Effect of dietary polyunsaturated fatty acids on age-related changes in cardiac mitochondrial membranes

Comprehensive Mechanism, Novel Markers and Multidisciplinary Treatment of Severe Acute Pancreatitis-Associated Cardiac Injury - A Narrative Review

Acute pancreatitis (AP) is one of the common acute abdominal inflammatory diseases in clinic with acute onset and rapid progress. About 20% of the patients will eventually develop into severe acute pancreatitis (SAP) characterized by a large number of inflammatory cells infiltration, gland flocculus flaky necrosis and hemorrhage, finally inducing systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS). Pancreatic enzyme activation, intestinal endotoxemia (IETM), cytokine activation, microcirculation disturbance, autonomic nerve dysfunction and autophagy dysregulation all play an essential role in the occurrence and progression of SAP. Organ dysfunction is the main cause of early death in SAP. Acute kidney injury (AKI) and acute lung injury (ALI) are common, while cardiac injury (CI) is not, but the case fatality risk is high. Many basic studies have observed obvious ultrastructure change of heart in SAP, including myocardial edema, cardiac hypertrophy, myocardial interstitial collagen deposition. Moreover, in clinical practice, patients with SAP often presented various abnormal electrocardiogram (ECG) and cardiac function. Cases complicated with acute myocardial infarction and pericardial tamponade have also been reported and even result in stress cardiomyopathy. Due to the molecular mechanisms underlying SAP-associated cardiac injury (SACI) remain poorly understood, and there is no complete, unified treatment and sovereign remedy at present, this article reviews reports referring to the pathogenesis, potential markers and treatment methods of SACI in recent years, in order to improve the understanding of cardiac injury in severe pancreatitis.

Mitochondrial Bioenergetics and Dysfunction in Failing Heart

Energy insufficiency has been recognized as a key feature of systolic heart failure. Although mitochondria have long been known to sustain myocardial work energy supply, the capacity to therapeutically target mitochondrial bioenergetics dysfunction is hampered by a complex interplay of multiple perturbations that progressively compound causing myocardial failure and collapse. Compared to non-failing human donor hearts, activity rates of complexes I and IV, nicotinamide nucleotide transhydrogenase (NADPH-transhydrogenase, Nnt) and the Krebs cycle enzymes isocitrate dehydrogenase, malate dehydrogenase and aconitase are markedly decreased in end-stage heart failure. Diminished REDOX capacity with lower total glutathione and coenzyme Q₁₀ levels are also a feature of chronic left ventricular failure. Decreased enzyme activities in part relate to abundant and highly specific oxidative, nitrosylative, and hyperacetylation modifications. In this brief review we highlight that energy deficiency in end-stage failing human left ventricle predominantly involves concomitantly impaired activities of key electron transport chain and Krebs cycle enzymes rather than altered expression of respective genes or proteins. Augmented oxidative modification of these enzyme subunit structures, and the formation of highly reactive secondary metabolites, implicates dysfunction due to diminished capacity for management of mitochondrial reactive oxygen species, which contribute further to progressive decreases in bioenergetic capacity and contractile function in human heart failure.

Sarcolemmal dependence of cardiac protection and stress-resistance: roles in aged or diseased hearts

Disruption of the sarcolemmal membrane is a defining feature of oncotic death in cardiac ischaemia-reperfusion (I-R), and its molecular makeup not only fundamentally governs this process but also affects multiple determinants of both myocardial I-R injury and responsiveness to cardioprotective stimuli. Beyond the influences of membrane lipids on the cytoprotective (and death) receptors intimately embedded within this bilayer, myocardial ionic homeostasis, substrate metabolism, intercellular communication and electrical conduction are all sensitive to sarcolemmal makeup, and critical to outcomes from I-R. As will be outlined in this review, these crucial sarcolemmal dependencies may underlie not only the negative effects of age and common co-morbidities on myocardial ischaemic tolerance but also the on-going challenge of implementing efficacious cardioprotection in patients suffering accidental or surgically induced I-R. We review evidence for the involvement of sarcolemmal makeup changes in the impairment of stress-resistance and cardioprotection observed with ageing and highly prevalent co-morbid conditions including diabetes and hypercholesterolaemia. A greater understanding of membrane changes with age/disease, and the inter-dependences of ischaemic tolerance and cardioprotection on sarcolemmal makeup, can facilitate the development of strategies to preserve membrane integrity and cell viability, and advance the challenging goal of implementing efficacious 'cardioprotection' in clinically relevant patient cohorts. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.

Marine n-3 PUFA protects hearts from I/R injury via restoration of mitochondrial function

OBJECTIVES

Overwhelming evidence shows that dietary supplementation with n-3 polyunsaturated fatty acids (PUFAs) elicits protective effects on patients with cardiovascular disease. However, the detailed mechanisms underlying n-3 PUFA-mediated cardioprotection are unknown, and examined in the present study.

METHODS

We evaluated heart performances with Langendorff perfusion apparatus. Meanwhile, whole mitochondria were purified from non-perfused hearts for functional assessment, and lipid peroxidation level was measured as well.

RESULTS

Compared with control groups, hearts from n-3 PUFA-supplemented rats showed improved functional recovery and reduced tissue injury following ischemia/reperfusion (I/R). Furthermore, the mitochondrial function of PUFA-treated hearts was significantly enhanced, as demonstrated by biochemical analysis of respiratory chain activity. In addition, thiobarbituric acid-reactive substance or TBARS assay revealed that lipid peroxidation product, malondialdehyde or MDA, in the mitochondria was significantly reduced by PUFA treatment.

CONCLUSION

Taken together, our data indicate that marine n-3 PUFA could improve cardiac performance after I/R injury by restoring mitochondrial respiratory activities and attenuating lipid peroxidation.

Impact of lipid oxidization on biophysical properties of model cell membranes

The oxidization of glycerophospholipids in cell membranes due to aging and environmental stresses may cause a variety of pathological and physiological consequences. A variety of oxidized phospholipid products (OxPl) are produced by the chemical oxidization of unsaturated hydrocarbon chains, which would significantly change the physicochemical properties of cell membranes. In this work, we constructed cell membrane models in the absence and presence of two stable oxidized lipid products and investigated their impact on physical properties of supported membranes using quartz crystal microbalance with dissipation (QCM-D) and high-energy X-ray reflectivity (XRR). Our experimental findings suggest that the lipid oxidization up to 20 mol % leads to the rupture of vesicles right after the adsorption. Our XRR analysis unravels the membrane thinning and the decrease in the lateral ordering of lipids, which can be explained by the decrease in the lateral packing of hydrocarbon chains. Further studies on mechanics of membranes incorporating oxidized lipids can be attributed to the decrease in the bending rigidity and the increase in the permeability.

Caveolins in cardioprotection - translatability and mechanisms

Translation of preclinical treatments for ischaemia-reperfusion injury into clinical therapies has been limited by a number of factors. This review will focus on a single mode of cardiac protection related to a membrane scaffolding protein, caveolin, which regulates protective signalling as well as myocyte ultrastructure in the setting of ischaemic stress. Factors that have limited the clinical translation of protection will be considered specifically in terms of signalling and structural defects. The potential of caveolin to overcome barriers to protection with the ultimate hope of clinical translation will be discussed.

Ameliorative effects of docosahexaenoic acid on the toxicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in cultured rat hepatocytes

The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant toxicant that mediates carcinogenic effects associated with oxidative DNA damage. Docosahexaenoic acid (DHA) with antioxidant functions has many biochemical, cellular, and physiological functions for cells. The present study assessed, for the first time, the ameliorative effect of DHA in alleviating the toxicity of TCDD on primary cultured rat hepatocytes (HEPs). In vitro, isolated HEPs were incubated with TCDD (5 and 10 μM) in the presence and absence of DHA (5, 10, and 20 μM) for 48 h. The cell viability was detected by 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) release. DNA damage was analyzed by liver micronucleus assay and 8-oxo-2-deoxyguanosine (8-OH-dG) level. In addition, total antioxidant capacity (TAC) and total oxidative stress (TOS) were assessed to determine the oxidative injury in HEPs. The results of MTT and LDH assays showed that TCDD decreased cell viability but not DHA. On the basis of increasing treatment concentrations, the dioxin caused significant increases of micronucleated HEPs and 8-OH-dG as compared to control culture. TCDD also led to significant increases in TOS content. On the contrary, in cultures treated with DHA, the level of TAC was significantly increased during treatment in a concentration-dependent fashion. DHA showed therapeutic potential against TCDD-mediated cell viability and DNA damages. As conclusion, this study provides the first evidence that DHA has protective effects against TCDD toxicity on primary cultured rat hepatocytes.

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.

Mechanisms of arrhythmias and conduction disorders in older adults

Aging is associated with an increased prevalence of cardiac arrhythmias, which contribute to higher morbidity and mortality in the elderly. The frequency of cardiac arrhythmias, particularly atrial fibrillation and ventricular tachyarrhythmia, is projected to increase as the population ages, greatly impacting health care resource utilization. Several clinical factors associated with the risk of arrhythmias have been identified in the population, yet the molecular bases for the increased predisposition to arrhythmogenesis in the elderly are not fully understood. This review highlights the epidemiology of cardiac dysrhythmias, changes in cardiac structure and function associated with aging, and the basis for arrhythmogenesis in the elderly.

Dietary Omega-3 Fatty Acids Do Not Change Resistance of Rat Brain or Liver Mitochondria to Ca(2+) and/or Prooxidants

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) block apoptotic neuronal cell death and are strongly neuroprotective in acute and chronic neurodegeneration. Theoretical considerations, indirect data, and consideration of parsimony lead to the hypothesis that modulation of mitochondrial pathway(s) underlies at least some of the neuroprotective effects of n-3 PUFAs. We therefore systematically tested this hypothesis on healthy male FBFN1 rats fed for four weeks with isocaloric, 10% fat-containing diets supplemented with 1, 3, or 10% fish oil (FO). High resolution mass spectrometric analysis confirmed expected diet-driven increases in docosahexaenoic acid (DHA, 22:6, n-3) and eicosapentaenoic acid (EPA, 20:5, n-3) in sera, liver and nonsynaptosomal brain mitochondria. We further evaluated the resistance of brain and liver mitochondria to Ca(2+) overload and prooxidants. Under these conditions, neither mitochondrial resistance to Ca(2+) overload and prooxidants nor mitochondrial physiology is altered by diet, despite the expected incorporation of DHA and EPA in mitochondrial membranes and plasma. Collectively, the data eliminate one of the previously proposed mechanism(s) that n-3 PUFA induced augmentation of mitochondrial resistance to the oxidant/calcium-driven dysfunction. These data furthermore allow us to define a specific series of follow-up experiments to test related hypotheses about the effect of n-3 PUFAs on brain mitochondria.

Ceramide and mitochondrial function in aging oocytes: joggling a new hypothesis and old players

Maternal aging adversely affects oocyte quality (function and developmental potential) and consequently lowers pregnancy rates while increasing spontaneous abortions. Substantial evidence, especially from egg donation studies, implicates the decreased quality of an aging oocyte as a major factor in the etiology of female infertility. Nevertheless, the cellular and molecular mechanisms responsible for the decreased oocyte quality with advanced maternal aging are not fully characterized. Herein we present information in the published literature and our own data to support the hypothesis that during aging induced decreases in mitochondrial ceramide levels and associated alterations in mitochondrial structure and function are prominent elements contributing to reduced oocyte quality. Hence, by examining the molecular determinants that underlie impairments in oocyte mitochondria, we expect to sieve to a better understanding of the mechanistic anatomy of oocyte aging.

Dietary fish oil modestly attenuates the effect of age on diastolic function but has no effect on memory or brain inflammation in aged rats

Fish oil (FO) mediates a number of cardioprotective benefits in patients with cardiovascular disease. In the absence of cardiovascular disease, however, the effects of FO on cardiac structure and function are not clear. In addition, it is not known if an effective dosing strategy for attenuating age-related cardiac dysfunction is also effective at limiting cognitive dysfunction. Therefore, we determined if 4 months of FO supplementation in aged rats would lessen age-related cardiac dysfunction while concomitantly preventing the cognitive decline that is normally observed in this population. The results indicate that FO initiated late in life modifies diastolic function in a small but positive way by attenuating the age-related increases in filling pressure, posterior wall thickness, and interstitial collagen without mitigating age-related deficits in memory or increases in brain inflammation. These data raise the possibility that FO supplementation for purposes of cardiac and brain protection may need to occur earlier in the life span.

Animal products, diseases and drugs: a plea for better integration between agricultural sciences, human nutrition and human pharmacology

Eicosanoids are major players in the pathogenesis of several common diseases, with either overproduction or imbalance (e.g. between thromboxanes and prostacyclins) often leading to worsening of disease symptoms. Both the total rate of eicosanoid production and the balance between eicosanoids with opposite effects are strongly dependent on dietary factors, such as the daily intakes of various eicosanoid precursor fatty acids, and also on the intakes of several antioxidant nutrients including selenium and sulphur amino acids. Even though the underlying biochemical mechanisms have been thoroughly studied for more than 30 years, neither the agricultural sector nor medical practitioners have shown much interest in making practical use of the abundant high-quality research data now available. In this article, we discuss some specific examples of the interactions between diet and drugs in the pathogenesis and therapy of various common diseases. We also discuss, using common pain conditions and cancer as specific examples, how a better integration between agricultural science, nutrition and pharmacology could lead to improved treatment for important diseases (with improved overall therapeutic effect at the same time as negative side effects and therapy costs can be strongly reduced). It is shown how an unnaturally high omega-6/omega-3 fatty acid concentration ratio in meat, offal and eggs (because the omega-6/omega-3 ratio of the animal diet is unnaturally high) directly leads to exacerbation of pain conditions, cardiovascular disease and probably most cancers. It should be technologically easy and fairly inexpensive to produce poultry and pork meat with much more long-chain omega-3 fatty acids and less arachidonic acid than now, at the same time as they could also have a similar selenium concentration as is common in marine fish. The health economic benefits of such products for society as a whole must be expected vastly to outweigh the direct costs for the farming sector.

Effects of alpha-linolenic acid vs. docosahexaenoic acid supply on the distribution of fatty acids among the rat cardiac subcellular membranes after a short- or long-term dietary exposure

BACKGROUND

Previous work showed that the functional cardiac effect of dietary alpha-linolenic acid (ALA) in rats requires a long feeding period (6 months), although a docosahexaenoic (DHA) acid-supply affects cardiac adrenergic response after 2 months. However, the total cardiac membrane n-3 polyunsaturated fatty acid (PUFA) composition remained unchanged after 2 months. This delay could be due to a specific reorganization of the different subcellular membrane PUFA profiles. This study was designed to investigate the evolution between 2 and 6 months of diet duration of the fatty acid profile in sarcolemmal (SL), mitochondrial (MI), nuclear (NU) and sarcoplasmic reticulum (SR) membrane fractions.

METHODS

Male Wistar rats were randomly assigned to 3 dietary groups (n = 10/diet/period), either n-3 PUFA-free diet (CTL), or ALA or DHA-rich diets. After 2 or 6 months, the subcellular cardiac membrane fractions were separated by differential centrifugations and sucrose gradients. Each membrane profile was analysed by gas chromatography (GC) after lipid extraction.

RESULTS

As expected the n-3 PUFA-rich diets incorporated n-3 PUFA instead of n-6 PUFA in all the subcellular fractions, which also exhibited individual specificities. The diet duration increased SFA and decreased PUFA in SL, whereas NU remained constant. The SR and MI enriched in n-3 PUFA exhibited a decreased DHA level with ageing in the DHA and CTL groups. Conversely, the n-3 PUFA level remained unchanged in the ALA group, due to a significant increase in docosapentaenoic acid (DPA). N-3 PUFA rich diets lead to a better PUFA profile in all the fractions and significantly prevent the profile modifications induced by ageing.

CONCLUSION

With the ALA diet the n-3 PUFA content, particularly in SR and SL kept increasing between 2 and 6 months, which may partly account for the delay to achieve the modification of adrenergic response.

Increased levels of a particular phosphatidylcholine species in senescent human dermal fibroblasts in vitro

Plasma membranes are essential components of living cells, and phospholipids are major components of cellular membranes. Here, we used liquid chromatography/mass spectrometry to investigate changes in the membrane phospholipid content that occur in association with aging. Our results indicate that the levels of a particular species of phosphatidylcholine comprised of stearic acid and arachidonic acid increased with age. To determine the reason for the increased levels of this particular phosphatidylcholine, we examined the effect of highly unsaturated fatty acids, such as arachidonic acid and eicosapentaenoic acid, on cellular aging. Applied arachidonic acid was incorporated into phosphatidylcholine molecules, but neither arachidonic acid nor other related unsaturated fatty acids had any effect. We conclude that increased levels of this distinctive phosphatidylcholine are a result of in vitro senescence.

Intervention with flaxseed and borage oil supplements modulates skin condition in women

Ingestion of selected nutrients modulates dermal properties. In the present study, two groups of women ingested flaxseed or borage oil for 12 weeks. The control group received a placebo containing medium-chain fatty acids. Dose was 2·2 g total fatty acids/d with α-linolenic acid and linoleic acid as major constituents in the flaxseed oil group; in the borage oil group linoleic and γ-linolenic acid were predominant. In the flaxseed oil group, the contribution of α-linolenic acid to total fatty acids in plasma was significantly increased on weeks 6 and 12, whereas there was an increase in γ-linolenic acid in the borage oil group (P < 0·05). Skin irritation was performed by nicotinate treatment, and changes in skin reddening and blood flow were monitored. Compared to week 0, skin reddening was diminished in both groups; blood flow was also lowered. Skin hydration was significantly increased after 12 weeks of treatment compared to week 0, with flaxseed or borage oil (P < 0·05). Transepidermal water loss was decreased in both oil groups by about 10 % after 6 weeks of supplementation. A further decrease was determined after 12 weeks in the flaxseed oil group. Surface evaluation of living skin revealed that roughness and scaling of the skin were significantly decreased with flaxseed and borage oil comparing week 0 and week 12 (P < 0·05). Except for hydration, none of the parameters was affected in the placebo group. The present data provide evidence that skin properties can be modulated by an intervention with dietary lipids.

[Metabolic therapy for early treatment of age-related macular degeneration]

Currently, age-related macular degeneration is one of the most common eye diseases causing severe and permanent loss of vision. This disease is estimated to affect approximately 300-500 thousand Hungarians. While earlier no treatment was available, in the recent decade an antioxidant therapy became very popular using combinations of high dosage antioxidant vitamins C, E, beta carotene and zinc. Based on theoretical concepts and mostly in vitro experiences, this combination was thought to be effective through neutralizing reactive oxygen species. According to a large clinical trial (AREDS) it reduced progression of intermediate state disease to advanced state, but did not influence early disease. This original combination, due to potential severe side effects, is not on the market anymore. However, the efficacy of modified formulas has not been proved yet. Recently, the metabolic therapy, a combination of omega-3 fatty acids, coenzyme Q10 and acetyl-L-carnitine has been introduced for treating early age-related macular degeneration through improving mitochondrial dysfunction, specifically improving lipid metabolism and ATP production in the retinal pigment epithelium, improving photoreceptor turnover and reducing generation of reactive oxygen species. According to a pilot study and a randomized, placebo-controlled, double blind clinical trial, both central visual field and visual acuity slightly improved after 3-6 months of treatment and they remained unchanged by the end of the study. The difference was statistically significant as compared to the base line or to controls. These functional changes were accompanied by an improvement in fundus alterations: drusen covered area decreased significantly as compared to the base line or to control. Characteristically, all these changes were more marked in less affected eyes. A prospective case study on long-term treatment confirmed these observations. With an exception that after slight improvement, visual functions remained stable, drusen regression continued for years. Sometimes significant regression of drusen was found even in intermediate and advanced cases. All these findings strongly suggested that the metabolic therapy may be the first choice for treating age-related macular degeneration. Currently, this is the only combination of ingredients corresponding to the recommended daily allowance, and at the same time, which showed clinically proved efficacy.

Dietary polyunsaturated fatty acids and age-related membrane changes in the heart

Age-associated modification of cardiac membrane composition and related metabolic processes are major factors underlying the reduced capacity for invoking intrinsic cardioprotective survival mechanisms. In this brief review we examine some of these key membrane lipid modifications, which include alterations in the type and proportion of long-carbon chain polyunsaturated fatty acids (PUFAs). These changes have profound consequences on the efficacy of membrane proteins and lipids involved with numerous processes including ion homeostasis, intracellular signal transduction, free radical metabolism, and mitochondrial energy production. The resultant postoxidative modification of lipids, proteins, and DNA leads to a reduction in capacity for repair and ultimately worsening cellular dysfunction. However, some age-related detrimental adaptations may be counteracted by selectively manipulating membrane lipid and protein composition via dietary treatment with key omega-3 PUFAs. Such pervasive treatment results in manipulation of cellular function at multiple levels from cell membrane to the genome.

What Cardiologists Should Know About Calcium Ion Channels and Their Regulation by Reactive Oxygen Species

Ion channels underlie the electrical activity of cells. Calcium channels have a unique functional role, because not only do they participate in this activity, they form the means by which electrical signals are converted to responses within the cell. Calcium channels play an integral role in excitation in the heart and shaping the cardiac action potential. In addition, calcium influx through calcium channels is responsible for initiating contraction. Abnormalities in calcium homeostasis underlie cardiac arrhythmia, contractile dysfunction and cardiac remodelling. Reactive oxygen species participate in the development of pathology by altering the redox state of regulatory proteins. There is now good evidence that reactive oxygen species regulate the function of calcium channels. In this mini-review, the evidence for regulation of calcium channels by reactive oxygen species and implications with respect to pathology are presented. Calcium channels may represent a target for intervention during hypoxic trigger of arrhythmia or chronic pathological remodelling.

Aging and cardioprotection

Advanced age is a strong independent predictor for death, disability, and morbidity in patients with structural heart disease. With the projected increase in the elderly population and the prevalence of age-related cardiovascular disabilities worldwide, the need to understand the biology of the aging heart, the mechanisms for age-mediated cardiac vulnerability, and the development of strategies to limit myocardial dysfunction in the elderly have never been more urgent. Experimental evidence in animal models indicate attenuation in cardioprotective pathways with aging, yet limited information is available regarding age-related changes in the human heart. Human cardiac aging generates a complex phenotype, only partially replicated in animal models. Here, we summarize current understanding of the aging heart stemming from clinical and experimental studies, and we highlight targets for protection of the vulnerable senescent myocardium. Further progress mandates assessment of human tissue to dissect specific aging-associated genomic and proteomic dynamics, and their functional consequences leading to increased susceptibility of the heart to injury, a critical step toward designing novel therapeutic interventions to limit age-related myocardial dysfunction and promote healthy aging.

The Clinical Application of Metabolic Therapy for Cardiovascular Disease

Metabolic therapy involves the administration of a substance normally found in the body to enhance a metabolic reaction within the cell. This may be achieved in two ways. Firstly, for some systems a substance can be given to achieve greater than normal levels in the body so as to drive an enzymic reaction in a preferred direction. Secondly, metabolic therapy may be used to correct an absolute or relative deficiency of a cellular component. Thus, metabolic therapy differs greatly from most standard cardiovascular pharmacologic therapies such as the use of ACE Inhibitors, beta-blockers, statins and calcium channel antagonists that are given to block rather than enhance cellular processes.

Oxidative phosphorylation and aging

This review addresses the data that support the presence and contribution of decreased mitochondrial oxidative phosphorylation during aging to impaired cellular metabolism. Aging impairs substrate oxidation, decreases cellular energy production and increases the production of reactive intermediates that are toxic to the cell. First, the basic principles of mitochondrial oxidative physiology are briefly reviewed. Second, the focus on the relationship of altered mitochondrial respiration to the increased production of reactive oxygen species that are employed by the "rate of living" and the "uncoupling to survive" theories of aging are discussed. Third, the impairment of function of respiration in aging is reviewed using an organ-based approach in mammalian systems. Fourth, the current state of knowledge regarding aging-induced alterations in the composition and function of key mitochondrial constituents is addressed. Model organisms, including C. elegans and D. melanogaster are included where pertinent. Fifth, these defects are related to knowledge regarding the production of reactive oxygen species from specific sites of the electron transport chain.

Induction of mitochondrial nitrative damage and cardiac dysfunction by chronic provision of dietary omega-6 polyunsaturated fatty acids

Increased awareness of obesity has led to a dietary shift toward "heart-friendly" vegetable oils containing omega-6 polyunsaturated fatty acid (omega-6 PUFA). In addition to its beneficial effects, omega-6 PUFA also exhibits proinflammatory and prooxidative properties. We hypothesized that chronic dietary omega-6 PUFA can induce free radical generation, predisposing the cardiac mitochondria to oxidative damage. Male Wistar rats were fed a diet supplemented with 20% w/w sunflower oil, rich in omega-6 PUFA (HP) or normal laboratory chow (LP) for 4 weeks. HP feeding augmented phospholipase A(2) activity and breakdown of cardiolipin, a mitochondrial phospholipid. HP hearts also demonstrated elevated inducible nitric oxide synthase expression, loss of Mn superoxide dismutase, and increased mitochondrial nitrotyrosine levels. In these hearts, oxidative damage to mitochondrial DNA (mDNA) was demonstrated by 8-hydroxyguanosine immunopositivity, overexpression of DNA repair enzymes, and a decrease in the mRNA expression of specific respiratory subunits encoded by the mDNA. Functionally, at higher workloads, HP hearts also demonstrated a greater decline in cardiac work than LP, suggesting a compromised mitochondrial reserve. Our study, for the first time, demonstrates that consumption of a high fat diet rich in omega-6 PUFA for only 4 weeks instigates mitochondrial nitrosative damage and causes cardiac dysfunction at high afterloads.

Energy deficiency in the failing heart: linking increased reactive oxygen species and disruption of oxidative phosphorylation rate

Heart failure is a complex syndrome of numerous dysfunctional components which converge to cause chronic progressive failure of ventricular contractile function and maintenance of cardiac output demand. The aim of this brief review is to highlight some of the mounting evidence indicating that augmented superoxide, related reactive oxygen species and other free radicals contribute to the oxidative stress evident during the progression of heart failure. While much of the source of increased reactive oxygen species is mitochondrial, there are other intracellular sources, which together are highly reactive with functional and structural cellular lipids and proteins. Bioenergetic defects limiting ATP synthesis in the failing myocardium relate not only to post-translational modification of electron transport respiratory chain proteins but also to perturbation of Krebs Cycle enzyme-dependent synthesis of NADH. Accumulation of pathological levels of lipid peroxides relate to dysfunction in the intrinsic capacity to clear and renew dysfunctional proteins. This review also features key limitations of human heart failure studies and potential clinical therapies that target the elevated oxidative stress that is a hallmark of human heart failure.