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Kobayashi I, Forcelli PA. The effects of a dual orexin receptor antagonist on fear extinction memory and sleep in mice: Implications for exposure therapy. Behav Brain Res 2024; 458:114741. [PMID: 37931704 PMCID: PMC10841840 DOI: 10.1016/j.bbr.2023.114741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 10/18/2023] [Accepted: 11/01/2023] [Indexed: 11/08/2023]
Abstract
Extinction of conditioned fear is considered a fundamental process in the recovery from posttraumatic stress disorder and anxiety disorders. Sleep, especially rapid-eye-movement (REM) sleep, has been implicated in promoting extinction memory. The orexin system contributes to the regulation of sleep and wakefulness and emotional behaviors. In rodents, administrations of an orexin receptor antagonist following fear extinction training enhanced consolidation of extinction memory. Although orexin antagonists increase sleep, including REM sleep, the possible contribution of sleep to the effects of orexin antagonists on extinction memory has not been examined. Therefore, this study examined the effects of suvorexant, a dual orexin receptor antagonist, on extinction memory and sleep and their associations in mice. C57BL/6 mice underwent sleep recording for 24 h before and after contextual fear conditioning with footshocks and extinction learning during the early light phase or early dark phase. Mice were systemically injected with either 25 mg/kg of suvorexant or vehicle immediately after the extinction session. We found that suvorexant neither altered sleep nor improved extinction memory recall compared with vehicle. The higher percentages of REM sleep during the post-extinction dark phase were associated with lower extinction memory recall and greater freezing responses to the fear context. Results also indicate that animals did not reach complete extinction of fear with the fear extinction training protocol used in this study. These findings suggest that promoting REM sleep may not enhance fear extinction memory when extinction of fear is incomplete.
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Affiliation(s)
- Ihori Kobayashi
- Howard University College of Medicine, 520 W St. NW, Washington, DC 20059, USA.
| | - Patrick A Forcelli
- Georgetown University School of Medicine, 3970 Reservoir Rd NW, Washington, DC 20007, USA
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Sex-dependent role of orexin deficiency in feeding behavior and affective state of mice following intermittent access to a Western diet - Implications for binge-like eating behavior. Physiol Behav 2023; 260:114069. [PMID: 36572152 DOI: 10.1016/j.physbeh.2022.114069] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 12/02/2022] [Accepted: 12/22/2022] [Indexed: 12/24/2022]
Abstract
Binge eating disorder is a debilitating disease characterized by recurrent episodes of excessive food consumption and associated with psychiatric comorbidities. Despite a growing body of research investigating the neurobiological underpinnings of eating disorders, specific treatments are lacking. Given its fundamental role in feeding behaviors, we investigated the role of the orexin (hypocretin) neuropeptide system in binge-like eating and associated phenotypes. Specifically, we submitted female and male orexin-deficient mice to a paradigm of intermittent access (once weekly for 24 h) to a Western diet (WD) to induce binge-like eating. Additionally, we measured their anxiety-like behavior and plasma corticosterone levels. All mice showed binge-like eating in response to the intermittent WD access, but females did so to a greater extent than males. While orexin deficiency did not affect binge-like eating in this paradigm, we found that female orexin-deficient mice generally weighed more, and they expressed increased hypophagia and stress levels compared to wild-type mice following binge-like eating episodes. These detrimental effects of orexin deficiency were marginal or absent in males. Moreover, male wild-type mice expressed post-binge anxiety, but orexin-deficient mice did not. In conclusion, these results extend our knowledge of orexin's role in dysregulated eating and associated negative affective states, and contribute to the growing body of evidence indicating a sexual dimorphism of the orexin system. Considering that many human disorders, and especially eating disorders, have a strong sex bias, our findings further emphasize the importance of testing both female and male subjects.
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Gao X, Lyu M, Zhang M, Lin S, Ke C. Structural characteristics of orexin receptor type 2 in Pacific abalone and its diurnal expression pattern after fasting and re-feeding. Int J Biol Macromol 2023; 229:873-884. [PMID: 36587646 DOI: 10.1016/j.ijbiomac.2022.12.313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 12/26/2022] [Accepted: 12/27/2022] [Indexed: 12/30/2022]
Abstract
Pacific abalone (Haliotis discus hannai) is a typical nocturnal organism. To examine the circadian expression pattern of orexin receptor type 2 (OX2R) and its potential effect on the feeding behavior of abalone, the coding region sequence of OX2R that is 1215 bp in length and encodes 404 amino acids was first cloned using the rapid amplification of cDNA ends technique. A recombinant expression vector was constructed for H. discus hannai based on the OX2R protein, obtaining a recombinant protein with a molecular weight of 46 kDa. Polyclonal antibody was prepared with the purified recombinant protein used as the antigen, and the antibody titer of ≥512 K was detected by enzyme-linked immunosorbent assay. The expression levels of OX2R determined using western blotting were highest in the intestinal tract (P < 0.05), but they were not significantly different from the levels in the pedal. Immunofluorescence experiments affirmed that OX2R was widely expressed in the columnar cells of the intestinal mucosal epithelium. To further account for the relationship between the onset of feeding behavior and the expression level of OX2R in abalone, the circadian expression characteristics of OX2R were analyzed by dissecting the intestinal tissues after three days of normal feeding and fasting and following the refeeding treatment. The expression levels of OX2R in the refeeding group were significantly higher than those in the normal feeding and fasting groups at any time point (P < 0.05). The cosine curve analysis revealed that the expression levels of OX2R lost rhythmicity after fasting. Based on the quantification of behavioral data for abalone after fasting and refeeding, the cumulative movement distance and movement duration in each group followed a significant cosine rhythm (P < 0.05), which is consistent with abalone's nocturnal ecological habits. However, the cumulative movement distance and movement duration in the fasting group were significantly lower than those in the normal feeding and refeeding groups (P < 0.05). The peak phases of the cumulative movement distance and movement duration in the refeeding group (ZT08:22 and ZT08:44) shifted backward compared to the normal feeding group (ZT07:33 and ZT07:39). The above results first identified the structural characteristics and circadian expression patterns of OX2R in the marine mollusk abalone, which may reveal the molecular mechanism behind the generation of a feeding rhythm in marine nocturnal organisms and serve as a tool helping to maintain the diversity of marine benthic resources.
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Affiliation(s)
- Xiaolong Gao
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Mingxin Lyu
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Mo Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Shihui Lin
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Caihuan Ke
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China.
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Christensen J, Li C, Mychasiuk R. Choroid plexus function in neurological homeostasis and disorders: The awakening of the circadian clocks and orexins. J Cereb Blood Flow Metab 2022; 42:1163-1175. [PMID: 35296175 PMCID: PMC9207490 DOI: 10.1177/0271678x221082786] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
As research regarding the role of circadian rhythms, sleep, and the orexinergic system in neurodegenerative diseases is growing, it is surprising that the choroid plexus (CP) remains underappreciated in this realm. Despite its extensive role in the regulation of circadian rhythms and orexinergic signalling, as well as acting as the primary conduit between cerebrospinal fluid (CSF) and the circulatory system, providing a mechanism by which toxic waste molecules can be removed from the brain, the CP has been largely unexplored in neurodegeneration. In this review, we explore the role of the CP in maintaining brain homeostasis and circadian rhythms, regulating CSF dynamics, and how these functions change across the lifespan, from development to senescence. In addition, we examine the relationship between the CP, orexinergic signalling, and the glymphatic system, highlighting gaps in the literature and areas that require immediate exploration. Finally, we assess current knowledge, including possible therapeutic strategies, regarding the role of the CP in neurological disorders, such as traumatic brain injury, migraine, Alzheimer's disease, and multiple sclerosis.
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Affiliation(s)
- Jennaya Christensen
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Crystal Li
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Richelle Mychasiuk
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
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Lonstein JS, Linning-Duffy K, Tang Y, Moody A, Yan L. Impact of daytime light intensity on the central orexin (hypocretin) system of a diurnal rodent (Arvicanthis niloticus). Eur J Neurosci 2021; 54:4167-4181. [PMID: 33899987 DOI: 10.1111/ejn.15248] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 04/14/2021] [Accepted: 04/17/2021] [Indexed: 11/29/2022]
Abstract
The neuropeptide orexin/hypocretin is implicated in sleep and arousal, energy expenditure, reward, affective state and cognition. Our previous work using diurnal Nile grass rats (Arvicanthis niloticus) found that orexin mediates the effects of environmental light, particularly daytime light intensity, on affective and cognitive behaviours. The present study further investigated how daytime light intensity affects the central orexin system in male and female grass rats. Subjects were housed for 4 weeks in 12:12 hr dim light:dark (50 lux, dimLD) or in 12:12 hr bright light:dark cycle (1000 lux, brightLD). Day/night fluctuations in some orexin measures were also assessed. Despite similar hypothalamic prepro-orexin mRNA expression across all conditions, there were significantly more orexin-immunoreactive neurons, larger somata, greater optical density or higher orexin A content at night (ZT14) than during the day (ZT2), and/or in animals housed in brightLD compared to dimLD. Grass rats in brightLD also had higher cisternal CSF levels of orexin A. Furthermore, orexin receptor OX1R and OX2R proteins in the medial prefrontal cortex were higher in brightLD than dimLD males, but lower in brightLD than dimLD females. In the CA1 and dorsal raphe nucleus, females had higher OX1R than males without any significant effects of light condition, and OX2R levels were unaffected by sex or light. These results reveal that daytime light intensity alters the central orexin system of both male and female diurnal grass rats, sometimes sex-specifically, and provides insight into the mechanisms underlying how daytime light intensity impacts orexin-regulated functions.
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Affiliation(s)
- Joseph S Lonstein
- Department of Psychology, Michigan State University, East Lansing, MI, USA
- Neuroscience Program, Michigan State University, East Lansing, MI, USA
| | - Katrina Linning-Duffy
- Department of Psychology, Michigan State University, East Lansing, MI, USA
- Neuroscience Program, Michigan State University, East Lansing, MI, USA
| | - Yuping Tang
- Department of Psychology, Michigan State University, East Lansing, MI, USA
- Neuroscience Program, Michigan State University, East Lansing, MI, USA
| | - Anna Moody
- Department of Psychology, Michigan State University, East Lansing, MI, USA
| | - Lily Yan
- Department of Psychology, Michigan State University, East Lansing, MI, USA
- Neuroscience Program, Michigan State University, East Lansing, MI, USA
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Beuckmann CT, Suzuki H, Musiek ES, Ueno T, Sato T, Bando M, Osada Y, Moline M. Evaluation of SAMP8 Mice as a Model for Sleep-Wake and Rhythm Disturbances Associated with Alzheimer's Disease: Impact of Treatment with the Dual Orexin (Hypocretin) Receptor Antagonist Lemborexant. J Alzheimers Dis 2021; 81:1151-1167. [PMID: 33843668 PMCID: PMC8293654 DOI: 10.3233/jad-201054] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Background: Many patients with Alzheimer’s disease (AD) display circadian rhythm and sleep-wake disturbances. However, few mouse AD models exhibit these disturbances. Lemborexant, a dual orexin receptor antagonist, is under development for treating circadian rhythm disorders in dementia. Objective: Evaluation of senescence-accelerated mouse prone-8 (SAMP8) mice as a model for sleep-wake and rhythm disturbances in AD and the effect of lemborexant by assessing sleep-wake/diurnal rhythm behavior. Methods: SAMP8 and control senescence-accelerated mouse resistant-1 (SAMR1) mice received vehicle or lemborexant at light onset; plasma lemborexant and diurnal cerebrospinal fluid (CSF) orexin concentrations were assessed. Sleep-wake behavior and running wheel activity were evaluated. Results: Plasma lemborexant concentrations were similar between strains. The peak/nadir timing of CSF orexin concentrations were approximately opposite between strains. During lights-on, SAMP8 mice showed less non-rapid eye movement (non-REM) and REM sleep than SAMR1 mice. Lemborexant treatment normalized wakefulness/non-REM sleep in SAMP8 mice. During lights-off, lemborexant-treated SAMR1 mice showed increased non-REM sleep; lemborexant-treated SAMP8 mice displayed increased wakefulness. SAMP8 mice showed differences in electroencephalogram architecture versus SAMR1 mice. SAMP8 mice exhibited more running wheel activity during lights-on. Lemborexant treatment reduced activity during lights-on and increased activity in the latter half of lights-off, demonstrating a corrective effect on overall diurnal rhythm. Lemborexant delayed the acrophase of activity in both strains by approximately 1 hour. Conclusion: SAMP8 mice display several aspects of sleep-wake and rhythm disturbances in AD, notably mistimed activity. These findings provide some preclinical rationale for evaluating lemborexant in patients with AD who experience sleep-wake and rhythm disturbances.
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Affiliation(s)
| | | | - Erik S Musiek
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA
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Ventzke K, Oster H, Jöhren O. Diurnal Regulation of the Orexin/Hypocretin System in Mice. Neuroscience 2019; 421:59-68. [DOI: 10.1016/j.neuroscience.2019.10.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 09/17/2019] [Accepted: 10/01/2019] [Indexed: 01/10/2023]
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Abstract
Feeding, which is essential for all animals, is regulated by homeostatic mechanisms. In addition, food consumption is temporally coordinated by the brain over the circadian (~24 h) cycle. A network of circadian clocks set daily windows during which food consumption can occur. These daily windows mostly overlap with the active phase. Brain clocks that ensure the circadian control of food intake include a master light-entrainable clock in the suprachiasmatic nuclei of the hypothalamus and secondary clocks in hypothalamic and brainstem regions. Metabolic hormones, circulating nutrients and visceral neural inputs transmit rhythmic cues that permit (via close and reciprocal molecular interactions that link metabolic processes and circadian clockwork) brain and peripheral organs to be synchronized to feeding time. As a consequence of these complex interactions, growing evidence shows that chronodisruption and mistimed eating have deleterious effects on metabolic health. Conversely, eating, even eating an unbalanced diet, during the normal active phase reduces metabolic disturbances. Therefore, in addition to energy intake and dietary composition, appropriately timed meal patterns are critical to prevent circadian desynchronization and limit metabolic risks. This Review provides insight into the dual modulation of food intake by homeostatic and circadian processes, describes the mechanisms regulating feeding time and highlights the beneficial effects of correctly timed eating, as opposed to the negative metabolic consequences of mistimed eating.
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Affiliation(s)
- Etienne Challet
- Circadian clocks and metabolism team, Institute of Cellular and Integrative Neurosciences, Centre National de la Recherche Scientifique (CNRS), University of Strasbourg, Strasbourg, France.
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Aras E, Ramadori G, Kinouchi K, Liu Y, Ioris RM, Brenachot X, Ljubicic S, Veyrat-Durebex C, Mannucci S, Galié M, Baldi P, Sassone-Corsi P, Coppari R. Light Entrains Diurnal Changes in Insulin Sensitivity of Skeletal Muscle via Ventromedial Hypothalamic Neurons. Cell Rep 2019; 27:2385-2398.e3. [DOI: 10.1016/j.celrep.2019.04.093] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 01/28/2019] [Accepted: 04/19/2019] [Indexed: 12/17/2022] Open
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Hypocretin/Orexin Peptides Excite Rat Neuroendocrine Dopamine Neurons through Orexin 2 Receptor-Mediated Activation of a Mixed Cation Current. Sci Rep 2017; 7:41535. [PMID: 28145492 PMCID: PMC5286397 DOI: 10.1038/srep41535] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 12/19/2016] [Indexed: 11/11/2022] Open
Abstract
Hypocretin/Orexin (H/O) neurons of the lateral hypothalamus are compelling modulator candidates for the chronobiology of neuroendocrine output and, as a consequence, hormone release from the anterior pituitary. Here we investigate the effects of H/O peptides upon tuberoinfundibular dopamine (TIDA) neurons – cells which control, via inhibition, the pituitary secretion of prolactin. In whole cell recordings performed in male rat hypothalamic slices, application of H/O-A, as well as H/O-B, excited oscillating TIDA neurons, inducing a reversible depolarising switch from phasic to tonic discharge. The H/O-induced inward current underpinning this effect was post-synaptic (as it endured in the presence of tetrodotoxin), appeared to be carried by a Na+-dependent transient receptor potential-like channel (as it was blocked by 2-APB and was diminished by removal of extracellular Na+), and was a consequence of OX2R receptor activation (as it was blocked by the OX2R receptor antagonist TCS OX2 29, but not the OX1R receptor antagonist SB 334867). Application of the hormone, melatonin, failed to alter TIDA membrane potential or oscillatory activity. This first description of the electrophysiological effects of H/Os upon the TIDA network identifies cellular mechanisms that may contribute to the circadian rhythmicity of prolactin secretion.
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Shechter A. Effects of continuous positive airway pressure on energy balance regulation: a systematic review. Eur Respir J 2016; 48:1640-1657. [PMID: 27824596 PMCID: PMC5201109 DOI: 10.1183/13993003.00689-2016] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 08/12/2016] [Indexed: 11/05/2022]
Abstract
Obesity is both a cause and a possible consequence of obstructive sleep apnoea (OSA), as OSA seems to affect parameters involved in energy balance regulation, including food intake, hormonal regulation of hunger/satiety, energy metabolism and physical activity. It is known that weight loss improves OSA, yet it remains unclear why continuous positive airway pressure (CPAP) often results in weight gain.The goal of this systematic review is to explore if and how CPAP affects the behaviour and/or metabolism involved in regulating energy balance.CPAP appears to correct for a hormonal profile characterised by abnormally high leptin and ghrelin levels in OSA, by reducing the circulating levels of each. This is expected to reduce excess food intake. However, reliable measures of food intake are lacking, and not yet sufficient to make conclusions. Although studies are limited and inconsistent, CPAP may alter energy metabolism, with reports of reductions in resting metabolic rate or sleeping metabolic rate. CPAP appears to not have an appreciable effect on altering physical activity levels. More work is needed to characterise how CPAP affects energy balance regulation.It is clear that promoting CPAP in conjunction with other weight loss approaches should be used to encourage optimal outcomes in OSA patients.
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Affiliation(s)
- Ari Shechter
- Department of Medicine, Columbia University, New York, NY, USA
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12
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Shechter A. Obstructive sleep apnea and energy balance regulation: A systematic review. Sleep Med Rev 2016; 34:59-69. [PMID: 27818084 DOI: 10.1016/j.smrv.2016.07.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 05/17/2016] [Accepted: 07/05/2016] [Indexed: 01/19/2023]
Abstract
Obesity and obstructive sleep apnea (OSA) have a reciprocal relationship. Sleep disruptions characteristic of OSA may promote behavioral, metabolic, and/or hormonal changes favoring weight gain and/or difficulty losing weight. The regulation of energy balance (EB), i.e., the relationship between energy intake (EI) and energy expenditure (EE), is complex and multi-factorial, involving food intake, hormonal regulation of hunger/satiety/appetite, and EE via metabolism and physical activity (PA). The current systematic review describes the literature on how OSA affects EB-related parameters. OSA is associated with a hormonal profile characterized by abnormally high leptin and ghrelin levels, which may encourage excess EI. Data on actual measures of food intake are lacking, and not sufficient to make conclusions. Resting metabolic rate appears elevated in OSA vs. CONTROLS Findings on PA are inconsistent, but may indicate a negative relationship with OSA severity that is modulated by daytime sleepiness and body weight. A speculative explanation for the positive EB in OSA is that the increased EE via metabolism induces an overcompensation in the drive for hunger/food intake, which is larger in magnitude than the rise in EI required to re-establish EB. Understanding how OSA affects EB-related parameters can help improve weight loss efforts in these patients.
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Affiliation(s)
- Ari Shechter
- New York Obesity Research Center, Department of Medicine, Columbia University, 1150 St. Nicholas Ave. Room 121, New York, NY 10032, United States.
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Zhou Y, Wong JM, Mabrouk OS, Kennedy RT. Reducing adsorption to improve recovery and in vivo detection of neuropeptides by microdialysis with LC-MS. Anal Chem 2015; 87:9802-9. [PMID: 26351736 PMCID: PMC5118035 DOI: 10.1021/acs.analchem.5b02086] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Neuropeptides are an important class of neurochemicals; however, measuring their concentration in vivo by using microdialysis sampling is challenging due to their low concentration and the small samples generated. Capillary liquid chromatography with mass spectrometry (cLC-MS) can yield attomole limits of detection (LOD); however, low recovery and loss of sample to adsorptive surfaces can still hinder detection of neuropeptides. We have evaluated recovery during sampling and transfer to the cLC column for a selection of 10 neuropeptides. Adding acetonitrile to sample eliminated carryover and improved LOD by 1.4- to 60-fold. The amount of acetonitrile required was found to have an optimal value that correlated with peptide molecular weight and retention time on a reversed phase LC column. Treating AN69 dialysis membrane, which bears negative charge due to incorporated sulfonate groups, with polyethylenimine (PEI) improved recovery by 1.2- to 80-fold. The effect appeared to be due to reducing electrostatic interaction between peptides and the microdialysis probe because modification increased recovery only for peptides that carried net positive charge. The combined effects improved LOD of the entire method by 1.3- to 800-fold for the different peptides. We conclude that peptides with both charged and hydrophobic regions require combined strategies to prevent adsorption and yield the best possible detection. The method was demonstrated by determining orexin A, orexin B, and a novel isoform of rat β-endorphin in the arcuate nucleus. Dialysate concentrations were below 10 pM for these peptides. A standard addition study on dialysates revealed that while some peptides can be accurately quantified, some are affected by the matrix.
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Affiliation(s)
- Ying Zhou
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055
| | - Jenny-Marie Wong
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055
| | - Omar S. Mabrouk
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055
| | - Robert T. Kennedy
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055
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Fang L, Zhou J, Cheng S, Ying J, Yang Z, Yin L, Li S, Hou W, Wang Z. High orexin-A neuron activity and RACK1 expression might be involved in the restricted feeding-entrained behaviors in mice. BIOL RHYTHM RES 2015. [DOI: 10.1080/09291016.2015.1004841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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15
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Willie JT, Lim MM, Bennett RE, Azarion AA, Schwetye KE, Brody DL. Controlled cortical impact traumatic brain injury acutely disrupts wakefulness and extracellular orexin dynamics as determined by intracerebral microdialysis in mice. J Neurotrauma 2013; 29:1908-21. [PMID: 22607167 DOI: 10.1089/neu.2012.2404] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Among other deficits, traumatic brain injury (TBI) causes impaired arousal and cognitive dysfunction. Hypothalamic orexin neuropeptides (also called hypocretins) regulate levels of arousal, and cerebrospinal fluid orexin levels are reportedly low in TBI patients. We hypothesized that TBI acutely impairs the dynamics of orexin release into brain interstitial fluid, and that these extracellular orexin levels correlate with wakefulness and motor activity. To test this in mice, we combined an electromagnetic controlled cortical impact (CCI) model of experimental TBI with dual intracerebral microdialysis using one catheter in the hypothalamus and one catheter in the hippocampus, plus electroencephalography/electromyography (EEG/EMG), and motor activity monitoring. Baseline data were continuously collected in tethered but relatively freely moving mice for 2 days. Then, ipsilateral CCI or sham surgery was performed, and data collection was continued for 3 additional days. At baseline, extracellular orexin levels in the hypothalamus showed a circadian rhythm, with peak levels during the dark (wake) phase, and a nadir during the light (rest) phase. Following CCI but not sham surgery, orexin levels were depressed in both the hypothalamus and hippocampus, and diurnal fluctuation amplitudes were blunted in the hypothalamus. At baseline, correlations of orexin with wakefulness and motor activity were positive and highly significant. Following CCI but not sham surgery, the mice exhibited reduced wakefulness and motor activity, and correlations between orexin and these measures were diminished. These abnormal orexin dynamics were associated with hypothalamic astrogliosis, but not acute loss of orexin neurons, as assessed by immunohistochemistry 3 days after injury. Future studies involving experimental manipulations of the orexin system will be required to determine its contribution to neurological outcomes following injury.
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Affiliation(s)
- Jon T Willie
- Department of Neurological Surgery, Emory University School of Medicine, Atlanta, GA, USA
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Williams RH, Morton AJ, Burdakov D. Paradoxical function of orexin/hypocretin circuits in a mouse model of Huntington's disease. Neurobiol Dis 2011; 42:438-45. [PMID: 21324360 PMCID: PMC5767114 DOI: 10.1016/j.nbd.2011.02.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 02/04/2011] [Accepted: 02/07/2011] [Indexed: 10/18/2022] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder involving progressive motor disturbances, cognitive decline, and desynchronized sleep-wake rhythms. Recent studies revealed that restoring normal sleep-wake cycles can improve cognitive function in HD mice, suggesting that some sleep/wake systems remain operational and thus represent potential therapeutic targets for HD. Hypothalamic neurons expressing orexins/hypocretins (orexin neurons) are fundamental orchestrators of arousal in mammals, but it is unclear whether orexin circuits operate normally in HD. Here we analyzed the electrophysiology, histology, and gene expression of orexin circuits in brain slices from R6/2 mice, a transgenic model of HD with a progressive neurological phenotype. We report that in R6/2 mice, the size of an electrically distinct subpopulation of orexin neurons is reduced, as is the number of orexin-immunopositive cells in some hypothalamic regions. R6/2 orexin cells display altered glutamatergic inputs, and have an abnormal circadian profile of activity, despite normal circadian rhythmicity of the suprachiasmatic nucleus (SCN), the "master clock" of the brain. Nevertheless, even at advanced stages of HD, intrinsic firing properties of orexin cells remain normal and suppressible by serotonin, noradrenaline, and glucose. Furthermore, histaminergic neurons (key cells required for the propagation of orexin-induced arousal) also display normal responses to orexin. Together, these data suggest that the orexin system remains functional and modifiable in HD mice, although its circadian activity profile is disrupted and no longer follows that of the SCN.
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Affiliation(s)
- Rhîannan H. Williams
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - A. Jennifer Morton
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Denis Burdakov
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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Fenzl T, Romanowski CPN, Flachskamm C, Deussing JM, Kimura M. Wake-promoting effects of orexin: Its independent actions against the background of an impaired corticotropine-releasing hormone receptor system. Behav Brain Res 2011; 222:43-50. [PMID: 21420442 DOI: 10.1016/j.bbr.2011.03.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 03/04/2011] [Accepted: 03/11/2011] [Indexed: 01/08/2023]
Abstract
It is widely accepted that orexin (hypocretin) bears wake-promoting effects. While under normal conditions the circadian rhythm of orexin release has a clear circadian distribution, the amplitude of orexin fluctuation is dampened in depression. Interestingly, clinical symptoms of depression include several sleep disturbances. In this disease, corticotropin-releasing hormone (CRH) seems to be another factor influencing sleep. As neurophysiological interactions and anatomical connections between the orexinergic and the CRH system point to mutual influences of these two neuropeptides, we examined whether a dysfunctional CRH-receptor system in two different CRH receptor knock out models alters general wake-promoting effects of orexin applied exogenously. Orexin was injected intracerebroventricularlly into CNS-restricted CRH-receptor type 1 knockout mice (CRH-R1 KO) and CRH-receptor type 2 knockout mice (CRH-R2 KO) and baseline sleep was recorded from the freely behaving mice. A third experiment included antisauvagine-30 injections (CRH-R2 antagonist) into CRH-R1 KO animals. Orexin had similar wake-promoting effects in CRH-R1KO mice, in CRH-R2 KO animals and in CRH-R1KO mice treated with antisauvagine-30. Consistent results were obtained from all corresponding control littermate experiments. According to our results we conclude that the wake-promoting effects of orexin are not influenced by a possible contribution of CRH.
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Affiliation(s)
- Thomas Fenzl
- Max-Planck-Institute of Psychiatry, Kraepelinstrasse 2, 80804 Munich, Germany.
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