Organ-specific fuel rewiring in acute and chronic hypoxia redistributes glucose and fatty acid metabolism.

Oxygen deprivation can be detrimental. However, chronic hypoxia is also associated with decreased incidence of metabolic syndrome and cardiovascular disease in high-altitude populations. Previously, hypoxic fuel rewiring has primarily been studied in immortalized cells. Here, we describe how systemic hypoxia rewires fuel metabolism to optimize whole-body adaptation. Acclimatization to hypoxia coincided with dramatically lower blood glucose and adiposity. Using in vivo fuel uptake and flux measurements, we found that organs partitioned fuels differently during hypoxia adaption. Acutely, most organs increased glucose uptake and suppressed aerobic glucose oxidation, consistent with previous in vitro investigations. In contrast, brown adipose tissue and skeletal muscle became "glucose savers," suppressing glucose uptake by 3-5-fold. Interestingly, chronic hypoxia produced distinct patterns: the heart relied increasingly on glucose oxidation, and unexpectedly, the brain, kidney, and liver increased fatty acid uptake and oxidation. Hypoxia-induced metabolic plasticity carries therapeutic implications for chronic metabolic diseases and acute hypoxic injuries.

The landscape of metabolic pathway dependencies in cancer cell lines.

The metabolic reprogramming of cancer cells creates metabolic vulnerabilities that can be therapeutically targeted. However, our understanding of metabolic dependencies and the pathway crosstalk that creates these vulnerabilities in cancer cells remains incomplete. Here, by integrating gene expression data with genetic loss-of-function and pharmacological screening data from hundreds of cancer cell lines, we identified metabolic vulnerabilities at the level of pathways rather than individual genes. This approach revealed that metabolic pathway dependencies are highly context-specific such that cancer cells are vulnerable to inhibition of one metabolic pathway only when activity of another metabolic pathway is altered. Notably, we also found that the no single metabolic pathway was universally essential, suggesting that cancer cells are not invariably dependent on any metabolic pathway. In addition, we confirmed that cell culture medium is a major confounding factor for the analysis of metabolic pathway vulnerabilities. Nevertheless, we found robust associations between metabolic pathway activity and sensitivity to clinically approved drugs that were independent of cell culture medium. Lastly, we used parallel integration of pharmacological and genetic dependency data to confidently identify metabolic pathway vulnerabilities. Taken together, this study serves as a comprehensive characterization of the landscape of metabolic pathway vulnerabilities in cancer cell lines.

Deep Protein Methylation Profiling by Combined Chemical and Immunoaffinity Approaches Reveals Novel PRMT1 Targets.

Protein methylation has been implicated in many important biological contexts including signaling, metabolism, and transcriptional control. Despite the importance of this post-translational modification, the global analysis of protein methylation by mass spectrometry-based proteomics has not been extensively studied because of the lack of robust, well-characterized techniques for methyl peptide enrichment. Here, to better investigate protein methylation, we compared two methods for methyl peptide enrichment: immunoaffinity purification (IAP) and high pH strong cation exchange (SCX). Using both methods, we identified 1720 methylation sites on 778 proteins. Comparison of these methods revealed that they are largely orthogonal, suggesting that the usage of both techniques is required to provide a global view of protein methylation. Using both IAP and SCX, we then investigated changes in protein methylation downstream of protein arginine methyltransferase 1 (PRMT1). PRMT1 knockdown resulted in significant changes to 127 arginine methylation sites on 78 proteins. In contrast, only a single lysine methylation site was significantly changed upon PRMT1 knockdown. In PRMT1 knockdown cells, we found 114 MMA sites that were either significantly downregulated or upregulated on proteins enriched for mRNA metabolic processes. PRMT1 knockdown also induced significant changes in both asymmetric dimethyl arginine (ADMA) and symmetric dimethyl arginine (SDMA). Using characteristic neutral loss fragmentation ions, we annotated dimethylarginines as either ADMA or SDMA. Through integrative analysis of methyl forms, we identified 18 high confidence PRMT1 substrates and 12 methylation sites that are scavenged by other non-PRMT1 arginine methyltransferases in the absence of PRMT1 activity. We also identified one methylation site, HNRNPA1 R206, which switched from ADMA to SDMA upon PRMT1 knockdown. Taken together, our results suggest that deep protein methylation profiling by mass spectrometry requires orthogonal enrichment techniques to identify novel PRMT1 methylation targets and highlight the dynamic interplay between methyltransferases in mammalian cells.

Biomechanics of Posterior Dynamic Fusion Systems in the Lumbar Spine: Implications for Stabilization With Improved Arthrodesis.

STUDY DESIGN: A comparative biomechanical human cadaveric spine study of a dynamic fusion rod and a traditional titanium rod. OBJECTIVE: The purpose of this study was to measure and compare the biomechanical metrics associated with a dynamic fusion device, Isobar TTL Evolution, and a rigid rod. SUMMARY OF BACKGROUND DATA: Dynamic fusion rods may enhance arthrodesis compared with a rigid rod. Wolff's law implies that bone remodeling and growth may be enhanced through anterior column loading (AL). This is important for dynamic fusion rods because their purpose is to increase AL. METHODS: Six fresh-frozen lumbar cadaveric specimens were used. Each untreated specimen (Intact) underwent biomechanical testing. Next, each specimen had a unilateral transforaminal lumbar interbody fusion performed at L3-L4 using a cage with an integrated load cell. Pedicle screws were also placed at this time. Subsequently, the Isobar was implanted and tested, and finally, a rigid rod replaced the Isobar in the same pedicle screw arrangement. RESULTS: In terms of range of motion, the Isobar performed comparably to the rigid rod and there was no statistical difference found between Isobar and rigid rod. There was a significant difference between the intact and rigid rod and also between intact and Isobar conditions in flexion extension. For interpedicular displacement, there was a significant increase in flexion extension (P=0.017) for the Isobar compared with the rigid rod. Isobar showed increased AL under axial compression compared with the rigid rod (P=0.024). CONCLUSIONS: Isobar provided comparable stabilization to a rigid rod when using range of motion as the metric, however, AL was increased because of the greater interpedicular displacement of dynamic rod compared with a rigid rod. By increasing interpedicular displacement and AL, it potentially brings clinical benefit to procedures relying on arthrodesis.

Cervical spine clearance in the traumatically injured patient: is multidetector CT scanning sufficient alone? Clinical article.

OBJECT: Clearance of the cervical spine in patients who have sustained trauma remains a contentious issue. Clinical examination alone is sufficient in neurologically intact patients without neck pain. Patients with neck pain or those with altered mental status or a depressed level of consciousness require further radiographic evaluation. However, no consensus exists as to the appropriate imaging modality. Some advocate multidetector CT (MDCT) scanning alone, but this has been criticized because MDCT is not sensitive in detecting ligamentous injuries that can often only be identified on MRI. METHODS: Patients were identified retrospectively from a prospectively maintained database at a Level I trauma center. All patients admitted between January 2004 and June 2011 who had a cervical MDCT scan interpreted by a board-certified radiologist as being without evidence of acute traumatic injury and who also had a cervical MRI study obtained during the same hospital admission were included. Data collected included patient demographics, mechanism of injury, Glasgow Coma Scale score at the time of MRI, the indication for and findings on MRI, and the number, type, and indication for cervical spine procedures. RESULTS: A total of 1004 patients were reviewed, of whom 614 were male, with an overall mean age of 47 years. The indication for MRI was neck pain in 662 patients, altered mental status in 467, and neurological signs or symptoms in 157. The MRI studies were interpreted as normal in 645 patients, evidencing ligamentous injury alone in 125, and showing nonspecific degenerative changes in the remaining patients. Of the 125 patients with ligamentous injuries, 66 (52.8%) had documentation of clearance (29 clinical, 37 with flexion-extension radiographs). Another 32 patients were presumed to be self-cleared, bringing the follow-up rate to 82% (98 of 119). Five patients died prior to clearance, and 1 patient was transferred to another facility prior to clearance. Based on these data, the 95% confidence interval for the assertion that clinically irrelevant ligamentous injury in the face of normal MDCT is 97%-100%. No patient with ligamentous injury on MRI was documented to require a surgical procedure or halo orthosis for instability. Thirty-nine patients ultimately underwent cervical surgical procedures (29 anterior and 10 posterior; 5 delayed) for central cord syndrome (21), quadriparesis (9), or discogenic radicular pain (9). None had an unstable spine. CONCLUSIONS: In this study population, MRI did not add any additional information beyond MDCT in identifying unstable cervical spine injuries. Magnetic resonance imaging frequently detected ligamentous injuries, none of which were found to be unstable at the time of detection, during the course of admission, or on follow-up. Magnetic resonance imaging provided beneficial clinical information and guided surgical procedures in patients with neurological deficits or radicular pain. An MDCT study with sagittal and coronal reconstructions negative for acute injury in patients without an abnormal motor examination may be sufficient alone for clearance.

The clinical significance of isolated traumatic subarachnoid hemorrhage.

BACKGROUND: Mild traumatic brain injury is a clinical diagnosis predicated on a patient's neurologic status and encompasses a variety of pathologies on computed tomography. We wondered whether isolated traumatic subarachnoid hemorrhage (iSAH) without other intracranial pathologic diagnosis is a more benign form of minor head injury that does not warrant extensive (and expensive) observation and follow-up. METHODS: This is a retrospective review of patients identified prospectively via a trauma registry during a period of 7 years, who had the computed tomographic finding of iSAH on admission scan and a Glasgow Coma Scale (GCS) score of 13 or greater. RESULTS: There were 478 patients identified, with a mean age 61 years, and 223 were male. Median Injury Severity Score (ISS) was 10 (range, 9-48), and the distribution was 415, 54, and 12 for those with GCS score of 15, 14, and 13, respectively. In-hospital follow-up imaging in nine patients demonstrated increased pathologic findings, but subsequent imaging showed stable or decreasing blood, and none experienced a neurologic decline or underwent a neurosurgical procedure.Among those with no other injuries (ISS = 9, n = 118) patients spent a mean of 2.0 (95% confidence interval, 1.1-2.9) days in intensive care unit and 4.9 (95% confidence interval, 3.9-6.0) days in hospital. The likelihood of discharge home was significantly related to age (p < 0.0001), ISS (p < 0.01), and admission GCS (p < 0.01) (stepwise logistic regression), but not progression of SAH.At 6-week follow-up, one patient (0.2%) developed bilateral chronic subdurals requiring drainage, without neurologic sequela. CONCLUSION: In this largest reported series to date of iSAH in the setting of mild traumatic brain injury, the finding seems to be benign and can likely be managed without routine follow-up imaging or intensive care unit admission in the absence of other significant trauma. LEVEL OF EVIDENCE: Epidemiologic/prognostic study, level III; therapeutic study, level IV.

The shifting landscape of metastatic breast cancer to the CNS.

The improved survival following the diagnosis of breast cancer has potentially altered the characteristics and course of patients presenting with CNS involvement. We therefore sought to define our current cohort of breast cancer patients with metastatic disease to the CNS in regard to modern biomarkers and clinical outcome. Review of clinical and radiographic records of women presenting to a tertiary medical center with the new diagnosis of CNS metastatic disease from breast cancer. This was a retrospective review from patients identities obtained from two prospective databases. There were 88 women analyzed who were treated over the period of January 2003 to February 2010, average age 56.9 years. At the time of initial presentation of CNS disease, 68 % of patients had multiple brain metastases, 17 % had a solitary metastasis, and 15 % had only leptomeningeal disease (LMD). The median survival for all patients from the time of diagnosis of breast disease was 50.0 months, and 9.7 months from diagnosis of CNS involvement. The only factor related to overall survival was estrogen receptor-positive pathology (57.6 v. 38.2 months, p = .02 log-rank); those related to survival post CNS diagnosis were presentation with LMD (p = .004, HR = 3.1, Cox regression) and triple-negative hormonal/HER2 status (p = .02, HR = 2.3, Cox regression). Patients with either had a median survival of 3.1 months (no patients in common). Of the 75 patients who initially presented with metastatic brain lesions, 20 (26 %) subsequently developed LMD in the course of their disease (median 10.4 months), following which survival was grim (1.8 months median). Symptoms of LMD were most commonly lower extremity weakness (14/33), followed by cranial nerve deficits (11/33). The recently described Graded Prognostic Assessment (GPA) tumor index stratified median survival at 2.5, 5.9, 13.1, and 21.7 months, respectively, for indices of 1-4 (p = .004, log-rank), which contrasted with the nonsignificant survival difference between Radiation Therapy Oncology Group Recursive Partitioning Analysis classes one and two. (13.1 v. 13.2, p = .8, log-rank). Treatment of patients with metastatic brain disease from breast cancer should be tailored to the patient's hormonal status and GPA index. Practitioners must be vigilant for the development of LMD, especially as it often presents with nondescript complaints such as back pain.

Causes of sudden unexpected death of adult hospital patients.

The sudden unexpected death of a hospitalized patient is distressing to the family and the healthcare team. It is also common. Assessment of the causes without autopsy is frequently incorrect. To elucidate the causes of death, 175 cases of adult hospital patients in the University of Pittsburgh Medical Center Health System, who died suddenly and unexpectedly, were investigated with autopsies. The most common cause was judged to be a cardiac arrhythmia, in 58 (33%) of cases, presumptive in 46 cases, because only 12 of these patients were on cardiac monitoring. Of the arrhythmia patients, 36 (62%) had ≥75% coronary artery stenosis and 31 (53%) had histological evidence of myocardial infarction, with 15 (26%) of those with subacute or old myocardial infarction lacking a history of myocardial infarction. Hemorrhage was judged the cause of death in 38 (22%) of cases, including 31 (82%) with endogenous coagulopathy, anticoagulation, or antiplatelet therapy. Pulmonary thromboembolism was judged the cause of death in 27 (15%) of cases. Overall, hemorrhage deserves better appreciation as a cause of sudden unexpected death of hospitalized adults.

The prognostic significance of traumatic brainstem injury detected on T2-weighted MRI.

OBJECT: Magnetic resonance imaging is frequently used to evaluate patients with traumatic brain injury in the acute and subacute setting, and it can detect injuries to the brainstem, which are often associated with poor outcomes. This study was undertaken to determine which MRI and clinical factors provide prognostic information in patients with traumatic brainstem injuries. METHODS: The authors performed a retrospective analysis of cases involving patients admitted to a Level I trauma center who were identified in a prospective database as having suffered traumatic brainstem injury identified on MRI. Patient outcomes were dichotomized to dead/vegetative versus functional groups. Standard demographic data, admission Glasgow Coma Scale (GCS) scores, results of the motor component of the GCS examination at admission and 24 hours later, CT scan findings, and peak intracranial pressure were collected from medical records. Volumetric analysis of each patient's injuries was performed with T2-weighted and gradient echo sequences. The T2-weighted MRI sequence for each patient was reviewed to determine the anatomical location of injury within the brainstem and whether the injury crossed the midline. RESULTS: Thirty-six patients who met the study inclusion criteria were identified. At 6-month follow-up, 53% of these patients had poor outcomes and 47% had recovered. Patients with injuries to the medulla or deep bilateral injuries to the pons did not recover. The T2 volumes were found superior to gradient echo sequences in regard to predicting survival (ROC/AUC 0.67, p = 0.07 vs 0.60, p = 0.29, respectively), but neither reached statistical significance. The timing of MR image acquisition did not influence the findings. The time from admission to MRI did not differ significantly between the recovered group and the poor-outcome group (p = 0.52, Mann-Whitney test), and lesion size as measured by T2 volume did not vary with time to scan (R(2) = 0.03, p = 0.3, linear regression). Performing a stepwise logistic regression with all the variables yielded the following factors related to recovery: crossing midline, p = 0.0156, OR 0.075; and 24-hour GCS motor score, p = 0.0045, OR = 2.25, c-statistic 0.913. Further examination of these 2 factors disclosed the following: none of 15 patients with midline-crossing lesions and a 24-hour GCS motor score of 4 or less recovered; conversely, 12 of 13 patients with lesions that did not cross midline recovered, regardless of GCS motor score. CONCLUSIONS: Bilateral injury to the pons and medulla as detected on T2-weighted MRI sequences was associated with poor outcome in patients with brainstem injuries; T2 volumes were found superior to gradient echo sequences in regard to predicting survival, but neither reached statistical significance. When MRI findings were coupled with clinical examination findings, a strong correlation existed between poor outcome and the combination of bilateral brainstem injury and a motor GCS score of 4 or less 24 hours after admission.

MRI is unnecessary to clear the cervical spine in obtunded/comatose trauma patients: the four-year experience of a level I trauma center.

BACKGROUND: Cervical (C)-spine clearance protocols exist both to identify traumatic injury and to expedite rigid collar removal. Computed tomography (CT) of the C-spine in trauma patients facilitates the removal of immobilization collars in patients who are neurologically intact, and magnetic resonance imaging (MRI) has become an indispensable adjunct for evaluating trauma patients with neurologic deficits. Yet, the management of patients with impaired mental status who lack neurologic deficits attributable to the spinal cord remains controversial. C-spine MRI has been suggested and employed as an imaging modality to exclude occult C-spine instability in this population of patients. However, currently available data are inconclusive as to the necessity of MRI in the C-spine clearance of obtunded or comatose trauma patients with a normal CT. METHODS: The records of patients undergoing contemporaneous CT and MRI of the C-spine in a level I trauma center from January 2003 to December 2006 were retrospectively analyzed. From this group, patients admitted with a Glasgow Coma Scale score