Electroencephalogram Biomarkers from Anesthesia Induction to Identify Vulnerable Patients at Risk for Postoperative Delirium

BACKGROUND

Postoperative delirium is a common complication in elderly patients undergoing anesthesia. Even though it is increasingly recognized as an important health issue, the early detection of patients at risk for postoperative delirium remains a challenge. This study aims to identify predictors of postoperative delirium by analyzing frontal electroencephalogram at propofol-induced loss of consciousness.

METHODS

This prospective, observational single-center study included patients older than 70 yr undergoing general anesthesia for a planned surgery. Frontal electroencephalogram was recorded on the day before surgery (baseline) and during anesthesia induction (1, 2, and 15 min after loss of consciousness). Postoperative patients were screened for postoperative delirium twice daily for 5 days. Spectral analysis was performed using the multitaper method. The electroencephalogram spectrum was decomposed in periodic and aperiodic (correlates to asynchronous spectrum wide activity) components. The aperiodic component is characterized by its offset (y intercept) and exponent (the slope of the curve). Computed electroencephalogram parameters were compared between patients who developed postoperative delirium and those who did not. Significant electroencephalogram parameters were included in a binary logistic regression analysis to predict vulnerability for postoperative delirium.

RESULTS

Of 151 patients, 50 (33%) developed postoperative delirium. At 1 min after loss of consciousness, postoperative delirium patients demonstrated decreased alpha (postoperative delirium: 0.3 μV2 [0.21 to 0.71], no postoperative delirium: 0.55 μV2 [0.36 to 0.74]; P = 0.019] and beta band power [postoperative delirium: 0.27 μV2 [0.12 to 0.38], no postoperative delirium: 0.38 μV2 [0.25 to 0.48]; P = 0.003) and lower spectral edge frequency (postoperative delirium: 10.45 Hz [5.65 to 15.04], no postoperative delirium: 14.56 Hz [9.51 to 16.65]; P = 0.01). At 15 min after loss of consciousness, postoperative delirium patients displayed a decreased aperiodic offset (postoperative delirium: 0.42 μV2 (0.11 to 0.69), no postoperative delirium: 0.62 μV2 [0.37 to 0.79]; P = 0.004). The logistic regression model predicting postoperative delirium vulnerability demonstrated an area under the curve of 0.73 (0.69 to 0.75).

CONCLUSIONS

The findings suggest that electroencephalogram markers obtained during loss of consciousness at anesthesia induction may serve as electroencephalogram-based biomarkers to identify at an early time patients at risk of developing postoperative delirium.

EDITOR’S PERSPECTIVE

European Society of Anaesthesiology and Intensive Care consensus document on sustainability: 4 scopes to achieve a more sustainable practice

Climate change is a defining issue for our generation. The carbon footprint of clinical practice accounts for 4.7% of European greenhouse gas emissions, with the European Union ranking as the third largest contributor to the global healthcare industry's carbon footprint, after the United States and China. Recognising the importance of urgent action, the European Society of Anaesthesiology and Intensive Care (ESAIC) adopted the Glasgow Declaration on Environmental Sustainability in June 2023. Building on this initiative, the ESAIC Sustainability Committee now presents a consensus document in perioperative sustainability. Acknowledging wider dimensions of sustainability, beyond the environmental one, the document recognizes healthcare professionals as cornerstones for sustainable care, and puts forward recommendations in four main areas: direct emissions, energy, supply chain and waste management, and psychological and self-care of healthcare professionals. Given the urgent need to cut global carbon emissions, and the scarcity of evidence-based literature on perioperative sustainability, our methodology is based on expert opinion recommendations. A total of 90 recommendations were drafted by 13 sustainability experts in anaesthesia in March 2023, then validated by 36 experts from 24 different countries in a two-step Delphi validation process in May and June 2023. To accommodate different possibilities for action in high- versus middle-income countries, an 80% agreement threshold was set to ease implementation of the recommendations Europe-wide. All recommendations surpassed the 80% agreement threshold in the first Delphi round, and 88 recommendations achieved an agreement >90% in the second round. Recommendations include the use of very low fresh gas flow, choice of anaesthetic drug, energy and water preserving measures, "5R" policies including choice of plastics and their disposal, and recommendations to keep a healthy work environment or on the importance of fatigue in clinical practice. Executive summaries of recommendations in areas 1, 2 and 3 are available as cognitive aids that can be made available for quick reference in the operating room.

Isolation of circulating endothelial cells provides tool to determine endothelial cell senescence in blood samples

Circulating endothelial cells (CEC) are arising as biomarkers for vascular diseases. However, whether they can be utilized as markers of endothelial cell (EC) senescence in vivo remains unknown. Here, we present a protocol to isolate circulating endothelial cells for a characterization of their senescent signature. Further, we characterize different models of EC senescence induction in vitro and show similar patterns of senescence being upregulated in CECs of aged patients as compared to young volunteers. Replication-(ageing), etoposide-(DNA damage) and angiotensin II-(ROS) induced senescence models showed the expected cell morphology and proliferation-reduction effects. Expression of senescence-associated secretory phenotype markers was specifically upregulated in replication-induced EC senescence. All models showed reduced telomere lengths and induction of the INK4a/ARF locus. Additional p14ARF-p21 pathway activation was observed in replication- and etoposide-induced EC senescence. Next, we established a combined magnetic activated- and fluorescence activated cell sorting (MACS-FACS) based protocol for CEC isolation. Interestingly, CECs isolated from aged volunteers showed similar senescence marker patterns as replication- and etoposide-induced senescence models. Here, we provide first proof of senescence in human blood derived circulating endothelial cells. These results hint towards an exciting future of using CECs as mirror cells for in vivo endothelial cell senescence, of particular interest in the context of endothelial dysfunction and cardiovascular diseases.

Update of the European Society of Anaesthesiology and Intensive Care Medicine evidence-based and consensus-based guideline on postoperative delirium in adult patients

Postoperative delirium (POD) remains a common, dangerous and resource-consuming adverse event but is often preventable. The whole peri-operative team can play a key role in its management. This update to the 2017 ESAIC Guideline on the prevention of POD is evidence-based and consensus-based and considers the literature between 01 April 2015, and 28 February 2022. The search terms of the broad literature search were identical to those used in the first version of the guideline published in 2017. POD was defined in accordance with the DSM-5 criteria. POD had to be measured with a validated POD screening tool, at least once per day for at least 3 days starting in the recovery room or postanaesthesia care unit on the day of surgery or, at latest, on postoperative day 1. Recent literature confirmed the pathogenic role of surgery-induced inflammation, and this concept reinforces the positive role of multicomponent strategies aimed to reduce the surgical stress response. Although some putative precipitating risk factors are not modifiable (length of surgery, surgical site), others (such as depth of anaesthesia, appropriate analgesia and haemodynamic stability) are under the control of the anaesthesiologists. Multicomponent preoperative, intra-operative and postoperative preventive measures showed potential to reduce the incidence and duration of POD, confirming the pivotal role of a comprehensive and team-based approach to improve patients' clinical and functional status.

Peroral endoscopic myotomy: a two-center retrospective study of practice and adverse events

Background and study aims

Peroral endoscopic myotomy (POEM) is the preferred technique for the treatment of esophageal motility disorders and is less invasive than surgery. This study was performed to compare two university centers in the practice of POEM, in terms of efficacy and adverse events, for the treatment of esophageal motility disorder.

Patients and methods

Retrospective comparative study of patients undergoing a POEM between September 2020 and December 2022 from the University Hospital of Liège (Belgium) and Besançon (France). The clinical success was defined by an Eckardt score ≤ 3 after the procedure.

Results

Fifty-five patients were included. In both centers, 87,3% of the patients had achalasia (mostly type II), and 12,7% had another esophageal motility disorder. The use of antibiotic prophylaxis was systematic in Liège center but not in Besançon center (100% and 9.1% respectively). The mean value of the post-operative Eckardt score was 1.55± 2.48 in both center with 93.2% of patients with a score ≤ 3 (92% in Besançon and 94.74% in Liège). The rate of adverse event was generally low. There were two minor adverse events more frequent in Liège, clinical capnomediastinum and pain at day one, but they were managed with conservative treatment. Only 7.3% of the total patients had an infectious phenomenon that did not correlate with the use of antibiotic prophylaxis.

Conclusion

The post-operative Eckardt score and the adverse event rate were comparable between the university centers. This study confirmed that POEM is a safe and effective technique. It also showed that using an antibiotic prophylaxis does not influence the development of infectious adverse events.

Desflurane is risk factor for postoperative delirium in older patients' independent from intraoperative burst suppression duration

Background

Postoperative Delirium (POD) is the most frequent neurocognitive complication after general anesthesia in older patients. The development of POD is associated with prolonged periods of burst suppression activity in the intraoperative electroencephalogram (EEG). The risk to present burst suppression activity depends not only on the age of the patient but is also more frequent during propofol anesthesia as compared to inhalative anesthesia. The aim of our study is to determine, if the risk to develop POD differs depending on the anesthetic agent given and if this correlates with a longer duration of intraoperative burst suppression.

Methods

In this secondary analysis of the SuDoCo trail [ISRCTN 36437985] 1277 patients, older than 60 years undergoing general anesthesia were included. We preprocessed and analyzed the raw EEG files from each patient and evaluated the intraoperative burst suppression duration. In a logistic regression analysis, we assessed the impact of burst suppression duration and anesthetic agent used for maintenance on the risk to develop POD.

Results

18.7% of patients developed POD. Burst suppression duration was prolonged in POD patients (POD 27.5 min ± 21.3 min vs. NoPOD 21.4 ± 16.2 min, p < 0.001), for each minute of prolonged intraoperative burst suppression activity the risk to develop POD increased by 1.1% (OR 1.011, CI 95% 1.000-1.022, p =  0.046). Burst suppression duration was prolonged under propofol anesthesia as compared to sevoflurane and desflurane anesthesia (propofol 32.5 ± 20.3 min, sevoflurane 17.1 ± 12.6 min and desflurane 20.1 ± 16.0 min, p < 0.001). However, patients receiving desflurane anesthesia had a 1.8fold higher risk to develop POD, as compared to propofol anesthesia (OR 1.766, CI 95% 1.049-2.974, p =  0.032).

Conclusion

We found a significantly increased risk to develop POD after desflurane anesthesia in older patients, even though burst suppression duration was shorter under desflurane anesthesia as compared to propofol anesthesia. Our finding might help to explain some discrepancies in studies analyzing the impact of burst suppression duration and EEG-guided anesthesia on the risk to develop POD.

Unveiling age-independent spectral markers of propofol-induced loss of consciousness by decomposing the electroencephalographic spectrum into its periodic and aperiodic components

Background

Induction of general anesthesia with propofol induces radical changes in cortical network organization, leading to unconsciousness. While perioperative frontal electroencephalography (EEG) has been widely implemented in the past decades, validated and age-independent EEG markers for the timepoint of loss of consciousness (LOC) are lacking. Especially the appearance of spatially coherent frontal alpha oscillations (8-12 Hz) marks the transition to unconsciousness.Here we explored whether decomposing the EEG spectrum into its periodic and aperiodic components unveiled markers of LOC and investigated their age-dependency. We further characterized the LOC-associated alpha oscillations by parametrizing the adjusted power over the aperiodic component, the center frequency, and the bandwidth of the peak in the alpha range.

Methods

In this prospective observational trial, EEG were recorded in a young (18-30 years) and an elderly age-cohort (≥ 70 years) over the transition to propofol-induced unconsciousness. An event marker was set in the EEG recordings at the timepoint of LOC, defined with the suppression of the lid closure reflex. Spectral analysis was conducted with the multitaper method. Aperiodic and periodic components were parametrized with the FOOOF toolbox. Aperiodic parametrization comprised the exponent and the offset. The periodic parametrization consisted in the characterization of the peak in the alpha range with its adjusted power, center frequency and bandwidth. Three time-segments were defined: preLOC (105 - 75 s before LOC), LOC (15 s before to 15 s after LOC), postLOC (190 - 220 s after LOC). Statistical significance was determined with a repeated-measures ANOVA.

Results

Loss of consciousness was associated with an increase in the aperiodic exponent (young: p = 0.004, elderly: p = 0.007) and offset (young: p = 0.020, elderly: p = 0.004) as well as an increase in the adjusted power (young: p < 0.001, elderly p = 0.011) and center frequency (young: p = 0.008, elderly: p < 0.001) of the periodic alpha peak. We saw age-related differences in the aperiodic exponent and offset after LOC as well as in the power and bandwidth of the periodic alpha peak during LOC.

Conclusion

Decomposing the EEG spectrum over induction of anesthesia into its periodic and aperiodic components unveiled novel age-independent EEG markers of propofol-induced LOC: the aperiodic exponent and offset as well as the center frequency and adjusted power of the power peak in the alpha range.

Sustainability of dermatological offices and clinics: challenges and potential solutions

Ongoing high consumption of resources results in exceeding the planetary boundaries. Modern healthcare systems contribute to this problem. To address this issue, this article provides an overview of various aspects of sustainable actions in medical offices and clinics that can also be applied to dermatology. Specific fields of action include energy consumption, structural measures, traffic and mobility, organization including digitalization as well as personnel and evaluation. Moreover, we discuss specific topics such as hygiene and cleansing, dermatosurgery and prescription practices. External treatments and cosmetics are discussed separately as dermatological peculiarities. Finally, we provide information on established initiatives for more sustainable health care in Germany. We aim to encourage critical reappraisal of currently established practices and to stimulate the implementation of sustainable measures.

Muscular myostatin gene expression and plasma concentrations are decreased in critically ill patients

Background

The objective was to investigate the role of gene expression and plasma levels of the muscular protein myostatin in intensive care unit-acquired weakness (ICUAW). This was performed to evaluate a potential clinical and/or pathophysiological rationale of therapeutic myostatin inhibition.

Methods

A retrospective analysis from pooled data of two prospective studies to assess the dynamics of myostatin plasma concentrations (day 4, 8 and 14) and myostatin gene (MSTN) expression levels in skeletal muscle (day 15) was performed. Associations of myostatin to clinical and electrophysiological outcomes, muscular metabolism and muscular atrophy pathways were investigated.

Results

MSTN gene expression (median [IQR] fold change: 1.00 [0.68–1.54] vs. 0.26 [0.11–0.80]; p = 0.004) and myostatin plasma concentrations were significantly reduced in all critically ill patients when compared to healthy controls. In critically ill patients, myostatin plasma concentrations increased over time (median [IQR] fold change: day 4: 0.13 [0.08/0.21] vs. day 8: 0.23 [0.10/0.43] vs. day 14: 0.40 [0.26/0.61]; p < 0.001). Patients with ICUAW versus without ICUAW showed significantly lower MSTN gene expression levels (median [IQR] fold change: 0.17 [0.10/0.33] and 0.51 [0.20/0.86]; p = 0.047). Myostatin levels were directly correlated with muscle strength (correlation coefficient 0.339; p = 0.020) and insulin sensitivity index (correlation coefficient 0.357; p = 0.015). No association was observed between myostatin plasma concentrations as well as MSTN expression levels and levels of mobilization, electrophysiological variables, or markers of atrophy pathways.

Conclusion

Muscular gene expression and systemic protein levels of myostatin are downregulated during critical illness. The previously proposed therapeutic inhibition of myostatin does therefore not seem to have a pathophysiological rationale to improve muscle quality in critically ill patients.

Trial registration: ISRCTN77569430—13th of February 2008 and ISRCTN19392591 17th of February 2011.

Graphical abstract

Air quality in Germany as a contributing factor to morbidity from COVID-19

BACKGROUND

The SARS-CoV-2 virus has been spreading in Germany since January 2020, with regional differences in incidence, morbidity, and mortality. Long-term exposure to air pollutants as nitrogen dioxide (NO₂), nitrogen monoxide (NO), ozone (O₃), and particulate matter (<10 μm PM₁₀, <2.5 μm PM_2.5) has a negative impact on respiratory functions. We analyze the association between long-term air pollution and the outcome of SARS-CoV-2 infections in Germany.

METHODS

We conducted an observational study in Germany on county-level, investigating the association between long-term (2010-2019) air pollutant exposure (European Environment Agency, AirBase data set) and COVID-19 incidence, morbidity, and mortality rate during the first outbreak of SARS-CoV-2 (open source data Robert Koch Institute). We used negative binominal models, including adjustment for risk factors (age, sex, days since first COVID-19 case, population density, socio-economic and health parameters).

RESULTS

After adjustment for risk factors in the tri-pollutant model (NO₂, O₃, PM_2.5) an increase of 1 μg/m³ NO₂ was associated with an increase of the need for intensive care due to COVID-19 by 4.2% (95% CI 1.011-1.074), and mechanical ventilation by 4.6% (95% CI 1.010-1.084). A tendency towards an association of NO₂ with COVID-19 incidence was indicated, as the results were just outside of the defined statistical significance (+1.6% (95% CI 1.000-1.032)). Long-term annual mean NO₂ level ranged from 4.6 μg/m³ to 32 μg/m³.

CONCLUSIONS

Our results indicate that long-term NO₂ exposure may have increased susceptibility for COVID-19 morbidity in Germany. The results demonstrate the need to reduce ambient air pollution to improve public health.

Machine-learning model predicting postoperative delirium in older patients using intraoperative frontal electroencephalographic signatures

Objective

In older patients receiving general anesthesia, postoperative delirium (POD) is the most frequent form of cerebral dysfunction. Early identification of patients at higher risk to develop POD could provide the opportunity to adapt intraoperative and postoperative therapy. We, therefore, propose a machine learning approach to predict the risk of POD in elderly patients, using routine intraoperative electroencephalography (EEG) and clinical data that are readily available in the operating room.

Methods

We conducted a retrospective analysis of the data of a single-center study at the Charité-Universitätsmedizin Berlin, Department of Anesthesiology [ISRCTN 36437985], including 1,277 patients, older than 60 years with planned surgery and general anesthesia. To deal with the class imbalance, we used balanced ensemble methods, specifically Bagging and Random Forests and as a performance measure, the area under the ROC curve (AUC-ROC). We trained our models including basic clinical parameters and intraoperative EEG features in particular classical spectral and burst suppression signatures as well as multi-band covariance matrices, which were classified, taking advantage of the geometry of a Riemannian manifold. The models were validated with 10 repeats of a 10-fold cross-validation.

Results

Including EEG data in the classification resulted in a robust and reliable risk evaluation for POD. The clinical parameters alone achieved an AUC-ROC score of 0.75. Including EEG signatures improved the classification when the patients were grouped by anesthetic agents and evaluated separately for each group. The spectral features alone showed an AUC-ROC score of 0.66; the covariance features showed an AUC-ROC score of 0.68. The AUC-ROC scores of EEG features relative to patient data differed by anesthetic group. The best performance was reached, combining both the EEG features and the clinical parameters. Overall, the AUC-ROC score was 0.77, for patients receiving Propofol it was 0.78, for those receiving Sevoflurane it was 0.8 and for those receiving Desflurane 0.73. Applying the trained prediction model to an independent data set of a different clinical study confirmed these results for the combined classification, while the classifier on clinical parameters alone did not generalize.

Conclusion

A machine learning approach combining intraoperative frontal EEG signatures with clinical parameters could be an easily applicable tool to early identify patients at risk to develop POD.

Inflammatory and diabetic conditions trigger SHP2 tyrosine phosphatase expression and subsequent aberrant activation of primary human monocytes

Purpose

Atherosclerosis is an inflammatory process that is particularly accelerated in diabetics, leading to increased incidence of cardiovascular diseases such as CAD and PAD in diabetic patients. Monocytes are the main component of atherosclerosis development. SHP-2 tyrosine phosphatase has been identified as an important regulator of monocyte function. The present study therefore aims to investigate the regulation of SHP-2 in inflammatory and diabetic conditions.

Methods

Primary human monocytes were isolated from the peripheral blood of type 2 Diabetes mellitus (T2DM) patients and healthy individuals. Monocytes were incubated with pro-inflammatory cytokine TNFa. For diabetic conditions, monocytes were incubated with methylglyoxal (MG), a highly reactive side product of glycolysis, or Receptor for advanced glycation end product (RAGE) ligand AGE-bovine serum (AGE-BSA). Monocyte migration was studied with Transwell migration assays. Expression of important molecules was investigated with Western Blot, RT-qPCR or FACS. Pharmacological inhibitors for SHP2, RAGE or NFκB were used.

Results

First, we could detect a significant correlation between SHP-2 mRNA and TNFa levels in T2DM monocytes in comparison to monocytes from healthy individuals. In line with that, incubation of monocytes with TNFa lead to an enhanced expression of SHP-2. Co-incubation with NFκB-inhibitor blocked TNFa-induced SHP-2 upregulation. Interestingly, incubation of monocytes with methylglyoxal caused increased release of TNFa and also augmented expression of SHP-2, indicating a pro-inflammatory effect of diabetic conditions.

Moreover, AGE-BSA treatment induced enhanced SHP-2 expression, reflecting an inflammatory-independent pathway which regulates SHP-2 additionally. This could be supported by the observation that pharmacological inhibition of RAGE attenuated both AGE-BSA and MG-induced SHP-2 activation. On a functional level, increased expression of SHP-2 in each treatment resulted in a pro-migratory phenotype that could be completely reversed by inhibition of RAGE, respectively. Fittingly, monocytes from T2DM patients showed increased migration, which normalized to an ordinary level after application of a SHP-2 inhibitor.

Conclusions

The present results reveal a new mechanism for accelerated atherosclerosis development in diabetic patients. MG and advanced glycated end products, as crucial components of the diabetic milieu, lead to increased expression of SHP-2 via the RAGE-NFkB signalling axis. Interestingly, this diabetic environment causes an increased inflammatory response through the release of TNFa cytokine, which itself leads to enhanced SHP-2 expression through activation of the NFkB transcription factor. Finally, by pharmacological inhibition of each component in this outlined SHP-2 regulatory pathway, we were able to prevent the pro-migratory activation of monocytes, offering a new approach to the treatment of diabetes-induced atherosclerosis.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): IZKF SEED Project 14/20

Primary human monocytes are stimulated in a pro-atherosclerotic manner in hyperhomocysteine conditions by attenuated PTEN phosphatase function

Purpose

Monocytes are essential for atherosclerosis and hereby crucial for the detrimental consequences of cardiovascular diseases like coronary heart disease. Interestingly, homocysteine (HCY) was identified as an idependent risk factor for atherosclerosis development. However, the specific implication of HCY on monocytes has not yet been clarified and was therefore investigated in the present study.

Methods

Primary human monocytes, isolated from peripheral blood through the immuno-magnetic method, were treated with a clinically relevant dose of 400 μM HCY for 24 hours. Monocyte migration was investigated with transwell migration assays. Adhesion to inflamed endothelium (HUVECs) was studied under static and physiological flow conditions. Expression of relevant molecules was quantified with Western Blot, RT-qPCR and FACS. 5-azacytidine (AZA) was used to inhibit DNA methyltransferase 1 (DNMT1) and SF1670 to inhibit PTEN.

Results

First, we studied monocyte migration phenotype. Under hyperhomocysteine conditons monocytes revealed elevated chemokinesis and enhance chemotaxis towards MCP-1. In addition, monocytes show a pro-adhesive phenotype under HCY treatment which was indicated by heightened adhesion to inflamed endothelial cells, both in static and physiological flow conditions. These data could be sustained by observation of HCY-induced augmented expression of adhesion molecule CD11a on primary human monocytes. Interestingly, we observed decreased PTEN phosphatase function and activity in HCY-treated monocytes, which was reflected downstream in increased activation of AKT at serine 473. Based on these data, it was also possible to induce the pro-migratory phenotype in monocytes by pharmacological inhibition of PTEN alone. Since HCY can modify the methylation status of PTEN and hereby regulates its expression, we inhibited DNMT1 with AZA which could prevent downregulation of PTEN expression by HCY treatment. In addition, through inhibition of DNMT1 HCY-induced aberrant migration and adhesion was rescued. In line with that, HCY-induced pro-migratory and pro-adhesive phenotype was also rescued by co-treatment with the cofactors (30 μM Vitamin B12 and 3 μM folic acid) responsible for homocysteine to methionine catabolism due to normalized PTEN expression.

Conclusions

The present work deciphers a previously unknown mechanism how an increased concentration of HCY induces a pro-atherosclerotic activation of monocytes.

Accumulation of HCY leads to a methylation-dependent inactivation of PTEN phosphatase. This subsequently causes increased phosphorylation of AKT at serine 473, which results in an augmented migration behaviour of monocytes. At the same time, we were able to reduce HCY-induced aberrant monocyte activation by inhibiting DNTM1 or by interfering with HCY metabolism by adding vitamin B12 or folic acid. In summary, these findings provide a new approach to reset pro-atherosclerotic monocytes in hyperhomocysteinemic conditions.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): IZKF SEED Project 14/20

Empagliflozin prevents neointima formation by impairing smooth muscle cell proliferation and accelerating endothelial regeneration

Background

Empagliflozin, an inhibitor of the sodium glucose co-transporter 2 (SGLT2) and developed as an anti-diabetic agent exerts additional beneficial effects on heart failure outcomes. However, the effect of empagliflozin on vascular cell function and vascular remodeling processes remains largely elusive.

Methods/Results

Immunocytochemistry and immunoblotting revealed SGLT2 to be expressed in human smooth muscle (SMC) and endothelial cells (EC) as well as in murine femoral arteries. In vitro, empagliflozin reduced serum-induced proliferation and migration of human diabetic and non-diabetic SMCs in a dose-dependent manner. In contrast, empagliflozin significantly increased the cell count and migration capacity of human diabetic ECs, but not of human non-diabetic ECs. In vivo, application of empagliflozin resulted in a reduced number of proliferating neointimal cells in response to femoral artery wire-injury in C57BL/6J mice and prevented neointima formation. Comparable effects were observed in a streptozocin-induced diabetic model of apolipoprotein E–/– mice. Conclusive to the in vitro-results, re-endothelialization was not significantly affected in C57BL/6 mice, but improved in diabetic mice after treatment with empagliflozin assessed by Evan’s Blue staining 3 days after electric denudation of the carotid artery. Ribonucleic acid (RNA) sequencing (RNA-seq) of human SMCs identified the vasoactive peptide apelin to be decisively regulated in response to empagliflozin treatment. Recombinant apelin mimicked the in vitro-effects of empagliflozin in ECs and SMCs.

Conclusion

Empagliflozin significantly reduces serum-induced proliferation and migration of SMCs in vitro and prevents neointima formation in vivo, while augmenting EC proliferation in vitro and re-endothelialization in vivo after vascular injury. These data document the functional impact of empagliflozin on vascular human SMCs and ECs and vascular remodeling in mice for the first time.

Increased Direct Current-Electroencephalography Shifts During Induction of Anesthesia in Elderly Patients Developing Postoperative Delirium

Background

Changes in the direct current (DC) electroencephalography (EEG), so-called DC shifts, are observed during hypoxia, hypo-/hypercapnia, anesthetic administration, epileptic seizures, and spreading depolarizations. They are associated with altered cerebral ion currents across cell membranes and/or the blood–brain barrier (BBB). Here, we measured DC shifts in clinical practice during hyperventilation (HV) and anesthesia induction, and investigated whether such DC shifts correlate with the occurrence of postoperative delirium (POD) in older patients.

Methods

In this prospective observational study (subproject of the BioCog study, NCT02265263; EA2/092/14), a continuous pre- and perioperative DC-EEG was recorded in patients aged ≥65 years. The preoperative DC-EEG included a 2 min HV with simultaneous measurement of end-tidal CO₂. Of the perioperative recordings, DC-EEG segments were chosen from a 30 s period at the start of induction of anesthesia (IOA), loss of consciousness (LOC), and during a stable anesthetic phase 30 min after skin incision (intraOP). The DC shift at Cz was determined in μV/s. All patients were screened twice daily for the first seven postoperative days for the occurrence of POD. DC-EEG shifts were compared in patients with (POD) and without postoperative delirium (noPOD).

Results

Fifteen patients were included in this subproject of the BioCog study. DC shifts correlated significantly with concurrent HV, with DC shifts increasing the more end-tidal CO₂ decreased (P = 0.001, Spearman’s rho 0.862). During the perioperative DC-EEG, the largest DC shift was observed at LOC during IOA. POD patients (n = 8) presented with significantly larger DC shifts at LOC [POD 31.6 (22.7; 38.9) μV/s vs. noPOD 4.7 (2.2; 12.5) μV/s, P = 0.026].

Conclusion

DC shifts can be observed during HV and IOA in routine clinical practice. At anesthesia induction, the DC shift was greatest at the time of LOC, with POD patients presenting with significantly stronger DC shifts. This could indicate larger changes in gas tensions, hypotension and impaired cerebral autoregulation or BBB dysfunction in these patients.

Clinical Trial Registration

www.clinicaltrials.gov, identifier NCT02265263.

Identifying content to improve risk assessment communications within the Risk Profile: Literature reviews and focus groups with expert and non-expert stakeholders

Objective

To improve consumer decision making, the results of risk assessments on food, feed, consumer products or chemicals need to be communicated not only to experts but also to non-expert audiences. The present study draws on evidence from literature reviews and focus groups with diverse stakeholders to identify content to integrate into an existing risk assessment communication (Risk Profile).

Methods

A combination of rapid literature reviews and focus groups with experts (risk assessors (n = 15), risk managers (n = 8)), and non-experts (general public (n = 18)) were used to identify content and strategies for including information about risk assessment results in the “Risk Profile” from the German Federal Institute for Risk Assessment. Feedback from initial focus groups was used to develop communication prototypes that informed subsequent feedback rounds in an iterative process. A final prototype was validated in usability tests with experts.

Results

Focus group feedback and suggestions from risk assessors were largely in line with findings from the literature. Risk managers and lay persons offered similar suggestions on how to improve the existing communication of risk assessment results (e.g., including more explanatory detail, reporting probabilities for individual health impairments, and specifying risks for subgroups in additional sections). Risk managers found information about quality of evidence important to communicate, whereas people from the general public found this information less relevant. Participants from lower educational backgrounds had difficulties understanding the purpose of risk assessments. User tests found that the final prototype was appropriate and feasible to implement by risk assessors.

Conclusion

An iterative and evidence-based process was used to develop content to improve the communication of risk assessments to the general public while being feasible to use by risk assessors. Remaining challenges include how to communicate dose-response relationships and standardise quality of evidence ratings across disciplines.

Amorphization and nanocrystal formation in a Pd-Ni-Cu-P alloy after cooling under different conditions

Structure formation during solidification of a Pd-Ni-Cu-P melt is studied. It is demonstrated that changes in the heat transfer conditions lead to a nonlinear change in the characteristics of the structure. The article presents the regimes of cooling the samples and the results of their structure and composition studies. It is found that a decrease in the cooling rate of the alloy leads to an increase in the size, proportion and composition of nanoinclusions in an amorphous matrix. X-ray diffraction method, electron probe microanalysis, transmission microscopy and scanning calorimetry are used for samples characterization. This article is part of the theme issue 'Transport phenomena in complex systems (part 2)'.

[Wind turbine and infrasound: No evidence for health-related impairment - a physical, medical and social report]

Based on the recent discussion about health impacts of wind turbine noise and infrasound emissions, we present the physical facts and summarize related studies in a narrative review. We are exposed to infrasound emissions from different sources, where wind turbine farms do not cause particularly high infrasound emissions. Epidemiological studies found no association between wind turbine farms and the incidence of diabetes mellitus, heart attacks, strokes and medication with antihypertensive drugs, but a more frequent prescription of sleep medication. In contrast, key indicators of objective sleep outcomes are not impacted by wind turbine noise. Health complaints are more frequently proven, if anti-wind-turbine-groups were active, which is consistent with the psychogenic hypotheses with nocebo effects likely play an important role. Without evidence of health impacts from wind turbine farms, an ongoing slowdown in the urgently needed expansion of renewable energies is not justifiable.

The descending pain modulation system predicts short term efficacy of multimodal pain therapy - an observational prospective cohort study

OBJECTIVES

Treating chronic pain patients with multimodal pain therapy (MMPT) alters perception, awareness, and processing of pain at multiple therapeutic levels. Several clinical observations suggest that the effects of therapy may go beyond the possible sum of each level of therapy and may be due to a central descending inhibitory effect measurable by conditioned pain modulation (CPM). Thus, we investigated whether CPM is able to identify a group of patients that benefit particularly from MMPT.

METHODS

This was an observational prospective cohort study. Patients were hospitalized on a special pain medicine ward with specially trained staff for 10 days. The patients were questioned and had investigations before and shortly after MMPT and were followed-up on 3 months post discharge. Before and after treatment, subjects were investigated via CPM and quantitative sensory testing (QST) as well as completing questionnaires. The study was registered in the German Clinical Trials Register (DRKS00006850).

RESULTS

During the study period of 24 months, 224 chronic pain patients were recruited. 51 percent of patients completed the study period. There was an improvement in overall groups regarding all domains assessed, lasting beyond the end of the intervention. Patients with a sufficient CPM effect, defined as a reduction in pain during the conditioning stimulus, at baseline did show a more pronounced reduction in mean pain ratings than those without. This was not the case 3 months after therapy. Furthermore, sufficient CPM was identified as a predictor for pain reduction using a linear regression model.

CONCLUSION

In conclusion, this study shows that while a heterogeneous group of patients with chronic pain disorders does sustainably benefit from MMPT in general, patients with a sufficient CPM effect do show a more pronounced decrease in pain ratings directly after therapy in comparison to those without.

Water management in anion-exchange membrane water electrolyzers under dry cathode operation

Dry cathode operation is a desired operation mode in anion-exchange membrane water electrolyzers to minimize contamination of the generated hydrogen. However, water management under such operation conditions makes it challenging to maintain reliable performance and durability. Here, we utilize high-resolution in situ neutron imaging (∼6 μm effective resolution) to analyze the water content inside the membrane-electrode-assembly of an anion-exchange membrane water electrolyzer. The ion-exchange capacity (IEC) and thus hydrophilicity of the polymer binder in the cathode catalyst layer is varied to study the influence on water content in the anode (mid IEC, 1.8–2.2 meq. g⁻¹ and high IEC, 2.3–2.6 meq. g⁻¹). The neutron radiographies show that a higher ion-exchange capacity binder allows improved water retention, which reduces the drying-out of the cathode at high current densities. Electrochemical measurements confirm a generally better efficiency for a high IEC cell above 600 mA cm⁻². At 1.5 A cm⁻² the high IEC has a 100 mV lower overpotential (2.1 V vs. 2.2 V) and a lower high frequency resistance (210 mΩ cm⁻²vs. 255 mΩ cm⁻²), which is believed to be linked to the improved cathode water retention and membrane humidification. As a consequence, the performance stability of the high IEC cell at 1 A cm⁻² is also significantly better than that of the mid IEC cell (45 mV h⁻¹vs. 75 mV h⁻¹).

Dry cathode operation is a desired operation mode in anion-exchange membrane water electrolyzers, but water management is crucial. This is visualized using high-resolution neutron radiography and the ion-exchange capacity of the cathode ionomer is varied.

Perioperative Electroencephalogram Spectral Dynamics Related to Postoperative Delirium in Older Patients

BACKGROUND

Intraoperative electroencephalography (EEG) signatures related to the development of postoperative delirium (POD) in older patients are frequently studied. However, a broad analysis of the EEG dynamics including preoperative, postinduction, intraoperative and postoperative scenarios and its correlation to POD development is still lacking. We explored the relationship between perioperative EEG spectra-derived parameters and POD development, aiming to ascertain the diagnostic utility of these parameters to detect patients developing POD.

METHODS

Patients aged ≥65 years undergoing elective surgeries that were expected to last more than 60 minutes were included in this prospective, observational single center study (Biomarker Development for Postoperative Cognitive Impairment [BioCog] study). Frontal EEGs were recorded, starting before induction of anesthesia and lasting until recovery of consciousness. EEG data were analyzed based on raw EEG files and downloaded excel data files. We performed multitaper spectral analyses of relevant EEG epochs and further used multitaper spectral estimate to calculate a corresponding spectral parameter. POD assessments were performed twice daily up to the seventh postoperative day. Our primary aim was to analyze the relation between the perioperative spectral edge frequency (SEF) and the development of POD.

RESULTS

Of the 237 included patients, 41 (17%) patients developed POD. The preoperative EEG in POD patients was associated with lower values in both SEF (POD 13.1 ± 4.6 Hz versus no postoperative delirium [NoPOD] 17.4 ± 6.9 Hz; P = .002) and corresponding γ-band power (POD -24.33 ± 2.8 dB versus NoPOD -17.9 ± 4.81 dB), as well as reduced postinduction absolute α-band power (POD -7.37 ± 4.52 dB versus NoPOD -5 ± 5.03 dB). The ratio of SEF from the preoperative to postinduction state (SEF ratio) was ~1 in POD patients, whereas NoPOD patients showed a SEF ratio >1, thus indicating a slowing of EEG with loss of unconscious. Preoperative SEF, preoperative γ-band power, and SEF ratio were independently associated with POD (P = .025; odds ratio [OR] = 0.892, 95% confidence interval [CI], 0.808-0.986; P = .029; OR = 0.568, 95% CI, 0.342-0.944; and P = .009; OR = 0.108, 95% CI, 0.021-0.568, respectively).

CONCLUSIONS

Lower preoperative SEF, absence of slowing in EEG while transitioning from preoperative state to unconscious state, and lower EEG power in relevant frequency bands in both these states are related to POD development. These findings may suggest an underlying pathophysiology and might be used as EEG-based marker for early identification of patients at risk to develop POD.

[Intraoperative Neuromonitoring: Electroencephalography]

Intraoperative neuromonitoring using electroencephalography (EEG) enables anaesthesiologists to monitor the depth of anaesthesia. It is intended to reduce the occurrence of intraoperative wakefulness, postoperative delirium and postoperative cognitive deficits and to shorten process times in the operating room. This article shows how to interpret the raw EEG, spectrograms and processed indices for different age groups and anaesthetics and summarizes the resulting clinical benefits. While propofol and volatile anesthetics produce characteristic frontal EEG signatures with a high activity of coherent α- and δ-waves, ketamine triggers an increase in rapid γ-waves, which leads to incorrectly high indices (BIS, PSI, NI) despite deep anaesthetic levels.In children, frontal α-waves do not appear until the age of approx. 6 months and valid indices (BIS, PSI, NI) can only be derived starting at an age of approx. 12 months. Furthermore, children of preschool and elementary school age often show epileptiform discharges in the EEG during induction of anaesthesia, what is linked to emergence delirium. In adults, the intraoperative frontal α-power decreases significantly with increasing age and older patients tend to have an increased occurrence of burst suppression patterns during anaesthesia. Clinical benefits of EEG-based neuromonitoring comprise reduced doses of anaesthesia, shorter wake-up times after surgery and a lower incidence of intraoperative awareness during total intravenous anaesthesia. Moreover, anaesthesia guided by processed EEG indices can reduce the incidence of postoperative delirium and postoperative cognitive deficits in older patients. In-depth knowledge about intraoperative EEG changes that go beyond the interpretation of processed indices could lead to a further reduction in intra- and postoperative complications in the future.

Peri- and intraoperative EEG signatures in newborns and infants

OBJECTIVE

The electroencephalographic derived indices have been developed for adult patients, however these monitors have not been validated for infants.

METHODS

Frontal EEGs were recorded in 115 infants aged <1 year [0-3-months (N = 27), 4-6-months (N = 30), 7-9-months (N = 29) and 10-12-months (N = 29)] who received general anaesthesia with sevoflurane. Total power (µV²) and relative β-, α-, θ-, δ-power (%) were analyzed. Additionally, in 20 EEGs event marker were added (baseline, loss of consciousness, intraoperative situation, extubation) to assess perioperative EEG dynamics.

RESULTS

Newborns show a mean relative δ-power at 80% in intraoperative EEG compared to infants (10-12 months) showing 47.5%. Relative β-power and α-power are low in newborns (mean 3.2% and 4.6%; respectively), with a marked increase in the older infants (4-6 months) (mean 10.9% and 14.4%; respectively). EEG dynamic in newborns from baseline (relative δ-power of 88%) to the intraoperative situation (80.5%) are discrete. In contrast infants >6-months have a strong reduction of relative δ-power from baseline to the intraoperative situation, which corresponds to an increase of faster frequencies.

CONCLUSIONS

Age dependent perioperative EEG signatures can be demonstrated in infants younger than one year.

SIGNIFICANCE

We demonstrate significant differences in EEG readouts between newborns and infants which questions our monitoring systems in paediatric anaesthesia.

Induction of RAGE-NFkB signalling axis enhances SHP-2 tyrosine phosphatase expression resulting in deviant activation of diabetic monocytes

Purpose

Aberrant activation of Type 2 Diabetes mellitus (T2DM) monocytes is an important pathomechanism leading to restricted arteriogenesis and augmented atherosclerosis, hereby, accelerating CAD and PAD. Tyrosine phosphatase SHP-2 was found to be upregulated in T2DM-monocytes. This study aimed to identify the pathways regulating SHP-2 expression in T2DM-monocytes.

Methods

Primary human monocytes were isolated from the peripheral blood of T2DM patients and healthy individuals. Monocytes were incubated with Methylglyoxal (MG), a highly reactive side product of glycolysis, Receptor for advanced glycation end product (RAGE) ligand AGE-bovine serum (AGE-BSA) or TNFα for 24 hours. Transwell migration assays were used to analyse the migratory potential of monocytes. Western Blot, RT-qPCR and FACS were performed to quantify the expression of relevant molecules. Pharmacological inhibitors were used to study functional relevance of the RAGE-NFκB-SHP-2 signalling axis.

Results

Significantly enhanced SHP-2 expression was detected in monocytes, which were incubated with TNFα, MG or AGE-BSA, respectively. Co-incubation of these molecules with NFκB-inhibitor blocked SHP-2 upregulation. Pharmacological inhibition of RAGE reversed the MG or AGE-BSA induced SHP-2 expression and activity in monocytes. RAGE expression on monocytes was upregulated after the incubation with MG or AGE-BSA, consistent with enhanced RAGE mRNA levels in T2DM monocytes. Besides, we also detected elevated SHP-2 transcripts in monocytes of T2DM patients which was more pronounced in monocytes with augmented TNFα expression. Furthermore, MG and AGE-BSA provoked the enhanced migration of monocytes which could be significantly reduced after the application of an allosteric SHP-2 inhibitor. Interestingly, pharmacological inhibition of RAGE in these conditions alone was sufficient to block the elevated monocyte migration. Moreover, monocytes isolated from T2DM patients revealed a comparable pro-migratory phenotype, which was completely restored after the pharmacological inhibition of SHP-2.

Conclusions

This study identified the upstream signalling mediators that contribute to SHP-2 dependent monocyte activation in T2DM conditions. Glucose metabolite (MG) or RAGE ligand (AGE-BSA) alone were sufficient to induce a pro-migratory phenotype in monocytes by upregulating SHP-2. Of note, an inflammatory state seems to accelerate this effect since enhanced TNFα levels were found to be positively correlated with the augmented SHP-2 expression. Moreover, we identified the RAGE-NFκB signalling axis through which the SHP-2 upregulation is conveyed when augmented accumulation of glucose metabolites occur. These findings reveal a basis for potential new therapeutic approaches to prevent accelerated CAD and PAD in diabetic patients since independent pharmacological inhibition of every step in the RAGE-NFκB-SHP-2 axis was sufficient to reset the aberrant monocyte activation.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Interdisciplinary Center for Clinical Research of the Medical Faculty of the University of Münster

Rapid wet-chemical oxidative activation of graphite felt electrodes for vanadium redox flow batteries

To boost the performance of vanadium redox flow batteries, modification of the classically used felt electrodes is required to enable higher cycling performance and longer life cycles. Alternative approaches to the standard thermal oxidation procedure such as wet chemical oxidation are promising to reduce the thermal budget and thus the cost of the activation procedure. In this work we report a rapid 1 hour activation procedure in an acidified KMnO₄ solution. We show that the reported modification process of the felt electrodes results in an increase in surface area, density of oxygenated surface functionalities as well as electrolyte wettability, as demonstrated by N₂-physisorption, XPS, Raman spectroscopy as well as contact angle measurements. The activation process enables battery cycling at remarkably high current densities up to 400 mA cm⁻². Stable cycling at 400 mA cm⁻² over 30 cycles confirms promising stability of the reported activation procedure.

Schematic diagram of the K-GF fabrication process. Step 1: deposition of MnO_x layers onto the P-GF electrode surface using acidified KMnO₄ solutions. Step 2: removal of MnO_x layers using an acidified H₂O₂ solution to produce the K-GF electrode.

Demonstration of the effect of stirring on nucleation from experiments on the International Space Station using the ISS-EML facility

The effect of fluid flow on crystal nucleation in supercooled liquids is not well understood. The variable density and temperature gradients in the liquid make it difficult to study this under terrestrial gravity conditions. Nucleation experiments were therefore made in a microgravity environment using the Electromagnetic Levitation Facility on the International Space Station on a bulk glass-forming Zr₅₇Cu_15.4Ni_12.6Al₁₀Nb₅ (Vit106), as well as Cu₅₀Zr₅₀ and the quasicrystal-forming Ti_39.5Zr_39.5Ni₂₁ liquids. The maximum supercooling temperatures for each alloy were measured as a function of controlled stirring by applying various combinations of radio-frequency positioner and heater voltages to the water-cooled copper coils. The flow patterns were simulated from the known parameters for the coil and the levitated samples. The maximum nucleation temperatures increased systematically with increased fluid flow in the liquids for Vit106, but stayed nearly unchanged for the other two. These results are consistent with the predictions from the Coupled-Flux model for nucleation.

[New challenges for anesthesia due to the climate change]

BACKGROUND

The climate crisis is the most serious threat to global health in the twenty-first century. In western countries 5-10% of all greenhouse gas emissions originate from the healthcare sector and the main contributing factors are energy-intense departments (intensive care units, operating suits and prehospital emergency services).

OBJECTIVE

The aim of this review is to provide background knowledge and practical ideas to achieve climate-neutral hospitals.

MATERIAL AND METHODS

Narrative review with information on the topics of (I) volatile anesthetics as greenhouse gases, (II) energy supply in hospitals and (III) solid waste management.

RESULTS AND CONCLUSION

(I) Volatile anesthetics are highly potent greenhouse gases, especially desflurane has a major global warming potential. Total intravenous anesthesia (TIVA) with propofol or regional anesthetic techniques have a much lower impact on the climate. (II) Using sustainable energy sources as well as initiating energy sparing techniques, such as light-emitting diodes (LED) and motion sensors, can reduce CO₂ emissions. (III) Waste can be managed by the reduce, reuse, recycle, rethink and research concept. Doctors should actively contribute to reach the climate goals.

Vitamin D3-Induced Promotor Dissociation of PU.1 and YY1 Results in FcεRI Reduction on Dendritic Cells in Atopic Dermatitis

Atopic dermatitis (AD) is a severe inflammatory skin disease. Langerhans cells and inflammatory dendritic epidermal cells (IDEC) are located in the epidermis of AD patients and contribute to the inflammatory processes. Both express robustly the high-affinity receptor for IgE, FcεRI, and thereby sense allergens. A beneficial role of vitamin D₃ in AD is discussed to be important especially in patients with allergic sensitization. We hypothesized that vitamin D₃ impacts FcεRI expression and addressed this in human ex vivo skin, in vitro Langerhans cells, and IDEC models generated from primary human precursor cells. We show in this article that biologically active vitamin D₃ [1,25(OH)₂-D₃] significantly downregulated FcεRI at the protein and mRNA levels of the receptor's α-chain, analyzed by flow cytometry and quantitative RT-PCR. We also describe the expression of a functional vitamin D receptor in IDEC. 1,25(OH)₂-D₃-mediated FcεRI reduction was direct and resulted in impaired activation of IDEC upon FcεRI engagement as monitored by CD83 expression. FcεRI regulation by 1,25(OH)₂-D₃ was independent of maturation and expression levels of microRNA-155 and PU.1 (as upstream regulatory axis of FcεRI) and transcription factors Elf-1 and YY1. However, 1,25(OH)₂-D₃ induced dissociation of PU.1 and YY1 from the FCER1A promotor, evaluated by chromatin immunoprecipitation. We show that vitamin D₃ directly reduces FcεRI expression on dendritic cells by inhibiting transcription factor binding to its promotor and subsequently impairs IgE-mediated signaling. Thus, vitamin D₃ as an individualized therapeutic supplement for those AD patients with allergic sensitization interferes with IgE-mediated inflammatory processes in AD patients.

Critical illness myopathy precedes hyperglycaemia and high glucose variability

BACKGROUND

Critical Illness Myopathy (CIM) is a serious ICU complication, and dysglycaemia is widely regarded as a risk factor. Although glucose variability (GV) has been independently linked to ICU mortality, an association with CIM has not been investigated. This study examines the relationship between CIM and GV.

METHODS

Retrospective investigation including ICU patients with SOFA ≥8, mechanical ventilation, and CIM diagnostics. Glucose readings were collected every 6 h throughout the first week of treatment, when CIM is thought to develop. GV was measured using standard deviation (SD), coefficient of variability (CV), mean absolute glucose (MAG), mean amplitude of glycaemic excursions (MAGE), and mean of daily difference (MODD).

RESULTS

74 patients were included, and 50 (67.6%) developed CIM. Time on glycaemic target (70-179 mg/dL), caloric and insulin intakes, mean, maximum and minimum blood glucose values were similar for all patients until the 5th day, after which CIM patients exhibited higher mean and maximum glucose levels. Significantly higher GV in CIM patients were observed on day 5 (SD, CV, MAG, MAGE), day 6 (MODD), and day 7 (SD, CV, MAG).

CONCLUSIONS

CIM patients developed transient increases in GV and hyperglycaemia only late in the first week, suggesting that myopathy precedes dysglycaemia.

PDGF Receptor Alpha Signaling Is Key for Müller Cell Homeostasis Functions

Müller cells, the major retinal macroglia, are key to maintaining vascular integrity as well as retinal fluid and ion homeostasis. Although platelet derived growth factor (PDGF) receptor expression in Müller glia has been reported earlier, their actual role for Müller cell function and intimate interaction with cells of the retinal neurovascular unit remains unclear. To close this gap of knowledge, Müller cell-specific PDGF receptor alpha (PDGFRα) knockout (KO) mice were generated, characterized, and subjected to a model of choroidal neovascularization (CNV). PDGFRα-deficient Müller cells could not counterbalance hypoosmotic stress as efficiently as their wildtype counterparts. In wildtypes, the PDGFRα ligand PDGF-BB prevented Müller cell swelling induced by the administration of barium ions. This effect could be blocked by the PDGFR family inhibitor AC710. PDGF-BB could not restore the capability of an efficient volume regulation in PDGFRα KO Müller cells. Additionally, PDGFRα KO mice displayed reduced rod and cone-driven light responses. Altogether, these findings suggest that Müller glial PDGFRα is central for retinal functions under physiological conditions. In contrast, Müller cell-specific PDGFRα KO resulted in less vascular leakage and smaller lesion areas in the CNV model. Of note, the effect size was comparable to pharmacological blockade of PDGF signaling alone or in combination with anti-vascular endothelial growth factor (VEGF) therapy—a treatment regimen currently being tested in clinical trials. These data imply that targeting PDGF to treat retinal neovascular diseases may have short-term beneficial effects, but may elicit unwarranted side effects given the putative negative effects on Müller cell homeostatic functions potentially interfering with a long-term positive outcome.