The research interests of our group are:
- Effect of exercise on the fatty acid composition of tissues. It is known that exercise, both acute and chronic, can modify the lipid concentration in animal tissues. Less known is the fact that, in addition, exercise can alter the fatty acid composition of the various lipid classes in these tissues. Our laboratory measures the individual fatty acids by a combination of thin-layer chromatography and gas chromatography. Our data show that prolonged moderate-intensity exercise increases the ratio of unsaturated to saturated non-esterified fatty acid (NEFA) in the serum of athletes and non-athletes. This may contribute to the cardioprotective role of exercise given the fact that unsaturated fatty acids decrease the risk for atherosclerosis. Additionally, we find that chronic exercise causes a large number of significant changes in the fatty acid composition of triacylglycerols (triglycerides) in rat tissues. The most consistent of these changes is a reduction in the percentage of monounsaturated fatty acids.
Relevant publications: 8 10 15 24 28 31 37 38 54 63
- Effect of supplementation with conjugated linoleic acid on human body composition and lipid metabolism. Conjugated linoleic acid (CLA) has been recognized as a natural component of human diet sice the end of the 1980s. It is an unusual fatty acid comprising less than 1 % of the fat of milk, dairy products and ruminant meat. Studies on experimental animals during the past years have attributed a wealth of beneficial characteristics to CLA, including cancer prevention, reduction of blood lipids, reduction of body fat, increase of lean body mass and antidiabetic activity. These characteristics attracted the attention of our team because of the similarity of CLA with exercise as far as the reduction of body fat and blood lipids is concerned. In the first of 2 studies that we have published, we found a reduction in body fat and serum HDL-cholesterol (the so-called good cholesterol), as well as a trend toward a reduction in serum total cholesterol and triacylglycerols by CLA supplementation. On the contrary, in our second study, we did not find any significant changes in these parameters with CLA supplementation. In both studies, we also measured (for the first time) the incorporation of CLA into individual lipid classes of human serum (NEFA, triacylglycerols, phospholipids, and cholesterol esters) before and after CLA supplementation.
Relevant publications: 13 18
- Acceleration of lipolysis in adipose tissue by exercise. During exercise the efflux of lipolytic products (glycerol and NEFA) from adipose tissue increases, which is attributed to activation of the cognate enzyme, triacylglycerol lipase. However, the activity of the enzyme during exercise had not been measured directly until our group devised a method to monitor changes in the activity of the enzyme in fat biopsy samples taken while a person is exercising. Our findings show that both aerobic and resistance exercise multiply the lipolytic rate in adipose tissue within as little as 5 minutes and that lipolytic rate decreases afterward although exercise is continued. In obese men, however, we found a delay in the acceleration of lipolysis (peak at 10 minutes) which may be due to an unusual exercise-induced increase in insulin, an antilipolytic hormone.
Relevant publications: 14 52
- Effects of chronic exercise on body composition and the lipidaemic profile. Studies have repeatedly shown a strong correlation of the serum concentrations of total cholesterol, HDL-cholesterol and triacylglycerols with the risk for atherosclerosis. Athletes and physically active individuals usually have a more favorable lipidemic profile compared to sedentary individuals. However, it is known that the lipidemic profile is also affected by body composition and nutrition. Thus, our team is investigating whether the different lipidemic profile of athletes is due to exercise training or to differences in body composition or nutrition. Our results show that body composition is the strongest of these factors.
Relevant publications: 33 36
- Effects of acute exercise on postprandial lipemia. After a fatty meal, there is an increase in the blood triacylglycerol concentration for several hours, until the components of the food are absorbed. This postprandial lipemia correlates with the development of atherogenesis and cardiovascular disease in general. Many studies have shown that exercise prior to a meal reduces postprandial lipemia. However, most relevant studies have used meals of exaggerated fat content. Our research group investigated the effect of endurance exercise immediately or several hours before a meal of moderate fat content on postprandial lipemia. Our data show that, in this case too, there is a beneficial effect of exercise as long as it has been performed the day before and not shortly before the meal. Another recent study of ours shows that also resistance exercise (in fact, of a lower energy expenditure than that of endurance training) decreases postprandial lipemia after a high-fat meal.
Relevant publications: 21 25 34 41
- Effect of training on biochemical and hematological parameters related to health and sport performance. A wealth of studies on adults and adolescents have shown that athletes have certain biochemical and hematological values that diverge from those of the general population. Our team attempts to provide a global view of the issue by comparing the values of basic biochemical and hematological parameters in adult and adolescent Greek athletes and non-athletes of both sexes in order to draw conclusions about the adaptations of human metabolism to exercise. Recently we proposed reference intervals (normal values) for creatine kinase in athletes, a parameter used frequently as an index of muscle damage by exercise.
Relevant publications: 4 5 6 11 17 19 23 27 29 30 32 35 40 42 45 50 53 55
- Effect of increased iron intake on performance and iron status of adolescent athletes. Despite the rich literature on hematological and biochemical parameters of iron status, studies referring to adolescent athletes, in particular with reference to the particular training period, are limited. Moreover, there is a lack of data on the effect of iron supplements or nutrition rich in iron on the performance of adolescent athletes. Studies from our team are monitoring iron status and sport performance of adolescent swimmers during different training periods under a broad spectrum of iron intake. Our findings show that athletes with adequate iron intake through the food do not benefit from supplements.
Relevant publications: 22 44
- Effect of exercise on gene expression. Exercise has spectacular effects on the expression of a multitude of genes in the exercising muscles and other tissues. Our group examines the effect of chronic exercise on the expression of genes related to lipid metabolism in rat tissues. Our recent research showed that, among the tissues examined (muscle, liver and adipose tissue), the one affected most was adipose tissue, in which chronic exercise increased the activity of a transcription factor ( PPARγ) that controls the expression of genes involved in lipid metabolism and is related to insulin-sensitivity.
Relevant publications: 16 26 43 46
- Effect of exercise on the redox status of the body. Redox status refers to the balance between axodative and reductive processes in an organism. What interests, in particular, is the balance between mechanisms that cause oxidative damage to biological molecules (such as proteins, DNA, and lipids) and antioxidant (reductive) mechanisms that protect against such damage. Exercise affects the redox balance and is therefore studied intensely as a model of modifying the redox balance. Our research group studies the effect of both acute and chronic exercise on the redox status of athletes and nonathletes.
Relevant publications: 53 71
- Effect of particular dietary manipulations on sport performance. Our research group has collaborated with other researchers in studying the possible effects of the frequency of pre-exercise meals and of a high-protein diet on body function and exercise performance.
Relevant publications: 47 51
- Effect of acute and chronic exercise on energy metabolism in human muscle. Our research group is collaborating with other researchers in studying the effect of particular training loads on energy metabolism by measuring metabolites and enzymes in muscle biopsy samples from exercising persons.
Relevant publications: 60
- Application of holistic technologies on the analysis of biological samples after exercise. Our research group is collaborating with other researchers in the analysis of biological samples from exercising persons and laboratory animals through techniques, such as magnetic resonance spectroscopy, liquid chromatography - mass spectrometry and gas chromatography - mass spectrometry, used in metabolomics, or metabonomics, and proteomics. These research areas aim at addressing the sum of the corresponding biological substances (metabolites and proteins) rather than a few specific substances (in other words, the forest rather than the tree).
Relevant publications: 57 68 72 77
- Acute effects of exercise on other biochemical parameters. Apart from the biochemical parametres mentioned above, our research team examines a variety of other parameters in the context of evaluating the health and performance of athletes and exercisers, in general. Such parameters include lactate, creatine kinase, hormones and iron status parameters.
Relevant publications: 4 5 6 11 17 23 27 30 32 35 40 50 55 57 64
- Correlation among demographic and somatometric characteristics, nutrition, physical activity, and biochemical parameters. Our research group participates in epidemiologic studies aiming at exploring the relationships among the aforementioned parameters in large samples of the Greek population, especially children and adolescents.
Relevant publications: 61 66 67 69 70 a b c
- Gene expression of irisin and effects of irisin on the physiology and biochemistry of human tissues. Our research group cooperates with that of Christos Mantzoros at Harvard Medical School in examining how exercise, body composition, and disease affect the mRNA and protein levels of irisin, a recently discovered hormone that is produced by muscle and seems to play an important role in the physiology and biochemistry of adipose tissue.
Relevant publications: 65 73 74 75 76