Characterization of cerebrospinal fluid (CSF) and plasma NPY levels in normal volunteers over a 24-h timeframe

Kidney-brain axis in the pathogenesis of cognitive impairment

The kidney-brain axis is a bidirectional communication network connecting the kidneys and the brain, potentially affected by inflammation, uremic toxin, vascular injury, neuronal degeneration, and so on, leading to a range of diseases. Numerous studies emphasize the disruptions of the kidney-brain axis may contribute to the high morbidity of neurological disorders, such as cognitive impairment (CI) in the natural course of chronic kidney disease (CKD). Although the pathophysiology of the kidney-brain axis has not been fully elucidated, epidemiological data indicate that patients at all stages of CKD have a higher risk of developing CI compared with the general population. In contrast to other reviews, we mentioned some commonly used medicines in CKD that may play a pivotal role in the pathogenesis of CI. Revealing the pathophysiology interactions between kidney damage and brain function can reduce the potential risk of future CI. This review will deeply explore the characteristics, indicators, and potential pathophysiological mechanisms of CKD-related CI. It will provide a theoretical basis for identifying CI that progresses during CKD and ultimately prevents and treats CKD-related CI.

Link between emotional and external eating behaviors, peripheral neuropeptide Y, and β-hydroxybutyrate in participants with obesity on 12-week ketogenic diet

Objective: Understanding the impact of stress on emotional and external eating behaviors and the psychological and the associated metabolic factors can help in designing subsequent interventions to protect health. In particular, psychological trait-like construct related to eating has been shown to be an important target for intervention. Methods and measures: This study aimed to investigate the biochemical variables associated with a decrease in emotional and external eating behaviors due to 12-week ketogenic diet (12KD) in 35 adult participants (12 males) with obesity. Results: Absolute changes in emotional and external eating were independent of changes in body mass, nutritional intake, and Δ cortisol, but were predicted with increases in serum β-hydroxybutyrate (BHB) and decreases in serum peripheral neuropeptide Y (pNPY) (all p's < 0.050). Decrease in pNPY was also associated with an increase in BHB but was independent of anthropometrical changes, Δ fasting glucose, and Δ insulin. Conclusion: The reductions in emotional and external eating behaviors in participants with obesity were uniquely predicted by an increase in BHB and a decrease in pNPY after 12KD. In ketosis, emotional and external eating dropped independently of body mass change. Change in pNPY predicted changes in emotional and external eating. The role of BHB in modulating eating behavior should be further explored.

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.

Anxiety Is Associated With DPPIV Alterations in Children With Selective Mutism and Social Anxiety Disorder: A Pilot Study

Background: Both selective mutism (SM) and social anxiety disorder (SAD) are severe pediatric anxiety disorders with the common trait of behavioral inhibition (BI). The underlying pathophysiology of these disorders remains poorly understood, however converging evidence suggests that alterations in several peripheral molecular pathways might be involved. In a pilot study, we investigated alterations in plasma molecular markers (dipeptidyl peptidase-4 [DPPIV], interleukin-6 [IL-6], tumor necrosis factor-β [TNF-β] and neuropeptide-Y [NPY]) in children with SM, SAD, and healthy controls, as well as the correlation of these markers to symptom severity. Methods: We included 51 children and adolescents (aged 5-18 years; n = 29 girls): n = 20 children in the SM-, n = 16 in the SAD- and n = 15 in the control-group (CG). Peripheral blood samples were analyzed for DPPIV, IL-6, TNF-β, and NPY concentrations. Diverse psychometric measures were used for BI, anxiety, and mutism symptoms. Results: Lower DPPIV-levels were correlated with more anxiety symptoms. However, we could not find a difference in any molecular marker between the patients with SAD and SM in comparison to the CG. Conclusion: DPPIV is proposed as relevant marker for child and adolescent anxiety. Investigating the pathophysiology of SM and SAD focusing on state and trait variables as anxiety or BI might help better understanding the underlying mechanisms of these disorders. Further studies with especially larger cohorts are needed to validate the current pilot-findings.

Composite contributions of cerebrospinal fluid GABAergic neurosteroids, neuropeptide Y and interleukin-6 to PTSD symptom severity in men with PTSD

Given that multiple neurobiological systems, as well as components within these systems are impacted by stress, and may interact in additive, compensatory and synergistic ways to promote or mitigate PTSD risk, severity, and recovery, we thought that it would be important to consider the collective, as well as separate effects of these neurobiological systems on PTSD risk. With this goal in mind, we conducted a proof-of-concept study utilizing cerebrospinal fluid (CSF) collected from unmedicated, tobacco- and illicit substance-free men with PTSD (n = 13) and trauma-exposed healthy controls (TC) (n = 17). Thirteen neurobiological factors thought to contribute to PTSD risk or severity based on previous studies were assayed. As the small but typical sample size of this lumbar puncture study limited the number of factors that could be considered in a hierarchical regression model, we included only those five factors with at least a moderate correlation (Spearman rho > 0.30) with total Clinician-Administered PTSD Scale (CAPS-IV) scores, and that did not violate multicollinearity criteria. Three of the five factors meeting these criteria—CSF allopregnanolone and pregnanolone (Allo + PA: equipotent GABAergic metabolites of progesterone), neuropeptide Y (NPY), and interleukin-6 (IL-6)—were found to account for over 75% of the variance in the CAPS-IV scores (R² = 0.766, F = 8.75, p = 0.007). CSF Allo + PA levels were negatively associated with PTSD severity (β = −0.523, p = 0.02) and accounted for 47% of the variance in CAPS-IV scores. CSF NPY was positively associated with PTSD severity (β = 0.410, p = 0.04) and accounted for 14.7% of the CAPS-IV variance. There was a trend for a positive association between PTSD severity and CSF IL-6 levels, which accounted for 15.3% of the variance in PTSD severity (β = 0.423, p = 0.05). Z-scores were then computed for each of the three predictive factors and used to depict the varying relative degrees to which each contributed to PTSD severity at the individual PTSD patient level. This first of its kind, proof-of-concept study bears replication in larger samples. However, it highlights the collective effects of dysregulated neurobiological systems on PTSD symptom severity and the heterogeneity of potential biological treatment targets across individual PTSD patients—thus supporting the need for precision medicine approaches to treatment development and prescribing in PTSD.

Mechanisms of cognitive dysfunction in CKD

Cognitive impairment is an increasingly recognized major cause of chronic disability and is commonly found in patients with chronic kidney disease (CKD). Knowledge of the relationship between kidney dysfunction and impaired cognition may improve our understanding of other forms of cognitive dysfunction. Patients with CKD are at an increased risk (compared with the general population) of both dementia and its prodrome, mild cognitive impairment (MCI), which are characterized by deficits in executive functions, memory and attention. Brain imaging in patients with CKD has revealed damage to white matter in the prefrontal cortex and, in animal models, in the subcortical monoaminergic and cholinergic systems, accompanied by widespread macrovascular and microvascular damage. Unfortunately, current interventions that target cardiovascular risk factors (such as anti-hypertensive drugs, anti-platelet agents and statins) seem to have little or no effect on CKD-associated MCI, suggesting that the accumulation of uraemic neurotoxins may be more important than disturbed haemodynamic factors or lipid metabolism in MCI pathogenesis. Experimental models show that the brain monoaminergic system is susceptible to uraemic neurotoxins and that this system is responsible for the altered sleep pattern commonly observed in patients with CKD. Neural progenitor cells and the glymphatic system, which are important in Alzheimer disease pathogenesis, may also be involved in CKD-associated MCI. More detailed study of CKD-associated MCI is needed to fully understand its clinical relevance, underlying pathophysiology, possible means of early diagnosis and prevention, and whether there may be novel approaches and potential therapies with wider application to this and other forms of cognitive decline.

Neuropeptide Y in PTSD, MDD, and chronic stress: A systematic review and meta-analysis

Previous studies have suggested that neuropeptide Y (NPY) levels may be altered in patients with major depressive disorder (MDD), post-traumatic stress disorder (PTSD) and chronic stress. We investigated, through systematic review and meta-analysis, whether the mean levels of NPY are significantly different in patients with MDD, PTSD or chronic stress, compared to controls. The main outcome was the pooled standardized mean difference (SMD) with 95% confidence intervals between cases and controls, using the random-effects model. Heterogeneity and publication bias were evaluated. Thirty-five studies met eligibility criteria. Meta-regression determined that medication and sex could explain 27% of the between-study variance. Females and participants currently prescribed psychotropic medications had significantly higher levels of NPY. NPY levels were significantly lower in plasma and cerebrospinal fluid (CSF) in PTSD patients versus controls. Patients with MDD had significantly lower levels of NPY in plasma compared to controls, but not in the CSF. The magnitudes of the decrease in plasma NPY levels were not significantly different between PTSD and MDD. However, chronic stress patients had significantly higher plasma NPY levels compared to controls, PTSD or MDD. Our findings may imply a shared role of NPY in trauma and depression: nevertheless, it is not clear that the association is specific to these disorders. Psychotropic medications may help restore NPY levels. Further controlled studies are needed to better delineate the contribution of confounding variables such as type of depression, body mass index, appetite or sleep architecture.

Predicting psychogenic non-epileptic seizures from serum levels of neuropeptide Y and adrenocorticotropic hormone

OBJECTIVE

Patients with psychogenic non-epileptic seizures (PNES) may present with convulsive events that are not accompanied by epileptiform brain activity. Video-electroencephalography (EEG) monitoring is the gold standard for diagnosis, yet not all patients experience convulsive episodes during video-EEG sessions. Hence, we aimed to construct a predictive model in order to detect PNES from serum hormone levels, detached from an evaluation of patients' convulsive episodes.

METHODS

Fifteen female patients with PNES and 60 healthy female controls participated in the study, providing blood samples for hormone analysis. A binomial logistic regression model and the leave-one-out cross-validation were employed.

RESULTS

We found that levels of neuropeptide Y and adrenocorticotropic hormone were the optimal combination of predictors, with over 90% accuracy (area under the curve=0.980).

CONCLUSIONS

The ability to diagnose PNES irrespective of convulsive events would represent an important step considering its feasibility and affordability in daily clinical practice.

Exercise Attenuates Anabolic Steroids-Induced Anxiety via Hippocampal NPY and MC4 Receptor in Rats

The aim of our study was to evaluate the effects of chronic administration of nandrolone-decanoate (ND) or testosterone-enanthate (TE) in supraphysiological doses and a prolonged swimming protocol, alone and in combination with ND or TE, on anxiety-like behavior in rats. We investigated the immunohistochemical alterations of the hippocampal neuropeptide Y (NPY) and melanocortin 4 receptor (MC4R) neurons, as a possible underlying mechanism in a modulation of anxiety-like behavior in rats. Both applied anabolic androgenic steroids (AASs) induced anxiogenic effect accompanied with decreased serum and hippocampal NPY. The exercise-induced anxiolytic effect was associated with increased hippocampal NPY expression. ND and TE increased the number of MC4R, while the swimming protocol was followed by the reduction of MC4R in the CA1 region of the hippocampus. However, NPY/MC4R ratio in hippocampus was lowered by AASs and elevated by exercise in all hippocampal regions. An augmentation of this ratio strongly and positively correlated to increased time in open arms of elevated plus maze, in the context that indicates anxiolytic effect. Our findings support the conclusion that alterations in both hippocampal NPY and MC4R expression are involved in anxiety level changes in rats, while their quantitative relationship (NPY/MC4R ratio) is even more valuable in the estimation of anxiety regulation than individual alterations for both NPY and MC4R expression in the hippocampus.

Eating peptides: biomarkers of neurodegeneration in amyotrophic lateral sclerosis and frontotemporal dementia

Objective

Physiological changes potentially influence disease progression and survival along the Amyotrophic Lateral Sclerosis (ALS)-Frontotemporal dementia (FTD) spectrum. The peripheral peptides that regulate eating and metabolism may provide diagnostic, metabolic, and progression biomarkers. The current study aimed to examine the relationships and biomarker potential of hormonal peptides.

Methods

One hundred and twenty-seven participants (36 ALS, 26 ALS- cognitive, patients with additional cognitive behavioral features, and 35 behavioral variant FTD (bvFTD) and 30 controls) underwent fasting blood analyses of leptin, ghrelin, neuropeptide Y (NPY), peptide YY (PYY), and insulin levels. Relationships between endocrine measures, cognition, eating behaviors, and body mass index (BMI) were investigated. Biomarker potential was evaluated using multinomial logistic regression for diagnosis and correlation to disease duration.

Results

Compared to controls, ALS and ALS-cognitive had higher NPY levels and bvFTD had lower NPY levels, while leptin levels were increased in all patient groups. All groups had increased insulin levels and a state of insulin resistance compared to controls. Lower NPY levels correlated with increasing eating behavioral change and BMI, while leptin levels correlated with BMI. On multinomial logistic regression, NPY and leptin levels were found to differentiate between diagnosis. Reduced Neuropeptide Y levels correlated with increasing disease duration, suggesting it may be useful as a potential marker of disease progression.

Interpretation

ALS-FTD is characterized by changes in NPY and leptin levels that may impact on the underlying regional neurodegeneration as they were predictive of diagnosis and disease duration, offering the potential as biomarkers and for the development of interventional treatments.

Responses to peripheral neuropeptide Y in avian adipose tissue are diet, depot, and time specific

The goal of this research was to determine the effect of dietary macronutrient composition on peripheral neuropeptide Y (NPY)-induced changes in adipose tissue dynamics in chicks. Chicks were fed one of three isocaloric diets from the day of hatch: high carbohydrate (HC), high fat (HF), or high protein (HP). On day 4 post-hatch, 0 (vehicle), 60, or 120 µg/kg BW of NPY was injected intraperitoneally, and subcutaneous, clavicular and abdominal adipose tissue samples were collected at 1 and 3 h post-injection. The effect of NPY was most pronounced in chicks fed the HF or HP diet. In the subcutaneous fat at 1 h post-injection, 60 µg/kg BW of NPY was associated with an increase in NPY receptor 2 (NPYR2) mRNA in chicks fed the HP diet and a decrease in 1-acylglycerol-3-phosphate O-acyltransferase 2 (AGPAT2) mRNA in chicks fed the HC diet. In response to 120 µg/kg BW of NPY, there was greater AGPAT2 mRNA in the clavicular fat of chicks that consumed the HP diet and less CCAAT/enhancer-binding protein alpha in the abdominal fat of chicks that were provided the HF diet. There were no gene expression changes in the abdominal fat at 3 h post-injection, whereas there were decreases in AGPAT2, adipose triglyceride lipase, fatty acid binding protein 4 and NPY mRNA in the clavicular fat of chicks fed the HP diet. Results demonstrate that diet affects exogenous NPY-dependent physiological effects in a time- and depot-dependent manner in chick adipose tissue.

A Randomized Dose-Ranging Study of Neuropeptide Y in Patients with Posttraumatic Stress Disorder

BACKGROUND

Anxiety and trauma-related disorders are among the most prevalent and disabling medical conditions in the United States, and posttraumatic stress disorder in particular exacts a tremendous public health toll. We examined the tolerability and anxiolytic efficacy of neuropeptide Y administered via an intranasal route in patients with posttraumatic stress disorder.

METHODS

Twenty-six individuals were randomized in a cross-over, single ascending dose study into 1 of 5 cohorts: 1.4 mg (n=3), 2.8 mg (n=6), 4.6 mg (n=5), 6.8 mg (n=6), and 9.6 mg (n=6). Each individual was dosed with neuropeptide Y or placebo on separate treatment days 1 week apart in random order under double-blind conditions. Assessments were conducted at baseline and following a trauma script symptom provocation procedure subsequent to dosing. Occurrence of adverse events represented the primary tolerability outcome. The difference between treatment conditions on anxiety as measured by the Beck Anxiety Inventory and the State-Trait Anxiety Inventory immediately following the trauma script represented efficacy outcomes.

RESULTS

Twenty-four individuals completed both treatment days. Neuropeptide Y was well tolerated up to and including the highest dose. There was a significant interaction between treatment and dose; higher doses of neuropeptide Y were associated with a greater treatment effect, favoring neuropeptide Y over placebo on Beck Anxiety Inventory score (F1,20=4.95, P=.038). There was no significant interaction for State-Trait Anxiety Inventory score.

CONCLUSIONS

Our study suggests that a single dose of neuropeptide Y is well tolerated up to 9.6 mg and may be associated with anxiolytic effects. Future studies exploring the safety and efficacy of neuropeptide Y in stress-related disorders are warranted. The reported study is registered at: http://clinicaltrials.gov (ID: NCT01533519).

Neuropeptide Y, resilience, and PTSD therapeutics

Resilience to traumatic stress is a complex psychobiological process that protects individuals from developing posttraumatic stress disorder (PTSD) or other untoward consequences of exposure to extreme stress, including depression. Progress in translational research points toward the neuropeptide Y (NPY) system - among others - as a key mediator of stress response and as a potential therapeutic focus for PTSD. Substantial preclinical evidence supports the role of NPY in the modulation of stress response and in the regulation of anxiety in animal models. Clinical studies testing the safety and efficacy of modulating the NPY system in humans, however, have lagged behind. In the current article, we review the evidence base for targeting the NPY system as a therapeutic approach in PTSD, and consider impediments and potential solutions to therapeutic development.

Neuropeptide Y (NPY) and posttraumatic stress disorder (PTSD): A translational update

Posttraumatic stress disorder (PTSD) is a trauma-evoked syndrome, with variable prevalence within the human population due to individual differences in coping and resiliency. In this review, we discuss evidence supporting the relevance of neuropeptide Y (NPY), a stress regulatory transmitter in PTSD. We consolidate findings from preclinical, clinical, and translational studies of NPY that are of relevance to PTSD with an attempt to provide a current update of this area of research. NPY is abundantly expressed in forebrain limbic and brainstem areas that regulate stress and emotional behaviors. Studies in rodents demonstrate a role for NPY in stress responses, anxiety, fear, and autonomic regulation, all relevant to PTSD symptomology. Genetic studies support an association of NPY polymorphisms with stress coping and affect. Importantly, cerebrospinal fluid (CSF) measurements in combat veterans provide direct evidence of NPY association with PTSD diagnosis and symptomology. In addition, NPY involvement in pain, depression, addiction, and metabolism may be relevant to comorbidities associated with PTSD. Collectively, the literature supports the relevance of NPY to PTSD pathophysiology, although knowledge gaps remain. The NPY system is an attractive target in terms of understanding the physiological basis of PTSD as well as treatment of the disorder.

The Blood-Brain Barrier: Regulatory Roles in Wakefulness and Sleep

Sleep and its disorders are known to affect the functions of essential organs and systems in the body. However, very little is known about how the blood-brain barrier (BBB) is regulated. A few years ago, we launched a project to determine the impact of sleep fragmentation and chronic sleep restriction on BBB functions, including permeability to fluorescent tracers, tight junction protein expression and distribution, glucose and other solute transporter activities, and mediation of cellular mechanisms. Recent publications and relevant literature allow us to summarize here the sleep-BBB interactions in five sections: (1) the structural basis enabling the BBB to serve as a huge regulatory interface; (2) BBB transport and permeation of substances participating in sleep-wake regulation; (3) the circadian rhythm of BBB function; (4) the effect of experimental sleep disruption maneuvers on BBB activities, including regional heterogeneity, possible threshold effect, and reversibility; and (5) implications of sleep disruption-induced BBB dysfunction in neurodegeneration and CNS autoimmune diseases. After reading the review, the general audience should be convinced that the BBB is an important mediating interface for sleep-wake regulation and a crucial relay station of mind-body crosstalk. The pharmaceutical industry should take into consideration that sleep disruption alters the pharmacokinetics of BBB permeation and CNS drug delivery, being attentive to the chrono timing and activation of co-transporters in subjects with sleep disorders.

The role of Neuropeptide Y in fear conditioning and extinction

While anxiety disorders are the brain disorders with the highest prevalence and constitute a major burden for society, a considerable number of affected people are still treated insufficiently. Thus, in an attempt to identify potential new anxiolytic drug targets, neuropeptides have gained considerable attention in recent years. Compared to classical neurotransmitters they often have a regionally restricted distribution and may bind to several distinct receptor subtypes. Neuropeptide Y (NPY) is a highly conserved neuropeptide that is specifically concentrated in limbic brain areas and signals via at least 5 different G-protein-coupled receptors. It is involved in a variety of physiological processes including the modulation of emotional-affective behaviors. An anxiolytic and stress-reducing property of NPY is supported by many preclinical studies. Whether NPY may also interact with processing of learned fear and fear extinction is comparatively unknown. However, this has considerable relevance since pathological, inappropriate and generalized fear expression and impaired fear extinction are hallmarks of human post-traumatic stress disorder and a major reason for its treatment-resistance. Recent evidence from different laboratories emphasizes a fear-reducing role of NPY, predominantly mediated by exogenous NPY acting on Y1 receptors. Since a reduction of fear expression was also observed in Y1 receptor knockout mice, other Y receptors may be equally important. By acting on Y2 receptors, NPY promotes fear extinction and generates a long-term suppression of fear, two important preconditions that could support cognitive behavioral therapies in human patients. A similar effect has been demonstrated for the closely related pancreatic polypeptide (PP) when acting on Y4 receptors. Preliminary evidence suggests that NPY modulates fear in particular by activation of Y1 and Y2 receptors in the basolateral and central amygdala, respectively. In the basolateral amygdala, NPY signaling activates inhibitory G protein-coupled inwardly-rectifying potassium channels or suppresses hyperpolarization-induced I(h) currents in a Y1 receptor-dependent fashion, favoring a general suppression of neuronal activity. A more complex situation has been described for the central extended amygdala, where NPY reduces the frequency of inhibitory and excitatory postsynaptic currents. In particular the inhibition of long-range central amygdala output neurons may result in a Y2 receptor-dependent suppression of fear. The role of NPY in processes of learned fear and fear extinction is, however, only beginning to emerge, and multiple questions regarding the relevance of endogenous NPY and different receptor subtypes remain elusive. Y2 receptors may be of particular interest for future studies, since they are the most prominent Y receptor subtype in the human brain and thus among the most promising therapeutic drug targets when translating preclinical evidence to potential new therapies for human anxiety disorders.

Neuropeptide Y: A stressful review

Stress is defined as an adverse condition that disturbs the homeostasis of the body and activates adaptation responses. Among the many pathways and mediators involved, neuropeptide Y (NPY) stands out due to its unique stress-relieving, anxiolytic and neuroprotective properties. Stress exposure alters the biosynthesis of NPY in distinct brain regions, the magnitude and direction of this effect varying with the duration and type of stress. NPY is expressed in particular neurons of the brainstem, hypothalamus and limbic system, which explains why NPY has an impact on stress-related changes in emotional-affective behaviour and feeding as well as on stress coping. The biological actions of NPY in mammals are mediated by the Y1, Y2, Y4 and Y5 receptors, Y1 receptor stimulation being anxiolytic whereas Y2 receptor activation is anxiogenic. Emerging evidence attributes NPY a role in stress resilience, the ability to cope with stress. Thus there is a negative correlation between stress-induced behavioural disruption and cerebral NPY expression in animal models of post-traumatic stress disorder. Exogenous NPY prevents the negative consequences of stress, and polymorphisms of the NPY gene are predictive of impaired stress processing and increased risk of neuropsychiatric diseases. Stress is also a factor contributing to, and resulting from, neurodegenerative diseases such as Alzheimer's, Parkinson's and Huntington's disease, in which NPY appears to play an important neuroprotective role. This review summarizes the evidence for an implication of NPY in stress-related and neurodegenerative pathologies and addresses the cerebral NPY system as a therapeutic target.

The homeostatic role of neuropeptide Y in immune function and its impact on mood and behaviour

Neuropeptide Y (NPY), one of the most abundant peptides in the nervous system, exerts its effects via five receptor types, termed Y1, Y2, Y4, Y5 and Y6. NPY's pleiotropic functions comprise the regulation of brain activity, mood, stress coping, ingestion, digestion, metabolism, vascular and immune function. Nerve-derived NPY directly affects immune cells while NPY also acts as a paracrine and autocrine immune mediator, because immune cells themselves are capable of producing and releasing NPY. NPY is able to induce immune activation or suppression, depending on a myriad of factors such as the Y receptors activated and cell types involved. There is an intricate relationship between psychological stress, mood disorders and the immune system. While stress represents a risk factor for the development of mood disorders, it exhibits diverse actions on the immune system as well. Conversely, inflammation is regarded as an internal stressor and is increasingly recognized to contribute to the pathogenesis of mood and metabolic disorders. Intriguingly, the cerebral NPY system has been found to protect against distinct disturbances in response to immune challenge, attenuating the sickness response and preventing the development of depression. Thus, NPY plays an important homeostatic role in balancing disturbances of physiological systems caused by peripheral immune challenge. This implication is particularly evident in the brain in which NPY counteracts the negative impact of immune challenge on mood, emotional processing and stress resilience. NPY thus acts as a unique signalling molecule in the interaction of the immune system with the brain in health and disease.

Cerebrospinal fluid neuropeptide Y levels in major depression and reported childhood trauma

BACKGROUND

Neuropeptide Y (NPY) may enhance resilience to chronic stress. Low brain NPY reported in major depression may normalize in response to antidepressants.

METHODS

In this study, we examined the relationship of reported childhood trauma to cerebrospinal fluid (CSF) NPY-like immunoreactivity (NPY-LI) in 61 medication-free major depressive disorder (MDD) patients and 20 matched healthy volunteers.

RESULTS

Higher CSF NPY-LI was found in MDD compared to the healthy volunteer group (p = 0.01). A positive correlation of CSF NPY-LI with more adverse childhood trauma (p = 0.001) may be indicative of an intact but insufficient NPY-related stress response.

CONCLUSIONS

We hypothesize that differences in published results may be explained by the existence of two groups of MDD in terms of CSF NPY levels: MDD with low CSF NPY prior to stress or in response to stress, and those with robust NPY responses to stress. Future studies should confirm the two groups and seek the molecular mechanism for their differences.

Cerebrospinal fluid proteomics in multiple sclerosis

Multiple sclerosis (MS) is an immune mediated chronic inflammatory disease of the central nervous system usually initiated during young adulthood, affecting approximately 2.5 million people worldwide. There is currently no cure for MS, but disease modifying treatment has become increasingly more effective, especially when started in the first phase of the disease. The disease course and prognosis are often unpredictable and it can be challenging to determine an early diagnosis. The detection of novel biomarkers to understand more of the disease mechanism, facilitate early diagnosis, predict disease progression, and find treatment targets would be very attractive. Over the last decade there has been an increasing effort toward finding such biomarker candidates. One promising strategy has been to use state-of-the-art quantitative proteomics approaches to compare the cerebrospinal fluid (CSF) proteome between MS and control patients or between different subgroups of MS. In this review we summarize and discuss the status of CSF proteomics in MS, including the latest findings with a focus on the last five years. This article is part of a Special Issue entitled: Neuroproteomics: Applications in Neuroscience and Neurology.

Hypothalamus-adipose tissue crosstalk: neuropeptide Y and the regulation of energy metabolism

Neuropeptide Y (NPY) is an orexigenic neuropeptide that plays a role in regulating adiposity by promoting energy storage in white adipose tissue and inhibiting brown adipose tissue activation in mammals. This review describes mechanisms underlying NPY's effects on adipose tissue energy metabolism, with an emphasis on cellular proliferation, adipogenesis, lipid deposition, and lipolysis in white adipose tissue, and brown fat activation and thermogenesis. In general, NPY promotes adipocyte differentiation and lipid accumulation, leading to energy storage in adipose tissue, with effects mediated mainly through NPY receptor sub-types 1 and 2. This review highlights hypothalamus-sympathetic nervous system-adipose tissue innervation and adipose tissue-hypothalamus feedback loops as pathways underlying these effects. Potential sources of NPY that mediate adipose effects include the bloodstream, sympathetic nerve terminals that innervate the adipose tissue, as well as adipose tissue-derived cells. Understanding the role of central vs. peripherally-derived NPY in whole-body energy balance could shed light on mechanisms underlying the pathogenesis of obesity. This information may provide some insight into searching for alternative therapeutic strategies for the treatment of obesity and associated diseases.

Serum neuropeptide Y in accident survivors with depression or posttraumatic stress disorder

Although neuropeptide Y (NPY) has received attention for its potential anti-depressive and anti-anxiety effect, evidence in humans has been limited. This study aimed to clarify the relationships between serum NPY and depressive disorders, and posttraumatic stress disorder (PTSD) in accident survivors. Depressive disorders and PTSD were diagnosed by structural interviews at 1-month follow-up, and serum NPY was measured at the first assessment and 1-month follow-up. Analysis of variance was used to investigate significance of the differences identified. Furthermore, resilience was measured by self-report questionnaires. Multiple linear regression analyses were used to examine the relationship between resilience and serum NPY. Three hundred accident survivors participated in the assessment at the first assessment, and 138 completed the assessment at 1-month follow-up. Twenty-six participants had major depressive disorder and 6 had minor depressive disorder. Nine participants had PTSD and 16 had partial PTSD. No relationship existed between serum NPY and depressive disorders, PTSD, and resilience. The results of cannot be compared with those of NPY in the central nervous system (CNS), but these findings might be due to the nature of depression and PTSD in accident survivors. Further studies are needed to examine the relationships between NPY in CNS and depression and PTSD.

Cerebrospinal fluid neuropeptide Y in combat veterans with and without posttraumatic stress disorder

Accruing evidence indicates that neuropeptide Y (NPY), a peptide neurotransmitter, is a resilience-to-stress factor in humans. We previously reported reduced cerebrospinal fluid (CSF) NPY concentrations in combat-related posttraumatic stress disorder (PTSD) subjects as compared with healthy, non-combat-exposed volunteers. Here we report CSF NPY in combat-exposed veterans with and without PTSD. We quantified NPY concentrations in morning CSF from 11 male subjects with PTSD from combat in Iraq and/or Afghanistan and from 14 combat-exposed subjects without PTSD. NPY-like immunoreactivity (NPY-LI) was measured by EIA. The relationship between CSF NPY and clinical symptoms, as measured by the Clinician-Administered PTSD Scale (CAPS) and Beck Depression Inventory (BDI), was assessed, as was the relationship between combat exposure scale (CES) scores and CSF NPY. As compared with the combat-exposed comparison subjects without PTSD, individuals with PTSD had significantly lower concentrations of CSF NPY [mean CSF NPY was 258. 6 ± 21.64 pg/mL in the combat trauma-no PTSD group but only 180.5 ± 12.62 pg/mL in PTSD patients (p=0.008)]. After adjusting for CES and BDI scores the two groups were still significantly different with respect to NPY. Importantly, CSF NPY was negatively correlated with composite CAPS score and intrusive (re-experiencing) subscale scores, but did not significantly correlate with CES or BDI scores. Our current findings further suggest that NPY may regulate the manifestation of PTSD symptomatology, and extend previous observations of low CSF NPY concentrations in the disorder. Central nervous system NPY may be a clinically important pharmacotherapeutic target, and/or diagnostic measure, for PTSD.