Semi-automated quantification of left ventricular volumes and ejection fraction by real-time three-dimensional echocardiography

<p>Abstract</p> <p>Background</p> <p>Recent studies have shown that real-time three-dimensional (3D) echocardiography (RT3DE) gives more accurate and reproducible left ventricular (LV) volume and ejection fraction (EF) measurements than traditional two-dimensional methods. A new semi-automated tool (4DLVQ) for volume measurements in RT3DE has been developed. We sought to evaluate the accuracy and repeatability of this method compared to a 3D echo standard.</p> <p>Methods</p> <p>LV end-diastolic volumes (EDV), end-systolic volumes (ESV), and EF measured using 4DLVQ were compared with a commercially available semi-automated analysis tool (TomTec 4D LV-Analysis ver. 2.2) in 35 patients. Repeated measurements were performed to investigate inter- and intra-observer variability.</p> <p>Results</p> <p>Average analysis time of the new tool was 141s, significantly shorter than 261s using TomTec (<it>p </it>< 0.001). Bland Altman analysis revealed high agreement of measured EDV, ESV, and EF compared to TomTec (<it>p </it>= <it>NS</it>), with bias and 95% limits of agreement of 2.1 ± 21 ml, -0.88 ± 17 ml, and 1.6 ± 11% for EDV, ESV, and EF respectively. Intra-observer variability of 4DLVQ vs. TomTec was 7.5 ± 6.2 ml vs. 7.7 ± 7.3 ml for EDV, 5.5 ± 5.6 ml vs. 5.0 ± 5.9 ml for ESV, and 3.0 ± 2.7% vs. 2.1 ± 2.0% for EF (<it>p </it>= <it>NS</it>). The inter-observer variability of 4DLVQ vs. TomTec was 9.0 ± 5.9 ml vs. 17 ± 6.3 ml for EDV (<it>p </it>< 0.05), 5.0 ± 3.6 ml vs. 12 ± 7.7 ml for ESV (<it>p </it>< 0.05), and 2.7 ± 2.8% vs. 3.0 ± 2.1% for EF (<it>p </it>= <it>NS</it>).</p> <p>Conclusion</p> <p>In conclusion, the new analysis tool gives rapid and reproducible measurements of LV volumes and EF, with good agreement compared to another RT3DE volume quantification tool.</p

Starting the engine of the powerhouse: mitochondrial transcription and beyond

International audienceMitochondria are central hubs for cellular metabolism, coordinating a variety of metabolic reactions crucial for human health. Mitochondria provide most of the cellular energy via their oxidative phosphorylation (OXPHOS) system, which requires the coordinated expression of genes encoded by both the nuclear (nDNA) and mitochondrial genomes (mtDNA). Transcription of mtDNA is not only essential for the biogenesis of the OXPHOS system, but also generates RNA primers necessary to initiate mtDNA replication. Like the prokaryotic system, mitochondria have no membrane-based compartmentalization to separate the different steps of mtDNA maintenance and expression and depend entirely on nDNA-encoded factors imported into the organelle. Our understanding of mitochondrial transcription in mammalian cells has largely progressed, but the mechanisms regulating mtDNA gene expression are still poorly understood despite their profound importance for human disease. Here, we review mechanisms of mitochondrial gene expression with a focus on the recent findings in the field of mammalian mtDNA transcription and disease phenotypes caused by defects in proteins involved in this process

Mitochondrial phosphoproteomes are functionally specialized across tissues

Mitochondria are essential organelles involved in critical biological processes such as energy metabolism and cell survival. Their dysfunction is linked to numerous human pathologies that often manifest in a tissue-specific manner. Accordingly, mitochondrial fitness depends on versatile proteomes specialized to meet diverse tissue-specific requirements. Furthermore, increasing evidence suggests that phosphorylation may also play an important role in regulating tissue-specific mitochondrial functions and pathophysiology. We hypothesized that recent advances in mass spectrometry (MS)-based proteomics would now enable in-depth measurement to quantitatively profile mitochondrial proteomes along with their matching phosphoproteomes across tissues. We isolated mitochondria from mouse heart, skeletal muscle, brown adipose tissue, kidney, liver, brain, and spleen by differential centrifugation followed by separation on Percoll gradients and high-resolution MS analysis of the proteomes and phosphoproteomes. This in-depth map substantially quantifies known and predicted mitochondrial proteins and provides a resource of core and tissue modulated mitochondrial proteins (mitophos.de). We also uncover tissue-specific repertoires of dozens of kinases and phosphatases. Predicting kinase substrate associations for different mitochondrial compartments indicates tissue-specific regulation at the phosphoproteome level. Illustrating the functional value of our resource, we reproduce mitochondrial phosphorylation events on DRP1 responsible for its mitochondrial recruitment and fission initiation and describe phosphorylation clusters on MIGA2 linked to mitochondrial fusion

IMPACT ON MITOCHONDRIAL FUNCTION BY INCREASED LEVELS OF MITOCHONDRIAL RNA POLYMERASE

International audienc

Regulation of iron metabolism by sideroflexin SFXN1

International audienceThe mitochondrion is at the crossroad of critical metabolic pathways, thus being a crucial player in cell fate in response to stress or infection. The mitochondrion is also an essential organelle for iron metabolism, being the place of heme and iron-sulfur clusters (Fe-S), two co-factors required for mitochondrial respiration. Iron intracellular levels are thus tightly controlled to prevent the accumulation of free ferrous iron that, when in excess, generates oxidative stress and may induce ferroptosis, an iron-dependent regulated cell death (RCD). Ferrous iron will react with ROS and generate, by Fenton reaction, lipids peroxidation. Oxidized lipids accumulation into cellular membranes can be lethal and drives ferroptosis. Ferroptosis, a physiological cell death contributing to tissue homeostasis aging and diseases as neurodegenerative, organ injury. Furthermore a number of tumor suppressors exert part of their tumor-suppression function through the induction of ferroptosis. Sideroflexins (SFXNs) are mitochondrial transporters localized in the inner mitochondrial membrane whose functions are progressively being specified. SFXNs are conserved in eukaryote forming a family of five mitochondrial proteins in mammals. The main function reported to date for Sideroflexin 1 (SFXN1) is to transport serine but SFXN1 may also be involved in iron metabolism. The serine transporter function appears to be conserved between mammalian and yeast. Our project is to study if SFXN1 can regulate cell viability, mitochondrial functions and structure, as well as its role in iron homeostasis and if SFXN1 can modulate cell sensitivity to ferroptosis inducers.References :Kory N, Wyant GA, Prakash G, Uit de Bos J, Bottanelli F, Pacold ME, Chan SH, Lewis CA, Wang T, Keys HR, Guo YE, Sabatini DM. SFXN1 is a mitochondrial serine transporter required for one-carbon metabolism. Science. 2018 Nov 16;362(6416):eaat9528. doi: 10.1126/science.aat9528. PMID: 30442778; PMCID: PMC6300058.Acoba MG, Alpergin ESS, Renuse S, Fernández-Del-Río L, Lu YW, Khalimonchuk O, Clarke CF, Pandey A, Wolfgang MJ, Claypool SM. The mitochondrial carrier SFXN1 is critical for complex III integrity and cellular metabolism. Cell Rep. 2021 Mar 16;34(11):108869. doi: 10.1016/j.celrep.2021.108869. PMID: 33730581; PMCID: PMC8048093.Tifoun N, De Las Heras JM, Guillaume A, Bouleau S, Mignotte B, Le Floch N. Insights into the Roles of the Sideroflexins/SLC56 Family in Iron Homeostasis and Iron-Sulfur Biogenesis. Biomedicines. 2021 Jan 21;9(2):103. doi: 10.3390/biomedicines9020103. PMID: 33494450; PMCID: PMC7911444.Stockwell BR. Ferroptosis turns 10: Emerging mechanisms, physiological functions, and therapeutic applications. Cell. 2022 Jul 7;185(14):2401-2421. doi: 10.1016/j.cell.2022.06.003. PMID: 35803244; PMCID: PMC9273022

Artemisinin and its derivatives target mitochondrial c-type cytochromes in yeast and human cells

[email protected]@i2bc.paris-saclay.frInternational audienceArtemisinin and its derivatives kill malaria parasites and inhibit the proliferation of cancer cells. In both processes, heme was shown to play a key role in artemisinin bioactivation. We found that artemisinin and clinical artemisinin derivatives are able to compensate for a mutation in the yeast Bcs1 protein, a key chaperon involved in biogenesis of the mitochondrial respiratory complex III. The equivalent Bcs1 variant causes an encephalopathy in human by affecting complex III assembly. We show that artemisinin derivatives decrease the content of mitochondrial cytochromes and disturb the maturation of the complex III cytochrome c1. This last effect is likely responsible for the compensation by decreasing the detrimental over-accumulation of the inactive pre-complex III observed in the bcs1 mutant. We further show that a fluorescent dihydroartemisinin probe rapidly accumulates in the mitochondrial network and targets cytochromes c and c1 in yeast, human cells and isolated mitochondria. In vitro this probe interacts with purified cytochrome c only under reducing conditions and we detected cytochrome c-dihydroartemisinin covalent adducts by mass spectrometry analyses. We propose that reduced mitochondrial c-type cytochromes act as both targets and mediators of artemisinin bioactivation in yeast and human cells