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1. Deep Ritz -- Finite Element methods: Neural Network Methods trained with Finite Elements

Author

Grekas, Georgios and Makridakis, Charalambos G.

Subjects
Mathematics - Numerical Analysis, Physics - Computational Physics
Abstract

While much attention of neural network methods is devoted to high-dimensional PDE problems, in this work we consider methods designed to work for elliptic problems on domains $\Omega \subset \mathbb{R} ^d, $ $d=1,2,3$ in association with more standard finite elements. We suggest to connect finite elements and neural network approximations through training, i.e., using finite element spaces to compute the integrals appearing in the loss functionals. This approach, retains the simplicity of classical neural network methods for PDEs, uses well established finite element tools (and software) to compute the integrals involved and it gains in efficiency and accuracy. We demonstrate that the proposed methods are stable and furthermore, we establish that the resulting approximations converge to the solutions of the PDE. Numerical results indicating the efficiency and robustness of the proposed algorithms are presented.

Published
2024

2. A class of Discontinuous Galerkin methods for nonlinear variational problems

Author

Grekas, Georgios, Koumatos, Konstantinos, Makridakis, Charalambos, and Vikelis, Andreas

Subjects
Mathematics - Numerical Analysis
Abstract

In the context of Discontinuous Galerkin methods, we study approximations of nonlinear variational problems associated with convex energies. We propose element-wise nonconforming finite element methods to discretize the continuous minimisation problem. Using $\Gamma$-convergence arguments we show that the discrete minimisers converge to the unique minimiser of the continuous problem as the mesh parameter tends to zero, under the additional contribution of appropriately defined penalty terms at the level of the discrete energies. We finally substantiate the feasibility of our methods by numerical examples.

Published
2023

3. Theory of intermediate twinning and spontaneous polarization in the phase transformations of ferroelectric potassium sodium niobate

Author

Grekas, Georgios, Pop-Ghe, Patricia-Lia, Quandt, Eckhard, and James, Richard D.

Subjects
Condensed Matter - Materials Science
Abstract

Potassium sodium niobate is considered a prominent material system as a substitute for toxic lead-containing ferroelectric materials. It exhibits first-order phase transformations and ferroelectricity with potential applications ranging from energy conversion to innovative cooling technologies, hereby addressing urgent societal challenges. However, a major obstacle in the application of potassium sodium niobate is its multi-scale heterogeneity and the lack of understanding of its phase transition pathway and microstructure. This can be seen from the findings of Pop-Ghe 2021 et al. [1] which also reveal the occurrence of intermediate twinning during the phase transition. Here we show that intermediate twinning is a consequence of energy minimization. We employ a geometrically nonlinear electroelastic energy function for potassium sodium niobate, including the cubic-tetragonal-orthorhombic transformations and ferroelectricity. The construction of the minimizers is based on compatibility conditions which ensure continuous deformations and pole-free interfaces. These minimizers agree with the experimental observations, including laminates between the tetragonal variants under the cubic to tetragonal transformation, crossing twins under the tetragonal to orthorhombic transformation, intermediate twinning and spontaneous polarization. This shows how the full nonlinear electroelastic model provides a powerful tool in understanding, exploring and tailoring the electromechanical properties of complex ferroelectric ceramics.

Published
2023

4. Compressive Instabilities Enable Cell-Induced Extreme Densification Patterns in the Fibrous Extracellular Matrix: Discrete Model Predictions

Author

Kalaitzidou, Chrysovalantou, Grekas, Georgios, Zilian, Andreas, Makridakis, Charalambos, and Rosakis, Phoebus

Subjects
Physics - Biological Physics, Condensed Matter - Soft Condensed Matter
Abstract

Through modelling and simulations we show that material instabilities play a dominant role in the mechanical behavior of the fibrous collagen Extracellular Matrix (ECM), as observed when the ECM is deformed by contractile biological cells. We compare two families of fiber network models, Family 1 with stable and Family 2 with unstable force-stretch response of individual fibers in compression. The latter is a characteristic of post-buckling of beams with hierarchical structure. Our simulations reveal different compression instabilities at play in each family, namely, fiber collapse (buckling) in Family 2 and fiber element collapse (snap-through) in Family 1. These result in highly localized densification zones consisting of strongly aligned fibers emanating from individual contractile cells or joining neighbouring cells, as observed in experiments. Despite substantial differences in the response of the two families, our work underscores the importance of buckling/compression instabilities in the behavior of fibrous biological tissues, with implications in cancer invasion and metastasis.

Published
2022

5. Compressive instabilities enable cell-induced extreme densification patterns in the fibrous extracellular matrix: Discrete model predictions.

Author

Chrysovalantou Kalaitzidou, Georgios Grekas, Andreas Zilian, Charalambos Makridakis, and Phoebus Rosakis

Subjects
Biology (General), QH301-705.5
Abstract

We present a new model and extensive computations that explain the dramatic remodelling undergone by a fibrous collagen extracellular matrix (ECM), when subjected to contractile mechanical forces from embedded cells or cell clusters. This remodelling creates complex patterns, comprising multiple narrow localised bands of severe densification and fiber alignment, extending far into the ECM, often joining distant cells or cell clusters (such as tumours). Most previous models cannot capture this behaviour, as they assume stable mechanical fiber response with stress an increasing function of fiber stretch, and a restriction to small displacements. Our fully nonlinear network model distinguishes between two types of single-fiber nonlinearity: fibers that undergo stable (supercritical) buckling (as in previous work) versus fibers that suffer unstable (subcritical) buckling collapse. The model allows unrestricted, arbitrarily large displacements (geometric nonlinearity). Our assumptions on single-fiber instability are supported by recent simulations and experiments on buckling of individual beams with a hierarchical microstructure, such as collagen fibers. We use simple scenarios to illustrate, for the first time, two distinct compressive-instability mechanisms at work in our model: unstable buckling collapse of single fibers, and snap-through of multiple-fiber groups. The latter is possible even when single fibers are stable. Through simulations of large fiber networks, we show how these instabilities lead to spatially extended patterns of densification, fiber alignment and ECM remodelling induced by cell contraction. Our model is simple, but describes a very complex, multi-stable energy landscape, using sophisticated numerical optimisation methods that overcome the difficulties caused by instabilities in large systems. Our work opens up new ways of understanding the unique biomechanics of fibrous-network ECM, by fully accounting for nonlinearity and associated loss of stability in fiber networks. Our results provide new insights on tumour invasion and metastasis.

Published
2024
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6. Approximations of energy minimization in cell-induced phase transitions of fibrous biomaterials: $\Gamma$-convergence analysis

Author

Grekas, Georgios, Koumatos, Konstantinos, Makridakis, Charalambos, and Rosakis, Phoebus

Subjects
Mathematics - Numerical Analysis, Mathematical Physics
Abstract

We consider a model of energy minimization arising in the study of the mechanical behavior caused by cell contraction within a fibrous biological medium. The macroscopic model is based on the theory of non rank-one convex nonlinear elasticity for phase transitions. We study appropriate numerical approximations based on the discontinuous Galerkin treatment of higher gradients and used succesfully in numerical simulations of experiments. We show that the discrete minimizers converge in the limit to minimizers of the continuous problem. This is achieved by employing the theory of $\Gamma$-convergence of the approximate energy functionals to the continuous model when the discretization parameter tends to zero. The analysis is involved due to the structure of numerical approximations which are defined in spaces with lower regularity than the space where the minimizers of the continuous variational problem are sought. This fact leads to the development of a new approach to $\Gamma$-convergence, appropriate for discontinuous finite element discretizations, which can be applied to quite general energy minimization problems. Furthermore, the adoption of exponential terms penalising the interpenetration of matter requires a new framework based on Orlicz spaces for discontinuous Galerkin methods which is developed in this paper as well.

Published
2019

7. Cells exploit a phase transition to mechanically remodel the fibrous extracellular matrix

Author

Grekas, Georgios, Proestaki, Maria, Rosakis, Phoebus, Notbohm, Jacob, Makridakis, Charalambos, and Ravichandran, Guruswami

Subjects
Physics - Biological Physics, Condensed Matter - Soft Condensed Matter
Abstract

Through mechanical forces, biological cells remodel the surrounding collagen network, generating striking deformation patterns. Tethers-tracts of high densification and fiber alignment-form between cells, thinner bands emanate from cell clusters. While tethers facilitate cell migration and communication, how they form is unclear. Combining modeling, simulation and experiment, we show that tether formation is a densification phase transition of the extracellular matrix, caused by buckling instability of network fibers under cell-induced compression, featuring unexpected similarities with martensitic microstructures. Multiscale averaging yields a two-phase, bistable continuum energy landscape for fibrous collagen, with a densified/aligned second phase. Simulations predict strain discontinuities between the undensified and densified phase, which localizes within tethers as experimentally observed. In our experiments, active particles induce similar localized patterns as cells. This shows how cells exploit an instability to mechanically remodel the extracellular matrix simply by contracting, thereby facilitating mechanosensing, invasion and metastasis.

Published
2019
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8. Application For Reduced VAT Rate - Private Dwellings

Author

Grekas, Michael C.

Subjects
Tax rates -- Laws, regulations and rules, Value-added tax -- Laws, regulations and rules, Government regulation, Business, international
Abstract

Application for the Reduced VAT Rate of 5% on the supply or construction of a private dwelling The objective of this Indirect Tax Update is to inform you that effective [...]

Published
2024

9. Compressive instabilities enable cell-induced extreme densification patterns in the fibrous extracellular matrix: Discrete model predictions.

Author

Kalaitzidou, Chrysovalantou, Grekas, Georgios, Zilian, Andreas, Makridakis, Charalambos, and Rosakis, Phoebus

Subjects
*EXTRACELLULAR matrix, *EXTRACELLULAR matrix proteins, *CELL contraction, *PREDICTION models
Abstract

We present a new model and extensive computations that explain the dramatic remodelling undergone by a fibrous collagen extracellular matrix (ECM), when subjected to contractile mechanical forces from embedded cells or cell clusters. This remodelling creates complex patterns, comprising multiple narrow localised bands of severe densification and fiber alignment, extending far into the ECM, often joining distant cells or cell clusters (such as tumours). Most previous models cannot capture this behaviour, as they assume stable mechanical fiber response with stress an increasing function of fiber stretch, and a restriction to small displacements. Our fully nonlinear network model distinguishes between two types of single-fiber nonlinearity: fibers that undergo stable (supercritical) buckling (as in previous work) versus fibers that suffer unstable (subcritical) buckling collapse. The model allows unrestricted, arbitrarily large displacements (geometric nonlinearity). Our assumptions on single-fiber instability are supported by recent simulations and experiments on buckling of individual beams with a hierarchical microstructure, such as collagen fibers. We use simple scenarios to illustrate, for the first time, two distinct compressive-instability mechanisms at work in our model: unstable buckling collapse of single fibers, and snap-through of multiple-fiber groups. The latter is possible even when single fibers are stable. Through simulations of large fiber networks, we show how these instabilities lead to spatially extended patterns of densification, fiber alignment and ECM remodelling induced by cell contraction. Our model is simple, but describes a very complex, multi-stable energy landscape, using sophisticated numerical optimisation methods that overcome the difficulties caused by instabilities in large systems. Our work opens up new ways of understanding the unique biomechanics of fibrous-network ECM, by fully accounting for nonlinearity and associated loss of stability in fiber networks. Our results provide new insights on tumour invasion and metastasis. Author summary: Living tissue often comprises a complex network of fibrous collagen and other proteins called the Extracellular Matrix, or ECM, containing embedded cells at various distances from one another. Cells can interact with their environment and communicate with peers by exerting mechanical forces onto the ECM, which acts as a medium for signalling, migration and invasion. Observed mechanical response of the ECM to forces from contracting cells is unexpected. Distinctive patterns of narrow bands emerge, where fibers are collapsed and aligned, extending unusually far into the ECM, often joining distant cells or cell clusters, such as tumours. These bands serve as conduits for mechanical signalling or highways for cell migration, tumour invasion and cancer metastasis. We hypothesise that the formation of these striking patterns results from the inability of fibers to resist compression, much like rubber bands, and the fact that in a network, there is room for fibers to rotate, buckle and collapse. Our computations successfully predict the emergent striking patterns of ECM pathways consisting of densified aligned fibers and confirm our hypothesis that multiple compressive instability mechanisms are behind the phenomenon. This brings new understanding of the role of unstable mechanical behaviour of the ECM in aiding and abetting tumour invasion and metastasis. [ABSTRACT FROM AUTHOR]

Published
2024
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15. Compulsory Transmission & Exchange Of Cross-border Payment Data To Fight VAT Fraud As Of 2024

Author

Grekas, Michael C.

Subjects
Transborder data flow -- Laws, regulations and rules, Tax evasion -- Laws, regulations and rules, Value-added tax -- Laws, regulations and rules, Online payment services -- Laws, regulations and rules, Government regulation, Online payment services, Business, international
Abstract

In accordance with Regulation (EU) 2020/284 and Directive (EU) 2020/283, the EU in another endeavor to detect and eliminate fraud in VAT, will implement CESOP, namely the Central Electronic System [...]

Published
2022

16. Important Amendment To The VAT Law Regarding The Supply Of Buildings

Author

Grekas, Michael C.

Subjects
Value-added tax -- Laws, regulations and rules, Real property tax -- Laws, regulations and rules, Government regulation, Business, international
Abstract

The Council of Ministers has recently approved the amendment of Schedule 8 of the VAT Law (95(I)/2000) regarding the conditions that must be satisfied for the imposition of VAT on [...]

Published
2022

17. Indirect Tax Update - European Commission

Author

Grekas, Michael C.

Subjects
Energy industry -- Laws, regulations and rules, Government regulation, Business, international, European Union. European Commission -- Laws, regulations and rules
Abstract

Pressures exercised on European Union's energy markets have been tackled by the European Commission since last year. As a first step to restrain the rapid increase in energy prices, EU [...]

Published
2022

18. Elevated Asymmetric Dimethylarginine is Associated With Oxidant Stress Aggravation in Patients With Early Stage Autosomal Dominant Polycystic Kidney Disease

Author

Vassilios Raptis, Panagiotis I. Georgianos, Pantelis A. Sarafidis, Athanasios Sioulis, Kali Makedou, Areti Makedou, Dimitrios M. Grekas, and Stergios Kapoulas

Subjects
ADPKD, Asymmetric dimethylarginine, ADMA, autosomal dominated polycystic kidney disease, eGFR, Oxidative stress, Dermatology, RL1-803, Diseases of the circulatory (Cardiovascular) system, RC666-701, Diseases of the genitourinary system. Urology, RC870-923
Abstract

Background/Aims: In experimental models of polycystic kidney disease impaired bioavailability of nitric oxide (NO) and elevated mRNA expression of oxidative stress markers at the kidney level was noted. However, clinical studies investigating the potential role of endothelial dysfunction and oxidative stress in the pathogenesis of autosomal dominant polycystic kidney disease (ADPKD) are limited. We evaluated asymmetric dimethylarginine (ADMA) as marker of NO synthase inhibitor as well as 15-F2t-Isoprostane and oxidized-low density lipoprotein (oxidized-LDL) as measures of oxidative stress in patients with early stages ADPKD. Methods: We recruited 26 ADPKD patients (Group A) with modestly impaired renal function (eGFR 45-70 ml/min/1.73m2), 26 age- and sex-matched ADPKD patients (Group B) with relatively preserved renal function (eGFR)>70 ml/min/1.73m2), and 26 age- and sex-matched controls (Group C). Determination of circulating levels of ADMA, 15-F2t-Isoprostane, oxidized-LDL and routine biochemistry was performed. Results: Group A and B had significantly higher ADMA levels as compared to controls (1.68±0.7 vs 0.51±0.2 μmol/l, P2t-IsoP and oxidized-LDL levels were also significantly higher in Group B relative to controls (788.8±185.0 vs 383.1±86.0 pgr/ml, P2t-Isoprostane (r=0.811, PConclusion: This study shows elevation in circulating levels of ADMA along with aggravation of oxidative stress from the early stages of ADPKD.

Published
2014
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19. P1544: BONE MINERAL DENSITY REMAINS STABLE IN PYRUVATE KINASE DEFICIENCY PATIENTS RECEIVING LONG-TERM TREATMENT WITH MITAPIVAT

Author

Al-Samkari, H., primary, Grace, R. F., additional, Glenthøj, A., additional, Andres, O., additional, Barcellini, W., additional, Galactéros, F., additional, Kuo, K. H. M., additional, Layton, D. M., additional, Morado Arias, M., additional, Viprakasit, V., additional, Dong, Y., additional, Tai, F., additional, Grekas, L., additional, Khoja, K., additional, Gheuens, S., additional, McGee, B., additional, Porter, J. B., additional, and van Beers, E. J., additional

Published
2022
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20. MO639: Evaluation of Glycemic Control and Interday Glucose Variability Using Continuous Glucose Monitoring in Diabetic Hemodialysis Patients

Author

Maria Divani, Panagiotis Georgianos, Vassilios Liakopoulos, Triantafillos Didangelos, Kali Makedou, Christos Savopoulos, and Dimitrios Grekas

Subjects
Transplantation, Nephrology
Abstract

BACKGROUND AND AIMS Continuous-glucose-monitoring (CGM) facilitates the assessment of interday glucose variability and identification of acute excursions of hyper- and hypoglycemia [1–4). METHOD Among 37 diabetic hemodialysis patients who underwent 7-day CGM with the iPRO2 device (Medtronic Diabetes, Northridge, CA, USA), we explored the accuracy of GA and hemoglobin A1c (HbA1c) in assessing glycemic control, using CGM-derived metrics as the reference standard. RESULTS In receiver-operating-characteristic (ROC) analysis, the area under the curve (AUC) in diagnosing a time in target glucose range of 70–180 mg/dL (TIR70-180) in 250 mg/dL (TAR >250) in >10% of readings did not differ from that of HbA1c [AUC 0.854 (95% CI 0.699–0.948)] (P = 0.16). GA [AUC 0.712 (95% CI 0.539–0.848)] and HbA1c [AUC 0.740 (95% CI 0.570–0.870)] had a similarly lower efficiency in detecting a time below target glucose range 1% of readings (P = 0.71). Although the mean glucose levels were similar, the coefficient of variation of glucose recordings (39.2% ± 17.3% versus 32.0% ± 7.8%, P CONCLUSION The present diagnostic test study shows that among diabetic hemodialysis patients, GA had higher accuracy than HbA1c in detecting a 7-day CGM-derived TIR70-180 in

Published
2022

21. Frequent COL4 mutations in familial microhematuria accompanied by later‐onset Alport nephropathy due to focal segmental glomerulosclerosis

Author

Papazachariou, L., Papagregoriou, G., Hadjipanagi, D., Demosthenous, P., Voskarides, K., Koutsofti, C., Stylianou, K., Ioannou, P., Xydakis, D., Tzanakis, I., Papadaki, A., Kallivretakis, N., Nikolakakis, N., Perysinaki, G., Gale, D.P., Diamantopoulos, A., Goudas, P., Goumenos, D., Soloukides, A., Boletis, I., Melexopoulou, C., Georgaki, E., Frysira, E., Komianou, F., Grekas, D., Paliouras, C., Alivanis, P., Vergoulas, G., Pierides, A., Daphnis, E., and Deltas, C.

Published
2017
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24. Compressive Instabilities Enable Cell-Induced Extreme Densification Patterns in the Fibrous Extracellular Matrix: Discrete Model Predictions

Author

Chrysovalantou Kalaitzidou, Georgios Grekas, Andreas Zilian, Charalambos Makridakis, and Phoebus Rosakis

Subjects
Multidisciplinaire, généralités & autres [C99] [Ingénierie, informatique & technologie], Biological Physics (physics.bio-ph), Multidisciplinary, general & others [C99] [Engineering, computing & technology], Soft Condensed Matter (cond-mat.soft), FOS: Physical sciences, Physics - Biological Physics, Condensed Matter - Soft Condensed Matter
Abstract

Through modelling and simulations we show that material instabilities play a dominant role in the mechanical behavior of the fibrous collagen Extracellular Matrix (ECM), as observed when the ECM is deformed by contractile biological cells. We compare two families of fiber network models, Family 1 with stable and Family 2 with unstable force-stretch response of individual fibers in compression. The latter is a characteristic of post-buckling of beams with hierarchical structure. Our simulations reveal different compression instabilities at play in each family, namely, fiber collapse (buckling) in Family 2 and fiber element collapse (snap-through) in Family 1. These result in highly localized densification zones consisting of strongly aligned fibers emanating from individual contractile cells or joining neighbouring cells, as observed in experiments. Despite substantial differences in the response of the two families, our work underscores the importance of buckling/compression instabilities in the behavior of fibrous biological tissues, with implications in cancer invasion and metastasis.

Published
2022
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27. Bone Mineral Density Remains Stable in Pyruvate Kinase Deficiency Patients Receiving Long-Term Treatment with Mitapivat

Author

Al-Samkari, Hanny, primary, Grace, Rachael F., additional, Glenthoej, Andreas, additional, Andres, Oliver, additional, Barcellini, Wilma, additional, Galactéros, Frédéric, additional, Kuo, Kevin H.M., additional, Layton, D. Mark, additional, Morado, Marta, additional, Viprakasit, Vip, additional, Dong, Yan, additional, Tai, Feng, additional, Grekas, Liz, additional, Khoja, Karishma, additional, Gheuens, Sarah, additional, McGee, Bryan, additional, Porter, John B., additional, and Van Beers, Eduard J., additional

Published
2021
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30. Exploring the competition between proliferative and invasive cancer phenotypes in a continuous spatial model.

Author

Eleftheria Tzamali, Georgios Grekas, Konstantinos Marias, and Vangelis Sakkalis

Subjects
Medicine, Science
Abstract

Tumor is characterized by extensive heterogeneity with respect to its microenvironment and its genetic composition. We extend a previously developed monoclonal continuous spatial model of tumor growth to account for polyclonal cell populations and investigate the interplay between a more proliferative and a more invasive phenotype under different conditions. The model simulations demonstrate a transition from the dominance of the proliferative to the dominance of the invasive phenotype resembling malignant tumor progression and show a time period where both subpopulations are abundant. As the dominant phenotype switches from proliferative to invasive, the geometry of tumor changes from a compact and almost spherical shape to a more diffusive and fingered morphology with the proliferative phenotype to be restricted in the tumor bulk and the invasive to dominate at tumor edges. Different micro-environmental conditions and different phenotypic properties can promote or inhibit invasion demonstrating their mutual importance. The model provides a computational framework to investigate tumor heterogeneity and the constant interplay between the environment and the specific characteristics of phenotypes that should be taken into account for the prediction of tumor evolution, morphology and effective treatment.

Published
2014
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40. Evaluation of the clinical efficacy of the fluticasone-salmeterol fixed dose combination (FDC) in Greek patients with Chronic Obstructive Pulmonary Disease-AEOLOS study

Author

Nikolaos Grekas, Stavros Tryfon, Alexandros Ginis, Paschalis Steiropoulos, Aikaterini Athanassiou, and Ioanna-Laoutselnta Markou

Subjects
COPD, medicine.medical_specialty, Inflammatory lung disease, Salmeterol fluticasone, business.industry, Fixed-dose combination, Pulmonary disease, medicine.disease, respiratory tract diseases, Pulmonary function testing, Internal medicine, medicine, Respiratory function, Clinical efficacy, business
Abstract

Introduction: Chronic obstructive pulmonary disease (COPD) is a chronic, inflammatory lung disease characterized by a progressive decline in respiratory function and persistent symptoms such as dyspnea. Objectives: We evaluated the change in %FEV1pred. and MRC dyspnea score in COPD patients treated with fluticasone-salmeterol FDC via Elpenhaler® device for 12 months. Methods: In this prospective, multicenter clinical study (NCT02978703) 1,016 COPD patients, with a mean age of 69.54 ± 9.57 years and a mean BMI of 28.65 ± 5.38 Kg/m2 were enrolled. The efficacy of the fluticasone-salmeterol FDC administered via Elpenhaler® device was assessed by evaluating the %FEV1pred. change and MRC dyspnea score. The corresponding data were collected at baseline (V0), 6 (V1) and 12 (V2) months, respectively. Results: There was a statistically significant improvement (p˂0.0001) in the %FEV1pred. among consecutive visits V0 (baseline) (Mean±SD:48.43±8.61), V1 (Mean±SD:54.17±10.87) and V2 (Mean±SD:56.47±11.82) as well as between baseline and final visit. Similar significant improvement was observed in the values of the MRC dyspnea score between consecutive visits (p˂0.0001, Kruskal-Wallis test). Conclusion: Patients with COPD who were treated with a fluticasone-salmeterol FDC via the Elpenhaler® device showed a significant improvement in pulmonary function and dyspnea, as assessed by the change in %FEV1pred. and by the dyspnea MRC score after 6 and 12 months respectively.

Published
2020

41. Dairy products, surrogate markers, and cardiovascular disease; a sex-specific analysis from the ATTICA prospective study

Author

Mary Yannakoulia, N. Skourlis, Constantina Masoura, N. Katinioti, C. Papanikolaou, Eleni Kokkou, S. Vellas, K. Paliou, C. Tselika, Yannis Skoumas, V. Metaxa, A. Grekas, Yannis Lentzas, Dimitrios Tousoulis, Christos Pitsavos, Ekavi N. Georgousopoulou, G. Dedousis, M. Toutouza-Giotsa, A. Laskaris, M. Hatzigeorgiou, Evangelia Pitaraki, M. Toutouza, Demosthenes B. Panagiotakos, Aikaterini Kalogeropoulou, Carmen Vassiliadou, S. Poulopouloou, Christina Chrysohoou, Matina Kouvari, M. Kambaxis, and L. Papadimitriou

Subjects
Adult, Male, medicine.medical_specialty, Time Factors, Endocrinology, Diabetes and Metabolism, Serving Size, Medicine (miscellaneous), 030209 endocrinology & metabolism, 030204 cardiovascular system & hematology, Lower risk, Recommended Dietary Allowances, Risk Assessment, Food group, 03 medical and health sciences, 0302 clinical medicine, Insulin resistance, Sex Factors, Internal medicine, medicine, Humans, Prospective Studies, Prospective cohort study, Nutrition and Dietetics, Greece, business.industry, Incidence (epidemiology), Incidence, Hazard ratio, Middle Aged, Protective Factors, medicine.disease, Confidence interval, Cardiovascular Diseases, Heart Disease Risk Factors, Female, Dairy Products, Steatosis, Diet, Healthy, Cardiology and Cardiovascular Medicine, business, Nutritive Value
Abstract

Background and aims Dairy products are a very diverse food group with multiple effects on the cardiac health of men and women. The aim of this work was to evaluate the sex-specific association between dairy products (total and subtypes) and 10-year first fatal/nonfatal cardiovascular disease (CVD) incidence. Methods and results In 2001–2002, n = 1514 men and n = 1528 women (>18 years old) from greater Athens area, Greece, were enrolled. Dietary assessment was based on a validated semi-quantitative food frequency questionnaire. Dairy product consumption was examined in relation to 10-year CVD incidence. Follow-up (2011–2012) was achieved in n = 2020 participants (n = 317 CVD cases). Ranking from lowest ( 2 servings/day) total dairy intake, CVD incidence in men was 17.8%, 15.0%, and 10.9% (p = 0.41), while in women it was 14%, 6.0%, and 5.7% (p = 0.02). Multiadjusted analysis revealed that total dairy intake protected against CVD only in women [Hazard Ratio (HR) = 0.48 and 95% Confidence Interval (95% CI) (0.23, 0.90)], irrespective of the fat content. Further analysis revealed that only fermented products (yogurt and cheese), protected against CVD. For per 200 g/day yogurt consumption, CVD risk was 20%–30% lower with this claim being more evident in women, while for per 30 g/day cheese intake, about 5% lower risk was observed particularly in men. As for butter, nonsignificant associations were highlighted. These associations were mainly retained in the case of hepatic steatosis, insulin resistance, and systemic inflammation. Conclusions This work provides incentives for researchers to elucidate the diversity of ingredients and mechanisms through which dairy products exert their effect on cardiac health separately for men and women.

Published
2020

43. Dairy products, surrogate markers, and cardiovascular disease; a sex-specific analysis from the ATTICA prospective study

Author

Kouvari, M. Panagiotakos, D.B. Chrysohoou, C. Georgousopoulou, E.N. Yannakoulia, M. Tousoulis, D. Pitsavos, C. Skoumas, Y. Katinioti, N. Papadimitriou, L. Masoura, C. Vellas, S. Lentzas, Y. Kambaxis, M. Paliou, K. Metaxa, V. Skourlis, N. Papanikolaou, C. Kalogeropoulou, A. Pitaraki, E. Laskaris, A. Hatzigeorgiou, M. Grekas, A. Kokkou, E. Vassiliadou, C. Dedousis, G. Toutouza-Giotsa, M. Tselika, C. Poulopouloou, S. Toutouza, M. The ATTICA study Investigators

Abstract

Background and aims: Dairy products are a very diverse food group with multiple effects on the cardiac health of men and women. The aim of this work was to evaluate the sex-specific association between dairy products (total and subtypes) and 10-year first fatal/nonfatal cardiovascular disease (CVD) incidence. Methods and results: In 2001–2002, n = 1514 men and n = 1528 women (>18 years old) from greater Athens area, Greece, were enrolled. Dietary assessment was based on a validated semi-quantitative food frequency questionnaire. Dairy product consumption was examined in relation to 10-year CVD incidence. Follow-up (2011–2012) was achieved in n = 2020 participants (n = 317 CVD cases). Ranking from lowest (2 servings/day) total dairy intake, CVD incidence in men was 17.8%, 15.0%, and 10.9% (p = 0.41), while in women it was 14%, 6.0%, and 5.7% (p = 0.02). Multiadjusted analysis revealed that total dairy intake protected against CVD only in women [Hazard Ratio (HR) = 0.48 and 95% Confidence Interval (95% CI) (0.23, 0.90)], irrespective of the fat content. Further analysis revealed that only fermented products (yogurt and cheese), protected against CVD. For per 200 g/day yogurt consumption, CVD risk was 20%–30% lower with this claim being more evident in women, while for per 30 g/day cheese intake, about 5% lower risk was observed particularly in men. As for butter, nonsignificant associations were highlighted. These associations were mainly retained in the case of hepatic steatosis, insulin resistance, and systemic inflammation. Conclusions: This work provides incentives for researchers to elucidate the diversity of ingredients and mechanisms through which dairy products exert their effect on cardiac health separately for men and women. © 2020 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University

Published
2020

47. Comparison of Glycemic Markers in Chronic Hemodialysis Using Continuous Glucose Monitoring

Author

Triantafyllos Didangelos, Areti Makedou, Fotios Iliadis, Maria Divani, Panagiotis I. Georgianos, Apostolos I. Hatzitolios, Vassilios Liakopoulos, and Dimitrios Grekas

Subjects
Adult, Blood Glucose, Glycation End Products, Advanced, Male, medicine.medical_specialty, endocrine system diseases, Glycated hemoglobin-A1c, medicine.medical_treatment, 030232 urology & nephrology, 030209 endocrinology & metabolism, Gastroenterology, End stage renal disease, 03 medical and health sciences, 0302 clinical medicine, Glycated albumin, Renal Dialysis, Internal medicine, Humans, Hypoglycemic Agents, Medicine, Glycated Serum Albumin, Chronic hemodialysis, Serum Albumin, Aged, Monitoring, Physiologic, Glycemic, Aged, 80 and over, Glycated Hemoglobin, business.industry, Continuous glucose monitoring, nutritional and metabolic diseases, Middle Aged, Diabetes Mellitus, Type 2, Nephrology, Hyperglycemia, Glycated Serum Protein, Kidney Failure, Chronic, Female, Hemodialysis, business, Biomarkers
Abstract

Background: Glycated hemoglobin A1c (HbA1c) among diabetic hemodialysis patients continues to be the standard of care, although its limitations are well recognized. This study evaluated glycated albumin (GA) and glycated serum protein (GSP) as alternatives to HbA1c in detecting glycemic control among diabetic hemodialysis patients using continuous-glucose-monitoring (CGM)-derived glucose as reference standard. Methods: A CGM system (iPRO) was applied for 7 days in 37 diabetic hemodialysis patients to determine glycemic control. The accuracy of GA and GSP versus HbA1c in detecting a 7-day average glucose ≥184 mg/dL was evaluated via receiver-operating-characteristic (ROC) analysis. Results: CGM-derived glucose exhibited strong correlation (r = 0.970, p < 0.001) and acceptable agreement with corresponding capillary glucose measurements obtained by the patients themselves in 1,169 time-points over the 7-day-long CGM. The area under ROC curve (AUC) for GA, GSP, and HbA1c to detect poor glycemic control was 0.976 (0.862–1.000), 0.682 (0.502–0.862), and 0.776 (0.629–0.923) respectively. GA levels >20.3% had 90.9% sensitivity and 96.1% specificity in detecting a 7-day average glucose ≥184 mg/dL. The AUC for GA was significantly higher than the AUC for GSP (difference between areas: 0.294, p < 0.001) and the AUC for HbA1c (difference between areas: 0.199, p < 0.01). Conclusion: Among diabetic hemodialysis patients, GA is a stronger indicator of poor glycemic control assessed with 7-day-long CGM when compared to GSP and HbA1c.

Published
2017

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