Zeman Michal

Comenius University Bratislava · Department of Animal Physiology and Ethology

Purpose: The incidence of acute myocardial infarctions (AMI) shows circadian variation typically peaking during morning hours with a decline at night. However, this variation does not occur in patients with diabetes mellitus (DM). The night's decline of AMI may be partially explained by melatonin-related platelet inhibition. Whether this effect is...

Aldosterone regulates blood pressure (BP) through water and sodium balance. In our study, we studied if continuous treatment with a mineralocorticoid receptor antagonist, spironolactone (30 mg/kg/day) for 20 days can: 1) attenuate hypertension development and restore inverted 24-h BP rhythm in hypertensive transgenic (mRen-2)27 rats (TGR) measured...

The circadian rhythms evolved to anticipate and cope with cyclic changes in environmental conditions. This adaptive function is currently compromised by increasing levels of artificial light at night (ALAN), which can represent a risk for the development of diseases of civilisation. The causal links are not completely understood, and this featured...

Artificial light at night (ALAN) is considered an environmental risk factor that can interfere with the circadian control of the endocrine system and metabolism. We studied the impact of ALAN during pregnancy on the hormonal and biochemical parameters in rat pups at postnatal (P) days P3, P10, and P20. Control dams (CTRL) were kept in a standard li...

Activated endothelial, immune, and cancer cells prefer glycolysis to obtain energy for their proliferation and migration. Therefore, the blocking of glycolysis can be a promising strategy against cancer and autoimmune disease progression. Inactivation of the glycolytic enzyme PFKFB3 (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase) suppresses g...

Circadian rhythms control almost all aspects of physiology and behavior, allowing temporal synchrony of these processes between each other, as well as with the external environment. In the immune system, daily rhythms of leukocyte functions can determine the strength of the immune response, thereby regulating the efficiency of defense mechanisms to...

Nocturnal light pollution has been rapidly increasing during the last decades and even though dim artificial light at night (ALAN) has been associated with metabolic diseases, its mechanism is still far from clear. Therefore, the aim of our study was to thoroughly analyze the effects of ALAN on energy metabolism, metabolites, metabolic hormones, an...

Aims: Our study addresses underlying mechanisms of disruption of the circadian timing system by low-intensity artificial light at night (ALAN), which is a growing global problem, associated with serious health consequences. Methods: Rats were exposed to low-intensity (~2 lx) ALAN for 2 weeks. Using in situ hybridization, we assessed 24-h profile...

Prenatal hypoxia during the prenatal period can interfere with the developmental trajectory and lead to developing hypertension in adulthood. Prenatal hypoxia is often associated with intrauterine growth restriction that interferes with metabolism and can lead to multilevel changes. Therefore, we analysed the effects of prenatal hypoxia predominant...

1. The light regime during incubation can influence embryonic and post-embryonic life and its effects can be mediated by rhythmic melatonin production in the embryonic pineal gland. 2. This study explored whether the incubation of chick embryos under red or blue monochromatic light, which induces maximum and minimum melatonin production, respective...

Glycolysis is considered a main metabolic pathway in highly proliferative cells, including endothelial, epithelial, immune, and cancer cells. Although oxidative phosphorylation (OXPHOS) is more efficient in ATP production per mole of glucose, proliferative cells rely predominantly on aerobic glycolysis, which generates ATP faster compared to OXPHOS...

Angiotensin-converting enzyme 2 (ACE2) was identified as a molecule that mediates the cellular entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Several membrane molecules of the host cell must cooperate in this process. While ACE2 serves in a membrane receptor-mediating interaction with the surface spike (S) glycoprotein of SA...

Melatonin is released by the pineal gland and can modulate cardiovascular system function via the G protein-coupled melatonin receptors MT1 and MT2. Most vessels are surrounded by perivascular adipose tissue (PVAT), which affects their contractility. The aim of our study was to evaluate mRNA and protein expression of MT1 and MT2 in the mesenteric a...

Light during incubation can influence embryonic and postembryonic development of chickens, but the underlying mechanisms are poorly understood. Previous studies have demonstrated that red and blue lights during incubation had opposite effects on the development of embryonic melatonin biosynthesis; red light results in the highest and blue light in...

We recently reported that artificial light at night (ALAN), at ecologically relevant intensities (1.5, 5 lux), increases cell proliferation in the ventricular zone and recruitment of new neurons in several forebrain regions of female zebra finches (Taeniopygia guttata), along with a decrease of total neuronal densities in some of these regions (ind...

A high rate of glycolysis is considered a hallmark of tumor progression and is caused by overexpression of the enzyme 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3). Therefore, we analyzed the possibility of inhibiting tumor and endothelial cell metabolism through the inhibition of PFKFB3 by a small molecule, (E)-1-(pyridin-4-yl)-3-...

Dim light at night (dLAN) has become a pervasive part of the modern world, and growing evidence shows its association with increased health risks. Though this link is attributed to a disturbed circadian clock, the underlying mechanisms that can explain how circadian disruption from dLAN causes negative health effects remain unclear. Here, we expose...

Lighting conditions during incubation can influence embryonic development, post-hatching ontogeny and production efficiency. Previous studies revealed that different light colours differently affect pineal melatonin biosynthesis in embryos and postembryonic development of broiler chickens, but physiological mechanisms mediating these effects are no...

Prenatal hypoxia (PH) has negative consequences on the cardiovascular system in adulthood and can affect the responses to additional insults later in life. We explored the effects of PH imposed during embryonic day 20 (10.5% O 2 for 12 h) on circadian rhythms of systolic blood pressure (BP) and heart rate (HR) in mature male rat offspring measured...

Artificial light at night can have negative effects on human wellbeing and health. It can disrupt circadian rhythms, interfere with sleep, and participate in the progress of civilisation diseases. The aim of the present study was to explore if dim artificial light during the entire night (ALAN) can affect melatonin production and sleep quality in y...

Dim light at night (dLAN) is associated with metabolic risk but the specific effects on lipid metabolism have only been evaluated to a limited extent. Therefore, to explore whether dLAN can compromise lipid metabolic homeostasis in healthy individuals, we exposed Wistar rats to dLAN (~2 lx) for 2 and 5 weeks and analyzed the main lipogenic pathways...

Despite growing evidence that demonstrate adverse effects of artificial light at night (ALAN) on many species, relatively little is known regarding its effects on brain plasticity in birds. We recently showed that although ALAN increases cell proliferation in brains of birds, neuronal densities in two brain regions decreased, indicating neuronal de...

The disruption of circadian rhythms by environmental conditions can induce alterations in body homeostasis, from behavior to metabolism. The light:dark cycle is the most reliable environmental agent, which entrains circadian rhythms, although its credibility has decreased because of the extensive use of artificial light at night. Light pollution ca...

The incidence of colorectal cancer (CRC) shows a sex-dependent difference in humans. The aim of this study was to analyze estrogen receptor beta mRNA (ERbeta) expression in patients with CRC with respect to their gender and clinicopathological features. Since cancer progression is accompanied by tumor vascularization, VEGF-A (vascular endothelial g...

Artificial light at night (ALAN) is increasing exponentially worldwide, accelerated by the transition to new efficient lighting technologies. However, ALAN and resulting light pollution can cause unintended physiological consequences. In vertebrates, production of melatonin-the "hormone of darkness" and a key player in circadian regulation-can be s...

Maternal reproductive effort can be adjusted through the transfer of hormones into the eggs, where they influence embryo development, mediating short- and long-term maternal effects on offspring phenotype. While studies usually explore how females can increase their reproductive success through an allocation of yolk testosterone (T) under external...

Artificial light at night (ALAN), which disrupts the daily cycle of light, has vast biological impacts on all organisms, and is also associated with several health problems. The few existing studies on neuronal plasticity and cognitive functions in mammals indicate that a disruption of the circadian cycle impairs learning and memory and suppresses...

Colorectal cancer represents a leading cause of cancer death. MicroRNAs (miRNAs) are small non-coding RNA molecules that have been extensively studied in tumours, since changes in their levels can reveal patient prognosis. Cancer progression is also influenced by the circadian system whose functioning is based on the rhythmic expression of clock ge...

INTRODUCTION Artificial light at night (ALAN) has vast biological impacts on animals and humans, and findings suggest that it is associated with several physical and mental health problems. Studies on neuronal plasticity and cognitive functions in mammals indicate that the disruption of the circadian cycle induces learning and memory deficits and s...

1. Selection strategies for broilers must balance rapid growth with the welfare and health of animals, strategies must deal with the trade-off with other vital functions. 2. Divergent selection of Japanese quail for high (HG) and low (LG) relative body weight gain between 11 and 28 days of age has been conducted to accelerate linear phase growth wi...

Providing a broiler chicken embryo with a lighting schedule during incubation may stimulate leg bone development. Bone development may be stimulated through melatonin, a hormone released in darkness that stimulates bone development, or increased activity in embryos exposed to a light-dark rhythm. Aim was to investigate lighting conditions during in...

Circadian rhythms are an inherent property of physiological processes and can be disturbed by irregular environmental cycles, including artificial light at night (ALAN). Circadian disruption may contribute to many pathologies, such as hypertension, obesity, and type 2 diabetes, but the underlying mechanisms are not understood. Our study investigate...

Aims: Cardiovascular parameters exhibit significant 24-h variability, which is coordinated by the suprachiasmatic nucleus (SCN), and light/dark cycles control SCN activity. We aimed to study the effects of light at night (ALAN; 1-2 lx) on cardiovascular system control in normotensive rats. Main methods: Heart rate (HR) and blood pressure (BP) we...

Impact statement: Suboptimal prenatal conditions can contribute to development of cardiovascular diseases and an altered renin-angiotensin-aldosterone system (RAAS) can be involved in the process. In our study, increased angiotensin II in pregnant female rats resulted in renal cortical interstitial damage, and renal ultrastructural changes in the...

We aimed to explore whether specific high-sucrose intake in older female rats affects myocardial electrical coupling protein, connexin-43 (Cx43), protein kinase C (PKC) signaling, miR-1 and miR-30a expression, and susceptibility of the heart to malignant arrhythmias. Possible benefit of the supplementation with melatonin (40 µg/ml/day) and omega-3...

Several functions have been proposed to explain eggshell colouration in birds. Eggshell colour may, for instance, signal female egg investment and hence the quality of the female and/or the egg. Such a covariation between eggshell colour and egg quality is supported by several studies, but what is related to eggshell colour is not necessarily consi...

Activated endothelial cells play a crucial role in the formation of new blood vessels, a process known as angiogenesis, which can underlie the development of several diseases. Different antiangiogenic therapies aimed against vascular endothelial growth factor (VEGF), the dominant pro-angiogenic cytokine, have been developed. Because the treatment i...

Rhythmic pineal melatonin biosynthesis develops in chick embryos incubated under a light (L)-dark (D) cycle of polychromatic white light. The spectral sensitivity of the embryonic pineal gland is not known and was investigated in this study. Broiler breeder eggs (Ross 308, n =450) were incubated under white, red, green or blue light under the 12L :...

Suboptimal conditions during prenatal and early postnatal development can increase risk of hypertension later in life. We studied consequences of a changed perinatal environment by initiating the cross-fostering of homozygous Ren-2 transgenic rat (TGR) offspring to normotensive, transgene-negative control mothers, and vice versa. We hypothesized th...

BACKGROUND: This study compares the acute hormonal and neuromuscular responses to different resistance protocols in young and middle-aged postmenopausal women. METHODS: Eight premenopausal (age: 22.6±2.5) and nine postmenopausal (age: 55.2±5.7) non-trained women volunteered in a repeated crossover study. They performed two different acute loading s...

The purpose of the study was to investigate the effect of oral contraceptives on static postural stability in young healthy women during their menstrual cycle. Twenty-three women with the regular menstrual cycle, using or not using oral contraceptives, participated in this study. Salivary progesterone and estradiol levels were measured during one m...

While a treatment of tumours by anti-angiogenic kinase inhibitors has limited efficacy and is associated with resistance and side effects, also other key biological pathways should be targeted to fight cancer more effectively. Active endothelial and cancer cells acquire energy predominantly via a glycolysis (Warburg effect) in contrast to most of o...

Recent evidence supports the important role of the circadian system in cancer progression in humans. The aim of the present study is to evaluate clock (cry1, cry2 and per2) and clock-controlled (vascular endothelial growth factor-a, early growth response protein 1 and estrogen receptor β) gene expression in colorectal cancer and adjacent tissue and...

Colorectal cancer (CRC) exhibits differences in its features depending on the location of the tumor. The role of the circadian system in the carcinogenesis is accepted and many studies report different clock gene expression in tumors compared to healthy tissue, although a little attention is given to the changes in clock genes in tumors arising fro...

Mothers can influence prenatal conditions by varying the amount of nutrients, hormones or antioxidants they provide to their developing young. Some of these substances even affect the transfer of these compounds in the next generation, but it is less clear how different maternally transmitted compounds interact with each other to shape reproductive...

In rodents, increased angiotensin 2 (Ang2) during pregnancy increases blood pressure and decreases salt sensitivity in the offspring. To explore the underlying mechanisms, this study evaluated the effects of prenatal Ang2 exposure on the activity of renal Na,K-ATPase, which is one of the main systems that maintains sodium ion homeostasis in an orga...

miRNAs are small regulatory RNA molecules involved in posttranscriptional gene silencing. Their biosynthesis results in the formation of duplex consisting of a leading and a passenger strand of mature miRNA. The leading strand exhibits the main activity but recent findings indicate a certain role of the passenger strand as well. Deregulated levels...

It has been clearly established that maximal force and power is lower in the morning compared to noon or afternoon hours. This morning neuromuscular deficit can be diminished by regularly training in the morning hours. However, there is limited and contradictory information upon hypertrophic adaptations to time-of-day-specific resistance training....

Cardiovascular diseases (CVDs) are the leading cause of mortality and hypertension contributes substantially to the incidence of stroke, coronary artery disease, heart failure, atrial fibrillation and peripheral vascular disease. The origin of hypertension is clearly multifactorial, and a complex and multifaceted approach is necessary to decrease i...

Background/aims: Melatonin is a hormone transferring information about duration of darkness to the organism and is known to modulate several signaling pathways in the cells, e.g. generation of endoplasmic reticulum stress, oxidative status of the cells, etc. Melatonin has been shown to exert antiproliferative and cytotoxic effects on various human...

Renin angiotensin aldosterone system (RAAS) plays an essential role in the homeostatic control of arterial blood pressure, perfusion of tissues, and control of extracellular fluid. Its components are highly expressed in the developing kidney, general vasculature, brain, and heart. A modified intrauterine environment alters mechanisms controlling bl...

Physiological variables such as heart rate (HR) and blood pressure (BP) exhibit long-term circadian rhythms, which can be disturbed by shift work. On the other hand, short-term oscillations in HR and BP have a high prognostic value. Therefore, we aimed to determine if the short-term variability, complexity and entropy of HR and BP would be affected...

Differential transfer of maternal testosterone (T) into egg yolk provides a means of adjusting an offspring’s phenotype to ambient environmental conditions. While the environmental and genetic driven variability in yolk T levels is widely described, the underlying mechanisms are poorly understood. Here, we investigated whether neuroendocrine mechan...

Objective. Melatonin is a hormone predominantly synthesized and secreted during the night by the pineal gland. Artificial light at night, especially its blue part, acutely suppresses the melatonin production. Th e aim of the present study was to find out, whether an intense blue light phototherapy of severe hyperbilirubinemia, may suppress the mela...

Sex-linkage is predicted to evolve in response to sex-specific or sexually antagonistic selection. In line with this prediction, most sex-linked genes are associated with reproduction in the respective sex. In addition to traits directly involved in fertility and fecundity, mediators of maternal effects may be predisposed to evolve sex-linkage, bec...

Disturbances in regular circadian oscillations can have negative effects on cardiovascular function, but epidemiological data are inconclusive and new data from animal experiments elucidating critical biological mechanisms are needed. To evaluate the consequences of chronic phase shifts of the light/dark (LD) cycle on hormonal and cardiovascular rh...

Inhibition of angiogenesis involves blocking of tyrosine kinases (TK) implicated in signalling of vascular endothelial growth factor receptors (VEFGR). The inhibition of TK results in a disruption of Ras/Raf/MEK/ERK1/2 and PI3K/Akt signalling pathways. We evaluated recently developed TK inhibitor 22SYM and compared its anti-angiogenic effects with...

Yolk androgens of maternal origin are important mediators of prenatal maternal effects. Although in many species short-term benefits of exposure to high yolk androgen concentrations for the offspring have been observed, females differ substantially in the amount of androgens they transfer to their eggs. It suggests that costs for the offspring or t...

Sex steroid levels increase during sexual maturation and cause alterations in many physiological and morphological traits. Some of these changes may be connected with age-dependent and intersexual differences in the immune system. This topic is still insufficiently understood, especially in avian species, partially due to methodological limitations...

Decreased oxygenation during pregnancy and early periods of ontogeny can affect normal body development and result in diseases in adulthood. The aim of this study was to use the model of prenatal intermittent hypoxia (PIH) and evaluate the effects of short-term hypoxia at the end of gestation on blood pressure (BP) control in adulthood. Wistar rats...

Sex-linkage is predicted to evolve in response to sex-specific or sexually antagonistic selection. In line with this prediction, most sex-linked genes are associated with reproduction in the respective sex. In addition to traits directly involved in fertility and fecundity, mediators of maternal effects may be predisposed to evolve sex-linkage, bec...

Sex-linkage is predicted to evolve in response to sex-specific or sexually antagonistic selection. In line with this prediction, most sex-linked genes are associated with reproduction in the respective sex. In addition to traits directly involved in fertility and fecundity, mediators of maternal effects may be predisposed to evolve sex-linkage, bec...

Effects of phase delay shifts (PDS) of light in combination with moderately increased salt intake (SL) (2%) or time restriction of food (FR) during the light-time (passive phase) on heart rate (HR), blood pressure (BP) and locomotor activity (LA) in radiotelemetry-measured rats were evaluated. PDS decreased amplitude and spectral power of circadian...

Under physiological conditions the mammalian circadian system is synchronized to a cyclic environment. The central oscillator in the suprachiasmatic nuclei (SCN) responds predominantly to an external light (L) dark (D) cycle. Peripheral oscillators are more efficiently synchronized by metabolic cues. When the circadian system is exposed to opposing...