The impact of sleep disordered breathing on cardiac troponin in acutely decompensated heart failure.

PURPOSE: Sleep disordered breathing in decompensated heart failure has physiological consequences (e.g., intermittent hypoxemia) that may predispose to subclinical myocardial injury, yet a temporal relationship between sleep apnea and troponin elevation has not been established. METHODS: We assessed the feasibility of performing respiratory polygraphy and measuring overnight high-sensitivity cardiac troponin T change in adults admitted to the hospital with acutely decompensated heart failure. Repeat sleep apnea tests (SATs) were performed to determine response to optimal medical heart failure therapy. Multivariable logistic regression was used to identify associations between absolute overnight troponin change and sleep apnea characteristics. RESULTS: Among the 19 subjects with acutely decompensated heart failure, 92% of SATs demonstrated sleep disordered breathing (apnea-hypopnea index [AHI] > 5 events/h). For those with repeat SATs, AHI increased in 67% despite medical management of heart failure. Overnight troponin increase was associated with moderate to severe sleep apnea (vs. no to mild sleep apnea, odds ratio (OR = 18.4 [1.51-224.18]), central apnea index (OR = 1.11 [1.01-1.22]), and predominantly central sleep apnea (vs. obstructive, OR = 22.9 [1.29-406.32]). CONCLUSIONS: Sleep apnea severity and a central apnea pattern may be associated with myocardial injury. Respiratory polygraphy with serial biomarker assessment is feasible in this population, and combining this approach with interventions (e.g., positive airway pressure) may help establish if a link exists between sleep apnea and subclinical myocardial injury.

Private security and national security: The case of Estonia.

Most studies of private security postulate exclusively internal, primarily economic, causes of the industry's growth and regulation. In contrast, based on the case of post-Soviet Estonia, we investigate how a state's external security environment influences private security. Estonia's tense relations with neighbouring Russia and related pursuit of EU and NATO membership have generated several policies through which private security evolved from a lawless, politically contested industry to a modest, lightly regulated one: (1) the exclusion of public police from private security and an effective campaign against organized crime that together enabled an autonomous and non-criminalized security industry to emerge, (2) free-trade policies that permitted western companies to acquire Estonian security firms, and (3) an 'all-of-nation' approach to national security that promotes comprehensive state-civil society security cooperation. Estonia thus clarifies how high politics shapes private security, while also revealing the factors that make the industry relatively uncontentious in most industrialized democracies.

Strategies to augment adherence in the management of sleep-disordered breathing.

Continuous positive airway pressure (CPAP) is highly effective in treating sleep-disordered breathing (SDB). However, unlike surgical interventions, this treatment modality relies heavily on patient acceptance and adherence. The current definition of adherence is largely arbitrary and is mainly used by third-party payers to determine CPAP reimbursement but CPAP adherence remains sub-optimal. Strategies to augment adherence, especially early in the course of a CPAP trial, are needed in the management of SDB. An understanding of the basis for observed differences in CPAP and oral appliance (OA) use is necessary in developing these strategies, but to date no single factor has been consistently identified. Consequently, a multidimensional approach using educational, behavioural, technological and potentially pharmacological strategies to target (i) disease characteristics, (ii) patient characteristics including psychosocial factors, (iii) treatment protocols and (iv) technological devices and side effects that may influence adherence, is likely required to augment the complex behaviour of CPAP and OA use. In the near future, we envision a personalized medicine approach to determine the risk of non-adherence and set individualized adherence goals aimed at treating specific symptoms (e.g. excessive daytime sleepiness) and reducing the risk of patient-specific SDB consequences (e.g. atherosclerosis). Resources for interventions to improve adherence such as educational programmes and telemedicine encounters could then be more efficiently allocated.

Noninvasive measurement of pulmonary gas exchange: comparison with data from arterial blood gases.

A new noninvasive method was used to measure the impairment of pulmonary gas exchange in 34 patients with lung disease, and the results were compared with the traditional ideal alveolar-arterial Po2 difference (AaDO2) calculated from arterial blood gases. The end-tidal Po2 was measured from the expired gas during steady-state breathing, the arterial Po2 was derived from a pulse oximeter if the SpO2 was 95% or less, which was the case for 23 patients. The difference between the end-tidal and the calculated Po2 was defined as the oxygen deficit. Oxygen deficit was 42.7 mmHg (SE 4.0) in this group of patients, much higher than the means previously found in 20 young normal subjects measured under hypoxic conditions (2.0 mmHg, SE 0.8) and 11 older normal subjects (7.5 mmHg, SE 1.6) and emphasizes the sensitivity of the new method for detecting the presence of abnormal gas exchange. The oxygen deficit was correlated with AaDO2 ( R2 0.72). The arterial Po2 that was calculated from the noninvasive technique was correlated with the results from the arterial blood gases ( R2 0.76) and with a mean bias of +2.7 mmHg. The Pco2 was correlated with the results from the arterial blood gases (R2 0.67) with a mean bias of -3.6 mmHg. We conclude that the oxygen deficit as obtained from the noninvasive method is a very sensitive indicator of impaired pulmonary gas exchange. It has the advantage that it can be obtained within a few minutes by having the patient simply breathe through a tube.

Addition of frontal EEG to adult home sleep apnea testing: does a more accurate determination of sleep time make a difference?

RATIONALE: Home sleep apnea testing (HSAT) typically does not include electroencephalogram (EEG) monitoring for sleep assessment. In patients with insomnia and low sleep efficiency, overestimation of the sleep period can result from absence of EEG, which will reduce sleep disordered breathing (SDB) indices and may lead to a false-negative result. OBJECTIVE: To validate a single channel frontal EEG for scoring sleep versus wake against full EEG during polysomnography, and then to examine the utility of adding this single channel EEG to standard HSAT to prevent false-negative results. METHODS: Epoch-by-epoch validation for sleep scoring of single channel EEG versus full PSG was first performed in 21 subjects. This was followed by a separate retrospective analysis of 207 consecutive HSATs in adults performed in a university-affiliated sleep center using the Somte (Compumedics) HSAT with one frontal EEG as well as chin EMG, nasal airflow, oxyhemoglobin saturation, respiratory effort, pulse rate, and body position. Each study was scored twice, with (HSATEEG) and without the EEG signal visible (HSATPolygraphy), to calculate AHI4 and RDI and the effect on OSA diagnosis and severity. Analyses were repeated in 69 patients with poor sleep suggesting insomnia plus Epworth Sleepiness Scale < 7 as well as in 38 patients ultimately shown to have sleep efficiency < 70% on HSAT with EEG. MEASUREMENTS AND MAIN RESULTS: Single channel and full EEG during polysomnography agreed on sleep versus wake in 92-95% of all epochs. HSAT without EEG overestimated the sleep period by 20% (VST = 440 ± 76 min vs TST = 356 ± 82 min), had a false-negative rate of 8% by AHI4 criteria, and underestimated disease severity in 11% of all patients. Sub-group analysis of patients with subjective poor sleep suggesting insomnia did not change the results. Patients later shown to have low sleep efficiency had lower SDB indices and a 20.8% false negative rate of sleep apnea diagnosis. CONCLUSIONS: Although overall false negative rates using HSATPolygraphy were moderate, suggesting utility for ruling out OSA, there was a specific subgroup in whom there were significant missed diagnoses. However, we were unable to identify this subgroup a priori.

Multiplex array proteomics detects increased MMP-8 in CSF after spinal cord injury.

INTRODUCTION: A variety of methods have been used to study inflammatory changes in the acutely injured spinal cord. Recently novel multiplex assays have been used in an attempt to overcome limitations in numbers of available targets studied in a single experiment. Other technical challenges in developing pre-clinical rodent models to investigate biomarkers in cerebrospinal fluid (CSF) include relatively small volumes of sample and low concentrations of target proteins. The primary objective of this study was to characterize the inflammatory profile present in CSF at a subacute time point in a clinically relevant rodent model of traumatic spinal cord injury (SCI). Our other aim was to test a microarray proteomics platform specifically for this application. METHODS: A 34 cytokine sandwich ELISA microarray was used to study inflammatory changes in CSF samples taken 12 days post-cervical SCI in adult rats. The difference between the median foreground signal and the median background signal was measured. Bonferroni and Benjamini-Hochburg multiple testing corrections were applied to limit the False Discovery Rate (FDR), and a linear mixed model was used to account for repeated measures in the array. RESULTS: We report a novel subacute SCI biomarker, elevated levels of matrix metalloproteinase-8 protein in CSF, and discuss application of statistical models designed for multiplex testing. CONCLUSIONS: Major advantages of this assay over conventional methods include high-throughput format, good sensitivity, and reduced sample consumption. This method can be useful for creating comprehensive inflammatory profiles, and biomarkers can be used in the clinic to assess injury severity and to objectively grade response to therapy.

Induction of proneurotrophins and activation of p75NTR-mediated apoptosis via neurotrophin receptor-interacting factor in hippocampal neurons after seizures.

Seizure-induced damage elicits a loss of hippocampal neurons mediated to a great extent by the p75 neurotrophin receptor (NTR). Proneurotrophins, which are potent apoptosis-inducing ligands for p75(NTR), were increased in the hippocampus, particularly in astrocytes, by pilocarpine-induced seizures; and infusion of anti-pro-NGF dramatically attenuated neuronal loss after seizures. The p75(NTR) is expressed in many different cell types in the nervous system, and can mediate a variety of different cellular functions by recruiting specific intracellular binding proteins to activate distinct signaling pathways. In this study, we demonstrate that neurotrophin receptor-interacting factor (NRIF) mediates apoptotic signaling via p75(NTR) in hippocampal neurons in vitro and in vivo. After seizure-induced injury, NRIF(-/-) mice showed an increase in p75(NTR) expression in the hippocampus; however, these neurons failed to undergo apoptosis in contrast to wild-type mice. Treatment of cultured hippocampal neurons with proneurotrophins induced association of NRIF with p75(NTR) and subsequent translocation of NRIF to the nucleus, which was dependent on cleavage of the receptor. Neurons lacking NRIF were resistant to p75(NTR)-mediated apoptosis in vitro and in vivo. In addition, we demonstrate some mechanistic differences in p75(NTR) signaling in hippocampal neurons compared with other cell types. Overall, these studies demonstrate the requirement for NRIF to signal p75(NTR)-mediated apoptosis of hippocampal neurons and that blocking pro-NGF can inhibit neuronal loss after seizures.

Precision Medicine for Obstructive Sleep Apnea.

Increasingly, obstructive sleep apnea treatment is being recognized as amenable to a precision medicine approach. Many pathophysiologic mechanisms (endotypes) beyond anatomic compromise have now been identified and are readily determined during polysomnography, although randomized controlled trials of endotype-specific therapies are needed. Research indicates that endotypes may also be important in predicting both adherence to therapy and disease consequences (phenotypes). Biomarker discovery and Big Data approaches derived from wearable technology are areas of active investigation and may allow more robust conclusions to be drawn over time, such that patients may soon fully realize the benefits from fresh insights into sleep science.

A 37-Year-Old Man With Pleuritic Chest Pain.

CASE PRESENTATION: A 37-year-old man with poorly controlled type 2 diabetes presented with severe right-sided pleuritic chest pain, respiratory splinting, and cough. Two weeks earlier, he had been evaluated at an urgent care for cough and was prescribed a 5-day course of azithromycin for bronchitis. He then presented to our ED reporting mild, right-sided pleuritic chest pain. Vital signs were normal, and his chest radiograph showed a trace right pleural effusion (Fig 1A). He was discharged with naproxen for pleurisy. Three days later, he returned, reporting a dramatic increase in the severity of his pleuritic chest pain and a cough that had become productive of yellow-brown sputum. He denied fever, but endorsed chills and night sweats. His medications included atorvastatin, lisinopril, metformin, and saxagliptin. His parents were from Guam, although he was born and raised in San Diego, CA. He was employed as a social worker and denied any history of cigarette smoking, alcohol, or drug use.

Sleep apnea, metabolic disease, and the cutting edge of therapy.

Obstructive sleep apnea (OSA) is common, and many cross-sectional and longitudinal studies have established OSA as an independent risk factor for the development of a variety of adverse metabolic disease states, including hypertension, insulin resistance, type 2 diabetes, nonalcoholic fatty liver disease, dyslipidemia, and atherosclerosis. Nasal continuous positive airway pressure (CPAP) has long been the mainstay of therapy for OSA, but definitive studies demonstrating the efficacy of CPAP in improving metabolic outcomes, or in reducing incident disease burden, are lacking; moreover, CPAP has variable rates of adherence. Therefore, the future of OSA management, particularly with respect to limiting OSA-related metabolic dysfunction, likely lies in a coming wave of alternative approaches to endophenotyping OSA patients, personalized care, and defining and targeting mechanisms of OSA-induced adverse health outcomes.

A Novel Neuroprotective Mechanism for Lithium That Prevents Association of the p75NTR-Sortilin Receptor Complex and Attenuates proNGF-Induced Neuronal Death In Vitro and In Vivo.

Neurotrophins play critical roles in the survival, maintenance and death of neurons. In particular, proneurotrophins have been shown to mediate cell death following brain injury induced by status epilepticus (SE) in rats. Previous studies have shown that pilocarpine-induced seizures lead to increased levels of proNGF, which binds to the p75NTR-sortilin receptor complex to elicit apoptosis. A screen to identify compounds that block proNGF binding and uptake into cells expressing p75 and sortilin identified lithium citrate as a potential inhibitor of proNGF and p75NTR-mediated cell death. In this study, we demonstrate that low, submicromolar doses of lithium citrate effectively inhibited proNGF-induced cell death in cultured neurons and protected hippocampal neurons following pilocarpine-induced SE in vivo. We analyzed specific mechanisms by which lithium citrate afforded neuroprotection and determined that lithium citrate prevented the association and internalization of the p75NTR-sortilin receptor complex. Our results demonstrate a novel mechanism by which low-dose treatments of lithium citrate are effective in attenuating p75NTR-mediated cell death in vitro and in vivo.

Molecular and structural insight into proNGF engagement of p75NTR and sortilin.

Nerve growth factor (NGF) is initially synthesized as a precursor, proNGF, that is cleaved to release its C-terminal mature form. Recent studies suggested that proNGF is not an inactive precursor but acts as a signaling ligand distinct from its mature counterpart. proNGF and mature NGF initiate opposing biological responses by utilizing both distinct and shared receptor components. In this study, we carried out structural and biochemical characterization of proNGF interactions with p75NTR and sortilin. We crystallized proNGF complexed to p75NTR and present the structure at 3.75-A resolution. The structure reveals a 2:2 symmetric binding mode, as compared with the asymmetric structure of a previously reported crystal structure of mature NGF complexed to p75NTR and the 2:2 symmetric complex of neurotrophin-3 (NT-3) and p75NTR. Here, we discuss the possible origins and implications of the different stoichiometries. In the proNGF-p75NTR complex, the pro regions of proNGF are mostly disordered and two hairpin loops (loop 2) at the top of the NGF dimer have undergone conformational changes in comparison with mature NT structures, suggesting possible interactions with the propeptide. We further explored the binding characteristics of proNGF to sortilin using surface plasmon resonance and cell-based assays and determined that calcium ions promote the formation of a stable ternary complex of proNGF-sortilin-p75NTR. These results, together with those of previous structural and mechanistic studies of NT-receptor interactions, suggest the potential for distinct signaling activities through p75NTR mediated by different NT-induced conformational changes.