Dietary linoleate preserves cardiolipin and attenuates mitochondrial dysfunction in the failing rat heart

Dietary linoleic acid supplementation fails to rescue established cardiomyopathy in Barth syndrome

Barth syndrome (BTHS) is a mitochondrial lipid disorder caused by mutations in TAFAZZIN (TAZ), required for cardiolipin (CL) remodeling. Cardiomyopathy is a major clinical feature, with no curative therapy. Linoleic acid (LA) supplementation is proposed to ameliorate BTHS cardiomyopathy by enhancing linoleoyl group incorporation into CL. While the beneficial effect of dietary LA supplementation in delaying the development of BTHS cardiomyopathy has been recently tested, its potential to reverse established BTHS cardiomyopathy remains unclear. Our study revealed that LA supplementation cannot rescue established BTHS cardiomyopathy in mice, highlighting the importance of early initiation of LA supplementation for maximum benefits.

Impact of Mitochondrial Architecture, Function, Redox Homeostasis, and Quality Control on Organismic Aging: Lessons from a Fungal Model System

Significance: Mitochondria are eukaryotic organelles with various essential functions. They are both the source and the targets of reactive oxygen species (ROS). Different branches of a mitochondrial quality control system (mQCS), such as ROS balancing, degradation of damaged proteins, or whole mitochondria, can mitigate the adverse effects of ROS stress. However, the capacity of mQCS is limited. Overwhelming this capacity leads to dysfunctions and aging. Strategies to interfere into mitochondria-dependent human aging with the aim to increase the healthy period of life, the health span, rely on the precise knowledge of mitochondrial functions. Experimental models such as Podospora anserina, a filamentous fungus with a clear mitochondrial aging etiology, proved to be instrumental to reach this goal. Recent Advances: Investigations of the P. anserina mQCS revealed that it is constituted by a complex network of different branches. Moreover, mitochondrial architecture and lipid homeostasis emerged to affect aging. Critical Issues: The regulation of the mQCS is only incompletely understood. Details about the involved signaling molecules and interacting pathways remain to be elucidated. Moreover, most of the currently generated experimental data were generated in well-controlled experiments that do not reflect the constantly changing natural life conditions and bear the danger to miss relevant aspects leading to incorrect conclusions. Future Directions: In P. anserina, the precise impact of redox signaling as well as of molecular damaging for aging remains to be defined. Moreover, natural fluctuation of environmental conditions needs to be considered to generate a realistic picture of aging mechanisms as they developed during evolution.

Consuming a Linoleate-Rich Diet Increases Concentrations of Tetralinoleoyl Cardiolipin in Mouse Liver and Alters Hepatic Mitochondrial Respiration

BACKGROUND

Hepatic mitochondrial dysfunction is a major cause of fat accumulation in the liver. Individuals with fatty liver conditions have hepatic mitochondrial structural abnormalities and a switch in the side chain composition of the mitochondrial phospholipid, cardiolipin, from poly- to monounsaturated fatty acids. Linoleic acid (LA), an essential dietary fatty acid, is required to remodel nascent cardiolipin (CL) to its tetralinoleoyl cardiolipin (L4CL, CL with 4 LA side chains) form, which is integral for mitochondrial membrane structure and function to promote fatty acid oxidation. It is unknown, however, whether increasing LA in the diet can increase hepatic L4CL concentrations and improve mitochondrial respiration in the liver compared with a diet rich in monounsaturated and saturated fatty acids.

OBJECTIVES

The main aim of this study was to test the ability of a diet fortified with LA-rich safflower oil (SO), compared with the one fortified with lard (LD), to increase concentrations of L4CL and improve mitochondrial respiration in the livers of mice.

METHODS

Twenty-four (9-wk-old) C57 BL/J6 male mice were fed either the SO or LD diets for ∼100 d, whereas food intake and body weight, fasting glucose, and glucose tolerance tests were performed to determine any changes in glycemic control.

RESULTS

Livers from mice fed SO diet had higher relative concentrations of hepatic L4CL species compared with LD diet-fed mice (P value = 0.004). Uncoupled mitochondria of mice fed the SO diet, compared with LD diet, had an increased baseline oxygen consumption rate (OCR) and succinate-driven respiration (P values = 0.03 and 0.01). SO diet-fed mice had increased LA content in all phospholipid classes compared with LD-fed mice (P < 0.05).

CONCLUSIONS

Our findings reveal that maintaining or increasing hepatic L4CL may result in increased OCR in uncoupled hepatic mitochondria in healthy mice whereas higher oleate content of CL reduced mitochondrial function shown by lower OCR in uncoupled mitochondria.

The involvement of the mitochondrial membrane in drug delivery

Treatment effectiveness and biosafety are critical for disease therapy. Bio-membrane modification facilitates the homologous targeting of drugs in vivo by exploiting unique antibodies or antigens, thereby enhancing therapeutic efficacy while ensuring biosafety. To further enhance the precision of disease treatment, future research should shift focus from targeted cellular delivery to targeted subcellular delivery. As the cellular powerhouses, mitochondria play an indispensable role in cell growth and regulation and are closely involved in many diseases (e.g., cancer, cardiovascular, and neurodegenerative diseases). The double-layer membrane wrapped on the surface of mitochondria not only maintains the stability of their internal environment but also plays a crucial role in fundamental biological processes, such as energy generation, metabolite transport, and information communication. A growing body of evidence suggests that various diseases are tightly related to mitochondrial imbalance. Moreover, mitochondria-targeted strategies hold great potential to decrease therapeutic threshold dosage, minimize side effects, and promote the development of precision medicine. Herein, we introduce the structure and function of mitochondrial membranes, summarize and discuss the important role of mitochondrial membrane-targeting materials in disease diagnosis/treatment, and expound the advantages of mitochondrial membrane-assisted drug delivery for disease diagnosis, treatment, and biosafety. This review helps readers understand mitochondria-targeted therapies and promotes the application of mitochondrial membranes in drug delivery. STATEMENT OF SIGNIFICANCE: Bio-membrane modification facilitates the homologous targeting of drugs in vivo by exploiting unique antibodies or antigens, thereby enhancing therapeutic efficacy while ensuring biosafety. Compared to cell-targeted treatment, targeting of mitochondria for drug delivery offers higher efficiency and improved biosafety and will promote the development of precision medicine. As a natural material, the mitochondrial membrane exhibits excellent biocompatibility and can serve as a carrier for mitochondria-targeted delivery. This review provides an overview of the structure and function of mitochondrial membranes and explores the potential benefits of utilizing mitochondrial membrane-assisted drug delivery for disease treatment and biosafety. The aim of this review is to enhance readers' comprehension of mitochondrial targeted therapy and to advance the utilization of mitochondrial membrane in drug delivery.

Natural compounds targeting mitochondrial dysfunction: emerging therapeutics for target organ damage in hypertension

Hypertension generally causes target organ damage (TOD) in the heart, brain, kidney, and blood vessels. This can result in atherosclerosis, plaque formation, cardiovascular and cerebrovascular events, and renal failure. Recent studies have indicated that mitochondrial dysfunction is crucial in hypertensive target organ damage. Consequently, mitochondria-targeted therapies attract increasing attention. Natural compounds are valuable resources for drug discovery and development. Many studies have demonstrated that natural compounds can ameliorate mitochondrial dysfunction in hypertensive target organ damage. This review examines the contribution of mitochondrial dysfunction to the development of target organ damage in hypertension. Moreover, it summarizes therapeutic strategies based on natural compounds that target mitochondrial dysfunction, which may be beneficial for preventing and treating hypertensive target organ damage.

Linoleate-Enrichment of Mitochondrial Cardiolipin Molecular Species Is Developmentally Regulated and a Determinant of Metabolic Phenotype

Cardiolipin (CL), the major mitochondrial phospholipid, regulates the activity of many mitochondrial membrane proteins. CL composition is shifted in heart failure with decreases in linoleate and increases in oleate side chains, but whether cardiolipin composition directly regulates metabolism is unknown. This study defines cardiolipin composition in rat heart and liver at three distinct ages to determine the influence of CL composition on beta-oxidation (ß-OX). CL species, expression of ß-OX and glycolytic genes, and carnitine palmitoyltransferase (CPT) activity were characterized in heart and liver from neonatal, juvenile, and adult rats. Ventricular myocytes were cultured from neonatal, juvenile, and adult rats and cardiolipin composition and CPT activity were measured. Cardiolipin composition in neonatal rat ventricular cardiomyocytes (NRVMs) was experimentally altered and mitochondrial respiration was assessed. Linoleate-enrichment of CL was observed in rat heart, but not liver, with increasing age. ß-OX genes and CPT activity were generally higher in adult heart and glycolytic genes lower, as a function of age, in contrast to liver. Palmitate oxidation increased in NRVMs when CL was enriched with linoleate. Our results indicate (1) CL is developmentally regulated, (2) linoleate-enrichment is associated with increased ß-OX and a more oxidative mitochondrial phenotype, and (3) experimentally induced linoleate-enriched CL in ventricular myocytes promotes a shift from pyruvate metabolism to fatty acid ß-OX.

The feto-placental metabolome of spontaneous labour is not reproduced following induction of labour

INTRODUCTION

The mechanism for human labour remains poorly understood, limiting our ability to manage complications including spontaneous preterm birth and induction of labour (IOL). The study of fetal signals poses specific challenges. Metabolomic analysis of maternal blood, the cord artery (CA), and cord vein (CV), allows simultaneous interrogation of multiple metabolic pathways associated with different modes of labour onset and birth.

METHODS

Global mass spectrometry metabolomics analysis was performed on serial samples collected from participants during pregnancy, in latent phase of labour, and following birth (CA, CV, and intervillous (IV) blood), from those who spontaneously laboured and birthed vaginally (SL group), had IOL and birthed vaginally (IOL group), or birthed via elective caesarean section (no labour; ECS group).

RESULTS

There were clear differences in fetal and maternal steroid, arachidonate and sphingosine pathways between the SL and IOL groups, despite similar uterine contractions and vaginal birth. The CA/CV ratio for key steroids of the IOL group were more alike the ECS group than the SL group, including progesterone (CA/CV ratio for: SL group=3.5; IOL group=0.5; and ECS group=0.5), and oestriol (CA/CV ratio for: SL group=4.3; IOL group=0.4; and for ECS group=0.2). There were no such changes in the maternal samples.

DISCUSSION

These findings indicate that IOL does not reproduce the pathways activated in spontaneous labour. The decreased placental progesterone production observed with spontaneous labour may represent a local intrauterine progesterone withdrawal, which, together with other signals, would activate parturition pathways involving arachidonate and sphingosine metabolism.

Linoleic Acid-Rich Oil Alters Circulating Cardiolipin Species and Fatty Acid Composition in Adults: A Randomized Controlled Trial

SCOPE

Higher circulating linoleic acid (LA) and muscle-derived tetralinoleoyl-cardiolipin (LA₄ CL) are each associated with decreased cardiometabolic disease risk. Mitochondrial dysfunction occurs with low LA₄ CL. Whether LA-rich oil fortification can increase LA₄ CL in humans is unknown. The aims of this study are to determine whether dietary fortification with LA-rich oil for 2 weeks increases: 1) LA in plasma, erythrocytes, and peripheral blood mononuclear cells (PBMC); and 2) LA₄ CL in PBMC in adults.

METHODS AND RESULTS

In this randomized controlled trial, adults are instructed to consume one cookie per day delivering 10 g grapeseed (LA-cookie, N = 42) or high oleate (OA) safflower (OA-cookie, N = 42) oil. In the LA-cookie group, LA increases in plasma, erythrocyte, and PBMC by 6%, 7%, and 10% respectively. PBMC and erythrocyte OA increase by 7% and 4% in the OA-cookie group but is unchanged in the plasma. PBMC LA₄ CL increases (5%) while LA₃ OA₁ CL decreases (7%) in the LA-cookie group but are unaltered in the OA-cookie group.

CONCLUSIONS

LA-rich oil fortification increases while OA-oil has no effect on LA₄ CL in adults. Because LA-rich oil fortification reduces cardiometabolic disease risk and increases LA₄ CL, determining whether mitochondrial dysfunction is repaired through dietary fortification is warranted.

Lifespan Extension of Podospora anserina Mic60-Subcomplex Mutants Depends on Cardiolipin Remodeling

Function of mitochondria largely depends on a characteristic ultrastructure with typical invaginations, namely the cristae of the inner mitochondrial membrane. The mitochondrial signature phospholipid cardiolipin (CL), the F₁F_o-ATP-synthase, and the ‘mitochondrial contact site and cristae organizing system’ (MICOS) complex are involved in this process. Previous studies with Podospora anserina demonstrated that manipulation of MICOS leads to altered cristae structure and prolongs lifespan. While longevity of Mic10-subcomplex mutants is induced by mitohormesis, the underlying mechanism in the Mic60-subcomplex deletion mutants was unclear. Since several studies indicated a connection between MICOS and phospholipid composition, we now analyzed the impact of MICOS on mitochondrial phospholipid metabolism. Data from lipidomic analysis identified alterations in phospholipid profile and acyl composition of CL in Mic60-subcomplex mutants. These changes appear to have beneficial effects on membrane properties and promote longevity. Impairments of CL remodeling in a PaMIC60 ablated mutant lead to a complete abrogation of longevity. This effect is reversed by supplementation of the growth medium with linoleic acid, a fatty acid which allows the formation of tetra-octadecanoyl CL. In the PaMic60 deletion mutant, this CL species appears to lead to longevity. Overall, our data demonstrate a tight connection between MICOS, the regulation of mitochondrial phospholipid homeostasis, and aging of P. anserina.

Lipidomic approaches to dissect dysregulated lipid metabolism in kidney disease

Dyslipidaemia is a hallmark of chronic kidney disease (CKD). The severity of dyslipidaemia not only correlates with CKD stage but is also associated with CKD-associated cardiovascular disease and mortality. Understanding how lipids are dysregulated in CKD is, however, challenging owing to the incredible diversity of lipid structures. CKD-associated dyslipidaemia occurs as a consequence of complex interactions between genetic, environmental and kidney-specific factors, which to understand, requires an appreciation of perturbations in the underlying network of genes, proteins and lipids. Modern lipidomic technologies attempt to systematically identify and quantify lipid species from biological systems. The rapid development of a variety of analytical platforms based on mass spectrometry has enabled the identification of complex lipids at great precision and depth. Insights from lipidomics studies to date suggest that the overall architecture of free fatty acid partitioning between fatty acid oxidation and complex lipid fatty acid composition is an important driver of CKD progression. Available evidence suggests that CKD progression is associated with metabolic inflexibility, reflecting a diminished capacity to utilize free fatty acids through β-oxidation, and resulting in the diversion of accumulating fatty acids to complex lipids such as triglycerides. This effect is reversed with interventions that improve kidney health, suggesting that targeting of lipid abnormalities could be beneficial in preventing CKD progression.

Shengmai Yin formula exerts cardioprotective effects on rats with chronic heart failure via regulating Linoleic Acid metabolism

The objective of this study was to investigate the protective effects of Shengmai Yin(SMY) on rats with chronic heart failure(CHF).Sprague-Dawley rats were used to establish a CHF animal model via ligation of the left anterior descending branch of the coronary artery and exhaustive swimming.Echocardiography, serum biochemical indicators and histopathology were used to evaluate the pharmacodynamics of SMY in CHF rats.UPLC-Q-TOF/MS analysis based on serum was performed to identify the potential metabolites in the pathological process of CHF. Metabolic pathway analysis was carried out to elucidate the metabolic network associated with SMY treatment of CHF.Moreover,quantitative real-time PCR (qRT-PCR), Western blotting (WB), and Enzyme-linked immunosorbent assay (ELISA) were used to measure the RNA and protein expression levels in related pathways. Results revealed that SMY significantly restored the cardiac function of CHF rats, reduced the serum biochemical indicators, and alleviated cardiac histological damage. Metabolomics analysis shows that the therapeutic effect of SMY for CHF involves 14 biomarkers and 8 metabolic pathways, especially linoleic acid pathway, to be influenced, which implied the potential mechanism of SMY in treating CHF. Two key indicators Lipoxygenase arachidonic acid 15 lipoxygenase (ALOX15) and Cytochrome P450 1A2(CYP1A2) of linoleic acid metabolism pathway were verified by RT-PCR, WB and ELISA. Verification result showed that compared with the model group, expression levels of ALOX15 and CYP1A2 in SMY group were lower. In conclusion, SMY has cardioprotective effect on chronic heart failure rats, and its mechanism may be related to linoleic acid metabolism pathway.

Phytochemical profiles of edible flowers of medicinal plants of Dendrobium officinale and Dendrobium devonianum

The discovery of new edible flowers that are nontoxic, innocuous flowers having human health benefits, surveys of their phytochemicals and utilization are of great scientific and commercial interest. Dendrobium officinale and Dendrobium devonianum are precious Traditional Chinese Medicine. During the massive commercial cultivation, a lot of flowers were produced and certified as edible flowers, and the phytochemical profiles and bioactivities warrant evaluate. The present study aimed to investigate the phytochemicals and antioxidative activities in flowers of D. officinale (DOF) and D. devonianum (DDF). In total, 474 metabolites were identified using a widely targeted metabonomics method, 16 amino acids and 6 flavonoids were measured using high-performance liquid chromatography (HPLC), and 8 fatty acids were detected using gas chromatography-mass spectrometry (GC-MS). Both flowers contained various amino acids, including 7 essential amino acids, diverse flavonoids, especially quercetin, kaempferol and their derivatives, and high levels of methyl linoleate and methyl linolenate. The relative levels of quercetin, kaempferol and their glycosides were higher in DDF than in DOF, whereas the relative levels of several flavonoids C-glycosides were high in DOF. Ethanol extracts of both DOF and DDF showed antioxidative capacities including the scavenging of 1,1-diphenyl-2-picrylhydrazyl and hydroxyl radicals. Both edible flowers contained flavonoids, amino acids, and fatty acids and have antioxidative activities, which should be explored for use in functional foods and pharmaceuticals.

Mitochondrial Phospholipid Homeostasis Is Regulated by the i-AAA Protease PaIAP and Affects Organismic Aging

Mitochondria are ubiquitous organelles of eukaryotic organisms with a number of essential functions, including synthesis of iron-sulfur clusters, amino acids, lipids, and adenosine triphosphate (ATP). During aging of the fungal aging model Podospora anserina, the inner mitochondrial membrane (IMM) undergoes prominent morphological alterations, ultimately resulting in functional impairments. Since phospholipids (PLs) are key components of biological membranes, maintenance of membrane plasticity and integrity via regulation of PL biosynthesis is indispensable. Here, we report results from a lipidomic analysis of isolated mitochondria from P. anserina that revealed an age-related reorganization of the mitochondrial PL profile and the involvement of the i-AAA protease PaIAP in proteolytic regulation of PL metabolism. The absence of PaIAP enhances biosynthesis of characteristic mitochondrial PLs, leads to significant alterations in the acyl composition of the mitochondrial signature PL cardiolipin (CL), and induces mitophagy. These alterations presumably cause the lifespan increase of the PaIap deletion mutant under standard growth conditions. However, PaIAP is required at elevated temperatures and for degradation of superfluous CL synthase PaCRD1 during glycolytic growth. Overall, our study uncovers a prominent role of PaIAP in the regulation of PL homeostasis in order to adapt membrane plasticity to fluctuating environmental conditions as they occur in nature.

The Influence of Supplemental Dietary Linoleic Acid on Skeletal Muscle Contractile Function in a Rodent Model of Barth Syndrome

Barth syndrome is a rare and incurable X-linked (male-specific) genetic disease that affects the protein tafazzin (Taz). Taz is an important enzyme responsible for synthesizing biologically relevant cardiolipin (for heart and skeletal muscle, cardiolipin rich in linoleic acid), a critical phospholipid of mitochondrial form and function. Mutations to Taz cause dysfunctional mitochondria, resulting in exercise intolerance due to skeletal muscle weakness. To date, there has been limited research on improving skeletal muscle function, with interventions focused on endurance and resistance exercise. Previous cell culture research has shown therapeutic potential for the addition of exogenous linoleic acid in improving Taz-deficient mitochondrial function but has not been examined in vivo. The purpose of this study was to examine the influence of supplemental dietary linoleic acid on skeletal muscle function in a rodent model of Barth syndrome, the inducible Taz knockdown (TazKD) mouse. One of the main findings was that TazKD soleus demonstrated an impaired contractile phenotype (slower force development and rates of relaxation) in vitro compared to their WT littermates. Interestingly, this impaired contractile phenotype seen in vitro did not translate to altered muscle function in vivo at the whole-body level. Also, supplemental linoleic acid attenuated, to some degree, in vitro impaired contractile phenotype in TazKD soleus, and these findings appear to be partially mediated by improvements in cardiolipin content and resulting mitochondrial supercomplex formation. Future research will further examine alternative mechanisms of dietary supplemental LA on improving skeletal muscle contractile dysfunction in TazKD mice.

High-resolution mass spectrometric analysis of cardiolipin profiles in Barth syndrome

Barth syndrome is an X-linked recessive disorder caused by pathogenic variants in TAZ, which leads to a reduction in cardiolipin with a concomitant elevation of monolysocardiolipins. There is a paucity of studies characterizing changes in individual species of monolysocardiolipins, dilysocardiolipins and cardiolipin in Barth syndrome using high resolution untargeted lipidomics that can accurately annotate and quantify diverse lipids. We confirmed the structural diversity monolysocardiolipins, dilysocardiolipins and cardiolipin and identified individual species that showed previously unreported alterations in BTHS. Development of mass spectrometry-based targeted assays for these lipid biomarkers should provide an important tool for clinical diagnosis of Barth syndrome.

Specialized Pro-Resolving Lipid Mediators in Neonatal Cardiovascular Physiology and Diseases

Cardiovascular disease remains a leading cause of mortality worldwide. Unresolved inflammation plays a critical role in cardiovascular diseases development. Specialized Pro-Resolving Mediators (SPMs), derived from long chain polyunsaturated fatty acids (LCPUFAs), enhances the host defense, by resolving the inflammation and tissue repair. In addition, SPMs also have anti-inflammatory properties. These physiological effects depend on the availability of LCPUFAs precursors and cellular metabolic balance. Most of the studies have focused on the impact of SPMs in adult cardiovascular health and diseases. In this review, we discuss LCPUFAs metabolism, SPMs, and their potential effect on cardiovascular health and diseases primarily focusing in neonates. A better understanding of the role of these SPMs in cardiovascular health and diseases in neonates could lead to the development of novel therapeutic approaches in cardiovascular dysfunction.

A Novel Calcium-Mediated EMT Pathway Controlled by Lipids: An Opportunity for Prostate Cancer Adjuvant Therapy

The composition of periprostatic adipose tissue (PPAT) has been shown to play a role in prostate cancer (PCa) progression. We recently reported an inverse association between PCa aggressiveness and elevated PPAT linoleic acid (LA) and eicosapentaenoic acid (EPA) content. In the present study, we identified a new signaling pathway with a positive feedback loop between the epithelial-to-mesenchymal transition (EMT) transcription factor Zeb1 and the Ca²⁺-activated K⁺ channel SK3, which leads to an amplification of Ca²⁺ entry and cellular migration. Using in vitro experiments and ex vivo cultures of human PCa slices, we demonstrated that LA and EPA exert anticancer effects, by modulating Ca²⁺ entry, which was involved in Zeb1 regulation and cancer cellular migration. This functional approach using human prostate tumors highlights the clinical relevance of our observations, and may allow us to consider the possibility of targeting cancer spread by altering the lipid microenvironment.

Linoleic acid improves assembly of the CII subunit and CIII2/CIV complex of the mitochondrial oxidative phosphorylation system in heart failure

Background

Linoleic acid is the major fatty acid moiety of cardiolipin, which is central to the assembly of components involved in mitochondrial oxidative phosphorylation (OXPHOS). Although linoleic acid is an essential nutrient, its excess intake is harmful to health. On the other hand, linoleic acid has been shown to prevent the reduction in cardiolipin content and to improve mitochondrial function in aged rats with spontaneous hypertensive heart failure (HF). In this study, we found that lower dietary intake of linoleic acid in HF patients statistically correlates with greater severity of HF, and we investigated the mechanisms therein involved.

Methods

HF patients, who were classified as New York Heart Association (NYHA) functional class I (n = 45), II (n = 93), and III (n = 15), were analyzed regarding their dietary intakes of different fatty acids during the one month prior to the study. Then, using a mouse model of HF, we confirmed reduced cardiolipin levels in their cardiac myocytes, and then analyzed the mechanisms by which dietary supplementation of linoleic acid improves cardiac malfunction of mitochondria.

Results

The dietary intake of linoleic acid was significantly lower in NYHA III patients, as compared to NYHA II patients. In HF model mice, both CI-based and CII-based OXPHOS activities were affected together with reduced cardiolipin levels. Silencing of CRLS1, which encodes cardiolipin synthetase, in cultured cardiomyocytes phenocopied these events. Feeding HF mice with linoleic acid improved both CI-based and CII-based respiration as well as left ventricular function, together with an increase in cardiolipin levels. However, although assembly of the respirasome (i.e., CI/CIII₂/CIV complex), as well as assembly of CII subunits and the CIII₂/CIV complex statistically correlated with cardiolipin levels in cultured cardiomyocytes, respirasome assembly was not notably restored by dietary linoleic acid in HF mice. Therefore, although linoleic acid may significantly improve both CI-based and CII-based respiration of cardiomyocytes, respirasomes impaired by HF were not easily repaired by the dietary intake of linoleic acid.

Conclusions

Dietary supplement of linoleic acid is beneficial for improving cardiac malfunction in HF, but is unable to completely cure HF.

Tetra-linoleoyl cardiolipin depletion plays a major role in the pathogenesis of sarcopenia

Sarcopenia, the progressive loss of muscle mass, strength, and physical performance that occurs during aging, is highly prevalent among the elderly. Sarcopenia increases the risk of falls, disability, and death. The biological basis for sarcopenia is not well understood. There are no specific preventive or therapeutic strategies for sarcopenia except exercise. The elucidation of biological pathways and identification of therapeutic targets for treating or preventing sarcopenia remain a high priority in aging research. Mitochondria play a critical role in skeletal muscle by providing energy in the form of ATP, regulation of signaling, calcium homeostasis, autophagy, and other functions. Cardiolipin, a unique dimeric phospholipid specific to mitochondria and an essential component of mitochondrial membranes, is involved in mitochondrial protein transport, maintaining structural organization of mitochondrial membranes, cellular signaling, regulating enzymes involved in β-oxidation of fatty acids, and facilitating normal electron transport chain (ETC) function and generation of ATP. The fatty acid species composition of cardiolipin is critical to mitochondrial bioenergetics, as cardiolipin affects membrane biophysical properties, binds and stabilizes ETC protein complexes, and shapes the curvature of the mitochondrial cristae. Tetra-linoleoyl cardiolipin (18:2)₄ comprises ∼80% of cardiolipin in mitochondria in normal human skeletal and cardiac muscle and is optimal for effective ETC function and ATP generation. Aging is associated with a decrease in cardiolipin content, decrease in tetra-linoleoyl cardiolipin (18:2)₄ and replacement of linoleic acid (18:2) with other fatty acids in cardiolipin composition, decline of ETC function, and increased generation of reactive oxygen species in muscle. Together, these findings from the literature prompt the hypothesis that depletion of the cardiolipin (18:2)₄ species may be at the root of mitochondrial dysfunction with aging, in turn leading to sarcopenia. Corroboration of the tetra-linoleoyl cardiolipin depletion hypothesis suggests new leads for the prevention and treatment of sarcopenia by enhancing the biosynthesis, accretion, and integrity of tetra-linoleoyl cardiolipin.

The role of cardiolipin concentration and acyl chain composition on mitochondrial inner membrane molecular organization and function

Cardiolipin (CL) is a key phospholipid of the mitochondria. A loss of CL content and remodeling of CL's acyl chains is observed in several pathologies. Strong shifts in CL concentration and acyl chain composition would presumably disrupt mitochondrial inner membrane biophysical organization. However, it remains unclear in the literature as to which is the key regulator of mitochondrial membrane biophysical properties. We review the literature to discriminate the effects of CL concentration and acyl chain composition on mitochondrial membrane organization. A widely applicable theme emerges across several pathologies, including cardiovascular diseases, diabetes, Barth syndrome, and neurodegenerative ailments. The loss of CL, often accompanied by increased levels of lyso-CLs, impairs mitochondrial inner membrane organization. Modest remodeling of CL acyl chains is not a major driver of impairments and only in cases of extreme remodeling is there an influence on membrane properties.

Pathological hypertrophy and cardiac dysfunction are linked to aberrant endogenous unsaturated fatty acid metabolism

Pathological cardiac hypertrophy leads to derangements in lipid metabolism that may contribute to the development of cardiac dysfunction. Since previous studies, using high saturated fat diets, have yielded inconclusive results, we investigated whether provision of a high-unsaturated fatty acid (HUFA) diet was sufficient to restore impaired lipid metabolism and normalize diastolic dysfunction in the pathologically hypertrophied heart. Male, Wistar rats were subjected to supra-valvar aortic stenosis (SVAS) or sham surgery. After 6 weeks, diastolic dysfunction and pathological hypertrophy was confirmed and both sham and SVAS rats were treated with either normolipidic or HUFA diet. At 18 weeks post-surgery, the HUFA diet failed to normalize decreased E/A ratios or attenuate measures of cardiac hypertrophy in SVAS animals. Enzymatic activity assays and gene expression analysis showed that both normolipidic and HUFA-fed hypertrophied hearts had similar increases in glycolytic enzyme activity and down-regulation of fatty acid oxidation genes. Mass spectrometry analysis revealed depletion of unsaturated fatty acids, primarily linoleate and oleate, within the endogenous lipid pools of normolipidic SVAS hearts. The HUFA diet did not restore linoleate or oleate in the cardiac lipid pools, but did maintain body weight and adipose mass in SVAS animals. Overall, these results suggest that, in addition to decreased fatty acid oxidation, aberrant unsaturated fatty acid metabolism may be a maladaptive signature of the pathologically hypertrophied heart. The HUFA diet is insufficient to reverse metabolic remodeling, diastolic dysfunction, or pathologically hypertrophy, possibly do to preferentially partitioning of unsaturated fatty acids to adipose tissue.

Maternal exercise upregulates mitochondrial gene expression and increases enzyme activity of fetal mouse hearts

Maternal exercise during pregnancy has been shown to improve the long‐term health of offspring in later life. Mitochondria are important organelles for maintaining adequate heart function, and mitochondrial dysfunction is linked to cardiovascular disease. However, the effects of maternal exercise during pregnancy on mitochondrial biogenesis in hearts are not well understood. Thus, the purpose of this study was to test the hypothesis that mitochondrial gene expression in fetal myocardium would be upregulated by maternal exercise. Twelve‐week‐old female C57BL/6 mice were divided into sedentary and exercise groups. Mice in the exercise group were exposed to a voluntary cage‐wheel from gestational day 1 through 17. Litter size and individual fetal weights were taken when pregnant dams were sacrificed at 17 days of gestation. Three to four hearts from the same group were pooled to study gene expression, protein expression, and enzyme activity. There were no significant differences in litter size, sex distribution, and average fetal body weight per litter between sedentary and exercised dams. Genes encoding mitochondrial biogenesis and dynamics, including nuclear respiratory factor‐1 (Nrf1), Nrf2, and dynamin‐related GTPase termed mitofusin‐2 (Mfn2) were significantly upregulated in the fetal hearts from exercised dams. Cytochrome c oxidase activity and ATP production were significantly increased, while the hydrogen peroxide level was significantly decreased in the fetal hearts by maternal exercise. Our results demonstrate that maternal exercise initiated at day 1 of gestation could transfer the positive mitochondrial phenotype to fetal hearts.

Pathophysiology of mitochondrial lipid oxidation: Role of 4-hydroxynonenal (4-HNE) and other bioactive lipids in mitochondria

Mitochondrial lipids are essential for maintaining the integrity of mitochondrial membranes and the proper functions of mitochondria. As the "powerhouse" of a cell, mitochondria are also the major cellular source of reactive oxygen species (ROS). Oxidative stress occurs when the antioxidant system is overwhelmed by overproduction of ROS. Polyunsaturated fatty acids in mitochondrial membranes are primary targets for ROS attack, which may lead to lipid peroxidation (LPO) and generation of reactive lipids, such as 4-hydroxynonenal. When mitochondrial lipids are oxidized, the integrity and function of mitochondria may be compromised and this may eventually lead to mitochondrial dysfunction, which has been associated with many human diseases including cancer, cardiovascular diseases, diabetes, and neurodegenerative diseases. How mitochondrial lipids are oxidized and the underlying molecular mechanisms and pathophysiological consequences associated with mitochondrial LPO remain poorly defined. Oxidation of the mitochondria-specific phospholipid cardiolipin and generation of bioactive lipids through mitochondrial LPO has been increasingly recognized as an important event orchestrating apoptosis, metabolic reprogramming of energy production, mitophagy, and immune responses. In this review, we focus on the current understanding of how mitochondrial LPO and generation of bioactive lipid mediators in mitochondria are involved in the modulation of mitochondrial functions in the context of relevant human diseases associated with oxidative stress.

Troxerutin abrogates mitochondrial oxidative stress and myocardial apoptosis in mice fed calorie-rich diet

Mitochondrial oxidative stress plays a major role in the pathogenesis of myocardial apoptosis in metabolic syndrome (MS) patients. In this study, we investigated the effect of troxerutin (TX), an antioxidant on mitochondrial oxidative stress and apoptotic markers in heart of mice fed fat and fructose-rich diet. Adult male Mus musculus mice were fed either control diet or high fat, high fructose diet (HFFD) for 60 days to induce MS. Mice from each dietary group were divided into two on the 16th day and were either treated or untreated with TX (150 mg/kg bw, p.o) for the next 45 days. At the end of the study, mitochondrial reactive oxygen species (ROS) generation, oxidative stress markers, levels of intracellular calcium, cardiolipin content, cytochrome c release and apoptotic markers were examined in the myocardium. HFFD-feeding resulted in diminution of antioxidants and increased ROS production, lipid peroxidation and oxidatively modified adducts of 8-OHG, 4-HNE and 3-NT. Further increase in Ca²⁺ levels, low levels of calcium transporters and decrease in cardiolipin content were noted. Changes in the mitochondrial structure were observed by electron microscopy. Furthermore, cytochrome c release, increase in proapoptotic proteins (APAF-1, BAX, caspases-9 and-3) and decrease in antiapoptotic protein (BCL-2) in HFFD-fed mice suggest myocardial apoptosis. These changes were significantly restored by TX supplementation. TX administration effectively attenuated cardiac apoptosis and exerted a protective role by increasing antioxidant potential and by improving mitochondrial function. Thus, TX could be a promising therapeutic candidate for treating cardiac disease in MS patients.

Circulating Omega-6, But Not Omega-3 Polyunsaturated Fatty Acids, Are Associated with Clinical Outcomes in Patients with Acute Decompensated Heart Failure

Background

Circulating polyunsaturated fatty acid (PUFA) levels are associated with clinical outcomes in cardiovascular diseases including coronary artery disease and chronic heart failure (HF). However, their clinical implications in acute decompensated HF (ADHF) remain unclear. The aim of this study was to investigate the clinical roles of circulating PUFAs in patients with ADHF.

Methods

Circulating levels of PUFAs, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (AA) and dihomo-gamma linoleic acid (DGLA), were measured on admission in 685 consecutive ADHF patients. Adverse events were defined as all-cause death and worsening HF.

Results

During a median follow-up period of 560 days, 262 (38.2%) patients had adverse events. Although patients with adverse events had lower n-6 PUFA (AA + DGLA) level than those without, n-3 PUFA (EPA + DHA) level was comparable between the groups. Kaplan-Meier analyses showed that lower n-6 PUFA level on admission was significantly associated with the composite of all-cause death and worsening HF, all-cause death, cardiovascular death and worsening HF (p < 0.001, p = 0.005, p = 0.021, p = 0.019, respectively). In a multivariate Cox model, lower n-6 PUFA level was independently associated with increased risk of adverse events (HR 0.996, 95% CI: 0.993–0.999, p = 0.027).

Conclusions

Lower n-6 but not n-3 PUFA level on admission was significantly related to worse clinical outcomes in ADHF patients. Measurement of circulating n-6 PUFA levels on admission might provide information for identifying high risk ADHF patients.

Thrombomodulin-dependent protein C activation is required for mitochondrial function and myelination in the central nervous system

Essentials The role of protein C (PC) activation in experimental autoimmune encephalitis (EAE) is unknown. PC activation is required for mitochondrial function in the central nervous system. Impaired PC activation aggravates EAE, which can be compensated for by soluble thrombomodulin. Protection of myelin by activated PC or solulin is partially independent of immune-modulation.

SUMMARY

Background Studies with human samples and in rodents established a function of coagulation proteases in neuro-inflammatory demyelinating diseases (e.g. in multiple sclerosis [MS] and experimental autoimmune encephalitis [EAE]). Surprisingly, approaches to increase activated protein C (aPC) plasma levels as well as antibody-mediated inhibition of PC/aPC ameliorated EAE in mice. Hence, the role of aPC generation in demyelinating diseases and potential mechanisms involved remain controversial. Furthermore, it is not known whether loss of aPC has pathological consequences at baseline (e.g. in the absence of disease). Objective To explore the role of thrombomodulin (TM)-dependent aPC generation at baseline and in immunological and non-immunological demyelinating disease models. Methods Myelination and reactive oxygen species (ROS) generation were evaluated in mice with genetically reduced TM-mediated protein C activation (TMPro/Pro ) and in wild-type (WT) mice under control conditions or following induction of EAE. Non-immunological demyelination was analyzed in the cuprizone-diet model. Results Impaired TM-dependent aPC generation already disturbs myelination and mitochondrial function at baseline. This basal phenotype is linked with increased mitochondrial ROS and aggravates EAE. Reducing mitochondrial ROS (p66Shc deficiency), restoring aPC plasma levels or injecting soluble TM (solulin) ameliorates EAE in TMPro/Pro mice. Soluble TM additionally conveyed protection in WT-EAE mice. Furthermore, soluble TM dampened demyelination in the cuprizone-diet model, demonstrating that its myelin-protective effect is partially independent of an immune-driven process. Conclusion These results uncover a novel physiological function of TM-dependent aPC generation within the CNS. Loss of TM-dependent aPC generation causes a neurological defect in healthy mice and aggravates EAE, which can be therapeutically corrected.

Impaired Cardiolipin Biosynthesis Prevents Hepatic Steatosis and Diet-Induced Obesity

Mitochondria are the nexus of energy metabolism, and consequently their dysfunction has been implicated in the development of metabolic complications and progression to insulin resistance and type 2 diabetes. The unique tetra-acyl phospholipid cardiolipin (CL) is located in the inner mitochondrial membrane, where it maintains mitochondrial integrity. Here we show that knockdown of Tafazzin (TAZ kd), a CL transacylase, in mice results in protection against the development of obesity, insulin resistance, and hepatic steatosis. We determined that hypermetabolism protected TAZ kd mice from weight gain. Unexpectedly, the large reduction of CL in the heart and skeletal muscle of TAZ kd mice was not mirrored in the liver. As a result, TAZ kd mice exhibited normal hepatic mitochondrial supercomplex formation and elevated hepatic fatty acid oxidation. Collectively, these studies identify a key role for hepatic CL remodeling in regulating susceptibility to insulin resistance and as a novel therapeutic target for diet-induced obesity.

Cardiac Myocyte-specific Knock-out of Calcium-independent Phospholipase A2γ (iPLA2γ) Decreases Oxidized Fatty Acids during Ischemia/Reperfusion and Reduces Infarct Size

Calcium-independent phospholipase A2γ (iPLA2γ) is a mitochondrial enzyme that produces lipid second messengers that facilitate opening of the mitochondrial permeability transition pore (mPTP) and contribute to the production of oxidized fatty acids in myocardium. To specifically identify the roles of iPLA2γ in cardiac myocytes, we generated cardiac myocyte-specific iPLA2γ knock-out (CMiPLA2γKO) mice by removing the exon encoding the active site serine (Ser-477). Hearts of CMiPLA2γKO mice exhibited normal hemodynamic function, glycerophospholipid molecular species composition, and normal rates of mitochondrial respiration and ATP production. In contrast, CMiPLA2γKO mice demonstrated attenuated Ca(2+)-induced mPTP opening that could be rapidly restored by the addition of palmitate and substantially reduced production of oxidized polyunsaturated fatty acids (PUFAs). Furthermore, myocardial ischemia/reperfusion (I/R) in CMiPLA2γKO mice (30 min of ischemia followed by 30 min of reperfusion in vivo) dramatically decreased oxidized fatty acid production in the ischemic border zones. Moreover, CMiPLA2γKO mice subjected to 30 min of ischemia followed by 24 h of reperfusion in vivo developed substantially less cardiac necrosis in the area-at-risk in comparison with their WT littermates. Furthermore, we found that membrane depolarization in murine heart mitochondria was sensitized to Ca(2+) by the presence of oxidized PUFAs. Because mitochondrial membrane depolarization and calcium are known to activate iPLA2γ, these results are consistent with salvage of myocardium after I/R by iPLA2γ loss of function through decreasing mPTP opening, diminishing production of proinflammatory oxidized fatty acids, and attenuating the deleterious effects of abrupt increases in calcium ion on membrane potential during reperfusion.

Cardiac mitochondrial energy metabolism in heart failure: Role of cardiolipin and sirtuins

Mitochondrial oxidation of fatty acids accounts for the majority of cardiac ATP production in the heart. Fatty acid utilization by cardiac mitochondria is controlled at the level of fatty acid uptake, lipid synthesis, mobilization and mitochondrial import and oxidation. Consequently defective mitochondrial function appears to be central to the development of heart failure. Cardiolipin is a key mitochondrial phospholipid required for the activity of the electron transport chain. In heart failure, loss of cardiolipin and tetralinoleoylcardiolipin helps to fuel the generation of excessive reactive oxygen species that are a by-product of inefficient mitochondrial electron transport chain complexes I and III. In this vicious cycle, reactive oxygen species generate lipid peroxides and may, in turn, cause oxidation of cardiolipin catalyzed by cytochrome c leading to cardiomyocyte apoptosis. Hence, preservation of cardiolipin and mitochondrial function may be keys to the prevention of heart failure development. In this review, we summarize cardiac energy metabolism and the important role that fatty acid uptake and metabolism play in this process and how defects in these result in heart failure. We highlight the key role that cardiolipin and sirtuins play in cardiac mitochondrial β-oxidation. In addition, we review the potential of pharmacological modulation of cardiolipin through the polyphenolic molecule resveratrol as a sirtuin-activator in attenuating mitochondrial dysfunction. Finally, we provide novel experimental evidence that resveratrol treatment increases cardiolipin in isolated H9c2 cardiac myocytes and tetralinoleoylcardiolipin in the heart of the spontaneously hypertensive rat and hypothesize that this leads to improvement in mitochondrial function. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.

Non-targeted metabolomics of Brg1/Brm double-mutant cardiomyocytes reveals a novel role for SWI/SNF complexes in metabolic homeostasis

Mammalian SWI/SNF chromatin-remodeling complexes utilize either BRG1 or Brm as alternative catalytic subunits to alter the position of nucleosomes and regulate gene expression. Genetic studies have demonstrated that SWI/SNF complexes are required during cardiac development and also protect against cardiovascular disease and cancer. However, Brm constitutive null mutants do not exhibit a cardiomyocyte phenotype and inducible Brg1 conditional mutations in cardiomyocyte do not demonstrate differences until stressed with transverse aortic constriction, where they exhibit a reduction in cardiac hypertrophy. We recently demonstrated the overlapping functions of Brm and Brg1 in vascular endothelial cells and sought here to test if this overlapping function occurred in cardiomyocytes. Brg1/Brm double mutants died within 21 days of severe cardiac dysfunction associated with glycogen accumulation and mitochondrial defects based on histological and ultrastructural analyses. To determine the underlying defects, we performed nontargeted metabolomics analysis of cardiac tissue by GC/MS from a line of Brg1/Brm double-mutant mice, which lack both Brg1 and Brm in cardiomyocytes in an inducible manner, and two groups of controls. Metabolites contributing most significantly to the differences between Brg1/Brm double-mutant and control-group hearts were then determined using the variable importance in projection analysis. Increased cardiac linoleic acid and oleic acid suggest alterations in fatty acid utilization or intake are perturbed in Brg1/Brm double mutants. Conversely, decreased glucose-6-phosphate, fructose-6-phosphate, and myoinositol suggest that glycolysis and glycogen formation are impaired. These novel metabolomics findings provide insight into SWI/SNF-regulated metabolic pathways and will guide mechanistic studies evaluating the role of SWI/SNF complexes in homeostasis and cardiovascular disease prevention.

Acyl-CoA synthetase 1 deficiency alters cardiolipin species and impairs mitochondrial function

Long-chain acyl-CoA synthetase 1 (ACSL1) contributes more than 90% of total cardiac ACSL activity, but its role in phospholipid synthesis has not been determined. Mice with an inducible knockout of ACSL1 (Acsl1(T-/-)) have impaired cardiac fatty acid oxidation and rely on glucose for ATP production. Because ACSL1 exhibited a strong substrate preference for linoleate, we investigated the composition of heart phospholipids. Acsl1(T-/-) hearts contained 83% less tetralinoleoyl-cardiolipin (CL), the major form present in control hearts. A stable knockdown of ACSL1 in H9c2 rat cardiomyocytes resulted in low incorporation of linoleate into CL and in diminished incorporation of palmitate and oleate into other phospholipids. Overexpression of ACSL1 in H9c2 and HEK-293 cells increased incorporation of linoleate into CL and other phospholipids. To determine whether increasing the content of linoleate in CL would improve mitochondrial respiratory function in Acsl1(T-/-) hearts, control and Acsl1(T-/-) mice were fed a high-linoleate diet; this diet normalized the amount of tetralinoleoyl-CL but did not improve respiratory function. Thus, ACSL1 is required for the normal composition of several phospholipid species in heart. Although ACSL1 determines the acyl-chain composition of heart CL, a high tetralinoleoyl-CL content may not be required for normal function.

Mitochondrial dysfunction in uremic cardiomyopathy

Uremic cardiomyopathy (UCM) is characterized by metabolic remodelling, compromised energetics, and loss of insulin-mediated cardioprotection, which result in unsustainable adaptations and heart failure. However, the role of mitochondria and the susceptibility of mitochondrial permeability transition pore (mPTP) formation in ischemia-reperfusion injury (IRI) in UCM are unknown. Using a rat model of chronic uremia, we investigated the oxidative capacity of mitochondria in UCM and their sensitivity to ischemia-reperfusion mimetic oxidant and calcium stressors to assess the susceptibility to mPTP formation. Uremic animals exhibited a 45% reduction in creatinine clearance (P < 0.01), and cardiac mitochondria demonstrated uncoupling with increased state 4 respiration. Following IRI, uremic mitochondria exhibited a 58% increase in state 4 respiration (P < 0.05), with an overall reduction in respiratory control ratio (P < 0.01). Cardiomyocytes from uremic animals displayed a 30% greater vulnerability to oxidant-induced cell death determined by FAD autofluorescence (P < 0.05) and reduced mitochondrial redox state on exposure to 200 μM H2O2 (P < 0.01). The susceptibility to calcium-induced permeability transition showed that maximum rates of depolarization were enhanced in uremia by 79%. These results demonstrate that mitochondrial respiration in the uremic heart is chronically uncoupled. Cardiomyocytes in UCM are characterized by a more oxidized mitochondrial network, with greater susceptibility to oxidant-induced cell death and enhanced vulnerability to calcium-induced mPTP formation. Collectively, these findings indicate that mitochondrial function is compromised in UCM with increased vulnerability to calcium and oxidant-induced stressors, which may underpin the enhanced predisposition to IRI in the uremic heart.

Circulating omega-6 polyunsaturated fatty acids and total and cause-specific mortality: the Cardiovascular Health Study

BACKGROUND

Although omega-6 polyunsaturated fatty acids (n-6 PUFA) have been recommended to reduce coronary heart disease (CHD), controversy remains about benefits versus harms, including concerns over theorized proinflammatory effects of n-6 PUFA. We investigated associations of circulating n-6 PUFA including linoleic acid (the major dietary PUFA), γ-linolenic acid, dihomo-γ-linolenic acid, and arachidonic acid, with total and cause-specific mortality in the Cardiovascular Health Study, a community-based U.S. cohort.

METHODS AND RESULTS

Among 2792 participants(aged ≥65 years) free of cardiovascular disease at baseline, plasma phospholipid n-6 PUFA were measured at baseline using standardized methods. All-cause and cause-specific mortality, and total incident CHD and stroke, were assessed and adjudicated centrally. Associations of PUFA with risk were assessed by Cox regression. During 34 291 person-years of follow-up (1992-2010), 1994 deaths occurred (678 cardiovascular deaths), with 427 fatal and 418 nonfatal CHD, and 154 fatal and 399 nonfatal strokes. In multivariable models, higher linoleic acid was associated with lower total mortality, with extreme-quintile hazard ratio =0.87 (P trend=0.005). Lower death was largely attributable to cardiovascular disease causes, especially nonarrhythmic CHD mortality (hazard ratio, 0.51; 95% confidence interval, 0.32-0.82; P trend=0.001). Circulating γ-linolenic acid, dihomo-γ-linolenic acid, and arachidonic acid were not significantly associated with total or cause-specific mortality (eg, for arachidonic acid and CHD death, the extreme-quintile hazard ratio was 0.97; 95% confidence interval, 0.70-1.34; P trend=0.87). Evaluated semiparametrically, linoleic acid showed graded inverse associations with total mortality (P=0.005). There was little evidence that associations of n-6 PUFA with total mortality varied by age, sex, race, or plasma n-3 PUFA. Evaluating both n-6 and n-3 PUFA, lowest risk was evident with highest levels of both.

CONCLUSIONS

High circulating linoleic acid, but not other n-6 PUFA, was inversely associated with total and CHD mortality in older adults.

Dysregulation of cardiolipin biosynthesis in pediatric heart failure

Cardiolipin, a unique phospholipid in the inner mitochondrial membrane, is critical for optimal mitochondrial function. CL abnormalities have been demonstrated in the failing rodent and adult human heart. The aim of this study was to determine whether abnormalities in CL content and the CL biosynthesis and remodeling pathways are present in pediatric idiopathic dilated cardiomyopathy (IDC). A cross-sectional analysis of myocardial tissue from 119 IDC and non-failing (NF) control samples was performed. Electrospray ionizing mass spectrometry was used to measure total CL and CL species content in LV tissue. RT-PCR was employed to measure gene expression of the enzymes in the CL biosynthesis and remodeling pathways in both the adult and pediatric heart. Significantly lower total and (18:2)4CL (the beneficial species) content was demonstrated in myocardium from pediatric patients with IDC compared to NF controls. Analysis of mitochondrial gene transcripts was used to demonstrate that there is no decrease in mitochondrial content. Expression of two biosynthesis enzymes and one remodeling enzyme was significantly lower in pediatric IDC compared to NF controls. Expression of two phospholipases involved in CL degradation were also altered, one up- and one down-regulated. Except for one remodeling enzyme, these changes are unique from those in the failing adult heart. Similar to what has been seen in adults and in a rat model of IDC, total and (18:2)4CL are lower in pediatric IDC. Unique CL species profiles are seen in heart tissue from children with IDC compared to adults. Differences in CL biosynthesis and remodeling enzyme expression likely explain the differences in CL profiles observed in IDC and implicate unique age-related mechanisms of disease.

Mitochondria: a possible nexus for the regulation of energy homeostasis by the endocannabinoid system?

The endocannabinoid system (ECS) regulates numerous cellular and physiological processes through the activation of receptors targeted by endogenously produced ligands called endocannabinoids. Importantly, this signaling system is known to play an important role in modulating energy balance and glucose homeostasis. For example, current evidence indicates that the ECS becomes overactive during obesity whereby its central and peripheral stimulation drives metabolic processes that mimic the metabolic syndrome. Herein, we examine the role of the ECS in modulating the function of mitochondria, which play a pivotal role in maintaining cellular and systemic energy homeostasis, in large part due to their ability to tightly coordinate glucose and lipid utilization. Because of this, mitochondrial dysfunction is often associated with peripheral insulin resistance and glucose intolerance as well as the manifestation of excess lipid accumulation in the obese state. This review aims to highlight the different ways through which the ECS may impact upon mitochondrial abundance and/or oxidative capacity and, where possible, relate these findings to obesity-induced perturbations in metabolic function. Furthermore, we explore the potential implications of these findings in terms of the pathogenesis of metabolic disorders and how these may be used to strategically develop therapies targeting the ECS.

Fatty acids and cardiac disease: fuel carrying a message

From the viewpoint of the prevention of cardiovascular disease (CVD) burden, there has been a continuous interest in the detrimental effects of the Western-type high-fat diet for more than half a century. More recently, this general view has been subject to change as epidemiological studies showed that replacing fat by carbohydrate may even be worse and that various polyunsaturated fatty acids (FA) have beneficial rather than detrimental effects on CVD outcome. At the same time, advances in lipid biology have provided insight into the mechanisms by which the different lipid components of the Western diet affect the cardiovascular system. In fact, this still is a rapidly growing field of research and in recent years novel FA derivatives and FA receptors have been discovered. This includes fish-oil derived FA-derivatives with anti-inflammatory properties, the so-called resolvins, and various G-protein-coupled receptors that recognize FA as ligands. In the present review, we will extensively discuss the role of FA and their metabolites on cardiac disease, with special emphasis on the role of the different saturated and polyunsaturated FA and their respective metabolites in cellular signal transduction and the possible implications for the development of cardiac hypertrophy and cardiac failure.

Cardiolipin and mitochondrial function in health and disease

Cardiolipin (CL) is a unique phospholipid that is almost exclusively localized at the level of the inner mitochondrial membrane (IMM), where it is biosynthesized. This phospholipid is associated with membranes which are designed to generate an electrochemical gradient that is used to produce ATP. Such membranes include the bacterial plasma membrane and IMM. This ubiquitous and intimate association between CL and energy-transducing membranes suggests an important role for CL in mitochondrial bioenergetic processes. CL has been shown to interact with a number of IMM proteins, including the respiratory chain complexes and substrate carriers. Moreover, CL is involved in different stages of the mitochondrial apoptosis process as well as in mitochondrial membrane stability and dynamics. Alterations in CL structure, content, and acyl chain composition have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions and aging. In this review, we provide an overview of the roles of CL in mitochondrial function and bioenergetics in health and disease.

Inhibition of delta-6 desaturase reverses cardiolipin remodeling and prevents contractile dysfunction in the aged mouse heart without altering mitochondrial respiratory function

Aging results in a redistribution of polyunsaturated fatty acids (PUFAs) in myocardial phospholipids. In particular, a selective loss of linoleic acid (18:2n6) with reciprocal increases of long-chain PUFAs (eg, arachidonic and docosahexaenoic acids) in the mitochondrial phospholipid cardiolipin correlates with cardiac mitochondrial dysfunction and contractile impairment in aging and related pathologies. In this study, we demonstrate a reversal of this aged-related PUFA redistribution pattern in cardiac mitochondria from aged (25 months) C57Bl/6 mice by inhibition of delta-6 desaturase, the rate limiting enzyme in long-chain PUFA biosynthesis. Interestingly, delta-6 desaturase inhibition had no effect on age-related mitochondrial respiratory dysfunction, H2O2 release, or lipid peroxidation but markedly attenuated cardiac dilatation, hypertrophy, and contractile dysfunction in aged mice. Taken together, our studies indicate that PUFA metabolism strongly influences phospholipid remodeling and cardiac function but dissociates these processes from mitochondrial respiratory dysfunction and oxidant production in the aged mouse heart.

Omega-3 supplementation alters mitochondrial membrane composition and respiration kinetics in human skeletal muscle

Studies have shown increased incorporation of omega-3 fatty acids into whole skeletal muscle following supplementation, although little has been done to investigate the potential impact on the fatty acid composition of mitochondrial membranes and the functional consequences on mitochondrial bioenergetics. Therefore, we supplemented young healthy male subjects (n = 18) with fish oils [2 g eicosapentaenoic acid (EPA) and 1 g docosahexanoic acid (DHA) per day] for 12 weeks and skeletal muscle biopsies were taken prior to (Pre) and following (Post) supplementation for the analysis of mitochondrial membrane phospholipid composition and various assessments of mitochondrial bioenergetics. Total EPA and DHA content in mitochondrial membranes increased (P < 0.05) ∼450 and ∼320%, respectively, and displaced some omega-6 species in several phospholipid populations. Mitochondrial respiration, determined in permeabilized muscle fibres, demonstrated no change in maximal substrate-supported respiration, or in the sensitivity (apparent Km) and maximal capacity for pyruvate-supported respiration. In contrast, mitochondrial responses during ADP titrations demonstrated an enhanced ADP sensitivity (decreased apparent Km) that was independent of the creatine kinase shuttle. As the content of ANT1, ANT2, and subunits of the electron transport chain were unaltered by supplementation, these data suggest that prolonged omega-3 intake improves ADP kinetics in human skeletal muscle mitochondria through alterations in membrane structure and/or post-translational modification of ATP synthase and ANT isoforms. Omega-3 supplementation also increased the capacity for mitochondrial reactive oxygen species emission without altering the content of oxidative products, suggesting the absence of oxidative damage. The current data strongly emphasize a role for omega-3s in reorganizing the composition of mitochondrial membranes while promoting improvements in ADP sensitivity.

Cardiolipin remodeling in diabetic heart

Cardiolipin, a signature phospholipid of mitochondria, is predominantly present in the mitochondrial inner membrane and plays an important role in keeping optimal mitochondrial function. In addition to the cardiolipin content, the composition of four fatty acid chain is thought determine cardiolipin biological function. These acyl chains of cardiolipin are dynamically remodeled via tafazzin, monolysocardiolipin acyltransferase, and acyl-CoA lysocardiolipin acyltransferase especially in the heart under pathological conditions. The major species of cardiolipin in the normal heart, tetralinoleoyl cardiolipin, is dramatically decreased in the diabetic heart, but other species, typically those containing long fatty acyl chains, are increased. This remodeling of cardiolipin has detrimental effects on mitochondrial function and thereafter cardiac function. Approaches for manipulating cardiolipin acyl chains have been examined including via molecular biology and through supplementation of linoleic acid. The efficiency of cardiolipin remodeling and functional improvement is still under investigation.

Dietary polyunsaturated fatty acids and inflammation: the role of phospholipid biosynthesis

The composition of fatty acids in the diets of both human and domestic animal species can regulate inflammation through the biosynthesis of potent lipid mediators. The substrates for lipid mediator biosynthesis are derived primarily from membrane phospholipids and reflect dietary fatty acid intake. Inflammation can be exacerbated with intake of certain dietary fatty acids, such as some ω-6 polyunsaturated fatty acids (PUFA), and subsequent incorporation into membrane phospholipids. Inflammation, however, can be resolved with ingestion of other fatty acids, such as ω-3 PUFA. The influence of dietary PUFA on phospholipid composition is influenced by factors that control phospholipid biosynthesis within cellular membranes, such as preferential incorporation of some fatty acids, competition between newly ingested PUFA and fatty acids released from stores such as adipose, and the impacts of carbohydrate metabolism and physiological state. The objective of this review is to explain these factors as potential obstacles to manipulating PUFA composition of tissue phospholipids by specific dietary fatty acids. A better understanding of the factors that influence how dietary fatty acids can be incorporated into phospholipids may lead to nutritional intervention strategies that optimize health.

NAD(P)H cytochrome b5 oxidoreductase deficiency in Leishmania major results in impaired linoleate synthesis followed by increased oxidative stress and cell death

NAD(P)H cytochrome b(5) oxidoreductase (Ncb5or), comprising cytochrome b(5) and cytochrome b(5) reductase domains, is widely distributed in eukaryotic organisms. Although Ncb5or plays a crucial role in lipid metabolism of mice, so far no Ncb5or gene has been reported in the unicellular parasitic protozoa Leishmania species. We have cloned, expressed, and characterized Ncb5or gene from Leishmania major. Steady state catalysis and spectral studies show that NADH can quickly reduce the ferric state of the enzyme to the ferrous state and is able to donate an electron(s) to external acceptors. To elucidate its exact physiological role in Leishmania, we attempted to create NAD(P)H cytochrome b(5) oxidoreductase from L. major (LmNcb5or) knock-out mutants by targeted gene replacement technique. A free fatty acid profile in knock-out (KO) cells reveals marked deficiency in linoleate and linolenate when compared with wild type (WT) or overexpressing cells. KO culture has a higher percentage of dead cells compared with both WT and overexpressing cells. Increased O(2) uptake, uncoupling and ATP synthesis, and loss of mitochondrial membrane potential are evident in KO cells. Flow cytometric analysis reveals the presence of a higher concentration of intracellular H(2)O(2), indicative of increased oxidative stress in parasites lacking LmNcb5or. Cell death is significantly reduced when the KO cells are pretreated with BSA bound linoleate. Real time PCR studies demonstrate a higher Δ12 desaturase, superoxide dismutase, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA with a concomitant fall in Δ9 desaturase mRNA expression in LmNcb5or null cell line. Together these findings suggest that decreased linoleate synthesis, and increased oxidative stress and apoptosis are the major consequences of LmNcb5or deficiency in Leishmania.