The effect of normobaric hypoxia on acute exercise-induced changes in blood sphingoid base-1-phosphates metabolism in cyclists

Extracellular sphingosine-1-phosphate (S1P) emerged as an important regulator of muscle function. We previously found that plasma S1P concentration is elevated in response to acute exercise and training. Interestingly, hypoxia, which is commonly utilized in training programs, induces a similar effect. Therefore, the aim of the current study was to determine the effect of normobaric hypoxia on exercise-induced changes in blood sphingolipid metabolism. Fifteen male competitive cyclists performed a graded cycling exercise until exhaustion (GE) and a simulated 30 km individual time trial (TT) in either normoxic or hypoxic (FiO2 = 16.5%) conditions. Blood samples were taken before the exercise, following its cessation, and after 30 min of recovery. We found that TT increased dihydrosphingosine-1-phosphate (dhS1P) concentration in plasma (both HDL- and albumin-bound) and blood cells, as well as the rate of dhS1P release from erythrocytes, regardless of oxygen availability. Plasma concentration of S1P was, however, reduced during the recovery phase, and this trend was augmented by hypoxia. On the other hand, GE in normoxia induced a selective increase in HDL-bound S1P. This effect disappeared when the exercise was performed in hypoxia, and it was associated with reduced S1P level in platelets and erythrocytes. We conclude that submaximal exercise elevates total plasma dhS1P concentration via increased availability of dihydrosphingosine resulting in enhanced dhS1P synthesis and release by blood cells. Maximal exercise, on the other hand, induces a selective increase in HDL-bound S1P, which is a consequence of mechanisms not related to blood cells. We also conclude that hypoxia reduces post-exercise plasma S1P concentration.

Evaluation of Oromucosal Natural Gum-Based Emulgels as Novel Strategy for Photodynamic Therapy of Oral Premalignant Lesions

Photodynamic therapy (PDT) recently has been shown as a promising option in the treatment of premalignant lesions of the soft oral tissues. Effective delivery of photosensitizer is challenging due to poor drug adherence to the oromucosal epithelium. In the present work, emulgels composed of natural polysaccharide gums (tragacanth, xanthan and gellan) were evaluated as novel oromucosal platforms of delta-aminolevulinic acid (ALA) for PDT. Apart from mucoadhesive and textural analysis, the specific steps involved studies on drug penetration behavior and safety profile using a three-dimensional human oral epithelium model (HOE). All designed emulgels presented greater mucoadhesiveness when compared to commercial oromucosal gel. Incorporation of ALA affected textural properties of emulgels, and tragacanth/xanthan formulation with greater hardness and cohesiveness exhibited a protective function against the mechanical tongue stress. Permeability studies revealed that ALA is capable of penetrating across oromucosal epithelium by passive transport and all formulations promoted its absorption rate when compared to a commercial topical product with ALA. Importantly, the combination of tragacanth and xanthan profoundly enhanced photosensitizer retention in the buccal epithelium. Tested samples performed negligible reduction in cell viability and moderately low IL-1β release, confirming their non-irritancy and compatibility with HOE. Overall, the presented findings indicate that tragacanth/xanthan emulgel holds promise as an oromucosal ALA-carrier for PDT strategy.

Interlayer excitons in MoSe2/2D perovskite hybrid heterostructures - the interplay between charge and energy transfer

van der Waals crystals have opened a new and exciting chapter in heterostructure research, removing the lattice matching constraint characteristics of epitaxial semiconductors. They provide unprecedented flexibility for heterostructure design. Combining two-dimensional (2D) perovskites with other 2D materials, in particular transition metal dichalcogenides (TMDs), has recently emerged as an intriguing way to design hybrid opto-electronic devices. However, the excitation transfer mechanism between the layers (charge or energy transfer) remains to be elucidated. Here, we investigate PEA₂PbI₄/MoSe₂ and (BA)₂PbI₄/MoSe₂ heterostructures by combining optical spectroscopy and density functional theory (DFT) calculations. We show that band alignment facilitates charge transfer. Namely, holes are transferred from TMDs to 2D perovskites, while the electron transfer is blocked, resulting in the formation of interlayer excitons. Moreover, we show that the energy transfer mechanism can be turned on by an appropriate alignment of the excitonic states, providing a rule of thumb for the deterministic control of the excitation transfer mechanism in TMD/2D-perovskite heterostructures.

Exposure to Normobaric Hypoxia Combined with a Mixed Diet Contributes to Improvement in Lipid Profile in Trained Cyclists

This study aimed to analyze the effects of live high-train low method (LH-TL) and intermittent hypoxic training (IHT) with a controlled mixed diet on lipid profile in cyclists. Thirty trained male cyclists at a national level with at least six years of training experience participated in the study. The LH-TL group was exposed to hypoxia (FiO2 = 16.5%) for 11-12 h a day and trained under normoxia for 3 weeks. In the IHT group, participants followed the IHT routine three times a week under hypoxia (FiO2 = 16.5%) at lactate threshold intensity. The control group (N) lived and trained under normoxia. The results showed that the 3-week LH-TL method significantly improved all lipid profile variables. The LH-TL group showed a significant increase in HDL-C by 9.0% and a decrease in total cholesterol (TC) by 9.2%, LDL-C by 18.2%, and triglycerides (TG) by 27.6%. There were no significant changes in lipid profiles in the IHT and N groups. ∆TG and ∆TC were significantly higher in the LH-TL group compared to the N group. In conclusion, hypoxic conditions combined with a mixed diet can induce beneficial changes in lipid profile even in highly trained athletes. The effectiveness of the hypoxic stimulus is closely related to the hypoxic training method.

Red Blood Cell 2,3-Diphosphoglycerate Decreases in Response to a 30 km Time Trial Under Hypoxia in Cyclists

Red blood cell 2,3-diphosphoglycerate (2,3-DPG) is one of the factors of rightward-shifted oxygen dissociation curves and decrease of Hb-O₂ affinity. The reduction of Hb-O₂ affinity is beneficial to O₂ unloading at the tissue level. In the current literature, there are no studies about the changes in 2,3-DPG level following acute exercise in moderate hypoxia in athletes. For this reason, the aim of this study was to analyze the effect of prolonged intense exercise under normoxic and hypoxic conditions on 2,3-DPG level in cyclists. Fourteen male trained cyclists performed a simulation of a 30 km time trial (TT) in normoxia and normobaric hypoxia (FiO₂ = 16.5%, ~2,000 m). During the TT, the following variables were measured: power, blood oxygen saturation (SpO₂), and heart rate (HR). Before and immediately after exercise, the blood level of 2,3-DPG and acid–base equilibrium were determined. The results showed that the mean SpO₂ during TT in hypoxia was 8% lower than in normoxia. The reduction of SpO₂ in hypoxia resulted in a decrease of average power by 9.6% (p < 0.001) and an increase in the 30 km TT completion time by 3.8% (p < 0.01) compared to normoxia. The exercise in hypoxia caused a significant (p < 0.001) decrease in 2,3-DPG level by 17.6%. After exercise in normoxia, a downward trend of 2,3-DPG level was also observed, but this effect was not statistically significant. The analysis also revealed that changes of acid–base balance were significantly larger (p < 0.05) after exercise in hypoxia than in normoxia. In conclusion, intense exercise in hypoxic conditions leads to a decrease in 2,3-DPG concentration, primarily due to exercise-induced acidosis.

Sphingosine-1-phosphate in acute exercise and training

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid found in all eukaryotic cells. Although it may function as an intracellular second messenger, most of its effects are induced extracellularly via activation of a family of five specific membrane receptors. Sphingosine-1-phosphate is enriched in plasma, where it is transported by high-density lipoprotein and albumin, as well as in erythrocytes and platelets which store and release large amounts of this sphingolipid. Sphingosine-1-phosphate regulates a host of cellular processes such as growth, proliferation, differentiation, migration, and apoptosis suppression. It was also shown to play an important role in skeletal muscle physiology and pathophysiology. In recent years, S1P metabolism in both muscle and blood was found to be modulated by exercise. In this review, we summarize the current knowledge on the effect of acute exercise and training on S1P metabolism, highlighting the role of this sphingolipid in skeletal muscle adaptation to physical effort.

Pharmacological inhibition of sphingosine-1-phosphate lyase partially reverses spatial memory impairment in streptozotocin-diabetic rats

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid with strong neuroprotective properties that is important for normal excitability and synaptic transmission in the hippocampal neurons. Considering the above, the aim of the present study was to determine whether increasing brain S1P level is able to reverse spatial memory impairment in streptozotocin-diabetic rats. The experiment was carried out on diabetic (n = 22) and nondiabetic (n = 10) male Wistar rats. Diabetes was induced by a single injection of streptozotocin. Eleven weeks later, 11 diabetic animals received injections of THI (S1P lyase inhibitor) for seven days. During the last five days of the experiment spatial reference memory acquisition and retention were tested in the Morris water maze task. The animals were then anaesthetized and samples of the hippocampus, prefrontal cortex, striatum, and cerebellum were excised. The content of S1P and related sphingolipids was measured using a HPLC method. Diabetes induced a depletion of ceramide in the hippocampus and cerebellum that was associated with impaired spatial memory and learning. Administration of THI to the diabetic animals prevented ceramide depletion in the hippocampus and cerebellum, and induced an increase in S1P content in all examined brain structures. These effects were associated with an improvement in spatial memory. We conclude that pharmacological inhibition of S1P lyase partially reverses the impairment in spatial memory induced by chronic hyperglycemia, and that this effect may be related to the prevention of ceramide depletion in the hippocampus and cerebellum, the increase in brain S1P level, or both.

The Influence of Age and Cardiorespiratory Fitness on Bioactive Lipids in Muscle

Reduced insulin sensitivity is observed with aging and often explained by decreased physical activity. The mechanisms involved are not clarified, but bioactive lipids may play a role. We aimed to evaluate the influence of age and cardiorespiratory fitness on ceramide and diacylglycerol content in muscle and key proteins in lipid metabolism and insulin signaling. Healthy males were stratified by age into trained and untrained groups including 27 young (23.2 ± 0.3 years) and 33 aged (65.2 ± 0.6 years). Maximal oxygen uptake and body composition were measured and fasting blood samples and muscle biopsies obtained. Muscle ceramide and diacylglycerol were determined by thin-layer and gas-liquid chromatography and proteins by western blotting. We show that HOMA-IR was higher and VO2 peak lower in aged compared with young. Total, saturated, C16:0 and C18:0 ceramide content were lower in muscle from aged compared with young. Intramuscular C18:1n9 and C20:4n6 content were higher in trained versus untrained. Content of total unsaturated and C16:1n7 diacylglycerol fatty acids were higher and C24:0 lower in muscle of aged versus young. Cardiorespiratory fitness had no impact on total diacylglycerol content. In conclusion, these data argue against intramuscular ceramide or diacylglycerol accumulation as driver of age-related insulin resistance in lean individuals.

Plasma concentration and expression of adipokines in epicardial and subcutaneous adipose tissue are associated with impaired left ventricular filling pattern

Background

Adipokines in serum derive mainly from subcutaneous and visceral adipose tissues. Epicardial adipose tissue (EAT), being a relatively small but unique fat depot, probably does not make an important contribution to systemic concentrations of adipokines. However, proximity of EAT to cardiac muscle and coronary arteries allows cells and proteins to penetrate between tissues. It is hypothesized that overexpression of proinflammatory cytokines in EAT plays an important role in pathophysiology of the heart. The aim of the study was to analyze the relationship between echocardiographic heart parameters and adipokines in plasma, epicardial, and subcutaneous fat in patients with obesity and type 2 diabetes mellitus (T2DM). Additionally, we evaluate proinflammatory properties of EAT by comparing that depot with subcutaneous adipose tissue.

Methods

The study included 55 male individuals diagnosed with coronary artery disease (CAD) who underwent planned coronary artery bypass graft. Plasma concentrations of leptin, adiponectin, resistin, visfatin, apelin, IL-6, and TNF-α, as well as their mRNA and protein expressions in EAT and subcutaneous adipose tissue (SAT) were determined.

Results

Obesity and diabetes were associated with increased leptin and decreased adiponectin plasma levels, higher protein expression of leptin and IL-6 in SAT, and higher visfatin protein expression in EAT. Impaired left ventricular (LV) diastolic function was associated with increased plasma concentrations of leptin, resistin, IL-6, and adiponectin, as well as with increased expressions of resistin, apelin, and adiponectin in SAT, and leptin in EAT.

Conclusions

Obesity and T2DM in individuals with CAD have a limited effect on adipokines. Expression of adipokines in EAT and SAT is linked to certain heart parameters, however diastolic dysfunction of the LV is strongly associated with circulating adipokines.

Effect of acute exercise on mRNA and protein expression of main components of the lipolytic complex in different skeletal muscle types in the rat

Adipose triglyceride lipase (ATGL) hydrolyses the first bond of triacylglycerols. The activity of the enzyme is elevated by comparative gene identification 58 (CGI-58), and reduced by G0/G1 switch gene 2 (G0S2) protein. There are no data on the effect of acute exercise on the behavior of particular components of the lipolytic complex in different skeletal muscle types, therefore, the aim of the present study was to examine that topic. The experiments were carried out on four groups of male Wistar rats: 1) control 2) rats running on a treadmill at the speed of 18 m/min for 30 min, 3) at the speed of 18 m/min for 120 min, 4) for 30 min at the speed of 28 m/min. We found that each exercise bout induced numerous changes in the expression of mRNA and protein ATGL, hormone-sensitive lipase, CGI-58 and G0S2 in the investigated muscles. These changes, depended to a large extent on a muscle type. In general, the strongest pro-lipolytic response was observed in the soleus, followed by the red section of the gastrocnemius (RG). On the other hand, in the white section of the gastrocnemius protein expression of the components of the lipolytic complex was reduced in response to exercise. These changes were not accompanied by alterations in muscle triacylglycerol content, with the exception of a reduction observed in the RG following 2-hour run. We conclude that a single bout of exercise induces significant effect on the expression of components of the lipolytic complex in skeletal muscle, and that the magnitude of this effect depends on muscle oxidative capacity, as well as the duration and intensity of exercise.

Low expression of IL-18 and IL-18 receptor in human skeletal muscle is associated with systemic and intramuscular lipid metabolism-Role of HIV lipodystrophy

Introduction

Interleukin (IL)-18 is involved in regulation of lipid and glucose metabolism. Mice lacking whole-body IL-18 signalling are prone to develop weight gain and insulin resistance, a phenotype which is associated with impaired fat oxidation and ectopic skeletal muscle lipid deposition. IL-18 mRNA is expressed in human skeletal muscle but a role for IL-18 in muscle has not been identified. Patients with HIV-infection and lipodystrophy (LD) are characterized by lipid and glucose disturbances and increased levels of circulating IL-18. We hypothesized that skeletal muscle IL-18 and IL-18 receptor (R) expression would be altered in patients with HIV-lipodystrophy.

Design and methods

Twenty-three HIV-infected patients with LD and 15 age-matched healthy controls were included in a cross-sectional study. Biopsies from the vastus lateralis muscle were obtained and IL-18 and IL-18R mRNA expression were measured by real-time PCR and sphingolipids (ceramides, sphingosine, sphingosine-1-Phosphate, sphinganine) were measured by HPLC. Insulin resistance was assessed by HOMA and the insulin response during an OGTT.

Results

Patients with HIV-LD had a 60% and 54% lower level of muscular IL-18 and IL-18R mRNA expression, respectively, compared to age-matched healthy controls. Patients with HIV-LD had a trend towards increased levels of ceramide (18.3±4.7 versus 14.8±3.0,p = 0.06) and sphingosine (0.41±0.13 versus 0.32±0.07, and lower level of sphinganine (p = 0.06). Low levels of muscle IL-18 mRNA correlated to high levels of ceramides (r = -0.31, p = 0.038) and sphingosine-1P (r = -0.29, p = 0.046) in skeletal muscle, whereas such a correlation was not found in healthy controls. Low expression of IL-18 mRNA in skeletal muscle correlated to elevated concentration of circulating triglycerides (R_p = -0.73, p<0.0001). Neither muscle expression of IL-18 mRNA or ceramide correlated to parameters of insulin resistance.

Conclusion

IL-18 (mRNA) in skeletal muscle appears to be involved in the regulation of intramuscular lipid metabolism and hypertriglyceridemia.

Arteriovenous Sphingosine-1-Phosphate Differences Across Selected Organs of the Rat

Background/Aims: Sphingosine-1-phosphate (S1P) is a bioactive lysosphingolipid that is found in high concentration in plasma. The majority of plasma S1P is transported bound to HDL and albumin. Although the major sources of circulating S1P have been identified, it remains obscure what is the contribution of different organs/tissues to S1P homeostasis in plasma. Answering this question was the major aim of the present study. Methods: The experiment was performed on male Wistar rats from whom blood samples were taken from either: 1) femoral vein, right ventricle of the heart, and abdominal aorta (n=15) or 2) hepatic vein, portal vein, and abdominal aorta (n=11). Plasma was fractionated by sequential flotation ultracentrifugation and sphingolipids were quantified by a HPLC method. Results: Compared to the mixed venous blood sampled from the right ventricle, total plasma and lipoprotein-depleted plasma (LPDP) concentration of S1P in the arterial blood was lower. On the other hand, the level of S1P increased across the leg both in plasma and LPDP. The concentration of S1P, sphingosine, and sphinganine in the plasma, HDL, and LPDP isolated from the blood taken from the hepatic vein was markedly higher compared to both arterial and portal blood. Conclusions: We conclude that, in contrast to HDL-bound S1P, albumin-associated S1P is very labile in the circulation. It is degraded in the pulmonary, and to a lesser extent, gastrointestinal circulation, and released across the liver and skeletal muscle. We also conclude that liver is an important source of HDL-bound S1P and circulating free sphingoid bases.

Observation of A Raman mode splitting in few layer black phosphorus encapsulated with hexagonal boron nitride

We investigate the impact of encapsulation with hexagonal boron nitride (h-BN) on the Raman spectrum of few layer black phosphorus. The encapsulation results in a significant reduction of the line width of the Raman modes of black phosphorus, due to a reduced phonon scattering rate. We observe a so far elusive peak in the Raman spectra ∼4 cm^-1 above the A mode in trilayer and thicker flakes, which had not been observed experimentally. The newly observed mode originates from the strong black phosphorus inter-layer interaction, which induces a hardening of the surface atom vibration with respect to the corresponding modes of the inner layers. The observation of this mode suggests a significant impact of h-BN encapsulation on the properties of black phosphorus and can serve as an indicator of the quality of its surface.

Probing the Interlayer Exciton Physics in a MoS2/MoSe2/MoS2 van der Waals Heterostructure

Stacking atomic monolayers of semiconducting transition metal dichalcogenides (TMDs) has emerged as an effective way to engineer their properties. In principle, the staggered band alignment of TMD heterostructures should result in the formation of interlayer excitons with long lifetimes and robust valley polarization. However, these features have been observed simultaneously only in MoSe₂/WSe₂ heterostructures. Here we report on the observation of long-lived interlayer exciton emission in a MoS₂/MoSe₂/MoS₂ trilayer van der Waals heterostructure. The interlayer nature of the observed transition is confirmed by photoluminescence spectroscopy, as well as by analyzing the temporal, excitation power, and temperature dependence of the interlayer emission peak. The observed complex photoluminescence dynamics suggests the presence of quasi-degenerate momentum-direct and momentum-indirect bandgaps. We show that circularly polarized optical pumping results in long-lived valley polarization of interlayer exciton. Intriguingly, the interlayer exciton photoluminescence has helicity opposite to the excitation. Our results show that through a careful choice of the TMDs forming the van der Waals heterostructure it is possible to control the circular polarization of the interlayer exciton emission.

Endurance training selectively increases high-density lipoprotein-bound sphingosine-1-phosphate in the plasma

Sphingosine-1-phosphate (S1P) is a bioactive lysosphingolipid that is found in relatively high concentration in human plasma. Erythrocytes, endothelial cells, and activated platelets are the main sources of circulating S1P. The majority of plasma S1P is transported bound to high-density lipoprotein (HDL) and albumin. In recent years, HDL-bound S1P attracted much attention due to its cardioprotective and anti-atherogenic properties. We have previously found that endurance-trained athletes are characterized by higher plasma S1P concentration compared to untrained individuals. This finding prompted us to examine the effect of endurance training on S1P metabolism in blood. Thirteen healthy, untrained, male subjects completed an 8-week training program on a rowing ergometer. Three days before the first, and 3 days after the last training session, blood samples were drawn from an antecubital vein. We found that total plasma S1P concentration was increased after the training. Further analysis of different plasma fractions showed that the training selectively elevated HDL-bound S1P. This effect was associated with activation of sphingosine kinase in erythrocytes and platelets and enhanced S1P release from red blood cells. We postulate that increase in HDL-bound S1P level is one of the mechanisms underlying beneficial effects of regular physical activity on cardiovascular diseases.

Effect of metformin on bioactive lipid metabolism in insulin-resistant muscle

Intramuscular accumulation of bioactive lipids leads to insulin resistance and type 2 diabetes (T2D). There is lack of consensus concerning which of the lipid mediators has the greatest impact on muscle insulin action in vivo Our aim was to elucidate the effects of high-fat diet (HFD) and metformin (Met) on skeletal muscle bioactive lipid accumulation and insulin resistance (IR) in rats. We employed a [U-¹³C]palmitate isotope tracer and mass spectrometry to measure the content and fractional synthesis rate (FSR) of intramuscular long-chain acyl-CoA (LCACoA), diacylglycerols (DAG) and ceramide (Cer). Eight weeks of HFD-induced intramuscular accumulation of LCACoA, DAG and Cer accompanied by both systemic and skeletal muscle IR. Metformin treatment improved insulin sensitivity at both systemic and muscular level by the augmentation of Akt/PKB and AS160 phosphorylation and decreased the content of DAG and Cer and their respective FSR. Principal component analysis (PCA) of lipid variables revealed that altered skeletal muscle IR was associated with lipid species containing 18-carbon acyl-chain, especially with C18:0-Cer, C18:1-Cer, 18:0/18:2-DAG and 18:2/18:2-DAG, but not palmitate-derived lipids. It is concluded that the insulin-sensitizing action of metformin in skeletal muscle is associated with decreased 18-carbon acyl-chain-derived bioactive lipids.

Multicolor emission from intermediate band semiconductor ZnO1-xSex

Photoluminescence and photomodulated reflectivity measurements of ZnOSe alloys are used to demonstrate a splitting of the valence band due to the band anticrossing interaction between localized Se states and the extended valence band states of the host ZnO matrix. A strong multiband emission associated with optical transitions from the conduction band to lower E₋ and upper E₊ valence subbands has been observed at room temperature. The composition dependence of the optical transition energies is well explained by the electronic band structure calculated using the kp method combined with the band anticrossing model. The observation of the multiband emission is possible because of relatively long recombination lifetimes. Longer than 1 ns lifetimes for holes photoexcited to the lower valence subband offer a potential of using the alloy as an intermediate band semiconductor for solar power conversion applications.

Liver X Receptor Agonist TO901317 Prevents Diacylglycerols Accumulation in the Heart of Streptozotocin-Diabetic Rats

BACKGROUND/AIMS

Liver X receptors (LXRα and LXRβ) are ligand-activated transcription factors that regulate expression of genes involved in lipid and cholesterol metabolism. LXR expression has been identified in the heart, and enhanced LXR activity in the streptozotocin (STZ) diabetic myocardium was reported recently. The aim of this study was to investigate effect of in vivo LXR activation on myocardial lipid metabolism under conditions of STZ-induced diabetes.

METHODS

Wistar rats were randomly divided into three experimental groups: non-diabetic control, treated with STZ, and treated with STZ and LXR agonist - TO901317. Diabetes was induced by a single intraperitonal injection of STZ at a dose of 55 mg/kg. LXR agonist was administrated once daily in the morning by an oral gavage at a dose of 10 mg/kg/d during the last week of the experiment. After anesthesia samples of blood and the left ventricle were taken.

RESULTS

TO901317 administration increased expression of both LXR isoforms and its target genes: sterol response element binding protein 1c (SREBP-1c) and acetyl-coenzyme A carboxylase 1 (ACC1) in the heart of streptozotocin-diabetic rats. Treatment with LXR agonist had no effect on plasma lipids and glucose in the diabetic rats. Concomitantly, content of the examined lipid classes in the diabetic heart (nonesterified fatty acids, triacylglycerols, phospholipids, cholesterol esters, ceramide) was unchanged after treatment with TO901317. On the contrary, myocardial level of cholesterol and diacylglycerols (DAG) was decreased after LXR activation in diabetic rats, the change in DAG level was associated with downregulated expression of adipose triglyceride lipase (ATGL).

CONCLUSION

Activation of LXRs by TO901317 protects cardiomyocytes against DAG accumulation and thus may reverse disturbances in lipid metabolism observed in streptozotocin-diabetic heart.

Unified Model of Nanosecond Charge Recombination in Closed Reaction Centers from Rhodobacter sphaeroides: Role of Protein Polarization Dynamics

Ongoing questions surround the influence of protein dynamics on rapid processes such as biological electron transfer. Such questions are particularly addressable in light-activated systems. In Rhodobacter sphaeroides reaction centers, charge recombination or back electron transfer from the reduced bacteriopheophytin, HA(-), to the oxidized dimeric bacteriochlorophyll, P(+), may be monitored by both transient absorption spectroscopy and transient fluorescence spectroscopy. Signals measured with both these techniques decay in a similar three-exponential fashion with lifetimes of ∼0.6-0.7, ∼2-4, and ∼10-20 ns, revealing the complex character of this electron transfer reaction. In this study a single kinetic model was developed to connect lifetime and amplitude data from both techniques. The model took into account the possibility that electron transfer from HA(-) to P(+) may occur with transient formation of the state P(+)BA(-). As a result it was possible to model the impact of nanosecond protein relaxation on the free energy levels of both P(+)HA(-) and P(+)BA(-) states relative to that of the singlet excited state of P, P*. Surprisingly, whereas the free energy gap between P* and P(+)HA(-) increased with time in response to protein reorganization, the free energy gap between P* and P(+)BA(-) decreased. This finding may be accounted for by a gradual polarization of the protein environment which stabilizes the state P(+)HA(-) and destabilizes the state P(+)BA(-), favoring productive charge separation over unproductive charge recombination.

The Lipari-Szabo Model-Free Analysis as a Method for Study of Molecular Motion in Solid State Heteronuclear Systems Using NMR Off-Resonance

In the present work, a new method for measuring motional parameters using the off-resonance technique was described. The Lipari-Szabo model-free formalism was used to analyze molecular dynamics in a heteronuclear system [1, 2]. Cross-relaxation solid state nuclear magnetic resonance off-resonance experiments were performed on a homebuilt pulse spectrometer operating at the frequency of 30.2 MHz for protons at temperature 173 K. The proton spins were spin-locked in the effective field [Formula: see text] while ¹⁹F spins were continuously saturated for a long time. It was possible to carry out these experiments because a uniquely designed probe was able to produce three slightly differing frequencies on and off-resonance for protons and the frequency of 28.411 MHz for fluorine [3-6]. The off-resonance frequencies can be changed within the range of 30.2-30.6 MHz.

Reduction of ceramide de novo synthesis in solid tissues changes sphingolipid levels in rat plasma, erythrocytes and platelets

PURPOSE

De novo sphingolipid synthesis does not occur in plasma, erythrocytes and platelets. The purpose of the study was to examine the effect of inhibition of sphingolipid synthesis in solid tissues on the level of the following bioactive sphingolipids: sphinganine, ceramide, sphingosine and sphingosine 1-phosphate in plasma, erythrocytes and platelets.

MATERIAL/METHODS

The experiments were carried out on male Wistar rats. Myriocin was used to inhibit serine palmitoyltransferase activity (the enzyme catalyzes the first step of ceramide de novo synthesis) and nicotinic acid was used to reduce the concentration of plasma free fatty acids (a substrate for the de novo ceramide synthesis). The sphingolipids were quantified by means of liquid chromatography/mass spectrometry.

RESULTS

Myriocin reduced the level of each compound in plasma. It reduced the level of sphinganine, sphingosine-1-phosphate and total ceramide and elevated the level of sphingosine in erythrocytes. In platelets, myriocin reduced the total level of ceramide. Nicotinic acid reduced the plasma level of sphinganine, sphingosine and total ceramide. It increased the level of sphingosine-1-phosphate in erythrocytes. In platelets, nicotinioc acid increased the level of sphinganine and sphingosine and reduced the level of sphingosine-1-phosphate and total ceramide.

CONCLUSIONS

Inhibition of serine palmitoyltransferase activity in solid tissues and reduction in plasma free fatty acids concentration affects sphingolipid level in plasma, erythrocytes and platelets. The changes in erythrocytes and platelets depend both on the cell type and the sphingolipid studied and only partially follow the changes in the plasma.

Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems

The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2MHz and 28.411MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins (1)H are polarized in the magnetic field B0 while fluorine spins (19)F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal.

Training Does Not Alter Muscle Ceramide and Diacylglycerol in Offsprings of Type 2 Diabetic Patients Despite Improved Insulin Sensitivity

Ceramide and diacylglycerol (DAG) may be involved in the early phase of insulin resistance but data are inconsistent in man. We evaluated if an increase in insulin sensitivity after endurance training was accompanied by changes in these lipids in skeletal muscle. Nineteen first-degree type 2 diabetes Offsprings (Offsprings) (age: 33.1 ± 1.4 yrs; BMI: 26.4 ± 0.4 kg/m²) and sixteen matched Controls (age: 31.3 ± 1.5 yrs; BMI: 25.3 ± 0.7 kg/m²) performed 10 weeks of endurance training three times a week at 70% of VO₂max on a bicycle ergometer. Before and after the intervention a hyperinsulinemic-euglycemic clamp and VO₂max test were performed and muscle biopsies obtained. Insulin sensitivity was significantly lower in Offsprings compared to control subjects (p < 0.01) but improved in both groups after 10 weeks of endurance training (Off: 17 ± 6%; Con: 12 ± 9%, p < 0.01). The content of muscle ceramide, DAG, and their subspecies were similar between groups and did not change in response to the endurance training except for an overall reduction in C22:0-Cer (p < 0.05). Finally, the intervention induced an increase in AKT protein expression (Off: 27 ± 11%; Con: 20 ± 24%, p < 0.05). This study showed no relation between insulin sensitivity and ceramide or DAG content suggesting that ceramide and DAG are not major players in the early phase of insulin resistance in human muscle.

Myocardial lipid profiling during time course of high fat diet and its relationship to the expression of fatty acid transporters

BACKGROUND/AIMS

It is well documented that increased fatty acids (FA) supply causes lipid accumulation and insulin resistance in skeletal muscles. Whether the same mechanism is present in the heart is still unclear. Therefore, the goal of our study was to determine the content of specific myocardial lipid fractions during feeding rats a high fat diet (HFD) for 5 weeks. Moreover, the relation between changes in myocardial lipid content, whole body insulin resistance and the expression of fatty acid transporters in each week of HFD was established.

METHODS

Gas liquid chromatography and high performance liquid chromatography were used to determine the content of lipid fractions in the left ventricle. Expression of selected proteins was estimated by Western blot technique. All measurements were made after each week of HFD.

RESULTS

As expected, lipid profile in myocardium was altered by HFD in different weeks of the study with the most intense changes in triacylglycerols, long chain fatty acid-CoA and ceramide. Furthermore, there was a significant elevation of plasmalemmal (the 4th and the 5th week) and mitochondrial expression (from the 3rd to the 5th week) of fatty acid translocase.

CONCLUSION

High fat diet affects myocardial lipid profile in each week of its duration and causes alternations in FA metabolism in cardiomyocytes.

Sources, metabolism, and regulation of circulating sphingosine-1-phosphate

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid that acts either as an intracellular messenger or as a ligand for its membrane receptors. S1P is a normal constituent of blood, where it is found both in plasma and blood cells. Compared with other cell types, sphingolipid metabolism in erythrocytes and platelets has unique features that allow the erythrocytes and platelets to accumulate S1P. In plasma, S1P is bound mainly to HDLs and albumin. Of note, metabolism and biological activity of S1P is to a large extent affected by the type of its carrier. Plasma S1P is characterized by a short half-life, indicating rapid clearance by degradative enzymes and the presence of high-capacity sources involved in maintaining its high concentration. These sources include blood cells, vascular endothelium, and hepatocytes. However, the extent to which each of these contributes to the plasma pool of S1P is a matter of debate. Circulating S1P plays a significant physiological role. It was found to be the key regulator of lymphocyte trafficking, endothelial barrier function, and vascular tone. The purpose of this review is to summarize the present state of knowledge on the metabolism, transport, and origin of plasma S1P, and to discuss the mechanisms regulating its homeostasis in blood.

Effect of atrial pacing on the level of bioactive sphingolipids in the heart ventricles of the rat

Bioactive sphingolipids play important role in regulation of the function of the cardiomyocytes. There are no data available on metabolism of the sphingolipids in the heart under increased work-load produced by tachycardia. The aim of the present study was to examine effect of tachycardia on the level of the principal bioactive sphingolipids in the left and right ventricles. The experiments were carried out on male Wistar rats. After anesthesia, two electrodes were administered into the right common jugular vein so that their tips were placed at the vein's aperture. The resting heart rate was 355 ± 24/min and the rate of stimulation was 600/min. EKG was continuously monitored. The stimulation time was 30 and 60 min. Thereafter, blood from the abdominal aorta and samples of the left and right ventricle were taken. The following bioactive sphingolipids were quantified by means of high performance liquid chromatography: sphinganine, ceramide, sphingosine, sphingosine-1-phosphate and sphinganine-1-phosphate. In the left ventricle, 30 and 60 min tachycardia elevated the level of sphingosine, reduced the level of sphingosine-1-phosphate and sphinganine-1-phosphate. The level of ceramide was reduced only after 60 min. In the right ventricle, 60 min pacing resulted in elevation in the level of sphingosine and sphinganine and reduction in the level of other compounds studied. It is concluded that tachycardia induces changes in metabolism of bioactive sphingolipids in each ventricle. The changes may affect cardiomyocyte functions. Also, differences in sphingolipid metabolism between both ventricles are reported.

Positive effects of voluntary running on metabolic syndrome-related disorders in non-obese hereditary hypertriacylglycerolemic rats

While metabolic syndrome is often associated with obesity, 25% of humans suffering from it are not obese and the effect of physical activity remains unclear in such cases. Therefore, we used hereditary hypertriaclyglycerolemic (HHTg) rats as a unique model for studying the effect of spontaneous physical activity [voluntary running (VR)] on metabolic syndrome-related disorders, such as dyslipidemia, in non-obese subjects. Adult HHTg males were fed standard (CD) or high-sucrose (HSD) diets ad libitum for four weeks. Within both dietary groups, some of the rats had free access to a running wheel (CD+VR, HSD+VR), whereas the controls (CD, HSD) had no possibility of extra physical activity. At the end of the four weeks, we measured the effects of VR on various metabolic syndrome-associated parameters: (i) biochemical parameters, (ii) the content and composition of triacylglycerols (TAG), diacylglycerols (DAG), ceramides and membrane phospholipids, and (iii) substrate utilization in brown adipose tissue. In both dietary groups, VR led to various positive effects: reduced epididymal and perirenal fat depots; increased epididymal adipose tissue lipolysis; decreased amounts of serum TAG, non-esterified fatty acids and insulin; a higher insulin sensitivity index. While tissue ceramide content was not affected, decreased TAG accumulation resulted in reduced and modified liver, heart and skeletal muscle DAG. VR also had a beneficial effect on muscle membrane phospholipid composition. In addition, compared with the CD group, the CD+VR rats exhibited increased fatty acid oxidation and protein content in brown adipose tissue. Our results confirm that physical activity in a non-obese model of severe dyslipidemia has many beneficial effects and can even counteract the negative effects of sucrose consumption. Furthermore, they suggest that the mechanism by which these effects are modulated involves a combination of several positive changes in lipid metabolism.

LXR Agonist T0901317-Induced Hyperlipidemia Does Not Lead to Lipid Accumulation in the Rat Heart

Background/Aims: Liver X receptors (LXRα and LXRβ) are ligand-activated transcription factors that regulate expression of genes involved in lipid and cholesterol metabolism. LXR expression has been identified in human and rodent cardiac tissue, however, its role in this tissue remains unclear. The aim of this study was to investigate effects of in vivo LXR activation on lipid metabolism in the rat myocardium under the conditions of low and high lipid intake. Methods: The experiments were performed on male Wistar rats fed for 5 weeks on either low fat diet (LFD) or high fat diet (HFD). Next, the animals were randomly divided into two groups receiving either LXR agonist - T0901317 (10mg/kg/d) or vehicle for the last week of the experiment. After anesthesia samples of the left ventricle and blood were taken. Results: It was found that LXRβ is the dominant isoform in the rat myocardium and the expression of both LXR isoforms did not change after administration of T0901317. Agonist treatment induced hyperlipidemia in low fat fed rats and this effect was amplified in high fat fed rats. LXR agonist elevated content of myocardial triacylglycerols in animals fed on LFD and content of phospholipids in animals fed on HFD. Levels of the remaining examined lipid classes (nonesterified fatty acids, diacylglycerol, free cholesterol, cholesterol esters, ceramide) was decreased or unchaged after LXR activation. Conclusion: We conclude that administration of T0901317 does not lead to severe myocardial lipid accumulation in rats despite of its high plasma availability.

New evidence for the role of ceramide in the development of hepatic insulin resistance

Aim

There are few and contradictory data on the role of excessive accumulation of intracellular sphingolipids, particularly ceramides, in the development of hepatic insulin resistance. In our study we assessed accumulated sphingolipid fractions and clarify the mechanisms of hepatic insulin resistance development as well as involvement of fatty acid and ceramide transporters in this process.

Methods

In culture of primary rat hepatocytes, exposed to high concentration of palmitic acid (0.75mM) during short and prolonged incubation, high performance liquid chromatography was used to assess intra- and extracellular sphingolipid fractions content. Degree of palmitate-induced insulin resistance was estimated by measuring changes in phosphorylation of insulin pathway proteins by western blotting as well as changes in expression of different type of transporters.

Results

In our study short and prolonged exposure of primary hepatocytes to palmitic acid resulted in increased intracellular accumulation of ceramide which inhibited insulin signaling pathway. We observed a significant increase in the expression of fatty-acid transport protein (FATP2) and ceramide transfer protein (CERT) what is consistent with enhanced intracellular ceramide content. The content of extracellular ceramide was increased nearly threefold after short and twofold after long incubation period. Expression of microsomal triglyceride transfer protein (MTP) and ATP-binding cassette transporter (ABCA1) was increased significantly mainly after short palmitate incubation.

Conclusion

Our data showed that increase in intarcellular ceramide content contributes to the development of hepatic insulin resistance. We suggest pivotal role of transporters in facilitating fatty acid influx (FATP2), accumulation of ceramides (CERT) and export to the media (MTP and ABCA1).

Exercise increases sphingoid base-1-phosphate levels in human blood and skeletal muscle in a time- and intensity-dependent manner

Purpose

Sphingosine-1-phosphate (S1P) regulates cardiovascular function and plays an important role in muscle biology. We have previously reported that cycling exercise increased plasma S1P. Here, we investigated the effect of exercise duration and intensity on plasma and skeletal muscle S1P levels.

Methods

In the first experiment, 13 male athletes performed a 60-min exercise at 65 % of VO_2max and a graded exercise until exhaustion on a rowing ergometer. Samples of the venous blood were taken, and plasma, erythrocytes and platelets were isolated. In the second experiment, ten male moderately active subjects performed three consecutive periods of one-leg knee extension exercise (at 25, 55 and 85 % of the maximal workload). Muscle biopsies and blood samples from the radial artery and femoral veins were taken.

Results

Under basal conditions, S1P was released from the leg, as its concentration was lower in the arterial than in the venous plasma (p < 0.01). Exercise until exhaustion increased plasma S1P and sphinganine-1-phosphate (SA1P) concentration (p < 0.05), whereas moderate-intensity exercise elevated only SA1P (p < 0.001). Although knee extension increased muscle S1P content (p < 0.05), it was not released but taken up across the leg during exercise. However, sphingosine was released from both working and resting leg at the highest workload (p < 0.05).

Conclusions

Plasma S1P concentration is elevated only by high-intensity exercise which results, at least in part, from increased availability of sphingosine released by skeletal muscle. In addition, exercise markedly affects S1P dynamics across the leg. We speculate that S1P may play an important role in adaptation of skeletal muscle to exercise.

Electronic supplementary material

The online version of this article (doi:10.1007/s00421-014-3080-x) contains supplementary material, which is available to authorized users.

Two-dimensional EPR imaging with the rapid scan and rotated magnetic field gradient

A new method for fast 2D Electron Paramagnetic Resonance Imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradient, whose orientation is changed at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples. The images from the acquired data are reconstructed using iterative algorithms. The proposed method allows to reduce the image acquisition time up to 10 ms for 2D EPRI, and to detect the sinogram with infinitesimal angular step between projections.

Two-dimensional spectral-spatial EPR imaging with the rapid scan and modulated magnetic field gradient

A new method for fast spectral-spatial electron paramagnetic resonance imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradients, whose amplitude is modulated at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples. The spectral-spatial images from the acquired data are reconstructed using iterative algorithms. The proposed method allows to acquire the spectral-spatial image with 800 projections at 200ms.

Change in blood gelsolin concentration in response to physical exercise

Plasma gelsolin (pGSN) produced by muscle is an abundant protein of extracellular fluids capable of severing actin filaments and eliminating actin from the circulation. Additionally, pGSN modulates the cellular effects of some bioactive lipids. In this study we test the hypothesis that hormonal and metabolic adaptations to exercise are associated with changes in gelsolin concentration in blood. Plasma samples were collected from twenty healthy males recruited from untrained (UT, n=10) and endurance trained (ET, n=10) groups that performed 30-60 minutes of exercise on a cycloergometer at a workload corresponding to 70% of VO2max. Gelsolin concentration was determined by quantitative Western blot analysis with an anti-human gelsolin antibody. The gelsolin concentration in UT and ET subjects before starting exercise ranged from 104 to 330 and 163 to 337 µg · ml(-1) respectively. After 30 minutes of exercise we observed a significant decrease of plasma gelsolin in the UT group (p<0.05) while the gelsolin concentration in the ET group rose on average from 244 to 271 µg · ml(-1). However, this increase did not reach statistical significance. Endurance training might increase the ability of muscle tissue to express plasma gelsolin as part of an adaptive mechanism.

Effects of inhibition of serine palmitoyltransferase (SPT) and sphingosine kinase 1 (SphK1) on palmitate induced insulin resistance in L6 myotubes

Background

The objective of this study was to examine the effects of short (2 h) and prolonged (18 h) inhibition of serine palmitoyltransferase (SPT) and sphingosine kinase 1 (SphK1) on palmitate (PA) induced insulin resistance in L6 myotubes.

Methods

L6 myotubes were treated simultaneously with either PA and myriocin (SPT inhibitor) or PA and Ski II (SphK1inhibitor) for different time periods (2 h and 18 h). Insulin stimulated glucose uptake was measured using radioactive isotope. Expression of insulin signaling proteins was determined using Western blot analyses. Intracellular sphingolipids content [sphinganine (SFA), ceramide (CER), sphingosine (SFO), sphingosine-1-phosphate (S1P)] were estimated by HPLC.

Results

Our results revealed that both short and prolonged time of inhibition of SPT by myriocin was sufficient to prevent ceramide accumulation and simultaneously reverse palmitate induced inhibition of insulin-stimulated glucose transport. In contrast, prolonged inhibition of SphK1 intensified the effect of PA on insulin-stimulated glucose uptake and attenuated further the activity of insulin signaling proteins (pGSK3β/GSK3β ratio) in L6 myotubes. These effects were related to the accumulation of sphingosine in palmitate treated myotubes.

Conclusion

Myriocin is more effective in restoration of palmitate induced insulin resistance in L6 myocytes, despite of the time of SPT inhibition, comparing to SKII (a specific SphK1 inhibitor). Observed changes in insulin signaling proteins were related to the content of specific sphingolipids, namely to the reduction of ceramide. Interestingly, inactivation of SphK1 augmented the effect of PA induced insulin resistance in L6 myotubes, which was associated with further inhibition of insulin stimulated PKB and GSK3β phosphorylation, glucose uptake and the accumulation of sphingosine.

Mitochondrial substrate availability and its role in lipid-induced insulin resistance and proinflammatory signaling in skeletal muscle

The relationship between glucose and lipid metabolism has been of significant interest in understanding the pathogenesis of obesity-induced insulin resistance. To gain insight into this metabolic paradigm, we explored the potential interplay between cellular glucose flux and lipid-induced metabolic dysfunction within skeletal muscle. Here, we show that palmitate (PA)-induced insulin resistance and proinflammation in muscle cells, which is associated with reduced mitochondrial integrity and oxidative capacity, can be attenuated under conditions of glucose withdrawal or glycolytic inhibition using 2-deoxyglucose (2DG). Importantly, these glucopenic-driven improvements coincide with the preservation of mitochondrial function and are dependent on PA oxidation, which becomes markedly enhanced in the absence of glucose. Intriguingly, despite its ability to upregulate mitochondrial PA oxidation, glucose withdrawal did not attenuate PA-induced increases in total intramyocellular diacylglycerol and ceramide. Furthermore, consistent with our findings in cultured muscle cells, we also report enhanced insulin sensitivity and reduced proinflammatory tone in soleus muscle from obese Zucker rats fed a 2DG-supplemented diet. Notably, this improved metabolic status after 2DG dietary intervention is associated with markedly reduced plasma free fatty acids. Collectively, our data highlight the key role that mitochondrial substrate availability plays in lipid-induced metabolic dysregulation both in vitro and in vivo.

Defining the role of DAG, mitochondrial function, and lipid deposition in palmitate-induced proinflammatory signaling and its counter-modulation by palmitoleate

Chronic exposure of skeletal muscle to saturated fatty acids, such as palmitate (C16:0), enhances proinflammatory IKK-NFκB signaling by a mechanism involving the MAP kinase (Raf-MEK-ERK) pathway. Raf activation can be induced by its dissociation from the Raf-kinase inhibitor protein (RKIP) by diacylglycerol (DAG)-sensitive protein kinase C (PKC). However, whether these molecules mediate the proinflammatory action of palmitate, an important precursor for DAG synthesis, is currently unknown. Here, involvement of DAG-sensitive PKCs, RKIP, and the structurally related monounsaturated fatty acid palmitoleate (C16:1) on proinflammatory signaling are investigated. Palmitate, but not palmitoleate, induced phosphorylation/activation of the MEK-ERK-IKK axis and proinflammatory cytokine (IL-6, CINC-1) expression. Palmitate increased intramyocellular DAG and invoked PKC-dependent RKIP(Ser153) phosphorylation, resulting in RKIP-Raf1 dissociation and MEK-ERK signaling. These responses were mimicked by PMA, a DAG mimetic and PKC activator. However, while pharmacological inhibition of PKC suppressed PMA-induced activation of MEK-ERK-IKK signaling, activation by palmitate was upheld, suggesting that DAG-sensitive PKC and RKIP were dispensable for palmitate's proinflammatory action. Strikingly, the proinflammatory effect of palmitate was potently repressed by palmitoleate. This repression was not due to reduced palmitate uptake but linked to increased neutral lipid storage and enhanced cellular oxidative capacity brought about by palmitoleate's ability to restrain palmitate-induced mitochondrial dysfunction.

[Epicardial adipose tissue and its role in cardiac physiology and disease]

Adipose tissue secretes a number of cytokines, referred to as adipokines. Intensive studies conducted over the last two decades showed that adipokines exert broad effects on cardiac metabolism and function. In addition, the available data strongly suggests that these cytokines play an important role in development of cardiovascular diseases. Epicardial adipose tissue (EAT) has special properties that distinguish it from other deposits of visceral fat. Overall, there appears to be a close functional and anatomic relationship between the EAT and the cardiac muscle. They share the same coronary blood supply, and there is no structure separating the adipose tissue from the myocardium or coronary arteries. The role of EAT in osierdziocardiac physiology remains unclear. Its putative functions include buffering coronary arteries against the torsion induced by the arterial pulse wave and cardiac contraction, regulating fatty acid homeostasis in the coronary microcirculation, thermogenesis, and neuroprotection of the cardiac autonomic ganglia and nerves. Obesity (particularly the abdominal phenotype) leads to elevated EAT content, and the available data suggests that high amount of this fat depot is associated with increased risk of ischemic heart disease, cardiac hypertrophy and diastolic dysfunction. The mass of EAT is small compared to other fat deposits in the body. Nevertheless, its close anatomic relationship to the heart suggests that this organ is highly exposed to EAT-derived adipokines which makes this tissue a very promising area of research. In this paper we review the current knowledge on the role of EAT in cardiac physiology and development of heart disease.

Liver X receptor agonist T0901317 enhanced peroxisome proliferator-activated receptor-delta expression and fatty acid oxidation in rat skeletal muscle

Liver X receptors (LXR) have been characterized as key transcriptional regulators of hepatic lipid and carbohydrate metabolism. LXR are expressed also in skeletal muscle, however, their role in this tissue is poorly investigated and the vast majority of available data comes from studies on cultured myotubes. Therefore, we aimed to examine effects of in vivo LXR activation on muscle lipid metabolism. The experiments were performed on male Wistar rats fed on a standard rodent chow. The animals were divided into two groups (n=10) receiving either LXR activator (T0901317, 10 mg/kg/day) or vehicle for one week. Samples of the soleus as well as red and white sections of the gastrocnemius muscle were excised. T0901317 increased muscle expression of peroxisome proliferator-activated receptor-δ and its target genes involved in fatty acid uptake and oxidation. In addition, LXR agonist enhanced palmitate oxidation (by 55%) in isolated soleus muscle. However, palmitate incorporation into triacylglycerol was decreased (by 38%), which was associated with reduced diacylglycerol acyltransferase expression (by 66%). Despite markedly increased plasma lipid concentration upon T0901317 treatment, muscle triacylglycerol level was elevated only in the red section of the gastrocnemius muscle. We conclude that T0901317 enhances muscle fatty acid oxidation, which prevents overt accumulation of intramuscular lipids that could be expected considering T0901317-induced hyperlipidemia.

Analysis of Uniformity of Magnetic Field Generated by the Two-Pair Coil System

In this paper we use a simple analysis based on properties of the axial field generated by symmetrical multipoles to reveal all possible distributions of two coaxial pairs of circular windings, which result in systems featuring zero octupole and 32 pole magnetic moments (six-order systems). Homogeneity of magnetic field of selected systems is analyzed. It has been found that one of the derived systems generates homogenous magnetic field whose volume is comparable to that yielded by the eight-order system. The influence of the current distribution and the windings placement on the field homogeneity is considered. The table, graphs and equations given in the paper facilitate the choice of the most appropriate design for a given problem. The systems presented may find applications in low field electron paramagnetic resonance imaging, some functional f-MRI (nuclear magnetic resonance imaging) and bioelectromagnetic experiments requiring the access to the working space from all directions.

Enhancement of photoluminescence from GaInNAsSb quantum wells upon annealing: improvement of material quality and carrier collection by the quantum well

In this study we apply time resolved photoluminescence and contactless electroreflectance to study the carrier collection efficiency of a GaInNAsSb/GaAs quantum well (QW). We show that the enhancement of photoluminescence from GaInNAsSb quantum wells annealed at different temperatures originates not only from (i) the improvement of the optical quality of the GaInNAsSb material (i.e., removal of point defects, which are the source of nonradiative recombination) but it is also affected by (ii) the improvement of carrier collection by the QW region. The total PL efficiency is the product of these two factors, for which the optimal annealing temperatures are found to be ~700 °C and ~760 °C, respectively, whereas the optimal annealing temperature for the integrated PL intensity is found to be between the two temperatures and equals ~720 °C. We connect the variation of the carrier collection efficiency with the modification of the band bending conditions in the investigated structure due to the Fermi level shift in the GaInNAsSb layer after annealing.

The Instrument Set for Generating Fast Adiabatic Passage

The design and construction of a high-performance, low-cost, and easy to assemble adiabatic extension set for homebuilt and commercial spectrometers is described. Described apparatus set was designed for the fast adiabatic passage generation and is based on direct digital synthesizer DDS. This solution gives generator high signal to noise ratio, phase stability even during frequency change which is only possible in expansive commercial high-end hardware. Critical synchronization and timing issues are considered and solutions are discussed. Different experimental conditions and techniques for the measurements are briefly discussed. The proposed system is very flexible and might be used for the measurement of low-frequency nuclear magnetic resonance.