Targeting myostatin/activin A protects against skeletal muscle and bone loss during spaceflight.

Among the physiological consequences of extended spaceflight are loss of skeletal muscle and bone mass. One signaling pathway that plays an important role in maintaining muscle and bone homeostasis is that regulated by the secreted signaling proteins, myostatin (MSTN) and activin A. Here, we used both genetic and pharmacological approaches to investigate the effect of targeting MSTN/activin A signaling in mice that were sent to the International Space Station. Wild type mice lost significant muscle and bone mass during the 33 d spent in microgravity. Muscle weights of Mstn-/- mice, which are about twice those of wild type mice, were largely maintained during spaceflight. Systemic inhibition of MSTN/activin A signaling using a soluble form of the activin type IIB receptor (ACVR2B), which can bind each of these ligands, led to dramatic increases in both muscle and bone mass, with effects being comparable in ground and flight mice. Exposure to microgravity and treatment with the soluble receptor each led to alterations in numerous signaling pathways, which were reflected in changes in levels of key signaling components in the blood as well as their RNA expression levels in muscle and bone. These findings have implications for therapeutic strategies to combat the concomitant muscle and bone loss occurring in people afflicted with disuse atrophy on Earth as well as in astronauts in space, especially during prolonged missions.

Diagnostic performance of a biomarker panel as a negative predictor for acute appendicitis in adult ED patients with abdominal pain.

OBJECTIVES: Evaluate the diagnostic accuracy of the APPY1TM biomarker panel, previously described for use in pediatric patients, for identifying adult ED patients with abdominal pain who are at low risk of acute appendicitis. METHODS: This study prospectively enrolled subjects >18years of age presenting to seven U.S. emergency departments with <72hours of abdominal pain suggesting possible acute appendicitis. The APPY1 panel was performed on blood samples drawn from each patient at the time of initial evaluation and results were correlated with the final diagnosis either positive or negative for acute appendicitis. RESULTS: 431 patients were enrolled with 422 completing all aspects of the study. The APPY1 biomarker panel exhibited a sensitivity of 97.5% (95% CI, 91.3-99.3%), a negative predictive value of 98.4% (95% CI, 94.4-99.6%), a negative likelihood ratio of 0.07 (95% CI, 0.02-0.27), with a specificity of 36.5% (95% CI, 31.6-41.8%) for acute appendicitis. The panel correctly identified 125 of 342 (36.6%) patients who did not have appendicitis with 2 (2.5%) false negatives. The CT utilization rate in this population was 72.7% (307/422). Of 307 CT scans, 232 were done for patients who did not have appendicitis and 79 (34%) of these patients were correctly identified as negative with "low risk" biomarker panel results, representing 26% (79/307) of all CT scans performed. CONCLUSION: This biomarker panel exhibited high sensitivity and negative predictive value for acute appendicitis in this prospective adult cohort, thereby potentially reducing the dependence on CT for the evaluation of possible acute appendicitis.

Prospective validation of a biomarker panel to identify pediatric ED patients with abdominal pain who are at low risk for acute appendicitis.

OBJECTIVES: The objective of the study is to prospectively validate the diagnostic accuracy of a biomarker panel consisting of white blood cell, C-reactive protein, and myeloid-related protein 8/14 levels in identifying pediatric patients with abdominal pain who are at low risk for appendicitis. METHODS: This prospective observational study enrolled subjects aged 2 to 20 years presenting to 29 US emergency departments with abdominal pain suggesting possible acute appendicitis. Blood samples were analyzed for white blood cell, C-reactive protein, and myeloid-related protein 8/14 levels from which the composite biomarker panel results were calculated, then correlated with the final diagnosis either positive or negative for acute appendicitis. RESULTS: A total of 2201 patients were enrolled, with 1887 completing all aspects of the study. Prevalence of appendicitis in this cohort was 25.3%. The biomarker panel exhibited a sensitivity of 97.1% (95% confidence interval [CI], 95.1%-98.2%), negative predictive value of 97.4% (95% CI, 95.8%-98.5%), negative likelihood ratio of 0.08 (95% CI, 0.05-0.13), with a specificity of 37.9% (95% CI, 35.4%-40.4%) for appendicitis. The panel correctly identified 534 (37.8%) of 1410 patients who did not have appendicitis with 14 false negatives (2.9%). Overall, 23.7% (132/557) of computed tomographic (CT) scans were done for patients with negative biomarker panel results, including 31.2% (131/420) of patients who had CT but did not have appendicitis. CONCLUSION: This biomarker panel exhibited high sensitivity and negative predictive value for acute appendicitis in this large prospective cohort. This panel may be useful in identifying pediatric patients who are at low risk for appendicitis and might be followed clinically, potentially reducing the dependence on CT in the evaluation for acute appendicitis.

Addition of a biomarker panel to a clinical score to identify patients at low risk for appendicitis.

BACKGROUND: The diagnosis of pediatric acute appendicitis can be difficult. Although scoring systems such as the Pediatric Appendicitis Score (PAS) are helpful, they lack adequate sensitivity and specificity as standalone diagnostics. When used for risk stratification, they often result in large percentages of moderate-risk patients requiring further diagnostic evaluation. METHODS: We applied a biomarker panel (the APPY1 Test) that has high sensitivity and negative predictive value (NPV) to patients with PAS in the moderate-risk range (3-7) and reclassified those patients with a negative result to the low-risk group. We compared the specificity, sensitivity, and NPV of the original and reclassified low-risk groups at several different PAS low-risk cutoffs. RESULTS: The application of a negative biomarker panel to a group of patients with a moderate risk for appendicitis (PAS, 3-7) resulted in 4 times more patients (586 vs 145) being safely classified as low risk. Reclassification increased the overall specificity or the proportion of patients without appendicitis who were correctly identified as low risk, from 10.3% to 42.0%. The high NPV (97.2%) in the original group was preserved (97.6%) in the reclassified low-risk group, as was the sensitivity (original 99.1% vs reclassified 96.9%). CONCLUSION: The addition of negative biomarker test results to patients with a moderate risk of appendicitis based on the PAS can safely reclassify many to a low-risk group. This may allow clinicians to provide more conservative management in children with suspected appendicitis and decrease unnecessary resource utilization.

A novel biomarker panel to rule out acute appendicitis in pediatric patients with abdominal pain.

OBJECTIVES: To identify a biomarker panel with sufficient sensitivity and negative predictive value to identify children with abdominal pain at low risk for acute appendicitis in order to avoid unnecessary imaging. METHODS: We prospectively enrolled 503 subjects aged two to 20 years with <72 hours of abdominal pain consistent with appendicitis. Blood samples from each patient were analyzed for CBC, differential, and 5 candidate proteins. Biomarker values were evaluated using principal component, recursive partitioning and logistic regression to select the combination that best discriminated between those subjects with and without disease. RESULTS: The prevalence of acute appendicitis was 28.6%. A mathematical combination of three inflammation-related markers in a panel comprised of white blood cell count (WBC), C-reactive protein (CRP), and myeloid-related protein 8/14 complex (MRP 8/14) provided the best discrimination. This panel exhibited a sensitivity of 96.5% (95% CI, 92-99%), a negative predictive value of 96.9% (95% CI, 93-99%), a negative likelihood ratio of 0.08 (95% CI, 0.03- 0.19), and a specificity of 43.2% (95% CI, 38-48%) for acute appendicitis. Sixty of 185 CT scans (32.4%) were done for patients with negative biomarker panel results which, if deferred, would have reduced CT utilization at initial presentation by one third at the cost of missing five of 144 (3.5%) patients with appendicitis. CONCLUSION: This panel may be useful in identifying pediatric patients with signs and symptoms suggestive of acute appendicitis who are at low risk and can be followed clinically, potentially sparing them exposure to the ionizing radiation of CT.

Proteomic Analysis of Effects of Spironolactone in Heart Failure With Preserved Ejection Fraction.

BACKGROUND: The TOPCAT trial (Treatment of Preserved Cardiac Function Heart Failure With an Aldosterone Antagonist Trial) suggested clinical benefits of spironolactone treatment among patients with heart failure with preserved ejection fraction enrolled in the Americas. However, a comprehensive assessment of biologic pathways impacted by spironolactone therapy in heart failure with preserved ejection fraction has not been performed. METHODS: We conducted aptamer-based proteomic analysis utilizing 5284 modified aptamers to 4928 unique proteins on plasma samples from TOPCAT participants from the Americas (n=164 subjects with paired samples at baseline and 1 year) to identify proteins and pathways impacted by spironolactone therapy in heart failure with preserved ejection fraction. Mean percentage change from baseline was calculated for each protein. Additionally, we conducted pathway analysis of proteins altered by spironolactone. RESULTS: Spironolactone therapy was associated with proteome-wide significant changes in 7 proteins. Among these, CARD18 (caspase recruitment domain-containing protein 18), PKD2 (polycystin 2), and PSG2 (pregnancy-specific glycoprotein 2) were upregulated, whereas HGF (hepatic growth factor), PLTP (phospholipid transfer protein), IGF2R (insulin growth factor 2 receptor), and SWP70 (switch-associated protein 70) were downregulated. CARD18, a caspase-1 inhibitor, was the most upregulated protein by spironolactone (-0.5% with placebo versus +66.5% with spironolactone, P<0.0001). The top canonical pathways that were significantly associated with spironolactone were apelin signaling, stellate cell activation, glycoprotein 6 signaling, atherosclerosis signaling, liver X receptor activation, and farnesoid X receptor activation. Among the top pathways, collagens were a consistent theme that increased in patients receiving placebo but decreased in patients randomized to spironolactone. CONCLUSIONS: Proteomic analysis in the TOPCAT trial revealed proteins and pathways altered by spironolactone, including the caspase inhibitor CARD18 and multiple pathways that involved collagens. In addition to effects on fibrosis, our studies suggest potential antiapoptotic effects of spironolactone in heart failure with preserved ejection fraction, a hypothesis that merits further exploration.

The association of TIF-IA and polymerase I mediates promoter recruitment and regulation of ribosomal RNA transcription in Acanthamoeba castellanii.

Large amounts of energy are expended for the construction of the ribosome during both transcription and processing, so it is of utmost importance for the cell to efficiently regulate ribosome production. Understanding how this regulation occurs will provide important insights into cellular growth control and into the coordination of gene expression mediated by all three transcription systems. Ribosomal RNA (rRNA) transcription rates closely parallel the need for protein synthesis; as a cell approaches stationary phase or encounters conditions that negatively affect either growth rate or protein synthesis, rRNA transcription is decreased. In eukaryotes, the interaction of RNA polymerase I (pol I) with the essential transcription initiation factor IA (TIF-IA) has been implicated in this downregulation of transcription. In agreement with the first observation that rRNA transcription is regulated by altering recruitment of pol I to the promoter in Acanthamoeba castellanii, we show here that pol I and an 80-kDa homologue of TIF-IA are found tightly associated in pol I fractions competent for specific transcription. Disruption of the pol I-TIF-IA complex is mediated by a specific dephosphorylation of either pol I or TIF-IA. Phosphatase treatment of TIF-IA-containing A. castellanii pol I fractions results in a downregulation of both transcriptional activity and promoter binding, reminiscent of the inactive pol I fractions purified from encysted cells. The fraction of pol I competent for promoter recruitment is enriched in TIF-IA relative to that not bound by immobilized promoter DNA. This downregulation coincides with an altered electrophoretic mobility of TIF-IA, suggesting at least it is phosphorylated.