Publications by authors named "Fotios Tekos"

9 Publications

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A novel combined bioactivity / chemoactivity holistic approach for the evaluation of dietary supplements.

Food Chem Toxicol 2021 Mar 28:112159. Epub 2021 Mar 28.

Department of Biochemistry-Biotechnology, University of Thessaly, 41500 Larissa, Greece. Electronic address:

There is increased evidence that the excessive production of free radicals in the human body plays a major role in the pathophysiology and development of various diseases, closely associated with oxidative damage. In this frame, the consumption of antioxidant nutrients through food or dietary supplements may prevent free radicals from harming human cells. This work proposes a holistic approach consisting of distinct methodologies, suitable to evaluate the antioxidant and chemoprotective activity of three novel dietary supplements, each one containing active substances with complementary properties. In one step, this approach includes in vitro studies to evaluate the antioxidant activity of the dietary supplements by measuring the parameters of free radical scavenging capacity, of reductive power activity, as well as, their ability to protect biomolecules from oxidation. Furthermore, their antimutagenic and antigenotoxic evaluation is also presented. In another step, the specific effects of the dietary supplements were examined in three cancer cell lines (HepG2, HeLa, MKN45), by measuring redox biomarkers such as glutathione, reactive oxygen species and thiobarbituric acid reactive substances, using flow cytometry and spectrophotometry. Our results indicatthat all the dietary supplements exhibit high antioxidant, antimutagenic, antigenotoxic and lipid protective activity. The most prominent result is their capability to induce the damage caused by cancer cells due to critical downregulation of the levels of their intracellular glutathione as well as increase of ROS and lipid peroxidation levels after the administration of non-cytotoxic concentrations. We suggest that the proposed methodology could constitute a valuable tool for the characterization of dietary supplements based on their chemical and functional properties.
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http://dx.doi.org/10.1016/j.fct.2021.112159DOI Listing
March 2021

An integrated approach for assessing the in vitro and in vivo redox-related effects of nanomaterials.

Environ Res 2021 Mar 25:111083. Epub 2021 Mar 25.

Department of Biochemistry-Biotechnology, University of Thessaly, 41500 Larissa, Greece. Electronic address:

Over the last few decades, nanotechnology has risen to the forefront of both the research and industrial interest, resulting in the manufacture and utilization of various nanomaterials and in their integration into a wide range of fields. However, the consequent elevated exposure to nanomaterials raises serious concerns regarding their effects on human health and safety. Existing scientific data indicate that the induction of oxidative stress, through the excessive generation of Reactive Oxygen Species (ROS), might be the principal mechanism of exerting their toxicity. Meanwhile, various nanomaterials exhibit antioxidant properties, either intrinsic or resulting from their functionalization with conventional antioxidants. Since their redox properties are implicated in the manifestation of their biological effects, we propose an integrated approach for the assessment of the redox-related activities of nanomaterials at three biological levels (in vitro-cell free systems, cell cultures, in vivo). Towards this direction, a battery of translational biomarkers is recommended, and the most reliable protocols in our opinion are presented in detail. The aim of the present approach is to acquire a better understanding concerning the biological actions of nanomaterials in the interrelated fields of redox biology and toxicology.
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http://dx.doi.org/10.1016/j.envres.2021.111083DOI Listing
March 2021

Interplay between oxidative damage, the redox status, and metabolic biomarkers during long-term fasting.

Food Chem Toxicol 2020 Nov 25;145:111701. Epub 2020 Aug 25.

Buchinger Wilhelmi Clinic, 88662, Überlingen, Germany. Electronic address:

Obesity and its related metabolic disorders, as well as infectious diseases like covid-19, are important health risks nowadays. It was recently documented that long-term fasting improves metabolic health and enhanced the total antioxidant capacity. The present study investigated the influence of a 10-day fasting on markers of the redox status in 109 subjects. Reducing power, 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation(ABTS) radical scavenging capacity, and hydroxyl radical scavenging capacity increased significantly, and indicated an increase of circulating antioxidant levels. No differences were detected in superoxide scavenging capacity, protein carbonyls, and superoxide dismutase when measured at baseline and after 10 days of fasting. These findings were concomitant to a decrease in blood glucose, insulin, glycated hemoglobin (HbA1c), total cholesterol, low-density lipoprotein (LDL) and triglycerides as well as an increase in total cholesterol/high-density lipoprotein (HDL) ratio. In addition, the well-being index as well as the subjective energy levels increased, documenting a good tolerability. There was an interplay between redox and metabolic parameters since lipid peroxidation baseline levels (thiobarbituric acid reactive substances [TBARS]) affected the ability of long-term fasting to normalize lipid levels. A machine learning model showed that a combination of antioxidant parameters measured at baseline predicted the efficiency of the fasting regimen to decrease LDL levels. In conclusion, it was demonstrated that long-term fasting enhanced the endogenous production of antioxidant molecules, that act protectively against free radicals, and in parallel improved the metabolic health status. Our results suggest that the outcome of long-term fasting strategies could be depending on the baseline values of the antioxidative and metabolic status of subjects.
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http://dx.doi.org/10.1016/j.fct.2020.111701DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7446623PMC
November 2020

The Importance of Redox Status in the Frame of Lifestyle Approaches and the Genetics of the Lung Innate Immune Molecules, SP-A1 and SP-A2, on Differential Outcomes of COVID-19 Infection.

Antioxidants (Basel) 2020 Aug 25;9(9). Epub 2020 Aug 25.

Department of Biochemistry-Biotechnology, University of Thessaly, 41500 Larissa, Greece.

The pandemic of COVID-19 is of great concern to the scientific community. This mainly affects the elderly and people with underlying diseases. People with obesity are more likely to experience unpleasant disease symptoms and increased mortality. The severe oxidative environment that occurs in obesity due to chronic inflammation permits viral activation of further inflammation leading to severe lung disease. Lifestyle affects the levels of inflammation and oxidative stress. It has been shown that a careful diet rich in antioxidants, regular exercise, and fasting regimens, each and/or together, can reduce the levels of inflammation and oxidative stress and strengthen the immune system as they lead to weight loss and activate cellular antioxidant mechanisms and reduce oxidative damage. Thus, a lifestyle change based on the three pillars: antioxidants, exercise, and fasting could act as a proactive preventative measure against the adverse effects of COVID-19 by maintaining redox balance and well-functioning immunity. Moreover, because of the observed diversity in the expression of COVID-19 inflammation, the role of genetics of innate immune molecules, surfactant protein A (SP-A)1 and SP-A2, and their differential impact on the local lung microenvironment and host defense is reviewed as genetics may play a major role in the diverse expression of the disease.
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http://dx.doi.org/10.3390/antiox9090784DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7554878PMC
August 2020

Chronic Inflammation in the Context of Everyday Life: Dietary Changes as Mitigating Factors.

Int J Environ Res Public Health 2020 06 10;17(11). Epub 2020 Jun 10.

Department Forensic Sciences and Toxicology, University of Crete, Faculty of Medicine, 71003 Heraklion, Greece.

The lifestyle adopted by most people in Western societies has an important impact on the propensity to metabolic disorders (e.g., diabetes, cancer, cardiovascular disease, neurodegenerative diseases). This is often accompanied by chronic low-grade inflammation, driven by the activation of various molecular pathways such as STAT3 (signal transducer and activator of transcription 3), IKK (IκB kinase), MMP9 (matrix metallopeptidase 9), MAPK (mitogen-activated protein kinases), COX2 (cyclooxigenase 2), and NF-Kβ (nuclear factor kappa-light-chain-enhancer of activated B cells). Multiple intervention studies have demonstrated that lifestyle changes can lead to reduced inflammation and improved health. This can be linked to the concept of real-life risk simulation, since humans are continuously exposed to dietary factors in small doses and complex combinations (e.g., polyphenols, fibers, polyunsaturated fatty acids, etc.). Inflammation biomarkers improve in patients who consume a certain amount of fiber per day; some even losing weight. Fasting in combination with calorie restriction modulates molecular mechanisms such as m-TOR, FOXO, NRF2, AMPK, and sirtuins, ultimately leads to significantly reduced inflammatory marker levels, as well as improved metabolic markers. Moving toward healthier dietary habits at the individual level and in publicly-funded institutions, such as schools or hospitals, could help improving public health, reducing healthcare costs and improving community resilience to epidemics (such as COVID-19), which predominantly affects individuals with metabolic diseases.
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http://dx.doi.org/10.3390/ijerph17114135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7312944PMC
June 2020

Influence of Long-Term Fasting on Blood Redox Status in Humans.

Antioxidants (Basel) 2020 Jun 6;9(6). Epub 2020 Jun 6.

Department of Biochemistry-Biotechnology, School of Health Sciences, University of Thessaly, Viopolis, 41500 Larissa, Greece.

Fasting is increasingly practiced to improve health and general well-being, as well as for its cytoprotective effects. Changes in blood redox status, linked to the development of a variety of metabolic diseases, have been recently documented during calorie restriction and intermittent fasting, but not with long-term fasting (LF). We investigated some parameters of the blood redox profile in 109 subjects before and after a 10-day fasting period. Fasting resulted in a significant reduction in body weight, improved well-being and had a beneficial modulating effect on blood lipids and glucose regulation. We observed that fasting decreased lipid peroxidation (TBARS) and increased total antioxidant capacity (TAC) in plasma, concomitant with a uric acid elevation, known to be associated with fasting and did not cause gout attacks. Reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx) and catalase in erythrocytes did not show significant changes. In addition, reduction in body weight, waist circumference, and glucose levels were associated to a reduced lipid peroxidation. Similar results were obtained by grouping subjects on the basis of the changes in their GSH levels, showing that a period of 10 days fasting improves blood redox status regardless of GSH status in the blood.
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http://dx.doi.org/10.3390/antiox9060496DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7346198PMC
June 2020

Obesity ‑ a risk factor for increased COVID‑19 prevalence, severity and lethality (Review).

Mol Med Rep 2020 Jul 5;22(1):9-19. Epub 2020 May 5.

Laboratory of Toxicology, Medical School, University of Crete, 71409 Heraklion, Greece.

Coronaviruses (CoVs), enveloped positive-sense RNA viruses, are a group of viruses that cause infections in the human respiratory tract, which can be characterized clinically from mild to fatal. The severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is the virus responsible. The global spread of COVID‑19 can be described as the worst pandemic in humanity in the last century. To date, COVID‑19 has infected more than 3,000,000 people worldwide and killed more than 200,000 people. All age groups can be infected from the virus, but more serious symptoms that can possibly result in death are observed in older people and those with underlying medical conditions such as cardiovascular and pulmonary disease. Novel data report more severe symptoms and even a negative prognosis for the obese patients. A growing body of evidence connects obesity with COVID‑19 and a number of mechanisms from immune system activity attenuation to chronic inflammation are implicated. Lipid peroxidation creates reactive lipid aldehydes which in a patient with metabolic disorder and COVID‑19 will affect its prognosis. Finally, pregnancy‑associated obesity needs to be studied further in connection to COVID‑19 as this infection could pose high risk both to pregnant women and the fetus.
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http://dx.doi.org/10.3892/mmr.2020.11127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7248467PMC
July 2020

Olive oil with high polyphenolic content induces both beneficial and harmful alterations on rat redox status depending on the tissue.

Toxicol Rep 2020 13;7:421-432. Epub 2020 Feb 13.

Department of Biochemistry and Biotechnology, University of Thessaly, Viopolis, Mezourlo, 41500 Larissa, Greece.

Olive oil (OO) possesses a predominant role in the diet of Mediterranean countries. According to a health claim approved by the European Food Safety Authority, OO protects against oxidative stress‑induced lipid peroxidation in human blood, when it contains at least 5 mg of hydroxytyrosol and its derivatives per 20 g. However, studies regarding the effects of a total OO biophenols on redox status are scarce and either observational and do not provide a holistic picture of their action in tissues. Following a series of screening tests an OO containing biophenols at 800 mg/kg of OO was administered for 14 days to male Wistar rats at a dose corresponding to 20 g OO/per day to humans. Our results showed that OO reinforced the antioxidant profile of blood, brain, muscle and small intestine, it induced oxidative stress in spleen, pancreas, liver and heart, whereas no distinct effects were observed in lung, colon and kidney. The seemingly negative effects of OO follow the recently formulated idea in toxicology, namely the real life exposure scenario. This study reports that OO, although considered a nutritional source rich in antioxidants, it exerts a tissues specific action when administered .
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http://dx.doi.org/10.1016/j.toxrep.2020.02.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052070PMC
February 2020

Οlive tree blossom polyphenolic extracts exert antioxidant and antimutagenic activities in vitro and in various cell lines.

Oncol Rep 2019 Dec 23;42(6):2814-2825. Epub 2019 Oct 23.

Department of Biochemistry and Biotechnology, University of Thessaly, 41500 Larissa, Greece.

Olive oil has held a prominent place in the Mediterranean diet since ancient times due to its beneficial effects on human health thus, becoming the subject of great scientific interest. Although numerous studies have examined the biological action of olive and olive oil extracts, the literature lacks studies investigating the putative antioxidant capacity of olive tree flower extracts. Given that olive tree flowers are actually by-products of the olive oil production process with high waste burden for the environment, it becomes evident that their exploitation could increase their added value. Therefore, in this study the potential antioxidant action of four olive flower extracts was investigated. All the extracts exerted potent antioxidant activity as indicated using the DPPH• and ABTS•+ assays, as well as antigenotoxic and antimutagenic properties, identified by the results of the plasmid relaxation assay and the Ames test, respectively. Furthermore, the extracts also improved redox status of four cell lines (i.e., EA.hy926, C2C12, HeLa, and HepG2) enhancing reduced glutathione and reducing reactive oxygen species levels using flow cytometry. Taking into account that during olive tree cultivation a considerable amount of olive flowers is generated, the waste burden is high and the management is difficult. Given the optimistic findings of the present study, we believe that the flower-derived extracts may have high added value since they could be used as antioxidants or as foodstuff, food additives and functional food constituents.
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http://dx.doi.org/10.3892/or.2019.7386DOI Listing
December 2019