We aimed to study the impact of altered thyroid status on myocardial expression of electrical coupling protein connexin-43 (Cx43), the susceptibility of rats to ventricular fibrillation (VF) and the effects of antioxidant-rich red palm oil (RPO). Adult male and female euthyroid, hyperthyroid (treated with T3/T4), hypothyroid (treated with methimazole) Wistar rats supplemented or not with RPO for 6 weeks were used. Function of isolated perfused heart and VF threshold were determined. Left ventricular tissue was used for assessment of mRNA and protein levels of Cx43, its phosphorylated forms and topology. Protein kinase C signaling (PKC) and gene transcripts of some proteins related to cardiac arrhythmias were assessed. Hyperthyroid state resulted in decrease of total and phosphorylated forms of Cx43 and suppression of PKC-ε expression in males and females, decrease of Cx43 mRNA in females, decrease of VF threshold and increase of functional parameters in male rat hearts. In contrast, hypothyroid status resulted in the increase of total and phosphorylated forms of Cx43, enhancement PKC-ε expression in males and females, increase of Cx43 mRNA in females, increase of VF threshold and decrease of functional parameters in male rat hearts. Function of the heart was partially normalized by RPO intake, which also enhanced myocardial Cx43 and PKC-ε expression as well as increased VF threshold in hyperthyroid male rats. We conclude that there is an inverse relationship between myocardial expression of Cx43, including its functional phosphorylated forms, and susceptibility of male rat hearts to VF in condition of altered thyroid status. RPO intake partly ameliorated adverse changes caused by excess of thyroid hormones.

Adaptation to chronic hypoxia represents a potential cardioprotective intervention reducing the extent of acute ischemia/reperfusion (I/R) injury, which is a major cause of death worldwide. The main objective of this study was to investigate the anti-apoptotic Akt/hexokinase 2 (HK2) pathway in hypoxic hearts subjected to I/R insult. Hearts isolated from male Wistar rats exposed either to continuous normobaric hypoxia (CNH; 10% O2) or to room air for 3 weeks were perfused according to Langendorff and subjected to 10 min of no-flow ischemia and 10 min of reperfusion. The hearts were collected either after ischemia or after reperfusion and used for protein analyses and quantitative fluorescence microscopy. The CNH resulted in increased levels of HK1 and HK2 proteins and the total HK activity after ischemia compared to corresponding normoxic group. Similarly, CNH hearts exhibited increased ischemic level of Akt protein phosphorylated on Ser473. The CNH also strengthened the interaction of HK2 with mitochondria and prevented downregulation of mitochondrial creatine kinase after reperfusion. The Bax/Bcl-2 ratio was significantly lower after I/R in CNH hearts than in normoxic ones, suggesting a lower probability of apoptosis. In conclusion, the Akt/HK2 pathway is likely to play a role in the development of a cardioprotective phenotype of CNH by preventing the detachment of HK2 from mitochondria at reperfusion period and decreases the Bax/Bcl-2 ratio during I/R insult, thereby lowering the probability of apoptosis activation in the mitochondrial compartment.

Sir, We read with interest the study of Andraweera et al., published recently in Acta Obstetricia et Gynecologica Scandinavica (1), reporting a strong association between maternal FTO (rs9939609) genotype and the risk of miscarriage and recurrent pregnancy loss. Inspired by the report, we attempted to test a related hypothesis that the FTO polymorphism is associated with spontaneous abortions when tissue sample from aborted fetus is used instead of maternal DNA. Such an association would indirectly confirm the findings by Andraweera et al. (1). We compared 457 tissue samples of spontaneous abortions during the first trimester (cases) with a general population sample of 6681 middle-aged adults (aged 45–69 years) used as controls (2). All cases and controls were genotyped for the FTO rs17817449 polymorphism; this single nucleotide polymorphism is in almost complete linkage disequilibrium with neighboring rs9939609. No association between number of children and FTO genotype was detected among controls. The distribution of the FTO genotypes did not differ between the cases and controls. The frequencies for GG vs. GT vs. TT alleles were 19.9% vs. 46.8% vs. 33.3% in cases and 19.3% vs. 47.7% vs. 32.9% among controls (P = 0.92). The odds ratio for GG vs. GT/TT carriers was 1.04 (95% CI 0.82–1.32; P = 0.75). The FTO gene was first identified by a genome-wide association study as an independent genetic risk factor for obesity (3); more recently, the polymorphism has also been implicated in other conditions, such as diabetes mellitus, myocardial infarction, renal failure or cancer. However, the exact biological role of the FTO gene remains unclear (4). The gene is involved in demethylation of nucleic acids. As the correct fetal development is based on the DNA-methylation-based programming, in theory the FTO gene is a promising candidate gene for predisposition to spontaneous abortion. The potential role of FTO in fetal development is further supported by the finding that in humans, FTO is highly expressed in placenta and its expression appears to correlate with increased fetal weight and length (5). The fact that our study did not find any difference in FTO genotype between spontaneous abortions and healthy adults may be due to at least two reasons. First, the geographical localization and ethnic composition of our study sample differs from that in the study by Andraweera et al. (1). Second, there was a major difference in the selection of cases between the studies. Our study has focused on analysis of aborted fetal tissues, not on females with experience of pregnancy loss. It is possible that the methylation status and subsequent fetal development depends on the genetic characteristics/FTO variant of females with a history of recurrent pregnancy loss, rather than on characteristics of the fetus. On the other hand, one would expect that even if the main risk factor is maternal genotype it would be detected in studies using fetal DNA (as it reflects the genotype inherited from the mother). Further studies are needed to confirm or refute the putative association between the FTO and recurrent miscarriage.

Dexras1 has been shown to exhibit clock-dependent rhythm in mice suprachiasmatic nucleus (SCN), and its genetic deletion modulates circadian responses to photic and nonphotic cues. We show that the rhythmic expression of Dexras1 mRNA and protein in rat SCN already oscillates with low amplitude at postnatal day 3 and can be detected as early as embryonic day 20. In contrast, its expression in peripheral tissues is not rhythmic in adult rats either. The Dexras1 protein is expressed predominantly in the dorsomedial part of the SCN and the light pulse has only a limited effect on its expression. Our data provide the descriptive basis for speculation about the Dexras1 involvement in the rat circadian physiology.

Chronic hypoxia may produce a cardioprotective phenotype characterized by increased resistance to ischemia-reperfusion injury. Nevertheless, the molecular basis of cardioprotective effects of hypoxia is still not quite clear. The present study investigated the consequences of a 3-week adaptation to cardioprotective (CNH, continuous normobaric hypoxia) and nonprotective (INH, intermittent normobaric hypoxia; 23 h/day hypoxia followed by 1 h/day reoxygenation) regimen of hypoxia on β-adrenergic signaling in the rat myocardium. Both regimens of hypoxia lowered body weight and led to marked right ventricular (RV) hypertrophy, which was accompanied by 25% loss of β1-adrenergic receptors (β1-ARs) in the RV. No significant changes were found in β-ARs in left ventricular (LV) preparations from animals adapted to hypoxia. Although adenylyl cyclase (AC) activity stimulated through the G proteins was decreased in the RV and increased in the LV after exposure to hypoxia, there were no significant changes in the expression of the dominant myocardial AC 5/6 isoforms and the stimulatory G proteins. These data suggest that chronic normobaric hypoxia may strongly affect myocardial β-adrenergic signaling but adaptation to cardioprotective and nonprotective regimens of hypoxia does not cause notably diverse changes.

Chronic hypoxia increases the myocardial resistance to acute ischemia-reperfusion injury by affecting the mitochondrial redox balance. Hexokinase (HK) bears a high potential to suppress the excessive formation of reactive oxygen species because of its increased association with mitochondria, thereby inhibiting the membrane permeability transition pore opening and preventing cell death. The purpose of this study was to determine the effect of severe intermittent hypobaric hypoxia (7,000 m, 8 h/day, 5 wk) on the function and colocalization of HK isoforms with mitochondria in the left (LV) and right ventricles of rat myocardium. The real-time RT-PCR, Western blot, enzyme coupled assay, and quantitative immunofluorescence techniques were used. Our results showed significantly elevated expression of HK isoforms (HK1 and HK2) in the hypoxic LV. In addition, intermittent hypoxia increased the total HK activity and the association of HK isoforms with mitochondria in both ventricles. These findings suggest that HK may contribute to the cardioprotective phenotype induced by adaptation to severe intermittent hypobaric hypoxia.

It has been documented that adaptation to hypoxia increases myocardial tolerance to ischemia-reperfusion (I/R) injury depending on the regimen of adaptation. Reactive oxygen species (ROS) formed during hypoxia play an important role in the induction of protective cardiac phenotype. On the other hand, the excess of ROS can contribute to tissue damage caused by I/R. Here we investigated the relationship between myocardial tolerance to I/R injury and transcription activity of major antioxidant genes, transcription factors, and oxidative stress in three different regimens of chronic hypoxia. Adult male Wistar rats were exposed to continuous normobaric hypoxia (FiO2 0.1) either continuously (CNH) or intermittently for 8 h/day (INH8) or 23 h/day (INH23) for 3 wk period. A control group was kept in room air. Myocardial infarct size was assessed in anesthetized open-chest animals subjected to 20 min coronary artery occlusion and 3 h reperfusion. Levels of mRNA transcripts and the ratio of reduced and oxidized glutathione (GSH/GSSG) were analyzed by real-time RT-PCR and by liquid chromatography, respectively. Whereas CNH as well as INH8 decreased infarct size, 1 h daily reoxygenation (INH23) abolished the cardioprotective effect and decreased GSH/GSSG ratio. The majority of mRNAs of antioxidant genes related to mitochondrial antioxidant defense (manganese superoxide dismutase, glutathione reductase, thioredoxin/thioredoxin reductase, and peroxiredoxin 2) were upregulated in both cardioprotective regimens (CNH, INH8). In contrast, INH23 increased only PRX5, which was not sufficient to induce the cardioprotective phenotype. Our results suggest that the increased mitochondrial antioxidant defense plays an important role in cardioprotection afforded by chronic hypoxia.

Aim: Up to 20% of pregnancies end in the first trimester by spontaneous abortion but the cause of a large proportion remains unexplained. The aim of this study was to investigate the role of two common variants (rs1801133, C677T and rs1801131, A1298C) within the MTHFR gene in the genetic determination of spontaneous abortions.Methods: DNA from 464 tissue samples of spontaneous abortions and population sample of adults (N = 2,486) were genotyped for both MTHFR polymorphisms of interest.Results: The frequencies of the MTHFR polymorphisms in tissues from spontaneous abortions did not differ from the population cohort. However, when combined, carriers of at least three rs1801133 and/or rs1801131 alleles were more common in the spontaneous abortions (61.4%) than in controls (55.4%) and this combination was associated with higher risk of abortion (OR 1.28; 95% CI 1.05-1.57; P = 0.017). In contrast, carriers of at least three minor alleles (T677 and C1298) of these polymorphisms were very rare in both groups (0.8% and 0.9% respectively).Conclusions: Our study suggests that distinct combinations of the MTHFR polymorphisms could be associated with higher risk of spontaneous abortions in Caucasians. (C) 2014 Elsevier B.V. All rights reserved.

Background: Creatine kinase (CK) and hexokinase (HK) play a key role in myocardial energy homeostasis. We aimed to determine CK and HK expression and enzyme activity in the left (LV) and right (RV) ventricles of rats adapted for 3 weeks to normobaric hypoxia (10 % O2) either continuously (CNH) or intermittently with 1-h or 16-h normoxic episode per day. Methods: The Real-Time RT-PCR, Western blot, and enzyme-coupled assays were used. In addition, the effect of CNH on the HK co-localization with mitochondria, which can inhibit apoptosis, was assessed using immunofluorescence techniques. Results: CK and HK activities increased in the LV during all hypoxic adaptations, which was consistent with elevated protein levels of mitochondrial mtCKs, cytosolic CKB, HK1, and HK2 isoforms. Enzyme activities also increased in the hypoxic RV, but only CKB protein was elevated. No effect of CNH on HK1 or HK2 co-localization with mitochondria was observed. Conclusion: Up-regulation of mtCKs and HK isoforms may stimulate the respiratory chain and help to maintain energy homeostasis of chronically hypoxic myocardium and prevent oxidative stress. In this way, CK and HK enzymes can possibly participate in the establishment of ischemia-resistant phenotype of chronically hypoxic hearts.

Dysfunction or abnormalities in the regulation of fatty acid translocase Cd36, a multifunctional membrane protein participating in uptake of long-chain fatty acids, has been linked to the development of heart diseases both in animals and humans. We have previously shown that the Cd36 transgenic spontaneously hypertensive rat (SHR-Cd36), with a wild type Cd36, has higher susceptibility to ischemic ventricular arrhythmias when compared to spontaneously hypertensive rat (SHR) carrying a mutant Cd36 gene, which may have been related to increased β-adrenergic responsiveness of these animals (Neckar et al., 2012 Physiol. Genomics 44:173–182). The present study aimed to determine whether the insertion of the wild type Cd36 into SHR would affect the function of myocardial G protein-regulated adenylyl cyclase (AC) signaling. β-Adrenergic receptors (β-ARs) were characterized by radioligand-binding experiments and the expression of selected G protein subunits, AC, and protein kinase A (PKA) was determined by RT-PCR and Western blot analyses. There was no significant difference in the amount of trimeric G proteins, but the number of β-ARs was higher (by about 35 %) in myocardial preparations from SHR-Cd36 as compared to SHR. Besides that, transgenic rats expressed increased amount (by about 20 %) of the dominant myocardial isoforms AC5/6 and contained higher levels of both nonphosphorylated (by 11 %) and phosphorylated (by 45 %) PKA. Differently stimulated AC activity in SHR-Cd36 significantly exceeded (by about 18–30 %) the enzyme activity in SHR. Changes at the molecular level were reflected by higher contractile responses to stimulation by the adrenergic agonist dobutamine. In summary, it can be concluded that the increased susceptibility to ischemic arrhythmias of SHR-Cd36 is attributable to upregulation of some components of the β-AR signaling pathway, which leads to enhanced sensitization of AC and increased cardiac adrenergic responsiveness.

Background/Aims: Hexokinase (HK) is a key glycolytic enzyme which promotes the maintenance of glucose homeostasis in cardiomyocytes. HK1 isoform is predominantly bound to the outer mitochondrial membrane and highly supports oxidative phosphorylation by increasing the availability of ADP for complex V of the respiratory chain. HK2 isoform is under physiological conditions predominantly localized in the cytosol and upon stimulation of PI3K/ Akt pathway associates with mitochondria and thus can prevent apoptosis. The purpose of this study was to investigate expression and subcellular localization of both HK isoforms in left (LV) and right (RV) heart ventricles of adult male Wistar rats. Methods: Real-Time RT-PCR, Western blotting, and quantitative immunofluorescence microscopy were used. Results: Our results showed a significantly higher expression of both HK1 and HK2 at mRNA and protein levels in the RV compared to the LV. These findings were corroborated by immunofluorescence staining which revealed substantially higher fluorescence signals of both HKs in the RV than in the LV. The ratios of phospho-Ser473-Akt/non-phospho-Akt and phospho-Thr308-Akt/non-phospho-Akt were also markedly higher in the RV than in the LV. Conclusion: These results suggest that the RV has a higher activity of aerobic glycolytic metabolism and may be able to respond faster and more powerfully to stressful stimuli than the LV.

OBJECTIVE: The aim of the study was to evaluate the importance of screening for thrombophilic mutations after the first early pregnancy loss.SETTING: Thrombophilic mutations were examined in a sample of 100 women with at least one miscarriage. DNA was isolated from venous blood sample. We used methods of microarray, fragmentation analysis, High Resolution Melting and PCR-ARMS with following gel electrophoresis and visualisation. Chi-square test and in cases of low expected frequencies Yates correction were used to compare relative frequencies of individual mutations. The comparison of averages was performed by t-test.RESULTS: We detected prevalence of factor V and II mutation of 9% and 3%, respectively. Single MTHFR mutation was found in 59% and double heterozygous MTHFR mutation in 23% of cases. No mutation was present in only 6% of the study group. Heterozygous mutations of factor V occurred 1.8 times more frequently in our study group compared to the general Czech women population. Also, the frequency of factor II mutation was 1.5-3 times higher. No carrier of these mutations had overt coagulation disorder, history of thromboembolic disease or that of habitual abortions.CONCLUSIONS: The frequency of thrombophilic mutations in the group of women with early pregnancy loss is 1.5-3 times higher than in the general population.

PROBLEM:Up to 20% of pregnancies end in the first trimester by spontaneous abortion, but a significant number remains unexplained. The aim of this study is to investigate the role of variants within the gene for apolipoprotein E (APOE) in the genetic determination of spontaneous abortions.METHOD OF STUDY:We collected DNA from 410 tissue samples of spontaneous abortions, and APOE was genotyped by PCR-RFLP method. The frequencies were compared with a population sample of adults (N = 2606) and with a positive control (1060 women with at least two children).RESULTS:The frequencies of the APOE genotypes in abortions (APOE2E2 + E3E2 = 0.132; APOE3E3 = 0.661; APOE3E4 + E4E4 = 0.195; APOE4E2 = 0.012) did not significantly differ (P = 0.604) from the frequencies in analyzed adult population study (APOE2E2 + E3E2 = 0.132; APOE3E3 = 0.686; APOE3E4 + E4E4 = 0.169; APOE4E2 = 0.014) or from the positive control (APOE2E2 + E3E2 = 0.133; APOE3E3 = 0.691; APOE3E4 + E4E4 =0.166; APOE4E2 = 0.010; P = 0.592).CONCLUSION:Our study suggests that APOE may not be associated with spontaneous abortions in Caucasians.