Function Of Subcellular Organelles Research Articles

HCMV strain- and cell type-specific alterations in membrane contact sites point to the convergent regulation of organelle remodeling.

Viruses are ubiquitous entities that infect organisms across the kingdoms of life. While viruses can infect a range of cells, tissues, and organisms, this aspect is often not explored in cell culture analyses. There is limited information about which infection-induced changes are shared or distinct in different cellular environments. The prevalent pathogen human cytomegalovirus (HCMV) remodels the structure and function of subcellular organelles and their interconnected networks formed by membrane contact sites (MCSs). A large portion of this knowledge has been derived from fibroblasts infected with a lab-adapted HCMV strain. Here, we assess strain- and cell type-specific alterations in MCSs and organelle remodeling induced by HCMV. Integrating quantitative mass spectrometry, super-resolution microscopy, and molecular virology assays, we compare infections with lab-adapted and low-passage HCMV strains in fibroblast and epithelial cells. We determine that, despite baseline proteome disparities between uninfected fibroblast and epithelial cells, infection induces convergent changes and is remarkably similar. We show that hallmarks of HCMV infection in fibroblasts, mitochondria-endoplasmic reticulum (ER) encapsulations and peroxisome proliferation, are also conserved in infected epithelial and macrophage-like cells. Exploring cell type-specific differences, we demonstrate that fibroblasts rely on endosomal cholesterol transport while epithelial cells rely on cholesterol from the Golgi. Despite these mechanistic differences, infections in both cell types result in phenotypically similar cholesterol accumulation at the viral assembly complex. Our findings highlight the adaptability of HCMV, in that infections can be tailored to the initial cell state by inducing both shared and unique proteome alterations, ultimately promoting a unified pro-viral environment.IMPORTANCEHuman cytomegalovirus (HCMV) establishes infections in diverse cell types throughout the body and is connected to a litany of diseases associated with each of these tissues. However, it is still not fully understood how HCMV replication varies in distinct cell types. Here, we compare HCMV replication with lab-adapted and low-passage strains in two primary sites of infection, lung fibroblasts and retinal epithelial cells. We discover that, despite displaying disparate protein compositions prior to infection, these cell types undergo convergent alterations upon HCMV infection, reaching a more similar cellular state late in infection. We find that remodeling of the subcellular landscape is a pervasive feature of HCMV infection, through alterations to both organelle structure-function and the interconnected networks they form via membrane contact sites. Our findings show how HCMV infection in different cell types induces both shared and divergent changes to cellular processes, ultimately leading to a more unified state.

Emerging field: O-GlcNAcylation in ferroptosis.

In 2012, researchers proposed a non-apoptotic, iron-dependent form of cell death caused by lipid peroxidation called ferroptosis. During the past decade, a comprehensive understanding of ferroptosis has emerged. Ferroptosis is closely associated with the tumor microenvironment, cancer, immunity, aging, and tissue damage. Its mechanism is precisely regulated at the epigenetic, transcriptional, and post-translational levels. O-GlcNAc modification (O-GlcNAcylation) is one of the post-translational modifications of proteins. Cells can modulate cell survival in response to stress stimuli, including apoptosis, necrosis, and autophagy, through adaptive regulation by O-GlcNAcylation. However, the function and mechanism of these modifications in regulating ferroptosis are only beginning to be understood. Here, we review the relevant literature within the last 5years and present the current understanding of the regulatory function of O-GlcNAcylation in ferroptosis and the potential mechanisms that may be involved, including antioxidant defense system-controlled reactive oxygen species biology, iron metabolism, and membrane lipid peroxidation metabolism. In addition to these three areas of ferroptosis research, we examine how changes in the morphology and function of subcellular organelles (e.g., mitochondria and endoplasmic reticulum) involved in O-GlcNAcylation may trigger and amplify ferroptosis. We have dissected the role of O-GlcNAcylation in regulating ferroptosis and hope that our introduction will provide a general framework for those interested in this field.

Advances in mitochondrial medicine and translational research

Current knowledge of mitochondrial biology and function has provided tools and technologies that helped a better understanding of the molecular etiology of complex mitochondrial disorders. Dual genetic control of this subcellular organelle function regulates various signaling mechanisms which are essential for metabolism, bioenergetics, fatty acid biosynthesis, and DNA replication & repair. Understanding nuclear mitochondrial crosstalk through advanced genomics as well as clinical perspectives is the overall basis of mitochondrial research and medicine, also the sole objective of Society for Mitochondrial Medicine and Research (SMRM) - India. The eighth virtual international conference on ‘Advances in Mitochondrial Medicine and Translational Research’ was organized at the Manipal School of Life Sciences, MAHE, Manipal, India, during 6 – 7 November 2020. The aim of the virtual conference was to highlight the recent advances and future perspectives that represent comprehensive clinical and fundamental research interests in the area of mitochondrial biology of human diseases. To systematically present the various findings in mitochondrial biology, the meeting was themed with specific aspects comprising (a) mitochondrial disorders: clinical & genomic perspectives, (b) mitochondria in cancer, (c) mitochondrial metabolism & disorders, and (d) mitochondrial diseases & therapy. This report provides an overview of the recent advancements in the area of mitochondrial biology and medicine that was discussed at the conference.

WITHDRAWN: Advances in mitochondrial medicine and translational research

Current knowledge of mitochondrial biology and function has provided with tools and technologies that helped a better understanding of the molecular etiology of complex mitochondrial disorders. Dual genetic control of this subcellular organelle function regulates various signaling mechanisms which are essential for metabolism, bioenergetics, fatty acid biosynthesis, and DNA replication & repair. Understanding nuclear mitochondrial crosstalk through advanced genomics as well as clinical perspectives is the overall basis of mitochondrial research and medicine, also the sole objective of Society for Mitochondrial Medicine and Research (SMRM) - India. The eighth virtual international conference on 'Advances in Mitochondrial Medicine and Translational Research' was organized at the Manipal School of Life Sciences, MAHE, Manipal, India, during 6 - 7 November 2020. The aim of the virtual conference was to highlight the recent advances and future perspectives that represent comprehensive clinical and fundamental research interests in the area of mitochondrial biology of human diseases. To systematically present the various findings in mitochondrial biology, the meeting was themed with specific aspects comprising (a) mitochondrial disorders: clinical & genomic perspectives, (b) mitochondria in cancer, (c) mitochondrial metabolism & disorders, and (d) mitochondrial diseases & therapy. This report provides an overview of the recent advancements in the area of mitochondrial biology and medicine that was discussed at the conference.

Fatty Acid Synthase: An Emerging Target in Cancer.

In recent years, lipid metabolism has garnered significant attention as it provides the necessary building blocks required to sustain tumor growth and serves as an alternative fuel source for ATP generation. Fatty acid synthase (FASN) functions as a central regulator of lipid metabolism and plays a critical role in the growth and survival of tumors with lipogenic phenotypes. Accumulating evidence has shown that it is capable of rewiring tumor cells for greater energy flexibility to attain their high energy requirements. This multi-enzyme protein is capable of modulating the function of subcellular organelles for optimal function under different conditions. Apart from lipid metabolism, FASN has functional roles in other cellular processes such as glycolysis and amino acid metabolism. These pivotal roles of FASN in lipid metabolism make it an attractive target in the clinic with several new inhibitors currently being tested in early clinical trials. This article aims to present the current evidence on the emergence of FASN as a target in human malignancies.

Mechanisms for the transition from physiological to pathological cardiac hypertrophy.

The heart is capable of responding to stressful situations by increasing muscle mass, which is broadly defined as cardiac hypertrophy. This phenomenon minimizes ventricular wall stress for the heart undergoing a greater than normal workload. At initial stages, cardiac hypertrophy is associated with normal or enhanced cardiac function and is considered to be adaptive or physiological; however, at later stages, if the stimulus is not removed, it is associated with contractile dysfunction and is termed as pathological cardiac hypertrophy. It is during physiological cardiac hypertrophy where the function of subcellular organelles, including the sarcolemma, sarcoplasmic reticulum, mitochondria, and myofibrils, may be upregulated, while pathological cardiac hypertrophy is associated with downregulation of these subcellular activities. The transition of physiological cardiac hypertrophy to pathological cardiac hypertrophy may be due to the reduction in blood supply to hypertrophied myocardium as a consequence of reduced capillary density. Oxidative stress, inflammatory processes, Ca2+-handling abnormalities, and apoptosis in cardiomyocytes are suggested to play a critical role in the depression of contractile function during the development of pathological hypertrophy.

Hybrid experimental‐mathematical methods for probing dynamic proteome organization during viral infections

Every year, a major cause of human disease and death worldwide is infection with the various viral pathogens that are intrinsic to our ecosystem. The outcomes of viral infections derive from dynamic virus‐host cell interactions that function either in promoting virus replication or in host defense against invading pathogens. An essential component of these virus‐host interactions is spatial organization. Eukaryotic viruses replicate within highly organized host cells that compartmentalize their vast cellular proteomes within organelles. Alterations in organelle shape, composition, function, and dynamics are prominent features of virus replication cycles, although the knowledge of the mechanisms involved remains limited.This presentation will describe the integration of experimental studies, mathematical modeling and inference methods for understanding the dynamic regulation of organelles during viral infection. The experimental methods presented will include live‐cell microscopy and quantitative mass spectrometry‐based proteomics for characterizing both organelle changes and virus‐host protein interactions during the progression of an infection. These studies discovered 1) dynamic changes in organelle composition, 2) translocation of cellular proteins from one subcellular compartment to another, and 3) temporal virus‐host protein interactions within organelles that induce alterations in host biological pathways (Figure 1).The value of these integrative methods is demonstrated by the identification of mechanisms through which viruses remodel subcellular organelle function to suppress host defense and promote viral replication. Furthermore, our findings are starting to uncover how viruses regulate the dynamics of organelle biogenesis during infection. Overall, these studies highlight how integrative omic technologies can help paint a picture of the pathogen's life cycle and aid in the future development of antiviral therapies.Support or Funding InformationNIH grants GM114141 and HL127640, and Mallinckrodt Scholar AwardThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

β-Amyloid and the Pathomechanisms of Alzheimer's Disease: A Comprehensive View.

Protein dyshomeostasis is the common mechanism of neurodegenerative diseases such as Alzheimer’s disease (AD). Aging is the key risk factor, as the capacity of the proteostasis network declines during aging. Different cellular stress conditions result in the up-regulation of the neurotrophic, neuroprotective amyloid precursor protein (APP). Enzymatic processing of APP may result in formation of toxic Aβ aggregates (β-amyloids). Protein folding is the basis of life and death. Intracellular Aβ affects the function of subcellular organelles by disturbing the endoplasmic reticulum-mitochondria cross-talk and causing severe Ca2+-dysregulation and lipid dyshomeostasis. The extensive and complex network of proteostasis declines during aging and is not able to maintain the balance between production and disposal of proteins. The effectivity of cellular pathways that safeguard cells against proteotoxic stress (molecular chaperones, aggresomes, the ubiquitin-proteasome system, autophagy) declines with age. Chronic cerebral hypoperfusion causes dysfunction of the blood-brain barrier (BBB), and thus the Aβ-clearance from brain-to-blood decreases. Microglia-mediated clearance of Aβ also declines, Aβ accumulates in the brain and causes neuroinflammation. Recognition of the above mentioned complex pathogenesis pathway resulted in novel drug targets in AD research.

3D membrane segmentation and quantification of intact thick cells using cryo soft X-ray transmission microscopy: A pilot study.

Structural analysis of biological membranes is important for understanding cell and sub-cellular organelle function as well as their interaction with the surrounding environment. Imaging of whole cells in three dimension at high spatial resolution remains a significant challenge, particularly for thick cells. Cryo-transmission soft X-ray microscopy (cryo-TXM) has recently gained popularity to image, in 3D, intact thick cells (∼10μm) with details of sub-cellular architecture and organization in near-native state. This paper reports a new tool to segment and quantify structural changes of biological membranes in 3D from cryo-TXM images by tracking an initial 2D contour along the third axis of the microscope, through a multi-scale ridge detection followed by an active contours-based model, with a subsequent refinement along the other two axes. A quantitative metric that assesses the grayscale profiles perpendicular to the membrane surfaces is introduced and shown to be linearly related to the membrane thickness. Our methodology has been validated on synthetic phantoms using realistic microscope properties and structure dimensions, as well as on real cryo-TXM data. Results demonstrate the validity of our algorithms for cryo-TXM data analysis.

Living cell intracellular temperature imaging with biocompatible dye-conjugated carbon dots.

Within living cells, the biological functions of subcellular organelles are highly dependent on the distribution of local temperature. In this regard, sensitive and accurate measurement of cellular temperature with subcellular resolution is fundamentally and practically significant. In this work, we demonstrated a fluorescence-based self-calibration method for the quantitative analysis of living cell temperature. A ratiometric temperature sensor was designed by conjugating a temperature sensitive dye, Rhodamine B (RhB), with biocompatible carbon dots (CDs) via a covalent bond. The as-prepared CDs-RhB probe showed excellent ratiometric temperature sensing capability in solution under a single wavelength excitation and displayed a linear temperature sensing range from 5 to 50 °C, which matches the requirement well for the physiologically relevant temperature assay. Furthermore, this probe was applied to map intracellular temperature inside living cells. The fast and accurate temperature response of the probe makes it a promising tool for monitoring the intracellular temperature change, which will promote a better understanding of the temperature relevant biological processes inside living cells.

Etiology and management of dyslipidemia in children with chronic kidney disease and end-stage renal disease.

Lipids are essential components of cell membranes, contributing to cell fuel, myelin formation, subcellular organelle function, and steroid hormone synthesis. Children with chronic kidney disease (CKD) and end-stage renal disease (ESRD) exhibit various co-morbidities, including dyslipidemia. The prevalence of dyslipidemias in children with CKD and ESRD is high, being present in 39-65% of patients. Elevated lipid levels in children without renal disease are a risk factor for cardiovascular disease (CVD), while the risk for CVD in pediatric CKD/ESRD is unclear. The pathogenesis of dyslipidemia in CKD features various factors, including increased levels of triglycerides, triglyceride-rich lipoproteins, apolipoprotein C3 (ApoC-III), decreased levels of cholesterylester transfer protein and high-density lipoproteins, and aberrations in serum very low-density and intermediate-density lipoproteins. If initial risk assessment indicates that a child with advanced CKD has 2 or more co-morbidities for CVD, first-line treatment should consist of non-pharmacologic management such as therapeutic lifestyle changes and dietary counseling. Pharmacologic treatment of dyslipidemia may reduce the incidence of CVD in children with CKD/ESRD, but randomized trials are lacking. Statins are the only class of lipid-lowering drugs currently approved by the U.S. Food and Drug Administration (FDA) for use in the pediatric population. FDA-approved pediatric labeling for these drugs is based on results from placebo-controlled trial results, showing 30-50% reductions in baseline low-density lipoprotein cholesterol. Although statins are generally well tolerated in adults, a spectrum of adverse events has been reported with their use in both the clinical trial and post-marketing settings.

Analytical tools for characterizing heterogeneity in organelle content

Heterogeneity in the content and function of subcellular organelles on the intercellular and intracellular level plays an important role in determining cell fate. These variations extend to normal-state and disease-state cellular functions and responses to environmental stimuli, such as oxidative stress and therapeutic drugs. Analytical tools to characterize variation in all types of organelles are essential to provide insights that can lead to advances in medicine, such as therapies targeted to specific subcellular regions. In this review, we discuss analytical techniques for interrogating individual intact organelles (e.g. mitochondria and synaptic vesicles) and lysates in a high-throughput manner, including a recently developed nanoscale fluorescence-activated subcellular sorter and techniques based on capillary electrophoresis with laser-induced fluorescence detection. We then highlight the advantages that droplet microfluidics offers for probing subcellular heterogeneity.

Nanoparticles and cells: good companions and doomed partnerships

Engineered nanoparticles are emerging as useful tools for different purposes in life sciences, medicine and agriculture. Nanomedicine, an emerging discipline, involves the application of nanotechnology (usually regarded within the size range of 1-1000 nm) in the design of systems and devices that can facilitate our understanding of disease pathophysiology, nano-imaging, nanomedicines and nano-diagnostics. Among the different nanomaterials used to construct nanoparticles, are organic polymers, co-polymers and metals. Some of these materials can self assemble, and depending on the conditions under which the self-assembly process occurs, a vast array of shapes can be formed. Frequently, the nanoparticle morphology is spherical or tubular, mimicking the shape, but thus far, not the functions of subcellular organelles. We discuss here several representative nanoparticles, made of block copolymers and metals, highlighting some of their current uses, advantages and limitations in medicine. Nano-oncology and nano-neurosciences will also be discussed in more detail in the context of the intracellular fate of nanoparticles and possible long-term consequences on cell functions.

An N-terminally acetylated Arf-like GTPase is localised to lysosomes and affects their motility

Small GTPases of the Arf and Rab families play key roles in the function of subcellular organelles. Each GTPase is usually found on only one compartment and, hence, they confer organelle specificity to many intracellular processes. However, there has so far been little evidence for specific GTPases present on lysosomes. Here, we report that two closely related human Arf-like GTPases, Arl8a and Arl8b (also known as Arl10b/c and Gie1/2), localise to lysosomes in mammalian cells, with the single homologue in Drosophila cells having a similar location. Conventionally, membrane binding of Arf and Arl proteins is mediated by both an N-terminal myristoyl group and an N-terminal amphipathic helix that is inserted into the lipid bilayer upon activation of the GTPase. Arl8a and Arl8b do not have N-terminal myristoylation sites, and we find that Arl8b is instead N-terminally acetylated, and an acetylated methionine is necessary for its lysosomal localization. Overexpression of Arl8a or Arl8b results in a microtubule-dependent redistribution of lysosomes towards the cell periphery. Live cell imaging shows that lysosomes move more frequently both toward and away from the cell periphery, suggesting a role for Arl8a and Arl8b as positive regulators of lysosomal transport.

2D LC/MS Analysis of Membrane Proteins from Breast Cancer Cell Lines MCF7 and BT474

Membrane proteins play a central role in the interaction of the cell with its environment and in the function of subcellular organelles. The current study focused on developing a better understanding of the membrane proteome of two well-characterized breast cancer cell lines. Membranes from osmotically lysed BT474 and MCF7 cells were treated with cyanogen bromide followed by a combination of trypsin and Staphylococcus V8 protease to obtain hydrophilic peptides from membrane proteins. The complex peptide mixtures obtained were separated by 2-dimensional liquid chromatography coupled online with a nano-electrospray ionization ion trap mass spectrometer (2D LC/nanoESI-MS). The strong cation exchange column used in the first dimension of the separation was eluted in an automated fashion using a series of salt steps of increasing concentration. Peptides eluted from each of the salt steps were separated using a capillary reversed-phase HPLC column, the output of which was directed through a nano-electrospray fused silica tip into the mass spectrometer. Peptides were fragmented by collision-induced dissociation (CID) and analyzed by data-dependent MS/MS followed by database searching using the Sequest algorithm. Analysis of the data revealed both similarities and expected differences between proteins identified from these cell lines. As demonstrated by others, mRNA and the HER2/neu protein tyrosine kinase-linked receptor in BT474 cells is up regulated compared to its level in MCF7, while the expression of the estrogen receptor alpha is known to be up regulated in MCF7 cells. As expected, our studies showed identification of peptides from HER2 in BT474 while estrogen receptor peptides were detected in the MCF7 line. A total of 604 proteins were identified from BT474 membranes while 313 proteins were found from MCF7. The results are discussed in terms of the known differences in both protein and mRNA expression between these two breast cancer cell lines and also in the context of other known phenotypic differences between these cells.

Effects of a magnetic fields on the various functions of subcellular organelles and cells

Magnetic fields (MF) are widely distributed in environment and their effects are increasing by the development of electrical machines. Several investigators reported that the MF might affect various functions of cells. However, an acceptable hypothesis has not yet been proposed. Thus, we studied the effects of weak MFs on various biological functions of cells, such as mitochondrial functions, stimulation dependent signal transduction of neutrophils, cell growth and transformation of HL-60 cells, H 2O 2-induced apoptosis and the expression of apoptotic genes in HL-60 cells. As a result of the study, a weak MF has scarcely any effects on various biological functions of cells. We also studied the direct effect of a static strong MF (SSMF, 600–2000 G) on the functions of cells or on Fe 2+-induced lipid peroxidation and on reactive oxygen species (ROS) generation in oral polymorphonuclear leukocytes (OPMN) without stimulation using Ferrite magnets. The generation of ROS from OPMN was slightly inhibited but Fe 2+-induced lipid peroxidation of biological membrane was slightly stimulated by exposure to the SSMF. At present, however, conclusive results have been neither obtained experimentally nor any acceptable idea proposed.

Amiodarone induces a different pattern of ultrastructural change in the thyroid to iodine excess alone in both the BB/W rat and the Wistar rat.

Amiodarone (AMD)-induced toxicity can be a life-threatening complication which limits the use of amiodarone as an anti-arrhythmic agent. The aim of the present study was to determine the nature of AMD toxicity by comparing ultrastructural changes induced by AMD and equivalent amounts of iodide in two animal models, the Wistar and the autoimmune BB/W rat. Rats were divided into control (water), AMD- (30 mg AMD/kg) or iodide-treated (10 mg/kg) groups. Thyroids were removed at 15 weeks and processed for electron microscopy. We found that AMD induced specific ultrastructural changes of thyroid cytotoxicity in both rat models, which were distinct compared with changes induced by excess iodide alone. Specific changes included marked distortion of thyroid architecture, evidence of necrosis and apoptosis, inclusion bodies, lipofuscinogenesis and markedly dilated endoplasmic reticulum (ER). Our data indicate that AMD is directly cytotoxic to the thyroid an effect mediated by disruption of subcellular organelle function. ER dilatation is suggestive that AMD cytotoxicity may be mediated through disruption of the protein sorting pathways leading to a drug-induced form of ER storage disease. The predilection of the thyroid to AMD may be explained by the additive effects of excess iodine and AMD drug toxicity on protein sorting pathways.

Cardioprotective effect of taurine on calcium paradox in streptozotocin-induced diabetic rat hearts.

Through the modification of Ca2+ metabolism, taurine is known to have several beneficial physiological actions, including antiarrhythmic18, positive inotropic2–4, and membrane stabilizing effects7. In addition, it has been reported that taurine protects the heart against Ca2+ paradox-induced myocardial injury9. However, it is unclear whether taurine has a similar cardioprotective effect in diabetic hearts, which exhibit a number of alterations in metabolism. Diabetes mellitus is a disorder of carbohydrate, lipid, and protein metabolism affecting many organs. In addition to contractile abnormalities, previous studies revealed disturbances in function of subcellular organelles in diabetic hearts, including impaired glucose utilization, mitochondrial dysfunction, and depressed Na+-Ca2+ Na+-H+ exchange activities12, 17, 22.

Modification of myosin isozymes and SR Ca(2+)-pump ATPase of the diabetic rat heart by lipid-lowering interventions.

To define metabolic influences on cardiac myosin expression and sarcoplasmic reticulum (SR) Ca(2+)-stimulated ATPase streptozotocin-diabetic rats were treated for 9-10 wk with etomoxir, an inhibitor of carnitine palmitoyl transferase I (CPT-1) and fatty acid synthesis, or an antilipolytic drug, acipimox. Etomoxir reduced myosin V3 of diabetic rats but did not normalize it. However, the high serum triglyceride, free-fatty acid and cholesterol concentrations in diabetic animals were greatly reduced. After bypassing the CPT-1 inhibition with a medium-chain fatty acid (miglyol) diet, the V3 contents and serum lipids were still reduced in the etomoxir-treated diabetic rats; V3 was also reduced in diabetic rats fed miglyol or treated with acipimox. Since low serum insulin or triiodothyronine concentrations in diabetic rats were not improved by these interventions but changes in V3 were correlated with those in triglyceride, free-fatty acid and cholesterol concentrations, it is likely that myosin may be influenced by some metabolic factors. To assess the role of adrenergic influences, diabetic rats (7-8 wk) were treated with an antisympathotonic drug, moxonidine, a beta-adrenoceptor blocking drug, propranolol, and a bradycardic drug, tedisamil. Myosin V3 was not reduced significantly in moxonidine-treated or propranolol-treated rats in comparison to untreated diabetic rats. Serum thyroid hormones and insulin were not altered, whereas triglycerides were reduced but not significantly by these antiadrenergic agents. Lowering serum lipids in diabetic rats by treatment with etomoxir, miglyol and acipimox increased the depressed SR Ca(2+)-stimulated ATPase activity. On the other hand, in diabetic rats treated with moxonidine, propranolol or tedisamil, the ATPase activity was not increased significantly. These results suggest that normalization of blood lipids is important for improving subcellular organelle function in diabetic hearts with impaired glucose utilization.

Influence of dietary fish oil on mitochondrial function and response to ischemia.

Dietary supplementation with marine oils may reduce the incidence of thromboembolism and decrease cardiac arrhythmias during myocardial ischemia. However, function of subcellular organelles isolated from hearts of these animals is impaired. In contrast to studies where marine oil was the sole source of dietary lipid in rats, menhaden oil was used to supplement standard canine laboratory chow. In mitochondria isolated from hearts of dogs fed this diet for 60 wk, the phospholipid content of arachidonic acid was replaced by the n-3 fatty acids, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Mitochondrial levels of linoleic and linolenic acids were not altered. The mitochondrial membrane phospholipid from the menhaden oil-fed dogs demonstrated increased cardiolipin. The respiratory function of heart mitochondria from the menhaden oil-supplemented dogs was not decreased from that of dogs on standard chow only. Increased succinate-supported respiration paralleled increased cytochrome oxidase in mitochondria from menhaden oil-fed dogs. The activity of the cardiolipin-dependent carnitine acylcarnitine translocase was unaffected. Myocardial ischemia decreased mitochondrial respiration in menhaden-fed dogs. Decreased palmitoylcarnitine-carnitine exchange following ischemia resulted from decreased matrix carnitine rather than decreased translocase activity. Normal levels of the essential fatty acids in the n-3-enriched mitochondrial membrane phospholipids appear to eliminate the mitochondrial dysfunction observed in essential fatty acid-deficient membranes.