Kidney derived apolipoprotein M and its role in acute kidney injury.

Aim: Apolipoprotein M (apoM) is mainly expressed in liver and in proximal tubular epithelial cells in the kidney. In plasma, apoM associates with HDL particles via a retained signal peptide and carries sphingosine-1-phosphate (S1P), a small bioactive lipid. ApoM is undetectable in urine from healthy individuals but lack of megalin receptors in proximal tubuli cells induces loss of apoM into the urine. Besides this, very little is known about kidney-derived apoM. The aim of this study was to address the role of apoM in kidney biology and in acute kidney injury. Methods: A novel kidney-specific human apoM transgenic mouse model (RPTEC-hapoMTG) was generated and subjected to either cisplatin or ischemia/reperfusion injury. Further, a stable transfection of HK-2 cells overexpressing human apoM (HK-2-hapoMTG) was developed to study the pattern of apoM secretion in proximal tubuli cells. Results: Human apoM was present in plasma from RPTEC-hapoMTG mice (mean 0.18 µM), with a significant increase in plasma S1P levels. In vitro apoM was secreted to both the apical (urine) and basolateral (blood) compartment from proximal tubular epithelial cells. However, no differences in kidney injury score was seen between RPTEC-hapoMTG and wild type (WT) mice upon kidney injury. Further, gene expression of inflammatory markers (i.e., IL6, MCP-1) was similar upon ischemia/reperfusion injury. Conclusion: Our study suggests that kidney-derived apoM is secreted to plasma, supporting a role for apoM in sequestering molecules from excretion in urine. However, overexpression of human apoM in the kidney did not protect against acute kidney injury.

A randomised trial comparing weaning from CPAP alone with weaning using heated humidified high flow nasal cannula in very preterm infants: the CHiPS study.

OBJECTIVE: To determine whether weaning from nasal continuous positive airway pressure (nCPAP) using heated humidified high flow nasal cannula (nHF) was non-inferior to weaning using nCPAP alone in relation to time on respiratory support. STUDY DESIGN: Single-centre, non-inferiority, randomised controlled trial. SETTING: Neonatal Intensive Care Unit, Middlemore Hospital, Auckland, New Zealand. PATIENTS: 120 preterm infants, <30 weeks' gestation at birth, stable on nCPAP for at least 48 hours. INTERVENTIONS: Infants underwent stratified randomisation to nHF 6 L/min or bubble CPAP 6 cm water. In both groups, stepwise weaning of their respiratory support over 96 hours according to a strict weaning protocol was carried out. MAIN OUTCOME MEASURES: Time on respiratory support from randomisation to 72 hours off respiratory support or 36 weeks' postmenstrual age. The non-inferiority threshold was set at 15%. RESULTS: 59 infants were randomised to weaning using nHF and 61 using nCPAP. The groups were well balanced in regards to baseline demographics. The restricted mean duration of respiratory support following randomisation for the nCPAP group, using per-protocol analysis was 401 hours (upper boundary, mean plus 0.15, was 461 hours) and 375 hours in the nHF group (upper 95% CI 413 hours). nHF weaning was, therefore, non-inferior to nCPAP weaning at the non-inferiority threshold. There was no significant difference in time to discharge. CONCLUSION: For infants ready to wean from nCPAP, the CHiPS study found that nHF was non-inferior to discontinuing nCPAP at 5 cm water. TRIAL REGISTRATION NUMBER: Australia and New Zealand Clinical Trials Registry (ACTRN12615000077561).

Radial-probe endobronchial ultrasound outcomes in the investigation of peripheral pulmonary lesions: a New Zealand perspective.

BACKGROUND: Radial-probe endobronchial ultrasound (radial-EBUS) is becoming an important investigation for peripheral pulmonary lesions (PPL). A key advantage of radial-EBUS is the favourable risk profile compared with current gold-standard computerised tomography-guided biopsy. AIM: To investigate the diagnostic yield, predictors of positive yield and radial-EBUS safety in a New Zealand institution. We also determined whether molecular analysis was possible on the same tissue samples. METHODS: We performed a retrospective analysis of all patients (n = 68) from Middlemore Hospital, Auckland, undergoing radial-EBUS with guide-sheath for PPL from March 2015 to August 2016. Clinical, radiological and procedural data were collected. Radial-EBUS diagnostic yield was determined for malignant and benign diagnoses, and molecular analysis yield was determined on appropriate malignant samples. Logistic regression was used to determine factors predicting successful radial-EBUS. RESULTS: Overall diagnostic yield of radial-EBUS was 55.9% (95% confidence interval (CI): 44.3-67.9). Malignant diagnostic sensitivity was 60.8% (95% CI: 46.1-74.2) and benign diagnostic sensitivity was 50% (95% CI: 23-77). Lesions close to the hilum (P = 0.039), concentric radial-probe positioning (P = 0.008) and the use of forceps as first instrument (P = 0.0049) significantly predicted successful diagnostic yield. Of the malignant cases 81.0% (95% CI: 58.1-94.6) were sufficient for molecular analysis. Pneumothorax occurred in 4.4% (95% CI: 0.9-12.4), none required chest drain intervention. There were no cases of significant pulmonary haemorrhage. CONCLUSION: Radial-EBUS was shown to be safe with diagnostic yield similar to international reports. Important predictors of success include distance from hilum, probe position and forceps as first instrument. We also demonstrated that molecular analysis is possible in radial-EBUS obtained samples.

The Apolipoprotein M/S1P Axis Controls Triglyceride Metabolism and Brown Fat Activity.

Apolipoprotein M (apoM) is the carrier of sphingosine-1-phosphate (S1P) in plasma high-density lipoproteins. S1P is a bioactive lipid interacting with five receptors (S1P1-5). We show that lack of apoM in mice increases the amount of brown adipose tissue (BAT), accelerates the clearance of postprandial triglycerides, and protects against diet-induced obesity (i.e., a phenotype similar to that induced by cold exposure or ß3-adrenergic stimulation). Moreover, the data suggest that the phenotype of apoM-deficient mice is S1P dependent and reflects diminished S1P1 stimulation. The results reveal a link between the apoM/S1P axis and energy metabolism.

Apolipoprotein M mediates sphingosine-1-phosphate efflux from erythrocytes.

Sphingosine-1-phosphate (S1P) is a bioactive lipid implicated in e.g. angiogenesis, lymphocyte trafficking, and endothelial barrier function. Erythrocytes are a main source of plasma S1P together with platelets and endothelial cells. Apolipoprotein M (apoM) in HDL carries 70% of plasma S1P, whereas 30% is carried by albumin. The current aim was to investigate the role of apoM in export of S1P from human erythrocytes. Erythrocytes exported S1P more efficiently to HDL than to albumin, particularly when apoM was present in HDL. In contrast, export of sphingosine to HDL was unaffected by the presence of apoM. The specific ability of apoM to promote export of S1P was independent of apoM being bound in HDL particles. Treatment with MK-571, an inhibitor of the ABCC1 transporter, effectively reduced export of S1P from human erythrocytes to apoM, whereas the export was unaffected by inhibitors of ABCB1 or ATPase. Thus, ABCC1 could be involved in export of S1P from erythrocytes to apoM.

Impaired endothelial barrier function in apolipoprotein M-deficient mice is dependent on sphingosine-1-phosphate receptor 1.

Apolipoprotein M (ApoM) transports sphingosine-1-phosphate (S1P) in plasma, and ApoM-deficient mice (Apom(-/-)) have ∼50% reduced plasma S1P levels. There are 5 known S1P receptors, and S1P induces adherens junction formation between endothelial cells through the S1P1 receptor, which in turn suppresses vascular leak. Increased vascular permeability is a hallmark of inflammation. The purpose of this study was to explore the relationships between vascular leakage in ApoM deficiency and S1P1 function in normal physiology and in inflammation. Vascular permeability in the lungs was assessed by accumulation of dextran molecules (70 kDa) and was increased ∼40% in Apom(-/-) mice compared to WT (C57Bl6/j) mice. Reconstitution of plasma ApoM/S1P or treatment with an S1P1 receptor agonist (SEW2871) rapidly reversed the vascular leakage to a level similar to that in WT mice, suggesting that it is caused by decreased plasma levels of S1P and reduced S1P1 stimulation. In a carrageenan-induced model of inflammation, Apom(-/-) mice had increased vascular leakage compared with that in WT mice. Adenoviral overexpression of ApoM in Apom(-/-) mice decreased the vascular leakage compared to adenoviral overexpression of green fluorescent protein. The study suggests that vascular leakage of albumin-sized particles in ApoM deficiency is S1P- and S1P1-dependent and this dependency exacerbates the response to inflammatory stimuli.-Christensen, P. M., Liu, C. H., Swendeman, S. L., Obinata, H., Qvortrup, K., Nielsen, L B., Hla, T., Di Lorenzo, A., Christoffersen, C. Impaired endothelial barrier function in apolipoprotein M-deficient mice is dependent on sphingosine-1-phosphate receptor 1.

Comparison between two assessment methods for exercise-induced laryngeal obstructions.

Exercise-induced laryngeal obstructions (E-ILOs) are important differential diagnoses to exercise-induced asthma and are diagnosed by the continuous laryngoscopy exercise (CLE) test. There are two different methods for evaluating the severity of E-ILOs using recordings from the CLE test; the CLE score and EILOMEA. The aim of this study was to investigate the consistency between these methods. Using their respective method, the developers of each method evaluated 60 laryngoscopic recordings from patients with different subtypes and various levels of severity of E-ILOs. The CLE score evaluates glottic and supraglottic obstructions on a 4-grade scale. EILOMEA uses software to calculate the obstruction severity on continuous scales from a still frame of the larynx during maximal obstruction giving three parameters reflecting glottic and supraglottic obstruction. The means of the EILOMEA measures differed significantly for CLE score 1 vs. 2 and 2 vs. 3, but not for 0 vs. 1 for glottic as well as supraglottic obstructions. The EILOMEA method does not distinguish between CLE score 0 and 1, but otherwise the methods correlate. Since previous studies have suggested that only CLE scores of 2 and 3 reflect a severity of E-ILOs of clinical importance, this lack of the EILOMEA method is not crucial for a correct medical evaluation.

ERS/ELS/ACCP 2013 international consensus conference nomenclature on inducible laryngeal obstructions.

Individuals reporting episodes of breathing problems caused by re-occurring variable airflow obstructions in the larynx have been described in an increasing number of publications, with more than 40 different terms being used without consensus on definitions. This lack of an international consensus on nomenclature is a serious obstacle for the development of the area, as knowledge from different centres cannot be matched, pooled or readily utilised by others. Thus, an international Task Force has been created, led by the European Respiratory Society/European Laryngological Society/American College of Chest Physicians. This review describes the methods used to reach an international consensus on the subject and the resulting nomenclature, the 2013 international consensus conference nomenclature.

Apolipoprotein M in lipid metabolism and cardiometabolic diseases.

PURPOSE: This review will address recent findings on apolipoprotein M (apoM) and its ligand sphingosine-1-phosphate (S1P) in lipid metabolism and inflammatory diseases. RECENT FINDINGS: ApoM's likely role(s) in health and disease has become more diverse after the discovery that apoM functions as a chaperone for S1P. Hence, apoM has recently been implicated in lipid metabolism, diabetes and rheumatoid arthritis through in-vivo, in-vitro and genetic association studies. It remains to be established to which degree such associations with apoM can be attributed to its ability to bind S1P. SUMMARY: The apoM/S1P axis and its implications in atherosclerosis and lipid metabolism have been thoroughly studied. Owing to the discovery of the apoM/S1P axis, the scope of apoM research has broadened. ApoM and S1P have been implicated in lipid metabolism, that is by modulating HDL particles. Also, the importance in regulating endothelial function is being investigated. Furthermore, both apoM and S1P have been linked to diabetes and glucose and insulin metabolism. Finally, genetic variations in the apoM gene are associated with lipid disturbances, diabetes and rheumatoid arthritis. These findings suggest not only diverse effects of apoM, but also the important question of whether apoM mainly acts as a S1P carrier, if apoM carries other substances with biological effects as well, or whether the apoM protein has effects on its own.

Can flow-volume loops be used to diagnose exercise induced laryngeal obstructions? A comparison study examining the accuracy and inter-rater agreement of flow volume loops as a diagnostic tool.

BACKGROUND: Pre- and post-exercise flow-volume loops are often recommended as an easy non-invasive method for diagnosing or excluding exercise-induced laryngeal obstructions in patients with exercise-related respiratory symptoms. However, at present there is no evidence for this recommendation. AIMS: To compare physician evaluated pre- and post-exercise flow-volume loops and flow data with laryngoscopic findings during exercise. METHODS: Data from 100 consecutive exercise tests with continuous laryngoscopy during the test were analysed. Laryngoscopic images were compared with the corresponding pre- and post-exercise flow-volume loops assessed by four separate physicians and with data from the loops (forced inspiratory flow (FIF) at 25% vs. FIF at 75% of forced inspiratory vital capacity (FIVC), forced expiratory flow at 50% of forced expiratory volume vs. FIF at 50% of FIVC, and FIVC vs. FIF at 50% of FIVC). RESULTS: There was no significant association between the laryngoscopic findings and the flow-volume data. There was no agreement between the four physicians in their assessment of the flow-volume loops (kappa <0.00), and none of the individual physician's assessments were significantly associated with the laryngoscopic findings. CONCLUSIONS: Exercise-induced laryngeal obstructions cannot be diagnosed or excluded by physician evaluated pre- and post-exercise flow-volume loops or flow data alone.

Eucapnic voluntary hyperventilation in diagnosing exercise-induced laryngeal obstructions.

Exercise-induced laryngeal obstructions (EILOs) cause exercise-related respiratory symptoms (ERRS) and are important differential diagnoses to exercise-induced asthma. The diagnostic method for EILOs includes provocation to induce the obstruction followed by a verification of the obstruction and the degree thereof. The objective of the present study was to examine if a eucapnic voluntary hyperventilation (EVH) test could induce laryngeal obstructions laryngoscopically identical in subtypes and development as seen during an exercise test. EVH and exercise testing with continuous laryngoscopy were performed during a screening of two national athletic teams (n = 67). The laryngoscopic recordings were examined for usability, abnormalities and maximal supraglottic and glottic obstruction using two currently available methods (Eilomea and CLE-score). The participants were asked questions on ERRS, and whether the symptoms experienced during each provocation matched those experienced during regular training. A total of 39 completed both tests. There were no significant differences in subtypes and development thereof, the experience of symptoms, and specificity and sensitivity between the methods. Significantly more recordings obtained during the exercise test were usable for evaluation primarily due to resilient mucus on the tip of the fiber-laryngoscope in the EVH test. Only recordings of six athletes from both provocation methods were usable for evaluation using the Eilomea method (high-quality demand). Amongst these, a linear correlation was found for the glottic obstruction. EVH tests can induce EILOs. However, the present test protocol needs adjustments to secure better visualisation of the larynx during provocation.

The plasma concentration of HDL-associated apoM is influenced by LDL receptor-mediated clearance of apoB-containing particles.

ApoM is mainly associated with HDL. Nevertheless, we have consistently observed positive correlations of apoM with plasma LDL cholesterol in humans. Moreover, LDL receptor deficiency is associated with increased plasma apoM in mice. Here, we tested the idea that plasma apoM concentrations are affected by the rate of LDL receptor-mediated clearance of apoB-containing particles. We measured apoM in humans each carrying one of three different LDL receptor mutations (n = 9) or the apoB3500 mutation (n = 12). These carriers had increased plasma apoM (1.34 ± 0.13 µM, P = 0.003, and 1.23 ± 0.10 µM, P = 0.02, respectively) as compared with noncarriers (0.93 ± 0.04 µM). When we injected human apoM-containing HDL into Wt (n = 6) or LDL receptor-deficient mice (n = 6), the removal of HDL-associated human apoM was delayed in the LDL receptor-deficient mice. After 2 h, 54 ± 5% versus 90 ± 8% (P < 0.005) of the initial amounts of human apoM remained in the plasma of Wt and LDL receptor-deficient mice, respectively. Finally, we compared the turnover of radio-iodinated LDL and plasma apoM concentrations in 45 normocholesterolemic humans. There was a negative correlation between plasma apoM and the fractional catabolic rate of LDL (r = -0.38, P = 0.009). These data suggest that the plasma clearance of apoM, despite apoM primarily being associated with HDL, is influenced by LDL receptor-mediated clearance of apoB-containing particles.

Exercise-induced laryngeal obstructions: prevalence and symptoms in the general public.

Respiratory difficulties caused by exercise-induced laryngeal obstructions (EILOs) are reported with increasing frequency. The aim of this study was to assess the prevalence and symptoms of EILOs and their relation to airway hyperresponsiveness (AHR). In total, 556 randomly selected youths in Copenhagen aged 14-24 years were invited over a 2-year period. The study included a mailed questionnaire and two visits: day 1 (an interview-based questionnaire, methacholine bronchial provocation test and physical exertion test); and day 2 [an exercise test with continuous laryngoscopic recordings (CLE test)]. The diagnosis of EILOs was based on the CLE test. In total, 237 answered the mailed questionnaire and 150 participated on day 1 whereof 98 participated on day 2 also. AHR was verified in 23 (4.1% of invitees) and EILOs in 42 (7.5% of invitees). Co-morbidity was verified in 6 cases (26.1% of verified AHR cases). No symptoms were found specific for either AHR or EILOs. The minimum prevalence of EILOs in this cohort was 7.5%. EILOs were verified in 26.1% of participants with AHR. Questionnaires could not differentiate between AHR and EILOs.