas NPY levels of bipolar patients were lower than unipolar patients. There was a negative correlation between NPY levels and emotional eating in the bipolar group.

CONCLUSION

While lower ORX-A, GRL, and NPY levels are associated with depressive episodes regardless of the diagnosis; NPY levels also differ in bipolar and unipolar depression patients.

Narcolepsy-like symptoms triggered by lemborexant in the context of hyperactive delirium in a patient with bipolar depression: a case report

Lemborexant is a dual orexin antagonist (DORA) and is considered a safe and effective hypnotic. DORAs induce physiological sleep by blocking orexin receptors. Although the blockade of orexin signaling has triggered narcolepsy-like symptoms in rodents, there is currently no evidence of lemborexant inducing narcolepsy-like symptoms in humans. We describe the case of a 79-year-old Japanese woman with bipolar depression who experienced lemborexant-induced cataplexy and sleep attack. Her previous results on the Multiple Sleep Latency Test excluded the diagnosis of narcolepsy. She experienced narcolepsy-like symptoms on two occasions after she was administered lemborexant, in the context of hyperactive delirium, but not in a relaxed state. Her case suggests that lemborexant could trigger narcolepsy-like symptoms in patients with hyperactive delirium, even those with no history of narcolepsy. This case also emphasizes that clinicians must be very careful when they prescribe lemborexant to patients who experience hyperactive delirium.

Orexin/Hypocretin System Dysfunction in ESSENCE (Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations)

Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations (ESSENCE) is an umbrella term covering a wide range of neurodevelopmental difficulties and disorders. Thus, ESSENCE includes attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and other neurodevelopmental disorders (NDDs) and difficulties, with a variety of symptoms in cognitive, motor, sensory, social, arousal, regulatory, emotional, and behavioral developmental domains, frequently co-occurring and likely having partly common neurobiological substrates. The ESSENCE concept is a clinical paradigm that promotes organizing NDDs in everyday clinical practice according to their coexistence, symptom dimensions overlapping, and treatment possibilities. Despite increased knowledge regarding NDDs, the neurobiological mechanisms that underlie them and other ESSENCE-related problems, are not well understood. With its wide range of neural circuits and interactions with numerous neurotransmitters, the orexin/hypocretin system (Orx-S) is possibly associated with a variety of neurocognitive, psychobiological, neuroendocrine, and physiological functions and behaviors. Dysfunction of Orx-S has been implicated in various psychiatric and neurological disorders. This article provides an overview of Orx-S dysfunctions' possible involvement in the development, presentation, and maintenance of ESSENCE. We provide a focused review of current research evidence linking orexin neuropeptides with specific clinical NDDs symptoms, mostly in ADHD and ASD, within the Research Domain Criteria (RDoC) framework. We propose that Orx-S dysfunction might have an important role in some of these neurodevelopmental symptom domains, such as arousal, wakefulness, sleep, motor and sensory processing, mood and emotional regulation, fear processing, reward, feeding, attention, executive functions, and sociability. Our perspective is presented from a clinical point of view. Further, more thorough systematic reviews are needed as well as planning of extensive new research into the Orx-S's role in ESSENCE, especially considering RDoC elements.

Plasma Orexin-A Levels in Patients With Schizophrenia: A Systematic Review and Meta-Analysis

BACKGROUND

Orexins are polypeptides regulating appetite, sleep-wake cycle, and cognition functions, which are commonly disrupted in patients with schizophrenia. Patients with schizophrenia show a decreased connectivity between the prefrontal cortex and midline-anterior thalamus, and orexin can directly activate the axon terminal of cells within the prefrontal cortex and selectively depolarize neurons in the midline intralaminar nuclei of the thalamus. To address the relationship between orexin and schizophrenia, this study performed a meta-analysis on the alteration of plasma orexin-A levels in patients with schizophrenia.

METHOD

We searched eligible studies in PubMed, Embase, Cochrane, and China National Knowledge Infrastructure (CNKI) from 1998 to September 3, 2021. A total of 8 case-control studies were included in the meta-analyses, providing data on 597 patients with schizophrenia and 370 healthy controls. The Stata version 16.0 software was used to calculate the Hedges's adjusted g with 95% confidence intervals (CI).

RESULTS

The plasma orexin-A levels were not altered in subjects with schizophrenia (n = 597) when compared to healthy controls (n = 370). Subgroup analyses of gender (male and female vs. only male), country (China vs. other countries), medication (medication vs. non-medication), and the measurement of plasma orexin-A (Enzyme-linked immunosorbent assay vs. radioimmunoassay) revealed heterogeneity ranging from 30.15 to 98.15%, but none showed a significant alteration of plasma orexin-A levels in patients with schizophrenia. Heterogeneity was lower in the other countries and radioimmunoassay subgroup, while other subgroups remained to be highly heterogeneous. No significant evidence of publication bias was found either in Begg's test or the Egger's test.

CONCLUSION

The present meta-analysis indicated that patients with schizophrenia did not show abnormal plasma levels of orexin-A.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021283455, identifier: CRD42021283455.

Circadian Rhythms of the Hypothalamus: From Function to Physiology

The nearly ubiquitous expression of endogenous 24 h oscillations known as circadian rhythms regulate the timing of physiological functions in the body. These intrinsic rhythms are sensitive to external cues, known as zeitgebers, which entrain the internal biological processes to the daily environmental changes in light, temperature, and food availability. Light directly entrains the master clock, the suprachiasmatic nucleus (SCN) which lies in the hypothalamus of the brain and is responsible for synchronizing internal rhythms. However, recent evidence underscores the importance of other hypothalamic nuclei in regulating several essential rhythmic biological functions. These extra-SCN hypothalamic nuclei also express circadian rhythms, suggesting distinct regions that oscillate either semi-autonomously or independent of SCN innervation. Concurrently, the extra-SCN hypothalamic nuclei are also sensitized to fluctuations in nutrient and hormonal signals. Thus, food intake acts as another powerful entrainer for the hypothalamic oscillators' mediation of energy homeostasis. Ablation studies and genetic mouse models with perturbed extra-SCN hypothalamic nuclei function reveal their critical downstream involvement in an array of functions including metabolism, thermogenesis, food consumption, thirst, mood and sleep. Large epidemiological studies of individuals whose internal circadian cycle is chronically disrupted reveal that disruption of our internal clock is associated with an increased risk of obesity and several neurological diseases and disorders. In this review, we discuss the profound role of the extra-SCN hypothalamic nuclei in rhythmically regulating and coordinating body wide functions.

Increased Hypocretin (Orexin) Plasma Level in Depression, Bipolar Disorder Patients

As hypocretin can markedly affect neurophysiological and behavioural processes in mood disorders. However, few studies have measured changes in hypocretin levels in patients with mood disorders. We estimated the hypocretin-1 plasma levels in mood disorder patients and controls (CON) using an enzyme-linked immunosorbent assay. Results: (i) The hypocretin-1 plasma level was significantly higher in major depressive disorder (MDD) patients [59.04 (35.78-80.12) pg/ml, P < 0.001] and bipolar disorder (BD) patients [65.50 (58.46-74.57) pg/ml, P < 0.001] patients than in CON [49.25 (28.51-80.40) pg/ml]. Moreover, the plasma hypocretin-1 levels in the BD group were significantly higher than those in the MDD group (P < 0.001). (ii). In the MDD group, patients with higher suicidal ideation had higher hypocretin-1 levels [62.09 (38.23-80.12) pg/ml] than those with lower suicidal ideation [59.63 (35.79-77.37) pg/ml), P = 0.032]. (iii). Plasma hypocretin-1 levels were increased in both female and male mood disorder patients compared to CON [male: MDD 60.51 (35.79-80.12) pg/ml; BD 65.40 (58.76-74.14) pg/ml; CON 45.63 (28.51-62.05) pg/ml; all P < 0.016; female: MDD 57.37 (34.59-80.40) pg/ml; BD 65.61 (58.46-74.57) pg/ml; CON 52.92 (38.23-78.89) pg/ml; all P < 0.015]. (iv). In CON, we found a significant negative correlation between plasma hypocretin-1 levels and age (rho = -0.251, P = 0.032), while this negative correlation was absent in the MDD and BD groups. Limitations may partly arise from the relatively small sample size and the medication history of patients participating in our research. We concluded that the clear changes found in plasma hypocretin-1 levels might be applied in the diagnosis of depression and the differential diagnosis of MDD and BD. The clear suicidal-ideation-related change found in hypocretin-1 levels in depression might be taken into account in the prevention of suicidal behaviour and further study of hypocretin-targeted therapies.

A higher body mass index in Chinese inpatients with chronic schizophrenia is associated with elevated plasma orexin-A levels and fewer negative symptoms

Objective: Orexin-A is involved in numerous physiological functions, such as feeding behavior and energy balance. Yet, the associations among the orexin system, weight changes and the clinical symptoms of schizophrenia patients remain uncertain, especially in inpatients with chronic schizophrenia (CS). The purpose of this study was to investigate the relationship between the orexin-A levels, body mass index (BMI) and clinical symptoms of CS inpatients.Methods: Altogether, 324 inpatients were enrolled in our study. The clinical symptoms of all inpatients were measured using a 30-item Positive and Negative Syndrome Scale (PANSS), and then we calculated the BMI of each subject and tested the orexin-A levels by ELISA methods.Results: The orexin-A levels of the CS inpatients in the obesity group (1.24 ± 1.45 ng/ml, n = 52) were significantly higher than those in the non-overweight group (0.85 ± 1.18 ng/ml, n = 176) and the overweight group (0.97 ± 1.15 ng/ml, n = 96). Spearman's correlation analysis showed that higher BMIs were associated with higher plasma orexin-A levels and fewer negative symptoms. Furthermore, the multiple regression analysis indicated that the orexin-A level could be a contributor to BMI (F = 30.21, p < 0.001). However, there was no correlation between plasma orexin-A concentrations and clinical symptoms in our research.Conclusion: A higher plasma orexin-A level may be a factor influencing the BMI of inpatients with CS, and fewer negative symptoms seem to be correlated with higher BMI, but the causality among BMI, orexin-A and clinical symptoms of schizophrenia requires further clinical research.

Significance of determining plasma orexin levels and analysis of related factors for the diagnosis of patients with narcolepsy

OBJECTIVES

Decreased cerebrospinal fluid (CSF) orexin levels are one of the diagnostic and classification criteria for narcolepsy. Because of the difficulty in obtaining CSF, its clinical application is limited. Here, we aimed to confirm the significance of determining plasma orexin levels in the diagnosis and treatment of narcolepsy by comparing the differences in these levels between narcolepsy patients and healthy controls and analyzing related factors.

METHODS

Twenty-four patients with type I narcolepsy who visited our hospital from October 2017 to January 2020 and who met the relevant inclusion and exclusion criteria were selected. Simultaneously, healthy controls with matched basic characteristics were selected at a 1:1 proportion. Patient basic information was collected, the Epworth Sleepiness Scale was recorded, the nocturnal polysomnogram and multiple sleep latency test were performed, and the patients' electrophysiological characteristics were analyzed. The blood samples of the patient and control groups were collected and stored at -80°Caftercentrifugation. Plasma orexin levels were determined by ELISA, following which the results of the two groups were compared, and the relevant factors were analyzed.

RESULTS

Our results revealed significantly lower plasma orexin levels in the narcolepsy patients compared to in healthy subjects. There were no correlations between plasma orexin levels and sex, age, body mass index, disease duration, and the severity of sleepiness, and between plasma orexin levels and electrophysiological indicators, including mean sleep latency and sleep-onset rapid eye movement periods.

CONCLUSIONS

Determining plasma orexin levels has the potential to replace the detection of CSF orexin levels.