Comparison of different prognostic scores in estimating short- and long-term mortality in COVID-19 patients above 60 years old in a university hospital in Belgium.

BACKGROUND AND OBJECTIVES: Multiple scoring systems were used for risk stratification in COVID-19 patients. The objective was to determine among 6 scores which performed the best in predicting short-and long-term mortality in hospitalized COVID-19 patients ≥ 60 years. METHODS: An observational, retrospective cohort study conducted between 21/10/2020 and 20/01/2021. 6 scores were calculated (Clinical Frailty Scale (CFS), Charlson Comorbidity Index (CCI), 4C Mortality Score (4CMS), NEWS score (NEWS), quick-SOFA score (qSOFA), and Quick COVID-19 Severity Index (qCSI)). We included unvaccinated hospitalized patients with COVID-19 ≥ 60 years old in Brugmann hospital, detected by PCR and/or suggestive CT thorax images. Old and nosocomial infections, and patients admitted immediately at the intensive care unit were excluded. RESULTS: 199 patients were included, mean age was 76.2 years (60-99). 47.2% were female. 56 patients (28%) died within 1 year after the first day of hospitalization. The 4CMS predicted the best intrahospital, 30 days and 6 months mortality, with area under the ROC curve (AUROC) 0.695 (0.58-0.81), 0.76 (0.65-0.86) and 0.72 (0.63-0.82) respectively. The CCI came right after with respectively AUROC of 0.69 (0.59-0.79), 0.74 (0.65-0.83) and 0.71 (0.64-0.8). To predict mortality at 12 months after hospitalization, the CCI had the highest AUROC with 0.77 (0.69-0.85), before the 4CMS with 0.69 (0.60-0.79). DISCUSSION: Among 6 scores, the 4CMS was the best to predict intrahospital, 30-day and 6-month mortality. To predict mortality at 12 months, CCI had the best performance before 4CMS. This reflects the importance of considering comorbidities for short- and long-term mortality after COVID 19. REGISTRATION: This study was approved by the ethical committee of Brugmann University Hospital (reference CE 2020/228).

[Factors associated with intrahospital mortality in older patients with COVID-19 in Belgium : The COVID-AgeBru study]. / Face à la COVID-19. Mortalité intra-hospitalière chez les patients âgés de plus de 70 ans avec COVID-19 dans un hôpital universitaire en Belgique :l'étude COVID-AgeBru.

OBJECTIVE: We aimed at assessing the association between demographical and clinical data and the intrahospital mortality in older patients with COVID-19 in Belgium. METHODS: Descriptive, retrospective study of consecutive patients admitted to Brugmann university hospital, Brussels (Belgium) due to COVID-19 (Mars-September-2020). INCLUSION CRITERIA: Patients aged ≥ 70 years admitted to acute care with a positive PCR-RT test, or a highly indicative computed tomography scan. EXCLUSION CRITERIA: Patients transferred to another institution during hospitalization. OUTCOME MEASURE: All-cause intrahospital mortality. Demographic, clinical data, presence of comordibidties and comprehensive geriatric assessment were collected. Adjusted and unadjusted logistic regression were performed. RESULTS: From the 226 eligible patients, 160 (82.7 ± 6.5-year-old; 57.5 % females) met inclusion criteria, from which 67 (42 %) died during hospital stay. The adjusted logistic regression showed an association between intrahospital mortality and increasing age [OR = 1.09 per every year increase (95 % CI 1.02-1.16); p <0.001], type 2 diabetes [OR = 2.75 ( 1.17-6.46); p = 0.021], and acute respiratory distress syndrome (ARDS) [OR = 8.67 ( 3.48-21.61); p < 0.01]. CONCLUSIONS: A higher positive association between intrahospital mortality and increasing age, type 2 diabetes, and ARDS was found. The prognosis value of the comprehensive geriatric assessment in older people with COVID-19 in Belgium requires further studies.

INTRODUCTION: Les études sur l'impact de la pandémie en Belgique sont rares. L'objectif est d'évaluer l'association de l'âge et des comorbidités à la mortalité intra-hospitalière de toutes causes chez les patients âgés ? 70 ans avec COVID-19 dans un hôpital universitaire à Bruxelles, Belgique. Méthodes : Etude rétrospective descriptive des patients admis au CHU Brugmann pour cause de maladie COVID-19 (mars-septembre 2020). Critères d'inclusion : âge ≥ 70 ans admis avec PCR-RT positif ou haute probabilité d'infection au CT-scan thoracique. Critères d'exclusion : transfert dans un autre hôpital. Critère de jugement : toute cause de mortalité intra-hospitalière. Variables collectées : démographiques, cliniques et gériatriques [Katz, Lawton, MMSE, MNA, MNA-SF]. Une régression logistique non ajustée et ajustée a été réalisée. Résultats : Parmi les 226 patients éligibles, 160 (82,7 ± 6,5 ans; 57,5 % femmes) ont rempli les critères d'inclusion. Au total, 67 (42 %) sont décédés durant l'hospitalisation. La régression logistique a montré une association augmentée entre la mortalité et l'âge [odds ratio ou OR = 1,09/année en plus (IC 95 % 1,02-1,16) ; p< 0,001], le diabète de type 2 [OR = 2,75 (1,17-6,46); p = 0,021], l'ARDS [OR = 8,67 (3,48-21,61); p < 0,01]. CONCLUSION: L'âge, le diabète de type 2 et le syndrome de détresse respiratoire aiguë (ARDS) sont associés à une augmentation de la mortalité chez les patients âgés hospitalisés avec COVID-19 en Belgique.

Photonic emitter manipulation to sample nanoscale topography.

We demonstrate that photonic emitter manipulation can be used to image the nanoscale topography of a fluorescently labeled layer in confocal imaging. We exploit the fact that a metallic probe manipulates a fluorophore's photonic environment, and thereby its fluorescent lifetime, in a strongly distance-dependent manner. To image surface topography, a metallic probe that is not in contact with the surface is rasterscanned over a fluorescently labeled sample. The axial position of the probe is kept constant. At each lateral probe position, the fluorescence decay is recorded and analyzed to obtain probe - sample distances and hence, the topography of the sample. We present images resolving a microfabricated step of 14 nm in topography, with the probe positioned at different axial positions.

Exogenous α-synuclein hinders synaptic communication in cultured cortical primary rat neurons.

Amyloid aggregates of the protein α-synuclein (αS) called Lewy Bodies (LB) and Lewy Neurites (LN) are the pathological hallmark of Parkinson's disease (PD) and other synucleinopathies. We have previously shown that high extracellular αS concentrations can be toxic to cells and that neurons take up αS. Here we aimed to get more insight into the toxicity mechanism associated with high extracellular αS concentrations (50-100 µM). High extracellular αS concentrations resulted in a reduction of the firing rate of the neuronal network by disrupting synaptic transmission, while the neuronal ability to fire action potentials was still intact. Furthermore, many cells developed αS deposits larger than 500 nm within five days, but otherwise appeared healthy. Synaptic dysfunction clearly occurred before the establishment of large intracellular deposits and neuronal death, suggesting that an excessive extracellular αS concentration caused synaptic failure and which later possibly contributed to neuronal death.

Dietary energy density in young children across Europe.

OBJECTIVES: To describe energy density (ED; kcal g(-1)) of dietary intake of European children. METHODS: From 16, 228 children who participated in the IDEFICS (Identification and prevention of Dietary- and lifestyle-induced health EFfects In Children and infantS) baseline examination, 8551 children with 24-h dietary recalls (24-HDR), with plausible reported energy intakes and complete covariate information were included in the present analysis. ED was calculated using two methods: (1) ED including solid foods (EDF) and (2) ED including solid foods and energy-containing beverages (EDF&B). Beverage energy was calculated in kcal per day. Dietary characteristics and body mass index (BMI) z-score of children aged 2 to <6 years and 6 to <10 years were compared between children with an overall EDF below the <25th percentile, between the 25th and 75th percentile as well as above the >75th percentile. Standardised regression coefficients were estimated to assess the association between dietary characteristics, BMI z-score and ED of the diet. RESULTS: Children with low EDF and EDF&B diets consumed less energy but higher quantity of food and beverages than children with high EDF and EDF&B diets. Consumption of caloric beverages decreased with increasing EDF&B of the diet owing to the relatively low ED of the beverages, in relation to solid foods. Generally, children with low EDF and EDF&B diets showed healthier food choices than peers with higher EDF and EDF&B diets. In this sample, EDF and EDF&B were not associated with BMI z-score. CONCLUSION: Health promotion strategies should proclaim lower ED diets by means of foods with high water and low fat content and mainly fruit and vegetable components. Excluding caloric beverages from EDF calculation is a useful method to avoid misinterpretation of true exposure to a high energy dense diet. We recommend excluding caloric beverages from EDF calculation when investigating the effect of ED on a certain (health) outcome.

Percentile reference values for anthropometric body composition indices in European children from the IDEFICS study.

INTRODUCTION: To characterise the nutritional status in children with obesity or wasting conditions, European anthropometric reference values for body composition measures beyond the body mass index (BMI) are needed. Differentiated assessment of body composition in children has long been hampered by the lack of appropriate references. OBJECTIVES: The aim of our study is to provide percentiles for body composition indices in normal weight European children, based on the IDEFICS cohort (Identification and prevention of Dietary- and lifestyle-induced health Effects in Children and infantS). METHODS: Overall 18,745 2.0-10.9-year-old children from eight countries participated in the study. Children classified as overweight/obese or underweight according to IOTF (N=5915) were excluded from the analysis. Anthropometric measurements (BMI (N=12 830); triceps, subscapular, fat mass and fat mass index (N=11,845-11,901); biceps, suprailiac skinfolds, sum of skinfolds calculated from skinfold thicknesses (N=8129-8205), neck circumference (N=12,241); waist circumference and waist-to-height ratio (N=12,381)) were analysed stratified by sex and smoothed 1st, 3rd, 10th, 25th, 50th, 75th, 90th, 97th and 99th percentile curves were calculated using GAMLSS. RESULTS: Percentile values of the most important anthropometric measures related to the degree of adiposity are depicted for European girls and boys. Age- and sex-specific differences were investigated for all measures. As an example, the 50th and 99th percentile values of waist circumference ranged from 50.7-59.2 cm and from 51.3-58.7 cm in 4.5- to <5.0-year-old girls and boys, respectively, to 60.6-74.5 cm in girls and to 59.9-76.7 cm in boys at the age of 10.5-10.9 years. CONCLUSION: The presented percentile curves may aid a differentiated assessment of total and abdominal adiposity in European children.

Tryptophan fluorescence reveals structural features of alpha-synuclein oligomers.

Oligomeric alpha-synuclein (alphaS) is considered to be the potential toxic species responsible for the onset and progression of Parkinson's disease, possibly through the disruption of lipid membranes. Although there is evidence that oligomers contain considerable amounts of secondary structure, more detailed data on the structural characteristics and how these mediate oligomer-lipid binding are critically lacking. This report is, to our knowledge, the first study that aimed to address the structure of oligomeric alphaS on a more detailed level. We have used tryptophan (Trp) fluorescence spectroscopy to gain insight into the structural features of oligomeric alphaS and the structural basis for oligomer-lipid interactions. Several single Trp mutants of alphaS were used to gain site-specific information about the microenvironments of monomeric alphaS, oligomeric alphaS and lipid-bound oligomeric alphaS. Acrylamide quenching and spectral analyses indicate that the Trp residues are considerably more solvent protected in the oligomeric form compared with the monomeric protein. In the oligomers, the negatively charged C-terminus was the most solvent exposed part of the protein. Upon lipid binding, a blue shift in fluorescence was observed for alphaS mutants where the Trp is located within the N-terminal region. These results suggest that, as in the case of monomeric alphaS, the N-terminus is critical in determining oligomer-lipid binding.

Cytoskeletal polymer networks: viscoelastic properties are determined by the microscopic interaction potential of cross-links.

Although the structure of cross-linking molecules mainly determines the structural organization of actin filaments and with that the static elastic properties of the cytoskeleton, it is largely unknown how the biochemical characteristics of transiently cross-linking proteins (actin-binding proteins (ABPs)) affect the viscoelasticity of actin networks. In this study, we show that the macroscopic network response of reconstituted actin networks can be traced back to the microscopic interaction potential of an individual actin/ABP bond. The viscoelastic response of cross-linked actin networks is set by the cross-linker off-rate, the binding energy, and the characteristic bond length of individual actin/ABP interactions.

The effect of a low-fat, high-protein or high-carbohydrate ad libitum diet on weight loss maintenance and metabolic risk factors.

BACKGROUND: High-protein (HP) diets are often advocated for weight reduction and weight loss maintenance. OBJECTIVE: The aim was to compare the effect of low-fat, high-carbohydrate (HC) and low-fat, HP ad libitum diets on weight maintenance after weight loss induced by a very low-calorie diet, and on metabolic and cardiovascular risk factors in healthy obese subjects. DESIGN: Forty-eight subjects completed the study that consisted of an energy restriction period of 5-6 weeks followed by a weight maintenance period of 12 weeks. During weight maintenance subjects received maltodextrin (HC group) or protein (HP group) (casein (HPC subgroup) or whey (HPW subgroup)) supplements (2 x 25 g per day), respectively and consumed a low-fat diet. RESULTS: Subjects in the HP diet group showed significantly better weight maintenance after weight loss (2.3 kg difference, P=0.04) and fat mass reduction (2.2 kg difference, P=0.02) than subjects in the HC group. Triglyceride (0.6 mM difference, P=0.01) and glucagon (9.6 pg ml(-1) difference, P=0.02) concentrations increased more in the HC diet group, while glucose (0.3 mM difference, P=0.02) concentration increased more in the HP diet group. Changes in total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, insulin, HOMAir index, HbA1c, leptin and adiponectin concentrations did not differ between the diets. No differences were found between the casein- or whey-supplemented HP groups. CONCLUSIONS: These results show that low-fat, high-casein or whey protein weight maintenance diets are more effective for weight control than low-fat, HC diets and do not adversely affect metabolic and cardiovascular risk factors in weight-reduced moderately obese subjects without metabolic or cardiovascular complications.

The effect of different protein hydrolysate/carbohydrate mixtures on postprandial glucagon and insulin responses in healthy subjects.

OBJECTIVES: To study the effect of four protein hydrolysates from vegetable (pea, gluten, rice and soy) and two protein hydrolysates from animal origin (whey and egg) on glucagon and insulin responses. SUBJECTS/METHODS: Eight healthy normal-weight male subjects participated in this study. The study employed a repeated-measures design with Latin square randomization and single-blind trials. Protein hydrolysates used in this study (pea, rice, soy, gluten, whey and egg protein hydrolysate) consisted of 0.2 g hydrolysate per kg body weight (bw) and 0.2 g maltodextrin per kg bw and were compared to maltodextrin alone. Postprandial plasma glucose, glucagon, insulin and amino acids were determined over 2 h. RESULTS: All protein hydrolysates induced an enhanced insulin secretion compared to maltodextrin alone and a correspondingly low plasma glucose response. A significant difference was observed in area under the curve (AUC) for plasma glucagon between protein hydrolysates and the maltodextrin control drink (P<0.05). Gluten protein hydrolysate induced the lowest glucagon response. CONCLUSIONS: High amino-acid-induced glucagon response does not necessarily go together with low insulin response. Protein hydrolysate source affects AUC for glucagon more profoundly than for insulin, although the protein load used in this study seemed to be at lower level for significant physiological effects.

Transient binding and dissipation in cross-linked actin networks.

In contrast with entangled actin solutions, transiently cross-linked actin networks can provide highly elastic properties while still allowing for local rearrangements in the microstructure-on biological relevant time scales. Here, we show that thermal unbinding of transient cross-links entails local stress relaxation and energy dissipation in an intermediate elasticity dominated frequency regime. We quantify the viscoelastic response of an isotropically cross-linked actin network by experimentally tuning the off rate of the transiently cross-linking molecules, their density, and the solvent viscosity. We reproduce the measured frequency response by a semiphenomenological model that is predicated on microscopic unbinding events.

Helical twist controls the thickness of F-actin bundles.

In the presence of condensing agents such as nonadsorbing polymer, multivalent counter ions, and specific bundling proteins, chiral biopolymers typically form bundles with a finite thickness, rather than phase-separating into a polymer-rich phase. Although short-range repulsive interactions or geometrical frustrations are thought to force the equilibrium bundle size to be limited, the precise mechanism is yet to be resolved. The importance of the tight control of biopolymer bundle size is illustrated by the ubiquitous cytoskeletal actin filament bundles that are crucial for the proper functioning of cells. Using an in vitro model system, we show that size control relies on a mismatch between the helical structure of individual actin filaments and the geometric packing constraints within bundles. Small rigid actin-binding proteins change the twist of filamentous actin (F-actin) in a concentration-dependent manner, resulting in small, well defined bundle thickness up to approximately 20 filaments, comparable to those found in filopodia. Other F-actin cross-linking proteins can subsequently link these small, well organized bundles into larger structures of several hundred filaments, comparable to those found in, for example, Drosophila bristles. The energetic tradeoff between filament twisting and cross-linker binding within a bundle is suggested as a fundamental mechanism by which cells can precisely adjust bundle size and strength.

Osmotic shrinkage and reswelling of giant vesicles composed of dioleoylphosphatidylglycerol and cholesterol.

The osmotic shrinkage of giant unilamellar dioleoylphosphatidylglycerol (DOPG) vesicles in a hypertonic osmotic solution is investigated. The volume reduction for given membrane area leads to a vesiculation of the bilayer into the interior of the giant. The size of the daughter vesicles that appear inside the giant is uniform and an increasing function of the cholesterol content, but independent of the osmotic gradient applied. The radius of the daughter vesicles increases from 0.2 microm to 3.0 microm when the cholesterol content is changed from 0 to 40%. It is argued that the size of the daughter vesicles is regulated by the membrane persistence length, which is an exponential function of the mean bending modulus. From the kinetics of shrinkage it follows that approximately 14% of the daughter vesicles remain attached to the mother giant. This is in reasonable agreement with osmotic swelling experiments which show that approximately 11% of the daughter vesicles is available for area expansion.

Mechanics of bundled semiflexible polymer networks.

While actin bundles are used by living cells for structural fortification, the microscopic origin of the elasticity of bundled networks is not understood. Here, we show that above a critical concentration of the actin binding protein fascin, a solution of actin filaments organizes into a pure network of bundles. While the elasticity of weakly cross-linked networks is dominated by the affine deformation of tubes, the network of bundles can be fully understood in terms of nonaffine bending undulations.

Bending rigidity of mixed phospholipid bilayers and the equilibrium radius of corresponding vesicles.

In spite of the large mean bending moduli observed for phospholipid bilayers, stable vesicle phases were recently observed for dilute solutions of charged phospholipids. A correspondingly large negative Gaussian bending modulus associated with charged membranes results in an overall curvature energy that is so low that entropic stabilization is possible. The mean bending modulus determines the membrane persistence length and therefore it is reasonable that there is a correlation between the membrane rigidity and the size of the lipid vesicles. Here we show that in mixtures of the anionic phospholipid dioleoylphosphatidylglycerol and the zwitterionic phospholipid dioleoylphosphatidylcholine the radius of vesicles produced by repetitive freeze-thaw cycles is considerably smaller than expected from the rigidities of the corresponding pure lipid bilayers. Self-consistent field calculations indicate that the changes in the equilibrium radius of mixed bilayers can be attributed to the dependences of the mean bending modulus k(c) on lipid mixing and the average surface charge density.

Opposing effects of cation binding and hydration on the bending rigidity of anionic lipid bilayers.

We correlate the molecularly realistic self-consistent field predictions for the mean bending modulus kc of charged lipid vesicles with experimental observations of the size R of corresponding vesicles that are produced by the freeze-thaw method. We elaborate on the Ansatz that the bending modulus is related to the membrane persistence length and that this length scale sets the radius of the vesicles. Alkali cations have a remarkable effect on the mean bending modulus and thus on the equilibrium radius of negatively charged entropically stabilized dioleoylphosphatidylglycerol (DOPG) vesicles. Where cation hydration typically results in thicker and thus stiffer membranes, specific adsorption to the bilayer surface results in a decrease of the surface charge density and the thickness of the membrane-associated electric double layer. As a result of these opposing effects on kc and R, the largest DOPG vesicles are found in the presence of K+, which combines an intermediate hydration enthalpy and PG-binding affinity.

Entropic stabilization and equilibrium size of lipid vesicles.

We have studied the phase behavior of zwitterionic phospholipid dioleoylphosphatidylcholine (DOPC) vesicles (membranes) and interpreted our results using scaling arguments in combination with molecular realistic self-consistent field (SCF) calculations. DOPC membranes acquire a partial negative charge per lipid molecule at intermediate NaBr concentrations. As a result of this, dilute DOPC solutions form stable unilamellar vesicles. Both at low and high salt concentrations phase separation into a lamellar and a vesicular phase is observed. The vesicle radius decreases as a power law with decreasing lipid concentration. This power-law concentration dependence indicates that the vesicle phase is entropically stabilized; the size of the DOPC vesicles result from a competition between the bending energy and translation and undulation entropy. This scaling behavior breaks down for very small vesicles. This appears to be consistent with SCF predictions that point to the fact that in this regime the mean bending modulus kc increases with curvature. The SCF theory predicts that, at low ionic strength, the membrane stability improves when there is more charge on the lipids. Upon a decrease of the ionic strength, lipids with a full negative charge form vesicles that grow exponentially in size because the mean bending modulus increases with decreasing ionic strength. At the same time the Gaussian bending modulus becomes increasingly negative such that the overall bending energy tends to zero. This indicates that small micelles become the dominant species. The SCF theory thus predicts a catastrophic break down of giant vesicles in favor of small micelles at sufficiently low ionic strength and high charge density on the lipids.

Viscoelasticity of isotropically cross-linked actin networks.

Despite their importance for the proper function of living cells, the physical properties of cross-linked actin networks remain poorly understood as the occurrence of heterogeneities hamper a quantitative physical description. The isotropic homogeneously cross-linked actin network presented here enables us to quantitatively relate the network response to a single filament model by determining the dominating length scale. The frequency dependence of the linear response and nonuniversal form of the nonlinear response reveal the importance of cross-linker unbinding events.

Micro- and macrorheological properties of actin networks effectively cross-linked by depletion forces.

The structure and rheology of cytoskeletal networks are regulated by actin binding proteins. Aside from these specific interactions, depletion forces can also alter the properties of cytoskeletal networks. Here we demonstrate that the addition of poly(ethylene glycol) (PEG) as a depletion agent results not only in severe structural changes, but also in alterations in mechanical properties of actin solutions. In the plateau of the elastic modulus two regimes can be distinguished by micro and macrorheological methods. In the first, the elastic modulus increases only slightly with increasing depletion agent, whereas above a critical concentration c*, a strong increase of cPEG6k3.5 is observed in a distinct second regime. Microrheological data and electron microscopy images show a homogenous network of actin filaments in the first regime, whereas at higher PEG concentrations a network of actin bundles is observed. The concentration dependence of the plateau modulus G0, the shift in entanglement time taue, and the nonlinear response indicate that below c* the network becomes effectively cross-linked, whereas above c* G0(cPEG6k) is primarily determined by the network of bundles that exhibits a linearly increasing bundle thickness.