Metabolic profiling shows pre-existing mitochondrial dysfunction contributes to muscle loss in a model of ICU-acquired weakness.

BACKGROUND: Surgery can lead to significant muscle loss, which increases recovery time and associates with increased mortality. Muscle loss is not uniform, with some patients losing significant muscle mass and others losing relatively little, and is likely to be accompanied by marked changes in circulating metabolites and proteins. Determining these changes may help understand the variability and identify novel therapeutic approaches or markers of muscle wasting. METHODS: To determine the association between muscle loss and circulating metabolites, we studied 20 male patients (median age, 70.5, interquartile range, 62.5-75) undergoing aortic surgery. Muscle mass was determined before and 7 days after surgery and blood samples were taken before surgery, and 1, 3, and 7 days after surgery. The circulating metabolome and proteome were determined using commercial services (Metabolon and SomaLogic). RESULTS: Ten patients lost more than 10% of the cross-sectional area of the rectus femoris (RFCSA ) and were defined as wasting. Metabolomic analysis showed that 557 circulating metabolites were altered following surgery (q < 0.05) in the whole cohort and 104 differed between wasting and non-wasting patients (q < 0.05). Weighted genome co-expression network analysis, identified clusters of metabolites, both before and after surgery, that associated with muscle mass and function (r = -0.72, p = 6 × 10-4 with RFCSA on Day 0, P = 3 × 10-4 with RFCSA on Day 7 and r = -0.73, P = 5 × 10-4 with hand-grip strength on Day 7). These clusters were mainly composed of acyl carnitines and dicarboxylates indicating that pre-existing mitochondrial dysfunction contributes to muscle loss following surgery. Surgery elevated cortisol to the same extent in wasting and non-wasting patients, but the cortisol:cortisone ratio was higher in the wasting patients (Day 3 P = 0.043 and Day 7 P = 0.016). Wasting patients also showed a greater increase in circulating nucleotides 3 days after surgery. Comparison of the metabolome with inflammatory markers identified by SOMAscan® showed that pre-surgical mitochondrial dysfunction was associated with growth differentiation factor 15 (GDF-15) (r = 0.79, P = 2 × 10-4 ) and that GDF-15, interleukin (IL)-8), C-C motif chemokine 23 (CCL-23), and IL-15 receptor subunit alpha (IL-15RA) contributed to metabolic changes in response to surgery. CONCLUSIONS: We show that pre-existing mitochondrial dysfunction and reduced cortisol inactivation contribute to muscle loss following surgery. The data also implicate GDF-15 and IL-15RA in mitochondrial dysfunction.

MicroRNA-542 Promotes Mitochondrial Dysfunction and SMAD Activity and Is Elevated in Intensive Care Unit-acquired Weakness.

RATIONALE: Loss of skeletal muscle mass and function is a common consequence of critical illness and a range of chronic diseases, but the mechanisms by which this occurs are unclear. OBJECTIVES: To identify microRNAs (miRNAs) that were increased in the quadriceps of patients with muscle wasting and to determine the molecular pathways by which they contributed to muscle dysfunction. METHODS: miRNA-542-3p/5p (miR-542-3p/5p) were quantified in the quadriceps of patients with chronic obstructive pulmonary disease and intensive care unit-acquired weakness (ICUAW). The effect of miR-542-3p/5p was determined on mitochondrial function and transforming growth factor-ß signaling in vitro and in vivo. MEASUREMENTS AND MAIN RESULTS: miR-542-3p/5p were elevated in patients with chronic obstructive pulmonary disease but more markedly in patients with ICUAW. In vitro, miR-542-3p suppressed the expression of the mitochondrial ribosomal protein MRPS10 and reduced 12S ribosomal RNA (rRNA) expression, suggesting mitochondrial ribosomal stress. miR-542-5p increased nuclear phospho-SMAD2/3 and suppressed expression of SMAD7, SMURF1, and PPP2CA, proteins that inhibit or reduce SMAD2/3 phosphorylation, suggesting that miR-542-5p increased transforming growth factor-ß signaling. In mice, miR-542 overexpression caused muscle wasting, and reduced mitochondrial function, 12S rRNA expression, and SMAD7 expression, consistent with the effects of the miRNAs in vitro. Similarly, in patients with ICUAW, the expression of 12S rRNA and of the inhibitors of SMAD2/3 phosphorylation were reduced, indicative of mitochondrial ribosomal stress and increased transforming growth factor-ß signaling. In patients undergoing aortic surgery, preoperative levels of miR-542-3p/5p were positively correlated with muscle loss after surgery. CONCLUSIONS: Elevated miR-542-3p/5p may cause muscle atrophy in intensive care unit patients through the promotion of mitochondrial dysfunction and activation of SMAD2/3 phosphorylation.

Deficient retinoid-driven angiogenesis may contribute to failure of adult human lung regeneration in emphysema.

BACKGROUND: Molecular pathways that regulate alveolar development and adult repair represent potential therapeutic targets for emphysema. Signalling via retinoic acid (RA), derived from vitamin A, is required for mammalian alveologenesis, and exogenous RA can induce alveolar regeneration in rodents. Little is known about RA signalling in the human lung and its potential role in lung disease. OBJECTIVES: To examine regulation of human alveolar epithelial and endothelial repair by RA, and characterise RA signalling in human emphysema. METHODS: The role of RA signalling in alveolar epithelial repair was investigated with a scratch assay using an alveolar cell line (A549) and primary human alveolar type 2 (AT2) cells from resected lung, and the role in angiogenesis using a tube formation assay with human lung microvascular endothelial cells (HLMVEC). Localisation of RA synthetic (RALDH-1) and degrading (cytochrome P450 subfamily 26 A1 (CYP26A1)) enzymes in human lung was determined by immunofluorescence. Regulation of RA pathway components was investigated in emphysematous and control human lung tissue by quantitative real-time PCR and Western analysis. RESULTS: RA stimulated HLMVEC angiogenesis in vitro; this was partially reproduced with a RAR-α agonist. RA induced mRNA expression of vascular endothelial growth factor A (VEGFA) and VEGFR2. RA did not modulate AT2 repair. CYP26A1 protein was identified in human lung microvasculature, whereas RALDH-1 partially co-localised with vimentin-positive fibroblasts. CYP26A1 mRNA and protein were increased in emphysema. CONCLUSIONS: RA regulates lung microvascular angiogenesis; the endothelium produces CYP26A1 which is increased in emphysema, possibly leading to reduced RA availability. These data highlight a role for RA in maintenance of the human pulmonary microvascular endothelium.

Mechanical ventilation after lung transplantation.

INTRODUCTION: To explore the hypothesis that early ventilation strategies influence clinical outcomes in lung transplantation, we have examined our routine ventilation practices in terms of tidal volumes (Vt) and inflation pressures. METHODS: A total of 124 bilateral lung transplants between 2010 and 2013 were retrospectively assigned to low (<6 mL/kg), medium (6-8 mL/kg), and high (>8 mL/kg) Vt groups based on ventilation characteristics during the first 6 hours after surgery. Those same 124 patients were also stratified to low-pressure (<25 cm H2O) and high-pressure (≥25 cm H2O) groups. RESULTS: Eighty percent of patients were ventilated using pressure control mode. Low, medium, and high Vt were applied to 10%, 43%, and 47% of patients, respectively. After correcting for patients requiring extracorporeal support, there was no difference in short-term to midterm outcomes among the different Vt groups. Low inflation pressures were applied to 61% of patients, who had a shorter length of intensive care unit stay (5 vs 12 days; P = .012), higher forced expiratory volume in 1 second at 3 months (77.8% vs 60.3%; P < .001), and increased 6-month survival rate (95% vs 77%; P = .008). CONCLUSION: Low Vt ventilation has not been fully adopted in our practice. Ventilation with higher inflation pressures, but not Vt, was significantly associated with poorer outcomes after lung transplantation.

Systemic inflammation and oxidative stress post-lung resection: Effect of pretreatment with N-acetylcysteine.

BACKGROUND AND OBJECTIVE: N-acetylcysteine has been used to treat a variety of lung diseases, where is it thought to have an antioxidant effect. In a randomized placebo-controlled double-blind study, the effect of N-acetylcysteine on systemic inflammation and oxidative damage was examined in patients undergoing lung resection, a human model of acute lung injury. METHODS: Eligible adults were randomized to receive preoperative infusion of N-acetylcysteine (240 mg/kg over 12 h) or placebo. Plasma thiols, interleukin-6, 8-isoprostane, ischaemia-modified albumin, red blood cell glutathione and exhaled breath condensate pH were measured pre- and post-operatively as markers of local and systemic inflammation and oxidative stress. RESULTS: Patients undergoing lung resection and one-lung ventilation exhibited significant postoperative inflammation and oxidative damage. Postoperative plasma thiol concentration was significantly higher in the N-acetylcysteine-treated group. However, there was no significant difference in any of the measured biomarkers of inflammation or oxidative damage, or in clinical outcomes, between N-acetylcysteine and placebo groups. CONCLUSION: Preoperative administration of N-acetylcysteine did not attenuate postoperative systemic or pulmonary inflammation or oxidative damage after lung resection. CLINICAL TRIAL REGISTRATION: NCT00655928 at ClinicalTrials.gov.

The effects of pleural fluid drainage on respiratory function in mechanically ventilated patients after cardiac surgery.

BACKGROUND: Pleural effusions occur commonly after cardiac surgery and the effects of drainage on gas exchange in this population are not well established. We examined pulmonary function indices following drainage of pleural effusions in cardiac surgery patients. METHODS: We performed a retrospective study examining the effects of pleural fluid drainage on the lung function indices of patients recovering from cardiac surgery requiring mechanical ventilation for more than 7 days. We specifically analysed patients who had pleural fluid removed via an intercostal tube (ICT: drain group) compared with those of a control group (no effusion, no ICT). RESULTS: In the drain group, 52 ICTs were sited in 45 patients. The mean (SD) volume of fluid drained was 1180 (634) mL. Indices of oxygenation were significantly worse in the drain group compared with controls prior to drainage. The arterial oxygen tension (PaO2)/fractional inspired oxygen (FiO2) (P/F) ratio improved on day 1 after ICT placement (mean (SD), day 0: 31.01 (8.92) vs 37.18 (10.7); p<0.05) and both the P/F ratio and oxygenation index (OI: kPa/cm H2O=PaO2/mean airway pressure×FiO2) demonstrated sustained improvement to day 5 (P/F day 5: 39.85 (12.8); OI day 0: 2.88 (1.10) vs day 5: 4.06 (1.73); both p<0.01). The drain group patients were more likely to have an improved mode of ventilation on day 1 compared with controls (p=0.028). CONCLUSIONS: Pleural effusion after cardiac surgery may impair oxygenation. Drainage of pleural fluid is associated with a rapid and sustained improvement in oxygenation.

MiR-181a: a potential biomarker of acute muscle wasting following elective high-risk cardiothoracic surgery.

INTRODUCTION: Acute muscle wasting in the critically ill is common and associated with significant morbidity and mortality. Although some aetiological factors are recognised and muscle wasting can be detected early with ultrasound, it not possible currently to predict in advance of muscle loss those who will develop muscle wasting. The ability to stratify the risk of muscle wasting associated with critical illness prior to it becoming clinically apparent would provide the opportunity to predict prognosis more accurately and to intervene at an early stage. MicroRNAs are small non-coding RNAs that modulate post-transcriptional regulation of translation, some are tissue specific and can be detected and quantified in plasma. We hypothesised that certain plasma microRNAs could be biomarkers of ICU acquired muscle weakness. METHODS: Plasma levels of selected microRNAs were measured in pre- and post-operative samples from a previously reported prospective observational study of 42 patients undergoing elective high-risk cardiothoracic surgery, 55% of whom developed muscle wasting. RESULTS: The rise in miR-181a was significantly higher on the second post-operative day in those who developed muscle wasting at 1 week compared to those who did not (p = 0.03). A rise in miR-181a of greater than 1.7 times baseline had 91% specificity and 56% sensitivity for subsequent muscle wasting. Other microRNAs did not show significant differences between the groups. CONCLUSION: Plasma miR-181a deserves further investigation as a potential biomarker of muscle wasting. Additionally, since mir-181a is involved in both regulation of inflammation and muscle regeneration and differentiation; our observation therefore also suggests directions for future research.

Effect of simvastatin on physiological and biological outcomes in patients undergoing esophagectomy: a randomized placebo-controlled trial.

OBJECTIVE: To test whether simvastatin improves physiological and biological outcomes in patients undergoing esophagectomy. BACKGROUND: One-lung ventilation during esophagectomy is associated with inflammation, alveolar epithelial and systemic endothelial injury, and the development of acute lung injury (ALI). Statins that modify many of the underlying processes are a potential therapy to prevent ALI. METHODS: We conducted a randomized double-blind placebo-controlled trial in patients undergoing esophagectomy. Patients received simvastatin 80 mg or placebo enterally for 4 days preoperatively and 7 days postoperatively. The primary end point was pulmonary dead space (Vd/Vt) at 6 hours after esophagectomy or before extubation. Inflammation was assessed by plasma cytokines and intraoperative exhaled breath condensate pH; alveolar type 1 epithelial injury was assessed by plasma receptor for advanced glycation end products and systemic endothelial injury by the urine albumin-creatinine ratio. RESULTS: Thirty-nine patients were randomized; 8 patients did not undergo surgery and were excluded. Fifteen patients received simvastatin and 16 received placebo. There was no difference in Vd/Vt or other physiological outcomes. Simvastatin resulted in a significant decrease in plasma MCP-1 on day 3 and reduced exhaled breath condensate acidification. Plasma receptor for advanced glycation end products was significantly lower in the simvastatin-treated group, as was the urine albumin-creatinine ratio on day 7 postsurgery. ALI developed in 4 patients in the placebo group and no patients in the simvastatin group although this difference was not statistically significant (P=0.1). CONCLUSIONS: In this proof of concept study, pretreatment with simvastatin in esophagectomy decreased biomarkers of inflammation as well as pulmonary epithelial and systemic endothelial injury.

Methemoglobin-induced signaling and chemokine responses in human alveolar epithelial cells.

Diffuse alveolar hemorrhage is characterized by the presence of red blood cells and free hemoglobin in the alveoli and complicates a number of serious medical and surgical lung conditions including the pulmonary vasculitides and acute respiratory distress syndrome. In this study we investigated the hypothesis that exposure of human alveolar epithelial cells to hemoglobin and its breakdown products regulates chemokine release via iron- and oxidant-mediated activation of the transcription factor NF-κB. Methemoglobin alone stimulated the release of IL-8 and MCP-1 from A549 cells via activation of the NF-κB pathway; additionally, IL-8 required ERK activation and MCP-1 required JNK activation. Neither antioxidants nor iron chelators and knockdown of ferritin heavy and light chains affected these responses, indicating that iron and reactive oxygen species are not involved in the response of alveolar epithelial cells to methemoglobin. Incubation of primary cultures of human alveolar type 2 cells with methemoglobin resulted in a similar pattern of chemokine release and signaling pathway activation. In summary, we have shown for the first time that methemoglobin induced chemokine release from human lung epithelial cells independent of iron- and redox-mediated signaling involving the activation of the NF-κB and MAPK pathways. Decompartmentalization of hemoglobin may be a significant proinflammatory stimulus in a variety of lung diseases.

Sustained elevation of circulating growth and differentiation factor-15 and a dynamic imbalance in mediators of muscle homeostasis are associated with the development of acute muscle wasting following cardiac surgery.

OBJECTIVES: Acute muscle wasting in the critically ill is common and causes significant morbidity. In a novel human model of acute muscle wasting following cardiac surgery, known or potential circulating modulators of muscle mass--insulin-like growth factor-1, myostatin, and growth and differentiation factor-15--were measured over a week. It was hypothesized that patients who developed acute muscle wasting would show distinct patterns of change in these mediators. DESIGN: A prospective longitudinal observational study of high-risk elective cardiac surgical patients identifying, by ultrasound, those developing muscle wasting. SETTING: Tertiary cardiothoracic referral center: Royal Brompton Hospital, London, UK. PATIENTS: Forty-two patients undergoing elective high-risk cardiothoracic surgery. INTERVENTIONS: Circulating insulin-like growth factor-1, myostatin, and growth and differentiation factor-15 were assayed preoperatively and over the first week postoperatively. The ability of growth and differentiation factor-15 to cause muscle wasting in vitro was determined in C2C12 myotubes. MEASUREMENTS AND MAIN RESULTS: Of the 42 patients, 23 (55%) developed quadriceps atrophy. There was an acute decrease in insulin-like growth factor-1 and unexpectedly myostatin, known mediators of muscle hypertrophy and atrophy, respectively. By contrast, plasma growth and differentiation factor-15 concentrations increased in all patients. This increase in growth and differentiation factor-15 was sustained at day 7 in those who developed muscle wasting (day 7 compared with baseline, p<0.01), but recovered in the nonwasting group (p>0.05). Insulin-like growth factor-1 did not recover in those who developed muscle wasting (day 7 compared with baseline, p<0.01) but did in the nonwasting group (p>0.05). Finally, we demonstrated that growth and differentiation factor-15 caused atrophy of myotubes in vitro. CONCLUSION: These data support the hypothesis that acute muscle loss occurs as a result of an imbalance between drivers of muscle atrophy and hypertrophy. Growth and differentiation factor-15 is a potential novel factor associated with muscle atrophy, which may become a therapeutic target in patients with ICU acquired paresis and other forms of acute muscle wasting.

BMP-9 induced endothelial cell tubule formation and inhibition of migration involves Smad1 driven endothelin-1 production.

BACKGROUND: Bone morphogenetic proteins (BMPs) and their receptors, such as bone morphogenetic protein receptor (BMPR) II, have been implicated in a wide variety of disorders including pulmonary arterial hypertension (PAH). Similarly, endothelin-1 (ET-1), a mitogen and vasoconstrictor, is upregulated in PAH and endothelin receptor antagonists are used in its treatment. We sought to determine whether there is crosstalk between BMP signalling and the ET-1 axis in human pulmonary artery endothelial cells (HPAECs), possible mechanisms involved in such crosstalk and functional consequences thereof. METHODOLOGY/PRINCIPAL FINDING: Using western blot, real time RT-PCR, ELISA and small RNA interference methods we provide evidence that in HPAECs BMP-9, but not BMP-2, -4 and -6 significantly stimulated ET-1 release under physiological concentrations. This release is mediated by both Smad1 and p38 MAPK and is independent of the canonical Smad4 pathway. Moreover, knocking down the ALK1 receptor or BMPR II attenuates BMP-9 stimulated ET-1 release, whilst causing a significant increase in prepro ET-1 mRNA transcription and mature peptide release. Finally, BMP-9 induced ET-1 release is involved in both inhibition of endothelial cell migration and promotion of tubule formation. CONCLUSIONS/SIGNIFICANCE: Although our data does not support an important role for BMP-9 as a source of increased endothelial ET-1 production seen in human PAH, BMP-9 stimulated ET-1 production is likely to be important in angiogenesis and vascular stability. However, increased ET-1 production by endothelial cells as a consequence of BMPR II dysfunction may be clinically relevant in the pathogenesis of PAH.

Biomarkers of lung injury after one-lung ventilation for lung resection.

BACKGROUND AND OBJECTIVE: Acute lung injury contributes to the mortality of patients after lung resection and one-lung ventilation (OLV). The objective of this study was to characterise the effect of lung resection and OLV on proposed biomarkers of lung injury in exhaled breath condensate (EBC) and plasma. METHODS: In adults undergoing lung resection, EBC was collected before and at 30-min intervals during OLV. Inflammatory mediators were assayed in plasma samples taken preoperatively, immediately postoperatively and 24 h postoperatively. RESULTS: EBC pH decreased from 6.51 ± 0.43 preoperatively, to 6.17 ± 0.78 and 6.09 ± 0.83 at 30 and 60 min, respectively (mean ± SD, P = 0.034, n = 20). Plasma concentrations of the receptor for advanced glycation end-products, von Willebrand factor and interleukin-6 increased comparing preoperative and postoperative samples (all P < 0.001, n = 30). By contrast, levels of Krebs von den Lungen-6 and surfactant protein-D decreased (P < 0.001, n=30), and correlated inversely with the extent of lung resected. CONCLUSIONS: Lung resection and OLV was associated with a rapid reduction in EBC pH and differential changes in plasma biomarkers of lung injury. Further investigation of EBC pH as a marker of ventilator-induced lung injury is warranted.

A qualitative evaluation of patient experiences when diagnosed with oral cancer recurrence.

Loco-regional recurrence after radical primary treatment of oral cancer is associated with poor prognosis and major patient and career distress. The patient's psychosocial response to recurrence is underreported in the literature. This is one of the few papers to address in detail this stage in a patient's cancer journey. Qualitative methodology was used. Patients were recruited over a 13-month period. Analysis of recorded transcripts from 9 patients suggested that their illness experience and psychological response to diagnosis were multifaceted. Six key themes were identified, which were subdivided into 23 categories. Themes included emotional reactions, reevaluation, active coping strategies, life changes, support, and improvement in relationships. Emotional reactions ranged from shock and devastation, to fear and uncertainty, to hopelessness, to shame, to denial. Not all reactions were negative, and more positive experiences such as new found openness and improvement in relationships were expressed. There is heightened emotional vulnerability, and this leads to potentially difficult management issues among clinicians and members of the multidisciplinary team. Extreme sensitivity is required by all the individuals involved in providing healthcare at this acute time of patient and career distress.

Stem cells of the alveolar epithelium.

Elucidation of the biology of stem cells of the lung parenchyma could revolutionise treatment of patients with lung disorders such as cancer, acute respiratory distress syndrome, emphysema, and fibrotic lung disease. How close is this goal? Despite remarkable observations and ensuing advances, more questions than answers have been generated. Progenitors of the alveolar epithelium remain largely mysterious, so the prospect of isolating enough of these cells and delivering them effectively to cure disease remains remote. Similarly, the bone-marrow-derived cell that might most effectively engraft the lung remains unknown. If this mechanism is an important process for lung repair, why will the administration of additional cells be more effective? Finally, there is an issue of control of multipotent cells to avoid the generation of multiple teratomas, longevity of the graft, and possible immunological reactions to gene products inserted to replace a deficiency. The biology is exciting but not yet well enough understood to support therapeutic advances.

Exhaled breath condensate detects markers of pulmonary inflammation after cardiothoracic surgery.

Cardiac surgery using cardiopulmonary by-pass and, to a greater extent, lung resection, causes acute lung injury that is usually subclinical. Analysis of mediators in exhaled breath condensate is a promising means of monitoring inflammation in a variety of airway diseases but the contribution of the airway lining fluid from the lower respiratory tract is uncertain. We compared the analysis of markers of lung injury in exhaled breath condensate and bronchoalveolar lavage in endotracheally intubated patients before and after coronary artery bypass graft surgery with cardiopulmonary bypass and lobectomy. The neutrophil count and leukotriene B4 concentration in bronchoalveolar lavage fluid rose after coronary artery bypass graft surgery (p < 0.05), but there was no significant change in leukotriene B4, hydrogen peroxide, or hydrogen ion concentrations in exhaled breath condensate. By contrast, after lobectomy, the concentration in exhaled breath condensate of leukotriene B4, hydrogen peroxide and hydrogen ions rose significantly (p < 0.05). Exhaled breath condensate is a safe, noninvasive method of sampling the milieu of the distal lung and is sufficiently sensitive to detect markers of inflammation and oxidative stress in patients after lobectomy, but not after the milder insult associated with cardiac surgery.