Magnetic Resonance Spectroscopy in Patients with Insomnia: A Repeated Measurement Study

Elevated peripheral glutamate and upregulated expression of NMDA receptor NR1 subunit in insomnia disorder

Background

The present study explored the serum glutamate (Glu), glutamine (Gln), glutamic acid dehydrogenase (GAD) concentrations and the mRNA expression levels of the N-methyl-D-aspartate receptor (NMDAR) NR1 subunit in the peripheral blood of patients with insomnia disorder (ID). To our knowledge, this is the first study showing an increase in the mRNA expression levels of the NMDAR NR1 subunit in patients with ID.

Methods

This study included 30 ID patients and 30 matched healthy controls. We investigated the demographic and illness information and assessed subjective sleep quality using the Pittsburgh Sleep Quality Index. The Hamilton Depression Scale-17 and Hamilton Anxiety Scale were used to evaluate the patients' symptoms of depression and anxiety, respectively. The quantifications of Glu, Gln and GAD concentrations were performed by Enzyme-linked immunosorbent assay (ELISA). Real-time PCR was used to detect the mRNA expression levels of the NMDAR NR1 subunit in peripheral blood.

Results

Compared with the healthy control group, the serum Glu concentrations and the mRNA expression levels of the NMDAR NR1 subunit in the ID group were significantly higher. However, there was no significant difference in Gln and GAD between the two groups. The receiver operating characteristic (ROC) analysis showed that the mRNA expression levels of the NMDAR NR1 subunit could distinguish ID patients from healthy individuals (area under the curve: 0.758; sensitivity: 73.3%; specificity: 76.7%). A negative correlation was found between the mRNA expression levels of the NMDAR NR1 subunit for age, total duration of illness, and age of first onset in the ID group, whereas a positive correlation was detected for daytime dysfunction.

Conclusion

Glutamatergic neurotransmission was abnormal in ID patients. Additionally, the mRNA expression levels of the NMDAR NR1 subunit appeared to have potential as a clinical biomarker for ID. However, the sample size of our study was limited, and future studies with larger sample sizes are needed to further validate and explore the mechanisms involved and to assess the reliability of the biomarker.

Gut microbiome and metabolic pathways linked to sleep quality

Sleep quality is a vital determinant of human health as sleep disorders are associated with cognitive deficits, and chronic sleep deprivation is associated with a broad range of health complications. Previous studies on the association between the gut microbiome and sleep quality have been constrained by small sample sizes or have focused on specific sleep disorders, thus yielding inconsistent results. Herein, we investigated the relationship between microbial composition and sleep quality in a cohort of 159 Koreans. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI), determined through a self-administered questionnaire. Gut microbiome analyses were performed using 16S rRNA amplicons. We found no direct correlation between microbial alpha diversity metrics and sleep; however, we identified differences in beta diversity among sleep quality groups (with a PSQI score > 5 indicating poor sleep quality and PSQI ≤5 indicating good sleep quality). We also found differential microbial signatures (Bacteroides, Prevotella 9, and Faecalibacterium) among the groups. Furthermore, functional metabolic pathway profiles revealed significant linear correlations of the L-arginine and L-tryptophan biosynthetic pathways as well as 4-aminobutanoate degradation with sleep status. In particular, Faecalibacterium prausnitzii, which harbors these metabolic pathways, showed differences between sleep quality groups and a linear association with sleep quality scores and was thus identified as the species most strongly associated with sleep status. This study provides a significant advance in our understanding of the relationship between gut microbiota and sleep regulation. The current findings provide a basis for further research into potential therapeutic strategies for sleep disorders targeting the gut microbiome.

Microbiota Metabolite Profiles and Dietary Intake in Older Individuals with Insomnia of Short vs. Normal Sleep Duration

Recent evidence suggests that the gut microbiota plays a role in insomnia pathogenesis. This study compared the dietary habits and microbiota metabolites of older adults with insomnia of short vs. normal sleep duration (ISSD and INSD, respectively). Data collection included sleep assessment through actigraphy, dietary analysis using the Food Frequency Questionnaire, and metabolomic profiling of stool samples. The results show that ISSD individuals had higher body mass index and a greater prevalence of hypertension. Significant dietary differences were observed, with the normal sleep group consuming more kilocalories per day and specific aromatic amino acids (AAAs) phenylalanine and tyrosine and branch-chain amino acid (BCAA) valine per protein content than the short sleep group. Moreover, metabolomic analysis identified elevated levels of the eight microbiota metabolites, benzophenone, pyrogallol, 5-aminopental, butyl acrylate, kojic acid, deoxycholic acid (DCA), trans-anethole, and 5-carboxyvanillic acid, in the short compared to the normal sleep group. The study contributes to the understanding of the potential role of dietary and microbial factors in insomnia, particularly in the context of sleep duration, and opens avenues for targeted dietary interventions and gut microbiota modulation as potential therapeutic approaches for treating insomnia.

Towards the neurobiology of insomnia: A systematic review of neuroimaging studies

Insomnia disorder signifies a major public health concern. The development of neuroimaging techniques has permitted to investigate brain mechanisms at a structural and functional level. The present systematic review aims at shedding light on functional, structural, and metabolic substrates of insomnia disorder by integrating the available published neuroimaging data. The databases PubMed, PsycARTICLES, PsycINFO, CINAHL and Web of Science were searched for case-control studies comparing neuroimaging data from insomnia patients and healthy controls. 85 articles were judged as eligible. For every observed finding of each study, the effect size was calculated from standardised mean differences, statistic parameters and figures, showing a marked heterogeneity that precluded a comprehensive quantitative analysis. From a qualitative point of view, considering the findings of significant group differences in the reported regions across the articles, this review highlights the major involvement of the anterior cingulate cortex, thalamus, insula, precuneus and middle frontal gyrus, thus supporting some central themes in the debate on the neurobiology of and offering interesting insights into the psychophysiology of sleep in this disorder.

Insomnia nosology: a systematic review and critical appraisal of historical diagnostic categories and current phenotypes

Insomnia nosology has significantly evolved since the Diagnostic and Statistical Manual (DSM)-III-R first distinguished between 'primary' and 'secondary' insomnia. Prior International Classification of Sleep Disorders (ICSD) nosology 'split' diagnostic phenotypes to address insomnia's heterogeneity and the DSM nosology 'lumped' them into primary insomnia, while both systems assumed causality for insomnia secondary to health conditions. In this systematic review, we discuss the historical phenotypes in prior insomnia nosology, present findings for currently proposed insomnia phenotypes based on more robust approaches, and critically appraise the most relevant ones. Electronic databases PsychINFO, PubMED, Web of Science, and references of eligible articles, were accessed to find diagnostic manuals, literature on insomnia phenotypes, including systematic reviews or meta-analysis, and assessments of the reliability or validity of insomnia diagnoses, identifying 184 articles. The data show that previous insomnia diagnoses lacked reliability and validity, leading current DSM-5-TR and ICSD-3 nosology to 'lump' phenotypes into a single diagnosis comorbid with health conditions. However, at least two new, robust insomnia phenotyping approaches were identified. One approach is multidimensional-multimethod and provides evidence for self-reported insomnia with objective short versus normal sleep duration linked to clinically relevant outcomes, while the other is multidimensional and provides evidence for two to five clusters (phenotypes) based on self-reported trait, state, and/or life-history data. Some approaches still need replication to better support whether their findings identify true phenotypes or simply different patterns of symptomatology. Regardless, these phenotyping efforts aim at improving insomnia nosology both as a classification system and as a mechanism to guide treatment.

The importance of ligand gated ion channels in sleep and sleep disorders

On average, humans spend about 26 years of their life sleeping. Increased sleep duration and quality has been linked to reduced disease risk; however, the cellular and molecular underpinnings of sleep remain open questions. It has been known for some time that pharmacological modulation of neurotransmission in the brain can promote either sleep or wakefulness thereby providing some clues about the molecular mechanisms at play. However, the field of sleep research has developed an increasingly detailed understanding of the requisite neuronal circuitry and key neurotransmitter receptor subtypes, suggesting that it may be possible to identify next generation pharmacological interventions to treat sleep disorders within this same space. The aim of this work is to examine the latest physiological and pharmacological findings highlighting the contribution of ligand gated ion channels including the inhibitory GABA_A and glycine receptors and excitatory nicotinic acetylcholine receptors and glutamate receptors in the sleep-wake cycle regulation. Overall, a better understanding of ligand gated ion channels in sleep will help determine if these highly druggable targets could facilitate a better night's sleep.

Insomnia disorder with objective short sleep duration (ISS) phenotype and cognitive performance: a systematic review and meta-analysis

OBJECTIVE

Insomnia disorder with objective short sleep duration (ISS) has been considered as a biologically severe subtype. The aim of this meta-analysis was to reveal the association of the ISS phenotype and cognitive performance.

METHODS

We searched PubMed, EMBASE, and the Cochrane Library for studies that observed an association of cognitive performance and insomnia with objective short sleep duration (ISS) phenotype. The "metafor" and "MAd" packages in R software (version 4.2.0) were used to calculate the unbiased standardized mean difference (Hedge's g), which was adjusted so that a negative value indicated worse cognitive performance.

RESULTS

The pooled analysis with 1339 participants revealed that the ISS phenotype was associated with overall cognitive impairments (Hedges' g = - 0.56 [- 0.89, - 0.23]), as well as specific cognitive domains including attention (Hedges' g = - 0.86 [- 1.25, - 0.47]), memory (Hedges' g = - 0.47 [- 0.82, - 0.12]), and executive function (Hedges' g = - 0.39 [- 0.76, - 0.02]). However, cognitive performance was not significantly different between insomnia disorder with objective normal sleep duration (INS) and good sleepers (p > .05).

CONCLUSION

Insomnia disorder with the ISS phenotype, but not the INS phenotype, was associated with cognitive impairments, suggesting the possible utility of treating the ISS phenotype to improve cognitive performance.

Gut microbiome changes due to sleep disruption in older and younger individuals: a case for sarcopenia?

Major hallmarks of functional loss, loss of metabolic and musculoskeletal health and (multi)morbidity with aging are associated with sleep disturbances. With poor sleep shifts in gut microbial composition commonly manifest, which could mediate the pro-inflammatory state between sleep disturbances and sarcopenia. This systematic review presents the recent evidence on how sleep disturbances throughout the lifespan associate with and contribute to gut microbial composition changes, proposing a mechanism to understand the etiology of sarcopenia through sleep disturbances. The relationship between disturbed sleep and clinically relevant gut microbiota composition on health aspects of aging is discussed. A search was performed in PubMed, Cochrane Library, Scopus, Web of Science using keywords including (microbio* OR microflora) AND (sleep OR sleep disorder). Six cross-sectional population-based studies and five experimental clinical trials investigating healthy individuals with ages ranging from 4 to 71 were included. The cross-sectional studies reported similarities in associations with sleep disturbance and gut microbial diversity. In older adults, shorter sleep duration is associated with an increase in pro-inflammatory bacteria whereas increasing sleep quality is positively associated with an increase of beneficial Verrucomicrobia and Lentisphaerae phyla. In young adults, the effect of sleep disruption on gut microbiome composition, specifically the ratio of beneficial Firmicutes over Bacteroidetes phyla, remains contradictory and unclear. The findings of this review warrant further research in the modulation of the gut microbiome linking poor sleep with muscle-catabolic consequences throughout the lifespan.

Spindle-related brain activation in patients with insomnia disorder: An EEG-fMRI study

Sleep spindles have been implicated in sleep protection, depression and anxiety. However, spindle-related brain imaging mechanism underpinning the deficient sleep protection and emotional regulation in insomnia disorder (ID) remains elusive. The aim of the current study is to investigate the relationship between spindle-related brain activations and sleep quality, symptoms of depression and anxiety in patients with ID. Participants (n = 46, 28 females, 18-60 years) were recruited through advertisements including 16 with ID, according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, and 30 matched controls. Group differences in spindle-related brain activations were analyzed using multimodality data acquired with simultaneous electroencephalography and functional magnetic resonance imaging during sleep. Compared with controls, patients with ID showed significantly decreased bilateral spindle-related brain activations in the cingulate gyrus (familywise error corrected p ˂ 0.05, cluster size 4401 mm³). Activations in the cingulate gyrus were negatively correlated with Pittsburgh Sleep Quality Index scores (r = -0.404, p = 0.005) and Self-Rating Anxiety Scale scores (r = -0.364, p = 0.013), in the pooled sample. These findings underscore the key role of spindle-related brain activations in the cingulate gyrus in subjective sleep quality and emotional regulation in ID.

Insomnia with objective short sleep duration is associated with cognitive impairment: a first look at cardiometabolic contributors to brain health

STUDY OBJECTIVES

Insomnia with objective short sleep duration has been previously associated with adverse cardiometabolic health outcomes as well as poorer cognitive performance in otherwise noncognitively impaired adults. However, studies demonstrating an increased prevalence of cognitive impairment (CI) in this insomnia phenotype are lacking.

METHODS

We analyzed data from Penn State Adult Cohort (N = 1,524; 48.9 ± 13.4 years; 53.4% women). Self-reported sleep difficulty was defined as normal sleep (n = 899), poor sleep (n = 453), and chronic insomnia (n = 172). Objective short sleep duration was defined as less than 6-h of sleep, based on in-lab, 8-h polysomnography. CI (n = 155) and possible vascular cognitive impairment (pVCI, n = 122) were ascertained using a comprehensive neuropsychological battery. Analyses adjusted for age, sex, race, education, body mass index, apnea/hypopnea index, smoking, alcohol, psychoactive medication, and mental and physical health problems.

RESULTS

Participants who reported poor sleep or chronic insomnia and slept objectively less than 6 hours were associated with a 2-fold increased odds of CI (OR = 2.06, 95% confidence limits [CL] = 1.15-3.66 and OR = 2.18, 95% CL = 1.07-4.47, respectively) and of pVCI (OR = 1.94, 95% CL = 1.01-3.75 and OR = 2.33, 95% CL = 1.07-5.06, respectively). Participants who reported poor sleep or chronic insomnia and slept objectively more than 6 hours were not associated with increased odds of either CI (OR = 0.72, 95% CL = 0.30-1.76 and OR = 0.75, 95% CL = 0.21-2.71, respectively) or pVCI (OR = 1.08, 95% CL = 0.42-2.74 and OR = 0.76, 95% CL = 0.16-3.57, respectively).

CONCLUSIONS

Insomnia with objective short sleep duration is associated with an increased prevalence of CI, particularly as it relates to cardiometabolic health (i.e. pVCI). These data further support that this insomnia phenotype may be a more biologically severe form of the disorder associated with cardiovascular, cerebrovascular, and neurocognitive morbidity.

Analyses of peripheral blood dendritic cells and magnetic resonance spectroscopy support dysfunctional neuro-immune crosstalk in Tourette syndrome

BACKGROUND

Evidence supports that neurodevelopmental diseases, such as Tourette syndrome (TS), may involve dysfunctional neural-immune crosstalk. This could lead to altered brain maturation and differences in immune and stress responses. Dendritic cells (DCs) play a major role in immunity as professional antigen-presenting cells; changes in their frequency have been observed in several autoimmune conditions.

METHODS

In 18 TS patients (15 on stable pharmacological treatment, three unmedicated) and 18 age-matched healthy volunteers (HVs), we explored circulating blood-derived DCs and their relationship with clinical variables and brain metabolites, measured via proton magnetic resonance spectroscopy (1H-MRS). DC subsets, including plasmacytoid and myeloid type 1 and 2 dendritic cells (MDC1, MDC2), were studied with flow cytometry. 1H-MRS was used to measure total choline, glutamate plus glutamine, total creatine (tCr), and total N-acetylaspartate and N-acetylaspartyl-glutamate levels in frontal white matter (FWM) and the putamen.

RESULTS

We did not observe differences in absolute concentrations of DC subsets or brain inflammatory metabolites between patients and HVs. However, TS patients manifesting anxiety showed a significant increase in MDC1s compared to TS patients without anxiety (p = 0.01). We also found a strong negative correlation between MDC1 frequency and tCr in the FWM of patients with TS (p = 0.0015), but not of HVs.

CONCLUSION

Elevated frequencies of the MDC1 subset in TS patients manifesting anxiety may reflect a proinflammatory status, potentially facilitating altered neuro-immune crosstalk. Furthermore, the strong inverse correlation between brain tCr levels and MDC1 subset frequency in TS patients suggests a potential association between proinflammatory status and metabolic changes in sensitive brain regions.

Associations between fecal short-chain fatty acids and sleep continuity in older adults with insomnia symptoms

Insomnia is a disorder characterized by difficulty falling asleep and poor sleep continuity and is associated with increased risks for physical and cognitive decline. Insomnia with short sleep duration is considered the most biologically severe phenotype of the disorder. Evidence suggests that short-chain fatty acids (SCFAs), the main byproducts of fiber fermentation in the gut, may affect sleep via gut–brain communications. This study explores associations between SCFAs and sleep continuity and compares SCFA concentrations in short vs. normal sleep insomnia phenotypes in older adults. Fifty-nine participants with insomnia symptoms (≥ 65 years), completed 2 weeks of objective sleep monitoring (actigraphy), and were divided into short and normal sleep duration phenotypes via cluster analysis. Sleep measures included total sleep time (TST), sleep onset latency (SOL), sleep efficiency (SE), and wake after sleep onset (WASO). Stool samples were collected and fecal SCFA concentrations were determined by gas-chromatography-mass-spectrometry (GCMS). Higher concentrations of acetate, butyrate, and propionate, and total SCFAs, were associated with lower SE and longer SOL after controlling for Body Mass Index (BMI). Concentrations were higher in the short sleep duration phenotype. Age, BMI, TST, and SOL explained 40.7% of the variance in total SCFAs. Findings contribute to understanding pathways along the gut–brain axis and may lead to the use of SCFAs as biomarkers of insomnia phenotypes.

1H MRS Measurement of Cortical GABA and Glutamate in Primary Insomnia and Major Depressive Disorder: Relationship to Sleep Quality and Depression Severity

BACKGROUND

Both Major Depressive Disorder (MDD) and Primary Insomnia (PI) have been linked to deficiencies in cortical γ-aminobutyric acid (GABA) and glutamate (Glu) thus suggesting a shared neurobiological link between these two conditions. The extent to which comorbid insomnia contributes to GABAergic or glutamatergic deficiencies in MDD remains unclear.

METHODS

We used single-voxel proton magnetic resonance spectroscopy (1H MRS) at 4 Tesla to examine GABA+ and Glu relative to creatine (Cr) in the dorsal anterior cingulate cortex (dACC) and in the parieto-occipital cortex (POC) of 51 non-medicated adults with MDD, 24 adults with Primary Insomnia (PI), and 25 age- and sex-matched good sleeper controls (HC). Measures of depression severity and subjective and objective sleep quality were compared with 1H MRS metabolite measures.

RESULTS

MDD subjects exhibited a 15% decrease in Glu/Cr in the dACC compared to HC. Within the MDD group, there was a trend inverse correlation between dACC Glu/Cr and anhedonia ratings. We observed no significant association between measures of sleep quality with dACC Glu/Cr in those with MDD.

LIMITATIONS

The protocol and data interpretation would have been enhanced by the recruitment of MDD subjects with a broader range of affect severity and a more comprehensive assessment of clinical features.

CONCLUSIONS

These findings support the role of cortical glutamatergic mechanisms in the pathophysiology of MDD. Insomnia severity did not further contribute to the relative deficiency of glutamatergic measures in MDD.

The effect of repetitive transcranial magnetic stimulation for insomnia: a systematic review and meta-analysis

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) might be a promising technique in treating insomnia. A comprehensive meta-analysis of the available literature is conducted to offer evidence.

OBJECTIVE

To evaluate the efficacy and safety of rTMS for insomnia, either as monotherapy or as a complementary strategy.

METHODS

CENTRAL, PubMed, EMBASE, PsycINFO, CINAHL, PEDro, CBM, CNKI, WANFANG, and VIP were searched from earliest record to August 2019. Randomized control trials (RCTs) published in English and Chinese examining effects of rTMS on patients with insomnia were included. Two authors independently completed the article selection, data extraction and rating. Physiotherapy Evidence Database (PEDro) scale was used to assess the methodological quality of the included studies. The RevMan software was used for meta-analysis. The quality of the evidence was assessed by Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

RESULTS

A total of 36 trials from 28 eligible studies were included, involving a total of 2357 adult participants (mean age, 48.80 years; 45.33% males). Compared with sham rTMS, rTMS was associated with improved PSQI total score (SMD -2.31, 95% CI -2.95 to -1.66; Z = 7.01, P < 0.00001) and scores of seven subscales. Compared to other treatment, rTMS as an adjunct to other treatment was associated with improved PSQI total score (SMD -1.44, 95% CI -2.00 to -0.88; Z = 5.01, P < 0.00001), and may have effects on scores of seven subscales. Compared with other treatment, rTMS was associated with improved Pittsburgh sleep quality index (PSQI) total score (SMD -0.63, 95% CI -1.22 to -0.04; Z = 2.08, P = 0.04), and may have a better score in sleep latency, sleep disturbance and hypnotic using of seven subscales. In the three pair of comparisons, the results for polysomnography (PSG) outcomes were varied. In general, rTMS may improve sleep quality through increasing slow wave and rapid eye movement (REM) sleep. The rTMS group was more prone to headache than the sham or blank control group (RR 1.71, 95% CI 1.03 to 2.85; Z = 2.07, P = 0.04). No severe adverse events were reported. Reporting biases and low and very low grade of some evidences should be considered when interpreting the results of this meta-analysis.

CONCLUSIONS

Our findings indicate that rTMS may be a safe and effective option for insomnia. Further international, multicenter, high-quality RCTs with more objective, quality of life related and follow-up assessments are needed.

Shorter sleep duration is associated with lower GABA levels in the anterior cingulate cortex

BACKGROUND

Alterations in the levels of gamma-aminobutyric acid (GABA) and glutamate + glutamine (Glx), which are major inhibitory and excitatory neurotransmitters, respectively, are frequently associated with insomnia. Previous reports also suggested the involvement of the anterior cingulate cortex (ACC) and medial prefrontal cortex (mPFC) in insomnia and shorter sleep duration. In the current study, we investigated whether the GABA and Glx levels were altered in the ACC/mPFC in subclinical insomnia while focusing on the sleep duration.

METHODS

We examined levels of GABA and Glx in the ACC/mPFC of the brain with magnetic resonance spectroscopy in 166 individuals with subjective sleep complaints but without a diagnosis of insomnia. Participants were divided into two groups according to sleep duration (≥6 h/night: n = 79 vs. < 6 h/night: n = 74), which was measured using a wrist-worn actigraphy. Working memory function and overall subjective sleep quality were assessed with a computerized neuropsychological test and self-report questionnaire, respectively.

RESULTS

GABA levels in the ACC/mPFC were lower in the shorter sleep duration group relative to the longer sleep duration group (t = -2.21, p = 0.03). Glx levels did not differ between the two groups (t = -0.20, p = 0.84). Lower GABA levels were associated with lower spatial working memory performance in the shorter sleep duration group (β = -0.21, p = 0.03), but not the longer sleep duration group (β = 0.04, p = 0.72).

CONCLUSION

Shorter sleep duration was associated with lower GABA levels in the ACC/mPFC. These findings may provide insight into the underlying mechanisms of impaired working memory function related to insomnia and sleep loss.

Sleep quality is related to brain glutamate and symptom severity in schizophrenia

Up to 80% of patients with schizophrenia experience sleep disturbances, which negatively impact daytime functioning. Given that the glutamatergic system is involved in the pathophysiology of schizophrenia as well as normal sleep-wake neurobiology, the current project aimed to determine whether sleep quality was related to brain glutamate levels in schizophrenia. The Pittsburgh Sleep Quality Index (PSQI) was used to assess subjective sleep quality and proton magnetic resonance spectroscopy (MRS) was used to quantify glutamate in the bilateral anterior cingulate, left parietal cortex, and left hippocampus. Results indicate that global PSQI scores were negatively correlated with the anterior cingulate and parietal glutamate levels. In patients with schizophrenia, poorer sleep quality correlated with greater positive symptom severity. Our findings suggest that poor sleep quality is related to greater positive symptom severity and lower levels of anterior cingulate glutamate in individuals with schizophrenia. Interventions to enhance sleep quality may prove beneficial for patients. Future studies will examine whether glutamate relates to objective measures of sleep quality, and whether glutamate may mediate the relationship between sleep quality and symptom severity across the schizophrenia-spectrum.

Metabolism of sleep and aging: Bridging the gap using metabolomics

Sleep is a conserved behavior across the evolutionary timescale. Almost all known animal species demonstrate sleep or sleep like states. Despite extensive study, the mechanistic aspects of sleep need are not very well characterized. Sleep appears to be needed to generate resources that are utilized during the active stage/wakefulness as well as clearance of waste products that accumulate during wakefulness. From a metabolic perspective, this means sleep is crucial for anabolic activities. Decrease in anabolism and build-up of harmful catabolic waste products is also a hallmark of aging processes. Through this lens, sleep and aging processes are remarkably parallel- for example behavioral studies demonstrate an interaction between sleep and aging. Changes in sleep behavior affect neurocognitive phenotypes important in aging such as learning and memory, although the underlying connections are largely unknown. Here we draw inspiration from the similar metabolic effects of sleep and aging and posit that large scale metabolic phenotyping, commonly known as metabolomics, can shed light to interleaving effects of sleep, aging and progression of diseases related to aging. In this review, data from recent sleep and aging literature using metabolomics as principal molecular phenotyping methods is collated and compared. The present data suggests that metabolic effects of aging and sleep also demonstrate similarities, particularly in lipid metabolism and amino acid metabolism. Some of these changes also overlap with metabolomic data available from clinical studies of Alzheimer's disease. Together, metabolomic technologies show promise in elucidating interleaving effects of sleep, aging and progression of aging disorders at a molecular level.

Cerebral Metabolites on the Descending Limb of Acute Alcohol: A Preliminary 1H MRS Study

AIMS

Chronic alcohol use is associated with cerebral metabolite abnormalities, yet alcohol's acute effects on neurometabolism are not well understood. This preliminary study investigated cerebral metabolite changes in vivo on the descending limb of blood alcohol in healthy moderate drinkers.

METHODS

In a pre/post design, participants (N = 13) completed magnetic resonance imaging (MRI) scans prior to and approximately 5 hours after consuming a moderate dose of alcohol (0.60 grams alcohol per kilogram of body weight). Magnetic resonance spectroscopy (1H MRS) was used to quantify cerebral metabolites related to glutamatergic transmission (Glx) and neuroimmune activity (Cho, GSH, myo-inositol) in the thalamus and frontal white matter.

RESULTS

Breath alcohol concentration (BrAC) peaked at 0.070±0.008% (mean ± standard deviation) and averaged 0.025±0.011% directly prior to the descending limb scan. In the thalamus, Glx/Cr and Cho/Cr were significantly elevated on the descending limb scan relative to baseline. BrAC area under the curve, an index of alcohol exposure during the session, was significantly, positively associated with levels of Glx/Cr, Cho/Cr and GSH/Cr in the thalamus. GSH/Cr on the descending limb was inversely correlated with subjective alcohol sedation.

CONCLUSIONS

This study offers preliminary evidence of alcohol-related increases in Glx/Cr, Cho/Cr and GSH/Cr on the descending limb of blood alcohol concentration. Findings add novel information to previous research on neurometabolic changes at peak blood alcohol in healthy individuals and during withdrawal in individuals with alcohol use disorder.

Altered ultradian cortisol rhythmicity as a potential neurobiologic substrate for chronic insomnia

Chronic insomnia is highly prevalent and associated with significant morbidity (i.e., confers risk for multiple psychiatric and medical disorders, such as depression and hypertension). Therefore, it is essential to identify factors that perpetuate this disorder. One candidate factor in the neurobiology of chronic insomnia is hypothalamic-pituitary-adrenal-axis dysregulation, and in particular, alterations in circadian cortisol rhythmicity. Cortisol secretory patterns, however, fluctuate with both a circadian and an ultradian rhythm (i.e., pulses every 60-120 min). Ultradian cortisol pulses are thought to be involved in the maintenance of wakefulness during the day and their relative absence at night may allow for the consolidation of sleep and/or shorter nocturnal awakenings. It is possible that the wakefulness that occurs in chronic insomnia may be associated with the aberrant occurrence of cortisol pulses at night. While cortisol pulses naturally occur with transient awakenings, it may also be the case that cortisol pulsatility becomes a conditioned phenomenon that predisposes one to awaken and/or experience prolonged nocturnal awakenings. The current review summarizes the literature on cortisol rhythmicity in subjects with chronic insomnia, and proffers the suggestion that it may be abnormalities in the ultradian rather than circadian cortisol that is associated with the pathophysiology of insomnia.

Abnormal Functional Connectivity of Anterior Cingulate Cortex in Patients With Primary Insomnia: A Resting-State Functional Magnetic Resonance Imaging Study

Background: Recently, there have been many reports about abnormalities regarding structural and functional brain connectivity of the patients with primary insomnia. However, the alterations in functional interaction between the left and right cerebral hemispheres have not been well understood. The resting-state fMRI approach, which reveals spontaneous neural fluctuations in blood-oxygen-level-dependent signals, offers a method to quantify functional interactions between the hemispheres directly.

Methods: We compared interhemispheric functional connectivity (FC) between 26 patients with primary insomnia (48.85 ± 12.02 years) and 28 healthy controls (49.07 ± 11.81 years) using a voxel-mirrored homotopic connectivity (VMHC) method. The patients with primary insomnia and healthy controls were matched for age, gender, and education. Brain regions, which had significant differences in VMHC maps between the primary insomnia and healthy control groups, were defined as seed region of interests. A seed-based approach was further used to reveal significant differences of FC between the seeds and the whole contralateral hemisphere.

Results: The patients with primary insomnia showed higher VMHC than healthy controls in the anterior cingulate cortex (ACC) bilaterally. The seed-based analyses demonstrated increased FC between the left ACC and right thalamus (and the right ACC and left orbitofrontal cortex) in patients with primary insomnia, revealing abnormal connectivity between the two cerebral hemispheres. The VMHC values in the ACC were positively correlated with the time to fall asleep and Self-Rating Depression Scale scores (SDS).

Conclusions: The results demonstrate that there is abnormal interhemispheric resting-state FC in the brain regions of patients with primary insomnia, especially in the ACC. Our finding demonstrates valid evidence that the ACC is an area of interest in the neurobiology of primary insomnia.

Genome-wide association analysis of insomnia complaints identifies risk genes and genetic overlap with psychiatric and metabolic traits

Persistent insomnia is among the most frequent complaints in general practice. To identify genetic factors for insomnia complaints, we performed a genome-wide association study (GWAS) and a genome-wide gene-based association study (GWGAS) in 113,006 individuals. We identify three loci and seven genes associated with insomnia complaints, with the associations for one locus and five genes supported by joint analysis with an independent sample (n = 7,565). Our top association (MEIS1, P < 5 × 10-8) has previously been implicated in restless legs syndrome (RLS). Additional analyses favor the hypothesis that MEIS1 exhibits pleiotropy for insomnia and RLS and show that the observed association with insomnia complaints cannot be explained only by the presence of an RLS subgroup within the cases. Sex-specific analyses suggest that there are different genetic architectures between the sexes in addition to shared genetic factors. We show substantial positive genetic correlation of insomnia complaints with internalizing personality traits and metabolic traits and negative correlation with subjective well-being and educational attainment. These findings provide new insight into the genetic architecture of insomnia.

The insomnia with short sleep duration phenotype: an update on it's importance for health and prevention

PURPOSE OF REVIEW

It was first proposed in the late 1990s that objective markers of sleep disturbance could serve as an index of the biological severity of insomnia. In 2013, a heuristic model of two insomnia phenotypes based on objective sleep duration was proposed. Herein, we review the studies conducted in the past 3 years on the insomnia with short sleep duration phenotype and its implications for a clinical research agenda.

RECENT FINDINGS

Studies have shown that insomnia with objective short sleep duration is associated with physiologic hyperarousal and cardiometabolic and neurocognitive morbidity, whereas insomnia with normal sleep duration is not. Both insomnia phenotypes are associated with psychiatric morbidity albeit through different psychobiological mechanisms. Novel recent studies have included occupational outcomes, developmental approaches, at-home objective sleep testing, diagnostic accuracy measures, and response to cognitive-behavioral treatment.

SUMMARY

Accumulating evidence in the past years has continued to support that insomnia with short sleep duration is a more severe phenotype of the disorder associated with physiologic changes, significant morbidity and mortality and, potentially, a differential response to treatment.

Clinical Sleep-Wake Disorders II: Focus on Insomnia and Circadian Rhythm Sleep Disorders

Insomnia and circadian rhythm sleep disorders affect large proportions of the population and have pronounced effects on quality of life and daytime performance. While the neurobiology of insomnia is not yet fully understood, circadian rhythm sleep disorders are assumed to be caused by a mismatch between the individual circadian phase position and the desired sleep-wake schedule. Benzodiazepines and non-benzodiazepine positive allosteric GABA_A receptor modulators improve sleep onset and maintenance in the short-term treatment of insomnia. However, tolerance and dependence are important side effects. Sedating antidepressants are frequently prescribed for insomnia, however, only few randomised controlled trials have been published so far. Melatonin and melatonin receptor agonists are considered to be an option for the treatment of insomnia especially because of their minimal abuse potential and safety. First data on orexin (aka hypocretin) receptor antagonists are promising, however, the risk-benefit ratio needs to be further evaluated. With respect to circadian rhythm sleep disorders, there is solid evidence from meta-analyses supporting the use of melatonin in jet lag disorder to accelerate entrainment to the new time zone, and in delayed sleep phase disorder to advance sleep-wake rhythms. In addition to that, there is evidence supporting the use of melatonin in patients with shift work disorder in order to promote daytime sleep after night shifts.