Glycosylation and S-palmitoylation regulate SARS-CoV-2 spike protein intracellular trafficking.

Post-translational modifications (PTMs), such as glycosylation and palmitoylation, are critical to protein folding, stability, intracellular trafficking, and function. Understanding regulation of PTMs of SARS-CoV-2 spike (S) protein could help the therapeutic drug design. Herein, the VSV vector was used to produce SARS-CoV-2 S pseudoviruses to examine the roles of the 611LYQD614 and cysteine-rich motifs in S protein maturation and virus infectivity. Our results show that 611LY612 mutation alters S protein intracellular trafficking and reduces cell surface expression level. It also changes S protein glycosylation pattern and decreases pseudovirus infectivity. The S protein contains four cysteine-rich clusters with clusters I and II as the main palmitoylation sites. Mutations of clusters I and II disrupt S protein trafficking from ER-to-Golgi, suppress pseudovirus production, and reduce spike-mediated membrane fusion activity. Taken together, glycosylation and palmitoylation orchestrate the S protein maturation processing and are critical for S protein-mediated membrane fusion and infection.

Furin and TMPRSS2 Resistant Spike Induces Robust Humoral and Cellular Immunity Against SARS-CoV-2 Lethal Infection.

An effective COVID-19 vaccine against broad SARS-CoV-2 variants is still an unmet need. In the study, the vesicular stomatitis virus (VSV)-based vector was used to express the SARS-CoV-2 Spike protein to identify better vaccine designs. The replication-competent of the recombinant VSV-spike virus with C-terminal 19 amino acid truncation (SΔ19 Rep) was generated. A single dose of SΔ19 Rep intranasal vaccination is sufficient to induce protective immunity against SARS-CoV-2 infection in hamsters. All the clones isolated from the SΔ19 Rep virus contained R682G mutation located at the Furin cleavage site. An additional S813Y mutation close to the TMPRSS2 cleavage site was identified in some clones. The enzymatic processing of S protein was blocked by these mutations. The vaccination of the R682G-S813Y virus produced a high antibody response against S protein and a robust S protein-specific CD8+ T cell response. The vaccinated animals were protected from the lethal SARS-CoV-2 (delta variant) challenge. The S antigen with resistance to enzymatic processes by Furin and TMPRSS2 will provide better immunogenicity for vaccine design.

Associations of Telehealth Care Delivery with Pediatric Health Care Provider Well-Being.

BACKGROUND: The rapid, large-scale deployment of new health technologies can introduce challenges to clinicians who are already under stress. The novel coronavirus disease 19 (COVID-19) pandemic transformed health care in the United States to include a telehealth model of care delivery. Clarifying paths through which telehealth technology use is associated with change in provider well-being and interest in sustaining virtual care delivery can inform planning and optimization efforts. OBJECTIVE: This study aimed to characterize provider-reported changes in well-being and daily work associated with the pandemic-accelerated expansion of telehealth and assess the relationship of provider perceptions of telehealth effectiveness, efficiency, and work-life balance with desire for future telehealth. METHODS: A cross-sectional survey study was conducted October through November 2020, 6 months after the outbreak of COVID-19 at three children's hospitals. Factor analysis and structural equation modeling (SEM) were used to examine telehealth factors associated with reported change in well-being and desire for future telehealth. RESULTS: A total of 947 nontrainee physicians, advanced practice providers, and psychologists were surveyed. Of them, 502 (53.0%) providers responded and 467 (49.3%) met inclusion criteria of telehealth use during the study period. Of these, 325 (69.6%) were female, 301 (65.6%) were physicians, and 220 (47.1%) were medical subspecialists. Providers were 4.77 times as likely (95% confidence interval [CI]: 3.29-7.06) to report improved versus worsened well-being associated with telehealth. Also, 95.5% of providers (95% CI: 93.2-97.2%) wish to continue performing telehealth postpandemic. Our model explains 66% of the variance in telehealth-attributed provider well-being and 59% of the variance for future telehealth preference and suggests telehealth resources significantly influence provider-perceived telehealth care effectiveness which in turn significantly influences provider well-being and desire to perform telehealth. CONCLUSION: Telehealth has potential to promote provider well-being; telehealth-related changes in provider well-being are associated with both provider-perceived effectiveness of telemedicine for patients and adequacy of telehealth resources.

Rapid Development of a Telehealth Patient Satisfaction Survey Using a Multi-Stakeholder Approach.

Introduction: The COVID-19 pandemic has hastened the adoption of telehealth and the drastic shift to an unfamiliar process may impose significant impact to the quality-of-care delivery. Many providers are interested in understanding the quality of their telehealth services from the patients' experience. Materials and Methods: A telehealth patient satisfaction survey (TPSS) was developed by using an iterative stakeholder-centered design approach, incorporating elements from validated telemedicine and customer service survey instruments, and meeting the operational needs and constraints. A cross-sectional study design was employed to collect survey responses from patients and families of a large pediatric hospital. Finally, we performed exploratory factor analysis (EFA) to extract latent constructs and factor loadings of the survey items to further explain relationships. Results: A 22-item TPSS closely matched the existing in-person patient satisfaction survey and mapped to a revised SERVPERF conceptual model that was proposed by the interdisciplinary committee. Survey was implemented in the HIPAA-compliant online platform REDCap® with survey link embedded in an automated Epic MyChart (Verona, WI) visit follow-up message. In total, 2,394 survey responses were collected between July 7, 2020, and September 2, 2020. EFA revealed three constructs (with factor loadings >0.30): admission process, perceived quality of services, and telehealth satisfaction. Conclusions: We reported the development of TPSS that met the operational needs of compatibility with existing data and possible comparison to in-person survey. The survey is short and yet covers both the clinical experience and telehealth usability, with acceptable survey validity.

Identifying the Factors Influencing Patients' Telehealth Visit Satisfaction: Survey Validation Through a Structural Equation Modeling Approach.

Introduction: The COVID-19 pandemic accelerated the adoption of telehealth as an alternative to in-person hospital visits. To understand the factors impacting the quality of telehealth services, there is a need for validated survey instruments and conceptual frameworks. The objective of this study is to validate a telehealth patient satisfaction survey by structural equation modeling (SEM) and determine the relationship between the factors in the proposed telehealth patient satisfaction model (TPSM). Methods: We conducted a cross-sectional survey of pediatric patients and families receiving care from a comprehensive pediatric hospital in the Midwest between September 2020 and January 2021. In total, 2,039 usable responses were collected. We used an SEM approach by performing confirmatory factor analysis with Diagonally Weighted Least Squares modeling and Partial Least Squares-Path Modeling to establish the structural validity and examined the relationships among the constructs of "Admission Process" (AP), "Perceived Quality of Service" (PQS), and "Telehealth Satisfaction" (TS). Results: Participants were predominantly White (75%) and English-speaking (95%) parents (85%) of patients (mean age of patients was 10.2 years old). The survey responses were collected from patients visiting 43 department specialties, whereas 50% were behavioral and occupational therapy patients. The structural model showed that the admission process (AP) had a strong positive impact on perceived quality of service (PQS) (p = 0.67, t = 36.1, p < 0.001). The PQS had a strong positive impact on telehealth satisfaction (TS) (p = 0.66, t = 31.8, p < 0.001). The AP had a low positive direct impact on TS (p = 0.16, t = 7.46, p < 0.05). Overall, AP and PQS explained 61% variances (R2) of TS. Conclusions: We validated a newly proposed TS assessment model by using SEM. The TPSM will inform researchers to better understand the influencing factors in TS and help health care systems to improve telehealth patient satisfaction through a validated model.

Feasibility and usability study of a pilot immersive virtual reality-based empathy training for dental providers.

PURPOSE: Social determinants of health (SDOH) significantly impact individuals' engagement with the healthcare system. To address SDOH-related oral health disparities, providers must be equipped with knowledge, skills, and attitudes (KSAs) to understand how SDOH affect patients and how to mitigate these effects. Traditional dental school curricula provide limited training on recognizing SDOH or developing empathy for those with SDOH-related access barriers. This study describes the design and evaluation of such a virtual reality (VR)-based simulation in dental training. We hypothesize the simulation will increase post-training KSAs. METHODS: We developed "MPATHI" (Making Professionals Able THrough Immersion), a scripted VR simulation where participants take the role of an English-speaking caregiver with limited socioeconomic resources seeking dental care for a child in a Spanish-speaking country. The simulation is a combination of 360° video recording and virtual scenes delivered via VR headsets. A pilot was conducted with 29 dental residents/faculty, utilizing a pre-post design to evaluate effectiveness in improving immediate and retention of KSAs toward care delivery for families facing barriers. RESULTS: MPATHI led to increased mean scores for cognitive (pre = 3.48 ± 0.80, post = 4.56 ± 0.51, p < 0.001), affective (pre = 4.20 ± 0.4, post = 4.47 ± 0.44, p < 0.001), and skill-based learning (pre = 4.00 ± 0.47, post = 4.52 ± 0.37, p < 0.001) immediately post-training. There was not a significant difference between skills measured immediately post-training and in the 1-month post-training survey (p = 0.41). Participants reported high satisfaction with the content and methods used in this training. CONCLUSIONS: This pilot study supports using VR SDOH training in dental education. VR technology provides new opportunities for innovative content design.

Virtual Reality-Based Executive Function Rehabilitation System for Children With Traumatic Brain Injury: Design and Usability Study.

BACKGROUND: Traumatic brain injury (TBI) poses a significant threat to children's health. Cognitive rehabilitation for pediatric TBI has the potential to improve the quality of life following the injury. Virtual reality (VR) can provide enriched cognitive training in a life-like but safe environment. However, existing VR applications for pediatric TBIs have primarily focused on physical rehabilitation. OBJECTIVE: This study aims to design and develop an integrative hardware and software VR system to provide rehabilitation of executive functions (EF) for children with TBI, particularly in 3 core EF: inhibitory control, working memory, and cognitive flexibility. METHODS: The VR training system was developed by an interdisciplinary team with expertise in best practices of VR design, developmental psychology, and pediatric TBI rehabilitation. Pilot usability testing of this novel system was conducted among 10 healthy children and 4 children with TBIs. RESULTS: Our VR-based interactive cognitive training system was developed to provide assistive training on core EF following pediatric TBI. Pilot usability testing showed adequate user satisfaction ratings for both the hardware and software components of the VR system. CONCLUSIONS: This project designed and tested a novel VR-based system for executive function rehabilitation that is specifically adapted to children following TBI.

A deep learning model for pediatric patient risk stratification.

OBJECTIVES: Current models for patient risk prediction rely on practitioner expertise and domain knowledge. This study presents a deep learning model-a type of machine learning that does not require human inputs-to analyze complex clinical and financial data for population risk stratification. STUDY DESIGN: A comparative predictive analysis of deep learning versus other popular risk prediction modeling strategies using medical claims data from a cohort of 112,641 pediatric accountable care organization members. METHODS: "Skip-Gram," an unsupervised deep learning approach that uses neural networks for prediction modeling, used data from 2014 and 2015 to predict the risk of hospitalization in 2016. The area under the curve (AUC) of the deep learning model was compared with that of both the Clinical Classifications Software and the commercial DxCG Intelligence predictive risk models, each with and without demographic and utilization features. We then calculated costs for patients in the top 1% and 5% of hospitalization risk identified by each model. RESULTS: The deep learning model performed the best across 6 predictive models, with an AUC of 75.1%. The top 1% of members selected by the deep learning model had a combined healthcare cost $5 million higher than that of the group identified by the DxCG Intelligence model. CONCLUSIONS: The deep learning model outperforms the traditional risk models in prospective hospitalization prediction. Thus, deep learning may improve the ability of managed care organizations to perform predictive modeling of financial risk, in addition to improving the accuracy of risk stratification for population health management activities.

Environmental and Genetic Activation of Hypothalamic BDNF Modulates T-cell Immunity to Exert an Anticancer Phenotype.

Macroenvironmental factors, including a patient's physical and social environment, play a role in cancer risk and progression. Our previous studies show that living in an enriched environment (EE) providing complex stimuli confers an anticancer phenotype in mice mediated, in part by a specific neuroendocrine axis, with brain-derived neurotrophic factor (BDNF) as the key brain mediator. Here, we investigated how an EE modulated T-cell immunity and its role in the EE-induced anticancer effects. Our data demonstrated that CD8 T cells were required to mediate the anticancer effects of an EE in an orthotropic model of melanoma. In secondary lymphoid tissue (SLT), an EE induced early changes in the phenotype of T-cell populations, characterized by a decrease in the ratio of CD4 T helper to CD8 cytotoxic T lymphocytes (CTL). Overexpression of hypothalamic BDNF reproduced EE-induced T-cell phenotypes in SLT, whereas knockdown of hypothalamic BDNF inhibited EE-induced immune modulation in SLT. Both propranolol and mifepristone blocked the EE-associated modulation of CTLs in SLT, suggesting that both the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis were involved. Our results demonstrated that enhanced anticancer effect of an EE was mediated at least in part through modulation of T-cell immunity and provided support to the emerging concept of manipulating a single gene in the brain to improve cancer immunotherapy. Cancer Immunol Res; 4(6); 488-97. ©2016 AACR.

Social overcrowding as a chronic stress model that increases adiposity in mice.

Stress is a widely recognized risk factor for psychiatric and metabolic disorders. A number of animal models utilizing various stressors have been developed to facilitate our understanding in the pathophysiology of stress-related dysfunctions. The most commonly used chronic stress paradigms include the unpredictable chronic mild stress paradigm, the social defeat paradigm and the social deprivation paradigm. Here we assess the potential of social crowding as an alternative chronic stress model to study the effects on affective behaviors and metabolic disturbances. Ten-week-old male C57BL/6 mice were housed in groups of four (control) or eight (social crowding; SC) in standard cage for 9 weeks. Exploration, anxiety- and depressive-like behaviors were assessed in the open field test, the elevated T-maze, the novelty-suppressed feeding test and the forced swim test. SC mice exhibited a modest anxiety-like phenotype without change in depressive-like behaviors. Nine weeks of social crowding did not affect the body weight, but robustly increased adiposity as determined by increased mass of fat depots. Consistent with the increased fat content, serum leptin was markedly elevated in the SC mice. Specific changes in gene expression were also observed in the hypothalamus and the white adipose tissue following SC housing. Our study demonstrates the potential of social crowding as an alternative model for the study of stress-related metabolic and behavioral dysfunctions.

An Immunological Approach to Increase the Brain's Resilience to Insults.

We have previously demonstrated the therapeutic potential of inducing a humoral response with autoantibodies to the N-methyl D-aspartate (NMDA) receptor using a genetic approach. In this study, we generated three recombinant proteins to different functional domains of the NMDA receptor, which is implicated in mediating brain tolerance, specifically NR1[21-375], NR1[313-619], NR1[654-800], and an intracellular scaffolding protein, Homer1a, with a similar anatomical expression pattern. All peptides showed similar antigenicity and antibody titers following systemic vaccination, and all animals thrived. Two months following vaccination, rats were administered the potent neurotoxin, kainic acid. NR1[21-375] animals showed an antiepileptic phenotype but no neuroprotection. Remarkably, despite ineffective antiepileptic activity, 6 of 7 seizing NR1[654-800] rats showed absolutely no injury with only minimal changes in the remaining animal, whereas the majority of persistently seizing rats in the other groups showed moderate to severe hippocampal injury. CREB, BDNF, and HSP70, proteins associated with preconditioning, were selectively upregulated in the hippocampus of NR1[654-800] animals, consistent with the observed neuroprotective phenotype. These results identify NR1 epitopes important in conferring anticonvulsive and neuroprotective effects and support the concept of an immunological strategy to induce a chronic state of tolerance in the brain.

Metabolic Effects of Social Isolation in Adult C57BL/6 Mice.

Obesity and metabolic dysfunction are risk factors for a number of chronic diseases, such as type 2 diabetes, hypertension, heart disease, stroke, and certain forms of cancers. Both animal studies and human population-based and clinical studies have suggested that chronic stress is a risk factor for metabolic disorders. A good social support system is known to exert positive effects on the mental and physical well-being of an individual. On the other hand, long-term deprivation of social contacts may represent a stressful condition that has negative effects on health. In the present study, we investigated the effects of chronic social isolation on metabolic parameters in adult C57BL/6 mice. We found that individually housed mice had increased adipose mass compared to group-housed mice, despite comparable body weight. The mechanism for the expansion of white adipose tissue mass was depot-specific. Notably, food intake was reduced in the social isolated animals, which occurred around the light-dark phase transition periods. Similarly, reductions in heat generated and the respiratory exchange ratio were observed during the light-dark transitions. These phase-specific changes due to long-term social isolation have not been reported previously. Our study shows social isolation contributes to increased adiposity and altered metabolic functions.

Neuropeptides as therapeutic targets in anxiety disorders.

In addition to the classical neurotransmitters, neuropeptides represent an important class of modulators for affective behaviors and associated disorders, such as anxiety disorders. Many neuropeptides are abundantly expressed in brain regions involved in emotional processing and anxiety behaviors. Moreover, risk factors for anxiety disorders such as stress modulate the expression of various neuropeptides in the brain. Due to the high prevalence of anxiety disorders and yet limited treatment options, there is a clear need for more effective therapeutics. In this regard, the various neuropeptides represent exciting candidates for new therapeutic designs. In this review, I will provide an up-to-date summary on the evidences for the involvement of seven neuropeptides in anxiety: corticotropin-releasing factor, urocortins, vasopressin, oxytocin, substance P, neuropeptide Y and galanin. This review will cover the behavioral effects of these neuropeptides in animal models of anxiety by both genetic and pharmacological manipulations. Human studies indicating a role for these neuropeptides in anxiety disorders will also be discussed.

Cortical mechanisms of visual context processing in singleton search.

When searching for a target object presented in a context of other, irrelevant objects, the dissimilarity between target and surrounding context elements as well as the similarity between context elements themselves affect search efficiency. The present functional imaging study explored the cortical mechanisms involved in processing the same target when surrounded by context arrangements of varying homogeneity. Results showed that brain activity increased in the precuneus, cingulate gyrus, and the middle temporal gyrus as context homogeneity and local feature contrast increased. Contexts with low homogeneity and local feature contrast, compared to contexts with high homogeneity and local feature contrast, increasingly involved areas near the corpus callosum and the medial frontal gyrus. The results support the assumption that contextual grouping and local target detection both contribute to perform the visual search task.

Environmental enrichment exerts sex-specific effects on emotionality in C57BL/6J mice.

Environmental enrichment (EE) has been shown to exert various behavioral and mood effects in rodents including emotionality, which has a high propensity to be influenced by sex. However, there are only a few comparative studies evaluating the effect of EE and their results are both inconsistent and inconclusive. In the present study, male and female C57BL/6J adolescent mice were housed in either physical enrichment or standard conditions for four weeks with analysis of affective behaviors in the open field, elevated T-maze and forced swim tests. Hippocampal gene expression was characterized in an additional group of mice. In the open field test, exploration was similarly inhibited by EE in male and female mice. Both sex and housing condition influenced the time mice spent in the center of the arena. In the elevated T-maze, anxiety-like behavior was increased in female and decreased in male mice following EE. We observed a trend for EE-induced inhibition of glucocorticoid receptor (GR) mRNA expression in male but not in female mice. In contrast, mineralocorticoid receptor (MR) expression was unaffected by 10 days of physical enrichment but was lower in female mice compared to male mice. Our data suggest that the balance between hippocampal GR and MR may contribute to the observed sex-specific effect of physical enrichment on emotionality-related behavior.

Distraction and target selection in the brain: an fMRI study.

To attend successfully, a specification of what is currently relevant is necessary, but not sufficient. Irrelevant stimuli that are also present in the environment must be recognized as such and filtered out at the same time. Using functional magnetic resonance imaging, we showed that posterior brain regions in parietal, occipital and temporal cortex are recruited in order to ignore distracting visual stimuli, while the specification and selection of relevant stimuli is associated with differential activity in frontal cortex and hippocampal areas instead. The results thus suggest that the selection of relevant objects can be anatomically dissociated from the handling of competing irrelevant objects. The dissociation between the increased involvement of parietal and occipital cortex in handling distraction on one hand, and that of frontal cortex in target specification on the other provides neurophysiological support for models of attention that make this functional distinction.

Environmental and genetic activation of a brain-adipocyte BDNF/leptin axis causes cancer remission and inhibition.

Cancer is influenced by its microenvironment, yet broader, environmental effects also play a role but remain poorly defined. We report here that mice living in an enriched housing environment show reduced tumor growth and increased remission. We found this effect in melanoma and colon cancer models, and that it was not caused by physical activity alone. Serum from animals held in an enriched environment (EE) inhibited cancer proliferation in vitro and was markedly lower in leptin. Hypothalamic brain-derived neurotrophic factor (BDNF) was selectively upregulated by EE, and its genetic overexpression reduced tumor burden, whereas BDNF knockdown blocked the effect of EE. Mechanistically, we show that hypothalamic BDNF downregulated leptin production in adipocytes via sympathoneural beta-adrenergic signaling. These results suggest that genetic or environmental activation of this BDNF/leptin axis may have therapeutic significance for cancer.

Adult-onset hippocampal-specific neuropeptide Y overexpression confers mild anxiolytic effect in mice.

The anticonvulsive properties of neuropeptide Y (NPY) are opening up opportunity for the development of NPY gene transfer as a therapy for epilepsy. In order to pursue the potential clinical translation of this approach, the effects of somatic NPY gene transfer on other hippocampal functions need to be assessed. The present study characterized the behavioral effects of recombinant adeno-associated viral vector (rAAV)-mediated hippocampal NPY overexpression in adult male mice and also Y1 receptor knockout mice. In wild-type mice, there were no obvious adverse effects on the general health, motor function and cognition following rAAV-NPY treatment. Moreover, hippocampal NPY overexpression induced a moderate anxiolytic effect in the open field test and elevated plus maze. Intriguingly, the treatment also increased depressive-like behavior in the tail suspension test. Elevated hippocampal NPY levels in the absence of Y1 signalling had no effects on anxiety or cognition and actually improved the depressive-like phenotype observed in the wild-type mice treated with rAAV-NPY.

Critical role of arcuate Y4 receptors and the melanocortin system in pancreatic polypeptide-induced reduction in food intake in mice.

BACKGROUND: Pancreatic polypeptide (PP) is a potent anti-obesity agent known to inhibit food intake in the absence of nausea, but the mechanism behind this process is unknown. METHODOLOGY/PRINCIPAL FINDINGS: Here we demonstrate that in response to i.p. injection of PP in wild type but not in Y4 receptor knockout mice, immunostaining for the neuronal activation marker c-Fos is induced specifically in neurons of the nucleus tractus solitarius and the area postrema in the brainstem, notably in cells also showing immunostaining for tyrosine hydroxylase. Importantly, strong c-Fos activation is also detected in the arcuate nucleus of the hypothalamus (ARC), particularly in neurons that co-express alpha melanocyte stimulating hormone (alpha-MSH), the anorexigenic product of the proopiomelanocortin (POMC) gene. Interestingly, other hypothalamic regions such as the paraventricular nucleus, the ventromedial nucleus and the lateral hypothalamic area also show c-Fos induction after PP injection. In addition to c-Fos activation, PP injection up-regulates POMC mRNA expression in the ARC as detected by in situ hybridization. These effects are a direct consequence of local Y4 signaling, since hypothalamus-specific conditional Y4 receptor knockout abolishes PP-induced ARC c-Fos activation and blocks the PP-induced increase in POMC mRNA expression. Additionally, the hypophagic effect of i.p. PP seen in wild type mice is completely absent in melanocortin 4 receptor knockout mice. CONCLUSIONS/SIGNIFICANCE: Taken together, these findings show that PP reduces food intake predominantly via stimulation of the anorexigenic alpha-MSH signaling pathway, and that this effect is mediated by direct action on local Y4 receptors within the ARC, highlighting a potential novel avenue for the treatment of obesity.

Neuropeptide Y knockout mice reveal a central role of NPY in the coordination of bone mass to body weight.

Changes in whole body energy levels are closely linked to alterations in body weight and bone mass. Here, we show that hypothalamic signals contribute to the regulation of bone mass in a manner consistent with the central perception of energy status. Mice lacking neuropeptide Y (NPY), a well-known orexigenic factor whose hypothalamic expression is increased in fasting, have significantly increased bone mass in association with enhanced osteoblast activity and elevated expression of bone osteogenic transcription factors, Runx2 and Osterix. In contrast, wild type and NPY knockout (NPY (-/-)) mice in which NPY is specifically over expressed in the hypothalamus (AAV-NPY+) show a significant reduction in bone mass despite developing an obese phenotype. The AAV-NPY+ induced loss of bone mass is consistent with models known to mimic the central effects of fasting, which also show increased hypothalamic NPY levels. Thus these data indicate that, in addition to well characterized responses to body mass, skeletal tissue also responds to the perception of nutritional status by the hypothalamus independently of body weight. In addition, the reduction in bone mass by AAV NPY+ administration does not completely correct the high bone mass phenotype of NPY (-/-) mice, indicating the possibility that peripheral NPY may also be an important regulator of bone mass. Indeed, we demonstrate the expression of NPY specifically in osteoblasts. In conclusion, these data identifies NPY as a critical integrator of bone homeostatic signals; increasing bone mass during times of obesity when hypothalamic NPY expression levels are low and reducing bone formation to conserve energy under 'starving' conditions, when hypothalamic NPY expression levels are high.