Antidepressive-like Behavior-Related Metabolomic Signatures of Sigma-1 Receptor Knockout Mice

Sigma-1 receptor (Sig1R) has been proposed as a therapeutic target for neurological, neu-rodegenerative, and psychiatric disorders, including depression and anxiety. Identifying metabolites that are affected by Sig1R absence and cross-referencing them with specific mood-related behaviors would be helpful for the development of new therapies for Sig1R-associated disorders. Here, we examined metabolic profiles in the blood and brains of male CD-1 background Sig1R knockout (KO) mice in adulthood and old age and correlated them with the assessment of depression-and anxiety-related behaviors. The most pronounced changes in the metabolic profile were observed in the plasma of adult Sig1R KO mice. In adult mice, the absence of Sig1R significantly influenced the amino acid, sphingolipid (sphingomyelin and ceramide (18:1)), and serotonin metabolic pathways. There were higher serotonin levels in plasma and brain tissue and higher histamine levels in the plasma of Sig1R KO mice than in their age-matched wild-type counterparts. This increase correlated with the reduced behavioral despair in the tail suspension test and lack of anhedonia in the sucrose preference test. Overall, these results suggest that Sig1R regulates behavior by altering serotonergic and histaminergic systems and the sphingolipid metabolic pathway. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.This research was supported by the ERDF project 1.1.1.2/VIAA/1/16/244 “The role of sigma-1 receptor in sexual behavior”; Institute of Solid State Physics, University of Latvia as the Center of Excellence acknowledges funding from the European Union’s Horizon 2020 Framework Programme H2020- WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Inhibition of Fatty Acid Metabolism Increases EPA and DHA Levels and Protects against Myocardial Ischaemia-Reperfusion Injury in Zucker Rats

Publisher Copyright: © 2021 Janis Kuka et al.Long-chain ω-3 polyunsaturated fatty acids (PUFAs) are known to induce cardiometabolic benefits, but the metabolic pathways of their biosynthesis ensuring sufficient bioavailability require further investigation. Here, we show that a pharmacological decrease in overall fatty acid utilization promotes an increase in the levels of PUFAs and attenuates cardiometabolic disturbances in a Zucker rat metabolic syndrome model. Metabolome analysis showed that inhibition of fatty acid utilization by methyl-GBB increased the concentration of PUFAs but not the total fatty acid levels in plasma. Insulin sensitivity was improved, and the plasma insulin concentration was decreased. Overall, pharmacological modulation of fatty acid handling preserved cardiac glucose and pyruvate oxidation, protected mitochondrial functionality by decreasing long-chain acylcarnitine levels, and decreased myocardial infarct size twofold. Our work shows that partial pharmacological inhibition of fatty acid oxidation is a novel approach to selectively increase the levels of PUFAs and modulate lipid handling to prevent cardiometabolic disturbances.publishersversionPeer reviewe

Genetic inactivation of the sigma-1 chaperone protein results in decreased expression of the R2 subunit of the GABA-B receptor and increased susceptibility to seizures

Funding Information: This study was supported by European Regional Development Fund Project No. 1.1.1.2/VIAA/2/18/376 (PostDoc Latvia), “Sigma chaperone protein as a novel drug target”. We thank Laboratorios Dr. Esteve, S.A. (Barcelona, Spain) for providing CD-1 background sigma-1 receptor knockout mice. We thank Associate Professors Inga Kadisha and Thomas van Groen (University of Alabama at Birmingham, Birmingham, Alabama, USA) for fruitful discussions regarding immunohistochemistry. We also thank Dr. biol. Dace Pjanova (Latvian Biomedical Research and Study Centre, Riga, Latvia) for the help with confocal imaging and Abberior Instruments (Göttingen, Germany) for a kind gift of fluorescently labeled Abberior STAR antibodies. Publisher Copyright: © 2020 The Author(s)There is a growing body of evidence demonstrating the significant involvement of the sigma-1 chaperone protein in the modulation of seizures. Several sigma-1 receptor (Sig1R) ligands have been demonstrated to regulate the seizure threshold in acute and chronic seizure models. However, the mechanism by which Sig1R modulates the excitatory and inhibitory pathways in the brain has not been elucidated. The aim of this study was to compare the susceptibility to seizures of wild type (WT) and Sig1R knockout (Sig1R−/−) mice in intravenous pentylenetetrazol (PTZ) and (+)-bicuculline (BIC) infusion-induced acute seizure and Sig1R antagonist NE-100-induced seizure models. To determine possible molecular mechanisms, we used quantitative PCR, Western blotting and immunohistochemistry to assess the possible involvement of several seizure-related genes and proteins. Peripheral tissue contractile response of WT and Sig1R−/− mice was studied in an isolated vasa deferentia model. The most important finding was the significantly decreased expression of the R2 subunit of the GABA-B receptor in the hippocampus and habenula of Sig1R−/− mice. Our results demonstrated that Sig1R−/− mice have decreased thresholds for PTZ- and BIC-induced tonic seizures. In the NE-100-induced seizure model, Sig1R−/− animals demonstrated lower seizure scores, shorter durations and increased latency times of seizures compared to WT mice. Sig1R-independent activities of NE-100 included downregulation of the gene expression of iNOS and GABA-A γ2 and inhibition of KCl-induced depolarization in both WT and Sig1R−/− animals. In conclusion, the results of this study indicate that the lack of Sig1R resulted in decreased expression of the R2 subunit of the GABA-B receptor and increased susceptibility to seizures. Our results confirm that Sig1R is a significant molecular target for seizure modulation and warrants further investigation for the development of novel anti-seizure drugs.publishersversionPeer reviewe

Heart-Type Fatty Acid Binding Protein Binds Long-Chain Acylcarnitines and Protects against Lipotoxicity

Funding Information: This research was funded by the European Union’s Horizon 2020 research and innovation program project FAT4BRAIN under grant agreement No. 857394 and by Latvian Institute of Organic Synthesis internal student grants IG-2022-04 and IG-2023-04 (to D.Z.-G.). Publisher Copyright: © 2023 by the authors.Heart-type fatty-acid binding protein (FABP3) is an essential cytosolic lipid transport protein found in cardiomyocytes. FABP3 binds fatty acids (FAs) reversibly and with high affinity. Acylcarnitines (ACs) are an esterified form of FAs that play an important role in cellular energy metabolism. However, an increased concentration of ACs can exert detrimental effects on cardiac mitochondria and lead to severe cardiac damage. In the present study, we evaluated the ability of FABP3 to bind long-chain ACs (LCACs) and protect cells from their harmful effects. We characterized the novel binding mechanism between FABP3 and LCACs by a cytotoxicity assay, nuclear magnetic resonance, and isothermal titration calorimetry. Our data demonstrate that FABP3 is capable of binding both FAs and LCACs as well as decreasing the cytotoxicity of LCACs. Our findings reveal that LCACs and FAs compete for the binding site of FABP3. Thus, the protective mechanism of FABP3 is found to be concentration dependent.publishersversionPeer reviewe

Protective effects of meldonium in experimental models of cardiovascular complications with a potential application in COVID‐19

Funding Information: This study was supported by the Latvian State Research Program project VPP?COVID? 2020/1?0014 ?Towards new therapeutic and prophylactic treatments against Covid?19 and corona-viruses?. Dana Kigitovica received Doctoral study grant from Riga Stradins University. Funding Information: Funding: This study was supported by the Latvian State Research Program project VPP‐COVID‐ 2020/1‐0014 ʺTowards new therapeutic and prophylactic treatments against Covid‐19 and corona‐ virusesʺ. Dana Kigitovica received Doctoral study grant from Riga Stradins University. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Right ventricular (RV) and left ventricular (LV) dysfunction is common in a significant number of hospitalized coronavirus disease 2019 (COVID‐19) patients. This study was conducted to assess whether the improved mitochondrial bioenergetics by cardiometabolic drug meldonium can attenuate the development of ventricular dysfunction in experimental RV and LV dysfunction models, which resemble ventricular dysfunction in COVID‐19 patients. Effects of meldonium were assessed in rats with pulmonary hypertension‐induced RV failure and in mice with inflammation-induced LV dysfunction. Rats with RV failure showed decreased RV fractional area change (RVFAC) and hypertrophy. Treatment with meldonium attenuated the development of RV hyper-trophy and increased RVFAC by 50%. Mice with inflammation‐induced LV dysfunction had decreased LV ejection fraction (LVEF) by 30%. Treatment with meldonium prevented the decrease in LVEF. A decrease in the mitochondrial fatty acid oxidation with a concomitant increase in pyruvate metabolism was noted in the cardiac fibers of the rats and mice with RV and LV failure, respectively. Meldonium treatment in both models restored mitochondrial bioenergetics. The results show that meldonium treatment prevents the development of RV and LV systolic dysfunction by enhancing mitochondrial function in experimental models of ventricular dysfunction that resembles cardiovascular complications in COVID‐19 patients.publishersversionPeer reviewe

Acute and long-term administration of palmitoylcarnitine induces muscle-specific insulin resistance in mice

Publisher Copyright: © 2017 The Authors BioFactors published by Wiley Periodicals, Inc. on behalf of International Union of Biochemistry and Molecular BiologyAcylcarnitine accumulation has been linked to perturbations in energy metabolism pathways. In this study, we demonstrate that long-chain (LC) acylcarnitines are active metabolites involved in the regulation of glucose metabolism in vivo. Single-dose administration of palmitoylcarnitine (PC) in fed mice induced marked insulin insensitivity, decreased glucose uptake in muscles, and elevated blood glucose levels. Increase in the content of LC acylcarnitine induced insulin resistance by impairing Akt phosphorylation at Ser473. The long-term administration of PC using slow-release osmotic minipumps induced marked hyperinsulinemia, insulin resistance, and glucose intolerance, suggesting that the permanent accumulation of LC acylcarnitines can accelerate the progression of insulin resistance. The decrease of acylcarnitine content significantly improved glucose tolerance in a mouse model of diet-induced glucose intolerance. In conclusion, we show that the physiological increase in content of acylcarnitines ensures the transition from a fed to fasted state in order to limit glucose metabolism in the fasted state. In the fed state, the inability of insulin to inhibit LC acylcarnitine production induces disturbances in glucose uptake and metabolism. The reduction of acylcarnitine content could be an effective strategy to improve insulin sensitivity.publishersversionPeer reviewe

Low cardiac content of long-chain acylcarnitines in TMLHE knockout mice prevents ischaemia-reperfusion-induced mitochondrial and cardiac damage

Copyright © 2021. Published by Elsevier Inc.Increased tissue content of long-chain acylcarnitines may induce mitochondrial and cardiac damage by stimulating ROS production. N6-trimethyllysine dioxygenase (TMLD) is the first enzyme in the carnitine/acylcarnitine biosynthesis pathway. Inactivation of the TMLHE gene (TMLHE KO) in mice is expected to limit long-chain acylcarnitine synthesis and thus induce a cardio- and mitochondria-protective phenotype. TMLHE gene deletion in male mice lowered acylcarnitine concentrations in blood and cardiac tissues by up to 85% and decreased fatty acid oxidation by 30% but did not affect muscle and heart function in mice. Metabolome profile analysis revealed increased levels of polyunsaturated fatty acids (PUFAs) and a global shift in fatty acid content from saturated to unsaturated lipids. In the risk area of ischemic hearts in TMLHE KO mouse, the OXPHOS-dependent respiration rate and OXPHOS coupling efficiency were fully preserved. Additionally, the decreased long-chain acylcarnitine synthesis rate in TMLHE KO mice prevented ischaemia-reperfusion-induced ROS production in cardiac mitochondria. This was associated with a 39% smaller infarct size in the TMLHE KO mice. The arrest of the acylcarnitine biosynthesis pathway in TMLHE KO mice prevents ischaemia-reperfusion-induced damage in cardiac mitochondria and decreases infarct size. These results confirm that the decreased accumulation of ROS-increasing fatty acid metabolism intermediates prevents mitochondrial and cardiac damage during ischaemia-reperfusion.publishersversionPeer reviewe

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Long-Chain Acylcarnitines Decrease the Phosphorylation of the Insulin Receptor at Tyr1151 Through a PTP1B-Dependent Mechanism

The accumulation of lipid intermediates may interfere with energy metabolism pathways and regulate cellular energy supplies. As increased levels of long-chain acylcarnitines have been linked to insulin resistance, we investigated the effects of long-chain acylcarnitines on key components of the insulin signalling pathway. We discovered that palmitoylcarnitine induces dephosphorylation of the insulin receptor (InsR) through increased activity of protein tyrosine phosphatase 1B (PTP1B). Palmitoylcarnitine suppresses protein kinase B (Akt) phosphorylation at Ser473, and this effect is not alleviated by the inhibition of PTP1B by the insulin sensitizer bis-(maltolato)-oxovanadium (IV). This result indicates that palmitoylcarnitine affects Akt activity independently of the InsR phosphorylation level. Inhibition of protein kinase C and protein phosphatase 2A does not affect the palmitoylcarnitine-mediated inhibition of Akt Ser473 phosphorylation. Additionally, palmitoylcarnitine markedly stimulates insulin release by suppressing Akt Ser473 phosphorylation in insulin-secreting RIN5F cells. In conclusion, long-chain acylcarnitines activate PTP1B and decrease InsR Tyr1151 phosphorylation and Akt Ser473 phosphorylation, thus limiting the cellular response to insulin stimulation