Browsing by Author "Eimre, Margus"

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    Adaptation of striated muscles to Wolframin deficiency in mice: Alterations in cellular bioenergetics
    (Elsevier, 2020-01-11) Tepp, Kersti; Puurand, Marju; Timohhina, Natalja; Aid-Vanakova, Jekaterina; Reile, Indrek; Shevchuk, Igor; Chekulayev, Vladimir; Eimre, Margus; Peet, Nadežda; Kadaja, Lumme; Paju, Kalju; Käämbre, Tuuli
    Background: Wolfram syndrome (WS), caused by mutations in WFS1 gene, is a multi-targeting disease affecting multiple organ systems. Wolframin is localized in the membrane of the endoplasmic reticulum (ER), influencing Ca2+ metabolism and ER interaction with mitochondria, but the exact role of the protein remains unclear. In this study we aimed to characterize alterations in energy metabolism in the cardiac and in the oxidative and glycolytic skeletal muscles in Wfs1-deficiency. Methods: Alterations in the bioenergetic profiles in the cardiac and skeletal muscles of Wfs1-knock-out (KO) male mice and their wild type male littermates were determined using high resolution respirometry, quantitative RT-PCR, NMR spectroscopy, and immunofluorescence confocal microscopy. Results: Oxygen consumption without ATP synthase activation (leak) was significantly higher in the glycolytic muscles of Wfs1 KO mice compared to wild types. ADP-stimulated respiration with glutamate and malate was reduced in the Wfs1-deficient cardiac as well as oxidative and glycolytic skeletal muscles. Conclusions: Wfs1-deficiency in both cardiac and skeletal muscles results in functional alterations of energy transport from mitochondria to ATP-ases. There was a substrate-dependent decrease in the maximal Complex I –linked respiratory capacity of the electron transport system in muscles of Wfs1 KO mice. Moreover, in cardiac and gastrocnemius white muscles a decrease in the function of one pathway were balanced by the increase in the activity of the parallel pathway. General significance: This work provides new insights to the muscle involvement at early stages of metabolic syndrome like WS as well as developing glucose intolerance
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    Organization of energy transfer and feedback regulation in oxidative muscle cells
    (2009-03-10T13:34:34Z) Eimre, Margus
    Recently, it has been hypothesized that in oxidative muscle cells the mitochondria and ATPases form tight complexes, termed as the intracellular energetic units (ICEUs). At present the structure and molecular basis of the ICEUs are unclear and therefore an object of active research. Aims of the study: 1) To assess influence of alteration of the intracellular structure on mentioned units by hypercontraction in normal cardiomyocytes and in HL-1 cells, 2) to confirm existence of ICEUs by mathematical modeling of real experimental data, 3) to investigate whether ICEUs exist also in human heart atrium and in musculus gluteus medius (MGM), 4) to investigate whether these units may in MGM disintegrate during osteoarthritis. Results of the study: Differently from cardiomyocytes, where mitochondria and CaMgATPases are organized into ICEUs which ensure effective energy transfer and feedback signaling between these structures via specialized pathways mediated by CK and AK isoforms and direct adenine nucleotide channeling, the ICEUs do not exist in HL-1 cells due to less organized energy metabolism. Ca2+-induced hypercontraction leads in normal cardiomyocytes to the decreased direct transfer of ADP from ATPases to the mitochondria, thus to impairment of ICEU function. Mathematical modelling shows that in oxidative muscle cells diffusion restrictions of metabolites are not distributed uniformly within cardiac muscles, but are localized in certain areas, which supports the ICEU hypothesis. Energy metabolism in human atria and MGM cells is organized similarly to that in oxidative muscles − in the form of the ICEUs. Pathogenesis of OA involves disintegration of the ICEUs in association with dysfunction of CK-phosphotransfer system and increased diffusion of exogenous ADP to mitochondria. Hiljuti püstitati hüpotees, mille kohaselt oksüdatiivsetes lihasrakkudes moodustavad mitokondrid ja ATPaasid komplekse, e. rakusiseseid energeetilisi üksusi (RSEÜd). Praeguseks pole veel selge nende komplekside struktuuriline ja molekulaarne olemus, mis on seetõttu aktiivse uurimise objektiks. Töö eesmärgid: 1) Hinnata rakusiseste struktuurimuutuste toimet nimetud üksustele normaalsetes südamelihaskiududes hüperkontraktsiooni toimel ja HL-1 südamelihasrakkudes, 2) kinnitada RSEÜ-de olemasolu ka reaalsete eksperimenditulemuste matemaatilise modeleerimise abil, 3) uurida, kas RSEÜ-d eksisteerivad ka inimese südame kojas ja musculus gluteus medius-es (MGM) ning 4) kas nad võivad MGM-es osteoartriidi korral laguneda. Töö tulemused: Erinevalt südamelihasrakkudest, kus mitokondrid ja ATPaasid on organiseeritud RSEÜ-desse, mis kindlustavad efektiivse energia ülekande ja tagasiside nende struktuuride vahel otsese adeniinnukleotiidide ülekande teel ning kreatiinkinaasi ja adenülaatkinaasi isoensüümide vahendusel, puuduvad need üksüsed HL-1 rakkudes vähem organiseeritud energeetilise metabolismi tõttu. Ca2+ poolt põhjustatud hüperkontraktsioon põhjustab normaalsetes südamelihasrakkudes otsese adeniinukleotiidide ülekande nõrgenemise, seega RSEÜde funktsiooni häirumise. Reaalsete eksperimendiandmete matemaatiline modelleerimine näitab, et metaboliitide difusioonitakistused pole jaotunud oksüdatiivses lihasrakus ühtlaselt vaid on lokaliseerunud, mis toetab seega RSEÜ hüpoteesi. Energeetiline metabolism inimese südame kojas ja MGM-es on organiseeritud sarnaselt oksüdatiivsetele lihastele RSEÜde vormis. Osteoartroosi patogenees hõlmab RSEÜ-de osalist lagunemist, mis peegeldub kretiinkinaasse energiaülekande nõrgenemises ja eksogeense ADP suurenenud difusioonis mitokondrisse.